Demonstrate the use of blends of waste cooking oil

Transcription

Demonstrate the use of blends of waste cooking oil with biodiesels
and mineral fuel for engines and heating the County Council Offices
at Mallow County Cork
Altener Project No. 4.1030/0/00-014/2000
Final Report
Compiled by R.Howard-Hildige, A.P.O’Connell and J.J.Leahy
December 2002
Contents
Acknowledgements
6
1.
Introduction
7
1.1
Background
7
1.2
Recycled Vegetable oil
7
1.3
Cork County Council Energy Agency : Final Report
8
1.3.1
Waste Management in Ireland
8
1.3.2
Waste Cooking Oil Resource
10
1.3.3
Impacts of Harnessing Waste Cooking Oil (WCO) Resource
14
1.3.4
Demonstration at Cork County Council Offices
15
1.3.5
Dissemination
18
1.4
Objectives
19
2.
Recycled Vegetable Oil Collection
20
2.1
Background
20
2.2
The Collection Procedure
20
3.
RVO Processing
22
3.1
Introduction
22
3.2
Process
23
4.
RVO Characterisation
27
4.1
Introduction
27
4.2
Viscosity of RVO and Blends with Mineral Oil
28
4.2.1
Introduction
28
4.2.2
Apparatus
28
4.2.3
Results and Discussion
29
4.3
Low Temperature Viscosity of RVO
31
4.3.1
Introduction
31
4.3.2
Apparatus and Procedure
31
4.3.3
32
4.4
Calorific Value of RVO
37
2
4.4.1
Introduction
37
4.4.2
37
4.4.3
38
4.5
Gas Chromatography
40
4.5.1
Introduction
40
4.5.2
40
4.5.3
41
4.6
Differential Scanning Calorimetry
44
4.6.1
Introduction
44
4.6.2
44
4.6.3
45
4.7
Cetane Rating of RVO
48
4.7.1
Introduction
48
4.7.2
49
4.7.3
54
4.8
Low Temperature Solidification and Growth of Crystals of RVO
59
4.8.1
Introduction
59
4.8.2
63
4.8.3
66
5.
RVO Testing
82
5.1
Short Duration Boiler Fuel Blend Tests: Pilot Study
82
5.1.1
Introduction
82
5.1.2
82
5.1.3
86
5.2
Burner Modification and Adjustment for Heating Trial
91
ADEME –CIRAD Interim Report
Optimisation of burners to use waste cooking oil for domestic heating
Tests conducted at CIRAD, Montpellier, March 2002
5.2.1
Introduction
92
5.2.2
Waste Cooking Oil Fuel
92
3
5.2.3
Equipment
94
5.2.4
Optimisation
95
5.2.5
Experimental procedure
100
5.2.6
Results
103
5.2.7
Conclusions and Recommendations
105
5.3 Heating Demonstration at Cork County Council
107
5.3.1
Introduction
107
5.3.2
107
5.3.3
110
5.3.4
Analysis of Cuenod Burner Failure and Modification to ECOFLAM
Burner for 100%RVO (ADEME – CIRAD Final Report)
111
5.3.4.1 Introduction
113
5.3.4.2 On site trials Charleville: Cuenod NC4
114
5.3.4.3 Characteristics of test fuels
120
5.3.4.4 Ecoflam Minor 1 – Tests conducted at CIRAD
120
5.3.4.5 Results
124
5.3.4.6 Conclusions
127
5.4
Modified Engine in Vehicle Chassis Dynamometer Test
Pilot Study
132
5.4.1
Introduction
132
5.4.2
132
5.4.3
135
5.5
Modified Engine in Vehicle Chassis Dynamometer Test
141
Main Study
5.5.1
Introduction
141
5.5.2
Results
142
5.5.2.1 Discussion
146
5.5.3
Conclusions
149
5.6
Fuel Injector Fouling
150
4
5.6.1
Introduction
150
5.6.2
150
5.6.3
152
5.7
Effect of variation of injection timing and pressure upon exhaust
emissions and fuel consumption of a 4 cylinder diesel engine operating on
25% RVO/75% mineral fuel
156
5.7.1
Introduction
156
5.7.2
Apparatus and procedure
156
5.7.3
Results
160
5.7.4
Discussion
167
5.8
Demonstration at Ecotopia 2002
172
5.8.1
Introduction
172
5.8.2
172
5,8.2
173
6
Dissemination
174
6.1
Project Brochure
175
6.2
Workshop at Ecotopia 2002
177
5
Acknowledgements
DGTREN for support under the Altener Programme.
Adrian O’Connell for the sections on Recycled Vegetable Oil, RVO Processing and
Characterisation.
Aidan Hickey and Eric Mercier for the Cetane Rating of RVO blends.
Robert Nichol for the Vehicle Test Results.
John Kehily for the section on the Low Temperature Viscosity of RVO.
Jim Ryan, John Cunningham, Pat O’Shea and John Griffen for the Technical Support.
Bernard Rice and Des O’Connell for the RVO, Processing, and much valuable
information and support.
Brian Dwyer and Pat Walshe for the section on Waste Management
Etienne Poitrat, Gilles Vaitilingom and Alain Liennard for the Burner set up
methodology.
6
1. Introduction
1.1 Background:
Environmental concerns over greenhouse gases and depletion of source highlight the
need to move away from mineral diesel fuel oil. Vegetable oils may provide an
alternative as they are a form of renewable energy and are considered to be CO2
neutral. They have for some time been seen as an attractive alternative fuel, and have
been demonstrated in diesel engines as far back as the early years of the 20th century.
Recycled vegetable oil (RVO) from the catering industry (also known as waste
cooking oil (WCO)) is a source of this fuel and its traditional use as an animal feed
additive is now limited following the introduction of dioxins into the human food
chain via contaminated RVO.
1.2 Recycled Vegetable Oil:
In Ireland there is currently 100,000 tonnes of edible vegetable oil imported annually.
When the oil has completed it’s useful life cycle, it is considered to be a waste
material. Approximately 10,000 tonnes of this waste cooking oil is collected in
Ireland and recycled each year. This recycled vegetable oil, or RVO has traditionally
been used as an animal feed additive. However, a recent animal feed contamination in
Belgium has resulted in the prospect of this use of RVO being limited or banned. It is
necessary to dispose of the RVO, it cannot be simply dumped due to it’s status as a
toxic material.
One possible use of RVO is as a boiler fuel extender. If it can be used successfully in
this context, there would no need for the costly esterification process.
Standards covering the scope of this use of RVO in this context are possibly - Fatty
acid methyl ester requirements Draft EN 14213. Vegetable and animal oils and fats
principal context of use covered by standards seems to be for foodstuffs.
7
1.3
Cork County Energy Agency Final Report
1.3.1. Waste Management in Ireland.
Waste Management in Ireland is based on the Waste Management Act of 1996, which
paved the way for much needed environmental legislation in Ireland. Section 22 of the
Act requires that each local authority make a Waste Management Plan with respect to
the prevention, minimisation, collection, recovery and disposal of waste within its
functional area. The Act makes specific stipulations regarding the content of the
Waste Management Plan and requirements of the plan are further outlined in the
Waste Management (Planning) Regulations, SI No. 137 of 1997. The Act requires
that the Plan be reviewed every five years.
The document imposes on Local Authorities the responsibility for:
Developing the waste management plan
Enforcing the waste management regulations
The provision of collection and disposal services
Meeting national targets
The policy document “Changing Our Ways” which was published by the Department
of the Environment and Local Government (DoELG) in 1998 identifies who would be
responsible for operating the plan and set national targets for recycling and diversion
of waste from landfill.
The targets set in this document are as follows:
Diversion of 50% of MSW from landfill
65% reduction in biodegradable waste to landfill
Recycling of 35% of MSW
Development of composting facilities
80% reduction in CH4 emissions from landfill sites
Reduction in no. of operating landfill sites from 100 to 20
Waste Management in Cork.
Cork City and County produced a joint 5-year waste management plan in 1999. It
recommended 70 actions under the following headings
Waste prevention
Waste collection
Waste recovery
Disposal of residual waste
8
Waste packaging
Litter
General waste management
It is intended that this plan will improve on the current disposal methods utilised in
Cork. At present, only 4% of Cork’s waste is recycled, the rest is land filled. The
targets set out in the plan are given and illustrated in the table and figure below
respectively.
Waste Stream
Glass
Paper
Plastic
Organic
Metals
Other
Textiles
2000 (tonnes)
7,051
46,246
12,485
41,186
3,185
23,731
2,888
2004 (tonnes)
5,288
34,685
3,121
20,593
2,389
17,798
1,444
% Reduction
25%
25%
25%
50%
25%
25%
50%
Table 1.3.1. Targets for Waste Reduction, Cork Waste Management Plan 1999.
50,000
45,000
40,000
35,000
30,000
tonnes 25,000
2000
2004
20,000
15,000
10,000
5,000
0
Glass
Plastic
Metals
Textiles
Figure 1.3.1. Targets for Reduction of Waste in Cork.
Waste Cooking Oil and the Waste Management Plan.
Waste Cooking Oil (WCO) represents approximately 4% of the total organic waste
produced in Cork1. It has been described by the Head of Waste Management in Cork
County Council as “unsuitable for land filling under any circumstances”.
The use of WCO as a fuel is consistent with the “Reduce, Recycle, Reuse” policy of
Cork’s Waste Management Plan. Also if WCO is declared unsuitable for animal
1
Source: Cork City & County Waste Management Plan, 1999
9
feed2, the major outlet for recycled WCO will be removed and the majority of the oil
would only be fit for final disposal. Utilising WCO as a fuel would be consistent with
Action 42 of the Waste Management Plan, which states “Energy shall be recovered
from all waste restricted to final disposal, if possible.”
At present, with an outlet for the recycled WCO
1.3.2. Waste Cooking Oil Resource.
As with every renewable resource a distinction must be made between the available
resource and the collected resource. The available resource is all the oil that is used
for cooking. The collected resource is the amount of oil that has been collected for
recycling. A waste management plan would aim to have both resources equal to each
other.
Collected Resource.
It is difficult to establish the exact amount of Waste Cooking Oil in Ireland at present,
as there are no official figures for this waste stream and there are many different
companies involved.
National Resource.
Our own researches with a variety of WCO processors gave us a national total of
approximately 7,000 tonnes collected per annum with an annual increase of
approximately 500 tonnes p.a. This is in reasonable agreement a Teagasc report3,
which estimated the total collected WCO to be 6000 tonnes.
Cork’s Resource.
Within the Cork region, the WCO processors report just in excess of 1,000 tonnes of
WCO collected annually, increasing at approximately 8% per annum.
Waste Cooking Oil Composition and Quality.
There is no segregation of different types of oil and as a consequence the WCO is a
mixture of a wide variety of oils, some of which are solid at ambient temperatures.
This means that the oil must be kept heated throughout processing.
2
3
See §Future Utilisation of Recycled Waste Cooking Oil
Source: “Bio-diesel production from camelina oil, waste cooking oil & tallow”, Teagasc, 1998
10
Waste Cooking Oil Refining.
The oil collected has to be refined to remove particulate matter and moisture. As this
is done via settling tanks, which allow the particulates and water to settle out of the
oil. It is then treated with live steam to kill any pathogens and then settled again to
remove the moisture added by the steam. This process generates refined oil with a
yield of approximately 85%.
The current resale value of WCO in Ireland is €190.5 per tonne or 17.2€¢ per litre.
Current Utilisation of Recycled Waste Cooking Oil.
The table below shows the destination of the collected WCO at present. As can be
seen 98% of the oil collected goes to animal feed.
Outlet
Percentage Weight (tonnes)
66%
4,600
Animal Feed (export to UK)
32%
2300
Animal Feed (used in IRL)
2%
140
Research
Table 1.3.2: Destination of WCO produced in Ireland
Future Utilisation of Recycled Waste Cooking Oil.
However, this may not be allowed to continue for much longer. Fears have been
raised that the heat treatment the oil is exposed to, could lead to the formation of
dioxins or other carcinogenic chemicals. The EU is under pressure to ban WCO from
animal feed4.
Even if this doesn’t come to pass, the regulations governing the use of WCO are
becoming more stringent5, with the possible introduction of HACCP6 and ISO 9002
systems. The processor could also be required to provide a chemical analysis of the
WCO before it could be sold on.
These systems would add significantly to the running costs of the processor and could
affect the sales price of the WCO, making it too expensive for the animal feed market.
Resource Estimation
It was intended as part of this report to produce an estimate of the WCO produced in
Cork County, via a survey of all commercial food preparation by the local
Environmental Health Office. Unfortunately the dumping of WCO in has been banned
4
European Parliament Scientific & Technical Options Assessment, PE nr.289.889, February 2001.
Ibid.
6
Hazard Analysis & Critical Control Points. This is a system used in food preparation
5
11
therefore no one was prepared to admit how much cooking they would be utilising.
Therefore it was necessary to develop an estimate from national import and export
figures7. The CSO has trade figures for 37 different types of animal and vegetable fat.
Estimate Assumptions
•
Can exclude all animal fats as they are no longer popular in restaurant and
domestic sectors
•
Two sectors consume the majority of refined vegetable oils
1. Food processing
2. Cooking Oil
• Can exclude all unrefined oils as they are not used in spreads or cooking oil
• Can exclude all Soya oil as it is no longer used in food processing due to
GMO fears8
• Only palm-kernel oil found in WCO implies palm oil can be ignored
Spreads industry utilises a 2:1, Rape: Palm oil mixture9
• Fat content of spreads ranges form 38%-70%. Take an average figure of 50%
• Two main producers in Ireland
1.
Kerry Group
40,000 tonnes per annum
2.
Dairygold
2,000 tonnes per annum
• Other industrial consumers of oil in Ireland are the chips and crisps
manufacturers. The 3 main processors consume approx. 9,000 tonnes per
annum.The CSO figures for imports and exports of animal and vegetable fats,
combined with these assumptions produces the following Table 1.3.3.
7
Source: Central Statistics Office, 2002.
Source Dairygold & Glanbia
9
Source: Dairygold
8
12
Item
Sunflower Oil
Rape seed oil
Coconut
Palm-kernel
Tonnes per annum
8815
28605
6988
317
Total Imports
44725
Rape Oil consumed in spreads
14000
Other Industry
Chips & Crisps
9000
Oil absorbed in domestic cooking process
4345
Total Consumed
27345
Exports
6102.7
Total unaccounted oil
11277.3
Total available resource
17380
Table 1.3.3. Waste Cooking Oil Resource Estimation
This analysis gives an estimated total resource in excess of 17,000 tonnes. In 1998
Teagasc estimated a national available resource of 10,000 tonnes10, while a project
undertaken by the University of Limerick estimated a potential resource of 45-50,000
tonnes11. There are no figures available on a regional or local basis. The 2002 census
figures give cork city and county 11.5% of the population. If it is assumed that the
proportion of WCO generated in Cork City and County is the same as the
population12, then the total amount of WCO generated annually is approximately
2,000 tonnes. Approximately 1,000 tonnes is collected each year by professional
WCO traders, which leaves approx 1,000 tonnes unaccounted for.
As WCO is no longer accepted at landfills, and it is illegal to dump it anywhere else,
the most likely route of disposal is down the drain to the foul sewer system and on the
Council’s wastewater treatment plants.
10
Source: “Bio-diesel production from camelina oil, waste cooking oil & tallow”, Teagasc, 1998
“Production & Testing of Waste Cooking Oil Based Fuel Oil for Vehicles, R. Howard-Hildige & JJ
Leahy, University of Limerick, 1997.
12
This could be considered a minimum figure, as it takes no account of Cork’s intensive tourist
industry.
11
13
The wastewater treatment plants employ grease traps and Dissolved Air Flotation
(DAF) systems to separate about 85% of the fat from the water. This is then land
filled.
The remaining 15% is digested by microbes and is treated as BOD13. The cost
associated with processing the fat to the Council in this manner is given in the
following table:
Disposal Method
Treatment Area
Grease traps and DAF
Waste Water
Total
Amount (tonnes)
850
Landfill
150
Aerobic digestion
1000
Cost14 (€)
€ 97,750.00
€ 66,750.00
€164,500.00
Table 1.3.4. Destination and Cost of WCO Disposal
Ironically it is the banning of WCO from landfill that has led to it being poured down
the drain where, after treatment, 85% is land filled by the Council.
The savings available to the Council by disposing of WCO properly are significant,
but WCO can be harnessed as a resource and used in engines and boilers, as this
project has demonstrated.
1.3.3. Impacts of Harnessing WCO Resource
The following table provides an indication of what could be generated by WCO if it
was harnessed for electricity generation utilising a CHP plant. The assumptions used
were:
•
Plant thermal efficiency of 40%
•
Plant availability of 85%
•
Best new entrant sales price for electricity of €0.037815
Waste Cooking Oil (tonnes)
Calorific Value (MJ/ tonne)
Total Energy Available (MJ)
Potential Electricity Available (kWhr)*
Potential Income
Electricity Generation Capacity
No. of households powered16
Tonnes of CO2 avoided17
In Ireland
17380
40.1
696938
278775200
€10,537,702.56
37.5
61950
228596
In Cork
1998.7
40.1
80147.87
32059148
€1,211,835.79
4.3
7124
26289
Table 1.3.5. Outputs of Harnessed WCO Resource
13
Biological Oxygen Demand
Source: Cork County Council.
15
Source: CER Website, Nov. 2002.
16
Source: Sustainable Energy Ireland Website, Nov 2002
17
Source: ibid.
14
14
As can be seen from Table 1.3.5, there exists the potential to avoid almost 250,000
tonnes of CO2 annually. This is equivalent to the entire national saving expected from
the introduction of more stringent building regulations as envisaged by the National
Climate Change Strategy.
There is also a potential income stream from the operation of the CHP plant in excess
of €1.2 million.
Waste Cooking Oil and Excise Duty
However, all these financial estimates are predicated on the assumption that no excise
duty would be imposed on the collected WCO. The Revenue Commissioners, the
body responsible for operating excise duty in Ireland have indicated that they would
consider centrally collected WCO, used to generate useful light of heat, a “substitute
fuel”, as defined in section 94(1) of the Finance Act, 1999, (as amended by section
163 F.A. 2001).
There are two rates of duty applicable to WCO in this context:
•
€47.36 per 1,000 litres for use as boiler fuel
•
€301.94 per 1,000 litres for use as an automotive fuel.As can be seen from
table 1.3.6 the duty payable for use in a CHP plant would be almost half the current
cost of disposing of the WCO.
In Ireland
In Cork
17380
1998.7
Waste Cooking Oil (tonnes)
€ 823,116.80
€ 94,658.43
Duty Payable if used in boilers
€ 5,247,717.20
€ 603,487.48
Duty Payable if used in vehicles
Table 1.3.6 Potential Cost of Excise Duty on Centrally Collected WCO
The cost of excise duty would put severe strain on the economic viability of any
centralised collection system, and would make the use of WCO as an automotive fuel
completely uneconomic.
1.3.4. Demonstration at Cork County Council Area Offices, Charleville
One of the objectives of the project was to conduct a trial of the WCO as a fuel for an
area office of Cork County Council. Originally the machinery yard at Mallow was
considered for the trial. This was convenient for Cork County Energy Agency and the
University of Limerick, as Mallow is on the main Cork-Limerick road. However the
boiler in the yard was very old and in extremely poor condition. This would have
skewed readings taken for energy output, emissions etc. As the yard was to be
15
decommissioned this year, upgrading the boiler was viewed as not the best use of
resources. It was decided that another location for the trial would be necessary. The
area offices at Charleville were chosen for the trial, as the town lies on the main CorkLimerick road, to allow frequent monitoring by UL.
Description of the Office
The office consists of a large
bungalow, housing a number of
offices, of which at least one is
permanently occupied. There is also
a canteen, storerooms and changing
rooms for personnel working outside
the office. The cooperation of Mr.
Paddy O’Friel, Charleville Area
Engineer, and the rest of the staff at
the office were essential to the
Figure 1.3.2. Paddy O’Friel
& the staff of the Charleville Area Office
successful running of the trial.
Trial Set-up
The boiler that was in place at
Charleville was very old and it was
decided that, in order to make
accurate comparisons with the
performance of diesel fuel, the
boiler should be replaced. A new
Firebird Popular 150 was installed
and fitted with a modified Cuenod
optimised of UL NC4 burner. This
burner was at CIRAD in France for
a 25% WCO: diesel mix. The
Figure 1.3.3. Trial set up.
optimisation of the burner is
described in detail in chapter 5.
Outside the boiler house two Industrial Bulk Containers (IBCs) were positioned. The
bottom IBC acted as a mixing tank for the WCO diesel blend and the boiler was
supplied directly from this tank. The top IBC contained the processed WCO.
16
A simple T-junction with a couple
of valves ensured that supply of
mineral diesel could be reestablished quickly and easily.
For a detailed description of the set
up for the trial please see chapter 5.
Operational Issues
Within the first two weeks of
operation, a leak was reported. This
was investigated and a rubber seal on
Figure 1.3.4. Fuel line & valve layout
one of the IBCs had perished. The
IBCs had been used previously to store WCO and biodiesel by Teagasc. It was felt
that this seal was probably very near failure at the start of the trial and that its failure
was not directly related to the trial. This position is supported by the fact that this was
the only leak experienced by the system during the trial.
The trial was completed in the first week of December when the burner failed. The
failure was related to the fuel pump where the rotor had seized in its housing due
deposits forming from the RVO (WCO)/mineral fuel blend used.
The trial was restarted the last week in December using a new pump mounted in an
ECOFLAM burner which has proved to be unreliable operating on the 25% RVO –
75% mineral fuel blend.
Comfort levels
The occupants of the office were satisfied by the performance of the WCO as a fuel.
They found that the offices were heated to the same levels as the diesel fuel, and that
the demands for hot water were also met. The only indication that WCO was being
utilised was an aroma of fried food, which could be detected near the boiler.
Ease of use
The people in the office experienced no difficult in operating the system during the
trial, as no modifications were made to the operation of the system. However a drop
in response time was noted with the boiler having to be started approximately one
hour earlier than normal to ensure adequate temperature levels in the office in the
morning.
17
1.3.5. Dissemination
The summary of the project will be posted on the Agency’s website.widest possible
audience of interested parties. Also holding of the seminar “Waste to Warmth”,
Killaloe, Co. Tipperary, 5th September 2002. The seminar was promoted via the
following organisations:
•
Association of Irish Energy Agencies (National)
•
Waste Management Departments of other Irish Local Authorities
•
Energie-Cites
•
Islenet
•
FEDERENE
Also
Creation and distribution of seminar proceedings CD-ROM
Creation and distribution of Final Report CD-ROM
Creation of a poster to be displayed in the Energy Agency’s Public Office.
18
1.4 Objectives:
In addition to documenting the collection and processing of RVO in a typical Irish
setting this work investigates some of the chemical and physical properties of RVO in
relation to its use as a fuel.
Use mixtures of mineral home heating oil and RVO in the range 0 – 40% RVO in
mineral heating oil to fuel a 25kW home heating boiler and determine the resulting
exhaust gases for each blend.
Determine the performance of the RVO in a modified vehicle : use RVO to fuel a
modified Toyota Dyna pick up truck and determine the resulting power developed at
the road wheels and the exhaust emissions.
To operate a diesel generator on a blend of RVO and mineral fuel.
19
2. Recycled Vegetable Oil Collection
2.1 Background
Although there have been many tests carried out on recycled vegetable oils, very little
literature currently exists surrounding the actual recycling process.
Recycled vegetable oil (RVO) or waste cooking oil (WCO), is the name given to oils
and fats that have been used for the preparation of foodstuffs for human beings, but
which are no longer suitable for that purpose. They therefore need to be disposed of in
a suitable manner.
In Ireland the 10,000 tonnes of WCO currently collected annually is from the catering
industry, from where it is transported to a recycling plant. It is then steam treated and
filtered to remove unwanted solids and to lower its water content. The majority of the
recycled oil is then used as an animal feed additive.
2.2 The Collection Procedure
A study was carried out on a recycling plant currently operating in Co. Kildare. The
collecting involves using barrels to store the used vegetable oil at the point of use,
then transfer it to the recycling plant.
20
Fig. 2.2.1: Used vegetable oil containers
The oil is usually collected in 3 basic types of containers shown in above Fig. 2.2.1
A: 20 litre cans/buckets
B: 160/200 litre drums
C: IBC which are basically 1 metre square polymeric containers that hold
approximately 1 tonne of oil.
When caterers have finished using the cooking oil/fat, if the original containers for the
oil have been kept then these are refilled with the used oil. Otherwise, the used oil is
placed in drums. The quantitiy of oil determines how it is handled, larger quantities
being more easily placed into drums as opposed to 20 litre tins.
Even larger quantities, for example, the case of a factory using large volumes of
vegetable oil as part of a cooking process, would require the use of an IBC, and when
full, it can be easily lifted onto the collection van by forklift truck. Full IBCs and
drums are replaced with empty ones as required by the collection cycle.
21
3. RVO Processing
3.1 Introduction
Vegetable oils and fats can be found in solid, semi-solid, or liquid form. All RVO
material that has been collected for recycling requires some degree of processing to
reduce the impurities. It is assumed within the industry, that RVO prior to processing
contains by volume 20% water and/or impurities. After recycling, the oil should be of
a standard whereby it contains less than:
3% free fatty acids
1% water
1% solids other than fat
in order for it to be considered for use as an animal feed additive (Bolton R.V.O. Ltd.,
personal communication).
Fig. 3.1: Vegetable Oil Recycling Plant, Kildare.
The 20% waste by volume in the RVO is due to the following;
(a): large solids (food, papers etc)
(b): smaller sized solids, which have become suspended within the oil
(c): water, which will gradually settle out.
22
3.2 Process:
The RVO is passed through a series of sieves, which take out the unwanted solids.
Large solids tend to block up the sieves very quickly and impede the flow of oil.
Therefore the first sieve that the oil encounters is of a very coarse grade, with each
subsequent sieve being of an increasingly fine grade as the oil gradually gets cleaner.
Before processing, the first step is usually to separate any oils that have a sufficiently
low viscosity at room temperature such that there would be no need for heating in
order for them to pass through the sieves relatively quickly. These oils are processed
first, and in the meantime steam is applied to the solid fats, causing them to melt to
the degree that they too will be able to undergo filtration. Melting the fats is also a
necessary way to release any water that may have become trapped within the fat
during solidification following its original use as a frying oil.
Filtration:
The oil passes through the sieves and falls into a tank fitted with two valves
positioned one above the other near its base. The level in the tank is noted and the
yield of oil from a particular batch of RVO can be therefore be calculated. This is
necessary because the amount of vegetable oil obtained per tonne of waste cooking oil
bought, varies depending on the supplier. This is a necessary method for calculating
the value that a load of RVO is actually worth to the recycler.
The liquid is left to settle in the tank for a period of time which depends on the
volume, temperature and quality of the oil (i.e., did it originally contain a large
amount of impurities). The longer it is left settle, the more sediment and water
precipitates out, but the viscosity of the oil also increases as the oil cools so there
exists an optimum settling time for each batch.
23
Fig. 3.2: Schematic of valve layout
After settling, the lower valve is opened to drain the water and any suspended solids
that were too small to be caught in the sieves, but have now settled out. As soon as the
first sign of oil appears in the lower pipe, it is closed. The operator now knows that
there is oil in the tank down to this point. Therefore, the upper valve which leads to
the storage tank or possibly on to another settling tank, can now be opened.
Steam:
Steam is supplied to a coil to the base of every tank in the factory. The purpose of the
steam is twofold; firstly it maintains the temperature of the settling oil in the tanks,
ensuring it will flow to the next tank easily and stopping any fats from resolidifying.
Secondly some of the tanks have steam pipes branching off from the main heating coil
and protrude through the sieve from below. Cans of solid fat can be placed onto the
sieves with the steam pipe intruding inside. The steam is then applied causing the fat
to melt, fall through the sieve and into the tank below.
In the recycling plant in Kildare, there is a long, slender tank approximately 1m above
the ground upon which the 20 litre containers are lifted manually. It has a slight
gradient leading towards another tank in which the volume of oil can be measured.
To facilitate the 200 litre barrels, there is a tank approximately 160cm above the
ground onto which the barrels are lifted with a forklift truck. This tank could be
24
positioned at ground level which would negate the need for the forklift but would then
require a additional pump to transfer the oil to the next tank. The schematic shows
the general arrangement of the layout of the tanks in the process.
Fig. 3.3: RVO Plant Schematic
The sieves all need to be easily removed and cleaned because poor quality oil high in
unwanted solids can cause them to clog up very quickly. Also, the tanks are designed
in such a way that when empty, they too can be easily cleaned. Over time, deposits of
very small solids that passd through the sieves build up at the bottom of the tank and
eventually cover the heating coil. This effectively acts as insulation resulting in a loss
in heat transfer from the coil. As the volume of sediment increases, more is flushed
into the next tank by the oil leaving for the next filtration stage.
25
Fig. 3.4: Finished product storage tank
The storage tank’s design has a similar valve system to the other tanks, in that it has
two valves near it’s base and a heating coil. The valves can clearly be seen in Fig.
3.4., the steam coil entry is at the rear, and the access hatch for cleaning is visible to
the left of the tank. Further settling of the oil will also occur in this tank.
26
4.
RVO Characterisation
4.1
Introduction
It is necessary to characterise the RVO in terms of its chemical and physical
properties to assess its suitability for the intended use.
Most of the testing was carried out on a grade of RVO typically considered to be the
least viscous grade of the various types encountered by the RVO factory. This RVO
was liquid at room temperature and dark brown in colour, whereas the finished
product from the RVO factory was seen to be semi-solid at room temperature and a
lighter brown colour. This is due to the finished product containing a mix of both
solid fats and liquid oils that have been filtered.
In a 5 litre container in the laboratory, the finished RVO sample settled out into two
distinct phases after a period of about one week. It was seen that a yellowish semisolid phase settled out to the bottom of the, and on top of this was a darker, less dense
phase, similar in colour and viscosity to the RVO used in the short duration pilot
boiler tests. The less viscous nature of this grade of RVO makes it more suitable for
use in a boiler than the semi-solid RVO. Approximately 50% of the oil processed in
the RVO factory is of similar viscosity to this oil. It is regarded as the easiest and
certainly the least expensive type of oil to recycle, as it doesn’t require heating to pass
through the various sieves.
The low relative viscosity of this type of RVO is due to the distribution of the free
fatty acids that it contains.
27
4.2: Viscosity of RVO and Blends with Mineral Oil
4.2.1 Introduction:
The viscosity of home heating oil, vegetable oil, and various blends of both oils were
measured. The viscosity is considered to have a major effect on the ability of a fuel to
be atomised prior to combustion. The viscosities of the blends used in the boiler trials
were investigated at 13.5 oC which was representative of the ambient temperature
used during the boiler pilot study, while the viscosity of neat RVO was measured in
the range 14oC to 48oC.
4.2.2 Apparatus:
Ubbelholde/Schott-Geräte Automatic Viscometer.
Fig. 4.2.1: Schott-Geräte Automatic Viscometer
28
4.2.3 Results and Discussion:
120
Viscosity
80
2
Viscosity (mm /s)
100
60
40
20
0
0
10
20
30
40
50
60
70
80
90
100
RVO (%)
Fig. 4.2.2: Viscosity of Home Heating Oil with increasing fraction of WCO.
120
Viscosity
2
Viscosity (mm /s)
100
80
60
40
20
0
14 16 18 20 22 24 26 28 30 32 36 40 44 48
o
Temperature ( C)
Fig. 4.2.3: Viscosity of 100% RVO Vs temperature.
29
Viscosity: A fuel’s viscosity is considered to have the a significant effect on its ability
to atomise and hence combust. The viscosity of the various blends of RVO and home
heating oil used was investigated at the same temperature as the ambient temperature
during the boiler tests. The range was from 6.36mm2/s for 100% home heating oil
(HHO), to 14.99mm2/s for the blend containing 40% RVO, which was the fuel being
used when combustion failed in the pilot study boiler tests (see section 5.1).
30
4.3
Low Temperature Viscosity of RVO
4.3.1 Introduction
For use as a boiler fuel the low temperature viscosity is of obvious interest if the fuel
is stored in an outside tank during Winter.
4.3.2 Apparatus and Procedure
a Haake Roto Visco 1.cone and cup viscometer connected to a Haake K15 cooler unit
as shown in Fig 4.3.1
Fig 4.3.1 Haake Roto Visco Viscometer and Cooler
31
4.3.3 Results and Discussion
Viscosity curves were calculated for recycled vegetable oil (RVO) and Camelina
Sativa oil as a comparison with a typical cold pressed and filtered seed oil. The
viscosity of the fuels can be significantly affected by such variables as shear-rate,
temperature, pressure and time of shearing. This analysis focuses on the variation of
viscosity with shear rate and temperatures in the range –5oC to +20oC.
Comparison of the Viscosities of RVO and Camelina Oil
0.35
0.3
0.25
Viscosity Pa.s
0.2
0.15
0.1
0.05
0
0
500
1000
1500
2000
2500
3000
Shear Rate(1/s)
-0.05
-5oC Cam
10oC
1oC RVO
-3oC Cam
20oC Cam
4oC RVO
-1oC Cam
-5 oC RVO
10oC RVO
0oC Cam
-3oC RVO
20oC RVO
4oC Cam
-1oC RVO
Fig. 4.3.2 – Comparison of the viscosities of RVO and Camelina
Viscosity Variation with Shear Rate:
Fig. 4.3.2 shows how the viscosity of both RVO and Camelina varies with shear rate.
The viscosity of the RVO is much higher than the viscosity of Camelina. The higher
the viscosity the more problems are likely to occur with the material if it is used as a
fuel.
32
3500
As can be seen in Fig. 4.3.2, at shear rates higher than 1000s-1 the materials behaved
more as Newtonian fluids showing viscosity values practically constant.
In order to analyse the behaviour of the material more closely, Fig.4.3.3 shows just
the viscosity below shear rates of 1000s-1.
0.35
0.3
0.25
Viscosity Pa.s
0.2
0.15
0.1
0.05
0
0
-0.05
100
200
-5oC Cam
10oC
1oC RVO
300
400
-3oC Cam
20oC Cam
4oC RVO
500
600
Shear Rate(1/s)
700
-1oC Cam
-5 oC RVO
10oC RVO
0oC Cam
-3oC RVO
20oC RVO
800
900
4oC Cam
-1oC RVO
Fig. 4.3.3– Comparison of the viscosities of RVO and Camelina at low shear rates.
Both materials behave very similarly. The viscosity increases dramatically as the
shear rate increases from 0s-1 to 500s-1. This would imply that both RVO and
Camelina are dilatant liquids, although it should be noted that the accuracy of cone
and plate viscometers at low shear rates is questionable.
The viscometer is more accurate when the shear rates exceed 1000s-1. This section of
the graph is shown in Fig.4.3.4
33
1000
0.35
0.3
0.25
Viscosity Pa.s
0.2
0.15
0.1
0.05
0
1000
-0.05
1200
1400
-5oC Cam
10oC Cam
1oC RVO
1600
1800
-3oC Cam
20oC Cam
4oC RVO
2000
2200
Shear Rate(1/s)
-1oC Cam
-5 oC RVO
10oC RVO
2400
0oC Cam
-3oC RVO
20oC RVO
2600
2800
4oC Cam
-1oC RVO
Fig. 4.3.4 –Comparison of the viscosities of RVO and Camelina at higher shear
rates.
It can be seen that once the shear rate is increased beyond 1000s-1, then both materials
behave as shear thinning or pseudoplastic materials, with decreases in viscosity for
increasing shear rate.
Both materials behave like Newtonian materials with further increases in shear rate.
34
3000
Viscosity Variation with Temperature:
Fig. 4.3.5 shows how the viscosity of the two materials varies with temperature, for
shear rates of 517s-1, 1551-1 and 3000-1.
Comparison of Viscosity variation with temperature at different shear rates
0.35
0.3
Viscosity Pa.s
0.25
0.2
0.15
0.1
0.05
0
-10
-5
0
S.R. = 517(RVO)
S.R. = 517(Cam)
5 Temp. (oC) 10
S.R. = 1551(RVO)
S.R. = 1551(Cam)
15
20
25
S.R. = 3000(RVO)
S.R. = 3000(Cam)
Fig 4.3.5 – Comparison of Viscosity variation with temperature at different shear
rates for RVO and Camelina.
For the Camelina it can be seen from Fig.4.3.5 that the increase of viscosity is gradual
with decreasing temperature until 0oC. There is a sharp increase in viscosity as the
sample goes from 0oC to –1oC.
The viscosity decreases as the sample temperature goes from –3oC to –5oC. This
could be due to error in experiment.
The viscosity of the RVO increases more with decreasing temperature than the
Camelina particularly when the sample is at temperatures less than 1oC.
35
This would also indicate that RVO is less suitable for use as a diesel fuel in countries
with a cold climate.
Sources of Error
All cone and plate instruments allow the cone to be moved away from the plate to
facilitate sample changing. It is very important that the cone and plate be reset so that
the tip of the cone lies in the surface of the plate. For a 1o gap angle and a cone radius
of 50mm, every 10µm of error in the axial separation produces an additional 1% error
in the shear rate.
To avoid error in contacting the cone tip (which might be worn) and the plate (which
might be indented), the cone is often truncated by a small amount.
The alignment of the cone axis has to be coincident with the rotational axis, the
setting of the cone tip in the surface of the plate, and the minimising of, and correction
for viscous heating are other important matters to be taken into account for accurate
work.
36
4.4: Calorific Value of RVO
4.4.1 Introduction:
The calorific value is an important measure of the value of RVO as a fuel and allows
a comparison with other boiler fuels. The calorific value was determined according to
ASTM D 240 using a Parr Adiabatic Bomb Calorimeter.
4.4.2 Apparatus and Procedure:
Apparatus
Parr Adiabatic Bomb Calorimeter, 1180 Combustion Bomb.
Fig. 4.4.1: Parr Calorimeter Adiabatic Bomb
37
The first sample burned in the bomb was Benzoic Acid, whose calorific value is
known. The energy equivalent of the calorimeter was thus found which was then used
to calculate the calorific values of the other samples.
A sample of known weight is inserted into the brass sample jar in the bomb, the bomb
is sealed and charged with oxygen to a pressure of about 25atm. The bomb is inserted
into a two litre container of water and put into the calorimeter. The calorimeter is
closed and the temperature of the water is taken. Inside the bomb there is a nickelcadmium wire about 5cm long which is connected to two electrodes, which passes
just above the sample. When the bomb is fired, a current is passed through this wire
making it burn out completely, which in turn causes the sample to ignite. The water in
which the bomb is submerged heats up and the temperature of the water is taken after
it has stabilised, which in this case took approximately 10 minutes. The bomb is
removed from the calorimeter, the pressure is released.
However, even after repeated attempts, it was found that the RVO sample would not
ignite. It was decided to add benzoic acid and then mineral heating oil to the sample
of RVO in order for ignition to occur.
1
2
3
4
5
Sample
Weight T1oC
T2oC
∆T
Benzoic Acid
0.928g
17.2
19.4
2.2
RVO
0.918g
14.1
14.3
N/A
RVO plus Benzoic 0.918g
14.6
18.2
1.6
Acid
0.125g
Home Heating Oil 0.968g
10.8
15.4
4.6
Biodiesel
1.027g
11.5
15.5
4
Table 4.4.1: Temperature rise for various fuels tested.
.
Heats of Combustion J/g
Home Heating Oil
53.0274
Biodiesel
43.4617
RVO
40.1579
Table 4.4.2: Heat of Combustion for different fuels
38
A difficulty encountered was igniting the RVO samples in the bomb. It was decided
to add a small amount of one of the other fuels to aid ignition. 0.125g of Benzoic Acid
was added to 0.918g of vegetable oil. After combustion, the calorific value for the
mixture of the two fuels was found to be 39.998J/g. The calorific value of the Benzoic
Acid was known, so the temperature rise caused by burning 0.125g of acid was
calculated. Taking this temperature rise from the total temperature rise, gave the
temperature rise caused by the combustion of the RVO in the sample, which yielded a
calorific value of 40.158J/g.
39
4.5 Gas chromatography of RVO
4.5.1 Introduction:
Gas Chromatography can separate individual components from complex mixtures and
give a measure of each component present. There were two different types of RVO
analysed in the gas chromatograph. The first sample was of the finished product from
the RVO plant. It had been steam cleaned a number of times, left to settle in a tank,
and was made up of many different types of vegetable oils and fats. The second
sample was as delivered and had not been treated in the RVO plant. The RVO had
been settling for 1 week before the sample was taken.
4.5.2 Apparatus and procedure
Apparatus:
HP 5890 Series II Gas Chromatograph, Zebron ZB-wax column.
Fig. 4.5.1: Gas Chromatograph with results printer
40
A Zebron ZB-wax column (30m length x 0.53mm internal diameter x 0.1µm film
thickness) filled with polyethylene glycol was used in a HP 5890 Series II
chromatograph. Nitrogen was used as carrier gas.
Procedure
-Sample size:
1µlitre (Each test sample consisted of 60mg of WCO
dissolved in 10mls of dichloroethane)
-Injector temperature:
300oC
-Detector temperature:
300oC
-Initial temperature:
170oC
-Initial time:
10 min.
-Rate:
20deg / min.
-Final temperature:
245oC
-Final time:
5min.
4.5.3
With few exceptions, the carboxylic acids (or fatty acids), from which all fats and oils
are derived are straight-chain compounds ranging in size from 3 to 18 carbons. These
acids may be saturated, containing only single bonds, or unsaturated, containing one
or more double bonds. The gas chromatograph gave the percentages of the different
free fatty acids present in each sample, as a percentage of the total free fatty acid
content.
The results from the gas chromatograph were in graph form. Each peak on the graph
corresponds to a separate fatty acid, and the areas or the height of the peaks corespond
to the relative proportions of fatty acid in the sample. The results are shown for both
samples.
41
Fatty Acid Treated
GC Analysis RVO (%)
C14:0
1.25
C16:0
7.38
C16:1
1.61
C18:0
2.75
C18:1
58.09
C18:2
23.22
C18:3
5.69
Untreated
RVO (%)
0.3
10.61
0.88
4.73
49.83
28.9
4.74
Table 4.5.1: Gas Chromatograph Results
As can be seen from the results of the gas chromatograph, the highest proportion of
fatty acid contained in the sample was the unsaturated Oleic Acid (or C18:1), at
49.83%. Saturated acids exhibit higher freezing temperatures than the unsaturated
acids. Oleic acid also does not contain enough C-bonds to polymerise readily. A
similarly high percentage (58.09%), of this acid can be seen in the treated RVO. The
results shown below conducted in the Karl-Franzens-Universitat, Graz, compare well
with those obtained for this project.
Fatty Acid GC Analysis
C14:0
C16:0
C16:1
C18:0
C18:1
C18:2
C18:3
Treated RVO (%)
0.46
9.93
0.53
5.04
55.82
17.69
5.99
Table 4.5.2: Analysis of typical Irish waste cooking oil sample (Graz)
Note: The sample did contain very small concentrations of C20 and C22 fatty acids,
but these were ignored as their concentrations in the oil were extremely low.
The GC results appear to show a higher percentage of oleic acid in the finished RVO,
which is semi-solid at room temperature. This can be attributed to the sample used in
the GC tests had been taken from the darker, less viscous phase of the finished RVO.
42
C18:2 and C18:3 (Linoleic and Linoleic) acids are present in both samples at quite
high percentages. These fatty acids are undesirable because their C bonds are
susceptible to bonding with O atoms (oxidation), which would limit the length of time
they could be stored.
43
4.6 Differential Scanning Calorimetry
4.6.1 Introduction:
A measure of a fuel’s cold temperature properties can be found using Differential
Scanning Calorimetry (DSC). A 9.82mg sample of the untreated oil was analysed.
The energy needed to cause a change in phase in the oil and the temperatures at which
these changes take place are shown on the results graph.
4.6.2 Apparatus and Procedure:
Apparatus:
DSC 10 Differential Scanning Calorimeter,
TA 2000 Thermal Analyser,
Sample Encapsulating Press.
Fig. 4.6.1: Differential Scanning Calorimeter
44
Procedure:
The sample size was in the range 5 to 20mg. The sample was chilled to
approxiamately –70oC using liquid nitrogen. It was then sealed in a sample pan in the
Sample Encapsulating Press.
Heat capacity measurements require that a blank (reference) run be subtracted from
the standard and sample runs.
Following the reference run the temperature of the sample was increased in 2oC
increments.
4.6.3 Results and Discussion :
A graph of the results is shown overleaf.
45
46
The DSC showed the RVO to contain two distinct types of oil which changed phase at
different temperatures. There were two main significant minima on the graph at 56.65°C and –20.75°C. The energy required for these phase changes was shown to be
29.98J/g and 53.39J/g respectively.
47
4.7
Cetane Rating
4.7.1
Introduction
As well as the measurement of the cetane number of a diesel fuel under the standard
ASTM D613 in the Cooperative Fuel Research (C.F.R.) engine there are a number of
different procedures for establishing an approxiamate cetane number of a fuel sample.
IP 41/60 part b (throttling) is a method that requires little modification to a standard
engine. It requires the fitting of a chamber to the inlet manifold with a valve to throttle
the airflow. While the engine is running the valve is progressively closed and the inlet
manifold depression is measured at the point when the engine first misfires. This is
indicated by a puff of white smoke from the exhaust of the engine.
The measurement of the cetane number by methods that do not involve an engine test
are called the cetane index. The Calculated Cetane Index by Four Variable Equation
Test Method D4737-96a (2001) is not an optional method for expressing the ASTM
cetane number. The calculated Cetane Index by Four Variable Equation provides a
means for estimating the ASTM cetane number of distillate fuels from density and
recovery temperature measurements. The test method is particularly applicable to
diesel fuel oils containing straight-run and cracked stocks. It can also be used for
heavier fuels with 90% recovery points less than 382°C and for fuels containing nonpetroleum derivatives from tar sands and oil shale. It is not a method that is applicable
to biodiesel fuels because of the high boiling temperatures associated with liquid
biofuels.
This study involves use of a Petter single cylinder, direct injection, diesel engine. It is
fitted with an AVL piezoelectric pressure transducer and Cussens needle lift indicator
to enable measurement of the delay between injection and pressure rise due to ignition
of a fuel (ignition delay). The cetane rating of the fuel is then obtained by comparing
the ignition delay for the fuel with the ignition delay obtained from burning a
reference fuel of known cetane number.
48
Objective
To use a single factor multi level experiment, that involves the measurement of
ignition delay of fuel samples in order to obtain a cetane number for the fuels by
comparison with reference fuel of known cetane number. Fuels of interest are 0 to
25% recycled vegetable oil (R.V.O.) blends in mineral diesel fuel, tallow methyl ester
(T.M.E.), and waste cooking oil methyl ester (WCOME).
Cussons Engine Test Rig
The test rig consists of a Petter ACIW single cylinder diesel engine, a BKB 10 KW
electrical dynamometer, dynamometer control unit, Stuart Turner circulation pump
for the engines water-cooling system, Cussons cooling module (P4423) for the water
cooled AVL Piezo electric pressure transducer, and Cussons instrumentation
connection unit. This test rig is also set up to carry out cetane number experiments in
accordance with standard IP41/60.
Oscilloscope
Instrumentation
Connection Unit
Petter Diesel
Engine
Dynamometer
Figure 4.7.1 Cussons Engine Test Bed
49
Petter AC1Wb Diesel Engine
This is a single cylinder, four stroke, direct injection, water-cooled, diesel engine .
The main source of fuel to the engine is a header tank, this is filled with mineral diesel
fuel oil. Fuel samples can be run through the engine by opening and closing valves on
the fuel pipes while the engine is running. The exhaust system is fitted with two
sample points for exhaust gas analysis. The needle lift indicator shows when the fuel
is injected into the engine. The piezo electric pressure transducer shows the pressure
in the combustion chamber of the engine. The needle lift indicator and the pressure
transducer are connected to a cathode ray oscilloscope via a signal amplifier. The
traces from these two instruments are displayed on the screen of the oscilloscope.
Figure 4.7.2 Petter Diesel Engine
50
Piezoelectric Pressure Transducer
A quartz AVL water cooled piezo electric pressure transducer (P4420) is used for
measuring the dynamic pressure in the cylinder of the engine (Figure 4.5). The
transducer is rated to measure dynamic pressure up to 500 BAR. The piezo transducer
is connected to the oscilloscope through a piezo channel on the instrumentation
connection unit. The piezo channel is a very high impedance FET based charge
amplifer.
Pressure
Transducer
Figure 4.7.3 Pressure Transducer
51
Injector Needle Lift Indicator
The injector was modified by Cussons UK (part no p4427). To indicate the movement
or lift of the needle in a diesel engine injector requires a transducer of very small size
capable of monitoring very small movements. This consists of an external transducer
coil mounted on top of the injector with an extension of the needle acting as the core.
The transducer coil is mounted inside the injector body. The needle lift indicator is
connected to the oscilloscope through a frequency modulating channel.
Needle Lift
Indicator
Figure 4.7.4 Needle Lift Indicator
Electrical Dynamometer
The 10 KW BKB dynamometer can be used as a motor to start the engine and as an
alternator to absorb the engine’s power. This is achieved by a control unit that is used
for varying the supply voltage to the dynamometer when it is being used as a motor
and when it is being used as a dynamometer. The unit has a set of heating coils that
are used to dissipate any heat generated in the dynamometer when it is being used to
absorb the engine’s power.
Hewlett Packard 54602B Oscilloscope
The oscilloscope is used to measure the ignition delay. The pressure transducer and
needle lift indicator are connected to the oscilloscope via the Cussons instrumentation
connection unit. The traces from the instrumentation are displayed on the oscilloscope
52
display screen. By the moving of cursors it is possible to measure the time between
the two relevant points on the two curves.
Figure 4.7.5 Measurement of ignition delay from oscilloscope trace
53
4.7.3
Results
Ignition Delay
Plot of Mean Ignition Delay of Test Fuels
2.8
2.6
Ignition Delay (Milli Seconds)
2.4
2.2
2
1.8
1.6
1.4
1.2
1
40 CN
25% RVO
WCOME
20% RVO
15% RVO
10% RVO
45 CN
5% RVO
50 CN
MINERAL DIESEL
55 CN
TALLOW ME
Figure 4.7.6 Plot of Mean Ignition Delay of Test Fuels
R.V.O. /Mineral Diesel Blend Separation Test
Figure 4.7.7 R.V.O. /Mineral Diesel Blend Separation Test
54
60 CN
Discussion
From the literature it is clear that determination of the cetane rating of a fuel can be
approached by using a number of methods. As described by (Burt and Troth 1968),
there are problems with the accuracy of the experimental results obtained by
calculating the cetane number under the ASTM D613 method. In this study a number
of problems that were found in the literature were encountered. In preliminary tests
when running high percentage of R.V.O./ mineral diesel blends, problems with
fouling of the injector nozzle were encountered. Also fluctuations were noticed in
measurements of ignition delay due to different engine temperatures.
Experimental Procedure and Experimental Design
In the initial stages of the testing, it was necessary to access the validity of the results
that were obtained from the engine tests. An experiment was conducted to determine
if the ignition delay between fuels is significance to distinguish the fuels when
running at a speed of 1388 R.P.M. Analysis of variance showed that the level of
significance was low. The tests were repeated at a lower engine speed of 1280 R.P.M.
Analysis of variance showed that the lower engine speed produced a measureable
difference of ignition delay between fuels at a confidence level of better than 0.05
between fuels.
In order to design the next experiments it was necessary to determine the highest
blend of recycled vegetable oil (R.V.O)/ mineral diesel blend, that could be run
through the engine and still maintain steady operating conditions that would allow the
accurate measurement of ignition delay from the needle lift and pressure traces. It was
found through experiment that the highest blend that could be run through the engine
was a 25% R.V.O./ mineral diesel blend. When the engine was changed back to run
on mineral diesel, it was noted that the engine would not run smoothly. On noting this
the fuel supply was bled to rule out an air locked fuel system. The fuel injector was
then removed and on fitting a new injector nozzle the engine ran smoothly.
55
A separation test was also carried out on the R.V.O. blends. The results of this
experiment showed that a thin layer of R.V.O settled out at the bottom of the 30%
blend container (Figure 4.7.7). This experiment also verified that a 25% blend would
be the highest that would not separate. Running the engine on pure R.V.O. that had
settled out at the bottom of the burette would result in inaccurate measurements of
ignition delay for the mixture.
In order to obtain a cetane rating for the fuels that were to be tested, it was necessary
to conduct a factorial experiment that runs in a randomised order and incorporate the
burning of reference fuels of known cetane number as well as the fuels under test. The
fuels that were tested were 5%, 10%, 15%, 20%, 25% R.V.O / mineral diesel blends,
Waste Cooking Oil Methyl Ester (WCOME), Tallow Methyl Ester (TME), Mineral
Diesel, and reference fuels blended to give cetane ratings of 40, 45, 50, 55, and 60. A
total of 13 fuels. Each fuel was to run through the engine eight times. An
experimental design package, Design-Ease, was used to give the random run order for
eight replicates of each of the thirteen fuels.
To ensure that each fuel did not become contaminated with another, each fuel was
given its own burette. The fuel system was adapted to allow for change over of fuels
by the swapping of the burettes. Each fuel was stored in its own container, and blends
were made up by weight using a digital weighing scales.
Engine Operating Characteristics During Engine Testing
During the preliminary test on R.V.O blends, it was noted that the engine did not
operate steadily when running on the blends. The engine speed fluctuated, and it was
also noted that the pressure peaks of successive combustions were not uniform. The
engine was also noted to be misfiring. On inspection of the engine the tappets were
found to be out of adjustment from manufacturer’s requirements and were readjusted
to the correct setting. The injector nozzle was also examined and it was replaced as
the nozzle had become fouled. Following this the engine behaved well on all fuels
that were tested. It was observed for all fuels that once the speed was set that the
engine speed did not fluctuate while the Ignition delay was being measured.
56
Ignition Delay and Cetane Numbers
The Ignition Delay is the period that covers the time from the injection to the ignition
of the fuel in the combustion chamber. Different fuels have different ignition delays.
The ignition delay of a fuel is dependant on a number of factors. A fuel with high
cetane number will have a shorter ignition delay than a fuel with a low cetane number.
When measuring the ignition delay in order to compare it with other fuels it is
necessary to conduct the test at the same engine speed.
From the results of the initial ignition delay experiments that were carried out, it is
clear that the precision of the ignition delay measurement is dependent on the engine
speed. The analysis of variance that was carried out on the ignition delay results
shows that the method used produces significant results. The cetane rating of Tallow
Methyl Ester (TME). was calculated to be the highest (58.5) of the fuels on test, while
the 25% R.V.O blends was calculated to have the lowest at 41.56. The cetane rating
of the mineral diesel fuel that was tested was calculated at 53.5 while the 5% to 20%
blends of R.V.O. ranged between 47.5 and 42.8 respectively. The cetane rating of
Waste Cooking Oil Methyl Ester (WCOME) was calculated at 41.71.
During the measurement of the ignition delay of the different fuels it became apparent
that the different fuels have different pressure traces. With fuels like T.M.E. the initial
pressure rise due to combustion was very distinct and presented clear traces. When
measuring the ignition delay from the 25% R.V.O./ 75% mineral diesel blend it was
noted that the initial pressure rise was not as pronounced as for the T.M.E. pressure
curve, this region on the pressure curve seemed to fluctuate which made it difficult to
take the exact point each time the fuel was tested.
In an attempt to estimate the cetane number of a 100% blend of R.V.O. a graph was
plotted of the cetane number of the five R.V.O blends that were tested against the
percentage blend. A curve was fitted to these points and a value for a 100% blend of
R.V.O. was estimated by extrapolation to have a cetane number of 25. This is shown
in Figure .4.7.8.
.
57
Cetane Rating of 100% R.V.O
60
55
50
45
Cetane
40
35
-0.7135x
y = 48.518e
2
30
R = 0.9295
25
20
15
10
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
R.V.O/ Mineral Diesel % Blend
Figure 4.7.8 Plot of Estimated Cetane Rating of 100%R.V.O.
58
4.8
Low Temperature Solidification and Growth of Crystals of RVO
4.8.1
Introduction
The crystallisation of RVO, seed oils, biodiesel and biofuel blends at low temperature
is one of the main problems in using these fuels. The prevention of wax formation, at
low temperatures and the design of new and better additives require a good
understanding of the crystalline behaviour of the biofuel. In this work, thermomicroscopy was used to study the crystallisation of a range of fuels over time when
exposed to low temperatures.
This project involves the use of a cold stage device produced by Stritch (2000), and
modified by Fogarty (2001). The cold stage is placed under a microscope, and a small
sample is placed on the cold plate. The biofuels crystallisation can be thus viewed, as
the sample is kept at alower than ambient temperature. The sample is analysed for a
period of approximately 6 hours to allow full crystallisation to occur. The cold stage
uses a Peltier device which works on the principle that when two dissimilar materials,
constitute a circuit, a current will flow as long as there is a temperature gradient
between the junctions of the two conductors and vice versa.
Crystallisation
In a crystal the constituent materials, ions or atoms rearranged in a regular manner
with the result that the crystal shape is independent of size and, if a crystal grows,
each of the faces develops in a regular manner. The presence of impurities will,
however, usually result in the formation of an irregular crystal (Coulson and
Richardson, 1991)
The crystallisation process consists essentially of two stages, which generally proceed
simultaneously, but which can to some extent be independently controlled. The first
stage is the formation of small particles or nuclei, which must exist in the solution
before crystallisation can start, and the second stage is the growth of the nuclei. If the
number of nuclei can be controlled, the size of the crystals ultimately formed may be
regulated, and this forms one of the most important features of the crystallisation
process (Coulson and Richardson, 1991).
The crystallisation process is sensitive to a wide variety of factors (rate of cooling,
concentration, and temperature gradients, impurities, etc.).
59
Nucleation and Crystal Growth
Crystals are created when nuclei are formed and then grow. The kinetic processes of
nucleation and crystal growth require supersaturation, which can generally be
obtained by a change in temperature. The system then attempts to achieve
thermodynamic equilibrium through nucleation and the growth of nuclei (Mersmann,
1995).
The nucleation can be classified into two types depending on if the process occurs in
the presence, or in the absence, of crystals. They are known as primary and secondary
nucleation and they take place in the absence of crystals or with a growing “parent”
crystal, respectively. The primary nucleation can be also subdivided into
homogenous, if it is a spontaneous process, or heterogeneous, if the process is induced
by foreign particles (Mersmann, 1995).
The rate of growth of a crystal face is the distance moved per unit time, in a direction
that is perpendicular to the face. The crystal growth is a layer-by-layer process and
since the growth can only occur at the outer face of the crystal, the solute material
must be transported to that face from the bulk of the solution. The solute molecules
reach the face by diffusion through the liquid phase (Geankoplis, 1993).
The rate of growth in a solution is dependant on the temperature and concentration of
the liquid at the crystal face (Coulson and Richardson, 1991).
The rate of growth is also related to the conditions within the medium. In the process
of adding molecules required for the growth of crystals, some atoms form permanent
attachments immediately, or shortly after, the collision with the crystallites (nuclei
that exceeded the critical size). Others are adsorbed temporarily and return to the
medium after some time on the growth surface. The flow from the medium to the
crystal will determine the rate of growth (Gay, 1972).
Caking of Crystals
The tendency for crystalline materials to cake is attributable to a small amount of
dissolution taking place at the surface of the crystals and subsequent re-evaporation of
the solvent. The crystals can then become very tightly bonded together (Coulson and
Richardson, 1991).
Because the vapour pressure of a saturated solution of a crystalline solid is less than
that of pure water at the same temperature, condensation can occur on the surfaces of
the crystals even though the relative humidity of the atmosphere is less than 100 per
cent. The solution so formed then penetrates into the pack of crystals by virtue of the
capillary action of the small spaces between the crystals, and caking can occur if the
60
absorbed moisture subsequently evaporates when the atmospheric humidity falls
(Coulson and Richardson, 1991).
A crystalline material will cake more readily if the particle size is non-uniform,
because the porosity is less in a bed of particles of mixed sizes and fine particles are
more readily soluble (Coulson and Richardson, 1991).
Crystal Geometry
In crystallisation, the opportunity for individual crystals to develop, depends on the
processes of nucleation and growth. Rapid crystallisation from a large number of
nuclei is unlikely to allow the formation of any recognisable shapes in the crystallites.
Limited nucleation and slow growth will permit the formation of single crystals of
appreciable size. The particular conditions of crystallisation must be expected to play
some part in determining external shape, but even in undisturbed and controlled
growth there are wide variations in form and habit between crystals with the same
point group symmetry but different atomic structures. From this it seems probable that
features of the atomic structure must control growth forms to some extent
(Geankoplis, 1993).
Use of Additives
Waxy distillate fuels containing long-chain normal paraffins have the characteristic of
becoming less fluid as the temperature of the fuel decreases below its cloud point.
This is due to the crystallisation of wax molecules into plate-like crystals, which leads
to a loss of fluidity and filterability of the fuel (El-Gamal and Al-Sabbagh, 1995).
Chemical additives referred to as wax dispersants/flow improvers (WDFI) are
introduced to solve the problems economically. These additives modify the size and
shape of wax crystal in such a manner as to permit the oil to remain fluid at lower
temperature and thus pourable and able to pass through coarse filters (El-Gamal and
Al-Sabbagh, 1995).
Flow improver additives can decrease the size, or inhibit the formation of wax
crystallites formed upon cooling the fuel and thus lower the temperature at which wax
plugging becomes a problem. These additives can lower the temperature of fuel
“gelling” significantly, when blended with fuel at low concentrations. These tailormade additives can be matched to the wax in the fuel (Lewtas et al., 1991).
The additives adsorb on and block the growing of the fast growing edges. The crystals
now grow as thin columns, needles or prisms, which prevent the gelling and allow the
temperature operability range of the diesel fuel to be widened (Arkenbout, 1995).
61
Flow improvers ameliorate the cold flow properties of fuels in terms of pour point
depression through reduction of the size of the wax crystals (El-Gamal and AlSabbagh, 1995).
The cloud point (CP) is not generally affected by additives. (Graboski and
McCormick, 1998). But, studies conducted by Dunn et al. (1995, 1996) have shown a
nearly linear relationship between CP and low-temperature filterability of
distillate/methyl ester blends. That is cold-temperature operability limits predicted by
standard filterability tests were directly proportional to the corresponding CP. This
trend was observed for formulations containing 10 to 100% volume methyl esters.
These studies pointed out that approaches to improving the low temperature flow
properties of blends should concentrate on reducing CP. (Dunn and Bagby, 1996).
Literature Review Conclusions
Due to the lack of fundamental knowledge on the crystallisation of seed oil and
biodiesels at low temperatures a method is required to obtain consistently good
images of the shapes and sizes of crystals as they crystallise over time.
More knowledge in the area of crystallisation will help towards developing effective
additives and determining the optimal blends of fuels for use in the transport industry.
Objectives
The objectives of the work reported in this chapter were:
•
Make necessary alterations to the cold stage set up in order to be able to
maintain a constant temperature of cold stage for long periods of time (6
hours).
•
Improve on the measurement techniques used by Fogarty (2001) in measuring
the crystal size.
•
Determine the crystal growth rate and crystal structure of RVO, WCOME, and
Camelina seed oil (CSO).
•
Investigate the effect of the addition of Additive 240 on the crystal structure
and growth rate of RVO and WCOME.
•
Determine the crystal growth rate and crystal structure of mineral diesel/ RVO
blends.
62
4.8.2
The Apparatus
Central to the experiment is a cold stage (Fig.4.8.1)
P.I. Controller
Glycol Outlet
Glycol Inlet
Fig. 4.8.1 – The Cold Stage
Thermocouple
The apparatus consists of:
•
Cold Stage – the cold stage uses a Marlow Industries Inc. Model DT32-6
peltier device, which has a hot and a cold side.
•
Haake Cooling Unit – the cooling unit circulates glycol around the peltier
device to dissipitate the heat produced on the hot side. It also helps in
controlling the temperature to a constant level.
•
Voltage Generator - A Metronix Model MSV18-15 voltage generator supplies
the peltier device with the appropriate level of voltage and current. A P.I.
Controller controls the current that is being passed through the peltier device.
•
P.I. Controller – the controller controls the current that is being passed through
the peltier device. A Metronix Model MSV18-15 voltage generator supplies
the peltier device with the appropriate level of voltage and current.
•
Thermocouple – the thermocouple is attached to the cold plate; the
temperature is read using a digital thermocouple reader.
•
Microscope – the microscope used is an Olympus BX60 microscope. The
optical output from the microscope is recorded by a JVC Model TK-C1381EG
63
colour video camera and is displayed using Buehler Ltd. Omninet imaging
software on the computer screen.
•
Light Source – the sample is illuminated by a Rofin-Sinar (RS6160) light
source.
•
Skirt – a skirt is draped around the microscope and cold stage to shield the
sample from the ambient temperature.
• Video
Digital
Camera and
Microscope
‘Skirt’
External
Light Source
Temperature
Reader
P.I. Controller
Haake
Cooling Unit
Transformer
Voltage
Generator
Fig 4.8.2 - The Overall Setup
Experimental Procedure
•
Remove the microscope table by releasing the lock-nut located to the rear of
the table.
•
Remove the microscope table’s support (this lifts off).
•
Replace with special cold stage microscope table.
•
Place the cold stage on the table and under the microscope.
64
•
Connect the inlet and outlet hose from the cooling unit to the inlet and outlet
of the cold stage.
•
Set the cooler to 19.8°C, the temperature of the cooler may need to be adjusted
to maintain constant temperature.
•
Switch on the voltage generator, transformer and P.I. controller.
•
Set the voltage to 10V and the current to 3A.
•
Using the thermocouple reader check that the cold plate goes to -6°C.
•
Using a pipette place a small amount of the sample on the cold stage.
•
Take micrographs of the sample periodically for approximately six hours,
using the Buehler Ltd. Omninet imaging software on the computer.
•
The images recorded by the software can be exported as .jpg files. The images
can be arranged in a chronological order and a pattern emerges as to how the
sample crystallises.
Calibration
To calibrate the objective,
•
Place the graticule under the objective that needs to be calibrated.
•
Select the ‘Calibrate Objective’ option under ‘tools’ tab
•
A box called ‘Calibrate X’ shows up.
•
Select the units in millimetres
•
Extend the measuring device on screen so that it measures between 1 and 2 on
the graticule.
•
Enter a value of ‘1’ in the X distance box (the division shown in the image
window on the graticule represents 1mm).
Measuring Crystal Size
From each micrograph, ten crystals were randomly selected and measured as shown
in Figure .4.8.3. The diameters of the crystals were measured using the inbuilt ruler in
the program.
65
Figure 4.8.3 – Measuring Crystal Size
The process was repeated for each micrograph and the results were tabulated as
shown below in table 4.8.2. See Appendix for a full set of tables for each of the
micrographs.
4.8.3
Results
Time
102
Crystal
1
2
3
4
5
6
7
8
9
10
Total size
Mean size
St. Dev.
Diameter (micro m)
180.21
162.03
166.74
159.03
165.24
174.03
171.03
162.03
210.09
186.78
1737.21
173.721
15.465
Table 4.8.2 - Determining Mean Crystal Size
The time and mean crystal size value for each set of micrographs were further
tabulated (see Table 4.8.3).
66
Time
35
60
82
102
118
147
160
180
230
277
345
400
Crystal Size
72.957
116.499
134.106
173.721
186.795
257.817
255.636
271.962
286.158
263.259
285.939
273.183
Log time
1.544068
1.7781513
1.9138139
2.0086002
2.071882
2.1673173
2.20412
2.2552725
2.3617278
2.4424798
2.5378191
2.60206
Log size
1.86307
2.06632
2.12745
2.23985
2.27137
2.41131
2.40762
2.43451
2.45661
2.42038
2.45627
2.43645
Table 4.8.3 - Time vs. Crystal Size for WCOME
This allowed graphs of log mean crystal size vs. log time to be plotted using the
tables. A quadratic equation was fitted to all the graphs for all the fuels tested as
shown below using neat RVO as an example. The other graphs are presented in the
appendix.
RVO
3
2.5
2
y = 0.0635x + 0.7055x + 0.4472
2
R = 0.9577
Log size
(micro m)
2
3
2
y = -3.3799x + 21.362x - 43.499x + 30.611
2
R = 0.9919
1.5
Log Crystal Growth
Quadratic
Cubic
1
0.5
0
1.5
1.7
1.9
2.1
2.3
2.5
2.7
Log Time (min)
Figure A.4 - Crystal Size vs. Time for RVO
The values of the coefficients are tabulated below in table 4.8.4
67
1
2
3
4
5
6
7
8
9
Sample
a
b
c
r^2
WCOME
-0.5688 2.9543 -1.3753 0.9617
WCOME with 1% Additive 240
-4.058 20.207 -23.098 0.8889
WCOME with 0.1% Additive 240 -0.2127 1.5758 -0.3669 0.9741
RVO
0.0635 0.7055 0.4472 0.9577
RVO with 1% Additive 240
-1.1246 5.0239 -3.4069 0.8562
RVO with 0.1% Additive 240
0.0525 -0.0879 2.041 0.8262
Mineral Diesel with 10% RVO
-0.9376 4.3007 -2.8532 0.9253
-0.512 2.9683 -2.1358 0.9801
RVO Seed Oil
-2.8988 14.437 -15.49 0.7097
Table 4.8.4 – Coefficients for the quadratic equation for each sample.
Biodiesel Sample
a
b
c
Esterified WCOME (1)
-4.3849
20.443
-21.892
Esterified WCOME (2)
-0.4067
2.3835
-1.5071
Mineral Diesel
-0.4012
2.6155
-1.9814
WCOME with 0.5% Additive 240
-0.2433
1.9301
-1.5324
-0.5435
3.4283
-3.6815
-0.0959
1.281
-1.2982
-0.2773
1.4934
-0.3091
Esterified WCOME (2) (second test)
-0.6279
2.8906
-1.6402
Table 4.8.5 – Coefficients for the quadratic equation of each sample as
determined by Fogarty (2001)
Fogarty (2001) also determined coefficients for quadratic equations that relate log
time to log size (Table 4.8.5).
The coefficients determined for WCOME in this analysis relate closely to the
coefficients determined by Fogarty (2001), (WCOME (2)). This indicates good
repeatability in experiment.
The values of the coefficients of the WCOME with 1% additive 240 differ, although it
was unspecified whether the 1% additive used by Fogarty was 1% by weight or 1%
by volume. The blend used in this analysis was 1% by weight.
Poor values for the coefficient of determination in Table 4.8.4 indicated that a
quadratic equation is a poor fit for most of the samples, in particular the samples that
contained an additive.
68
A cubic equation of the form, proved to be a better fit.
1
2
3
4
5
6
7
8
9
Sample
WCOME
WCOME, 1% Additive 240
WCOME, 0.1% Additive 240
RVO
RVO, 1% Additive 240
RVO, 0.1% Additive 240
Mineral Diesel, 10% RVO
Mineral Diesel, 5% RVO
Camelina Seed Oil
a
-31.034
-1.3739
-3.3799
2.9513
1.4694
20.427
b
210.09
8.3563
21.362
-19.988
-9.4259
-147.4
c
-471.42
-16.044
-43.499
44.948
20.151
354.09
d
352.42
11.567
30.611
31.383
-12.259
-280.77
r^2
0.9399
0.9821
0.9919
0.993
0.959
0.8299
Table 4.8.6 – Coefficients for the cubic equation for each sample.
Discussion
Obtaining Images
Viewing the samples at low magnifications proved to be relatively easy, however, it
was more difficult to obtain images at higher magnifications. This is primarily due to
lack of clearance to focus the microscope.
To overcome this problem an alternative microscope table was used, designed by
Fogarty (2001). The alternative table adds 30mm to the focal range, and this allowed
higher magnification images to be viewed.
The design of the microscope is such that a sample is brought into focus on low
magnifications first and then if higher magnification images of the sample are
required; it is possible to rotate between objectives easily.
Due to the sensitivity of the crystalline process to temperature gradients, it is
important that the sample is shielded from ambient temperature. This was achieved by
using a ‘skirt’, which surrounded the cold stage and helped in obtaining a constant
temperature.
When illuminating the sample to obtain images, the microscope light cannot be used,
because the heat from the light would cause temperature gradients in the sample and
affect the accuracy of the experiment. To overcome this a Rofin-Sinar light source
was used. The light is transmitted to the sample using optical fibre. With these
modifications it was possible to obtain the images required to produce the graphs in
Appendix A
69
Cooling Methods
A Peltier device is used to create a cold stage. Ideally the cold plate temperature
should stay constant. Previously, in Fogarty’s study, this had not been the case, the
temperature often varied over as wide a range of 8oC. A Haake cooling unit is the
ideal solution to this. When this cooling unit was used the cold plate temperature was
maintained to within + 0.1°C. (Fig.4.8.4). However the variation in temperature used
by Fogarty shows the lack of sensitivity to constant temperature for crystal growth to
occur after nucleation.
Variation of Temperature with Time, 2002
25
20
Temp. ('C)
15
10
5
0
-5
0
50
-10
100
150
200
Time (mins)
250
300
350
400
Cold Plate Temp
Glycol Temp
Fig. 4.8.4 – Temperature vs. Time for cold stage
Crystal Growth
The growth rate of a crystal is described by Geankoplis (1993) as the distance moved
perpendicular to the crystal surface. The growth rate for each sample tested is
presented graphically in the Appendix B. Micrographs of every sample were
recorded periodically using Buehler Omninet imaging software. The log of the
crystal size was plotted against the log of the time and the results were plotted on a
graph and an empirically derived fit polynomial fit was derived for each graph. A
quadratic equation proved to be the best fit for the majority of the samples. However
a cubic equation proved to be the best fit where additives were used. Using the
derived equations, the mean crystal size in sample can be predicted, under carefully
70
controlled conditions. In general these equations appear satisfactory at
supersaturation.
From the graphs it can be seen that in general the crystal size increased with time.
This agrees with Fogarty (2001), and also with Gonzalez Gomez et al. (2001). In the
case of the WCOME, the crystal sizes ranged from 72µm after 35 minutes to 273µm
after 400 minutes. This agrees with Gonzalez Gomez et al., 2001 who found that the
crystals ranged from 2-252µm using laser diffraction techniques. The crystal sizes
obtained by Fogarty (2001) were smaller ranging from 19µm to 91µm. However the
cooling method used then, was unable to sustain constant temperature, hence, the
crystallisation occurred under different conditions.
Effect of Additives
WCOME
In the case of the WCOME, the effect of the additive was to maintain the crystal size
at a somewhat constant size between the times of 127 minutes (Log(time) = 2.1038)
and 155 minutes (Log (time) = 2.19033) in the case of the 1% additive. WCOME with
0.1% additive had a less dramatic effect. Crystals began to appear earlier in the
sample, and it suppressed the crystal growth between the times of 46 minutes (Log
(time) = 1.6627) and 93 minutes (Log (time)=1.9685). The additive had the effect of
suppressing the mean crystal size in both samples. The maximum crystal size for
WCOME with 0.1% Additive 240 and WCOME with 1% additive 240 after being left
to crystallise for approximately 6 hours were 172µm and 112µm respectively.
This indicates that increasing the percentage additive in the WCOME had the effect of
suppressing the mean crystal size. This is in agreement with the findings of Fogarty
(2001)
RVO
The maximum crystal size for RVO after being allowed to crystallise for
approximately 6 hours was 377µm. The maximum crystal size for the RVO with 0.1%
additive 240 and 1% additive 240 after 6 hours were found to be 145µm and 146µm
respectively. This indicates that increasing the percentage additive had very little
effect on the maximum crystal size in the sample. These results would indicate that
0.1% additive would be just as effective as a 1% additive blend.
71
The additive seemed to have a similar effect on the crystal growth for the RVO, as it
did for the WCOME, in that it maintained the crystal size for a period before the
growth rate increased again. This was especially true in the case of 0.1% additive
blend.
If a choice were to be made between the two blends, results suggest that a 0.1%
additive blend would be the optimal blend. Even though additives normally succeed
in suppressing the mean crystal size in a sample during crystallisation, they also tend
to increase the viscosity of the fuel, which can lead to poorer atomisation of the fuel
and pumping problems.
From examination of the micrographs obtained, it is clear that the effect of the
Additive 240 is one of making the RVO crystallise to form in long thin columns. This
is especially clear in the image obtained for RVO with 1% additive after 105 minutes,
see figure 4.8.5 . This agrees with Arkenbout (1995) who noted that the effect of
additives is one of making crystals grow as thin columns, needles or prisms.
Arkenbout noted that the additive had the effect of adsorbing on and blocking the
growth of the fast growing edges.
Figure 4.8.5 Crystalisation of RVO with 1% Additive 240 after 105 minutes
Mineral Diesel/RVO blends
The maximum crystal size for the mineral diesel with 10% RVO and mineral diesel
with 5% RVO were both approximately 119µm. The extra percentage RVO in the
10% RVO had the effect of making the initial crystal size much smaller (34µm for 5%
RVO as opposed to 98µm for the 10% RVO sample).
The size of the crystals occurring in the blends was much smaller than the other fuels.
The maximum value of crystal size recorded in the blends after being left to
crystallise for 6 hours was measured to be 119µm.
72
Conclusions
•
Using the Haake cooling unit with glycol proved to be a very effective method
of heat dissipitation from the hot side of the peltier device. The cooler helped
in controlling the temperature in excess of 6 hours to within ±0.1°C.
•
The Rofin-Sinar light source was an adequate replacement to the microscope
light.
•
When samples of RVO, CSO, WCOME or mineral diesel/RVO blends are left
to crystallise at -5°C approximately, generally the size of the crystals increase
with time.
•
The crystal sizes for RVO, CSO and WCOME were found to be 377µm,
298µm and 273µm respectively if left to crystallise for 6 hours.
•
The effect of the additive was to inhibit the growth of the crystals in both the
RVO and the WCOME. Increasing the percentage additive in the WCOME
had the effect of inhibiting the crystal growth even further.
•
The additive had the effect of maintaining the crystal to a constant size in the
RVO and the WCOME for a period before the crystal proceeded to grow
again.
•
The size of the crystals recorded for all the samples would indicate that all the
samples could cause blockages in the fuel filter had the fuel been exposed to
temperatures in the region of -6°C for 6 hours.
Recomendations
•
Following more tests on WCOME/additive 240 blends; it should be
investigated whether or not a pattern emerges in the coefficients of the
polynomial relating crystal size with time, as the percentage additive in the
sample is increased.
References
1. Arkenbout, G.F., 1995. “Melt Crystallisation Technology”. Technomic.
73
2. Coulson, J.M., J.F. Richardson,1991, “Chemical engineering - Particle
technology and separation processes ” Vol.2, 4th ed., Pergamon Press.
3. Coutinho, J.A.P., C. Dauphin and J.L. Dairdon, 1999. “Measurements and
modelling of wax formation in diesel fuels”. Fuel, 79, 607-616.
4. Dunn, R.O., M.W. Shockley, and M.O. Bagby, 1996. “ Improving the LowTemperature properties of Alternative Diesel Fuels: Vegetable Oil-Derived
Methyl Esters.” JAOCS, 73(12),1719-1728.
5. El-Gamal, I.M., A.M., Al-Sabbagh, 1996, “Polymeric Additives for Improving
the Flow Properties of Waxy Distillate Fuels and Crudes”, Fuel 75, 6, 743750.
6. Fogarty, C, 2001, “Crystallisation Analysis of Biodiesels”, BEng Final Year
Project, University of Limerick.
7. Gay, P (ed.), 1972. “The Crystalline State: An Introduction”. Oliver & Boyd.
8. Geankoplis, C.J. (ed.), 1993. “Transport Processes and Unit Operations”.
Prentice-Hall International.
9. González Gómez, M.E., R. Howard-Hildige and J.J. Leahy, 2001. “Growth of
Crystals from Waste Cooking Oil at Low Temperature”. Submitted to Fuel
2001.
10. Holman, J.P. (ed.), 2001. “Experimental Methods for Engineers 7th ed.”.
McGraw-Hill International Editions.
11. Kaghazchi, H., 2001.
“ ME4718 Fluid Process Control course notes”.
University of Limerick.
12. Korbitz, W., 1999. “Biodiesel Production in Europe and North America, an
Encouraging Prospect.” Renewable Energy, 16, 1078-1083.
74
13. Mersmann, A., 1995, “Crystallization Technology handbook”, NewYork:M
Dekker.
14. Mittelbach, M., 1998. “A European perspective on quality biodiesel”. In:
Peterson, C.L. (ed.), Commercialisation of Biodiesel: Producing a Quality
Fuel, Conference Proceedings, 9-10 July 1997, Boise ID. University of Idaho,
Moscow, ID, pp125-131.
15. Schwab, A.W., M.O. Bagby, and B. Freedman, 1987. “Preparation and
properties of diesel fuels from vegetable oils”. Fuel, 66, October, 1372-1378.
16. Srivastava, A. and R. Prasad, 1999. “Triglycerides-based diesel fuels”.
Renewable and Sustainable Energy Reviews, 4, 111-133.
17. Stritch, M., 2000. “Cold Stage Design and Bi 995. “Industrial Crystallisation”.
Plenum Press.
18. Tse, F.S., Morse, I.E., “Measurement and instrumentation in engineering
:principles and basic laboratory experiments”, New York:M. Dekker.
19. Winder, E.J., A.B. Ellis, G.C. Lisensky, 1996, “Thermoelectric Devices:
Solid-State Refrigerators and Electrical Generators in the Classroom”, Journal
of Chemical Education, 73, 10, 940
20 Zielinski, J.F., F. Rossi and A. Stephens, 1985. “Wax and Flow in Diesel Fuels”.
Society of Automotive Engineers, Technical paper series no. 841352:5.931-5.944.
75
APPENDIX A– CRYSTAL SIZE VS. TIME
GRAPHS OF CRYSTAL SIZE vs. TIME
76
WCOME
3
2.5
2
y = -0.5688x + 2.9543x - 1.3753
2
R = 0.9617
Log Size
(micro m)
2
Log Crystal Growth
1.5
Quadratic
1
0.5
0
1.5
1.7
1.9
2.1
2.3
2.5
2.7
Log Time (min)
Figure A.1 - Crystal Size vs. Time for WCOME
WCOME 1% 240
2.5
3
2
y = -31.034x + 210.09x - 471.42x + 352.42
2
R = 0.9399
2
y = -4.0538x + 20.207x - 23.098
2
2
R = 0.8889
Log Size
(micro m)
1.5
Log Crystal Growth
Cubic
Quadratic
1
0.5
0
2.05
2.1
2.15
2.2
2.25
2.3
2.35
2.4
2.45
2.5
2.55
Log Time (min)
Figure A.2 – Crystal Size vs. Time for WCOME with 1% Additive 240
77
WCOME 0.1%240
2.5
2
y = -0.2127x + 1.5758x - 0.3669
2
R = 0.9741
2
3
2
y = -1.3739x + 8.3563x - 16.044x + 11.567
Log Size
(micro m)
2
R = 0.9821
1.5
Log Crystal Growth
Cubic
1
Quadratic
0.5
0
1.5
1.7
1.9
2.1
2.3
2.5
2.7
Log Time (min)
Figure A.3 - Crystal Size vs. Time for WCOME with 0.1% Additive 240
RVO
3
2.5
2
y = 0.0635x + 0.7055x + 0.4472
2
R = 0.9577
Log size
(micro m)
2
3
2
y = -3.3799x + 21.362x - 43.499x + 30.611
2
R = 0.9919
1.5
Log Crystal Growth
Quadratic
Cubic
1
0.5
0
1.5
1.7
1.9
2.1
2.3
2.5
2.7
Log Time (min)
Figure A.4 - Crystal Size vs. Time for RVO
78
RVO with 1% 240
3
2.8
2.6
3
2
2
y = -1.1246x + 5.0239x - 3.4069
y = 2.9513x - 19.988x + 44.948x - 31.383
2.4
2
2
R = 0.8562
Log Size
(micro m)
R = 0.993
2.2
2
Log Crystal Growth
1.8
Cubic
1.6
Quadratic
1.4
1.2
1
1.6
1.7
1.8
1.9
2
2.1
2.2
2.3
2.4
2.5
2.6
Log Time (min)
Figure A.5 - Crystal Size vs. Time for RVO with 1% Additive 240
RVO with 0.1% 240
2.3
2.25
2.2
2
y = 0.0525x - 0.0879x + 2.041
2
Log Size
(micro m)
2.15
R = 0.8262
2.1
2.05
3
2
y = 1.4694x - 9.4259x + 20.151x - 12.259
Log Crystal Growth
2
2
R = 0.959
Cubic
1.95
Quadratic
1.9
1.85
1.8
1.7
1.8
1.9
2
2.1
2.2
2.3
2.4
2.5
2.6
Log Time(min)
FigureA.6 - Crystal Size vs. Time for RVO with 0.1% Additive 240
79
2.4
Log Size
(micro m)
2.2
2
2
y = -0.9376x + 4.3007x - 2.8532
2
R = 0.9253
1.8
Log Crystal Growth
Quadratic
1.6
1.4
1.9
2
2.1
2.2
2.3
2.4
2.5
2.6
Log Time (min)
Figure A.7- Crystal Size vs. Time for Mineral diesel with 10% RVO
80
2.6
2.4
2.2
2
Log Size
(micro m)
2
y = -0.512x + 2.9683x - 2.1358
2
R = 0.9801
1.8
1.6
Log Crystal Growth
1.4
Quadratic
1.2
1
1.5
1.7
1.9
2.1
2.3
2.5
2.7
Log Time(min)
Figure A.8 - Crystal Size vs. Time for Mineral Diesel with 5% RVO
Camelina
3
2
3
2
y = 20.427x - 147.4x + 354.09x - 280.77
y = -2.8988x + 14.437x - 15.49
2
R = 0.7097
2
R = 0.8299
2.5
Log Size
(micro m)
2
1.5
1
Log Crystal Growth
Quadratic
Cubic
0.5
0
2
2.1
2.2
2.3
2.4
2.5
2.6
2.7
Log Time (min)
Figure A.9 - Crystal Size vs. Time for Camelina Seed Oil
81
5.
RVO Testing
5.1 Short Duration Boiler Fuel Blend Tests : Pilot Study
5.1.1 Introduction:
An unmodified home central heating boiler was used to burn pilot blends of RVO and
Texaco mineral home heating oil (HHO) over the range 100% mineral oil to 60%
mineral oil / 40% RVO in 10% increments. The flue gas was also measured in each
case to determine flue gas emissions.
Apparatus:
Fig 5.1.1: Home Heating Boiler
82
Amanda Home Heating Boiler fitted with a Danfoss Nozzle, Bentene B9 27 kW
Burner as shown in Fig. 5.1.1.
IMR 2800P Exhaust Gas Analyser as shown in figures 5.1.4 and 5.1.5.
Procedure:
After an initial gas sample measurement of ambient air was conducted, the boiler was
started using 100% home heating oil fuel. After the heating system reached its normal
operating temperature (68oC water temperature), two exhaust samples were taken
using the gas analyser for each of the different fuel blends. The measurement probe
was positioned as shown in Fig. 5.1.2.
Fig. 5.1.2: Position of IMR 2800P probe.
The oil supply was switched from the main oil tank to an alternative supply line from
a 20 litre container into which contained the various blends of fuel, (see Fig. 5.1.3
overleaf). This made it possible to change the different fuel mixtures to the boiler
quickly and accurately. The size of each sample used was 500ml. After the boiler had
burned almost all of the sample, the flue gases were measured.
83
Fig. 5.1.3: Alternative fuel supply line
The boiler’s thermostat setting was increased before each flue gas measurement to
ensure continuous combustion during the measurement of the flue gas emissions.
Fig. 5.1.4: IMR Probe position during flue gas measurement
84
Fig. 5.1.5: IMR Flue Gas Analyser
This procedure was carried out for each of the different fuel blends of up to 40%
RVO. At 40% RVO blend to 60% mineral fuel, combustion was erratic, combustion
failed (cut out) however the boiler was restarted and samples were taken of the flue
gases.
85
5.1.3 Results and Discussion:
Flue Gas Emissions:
Fuel
Sample:
T-Room oC
T-Gas oC
CO2 %
O2 %
CO PPM
SO2 PPM
NO2 PPM
NO PPM
QA %
Lambda %
A: 100% B: 10% V C: 20% V D: 30% V E: 40% V (cut out) F: 40%V
13
335
11.1
5.9
0
32
0
70
17.1
1.4
13
410
10.6
6.7
0
23
0
68
22.2
1.5
13
352
10.6
6.7
0
7
0
61
18.9
1.5
12
362
10.7
6.5
0
9
0
66
19.2
1.4
13
392
10.8
6.4
10
22
0
38
20.7
1.4
13
390
10.1
7.3
500
24
0
26
22.3
1.5
Table 5.1.2. Flue Gas Emissions
A2
B2
C2
D2
E2
F2
G2
H2
I2
Fuel Sample: 100% Diesel Oil 10% 10% 20% 20% 30% 30% 40% 40%
11 11 11 11 11
11
11
11
12
12
11
12
T-Room oC
T-Gas oC
369 384 392 295 380
391
374
383
313
347
360
377
CO2 %
11 11 11 5.6 11.3
11.3
11.7
11.7
10.8
11.8
11.1
11.6
O2 %
5.8 5.9 6
13 5.7
5.7
5.2
5.2
6.3
5
6
5.3
CO ppm
SO2 ppm
0 0 0 0 0
24 26 28 30 19
0
27
0
17
0
21
50
12
0
12
260
11
0
17
NO2 ppm
0
0
0
0
0
0
0
0
NO ppm
66 67 67 45 68
69
70
72
48
71
37
42
qA %
Lambda %
19 20 20 30 19.3 19.8 18.4 18.8 16.4
1.4 1.4 1.4 2.8 1.4
1.4
1.3
1.3
1.4
Table 5.1.3. Flue Gas Emissions
16.7
1.3
18.7
1.4
18.6
1.3
0
0
0
0
86
The results in table 5.1.2 show a gradual decrease in SO2 gases from 32 to 9ppm with
increasing amounts of RVO. This figure returned to 22/24 ppm when the combustion
became intermittant at a vegetable oil concentration of approximately 40%. NO
decreased from 72ppm for HHO to 61ppm for the 20% RVO mix. The amount of
oxygen recorded increased with increasing concentrations of RVO. The percentage
CO2 recorded was lower for all the RVO blends than for 100%HHO.
The results in Table 5.1.3. are from the second boiler test. In the fourth case (A2),
where the gas temperature is 295 oC, the nitrogen monoxide figure is far lower than
the other readings taken for the same fuel.
This test also yielded the greatest amount of oxygen in the flue gas, 13%, and gave a
lambda figure of 2.8%. This result may due to the test being carried out immediately
after the boiler had restarted, and there may have been residual unburned fuel in the
flue, also the CO2 figure for the same fuel is the lowest of all the tests.
The results show a 1% increase in CO2 as soon as the burner started using the 20%
vegetable oil mix. There were two CO measurements in columns F2 and H2,
indicating incomplete combustion and suggesting that the upper limit of RVO in the
blend was being approached.
With incomplete combustion comes excess air, this should be kept low as it needs to
be heated resulting in a decrease in flame temperature and an increase in flue gas
temperature which results in a deterioration in efficiency. The decrease in flame
temperature is reflected in the lowest overall NO figures produced for both these
samples. In both cases where there was CO present, the temperatures of the
subsequent test for each mixture increased to a greater extent than with the other fuel
blends. Over time, deposits of unburnt fuel can cause insulation of the heat exchanger
surface and so an increase in flue gas temperatures.
87
The blended fuels showed a decrease in SO2 levels, the range being from 30ppm for
the home heating oil to the lowest figure of 11ppm for the 40% blend.
The qA values are a measure of flue gas losses. The loss due to free heat is caused by
the temp difference between the fuel air mixture entering the combustion furnace and
the outgoing gases.
Graphs of emissions Vs RVO% are shown overleaf. There is a general trend displayed
in Figs. 5.1.6 and 5.1.8 showing a gradual decrease in the percentage of NO and SO2
emissions with increasing RVO. Figs. 5.1.7 and 5.1.9 show a general decrease in the
amount of O2 with increasing amounts of RVO.
Parts Per Million (PPM)
80
70
NO
60
SO2
50
40
30
20
10
0
0
10
20
30
40
40
Percentage RVO
Fig.5.1.6: NO, CO2 Emission Levels Vs Percentage RVO
88
12
10
Gas Percentage
8
6
CO2
O2
4
2
0
0
10
20
30
40
40
Percentage RVO
Fig. 5.1.7: CO2 and O2 Emission Levels Vs. Percentage RVO
Parts Per Million (PPM)
80
70
NO
60
SO2
50
40
30
20
10
0
0
10
10
20
20
30
30
40
40
Percentage RVO
Fig. 5.1.8: NO, SO2 Emission Levels Vs Percentage RVO
89
12
Emission Percentage
10
8
6
CO2
O2
4
2
0
0
10
10
20
20
30
30
40
40
Percentage of RVO
Fig: 5.1.9:CO2,O2 Emission Levels Vs Percentage RVO
90
5.2
Burner Modification and Adjustment for Heating Trial
Optimisation of burners to use waste cooking oil for domestic heating
Tests conducted at CIRAD, Montpellier, March 2002
ALTENER Contract No.4.1030/C/00-014
91
5.2.1
Introduction
CIRAD successfully modified a 260kW burner to use 100% rape seed oil as a fuel.
The main modifications carried out on the burner were the addition of a high pressure
fuel pump and a 1kW fuel preheater. This experiment investigates the possibilities of
using blends of waste cooking oil and home heating oil in an unmodified 20 – 40kW
size home heating burner. The burner was optimised to use the highest percentage of
waste cooking oil it could burn efficiently. Various blends of waste cooking oil and
home heating oil were tested and the nozzle type, fuel pressure, air damper, flame
stabiliser setting and the position of the burner inside the boiler were altered and the
emissions were monitored. It was seen that as the percentage of vegetable oil was
increased in the fuel blend, higher fuel pump pressures were needed in order for
efficient combustion and reliable start-up to occur. Heating the fuel blends had a
similar positive effect on combustion efficiency. Using standard components and
without preheating the fuel, the optimised burner ran successfully using a blend of
50% waste cooking oil and 50% home heating oil.
While raw vegetable oil has been used successfully in burners (Vaitilingom et al,
1998), the use of waste cooking oil as a fuel has usually only occurred after it has
undergone transesterification; Rice et al (1997), Mittelbach et al (1992). The
transesterification process not only results in a fuel with properties closer to mineral
diesel fuel than unesterified oil, it also results in a more uniform fuel. The variation in
properties such as FFA, melting point, water and impurity content between batches of
waste cooking oil makes the transesterification process more difficult than with virgin
vegetable oil. This variation in turn creates difficulties when attempting to use the fuel
in its raw state.
5.2.2
Waste Cooking Oil Fuel
Prior to recycling, vegetable oil typically contains 20% water and/or impurities, so it
cannot be used directly in a burner without first going through a cleaning stage. It was
therefore decided to use oil from a commercial waste cooking oil recycler, Bolton
R.V.O. Their recycling process consists of steam treatment, filtration and a series of
92
settling tanks. After recycling, the oil should be of a standard whereby it contains less
than:
3% free fatty acids
1% water
1% Solids not fat
(Source; O’Connell, 2000).
While the previous tests carried out by Vaitilingom et al were successful in using
100% raw vegetable oil, their system required the addition of a fuel pre-heater and a
more powerful pump. In the context of a small home heating oil burner, these
modifications would be relatively expensive and could negate the cost savings made
through burning the cheaper waste cooking oil. It was decided to optimise a standard
burner, and to find out the highest percentage of waste cooking oil it could burn
reliably. It was also investigated if the optimised settings for the burner which enable
it to use this fuel blend, would adversely effect its ability to burn 100% home heating
oil.
As can be seen in figure 5.2.1 below, the waste cooking oil used in this experiment
settled out into two phases during storage: on the top there was a dark material that
was liquid at room temperature and on the bottom there was material of a lighter
colour (that had a higher melting point), i.e. was semi-solid at room temperature. As
this experiment involved the use of standard burner components, only RVO that was
liquid at room temperature could be used, and therefore the RVO for the experiment
was taken from the top of the IBC.
93
Fig. 5.2.1. IBC of waste cooking oil
There is a possibility that the oil at the top of the IBC would contain fewer impurities
than the oil below, simply because the IBC had been in the same position for a
number of months and impurities would have had the opportunity to settle out of the
top phase.
- Characteristics of waste cooking oil from Bolton RVO:
Viscosity at 20oC (mm2/s): 80
Calorific Value (kJ/kg): 40,160
Approx. Density (kg/m3): 900
5.2.3
Equipment
A test bench was set up consisting of the following main components: A Cuenod NC4
burner which was equipped with a preheater (this heats to approx. 60°C but only
during start-up), a water boiler, a CIAT heat exchanger, a Ciclade Energy meter and
two exhaust gas analysers (an IMR and a Quintox). During part of the experiment, it
was necessary to heat some of the fuel blends prior to combustion and this was
94
achieved using a small deep fat fryer with a 2kW heating element. Fuel consumption
was monitored using a digital scales and a stopwatch.
Fig. 5.2.2. Laboratory test bench
The burner parameters that could be adjusted were:
- the fuel pump pressure
- the type of nozzle
- the position of the flame stabiliser
- the air damper setting
- the position of the burner inside the boiler
5.2.4
Optimisation
Introduction
Optimal combustion of the different fuels and blends was achieved primarily by using
different nozzles and by altering the fuel injection pressure. The type of nozzle that
was selected depended not only on the fuel flowrate, but also on the boiler geometry.
The most suitable nozzle would be one that produced a spray pattern that took up as
much area inside the boiler as possible without coming in contact with the boiler
walls, where the formation of deposits of unburnt fuel could occur. Lowest CO
95
readings, together with high CO2 readings and oxygen readings of between 3 to 5%
would indicate optimal combustion.
Fig. 5.2.3. Inside of boiler prior to testing
After each test, the burner was removed from the boiler and the inside of the boiler
inspected (see figure 5.2.3) to check for the presence of unburnt fuel deposits and
provide a further indication to combustion efficiency. Nozzles having the following
different spray patterns were tested: solid cone, semi-solid cone and hollow cone. A
nozzle with an angle of 45o was also investigated but its pattern was too narrow and it
produced CO emissions far in excess of 60o nozzles with equivalent flowrates. A
schematic of the inside dimensions of the boiler used during testing is shown in figure
5.2.4.
96
Fig. 5.2.4. Boiler geometry
Parameter Adjustment
While attempts have been made to correlate between adjustments to various
parameters and their subsequent effects on the performance of the boiler
(Karagiannidis, 1996), it should be noted that boilers are multivariate and the
adjustment of one parameter (e.g. nozzle type), usually necessitates the adjustment of
one or more other parameters (e.g. fuel pressure, air damper setting) in order to
achieve optimum combustion. The effects adjustment of each parameter had on the
boiler performance are summarised in the following paragraphs.
Fuel Pressure: It was seen that in order to burn blends of vegetable oil and home
heating oil satisfactorily, higher fuel pressures were needed to ensure the higher
viscosity blends would be atomised properly. The fuel pressure was adjusted by
means of the screw at the side of the fuel pump. It was found the maximum pressure
attainable in this fashion was approximately 14 bar, but higher pressures could
subsequently be achieved by throttling the return fuel line (see figure 5.2.7).
97
Nozzle Spray Patterns: A solid cone nozzle would have a centrally concentrated
spray suited to a relatively narrow boiler such as that used in this experiment. There is
however the possibility of droplets from the spray reaching the back wall of the boiler
(point A in figure 5.2.4) and leaving deposits, especially considering the elevated
pressures that the system was working under. A semi-solid spray would tend to
concentrate more of the fuel away from the middle of the boiler and towards the sides
(points B and C in figure 5.2.4), while at the same time directing some fuel to the
centre of the spray, and a hollow cone spray would tend to concentrate all the fuel
towards the sides – this type of nozzle would be more suited to shorter and wider
boilers.
Fig. 5.2.5. Nozzle patterns
Nozzle Spray Angle: This is the angle of the cone of the fuel spray and again,
depending on the geometry of the boiler and fuel pressure used, a wide spray angle or
a narrower spray angle is preferable.
Fig. 5.2.6. Close-up of nozzle assembly
98
Nozzle Flowrate (Size): A nozzle with too low a flowrate rating would produce a
relatively small flame that wouldn’t take up enough area in the boiler chamber. There
would then be the possibility of unburnt gases forming in areas D and E in figure
5.2.4. Too high a flow rate and there is a greater possibility of incomplete combustion
through unburnt fuel coming in contact with the boiler walls.
Fig. 5.2.7. Adjustable burner components
Distance Inside Boiler: The burner could be moved horizontally in and out of the
boiler. This could be used to lessen the amount of unburnt fuel deposits on the back of
the boiler wall, or conversely to extend the flame further into the chamber.
Air damper setting: As the fuel flow was altered, so too was the air damper; the
greater the fuel flow, the more oxygen would be needed for combustion. The oxygen
content in the exhaust was maintained at between 3 and 5% - less than 3% oxygen
would be insufficient for combustion, greater than 5% and the excess air would
remove heat from the boiler and displace it into the chimney, lowering boiler
efficiency.
99
Optimising the burner for the various blends tested involved the manipulation and
consideration of all of these parameters. It was found that a solid-cone Danfoss nozzle
with a spray angle of 60o was most suited to the 50/50 blend.
5.2.5
Experimental Procedure
100% home heating oil
The burner was optimised initially while running on 100% home heating oil, and
subsequently on various blends of vegetable oil and home heating oil. The exhaust gas
analysers were used to monitor the CO and CO2 readings. During preliminary testing
it was noted that the temperature of the flue gases would reach approximately 120°C
and maintain that temperature while the burner was running constantly, thus the
exhaust gases were analysed at this temperature. Later on in the experiment a second
heat exchanger was added and the exhaust gases were seen to maintain a temperature
of approximately 90oC. The water pump, which recirculated the water through the
heat exchanger, was set to run at its highest speed in order to keep the heating
requirements on the boiler at a maximum.
The first nozzle tested was that which came fitted to the burner; a Danfoss 0.60 US
Gal 60oS. This would provide a baseline to compare emissions against and was also
an opportunity to become familiar with the equipment and the adjustments needed to
optimise combustion. (Shortly after beginning testing the IMR analyser didn’t appear
to be recording the CO measurements properly, therefore the exhaust figures quoted
in this chapter are from the Quintox analyser.
•
100% Home heating oil; Emissions - CO: 34 (ppm) and CO2: 13.3 (%)
•
50% sunflower oil and 50% home heating oil
Using the same settings as for 100% home heating oil, it was attempted to use a blend
of 50% sunflower oil and 50% home heating oil. This blend was heated to
approximately 63°C for the test but would not burn properly and therefore the burner
was optimised again. After adjustments, the CO emissions improved vastly but were
still slightly higher than when using 100% home heating oil. Fuel consumption was
100
seen to be quite high in comparison to home heating oil. This was due in part to the
higher injection pressure of the fuel (at 20 bar) as opposed to there being a problem of
incomplete fuel combustion – (a leak was seen at the side of the pump while it
operated at 20 bar, and would have been part of the cause of the elevated fuel
consumption figure). The settings and further results for the burner running on 100%
home heating oil and on the 50/50 blend with sunflower oil are shown in table 5.2.1.
•
50/50 blend with new oil; Emissions - CO: 65 (ppm) and CO2: 12.9 (%)
80% peanut oil and 20% home heating oil
A fuel blend containing 80% peanut oil and 20% home heating oil was tested and was
also seen to burn, although somewhat less efficiently. While not unsuccessful, burner
starting proved unreliable, with the fuel blend requiring heating to above 80oC and the
fuel pump operating at 30 bar. This pressure appeared to be too high for the pump to
maintain, even over a few minutes.
•
80/20 blend with new oil; Emissions - CO: 94 (ppm) and CO2: 11.9 (%)
100% Peanut Oil
An attempt was made to fuel the burner using 100% Peanut Oil. The oil was heated
using a deep fat fryer to approximately 160°C prior to use, however the burner cut out
almost instantly and the CO readings reached a very high level (>1500 ppm) attempts to restart the boiler failed, even with quite a high fuel pressure of
approximately 30 bar.
•
No emissions results available
Nozzle Size
It was felt at this point in the experiment, that the flowrate of the 0.60 US Gal/hr
Danfoss nozzle was too high (both heat exchangers were unable to dissipate the heat
rapidly enough), so a nozzle with the same characteristics but a lower flowrate was
tested.
101
•
The 0.50 US Gal/hr Danfoss nozzle produced CO readings as low as 50 (ppm)
with CO2 at 13.1 (%).
50% waste cooking oil and 50% home heating oil
Having found the upper limit of the burners’ capability to efficiently use a blend of
new vegetable oil to be approximately 50%, a blend containing 50% waste cooking
oil and 50% home heating oil was subsequently tested. Firstly, the burner settings for
the 50/50 blend with new vegetable oil (see table 1) were tested for accuracy given
that a slightly smaller nozzle was now being used, and the results were seen to be
approximately the same as before. Using these, a blend of 50% home heating oil and
50% waste cooking oil was tested. However, a leak developed on the fuel pump
shortly after beginning the test and no results were recorded. Upon inspection, it was
seen that a seal on the axle of the fuel pump had become faulty. It was thought that
the leak was not due to the waste cooking oil blend but was related to an earlier
problem encountered with the fuel return line. A replacement pump with a similar
output was sourced and mounted onto the burner. It was also decided that the
manometer on the fuel line was of too large scale than needed, making it too difficult
to read accurately, so a manometer with a smaller scale was fitted.
After repairs were made to the system, some medium term tests were carried out with
the burner using the 50% waste cooking oil/50% home heating oil blend, and a
comparison made with it’s performance while burning 100% home heating oil.
•
Using the same settings as for the 50% blend with new oil (and the 0.50 US
Gal/hr Danfoss nozzle), the 50% blend of waste cooking oil produced - CO:
49 (ppm) and CO2: 12.8 (%)
102
5.2.6
Results
Fuel
50/50 home heating oil
/sunflower oil
Nozzle: Danfoss US 0.60US Gal, 60oS
Burner Settings
Pump pressure (bar):
14
20
Air damper (dial setting):
10
12
Flame stabiliser (mm):
5
5
Distance of burner inside
35
25
2.29
3.89
34
65
CO2 (%):
13.3
12.9
O2 (%):
2.9
3.4
Gas temp (°C):
121
128
0.378
0.393
boiler (mm):
Fuel consumption
(kg/hr): *
Emissions
CO (ppm):
Energy Meter (MW/H)
Table 1: Initial optimisation of burner with (a) home heating oil and (b) a 50/50
blend with sunflower oil
103
Fuel
50/50 home heating
oil/WCO
Burner Settings
12
20
5.5
11
4.5
5
Distance of burner inside
25
25
1.83
2.3
66
49
12.5
12.8
O2 (%):
4
3.6
Gas temp (°C):
89
~90
boiler (mm):
Fuel consumption
(kg/hr):
Emissions
CO (ppm):
CO2 (%):
Table 5.2.2: Comparison of home heating oil and 50% WCO blend using WCO
setting
104
5.2.7
Conclusions and Recommendations
Conclusions
It was shown that 50% waste cooking oil could be burned in an optimised burner,
fitted with a preheater and using the standard components. The only additional
equipment used was a valve to throttle the return fuel line, thus the purchase of
expensive heaters and more powerful fuel pumps was avoided while at the same time
the burner used a usefully high percentage of waste cooking oil in its fuel blend.
It is possible to use higher percentages of vegetable oil in a standard burner. However
blends containing over 50% waste cooking oil displayed difficulties during start up
and showed high CO readings during running.
Having monitored the CO emissions, and carried out an inspection of the inside of the
boiler after the tests, the combustion of the 50% waste cooking oil blend appeared to
be satisfactory, however longer term tests would give a more accurate measure of
burner performance. It should also be noted that as the ambient temperature increased
(from approx. 10oC to 20oC), and hence the temperature of the fuel blend, the CO
readings would decrease slightly.
Recommendations
Apply a more structured approach to optimisation. There was quite a degree of codependence between the adjustable parameters; it may be possible to achieve lower
emissions (i.e. better optimisation) with the 50/50 blends.
It was noted that a small increase in ambient temperature lowered the CO emissions
slightly. Re-use of some of some of the waste heat present in the exhaust gases may
be used to increase system efficiency further.
CO emissions were slightly higher with the 50/50 blends than with 100% home
heating oil. Conduct longer term tests to investigate the possible effects this might
have; i.e. the possibility of the build up of deposits over long periods of time.
Properly assess the degree of separation that would occur in the fuel blends due to the
different densities of the two fuels.
105
RVO from the top of the IBC had been used in this experiment, therefore it remains to
be seen if RVO straight from the supplier could be used. It wouldn’t have settled out
to the same extent as the test RVO and therefore would contain more impurities and
water. Work on achieving a standard for the waste cooking oil fuel grade would be
useful.
Investigate and quantify the benefits versus the increased costs associated with
installing some of the modifications as outlined by Vaitilingom et al.
References
Karagiannidis, A. 1996. Burners of domestic heating boilers: a measurement-based
analysis approach aiming at quantifying correlations among the basic parameters of
operation. Energy Conservation Management, Vol. 37, No. 4, pp 447-456.
Mittelbach, M., Pokits, B., Silberholz, A., 1992. Production and fuel properties of
fatty acid methyl esters from used frying oil. Proc. Alternate energy conference on
Liquid fuels from renewable resources. Nashville, USA: 74-79.
O’Connell, A., 2000. Investigation into the potential of recycled cooking oil as a
boiler fuel. University of Limerick, final year project thesis.
O’Connell, D., 2002. (Personal communication) – Director of Bolton R.V.O. Ltd,
Waste Cooking Oil Recycling Company, Kildare, Ireland.
Rice, B., Fröhlich, A., Leonard, R., 1997. Biodiesel Production based on waste
Cooking Oil: Promotion of the Establishment of an Industry in Ireland. Teagsc, Oak
Park Research Centre, Carlow, Ireland.
Vaitilingom, G., Perlihon, C., Liennard, A., Gandon, M., 1998. Development of rape
seed oil burners for drying and heating. Industrial Crops and Products 7 (1998) 273279.
106
5.3
Heating Demonstration at Cork County Council
5.3.1
Introduction
The modified Cuenod burner described in section 5.2 was installed in a Firebird boiler
located at Cork County Council offices, Charleville, Co. Cork, for the purposes of
evaluation of the reliability of using a 25% RVO/ 75% mineral heating oil as fuel.
The offices are similar in construction to a typical 4 bedroom residential bungalow
that can be found throughout Ireland and many other countries within the European
Union.
A Cuenod NC4 burner was fitted to a Firebird boiler as shown in figure 5.3.1. Figure
5.3.2 shows the burner boiler assembly installed at Cork County Council offices in
Charleville.
The blend of 25% RVO/75% mineral fuel was decided from consideration of the
separation tests results in section 4.7.3 (see also figure 4.7.8) to be the maximum
RVO/mineral fuel ratio that did not separate with a lower layer of neat RVO.
The RVO/mineral fuel was blended on site using the containers shown in figure 5.3.2.
The elevation of the offices at Charleville are shown in figure 5.3.3.
107
Figure 5.3.1 Cuenod Burner and Firebird Boiler
108
Figure 5.3.2 Heating Installation at Cork County Council Offices, Charleville
Figure 5.3.3 Cork County Council Offices, Charleville (elevation).
109
5.3.3
The trial began on 24 June 2002
The burner settings and flue gas emissions are given in table 5.3.1.
Fuel: 25% blend of waste cooking oil & 75% mineral diesel fuel
Burner Settings
15
8
6
Dist inside boiler (mm):
20
Emissions
CO (ppm):
0
CO2 (%):
12.5
O2 (%):
4.0
Gas temp (°C):
162
Table 5.3.1 Cuenod NC4 Burner Settings and Flue Emissions
Following more than 4 months of satisfactory operation the burner failed on 1
November 2002 apparently due a seized fuel pump. The burner was removed at this
point in time and returned to CIRAD for further analysis and repair. The trial was
restarted the last week in December using a new pump in an ECOFLAM burner, but
the operation was unreliable when using a 25% RVO/75% mineral fuel blend. The
boiler was returned to mineral fuel on 3rd January 2003.
110
5.3.4
Analysis of
Cuenod Burner Failure and Modification to ECOFLAM
Burner for 100%RVO
ADEME – CIRAD Final Report
Utilisation of Recycled Vegetable Oil as a fuel in a Domestic Burner
Utilisation d’huile de friture usagée comme combustible dans un brûleur domestique
(ADEME n° 0201002)
Tests conducted at CIRAD, Montpellier November/December 2002
ALTENER Contract No.4.1030/C/00-014
with European Commission and Limerick University
111
Utilisation of recycled vegetable oil as a fuel in a domestic burner
5.3.4.1. Introduction
5.3.4.2. On site trials Charleville: Cuenod NC4
Performance using 25% RVO ...................................................................................................
System Failure.............................................................................................................................
5.3.4.3. Characteristics of test fuels
5.3.4.4. Ecoflam Minor 1 - Tests conducted at Cirad, Montpellier.
Performance using 100% home heating oil ..............................................................................
Modifications to use fuel blends containing >50% RVO - Additional Equipment...............
Performance of modified burner using 50% RVO..................................................................
Performance of modified burner using 100% RVO................................................................
5.3.4.5. Results
5.3.4.6. Conclusions
5.3.4.7. References
Appendix
112
Utilisation of recycled vegetable oil as a fuel in a domestic burner
5.3.4.1. Introduction
Previous tests on a Cuenod home heating burner showed it was possible to
successfully burn blends of recycled vegetable oil (RVO) and home heating oil by
optimising the burner components. To assess the long-term durability of such a
system, an optimised Cuenod burner was used to heat the Cork County Council
Offices in Charleville, fuelled by a blend containing 25% RVO and 75% home
heating oil. After operating successfully for a period of approximately 4 months, a
mechanical failure in the fuel pump caused the burner to malfunction. Difficulties
arose when attempting to repair the French sourced burner in Ireland, and it was
necessary to send it back to CIRAD (for detailed investigation into the failure of the
system). To avoid similar future problems, it was decided to optimise an Irish sourced
burner (type: Ecoflam Minor 1) for future experiments. CIRAD had previously
modified a large scale burner to burn 100% rape seed oil, and by carrying out similar
modifications on the Ecoflam home heating oil burner, it was hoped to burn fuel
blends containing more than 50% RVO.
By optimising the components of a standard Cuenod burner (see project interim
report), it can be seen that fuel blends containing up to 50% RVO can be burned
efficiently and with similarly low emissions levels as when using 100% home heating
oil. In order to burn blends containing greater than 50% RVO, it is necessary to preheat the fuel and to inject it into the combustion chamber at a high pressure
(Vaitilingom et al, 1999). The problems associated with burning RVO are both
technical and fiscal. Table 5.3.4.1 shows that RVO has a small price advantage per
litre compared with home heating oil, however this advantage can be negated when
the price of any necessary modifications are taken into account. The total cost of the
modification of the Ecoflam to run with 100 % RVO is roughly 300 € (excluding tax).
In the case of France, with an average yearly consumption of 2000 litres, that means
two years and a half to pay back this added investment.
113
Q1 2001 - fuel prices euros/l excluding tax
HHO - France
0.34
HHO - Ireland
0.36
RVO - Ireland
0.28
Table 5.3.4.1: Comparison of Fuel Prices
From a technical point of view, RVO may be filtered and also subjected to steam
treatment, depending on the type of recycling facility. Even after steam treatment and
filtration, properties such as water content and S.N.F. levels (solids not fat) vary,
leading to possible problems such as fuel filter/nozzle blockages.
5.3.4.2. On site trials Charleville: Cuenod NC4
To assess the durability of the optimised burner while using an RVO fuel blend, a
long-term test was set-up at Cork County Council Offices in Charleville. These
offices comprise of a single storey house with an approximate floor area of 150m2,
with the boiler housed outside in a purpose built shed. The boiler fuel is stored beside
the boiler house in a 1000 l. plastic fuel tank (see figure 5.3.4.1). A separate fuel tank
and fuel line were set-up (see also figure 5.3.4.1) in parallel to the original fuel line
and 400 litres of a fuel blend containing 25% RVO and 75% domestic heating oil
were prepared for use. It was decided to use a 25% blend for reliability reasons previous work at CIRAD had shown that a 50% blend was the upper inclusion limit
for an optimised system (such a system is quite sensitive to changes in ambient
temperatures, and it was thought that the lower ambient temperatures in Cork
compared to those found in Montpellier could result in operational problems).
114
Fig. 5.3.4.1. Charleville test site
Although the basic components on the Cuenod burner were the same as those which
would be seen on burners currently available on the Irish market, some modifications
were still required. Firstly, a new mounting flange had to be used (as the diameter of
the blast tube of the Ecoflam burner originally fitted to the boiler was 8 mm larger
than that of the Cuenod burner). Secondly, the burner required re-wiring due to the
differences between the French and Irish control systems; with the French system, the
burner power is fed through the boiler and is switched on and off by an internal
thermostat. On the Firebird model in use in Charleville, there is a separate thermostat
that controls a three-pin socket, into which the burner is plugged directly (see figure
5.3.4.2).
115
Fig. 5.3.4.2. New mounting flange & electrical supply
Fig. 5.3.4.3. Fuel supply lines
116
Performance using 25% RVO
For a period of 4 months, the burner ran successfully at the test site in Charleville.
The only attention the system required was after approx. a month when some
readjusting of its parameters were necessary as it was noted the burner was producing
higher CO and lower CO2 emissions than at the beginning of the trial.
Test Fuel
25% RVO - 75% HHO
Emissions
CO (ppm)
O2 (%)
2
0
15
8
10
6
4
CO (%)
12.5
Gas Temperature
C
162
o
Burner Settings
Pump pressure (bar)
Air damper (units 0 - 10)
Dist inside boiler (mm):
Nozzle Specification
Danfoss 0,50 US Gal 60oS
Table 5.3.4.2: Performance on trial site using 25% RVO
The drift in performance was thought to be due to a separation in the fuel tank
between the different density fuels (table 5.3.4.4 shows the density difference between
home heating oil and RVO). The fuel used at the start of the trial (i.e. that at the
bottom of the IBC) may have contained greater than 25% RVO, and this percentage
may have changed over time.
The only further attention the system required was the repair of a seal on one of the
IBC’s which had been incorrectly installed and had developed a small leak.
System Failure
After approximately 4 months of running on the 25% fuel blend, the burner stopped
operating. Upon inspection of the system, it was found that the fuel pump had seized
to the point where it had become difficult to rotate its shaft by hand. The pump was
dismantled and inspected and its internal filter was seen to contain a negligible
volume of dirt particles (see figure 5.3.4.9), certainly not enough to stop fuel flow.
117
The front plate from the gear section of the pump was removed and the gears
inspected (see figure 5.3.4.4); there appeared to be no large solid particles or
blockages between the pump gears that might stop them from rotating. The gear
wheels were then lubricated and this was seen to free up the shaft to a sufficient level
whereby it could be rotated easily by hand once more. This suggests that either
minute particles of dirt or insufficient lubricity due to the higher viscosity fuel blend
caused the fuel pump to seize (table 5.3.4.4 outlines the viscosity difference between
RVO and home heating oil).
Another interpretation could be linked to the characteristics and composition of the
RVO. Burners in real site condition are running according to a thermostat. Periods of
no combustion can be long enough for the fuel pump to cool down. Thermo-chemical
reactions, eg polymerisation can occur and cause a blockage of the small internal
valve. If the pressure is not sufficient the control command system of the burner
switches off the installation. This has to be investigated and verified. But it has to be
noted that the fatty acid analysis shows the presence of linolenic acid (C18:3), which
is not the case for rape seed oil or sunflower oil (see table below) which were
successfully tested before in industrial burners.
Fatty Acid
GC Analysis
Treated
RVO (%)
Untreated
RVO (%)
Rape seed oil
C12 : 0
Sunflower oil
0.1
C14 : 0
1.25
0.3
C16 : 0
7.38
10.61
C16 : 1
1.61
0.88
C18 : 0
2.75
C18 : 1
0.14
6.40
6.1
4.73
4.40
4.2
58.09
49.83
18.80
26.9
C18 : 2
23.22
28.9
68.90
61.4
C18 : 3
5.69
4.74
0.20
-
C20 : 1
0.20
0.3
C22 : 0
0.67
0.7
Table 5.3.4.3. Fatty Acid Distribution of Rape seed oil, Sunflower seed oil and RVO
118
Fig. 5.3.4.4. Close-up of seized fuel pump
Having experienced a number of difficulties both in the repair and use of the French
Cuenod burner in Ireland, it was decided to continue the tests using a burner which
could be easily sourced in Ireland. An Ecoflam Minor 1 burner was used for the
remainder of the experiments; it was of a similar output to the Cuenod and also had a
pre-heater fitted. Note: an attempt had been made to fit a new pump to the Cuenod
burner while in Ireland, however, differences in the diameter and position of fuel
pipes and differences in the diameters of the valve actuators (situated on top of the
fuel pump) made this task impractical.
119
5.3.4.3. Characteristics of test fuels
Samples of the fuels used during the experiments at CIRAD were taken and sent to
ETS18 laboratories for testing. Two samples of RVO were taken; a liquid sample from
the top of the IBC, and a semi-solid sample from the bottom of the IBC. It was
necessary to drain off a small volume of water from the bottom of the IBC before a
sample could be taken.
Analysis
Norme
HHO
RVO (l)
RVO (s)
Volumetric Mass
Calculated Cetane Index
Lower Calorific Value
Viscosity Kinematic 40°
NF EN ISO 12185/96
NF EN ISO 4264/97
NF M07030/96
837.8
50.4
n/a
921.7
31
36.735
921
33.1
36.45
NF EN ISO 3104/96
2.739
41.68
41.49
Cold Filter Plugging Point
EN 116/96
-16
too viscous
too viscous
Sunflower
Units
3
kg/m
926.2
n/a
Quotation
would not ignite MJ/kg
2
mm .s-1
36.25
too viscous
o
C
HHO = home heating oil
RVO (l) = liquid at room temp.
RVO (s) = solid at room temp.
Table 5.3.4.4: Characteristics of Test Fuels
5.3.4.4. Ecoflam Minor 1 - Tests conducted at Cirad, Montpellier.
A manual describing the Ecoflam burner is included in the appendix. The Ecoflam
was wired into the control unit of the test bench boiler, the circuit was similar to the
circuit used in the boiler in Charleville, except that the test bench system used two
safety cut-outs. It should also be noted that unlike with the previous Cuenod test
burner, the Ecoflam had a rigid flame stabiliser, limiting the optimisation procedure.
Performance using 100% home heating oil
The Ecoflam burner was mounted on the same test bench as used during the previous
tests with the Cuenod, and in its standard form was optimised using 100% home
heating oil.
18
Expertises Technologies & Services – Mont Saint Aignan - France
120
The burner’s heating performance and emissions levels were monitored and recorded.
It was noted that the oxygen level was slightly higher than required, and this was
thought to be linked to an incompletely sealed burner mounting (allowing the ingress
of excess oxygen into the combustion chamber). The burner mounting on the test
bench at CIRAD was designed for a Cuenod burner, and therefore a new flange was
made which had the effect of reducing O2 emissions.
It was noted that the burner would operate intermittently; running for approximately
30 seconds, stopping and beginning again without any operator input. The burner
would continue running in this fashion with the running times in between stops
increasing. This made it difficult to obtain stable combustion and hence have accurate
emissions readings. The problem was due to the fact that the power for the burner was
wired via a thermostat housed in the nozzle preheater (see A in figure 5.3.4.5). This
resulted in the preheater running continuously, but there was no longer a problem with
the burner running intermittently.
Fig. 5.3.4.5 Modification of control wiring for nozzle preheater
The burner would start its sequence, the preheater would heat up and combustion
would begin. However, as cold fuel was drawn through the nozzle, the inbuilt
thermostat would begin to cool and once it fell below its preset temperature, it would
cut power to the burner, stopping the sequence. To avoid this, the thermostat in the
nozzle pre-heater was wired out of the circuit (see B in figure 5.3.4.5), this rewiring
was carried out in the Landis & Gyr control box (type: LOA21.171B17).
121
Modifications to use fuel blends containing >50% RVO - Additional Equipment
Previous tests conducted using the Cuenod NC4 burner highlighted not only the need
for increased injection pressure, but also fuel preheating if blends of vegetable oil
greater than 50% were to be reliably used in an atomising burner. To achieve this, a
Heizbösch L-10-CR preheater was fitted to the system and the fuel supply line was
modified by the addition of a second electro valve.
Fig. 5.3.4.6. Ecoflam fuel circuit
The control circuit works in the following way: when the boiler is switched on, the
large fuel preheater begins to heat and once it reaches the pre-set temperature, the
burner sequence starts as per the original circuit. The signal from the original valve
(1) (situated on top of the fuel pump), is used to control the second electro-valve (2):
thus when the small preheater at the nozzle reaches 60 oC, valve (1) and also valve (2)
open directing fuel flow to the nozzle. When the water temperature in the boiler
reaches its desired level, the burner shuts down, both valves close and the flow of oil
to the nozzle is stopped.
The second electro-valve (2) was necessary to avoid unburnt oil dripping from the
nozzle after shutdown (the installation of the fuel preheater had resulted in their being
a substantial volume of pressurised fuel between the original cut-off valve and the
122
nozzle; without an extra valve this fuel would leak into the boiler once the flame had
stopped, raising emissions and leaving some unburnt fuel at the bottom of the
combustion chamber).
Although there is a small volume of fuel contained in the fuel line between the large
fuel heater and the nozzle which will not get properly preheated, it was calculated that
after approximately 1second this cold oil would be replaced by hot oil during the
injection process, and therefore there wouldn’t be any problems during start-up.
Fig. 5.3.4.7. Ecoflam burner on test bench at CIRAD
123
Fig. 5.3.4.8. Modified fuel line and nozzle assembly
5.3.4.5. Results
Performance using 100% mineral home heating oil
Test Fuel
Emissions
CO (ppm)
2
O (%)
2
CO (%)
Consumption
(kg/h)
Burner Settings
Pump pressure (bar)
40
6.1
10.9
Water Pump Setting
1, 2, 3
3
Flow - m /h
1
0.333
1.33
10
0.4
Blast Tube (dist. visible mm) 10
o
Danfoss 0,50 US Gal 60 S
Boiler Water Temperature
C
58
o
Water Pressure
Bar
1
Delta T
C
36.3
o
Ambient temperature
C
* analyser near boiler
o
17*
Table 5.3.4.5: Optimised performance of Ecoflam burner using 100% HHO
124
Performance of modified burner using 50% RVO
Test Fuel
50% recycled vegetable oil
Emissions
CO (ppm)
2
O (%)
53
C
n/a
o
4
2
CO (%)
12.5
Consumption
(kg/h)
Water Pump Setting
1, 2, 3
3
Flow - m /h
2
0.6037
2.71
Burner Settings
Pump pressure (bar)
14
5.5
o
o
Heizbösch setting ( C)
Water Pressure
Bar
1
Delta T
C
40.36
o
Ambient temperature
C
o
16.9
80
o
Fuel Pipe temperature ( C) 52
Table 5.3.4.6: Optimised performance of Ecoflam burner using 50% RVO
125
Performance of modified burner using 100% RVO
Test Fuel
100% recycled vegetable oil
Emissions
CO (ppm)
2
O (%)
54
C
58
o
3.3
2
CO (%)
13
Consumption
(kg/h)
Water Pump Setting
1, 2, 3
3
Flow - m /h
1
0.587
3.55
Burner Settings
Pump pressure (bar)
23
6.5
o
o
Heizbösch setting ( C)
Water Pressure
Bar
1
Delta T
C
44.92
o
Ambient temperature
C
o
13.3
150
o
Fuel Pipe temperature ( C) 86
Table 5.3.4.7: Optimised performance of Ecoflam burner using 100% RVO
As can be seen from tables 5.3.4.6 and 5.3.4.7, the modified burner ran successfully
on both 50% RVO and 100% RVO.
CO emissions for both the 50% and 100% RVO fuels were higher than for 100%
HHO. However, the HHO emissions contained a greater amount of excess air which
would dilute the CO emissions.
Although the 100% RVO fuel required the Heizbösch fuel heater to be set to its
maximum heating level (150 oC), a thermocouple on the fuel line after the heater
showed there was some loss in temperature after the heater, so the actual fuel
injection temperature would have been lower than 150 oC.
126
With the Heizbösch fuel heater to be set to its maximum heating level, the required
injection pressure was found to be 23 bar, which was lower than previously found by
Vaitilingom et al on an industrial scale boiler.
5.3.4.6. Conclusions
With the addition of a fuel preheater, and by increasing the injection pressure, it is
possible to use 100% RVO in a home heating burner over a short period of time.
Longer-term tests would be needed to ascertain the reliability of the system
(particularly during the start-up phase).
The possible influence of RVO minor chemical components on the durability of the
fuel pump must be verified.
The extra cost involved in modifying a burner to use 100% RVO must be looked at in
more detail.
There was a difference in the Calculated Cetane Index between the solid and liquid
RVO fractions. Further testing of combustion performance between different types of
RVO is required.
127
References
Bolton RVO Ltd. (Vegetable Oil Recycling Company, Ireland) 2002
IEA Energy and Taxes, 1st Quarter 2001 (ISBN 92-64-19069-4)
Project Interim Report, Altener contract no. 4.1030/C/00-014
Vaitilingom, G., Perilhon, C., Liennard, A., Gandon, M., 1998. Development of rape
seed oil burners for drying and heating. Industrial Crops and Products 7 (1998) 273279
128
Appendix
Fig. 5.3.4.9. Close-up of seized pump & filter
Ecoflam Oil Burner manual (edited)
Models: Minor 1 BR ST and Minor 1 M (578)BR ST
129
130
131
5.4
Modified Vehicle Chassis Dynamometer Test : Pilot Study
5.4.1 Introduction
The use of neat vegetable oils as fuel for Diesel engines requires either a purpose built
engine or a conventional engine modified to cater for greater viscosities normally
encountered with vegetable oils compared with mineral diesel fuel. Diesel engines
driving a generator of the type found in combined heat and power applications do not
lend themselves to power or emissions measurements at speeds other than their rated
speed, so a vehicle was used to determine performance and emissions characteristics
for neat RVO over a range of engine speeds.
A 2.4 litre indirect injection naturally aspirated Toyota Dyna fitted with a modified
‘Biocar kit’ which essentially heats the fuel from the the engine cooling system and
subsequently modified by the addition of a Parker Industries electrically heated fuel
filter, was tested on a Sun Roadamatic chassis dynamometer. Exhaust emissions of
CO, CO2, NO and O2 were measured using an IMR 2800P electrochemical gas
analyser in conjunction with a heated intake and a Hartridge MK 3 smokemeter was
used to determine exhaust opacity. See Figs 5.4.1, 5.4.2, 5.4.3 and 5.4.4.
Neat RVO was used as a fuel when using the modified fuel system and this was
compared to mineral diesel fuel in the same vehicle but using the conventional fuel
system.
All results were obtained using 4th gear.
132
Fig. 5.4.1 Vehicle on chassis dynamometer
Fig. 5.4.2 Heated Fuel Line and Filter
133
Fig. 5.4.3 Control and Display Unit for Multifuel Conversion
Fig. 5.4.4 Sampling Tail Pipe Emissions
134
It should be noted that the following results that are presented are typical of the
small number of preliminary tests that have been performed so far and as such are
considered to be a pilot study only. To date no statistical analysis has been
performed on the data.
Power
The power produced by the vehicle over its full range of engine speed while
running on neat RVO using the modified fuel system was compared the power
produced by mineral diesel fuel. It can be seen that the two fuels produced similar
results up to approxiamately 3000 rpm, at higher engine speeds the mineral fuel
produced higher power as can be seen in Fig. 5.4.6.
Power Vs Engine Speed
Power (KW)
40
30
Diesel
20
RVO
10
0
0
1000
2000
3000
4000
5000
6000
Engine Speed (RPM)
Fig. 5.4.6 Power Vs Engine Speed for RVO and Mineral Diesel Fuel
135
Tail Pipe Emissions.
CO
As can be seen from Fig 5.4.7 the CO emitted from the vehicle while running on
RVO was lower for almost all the speed range of the engine than for the vehicle while
running on mineral diesel fuel this particularly pronounced in the speed range 4000 –
5000 rpm.
CO Vs Engine Speed
12000
CO (ppm)
10000
8000
Diesel
6000
RVO
4000
2000
0
0
1000
2000
3000
4000
5000
6000
Engine Speed (RPM)
Fig. 5.4.7 CO Vs Engine Speed for RVO and Mineral Diesel Fuel
136
CO2 Vs Engine Speed
16
14
CO2 (%)
12
10
Diesel
8
RVO
6
4
2
0
0
1000
2000
3000
4000
5000
6000
Engine Speed (RPM)
Fig 5.4.8 CO2 Vs Engine Speed for RVO and Mineral Diesel Fuel
CO2
It can be from Fig 5.4.8 that the production of CO2 for both fuels was similar over the
entire speed range of the vehicle except for the very highest speed when RVO emitted
a little over half the CO2 of mineral diesel fuel.
137
NO Vs Engine Speed
300
NO (ppm)
250
200
Diesel
150
RVO
100
50
0
0
1000
2000
3000
4000
5000
6000
Engine Speed (RPM)
Fig 5.4.9 NO Vs Engine Speed for RVO and Mineral Diesel Fuel
NO2 Vs Engine Speed
14
NO2 (ppm)
12
10
8
Diesel
RVO
6
4
2
0
0
1000
2000
3000
4000
5000
6000
Engine Speed (RPM)
Fig 5.4.10 NO2 Vs Engine Speed for RVO and Mineral Diesel Fuel
NO and NO2
As can be seen from Figs 5.4.9 and 5.4.10 both NO and NO2 emissions from the
vehicle were similar when running on both RVO and Mineral Diesel Fuel except at
the very highest engine speed when RVO produced the lowest NO and NO2.
138
O2 Vs Engine Speed
12
CO2 (%)
10
8
Diesel
6
RVO
4
2
0
0
1000
2000
3000
4000
5000
6000
Engine Speed (RPM)
Fig 5.4.11 O2 Vs Engine Speed for RVO and Mineral Diesel Fuel
O2
From Fig. 5.4.11 it can be seen that the O2 produced by the vehicle when running on
RVO was similar to when running on mineral diesel fuel, except for the very highest
engine speed when RVO produced more.
139
Smoke Vs Engine Speed
Smoke (HSU)
100
80
60
Diesel
RVO
40
20
0
0
1000
2000
3000
4000
5000
6000
Engine Speed (RPM)
Fig 5.4.12 Smoke Vs Engine Speed for RVO and Mineral Diesel Fuel
Smoke
The smoke produced by the vehicle when running on RVO was much lower than
when running on mineral diesel fuel at engine speeds greater than approxiamately
1400 rpm. As can be seen from Fig. 5.4.12.
140
5.5
Modified Engine in Vehicle Chassis Dynamometer Test Main Study
5.5.1 Introduction
The main study involved further testing of the vehicle described in section 5.4. Each
run was conducted in random order and repeated 5 times, to enable a statistical
analysis of the data and the resulting 95% confidence limits are shown on each graph.
Initial tests carried out using RVO showed that power and tractive effort were similar
to that of mineral diesel fuel up to speeds of 3500 rpm. However during the testing the
maximum power produced from mineral diesel fuel dropped from 41 to 36.5 KW and
the maximum power produced from RVO dropped from 37 to 34 KW. The decrease
in power was found to be as a result of a build up of carbon on the fuel injector tips.
The injectors were then replaced with fresh injectors and the tests repeated. The
results from the second series of tests are used to compare the performance and
tailpipe emissions while running on mineral diesel fuel and RVO.
141
5.5.2 Results
Power and Tractive Effort
Power (KW)
Power Vs Engine Speed
45
40
35
30
25
20
15
10
5
0
Diesel
RVO
0
1000
2000
3000
4000
5000
6000
Engine Speed (rpm)
Fig 5.5.1
Tractive Effort Vs Engine Speed
Tractive Effort (KN)
2.5
2
1.5
Diesel
RVO
1
0.5
0
0
1000
2000
3000
4000
5000
6000
Engine Speed (rpm)
Fig 5.5.2
142
Tail Pipe Emissions
CO2 Vs Engine Speed
20
CO2 (%)
15
10
Diesel
RVO
5
0
0
1000
2000
3000
4000
5000
6000
-5
Engine Speed (rpm)
Fig 5.5.3
CO Vs Engine Speed
25000
CO (ppm)
20000
15000
Diesel
10000
RVO
5000
0
-5000
0
1000
2000
3000
4000
5000
6000
Engine Speed (rpm)
Fig 5.5.4
143
SO2 Vs Engine Speed
100
SO2 (ppm)
80
60
Diesel
40
RVO
20
0
-20
0
1000
2000
3000
4000
5000
6000
Engine Speed (rpm)
Fig 5.5.5
NO Vs Engine Speed
300
250
NO (ppm)
200
150
Diesel
100
RVO
50
0
-50 0
1000
2000
3000
4000
5000
6000
Engine Speed (rpm)
Fig 5.5.6
144
O2 Vs Engine Speed
25
20
O2 (%)
15
Diesel
10
RVO
5
0
-5
0
1000
2000
3000
4000
5000
6000
Engine Speed (rpm)
Fig 5.5.7
145
Smoke Opacity Vs Engine Speed
Smoke Opacity (HSU)
120
100
80
60
Diesel
40
RVO
20
0
-20 0
1000
2000
3000
4000
5000
6000
Engine Speed (rpm)
Fig 5.5.8
5.5.3 Discussion
Power and Tractive Effort
Power and tractive effort were found to be consistently lower while using RVO as
shown in fig 5.5.1 and 5.5.2. The percentage drop in power ranged between 4 and
30% with higher power losses at higher engine speeds.
While measuring the power and tractive effort while running on RVO it was noted
that the readings fluctuated. It was found that running the van at the required speed for
a minute and then applying the load reduced the amount of fluctuation significantly.
146
Emissions
Emissions were measured using an IMR 2800 P gas analyser and a Hartridge MK3
smoke meter.
Fig 5.5.3 shows that the mean carbon dioxide emitted from RVO is 45% less than that
emitted from mineral diesel fuel. This decrease is seen at all engine speeds. The
reduction in carbon dioxide is greater than reductions reported in literature. Barsic et
al (1992) notes similar carbon dioxide emissions between sunflower oil, peanut oil
and mineral diesel fuel.
RVO was found to produce 66% less carbon monoxide compared to mineral diesel
fuel. This is shown in fig 5.5.4. This decrease is particularly significant at speeds
between 4000 and 5000 rpm where carbon monoxide is up to 82% less than that from
mineral diesel fuel. This seems to contradict literature as vegetable oil is reported to
produce as much as twice the amount that is produced from mineral diesel fuel
(Barsic et al, 1982). However it must be taken into account that this is at equal energy
delivery. The decrease in carbon monoxide is considered to be mainly due to the
higher percentage of oxygen present during combustion indicated by a higher
percentage of oxygen present in RVO exhaust gas emissions (see fig 5.5.7).
Up to three and a half times as much sulphur was present in RVO exhaust gas
compared to mineral diesel (see fig 5.5.5). but this was not expected and contradicts
the literature. The most likely cause of this is lubricating oil leaking into the fuel
through worn piston seals causing an increase in sulphur dioxide emissions, though
why this should be higher with RVO than mineral diesel fuel is not clear.
147
Fig 5.5.8 shows that the smoke opacity from RVO was lower than that from mineral
diesel fuel particularly at speeds greater 2500 rpm. Condon (1993) also reports a
lower smoke opacity from vegetable oils as a direct effect of a reduction in carbon
dioxide levels and a dilution effect of the excess oxygen present in vegetable oils. A
lower smoke opacity indicates less un-burnt fuel present in the exhaust gasses.
The level of precision in the results for exhaust gas emissions is considerably lower
than the precision for power, tractive effort and smoke opacity results. The reason for
the low precision is not clear and further testing is required to investigate the cause of
this.
148
5.5.4
•
Conclusions
RVO produces less power than mineral diesel fuel especially at higher engine
speeds.
•
There is a difference of 4.75 KW in the maximum power produced by both fuels
at 90 km/hr, which is significant at the 5% confidence level.
•
Emissions of smoke, carbon monoxide and carbon dioxide were lower from RVO
compared to mineral diesel fuel.
References
Barsic, N.J. and Humke, A.L. (1982) “Performance and Emissions Characteristics of
a Naturally Aspirated Diesel Engine with Vegetable Oil Fuels”, Society of Automotive
Engineers.
Condon, S. (1993) “A Comparison of the Characteristics of Two Types of
Compression Ignition Engine when Running on Rape Seed Oil and Diesel”, Final
Year Project, University of Limerick.
149
5.6
Fuel Injector Fouling
5.6.1 Introduction
The four pintle-type injector nozzles were replaced at the start of the RVO trials.
However during the testing the maximum power produced from RVO dropped from
37 to 34KW and the maximum power produced from mineral diesel fuel dropped
from 41 to 36.5KW. This decrease in power was found to be as a result of injector
fouling.
Injector fouling/coking is the build up of unburned or residual carbon on the fuel
injector nozzles of an engine. It is caused by incomplete combustion of the fuel
leading to deposits of either carbon residue or soot particles around valve ports, piston
rings and injector nozzles.
Before installing new injectors, the airflow through each injector was measured in
order to establish a baseline for the build-up of carbon on the injector tips. The
injectors were then re-measured after 430km to assess the build up of carbon on the
injector tips.
A test rig was set-up in accordance with ISO 4010 to measure the reduction in airflow
through injectors as a result of the build-up of carbon on the injector tips. The nozzle
was placed in a holder and surrounded by a rubber boot. The rubber boot was
connected to a 1.5m long copper pipe (diameter 3.4 × 10-3 m) and the injector was
connected to a vacuum pump. All connections were made using flexible tubing and
joints were sealed using petroleum jelly. A pressure drop of 0.6 bar across the nozzle
was maintained at all times to ensure the flow through the nozzle was choked and
dependent only on the nozzle area of flow. The area of flow was varied by lifting the
needle from its seat in increments of 0.1mm using a threaded screw on top of the dial
gauge. The pressure drop across the pipe was measured at each 0.1mm increment
using a water manometer. The test rig used is shown in fig 5.6.1.
150
Fig 5.6.1. Injector fouling rig.
151
Results
Needle Lift Vs Flowrate Injector 1
Flowrate (cm3/s)
0.025
0.02
0.015
New
After 430 km
0.01
0.005
0
0
0.5
1
1.5
2
Needle Lift (mm)
Fig 5.6.2. Air flow rate through RVO injector # 1.
Needle Lift Vs Flowrate
Flowrate (cm 3/s)
0.025
0.02
0.015
New
After 430 km
0.01
0.005
0
0
0.5
1
1.5
2
Needle Lift (mm)
Fig 5.6.3 Air flow rate through RVO injector # 2.
152
Needle Lift Vs Flowrate
Flowrate (cm 3/s)
0.025
0.02
0.015
New
After 430 km
0.01
0.005
0
0
0.5
1
1.5
2
Needle Lift (mm)
Fig 5.6.4. Air flow rate through RVO injector # 3.
Reduction in Airflow Rate (%)
% Reduction in Airflow Rate Vs Needle Lift
120%
100%
80%
Injector 1
Injector 2
Injector 3
60%
40%
20%
0%
0
0.5
1
1.5
2
Needle Lift (mm)
Fig 5.6.5. Reduction in air flow rate through injector nozzles due to RVO
after 430km.
153
Discussion
A test method involving the use of a test rig specified by ISO 4010 was used to
quantify the build up of carbon on the fuel injector tips. This involved measuring the
airflow through the injector for different needle positions allowing comparisons to be
made between the new and fouled injectors.
After initial fouling was discovered all four injectors were replaced with fresh
injectors and the airflow was measured through each injector. The airflow was
measured again after the van had completed 430 km on RVO. The Reynolds number
was calculated to be less than 2000 for each needle increment to verify laminar flow.
The results of the airflow test are shown in fig 5.6.2 to fig 5.6.5. The results for the
fourth injector are not shown as the needle was found to have seized inside the
injector. This is thought to be as a result of the engine overheating due to a heating
coil that was installed on the van. Figs 5.6.2 to 5.6.4 show a decrease in the amount
of airflow through each injector after 430 km due to the build up of carbon on the
injector tips. Fig 5.6.5 shows the percentage reduction in airflow due to coking. The
greatest reduction in airflow is seen at lower needle lifts. A needle lift of 0.1mm is
needed in order for air to flow through clean injectors, however this is increased to
0.5mm through coked injectors.
Although the quantity of fuel injected is determined by the fuel pump and not the
condition of the injectors, the fuel spray pattern will be affected. Further work is
required to determine the effect the carbon coking has on the fuel spray pattern.
154
The carbon deposits on the injector tips required moderate scraping for removal
similar to that found by Barsic et al (1982). This increased the airflow through the
injectors but not to their original value.
Conclusions
•
Injector coking due to RVO decreased the airflow through pintle type injector
nozzles by approxiamately 40% after 430 km running on RVO.
•
Carbon deposits required moderate scraping for removal.
Recommendations for Future Work
Injector coking was found to decrease the airflow rate through the nozzles after 430
km however further testing after several thousand kilometres have been completed on
RVO would prove useful to investigate the build up of carbon over a longer period of
time. Further testing is also required to find the relationship between the reduction in
airflow through the nozzle and the quality of the fuel spray.
155
5.7
Effect of changing injection timing and injection pressure upon exhaust
emissions and fuel consumption from a 4-cylinder diesel engine operating on
25% RVO/75% mineral fuel.
5.7.1 Introduction
The use of waste cooking oil methyl-esters in CI engines has been documented (Nye
et al, 1983, Howard-Hildige and Leahy 1999, Mohamad et al, 2002). Filtered waste
cooking oil is a cheaper fuel than esterified oil but its increased viscosity, low
volatility and poor cold flow properties can result in difficulties when using it in a CI
engine.
A fuel blend containing 25% RVO was prepared and used to fuel a 1.5 litre Indirect
injection 4 cylinder Tempest diesel engine mounted on a Cussens test bed. An IMR
exhaust gas analyser was used to measure levels of CO2, O2, CO, SO2, NO2, NO, and
lambda (the ratio of the volume of air to the volume of air theoretically required).
Fuel
The RVO had been steam treated and passed through a 250 micron filter. Although
batches of RVO can vary depending on the material being recycled, tests by ETS on
the solid and liquid fractions of RVO indicate clearly show it’s lower calorific value,
higher viscosity and higher density (see appendix). The mineral diesel fuel was
TEXACO road vehicle fuel (DERV), complying with EN 590: 1999.(see appendix).
5.7.2
Apparatus
The engine used for the experiment was a 4-cylinder, 1.5l Tempest indirect-injection
compression ignition engine. The engine was mounted on a Cussons Automotive 30
test bed and was coupled to a D.C. dynamometer.
156
Fig.5.7.1 Cussons test bed
Fig.5.7.2 Exhaust sampling point
157
5.7.3 Close up of rotary DPA fuel injection pump
Procedure
The engine was started and run under a light load for 30 minutes to reach operating
temperature, after which all the data were gathered after 5 minutes at full load
conditions. The engine was tested in its standard injection timing and pressure (130
bar) while using both 25% RVO/mineral fuel (25%R) and mineral diesel fuel (D). The
IMR was used to sample the exhaust gases and the burette on the test bench was used
with a stopwatch to monitor fuel consumption. Engine speed was recorded with an
Ono Sokki Digital Tachometer. 1mm of travel of the baseplate of the pump equates to
a change in an injection timing of 2 degrees crank angle - the injection timing was
retarded by rotating the pump 2mm anti-clockwise (hence giving a timing retardation
of 4 degrees crank angle). Following this, the timing was advanced 4 degrees crank
angle and the results noted.
Fig.5.7.4 Plate indicating direction of pump rotation
158
The final test in the series involved the removal of all four injectors and the
adjustment of the injector springs to adjust the injection pressure. A Hartridge Poptester was used; the injector breaking pressure was changed from the original pressure
of 140 bar (LP) to an elevated pressure of 160 bar (HP), the injectors were replaced
and both fuels were tested.
Fig.5.7.5 Hartridge Pop tester and fuel injector
159
5.7.3 Results
Variation of Fuel Injection Pressure
CO2 (%)
IMR CO2 (%)
9
8.5
8
7.5
7
6.5
6
5.5
5
4.5
4
1000
D
(H.P.)
25%R
(H.P.)
D
(L.P.)
25%R
(L.P.)
1500
2000
2500
3000
RPM
Figure 5.7.7 CO2 Vs Engine Speed
O2 (%)
IMR O2 (%)
15
14.5
14
13.5
13
12.5
12
11.5
11
10.5
10
9.5
9
1000
D
(H.P.)
25%R
(H.P.)
D
(L.P.)
25%R
(L.P.)
1500
2000
2500
3000
RPM
Figure 5.7.8 O2 Vs Engine speed
160
IMR CO (ppm)
700
D
(H.P.)
600
CO (ppm)
500
25%R
(H.P.)
400
300
D
(L.P.)
200
25%R
(L.P.)
100
0
1000
1500
2000
2500
3000
RPM
Figure 5.7.9 CO Vs Engine speed
IMR NO (ppm)
500
D
(H.P.)
450
NO (ppm)
400
25%R
(H.P.)
350
D
(L.P.)
300
250
25%R
(L.P.)
200
150
1000
1500
2000
2500
3000
RPM
Figure 5.7.10 NO Vs Engine Speed
161
IMR NO2 (ppm)
40
35
D
(H.P.)
NO2 (ppm)
30
25%R
(H.P.)
25
20
D
(L.P.)
15
25%R
(L.P.)
10
1000
1500
2000
2500
3000
RPM
Figure 5.7.11 NO2 Vs Engine Speed
162
Fuel Consumption (kg/hr)
Pressure Tests - Fuel Consumption (kg/hr)
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
1000
D
(H.P.)
25%R
(H.P.)
D
(L.P.)
25%R
(L.P.)
1500
2000
2500
3000
RPM
Figure 5.7.12 Fuel Consumption Vs Engine Speed
Variation of Injection Timing
CO2 (%)
IMR CO2 (%)
9
8.5
8
7.5
7
6.5
6
5.5
5
4.5
4
1000
D
(ret.)
25%R
(ret.)
D
(adv.)
25%R
(adv.)
D
(std.)
25%R
(std.)
1500
2000
2500
3000
RPM
Figure 5.7.13 CO2 Vs Engine Speed
163
O2 (%)
IMR O2 (%)
15
14.5
14
13.5
13
12.5
12
11.5
11
10.5
10
9.5
9
1000
D (ret.)
25%R
(ret.)
D
(adv.)
25%R
(adv.)
D (std.)
25%R
(std.)
1500
2000
2500
3000
RPM
Figure 5.7.14 O2 Vs Engine Speed
CO (ppm)
IMR CO (ppm)
700
650
600
550
500
450
400
350
300
250
200
150
100
50
0
1000
D (ret.)
25%R
(ret.)
D
(adv.)
25%R
(adv.)
D
(std.)
25%R
(std.)
1500
2000
2500
3000
RPM
Figure 5.7.15 CO Vs Engine Speed
164
IMR NO (ppm)
D (ret.)
NO (ppm)
500
450
25%R
(ret.)
400
D
(adv.)
350
25%R
(adv.)
300
250
D
(std.)
200
25%R
(std.)
150
1000
1500
2000
2500
3000
RPM
Figure 5.7.16 NO Vs Engine Speed
IMR NO2 (ppm)
40
D
(ret.)
25%R
(ret.)
D
(adv.)
25%R
(adv.)
D
(std.)
25%R
(std.)
NO2 (ppm)
35
30
25
20
15
10
1000
1500
2000
2500
3000
RPM
Figure 5.7.17 NO2 Vs Engine Speed
165
Timing Tests - Fuel Consumption
Fuel Consumption (kg/hr)
6
D
(ret.)
25%R
(ret.)
D
(adv.)
25%R
(adv.)
D
(std.)
25%R
(std.)
5
4
3
2
1
0
1000
1500
2000
2500
3000
RPM
Figure 5.7.18 Fuel Consumption Vs Engine Speed
M ineral D iesel Fuel and R .V .O. Pow er (kW )
Po wer (kW)
18
16
14
12
10
8
D
(H.P.)
6
4
2
0
1000
25% R
(H.P.)
1500
2000
2 500
3000
RPM
Figure 5.7.19 Power Vs Engine Speed
166
5.7.4 Discussion
Variation of fuel injection pressure
Exhaust Emissions
CO2
Figure 5.7.7 shows that the 25% RVO blend (25%R) injected at low pressure (130
bar)(LP) produces the greatest amount of CO2 at engine speeds greater than approx
1700 RPM , this likely to be due to the higher fuel consumption occurring with this
fuel (see figure 5.7.12) than improvement of combustion. It is interesting to note that
at low pressure for both 25%R and mineral fuel (D) at low engine speed produces a
decrease of CO2 with increase of engine speed up to 1500-1700 RPM, followed by a
rapid increase than remains relatively constant above 2000-2300 RPM, as opposed to
the relatively steady increase of CO2 with engine speed for the fuels injected at 160
bar (HP). These results suggest that further work be done to clarify the cause of this
effect.
O2
O2 emitted (see figure 5.7.8) is the inverse trend of the CO2 for both fuels and fuel
injection pressures.
CO
CO produced by 25%R(LP) (see figure 5.7.9) is the largest for all engine speeds, up to
approx twice that produced by the other fuel/injection pressure tests, this suggests
that high CO emissions of 25%R can be controlled easily by increasing fuel injection
pressure. Also improvement of (D) emissions can be obtained, particularly at low
engine speeds.
NO
25%R at (HP) produces the greatest NO particularly at low engine speeds (see figure
5.7.10), this is expected due to the high indigenous oxygen content of vegetable oils
raising combustion temperatures. This also suggests that (HP) gives more complete
combustion, probably due to improved atomisation over (LP).
NO2
Similarly to NO, more NO2 is produced with 25%R at (HP) (see figure 5.7.11).
Fuel Consumption
167
25%R at (LP) gives the highest fuel consumption, as expected from exhaust
emissions, the other fuel/injection pressure combinations giving similar results (see
figure 5.7.12).
Effect of variation of injection timing
CO2
The standard timing curves show the same decrease in CO2 at engine speeds up to
1500-1700 RPM, then rapid increase, to become relatively constant above 2000-2300
RPM as in the variation with (LP) injection as this series of tests was conducted at the
standard injection pressure of 130 bar (ie LP)(see figure 5.7.13). The other injector
pressure settings showing remarkably similar CO2 emissions except for (D) at
advanced injection.
O2
The emissions of O2 from fuel/injection timing combinations from figure 5.7.14 have
as expected an inverse trend to the CO2 emissions.
CO
Except for the lowest engine speed of 25%R standard injection timing the CO
emissions all follow a similar trend of generally decreasing with increasing engine
speed. 25%R gives the highest emissions at all injection timings. Increasing the
advance of injection timing tends to reduce the CO emitted.
NO
Figure 5.7.16 shows that 25%R at advanced injection gives the highest NO emissions
at engine speeds above 1700RPM, except for this, both fuels perform similarly.
Generally, advancing the injection of the fuel produces higher NO, similarly to
previous emissions graphs, the NO emitted using standard injection timing is
relatively constant at low engine speeds, followed by a rapid rise at medium speeds to
become relatively constant at high speeds. Generally, the emissions of NO are similar
for both fuels, regardless of fuel injection timing.
NO2
From figure 5.7.17 it appears that advancing the injection of the fuel generally favours
the formation of NO2 and 25%R produces more at standard and advanced injection.
There is no clear effect of engine speed on NO2 emissions for the range of
fuel/injection advance combinations used in these tests.
168
Fuel Consumption
The fuel consumption does not appear to be a strong function of fuel injection
advance, but as expected increases steadily with engine speed at full load conditions.
Generally marginally more 25%R is consumed at any given engine speed at full load.
Note: A leak was found after the low pressure 4 degrees retarded timing tests which
would explain the abnormally high fuel consumption figures.
Power
Power developed vs engine speed at standard injection timing and 160bar injection
pressure for both fuels are shown in figure 5.7.19, it can be seen that both fuels
perform closely. It is not clear if maximum power had been achieved, and further
study is needed to determine the effects of fuel injection timing and pressure.
References
Humke, A.L. and Barsic, N.J. ‘Performance and Emissions Characteristics of a
Naturally Aspirated Diesel Engine with Vegetable Oil Fuels’ 0096-736X/82/90032925. Copyright 1982 Society of Automotive Engineers, Inc.
Mohamad I. A., Tashtoush, G. and Abu-Qudais, M. ‘Utilization of ethyl ester of waste
vegetable oils as fuel in diesel engines’. Fuel Processing Technology, Volume 76,
Issue 2, 20 May 2002, Pages 91-103
Nye, M. J., Williamson, T.W., Deshpande, S., Schrader, J.H., and Snively, W.H.
‘Conversion of Used Frying Oil to Diesel Fuel by Transesterification: Preliminary
Tests’ JAOCS, vol. 60, no. 8 (August 1983)
Peterson, C.L., and Hustrulid, T. ‘Carbon Cycle for Rapeseed Oil Biodiesel Fuels’
Biomass and Bioenergy, Vol. 14, No. 2, pp. 91 – 101, 1998
169
Howard-Hildige, R. and Leahy J.J.. (1999) ‘A trial of Esterified waste cooking oil as
a summer and winter fuel for vehicles and heating boilers, and investigation into the
feasibility of establishing a small scale processing plant’. Altener Contract
No.XVII/4.1030/Z?97-073.
170
Appendix
Properties of RVO and Winter grade Automotive Diesel
Analysis
Norme
RVO (l)
RVO (s)
Volumetric Mass
Calculated Cetane Index
Lower Calorific Value
NF EN ISO 12185/96
NF EN ISO 4264/97
NF M07030/96
921.7
31
36.735
921
33.1
36.45
Viscosity Kinematic
NF EN ISO 3104/96
41.68
41.49
Cold Filter Plugging Point
EN 116/96
too viscous too viscous
Aut. Diesel
min
max
820
46
845
2
4.5
-15
Units
kg/m3
Quotation
MJ/kg
mm2.s-1
o
C
Automotive diesel is considered winter grade (figures quoted from EN 590: 1999)
RVO (l) = liquid at room temp.
RVO (s) = solid at room temp.
171
5.8
Demonstration at Ecotopia 2002
5.8.1 Introduction
Ecotopia is a European Youth event which is held annually and has been in existence
for 14 years. It is a Summer Camp dedicated to Workshops and Presentations on a
wide range of Ecological and Environmental topics. Ecotopia 2002 was held in a 98
acre Broad Leaf Forest on the banks of Loch Derg near to Tuamagraney, Co. Clare,
Ireland from August 10 to August 24 2002. The Electrical Power for this event was
generated partially by manual means (person pedalled generators) and partially by a
6.5 kW diesel generator. This section describes the diesel engined power generation.
A 6.5 kW Yanmar Diesel Engine running on a 5% blend of RVO in mineral diesel
fuel was used to drive a 5 KVA , 240V ac generator as shown in Figures 5.8.1 and
5.8.2.
Figure 5.8.1 Yanmar 6.5 kW Diesel Generator
172
Figure 5.8.2 Yanmar Generator
The generator operated without any problems for the duration of the event without
any operating problems. No measurements were conducted of power consumed etc as
on site facilities did not permit this.
Conclusions
A 5% blend of RVO in mineral diesel fuel operated a generator at Ecotopia
satisfactorily.
173
6
Dissemination
As it was always intended to promote the public knowledge of this work. The results
of this work have been disseminated via the following media.
Project Brochure (see section 6.1) sent out to the following networks for further
dissemination.
FEDARENE
ISLENET
ENERGIE CITIES
National Radio – 2FM Gerry Ryan Show : Interview with Bernard Rice. February
2003.
Workshop – Ecotopia 2002 Workshop and presentation on the use of RVO as a fuel.
August 2002. (see section 6.2)
Seminar – Waste to Warmth : Biofuels from Waste. Lakeside Hotel,
Ballina/Killaloe. September 2002.
CD ROM – Altener Cluster No.4.1030/C/00.014. Waste to Warmth : Biofuels from
Waste. September 2002.
Technical papers (International and Global)
M.E. Gonzales Gomez, R. Howard-Hildige, J.J. Leahy and B. Rice. Winterisation of
Waste Cooking Oil Methyl Ester to improve low temperature fuel properties. Fuel
Vol. 2002.
B. Supple, M.E. Gonzales Gomez, R. Howard-Hildige and J.J. Leahy. Effect of steam
treatment on the yield of methyl ester from waste cooking oil. JAOCS Vol. 2002.
174
6.1
Project Brochure
175
176
6.2
Workshop at Ecotopia August 2002
Ecotopia is a participatory event which brings together people from all over Europe to
conduct and attend presentations and workshops on a wide range of social and
environmental topics. Ecotopia is coordinated by EYFA, a European-wide network
of young individuals and youth organizations, and has been held every year since
1989 at different locations all over Europe. Ecotopia 2002 was held on the banks of
Loch Derg, at Tuamagraney, Co.Clare, Ireland, from 10 – 24 August 2002. As part of
the dissemination activities of Altener Cluster No. 4.1030/C/00-014, a workshop on
the use of waste as a fuel was conducted. A demonstration of the use of
RVO/mineral oil blend as a diesel engine fuel was also conducted for the duration of
Ecotopia 2002 (see section 5.7).
6.2.1 Workshop
The workshop was held on the afternoon of 22 August, and a presentation on the use
of RVO as a fuel for diesel engines and heating was given by Adrian O’Connell,
University of Limerick and Eric Mercier, INSA Toulouse.
Figure 6.2.1 Waste as a Renewable Fuel Workshop Discussion Group
The resulting questions and answers discussion session tended towards the clean up of
used frying oil so that it could be esterified as many of the attendees had either made
177
or read about biodiesel. All attendees were well informed in the use of alternative
liquid bio fuels. Particular questions related to:
Increasing the yield of biodiesel, ratio of catalyst / methanol / RVO to be used in the
esterification process.
Safety and legislative considerations of storage of methanol.
Derrogation of fuel tax for use in road going vehicles.
Reliability of vehicles and engines using the various biodiesels.
The use of neat seed and waste cooking oil was also considered in the discussion,
questions included:
Details of engines modified to allow the use of neat seed oil.
Cost of conversion kits.
Reliability of engines using neat oils as a fuel.
Cost and availability of seed oils and waste oils.
Ecotopia 2002
Ecotopia 2002 was held in a 98 acre broad leaf forest on the banks of Loch Derg at
Tuamagraney Co. Clare, Ireland. Previously Ecotopia has been held at :
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
Koln, Germany.
Bugac, Hungary.
Tudulinna, Estonia.
Reslec, Bulgaria.
Durban sur Arige, France.
Tasca, Romania.
Wolmierg, Poland.
Libovice, Czech Republic.
Avonbridge, Scotland.
Emmendingen, Germany.
Bagda, Romania.
Turku, Finland.
Sinemorets, Bulgaria
178

Demonstrate the use of blends of waste cooking oil

Transcription

Similar documents

Improve Fuel Economy and Diesel Engine Performance

MBE 900 - Detroit

Member Discount Fuel Program - Terre Haute Chamber of Commerce

Kewatec_EASY

BioBor JF Spec Sheet 2

Untitled - Aeronautics

Window Sticker

the scangauge ii - parksoffroad.com

Pittsburgh Steelers - Mid Atlantic Dairy Association

Window Sticker - Pierson Ford