Energy modernisation of industrial heating systems.

Energy modernisation of
industrial heating systems.
Options for increasing efficiency and saving energy in large-scale combustion plants.
Contents.
Forewords.
dena foreword.
BDH foreword.
1. Introduction.
1.1 Energy usage and efficiency in industry and production in Germany.
1.2 Heating systems: applications and potential savings.
2. Overview of heating system optimisation.
3. Optimising heating demand.
3.1 Analysis of current energy status.
3.2 Minimising heat losses.
4. Energy-efficient heat generation.
4.1 Energy-efficient plant design.
4.2 Increasing burner and boiler efficiency.
4.3 Optimisation by measurement and control systems.
4.4 Waste gas control in steam and hot water generation.
4.5 Energy generation management in heating systems.
5. Heat recovery.
5.1 Mode of operation of heat recovery.
5.2 Waste gas heat recovery.
6. Energy-efficient conversion and generation technologies.
6.1 Combined heat and power generation.
6.2 Heat pumps.
6.3 Solar thermal energy.
6.4 Heat storage.
7. Partners for greater energy efficiency in industry and production.
8. Best practice examples.
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Energy efficiency pays off.
3
4
6
7
9
16
19
21
22
Forewords.
dena foreword.
BDH foreword.
The generation of heat for industrial processes accounts by far
for the largest proportion of energy demand in industry and
manufacturing. Virtually any manufacturing business is dependent on an industrial heating supply for generating steam
and hot water or for operating furnaces and drying plants.
Process heat has accordingly long been a significant cost factor for many companies.
Around 80 per cent of Germany‘s combustion plants are over
ten years old and are no longer in line with the current state
of the art. Energy modernisation of these 250,000 outdated
plants could save the German economy considerable quantities of oil and gas and, thus, considerable costs.
It is precisely in their heating systems that businesses can still
make significant energy savings. Investing in energy-efficient
systems is not only highly cost-effective, but it also pays companies back in many different respects: energy efficiency cuts
production costs, helps to reduce CO2 emissions and develops the
company‘s innovative strengths and, thus, its competitiveness.
This brochure shows how all the components of a heating system can be ideally adapted to one another, thereby enabling
the systematic exploitation of potential energy and cost savings.
The brochure concludes with brief descriptions of projects
from companies which have already successfully optimised
their heating systems as practical examples for others to
follow.
I hope this gives you some food for thought.
Your Stephan Kohler
Chief Executive
Deutsche Energie-Agentur GmbH (dena)
German Energy Agency
In the light of ambitious German and European climate protection targets, the need for action is urgent. Since 2006, Germany has already cut CO2emissions by around 3.2 million
tonnes by promoting investment in building energy efficiency. We estimate that, solely by focusing on the industrial sector and large buildings with a rated thermal input of 100 to
36,000 kW, energy optimised heating systems could generate
savings five times this magnitude.
This brochure will give you some idea of the potential energy
efficiencies lying dormant in your company. By modernising
your existing systems, not only are you contributing to climate and environmental protection, but you can also dramatically cut your own energy costs.
The benefits outlined in this brochure will prove persuasive
for your company to invest in the energy efficiency of your
combustion plants.
Your Andreas Lücke
MA, General Executive Manager
Bundesindustrieverband Deutschland Haus-, Energie- und
Umwelttechnik e. V. (BDH)
Federal Industrial Associ­ation of Germany House, Energy and
Environmental Technology
3
1. Introduction.
Figure 2: Economically viable potential energy savings
in industrial companies by field of application (in TWh/year).
30.0
350
20.0
TWh/year
400
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Final Report 18/06, Potential for energy saving and energy efficiency in the light of current price trends, commissioned by: Federal Ministry of Economics and Technology, Prognos AG, Basel and Berlin, 31 August 2007. All data on energy usage and potential energy efficiencies in this section are taken from this source.
2
Including hot water
1
Energy efficiency pays off.
ol
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Total potential energy savings for all fields of application
amount to approx. 98 TWh/year. The measures shown in
Figure 2 overlap, which means that the potential savings
cannot be added together.
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Figure 1: Energy end-use per field of application in
industry and production in Germany (in TWh/year).
s
Process heat accounts for some 400 TWh of energy end-use by
companies. This amounts to 57 per cent of total industrial energy end-use and is, thus, by far the most energy-intensive field of
application, ahead of electric motors, space heating2, lighting,
electroplating processes and biotechnology.
at
Companies from industry and production account for some
30 per cent of Germany‘s entire energy end-use. This amounts
to approx. 700 TWh per year (source Prognos1). The associated
expenditure is increasingly becoming a crucial cost and, thus,
competitive factor for companies. For instance, according to
statistics from the German Federal Ministry of Economics,
energy costs for manufacturing industry totalled around
€36 billion in 2008.
Process heat is generated from various energy sources (e.g.
electricity, oil and gas), transported by different media (e.g.
warm/hot water, steam and hot air) and, depending on specific process requirements, must be provided at different temperature levels. As in other fields of application, considerable
potential energy efficiency savings are open to companies
from industry and production: looking at all thermal processes, it may be conservatively estimated that there are economically viable savings totalling 30 TWh per year of e
­ nergy,
corresponding to approx. 7.5 per cent of industrial energy usage for process heat, to be made. Further annual savings of 17.5
TWh are available in space heating.
he
1.1 Energy usage and efficiency in industry
and production in Germany.
other combustion fuels (TWh/year)
electricity (TWh/year)
1.2 Heating systems: applications and
potential savings.
The majority of the measures for optimising heating systems
which are presented here are cross-sector applications, i.e.
they may be used across various sectors. Only in drying plants
are the measures almost exclusively industry-specific and so
limited to a particular field of application for heating systems.
Accordingly, this brochure takes no further account of them.
Figure 3 shows the energy requirements and potential savings
for the individual applications of heat.
Further potential savings amounting to 13 TWh per year may
be achieved by process- and system-specific optimisation
measures in all fields of application for process and space
heating.
Steam and hot water generation.
Around 40 per cent of demand for industrial process and
space heating arises in boiler plants for generating steam and
hot water. Germany uses some 92.9 TWh of energy each year
for process heat, mainly in the chemicals, papermaking, cap­­
ital goods and the food and beverage industries. As much as
96.2 TWh of energy are required each year for space heating.
The most important energy efficiency measures include g
­ reater use of heat recovery, burner and boiler optimisation, demand-based control and improvement of thermal insulation.
On average, energy savings of 15 per cent can be achieved for
each plant. Integrated optimisation of the entire heating system by adapting and better matching its component parts
to one another is the way to achieve additional energy and
cost savings. The following sections are a step-by-step guide to
achieving these potential savings.
Furnaces.
Furnaces are required for thermal processes such as firing, smelting and heating, for casting and shaping purposes, for heat
treatment or for sintering and calcination. These energy-intensive processes account for around half of industrial demand for
process heat and space heating, amounting to 240.1 TWh per
year. Furnaces, which are used across sectors, account for one
third of this. As described in the following section, major increases in energy efficiency may primarily be achieved by installing energy-efficient burners, combustion processes with oxygen, optimised control, improved insulation and by making
use of waste heat. Overall, economically viable savings of
13.3 TWh per year may be made in this energy-intensive field
of application.
Economically viable potential savings in steam and hot water
generation amount to 12 TWh annually, there being additional potential savings of 17.5 TWh in space heating.
Figure 3: Energy demand and potential savings for individual applications of heat.
Application
Sectors
Energy demand
in TWh/year
Potential savings
in TWh/year
Steam/hot water generation
and other thermal processes
Chemicals and papermaking industry, production
of capital goods and foodstuffs and beverages
92.9
12.0
Cross-sector generation of space heating
96.2
17.5
Furnaces and processes from
200 to over 500°C
Production of various primary materials, iron, nonferrous metal and steel production, cement, ceramics and glass production, capital goods industry,
industrial baking
240.1
13.3
Drying and other processes
below 200°C
Food industry processes and drying of wood, coal,
bricks, paper, paints and coatings, fine ceramics etc.
65.6
5.3
5
2. Overview of heating
system optimisation.
Measures for optimising heating system energy usage
should always be taken as part of optimisation of the
overall system, as the greatest increases in energy efficiency can only be achieved if all the components of the
overall system are of matching efficiency. If an optimum
result is to be achieved, it is advisable to take the system­atic approach explained step by step in the following
sections:
Optimising heating demand.
The first step to take when optimising a heating system‘s
energy usage, is initially to obtain a detailed analysis of
current energy consumption and to optimise heating demand.
analysis of a system‘s current energy usage and actual required heating demand
optimisation of production process energy usage
minimising heat losses
optimisation of heating demand
Energy-efficient heat generation.
In a second step, the energy usage of all the system‘s components and the overall system is optimised:
checking the components and the entire heating sys-
tem for energy efficiency or energy-efficient design
replacement or acquisition of new energy-efficient burners and boilers
boiler cascade control/multi-boiler control system
burner speed control
burner waste gas control
Waste gas system
Heating
demand
CHP station
Boiler and
burner
Heat recovery.
Industrial heat generation and use inevitably gives rise
to “waste heat”, on average 40 per cent, which is released
into the surrounding environment. Heat recovery
measures are a way of tapping this enormous potential:
economisers
condensing boiler technology
combustion air preheaters
recuperative and regenerative burners
6
Energy efficiency pays off.
Conversion and generation technologies.
The last step is to select the most suitable conversion and
generation technologies so as to reduce energy usage
still further:
combined heat, power (and cold) generation
heat pumps
solar thermal energy
heat storage
3. Optimising heating demand.
The first step in the energy optimisation of a heating system is a detailed analysis of current heat consumption
(current status) and of actual heating demand (target
status). The focus should be on eliminating energy losses
from the production process.
First of all, measures should be taken to minimise losses and possible ways of optimising demand in production processes, for example, by more efficient process technologies, should be investigated. In a second step the heating system may be optimised.
3.2 Minimising heat losses.
3.1 Analysis of current energy status.
An analysis of current energy status offers an overview of
energy usage, heating demand and the overall heating system and its individual components. Such an audit should
also include the performance parameters of the processes
and systems – amount of heat, pressure and temperature. In
many businesses total energy usage is known simply from
the cost statements for the respective energy sources which
do not give any idea of how usage is divided between the var­ious processes and plants. Such a breakdown is absolutely
essential, however, if a temperature- and time-dependent
heating demand profile is to be established for processes
and plants. An energy consultant can provide valuable assistance when carrying out this analysis. Of the various options available to anyone wanting to carry out the analysis
themselves, the Einstein Audit Guide (downloadable from
www.einstein-energy.net) provides a useful starting point.
The total thermal energy demand process engineering processes or of an entire company can be mapped using a pinch
analysis. The cornerstone of this analytical method is to record thermal energy streams to all a company‘s process systems and subsequently to implement measures to reduce
energy consumption.
Heat losses may occur at different points in the heating system: at the point of consumption, during transport or during
energy generation.
In processes, i.e. at the point of consumption, energy losses
can be kept low, for example, by suitably dimensioned thermal
insulation for tanks or furnaces, thereby reducing demand.
To limit heat losses at the point of energy generation, care
should be taken at the design stage to ensure that boilers release very little heat and have good heat storage capacity. In
existing plants losses can be reduced by cleaning the heating
surfaces and eliminating leaks in the furnace body. High losses
arise during energy generation as a result of high waste gas
temperatures of over 200 °C. This energy can be used if heat
recovery measures are taken.
7
To minimise radiation losses during generation and transport of heat, the heat generators, pipes and any heat storage
present should be thermally insulated and existing insulation
checked and repaired if necessary. Boiler feed water for steam
and hot water boilers contains salts which accumulate as a result of boiler water evaporation. This not only leads to corro­
sion damage to the boiler, but also to energy losses. The boiler
feed water must, therefore, be deionised. Sludge additionally
collects at the bottom of a steam and hot water boiler which
must be removed. This process likewise leads to heat losses
(see Figure 4). Good water pretreatment reduces the amount
of sludge.
Continuous maintenance of burners, boilers and the steam
and hot water distribution network may, not least, reduce
energy usage and, thus, also energy costs.
Shutdown or standby losses can be reduced significantly by
means of control systems which prevent superfluous switching on and off of burners (see Section 4.3).
Figure 4: Heat losses in steam and hot water boilers.
Radiation losses at the boiler surface
Flushing losses
Sludge losses
8
Energy efficiency pays off.
4. Energy-efficient heat generation.
When building a new plant, energy-efficient design of all
system components and the entire plant must be borne in
mind from the outset. In the case of existing plants, the individual components of a heating system must be checked
for their energy efficiency and any inefficient components
should be replaced with efficient ones. Fuel consumption
and costs may be further minimised by measurement and
control systems.
that they are now often operated inefficiently, for example,
with pressure-reducing valves.
4.1 Energy-efficient plant design.
In many businesses, steam pressure and temperature are
reduced by “deliberate” heat losses in uninsulated parts of the
pipework. In some cases, the desired temperature reduction is
even achieved by sprinkling the outside of the hot pipes with
water. It is substantially more efficient to reduce steam temperature by condensate injection. Reducing the temperature
level may also enable heat recovery or other energy-efficient
conversion or generation technologies such as Combined
Heat and Power generation (CHP) or heat pumps.
Fuel selection has a considerable impact on energy costs and
CO2 emissions. Natural gas has numerous advantages in this
respect, since, of all the fossil energy sources, it gives rise to
the lowest CO2 emissions and, moreover, may be particularly
efficiently used in condensing boilers. Heating oil‘s CO2 emission factor is only slightly higher than that for natural gas and
low-sulphur grades are available everywhere. Biogenic fuels
such as biogas and bio-oil not only conserve the world‘s finite
oil and gas resources, but also enhance a plant‘s CO2 balance.
Many heating plant components are also already designed
to use biogenic fuels. Electricity is the most expensive and,
on the basis of Germany‘s current “power mix”, the most CO2
intensive energy source for generating process heat. Using
speed-controlled burners and energy-efficient motors can gen­
erate considerable savings here. *
In the case of steam boilers, it is advisable to choose a boiler
with a good storage capacity. In most applications, shell boilers are, therefore, preferable to high-speed steam generators.
The large water capacity means that there is an energy buffer
which can equalise fluctuations in steam demand.
The heat consumer with the highest temperature or pressure
level in a system is always decisive when it comes to defining
the design pressure of the heat generator. It may, therefore,
make sense to operate a dedicated steam generator for an
individual very high pressure consumer.
If a plant‘s energy efficiency is to be increased, an energy-efficient energy supply medium should be selected for each process step depending on specific requirements. If possible, hot
water should be used instead of steam as a heat-transfer medium since steam generation is associated with high conversion
losses. The crucial factors in energy-efficient plant design are to
dimension the boiler correctly and to adapt operating pressure to the prevailing technical requirements. In the past, heating systems were often greatly overdimensioned, which means
* Commission Regulation (EC) No. 640/2009 from 22 July 2009 implementing Directive 2005/32/EC of the European Parliament and of the Council defines binding eco-design requirements for electric motors.
9
Case study: Agrana Fruit Germany GmbH.
At its Constance site, Agrana Fruit Germany GmbH operates two gas-fired steam boilers which generate the steam
for process heat and for sterilising the fruit. Depending on
base material and temperature, an anaerobic reactor produces biogas with a calorific value of approx. 6–7 kWh/Nm3 at
a rate of approx. 20–30 normal cubic metres (Nm3) per hour.
Installing a new gas burner in one of the two steam boilers
has meant that, instead of natural gas, a major part of the
bio­gas produced may be used for steam generation, whereas prior to modernisation it was flared off. Annual fuel consumption was reduced by 290,000 kWh and costs by approx.
Reduction in energy
consumption
448,000 kWh/year
Percentage energy saving
4.2 %
CO2 reduction*
109 t/year
Investment
€65,000
Cost reduction
€19,300/year
Return on investment
30 %
€10,000. Further savings of around 160,000 kWh were
achieved by a multifuel burner system (see below), speed
control (Page 12) and the installation of an O2- and CO-controlled waste gas control system (Page 14) for the new gas
burner. Implementing all these measures has resulted in an
annual reduction in fuel consumption of 448,000 kWh and
in costs of €19,300. Eliminating natural gas as a combustion
fuel has, in particular, made it possible to cut CO2 emissions
by approx. 109 tonnes. R
­ eturn on investment on the energy
saving investment amounts to 30 ­per cent.
* All the examples are based on the following GEMIS equivalent values: natural gas 244 g CO2/kWh.
4.2 Increasing burner and boiler efficiency.
Potential energy savings may also be made in heating systems
by installing more energy-efficient burner and boiler systems.
A plant‘s energy efficiency can be increased with the following
types of burners and boilers:
Multifuel burner systems with internal waste gas recirculation.
Modern multifuel burner systems with internal waste gas
recirculation for hot water and steam generation systems
make use of the principle of air and fuel staged mixing systems. An increased mixing pressure additionally increases
10
Energy efficiency pays off.
the discharge momentum of the air or air mixture stream
emerging in the outlet zone to such an extent that internal
flue or combustion gas recirculation takes place in the furnace body. This results in optimised and enlarged flame geom­
etry which leads to better heat transfer to the surrounding
furnace body and simultaneously reduces the flame temper­
ature, thereby also bringing about a distinct reduction in
nitrogen oxide (NOx) emissions. Biogenic fuels may also be
used in these systems. Burner motor power consumption may
also be reduced by means of speed-controlled operation.
In addition to conventional heating boilers with their elevat­
ed waste gas temperatures, steam and hot water systems
are today increasingly making use of condensing boilers.
Unlike conventional boilers, these boilers recover the heat
present in the waste gas by means of additional heat-transfer
surfaces. The heat may be used, for example, to preheat process or boiler feed water. The waste gas temperature of condensing boilers is consequently distinctly lower. Condensing
boilers are primarily of interest for relatively large capacity
plants and for retrofitting to existing plants.
Waste heat boilers use the heat from waste gases (often also
known as flue gases) from combustion processes or from hot
waste air streams to produce hot water or steam. Hot waste
gas is here passed through a tube bundle where it transfers
its heat to the water located in the boiler body.
Figure 5: Cross-section through a three-pass shell boiler by way of example of a steam or hot water boiler with burner.
Waste gas
connection to flue
Flame tube
(1st pass)
Smoke tube
(2nd pass)
Burner
Smoke tube
(3rd pass)
The boiler pressure vessel is a horizontal cylindrical tube, closed at both ends and
insulated all around. This pressure vessel accommodates a flame tube (1st pass),
which is fired by a burner, and an internal reversing chamber which reverses the
direction of the waste gases and recirculates them in the 2nd pass. On the front of
the boiler there is an external reversing chamber, which again deflects waste
gases and leads them to the end of the boiler in the 3rd pass.
The following burners and processes are primarily of relevance for furnaces:
Recuperative and regenerative burners are high effi ciency burners which use the waste gas heat directly for preheating the combustion air. These two types of burner are explained in greater detail in the Heat Recovery Sec-
tion (Page 16).
Flameless oxidation (FLOX®) is a high efficiency burner technology which enables compliance with stringent NOx limit values even at elevated combustion air preheat-­
ing temperatures.
The high outflow velocity of the combustion gases in high-velocity or high-momentum burners ensures internal recirculation of the furnace body gases in the combustion chambers or furnace bodies and, thus, uni­-
form temperature distribution, as a result of which these burners are more efficient than conventional burners.
In comparison with a combustion process with air, com-
bustion with pure oxygen has some advantages in furnaces: for instance, the combustion temperature and
cobustion efficiency are distinctly higher, since combustion with pure oxygen reduces the volume of waste gas and waste gas losses are, therefore, also distinctly lower.
11
4.3 Optimisation by measurement and
control systems.
Boiler cascade control and multi-boiler control.
By using boiler cascade control in steam and hot water gener­
ation, exactly the required volumetric flow rate may be continuously conveyed in the system. As a result, only the number
of boilers with appropriate capacity (speed-controlled) needed for generation have to be operated. The control system not
only reduces burner load and burner startups, but can immediately compensate any instabilities and faults. The boilers
can consequently always be operated at their ideal load point
and with optimum efficiency.
The efficiency of a plant may be further increased by installing
multi-boiler control. A “hydraulic separator” here decouples
all the primary circuit heat generators (generation system)
from the consumers in the secondary circuit. Control of volumetric flow in the primary circuit ensures hydraulically optimised operation of the plant which adapts the necessary
burner or boiler capacity to demand in the secondary circuit.
Blowdown flash tank and high pressure condensate
system.
The flushing-related waste heat arising in the boiler blowdown may largely be recovered by flashing and used for preheating the feed water. System efficiency may be ­increased
by up to two per cent in this way.
If the flash steam or vapours escape unused in an open condensate system, this results in a steam generation heat loss.
It is generally possible to use the vapours for preheating
boiler feed water or cleaning water, for example.
The lowest heat losses occur if the condensate is returned
to the boiler under pressure in a closed circuit. The high
pressure condensate system results in fuel savings of up
to twelve per cent and additionally reduces flushing and
sludge losses (see Section 3.2).
Figure 6: Measurement and control systems in modulating burners.
O2 probe
O2 module
Gas supply
Mixing device
Stepping
motors
Oil supply
Air supply
Visual displays
Pulse
generator
Frequency
converter
12
Energy efficiency pays off.
CAN bus
Firing management system
Display and
control unit
CAN
bus
Building management system
Bus system
Burner control.
By means of modulating or speed-controlled operation, burners may be purposefully controlled in partial load ranges
instead of controlling partial load by switching the burner
on and off. Since the combustion chamber has to be flushed
before each ignition, shut-down and start-up losses can be re­
duced in this way. Moreover, a distinctly lower power range may
be achieved in the event of load fluctuations by using speedcontrolled burner motors. This has a number of advantages:
not only are unnecessary burner shut-downs avoided, but
cooling of the boiler by pre-ventilation is similarly minimised.
Speed control for pump drives.
It is generally worthwhile investigating speed control of pump
drives. For each pump type, e.g. boiler feed pumps or circulation pumps, consideration must be given as to whether or
not speed control makes sense. Speed-controlled circulation
pumps are, for example, worthwhile if smaller masses of water
need to be circulated in summer than in winter. In the case of
boiler feed pumps for supplying a steam generator with feed
water, it must be ensured that the speed-controlled pump
maintains the necessary constant boiler pressure. The level of
potential savings is then dependent on how long the plant was
operated under partial load.
Fuel consumption and costs may be reduced by between 2
and 10 per cent in this way. Electric power consumption and
costs may also be considerably reduced by speed control of
the blower. In furnaces, model-assisted furnace management may be used for virtually all kinds of furnace, in particular, the small heating furnaces which are in widespread use.
Control is here based on measurements and the use of empir­
ical and analytical parameters of relevance to the process.
Operational management of the furnace may in this way be
continuously adapted to actual production conditions. Potential saving: up to 15 per cent of the energy costs for a furnace.
Case study: Teutoburger Mineralbrunnen GmbH & Co. KG.
In 2007, Teutoburger Mineralbrunnen GmbH & Co. KG carried out an analysis of its steam generation boiler systems
and had a plan drawn up for refurbishing the system. Prior
to the refurbishment, despite modulated operation, the boilers were regularly shut down, resulting in unnecessary energy usage. Now, thanks to the use of speed-controlled
burner motors, the burner motor speed is adapted to actual
requirements. In the event of load fluctuations, the system
may, thus, adopt a distinctly lower power range. This
prevents unnecessary burner shut-downs. Just thanks to
Reduction in energy
consumption
2,378,800 kWh/year
Percentage energy saving
26 %
CO2 reduction*
718 t/year
Investment
€219,000
Cost reduction
€142,700/year
Return on investment
65 %
speed control (Page 13) savings of approx. 800,000 kWh or
approx. €48,000 per year have been made. Measures to reduce
demand (Page 7), such as improved insulation, weekend
power reductions and a cut in steam pressure, were additionally implemented. Further energy savings were achieved
by installing an O2 controller (Page 14). Taken together, all
the energy efficiency measures reduced annual energy
usage by approx. 2.4 million kWh and energy costs by
€142,700. With its return on investment of 65 per cent, this
package of measures makes very definite economic sense.
* All the examples are based on the following GEMIS equivalent values:
heating oil 302 g CO2/kWh.
13
4.4 Waste gas control in steam and hot water
generation.
Depending on fuel type and plant age, burners are operated
with 5 to 20 per cent surplus air as a safety measure. However,
if more air is supplied to the combustion process than is required, the oxygen present in the air no longer participates in
the combustion and the air is heated up, thereby resulting in
heat losses. These losses may be reduced by an O2 controller
which continuously measures the O2 content of the waste gas
from the boiler and adjusts the air supply accordingly. This
can increase efficiency by up to three per cent. This approach
can also compensate the effects which occur when the boiler
is sited in locations with large temperature fluctuations be­
tween summer and winter and at different altitudes. Using a
CO controller, the residual oxygen content may be reduced
back down to values of below 1 per cent by volume, thereby increasing efficiency by up to 1 per cent. This approach to control
may only sensibly be applied to gaseous fuels since liquid
fuels may form soot before the measurement is carried out
which affects the measurement. In operation, the quantity of
air is reduced until the probe in the waste gas detects the pres­
ence of uncombusted fuel constituents in the waste gas. The
quantity of air is then raised again until no uncombusted constituents may any longer be detected in the waste gas.
Energy consumption can be further reduced by monitoring
and controlling further combustion parameters such as waste
gas temperature, soot index or furnace body pressure and by
installing automatic flue gas or combustion dampers. The
latter prevent the boiler from cooling down during regular,
relatively long boiler shut-downs (e. g. over weekends).
Figure 7: Improvement of combustion efficiency.
98
96
94
O2 content [%]
92
Combustion efficiency [%]
0
90
5
88
86
110
130
150
Waste gas temperature – feed air temperature [°C]
14
Energy efficiency pays off.
170
190
210
4.5 Energy generation management
in heating systems.
A range of important operating data may be used to carry out
a detailed analysis of a plant‘s fuel consumption or steam and
temperature profiles. An energy generation management
system may be developed on the basis of these data which,
by demand-based adjustments, can reduce the energy us­
age and costs of heating systems. One possible application is
consumption-controlled heating and start-up programs
which differentiate between priority and subordinate con-
sumers over time. In this case, the heat generator may be dimensioned to be of somewhat lower capacity than would be
suggested solely by adding the various demands together. In
modern burners, all functions are controlled and monitored
by sophisticated microprocessors. Such digital combustion
management also make it possible to communicate via an
integral bus with other systems, for example, building man­­agement systems.
Case study: Albertinen-Krankenhaus, Hamburg.
One aspect of a comprehensive program of new building
and expansion at the Albertinen-Krankenhaus in Hamburg in 2010 involved bringing the heating and air conditioning systems up to date. One boiler was fitted with
a low NOx dual-fuel burner for operation with heating
oil and natural gas. The other two boilers were modernised and equipped with the latest generation of gas burn­
ers which are, for example, optimised with regard to fluid
dynamics. The quantity of heat generated is adapted to
actual demand by energy-optimised operation both of
the burners (modulating operation, Page 13) and of the
blowers (speed control, Page 13). Using of an O2 controller (Page 14) eliminates the influence of disruptive vari-
Reduction in energy
consumption
19,150,000 kWh/year
Percentage energy saving
24 %
CO2 reduction*
4,673 t/year
Investment
€490,000
Cost reduction
€337,000/year
Return on investment
69 %
ables such as weather conditions or hysteresis and optimises the combustion process, i.e. combustion with an
optimised ratio of supplied and required air (combustion
air ratio) and any excess of air is minimised. This burner setup and combustion air preheating (Page 18) reduces losses
due to the energy carried away with the waste gas: in this
way, combustion efficiency of 97 per cent can be achieved
in the low and moderate power range. This comprehensive package of measures achieves an overall reduction in
annual energy usage of more than 19 million kWh, generating savings of around €337,000 per year. At 69 per cent,
the return on investment of the energy saving investment
is high.
* All the examples are based on the following GEMIS equivalent values:
natural gas 244 g CO2/kWh
15
5. Heat recovery.
The waste heat from heat generation and utilisation
can be used by taking steps to recover heat. Significant
amounts of waste heat can be recovered for further use
from steam boiler and furnace waste gases.
5.1 Mode of operation of heat recovery.
Waste heat can be transferred directly or indirectly (via an intermediate medium) to another process by heat exchangers,
providing the temperature of the source of (waste) heat is above
the temperature of the consumer. In principle, heat recovery
is, therefore, more worthwhile the higher the temperature
of the available waste heat. To minimise losses resulting from
transport and storage, heat potential should always be used
locally and as directly as possible. If this is impossible, the use
of storage technologies for interim storage of the waste heat
arising should be looked into. In such cases, it is important for
all pipework to be provided with good thermal insulation.
If the low temperature of the waste heat makes direct heat
recovery impossible, a heat pump can be a sensible solution.
Heat pumps (see Section 6) are capable of raising the temper­
ature of heat from a low to a higher level.
Case study: Textilveredlung an der Wiese GmbH.
In 2007, Textilveredlung an der Wiese GmbH carried out
the energy modernisation of a steam generator for textile finishing. Once heat generation energy efficiency
had been enhanced by implementing an O2 control system, it proved possible to make still further significant
improvements in system efficiency by installing an econ­
omiser. In optimised operation with feed water preheating by the economisers, a waste gas temperature of just
Reduction in energy
consumption
850,000 kWh/year
Percentage energy saving
3%
CO2 reduction*
207 t/year
Investment
€78,000
Cost reduction
€34,000/year
Return on investment
44 %
130 °C is now achieved, where it was formerly 230 °C. This
measure has enabled waste gas losses to be reduced by 20
per cent under minimum load conditions, and by around
45 per cent under full load conditions. By retrofitting the
steam boiler with an economiser, annual fuel consumption was reduced by three per cent. This means savings of
850,000 kWh of energy and €34,000 in operating costs per
year with a high return on investment of 44 per cent.
* All the examples are based on the following GEMIS equivalent values:
natural gas 244 g CO2/kWh.
5.2 Waste gas heat recovery.
Waste gas heat recovery can substantially boost the energy
efficiency of combustion plants which, due to the nature of
the process, are operated with elevated waste gas temperatures and for extended periods. It is, therefore, particularly
worth-while using such systems in steam and hot water
generators, furnaces, dryers or gas turbines. In this process, a waste gas heat exchanger draws some of the heat
16
Energy efficiency pays off.
from the waste gas and transfers it to a heat-transfer medium such as water or air. In this way, the heat can be supplied
to another point in the process. Heat transfer continues for
as long as the temperature of the (waste) heat source is above
the temperature of the consumer. The waste heat may be
used, for example, to preheat combustion air, to heat plant
or process water or to feed heat into the heating system return.
Economisers and condensing heat exchangers.
An economiser is a waste gas heat exchanger which is capable
of utilising boiler waste gas to heat boiler feed, heating or plant
water. If a condensing heat exchanger (or waste gas condenser) is arranged downstream of the economiser, the waste gas
temperature can be reduced to below the condensing temper­
ature of water, so that the heat of condensation of the steam
present in the waste gas can also be used (see condensing boiler
technology). However, the waste gas heat can be put to further
use in a downstream condensing heat exchanger (see Figure 8),
for preheating the cold make-up water from the chemical
water treatment process (approx. 10-12 °C), before it enters the
degasser. Heat recovery by means of economisers and condens­
ing heat exchangers can increase efficiency by between 5 and
12 per cent.
Figure 8: Circuit diagram of a high pressure steam boiler plant with two waste gas heat exchanger stages (economiser/
condensing heat exchanger)
Feed pump modules
Water service module
Waste gas
condenser
Steam
Economiser
Steam boiler
Condensing boiler technology.
The “calorific value of an energy source” includes not only
the thermal energy released on combustion but also the energy released by condensation of the steam contained in the
waste gas, the heat of condensation. In industry, usually
only the sensible heat of the waste gases (> 100 °C) is used in
boiler systems. The heat of condensation which arises on further cooling of the waste gases to below the condensing temperature of the steam is generally lost as waste gas loss via
the flue. In new plants, it is generally quite straightforwardly
possible to make use of the heat of condensation since the
corrosion-resistant materials in heat exchangers and moistureinsensitive waste gas systems and flues mean this is possible
without equipment damage. Condensing boiler technology
is used primarily in hot water boilers. In contrast, for high
Pump
modules
Make-up water
pressure hot water boilers waste gas condensation can only
be used if a low temperature circuit is available.
When selecting suitable fuels, natural gas offers the greatest
potential benefits for condensing boiler technology. Natural
gas stands out from all other fuels not only in that it has the
highest steam content in the waste gas and the highest waste
gas dew point, but also in that its waste gases contain virtually no soot or sulphur. However, heating oil is also a suitable
fuel for condensing boiler technology since the low-sulphur
heating oil available these days allows effective and troublefree boiler operation.
17
Case study: Westfalenhallen.
In the course of modernisation in 2008, the old central heating plant of the Westfalenhallen event centre in Dortmund was replaced by a new heating system comprising a gas condensing boiler (970 kW) and three steel
boilers with different outputs (1,900, 3,050 and 5,200
kW). By graduating the outputs of the boilers used, the
energy-efficient gas condensing boiler runs for very
long period as the guide boiler while the three downstream
boilers are operated as required. Modernisation allowed
the efficiency of the complete heating system to be in-
Reduction in energy
consumption
2,000,000 kWh/year
Percentage energy saving
11 %
CO2 reduction*
488 t/year
Investment
€500,000
Cost reduction
€100,000/year
Return on investment
20 %
creased from 83 per cent to 92 per cent. The intelligent interplay between the new heating system and a modern
building management system and a total of 40 heat counters distributed over the site additionally allows flexible
and demand-based heat supply. With the assis­tance of
the condensing boiler and the demand-based control system, it was possible to reduce annual fuel consumption by
2 million kWh, the company thus being able to make savings in energy costs of €100,000 per year. Return on investment on the energy saving investment is 20 per cent.
* All the examples are based on the following GEMIS equivalent values:
natural gas 244 g CO2/kWh.
Combustion air preheating.
A combustion air preheater uses hot waste gas to preheat the
combustion air. Heat recovery using combustion air preheat­
ing can increase combustion efficiency by five per cent. Combustion air can also be preheated using waste heat from compressed air generators or from the boiler house.
Recuperative and regenerative burners for furnaces.
With recuperative burners, a heat exchanger is used to
preheat combustion air to a temperature of 550 to 600 °C
using hot waste gas. Burner and combustion air preheaters
are combined into a structural unit.
18
Energy efficiency pays off.
With regenerative burners, two burners are used alternately. While the first burner is in operation, the hot waste gas is
extracted by the second burner and passed via a heat storage
medium. The waste gas releases approx. 85 to 90 per cent of
the heat to the regenerator. After a given burn time, the system switches over to the second burner. In the process, the
combustion air flows via the regenerator and is heated to
a temperature which is 100 to 150 °C below the combustion
chamber temperature. When used in the temperature range
from 800 to 1,500 °C, this technology allows fuel savings of up
to 60 per cent over burners without heat recovery.
6. Energy-efficient conversion and generation
technologies.
The final important step involves the selection of suitable conversion and generation technologies which
lower energy usage still further.
In principle, from the point of view of economic viability and
plant engineering, it is best to design CHP systems as base
load supply systems.
6.1 Combined heat and power generation.
Combined heat, power and cold generation (CHPC)
plants can compensate the fluctuations in heat requirements over the course of a year by using the excess heat in
the summer to generate cold (for example, for building airconditioning). Combined heat, power and cold generation
can be achieved by combining any CHP technology with a
thermal refrigeration unit, usually an absorption or adsorption refrigeration unit. The additional cold generation then
allows the CHP base-load proportion and annual working
hours to be increased, which has a positive effect on the
plant‘s economic viability.
Combined heat and power generation (CHP) is the generation of power while making simultaneous use of the heat
which arises. Up to 90 per cent of the energy content of fuels
can be utilised in this way. The waste heat arising when gen­
erating power can be used as process heat for space heating
or to heat water. The prerequisite for economically viable
operation of a combined heat and power plant is year-roundheating demand which allows a high operating time of at
least 5,000 operating hours per year.
Case study: Rittal International GmbH & Co. KG.
The Rittershausen plant of Rittal International GmbH &
Co. KG operates a bio-oil operated CHP plant with a capac­
ity of 420 kW for the plant‘s thermal base load. Two catalytic waste gas purifiers (catalytic afterburning) from the
production side are also available as suppliers of heat. The
main consumer is the paint shop, whose pretreatment
tanks have to be maintained at a constant temperature in
both summer and winter. In the winter, the majority of the
energy consumed is used to heat buildings. A multi-boiler
control system (Page 12) was installed at the site in 2007 to
optimise the plant. In the course of this work, the primary
Reduction in gas consumption
8,056,000 kWh/year
Bio-oil consumption for heating
6,720,000 kWh/year
Absolute energy saving
1,336,000 kWh/year
Percentage energy saving
9%
CO2 reduction*
1,095 t/year
Investment
€620,000
Cost reduction
€270,670/year
Return on investment
44 %
and secondary circuit pumps were replaced with speed-controlled pumps (Page 13). The volumetric flow rate meter required for the multi-boiler control system was fitted in the
primary circuit (heating system), while the secondary circuit
(secondary consumer) was decoupled by a hydraulic separator (Page 12). All the energy efficiency measures together
have reduced energy usage by approx. 1.3 million kWh and
energy costs by approx. €270,000 per year. With its return on
investment of 44 perc ent, this package of measures makes
very definite economic sense.
* All the examples are based on the following GEMIS equivalent values:
natural gas 244 g CO2/kWh, rapeseed oil 129.6 g CO2/kWh (German Biomass Electricity Sustainability Ordinance)
19
6.2 Heat pumps.
A heat pump brings heat flux (from the ground, water or air)
which is at a relatively low temperature to a relatively high
temperature. This allows ambient heat or waste heat to be
used for heating purposes.
To heat domestic and industrial and commercial buildings,
low temperature heat pumps are used which can utilise
heat from air, groundwater or the ground to provide t­ em­pe­r­atures of up to at most 65 °C. High temperature heat
pumps offer the possibility of raising unusable industrial
waste heat to a higher temperature so that it can be used for
space heat­ing, providing process water or steam or even for
drying and distillation purposes. State of the art high temperature systems which operate on the basis of cold vapour
compression processes, can achieve temperatures from
80 °C to a maximum of 95 °C. Although some manufacturers
offer a two-stage system with which vapour can also be produced at relatively high temperatures, this additional heat
pump stage reduces overall efficiency. Use of an industrial
heat pump can save up to 80 per cent of energy costs.
With open or semi-open heat pump systems (thermal and
mechanical vapour compressors) process steam can be used
directly as a working medium and brought to a higher pressure and temperature level. At source temperatures of 70 to
80 °C, these heat pumps can produce process steam or proc­
ess heat with a temperature of up to 200 °C.
A good parameter for measuring the efficiency of an electrical heat pump system is the annual coefficient of performance. This describes the ratio over a year between amount
of energy released (thermal heat) and supplied energy (drive
20
Energy efficiency pays off.
energy). It includes the different operating states and, therefore, the many different, good and poor performance ratings
over the year. To ensure that the energy balance of an electric heat pump is positive, the annual coefficient of performance for electrical heat pumps should achieve a value of at
least 3.0 since electricity generation in Germany is associated with high primary energy consumption.
6.3 Solar thermal energy.
In Germany, thermal solar systems are used primarily to provide process heat at a temperature of up to an approximate
maximum of 120 °C. Solar thermal energy should always be
connected to the existing heating system at the lowest possible temperature since the efficiency of all collector technologies falls with increasing temperature. Coupling solar
thermal energy directly to the process is suitable for: clean­
ing, drying, evaporation and distillation, bleaching, pasteurisation, sterilisation, boiling, painting, degreasing and
cooling as well as space heating.
6.4 Heat storage.
Storage technologies allow peak loads to be reduced and the
proportion of base load increased. For processes with pronounced temporary peak loads, supply systems and system
components can be dimensioned for an average output lev­
el. The heat storage is discharged during phases with high
power requirements, while energy is stored temporarily if
requirements are below average output.
7. Partners for greater energy efficiency in industry
and production.
dena‘s “Initiative EnergieEffizienz” (“Energy Efficiency Campaign”) is a Germany-wide information and motivation campaign which promotes efficient electricity use in all consumption sectors.
Target group-specific campaigns are used to inform end consumers in private households, in industry and production and
in the service and public sectors about the options for efficient
electricity use and to motivate them to act in an energy-effi­
cient way.
The campaign is funded by the German Federal Ministry of Economics and Technology (BMWi). “Initiative EnergieEffizienz”
also offers businesses information and practical assistance in
many further areas, ranging from energy management to financing, to help them make more efficient use of electricity
and cut costs.
This brochure was prepared jointly by dena‘s “Initiative EnergieEffizienz” and the Bundesindustrieverband Deutschland Haus-, Energie- und Umwelttechnik e. V. (BDH) with the
support of Interessengemeinschaft Energie Umwelt Feuerungen GmbH (IG).
Bundesindustrieverband Deutschland Haus-, Energie- und
Umwelttechnik e. V. (BDH)/Interessengemeinschaft Energie Umwelt Feuerungen GmbH (IG) is an industry association representing the commercial, technical and political
interests of its members to policy makers, government and
the general public. The companies in BDH manufacture innovative energy-efficient utility engineering systems based
on gas, oil and electricity and particularly for utilising
­renewable energy sources focusing on heat generation for
private households, commercial buildings and industrial
applications.
www.bdh-koeln.de
More details from:
www.industrie-energieeffizienz.de (in German)
Publisher.
Editorial office.
Deutsche Energie-Agentur GmbH (dena)
German Energy Agency
Energy Systems and Energy Services
Chausseestraße 128 a
10115 Berlin, Germany
Tel.: + 49(0) 30 72 61 65-677
Fax:+ 49(0) 30 72 61 65-699
E-mail: [email protected]
[email protected]
Internet: w ww.industrie-energieeffizienz.de
www.dena.de/en
Deutsche Energie-Agentur GmbH (dena)
German Energy Agency
Printed by: trigger.medien gmbh, Berlin
As at: December 2011
Layout: Müller Möller Bruss Werbeagentur GmbH, Berlin
All rights reserved. Any use is subject to consent by dena.
With the kind support of the Federal Industrial Association
of Germany House, Energy and Environmental Technol­
ogy (BDH) and the Syndicate of Energy Environmental
Combustion Systems Ltd. (IG)
Image credits.
Certificate Number:
164-10794-1111-1005
www.climatepartner.com
Pages 1 and 6: © Viessmann Werke GmbH & Co. KG
Pages 7, 8/9, 11 and 17: © Bosch Industriekessel GmbH
as well as Bosch Thermotechnik GmbH
Page 10: © Walter Dreizler GmbH
Pages 12, 13, 14, 19 and 20: © Max Weishaupt GmbH
Page 15: © ELCO GmbH
Page 16: © SAAKE GmbH
Page 18: © Westfalenhallen Dortmund GmbH
21
8. Best practice examples.
The following companies have already successfully carried out energy optimisation of their heating systems:
Operators
Manufacturer/System planner
Measures
Agrana Fruit Germany GmbH,
Konstanz plant
- production of fruit preparations, or­
ganic products since 1991
- 30 staff
Walter Dreizler GmbH
- manufacturer of burners and control
technology
- medium-sized company, 62 staff
- use of the biogas resulting from the
process for heat generation
- speed control and O2 and CO waste
gas control in a burner motor
contact: Hans-Joachim Wehrle
Maintenance, Workshop Manager
Tel.: +49 (0)7531 5807-0
[email protected]
Contact: Daniel Dreizler
Head of Distribution, pp.
Tel.: +49 (0)7424 700 90
[email protected]
Albertinen-Krankenhaus,
Hamburg-Schnelsen
- 628 beds and around 60,000 outpa­
tients and inpatients
- Hamburg University Teaching Hospital
ELCO GmbH, Mörfelden-Walldorf
- manufacturer of industrial burners and
the related measurement and control
technology
- 450 staff
Albertinen-Zentrale Dienste GmbH,
Technical service business unit
Süntelstr. 11A
22457 Hamburg
Contact: Harald Rohde
Industrial Sales Engineer,
Northern Division
Tel.: +49 (0)511 9668 212
[email protected]
Bayerische Staatsbrauerei
Weihenstephan
- brewery
- 100 staff
Bosch Industriekessel GmbH
- manufacturer of steam and
hot water boilers
- 600 staff
Contact: Hans Wolfinger
Technical Director
Tel.: +49 (0)8161 536-0
[email protected]
Manufacturer of industrial
boiler systems:
Bosch Industriekessel GmbH
Contact: Franz Dörr
Sales Manager, Germany
Tel.: +49 (0)9831 56-253
[email protected]
- low NOx dual-fuel burners
- flow-optimised gas burners
- modulating operation
- speed and O2 control
- combustion air preheating
- replacement of the existing heavy oil
boiler
- speed control/CO control
- feed water preheating by means of an
economiser
- brewing water heating by means of a
waste gas condenser
- combustion air preheater using waste
heat from the chilling plant
Consultancy, planning and performance:
Bayerische Ray Energietechnik
GmbH & Co. KG
Contact: Helmut Reiter
Sales Manager
Tel.: +49 (0)89 329 004-0
[email protected]
22
Dortmunder Energie- und Wasserversorgung GmbH (DEW21)
- supplier to around 330,000 house­
holds in the Dortmund region
- supply of the Westfalenhallen event
centre in Dortmund
Bosch Thermotechnik GmbH,
- gas-condensing boiler
Buderus Deutschland
- intelligent heat generation manage- manufacturer of equipment for heat­
ment and building management system
ing, cooling and air-conditioning, hot
water provision, solar installations, biomass systems, heat pumps
- 51 sales offices, 11 regional training
centres, 10 service centres, 13,000 staff
throughout Germany
Contact: Gabi Dobovisek
Corporate Communications
Tel.: +49 (0)231 544-3271
[email protected]
Contact: Luc Geerinck
Marketing Director, Buderus Germany
Tel.: +49 (0)6441 418 1610
[email protected]
Energy efficiency pays off.
Operators
Manufacturer/System planner
Measures
Grundfos Pumpenfabrik GmbH,
Werk Wahlstedt
- production and assembly of circulating
pumps for heating, air-conditioning
and ventilation and of high pressure
centrifugal pumps and pressure-boost­
ing systems for water supply
- 1,000 staff
Max Weishaupt GmbH
- manufacturer of burners, heating and
condensing systems, and of solar technology, heat pumps and building automation systems (Weishaupt/Neuberger), heat pumps and geothermal bore
systems (Weishaupt/BauGrund Süd)
- approx. 3,000 staff
- adaptation of entire hydraulic system
including decoupling of heating and
consumer circuits
- low temperature boiler with waste gas
heat exchanger
- multi-boiler control
- speed and O2 control as well as control
by measurement of volumetric flow rate
Contact: Matthias Wiese
Maintenance Manager
Tel.: +49 (0)45 54 98-0
[email protected]
Hamburg branch office
Contact: Frank Gries
Branch Manager
Tel.: +49 (0)40 5380-9420
[email protected]
Pulcra Chemicals GmbH,
Geretsried plant
- manufacture of process chemicals
such as dyestuffs and auxiliaries for the
textiles, fibres and leather industry
- 100 staff
SAACKE GmbH
- oil and gas burners and plant and energy technology for industrial applications, on ships and offshore installations
- 1,000 staff
Contact: Bernhard Neumaier
Technical Director
Tel.: +49 (0)81 71 6 280
[email protected]
Contact: Stefan Schult
Product Management Energy
Efficiency Systems
Tel.: +49 (0) 33203 8039-70
[email protected]
Rittal International GmbH & Co. KG,
Standort Rittershausen
- predominantly production of switch
cabinets
- 1,000 staff
Max Weishaupt GmbH,
Siegen branch office
Contact: Rafael Armbruster
Head of Group, Energy Efficiency and
Environmental Protection
Tel.: +49 (0)2772 505-0
[email protected]
Contact: Björn Kowohl
Branch Manager
Tel.: +49 (0)271 660 42-20
[email protected]
Teutoburger Mineralbrunnen GmbH
& Co. KG, Bielefeld
- production of “Christinen” brand natural mineral water and soft drinks
- 240 staff nationwide
Max Weishaupt GmbH,
Kassel branch office
(see Grundfos example)
Contact: Herbert Dörfler,
Managing Director
[email protected]
Contact: Frank Mosenhauer
Tel.: +49 (0)561 951 86-30
[email protected]
Textilveredlung an der Wiese GmbH,
Lörrach plant
- production of industrial textiles, bed
linen, table linen and shirt/blouse
fabrics
- 150 staff
SAACKE GmbH
(see Pulcra Chemicals GmbH example)
- low NOx burner
- economiser
- waste gas condenser
- multi-boiler control
- energy-efficient burner
- bio-oil operated CHP plant
- changeover from thermal waste gas
purification to catalytic waste gas
purification with heat recovery
- waste gas heat exchanger
- demand reduction: weekend power
reduction and cut in steam pressure
- speed and O2 control
economiser
Contact: Steffen Herrmannsdörfer
Executive Director
Tel.: +49 (0)7621 957 60
[email protected]
23
For all questions about efficient energy use
in industry and production:
Free-phone energy hotline 08000 736 734
E-mail: [email protected]
www.industrie-energieeffizienz.de
An initiative by:
Our partners:
Supported by: