Alternative charge materials for the cupola

Fig 1. C-bricks with mixed borings may
be magnetised and then charged using
a magnet crane
Alternative charge materials for the cupola
It doesn’t always have to be primary raw materials for cupola
melting, say Gotthard Wolf, Herbert Löblich and Timo Wysocki from
the Institut für Gießereitechnik IfG gGmbH, Düsseldorf.
Primary materials have become limited on the
global market, causing an increase in prices
that have reached a new level in 2008. But there
are ready-to-use alternatives for foundries that
can help economise in a difficult procurement
situation.
Because of the hike in raw material prices for
coke as well as for steel scrap that has been ongoing since 2002, availability of these materials
in the German market suffered badly, and foundry
coke was even apportioned for
some time. After the situation
had eased somewhat in 2007,
a new hike of prices ensued at
the beginning of 2008, mainly
due to the growing dependence
on China and other rapidly
developing countries for raw
material deliveries, such as
foundry coke.
Fig 2. HCS testing of self-reducing c-bricks (left) and apparatus (right). Specimen (hatched) is placed
between two refractory pistons within a protective tube, heated up to the desired temperature and then
loaded until breakage (left). (Photo courtesy of DIFK, Bonn)
252
From that background, it
is essential for foundries in
Germany and across the EU to
explore new ways to cope with
the tight price situation on the
world market and shortages of
raw materials, plus changes in
their quality in order to assure
cost-effectiveness when melting
in the cupola.
Meeting material
requirements
Implementation of a consequent
points-of-accrual-management
(recyclers/foundries) is one
way to ensure the increasing
requirements for charge
material are met and to provide
such materials with consistent
quality to foundries.
The aim of this publicly
funded research project
was to provide new ways of
substitution for small and
medium-sized foundries.
Substitutes that were
investigated included briquettes
made from GJL, GJS and mixed
GS / GJS borings and from
grinding swarf, as well as
alternative sorts of steel scrap
such as micro-alloyed, shredded
FTJ October 2008
Melting and Holding
Cupola melting trials
Melting trials were carried out
in two NRW foundries equipped
with cold-blast cupolas with
respective melt rates of five
and eight tonnes per hour.
During these trials, emphasis
was placed on the complete
coverage of all input and output
parameters. These included:
iron temperature, blast
pressure, iron, slag and gas
composition, dust, inoculation
and mechanical properties of
the iron. The results showed
most of the alternative charge
materials can be used safely
up to a certain amount.
Borings from the machining
of castings can be considered
as an ideal substitute for the
metallic charge if their chemical
composition is consistent and
they are briquetted.
Within the series of trials,
briquettes made from borings
with CCS of more than 20MPa
were used to replace up to 60%
FTJ October 2008
80
B502 (90 bar)
CCS / HCS [Mpa]
or electroplated steel scrap
that are drawn into the focus of
foundries.
In addition, fuel substitutes
available on the market
such as blast furnace coke,
Chinese foundry coke or limemalm bonded c-bricks were
investigated and synthetic
charge materials such as selfreducing c-bricks or c-bricks
with admixed borings that make
these briquettes magnetisable
were developed especially for
this project.
Pre-testing of the alternative
charge materials was
emphasised during the entire
project. Testing methods
included cold compressive
strength (CCS) and hot
compressive strength (HCS)
at temperatures of 800°C,
reduction under load (RuL)
and drop shatter testing, fuel
analysis, abrasion strength,
analysis of the chemical
composition of metallic charge
materials and trace elements
analysis.
Conditioning and briquetting
technology for borings
briquettes and c-bricks was
investigated and optimised,
including experiments using an
industrial briquetting press with
150 tonnes maximum load.
60
B504 (45 bar)
B503 (70 bar)
40
20
HCS
B502 (90 bar)
0
4.0
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
5.0
Apparent Density [g/cm!]
Fig 3. Comparison between CCS at various compaction pressures and HCS of borings briquettes
of iron without affecting blast
pressure. From that, it was
concluded that the briquettes
remained sturdy until their
meltdown. It was also possible
to replace all the steel scrap
and pig iron from the metallic
charge with borings briquettes.
Furthermore, c-bricks with
admixed GJS borings were
developed as a substitute for
both coke and the metallic
charge, and self-reducing
c-bricks made of coke breeze
and iron oxide were developed
as a substitute for steel scrap
and pig iron. Aluminium
phosphate was used as a
binder for that, as the special
advantages of this material
compared to cement and other
binders became apparent in
preliminary experiments.
It was found safe to use these
c-bricks in amounts up to about
10% of the metallic charge,
providing compression strength
exceeded 1.8MPa. For the selfreducing c-brick, a degree of
reduction of 99% of the included
Fe2O3 could be proven through
slag analysis. These bricks can
be used for replacing steel
scrap without problems.
C-bricks with admixed
borings are also suitable
and can be charged with the
usual magnet crane (fig. 1),
offering an advantage for small
foundries in that no further
investment cost for a second
coke bunker is required when
substituting foundry coke
with alternative fuels. They can be produced with
moderate investment and manpower or purchased
(which is likely to be the more economic solution
for medium and small-sized foundries) from a
commodity trader.
None of the alternative charge materials caused
significant metallurgical disadvantages concerning
trace elements, nucleation and chill depth when
tested - even in high amounts during the trials.
No increase in scrap was found in either foundry
during the period of the trials.
Monitoring dust and odour
During the trials, dust and odour emissions were
observed at the de-dusting plants. Samples for
analysis were taken directly from the undiluted
raw gas from the stack and analysed with methods
according to olfactometric standard EN 13725(1).
Dust measurements in front of and behind the filter
did not show significant changes in dust emission
and composition during any of the trials, except
for the trials with borings and grinding swarf
briquettes.
For these materials, a relation between oil and
cutting fluid residue and the odour emission was
developed and it was shown that odour emission
increased with an increase in total oil and cutting
fluid residue charged (fig. 5). Nevertheless, it
should be considered that the effective odour
effluents in the neighbourhoods of the foundries
are subjected to a variety of influences, such as
weather, direction of the wind, moisture, height
of the stack, distance between the foundry and its
neighbours, topography of the surroundings etc.
Producers of briquettes made from borings are
therefore required to ensure low enough oil and
cutting residue, one possible solution being the
combination of borings from dry and from wet
machining to a mixture with low residue.
Cost-effectiveness of the alternative charge
materials tested within this project depends on
the market situation and on the availability of
the alternative materials to the foundries. The
253
Moulding
Melting
and
and
Holding
Coremaking
are likely to increase further
in the future, foundries will
be able to flexibly adapt their
charge composition with the
results of this project.
Reference
1. Helber J, ‘Odour emission
reduction in foundries
- a report on the state
of the art’, 66th World
Foundry Congress, Casting
technology - 5000 years
and beyond, Vol 1, Istanbul,
Turkey, Sep 6-9, 2004.
Acknowledgements
Fig 4. Briquettes made from borings can be an ideal substitute for the metallic charge
18000
oil / cutting fluid residue
1,45 %
oil / cutting fluid residue oil / cutting fluid residue
2,64 %
3,41 %
14000
12000
scatter range of standard charge composition A
10000
About the authors
15% grinding swarf briquettes
9% grinding swarf briquettes
40% GS-/GJS borings briquettes
30% GS-/GJS borings briquettes
30% GJS borings briquettes
15% GJS borings briquettes
0
30% GJL borings briquettes
2000
15% GJL borings briquettes
4000
8% GJL borings briquettes
6000
50kg self-reducing c-bricks
8000
GJL standard charge composition B
scatter range of standard charge composition B
GJL standard charge composition A
Odour Units (OU)* per m! raw gas
16000
This research project was
funded by the NRW Ministry
of Innovation, Research and
Technology (funding no. 0050410-0005, in responsibility of
Forschungszentrum Jülich, file
number PTJ-Az. 0410MW14).
The authors also wish to
express their gratitude to
the foundries involved in
this project for making the
investigations possible during
regular operation.
The authors are Dr-Ing Herbert
Löblich (cupola melting,
cast iron production); B E
Timo Wysocki (briquetting
technology, binder systems);
and Dr-Ing Gotthard Wolf, IfG
Institute of Foundry Technology,
Düsseldorf (Germany).
1 OU = 1 EROM = 123 "g n-Butanol / 1 m3 neutral gas = 0,04
"mol/mol
Fig 5. Odour emissions increased with oil residue
situation is likely to improve with rising demand
for these materials, which should result in
increased investment of re-cyclers and foundries
into advanced briquetting technologies and to
emphasising the closing of idle material cycles
in foundries. The latter is
further accelerated through
government subsidies for
material effectiveness.
As prices for charge materials
Gießereiingenieur (BE) Metallurgie
und Werkstofftechnik, Institut
für Gießereitechnik IfG GmbH,
Düsseldorf, Germany;
Tel: +49 (0) 211 6871 327;
fax: +49 (0) 211 6871 255;
email: [email protected]
NRW Ministry of Innovation, Science, Research and Technology
The Ministry of Innovation, Science, Research and Technology of the state of North Rhine-Westphalia (NRW) in its
present form was established in June 2005. This is the first time that a German Ministry has focussed on a state’s
potential for innovation as a top priority.
The Ministry is responsible for all NRW-based universities and polytechnics, university clinics, colleges of art or
music, for non-university research institutions and for the promotion of technologies in the state.
The remit of the Ministry of Innovation, Science, Research and Technology reflects the entire innovation process
ranging from higher education training to university and non-university research on developments and inventions and
to industry’s activities aimed at making applications ready for the market and successfully marketing fundamental
innovations.
The Ministry’s objectives include: achieving excellence in research and higher education teaching in NRW, boosting
exchanges between the research and business communities, and considerably improving NRW’s technological capacity.
NRW boasts Europe’s most closely set research and higher education infrastructure.
The NRW government is firmly resolved to bring the state to the forefront of scientific, technological and economic
progress and to turn NRW into Germany’s number one innovation state by the year 2015.
www.innovation.nrw.de
254
FTJ October 2008
Melting and Holding
Focus on energy reduction
Limited space did little to deter
one aluminium diecaster from
installing new melting facilities to
improve energy efficiences and
reduce emissions.
Faced with increasing energy prices, in 2007
Alumasc Precision - the Burton Latimer,
England, based aluminium diecaster, made a
comprehensive review of its energy use and costs
associated with melting and holding aluminium
for its high-pressure diecasting facilities. A
detailed appraisal showed that there would be
significant cost savings and reduction of carbon
emissions by installing a new high-efficiency bulk
melting and holding furnace to replace some of
the existing older gas-fired crucible furnaces.
The new bulk melting furnace was supplied and
installed by the German company ZPF therm
GmbH of Siegelsbach.
Space was very limited in the chosen location
in Alumasc’s high-pressure foundry, but ZPF’s
very compact, highly efficient design meets
Alumasc’s energy reduction targets, and
complies with the latest mandatory emissions
limits without the need for filtering systems.
Norbert Feth, marketing manager of ZPF
therm GmbH explains: ‘The reason for such
low emission lies in the unique design of ZPF
therms furnaces. The core of the system is
the combustion chamber, which is made of
refractory concrete and weighs several tonnes.
The thick encasement functions as a protective
barrier between the thermal insulation layers
and external steel casing on one hand, and the
aggressive liquid aluminium on the other.
‘The heavy refractory lining also serves as
a heat accumulator that helps to maintain a
steady state interior temperature of the furnace.
A sophisticated system of insulation keeps the
thermal energy in the interior of the furnace and
contributes significantly to energy saving.’
milligrams and only 0.4 milligrams for hydrogen fluoride.
Herr Feth speculates: ‘Even if the limits become yet stricter in five
years time, we will still be able to meet without external filtering.’
The longer dwell time of the hot gases in the furnace chamber
also contributes greatly to the high energy-efficiency of the furnace.
ZPF therm say there is an average of 20 to 30% more performance
capacity through this method of optimal heat utilisation rather than
with open exhaust gas systems.
The furnace installed at Alumasc is rated to melt one tonne per
hour of aluminium alloy and has a holding bath capacity of two and a
quarter tonnes. The unique gas firing system employs two modulating
nozzle-mixing gas burners with automatic air/gas ratio control. Both
burners are used when the furnace is in the melting mode to give
rapid melting which reduces metal loss. Only one of the burners is
used when maintaining to give better turn-down and consequently
more accurate temperature control.
Integrated charging
An integrated charging machine automatically loads aluminium ingots
and foundry returns that are pre-loaded in wheeled charge cars.
The furnace is mounted on load cells giving the operators accurate
information of the weight of metal in the furnace. The weighing
system also controls the charging machine to automatically prevent
over-filling the furnace.
Weight monitoring allows the PLC system to accurately calculate the
melting time for each charge according to the weight and regulate the
time on ‘high-fire’, which saves energy and prevents over heating and
associated oxidation losses.
After a year’s continuous operation, the furnace has met Alumasc’s
expectations regarding energy cost saving and reduced emissions. An
inspection during the recent annual shut-down showed only minimal
lining wear; the furnace needed only general cleaning of dross and
metal residues.
Ramsell‑Naber is the sales and service representative of ZPF for the UK and
Ireland. ZPF specialises in gas- and oil-fired furnaces mainly for the aluminium
casting industry. The company has a unique range of furnaces for bulk melting
and holding, with melting rates up to five tonnes per hour and holding capacities
up to 20 tonnes.
Ramsell-Naber Ltd; Tel: +44 (0) 1922 455521; fax: +44 (0) 1922 455277;
web: www.ramsell-naber.co.uk
Reduction of emissions
An unconventional exhaust gas flow from the
melting chamber plays a very significant role
in the reduction of the furnace’s emissions
to air. Rather than being expelled directly to
atmosphere from the melting shaft through
a chimney as is typical in other furnaces, flue
gases are first held in the interior of the selfcontained system. In the process, residues from
the charged material - particularly those from
returns - are subsequently virtually combusted.
This means that complex filtration systems are
unnecessary.
The measured emissions values fall far
below the statutory limits. ZPF claims that the
proportion of particulate matter in waste gases
is less than three milligrams per cubic metre,
for nitrogen oxide, the value is about eleven
FTJ October 2008
ZPF therm aluminium melting furnace
255
Some of these are high melting rate with low energy consumption, minimum metal losses and/or high metal
yield and a safe and largely automated operation. It is also necessary to consider both the current and
future environmental and safety requirements. This view should also consider low breakdown and mainteMelting
and Holding
nance expenses and the potential lining life and replacement cost.
High efficiency Aluminium meltin
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256
FTJ October 2008
suitable quality to optimize the yield of good castings; and of course, this must be achieved as economically as possible. In this connection there are numerous other requirements to be taken into consideration.
in the industrial high pressure die-casting foundry of
autumn of 2005. Since 2001 there have been two
II-N 2000/1000 G-eg units and the investigation was
Other:
Melting and Holding
exhaust gas
STR
initial
metal
weight
[ kg ]
ome flitter
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STRIKOMELTER® at Hesse & Bauckhage
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output metal
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STRIKOMELTER® at Hesse & Bauckhage
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salt
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measured
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Table
1
contact of the melt with atmospheric oxygen
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the results
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the meltvalues.
chamberThey
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avoid
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ference
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that
the
metal
metal impingement. This allows melting only
losses were in all cases below 1%.
on the hearth and for the metal to flow quickly
but without turbulence into the holding bath.
A third measure for the maintenance of metal
quality is the avoidance of the contamination by
impurities entering the metal holding bath. This
is assured by allowing the metal to run laterally
into the holding bath. In this way, dross and
other impurities remain on the melt hearth to be
removed during cleaning.
An additional advantage of the separation
of the two chamber concept is a continuous
availability of molten metal at a very consistent
temperature (to +/- 5°C). This type of melting
system guarantees continuous melting whilst
tapping liquid metal. The automated charging
contributes to achieving a molten metal
availability of 98% during practical operation.
Measured data in foundry practice
The data stated by the manufacturer were
confirmed in the industrial high pressure diecasting foundry of W Hesse & Bauckhage GmbH
in Germany in the autumn of 2005. Since 2001
there have been two STRIKOMELTER® systems in
use in this foundry; these are MH II-N 2000/1000
G-eg units and the investigation was based on
the following operating conditions:
Alloy: Employment:
231 D, AlSi12Cu1 (Fe) EN-AC 47100
- StrikoWestofen GmbH –
239, EN-AC-43000
- customerThe
- manufacturer data for
metal loss specified in
50% ingotsbrochures
5-7 kg were therefore
50% dry returns,
size
- 0.3-2 kg
not only
confirmed,
but
with some clearly
flitterexceeded.
Other:
Flux was used on the melting ramp and in the holding bath
FTJ October 2008
The in
the ne
yield
weigh
Using
the va
refers
eration
300-k
meas
conta
achiev
ferenc
losses
melt
treatment
in the ladle:
- adding of salts
- impeller, …
dross in
the shaft
dross on
the bath
dross in the ladle
with / without melt
treatment
dross take-off from furnace
metal
portion
salts +
metal oxides
Draft testing procedure
Draft testing procedures
The investigation examined both the gross and the net metal
yields. Using only ingot, a gross yield (ratio of initial metal weight to
the metal weight at the tap) was determined at 99.75%.
Using a charge of 50% ingots and 50% returns the value was
approx. 99.40%. The net yield refers to the metal after additional
drossing operations in the ladle; for this, the weight of the 300-kgladle before and after drossing was measured on a precision weight
scale. Table 1 contains the results of the net metal yields achieved in
the foundry as well as previous reference values. They show that the
metal losses were in all cases below 1%.
The manufacturer data for metal loss specified in brochures were
therefore not only confirmed, but clearly exceeded.
Financial and technical advantages
Based on the determined values, the enormous advantages of the this
particular system can be calculated as follows:
• Metal price 2,400 €/t
• Total melting times 6,600 h/a
• Melting capacity 1 t/h
• Increased metal yield by 1%
• Savings / pa 158,000 €
The increased metal yield by only 1% permits a yearly saving of
€158,000! In comparison to many older furnace units with metal
losses of up to 8%, enormous saving potentials occur in connection
to the clearly higher efficiency of the sysytem. The investment in the
modern STRIKOMELTER® technology enables extremely short pay
back periods of 6 to 12 months.
A further financial factor is the savings in energy due to the high
efficiency of the ETAMAX® technology as well as a substantially low
scrap rate due to the better molten metal quality.
StrikoWestofen GmbH, Wiehl, Germany, July 2006
Charged material
100 % ingots
StrikoWestofen values
EN AC-47100 / 231 D
Metal yield %
HeBa values
EN AC-43000 / 239
Metal yield %
50 % ingots
50 % returns
99.55 %
99.20 %
99.61 %
99.01 %
Measured values
Hesse
& Bauckhage
Measured
valuesatat
Hesse
& Bauckhage
Financial and technical advantages
257
Based on the determined values, the enormous advantages of the STRIKOMELTER® can be calculated as
recuperator
anddon’t
energy
now how to reduce your rotating
energy bill and
save money? Well
worry,
ology is now available tothe
solvesystem
this problem
for works
you. Morgan’s
that
bestnew
with
ve crucible
furnace
range
is
the
answer
you’re
looking
for.
Melting and Holding
recovery ventilation, but the stand
fuel burner applications, to increa
efficiency, and for this reason is used in gas turbine engines.
andnew
Gas Components
Reduce your energy bill Air
with
technology
Morgan Recuperative
Gas Fired Crucible Furnace
Want to know how to reduce your energy
bill and save money? New technology is
now available to solve this growing problem
and Morgan Molten Metal Systems say its
new recuperative crucible furnace range is
the answer.
technique which would utilise
such that it could significantly
fuel more efficiently. To address
reduce foundries’ fuel costs. To
BACKGROUND
the latest fuel crisis they took
achieve this they looked to their
another
atthat
recuperation
own
existing
technology
Fuel
prices have
been rising atand
such a rapid rate
in recentlook
months
foundries
everywhere
it increasingly
to remain
cost to
effective
& competitive.
and
set out
improve
the
how
it couldarebefinding
redesigned
anddifficult
So foundries are looking to significantly reduce
their energyand
consumption
in order to
efficiency
cost effectiveness
enhanced.
remain competitive.
of the technology to breathe
Recuperation on furnaces is
new life and
intosupplier
the recuperator
notMorgan
a newMolten
concept,
havingisbeen
Metal Systems
a global manufacturer
of foundry
crucibles,
furnaces
associated
metal handling
and treatment products. With over
system.
around
since
the and
early
1900s.
150 years in the foundry business, Morgan has developed a leading position and
Take
up of the technology
enviable reputation in the market worldwide, as it can offer truly integrated crucible
accelerated
during&the
1970s
whatit designs
is recuperation?
based metal melting
holding
systems. This So
is because
and manufactures
oil both
crisis,
which created
similar
the crucibles
and the furnaces.
Morgan understands
that optimising
the waste
A ‘recuperator’
recycles
performance
any metal
melting and holdingheat
process
in the
foundry
is dependent
problems
to of
those
being
from
the
exhaust
gasesonto
balancing a complex set of variables. The furnace, customer working practices,
experienced today - rising
pre-heat
the
combustion
air to
crucible and metallurgical processes all interact. So to achieve the balance required,
energy
costs
and
supply
the
burner.
It
achieves
this
via
the system needs application specific design for both the consumables and the
equipment. Morgan was quick
restrictions.
a counter-flow heat exchanger
at the time to respond to
which, on a crucible furnace,
From this technological background, Morgan MMS was keen to address the concerns
thethat
situation
and developed
thesetstandard
exhaust
foundries had expressed about their risingreplaces
fuel bills. We
out to design
a
a range
crucible
furnaces
The recuperator
molten of
metal
system that
used fuel in a muchstack.
more efficient
way, such that ittransfers
could
significantly reduce
foundries fuel costs. To achieve
we looked
our existing
incorporating
a recuperation
wastethis
heat
in thetoexhaust
to the
By recovering some of the energy usually lost as waste heat, the r
fuel fired crucible furnace significantly more efficient. Morgan’s
designer of both furnaces and crucibles allowed us to significantly
Background
Fuel prices have been rising at such a rapid rate
efficiency of the design of the recuperative system as applied to fu
in recent months that foundries everywhere are
finding it increasingly difficult to remain cost
furnaces, through optimal selection of materials and components a
effective and competitive, so they are looking to
significantly reduce
energy consumption.
oftheirdesign.
Instead of just bolting a recuperator system onto an exis
Morgan Molten Metal Systems is a global
manufacturer and understood
supplier of foundry crucibles,
that optimum efficiency would only come by starting
furnaces and associated metal handling and
and
setinout to create a design which truly integrated the recu
treatment products.
With so
over we
150 years
the foundry business, Morgan has developed a
furnace
and the
leading position and
enviable reputation
for itscrucible. The result of this development work is th
truly integrated crucible based metal melting and
technology and how we might redesign and enhance it.
Morgan
Recuperative
Furnaces,
available as both static bale out a
holding systems. The
company says
its success
stems from the fact it designs and manufactures
Working
Metallurgy
foundries with
the lowest gas bills possible
at both the
both the cruciblesto
and provide
the furnaces. Morgan
Practice
understands that optimising the performance
stations.
of any metal melting
and holding process in the
foundry is dependent on balancing a complex
set of variables; the furnace, customer working
practices, crucible and metallurgical processes all
interact. So to achieve the balance required, the
system needs application specific design for both
the consumables and the equipment.
From this technological background, Morgan
MMS was keen to address the concerns that
foundries had expressed about their rising fuel
bills so they set out to design a molten metal
system that used fuel in a much more efficient way,
258
EXCEL E
Furnace
Recuperation on furnaces is not a new concept, having been around since the early
1900’s. Take up of the technology accelerated during the 1970s oil crisis, which
created similar problems with rising energy costs and supply restrictions as we are
experiencing today. Morgan was quick at the time to respond FTJ to the October
situation and2008
developed a range of crucible furnaces incorporating a recuperation technique which
would utilise fuel more efficiently. To address our latest fuel crisis we took another
look at recuperation and set out to improve the efficiency and cost effectiveness of the
face chamber lining, which incorporates Morgan’s patented gas radiant panel
technology which radiates heat directly onto the crucible and thereby to the metal,
rather than traditional brick designs, which allow more heat to be lost to the stack as
Melting and Holding
waste .
combustion air entering the fuel
burner, thus preheating it. Since
the gases have been pre-heated,
less fuel is needed to heat those
gases to the required furnace
melting/holding temperatures.
The recuperator technique
is used for heat recovery in
many other industries, such as
chemical plants and refineries,
in applications where there is
fluid-fluid counter flow and
in closed system processes
such as in refrigeration cycles.
There are several other systems
of heat recovery available
including the regenerative
heat exchanger, the rotating
recuperator and energy recovery
ventilation, but the standard
recuperator is the system that
works best with fuel burner
applications, to increase the
overall efficiency. For this
reason it is used in gas turbine
engines.
By recovering some of the
energy usually lost as waste
heat, the recuperator makes
a fuel fired crucible furnace
significantly more efficient.
Morgan’s unique position as
a designer of both furnaces
and crucibles allowed them
to significantly enhance the
efficiency of the design of the
recuperative system as applied
to fuel fired crucible furnaces,
through optimal selection of
materials and components
and true integration of design.
Instead of just bolting a
recuperator system on to
an existing furnace, they
understood that optimum
efficiency would only come by
starting from first principles,
and so they set out to create a
design which truly integrated
the recuperator with the furnace
and the crucible. The result
of this development work
is the new range of Morgan
recuperative furnaces, available
as both static bale out and
as tilting systems to provide
foundries with the lowest gas
bills possible at both the casting
and melting stations.
Performance benefits
Due to the integrated design,
the range of recuperative
furnaces gives a number of
benefits to the foundry far
beyond the key advantage of
FTJ October 2008
lowering their gas bill and they
Gas Radiant
are considered
here.Panel
Cost effective
The company says the new
technology incorporated into
the recuperative system makes
it the most cost effective
product of its kind. Existing
recuperative products on the
market quote a maximum of
25% energy reduction compared
with an equivalent nonrecuperative furnace. Morgan’s
new recuperative technology
provides a minimum of 35%
energy reduction, and often
higher. At some foundries,
as high as 50% reduction in
gas usage can be achieved,
compared to their existing
firebrick lined gas-fired
furnaces.
The cost savings achieved by
more efficient use of gas from
the new recuperator technology
are enhanced by incorporating
the very latest refractory and
insulation technology into the
furnace design. Using the latest
materials technology developed
within the Morgan Crucible
Group provides the lowest level
of thermal conductivity available
commercially, which minimises
heat losses from the furnace
chamber. Melting efficiencies
as high as 40% are achieved,
compared to conventional gasfired crucible furnaces, where
20-25% is typical.
The new recuperative furnace
also delivers more cost effective
running costs in terms of longer
consumable life. Crucible life
is enhanced due to the fully
modulating burner technology,
which has two advantages in
terms of crucible life. Firstly it
burns very close to stoichiometric combustion, so
Design
that no excess Integrated
oxygen is present
in the furnace
chamber, which would otherwise attack the high
graphite and carbon content of the crucible causing
oxidation. Secondly it introduces a high velocity
gas stream into the chamber, which creates an even
heat distribution over the whole crucible, ensuring
no hot spots exist that would otherwise cause
thermal stresses, leading to distortion. This highly
efficient thermal design feature is further enhanced
by the hot face chamber lining, which incorporates
Morgan’s patented gas radiant panel technology
which radiates heat directly on to the crucible and
thereby to the metal, rather than traditional brick
designs, which allow more heat to be lost to the
stack as waste.
The new integrated recuperative furnace
design also facilitates fast commissioning times,
minimising foundry downtime, if replacing a nonrecuperative unit. Traditional recuperative designs
are constructed using separate floor mounted
components, with gas pipes trailing across the
foundry floor. This leads to long and complicated
installation and commissioning times and presents
health and safety risks to the operator and risk of
damage to the critical components from fork-lift
traffic in the foundry.
Optimum metal quality
The same technological features that minimise the
running costs of the new recuperative furnace also
contribute to delivering optimum metal quality. The
fully modulating, high turn down ratio burner gives
tight control of metal temperature typically down
to ±5°C, allowing foundries to achieve the stringent
quality controls required for modern automotive
castings, reducing rejects and minimising costly
metal losses. The gas flow design is such that the
exhaust gases exit from the side of the chamber,
not over the top of the crucible, ensuring that
gases do not contact the molten metal, thus
minimising the potential for gas pick up which
would otherwise lead to porosity in castings.
Health, safety and the Environment
With operator comfort and safety in mind the highly
efficient insulation which helps minimise running
costs also ensures that casing temperatures are low
and that the ambient temperature of the working
259
years just by the reduction on their gas bill. On top of this, there is often additional
financial support available in terms of government grants and loans available to
support energy saving and carbon footprint reduction schemes. In the UK the Carbon
Trust provides interest free loans to fund the purchase of energy efficient capital
equipment to reduce carbon emissions. Similar schemes are available in a number of
other countries.
Melting and Holding
environment is as comfortable as possible. The
unique burner design also reduces noise levels
during use of the furnace to unparalleled levels,
with under 75dBA measured at 2m from the unit,
which is below current regulations for the UK
requiring PPE action.
The new burner technology in Morgan’s
recuperative crucible furnace also has the
added benefit of reducing ‘greenhouse’ gaseous
emissions. Typical CO2 emissions for a BT1300
size furnace are reduced to ~12 tonnes per year
compared to ~20 tonnes per year for a nonrecuperative equivalent furnace run under the
same conditions. Raising the temperature of the
input air by recuperation also raises the level of
NOx generated, such that conventional recuperative
forced air burners run above 400ppm. Input air is
typically pre-heated up to 250°C in a recuperative
crucible furnace. Under these conditions Morgan’s
recuperative burner technology reduces NOx
emissions below 125ppm.
Foundries save money
Initial foundry trials of the new recuperative
technology started in the UK, where the technology
was developed. Following initial commercialisation
in Europe, Morgan’s newest furnace technology is
now being utilised successfully in other markets.
In work with foundries across the world, typically,
a project to optimise their melting and holding
practices will start with a
detailed audit of the foundry’s
existing capabilities and a
comparison with their energy
costs, working practices and
alloy demands. To complement
the recuperative technology
Morgan has developed a series
of analytical tools which can
help a foundry identify where
it can save money on gas bills.
Invariably, the biggest potential
saving identified is replacement
of the existing furnaces with
this new recuperative furnace
technology. Depending on the
state of the furnaces being
replaced and the gas price, it is
not uncommon for a foundry to
find that the investment in new
recuperative furnaces is paid
for within two years just by the
reduction on the gas bill. On top
of this, there is often additional
financial support available in
terms of government grants and
loans to support energy saving
and carbon footprint reduction
schemes. In the UK the Carbon
Trust provides interest free
loans to fund the purchase
of energy efficient capital
equipment to reduce carbon
emissions. Similar schemes are
available in a number of other
countries.
For more information contact:
Dr Andy Wynn, global technical
director, e: andy.wynn@
morganplc.com or Bob Thomas,
chief furnace engineer, e: bob.
thomas@morganitecrucible.
com or Tim Heeks, furnace
design engineer, e: tim.heeks@
morganitecrucible.com at Morgan
Molten Metals Systems, Woodbury
Lane, Norton, Worcester WR5 2PU.
UK.
Web: www.morganmms.com
Introducing...
...the latest in improved technology
for your foundry,
MORGAN MOLTEN METAL SYSTEMS’
Recuperative Furnace:
Realize these benefits with this
new furnace:
� Up to 50% energy savings
� Improved crucible life
� Very low noise emissions
� Environmentally
friendly emissions
260
MORGANITE CRUCIBLE LTD
Woodbury Lane
Norton, Worcester WR5 2PU
Tel: +44 (0) 1905 728200
MORGANITE Fax: +44 (0) 1905 767877
CRUCIBLE LTD Web: www.morganmms.com
FTJ October 2008
Meltech Ltd has introduced a new
range of compact furnace bodies
designed specifically for the small and
medium foundry.
Mag-Melt furnaces meet all current and proposed EMF regulations and
come with a certificate of conformity
New induction furnace body hits the market
Having an all steel construction up to 1,000kg
capacity, the new compact furnace bodies can
easily be connected to all brands of inverter
system and in most cases without the need for any
modification to existing brickwork.
Up to 1,000kg steel capacity, the industry
has historically favoured unscreened box type
tilting bodies, this trend has been largely down
to economic and maintenance considerations. As
a knock-on effect, today’s second-hand furnace
market limits customers’ choice as to the brand
and style of equipment available. In Meltech’s
experience the market for furnace bodies outstrips
whole-system sales by around two to one and in
some cases has hampered sale potential because
quite simply, ‘there were not enough loose bodies
available at the time to meet demand’.
Limitations in availability and changing market
trends were the catalyst which encouraged
engineers at the UK based supplier to study the
possibility of developing a furnace body. In order
to succeed, the new system would have to meet
an exacting specification to include features which
were common to much larger steel frame or shell
furnaces but with simplicity and build cost equal
to, or better than, a box furnace.
Study complete . . furnace designed
Today, some 12 months after that initial study was
completed, the new furnace has been designed,
built, tested and certified with the first two units
now sold and completing commissioning trials.
The Mag-Melt furnace body has a fabricated
steel construction, which is magnetically screened,
utilising air cooled shunt gap technology offering
improved efficiency compared to other steel shell
or steel frame furnaces. Power ratings of well
above 750kw on a 1,000kg body are achievable.
On the 500kg capacity units already constructed,
fussy water manifold arrangements and shunt
cooling circuits common to other steel furnaces
have been completely designed out, leaving the
FTJ October 2008
interior of the body uncluttered
and free of pipe work. Each
shunt is easily lifted out by
undoing just two retaining
bolts. Unlike most other
furnaces, there are no shunt
compression bolts present on
the furnace either, inside or out.
In addition to the
simplification of the water
circuitry, there has been further
development. This includes
the almost total removal
of combustible insulation
materials within the furnace,
anywhere other than on the coil
itself, thus reducing ground
fault problems associated with
charred or burnt insulators.
This is possible by the clever
use of refractory within the
body which has eliminated the
need for coil backing materials,
Mica, insulation tubes, top hat
washers and so on.
While it is not possible to
eliminate lining failure, metal
run through and damage to any
furnace, the Mag-Melt design
does reduce potential electrical
or ground fault problems.
However, should they occur,
the simplicity of the furnace
construction also allows the
damaged coil to be removed in
minutes by undoing just four
bolts and the power leads.
Certification conformity
The furnaces meet all current
and proposed EMF regulations
and come with a certificate
of conformity. Options
include hydraulic lid, lip fume
extraction, refractory push out
and pre-tilt system for accurate
pour control.
Steve Macey of Meltech
explains the importance and the
customer reaction to this new
product line. ‘We accepted our
first two orders for Mag-Melt
furnace bodies several weeks
ago. Customers seem impressed
with the thought we have put
into the product. For example,
our access cover has proper
lifting handles, big enough to
take hands wearing heavy-duty
gloves – a small but important
point that demonstrates our
complete attention to detail.
Our design people have years
of experience fixing all makes
of systems and understand the
advantages and disadvantages.
They have been innovative and
used a systematic approach to
manufacture, and for that they
must take the credit for this
product.’
Meltech is also the service
and sales agent for ABP
induction and supply their
induction melting and heating
equipment to the UK and
Ireland.
Meltech Ltd.
Tel: +44 (0) 1902 722588;
fax: +44 (0) 1902 730142;
email: steve@induction-furnaces.
co.uk
web: www.induction-furnaces.co.uk
261