3 Reference sheet.
Low-temperature Oxyfuel. Uniform heating for higher
productivity, no hot spots and less emissions.
Low-temperature Oxyfuel in the melt shop at SAPA Heat Transfer, Sweden.
Summary
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Customer
SAPA Heat Transfer, Sweden.
Up to 100%, typically 30–50%, higher melt rate due to uniform heat distribution
Up to 50% lower fuel consumption
Low flame temperature, comparable to that of airfuel technology
Reduced CO2 and SO2 emissions and ultra-low NOX emissions
Challenge
With the increasing demands for non-ferrous metals, increasing the throughput of existing melting furnaces represents a challenge for the aluminum industry. Producers also need to constantly improve process yields, cut fuel
consumptions and reduce gas emissions, such as CO2 and NOX. This market situation is familiar to Linde, with extensive knowledge and experience of combustion and customer processes from over 130 oxyfuel installations in
aluminum.
Low-temperature Oxyfuel
Low-temperature Oxyfuel combustion technology is uniquely designed for the challenges that exist within the
aluminum industry. Such challenges include boosting capacity, reducing fuel consumption, improving yields, and
reducing emissions while avoiding hot spots with uniform furnace temperatures. The combustion occurs under a
diluted oxygen concentration by mixing the furnace gases into the combustion zone. This process slows down the
oxyfuel combustion reactions and results in lower flame temperatures, comparable to those of airfuel technology, which are below the point at which thermal NOX is created. The mixing of furnace gases into the flame also
disperses the energy throughout the entire furnace for uniform heating and more efficient melting. The dispersed
flame contains the same amount of energy but with a much more effective distribution. The overall result is more
homogenous heating and melting, enabling not only a higher power input and thus higher melt rates, but also reduced formation of dross and NOX emissions.
[°C]
In-furnace temperature measurement shows a uniform and
1400
low flame temperature without peaks, which helps to achieve
1200
higher melt rates and thus avoiding hot spots and thermal NOx.
1000
4000
3000
800
600
2000
500
0
[mm]
600
Fuel
Oxygen
CO2
H2O
Diluted flame
[mm]
1000
–500
700
800
0
900
1000
1100
1200
1300
1400
1500
1600
In Low-temperature Oxyfuel, the flame is diluted with the
furnace gases, which lowers the flame t­ emperature and
promotes an effective heat distribution.
CH4 + 2O2 + Hot furnace gases
CO2 + 2H2O + Heat
3 Low-temperature Oxyfuel. Uniform heating for higher productivity, no hot spots and less emissions.
With oxyfuel combustion, removing nitrogen from the combustion and heat transfer process has several
advantages including higher production output in new or existing furnaces, reduced fuel consumption, improved
process control, and lower emissions. The thermal efficiency of Low-temperature Oxyfuel is equal to that of
conventional oxyfuel.
100%
Thermal efficiency
100%
90%
90%
80%
80%
70%
70%
60%
60%
50%
Oxyfuel
50%
40%
Airfuel
40%
30%
Fuel saving
30%
20%
20%
10%
10%
Fuel saving
Oxyfuel combustion
2 of 2
0%
0%
0
100
200
300
400
500
600
700
800
900
1,000 1,100 1,200 1,300 1,400 1,500
Flue gas temperature [°C]
Features
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Comparable flame temperature to that of airfuel technology
Adjustable degree of flame dilution
Suitable for all types of reverberatory furnaces
Power: 0.2–3 MW
Self-cooling ceramic burner stone, 300 mm burner diameter, weight 80 kg
Compact, powerful and modular design of burner for easy installation and maintenance
Integrated flame monitoring by UV cell and pilot flame for automatic ignition
Customer benefits
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Low-temperature Oxyfuel for a homogenous melting, resulting in increased furnace throughput capacity.
Up to 100%, typically 30–50%, higher melt rate.
Up to 50% lower fuel consumption
Uniform furnace heating to avoid hot spots, thus reducing dross formation
Low maintenance: no need for recuperator, electrical air blower or regenerative solution
Substantially reduced flue gas volumes, up to 80%, for a compact exhaust solution
Major reductions in CO2 and SO2 emissions – up to 50%
Ultra-low levels of NOX emissions, reduced up to 90% reduction
SAPA Heat Transfer, Finspång, Sweden is a producer of aluminum heat-exchanger strip for the automotive ­market.
The company melts rolling mill scrap, wire mill scrap and primary ingots of various shapes and sizes. SAPA
installed oxyfuel back in 1995 to increase production and to reduce NOX emissions. The 28-tonne melting furnace
was optimized in collaboration with Linde in 2002. To further improve the furnace performance the new Lowtemperature Oxyfuel was brought into use in mid-2005. Since the switch from conventional oxyfuel, SAPA has seen
a 10% increase in melt rate, a 10% reduction in energy consumption, a 9% reduction in dross formation, and a
90% reduction in NOX emission.
Linde North America, Inc.
575 Mountain Ave., Murray Hill, NJ 07974 USA
Phone +1.800.755-9277, sales.lg.us@linde.com www.lindeus.com www.lindemetallurgy.com
Linde North America Inc. is a member of The Linde Group. Linde is a trading name used by companies within the Linde
Group. The Linde logo is a trademark of The Linde Group. © The Linde Group 2012.
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More capacity at SAPA