Oxy-fuel heating and direct flame impingement furnaces increase efficiency and save fuel

© Gorodenkoff, #168980917, 2019, source: stock.adobe.com


Air Energy Carbon
Manufacture of basic metals Manufacture and repair of metal products, machinery and equipment
Investment cost:
High cost
High cost
Resource savings: Energy:
The savings vary on different applications but are normally between 30-50 %

Combustion needs fuel, ignition, and oxygen. Normal air contains only 21 % oxygen and most of the rest is nitrogen which is only ballast and has no part in combustion. Using pure oxygen increases combustion efficiency significantly as there is no ballast to be heated up. This method has traditionally been used for smelting, but since the 1990s it has also been available for (re)heating furnaces. AGA which is part of the Linde Group has developed the technology and sells both new installations and refitted furnaces.

Potential fuel savings are significant; one tonne of steel, for example, requires around 350 kWh of energy to melt, but with oxy-fuel it is only 260 kWh. The savings vary in different applications, but range between 30 and 50 %. For industry, however, often the biggest benefit is increased production speed and efficiency (20-30 % gains) as less ballast is heated up.

The introduction of technologies, such as Flameless Combustion and Direct Flame Impingement, have also boosted efficiency by allowing the heat to be spread out more evenly.


  • Significantly lower fuel consumption with 30-50 % less fuel needed
  • Reduced CO2 and Nx emissions
  • Efficiency and productivity increase by up to 30 % 

Niemi, T. 2009, Increased efficiency in heating: state-of-the-art oxy-fuel combustion, http://www.ffrc.fi/FlameDays_2009/NiemiPaper.pdf

Von Scheele, J et al., Flameless oxyfuel combustion for increased production and reduced CO2 and NOx emissions. Stahl und Eisen 128 (2008) nro.7,http://www.linde-gas.com.ar/es/images/Flameless%20oxyfuel%20for%20more%20production%20CO2%20NOx%20SuE%200708_tcm245-10828.pdf

Heating Furnaces, AGA Industrial Gases, https://www.aga.fi/en/processes_ren/melting_heating/heating_furnaces/index.html

Laitala, M. 2006, Happipoltto säästää energiaa ja pudottaa päästöjä. Tekniikka & Talous (in Finnish), https://www.tekniikkatalous.fi/uutiset/happipoltto-saastaa-energiaa-ja-pudottaa-paastoja/d68494d7-830d-34fb-a3cc-05bbb83ea56b

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