Oxygen enrichment in steel production

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Oxygen enrichment in steel production

by Minxing on December 11, 2010

Reheating process is the final heating process in steel production. Semi-production needto be reached uniform temperature during this process. This process is one of the biggest

energy consumers at site. Energy consumption, processing heat and pollution formation

can be represented by the chemical reaction:

Therefore, reducing the exhaust of N2 by using oxygen-enriched air can increase energy

efficiency, reduce flue gas losses and emissions in furnaces. Schele (2007) stated that

the max efficiency of oxyfuel combustions is 72% without heat recovery.

The technology of oxygen enrichment in combustion air has been used in steel sectors for

decades. Two problems have been addressed from the real production. One is the

increase in flame temperature. The other is the potential of NOX forming.

Compared with conventional oxy-enrichment, flameless oxyfuel combustion became

attractive to steel manufacturing. The first flameless oxyfuel combustion furnace was

installed in 2003. Today, more than 115 reheat furnaces and annealing lines have beenequipped with flameless oxyfuel (Schele et al, 2009). Flameless combustion means the

flame is no longer seen or detected by human eye. There are two ways to obtain flameless

oxyfuel combustion. One is to dilute the flame by recirculating part of its flue gas to theburners. The other is to use separated injection of fuel and oxygen at high velocities(Schele et al, 2009). Fredriksson et al (2008) stated that flameless oxyfuel combustion

reduced heating time by 66% at Ovako, Hofor Works, Sweden.
http://www.minxing.us/wp-content/uploads/2010/12/Outokumpu-1.jpghttp://www.minxing.us/wp-content/uploads/2010/12/Heating-reaction.png


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Till now, some steel companies have implemented flameless oxyfuel combustion,

including ArcelorMittal, Ascomtal (SeverStal), Bhler-Uddeholm (Voestalpine),

Cosipa, Dongbei Special Steel, Outokumpu, Ovako, Scana Steel and SSAB (Schele etal, 2009).For example, Outokumpu stainless steel rebuilt a walking beam furnace in

Degerfors plant, Sweden. The air-fuel system was replaced by flameless oxyfuel in the

furnace by Linde group. The flameless oxyfuel increased heating capacity by 40%-50%and reduced fuel consumption by 25%. The NOX emissions were below 70 mg/MJ

(Ljungars 2004).

Summary

In a long term, converting airfuel burners to flameless oxyfuel burners is an optional for

energy efficiency improvement in Gerdau Ameristell MRM. From the experiences ofother steel companies, flameless oxyfuel combustion will reduce fuel consumption and

CO2 emissions by 50%, increase heating capacity by 50% and reduce NOX emission to

below 70 mg/MJ level (Scherello, 2007).

Reference

Fredriksson, P., Vesterberg, P., Claesson, E., Moroz, G., & Von Scheele, J. (2008).

Ovako, Hofors Works 13 Years Experience of Using Oxyfuel for Steel Reheating;Background, Solutions and Results.Iron & Steel Technology, 5(5), 323-328.

Ljungars, S. Gartz, M. & Von Scheele, J. (2004). Boosting heating capacity using new

technology.Nordic Steel & Mining Review. 49-50.

Schele, J.V, Ritzn, O., & Zilka, V.(2009). Substantial reduction of fuel consumption,

CO2 and NOX emissions when at same time increasing production capacity.Metal,5. 19-21

Scherello, A.(2007). Self recuperative burners, Heating processing.International

magazine for industrial furnaces, heat treatment plants and equipments, 1. 51-53

Scherello, A., Hgner, W., Claesson, E., Bamforth, P., & Mercier,C. (2007). State-of-the-art oxyfuel solutions for reheating and annealing furnaces in steel industry. Proc. METEC

InSteel Con, Dsseldorf, Germany.

Tagged as: Environment, steel

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