Oxgen Level Control and VSDs on Combustion Fans

Controlling oxygen levels and using Variable Speed Drives (VSDs) on the combustion air fans on the reheating furnace helps to optimize combustion in the furnace. Excess air can substantially decrease combustion efficiency as it leads to excessive waste gases. Fuel-air ratios of the burners should therefore be checked regularly. The use of VSDs on combustion air fans on the reheating furnace also helps to control the oxygen levels, specially as the load of the furnace may vary over time. The savings depend on the load factor of the furnace and the control strategies applied.

Another way to control the oxygen levels is to increase oxygen content of the combustion air. This can be done either by mixing in ambient air or by using 100% oxygen. The reduction in exhaust gases can lead to substantial fuel savings. The fuel savings have to be compared to the cost of oxygen to estimate economic benefits (Worrell et al., 2010. p. 103).

Development Status Products
Commercial
Rolled steel

Oxgen Level Control and VSDs on Combustion FansCosts & Benefits

Parent Process: Rolling Mills
Energy Savings Potential

A conservative approach estimates energy savings to be around 10%, or 0.33 GJ/t-rolled steel.
VSD on a combustion fan of a walking beam furnace at a UK based mill reduced the fuel consumption by 48%. 

CO2 Emission Reduction Potential

Emissions are reduced by 16.6 kg CO2/t-rolled steel.

Costs

Retrofit capital costs are estimated at $0.79/t-rolled steel.
Installation of VSDs in a UK based mill had a payback time of 16 months  (US EPA, 2010. p.29). 

Oxgen Level Control and VSDs on Combustion Fans Publications

Energy Efficiency Improvement and Cost Saving Opportunities for the U.S. Iron and Steel Industry

The U.S. Environmental Protection Agency’s (EPA) energy guide, Energy Efficiency Improvement and Cost Saving Opportunities for the U.S. Iron and Steel Industry, discusses energy efficiency practices and technologies that can be implemented in iron and steel manufacturing plants. This guide provides current real world examples of iron and steel plants saving energy and reducing cost and carbon dioxide emissions.

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