Continuous off-gas measurement and energy balance in electric arc steelmaking

A system has been developed for continuous determination of off-gas composition and off-gas volume rate during EAF steelmaking. It comprises devices for gas sampling and analysis of carbon monoxide, carbon dioxide, hydrogen, nitrogen, oxygen and argon, and of measurement of off-gas temperature. The data are processed by a computer to set up the differential heat balance which indicates the flow rates of chemical and sensible heat of the off-gas leaving the furnace at each moment. Several operations during the melting process were investigated with respect to energy utilization. For instance, the hydrogen content during injection of natural gas decreases strongly with increasing oxygen input. During coal injection there is high loss of chemical energy due to non-complete combustion. Also, the extent of combustion depends on the position of the coal lances. Injection of oxygen in the upper furnace part leads to lower loss of chemical but higher loss of sensible heat. The system is optimized at present to decrease the dead time between gas sampling and print out of the analysis.