Carbon Injection Into Electric Arc Furnace Slags

Abstract

The reaction between carbon and iron oxide-containing slag is crucial to efficient electric arc furnace steelmaking. The reaction occurs via gaseous intermediates, and the rate of gas generation by carbon gasification is limited by the chemical reactions at the slag-gas and carbon-gas interfaces. The aim of the present study was to obtain an understanding of the gasification rate limiting factors and slag foaming behaviour that could be readily applied to industrial electric arc furnace situations. The rate of carbon gasification was measured in experimental simulations of an electric arc furnace heat with slags containing between 21.6 and 48.2 wt% 'FeO'. It was found that rate control was dominated by the carbon-gas chemical reaction. A model was developed which describes the carbon gasification rate, amount of residual carbon in the slag, gas composition, slag-gas interfacial area and bubble diameter during carbon injection into slag. The model predicts rate control by the carbon-gas chemical reaction, in agreement with experimental observations. The slag foaming behaviour was investigated, and it was found that the foaming index is a useful parameter in quantifying foam height only if void fraction is constant with respect to gas flow rate. The average bubble size was observed to be an important factor in determining foam stability, with smaller bubble size resulting in greater foam height.