Reduction of FeO in Slag with Coal Char.

Abstract

Recently, many blast furnaces have increased pulverized coal injection. Unburnt coal char is generated from pulverized coal injection and a portion of it remains in the slag. This interferes with tapping by increasing slag viscosity, and can make blast furnace operation unstable. Reduction of FeO with different types of coal was measured in simulated blast furnace slags at 1450°C, using a constant volume pressure increase (CVPI). The reaction rate of FeO was observed to be independent of the type of coal used regardless of different components such as volatile matter and ash. The measured rates at 1.0% and 3.0% of FeO in the slag were 2.77 × 10 -7 and 1.58 × 10 -8 mol/cm 2 s respectively. The overall rate is controlled by a series of processes such as the reaction of CO 2 with C, CO with FeO in slag, liquid phase mass transfer of FeO in the slag, and gas phase mass transfer. For low FeO contents, when the gas evolution rate is low, liquid phase mass transfer is the primarily controlling mechanism. A model to predict the amount of char in the slag at tap based on these results is presented.