A model of post‐combustion and heat transfer at smelting reduction with a foamy slag

Abstract

A smelting reduction reactor with post‐combustion in a foamy stag has two slag layers. In the lower, iron oxide from the slag is reduced to iron by carbon. In the upper, the gas from the reduction is post‐combusted to CO2+H2O. The post‐combustion heat is transferred from the rising post‐combustion gas to the upper slag, and, therefrom, by slag circulation to the lower slag layer where the endothermic reduction reaction takes place. Unavoidably, slag circulation also transfers part of the char into the upper slag where it is oxidised. A kinetic post‐combustion and heat transfer model describes these phenomena. The main process parameters, namely real post‐combustion degree, carbon oxidation, heat transfer efficiency, distribution of temperatures of gas and slag in the single regions of the reactor, coal consumption, and iron production rate are given as functions of the ratio of post‐combustion oxygen to gas evolution rate of the system. The main influences on which heat efficiency and off‐gas temperature as the most important output parameter depend are discussed. Controlled stirring and a regular gas through‐put are of primary importance. The required values are given. A comparison with pilot plant results of the CSM process shows good agreement with the model results.