Integrated mathematical model of pulverised coal combustion in a blast furnace

Abstract

The shortage of coke production due to the closure of coke ovens has led in Japan and other industrialised countries to increasing the injection of auxiliary fuels, e.g. pulverised coal (PC) into blast furnace tuyeres. The PC injection at high rates of more than 200kg/t requires high burnout within the raceway zone. In order to analyse flow and combustion in the raceway and to assist improvement of burner design, a two-dimensional mathematical model of PC combustion has been developed with simulating both the blowpipe and raceway. Effects of a packed bed on the turbulent features of gas and particulate flow were introduced to the model along with all other pertinent phenomena such as heterogeneous reactions of coke and char particles. Validation work against measurements in two industrial blast furnaces indicated that the model has worked satisfactorily for simulation with and without PC injection. Various measures for burnout improvements were explored under an injection rate of 200kg/tHM. Notable improvements were observed by oxygen enrichment to the secondary air and enlargement of the outer diameter of the injection burner.