INTEGRATED MATHEMATICAL-MODEL OF PULVERIZED COAL COMBUSTION IN A BLAST-FURNACE

The shortage of coke production due to the closure of coke ovens has l ed in Japan and other industrialised countries to increasing the injec tion of auxiliary fuels, e.g. pulverised coal (PC) into blast furnace tuyeres. The PC injection at high rates of more than 200 kg/t requires high burnout within the raceway zone. In order to analyse flow and co mbustion 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 be d on the turbulent features of gas and particulate flow were introduce d to the model along with all other pertinent phenomena such as hetero geneous 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 injectio n. Various measures for burnout improvements were explored under an in jection rate of 200 kg/tHM. Notable improvements were observed by oxyg en enrichment to the secondary air and enlargement of the outer diamet er of the injection burner.