Fundamental Study on Combustion of Pulverized Coal Injected into Coke Bed at High Rate.

Abstract

In view of rebuilding coke ovens and flexible operation of blast furnace, it is one of the most important topics in ironmaking process to establish the stable operation of blast furnace at high pulverized coal injection.Especially, the clarification of the internal behavior of pulverized coal in blast furnace such as combustion behavior in the raceway and consumption or accumulation of unburnt char in the furnace is indispensable.This paper is concerned with the research on the effect of coal injection rate, coal types and coal size on the internal state of blast furnace, with use of a coke-packed hot model furnace and mathematical models which cosist of the combustion mathematical model in the raceway and gas and solid two phase mathematical model in the packed bed.(1) The combustibility of coal at the tuyere level decreased with increase of coal injection rate or decrease of volatile matter in coal. However, the combustibility of coal measured at 700 mm above the tuyere level is over 95%.(2) This phenomenon is explained by the two phase gas and solid mathematical model considering the rate of the solution loss reaction of unburnt char.(3) In case of coarse coal size of –3 mm, the combustibility of coal at 700 mm above tuyere level decreased as well as that at the tuyere level.