Experimental study of commercial charcoal as alternative fuel for coke breeze in iron ore sintering process

Abstract

Coke breeze and anthracite are the traditional heat suppliers to iron and steel industry while global warming issue has been a focus of concern. Using biomass for partial or complete replacement of coke breeze in the iron ore sintering process is an attractive technique for reducing emissions of greenhouse gas and gaseous pollutants. However, short supply of charred wood and low sinter quality for raw biomass are the biggest constraints for wide application in sinter production at present. In this paper, the commercial charcoal made from sawdust, nutshell and some other waste biomass (with extensive source and low cost) was employed as the alternative fuel in the sintering process. The primary fuel was coke breeze with 20%, 40%, 60%, 80% and 100% substitution of the fixed carbon input with charcoal. The flame front characteristics and sintering performance were compared at different substitution rates. The results indicated that the flame front accelerated with the increase of charcoal substitution rate due to its higher intrinsic reactivity and larger specific reaction area. Both duration time of melting temperature and melt quantity index reached their peak values at 60% charcoal substitution rate. When the substitution rate exceeded 60%, duration time of melting temperature and melt quantity index dropped sharply, suggesting that the sinter strength was deteriorated badly. Reasons for the weakened sinters were analyzed from the views of combustion efficiency (heat generation) and heat accumulation performance (heat utilization). NOx emission concentration reduced significantly with the increase of charcoal proportion. Finally, suggestions for improving charcoal sintering performance were discussed based on the present study. To maintain high sinter strength, it is recommended to avoid the excessively high combustion rate at high charcoal proportion.