Coke characteristics and formation mechanism based on the hot tamping coking

Superior quality coke with low CRI (Coke Reactivity Index) and high strength is indispensable for the safe and efficient operation of the blast furnace. The hot tamping coking technology is comprehensively investigated when the coal samples undergo plastic stage to improve the coke quality and save the coking coal resource. The influences of the tamping temperature, holding time and tamping stress on semicoke structures and coke characteristics were examined. Results show that hot tamping operation could effectively enhance the coke quality. When the tamping temperature is low and the holding time is short, lower tamping stress could produce coke with a compact pore structure and low CRI. High stress leads to a significant increase in coke porosity. It weakens the improvement of coke quality because the permeability of semicoke is low and abundant volatile gas is released in the latter coking process. When the tamping temperature and holding time are appropriate, higher stress could obtain high-quality coke with compact pore structure and low CRI due to the higher permeability of semicoke and less volatile gas resided in the semicoke. The crushing strength (SR) is influenced by the CRI, porosity, macropore wall thickness and coke homogeneity. Lower CRI, lower porosity, thicker pore wall and better homogeneity contribute to higher SR.