Preparation of pelletized coke by co-carbonization of caking coal and pyrolyzed char modified with tar produced during pyrolysis of woody biomass

Abstract

To further the utilization of biomass for cokemaking at ironmaking facilities and to reduce CO2 emissions, carbon/carbon composite (CC) from tar and char is produced from the pyrolysis of a woody biomass with quartz-made fixed-bed reactor at 10 °C/min to 200–500 °C. Then, the optimum conditions for preparing high-strength coke by blending caking coal and CC is investigated. The specific surface areas of char and tar yields via sawdust pyrolysis are maximized at 550 °C. When the mixture of pyrolyzed char and tar produced in large quantities during the same process is co-pyrolyzed, the pore observed in prepared char completely disappears due to filling of carbonaceous materials derived from tar-pyrolysis into char pores, and char yield is improved. When the strength of the coke prepared from the mixture and pelletization of caking coal and prepared CC is investigated, the indirect tensile strength of the prepared coke tends to decrease with an increase in temperature of CC preparation. And, it was found that the optimum CC preparation temperature is 250 °C (CC250) for high-strength coke preparation. Although increasing the blending ratio of CC250 to caking-coal decreases the strength of the coke, the extent of decreasing strength is smaller than that of slightly-caking coal or pyrolyzed char blended to caking coal. The filling of carbonaceous materials derived from tar-pyrolysis into pores of sawdust char during CC preparation influences the coke strength, such that the value is greater than that of physical mixture of sawdust char and carbonaceous materials from tar prepared with individually (carbonaceous materials derived from tar not loaded into pore in char).