Preparation of biochar from biomass and co-combustion behavior mixed with anthracite: Intrinsic characteristics, kinetics and mechanism.

The preparation of biochar (first hydrothermal carbonization at 240℃-60 min and then pyrolysis carbonization at 400, 600, 800℃), the co-combustion behavior of biochar mixed with anthracite were systematically analyzed, to explore the feasibility of using biochar to replace some coal for blast furnace (BF) injection. Microscopic results indicate that the large pore channel of biochar is conducive to reducing the resistance of oxygen diffusion and improving the oxygen permeation efficiency in the early stage of combustion. The ratio (D1/G) of biochar treated at 800℃ for 30 min is lower, which proves that its degree of graphitization is higher. The breakage of old functional groups and the generation of new functional groups make the structure of biochar denser, leaving better carbonization results. The highest combustion rate of co-combustion shows a trend of first increasing and then decreasing as the proportion of biochar increases. The kinetic model stands out that the significant synergistic effect is observed between biochar and anthracite in the co-combustion process, but this synergistic effect also shows its maximum value within a certain range (biochar proportion is 15 %). The mechanism of co-combustion shows biochar and anthracite complement each other in terms of volatile matter, activity, and process synergy, effectively forming a co-combustion reaction.