Coal gasification technology is a prominent technology in the coal chemical industry and serves as the fundamental basis for various process industries, including coal-based chemicals, coal-based liquid fuels, Integrated Gasification Combined Cycle (IGCC) power generation, multi-generation systems, hydrogen production, and fuel cells. The gasification process generates significant quantities of ash residue, with annual emissions exceeding tens of millions of tons and accumulation reaching hundreds of millions of tons. Accordingly, there is an urgent need to investigate methods for its disposal. The combustion of gasified fine ash (GFA) was conducted in a tube furnace, and the conventional shrinking core model was modified to accurately predict the combustion behaviors at different temperatures (900°C–1500°C). We divided the reaction temperatures into three ranges, which is defined as unmelted combustion (T<DT), melted combustion (T>FT) and mixed combustion (DT<T<FT) (DT: deformation temperature; FT: flow temperature). There is a large difference between the reaction rates of unmelted and melted combustion of GFA. In the range of DT<T<FT, the ash in the grains existed as a liquid-solid state, and had high viscosity and low fluidity, but still adhered to the grain surface, which prolonged the grain burnout time. At T>FT, the surface ash of GFA grains fell off, and the residual carbon and gas-phase reactants were nearly no longer affected by the diffusion resistance, thus significantly accelerated the reaction of internal residual carbon. In order to predict the melt combustion process more accurately, the time term of the shrinkage core model (SCM) is modified, and the effective diffusion coefficient of T>FT is defined.
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