Fragmentation and diffusion model for coal pyrolysis

A coal pyrolysis model is presented to describe fragmentation and diffusion of coal particles. This model combines chemical reactions and volatile matter diffusion inside the coal pores with the released primary products undergoing secondary reactions while the volatile matter diffuses inside the pores. Numerical simulations with the model show that the tar diffusivity significantly influences the final coal pyrolysis yields. The model qualitatively describes some mechanisms combining pore diffusion and secondary reactions in coal pyrolysis. The model explains high volatile releases at high temperatures and how coals with similar initial chemical compositions have different final yields in the same pyrolysis environment.