Abstract：A numerical model was developed to investigate the tar production during pyrolysis of a single coal particle. The model was based on the fragmentation and diffusion (FD) coal pyrolysis model and considered the secondary reactions and diffusion inside the coal particle. The model was validated by pyrolysis experiments in a drop-tube furnace and then used to investigate the influences of the final temperature, heating rate and particle diameter. The results show that the competition between the secondary reactions and tar diffusion greatly influences the tar production. Increases of the final temperature and the heating rate improve both the tar secondary reactions and the diffusion while increasing the particle diameter improves the tar secondary reactions and hinders the diffusion. The final tar yield decreases with increasing final temperature, increasing heating rate and increasing particle diameter.
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