Based on shapeless pore model (SPM) proposed by the authors

the equations of heterogeneous combustion kinetics

mass transfer

heat transfer

continuous momentum conservation of flow

which controll coal particle combustion were given. Numerical calculation of single particle combustion was made

and the effects of porosity

pore area

particle size and temperature on reactivities of chars were studied. It was found that ignition was heavily related to pore area

and was less related to porosity. The results were compared with the data of Smith. It was shown that SPM could be applied both to coal particle combustion and to heterogeneous reaction of other porous materials.