A Simplified Model for the Pyrolysis of Charring Materials

A simplified model of the pyrolysis of charring materials is analyzed. The effects of moisture are neglected, and the heat of pyrolysis is assumed equal to zero. Four stages of pyrolysis are obtained: (i) inert heating, (ii) initial pyrolysis, (iii) thin char, and (iv) thick char. Formulas for the volatile mass efflux, m, are obtained in stages (ii), (iii), and (iv); m = 0 in the first stage. The calculations indicate that the surface temperature controls the volatile production rate in the initial pyrolysis stages (the kinetically controlled regime), while the temperature gradient controls the volatile production rate in the thick char stage (the diffusion-controlled regime). Comparisons of the calculated results with numerical computations are made for the volatile mass efflux, the surface temperature, and the density.