THEORETICAL-STUDY OF BURNING CARBON PARTICLES

The dynamic behavior of single carbon particles in a hot oxidizing ambient is studied. The theoretical model is based on a uniform-temperature, constant-density, spherical particle of carbon surrounded by a quiescent gas phase. With simplifying assumptions regarding the transport and thermochemical properties of the gases, the influences of the gas phase are examined (for the limiting cases of frozen and equilibrium gas chemistry). These include the contributions of radial convection and radial diffusion in mass and energy transport from the particle. Both the direct oxidation of carbon via the reaction C + 1 2 O2 and the indirect oxidation via the reaction C + CO2 are taken into account, and both are found to play significant roles in the dynamic behavior of carbon particles. Several comparisons with available experimental data establish the validity of the theory for practical purposes. Comparison is also made when possible with previous theoretical studies. The theoretical results indicate that the history of a particle during consumption involves complex interactions of convective, diffusion, and thermochemical effects. Analytical expressions are derived and numerical results are presented for the rate of carbon mass loss showing the relative influences of the gas-phase chemistry, the gas-phase convective and diffusive transport, and the heterogeneous reaction kinetics on the overall reaction rate. © 1979.