Numerical Investigations of CO/CO₂ Ratio in Char Combustion

Abstract

The CO/CO₂ ratio of reactions during char combustion was investigated numerically. The simulations used the pore model with fractal properties, a gas diffusion model suitable for fractal pores, and a carbon-oxygen reaction model to describe the char oxidation. The CO/CO₂ ratio in the primary reactions was derived assuming Gaussian distributions of the activation energies and Maxwell distribution of the oxygen molecular velocity. The numerical simulations of the char combustion for various particle sizes, pore structures, and temperatures revealed that the effects of the secondary reactions and the pore structure on the CO/CO₂ ratio are the main reasons why different researchers obtain different experimental results for of the CO/CO₂ ratio.

Keywords:

• Char oxidation
• CO/CO₂ ratio
• Fractal
• Pores

ACKNOWLEDGMENTS

The work was financially supported by the IHI Corporation (Japan), the National Natural Science Foundation of China (No. 50676048) and the China Special Funds for Major State Basic Research Projects (No. 2006CB200305).