The burning properties of carbon particles in clusters were numerically studied using a mathematical model. Chemical reactions consist in heterogeneous reactions including char combustion and in gases homogeneous reactions. The numerical model predicted gas flux through a cluster, distributions of gas temperature and concentrations of gas species in clusters. Burnout of char particles in cluster is less than that of isolated char particles in the stream. Formation of NO and N2O are restrained from particle clustering. Effects of inlet gas temperature, inlet gas velocity, distribution of particles in cluster as well as particle size on char combustion and flow behavior are numerically investigated. (c) 2006 Elsevier B.V. All rights reserved.