A novel ghost-cell immersed boundary method for fully resolved simulation of char particle combustion has been developed. The boundary conditions at the solid particle surface, such as velocity, temperature, density, and chemical species concentration, are well enforced through the present method. Two semiglobal heterogeneous reactions and one homogeneous reaction are used to describe the chemical reactions in the domain, and the Stefan flow caused by the heterogeneous reactions is considered. A satisfactory agreement can be found between the present simulation results and experimental data in the literature. The method is then used to investigate the combustion property of a char particle and the interaction between CO2 gasification and O-2 oxidation. Furthermore, combustion effect on the exchange of mass, momentum and energy between gas- and solid- phase is explored. (c) 2018 American Institute of Chemical Engineers AIChE J, 64: 2851-2863, 2018