Abstract: Dense gas-solid reacting flow is practised in many industrial processes where the particle number may be huge and cannot be modelled using the conventional CFD-DEM approach. In this paper, a coarse-grained CFD-DEM model (CGM) is developed to simulate dense gas-solid reacting flow involving multiphase flow and heat and mass transfers. The CGM is first validated against the conventional CFD-DEM simulation results and experimental results. The CGM is then applied to simulate a reacting flow case of biomass gasification in a bubbling fluidised bed gasifier (BFBG) for capability demonstration. The results show that the size- and density-induced particle segregation and bubble evolution affect the hydrodynamics and thermochemical behaviours of biomass gasification in the BFBG significantly. The non-uniform distribution of gaseous species along with the radial and axial directions is captured. Compared with the conventional CFD-DEM, the CGM can reduce the computational cost significantly in the simulation of dense gas-solid reacting systems. The present work provides a cost-effective tool to simulate dense gas-solid reacting flow in various chemical reactors.