The unsteady state computational fluid dynamics model for gas-solid particle flow in industrial scale circulating fluidized bed boiler combining with combustion and desulfurization (using limestone solid sorbent) chemical reactions, both homogeneous and heterogeneous, was developed in this study. The effects of solid sorbent feeding position and solid sorbent particle size on sulfur dioxide concentration were investigated. The results showed that both the solid sorbent feeding position and solid sorbent particle size had an effect on the sulfur dioxide capture. Entering solid sorbent at the upper secondary air position gave lower sulfur dioxide concentration than the one at the lower secondary air position and fuel feed position, respectively. This can be explained by the influence of suitable temperature at the upper secondary air position for desulfurization chemical reaction. About the solid sorbent particle size, the sulfur dioxide capture was the lowest when using the largest solid sorbent particle size due to the system hydrodynamics.
