Assessment of combustion and heat transfer in Youngdong 100MWe retrofit boiler for demonstration of oxy-coal combustion

This study investigates the combustion and heat transfer under air- and oxy-fuel combustion in a 100MWe boiler at Youngdong, Korea, using computational fluid dynamics. The downshot-firing boiler burning anthracite and bituminous coal is to be retrofitted to opposed-wall-firing type for demonstration of oxy-fuel combustion while maintaining the original furnace shape. The results show that the retrofit boiler can achieve good combustion in both combustion modes for the sub-bituminous coal to be used. The partial removal of the refractory proposed is appropriate in keeping the furnace exit gas temperature below the initial deformation temperature of the ash. However, the unusually wide cross-section in the burner zone reduces the mixing between O₂ and char, and significantly increases the contribution of char gasification by CO₂ and H₂O. Compared to the air-coal mode, the wall heat flux in the oxy-coal mode is lower even with 30% O₂ in the oxidizer, due to the change in the stoichiometry of the burner zone. Local regions of very high wall heat flux also need to be considered in the further development of the process.