LAUSR

Abstract The combination of the advanced ultra-supercritical (AUSC) and oxy-fuel combustion technologies is considered the most feasible and promising choice for carbon capture and storage. The high efficiency of AUSC boilers compensates for the cost incurred in controlling CO 2 emissions. In this study, a new improved model was proposed for gas-radiative properties as a polynomial function of the continuous molar ratio of H 2 O to CO 2 and temperature, which was compiled as user-defined functions in C language. The modified radiative model was employed in the computational fluid dynamics analysis to simulate a tangentially fired 700 °C-USC boiler with a capacity of 300 MW under the oxy-fuel condition. The results show that the improved model has a good accuracy for gas-radiative properties compared to other classical models. In the oxy-fuel cases, the heat transfer obtained in the simulation is approximately 4–11% lower than that in the thermodynamic calculation because of the char gasification. The radiative capability of the flue gases in the oxy-fuel case is much greater than that in the air–fuel case with the increase in the molar fraction of oxygen. The heat transfer via the water wall is approximately 4–8% higher than that via air, when the molar fraction of oxygen increases from 26% to 29%. The increase in the heat absorption helps in better arrangement of the heat-exchanger surfaces in the furnace of the AUSC boiler.