Thermohydrodynamic analysis of the vertical gas wall and reheat gas wall in a 300 MW supercritical CO2 boiler

Supercritical CO2 (sCO(2)) Brayton cycle usually shows high efficiency and also has compact structure, which can be considered as a promising alternative in future coal-fired power plants. However, sCO(2) boiler has different structures and configurations compared with the conventional steam boiler, espe-cially for the arrangement of radiative heat transfer surfaces. Proper design of vertical gas wall and reheat gas wall is crucial to the success design of sCO(2) boiler. In this study, a thermohydrodynamic model of radiative heat transfer surfaces was developed to predict pressure drops and wall temperature distributions. A sCO(2) power cycle calculation model was employed to comprehensively analyze the influences of pressure drops on the thermal efficiency. A 300 MW sCO(2) boiler was taken into account as the baseline case and thermohydrodynamic analyses of gas wall and reheat gas wall were carried out. The influences of flow directions and mass fluxes on wall temperature, pressure drops and thermal efficiency were obtained by the present models. Then, optimized structures of radiative heat transfer surfaces were proposed, i.e., vertical downward gas wall with tubes of 434 x 4 mm and vertical upward reheat gas wall with tubes of 457 x 6 mm. Accordingly, the net cycle efficiency achieved an optimized value of 50.07% under the conditions that the wall temperatures of radiative heat transfer surfaces did not exceed the allowable temperature. (C) 2020 Elsevier Ltd. All rights reserved.