Off-design performance analysis of a new 300 MW supercritical CO2 coal-fired boiler

Abstract

In order to solve existing problems of large working fluid pressure drop and lower reheated working fluid temperature under part load conditions, a new 300 MW S–CO2 coal-fired boiler heating surface arrangement is proposed and its off-design performances are studied. The new S–CO2 boiler adopts the single furnace double-tangential circle arrangement without the center wall and increases the proportion of reheat radiant heat exchange surfaces. The performance analysis model is built. The variations of the reheated working fluid temperature, working fluid pressure drop and the off-design performances of the boiler with the changes of coal type, excess air coefficient and operating load are investigated. The results show under the design load, the total pressure drop of working medium in the furnace is reduced by 0.48 MPa, under 30% of the design load, the reheated working medium temperature is increased by 7.62 °C, and the lower heating value and components of coal greatly influence the boiler efficiency. When the excess air coefficient is 1.2–1.4, the best efficiency zone is reached. The load range with the optimal efficiency zone is about 70%–100% of the design load. Achievement of this paper will provide valuable references for the design of the S–CO2 coal-fired boiler.