Thermodynamic analysis of a 660 MW ultra-supercritical CFB boiler unit

Abstract

While the power plant units are the developing towards larger capacity, the relative shortage in thermal efficiency of the circulating fluidized bed (CFB) boiler unit, which has obtained significant development in recent years, is becoming more and more apparent. However, the thermal efficiency computational model applied for different CFB boiler units are not derived yet. Based on Generalized Energy Efficiency Distribution Matrix (GEEDM) model which is designed for normal pulverized coal boiler units, this paper innovatively built a computational model of cycle efficiency for CFB boiler units. Moreover, the mathematical influences of main local influencing factors like terminal difference, extraction steam pressure loss, heat loss, drained water cooling insufficient, steam desuperheater, shaft seal leakage of steam turbine and connection schemes of ash cooler to this model were further proposed to strengthen its industrial applications. In the meanwhile, the detailed thermodynamic analysis of a 660 MW ultra-supercritical unit in China was studied to provide some optimized design and operation suggestions. Particularly, for this unit, an optimized connection scheme of the ash cooler, a core component in the CFB boiler to reclaim physical heat in the bottom ash, was selected from 20 different connection schemes.