Enhancing the flexibility and stability of coal-fired power plants by optimizing control schemes of throttling high-pressure extraction steam

Abstract

Regulating the thermal system configuration can improve the ramp-up rate of the coal-fired power plants during peak shaving transient processes, while it may bring penalties in the performance of the steam temperature control and thermal efficiency. This study simulated the load ramping up transient processes when throttling the extraction steam of high-pressure heaters. The results show that there is a gap between the needed energy and energy supply caused by drastic fluctuations of reheat steam flowrate. Control schemes of steam temperatures and fuel demands were revised considering the dispatch of the fuel and working medium. According to economic optimality, the order of throttling high-pressure heaters was optimized. By implementing the revised control strategies, the fluctuations of steam temperatures were diminished and the maximum deviation of live and reheat steam temperatures was reduced by 23.5 °C and 11.4 °C, respectively. The flexibility indicator was increased by up to double at most. The average standard coal consumption rate variations with and without the revised control schemes were compared and the maximum difference is 1.23 g kW−1 h−1 with 2.5 % Pe min−1. The flexibility and economic performance were both improved when adopting the revised control schemes.