熔盐储热辅助燃煤机组调峰系统设计及性能对比

Design and performance comparison of peak shaving system of coal-fired unit aided by molten salt heat storage

能源生产向可再生能源转型是实现“双碳”目标的必经之路。当前燃煤机组调峰能力不足、灵活性差,阻碍了可再生能源的大规模消纳。以600 MW燃煤机组为研究对象,提出了8种熔盐储热辅助调峰系统设计方案,并通过模拟计算,对比分析了各方案的调峰能力和热力性能。结果表明:熔盐储热辅助调峰系统提高了燃煤机组灵活性,可有效调节机组出力,较大程度拓宽机组运行区间;电加热造成大量(火用)损失,中压缸排汽抽汽造成的(火用)损失则较小;储热时发电机输出电能直接加热熔盐,释热时熔盐加热旁路给水方案可获得最大调峰容量,调峰深度可达17.83%;储热时中压缸排汽抽汽加热熔盐,释热时熔盐加热旁路给水的方案可获得最高系统效率和经济性,系统热效率和(火用)效率分别为40.95%和40.29%,煤耗率为350.01 g/(k W·h)。

The transformation of energy production to renewable energy is the only way to achieve the dual-carbon goal. At present, the lack of peak shaving capacity and flexibility of coal-fired units hinders the large-scale consumption of renewable energy. In this paper, taking a 600 MW coal-fired unit as the research object, eight schemes for peak shaving system aided by molten salt heat storage are proposed, and the peak shaving capacity and thermal performance of each scheme are compared and analyzed through simulation calculation. The results show that, the peak shaving system can improve the flexibility of coal-fired unit, effectively regulate the output, and greatly expand the operating range. Heating by electricity causes a large amount of exergy loss, while extracted exhaust of intermediate pressure cylinder causes a small amount of exergy loss. The maximum peak shaving capacity can be obtained by the scheme of heating the molten salt directly by electric energy output by generator when charging, and heating the bypass feedwater by high-temperature molten salt when discharging, whose peak shaving depth can reach 17.83%. Moreover, the highest system efficiency and economy can be obtained by the scheme of heating the molten salt with extracted exhaust of intermediate-pressure cylinder when charging, and heating the bypass feedwater with high-temperature molten salt when discharging, of which the system thermal efficiency and exergy efficiency are 40.95% and 40.29% respectively, and the coal consumption rate is 350.01 g/(k W·h).