基于熔盐储热的燃煤机组调峰可行性分析

Feasibility analysis of peak shaving for coal-fired units based on molten salt heat storage

随着新能源发电装机量增加导致电网调峰压力增大,火电机组要承担更多调峰任务,但目前火电机组的灵活性和调峰能力都较差。针对某亚临界300 MW燃煤机组,进行熔盐储能改造,提出了6种储热策略和2种放热策略,分析了3种工况下储-放热过程对机组调峰能力及热力性能的影响,并用净现值法进行了技术经济分析。结果表明:抽再热蒸汽储热可行性高,调峰深度能到58.9%,但会增加煤耗;放热时,加热给水产生蒸汽做功的发电增量最大,能到额定发电量的11.3%,但对熔盐的温度水平要求高;高温熔盐代替低压加热器预热给水可行性高,但发电增量低;储-放热全过程中,循环电效率最高可达0.987;进行了储热改造经济性分析,计算得动态投资回收期为11.65年,净现值为4911.8万元,改造方案可行。

With the continuous increase of installed capacity of new energy generation in power grid,thermal power units have to undertake more peak shaving.However,the flexibility and peak shaving capacity of current thermal power units are generally insufficient.A subcritical 300 MW coal-fired unit is retrofitted for molten salt energy storage.Six heat storage strategies and two heat release strategies are proposed and investigated.The influence of heat storage and release process on the peak shaving capacity and thermal performance of the unit under three working conditions is analyzed,the technical and economic analysis is performed in terms of the net present value.The results show the feasibility of extracting reheated steam for heat storage is higher,with a peak shaving depth of 58.9%.However,the coal consumption would increase at the same time.During the releasing heat stage,the maximum increment of power generation up to 11.3% of the rated power generation is achieved by heating the water supply to generate steam,while the higher temperature of the molten salt is required.Using high-temperature molten salt instead of low-pressure heater to preheat water supply is proved to have more advantages,while the power generation increment is relatively small.During the whole process of heat storage and release,the maximum circulating electricity efficiency can reach 0.987.The economic analysis of heat storage transformation is conducted.The dynamic investment payback period is 11.65 years,and the net present value is 49.118 million yuan.Therefore,the renovation scheme is feasible.