超临界水煤气化工艺发电气轮机排气压力分析

Exhaust pressure analysis of a power turbine based on the coal supercritical water gasification technology

为确定超临界水煤气化工艺热力发电系统中的混合工质(H2O+CO2)气轮机排气压力,本文进行了水蒸汽和混合工质在凝汽器内部流动阻力的分析,研究了混合工质的凝结过程,定量分析了最佳排气压力的影响因素,为混合工质气轮机排气压力取值提供参考。结果表明:混合工质在凝汽器内气阻很小,为定压降温凝结。凝汽器内所建立的真空不仅与环境温度、凝汽器端差有关,还取决于蒸汽凝结率。环境温度、凝汽器出口端差和凝结率一定时,凝汽器内存在最低工作压力。所研究工况范围内,其他参数不变,蒸汽凝结率提高3%,最佳排气压力增加180%,系统净功率减小56%,系统效率降低3.3个百分点;环境温度提高10℃,最佳排气压力增大79.6%,净增功率减小23%,效率降低了2.8个百分点。

To determine the exhaust pressure of a turbine with mixed working fluid(H2O+CO2)in a thermal power generation system based on coal supercritical water gasification technology,we first calculate the internal flow resistance of steam and mixed working fluid in a condenser.We then study the condensing process of the mixed working fluid.Finally,we discuss quantitatively the parameters influencing the optimum exhaust pressure,providing a reference for the determination of the exhaust pressure of a turbine with mixed working fluid.The results show that the flow resistance of mixed working fluid in the condenser is very small and that the condensing process requires constant pressure and cooling.The vacuum created in the condenser is not only related to the ambient temperature and terminal difference of the condenser,but also dependent on the steam condensation ratio.When the ambient temperature,terminal difference of the condenser,and condensation ratio are determined,the lowest working pressure in the condenser can be found.In the range of working conditions studied,when other parameters are constant,the steam condensation ratio increases by 3%,the optimum exhaust pressure increases by 180%,the net power of the system decreases by 56%,and the system efficiency decreases by 3.3 percentage points.When the ambient temperature increases by 10℃,the optimum exhaust pressure increases by 79.6%,net power increment decreases by 23%,and efficiency decreases by 2.8 percentage points.