基于低真空运行模式的水电联产系统热力分析

Thermodynamic analysis of water-power cogeneration system based on low vacuum operation

提出了对于低真空运行后的凝汽式机组,直接利用其末级排汽作为低温多效蒸馏海水淡化系统的加热汽源,从而实现水电联产的方法.采用矩阵法建立电厂热力系统多级回热数学模型,基于弗留格尔公式对低真空运行进行变工况计算,进而采用等温差法建立低温多效蒸馏海水淡化系统的数学模型.在计算范围内,当满足不同淡水产量的需求时,可以优选出最佳排汽温度和蒸发器效数,使得制水成本最低.此外,还讨论了各效温差值不同对水电联产系统经济性的影响.

In order to achieve water-power cogeneration,the last-stage exhaust steam provided by condensing steam turbines under low vacuum operation is utilized as thermal resources for the low-temperature multi-effect distillation desalination system.Multi-stage heat-regenerative mathematical model of power plant thermodynamic system is constructed by matrix method.The off-design parameters under low vacuum operation are calculated on the basis of Friuli Nagel formula.Then,the mathematical model of low-temperature multi-effect distillation desalination system is built through equivalent temperature difference method.It can be concluded that within the selected temperature range of exhaust steam there exist optimal temperature of exhaust steam and the number of evaporators to make the fresh water cost lowest for different water demands.The effect of the temperature difference between desalination effects on the thermal economic performance of the water-power cogeneration system is also discussed.