低温多效蒸馏海水淡水—发电联产系统经济性分析

An Analysis of the Cost-effectiveness of a Cogeneration System for the Simultaneous Production of Electric Power and also Fresh Water by Low-temperature Multi-effect Distillation of Seawater

针对低温多效蒸馏海水淡化—发电联产系统,应用等效焓降理论,计算了制水的能量成本和加热抽汽对汽轮机组的影响。结合q-γ-τ矩阵方程,构造了通用性强、精度高和易于程序化的等效焓降法抽汽效率矩阵模型和局部定量分析矩阵模型。利用该矩阵模型可以方便、快捷、准确计算制水耗电率(ELWP)和制水燃料成本随抽汽压力和加热蒸汽温度的变化。计算结果显示,采用制水电耗率比传统的性能指标造水比(GOR)能够更准确的评价水电联产系统热性能;降低抽汽压力和加热蒸汽温度有利于降低制水能量成本,但抽汽压力和加热蒸汽温度的下限应分别满足蒸汽喷射器的引射系数和压缩比的要求;低温多效蒸馏海水淡化—发电联产系统能够经济有效地解决北方沿海地区,尤其是北方沿海火电厂的缺水问题。

With respect to a cogeneration system for the simultaneous production of electric power and also fresh water by low-temperature multi-effect distillation of seawater the energy cost of water-making and the impact of extracted-steam heating on a steam turbine unit were calculated using an equivalent enthalpy drop theory.In conjunction with a q-γ-τ matrix equation constructed were a partial quantitative analytic matrix model and an equivalent enthalpy drop method-based steamextraction efficiency matrix model featuring high versatility and precision as well as ease of sequencing.By employing the above matrix models it is possible to conveniently,rapidly and accurately calculate water-making power consumption rate and the variation of water-making fuel cost caused by a change in steam extraction pressure and steam heating temperature.The results of the calculation indicate that compared with the traditional performance index water-making ratio or gained output ratio(GOR) the use of water-making electric power consumption rate can more accurately evaluate the thermal performance of the water-electricity cogeneration system.The reduction of steam extraction pressure and steam heating temperature is favorable to lowering the water-making energy cost.However, the lower limit of steam extraction pressure and steam heating temperature should respectively meet the requirements of ejection factor of steam injector and compression ratio.The cogeneration system for the simultaneous production of electric power and also fresh water by low-temperature multi-effect distillation of seawater can effectively resolve the water shortage problem in northern China coastal areas,especially that of thermal power plants in those areas.