多级闪蒸海水淡化系统的稳态模拟与优化

Steady-state simulation and optimization of multi-stage flash desalination system

多级闪蒸海水淡化是提供淡水资源的重要方法之一,而装置的产水性能受进料海水温度等多个参数影响,对系统进行模拟分析和优化操作具有重要意义。本文针对典型多级闪蒸海水淡化流程系统,在建立系统严格机理模型的基础上,对影响产水性能的多个参数进行了分析,并在此基础上以日运行费用最小为目标对系统进行了优化研究。首先,基于质量平衡、能量平衡以及热传递方程等建立了严格的数学模型,该模型考虑了闪蒸室的结构、物性随温度和浓度的变化、非理想性的差异等基本的物理化学现象。然后,在MATLAB平台下对系统进行了模拟分析,讨论了闪蒸级数、海水温度、循环水量、蒸汽温度对系统产水性能的影响。最后,针对固定淡水需求,以日运行费用最小为目标研究了不同海水进料温度情况下的优化操作问题,得到了不同海水进料温度下最优的循环盐水流量、热排放海水流量和加热蒸汽温度,以及在此情况下的费用情况。结果表明,该优化操作与常规操作相比可明显的降低系统运行费用,提高其造水比。

Multi-stage flash desalination is one of the important methods to provide fresh water resources,but its performance is affected by operational parameters such as seawater feed temperatures,so it is of great significance to optimize the system through simulation.In this paper,the performance of the typical multi-stage flash desalination system was simulated and analyzed based on the process model established with rigorous mathematical model,and the operational optimization of the system was carried out with the goal to minimize the daily operational cost.First,a rigorous mathematical model was developed based on the laws of mass balance,energy balance,and heat transfer equations,which takes into account the structure of the flash chamber,the change of physical-chemical properties along temperature and concentration,and the differences of nonideal status.Then,the system was simulated under the MATLAB platform,and the effects of the number of stages,seawater temperature,recycle seawater mass flow rate and steam temperature on the performance of the system were analyzed and discussed.Finally,with fixed freshwater demand,the optimal operation problem under different seawater feed temperatures was studied for daily operational cost reduction,the optimal circulating brine flow,rejecting seawater flow,heating steam temperature and the cost under this situation were obtained.The results show that:compared with the conventional operation,the optimal operation can significantly reduce the daily operational cost and increase the gained output ratio.