Implementing multiple-effect distillation and reverse osmosis thermal coupling to improve desalination process performance in combined water and power plants

Abstract

Cogeneration has recently been an appropriate engineering approach to supply increasing energy demands. The present study demonstrates a significant influence on increase in productivity and reduction of utility consumption of thermal desalination, considering a novel internally coupled multiple-effect distillation and reverse osmosis desalination process in a cogeneration of water and power plant. The proposed power generation unit, consisting of two SGT600 gas turbines as prime movers, two heat recovery steam generators and one back-pressure steam turbine, has been applied. The objective is to propose a modified multiple-effect distillation process, due to availability of sufficient cooling water, provided by reverse osmosis reject water. The basic configuration comprises a hybrid desalination using a dual purpose condenser, results of which showed a 45% reduction in electrical energy consumption of multiple-effect distillation, accompanying a 67% decrease in intake water cost. In modified configuration, condenser temperature decreases from 48 to 45℃, allowing number of effects to increase from 5 to 7. Therefore, produced water rate and gain output ratio of the modified multiple-effect distillation increase by 30% and 31%, respectively, while specific energy consumption decreases by 6%, causing a two-year reduction in cogeneration of water and power plant pay-back period compared to the basic configuration.