Analysis of plate multi-effect distillation system coupled with thermal power generating unit

In order to explore the practical potential of plate exchanger as evaporator in multi-effect distillation (MED) system, the physico-mathematical model is established for a plate MED system coupled with thermal power generating unit. A MED seawater desalination system with shell and tube evaporator in operation producing freshwater 10,000 ton/day is selected as comparison. The system design with different types of plate evaporators and off-design operating performance are conducted. The results indicate that the overall area can be significantly reduced with plate evaporator compared with that of shell and tube evaporator. The plate MED system can achieve a greater gain of ratio (GOR) than that of original tubular system by selecting suitable entrainment ratio of the last effect. The performance of the plate MED system can be improved by reducing the length of single plate of evaporators, for more channels with shorter plate can enhance heat transfer in evaporator and restrain the boiling point evaluation of evaporating brine. Influences of inlet temperature and flow rate of feed brine, flow rate of extracting source vapor from steam turbine under off-design conditions on the performance of plate MED system are investigated either. The investigations may provide a reference for the application of plate MED technology coupled with waste heat utilization of thermal power generating unit.