Research On Low-temperature Multi-effect Distillation Seawater Desalination System Based On Waste Heat Utilization

Freshwater resource is an important resource for human society to survive.With the rapid development of human society,the world is currently in a situation of insufficient water resources.Seawater desalination,as an open source method of obtaining freshwater resources,has achieved rapid development.Currently,the research focus of seawater desalination systems is on cogeneration for power and desalination,as well as new and unconventional energy desalination.Low temperature multi effect distillation technology consumes a large amount of energy during its production process,limiting its development.On the one hand,the flue gas from the gas turbine electrical power station contains a large number of low-grade heat sources that can be coupled to the seawater desalination system.On the other hand,the air also contains a large number of low-grade heat sources that can be utilized.Based on the low-temperature multi-effect distillation seawater desalination technology,this paper studies the performance of cogeneration for power and desalination systems and unconventional energy desalination systems.This article uses Aspen to build a model of a low-temperature multi-effect distillation seawater desalination system,and analyzes the effects of different factors on the seawater desalination system,including the effects of three seawater feeding methods,seawater temperature,seawater flow,heat source steam flow,and the number of evaporators on system performance.The results show that increasing seawater temperature,increasing heat source steam flow,decreasing seawater flow,and increasing the number of evaporators can increase the freshwater output of the system.In order to utilize a large amount of residual heat from flue gas from gas turbine power stations,three different low-temperature multi-effect distillation seawater desalination systems with coupled flue gas were constructed in this paper.The first option is to use flue gas to preheat seawater and steam turbine extraction as a heat source for the seawater desalination system.The second option is to directly use flue gas as a heat source for the seawater desalination system.Scheme 3 is to use flue gas to generate low-temperature and low-pressure steam as part of the lowpressure steam of the steam injector,and use turbine extraction as power steam.The results show that the three schemes can recover waste heat from flue gas.The effects of steam turbine extraction flow,extraction pressure,exhaust temperature,and system variable load on the freshwater output and power generation of the system are also analyzed,and three different systems are analyzed and compared.In order to improve the energy adaptability of seawater desalination systems,this article constructs a new type of seawater desalination system,which couples air and circulates heat from seawater through a heat pump.And Aspen was used to model and calculate the system,and the impact of key operating parameters such as compressor pressure ratio,throttle valve pressure,and air temperature changes on system performance was analyzed.It was found that increasing the compressor pressure ratio,reducing the throttle valve pressure,and increasing the air temperature can all increase freshwater production.