Experimental Research On Seawater Desalination Based On LNG Cold Energy

The shortage of freshwater resources has made seawater desalination industry booming in recent years.China's 13th Five-Year Plan for Utilization of Seawater also proposed that at the end of the 13th Five-Year Plan,the total scale of seawater desalination will reach 2.2 million tons and more.At the same time,the 13th Five-Year Plan for Energy Development also proposed that the proportion of natural gas consumption will reach 10%during the 13th FYP.All of those will bring opportunity to solve the problem of high cost of cold source of the freezing method in the industry of seawater desalination and make seawater desalination technology based on LNG cold energy have practical application prospects.In this paper,we used the“freezing seawater desalination process simulation experiment device based on LNG cold energy”authorized by patent licensing of the research group to freeze the original seawater.The influence of melting rate under gravity on the desalination effect in FGCD(Freezing,gravity-driven and centrifugal desalination)process was studied experimentally.The energy consumption of the FGCD system was calculated and analyzed,and the possibility of applying the process to actual production was discussed.On this basis,the microwave treatment was applied to seawater desalination.The sea ice samples were obtained by static ice making in a low-temperature refrigerator and dynamic ice making by an experimental device respectively.The FMCD(Freezing,microwave treatment and centrifugal desalination)experiments were conducted to study the effect of microwave on desalination.In terms of the“freezing seawater desalination process simulation experiment device based on LNG cold energy”,HYSYS software was applied to model and calculate the energy consumption of the process without phase change refrigerant and that with phase change refrigerant and some advices about experimental system improvements were proposed.The experimental study mainly obtained the following conclusions:(1)After the flake produced by the experimental device is treated by the FGCD process,the Cl~-removal rate is used as the measurement standard.When the melting rate is greater than 40%,the water produced can meet application standards in some petrochemical industry.When the melting rate is more than 80%,the produced fresh water can meet the drinking water standard.Therefore,the classified utilization of water can be considered in the future industrial production.(2)Although the FMCD process desalination effect of ice flake produced by the experimental device is lower than that of FGCD process,the Cl~-removal rate can still reach more than 90%when the melting rate reaches about 60%.FMCD process time is far less than the FGCD process.In winter when temperature is lower,FMCD desalination process can be applied to speed up the process of desalination and increase the freshwater production rate.Under the condition of not changing the microwave treatment time,increasing the centrifugal speed can improve the desalination rate,while increasing the centrifugal time has a limited effect on the desalination rate and water production rate.(3)Combined the calculation of the power consumption of the experimental device with the HYSYS simulation study,it shows that the energy consumption of the FGCD process is acceptable.The energy consumption of the FGCD process can be further reduced when a phase change refrigerant system is used in the experimental device,making it more likely to be applied to future industrial production.