Study On The Key Influencing Factors Of LNG Cold Energy For Seawater Desalination And Concentration

LNG contains cold energy. As the propaganda of circular using of resource, cold energy, which is previously wasted, have drawn people's attention. The cold energy should be utilized appropriately. The research on utilization of cold energy of LNG focused on electricity generation at low temperature, refrigeration, air condition, air separation and low temperature shredding, some of them have achieved industrial production. In the meantime, freezing desalination technique has been studied as well. Due to the low desalination rate and shortage of could source, freezing desalination has not been applied industrially yet. However, the combination of utilizing cold energy and additional technique used to improve desalination rate seems to be the solution of the problem for freezing desalination.Through experimental research, technological process that can utilize cold energy of LNG has been put forward. On the basis of desalination process, the pilot-scale experiment has been conducted. Based on the researches mentioned before, the conclusions are shown as following:1) The impact of heat transfer mode on freezing desalination and concentration was studied, as well as the gravity-induced desalination and centrifugal desalination. Although the effect of unidirectional heat transfer is much better than that of multidirectional heat transfer, the high desalination rate cannot be achieved by freezing. In gravity-induced desalination process, the more volume of drained water was, the purer the ice was, which meant that the volume of drained water should be based on the need of purified water. Besides, temperature can affect gravity-induced desalination. The higher the temperature was, the less the time spent on desalination was. In addition, high temperature leaded to purer ice. In centrifugal desalination process, rotate speed is the key factor that influenced desalination rate. Beyond the critical point, the effect of rotate speed can be hardly observed. With appropriate melting, high desalination rate can be achieved in centrifugal desalination process.2) Gravity-induced desalination and centrifugal desalination can make up the weakness of freezing process. The highest desalination rate was 99.33%, with the concentration of sodium chloride in drained water being 200mg/L. The result has met the standard of drinkable water. But at this time, the process is relatively complex, and the ratio of fresh water production is low. Centrifugal desalination is the acceleration of gravity-induced desalination.3) Concentrated water as the by-product of freezing desalination process can be utilized as material of salt chemical engineering.4) Desalination rate in pilot-scale experiment was unsatisfactory, which should use gravity-induced desalination and centrifugal desalination in the coming process.