A seawater freeze desalination prototype system utilizing LNG cold energy

The freeze desalination method is not being used widely, since it needs refrigeration system that consumes much electricity. On the other hand, liquefied natural gas (LNG) releases a lot of cold energy during its vaporization process. Thus, combining the two processes of LNG vaporization and seawater freezing may produce freshwater in an economical and environment-friendly way. In this paper, a seawater freeze desalination prototype system is designed and manufactured. In this system, R410A is chosen as the secondary refrigerant to transfer cold energy from LNG to seawater, and a flake ice-maker is adopted to produce ice. Experiments are conducted with the prototype system, with liquid nitrogen as the cold source. The results show that the system is able to reach the designed fresh water capacity of 150 L h−1, with the converted cold energy efficiency above 2 kg (fresh water)·kg (LNG)−1. The salt removal rate of the system is about 50%, indicating that one cycle of the freeze desalination is not enough for producing drinking water. The influences of some key factors, such as refrigerant evaporating temperature, number of spraying nozzles at the water distributing disk, and seawater flowrate, on the salinity of the formed ice are also tested.