Influence of gravity-induced brine drainage on seawater ice desalination

Experimental platform that can use cold energy of liquefied natural gas (LNG) to freeze seawater was designed and installed in laboratory. Freezing, gravity-driven and centrifugal desalination (FGCD) technologies were combined in the experiments. Seawater taken from Bohai Bay was frozen and then the seawater ice samples were placed in ambient temperature to melt gradually with the brine drained induced by gravity. The gravity-induced brine drainage proportion for each sample was different because the melting time was not the same. Then the remaining ice was centrifuged for further brine removal. The influences of the gravity driven brine drainage on the gravity-induced salt removal efficiency, the overall salt removal efficiency after FGCD process and the ice yield rate were quantified. The results showed that the maximum Cl− removal efficiency can be > 99% and the Cl− concentration of the produced ice can meet the requirement of the standards for drinking water quality. Whereas the salt removal efficiency was negatively correlated with the ice yield rate: the more the ice yield, the lower the salt removal efficiency and vice versa.