Recovery rate is as critical as desalination efficiency in freeze desalination

Freeze desalination is an emerging technique since it uses much less energy than most other thermal technologies. As a portion of zero liquid discharge technologies, crystallization is being commercially used, however, it is probably the most expensive section of the desalination plant. Several freeze desalination techniques are being developed including progressive layer, falling film, suspension freeze, and gas hydrate desalination. The emphasis of most of these methods are to improve the desalination efficiency. In order to develop a full freeze desalination plant, it is shown that the recovery rate is as critical as the desalination efficiency. In our study, we designed a full freeze desalination plant with the recovery rate of 50% and the desalination efficiency of 50%. For a proper salt rejection from 73% of the incoming sea water, the plant requires 39 stages of desalination. The plant is then redesigned with the recovery rate of 90% and the desalination efficiency of 90%. It is shown that in only 4 stages of desalination, 85% of the whole seawater can be desalinated which is a cost reduction of at least one tenth.