Desalination by Freeze Crystallization: An Overview

Desalination by freeze crystallization is a freezing-melting process in which water is crystallized to ice and separated from saline solution. This area is observing a renascence to mitigate the staggering and sea rejected brine that has a negative environmental impact. Phase diagram of NaCl-H2O is the key point of designing freeze desalination systems. All freeze crystallization methods follow the same process, starting from nucleation, crystal growth, separation, and finally melting. Direct contact, indirect contact, vacuum, and eutectic point are the basic methods of crystallization. Furthermore, suspension freezing and freezing on a cold plate by indirect contact with refrigerant are the found to be the most suitable methods for desalination. Initial concentration, refrigerant temperature, growth rate, and flow rate are the main operating parameters that determine the final product properties and desalination efficiency. In this work, a quick review on the subject is brought up as the area is regaining renascence this followed with simulation of an indirect freeze crystallization process in a rectangular enclosure using computational fluid dynamics (CFD) modelling. These modeling are paradigm shift to gain more insight to the complex crystallization process being based on multiple species non-isothermal flow in a two phase flow representing the liquid and the ice formation. Results show that by combined CFD in multiple species modelling much insight into freeze crystallization can be revealed, optimized and re-designed.