Experimental & modeling studies on novel scraped surface falling film crystallizer for freeze desalination

Freeze Desalination (FD) is a low-temperature thermal desalination technique that utilizes the freezing process to form and harvest ice crystals from saline water for production of fresh water. FD consumes seven times less energy than evaporation-based desalination processes in addition to lesser corrosion and scaling issues. However, its commercial implementation is limited by issues like incomplete salt removal and scaling of heat transfer surfaces due to formation of ice layer. Recently, the availability of 'cold energy' at-162 degrees C during regasification of Liquified Natural Gas (LNG) has increased the potential for application of FD at LNG terminals, particularly in coastal areas facing water scarcity. This paper introduces a new equipment. the Scraped Surface Falling Film Crystallizer (SSFFC), specifically developed for the FD process. The SSFFC uses falling film freeze crystallization and an in-situ mechanism for harvesting ice crystal through scraping and filtration. Experiments were conducted using brackish water to evaluate the performance of the SSFFC unit, focusing on ice production and salt rejection across various feed salinities and coolant temperatures. The unit achieved ice production rates of 2.7 kg/h and 3.9 kg/h with coolant temperatures of-9 degrees C and-12 degrees C, respectively, for a feed salinity of 10,000 ppm. A mathematical model of the SSFFC unit was developed, validated with experimental results and used in parametric studies to explore the effect of varying operating conditions on its performance.