Parametric study of the progressive freeze concentration for desalination

Abstract

A progressive freeze concentration (PFC) process was applied to treat several waters where clean ice was generated one-dimensionally, and salt and impurities concentrate into the liquid phase. The impact of eight process parameters on salt percent removal and ice percent recovery were investigated. They were coolant temperature, stirring rate, advance speed of crystallizer, feed solution concentration, feed solution temperature, ice seeding, crystallizer material, and mixing flow pattern. The significant process parameters found were stirring rate, coolant temperature, and feed solution concentration. Temperature difference between feed solution temperature and coolant temperature is important in minimizing supercooling which has a negative effect on treatment. For example, our results showed a temperature difference of 10 °C for a feed solution temperature of 2.5 °C were needed to minimize supercooling. Salt percent removal was found to be directly related to while ice percent recovery was inversely related to the stirring rate. Treatment of an artificial seawater (salinity 35.67 g/L) and a RO brine concentrate (salinity 2600 mg/L) resulted in 51% and 70% ice percent recovery and 74% and 97.7% salt percent removal, respectively. An application of the PFC process includes brine concentrate treatment for inland desalination plants.