Process intensification using a novel continuous U-shaped crystallizer for freeze desalination

Abstract

Ice based Freeze Desalination (FD) offers a potential alternative to recover fresh water from seawater. There has been increased interest over the years in the development of continuous crystallizer configurations to address the combined challenge of ice yield and salinity reduction in FD. In this work, experimental studies have been conducted to establish the potential of a novel continuously operated U-shaped crystallizer for ice based Freeze Desalination (FD). Unlike conventional FD crystallizers researched till date, this crystallizer integrates pre-cooling, chilling and freezing of saline water in a single unit along with in-situ ice removal. Preliminary experiments were carried out using synthetic salt water to investigate the effect of salt water flow rate and coolant temperature on product water yield and salinity. Salinity was found to increase with water yield. The overall phase change heat transfer coefficient has also been estimated. Subsequently test runs were carried out using seawater samples under prescribed operating conditions identified from the synthetic salt water runs. Salinity reduction was observed to increase with an increase in number of washing steps and wash water requirement. The results obtained provide a strong case to promote the use of the U-shaped crystallizer for ice based FD.