Performance Investigation on a New Design for Progressive Freeze Concentration System

Abstract

Freeze concentration freezes or crystallizes water component in a solution out as ice crystals and leaves behind a highly concentrated solution. Conventional Suspension Freeze Concentration (SFC) system has to deal with difficult separation of ice formed in a suspension of the mother liquor, which leads to a high cost of operation. Scraped surface heat exchanger used to form seed ice to ensure production of large ice crystals also hiked up the capital cost involved. Progressive Freeze Concentration (PFC) is believed to be able to reduce the capital and operation cost by eliminating some unit operations used. In PFC, ice crystals were formed progressively as a single block of ice, on the surface where cooling is supplied. In this particular study, a new helical structured copper Crystallization Chamber (CC) was designed and fabricated. Three operating parameters which affect the performance of the system were investigated namely the circulation period, circulation flow rate and coolant temperature. Effective partition constant, K was used as an indication of the system efficiency and to assess its performance, calculated from the volume and concentration of the solid and liquid phase. Circulation period was found to produce a constant value of K at each period tested with the CC. It was also discovered that higher flowrate resulted in a lower K, which translated into high efficiency. The efficiency is the highest at 1000 mL min-1. The process also gives the highest efficiency at a coolant temperature of -6°C.