Effect of Heat Transfer Driving Force and Ice Seed Loading on the Production of Ice and Salt from a Dilute Brine Treated Using Eutectic Freeze Crystallization

Abstract

Eutectic Freeze Crystallization (EFC) is a separation technology that separates solute from solvent by cooling the brine to a temperature below its eutectic point, such that ice and salt simultaneously crystallize out of the solution. Achieving consistent production of ice and salt at high production rates has been a challenge for EFC. This is due to heat transfer limitations, which are more severe when EFC is applied to dilute brines. This work investigated the effect of the heat transfer driving force, ΔTLMTD, and ice seed loading (SL) on the production of ice and salt from a dilute brine. A 1.45 L stirred crystallizer was used for the experiments at varying coolant temperatures to investigate the effect of ΔTLMTD, and at varying seed masses to investigate the effect of seed loading. It was found that, as the ΔTLMTD increased, the yield of ice and salt increased. This was attributed to the increase in the heat transfer rate as ΔTLMTD and heat transfer rate are directly related. The ice yield was divided between ice in suspension and ice formed on the wall (scale layer), with a majority of the total ice yield being scale ice. Increasing the seed loading (SL) increased the yield of ice in suspension and decreased the yield of scale ice. The seeds allowed for increased surface area for crystallization in the bulk. This allowed for most of the supersaturation to be consumed in the bulk, leaving little supersaturation for crystallization at the wall. This reduced the propensity for scale formation. The reduction in the scale layer increased the heat transfer rate between the bulk and the coolant, allowing for more ice to be formed in suspension.