Design and Assessment of Eutectic Freeze Crystallizer for Sustainable Brine Management: A Zero Liquid Discharge Approach

Abstract

Conventional desalination technologies present grand challenges to the sustainable economy due to energy cost and brine rejection. Therefore, Freeze Desalination (FD) as a new contender holds good promise to address these challenges. FD is energy efficient because of the much lower heat of fusion for the brine than its latent heat of vaporization, less chemically aggressive, and handles high concentrated brines up to their eutectic. These are persisting issues that exist in conventional desalination technologies.

This thesis focuses on a recent trend in the field of FD which is Eutectic Freeze Concentration (EFC) where the eutectic of the brine is targeted to achieve, theoretically, total separation of the salts and water and hence near zero brine reject. The thesis contributes to the field of EFC by aiming to develop a novel continuous crystallizer design that can mitigate ice scaling. The objective is to propose a continuous crystallizer geometry and carry out two levels of detailed numerical studies. It comprises: (i) single phase geometrical sensitivity analysis of the heat transfer performance, and (ii) two-phase flow assessment of the crystal growth and attempt to lessen ice scaling on the crystallizer surface.

The triple concentric pipe flow seems to meet the needed continuous flow configuration which may thought of extension to the jacketed cooling batch crystallizer. Starting with this configuration, sensitivity analysis relied on computational fluid dynamics is carried out starting with a single-phase flow. In this setup a 3D-, steady-state, incompressible liquid that tangentially introduced in annual tube subjected variable mass flow at pre-set incoming and surface cooling temperate was analyzed. Four parameters are considered inlet mass flowrate, crystallizer height, the brine channel gap size as well as number of inlets. The sensitivity analysis provided the needed insight on the parameters’ interaction and their statistical analysis. The analysis presented the configuration with single inlet, height of 30cm, and inner brine channel radius of 2.5cm to be the most suitable configuration. This configuration was then utilized to carry our two-phase flow analysis following enthalpy porosity methodology for the I liquid/solid fractions and brine/fresh species. Due to higher computational need a 2D axisymmetric configuration was considered along with swirling. The results reveal the significant role swirling on mixing and mitigation both temperature as well as concentration polarizations that along with adjustment of the mass flow rate resulted in an increase in the ice production rate.

Date of Award	28 Aug 2024
Original language	American English
Supervisor	Isam Janajreh (Supervisor)