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Taona Chagwedera

Gypsum Seeding to Prevent Scale Formation and Improve Separation Efficiency


2015 BSc Eng (Hons) Metallurgy and Materials (University of the Witwatersrand)

Project Description

Disposal of brines from reverse osmosis and other hydrometallurgical processes has recently become a challenge. Current industrial practice entails pumping these brine solutions into lined evaporation ponds. This poses a risk of contaminating the environment in the event of a spillage due to flash floods or seepage to the underground water system.  Eutectic Freeze Crystallization (EFC) is a novel technology in which a brine solution is cooled to a temperature below its eutectic point resulting in the co‑crystallization of ice and salt. Calcium sulphate dihydrate (gypsum) scaling on the surfaces of crystallizers has been identified as a problem in the treatment of calcium sulphate-rich brines using EFC. This study seeks to utilise seeding as a method to enhance gypsum crystallization in the bulk solution and thus reduce scaling on the crystalliser walls.