Salt production from coal-mine brine in ED-evaporation-crystallization system

ED-EDR double step electrodialytic pre-treatment and pre-concentration of "Debiensko" coal-mine brine was examined. Univalent ion permeable Tokuyama Co. ACS and CMS membranes were applied in the first electrodialysis step and normal grade CMV, AMV Asahi Glass membranes in the second. Coal-mine brine with 32.8 g/L Cl^- content was desalinated and concentrated at a current density of 344-688 A/m² in the first step and 300 A/m² in the second. The total ED-EDR energy consumption found was in the range for 9.4-14.4 kWh/m³ of inlet brine depending on applied electric current density. The performance of crystallization step was then estimated based on chemical compositions of ED concentrates and compared with data from the "Debiensko" Desalination Plant, where currently a salt crystallizer is supplied with brine concentrated by RCC evaporation method. This comparison shows that unit energy consumption decreases from ca 970 kWh per 1 ton of evaporated salt for brine treated by RCC method to ca 500 kWh/t in the case of ED-EDR treated brine. At the same time the amount of salt in lye decreases from 110 kg per 1 ton of evaporated salt produced to 20 kg/t.