Cost and exergy analysis on integrated process of electrodialysis metathesis- reverse osmosis- evaporation for producing K2SO4 from Na2SO4

Electrodialysis metathesis (EDM) is a promising technology in synthesis of electrolyte and high-value reclama-tion of wastewater. The integration of EDM with other processes is a necessary way to maximize the use of raw solution and achieve zero liquid discharge. The exergy analysis is an efficient method to investigate the effective use and loss of energy, and optimize the process. Therefore, a novel integrated process of EDM-RO-MVR was proposed in this work. Membrane area, energy consumption, equipment cost, specific cost, and exergy of a 100 m3/h process were analyzed and discussed. It was shown that the current density has a great influence on the equipment cost of the process, and the proportion of the equipment cost of EDM decreased with the increase of the current density, while the concentration of raw water shown little effect. The specific cost was lowest when the current density was 200 A.m-2. Exergetic analysis showed that the exergy efficiency of the process was 1.5 %, and the largest exergetic loss occurred in the evaporation process. Therefore, it is of great significance to improve the heat transfer efficiency of the evaporator and reduce exergetic loss to improve the energy utilization effi-ciency of the coupled system. Several similar process fitting for different occasions was also proposed and compared. All above results indicated that EDM-RO-MVR was an economical and feasible methods for high-value conversion of sulfate wastewater and production of potassium sulfate.