Electrolysis-electrodialysis process for removing chloride ion in wet flue gas desulfurization wastewater (DW): Influencing factors and energy consumption analysis

Wastewater must be discharged for limestone-gypsum wet flue-gas desulfurization process in order to regulate the concentration of chloride in the desulfurization slurry. The desulfurization wastewater (DW) is difficult to be treated and recycled because of high amount of chloride. In this research, an electrolytic-electrodialysis process was proposed to resolve the difficulty of removing Cl− in DW and obtain Cl2, H2 and Ca(OH)2. The effects of the current densities, and the Cl− concentrations in the electrolysis and electrodialysis chambers on the current efficiency, electrolytic cell voltage, and energy consumption were studied using a triple-chambered electrolysis-electrodialysis apparatus, and the optimal operating condition of the lab-scale electrolytic-electrodialysis process was obtained. Pursuing extremely low average energy consumption can increase the actual volume of DW for treatment greatly in the electrolysis-electrodialysis process. Under the optimal condition, the Cl− treatment cost from the energy consumption is 0.15 $/(kg Cl−), with considering the by-products profit of the Cl2, H2, and Ca(OH)2. The results prove that the electrolytic-electrodialysis process for DW treatment can achieve the DW zero discharge and resource utilization, and be economically feasible.