Comparative study on the regeneration of flue-gas desulfurizing agents by using conventional electrodialysis (ED) and bipolar membrane electrodialysis (BMED)

Piperazine is an ideal desulfurizing agent but the heatstable salts formed in desulfurization have caused secondary pollution and waste of resources. In the previous paper, a method was reported to regenerate piperazine by using BMED. To find the variety of that regeneration process, we performed experiments on the regeneration of piperazine by using ED. In comparison, ED has higher piperazine yield and current efficiency, and much lower voltage drop and energy consumption. However, its process cost is higher than that of BMED due to an extra expenditure for the base and its tank and pumps. The process cost is estimated to be 0.96 $/kg Pz for BMED and 1.14 $/kg Pz for ED. Notably, BMED has more environmental benefits and will be more economically attractive as the control on secondary pollution is strengthened and the bipolar membrane cost decreases.