Mg^(2+)对脱硫废水电解-电渗析过程的影响

Influence of magnesium ions on electrolysis-electrodialysis process of desulfurization wastewater

石灰石-石膏湿法脱硫工艺是应用最广泛的烟气脱硫技术,该工艺运行过程中会产生一定量的脱硫废水,脱硫废水中富集的氯离子会导致浆液的腐蚀性增加并且难以用常规的处理方法除去。电解-电渗析法是一种有前景的资源化处理方式,但是脱硫废水中的镁离子会影响系统的可靠运行。本文采用三室两膜电解装置以及不同镁离子浓度的CaCl_2与MgCl_2的混合溶液模拟实际的脱硫废水,进行了Mg^(2+)对电解-电渗析影响的实验研究。实验结果发现,Mg^(2+)浓度的增加会导致pH难以上升、槽电压升高及电耗增加等不利因素。脱硫废水中的Mg^(2+)浓度大于0.179mol/L时,则需在电解前用化学沉淀法或其他合适方法控制Mg^(2+)浓度以保证电解-电渗析系统的可靠运行。

Limestone-gypsum wet desulfurization process is the most widely used flue-gasdesulfurization technology, this process produces a certain amount of desulfurization wastewaer.The enrichment of C1- included in desulfurization wastewater will increase the corrosivity of theslurry and they are difficult to be removed using conventional processing methods. Theelectrolysis-electrodialysis process is a promising recycling-treatment, but the Mgz＋ included indesulfurization wastewater will influence reliable operation of the system. This paper adopted anelectrolysis setup with three compartments and a pair of membranes and used a mixture of CaC12and MgC12 at different concentrations of Mg2＋ to simulate desulfurization wastewater, andproceeded to study the effect of Mg2＋ during the electrolysis-electrodialysis process. Resultsshow that the increase of the concentration of Mgz＋ can make the electrolyte pH difficult toincrease, increase the cell voltage and the energy consumption. When the concentration of Mg2＋is more than 0. 179mol/L, the desulfurization wastewater should be pretreated by chemicalprecipitation or other suitable methods before electrolysis to ensure reliable operation of theelectrolysis-electrodialysis system.