火电厂高镁硬度脱硫废水预处理技术研究

Research on Pretreatment Technology of High Magnesium Hardness Desulfurization Wastewater from Thermal Power Plants

以高镁硬度脱硫废水为研究对象,分析了药剂和反应条件等因素对其中Ca2 和Mg2 去除效果的影响。结果表明:当草酸钠添加量为n (C2O42-):n (Ca2 ) = 1.4:1,pH为4,陈化时间为8 h,草酸钙晶种添加量为0.35%时,Ca2 的去除率高达91.2%,Mg2 的去除率仅为2.5%。本方法可在基本不影响Mg2 含量的同时,实现对Ca2 的选择性去除。以本实验采用的废水为例,相对于常规双碱软化法,本方法可降低86.7%的沉淀量,降低93.4%的软化剂投加量,减少80.3%的软化剂成本,具有显著的技术和经济优势。

This study focused on the preferential softening of Ca2 in high magnesium desulfurization wastewater. Effects of softener and reaction conditions on the removal of Ca2 and Mg2 were investigated. When sodium oxalate was added as n (C2O42-):n (Ca2 ) = 1.4:1, pH was 4, aging time was 8h, and calcium oxalate (seed crystal) was added as 0.35%, the removal rate of Ca2 could reach up to 91.2%, while the removal rate of Mg2 was merely 2.5%. The content of Ca2 can be removed preferentially, with little Mg2 being removed. In comparison with the common NaOH-Na2CO3 softening process, the precipitation quantity, dosage of softener and cost of softener can be reduced by 86.7%, 93.4%, and 80.3%, respectively. The softening method proposed by this study has significant technological and economic advantages.