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

摘要: 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。

Abstract: 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.