高镁型脱硫废水零排放处理技术研究

Study on zero discharge treatment technology of desulfurization wastewater with high magnesium ions

国内燃煤电厂湿法烟气脱硫工艺产生的脱硫废水具有pH呈酸性、成分复杂、硬度高、TDS高等特点。尤其当石灰石原料中含有较多白云石时,脱硫废水中镁离子高达10 g/L以上,属于典型高镁型脱硫废水。以国内某燃煤电厂产生的高镁型脱硫废水为例,提出了一种新型适用于高镁型脱硫废水零排放工艺。主要分为预处理工艺、浓缩工艺、固化工艺三个阶段。其中预处理工艺采用石灰-硫酸钠联合软化工艺去除废水中硬度,生成高品质石膏产品。浓缩工艺采用NF-HSRO膜浓缩工艺进行分盐浓缩减量,废水中TDS可被浓缩至12%~15%,后续固化工艺采用MVR蒸发结晶工艺得到高纯度氯化钠结晶盐,从而实现真正意义的脱硫废水零排放,具有较好的经济效益、环境效益和社会效益,也为其他类型脱硫废水提供了参考及借鉴。

The desulfurization wastewater produced by WFGD process in domestic coal-burning power plants has the characteristics of acidic pH,complex composition,high difficulty and high TDS.Especially when the limestone raw material contains more dolomite,the magnesium ion in the desulfurization wastewater is more than 10 g/L,which belongs to the typical high magnesium desulfurization wastewater.A new zero-discharge process for desulphurization wastewater with high magnesium content produced by a domestic coal-fired power plant is proposed.It can be divided into three stages:pretreatment process,concentration process and curing process.The pretreatment process uses lime-sodium sulfate combined softening process to remove the hardness of wastewater and produce high-quality gypsum products.NF-HSRO membrane concentration process is used for salt separation concentration and reduction in the concentration process,and TDS in the wastewater can be concentrated to 12%~15%.MVR evaporation crystallization process is used in the subsequent solidification process to obtain high purity sodium chloride crystal salt,so as to achieve zero discharge of desulfurization wastewater in the real sense,with good economic benefits,environmental benefits and social benefits.It also provides reference for other types of desulfurization wastewater.