Abstract:

Taking the wastewater desalination project of a lead-zinc smelting plant in Yunnan Province as an example， the zero-discharge desalination process of decalcification softening+membrane concentration+evaporation crystallization was introduced from the perspectives of wastewater characteristics， design parameters， process flow， material balance and operation effect. CO₂+NaOH was used to remove hardness in the decalcification softening process. RO1+DTRO concentration was used in membrane concentration process， supplemented by RO2 for desalinate of produced water. Sodium sulfate tri-effect crystallization+freezing crystallization+sodium chloride single-effect crystallization+mixed salt drying was used in the evaporation crystallization process for sodium sulfate and sodium chloride separation. Calcium carbonate slag generated from the decalcification and softening could be used as a neutralizer for raw acid treatment of lead and zinc smelting， and no solid waste was generated. The water quality of produced water was better than the design requirements， including 11-23 mg/L total dissolved solids， 2-5 mg/L total hardness in CaCO₃， 20.2-34.9 μS/cm conductivity. Recovery rate of membrane concentration≥85%， desalination rate≥99%. The effluent reuse could significantly improve the water quality of the whole plant. The project has been running steadily since it was put into operation， with good water quality and sodium sulfate- sodium chloride separation. The crystalline salt mass fraction was more than 92% and was sold out as product salt. The operating cost was 18.26 yuan/m³ after deduction of return.

Key words: lead-zinc smelting wastewater, membrane concentration, multi-effect evaporation, desalination, zero-discharge

摘要：

以云南某铅锌冶炼厂废水脱盐工程为例，从废水特点、设计参数、工艺流程、物料平衡、运行效果等角度出发，对脱钙软化+膜浓缩+蒸发结晶的脱盐零排放综合工艺进行介绍。其中，脱钙软化工序采用CO₂+NaOH脱除硬度；膜浓缩工序采用高压海淡膜+碟管式反渗透浓缩，辅以中低压卷式膜对产水进行脱盐淡化；蒸发结晶工序采用硫酸钠三效结晶+冷冻结晶+氯化钠单效结晶+杂盐干燥进行盐硝分离。脱钙软化生成的碳酸钙渣可用作铅锌冶炼原污酸处理的中和剂，不产生固废。该工程产水水质优于设计要求，总溶解性固体11~23 mg/L、总硬度（以CaCO₃计）2~5 mg/L、电导率20.2~34.9 μS/cm，膜浓缩系统回收率≥85%、脱盐率≥99%，出水回用可显著改善全厂水质。该工程自投产以来运行稳定，产水水质良好，且实现盐硝分离，结晶盐质量分数均≥92%，并以产品盐外售，扣减收益后运行费用为18.26元/m³。

关键词: 铅锌冶炼废水, 膜浓缩, 多效蒸发, 脱盐, 零排放

CLC Number: 

• X703

• TU992.3