燃煤电厂循环水排污水预处理系统试验与优化

Test and Optimization of Cyclic Water Discharge Sewage Pretreatment System in Coal⁃fired Power Plant

燃煤电厂循环冷却水排污水成分复杂,污染物富集程度高。为提高预处理工艺对水中钙镁硬度、硅、有机物和悬浮物等的去除效率,确保后续深度净化单元的安全稳定运行,采用“化学软化+絮凝+沉淀”等预处理方法,对北方某电厂循环冷却水排污水预处理系统开展了现场模拟优化试验研究。试验结果表明:Ca(OH)_(2)+Na_(2)CO_(3)和NaOH+Na_(2)CO_(3)两种碱性组合药剂中,NaOH+Na_(2)CO_(3)对该厂循环水排污水的硬度、SiO_(2)去除效果更佳,在控制最佳pH为10.5时,出水指标为Ca^(2+)≤50mg/L、Mg^(2+)≤80mg/L、SiO_(2)≤1mg/L,软化剂和絮凝剂的加药顺序对COD去除水平和沉淀效果无明显差异,COD平均去除率为18.26%,SS去除率可达到60%,形成的污泥浓度(以SS浓度计)约为5500mg/L。通过试验研究,选择最适宜的药剂、投加顺序和投加量,为水处理工艺的降本增效提供数据支撑,研究成果可为电厂废水零排放项目的方案设计提供参考。

The wastewater from the cyclic water discharge sewage of coal⁃fired power plants is complex in composition and has a high degree of pollutant enrichment.To improve the removal efficiency of calcium,magnesium,silicon,organic matter,and suspended solids in the water during the pretreatment processes,and to ensure the safe and stable operation of subsequent deep purification units,pretreatment methods such as“chemical softening+coagulation+sedimentation”were adopted for on⁃site simulation and optimization experiments on the pretreatment system of the cyclic water discharge sewage from a power plant in Norther China.The experimental results showed that the alkaline combination NaOH+Na_(2) CO_(3) was more effective in reducing hardness of cyclic water discharge sewage and removing SiO_(2).When the optimal pH was controlled at 10.5,the effluent indicators were Ca^(2+)≤50 mg/L,Mg^(2+)≤80 mg/L,and SiO_(2)≤1 mg/L.The order of dosing of the softening agent and coagulant did not significantly differ in the level of COD removal and sedimentation effect,with an average COD removal rate of 18.26%,and an SS removal rate of 60%.The concentration of the formed sludge(measured by SS concentration)was about 5500 mg/L.Through the experimental research,the most suitable reagents,dosing order,and dosage were selected to provide data support for cost reduction and efficiency improvement in water treatment processes.The research results can provide a reference for the scheme design of zero discharge projects for power plant wastewater.