电化学法深度处理电厂脱硫废水

Electrochemical Advanced Treatment of Desulfurization Wastewater from Coal-Fired Power Plants

本文介绍了一种用于处理电厂脱硫废水的电聚浮+电解联合工艺深度,实现废水中SS、COD和氯离子的有效去除。通过线性伏安扫描法探究了电厂脱硫废水中亚硫酸根和氯离子在β-PbO_(2)电极表面的反应机理和相关动力学参数,以此验证了β-PbO_(2)是良好的亚硫酸盐电催化氧化和电产活性氯的材料。实验室自制方形连续推流式电解槽,分为电聚浮段和电解段。电沉积法自制钛基β-PbO_(2)网状电极为电解阳极。若以《火电厂石灰石-石膏湿法脱硫废水水质控制指标》(DL/T 997-20006)COD排放标准为处理终点,3.5 V电解电压下某电厂脱硫废水处理能耗仅为10.78 kWh·m^(–3)。电解电压为4.0 V时,电解槽运行300 min可去除废水中的绝大多数的COD和氯离子,二者去除率分别为91.43%和92.98%。验证了工艺路线的技术可行性和经济可行性。

Zero-emission of desulfurization wastewater is one of the main demands for coal-fired power plants.As typical high salinity wastewater,it is hard to purify the desulfurization wastewater from coal-fired power plants through traditional physicochemical treatment or biochemical treatment,e.g.,COD and Cl^(-).A high concentration of Cl^(-)ion in desulfurization wastewater restricts wastewater reuse and zero-emission.Electrochemical technology is an attractive method for high salinity wastewater zero-emission,which provides a versatile,efficient,cost-effective,easily automatable,and clean industrial process.For advanced treatment of effluent after triple box process treatment in power plants,this paper reports an electrochemical method to remove COD and Cl^(-)from the desulfurization wastewater,which combines electrolysis with electrocoagulation.Aluminum plate and stainless steel plate were applied as the anode and the cathode,respectively,for electrocoagulation.Homemadeβ-PbO_(2)coated Ti anode and stainless steel cathode were used for electrolysis.Homemadeβ-PbO_(2)coated Ti anode was prepared with a two-step galvanostatic electrodeposition.The electrodeposition solution was 1 mol·L^(-1) Pb(CH_(3)SO_(3))_(2)solution with pH=1~2.The temperature was set at 50℃.Firstly,an 80~100 mm dense and smoothβ-PbO_(2)coating was electrodeposited onto the titanium mesh at 5 mA·cm^(-2),which is used to protect the titanium substrate.Secondly,the electrodeposition current density was increased to 20 mA·cm^(-2).About 0.5 mm more electroactiveβ-PbO_(2)coating was deposited on the top layer.The electrooxidation mechanisms and dynamic parameters of SO_(3)^(2-),HSO_(3)^(-),and Cl^(-)on the homemadeβ-PbO_(2)/Ti were investigated particularly by linear scan voltammetry.It was testified that the homemadeβ-PbO_(2)/Ti is an excellent anode material for sulfite and chloride electrooxidations.A continuous plug flow electrolyser was homemade to test the feasibility and economy of the electrochemical method,which consisted of an electrocoagulation section and an electrolysis section.The electrocoagulation section could remove almost all suspended solids and a part of COD.To meet the industry-standard“Discharge standard of wastewater from limestone-gypsum flue gas desulfurization system in fossil fuel power plant”(COD<150 mg·L^(-1)),the energy consumptions of the electrolyser were 10.78 kWh·m^(3)and 15.17 kWh·m^(3)at 3.5 V and 4.0 V,respectively.For zero-emission,91.43%of COD and 92.98%of Cl^(-)could be removed within 300 min at 4.0 V.