电厂烟气脱硫废水零排放工艺中试研究
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摘要
电厂烟气脱硫废水零排放是行业的热点和难点问题。本文通过脱硫废水水质特性分析,集成预处理、深度处理、预浓缩和蒸发结晶模块建立了脱硫废水零排放工艺,并进行了每天25 m~3的中试试验。结果表明:该工艺各模块可优势互补,高效稳定运行,实现脱硫废水零排放;由预沉池和序批式反应器构成的预处理模块通过投加石灰、氢氧化钠、碳酸钠和絮凝剂,实现了悬浮物、硬度、有机物和重金属的同步去除,悬浮物、Ca~(2+)、Mg~(2+)和有机物去除率分别达到97.3%、38.1%、98.5%和74.3%;深度处理模块包括过滤器、超滤(微滤)和纳滤单元,能够高效截留二价离子和有机物,纳滤单元出水Ca~(2+)、Mg~(2+)和硫酸盐质量浓度分别为5.2、0.4、84.3 mg/L,降低了膜结垢风险,并保证了工业盐品质;经电渗析单元、离子交换单元与蒸发结晶后,所得工业盐纯度达到《工业盐国家标准》(GB 5462—2015)中二级工业湿盐的要求。
Zero liquid discharge(ZLD) of wastewater generated by flue gas desulfurization(FGD) system of coal-fired power plants is a hot and difficult issue in the industry. A ZLD process of FGD wastewater integrated with pre-treatment, intensive softening, pre-concentration and evaporation-crystallization units was established,through quality analysis for desulfurization waste water. Moreover, a 25 m~3/d pilot-scale test was carried out. The results show that, all units of the process operated efficiently and stably, and realized ZLD. The pretreatment module consisting of primary sedimentation tank and sequencing batch softening reactor realized simultaneous removal of suspended substance(SS), hardness, organic matter and heavy metals by adding lime, sodium hydroxide(Na OH),sodium carbonate(Na_2CO_3) and flocculants. The removal efficiency of SS, Ca~(2+), Mg~(2+) and organic compounds reached 97.3%, 38.1%, 98.5% and 74.3%, respectively. The intensive softening unit, including filter, ultrafiltration(microfiltration) and nanofiltration unit, could efficiently intercept divalent ions and organic compounds. The concentrations of Ca~(2+), Mg~(2+) and sulfate in the effluent of nanofiltration unit were 5.2, 0.4 and 84.3 mg/L,respectively, which reduced the risk of membrane fouling and guaranteed quality of industry salt product. After electrodialysis, ion exchange and evaporation crystallization, the purity of the obtained industrial salt met the requirements of the secondary industrial wet salt in the National Standard for Industrial Salt(GB 5462—2015).
Zero liquid discharge(ZLD) of wastewater generated by flue gas desulfurization(FGD) system of coal-fired power plants is a hot and difficult issue in the industry. A ZLD process of FGD wastewater integrated with pre-treatment, intensive softening, pre-concentration and evaporation-crystallization units was established,through quality analysis for desulfurization waste water. Moreover, a 25 m~3/d pilot-scale test was carried out. The results show that, all units of the process operated efficiently and stably, and realized ZLD. The pretreatment module consisting of primary sedimentation tank and sequencing batch softening reactor realized simultaneous removal of suspended substance(SS), hardness, organic matter and heavy metals by adding lime, sodium hydroxide(Na OH),sodium carbonate(Na_2CO_3) and flocculants. The removal efficiency of SS, Ca~(2+), Mg~(2+) and organic compounds reached 97.3%, 38.1%, 98.5% and 74.3%, respectively. The intensive softening unit, including filter, ultrafiltration(microfiltration) and nanofiltration unit, could efficiently intercept divalent ions and organic compounds. The concentrations of Ca~(2+), Mg~(2+) and sulfate in the effluent of nanofiltration unit were 5.2, 0.4 and 84.3 mg/L,respectively, which reduced the risk of membrane fouling and guaranteed quality of industry salt product. After electrodialysis, ion exchange and evaporation crystallization, the purity of the obtained industrial salt met the requirements of the secondary industrial wet salt in the National Standard for Industrial Salt(GB 5462—2015).
引文
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[9]TOLONEN E T,R?M OUML J,LASSI U.The effect of magnesium on partial sulphate removal from mine water as gypsum[J].Journal of Environmental Management,2015,159:143-146.
[10]庞胜林,陈戎,毛进,等.火电厂石灰石-石膏湿法脱硫废水分离处理[J].热力发电,2016,45(9):128-133.PANG Shenglin,CHEN Rong,MAO Jin,et al.Separation treatment process for limestone-gypsum wet FGDwastewater from coal-fired power plants[J].Thermal Power Generation,2016,45(9):128-133.
[11]ALMASRI D,MAHMOUD K,ABDEL-WAHAB A.Two-stage sulfate removal from reject brine in inland desalination with zero-liquid discharge[J].Desalination,2015,362:52-58.
[12]DOU W,ZHOU Z,JIANG L M,et al.Sulfate removal from wastewater using ettringite precipitation:Magnesium ion inhibition and process optimization[J].Journal of Envi-ronmental Management,2017,196:518-526.
[13]中华人民共和国国家质量监督检验检疫总局,中华人民共和国国家标准化管理委员会.工业盐国家标准:GB 5462-2015[S].北京:中国标准出版社,2015.General Administration of Quality Supervision,Inspection and Quarantine of the People’s Republic of China,Standardization Administration of the People’s Republic of China.National standard for industrial salt:GB 5462-2015[S].Beijing:Standards Press of China,2015.
[2]HLINCIK T,BURYAN P.Evaluation of limestones for the purposes of desulphurisation during the fluid combustion of brown coal[J].Fuel,2013,104(87):208-215.
[3]MA S,CHAI J,CHEN G,et al.Research on desulfuriza-tion wastewater evaporation:Present and future perspec-tives[J].Renewable Sustainable Energy Review,2016,58:1143-1151.
[4]韩飞超,汪旭,张荣,等.石灰石-石膏湿法烟气脱硫废水处理工艺的优化改造[J].中国给水排水,2016,32(14):99-102.HAN Feichao,WANG Xu,ZHANG Rong,et al.Optimized reconstruction of limestone-gypsum wet flue gas desulfurization wastewater treatment process[J].China Water&Wastewater,2016,32(14):99-102.
[5]刘海洋,夏怀祥,江澄宇,等.燃煤电厂湿法脱硫废水处理技术研究进展[J].环境工程,2016,34(1):31-35.LIU Haiyang,XIA Huaixiang,JIANG Chengyu,et al.Research advances in wet flue gas desulfurization wastewater treament technology in coal-fired power plant[J].Environmental Engineering,2016,34(1):31-35.
[6]叶春松,罗珊,张弦,等.燃煤电厂脱硫废水零排放处理工艺[J].热力发电,2016,45(9):105-108.YE Chunsong,LUO Shan,ZHANG Xian,et al.Key problems and developing trend of zero discharge technology of desulfurization waste water[J].Thermal Power Generation,2016,45(9):105-108.
[7]刘秋生.烟气脱硫废水“零排放”技术应用[J].热力发电,2014,43(12):114-117.LIU Qiusheng.Application and comparison of’zero discharge’technology for desulfurization waste water[J].Thermal Power Generation,2014,43(12):114-117.
[8]吴优福,刘捷,海玉琰,等.超超临界1 000 MW机组脱硫废水零排放技术[J].热力发电,2017,46(5):108-114.WU Youfu,LIU Jie,HAI Yuyan,et al.Discussions on zero-discharge technology of desulfurization wastewater for ultra-supercritical 1 000 MW units[J].Thermal Power Generation,2017,46(5):108-114.
[9]TOLONEN E T,R?M OUML J,LASSI U.The effect of magnesium on partial sulphate removal from mine water as gypsum[J].Journal of Environmental Management,2015,159:143-146.
[10]庞胜林,陈戎,毛进,等.火电厂石灰石-石膏湿法脱硫废水分离处理[J].热力发电,2016,45(9):128-133.PANG Shenglin,CHEN Rong,MAO Jin,et al.Separation treatment process for limestone-gypsum wet FGDwastewater from coal-fired power plants[J].Thermal Power Generation,2016,45(9):128-133.
[11]ALMASRI D,MAHMOUD K,ABDEL-WAHAB A.Two-stage sulfate removal from reject brine in inland desalination with zero-liquid discharge[J].Desalination,2015,362:52-58.
[12]DOU W,ZHOU Z,JIANG L M,et al.Sulfate removal from wastewater using ettringite precipitation:Magnesium ion inhibition and process optimization[J].Journal of Envi-ronmental Management,2017,196:518-526.
[13]中华人民共和国国家质量监督检验检疫总局,中华人民共和国国家标准化管理委员会.工业盐国家标准:GB 5462-2015[S].北京:中国标准出版社,2015.General Administration of Quality Supervision,Inspection and Quarantine of the People’s Republic of China,Standardization Administration of the People’s Republic of China.National standard for industrial salt:GB 5462-2015[S].Beijing:Standards Press of China,2015.