燃煤电厂脱硫浆液中汞迁移转化及添加剂对石膏中汞稳定性影响  

Migration and transformation of mercury in WFGD slurry from a coal-fired power unit and the effect of additive on mercury stability in gypsum

作　　者：苏银皎 滕阳[1] 张锴[1] 李丽锋 王鹏程 李圳 SU Yin-jiao;TENG Yang;ZHANG Kai;LI Li-feng;WANG Peng-cheng;LI Zhen(Beijing Key Laboratory of Emission Surveillance and Control for Thermal Power Generation,North China Electric Power University,Beijing 102206,China;Shanxi Hepo Power Generation Company Limited,Yangquan 045011,China)

机构地区：[1]华北电力大学热电生产过程污染物监测与控制北京市重点实验室,北京102206 [2]山西河坡发电有限责任公司,山西阳泉045011

出　　处：《燃料化学学报》2021年第7期1022-1033,共12页Journal of Fuel Chemistry and Technology

基　　金：国家重点研发计划(2020YFB0606201);国家自然科学基金委与山西煤基低碳联合基金重点项目(U1910215);中央高校基本科研业务费(2019QN020,2019QN019)资助。

摘　　要：以某300 MW超低排放燃煤机组现场脱硫浆液为研究对象,考察了浆液中汞迁移转化及添加剂对其影响行为,探讨了固相石膏中汞的热释放特性和环境风险。结果表明温度升高仅导致气相Hg^(0)增加,而浆液pH升高会导致气相和固相中汞含量均有增加,Cl^(-)或SO_(4)^(2-)浓度升高既可以抑制浆液中汞还原为Hg^(0)也可以促进固相石膏中汞含量增加,而SO_(3)^(2-)浓度升高虽然有利于汞富集于固相但会引起Hg^(2+)部分转化为Hg^(0)。Na_(2)S、EDTA-2Na或DTCR-4添加剂与Hg^(2+)反应分别生成HgS、Hg(EDTA)2或-[Hg-DTCR]_(-n),使浆液中75%以上汞转移至固相石膏中,并抑制了Hg^(2+)还原为Hg^(0),其中DTCR-4对汞的固化效果最好,但热稳定性依次为Gypsum+EDTA-2Na<Gypsum+DTCR-4<Gypsum+Na_(2)S<Gypsum,主要原因是所生成Hg(EDTA)2、-[Hg-DTCR]_(-n)和HgS(black)的稳定性差异所致。进而采用TCLP、SPLP和MEP三种方法获得了样品中汞的化学稳定性为Gypsum<Gypsum+Na_(2)S<Gypsum+EDTA-2Na<Gypsum+DTCR-4,其原因是石膏中水溶态汞、酸溶态汞和可氧化态汞含量的差异所致。Slurry sample was collected from a 300 MW ultra-low emissions coal^(-)fired power unit.The migration and transformation behaviors of mercury in the sample were investigated,and the effect of additive on the stability of mercury in solid gypsum was explored by considering the thermal release behavior and environmental risk.The results show that gaseous Hg^(0) is increased with the increase of slurry temperature,while Hg is increased in both gas phase and gypsum with the increase of slurry pH.The concentration of Cl^(-)or SO_(4)^(2-)the reduction of Hg^(2+)to Hg^(0) and increase Hg proportion in gypsum.However,the increase of SO_(3)^(2-)beneficial to the Hg enriched in gypsum and a part of Hg^(2+)reduced to Hg^(0).When Na_(2)S,EDTA-2 Na or DTCR-4 is added,Hg^(2+)is turned into HgS,Hg(EDTA)2 or[-Hg-DTCR]_(-n),respectively among which more than 75%Hg is transferred to gypsum and Hg^(2+)is inhibited to reduce into Hg^(0).The thermal stability of Hg in gypsum can be ordered as Gypsum+EDTA-2 Na<Gypsum+DTCR-4<Gypsum+Na_(2)S<Gypsum due to the stability difference among Hg(EDTA)2,[-Hg-DTCR]_(-n) and HgS(black).By using TCLP,SPLP and MEP,the chemical stability of Hg in gypsum can be ordered as Gypsum<Gypsum+Na_(2)S<Gypsum+EDTA-2 Na<Gypsum+DTCR-4 due to the concentration difference of water soluble mercury,acid soluble mercury and oxidizable mercury among gypsums.

关 键 词：燃煤机组 脱硫浆液 汞 迁移转化 添加剂 石膏 稳定性 

分 类 号：TQ53[化学工程—煤化学工程]