湿法脱硫溶液及脱硫石膏中汞的稳定性研究

发布时间：2018-01-18 07:30

  本文关键词：湿法脱硫溶液及脱硫石膏中汞的稳定性研究　出处：《华中科技大学》2015年硕士论文　论文类型：学位论文

  更多相关文章： 湿法脱硫溶液 脱硫石膏 汞 再释放 稳定

【摘要】：我国是世界上煤炭消费量最大的国家,燃煤所带来的汞污染问题日益突出。燃煤电厂是最大人为汞排放源之一,加强燃煤电厂汞排放控制十分必要。目前我国燃煤电厂主要利用现有除尘设备对汞进行联合脱除。湿法脱硫系统作为燃煤电厂主要除尘设备之一,在脱除SO2的同时能有效去除烟气中的Hg2+。然而被湿法脱硫系统吸收的汞并不稳定,脱硫液中的汞可能存在二次释放,而进入脱硫石膏中的汞可能在石膏资源化利用过程中再次转移到环境中。因此对湿法脱硫系统溶液及脱硫石膏中汞的稳定进行研究具有重要意义。由于还原性离子的存在,湿法脱硫溶液中的Hg2+会被还原成Hg0而释放出来。相关研究发现向脱硫溶液中加入稳定剂能够有效将溶液中的Hg2+捕集沉淀下来,但是湿法脱硫系统相关运行参数对稳定剂的稳定效果的影响尚不明确。因此,本文通过实验研究,考察了添加量,温度,pH,Cl-对Na2S和DTCR-3两种稳定剂对模拟电厂湿法脱硫溶液中Hg2+稳定效果的影响,发现两种稳定剂都能有效捕集溶液中的Hg2+,且最佳添加量都为2.0倍摩尔计量比,温度和pH的升高会提高两种稳定剂对Hg2+捕集沉淀效果,但Cl-浓度的增加会抑制两种稳定剂对Hg2+的捕集沉淀。脱硫石膏是湿法脱硫系统的主要产物,其在加工利用过程中会经过加热工序,因此会导致石膏中的汞重新释放出来。本文通过程序升温热解实验对EZ、XY、GD三个电厂脱硫石膏中汞的化物的热分解特性进行了研究,并初步判断了脱硫石膏中汞的化合物形态。发现在加热过程中脱硫石膏中汞的释放区间主要在200℃~500℃,脱硫石膏中汞的化合物主要是HgS(红)和HgS(黑),升温速率的变化不会改变汞的释放温度区间及峰值温度。升温速率的降低及氧气的存在会导致脱硫石膏在加热过程中Hg0的释放浓度降低。此外,存在于脱硫石膏中的有害元素会在雨水、地下水等浸润作用下转移到周围环境中造成污染。本文使用水平振荡法对三种电厂石膏进行了毒性鉴别实验和有害元素浸出特性实验。实验结果表明,三种电厂脱硫石膏中各有害元素的浸出浓度都远低于相关规定中的浓度限值。三种电厂脱硫石膏中各有害元素的浸出率在8h~16h时达到最大值。Pb、As、Cr、Se这四种元素的浸出率都随液固比的增大而逐渐增大。而Hg的浸出率会随液固比的增大而减小。对于Pb、As、Cr、Se这四种元素,主要以氧化物的形式存在于脱硫石膏中,主要在酸性条件下溶解,因此pH的升高都会明显降低其浸出率。
[Abstract]:China has the largest coal consumption in the world, and the mercury pollution caused by coal burning is increasingly prominent, and coal-fired power plant is one of the largest anthropogenic mercury emission sources. It is necessary to strengthen mercury emission control in coal-fired power plants. At present, coal-fired power plants in China mainly use the existing dust removal equipment for combined removal of mercury. Wet desulfurization system as one of the main dust removal equipment in coal-fired power plants. The removal of SO2 can effectively remove Hg2 from flue gas. However, the mercury absorbed by wet desulfurization system is not stable, and there may be secondary release of mercury in desulfurization solution. Therefore, it is important to study the stability of mercury in wet desulfurization system and desulphurized gypsum. The existence of son. Hg2 in wet desulfurization solution will be reduced to Hg0 and released. It is found that adding stabilizer to desulfurization solution can effectively capture and precipitate Hg2 in the solution. However, the influence of the operation parameters of wet desulfurization system on the stabilization effect of stabilizer is not clear. Therefore, through the experimental study, the addition amount, temperature and pH value of the stabilizer are investigated. The effect of CL- on Na2S and DTCR-3 stabilizers on the stability of Hg2 in wet desulfurization solution of power plant is simulated. It is found that both stabilizers can effectively capture Hg2 in the solution. And the optimum addition amount is 2.0 times molar ratio, the increase of temperature and pH will improve the effect of two stabilizers on Hg2 precipitation. However, the increase of Cl-concentration will inhibit the precipitation of Hg2 by two stabilizers. Desulfurization gypsum is the main product of wet desulphurization system, and it will go through heating process in the process of utilization. In this paper, the pyrolysis characteristics of mercury compounds in gypsum desulfurization gypsum in three power plants are studied by programmed pyrolysis experiments. It is found that the release range of mercury in desulfurized gypsum is mainly at 200 鈩，

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