电厂湿法脱硫系统中汞的二次释放特性的实验研究

发布时间：2018-06-12 03:09

本文选题：湿法烟气脱硫 + 脱汞　；参考：《华中科技大学》2014年硕士论文

【摘要】：燃煤电厂的汞排放问题越来越受重视，利用现有污染物排放控制装置脱除汞的方法得到更多应用。湿法烟气脱硫系统能有效脱除烟气中的二价汞，对零价汞则基本无法脱除，甚至有部分由湿法脱硫工艺吸收的二价汞被还原成零价汞而释放出来，，造成总汞脱除效率降低，这就是汞的二次释放。本文通过改变湿法脱硫浆液的参数来探索汞二次释放的特性，寻求有利于降低汞再释放率的实验条件；同时还研究了白泥作为脱硫剂时脱硫的效果和对汞二次释放的影响。在实验室中搭建小型实验台架，模拟烟气通过预先加入Hg2+的脱硫浆液，携带被还原的汞进入测量装置，由此进行汞的二次释放特性的实验研究。实验考察了初始汞浓度、温度、pH值、S(IV)浓度、SO42-浓度、Cl-浓度及添加剂Na2S和H2O2等对汞再释放的影响。结果表明：初始汞浓度对汞二次释放率影响不大；浆液温度升高促进了汞的还原；pH值对汞再释放效果影响显著，随着pH值的升高，汞再释放率先增大后降低，高pH时有较低的二次释放率；S(IV)起到还原汞的作用，随着其浓度增加，汞的二次释放率先增加后降低，高浓度S(IV)可以抑制汞的还原；SO42-能在一定程度上抑制汞的释放，其浓度变化对汞还原的影响不大；浆液加入Cl-后可以显著抑制汞的还原；添加剂Na2S对汞还原的抑制效果显著，H2O2也能降低汞的二次释放率。白泥主要成分以钙基为主，生产量较大且又具有较强的碱性，可以作为湿法脱硫系统的脱硫剂。本文通过实验对比了白泥浆液和石灰石浆液的脱硫效果，结果显示反应初期白泥能取得比石灰石更好的脱硫效果，但是白泥有效脱硫时间要短于石灰石。白泥对二价汞的还原作用要明显强于石灰石，通过改变模拟烟气中SO2浓度、浆液温度和pH值，或者加入Na2S和Cl-可以抑制汞的还原。
[Abstract]:More and more attention has been paid to mercury emission from coal-fired power plants, and the method of removing mercury from existing pollutant emission control devices has been applied more and more. The wet flue gas desulfurization system can effectively remove the bivalent mercury from the flue gas, but basically cannot remove the zero-valent mercury. Even some of the divalent mercury absorbed by the wet desulfurization process is reduced to zero valence mercury and released, resulting in the reduction of the total mercury removal efficiency. This is the secondary release of mercury. In this paper, by changing the parameters of wet desulfurization slurry, the characteristics of secondary release of mercury are explored, and the experimental conditions conducive to reducing the rerelease rate of mercury are sought. At the same time, the desulfurization effect of white mud as desulfurizer and its influence on the secondary release of mercury were studied. A small experimental bench was set up in the laboratory, and the flue gas was simulated by adding Hg2 desulphurization slurry in advance to carry the reduced mercury into the measuring device. Experimental study on the secondary release of mercury was carried out. The effects of initial mercury concentration, temperature and pH value (SIV), so _ 42- and additives Na _ 2S and H _ 2O _ 2 on the rerelease of mercury were investigated. The results showed that the initial concentration of mercury had little effect on the secondary release rate of mercury, and the increase of slurry temperature promoted the effect of mercury reduction and pH value on the rerelease of mercury, and with the increase of pH value, the rerelease of mercury increased first and then decreased. With the increase of the concentration, the secondary release of mercury increased first and then decreased, and the high concentration of Schiv could inhibit the reduction of mercury, so _ 4 _ 2-can inhibit the release of mercury to a certain extent. The concentration change had little effect on the reduction of mercury; the addition of Cl- into the slurry could significantly inhibit the reduction of mercury; the inhibitory effect of additive Na2S on the reduction of mercury was significant; H2O2 could also reduce the secondary release rate of mercury. The main component of white mud was calcium. It can be used as desulfurization agent in wet desulfurization system because of its large production and strong alkalinity. In this paper, the desulfurization effect of white mud slurry and limestone slurry is compared through experiments. The results show that white mud can achieve better desulfurization effect than limestone in the early stage of reaction, but the effective desulfurization time of white mud is shorter than that of limestone. The effect of white mud on the reduction of divalent mercury is stronger than that of limestone. The reduction of mercury can be inhibited by changing the concentration of so _ 2 in simulated flue gas, slurry temperature and pH value, or adding Na _ 2S and Cl-.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：X773

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