低温等离子体结合湿法过程氧化脱汞研究

发布时间：2018-03-14 11:03

本文选题：氧化脱汞　切入点：等离子体　出处：《华北电力大学(北京)》2017年硕士论文　论文类型：学位论文

【摘要】：汞由于其剧毒、高挥发性以及在生物链中能够富集等特性,危害人类的身体健康。燃煤电厂作为最大的人为汞排放源,如何安全、高效、经济的控制燃煤汞排放成为目前研究的热点。低温等离子体氧化脱汞技术以其适应性强,能够多种污染物联合控制的特点引起了广泛关注。本文利用等离子体结合湿法过程氧化烟气中的单质汞。采用介质阻挡放电(DBD)作为产生等离子体的方法,配比含汞的模拟烟气依次连续通入DBD反应器和湿法鼓泡反应器内反应,考察了含氧量、电压、温度、湿法过程、停留时间以及烟气成分变化等因素对氧化脱汞的影响。主要内容如下:在等离子体氧化单质汞过程中O原子和O3起主导作用,提高O2体积分数能够增加O原子和O3的含量,促进Hg0的氧化。实验中当氧含量为30%时,最高能达到97%的汞氧化效率。在放电电压小于10k V时升高电压能够增加单质汞的氧化效率,但电压过高时汞氧化效率反而会下降。系统中产生的活性氧化物质对于只有ppb浓度的汞而言是远远过量的,增加单质汞浓度,会增大汞原子与活性自由基间的碰撞几率,所以单质汞氧化效率会升高。模拟烟气温度升高能够使折合场强增大和化学反应速率增加,会促进单质汞氧化,在放电电压为6k V,氧含量为10%的条件下,温度从室温升高到403K时,单质汞氧化效率从61%增大到92%。在DBD反应器后添加湿法过程能够明显促进汞的氧化。在8kV放电条件下,添加湿法过程后Hg0的氧化效率从42.64%增加到81.48%,提高了近一倍。由于活性物质相对于单质汞是过量的,通过增加停留时间,也能够提高汞氧化效率。烟气成分对DBD结合湿法过程氧化脱汞有影响,NO会竞争消耗臭氧,对单质汞的氧化有明显的抑制作用,当加入750ppm的NO,有无湿法过程均只有12%的Hg0被氧化。而SO2在系统内会被氧化成SO3能够促进汞的氧化。CO2会轻微抑制等离子体对单质汞的氧化过程,但是CO2能够稳定放电,可以削弱高压放电时的负面效果。
[Abstract]:Mercury is harmful to human health because of its high toxicity, high volatility and ability to enrich in biological chain. As the largest anthropogenic mercury emission source, coal-fired power plants are safe and efficient. Economic control of mercury emissions from coal combustion has become a hot research topic. Low temperature plasma oxidation decarbonization technology has strong adaptability. In this paper, plasma combined with wet process is used to oxidize elemental mercury in flue gas. Dielectric barrier discharge (DBD) is used as the method to produce plasma. The simulated flue gas containing mercury was successively passed into the DBD reactor and the wet bubbling reactor. The oxygen content, voltage, temperature and wet process were investigated. The main contents are as follows: O atom and O 3 play a leading role in the process of plasma oxidation of elemental mercury, increasing the volume fraction of O 2 can increase the content of O atom and O 3. In the experiment, the maximum oxidation efficiency of mercury is 97% when the oxygen content is 30. When the discharge voltage is less than 10 kV, increasing the voltage can increase the oxidation efficiency of elemental mercury. However, when the voltage is too high, the efficiency of mercury oxidation will decrease. The active oxidized substance produced in the system is far excess for mercury with only ppb concentration, and increasing the concentration of elemental mercury increases the probability of collision between mercury atoms and active free radicals. So the oxidation efficiency of elemental mercury will increase, and the simulated flue gas temperature will increase the field strength and chemical reaction rate, which will promote the oxidation of mercury, at the discharge voltage of 6kV and the oxygen content of 10%. When the temperature increases from room temperature to 403K, the oxidation efficiency of elemental mercury increases from 61% to 9220.The wet process of adding mercury after DBD reactor can obviously promote the oxidation of mercury. After adding wet process, the oxidation efficiency of Hg0 increased from 42.64% to 81.48, which is nearly doubled. Because the active substance is excessive relative to elemental mercury, by increasing the residence time, The effect of flue gas composition on oxidative decarbonization of DBD combined with wet process will result in no competition for ozone depletion and obvious inhibition on the oxidation of elemental mercury. When 750ppm of no was added, only 12% of the Hg0 was oxidized in the wet process, while SO2 was oxidized to SO3 in the system, which could promote the oxidation of mercury. CO2 could slightly inhibit the oxidation of mercury by plasma, but CO2 could discharge steadily. It can weaken the negative effect of high voltage discharge.
【学位授予单位】：华北电力大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X773;O53

【参考文献】