类芬顿试剂、活化过硫酸铵和高铁酸钾氧化脱除烟气中单质汞的研究

发布时间：2019-03-23 18:03

【摘要】：燃煤产生的烟气汞具有很强的毒性,对人类的生存环境和身体健康造成了极大的危害,在全球范围内引起了广泛的关注。改进现有的湿法烟气脱硫装置(Wet Flue Gas Desulfurization,WFGD)脱汞和活性炭喷射(Activated carbon injection,ACI)脱汞是目前极具发展前景的燃煤烟气汞控制技术。本文筛选了三种绿色环保氧化剂(类芬顿试剂过硫酸铵和高铁酸钾),并且在喷淋塔和固定床两种常见反应器上分别研究了三种氧化剂氧化脱除燃煤烟气单质汞的基础理论问题。主要的研究内容和研究成果可分为如下三个部分:在喷淋塔反应器中,研究了溶液pH、反应温度、液-气比、H_2O_2浓度、Fe~(3+)浓度、Cu~(2+)浓度、初始汞浓度、NO浓度和SO_2浓度等工艺参数对类芬顿试剂脱汞性能的影响,并通过离子色谱、液相荧光光谱仪和电子自旋共振波谱仪测定了溶液中的液相反应产物和自由基,推测出烟气汞脱除的最终产物以及脱除路径。研究结果表明:(1)随着H_2O_2浓度、Fe~(3+)浓度、Cu~(2+)浓度和液-气比的增加,脱汞效率有了显著提升。然而,随着溶液pH、NO浓度和SO_2浓度的增加,脱汞效率大幅度下降。初始汞浓度和反应温度的变化对脱汞效率的影响很小。(2)羟基自由基氧化是汞脱除的主要路径,过氧化氢氧化是汞脱除的次要路径。在喷淋塔反应器中,研究了反应温度、(NH_4)_2S_2O_8浓度、液-气比、汞浓度、溶液pH、urea浓度和SO_2浓度等工艺参数对高温活化过硫酸铵氧化脱除单质汞的影响,并通过离子色谱、紫外分光光度法、液相荧光光谱仪和液质联用仪测定了溶液中的液相反应产物和自由基,推测出烟气汞脱除的最终产物以及脱除路径。研究结果表明:(1)随着反应温度、(NH_4)_2S_2O_8浓度和液-气比的增加,脱汞效率有了显著提升。然而,随着溶液pH和urea浓度的增加,脱汞效率反而大幅度降低。初始汞浓度和SO_2浓度的改变对脱汞效率的影响很小。(2)烟气中的单质汞主要是被溶液中的S_2O_8~(2-)、·OH和SO_4~-氧化成二价汞的方式脱除,且二价汞是最终产物。利用高温热解和化学改性的方法制备了麦秆焦吸附剂,并在固定床反应器中,研究了K_2FeO_4浓度、初始汞浓度、O_2浓度、NO浓度、SO_2浓度以及反应温度等工艺参数对该吸附剂脱汞性能的影响,研究结果表明:(1)改性后的麦秆焦的比表面积和孔隙结构均有了明显的改善。改性焦的表面成功负载了新的活性剂组分Fe_2O_3和K_2FeO_4。(2)随着O_2浓度的增加,脱汞效率得到提升。然而,随着初始汞浓度增加,脱汞效率反而下降。当烟气中加入NO时,脱汞效率上升。然而,当继续向烟气中加入SO_2时,脱汞效率反而下降。随着反应温度的增加,脱汞效率先提高后降低。
[Abstract]:The smoke mercury produced by coal combustion has strong toxicity, which has caused great harm to the living environment and health of human beings, and has attracted wide attention all over the world. The improvement of the existing wet flue gas desulfurization unit (Wet Flue Gas Desulfurization,WFGD) and activated carbon injection (Activated carbon injection,ACI) for mercury removal are promising technologies for mercury control in coal-fired flue gas. In this paper, three kinds of environmental protection oxidants (Fenton-like reagent) were selected. Ammonium persulfate and potassium ferrate), and the basic theory of removing mercury from coal-fired flue gas by oxidation of three oxidants were studied in two common reactors: spray column and fixed bed reactor. The main research contents and achievements can be divided into three parts as follows: in the spray column reactor, the solution pH, reaction temperature, liquid-gas ratio, H_2O_2 concentration, Fe~ (3) concentration, Cu~ (2) concentration and initial mercury concentration were studied. The effects of technological parameters such as NO concentration and SO_2 concentration on the performance of Fenton-like reagent for mercury removal were studied. The reaction products and free radicals in the solution were determined by ion chromatography, liquid phase fluorescence spectrometer and electron spin resonance spectroscopy. The final products of mercury removal from flue gas and the removal path were deduced. The results showed that: (1) with the increase of H_2O_2 concentration, Fe~ (3) concentration, Cu~ (2) concentration and liquid-gas ratio, the mercury removal efficiency increased significantly. However, with the increase of the concentration of pH,NO and SO_2, the efficiency of mercury removal decreased greatly. The change of initial mercury concentration and reaction temperature has little effect on the efficiency of mercury removal. (2) hydroxyl radical oxidation is the main pathway for mercury removal, and hydrogen peroxide oxidation is the secondary pathway for mercury removal. The reaction temperature, (NH_4) _ 2S_2O_8 concentration, liquid-gas ratio, mercury concentration and solution pH, were studied in a spray column reactor. The effects of technological parameters such as urea concentration and SO_2 concentration on the removal of mercury by activated ammonium persulfate oxidation at high temperature were studied by ion chromatography and ultraviolet spectrophotometry. Liquid phase reaction products and free radicals were determined by liquid phase fluorescence spectrometer and mass spectrometry. The final products and removal path of mercury removal from flue gas were deduced. The results showed that: (1) with the increase of reaction temperature, the concentration of (NH_4) _ 2S_2O_8 and the ratio of liquid to gas, the efficiency of mercury removal increased significantly. However, with the increase of the concentration of pH and urea, the efficiency of mercury removal decreased greatly. The change of initial mercury concentration and SO_2 concentration has little effect on the efficiency of mercury removal. (2) the primary mercury in flue gas is mainly removed by oxidation of Sz _ 2O _ 2O _ 8 ~ (2 -), OH) and SO_4~- into divalent mercury in the solution. And divalent mercury is the final product. The sorbents for wheat stalk coke were prepared by high temperature pyrolysis and chemical modification. The K_2FeO_4 concentration, initial mercury concentration, O ~ (2 +) concentration and NO concentration were studied in a fixed-bed reactor. The effects of SO_2 concentration and reaction temperature on the mercury removal performance of the adsorbent were studied. The results showed that: (1) the specific surface area and pore structure of the modified wheat stalk coke were obviously improved. The surface of the modified coke was successfully loaded with new active agent Fe_2O_3 and K _ 2O _ 2 FeO _ 4. (2) the efficiency of mercury removal was improved with the increase of O ~ (2 +) concentration. However, the efficiency of mercury removal decreases with the increase of initial mercury concentration. When NO was added to the flue gas, the mercury removal efficiency increased. However, when SO_ 2 was added to the flue gas, the mercury removal efficiency decreased instead. With the increase of reaction temperature, the mercury removal efficiency first increased and then decreased.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X701

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