【作者】 许绿丝；

【导师】 曾汉才；

【作者基本信息】 华中科技大学 ， 热能工程， 2007， 博士

【摘要】 鉴于我国目前燃煤排放SO₂、NO_x和Hg造成的环境污染严重状况,干法同时脱除技术具有脱除效率高、成本低、无二次污染以及便于布置等优点,特别是活性炭纤维（ACF）作为一种新型的炭质催化吸附材料,较以往的颗粒状活性炭、粉状活性炭,拥有更优越的吸附和脱附再生性能。虽然从上世纪60年代起国外已开始研制ACF,近年来国内外开始研究将其用于烟气净化,已取得了一些成果。其主要对脱除单种污染物的研究较多,但对于吸附氧化除汞研究较少,同时脱除SO₂/NO_x/Hg⁰的情况则比较复杂,目前这方面的研究更少,因此仍有不少问题值得深入探讨。本课题提出了对ACF合适的改性方法,以满足同时脱除SO₂/NO_x/Hg⁰的需要;并深入研究了改性ACF同时脱硫、脱硝和除汞的表面吸附过程和吸附机理,以及脱除性能,将复杂的反应过程清晰化;运用“混合模型法”建立了反应器模型;进行了实际燃煤电厂烟气同时脱除SO₂/NO_x/Hg的工艺系统设计及技术经济可行性分析。本课题研究开拓了ACF这种新型材料在大气污染控制工程中同时脱除多种污染物的环保应用前景,将对我国的燃煤污染物治理技术的发展及国产化有着重大的意义。本文针对同时脱除SO₂/NO/Hg多种污染物的要求,研究同时引进含氧官能团和含氮官能团的改性方法,并对改性前后的表面特性进行了分析研究。试验结果表明,经硫酸处理再经氨水溶液处理后,ACF表面含氧官能团特别是含氮官能团显著增加,对低温吸附氧化脱除SO₂/NO_x/Hg是十分有效的。用吸附能这一参数分析证明改性处理后化学吸附贡献量的增加是主要的。进行了同时脱除SO₂/NO/Hg的实验研究,并分析其反应机理及影响因素。当SO₂、NO同时存在时,活性炭纤维的脱硫性能有所提高,但对于NO的吸附有不利影响。Hg对SO₂、NO的脱除影响不大,然而SO₂和NO₂同时存在对Hg⁰的吸附有不利影响,NO和NO₂则有利于Hg⁰的吸附氧化。烟气中O₂和H₂O浓度高,有利于脱硫脱硝除汞,但过多的氧和水分将影响吸附。在大量实验研究获得的数据的基础上,结合机理分析,考虑多种污染物同时脱除的主要影响因素,建立了ACF脱除SO₂/NO/Hg反应器内浓度瞬态分布的数学模型;研究了传递过程对脱除污染物反应速率的影响,并将ACF与GAC的传递过程进行了比较。通过实验数据拟合建立了阻力计算数学模型。运用数学模型及实验数据对一些主要参数进行优化选择。评价了ACF脱附性能,分别采用水洗脱附和负压热空气脱附方法进行了脱附实验。认为负压热空气脱附具有较好的工业运用价值。进行了ACFs脱除SO₂/NO_x/Hg一体化工艺设计及技术经济比较。按脱硫效率90%,脱NO_x效率40%,Hg部分脱除。提出了两种方案:方案一,在ACF反应器中同时脱除SO₂/NO_x/Hg,布置在主体工程引风机与烟囱之间的烟道上。方案二,是针对已设有FGD系统的电厂,ACF主要脱除NO_x和Hg,反应器从FGD吸收塔出口至GGH进口的净烟道上并联接出。对工艺系统的主要设备进行了选型,并运用PDMS软件进行了三维布置设计。更多还原

【Abstract】 Pollutants such as SO₂,NO_x,Hg etc. emitted from coal combution procerres will do harm to environment and mankind health. Dry Flue gas Desulfurization （DFGD） have many advantages such as high efficiency, low cost, no secondary pollution, easy arrangement, etc.. Activated carbon fibers （ACF） especially as a new carbonaceous material for adsorption, have better adsorption and desorption performance than granular activated carbon （GAC） and powder activated carbon （PAC）. The research about ACF started from 60’s last century for several western. Recently, it is propsed to be used for flue gas purification and some achievements have be obtained. However, most of the research reports are about mono-pollutant removal, and the study on mercury removal is even less. Due to complexity of removal mechanisms for SO₂/ NO_x /Hg, The study is seldom reported as well. So there are many problems worth to be discussed further. Herein a suitable modified method was developed for ACF in order to meet the requirements of removal for SO₂/ NO_x /Hg, and the studies were carried out to investigate the surface adsorption process and mechanism for SO₂/ NO_x /Hg removal. A math model of ACF reactor was established through“compound model method”. Technical system designing and analysis of technical and economical feasibility for SO₂/ NO_x /Hg removal in flue gas from a power plant were also considered. Foreground of ACF used for removing multi-pollutants in air pollution control was developed for environment protection. There will be a great significance in developing and domestic of technology for coal-fired pollutants control.In order to removal SO₂/NO/Hg, ACF modified method, increasing the oxygen functional groups and nitrogen functional groups on the ACF’s surface, was studied. ACF were immersed into sulfuric acid before impregnated with ammonia solution. The analytical study for surface chemistry texture was carried out before and after modified. The results show that it can efficiently increase the oxygen functional groups, and nitrogen functional groups, and is feasible for oxygenating removal SO₂/NO_x/Hg at low temperature. That chemical adsorption was the main contribution as proved by the analysis of adsorption energy after modified. The experiment of removal SO₂/NO/Hg were carried out. The reaction mechanism and affecting factors were proposed. If SO₂ and NO presented, efficient of removal SO₂ would be available. However, it is not good for deNO_x. Hg had fewer effects on removal of SO₂ and NO. Whilst If SO₂ and NO₂ presented , which was unfavorable for Hg⁰adsorption. NO and NO₂ was favorable for Hg⁰adsorption and oxygenating. The oxygen and moisture in flue increasing were favorable for removal of SO₂/NO/Hg. but higher concentration of O₂ and H₂O were unfavorable for the adsorption.According to the data attained from experiments, based on the mechanism analysis and removal muti-pollutants effect, mathematical models of concentration distribution was devolped in an ACF reactor. The reaction rate of removal pollutants affected by transport phenomena was studied. Transport process in ACF were compare with those of GAC. Resistance mathematical models were established using data getting from experiment. Optimizing methods of main parameters using math models were introduced.The studis of ACF desorption performance were carried out, i.e., Water scrubbing and hot air suction desorption experiment, and hot air suction method was seen predominant.Technical designing and analysis of technical and economical feasibility for removal SO₂/ NO_x /Hg in flue gas were carried out. According to the efficiency of desulfurization, denitrification, removal mercury were 90% ,40% and part, respectively. Two suggestions were proposed as: The plan I was considered to removal SO₂/ NO_x /Hg in an ACF reactor. The reactor was arranged in duct between the induced fan and the stack. The plan II was considered to removal NO_x and Hg in the plant with FGD. The reactor was arranged in the duct between FGD absorber and GGH. Main equipments used were chosen. Design of three-dimensional arrangement was realized by a PDMS softer.更多还原