Study On Adsorption And Oxidation Removal Of SO₂/NO_X/Hg At Low-Temperature By Modified Activated Carbon Fiber

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.