Study On Simultaneous Removing Dioxide Sulfur And Mercury From Coal-Fired Flue Gas By Using AC-Ptfe Composite Materials

With the rapid development of our country economy and society, the demand of power energy would increase greatly as well. SO₂and mercury emissions in coal-fired flue gases become a significant environmental concern as it has done harm to human health, and environmental protection is imperative. In the existing flue gas purification technology at home and abroad, the removal of dust, SO₂, NOx and mercury are completed separately in different independent pollution control systems, and there is almost no simutaneos and integration processing. Fixed bed adsorption method is an advanced dry removal technology, and it can remove SO₂and Hg at the same time. The technology costing less investment is simple, and does not produce secondary pollution. In this paper, Composite material was prepared using coal-based activated carbon as raw material, ethanol solution as dispersant and PTFE （polytetrafluoroethylene） emulsion as binder. A bench-scale fixed bed by own design and build was employed to examine SO₂and mercury adsorption behaviors.The main study contents are as follows:The surface pore structure and topography of composite material were characterized by BET and SEM. BET analysis showed that composite material belonged to the mesoporous material and the aperture was only a few time of pollutant molecules. With appropriate average aperture, composite material had a better physical adsorption performance. SEM analysis showed that the PTFE uniform mixed with activated carbon, and a number of particles reunited together to form the micro pore structure. With the abundant pore structure, composite material had the good hydrophobic environment.A bench-scale fixed bed was employed to examine SO₂and mercury adsorption behaviors. The results showed that, composite material had hydrophobic properties, could prolong the adsorption time of SO₂, and improve the adsorption performance of SO₂and mercury. Composite material by KI, H2O₂and HNO₃modification all could improve the adsorptive capacities of SO₂and mercury. HNO₃modified composite had the best SO₂adsorption performance. SO₂adsoption increased25mg·g^-1. KI modified composite showed the best mercury adsorption. Mercury adsorption capacity increased1.6times. The desulfurizing process of HNO₃modified composite would continue to produce NOx which was secondary pollutants. Comprehensive consideration, KI modified composite was the more suitable modifier.The effect of the reaction temperature, SO₂concentration, oxygen concentration, the water vapor concentration, and other processing conditions on the adsorption capacity of composite, were investigated. The results showed that, with the increase of reaction temperature, the adsorption performance of SO₂and mercury of composite got worse. The concentration of SO₂had a certain influence on the adsorption performance of SO₂and mercury. SO₂could improve the desulfurization, but reduce the adsorption performance of mercury. The concentration of mercury had little influence on the desulfurization, and could be neglected. However, the concentration of mercury had the influence of both sides on the adsorption performance of mercury. In practice, it should choose a suitable adsorbent dosage for different elemental mercury emission levels.With the increase of O₂concentration, the adsorption performance of SO₂and mercury both improved. With the increase of concentration of water vapor, the desulfurization performance of composite became better and better, and the presence of water vapor was conductive of the adsorption performance of mercury. When the water concentration was10%, mercury adsorption was the maximum. High concentration of water vapor would hinder the mercury removal.