Influence of SCR catalysts and operating parameters on SO3 generation in coal-fired power plants
CHENG Junfeng1,, QING Mengxia2, WANG Lele3, XIANG Jun3,, 1.Beijing SPC Environment Protection Tech Co. Ltd., Beijing 100142, China 2.School of Energy and Power Engineering, Changsha University of Science and Technology, Changsha 410114, China 3.State Key Laboratory of Coal Combustion, Huazhong University of Science & Technology, Wuhan 430074, China
Abstract:In order to achieve the effective control of SO3 in flue gas of coal-fired power plants, the safe and economic operation of coal-fired power plants and the ultra-low emissions of pollutants, commercial V/W/Ti SCR catalysts used in different power plants were selected to study the characteristics of SO3 generation. The effects of different catalysts and the operating parameters (temperature, space velocity, contents of O2 and SO2, ratio of NH3∶NO) on SO3 generation in flue gas were systematically explored, which could provide guidance for SO3 control in coal-fired power plants. The results indicated that the chemical composition of catalyst significantly affected the generation of SO3. The amount of V supported in the catalyst was an important parameter that determined the generation of SO3. Within loading ratios of 1%~3%, the increase of V loading promoted the formation of SO3, while the existence of Si significantly inhibited the formation of SO3. For catalyst A, SO3 generation rate no longer changed with the increase of space velocity when space velocity reached 10 000 h?1. With the increase of reaction temperature, the SO3 generation rate on catalyst surface gradually increased. The increase of temperature was beneficial to the conversion reaction between V5+ and V4+, thus increasing the oxidation activity of the catalyst. Even the loading of coal-fired power plants was reduced, SO3 would be generated on the catalyst surface at the reaction temperature as low as 280 ℃. In addition, the different components in flus gas also affected the generation of SO3. With the increase of SO2 concentration, the generated SO3 inhibited the oxidation of SO2 through competitive adsorption, resulting in the reduction of SO3 generation rate. The presence of O2, NH3 and NO could promote the transformation of SO2, the higher the concentration, the greater the promoting effect. The above results showed that the characteristics of SO3 generation on the catalyst surface were affected by various factors such as catalyst composition, temperature, space velocity, O2, SO2 and NH3∶NO ratio, etc. In order to achieve effective control of SO3 in coal flue gas, the influences of various factors should be comprehensively considered in actual projects. Key words:catalyst/ SO2 transformation/ SO3 generation/ temperature/ space velocity/ oxygen content/ ratio of NH3∶NO.
图1SO3生成实验系统 Figure1.Experimental system of SO3 formation
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1.Beijing SPC Environment Protection Tech Co. Ltd., Beijing 100142, China 2.School of Energy and Power Engineering, Changsha University of Science and Technology, Changsha 410114, China 3.State Key Laboratory of Coal Combustion, Huazhong University of Science & Technology, Wuhan 430074, China Received Date: 2019-12-29 Accepted Date: 2020-03-01 Available Online: 2020-11-11 Keywords:catalyst/ SO2 transformation/ SO3 generation/ temperature/ space velocity/ oxygen content/ ratio of NH3∶NO Abstract:In order to achieve the effective control of SO3 in flue gas of coal-fired power plants, the safe and economic operation of coal-fired power plants and the ultra-low emissions of pollutants, commercial V/W/Ti SCR catalysts used in different power plants were selected to study the characteristics of SO3 generation. The effects of different catalysts and the operating parameters (temperature, space velocity, contents of O2 and SO2, ratio of NH3∶NO) on SO3 generation in flue gas were systematically explored, which could provide guidance for SO3 control in coal-fired power plants. The results indicated that the chemical composition of catalyst significantly affected the generation of SO3. The amount of V supported in the catalyst was an important parameter that determined the generation of SO3. Within loading ratios of 1%~3%, the increase of V loading promoted the formation of SO3, while the existence of Si significantly inhibited the formation of SO3. For catalyst A, SO3 generation rate no longer changed with the increase of space velocity when space velocity reached 10 000 h?1. With the increase of reaction temperature, the SO3 generation rate on catalyst surface gradually increased. The increase of temperature was beneficial to the conversion reaction between V5+ and V4+, thus increasing the oxidation activity of the catalyst. Even the loading of coal-fired power plants was reduced, SO3 would be generated on the catalyst surface at the reaction temperature as low as 280 ℃. In addition, the different components in flus gas also affected the generation of SO3. With the increase of SO2 concentration, the generated SO3 inhibited the oxidation of SO2 through competitive adsorption, resulting in the reduction of SO3 generation rate. The presence of O2, NH3 and NO could promote the transformation of SO2, the higher the concentration, the greater the promoting effect. The above results showed that the characteristics of SO3 generation on the catalyst surface were affected by various factors such as catalyst composition, temperature, space velocity, O2, SO2 and NH3∶NO ratio, etc. In order to achieve effective control of SO3 in coal flue gas, the influences of various factors should be comprehensively considered in actual projects.
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