脱硝工程优化模拟和催化剂小试
发布时间：2018-10-21 11:36
【摘要】：氮氧化物(NOx)是大气的主要污染物之一,严重危害生态环境和人类健康。燃煤锅炉等固定源和机动车等移动源排放的废气是NOx最主要的来源。选择性催化还原(Selective Catalytic Reduction,SCR)技术是目前国际上最成熟、应用最广泛的烟气脱硝技术。催化剂是SCR技术的核心和关键。本文通过计算流体力学(Computational Fluid Dynamics,CFD)对烟气脱硝系统进行数值模拟,优选出最佳的设计方案为实际工程应用提供理论参考。对烟气脱硝系统进行改进设计,改进内容包括整流格栅的数目、尺寸、反应器结构尺寸、和导流板的数目、尺寸,并通过CFD对设计方案进行优选。本论文在之前模型的基础上,增加整流格栅数目,反应器内部流场的气流分布的均匀性并未提高,优选整流格栅的数目为21。在优选整流格栅数目后,增加整流格栅的高度,内部流场气流分布的均匀性呈现先增大后降低的趋势,优选整流格栅的高度为0.5m。在此基础上内部流场气流分布的均匀性仍没有达到合格的要求,因此考虑改进SCR反应器的设计尺寸。在改进模型的基础上,改变直导流板的安装位置和数目后,对流场气流分布的均匀性有较大的改善作用,优选直导流板的数目为5。优选直导流板的数目后,改变直导流板的长度,当直导流板长度为1.2m时,内部流场的速度分布均匀,满足良好的要求,优选直导流板的长度为1.2m。本文利用水热法制备出SAPO-44分子筛,并通过离子交换法制备出新型分子筛SCR催化剂Cu-SAPO-44。运用XRD、N2吸脱附、ICP-AES、SEM、XPS、H2-TPR等技术对催化剂的结构、形貌和氧化还原性能等进行表征。结果显示:以一定的配料比可以制备出高纯度、高洁净度的SAPO-44分子筛,经离子交换后,Cu-SAPO-44的结晶度明显下降。Cu-SAPO-44催化剂的颗粒尺寸和孔尺寸较纯SAPO-44分子筛有所降低,催化剂的表面未发现含Cu物种,说明通过离子交换法制备的分子筛中,Cu物种可能较为均匀的分散在分子筛孔道内部,堵塞部分孔道,造成比表面积下降。对Cu-SAPO-44分子筛催化剂进行SCR活性测试,结果表明,催化剂在200℃~550℃显示出极高的脱硝活性,且具有较差的抗水抗硫性能和较差的水热稳定性。
[Abstract]:Nitrogen oxide (NOx) is one of the major pollutants in the atmosphere, which seriously endangers the ecological environment and human health. Emissions from fixed sources such as coal-fired boilers and moving sources such as motor vehicles are the main sources of NOx. Selective catalytic reduction (Selective Catalytic Reduction,SCR) technology is the most mature and widely used flue gas denitrification technology in the world. Catalyst is the core and key of SCR technology. In this paper, the numerical simulation of flue gas denitrification system is carried out by computational fluid dynamics (Computational Fluid Dynamics,CFD), and the optimal design scheme is selected to provide theoretical reference for practical engineering application. The improved design of flue gas denitrification system includes the number and size of rectifier grille, the size of reactor structure, and the number and size of diversion plate. The design scheme is optimized by CFD. On the basis of the previous model, the number of rectified grids is increased, the uniformity of the flow field in the reactor is not improved, and the optimal number of rectified grids is 21. With the increase of the height of the rectified grid when the number of the selected rectified grille increases, the distribution uniformity of the internal flow field increases first and then decreases, and the height of the optimized rectified grid is 0.5 m. On this basis, the uniformity of flow distribution in the internal flow field is still not up to the qualified requirements, so the design size of the SCR reactor is considered to be improved. On the basis of the improved model, the distribution uniformity of the flow field can be improved greatly by changing the installation position and the number of the straight guide plates, and the optimum number of the straight guide plates is 5. When the length of the straight guide plate is 1.2m, the velocity distribution of the internal flow field is uniform, which meets the good requirements, and the length of the optimized straight guide plate is 1.2 m. In this paper, SAPO-44 molecular sieve was prepared by hydrothermal method, and new molecular sieve SCR catalyst Cu-SAPO-44. was prepared by ion exchange method. The structure, morphology and redox properties of the catalyst were characterized by XRD,N2 adsorption and desorption, ICP-AES,SEM,XPS,H2-TPR and so on. The results showed that SAPO-44 molecular sieve with high purity and high cleanliness could be prepared with a certain proportion of mixture. The crystallinity of Cu-SAPO-44 decreased obviously after ion exchange, and the particle size and pore size of Cu-SAPO-44 catalyst were lower than that of pure SAPO-44 molecular sieve. No Cu species were found on the surface of the catalyst, indicating that the Cu species in the molecular sieve prepared by ion exchange method may be uniformly dispersed inside the molecular sieve channels, blocking part of the pore channels, resulting in a decrease in the specific surface area. The SCR activity of Cu-SAPO-44 molecular sieve catalyst was tested. The results showed that the catalyst exhibited extremely high denitrification activity at 200 鈩，
本文编号：2284976
[Abstract]:Nitrogen oxide (NOx) is one of the major pollutants in the atmosphere, which seriously endangers the ecological environment and human health. Emissions from fixed sources such as coal-fired boilers and moving sources such as motor vehicles are the main sources of NOx. Selective catalytic reduction (Selective Catalytic Reduction,SCR) technology is the most mature and widely used flue gas denitrification technology in the world. Catalyst is the core and key of SCR technology. In this paper, the numerical simulation of flue gas denitrification system is carried out by computational fluid dynamics (Computational Fluid Dynamics,CFD), and the optimal design scheme is selected to provide theoretical reference for practical engineering application. The improved design of flue gas denitrification system includes the number and size of rectifier grille, the size of reactor structure, and the number and size of diversion plate. The design scheme is optimized by CFD. On the basis of the previous model, the number of rectified grids is increased, the uniformity of the flow field in the reactor is not improved, and the optimal number of rectified grids is 21. With the increase of the height of the rectified grid when the number of the selected rectified grille increases, the distribution uniformity of the internal flow field increases first and then decreases, and the height of the optimized rectified grid is 0.5 m. On this basis, the uniformity of flow distribution in the internal flow field is still not up to the qualified requirements, so the design size of the SCR reactor is considered to be improved. On the basis of the improved model, the distribution uniformity of the flow field can be improved greatly by changing the installation position and the number of the straight guide plates, and the optimum number of the straight guide plates is 5. When the length of the straight guide plate is 1.2m, the velocity distribution of the internal flow field is uniform, which meets the good requirements, and the length of the optimized straight guide plate is 1.2 m. In this paper, SAPO-44 molecular sieve was prepared by hydrothermal method, and new molecular sieve SCR catalyst Cu-SAPO-44. was prepared by ion exchange method. The structure, morphology and redox properties of the catalyst were characterized by XRD,N2 adsorption and desorption, ICP-AES,SEM,XPS,H2-TPR and so on. The results showed that SAPO-44 molecular sieve with high purity and high cleanliness could be prepared with a certain proportion of mixture. The crystallinity of Cu-SAPO-44 decreased obviously after ion exchange, and the particle size and pore size of Cu-SAPO-44 catalyst were lower than that of pure SAPO-44 molecular sieve. No Cu species were found on the surface of the catalyst, indicating that the Cu species in the molecular sieve prepared by ion exchange method may be uniformly dispersed inside the molecular sieve channels, blocking part of the pore channels, resulting in a decrease in the specific surface area. The SCR activity of Cu-SAPO-44 molecular sieve catalyst was tested. The results showed that the catalyst exhibited extremely high denitrification activity at 200 鈩，
本文编号：2284976
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