脫硝工程優(yōu)化模擬和催化劑小試
發(fā)布時(shí)間：2018-10-21 11:36
【摘要】：氮氧化物(NOx)是大氣的主要污染物之一,嚴(yán)重危害生態(tài)環(huán)境和人類健康。燃煤鍋爐等固定源和機(jī)動車等移動源排放的廢氣是NOx最主要的來源。選擇性催化還原(Selective Catalytic Reduction,SCR)技術(shù)是目前國際上最成熟、應(yīng)用最廣泛的煙氣脫硝技術(shù)。催化劑是SCR技術(shù)的核心和關(guān)鍵。本文通過計(jì)算流體力學(xué)(Computational Fluid Dynamics,CFD)對煙氣脫硝系統(tǒng)進(jìn)行數(shù)值模擬,優(yōu)選出最佳的設(shè)計(jì)方案為實(shí)際工程應(yīng)用提供理論參考。對煙氣脫硝系統(tǒng)進(jìn)行改進(jìn)設(shè)計(jì),改進(jìn)內(nèi)容包括整流格柵的數(shù)目、尺寸、反應(yīng)器結(jié)構(gòu)尺寸、和導(dǎo)流板的數(shù)目、尺寸,并通過CFD對設(shè)計(jì)方案進(jìn)行優(yōu)選。本論文在之前模型的基礎(chǔ)上,增加整流格柵數(shù)目,反應(yīng)器內(nèi)部流場的氣流分布的均勻性并未提高,優(yōu)選整流格柵的數(shù)目為21。在優(yōu)選整流格柵數(shù)目后,增加整流格柵的高度,內(nèi)部流場氣流分布的均勻性呈現(xiàn)先增大后降低的趨勢,優(yōu)選整流格柵的高度為0.5m。在此基礎(chǔ)上內(nèi)部流場氣流分布的均勻性仍沒有達(dá)到合格的要求,因此考慮改進(jìn)SCR反應(yīng)器的設(shè)計(jì)尺寸。在改進(jìn)模型的基礎(chǔ)上,改變直導(dǎo)流板的安裝位置和數(shù)目后,對流場氣流分布的均勻性有較大的改善作用,優(yōu)選直導(dǎo)流板的數(shù)目為5。優(yōu)選直導(dǎo)流板的數(shù)目后,改變直導(dǎo)流板的長度,當(dāng)直導(dǎo)流板長度為1.2m時(shí),內(nèi)部流場的速度分布均勻,滿足良好的要求,優(yōu)選直導(dǎo)流板的長度為1.2m。本文利用水熱法制備出SAPO-44分子篩,并通過離子交換法制備出新型分子篩SCR催化劑Cu-SAPO-44。運(yùn)用XRD、N2吸脫附、ICP-AES、SEM、XPS、H2-TPR等技術(shù)對催化劑的結(jié)構(gòu)、形貌和氧化還原性能等進(jìn)行表征。結(jié)果顯示:以一定的配料比可以制備出高純度、高潔凈度的SAPO-44分子篩,經(jīng)離子交換后,Cu-SAPO-44的結(jié)晶度明顯下降。Cu-SAPO-44催化劑的顆粒尺寸和孔尺寸較純SAPO-44分子篩有所降低,催化劑的表面未發(fā)現(xiàn)含Cu物種,說明通過離子交換法制備的分子篩中,Cu物種可能較為均勻的分散在分子篩孔道內(nèi)部,堵塞部分孔道,造成比表面積下降。對Cu-SAPO-44分子篩催化劑進(jìn)行SCR活性測試,結(jié)果表明,催化劑在200℃~550℃顯示出極高的脫硝活性,且具有較差的抗水抗硫性能和較差的水熱穩(wěn)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，
本文編號：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，
本文編號：2284976
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