Research On Catalyst Active Properties Of SCR Technology

The emission of nitrogen oxide by the power plant has been a principal source of the problem of air pollution. It has become a restraining factor of the society and economic development. It has been widespread concern in society. According to the nitrogen oxide emissions from coal-fired power stations, it has appeared a variety of emission control technologies. The SCR technology is the most ideal removal effect technology of all the flue gas denitration technology at the present stage. So it has received the attention and recognition by the electric power industry. With the power plant’s pollutant emission requirements more harsh in China, there is a tendency for all of the coal-fired power plants to meet the standard requirements by installing SCR reactor. But with the lack of denitration technology and operating experience, the denitration units have many problems, such as the system pressure difference increasing caused by reactor blockage, catalyst worn seriously, the pore structure of the catalyst’s surface clogged by fly ash, which make the catalyst activity decreased, even inactivation. So it’s important to do a systematic research about the commercial catalyst. In this paper, the research has focused on the change regularity of denitration catalyst activity with the operating conditions, how to make the catalyst get the highest denitration efficiency scientifically and effectively, and analyzing the causes which make change of the activity of catalyst.In this paper, we studied how three factors effects on the catalysts’ denitration efficiency with different running time by single variable experiment. Through the experiment, with the catalysts’ running time increased, the optimum operating temperature increase from about 350℃ to 400℃, the optimal molar ratio changes from about 0.87 to 1, the denitration efficiency decreasing with the increasing of space velocity, the shorter running time of the catalyst with smaller change rate of efficiency.The experiment takes the orthogonal experimental method. By range analysis and variance analysis, the experiment obtained the order of three factors influence on catalysts’ denitration efficiency, the optimal combination of the factors’ levels and the results of significant analysis. The discoveries of three samples are as following. The order of the factors which influence on denitration efficiency is: space velocity, ammonia nitrogen ratio, temperature. Under the experimental conditions, the optimal combination of factor levels of samples are: S1,1630h-1,350℃,0.87;S2,1630h-1,350℃,0.87;S3,1630h-1,350℃,1. Highly significant influence factors of sample S1, S2 are the space velocity and molar ratio. Temperature is not a significant factor of sample S1 and S2. Highly significant influence factors of sample S3 are the space velocity and molar ratio, temperature is a significant effect factor.At last, the research studies the reasons of catalyst denitration efficiency’s change by doing microscopic characterization analysis to the catalyst. The catalysts were characterized and analyzed on the catalyst pore structure, surface morphology, crystal structure and chemical component element. The purpose is to study the mechanism of catalyst activity’s decrease in microcosmic aspect. It is found that with the increase of the running time, the surface of the catalyst pore clogging, especially the 20-30 nm hole plugged seriously. The heavy metals, such as As and Pb, and alkali metals, such as K, Na and Ca, deposit on the surface of the catalysts, which would be adsorbed on the active sites of the catalysts with the result of activity decreasing.