| Selective Catalytic Reduction?SCR?is currently a fixed source flue gas denitration technology with the most engineering applications and mature technologies in the world.In recent years,the SCR process with low temperature and low dust tail has become the focus of researchers.As the core of SCR denitration technology,the catalyst which has certain H2O/SO2resistance and good denitrification activity under low temperature environment-friendly low-temperature denitrification has become a hot spot in the field of denitrification research in recent years.At present,the research on the denitrification performance and resistance of low-temperature denitration catalysts is mainly concentrated on the small scale of the laboratory,and the performance of the shaped catalyst under actual flue gas conditions and the mechanism of poisoning are investigated for the basic research and industrial application of low-temperature denitration catalysts,which is profound and impelling.The Ce-based low-temperature denitrification honeycomb catalyst was the research subject in this thesis.During the research,the self-designed low-temperature denitrification pilot plant was used to study the effect of H2O and SO2 on the NOx adsorption capacity of the catalyst under simulated flue gas conditions,and its influence mechanism has been studied with in situ drifts.At the same time,the catalyst's denitration activity and optimal operating parameters were tested,and the catalyst's denitration activity,resistance and poisoning mechanism were studied under actual coal-fired flue gas conditions.The conclusions of the experiment were as follows:?1?The results of the study on the influence of the adsorption capacity of the shaped catalyst under different operating parameters show that:?1?As the NOx concentration and flue gas temperature increase,the adsorption amount gradually decreases,and the adsorption rate gradually increases;The total amount of catalyst adsorption and the adsorption rate are significantly reduced;?3?Compared with the case without H2O adsorption,the total adsorption of catalyst increased from 7528 ppm to 9824 ppm,but the adsorption equilibrium time was extended from 300 min to760 min.It shows that H2O and SO2 have certain inhibitory and competitive adsorption effects on NOx adsorption with the catalyst,and which reduces the adsorption rate of the catalyst,that is,to lower the activity of the active site.?2?During the NOx adsorption process,H2O will compete with NOx for competitive adsorption,which will affect the NOx adsorption and reduce the formation of nitrate,thereby reducing the catalyst's denitration activity;during the reaction,the addition of H2O will lower the activity of B acid site,which leads to a reduction in reaction activity;when SO2 and H2O are simultaneously introduced,the?NH4?2SO4 and other substances formed by the reaction of SO2 and H2O with NH3 act as acid sites,and the acid sites will have competitive effects on the nitrate ion of the B acid site.?3?Considering comprehensively the effects of reheat energy consumption and H2O on denitration efficiency,the flue gas reaction temperature is selected as 100 oC,the space velocity is selected as 3333 h-1,the ammonia-nitrogen ratio is selected as 0.9,and the NOx concentration is100 ppm as the experimental conditions Passing 10 vol.%H2O for 24 h H2O resistance test,the efficiency is stable above 80%,indicating that the catalyst has good H2O resistance and stability,at the same time,it proves that the effect of H2O on the catalyst is reversible.?4?The 168 h continuous experiment and high-load experiment results show that the denitration efficiency of the catalyst can be stabilized at more than 70%at 100 oC,and high concentration of SO2 will have a significant toxic effect on the catalyst.SEM,XRD,BET,TG,NH3-TPD characterization methods were used to characterize the catalyst after high-load experiments,the results of which show that the sulfates formed during operation and the sulfation of catalyst components were the main reasons for the decrease in catalyst activity.The above results indicate that the environmentally friendly low-temperature denitration catalyst has excellent low-temperature denitration performance and resistance to H2O/SO2resistance.The denitration process is easy to transform and has broad industrial application prospects. |
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