The Development Of Catalytic Filter/bag For The Simultaneous Removal Of NO_x And Dust From Flue Gas

The current flue gas denitration and dust removal purification technology is mainly completed in the denitration unit and the dust removal unit:the denitration process mainly includes selective catalytic reduction(SCR)and selective non-catalytic reduction technology(SNCR)based on the VW-Ti catalytic system;the dust removal process includes Wet process dust removal,electric dust removal,filter dust removal and other process technologies.The independent operation of the denitration and dust removal unit not only increases the flow space,but also significantly increases equipment investment and operating costs.Therefore,how to integrate flue gas denitrification and dust removal,shorten the process flow,and reduce process costs is an important development direction of the current flue gas denitration and dust removal purification field.Current research mainly focuses on coupling and optimization of denitrification and dust removal processes to reduce engineering and operating costs,but due to the relative independence of current denitrification and dust removal processes,how to achieve combustion flue gas denitrification and dust removal in the same unit is still a major challenge in this field.The catalytic filter element or the catalytic filter bag can realize the denitration and the dust removal unit in the same operation unit,which can significantly reduce the process and operating costs of flue gas denitration and dust removal,and has become an emerging hot spot in the field of flue gas purification.For the purification of medium and high temperature flue gas,this article first develops a vanadium-based catalytic filter material.The V-W-Mo-Ti catalytic filter for the industrial application was developed to remove NOx and dust simultaneously in the lab and pilot test.The catalytic slurry,catalyst loading,and space velocity were investigated to further optimize the catalytic filter for a better SCR activity and industrial applicability.Moreover,the effect of dust on catalytic activity and pressure drop was studied in the lab as a data support for the pilot application.The pilot test of 2700 catalytic filters over the flue gas from glass kiln exhibited excellent performance with above 95%NOx/SOx conversion and 99%dust removal efficiency at a stable pressure drop(1.4KPa)during the 90-day test under the conditions of 2600 mg/Nm3 inlet NOx concentration,3000 mg/Nm3 inlet SOx,500 mg/Nm3 inlet dust concentration and 350℃.V2O5-MoO3/TiO2 based catalytic bag filters were developed for the simultaneous removal of particulates and NO in the temperature range of 200-250℃,which exhibited good denitrification activity,dedust efficiency as well as high adhesion strength in the temperature range of 200-250℃.The study of catalyst powder for coating revealed that the increased V and Mo content in catalyst can elevate the low-temperature activity,and the chosen V10Mo10 sample for coating showed the best activity with 100%NO conversion at just 180℃.The further research on catalytic bag filter found the low ratio of PTFE,high loading and long residence time(e.g.,low filtration velocity or double layer filter)may help to achieve high DeNOx efficiency.The best performance was obtained with above 80%NO conversion at 200-250℃ even in the presence of SO2/H2O and 99.9%dust collection efficiency on the condition of 500 g/m2 loading,10%PTFE,0.5 m/min filtration velocity and double layers of filter,which demonstrated great feasibility for industrial application.In the field of small-medium boiler flue gas purification with high concentration of dust,the findings published here indicate that catalytic filter has great viability and great feasibility for industrial application.