Research On Preparation And Performance Of Catalytic Filter Element For Integrated Removal Of Multi-pollutants From Flue Gas

Catalytic filter element is the combination of DeNOx catalyst and high temperature dust removal ceramic filter element,when coupled with dry desulfurization technology,it can remove multiple pollutants in one purification device with high efficiency.Therefore,the process of catalytic filter element is the emerging development direction of flue gas purification in non-electric industries such as small and medium kilns.Due to the key technical barriers in the selection of catalytic filter element matrix material,the preparation of high-activity catalytic slurry and the implantation uniformity of catalyst,the catalytic filter element in China is heavily dependent on imports.In addition,the foreign catalytic filter element is not completely suitable for the complicated working conditions of Chinese industrial flue gas due to the limitation of operating temperature window.Therefore,it is an inevitable development trend to realize the domestic production of catalytic filter element.This study focused on the key technologies and core scientific issues faced by the preparation of catalytic filter element,combined with the characteristics of flue gas from non-electric industries such as small and medium-sized kilns in China,the catalytic filter element with high activity,low pressure drop,wide temperature range and low cost was developed to meet the Chinese flue gas purification needs,and the basic scientific principles and mechanisms of the technology development process were revealed.The main results obtained in this study are as follows:1.Research on the key technologies of the preparation of catalytic filter element.By investigating the domestic filter element matrix,the catalytic slurry,the operating temperature window and the cost of catalytic filter element,the composition,structure and morphology parameters suitable for use as the matrix material of the catalytic filter element were determined,the V-W/Ti catalytic slurry with high activity and uniform dispersion was prepared,the Mn2V2O7/TiO2 catalytic filter element with broad temperature range and the low-cost/non-toxic Fe-based catalytic filter element derived from red mud were developed,which broke through the key preparation technology of catalytic filter element with high activity,low pressure drop,wide temperature range and low cost.The results are as follows:1)The ceramic fiber filter element with aluminosilicate fiber material,fiber diameter less than 2 ?m,alkali/alkaline earth metals less than 0.5 wt.%and porosity greater than 70%,could be used as the matrix material for the preparation of catalytic filter element;2)The catalytic slurry with the particle size of less than 500 nm was prepared by using the catalyst composition of 12 wt.%V2O5,8 wt.%WO3,80 wt.%TiO2 and the method of wet ball milling,which could achieved the technical requirements of high activity and uniform dispersion;3)The Mn2V2O7/TiO2 catalytic filter element with broad temperature range and the low-cost Fe-based catalytic filter element derived from red mud were developed,respectively.Among them,the DeNOx efficiency of Mn2V2O7/TiO2 catalytic filter element was more than 85%at 200?400?.However,the introduction of SO2 with high concentration(300 ppm)significantly reduced the low-temperature activity of Mn2V2O7/TiO2 catalytic filter element below 250?,but obviously improved its DeNOx efficiency at 250?400?;The low-cost non-toxic Fe based catalytic filter element activated the red mud by using H2SO4 hydrothermal leaching and(NH4)2CO3 neutralization precipitation process to obtain the red mud based catalyst with high dispersion,high specific surface area and high DeNOx efficiency.And the prepared Fe based catalytic filter element derived from red mud displayed more than 80%DeNOx efficiency at 300?450? with the pressure drop was lower than 1.01 kPa.2.Research on the basic scientific principles and mechanisms during the development process of catalytic filter element.The effect of alkaline earth metal and matrix modification of the filter element on the activity of the catalytic filter element was discussed,the inner relationship among the particle size of the catalytic slurry,the implantation uniformity of the catalyst and the activity of the catalytic filter element was clarified,the SO2 poisoning mechanism of the Mn2V2O7/TiO2 catalytic filter element was revealed,and the mechanism of red mud activation process on the activity of the Fe based catalytic filter element derived from red mud was determined,which provided theoretical guidance for the preparation of catalytic filter element with high activity,low pressure drop,wide temperature range and low cost.The main results are as follows:1)The Ca element contained in the filter element matrix could react with the W active component in the DeNOx catalyst to form CaWO4,which reduced the number of acid sites and the redox performance on the surface of catalyst,resulting in the significant decrease in the DeNOx efficiency of the catalytic filter element.While the SO42-contained in the(NH4)2SO4 modifier could react with the Ca element in the filter element matrix to form CaSO4,which effectively inhibited the formation of CaWO4 and promoted the dispersion of V/W active components in the filter element.Meanwhile,it significantly increased the surface acidity of catalyst and the adsorption of NH3,weakened the Ca poisoning of the catalyst,resulting in that the modified catalytic filter element displayed more than 90%NO conversion at 250-400?;2)The research on the effect of catalytic slurry on the activity of catalytic filter element found that the small particle size of the catalytic slurry promoted the diffusion and the loading of catalyst particles in the filter element,increased the catalyst loading of the catalytic filter element,enhanced the dispersion/exposure of catalyst particles and catalytic active sites on the inner fibers of the filter element,reduced the blockage of the channels in filter element by the catalyst particles,thus improved the DeNOx efficiency and reduced the pressure drop of the catalytic filter element;3)The research of Mn2V2O7/TiO2 catalytic filter element found that SO2 with high concentration(300 ppm)could promote the decomposition of supported Mn2V2O7 to form dispersed MnOx and VOx active species on TiO2.Among them,MnOx reacted with SO2 to generate MnSO4,resulting in the deactivation of low-temperature Mn active sites and the obvious reduction of DeNOx efficiency below 250? for the Mn2V2O7/TiO2 catalytic filter element.On the other hand,SO2 also improved the dispersion of VOx active species,promoted the sulfation of the sample surface,increased the specific surface area,the active oxygen species and the number of acid sites,resulting in that the DeNOx efficiency of Mn2V2O7/TiO2 catalytic filter element remained above 95%at 250?400?;As for the low-cost non-toxic Fe based catalytic filter element derived from red mud,the H2SO4 hydrothermal leaching and(NH4)2CO3 neutralization precipitation process could effectively remove the alkali/alkaline earth metals such as Na and Ca in the red mud,improve the dispersion of active components,the acidity,the reducibility and the activity performance of the sample,thus realized the activation of red mud.Meanwhile,the Al2O3 in the red mud based catalyst sample was partially dissolved to form aluminum sol during the preparation of catalytic slurry,which effectively reduced the agglomeration of catalyst particles,promoted the uniform dispersion and exposure of catalyst particles in the filter element,reduced the blockage of the channels in filter element by the catalyst particles,thus improved the activity performance of the Fe-based catalytic filter element derived from red mud and reduced its pressure drop.3.Research on the pilot test of catalytic filter element for integrated removal of flue gas from glass factory.The V-W/Ti large-size catalytic filter element was prepared,the effect of scale-up preparation parameters as well as the simulated industrial flue gas conditions on the activity and pressure drop of the catalytic filter element were investigated,the pilot verification of V-W/Ti large-size catalytic filter element for flue gas purification in the glass factory was carried out,and the industrial application feasibility of the catalytic filter element was evaluated.The results showed that:1)The internal implantation process with catalytic slurry could promote the uniform dispersion of catalyst particles in the filter element,reduce the blockage of the channels in filter element by the catalyst particles,resulting in that the prepared V-W/Ti large-size catalytic filter element with the catalyst loading of 7.4-9.0 wt.%displayed more than 85%DeNOx efficiency and great resistance to H2O/SO2 with the pressure drop was lower than 1.40 kPa at 250?400? when the filtration face velocity was 1.0 Nm/min.The introduction of glass ash in the simulated flue gas had little effect on the activity of catalytic filter element,but it increased the pressure drop gradually.Therefore,it is necessary to blowback with the compressed air regularly;2)The pilot test results of flue gas purification in glass factory with V-W/Ti large-size catalytic filter element showed that SOx with the concentration of 2800?3100 mg/Nm3 was reduced to less than 150 mg/Nm3 after the dry desulfurization technology,NOx with the concentration of 2400?2600 mg/Nm3 and glass ash with the concentration of 360?420 mg/Nm3 were reduced to less than 100 mg/Nm3 and 5 mg/Nm3 after the purification with catalytic filter element,when the total gas flow was 100,000 Nm3/h,the operating temperature was 320?350?,and the filtration face velocity was 0.5 Nm/min,which displayed high-efficiency purification ability of flue gas under the complex working conditions(high pollutant concentration)and demonstrated great industrial application prospects.