Experimental Study On The Utilization Of Waste Denitration Catalyst Based On Catalytic Filtration Technology

In recent years,increasingly strict air pollution control policies have created a huge market for denitration.Due to the harsh working environment of the denitrification equipment and the limited life span of the catalyst,a large number of waste catalysts are produced.For the non-renewable waste catalyst,the current main wet recycling methods have the disadvantages of complicated procedures,high consumption of acid and alkali,and prone to secondary pollution,which hinders their further promotion.Catalytic filtration technology has developed rapidly in recent years,this paper presents a method of combining the resource recycling of waste catalyst and catalytic filtration technology.The filter material provides a carrier for the non-renewable catalyst that has lost its mechanical strength due to excessive wear.The pretreated waste catalyst was used to prepare catalytic filter cloth and catalytic filter ceramics suitable for different temperature ranges,combined with fast SCR technology to achieve high-efficiency denitrification,and finally achieved the purpose of resource reuse of waste catalysts and simultaneous denitrification and dust removal.In this paper,a commercial waste V2O5-WO3/Ti O2 catalyst was used as the research object.According to its deactivation reasons,the methods of oscillating water washing,oscillating sulfur washing and impregnation to supplement the active component were used to pretreat the waste catalyst.After impregnation with 1 wt.%V2O5,the standard SCR activity of the pretreated catalyst reached more than 90% of that of the fresh catalyst,and the fast SCR activity of the catalyst was higher than that of the fresh catalyst.In the experiment of the influence of space velocity,the reaction activity under 350 ℃ increased with the decrease of space velocity,but the activity decrease caused by NH3 oxidation in the high temperature region was aggravated.At the same time,the effects of different NO/NO2 proportion on the NOx conversion of the pretreated catalyst were studied,and it was found that the reaction activity was the best when NO/NO2=1:1(fast SCR reaction).Secondly,the waste catalysts before and after pretreatment were characterized by NH3-TPD,H2-TPR,FTIR,BET and XRD.The results showed that dust clogging and alkaline earth metal poisoning caused catalyst deactivation,and the pretreatment process removed the dust and most alkaline earth metals.The research results support the effectiveness of the waste catalyst reprocessing method.Subsequently,this article combined the pretreatment catalyst with the filter cloth by the impregnation method to prepare the catalytic filter cloth.The fast SCR denitration efficiency of the catalytic filter cloth at 220～250 ℃ reached more than 90%,and the denitration efficiency of the fast SCR reaction at 230～250 ℃ reached 93%,proving that the coated PTFE microporous membrane has little effect on the denitrification activity of the catalytic filter cloth.Based on the experimental results,the pretreated catalyst samples impregnated with 1 wt.% V2O5 were selected for the follow-up study of the catalytic filter.Then the space velocity effect experiment and the sulfur and water resistance experiment provided guidance for the practical application of the catalytic filter cloth: the denitration activity of the catalytic filter cloth below 250 ℃increased with the decrease of the reaction space velocity;SO2 and H2 O had greater impact on the standard SCR reaction activity of the coated catalytic filter cloth,but had less effect on its fast SCR reaction activity,which is because the presence of NO2 accelerated the decomposition of NH4HSO4,and also reduced the competitive adsorption effect of H2 O by accelerating the reaction.The catalytic filter cloth in fast SCR reaction showed excellent resistance to sulfur and water.Finally,the microstructure was characterized by SEM and BET.Combined with ultrasonic oscillation and N2 purge experiments,the firmness of the pretreated catalyst on the catalytic filter cloth was verified.Meanwhile,the pressure drop test proved that the pressure drop distribution of the coated catalytic filter cloth was within a reasonable range.At last,the catalytic filer ceramics were prepared by impregnation method with pretreated catalyst,binder and filter ceramics.Firstly,through the denitration activity experiment,10 wt.% methyl cellulose was selected as the best binder,and the denitration efficiency of the catalytic filter ceramics prepared by fast SCR reaction at300～350 ℃ reached more than 97%.Then,experiments on the effect of space velocity and the anti-sulfur and anti-water resistance were carried out to provide reference for the operation of catalytic filter ceramics under actual working conditions: The catalytic activity of catalytic filter ceramics under 350 ℃ increased with the decrease of space velocity,but the oxidation of NH3 at high temperature increased with the decrease of space velocity,leading to the deterioration of the reaction activity.The standard SCR reactivity of catalytic filter ceramics was significantly affected by SO2 and H2 O,while due to the higher fast SCR reaction activity of catalytic filter ceramics at high temperature,and the thermal decomposition of NH4HSO4 is strengthened,the catalytic filter ceramics showed higher sulfur and water resistance than the catalytic filter cloth at low temperature.Finally,the microstructure of the catalytic filter ceramics was studied by SEM and BET,and the loading stability of the pretreated catalyst on the catalytic filter was verified by ultrasonic oscillation and N2 purge experiments.