| The selective catalytic reduction of NOx with NH3as reductant is the most efficient and widely used technology for abating NOx emitted from stationary power stations at present. Catalysts, which are the core of SCR systems, are the main factor affecting the NOx removal efficiency and economical efficiency. As the time passing by, inactivation is inevitable for SCR catalysts in the actual application process due to pore blockage and toxic elements enrichment. We can save great money and prevent environment pollution by regenerating the deactivated catalysts. Therefore, the study on SCR regeneration is imperative, while with this technology we can reduce the cost, promote the application of SCR and protect the environment.This paper takes the vanadium SCR catalyst as the research object to investigate the regeneration methods for regeneration process and optimizing the physical structure. We developed suitable regeneration process and studied the influences of the treatments. The main results are shown as following:1. The effect of regeneration process was investigated. Washing with water can remove a certain amount of Na. Based on the data in the experiment, we can conclude that Na+dissolved in water first to increase exponentially, and then gradually to reach equilibrium and become stable. The relation between the Na+content and the time accord the fitting equation:y=57.57-68.85/(1+t/1.89)1.29. Washing with sulfate acid can remove almost all of the poisoning element (Na) loaded on the catalyst, which leads the amount of poisoning element return to the fresh catalyst level, while sulfate acid also wash away25%of V. After washing with water and then treating with sulfate acid, the ammonia adsorption capacity and the ability to oxide of the catalyst are greatly improved, which presents10%increased de-NOx efficiency than the fresh sample from300to350℃. The catalyst reloaded with active substances shows10%increase de-NOx efficiency below300℃, and nearly20%increase of de-NOx efficiency at300℃.2. Focus on the recovery of physical structure of the catalysts, especially on the optimization of pores blockade and micropore distribution, this paper compared high temperature/high pressure evaporation and normal evaporation processes. We found that the instantaneous evaporations under high temperature/high pressure conditions presents a more significant improvement on pore structure than conventional soak evaporation. What’s more, catalyst is also easier to load active substances after the optimization of pore structure.3. The effect of alcohol’s rapidly evaporation treatment to the physical structure of deactivated catalysts was investigated. BET analysis shows that the surface area of the catalyst regenerated is27%increase than the deactivated sample, while the total volume is2.5times. Both the NH3-TPD profiles and the SEM photos reveal the improvements on the surface conditions. The increase of NH3absorption ability and the porous/clean surface may due to the optimization of the pore structure. The XRD patterns proved that the regeneration didn’t affect the crystalline structure of catalyst. In addition, the catalysts regenerated show a significant increase (nearly40%at350℃) of de-NOx efficiency than the deactivated sample, moreover the catalyst with the procedure of pore structure optimizing performs much better (10%at350℃) than the one merely washed with de-ionized water and then reloaded with activity substances. |
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