Experimental Study On Regeneration Of Deactivated SCR Catalyst For Denitrification

A large number of NOx emissions from fossil fuel combustion have brought profound effects on human health and the environment such as smog, acid rain and photochemical smog, etc.. At present, the majority of domestic and foreign enterprises to control NOx emissions to adopt selective catalytic reduction (SCR) for DeNOx technology, and the denitration catalyst is the key part of the SCR. The catalyst is limited by the operational temperature range lead to it, which is directly arranged in the coal saver, is usually lost in the use of 3-5 years, because of various factors, such as dust, alkali metal K and As. The deactivated catalyst was regeneration and re-use, which not only reduce denitrification operation cost, but also reduce the pollution of the environment. An experimental present in this paper about studying on the regeneration of deactivated commercial selective catalytic, which is poisoned by potassium and arsenic.Denitration catalyst (V2O5-WO3/TiO2) is poisoned by an alkali metal K, and it was regeneration by the oxalic acid solution. At 350?, DeNOx activity test results show that K (load 2wt.%) poisoning catalyst DeNOx activity was 81% and it is decreased by 15% compared with the activity of the fresh catalyst. The activity of potassium catalyst poisoning regenerated by oxalic acid regained more than 95% of the initial catalyst, when at 60*C by oxalic acid concentration was 0.001mol/L after 30 minutes of regeneration. According to the characterization analysis, shows that the surface area of poisoning catalyst is decreased by 1.5m2/g. That is due to alkali metal K deposited on the catalyst surface and the micro channel. Potassium reacts with the proton in B acid is to generate V-OK, thus resulting in B acidic strength reduced and V5+binding energy reduce 0.3eV, at the same time, the number of active sites was reduced, and the adsorption performance of NH3 was decreased. The particles on the regenerated catalyst became smaller and uniform, and the specific surface area increased 6.7m2/g compared with the new catalyst, the B acid strength was fully recovered and the adsorption capacity of NH3 was restored, because of potassium was also effectively eliminated by washing.Denitration catalyst (V2O5-WO3/TiO2) is poisoned by arsenic, and it was regeneration by the ammonia solution. At 350?, DeNOx activity test results show that As (load 2wt.%) poisoning catalyst DeNOx activity was 78% and it is decreased by 18% compared with the activity of the fresh catalyst. The activity of arsenic catalyst poisoning regenerated by ammonia regained more than 94% of the initial catalyst. When at 80? by arsenic concentration was 0.0015mol/L with 60 minutes of regeneration. According to the characterization analysis shows that arsenic condensation leads to an aggregation change on the surface and the gap of catalyst particles, brought about the specific surface area lessen 34.6% than initial catalyst, amount of active sites are greatly reduced and a number of As-OH production on the surface, which leads to a decrease in activity. The particles on the regenerated catalyst became smaller and uniform, and the specific surface area was recovered, the blocked pores have been recovered well. The active sites are completely exposed after the arsenic was removed, so the denitration activity gets a better recovery.Denitration catalyst (V2O5-WO3/TiO2) is poisoned by arsenic and K, and it was regeneration by the ammonia and oxalic acid solution sequence. At 350?, DeNOx activity test results show that As (load 2wt.%) and K (load 2 wt.%) poisoning catalyst DeNOx activity was 60% and it is decreased by 36% compared with the activity of the fresh catalyst. The activity of compound poisoning catalyst regenerated by ammonia (0.0015mol/L-80?-1h) and oxalic acid (0.001mol/L-60?-0.5h) regained more than 97% of the initial catalys. According to the characterization analysis shows that the arsenic and K co deposition in the pore channels, on the surface and gaps between the particles of the catalyst, so that caused the surface area and the B acid strength decreased significantly, and H2 reduction peak increased of 50? ect. The surface area and surface acidity were recovered from the poisoned catalyst after regeneration, and the H2 reduction temperature is lower 70? than the new catalyst. At the same time in the process of regeneration does not generate new hazardous substances on the regenerated catalyst surface, it shows that the As and K can be removed by ammonia and oxalic acid effectively. Because of oxalic acid is easy to decompose and NH3 is the reducing agent. Therefore, the regenerated catalyst cannot be cleaned again, and provide environmental protection and a short process for the compound poisoning catalyst.