Regeneration of a vanadium pentoxide supported activated coke catalyst-sorbent used in simultaneous sulfur dioxide and nitric oxide removal from flue gas: Effect of ammonia

A vanadium pentoxide supported activated coke (V2O5/AC) catalyst-sorbent has been reported to be very active for simultaneous removal of SO2 and NO under dry conditions at temperatures of 200 °C and below. Regeneration of the SO2-captured catalyst-sorbent is a key step in operation of such a process, which influences the catalyst-sorbent's SO2 and NO removal activities, lifetime, as well as recovery of sulfur. Due to limited information in this regard, this paper studies thermal regeneration of a V2O5/AC catalyst-sorbent with emphases on the effect of atmosphere. The optimum regeneration temperature is found to be 380 °C in an Ar stream and 300 °C in a 5% NH3/Ar stream. Compared to the fresh V2O5/AC, the V2O5/ACs regenerated in Ar show lower SO2 adsorption capacities and higher NO removal activities, while the regenerated V2O5/ACs by 5% NH3/Ar show higher and stable SO2 adsorption capacities and higher NO removal activities. Two types of reactions occur during the regeneration: reduction of the adsorbed sulfur species by carbon to SO2 and CO2, and oxidation of carbon by oxygen in the V2O5/AC to CO2. The carbon consumption of the latter is much more than that of the former in an Ar atmosphere, but fully suppressed by the presence of 5% NH3. Detailed analysis and characterization of the V2O5/AC subjected to the regenerations are presented.