Study of NH3 Removal Based on Chemical-Looping Combustion

The removal characteristics of NH3 based on chemical-looping combustion (CLC), in which NH3 was used as a fuel, were studied. Results indicated that in the reduction reaction between oxidative oxygen carriers (OCs) and NH3, the oxidative OCs were converted to reductive OCs, and at the same time, NH3 was converted to N2 and H2O. Then, the reductive OCs were regenerated to the oxidative OCs with air in the subsequent oxidation reaction. As such, NH3 removal with high N2 selectivity was achieved based on CLC. Compared to MnO2/Al2O3 and Fe2O3/Al2O3, CuO/Al2O3 exhibited the highest NH3 removal activity, and an NH3 removal rate of 90% with a N2 selectivity of 99% was achieved at 250 °C. Among three Cu-based OCs, i.e., CuO/Al2O3, CuO/TiO2, and CuO/SiO2, CuO/Al2O3 using γ-Al2O3 as inert support performed the highest NH3 removal activity and N2 selectivity. Moreover, the required temperature for the complete regeneration of the reductive CuO/Al2O3 with air was as low as 200 °C. However, due to its overly high oxidizability, O2 that existed in the waste gas deteriorated the N2 selectivity. On the basis of these findings, a new process for NH3 deep removal with high N2 selectivity based on CLC coupled with adsorption enrichment was proposed.