Experimental and Kinetic Study on the Influence of CaO on the N₂O + NH₃ + O₂ System

Abstract

N 2 O is a non-negligible pollutant emitted from circulating fluidized bed (CFB) boilers, which may be reduced by NH 3 . The influence of bed material (mainly CaO) on the N 2 O + NH 3 + O 2 system was investigated using a fixed bed reactor in the temperature range from 873 to 1123 K. Experimental results showed that CaO catalyzed N 2 O decomposition and the reaction was first-order with respect to N 2 O. O 2 had no effect on N 2 O decomposition. In the CaO-involved N 2 O + NH 3 system, NH 3 did not influence N 2 O conversion, while N 2 O promoted NH 3 conversion and oxidized NH 3 partly to NO. In the CaOinvolved N 2 O + NH 3 + O 2 system, O 2 greatly enhanced NH 3 oxidation and the effect of N 2 O was negligible. H 2 O produced in NH 3 oxidation inhibited N 2 O decomposition. The mechanism study showed that adsorbed N 2 O formed cis-dimer nitroso, and the dissociation of cis-dimer nitroso was the rate-controlling step of N 2 O conversion. The cis-dimer nitroso dissociated to N 2 and peroxide ions. Peroxide ions donated electrons to form free radical oxygen, and free radical oxygen accelerated NH 3 dissociation to NH 2 . NH 2 reacted with free radical oxygen or NO to produce NO or N 2 or directly dissociated to N 2 and H 2 . NO selectivity was determined by the three reaction routes. A kinetic model was established and well-described the CaO-involved N 2 O + NH 3 + O 2 system.

Study on the Variance of N2O Concentration after Air Pollution Prevention Facility in Bituminous Coal-Firing Power Plant

“…According to a previous study, some free CaO surfaces cause the decomposition of N 2 O, through the catalytic reaction with the N 2 O . Influence of limestone and calcium carbonate on the N 2 O and NO concentrations have been actively studied for power plants with high N 2 O concentrations. − Through laboratory-scale reactor experiments, calcium carbonate was found to act as a strong catalyst in the decomposition of N 2 O. − As the CaO content of ash among the filler inside the furnace of CFBC increases, the catalytic decomposition of N 2 O increases. , The reaction catalyzed on the CaO surface is shown in the following equation …”