Gas-phase oxidation of NO at high pressure relevant to sour gas compression purification process for oxy-fuel combustion flue gas

The removal of NO from oxy-fuel combustion is typically incorporated in sour gas compression purification process. This process involves the oxidation of NO to NO₂ at a high pressure of 1-3 MPa, followed by absorption of NO₂ by water. In this pressure range, the NO conversion rates calculated using the existing kinetic constants are often higher than those obtained experimentally. This study aimed to achieve the regression of kinetic parameters of NO oxidation based on the existing experimental results and theoretical models.Based on three existing NO oxidation mechanisms, first, the expressions for NO conversion against residence time were derived. By minimizing the mean-square errors of NO conversion ratio, the optimum kinetic rate constants were obtained. Without considering the reverse reaction for NO oxidation, similar mean-square errors for NO conversion ratio were calculated. Considering the reverse reaction for NO oxidation based on the termolecular reaction mechanism, the minimum mean-square error for NO conversion ratio was obtained. Thus, the optimum NO oxidation rate in the pressure range 0.1-3 MPa can be expressed as follows:-dNO]/dt=dNO₂]/dt=0:0026NO]²O₂]-0:0034NO₂]²Detailed elementary reactions for N₂/NO/NO₂/O₂ system were established to simulate the NO oxidation rate. A sensitivity analysis showed that the critical elementary reaction is 2NO + O₂ ? 2NO₂. However, the simulated NO conversions at a high pressure of 10-30 bar are still higher than the experimental values and similar to those obtained from the models without considering the reverse reaction for NO oxidation.