Chemical mechanism for acrylonitrile-containing exhaust gas combustion

Acrylonitrile-containing exhaust gas (AEG) from the industrial production of carbon fibers contains a large number of toxic nitrogenous compounds that pose significant health hazards to humans. While post-combustion technology is an effective strategy by oxidizing AEG into non-toxic products, substantial amounts of fuel-NOx are generated during AEG combustion. In this context, a detailed chemical kinetic mechanism for AEG combustion is required to support the development of De-NOx combustion technologies. However, existing mechanisms do not account for the nitrogenous compounds unique to AEG. To address this gap, we develop both detailed and reduced chemical kinetic mechanisms specifically tailored for AEG combustion. The mechanisms are validated by comparing simulated and experimental NOx mole fractions for the oxidation of pyrrole, HCN, HNCO, and NH₃. Given the need for CH₄ addition to stabilize the flame in exhaust gas combustion, the impact of CH₄ blending ratios on NOx emissions is analyzed. Results show that the NO mole fraction decreases significantly when the CH₄ blending ratio increases from 0 to 20%, with only minor reductions observed beyond this point. A pathway analysis reveals that the decrease in the NO mole fraction is due to the competition between nitrogen-containing species and CH₄ for H and OH radicals, limiting the conversion of nitrogen-containing fuels to NO. Novelty and significance statement The post-combustion treatment of acrylonitrile-containing exhaust gas (AEG) is crucial for mitigating environmental pollutants, particularly addressing fuel-NOx formation from nitrogen-containing species. This study advances the understanding of AEG combustion through: 1. Mechanism development: A detailed chemical kinetic mechanism is developed to predict NOx formation in typical AEG combustion, covering nitrogenous and hydrocarbon fuel mixtures. 2. Mechanism reduction: The mechanism is systematically reduced using advanced techniques to enhance computational efficiency while maintaining predictive accuracy. 3. CH₄ Blending analysis: The impact of CH₄ addition on NOx emissions is investigated to optimize NOx reduction efficiency and CH₄ blending ratios in post-combustion processes.