Chemical Kinetic Mechanism and Experimental Validation of NOx Reburning–Equilibrium Disposal Technology

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Abstract
To address the critical challenge of treating high-concentration nitrogen oxide (NOx) regeneration off-gas generated from Cold Oxidation Adsorption Process (COAP), an innovative concept termed ‘NOx reburning–equilibrium disposal’ is proposed. In this approach, concentrated NOx is re-injected into the boiler combustion zone, where it undergoes efficient ammonia-free decomposition under the high-temperature reducing atmosphere inherently present within the furnace. A comprehensive investigation was conducted through chemical kinetic simulations and laboratory-scale tubular furnace experiments. Chemical equilibrium calculations performed using CHEMKIN demonstrated that thermally generated NOx increases exponentially with temperature and that a distinct thermodynamic equilibrium concentration exists at each temperature. For example, the equilibrium NO concentration reaches 4781 mg·m−3 at 1500 °C. Within the temperature window of 1250–1450 °C, reducing atmospheres significantly enhanced NO reburning reduction efficiencies exceeded 70–90%, reaching up to 95% under strongly reducing conditions, substantially exceeding the less than 10% reduction achieved through purely thermal decomposition. Among the reducing species examined, CH4 exhibited the strongest promoting effect by serving as an effective radical initiator. The simulation results were further verified through laboratory-scale tubular furnace experiments operating at temperatures up to 1700 °C. The combined theoretical and experimental findings systematically elucidate the reburning–equilibrium reaction mechanism of high-concentration NOx under high-temperature reducing conditions and establish a complete scientific evidence chain from fundamental theory to engineering validation. The proposed technology provides a novel pathway for deep ammonia-free NOx abatement in industrial flue gas treatment systems, such as those used in coal-fired power stations, gas-fired power stations, nuclear waste treatment facilities, glass furnaces and waste incineration plants.
Funding Information
  • National Key Research and Development Program of China (2022YFB4100200)

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