Nitrogen transformation during coal decoulping combustion Ⅲ: NO and N₂O reduction with multi-component of pyrolysis gas

Reduction of NO and N₂O with the simulated pyrolysis gas of NH₃-CO-H₂-CH₄-O₂ mixture was experimentally studied in an ideal plug flow reactor. The effects of temperature, excess air number λ, concentration of CH₄, CO, H₂, NH₃ in the simulated pyrolysis gas, concentration of NO and N₂O in the simulated flue gas on reduction of NO, N₂O and total nitrogen conversion efficiency were experimentally investigated. The results show that adding combustible or reducing species of CO, H₂, CH₄ into NH₃ can decease about 150~200 K of temperature range or window for reducing NO, the obtained optimal temperature range of reducing NO is in a range of 1 073~1 223 K. The excess air number λ or oxygen content in NH₃-CO-H₂-CH₄-O₂ mixture shows an important influence on reduction of NO and N₂O. When the excess air number λ is controlled as 0.6, i.e., similar to the case of fuel-rich, the maximum decomposition ratio of NO and N₂O in the simulated flue gas reaches 60.6% and 100%, respectively. When the excess air number λ is kept at 0.6 in a temperature range of 1 073~1 223 K, higher concentration of CH₄, CO, H₂ in the simulated pyrolysis gas can result in an effectively decomposition of N₂O, but lead to an increase of NO; however, higher conversion efficiency of NO can be achieved under the condition of increasing the concentration of NH₃ in the simulated pyrolysis gas.