H2S对CH4着火延迟及还原NO影响的数值模拟

Numerical simulation of the effect of H2S on CH4 ignition delay and NO reduction

摘要:

为探究硫化氢(H₂S)在常压范围内对甲烷(CH₄)燃烧特性的影响,采用化学动力学软件CHEMKIN-PRO中的0-D和PFR反应器研究H₂S浓度、过量空气系数、压力和温度对CH₄点火延迟及还原NO的影响,并通过敏感性和生成率分析揭示其化学动力学机理. 模拟结果表明:H₂S的存在促进活性基团(H,O,OH,HO₂,HO₂和H₂O₂)的生成速率,从而缩短预混气点火延迟时间,且在低温下的影响作用更加明显；预混气点火延迟时间随着过量空气系数的增大而减小；压力增加亦有利于缩短点火延迟时间. H₂S可降低CH₄/H₂S还原NO的温度,主要由于H₂S降低CH₄的反应温度,使还原性基团CH_i在较低温度下产生；但同时H₂S的存在,在一定程度上降低NO的还原效率,且在贫氧气氛中的影响更为显著.

Abstract:

To investigate the effects of hydrogen sulfide (H₂S) on the combustion characteristics of methane (CH₄) in atmospheric pressure range, the 0-D and PFR reactors were adopted in CHEMKIN-PRO chemical kinetics software to investigate the effects of H₂S concentration, excess air coefficient, pressure and temperature on CH₄ ignition delay and NO reduction, meanwhile sensitivity analysis was used to reveal the chemical kinetics mechanism. The modeling results showed that the H₂S could promote the formation rate of active groups (H, O, OH, HO₂, HO₂, H₂O₂), so premixed gas ignition delay time was reduced, and the effect was more obvious at low temperature. The premixed gas ignition delay time is decreased with the increase of excess air coefficient and pressure. The H₂S decreases the CH₄ reaction temperature and reductive group CH_i are generated at lower temperature, so the H₂S decreases the temperature of NO reduction by CH₄/H₂S. But the existing of H₂S reduces NO reduction efficiency to a certain extent, and the effect is more remarkable in fuel-rich atmosphere.