煤矿乏风中超低浓度甲烷燃烧特性研究及机理敏感性分析

Research on Combustion Characteristics and Mechanism Sensitivity

在国家“双碳”目标背景下,煤矿风排瓦斯中甲烷的减排日益重要;乏风氧化燃烧技术是目前乏风中甲烷减排利用的一个重要方向。基于甲烷燃烧详细化学动力学机理GRI-MECH 3.0,针对乏风瓦斯的气氛特点,开展了着火点、绝热火焰温度、点火延迟时间等燃烧特性的研究;基于敏感性分析方法,得到对反应温度有重要影响的基元反应过程。研究表明:乏风瓦斯着火点和甲烷浓度、停留时间有关,当乏风甲烷浓度小于等于0.4%时,着火点快速升高,大于0.4%时着火点变化不大;气体停留时间越长,乏风着火点越低,当停留时间是1 s时,常规乏风瓦斯的自燃温度在680℃~800℃。乏风瓦斯的最高火焰温度和甲烷浓度呈线性递增关系,在起始着火温度基础上,甲烷浓度每升高0.1%,火焰温度升高约23℃。900℃条件下不同浓度乏风瓦斯点火延迟时间几乎相同,但完全反应时间却随着浓度增加而缩短。表观气速对乏风中甲烷的转化率影响较为显著,700℃引燃温度条件下0.5%CH4的乏风进气流速需控制在1.31 m/s以内。最后基于温度敏感性,探讨了关键的基元反应。

Under the background of national"2030 Carbon Peak-2060 Carbon Neutrality"target,the emission reduction of methane in coal mine ventilation air becomes increasingly important.At present,oxidation combustion technology is an important direction of methane emission reduction and utilization.Based on GRI-MECH 3.0,the detailed chemical kinetic mechanism of methane combustion,the combustion characteristics such as ignition point,adiabatic flame temperature and ignition delay time were studied according to the atmosphere characteristics of coal mine ventilation air.The basic reaction processes which have an important influence on the reaction temperature were obtained based on the sensitivity analysis method.The results show that the ignition point of coal mine ventilation air is related to the concentration of methane and residence time.When the concentration of methane is less than or equal to 0.4%,the ignition point increases rapidly,and when it is more than 0.4%,the ignition point changes little.The longer the residence time of gas,the lower the ignition point of coal mine ventilation air.The spontaneous combustion temperature of conventional coal mine ventilation air is 680℃-800℃when the residence time is 1 s.There is a linear increasing relationship between the maximum flame temperature of the coal mine ventilation air and the methane concentration.Based on the initial ignition temperature,the flame temperature increases about 23℃for every 0.1%increase in the methane concentration.Under the condition of 900℃,the ignition delay times of different concentrations of coal mine ventilation air are almost the same,but the complete reaction time decreases with the increase of CH4 concentration.The apparent gas velocity has a significant effect on the conversion rate of methane.The inlet flow rate of 0.5%CH4 in the coal mine ventilation air should be controlled within 1.3 m/s at 700℃ignition temperature.Finally,the key elementary reactions are discussed based on temperature sensitivity.