超低浓度甲烷流态化燃烧反应模型的建立及实验验证
发布时间：2018-08-31 14:33
【摘要】：超低浓度甲烷广泛存在于矿井抽采的煤层气和化工废气中,它的浓度通常随着开采条件的变化而波动,通常其体积浓度不超过3%,热值很低,利用难度较大。在我国煤炭开采过程中,大量超低浓度甲烷不经处理直接排放到外界环境中,不仅污染环境而且浪费资源,因此,研究利用超低浓度甲烷具有节能和环保双重意义。流态化燃烧技术具有燃料适应性广、热容量大等优点,适用于低热值气体的燃烧利用,当超低浓度甲烷流化床内催化燃烧时,反映其流态化催化燃烧特点的反应模型需要进一步研究和建立。针对此问题,本文根据超低浓度在鼓泡流化床中催化燃烧特点,建立分区模型并进行耦合,并采用实验研究和理论分析相结合的方法研究了0.15~3 vol.%超低浓度甲烷在以0.5%Pd/Al2O3作为催化剂颗粒床料的鼓泡流化床反应器中催化燃烧特性并对反应模型进行了验证,最后通过模型计算,对甲烷在流化床反应器的变化进行了预测。基于超低浓度甲烷在鼓泡流化床催化燃烧特性,在流化床流动、反应和质量平衡的基础上,根据气固两相流理论,在密相区与稀相区分别建立反应模型,在密相区中考虑了气泡相与乳化相之间的传质以及甲烷在催化颗粒表面的催化反应;在稀相区,根据超低浓度甲烷燃烧的特点,又进一步划分为飞溅颗粒区和均相反应区,并分别建立反应模型。采用实验研究的方法对所建立的反应模型在不同工况下进行了验证,考察了床层温度、进气浓度、流化风速以及静态床层高度等因素对低浓度甲烷流态化催化燃烧的影响,并与常见流态化反应模型活塞流、混合流及K-L反应模型进行了对比分析,研究表明本文建立的反应模型与实验数据吻合较好,误差在5%以内。同时研究发现,床层温度增加到650℃时,甲烷的转化率可达100%,减小甲烷进气浓度和流化风速以及增加床层温度均可提高低浓度甲烷的转化率,并使反应向着床层下方移动;甲烷在密相区床层的反应主要发生在乳化相,气泡相甲烷浓度的变化主要是通过气泡相和乳化相间的传质来实现。本文根据超低浓度甲烷在鼓泡流态化燃烧反应不同区域的特点,建立了催化燃烧的反应模型,并对反应模型进行了实验验证,考察了操作条件等对低浓度甲烷流态化催化燃烧的影响规律,研究结果可为低热值气体的高效利用与转化提供理论支撑与依据。
[Abstract]:Ultra-low concentration methane widely exists in coalbed methane and chemical waste gas extracted from mine, its concentration usually fluctuates with the change of mining conditions, usually its volume concentration is not more than 3, the calorific value is very low, and it is difficult to use. In the process of coal mining in China, a large amount of ultra-low concentration methane is discharged directly into the outside environment without treatment, which not only pollutes the environment but also wastes resources. Therefore, it is of dual significance to study the utilization of ultra-low concentration methane for energy saving and environmental protection. Fluidized combustion technology has the advantages of wide fuel adaptability and large thermal capacity. It is suitable for the combustion and utilization of low calorific gas. The reaction model reflecting the characteristics of fluidized catalytic combustion needs further study and establishment. According to the catalytic combustion characteristics of ultra-low concentration in bubbling fluidized bed, a zonal model is established and coupled. The catalytic combustion characteristics of 0.15m3 vol.% ultra-low concentration methane in a bubbling fluidized bed reactor with 0.5%Pd/Al2O3 as catalyst particle bed material were studied by means of experimental study and theoretical analysis, and the reaction model was verified. Finally, the change of methane in fluidized bed reactor was predicted by model calculation. Based on the catalytic combustion characteristics of ultra-low concentration methane in bubbling fluidized bed and on the basis of fluidized bed flow, reaction and mass balance, the reaction models in dense phase region and dilute phase region were established according to the gas-solid two-phase flow theory. The mass transfer between the bubble phase and the emulsified phase and the catalytic reaction of methane on the surface of the catalytic particle are considered in the dense phase region, and in the dilute phase region, according to the combustion characteristics of the ultra-low concentration methane, it is further divided into the splash particle region and the homogeneous reaction region. Reaction models were established. The effects of bed temperature, inlet air concentration, fluidization velocity and static bed height on the fluidized catalytic combustion of low concentration methane were investigated. The results are compared with the piston flow, mixed flow and K-L reaction model. The results show that the reaction model is in good agreement with the experimental data, and the error is less than 5%. At the same time, it is found that when the bed temperature increases to 650 鈩，
本文编号：2215281
[Abstract]:Ultra-low concentration methane widely exists in coalbed methane and chemical waste gas extracted from mine, its concentration usually fluctuates with the change of mining conditions, usually its volume concentration is not more than 3, the calorific value is very low, and it is difficult to use. In the process of coal mining in China, a large amount of ultra-low concentration methane is discharged directly into the outside environment without treatment, which not only pollutes the environment but also wastes resources. Therefore, it is of dual significance to study the utilization of ultra-low concentration methane for energy saving and environmental protection. Fluidized combustion technology has the advantages of wide fuel adaptability and large thermal capacity. It is suitable for the combustion and utilization of low calorific gas. The reaction model reflecting the characteristics of fluidized catalytic combustion needs further study and establishment. According to the catalytic combustion characteristics of ultra-low concentration in bubbling fluidized bed, a zonal model is established and coupled. The catalytic combustion characteristics of 0.15m3 vol.% ultra-low concentration methane in a bubbling fluidized bed reactor with 0.5%Pd/Al2O3 as catalyst particle bed material were studied by means of experimental study and theoretical analysis, and the reaction model was verified. Finally, the change of methane in fluidized bed reactor was predicted by model calculation. Based on the catalytic combustion characteristics of ultra-low concentration methane in bubbling fluidized bed and on the basis of fluidized bed flow, reaction and mass balance, the reaction models in dense phase region and dilute phase region were established according to the gas-solid two-phase flow theory. The mass transfer between the bubble phase and the emulsified phase and the catalytic reaction of methane on the surface of the catalytic particle are considered in the dense phase region, and in the dilute phase region, according to the combustion characteristics of the ultra-low concentration methane, it is further divided into the splash particle region and the homogeneous reaction region. Reaction models were established. The effects of bed temperature, inlet air concentration, fluidization velocity and static bed height on the fluidized catalytic combustion of low concentration methane were investigated. The results are compared with the piston flow, mixed flow and K-L reaction model. The results show that the reaction model is in good agreement with the experimental data, and the error is less than 5%. At the same time, it is found that when the bed temperature increases to 650 鈩，
本文编号：2215281
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