超低浓度煤层气在流化床燃烧过程中相间的传热传质特性

气泡相和乳化相间的传热传质对超低浓度煤层气在流化床中的燃烧有重要的影响。基于流化床内能量平衡和质量平衡的建立了数学模型,结合催化动力学实验,研究了相间传热传质系数的变化,分析了床层温度、颗粒粒径、气泡直径、进气甲烷浓度对相间的传热传质特性的影响。研究表明:床层温度、颗粒粒径增加时,传热系数减小、传质系数增大、出口处无量纲甲烷浓度减小;存在一个临界气泡尺寸使相间的传热系数最大,颗粒粒径增大时,临界气泡尺寸略减小、出口处无量纲甲烷浓度增加;进气甲烷浓度对传热传质系数影响较小。

Heat and Mass Transfer During Ultra-low Concentration Coal-bed Methane Combustion in a Fluidized Bed

It is significant to study heat and mass transfer between bubble and emulsion phases during ultra-low concentration coal bed methane combustion in a fluidized bed.A mathematic model based on heat and mass balance was established.The characteristic of heat and mass transfer was studied combining with the model and kinetic experiments.The effects of bed temperature,particle size,bubble diameter and inlet methane concentration on inter-phase heat and mass transfer were analyzed.The results show that increasing either the bed temperature or particle size result in the heat transfer coefficient decreasing,mass transfer coefficient increasing and dimensionless methane concentration decreasing at the outlet.The critical bubble diameter,at which the heat transfer coefficient reaches the maximum,was decreasing with particle size growing.The dimensionless methane concentration at the outlet increases when the particle size is added.The inlet methane concentration has little influence on heat and mass transfer.