壁面热损失对超低热值煤层气热逆流氧化的影响

Influence of wall heat loss on the thermal flow-reversal oxidation of ultra-low heating value coalbed methane

建立了超低热值煤层气热逆流氧化的数学模型,运用计算流体力学软件进行数值计算,得到不同壁面热损失条件下超低热值煤层气热逆流氧化的温度场、甲烷转化率、最低甲烷浓度及最大换向半周期,并将数值计算结果与实验结果进行了对比。结果表明:改善氧化装置保温性能,降低壁面热损失,可以提高氧化床整体温度场和拓宽高温区域,有利于甲烷的充分氧化和热量提取;降低氧化装置壁面热损失,可以提高甲烷转化率,且进气速度越小影响越明显;减少氧化装置壁面热损失,可以降低装置维持自运行所需的最低甲烷浓度,有利于氧化装置的稳定运行;随着壁面热损失的下降,氧化床最大换向半周期不断延长,在装置实际运行中,通过改善装置保温性能降低壁面热损失,可以适当延长装置换向时间,减少换向次数。

A mathematical model of the thermal flow-reversal oxidation of ultra-low heating value coalbed methane was established. The computational fluid dynamic software was used to simulate the temperature field,the methane conversion rate,the lowest methane concentration and the maximum half cycle of the thermal flow-reversal oxidation of ultralow heating value coalbed methane under different wall heat losses. The calculated values showed a good agreement with the corresponding available experimental data. The study results show that,with the decrease of wall heat loss,the whole temperature field of oxidation device is raised,and the high-temperature zone widens accordingly,which is better for the oxidation of methane and heat extraction. The methane conversion rate increases as the wall heat loss decreases,and the degree decreases along with the intake speed. It can also reduce the lowest methane concentration by improving the thermal insulation performance of oxidation device and reducing the wall heat loss,which will be beneficial to the stable operation of the oxidation device. As the wall heat loss decreases,the maximum half cycle prolongs. In the actual operation,it can prolong the reversal time and reduce the switch times.