Numerical Study Of Oxidation Performance Of Basalt Fiber Bundle Thermal Flow-reversal Reactor

Methane is the second largest greenhouse gas,and mine exhaust gas is often directly discharged due to its large amount and wide range,which is difficult to use.According to statistics,About 17billion m³ of methane gas is emitted through mine ventilation every year in China,and this part of the gas waste has a high calorific value and causes serious greenhouse effect,so the recycling and utilization of exhaust gas can produce huge energy,economic and environmental benefits.The investigation found that thermal countercurrent oxidation technology is the most promising treatment technology.In view of the problems of small processing range,large area and large resistance loss in the ceramic honeycomb structure,the basalt fiber bundle thermal flow-reversal reactor with mixed flow channels is proposed in this paper.Using Ansys Fluent software,a two-dimensional numerical study was carried out on the oxidation performance of the basalt fiber bundle thermal flow-reversal reactor with constant parameters and variable parameters in the treatment of exhaust gas.At the same time,its cycle stability,self-sustaining concentration and economic performance were studied.The main research contents and conclusions are as follows:（1）The cycle stability of the reactor is numerically studied by using the average temperature difference between the two adjacent half cycles and the width of the high temperature platform,and it is found that the reactor could achieve cycle stability within 20 cycles.（2）A single-channel two-dimensional numerical model of the reactor is established,and the laws and characteristics of the temperature distribution,methane concentration distribution,flow field distribution and resistance distribution in the reactor under constant parameters were visually studied with the help of CFD-Post software.It is found that the mixed flow channel can effectively improve the flow field distribution in the reactor and reduce the resistance.（3）The evaluation index of oxidation performance was established,and the influence of four key parameters of the inlet methane concentration,inlet flow rate,commutation cycle and fiber bundle arrangement spacing on the oxidation performance and resistance characteristics of the reactor was studied by the control variable method.According to the numerical simulation results,it is found that in order to obtain good oxidation performance,it is necessary to select a moderate flow rate and commutation cycle.Meanwhile,the inlet methane concentration and commutation cycle have little influence on the resistance loss,which is almost negligible compared with the difference in resistance loss caused by the flow rate.In addition,considering the gas throughput and oxidation performance comprehensively,it is considered that the optimal arrangement spacing of the reactor is 2.0D₁ in the vertical flow channel direction and 1.0D₂ in the parallel flow channel direction.（4）The self-sustaining minimum methane concentration of the reactor is studied and analyzed,and it is found that reducing the inlet flow rate and shortening the commutation cycle could reduce the flammability limit of the reactor,and various operating parameter combinations could achieve a self-sustaining minimum of 0.1%.Compared with the ceramic honeycomb structure,the methane concentration is reduced by about 44%-50%,and an additional emission reduction benefit of 0.68times can be obtained.（5）The annual total income of the basalt fiber bundle thermal flow-reversal reactor is analyzed from the two aspects of emission reduction benefit and economic benefit by using the sensitivity analysis method and the comparative analysis method.Through the analysis,it is found that the pressure loss of the basalt fiber bundle structure reduced by 88.87%compared with the ceramic honeycomb structure.In addition,because the gas treatment volume per unit volume is 2.3 times that of the latter,the total annual benefit obtained by the basalt fiber bundle structure under the same treatment concentration is 2.51 times that of the latter.It means that better oxidation performance will bring higher application value.