Experimental And Simulation Study Of Coal Mine Ventilation Air Methane Preheat Catalytic Oxidation Reactor With Dual-reaction Chamber

There are a lot of potential energy in the coal mine ventilation air methane(VAM),but it's always discharged into air directly because of the low methane concentration.According to the statistics,more than 25 billion cubic meters of methane is discharged each year in China,which leads to severe environment pollution and energy waste.So,the efficient use of VAM is undoubtedly of considerable realistic significance.Based on the situation,the preheated catalytic oxidation reactor with dual-reaction chamber was built to oxidize the VAM,and the structural principle,system composition and working process were introduced in details.Then a series of simulation and experiments were done to study the performance of the reactor.The design of the flow distribution system was simulated studied,and the flow uniformity of the oxidation bed inlet was improved by fixing the deflector and optimizing the structure.The result show that,the oxidation bed inlet gets a better flow uniformity when the corner radius of the deflector is 140 mm,the number is 3 and the relative distance is between 0.3~0.4.The flow deviation coefficient of the optimal design is reduced to below 0.2.The stability of oxidation bed was studied through the starting experiments.The results show that the good symmetry of reaction chambers provides a favorable condition for the steady operation of oxidation bed;the axial temperature of oxidation bed gradually decreases which means the heat loss exist in the catalytic ceramics,and the heat loss is larger when the temperature raise to 700?;there is obvious thermal drift and higher temperature non-uniform coefficient at the initial stage,but it gets uniform at the steady stage and the temperature non-uniform coefficient is below 0.05;the stabilization time of heating condition is shorter than cooling condition,keep heating condition is easy to realize stability of oxidation bed.The effect of space velocity,the inlet temperature of oxidation bed and the methane concentration on oxidation process was studied experimentally.During this period the electric heater was kept open in order to control the inlet temperature of oxidation bed.The results show that the catalytic oxidation of methane mainly takes place in the first catalytic ceramic layer;with the increase of space velocity,the major area of methane oxidation extends gradually,the effective reaction length increases about 31% when the space velocity increase from 3800 h-1 to 7100 h-1,the rate of increase become greater when the space velocity over 7100 h-1 and the conversion rate of methane declines slightly;the major area of methane oxidation decreases with the increase of the inlet temperature,the effective reaction length reduces 53% when the inlet temperature increase from 422? to 485? and the conversion rate of methane increases,but the influence is weak when the inlet temperature over 485?;the increase of methane concentration has little influence on the oxidation process,the effective reaction length is little decreases and the conversion rate of methane increases slightly.The empirical equation of the effective reaction length was obtained by analyzing the experimental data.The heat balance of different methane concentration and space velocity at the self-maintain running was calculated studied,the results show that: the higher the concentration of methane,the more extra heat in the system and the greater proportion of the surface heat loss,the surface heat loss become the dominant when the methane concentration over 1.05%;the greater space velocity,the higher the needed methane concentration to achieve the self-maintain running and the greater proportion of the exhaust heat loss,the exhaust heat loss become the dominant when the space velocity over 7000h-1.Consequently,the surface heat loss should be mainly controlled in the high methane concentration condition and the exhaust heat loss should be mainly controlled in the high space velocity condition,the preheater and insulation should be rational designed to increase the extra heat and resource utilization rate.