Study On The Combustion Technology And Mechanism Exploration Of Low Concentration Gas Catalytic Combustion Based On Porous Media

CH₄ is not only a high-quality clean energy source,but also the second largest greenhouse gas in the world,with a greenhouse effect 21 times that of CO₂.The large amount of low concentration gas（CH₄ concentration between 3%and 9%）associated with coal mining has problems such as large evacuation volume and low utilization rate,which not only causes a large amount of clean energy waste,but also leads to serious greenhouse effect.The reduction and utilization of coal mine gas has become another major challenge for China to achieve the"dual carbon"goal.Porous medium catalytic combustion is a new unconventional combustion technology based on the theory of over enthalpy combustion.This technology adopts a direct combustion method,which can burn extremely low concentration gas without the need for an external heat source,achieving the goal of expanding the gas lean combustion limit and reducing pollutant emissions.The development of porous media catalysts is the key to breaking the limit of gas lean combustion and maintaining stable combustion in this technology.Therefore,this thesis develops a supported porous medium catalyst with transition metal oxide as active component and Al₂O₃ foam ceramic as carrier,studies the catalytic combustion characteristics of low concentration gas porous medium,and reveals the catalytic combustion mechanism of low concentration gas porous medium through characterization technology and molecular simulation,aiming to provide a theoretical basis for realizing efficient and clean utilization of low concentration gas.The specific research content and results are as follows:Firstly,porous media catalysts were prepared using Fe₂O₃,Cu O,and Co₃O₄ as active components,and the effects of different catalyst types on the combustion characteristics of low concentration gas were investigated to select the porous media catalysts with the best active load.The results show that catalysts loaded with Cu O and Co₃O₄ can enhance the combustion effect of low concentration gas,but the combustion flame stability is poor and is prone to high-temperature deactivation;The porous medium catalyst loaded with Fe₂O₃ has excellent high-temperature catalytic activity and thermal stability,which can broaden the lean burn limit equivalence ratio of gas stationary combustion to 0.46 and improve the CH₄ conversion rate to 98%.Secondly,the effect of catalyst loading and pore arrangement on the catalytic combustion characteristics of low concentration gas was further studied using porous media catalysts loaded with Fe₂O₃ as the research object.The results show that the catalytic combustion characteristics of gas decrease with the increase of Fe₂O₃ loading.The combustion effect is best when Fe₂O₃ loading is 1%,with methane conversion rate above 98%and CO emissions below 600ppm.The investigation of the different pore arrangements of the catalyst revealed that the heat storage capacity of the catalyst increased with increasing pore density,but the fluidity of CH₄ gas decreased and the CH₄ conversion rate decreased.The catalytic combustion of porous media with a uniform distribution of porosity of 20PPI has good heat storage capacity and flowability,further expanding the lean burn limit equivalence ratio of CH₄ combustion to 0.45,achieving stationary combustion under this lean burn limit and reducing combustion pollutant emissions.The emissions of CO and NO_x are 600ppm and 10ppm,respectively.Finally,the high-temperature catalytic performance and high-temperature thermal stability of each catalyst were characterized and analyzed,and the optimal catalyst was determined to be Fe₂O₃ loaded catalyst.The reaction mechanism of Fe₂O₃ loaded porous medium catalyst for CH₄ combustion was explored through the CASTEP module of Material Studio software.The results showed that the Fe atoms on the surface of Fe₂O₃ became active centers,causing CH₄ molecules and O₂ molecules to adsorb and dissociate.The lattice oxygen of Fe₂O₃ participated in the generation of CO and CO₂;The dissociation of O₂ promotes the generation of H₂O by adsorbing oxygen.The presence of Fe₂O₃ increases the CH₄ conversion rate at low flow rates.This thesis is based on porous medium combustion technology,with the focus on developing porous medium catalysts with efficient catalytic activity to explore the catalytic combustion characteristics and related combustion reaction mechanisms of low concentration gas.It provides important theoretical and technological innovation methods for achieving efficient and clean utilization of low concentration gas in coal mines in China.There are 95 figures,7 tables and 91 references in this thesis.