Study On Low Concentration Coal-Bed Methane With Chemical-Looping Combustion

Coalbed methane is an important unconventional natural gas resource with broad development prospects.Chemical Looping technology transfers oxygen by means of intermediate oxygen carriers,which has unique advantages in the field of coal-bed methane deoxidation,but its related research is very limited.This article focuses on the study of fixed bed chemical chain deoxidation of iron based copper based oxygen carriers,which are environmentally friendly and have abundant reserves.Firstly,copper based iron based oxygen carriers were prepared by mechanical mixing method,and the deoxidation performance of the oxygen carriers obtained by combining different active components（Cu,Fe）with different inert components（Al₂O₃,Si O₂）was investigated.The optimal composition of the oxygen carrier Fe Al was selected,and the Fe Al oxygen carrier was investigated under different reaction conditions such as temperature,flow rate The deoxygenation performance under reaction time is studied,and the optimal operating conditions are found.Based on this,the effect of doping Cu modification on the deoxygenation performance of the carrier is studied,and its cyclic performance is examined.Furthermore,a reaction kinetics model is established to analyze the deoxygenation mechanism.The main conclusions are as follows:（1）Copper based oxygen carriers have good low-temperature deoxygenation performance,but their deoxygenation performance decreases at high temperatures,with an optimal deoxygenation rate of 65.39%;The overall deoxygenation performance of iron based oxygen carriers is good,especially the deoxygenation rate of Fe Al oxygen carriers reaches 72.28%,and the outlet oxygen concentration drops to 5.8%;The study investigated the changes in deoxygenation performance of Fe Al oxygen carriers under temperature,flow rate,and reaction time.The results showed that temperature and flow rate both affect the deoxygenation effect.The optimal reaction conditions were 150ml/min,and the instantaneous value of outlet oxygen concentration could be reduced to 4.47%at 400℃.The conversion rate of oxygen carriers could reach about 47.37%,and the deoxygenation retention time could reach 600s.The unit mass oxygen carrier processing capacity was 0.1L/g.（2）The deoxygenation performance of modified oxygen carrier Fe2Cu8Al5（20%Fe-80%Cu-50%Al₂O₃）has been improved,and the outlet oxygen concentration can be reduced to 2.73%.The deoxygenation rate can reach 87%,and the oxygen carrier conversion rate is about 50.9%,which is nearly 21.7%higher than that of unmodified oxygen carriers.The circulation performance of the oxygen carrier was investigated,and it showed that the oxygen carrier Systemic circulation circulation performance was stable,and the conversion rate decreased about 13.6%after 10 cycles.A reaction kinetics model was established for the deoxygenation process of Fe2Cu8Al5 oxygen carrier,and it was found that the reaction mechanism conforms to the shrinking core model,with an apparent activation energy of 53.13k J/mol.（3）The reasons for the performance improvement of Fe2Cu8Al5 were analyzed through characterization methods such as XRD,SEM,and FM.The results showed that the addition of Cu improved the pore structure of the oxygen carrier,thereby enhancing the reaction performance.At the same time,the addition of Cu transformed the reactive phase,increased the reaction activity,and Fe played a more important role in improving the stability of the oxygen carrier and reducing sintering.In summary,chemical looping technology can achieve the deoxygenation of feed gas,which is a very promising technical means in the field of low concentration coalbed methane deoxygenation.The modified Fe2Cu8Al5 oxygen carrier has good deoxygenation performance.