Study On Performance And Optimization Of Oxygen Carrier For Preparation Of Mechanically Mixed Bayan Obo Iron Concentrate

Chemical looping combustion（CLC）is a new type of flameless combustion technology that uses oxygen carriers to transfer oxygen between fuel and air.It has the advantages of efficiently capturing CO₂,avoiding the generation of NO_x,and achieving energy cascade utilization.It is one of the effective methods for the current greenhouse effect.In Chemical Looping Combustion,the oxygen carrier is the medium that realizes the transfer of lattice oxygen and heat between the air reactor and the fuel reactor,and its reaction performance and mechanical strength are important factors that affect the CLC system.This theses mainly studies the reaction performance of the Baiyun Obo Zhudong Iron Concentrate and the Baiyun Obo Barun Iron Concentrate as the oxygen carrier of Chemical Looping Combustion and the CO reaction,and the performance of the oxygen carrier is optimized by mechanical mixing with the Al₂O₃inert carrier.Firstly,the oxygen carriers of Baiyun Obo Barun iron concentrate and Baiyun Obo Zhudong iron concentrate with different molar ratio were prepared by mechanical method.The oxygen carriers were characterized and analyzed by BET,XRD and SEM.The results show that the crystal form of the iron concentrate after calcination is stable and can be well supported on the inert carrier.The iron concentrate has a porous structure.After doping with the inert carrier Al₂O₃,the surface structure of the iron concentrate is obvious and the specific surface area increases.Secondly,based on the thermogravimetric analyzer,the Chemical-Looping Combustion experiment of the oxygen carrier doped with different content of Al₂O₃under CO atmosphere was studied by temperature program,and the reduction reaction performance of the oxygen carrier doped with different content of Al₂O₃with CO and the reaction speed were investigated.The value peak uses the kinetic analysis method to calculate the reaction activation energy and the pre-explicit factor,and conducts multi-temperature constant-temperature reduction experiments for the optimal performance iron oxygen carrier.The optimized composite oxygen carrier to study the effect of temperature on the final conversion rate of the oxygen carrier.At this temperature in the thermogravimetric analyzer for multiple redox cycle experiments to observe the mass loss of the oxygen carrier after multiple cycles.The results show that there are three extreme weight loss rate peaks in the reduction reaction in the temperature-programming experiment.Appropriate Al₂O₃doping can help accelerate the reaction rate of the oxygen carrier.With the more Al₂O₃doping,the extreme peak of the reaction rate corresponds to a lower temperature.Reaction kinetic analysis shows that the conversion rate of Barun iron concentrate/Al₂O₃（40%）is the highest,and the performance of Barun iron concentrate as an oxygen carrier is stronger than that of the Zhudong iron concentrate.After optimization of the hetero-inert carrier,the oxygen carrier is analyzed separately.The reduction reaction of the Fe:Al molar ratio 6:4 Baronite oxygen carrier and CO belongs to the one-dimensional diffusion model.The activation energy of the three extreme peaks of weight loss rate are respectively.It is 6.324×10⁴J/mol,7.372×10⁴J/mol and 1.761×10⁵J/mol.Among them,the activation energy at the fastest stage of weight loss rate is 7.372×10⁴J/mol.Compared with the fastest stage of weight loss rate of Barun iron concentrate,the activation energy is significantly lower.The results of constant temperature reduction experiments show that the final conversion rate of the oxygen carrier of the Barun iron concentrate is good at 800℃,and the conversion rate of the Barun iron concentrate/Al₂O₃（40%）within 40 minutes is the highest 75.88%.Comparing Barun iron concentrate and Barun iron concentrate/Al₂O₃（40%）in the redox cycle reaction shows that the Barun iron concentrate has a mass loss of 1.446%after 10 cycles and Barun iron concentrate/Al₂O₃（40%）has no obvious quality loss.Finally,the Barun iron concentrate and Barun iron concentrate/Al₂O₃（40%）were analyzed for the tail gas of the reduction and oxidation reaction in a small fixed bed.The results show that the Barun iron concentrate and Barun iron concentrate/Al₂O₃（40%）react quickly with CO and produce different degrees of carbon deposits.The reaction performance of the Barun iron concentrate declines significantly after 20 cycles at 800°C.Barun iron concentrate/Al₂O₃（40%）can maintain great reaction performance after multiple cycles.The carbon deposition phenomenon increases first and then decreases with the increase in the number of cycles.In summary,the above experimental results show that the reaction performance of the Barun iron concentrate as an oxygen carrier is significantly better than that of the Zhudong iron concentrate.The performance of the oxygen carrier is improved significantly after doping with the inert carrier Al₂O₃,in which Fe:Al moles Barunite’s oxygen carrier with a ratio of 6:4has the best reaction performance.