Study On Preparation And Performance Of Cu-based Combined Oxygen Carriers Used For Chemical Looping Air Separation

Chemical looping air separation(CLAS),as one kind of several chemical looping technologies,is adopted for pure oxygen or oxygen rich gas production.CLAS has some advantages such as low energy cost,no pollution and safety reliability,thus it has an encouraging prospect for development.The reactivity of oxygen carriers is a key factor for CLAS technology as well as other chemical looping technologies.Metal oxide oxygen carriers have always been the research hotspot in chemical looping field and Cu-based oxygen carriers have a higher oxygen capacity.The sol-gel method was used in this paper to prepare four different types of combined oxygen carriers with the use of CuO as the main oxygen release component.The effect of different mixing ratios on oxygen release reactivity was studied.The optimal oxygen carriers were selected.The results showed that the oxygen release rates of all combined oxygen carriers increased first and then decreased with the CuO content decrease.The CuO content of these selected oxygen carriers(40Cu60Fe?70Cu30Ni?60Cu40Co and 80Cu20Mn)was different.The oxygen release characteristics of CuO and four selected combined oxygen carriers were investigated under four different temperatures.The isothermal kinetic analysis was performed,the mechanism functions were obtained,then the activation energies and the pre-exponential factors were calculated.The results indicated that the oxygen release performances of the selected combined oxygen carriers were better than that of pure CuO,but the difference of oxygen release rates reduced with the temperature increase.The kinetic analysis showed that the oxygen release processes of four combined oxygen carriers can be described by A2 function except pure CuO,which fitted the P1 mechanism function.The activation energies of oxygen release processes of CuO?40Cu60Fe?70Cu30Ni?60Cu40Co and 80Cu20Mn oxygen carriers were 213.24 kJ/mol?114.06 kJ/mol?179.39 kJ/mol?176.25 kJ/mol and 168.14 kJ/mol,respectively.The activation energy values of combined oxygen carriers were all lower than that of pure CuO.It was consistent with their isothermal oxygen release performances.Cyclic reaction performances were tested on the thermogravimetric analyzer.Test results showed that CuO?40Cu60Fe and 60Cu40Co oxygen carriers had pretty good cyclic stabilities,while 70Cu30Ni and 80Cu20Mn oxygen carriers presented obvious drop.Several experiments were carried out on the fluidized bed system to research the oxygen release process properties of oxygen carriers.It was found that 40Cu60Fe oxygen carrier can reach the highest O2 concentration,and its reduction period was of the short duration.CuO had the largest oxygen release amount but its reaction time was longer.70Cu30Ni?60Cu40Co and 80Cu20Mn oxygen carriers exhibited almost the same reaction time while 80Cu20Mn had a lower O2 concentration during its oxygen release period.Considering the above test results,40Cu60Fe oxygen carrier should be the most suitable oxygen transport carrier for CLAS in our work.