Cyclic Calcination/Carbonatation Characteristic And Kinetics Of Modified Ca-based Sorbent For CO₂

Among technologies of carbon emission reduction, calcination/carbonationreaction receives more and more attention for advantages of rich aboundant of rawmaterials and large absorption capacity. During process of circular reaction, it’smeaningful to study reasons for absorption activity decay of calcium-based sorbents,influence of preparation methods on reversibility of sorbents and dynamiccharacteristics of reaction. Different metallic additions were used to modifycalcium-based sorbents. It has academic and application vales to study reversibility anddynamic characteristics of modified sorbents.Firstly, thermogravimetric analysis was utilized to study method ofcalcination/carbonation reaction. Effects of cycle times, reaction time and calcinationtemperature on rate of decomposition were studied. With observation with scaningelectric microscope, reason of reversibility decay was analyzed. Then, influence ofsol-gel combustion method, wet chemistry method and dry physical mixing method onsorbent ability was studied and an appropriate way was chosen. Aluminium andmanganese were added in sorbents to study the effect of additive, impurity content andsulfur dioxide on absorption ability. At last, kinetic analysis was launched on modifiednew sorbents. Based on characteristics of high rate reaction and slow rate reactionduring carbonation, kinetic equation was founded. And correlation equation of kineticparameters and concentration of carbon dioxide in calcination process was acquired.Results show that absorption activity of sorbent is strongly affected by reactiontemperature, reaction time and heating rate. Relation between activity of sorbent andmicropore-structure is important. The main reason of decay in activity is that sorbentcements under high temperature. Cementation narrows pores among particles andmakes pores disappear. Preparation methods have direct influence on activity ofsorbents. Activity rank from high to low is that sol-gel combustion method, wetchemistry method, dry physical mixing method, calcium carbonate. Addition of Al₂O₃,Mn₂O₃obviously increases activity and stability of calcium-based sorbents. Sorbents ofCaO/Al₂O₃（w/w=80%/20%）and CaO/Mn₂O₃（w/w=95%/5%）show best performanceof activity. SO₂hinders capture ability of CaO/Al₂O₃sorbents. With combiningexperimental data and Boltzmann equation simulation, kinetic equation of carbonationis founded. By kinetic analysis of calcinations in different concentration of carbon dioxide, it is found that activation energy which is need for reaction has a linear increasewith increasing of concentration of carbon dioxide.