Experimental Investigation Into CO₂Capture From Cement Industrial Gases By Ca-based Sorbents

CO₂as emitted from industrial production processes is the main cause of globalclimate change. Abatement of CO₂emissions is becoming the focus of governmentattention and academic research. CCCR technology （a Ca-based sorbents CyclingCalcination/Carbonation Reaction technology） is a kind of new and effective method tocapture CO₂in flue gas from industry.Effects of Ca-based sorbents’ mineral composition, its particle sizes, calciningtemperature and carbonating temperature were investigated in the present thesis on thecarbonation characteristics of a Ca-based absorbents and its stability in cyclingcarbonation reaction under high CO₂concentration, as commonly found in cementindustry. Orthogonal tests were carried out to determine the appropriate CO₂captureprocess control parameters, i.e. particle sizes of absorbents, calcining temperature,carbonating temperature and carbonating reaction time for the cycling carbonation rateof absorbents （XN）. The main conclusions are as follows.（1） The carbonation reaction process of absorbents occured in three stages, they area rapid chemical reaction phase, a transition phase and a slow product layer diffusionphase, the time needed for each phase is different under different testing conditions.（2） A certain amount of dolomite in absorbents could maintain a loose porestructure and good sintering resistance during cycling calcination/carbonation reaction,contributing to improving the cyclic carbonatation rate of absorbents. However, if thesorbent contained too much dolomite, with an increase of generated MgO, the amountof CO₂adsorption by per unit mass absorbent （YN） became less.（3） The cycling carbonation rate of absorbents XNwould reduce gradually with anincrease of absorbent particle size. XNappeared to be maximum at725℃during carbonation. The value of XNwould decrease with the rise of calcining temperature.CO₂concentration has an effect on the absorbents carbonatation rate of chemicalreaction phase. The more the CO₂concentration is, the greater XNbecame.Carbonatation rate approached to be stable eventually.（4） The size of pores （100nm） inside absorbent particles as formed duringcalcination is beneficial to carbonation reaction. However, the amount and area of thesepores would decrease due to sintering during cycling calcination and carbonation,,those pores grew into holes with a middle size, resulting in a decline in cyclingcarbonation rate.（5） According to the results of orthogonal tests, it was observed that, whensignificance level was0.05, particle sizes of sorbents, calcining temperature,carbonating temperature and carbonating reaction time had no significant impact on XNin the initial cycle, however, calcination temperature and carbonation reaction timemight have significant influence on XNduring multiple cycles （the cycle is5and10times）, It was found that the best process control parameters for the cycling carbonationrate of absorbents （XN） are: absorbent in an average particle size of17.04μm,calcination temperature at925℃, carbonation temperature at725℃and carbonationreaction time lasts60s.