CO₂Capture Characteristic Of CaO Under Cyclic Calcination/Carbonation Reactions Conditions

Post-combustion CO₂capture by cyclic calcination/carbonation reactions of Ca-basedsorbent is one of the most promising technologies for CO₂reduction. In this process, CO₂in the flue gas is separated by sorbents in a carbonator, which are then transferred to thecalciner for sorbent regeneration, Simultaneously, a highly concentrated CO₂stream isproduced for subsequent compression and sequestration.Factors known to influence sorbent cyclic reactivity include impurities in limestone,limestone precursors, particle size, fuel ash and operation conditions. However, up to date,most previous studies on CO₂capture cycles were performed under mild laboratoryconditions （e.g., low regeneration temperature and CO₂concentration）. In addition, thepossible effects of SO2and water vapor in flue gases were seldom considered. These aredifferent from the real operation conditions used in calcium looping process. Based on aspecially designed TGA reactor, this work, firstly, investigates the various parameters thatinfluence sorbent activity, and then focuses on the effects of high temperature and CO₂concentration sorbent regeneration conditions, sulfur dioxide and/or steam in flue gases onsorbent performances.At the same calcination time and regeneration conversion, the experiment resultsindicate that high temperature and CO₂concentration regeneration conditions deterioratesorbent performance due to the higher sintering extent compared to mild conditions.Sorbent reactivity is reduced whenever SO2was introduced to either the calcining orcarbonation streams. With the same SO2concentration, the presence of SO2duringcalcination has larger influence than during carbonation. The addition of10%or20%steamto carbonation streams has a positive effect on carbonation reaction because of theenhanced solid state diffusion. However, the addition of steam to calcining streams resultsin an inverse phenomenon.The main outcomes of this research suggest that special attention should be paid torealistic operation conditions. Desulphurization of fue gas before O2capture, steam incarbonation streams, or using a low sulfur-containing fuel for sorbent regeneration may have beneficial effects on sorbent cyclic performance. Moreover, further study is neededto investigate the effects of water and sulfur during calcination on subsequent carbonationreactivity of produced CaO.