Effect of Repeated Steam Hydration Reactivation on CaO-Based Sorbents for CO₂ Capture

Abstract

Samples of natural limestone and commercial calcium carbonate were subjected to successive calcination and carbonation reactions in a TGA and to repeated activity restoration by steam hydration. Steam hydration of spent lime, followed by heating in CO(2), was shown to be an effective method for repeatedly restoring high CO(2) capture activity to spent lime during a large number of CO(2) capture cycles. Steam hydration was also shown to reduce the decay rate of the CO(2) capture activity by increasing the rate of carbonation in the diffusion controlled regime. Repeated hydration-carbonation-calcination cycles led to a considerable expansion of the particles through the formation of large vesicles, likely to lead to high attrition levels when applied in fluidized beds. Based on SEM observation of the particles during hydration-carbonation-calcination cycling, a model was proposed for their progressive weakening. It was concluded that strategies to reduce this weakening must limit the growth of the cracks in the crystal as they are cycled repeatedly.

Fast, reversible CO2 capture in nanostructured Brownmillerite CaFeO2.5

“…The capture capacity is calculated from the data of the mass of CO 2 sorbed (mg) relative to the mass of nano-CaFeO 2.5 (g) and plotted as a function of the number of carbonationcalcination cycles (Figure 6(d)). It can be clearly seen that there is a vast increase in CO 2 capture capacity of nanoCaFeO 2.5 compared to bulk and it remains almost same for all 30 cycles and there is no decay observed in the capture capacity, unlike most of the CaO-based sorbents [33,34].…”

“…In general, the capture capacity of CaO-based compounds undergo a significant loss after few cycles, which is mainly attributed to the decrease in reactive surface area with the number of cycles as a result of high regeneration temperatures [34,35]. However, in nano-CaFeO 2.5 , no observable decrease in the capture capacity is noticed.…”

Role of MgxCa1−xCO3 on the physical–chemical properties and cyclic CO2 capture performance of dolomite by two-step calcination

“…One promising method is the development of highly efficient sorbents to improve long-term performance [8][9][10][11][12][13][14][15][16][17][18][19][20]. The other is using simple reactivation routes to reduce the rate of decay in reactivity [3,[21][22][23]. On the other hand, dolomite (CaMg(CO 3 ) 2 ) is a widely distributed natural CaO sorbent, considered a more efficient precursor than limestone.…”

The impact of calcium sulfate and inert solids accumulation in post-combustion calcium looping systems

“…2). Nevertheless, similar or even higher levels of sorbent reactivation can be attained by using other strategies, such as hydration [26][27][28][29][30][31][32][33][34] or other options which are also being studied to improve the CO 2 capture capacity of lime [42][43]. It should be also mentioned that the previous fitting parameters derive from thermogravimetric studies done in the absence of steam, which may enhance the activity of the sorbent [44][45].…”

“…[26][27][28][29][30][31][32][33][34], recarbonation [35] or any other means to increase the average activity of the circulating material or a fraction of such a solid stream. In order for the simulation to embrace any sorbent reactivation strategy no specific procedure to regenerate the solids is specified.…”