Long-Term Calcination/Carbonation Cycling and Thermal Pretreatment for CO₂ Capture by Limestone and Dolomite

Abstract

Capturing carbon dioxide is vital for the future of climate-friendly combustion, gasification, and steam-reforming processes. Dry processes utilizing simple sorbents have great potential in this regard. Long-term calcination/carbonation cycling was carried out in an atmospheric-pressure thermogravimetric reactor. Although dolomite gave better capture than limestone for a limited number of cycles, the advantage declined over many cycles. Under some circumstances, decreasing the carbonation temperature increased the rate of reaction because of the interaction between equilibrium and kinetic factors. Limestone and dolomite, after being pretreated thermally at high temperatures (1000 or 1100 °C), showed a substantial increase in calcium utilization over many calcination/carbonation cycles. Lengthening the pretreatment interval resulted in greater improvement. However, attrition was significantly greater for the pretreated sorbents. Greatly extending the duration of carbonation during one cycle was found to be capable of restoring the CO 2 capture ability of sorbents to their original behavior, offering a possible means of countering the long-term degradation of calcium sorbents for dry capture of carbon dioxide.

CO2 multicyclic capture of pretreated/doped CaO in the Ca-looping process. Theory and experiments

“…Eventually, multicyclic conversion of pretreated sorbents would converge towards a residual value for very large N as seen in experimental data [22]. In this limit, Eq.…”

“…Yet, the model cannot explain the evolution of conversion found in some cases of activated sorbents [24]. For example, Chen et al [22] have shown that a natural limestone and a dolomite showed a residual conversion after 1000 carbonation/calcination cycles that actually depended on the details of thermal pretreatment even though identical looping conditions are used. Furthermore, depending on the relative values of X 0 and k D , the model predicts either a continuous increase or a decrease of conversion from X 0 up to reaching a residual value for large N .…”

“…The effect of thermal pretreatment on multicyclic CaO conversion has been extensively analyzed by Manovic and co-workers in a series of papers [17,19,20] as well as by other authors in the last years [18,[21][22][23]29], being a subject of current debate in the literature [8,24,31]. The influence of preheating temperature, exposition time, type of atmosphere, type of sorbent, presence of additives, pre-hydration, pre-grinding and looping-carbonation conditions is thoroughly analyzed in these works.…”

“…Generally, Eq. 10 may describe the diversity of behaviors observed for pretreated sorbents in the first cycles [17][18][19][20][21][22] depending on the relative values of a, b and β such as the presence of a maximum of conversion at a certain value of N . This maximum will exist in the case b > a and β < 1 and will be placed at a cycle number N 0…”

The calcium looping cycle for CO2 capture from power generation, cement manufacture and hydrogen production

“…For example, very different results are obtained for deactivation rates when calcination is conducted under mild vs. severe conditions (Grasa and Abanades, 2006;Manovic and Anthony, 2008b;Manovic and Anthony, 2008d;Manovic et al, 2009;Wang et al, 2010) and also due to increases in carbonation temperature (Manovic and Anthony, 2008d) (both of which are reported to be due to the effect of sintering, see: Section 2.1 above). Longer carbonation times can regenerate the sorbent (Barker, 1973, Lysikov et al, 2007Chen et al, 2009) though the effect of this is somewhat inconsistent elsewhere (Manovic and Anthony, 2008d). A higher CO 2 concentration during carbonation has been shown to improve the uptake of some synthetic sorbents (Pacciani et al, 2008b).…”