CO₂ Looping Cycle Performance of a High-Purity Limestone after Thermal Activation/Doping

Abstract

The influence of thermal pretreatment on the performance of a high-purity limestone (La Blanca) during CO 2 capture cycles is investigated in this paper. This limestone was chosen for more detailed investigation because, in earlier research, it failed to show any favorable effect as a result of thermal pretreatment. Here, the original sample, with a particle size of 0.4-0.6 mm, and ground samples were thermally pretreated at 1000-1200°C , for 6-24 h, and then subjected to several carbonation/calcination cycles in a thermogravimetric analyzer (TGA). This work shows that thermal pretreatment failed to produce a significant self-reactivation effect during CO 2 cycles, despite the use of a wide range of conditions during pretreatment (grinding, temperature, and pretreatment duration) as well as during cycling (CO 2 concentration and duration of the carbonation stage).Additional doping experiments showed that both high Na content and lack of Al in La Blanca limestone cause poor self-reactivation performance after thermal pretreatment. Scanning electron microscope-energy-dispersive X-ray (SEM-EDX) analyses also confirmed more pronounced sintering and loss of activity, which we believe are caused by the relatively high Na content. However, stabilization of sorbent particle morphology by Al can allow this limestone to show self-reactivation performance and higher conversions over a longer series of CO 2 cycles.

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

“…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 . Yet, it is often seen that conversion of thermally pretreated sorbents increases up to reach a maximum value in a few number of cycles (N 15) after which X N decreases monotonously with N [17,19,20].…”

“…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.…”

“…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. Let us employ the equations derived in our model to analyze the data reported in [19]. In that work benchmark looping TGA tests after pretreatment were performed isothermally at 800 • C (10 min calcination and 30 min carbonation).…”

“…The effect of doping a powdered limestone with γ-Al 2 O 3 was also analyzed. A summary of the results on multicyclic CaO conversion data reported [19] is shown in Figs. 1-3 as well as best fit curves inferred from the theory.…”

“…10 provides good fits to multicyclic CaO conversion data reported in ref. [19] on pretreated sorbents as may be seen in Figs. 1-3.…”