Comparing the Performance of Calcium-based Adsorbents Prepared from Limestone and Eggshell Resources in CO2 Capture Calcium Looping Process and Improving their Efficiency

dioxide has been considered by the process of cyclic surface adsorption using calcium-based adsorbents. Despite a proper performance, the reduction of adsorption capacity due to the sintering of Ca-based adsorbents with increasing number of cycles is still a big challenge. In this study, the performance of two Ca-based adsorbents prepared from lime ore (limestone) and eggshell sources in terms of adsorption capacity during 20 consecutive carbonation and calcination cycles was investigated. Then, in order to overcome the sintering problem, both limestone and eggshell adsorbents were treated with acetic acid at a concentration of 10% by volume. The results showed that the presence of acetic acid in both types of adsorbents led to an increase in the effective conversion at the end of 20th cycle, so that the values of 0.38 and 0.33 were obtained for limestone and eggshell with 10% v/v acetic acid, respectively, which was comparable to the corresponding values for raw limestone and eggshell (in the absence of acetic acid), that is 0.24 and 0.20. The reason for the increase in the conversion by treating with acetic acid can be attributed to the formation of calcium acetate, which has led to the formation of more porous and stable structures. By comparing the two calcium sources used in this study, it was found that limestone has a better performance than eggshell in terms of CO2 adsorption capacity, so that the conversion rate of raw limestone was 1.2 times higher than raw eggshell, which could be related to its high purity as well as its larger crystal size compared to eggshell.