Decrease in the Adsorption Capacity of Adsorbents in the High-Temperature Carbonate Loop Process for CO2 Capture

Abstract

In this study, the sorption capacity of limestone samples for CO2 was investigated to determine the conditions under which they can be used in the high-temperature carbonate loop process. For the work, limestone samples from the Czech Republic were used, which contained a high proportion of CaO (more than 97 wt.%). A total of 20 cycles of calcination (950 °C) and subsequent CO2 sorption–carbonation (650 °C) were performed for each limestone sample tested. The sorption capacity towards CO2 in the 20th cycle was less than 10% of the value determined in the first carbonation cycle of the samples and the most significant decrease was observed between the first and second cycles. The highest sorption capacity was determined for the Branžovy sample, which captured 268 mL of CO2/per 1 g of sorbent by chemisorption. Only 15 mL of carbon dioxide per 1 g of sorbent was bound by physisorption. However, in repeated use, the Vitošov limestone had the highest sorption capacity for CO2. For all samples, the amount of carbon dioxide bound by physisorption was in the range of 4 to 10% of the amount bound by chemisorption. Due to sintering of the material, the BET specific surface area decreased by 95 to 96%.