CO2 capture performance of a CaO sorbent modified with fulvic acid for the calcium looping cycle

Capturing CO₂ from fossil fuel combustion is of importance for mitigation of climate warming. Among the CO₂ capture technologies, the calcium-based sorbent method is promising. However, the most prominent problem of this method at present is that the activity of the sorbent decreases as the number of cycle reactions increases. It seriously affects the industrial application of the calcium-based sorbent method in carbon capture technology. Fulvic acid (FA) is a biologically active and soluble component of humic acid. Compared with other humic acids, it contains more oxygen and heterocyclic rings. Also, the rings are connected by bridge bonds. Therefore, the ability of FA to chelate cations and its adsorption capacity is stronger than the other humic acids. Therefore, in this work, we first proposed using FA to modify CaO to improve CO₂ capture from flue gas. The effects of calcination temperature, carbonation temperature, reaction time and the amount of doped FA on the carbonation conversion rate (CCR) of CaO modified with FA (FA/CaO) were studied in the calcining/carbonizing room at atmospheric pressure. The experiment showed that the first CCR (X₁) of FA/CaO reached 0.872 under the optimal conditions, which was 31% higher than X₁ of original CaO. The 20th CCR (X₂₀) was still as high as 0.47, which was three times than X₂₀ of original CaO. In addition, the sorbent was analyzed and characterized by XRD, SEM, BET and LPSA. Due to the doped FA, the microstructure of CaO became fluffy and open, which improved the specific surface area and pore size of CaO. It indicated that the addition of FA was beneficial to the diffusion and absorption of CO₂ and delayed the appearance of sintering, which significantly enhanced the CO₂ capture performance of CaO. Using FA to modify CaO to capture CO₂ provides an idea for efficient carbon capture, and has practical application potential. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd.