Effect of acid treatment on cao for calcium looping process

• Main Author: Mohamad Danial Ikhmal Bin Mohamad Nawar
• Published: 2023
• Subjects: Calcium looping; Acid treatment; Carbon dioxide capture

Calcium looping process is one of the Carbon Capture and Storage Technology that traps the CO2 from flue gases using the calcination and carbonation cycle and is processed in an environmentally friendly space to reduce global warming due to greenhouse gas (GHG) emissions. The biggest challenge in calcium looping processes for CO2 capture is the degradation of CO2 carrying capacity of CaO-based sorbents with a growing number of cycles. By having this difficulty, this study suggested the treatment of sorbent using acetic acid for sorbent preparation in order to enhance and improve the reactivity of the sorbent and also the CO2 uptake. The identification of phase, morphology and structural mechanical properties of all samples were analyzed to clarify the effect of acid treatment on the limestone in order to increase the sorbent’s efficiency. 5 samples were prepared during the research that varied in terms of concentration of acid. The samples were then analyzed with SEM analysis, XRD analysis and BET surface area. The crystallite size and crushing strength also being done for the research to study the mechanical durability of the sorbent. The modified sorbents performed the best results compared to the original sorbent. The morphology of the modified sorbents was rod-shaped or lamellar in structure which enhanced the mechanical durability towards multiple cycles. Sample D that treated with 8M of acetic acid displayed the best results in morphology, crystallite size, crushing strength and BET surface area compared to sample A, sample B and sample C that were also undergone acetification with 2M, 4M and 6M of acetic acid. Sample D has the largest surface area which resulted in 31.116 m2/g that four times bigger than sample A and sample E that only has 15.466 m2/g and 14.733 m2/g. The absorption of carbon dioxide increases as the surface area increases. Sample A displayed the largest crystallite size which was 51.2 nm that caused the sample to degrade easily due to high sintering effect. However, sample D resulted in having the smallest crystallite size which was 42.20 nm due to acid properties that decreased the effect of sintering. Therefore, by having the outstanding results, sample D could therefore sustain longer during multiple cycles and higher CO2 absorption compared to other modified sorbents. Also, the modified sorbents will have the better CO2 uptake availability compared to the original sorbent. Thus, this study prove that the acid treatment is a good alternative and solution in enhancing the CO2 carrying capacity.