Background and Objective: Carbon dioxide (CO₂), as the main greenhouse gas, plays a critical role in global warming. One of the effective methods for CO₂ capture is the solar-driven calcium looping process. The stable performance and good fluidity of CaO-based sorbents are crucial for the efficiency and durability of this process. This study aims to investigate and enhance the stability and fluidization characteristics of CaO sorbents to improve the performance of solar calcium looping process.
Materials and Methods: To enhance the stability of CaO sorbents, chemical modification with phosphoric and acetic acids was applied. To improve the sorbent's, fluidity, silica particles were added. The performance of modified sorbents was evaluated over 19 cycles for CO₂ capture and regeneration to assess the quantitative and qualitative effects of these treatments on stability and fluidization.
Results: Regarding stability, sorbents modified with acetic acid showed better performance than those modified with phosphoric acid. In contrast, phosphoric acid modification was more effective in improving fluidization behavior. Limestone modified with 10% acetic acid retained a CO₂uptake of 0.3 g CO2/g sorbent after 19 cycles, corresponding to a 57% increase compared to the unmodified limestone. Additionally, at a superficial gas velocity of 5 cm/s, bed expansion of the phosphoric acid-modified sample increased by 27% compared to the raw limestone. By adding 5% silica particles to the acetic acid-modified sample, bed expansion increased by 32%.
Conclusion: Acid modification combined with silica particles addition provides an effective strategy to enhance the performance of CaO sorbents in solar calcium looping processes.
