SO2 retention by reactivated CaO-based sorbent from multiple CO2 capture cycles

Area of Science:

• Chemical Engineering
• Environmental Science
• Materials Science

Background:

• Spent sorbent from carbon dioxide (CO2) capture cycles often requires reactivation for reuse.
• Calcium oxide (CaO)-based sorbents are utilized for both CO2 capture and sulfur dioxide (SO2) retention.
• Understanding sorbent regeneration is crucial for sustainable industrial processes.

Purpose of the Study:

• To investigate the reactivation of spent CaO-based sorbent for effective SO2 capture.
• To evaluate the sulfation performance of reactivated sorbent compared to fresh sorbent.
• To propose a novel process integrating CO2 capture, sorbent reactivation, and SO2 retention.

Main Methods:

• Sorbent preparation from Kelly Rock limestone with varying particle sizes and impurities.
• Multiple calcination-carbonation cycles followed by steam reactivation in a pressurized reactor.
• Sulfation behavior analysis using thermogravimetric analysis (TGA), X-ray diffraction (XRD), N2 adsorption-desorption (BJH method), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX).

Main Results:

• Reactivated spent sorbent exhibited superior sulfation characteristics compared to the original sorbent.
• Over 80% CaO sulfation was achieved within 2 hours, and >95% within 4 hours.
• Steam hydration during reactivation induced particle swelling, enhancing pore structure and surface area for improved sulfation.

Conclusions:

• Spent CaO-based sorbent can be effectively reactivated for enhanced SO2 capture.
• The improved performance is attributed to favorable pore structure development post-reactivation.
• A new process for fluidized bed combustion (FBC) systems is proposed, combining CO2 capture, sorbent reactivation, and SO2 retention.