Performance and Durability of the Zr-Doped CaO Sorbent under Cyclic Carbonation–Decarbonation at Different Operating Parameters

Review on the modifications of natural and industrial waste CaO based sorbent of calcium looping with enhanced CO2 capture capacity

The calcium looping cycle (CaL) possesses outstanding CO2 capture capacity for future carbon-capturing technologies that utilise CaO sorbents to capture the CO2 in a looping cycle. However, sorbent degradation and the presence of inert materials stabilise the sorbent, thereby reducing the CO2 capture capacity. Consequently, the CaO sorbent that has degraded must be replenished, increasing the operational cost for industrial use. CaO sorbents have been modified to enhance their CO2 capture capacity and stability. However, various CaO sorbents, including limestone, dolomite, biogenesis calcium waste and industrial waste, exhibit distinct behaviour in response to these modifications. Thus, this work comprehensively reviews the CO2 capture capacity of sorbent improvement based on various CaO sorbents. Furthermore, this study provides an understanding of the effects of CO2 capture capacity based on the properties of the CaO sorbent. The properties of various CaO sorbents, such as surface area, pore volume, particle size and morphology, are influential in exhibiting high CO2 capture capacity. This review provides insights into the future development of CaL technology, particularly for carbon-capturing technologies that focus on the modifications of CaO sorbents and the properties that affect the CO2 capture capacity.

The Nanofibrous CaO Sorbent for CO2 Capture

The nanofibrous CaO sorbent for high-temperature CO₂ capture was fabricated by the calcination of electrospun composite filaments containing calcium acetylacetonate and polyacrylonitrile as a calcium-oxide precursor and a binder polymer, respectively. The calcination was carried out in air to prevent PAN carbonization and to obtain pure CaO nanofibers. The resulting mats of CaO nanofibers with the average diameter of 130 nm were characterized by a specific surface area of 31 m²/g, a CO₂-uptake capacity of 16.4 mmol/g at the carbonation temperature of 618 °C, a hardness of 1.87 MPa, and the indentation Young’s modulus of 786 MPa. The low decarbonation temperature makes the fabricated sorbent promising, for example, for the calcium-looping technology of CO₂ removal from the hot exhaust gases of fossil-fueled power plants.

Multicycle Performance of CaTiO3 Decorated CaO-Based CO2 Adsorbent Prepared by a Versatile Aerosol Assisted Self-Assembly Method

Calcium oxide (CaO) is a promising adsorbent to separate CO₂ from flue gas. However, with cycling of carbonation/decarbonation at high temperature, the serious sintering problem causes its capture capacity to decrease dramatically. A CaTiO₃-decorated CaO-based CO₂ adsorbent was prepared by a continuous and simple aerosol-assisted self-assembly process in this work. Results indicated that CaTiO₃ and CaO formed in the adsorbent, whereas CaO gradually showed a good crystalline structure with increased calcium loading. Owing to the high thermal stability of CaTiO₃, it played a role in suppressing the sintering effect and maintaining repeated high-temperature carbonation and decarbonation processes. When the calcium and titanium ratio was 3, the CO₂ capture capacity was as large as 7 mmol/g with fast kinetics. After 20 cycles under mild regeneration conditions (700 °C, N₂), the performance of CO₂ capture of CaTiO₃-decorated CaO-based adsorbent nearly unchanged. Even after 10 cycles under severe regeneration conditions (920 °C, CO₂), the performance of CO₂ capture still remained nearly 70% compared to the first cycle. The addition of CaTiO₃ induced good and firm CaO dispersion on its surface. Excellent kinetics and stability were evident.