Mass granulation of Al-promoted CaO-based sorbent via moulding-crushing methods for cyclic CO2 capture

• Granulation of kg-scale produced sorbent was executed via moulding-crushing methods. • Three peptizers and a pore-former were incorporated to facilitate sorbent granulates. • CO 2 capture capacities and mechanical strength of the sorbent granulates were reported. • Pseudo-boehmite can be disintegrated into aluminum sol with the addition of peptizer. Calcium looping (CaL) process, as an effective way to achieve CO 2 mitigation from high-temperature flue gas streams, is one of the most promising alternatives to amine scrubbing (a well-established technology for industrial post-combustion CO 2 capture). CaO sorbent is considered to be an ideal CO 2 adsorption material. Moreover, the development of granulation/pelletization techniques along with the mass preparation of the CaO-based sorbent is imperative for realistic large-scale applications. This work proposes two practicable moulding-crushing techniques for the scale-up granulation of CaO-based sorbents, in which the kilogram-scale produced Al-promoted CaO-based sorbent powders were first moulded and subsequently crushed into the granules of target sizes. Three types of organic acids–acetic acid, citric acid and malonic acid were employed as peptizing agents to optimize the granulation process. As a result, the anti-attrition properties and compressive strength of the synthetic sorbents were elevated owing to the introduction of an appropriate amount of acetic or malonic acid, for it expedited the disintegration of the pseudo-boehmite (served as binder agent) particles into sol particles, which allowed for tighter bonding of sorbent particles. In addition, corncob powder acted as a pore-forming agent, enhancing the porous structure of the sorbent particles due to the gases released from the thermal decomposition of organic groups during calcination. Nevertheless, the results revealed that the porous and loose structure adversely affected the mechanical strength of the granules.