Single step fabrication of spherical CaO pellets via novel agar-assisted moulding technique for high-temperature CO2 capture

CaO sorbents have received extensive attentions in the field of high-temperature CO2 removal due to its outstanding characters of low cost, fast sorption kinetics and high theoretical capacity. Granulating CaO powder into spherical pellets is requisite prior to its commercial application for post-combustion CO2 capture. This work proposed a facile agar-assisted moulding technique for the pelletization of CaO sorbents inspired from the strong coagulability and hydrophobicity of agar powder. In addition, finding efficient calcium precursors to produce CaO sorbents is also crucial to their CO2 sorption performance. Hence, two novel organometallic precursors, i.e., calcium laurate and calcium myristate, were employed in the current work. The obtained CaO sorbents exhibited a high degree of sphericility and uniform sizes of 3-4 mm. Besides, these sorbent pellets presented good CO2 sorption performance. In particular, the pellets using calcium laurate as precursor showed impressive performance, including high sorption rate and carbonation conversion (up to 0.92). The excellent performance was attributed to the rich porosity and porous structures of this sorbent. Such characters were believed to be brought by the burning of agar and organometallic precursors at high temperatures, which resulted in the quick release of large volumes of gases in a short time and, thus, led to the formation of porous structures. In addition, the burning out of the well dispersed agar powder in the sorbent pellet also left abundant pores in situ in the pellets. Generally, the good performance of the prepared CaO pellets demonstrates the effectiveness of the agar-assisted moulding technique for the sorbent granulation and the suitability of calcium laurate as calcium precursor.