Pelletizing and acid modifying of Zr-stabilized CaO-based sorbent for cyclic high-temperature CO2 capture

The process of calcium looping (CaL), which contained reversible carbonation/calcination periods, was one of the most promising candidates for high-temperature CO2 capture. Herein, kilogram-scale of Zr-stabilized CaO sorbent pellets were granulated via extrusion-spheronized methods, in which Zr species were well scattered into the CaO particles and effectively alleviated the thermal sintering. A typical binder of pseudo-boehmite (PB), with two types of peptizers including nitric acid (NA) and malonic acid (MA), was incorporated to improve the sorption capacity and mechanical strength of the sorbent pellets. The results revealed that the presence of PB, which provided mechanical strength to the pellets due to the binder effect, can promote the cyclic sorption capacity and thermal stability for pure CaO but had an adverse impact on the reactivity of the Zr-doped sorbent. And peptizer was employed to achieve homogeneity and enhance the strength of the pellets, for it can take chemical reaction with the hydroxyl groups on the surface of PB and disintegrate the PB particles into aluminum sol. In particular, the Ca/Zr sorbent pellets modified by MA were superior to the unmodified sorbent both on CO2 capture performance and mechanical strength due to the formation of smaller and dispersed CaO crystal particles.