Chemical looping with oxygen uncoupling of biomass-derived hydrochar with Cu-based oxygen carriers modified by alkaline earth metals

Abstract

In this paper, the effect of alkaline-earth metals (AEMs, Ca, Ba, and Sr) on the performance of CuO/ZrO2 oxygen carriers (OCs) and the hemical looping with oxygen uncoupling (CLOU) process of wheat-derived hydrochars with these Cu-based OCs were investigated. The results showed that after multiple cycles, the crystal phases of modified Cu-based OCs were the same as that of pure CuO/ZrO2 OC without any interaction between them. Due to the catalytic effects of AEMs, an increase in the decomposition of wheat and hydrochar-235 in modified Cu-based was observed at 500 °C. The combination of Ca and HTC promotes reoxidation, while Ba and Sr inhibit reoxidation. Notably, the Cu-based OCs exhibited moderate agglomeration after 20 redox cycles at 950 °C. The results of the kinetic analysis indicate that the chemical order models and diffusion models can suitably describe the first combustion stage for wheat and hydrochars with Cu-based OCs, respectively. The geometrical contraction model was also found to most suitably describe the second combustion stage of all samples. These results suggest that a combination of hydrothermal carbonization pretreatment with AEMs modification is an efficient approach for CLOU using CuO-based OCs.