Coal direct chemical looping hydrogen production with K-Fe-Al composite oxygen carrier.

Hydrogen production by coal direct chemical looping (CDCL) process with iron-based oxygen carrier is an attractive option to produce H 2 with sequestration-ready CO 2 . However, low reduction rate and high endothermicity are the two main difficulties of this process. In this work, the reduction rate of K-Fe-Al composite oxygen carrier by coal char, and the effect of Al 2 O 3 on the endothermic property and sintering of oxygen carrier during reduction were investigated by thermogravimetric analyzer (TGA), differential scanning calorimetry (DSC), X-ray diffractometer (XRD), and scanning electron microscopy (SEM). The feasibility of this process was preliminary analyzed using a fixed-bed reactor by simulating different reaction steps. It was found that the reduction rate of composite oxygen carrier increased remarkably with higher potassium amount, but decreased with increasing Al 2 O 3 amount. However, the addition of Al 2 O 3 into oxygen carrier could not only mitigate the sintering, but also alleviated the endothermicity of reduction by the exothermic formation of FeAl 2 O 4 . This preliminary feasibility analysis suggests that it is possible to produce H 2 using CDCL with the K-Fe-Al composite oxygen carrier [ABSTRACT FROM AUTHOR]