Oxidization and reduction kinetics of a manganese oxygen carrier granulated with the spray drying method at a tonnage scale for chemical looping combustion

Abstract

Upscaling the preparation of oxygen carrier particles is a challenge in the demonstration of chemical looping combustion (CLC) technology. In this work, tonnage-scale preparation of a manganese oxygen carrier is reported. Fines of original manganese ore and kaolin are manufactured as oxygen carrier particles by using industrial spray drying granulation. The oxidization and reduction kinetics were measured using microfluidized bed thermogravimetric analysis (MFB-TGA). Morphological characterization of the fresh and tested particles was performed by scanning electron microscope coupled with an energy dispersive spectrometer (SEM-EDS). The effects of the reaction temperature and gas concentrations of O2, H2 and CH4 on the redox kinetics were investigated. The oxidization and reduction processes were composed of an initially fast reaction stage dominated by a chemical reaction mechanism and a second slow reaction stage controlled by gas diffusion through the solid product layer. The influence of temperature on the fast stage of the oxidization reaction is not obvious. Reduction by H2 is ~6 times faster than reduction by CH4. The conversion vs. time curves were described by a reactor model coupled to a two-stage kinetics model to obtain the kinetic parameters.