The catalytic effect of inner minerals on the combustion of oil shale char: Characteristics and mechanism

Abstract

To determine the effects of minerals inside char particles and bed materials, the process and mechanism of char combustion in a fluidized bed were studied using a Micro Fluidized Bed Reactor Analyzer. A demineralization procedure using HCl and HF was employed to remove the minerals from pyrolyzed char samples. Raman spectroscopy was used to study the carbon structure of the remaining solid char after demineralization at 500 °C, 600 °C, 700 °C and 800 °C. From the regular changes in band area ratio and full width at half maximum, it can be concluded that as pyrolysis temperature increases, the carbon structure becomes highly ordered, the plane lattice size gradually increases, and the reaction activity decreases from 0.245 s−1 to 0.138 s−1.Furthermore, minerals both within the char particle and in the external bed had marked catalytic activity on char combustion, and their combined catalysis was most notable. CaO and Fe2O3 were the dominant active minerals components contributing to catalytic combustion of char in this study. The catalytic action of CaO was stronger than that of Fe2O3. The activation energy of char combustion ranged from 57.70 kJ/mol to 91.53 kJ/mol, and it significantly decreased in the presence of the bed materials.