The investigation on the attrition of hematite oxygen carrier particles in a fluidization-based chemical looping system

The oxygen carrier particle is usually used in the fluidization-based chemical looping system, which is subject to mechanical, thermal, and chemical stress. Therefore, the attrition of oxygen carriers, leading to the loss of oxygen carriers, cannot be ignored. In this work, an attrition device was built based on the modified ASTM D5727, followed by investigations on attrition characteristics of one selected hematite oxygen carrier under multiple conditions. After the careful removal effects from the coal ash, the real-time attrition curves and particle size distribution of attrition particles have been obtained. Studies revealed that the initial attrition rate was higher at ambient and elevated temperatures. The bed material's fluid dynamics and physical properties primarily affected the attrition rate during a steady-state period. The temperature elevation helped improve the attrition resistance of hematite in fluidization conditions. Under the reactive condition, SEM, XRD, and total iron content analysis implied that the chemical stress caused by crystalline phase change would bring cracks and enhance the attrition rate. The fitting results of the Gwyn kinetic equation revealed that the particles were more susceptible to surface abrasion under an elevated temperature. •An air jet attrition test device during thermochemical reaction process was designed and built based on the standard ASTM D5727.•The attrition of hematite oxygen carrier particles under mechanical, thermal and chemical stress was investigated.•Better attrition resistance of hematite oxygen carrier under non-reactive conditions was observed with elevated temperature.•Thermochemical-reaction derived chemical stress significantly increased the attrition of hematite particles.•More serious attrition was observed during the reduction stage than that of oxidation stage.