Understand relations between mechanical/thermal/chemical stresses and attrition of oxygen carrier in chemical looping process

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During the chemical looping process, oxygen carriers are subjected to extremely challenging conditions, such as high temperatures, fluidization, and redox reactions, which significantly increase their susceptibility to attrition. Overall, particle attrition is caused by mechanical, thermal, and chemical stresses, but their exact contribution and mechanism are unclear. In this work, five distinct experimental conditions and cold jet attrition tests were established to discern the contributions of different stresses to attrition and their impact on performance. Particle size versus strength was obtained for up to 1320 particles, and hotspot plots were used to reveal the relationship between the two. It was found that thermal stress was the dominant factor only during the pre-attrition phase, contributing 45 % to attrition. And then swiftly superseded by mechanical stress. Chemical stress emerged as the primary cause of attrition during the middle and late stages of the experiments, contributing up to 90 % of attrition. OC‘s strength typically ranged between 6 and 8 N without chemical stress and, conversely, dropped to below 1 N. Furthermore, chemical stress was found to induce an increase in particle volume and oxygen transport capacity, primarily achieved by reducing apparent density. The volume of particles can be enlarged by a factor of 1.56, and the oxygen release rate was increased from 4 % to 5.6 % under chemical stress. And a correlation was observed between apparent density and both attrition rate and strength.