Motion and\nCombustion Behavior of Single Char Particle\nin Oxy-Fuel Fluidized Bed: Experimental and Modeling Studies

Oxy-fuel\nfluidized bed combustion is a leading carbon\ncapture,\nutilization, and storage technology that is gaining considerable attention\nfrom both academia and industry. The combustion of char particles\nin a fluidized bed is intricately linked to their motion and chemical\nreactions, with variations in heat transfer, mass transfer, and reaction\nrates across different locations. However, many theoretical studies\non single-particle combustion assume a uniform emulsion phase, overlooking\nthe influence of particle movement on combustion, which will greatly\nreduce the accuracy of the combustion model, especially in oxy-fuel\ncombustion. In this study, we conducted combustion tests on char particles\nin a visualized fluidized bed reactor and systematically assessed\nthe effects of various operating conditions on combustion. A combustion\nmodel for a single char particle in a fluidized bed was developed,\nconsidering forces, movement, gasification, and heat and mass transfer.\nThe error of model was within 15% when compared to experimental results.\nWe quantitatively analyzed the relationship between particle movement\nand periodic temperature changes and investigated the impact of various\nparameters through sensitivity analysis. The results show that changes\nin atmosphere and bed temperature minimally affect particle motion,\nwhereas particle density, fluidization number, and size significantly\ninfluence it. Biomass char floats on the bed surface for about 30–40%\nof the combustion process, while bituminous coal char primarily remains\nin the emulsion phase. High oxygen concentrations or bed temperatures\nsignificantly enhance char gasification in O<sub>2</sub>/CO<sub>2</sub> atmosphere. The gasification conversion ratio is more closely related\nto the average char temperature than to peak temperature. Temperature\noscillations in char particles rise with oxygen concentration and\nfluidization number but decrease with bed temperature and particle\nsize.