The pressurised fluidized bed combustion (PFBC) of char from Australian black coals was studied, focussed on those coal/char properties that significantly affect combustion. To simulate the char combustion in UNSW's batch-fed PFBC rig, a mathematical model was developed that included detailed treatment of both char oxidation and secondary fragmentation. A sensitivity analysis of in-bed carbon loading to model input parameters ranked the coal-related parameters in decreasing order of importance as char reactivity, carbon/oxygen mole ratio consumed on the surface of a burning char particle in the bed and secondary fragmentation. These parameters were studied experimentally in our PFBC rig for five Australian black coals covering a range of Volatile Matter (VM) contents, at industrial PFBC conditions of 850°C, 1.6MPa and 0.9ms{sup}(-1). The intrinsic reactivity to oxygen of the PFBC chars was measured in a Pressurised Thermogravimetric Apparatus at 1.6MPa. Carbon monoxide was found to be the only product of char oxidation in PFBC. Two normal distribution functions were obtained to describe the secondary fragmentation in PFBC: the first function determined which particle broke up and the second predicted the size distribution of fragments. Using these measured coal-related parameters in our model, the results closely predicted the measured carbon loading in our bed at a different oxygen concentration, even though the parameters were determined at only one value of oxygen concentration. Model analysis revealed that, under PFBC conditions, external mass transfer controlled the combustion of large char particles ≥2mm, whereas the combustion of small char particles between 0.4mm and 0.9 - 2mm (depending on properties of the char such as intrinsic reactivity and pore structure) was controlled by both mass transfer and char oxidation. Char particle temperatures were predicted to vary significantly with differences in oxygen partial pressure, as occur in large-scale beds.
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