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Micro-CT-Based Approaches for Quantifying the Morphology of Pulverized Char Particles

Jorgensen, Scott, Singer, Simcha
Energy & fuels 2019 v.33 no.6 pp. 4826-4834
X-radiation, image analysis, micro-computed tomography, models, pulverized coal
Morphological analysis of pulverized coal char particles using two-dimensional (2-D) cross-sectional imaging has been widely employed, but its accuracy has not been adequately assessed. In this study, pulverized coal char particles are imaged in three dimensions (3-D) using high-resolution X-ray microcomputed tomography (micro-CT). Particle volume, macropore volume, and macroporosity are measured in three dimensions and analyzed as a function of distance from the particle center using averaging at each radial location. A technique for extracting each particle’s average wall thickness, another morphological parameter used for classification, is also presented based on micro-CT imaging. When applied to pulverized bituminous coal char particles, the micro-CT-based analysis revealed a similar spatial distribution of macroporosity among a population that would typically be classified as containing both group II (mixed porous-solid) and group III (dense) particles. Wall thicknesses determined by micro-CT were generally well predicted by a model representing the particles as thick- and thin-walled cenospheres. Comparisons between 2-D and 3-D techniques reveal significant differences because of the use of just a single cross-sectional image in 2-D approaches. A new method for estimating macroporosity from 2-D imaging, called the cylindrical stacking method, is proposed for cases in which the micro-CT analysis is not feasible.