3D shape and size characterization of micron-sized coal particle with XRCT and SH

Abstract

The shape and size of solid fuel particles are significant parameters in combustion process, and have attracted broad attentions in simulation and experiment studies. In this study, X-ray computer tomography (XRCT) and spherical harmonics (SH) were introduced and combined to conduct accurate morphology characterization of micron-sized coal powder in three dimensions (3D) with purpose of providing references for morphology characterization, size measurement, and modeling of solid fuel particles. The shape parameters including volume, surface area, sphericity index, specific surface area, enlongation index, and flatness index, and the size parameters including diameter of volume equivalent sphere, three principal dimensions, and sieve size, were obtained with SH expansion. Validation on standard geometries demonstrated the accuracy of the method under the SH degree N ≥ 20, with errors for volume, surface area, and sieve size within 1 %, 3 %, and 2.5 %, respectively. These parameters were analyzed statistically to reveal the morphological characteristics of micron-sized coal powder. The Zingg diagram indicated that nearly 60 % of the coal powder particles are nearly spherical. Comparison among 3D size, 2D size, and sieve size implied that characterizing with 2D size may overestimate the fineness of coal powder. Although there was a variance in the particle size distribution, it was demonstrated that there exists a strong linear relationship between the 3D size, 2D size, and sieve size. The method could serve as a functional auxiliary tool for fuel particle research.