Image processing techniques for three-dimensional analysis of multiphase multisize packed particle beds using x-ray tomography.

摘要

Characterization and analysis of multiphase particulate systems is important in the mineral processing industry. To analyze the multiphase characteristics in three dimensions (3D), x-ray computed tomography is now available and has been applied for the analysis of particle size, shape, liberation, etc. Based on the dissertation research, three contributions have been made in the analysis of a multiphase packed particle bed as follows: 1) Improved image segmentation of high density, fine particles using feature- based segmentation. 2) Determination of particle size distribution by modified marker-controlled segmentation. 3) Correction for partial volume effect (PVE) and the determination of exposed grain surface area in flotation products.;The first and the most important step in analysis of the three-dimensional multiphase mineral phases is image segmentation, which is the partitioning process to separate the image into objects of interest. In order to identify the particle boundaries of high density or fine particles, feature-based segmentation instead of traditional thresholding-based segmentation is applied to improve the segmentation accuracy based on the particle characteristics instead of only intensity information.;Moreover, modified marker-controlled segmentation has been developed to segment multisize particles since it is strongly needed for the purpose of saving time and analysis of multisize particles at a plant site. With reduction in scanning time by high- speed x-ray tomography and development of modified marker-controlled segmentation, analysis and characterization of multisize particles is possible and can be finished within minutes.;Another problem in analysis of multiphase particle populations is the partial volume effect (PVE), which can limit quantitative analysis. In order to overcome this problem, a correction based on the computation of boundary characteristics is presented to guide the identification of the correct boundaries for high-density mineral phases. With this new approach, determination of the exposed grain surface area is discussed and evaluated with respect to the analysis of coarse particle flotation separation. The results show that excellent coarse particle flotation (20x35 mesh) can be achieved with HydroFloat technology if the exposed grain surface area exceeds 1% of the total particle surface area. Such analysis has not been reported previously in the technical literature.