| Description |
Fine coal filtration and dewatering are of great importance to the coal industry due to the significant impact in the quality, shipping, and handling of clean coal. High moisture content in the clean coal product reduces its heating value, increases costs, and reduces the coke yield in the case of metallurgical coal. In this regard, it is of significant importance to improve our fundamental understanding of water removal from the pore network structures present in filtration cakes. This thesis research presents the results obtained from the analysis regarding fluid flow through packed particle beds such as those occurring during filtration in an effort to expand the studies of particle characterization and its influence on coal dewatering. The study shows the importance of high resolution x-ray microtomography (HRXMT) as an important analytical tool for the three-dimensional study of particle beds. The multiphase flow and dewatering that occurs during fine coal filtration is described, and important factors that influence the efficiency of filtration, including the particle size distribution, pressure drop, shape, and wetting characteristics of the coal particles are considered. The experiments are designed to simulate the process of coal filtration using the Lattice-Boltzmann methodology, and identify the conditions that lead to the improved water removal and moisture reduction. The thesis and research reported herein demonstrate how HRXMT and the Lattice-Boltzmann Method (LBM) can help in the short-term prediction and understanding of water removal from the pore network structures present in coal filtration cakes. Based on the analysis of HRXMT images, it is shown that the pore network structure has a significant influence on the retention of water in the filter cake. Narrow capillaries were found in the filter cakes with hydrophilic particles, while wider capillaries were mostly found in the filter cakes with hydrophobic particles. In addition, tests with different pressure drops were performed. Although the pore network structure analysis showed that the capillaries were narrower at higher initial pressures, the increase in pressure drop decreased the amount of water retained in the filter cake. The pressure drop increase helped overcome the capillary forces that retain the water in the filter cakes. |
