Date of Award
Master of Science
AN ABSTRACT OF THE THESIS OF BHASKAR BARIAR for the Masters of Science degree in Mechanical Engineering and Energy Processes presented on July 2nd, 2013, at Southern Illinois University, Carbondale. TITLE: WETTABILITY STUDIES AND ITS ROLE IN COAL AND QUARTZ DUST CONTROL. ADVISOR: Dr. Kanchan Mondal CO-ADVISOR: Dr. Y. P. Chugh This thesis presents the wettability studies conducted to determine the wettability characteristics of dust generated from different sections of typical coal seams from three Interior Basin coal mines for improved respirable coal and quartz dust (< 10μm) control. A modified form of film flotation was employed to determine absolute wettability (AW) which is a measure of the maximum wettability of a particular material in a given wetting fluid. AW was evaluated as a function of surface tension of the wetting fluid and surfactant concentration in the base wetting fluid which was water. Coal seam samples were found to be 89-96% wettable with water alone and increase in wettability was observed with reduction in the surface tension or increase in the surfactant concentration in the base wetting fluid. The surface tension of the fluid was reduced by the addition of predetermined amounts of methanol to water (0 to 1.5 wt %) or surfactant concentration (0.0005 to 0.005 wt %) in water. The effect of surfactant was evaluated by analyzing the overall effect on wettability obtained due to addition of surfactant in the wetting fluid in conjunction with the wettability results obtained from experiments aimed towards evaluating the alterations to the surface properties of the coal particles due to surfactant adsorption on these particles. A new technique, developed by Mondal and Chugh, was then used to evaluate wettability rates. Wettability rates were evaluated by identical wetting fluids used for estimating absolute wettability. It was found that 64-84% of the coal (depending on the coal sample source) was wetted in just 60 seconds. In addition, both the wettability and wettability rates were correlated with particle size, quartz and surface charge partitioning into the wetted and un-wetted fractions. Contrary to the popular belief that finer particles are difficult to wet, results from absolute wettability studies showed that larger fraction of the finer particles were wetted in water as compared to the coarser particles. On the other hand, it was found that the rate of particle capture by wetting and subsequent settling was higher for coarser particles. It was generally found that the quartz recovery was a function of the wettability of the coal sample. From the wettability rate studies, it was observed that the incremental quartz capture reached a maximum value within the first 20 seconds. Additional research should be conducted to assess wetting of different particle size coal and quartz dust. It is recommended that different types of surfactants be tested and additional characterizations should be developed for organic fraction recovery in the wetted fraction.
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