Development of advanced techniques for evaluating fine coal cleanability and froth flotation technologies

Separation performances obtained from column flotation technologies have been found to be superior to the characteristic flotation response curve generated from the traditional flotation washability procedures such as release and tree analysis. This phenomenon clearly indicates the inadequacy of the traditional flotation washability procedures. Thus, the main objective of this study was to develop a suitable process to characterize the ultimate flotation response of a fine coal sample, which can be utilized for a precise assessment of the cleaning potential of a coal and for an appropriate evaluation of the advanced flotation technologies.; A novel automated device using a batch-operated flotation column has been developed to obtain the ultimate separation performance and is referred to as Advanced Flotation Washability (AFW) analysis. The separation performances obtained from the AFW procedure were found to be superior to those obtained from the traditional flotation washability procedures such as release and tree analyses. To verify the maximum selectivity achieved by AFW analysis, an experimental program was conducted to obtain an enhanced flotation performance from multiple stage cleaning using continuously operating flotation columns. The resulting enhanced separation performances were found not to surpass the cleaning performance predicted from the AFW analysis, which is evidence that the AFW curve may represent the optimum flotation cleaning performance.; Based on this optimum performance, a new characteristic Flotation Index was derived, which provides a quantitative assessment of the ash and sulfur cleaning potential of a coal.; Utilizing the flotation index conception a comparative evaluation was conducted using three leading column flotation technologies, which utilize different types of bubble-particle attachment environments. One of the counter-current systems, which provides a near plug-flow flotation environment due to the presence of corrugated packing material in the cell, produced the best separation performance because of its ability to support an extremely deep froth zone. However, because of the absence of an air sparging system and, consequently, larger bubbles, the froth carrying capacity was the minimum. On the other hand, the carrying capacity achieved by a self air-inducing co-current system, which provides an intimate bubble-particle attachment environment characterized by an extremely high air fraction and ultrafine bubbles, was found to be the maximum.