The mineral processing industry has commonly utilized hydraulic separators throughout history for classification and gravity concentration of various minerals. More commonly referred to as hindered-bed or fluidized-bed separators, these units make use of differential particle settling rates to segregate particles according to shape, size, and/or density. As with any equipment, there are inefficiencies associated with its operation, which prompted an industry driven research program to further evaluate two novel high-efficiency hindered bed separators. These units, which are commercially called the CrossFlow separator and HydroFloat separator, have the potential to improve performance (separation efficiency and throughput) and reduce operating costs (power consumption, water and reagent usage). This thesis describes the results of recent laboratory and pilot-scale tests conducted with the CrossFlow and HydroFloat separators at several locations in the minerals and coal industries. Details of the testing programs (equipment setup, shakedown testing and detailed testing) associated with four coal plants and two phosphate plants are summarized in this work. In most of these applications, the high-efficiency units proved to provide a higher quality product at reduced costs when compared against the performance of conventional separators. As a result of this test work performed in this study, a full-scale CrossFlow separator is being installed at an industrial site. The separator is an integral part of an ultra-fine phosphate recovery system at a Florida processing plant. The unit will be used to classify the +400 mesh material prior to column flotation. The successful implementation of the ultra-fine phosphate recovery system will increase industry profits by the millions of dollars in addition to reducing tailing impoundments and energy requirements. / Master of Science

A better understanding of several mineral processing devices and applications was gained through studies conducted with mathematical analysis tools. Linear circuit analysis and population balance modeling were utilized to remedy inefficiencies found in a number of popular mineral processing water-based unit operations. Improvements were made in areas, including unit capacity and separation efficiency. One process-engineering tool, known as linear circuit analysis, identified an alternative coal spiral circuit configuration that offered improved performance while maintaining a reasonable circulating load. In light of this finding, a full-scale test circuit was installed and evaluated at an existing coal preparation facility. Data obtained from the plant tests indicate that the new spiral circuit can simultaneously reduce cut-point and improve separation efficiency. A mathematical population balance model has also been developed which accurately simulates a novel hindered-bed separator. This device utilizes a tangential feed presentation system to improve the performance of conventional teeter-bed separators. Investigations utilizing the mathematical model were carried out and have predicted solid feed rates of up to 71 tph/m² (6 tph/ft²) can be achieved at acceptable efficiencies. The model also predicts that the unfavorable impact of operating at low feed percent solids is severely reduced by the innovative feed presentation design. Tracer studies have verified that this system allows excess feed water to cross over the top of the separator without entering the separation chamber, thereby reducing turbulence. A hindered-bed separator population balance model was also developed whose results were utilized to improve the efficiencies encountered when using a teeter-bed separator as a mineral concentrator. It was found that by altering the apparent density of one of the feed components, the efficiency of the gravity separation could be greatly improved. These results led to the development of a new separator which segregates particles based on differences in mass after the selective attachment of air bubbles to the hydrophobic component of the feed stream. Proof-of-concept and in-plant testing indicate that significant improvements in separation efficiency can be achieved using this air-assisted teeter-bed system. The in-plant test data suggest that in some cases, recoveries of the plus 35 mesh plant feed material can be increased by more than 40% through the application of this new technology. / Ph. D.