UBC Theses and Dissertations

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UBC Theses and Dissertations

Dense particle concentration using thin channel flow with riffles George, Danny


As supplies of valuable minerals become scarcer and demand increases, the mining industry must develop more efficient and effective methods to recover these minerals from ore. Various gravity separation methods are extensively used in the industry for concentration of gold, platinum group metals (PGMs), mineral sands, chromite, tin, tantalum, tungsten, iron ore, cobalt and many other metals and minerals with sufficient differences in density. The Falcon enhanced gravity separator is one example of a semi-batch enhanced gravity separation device that uses centrifugal force to enable liberated precious metal recovery within grinding circuits and from placer deposits. During run cycle, concentrator accepts feed continuously, heavy particles are retained in the riffled section of the unit’s bowl, and concentrate is produced during periodic rinse cycles by water jets. Limited research has attempted to understand particle behaviour in the riffled section of the Falcon enhanced gravity separator, and little is known about the effect of design and operating parameters on the unit’s concentration efficiency. This thesis focuses on studying particle behaviour in the riffled section of the Falcon gravity separator’s bowl to recover the highest fraction of heavy particles. An open thin channel setup was built to emulate a cross-section of Falcon gravity separator’s riffled section. Testing was conducted on the effects of riffle designs, inclination angles, and flow rates on particle behaviour. This study shows the need and value of improving the gravity separators' bowl geometry, which would significantly benefit heavy retention capabilities of this equipment. Two experimental setups using a centrifugal pump and a peristaltic pump were developed to test 9 riffle designs over 4 flow rates and 3 inclination angles resulting in 99 distinct experimental cases. Semi-elliptical designs coupled with lower inclination angles and flow rates lead to higher heavy particle retention in riffles. This considerably improved particle recovery rates of the system possibly due to its ability to expel light particles from the riffles while pushing the heavy particles downward. Observations of particle behaviour in this study can serve as a foundation for study on Falcon enhanced gravity separator and any gravity separation devices using engineered riffles.

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