Osterberg’s E-tower was invented by Daniel Osterbergof California, patented in 1984 (US #4,451,359), and marketed as the Quick Gold Separator. The device causes black sand to fluidise and particles to hover. For ‘hovering’, the water velocity has to slackenupwards – impossible in a cylinder is of uniform diameter. Slackening is by the water escaping from the constricted space in the flow distributor. If a teetered bed E-tower then hovering is accompanied by hindered settling in the teetering fluidised bed, displacing lighter particles upward. The author suggests that Osterberg’s device is amultiple E-tower with many rising columns jetting upward,each decelerating once free of the flow distributor.Osterberg’s E-tower seems capable of achieving highpercentage fine gold recovery and merits testing.
Operation
Clean water is introduced into a 4-inch diameter column near its base, at 2 gallons/minute. Once inside, the water passes through a distributor in a sequence designed to create a non-turbulent up-flow:
- through a perforated plate secured to a bottom ring; then
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- through a disc of felted, fibrous synthetic polymer; then
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- through a screen with openings so fine that upward flow issubstantially unaffected in its lateral uniformity; and finally
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- through a coarse screen.
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Screened concentrate is spooned into the tower from above. The water rises with enough velocity to non-turbulently fluidise the concentrate yet without ejecting particles with the overflow of washwater.The upwelling water must decelerate for black sand to hover as a fluidised bed, the deceleration being due to the rising non-turbulent plumes of wash water have more width once free of the flow distributor, suggest the device is nota teetered bed settler as hindered settling seems minor. The patent suggests the fluidised bed be stirredgently at the start to encourage gold to fall to the bottom. The upper portion of the fluidised bed is deemed to be depleted of gold and is siphoned off as tailings. The dense gold particles remain behind and more concentrate is spooned into the top of the column. After processing many spoonfuls of material, the enriched gold concentrate is siphoned off from the device.
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OSTERBERG's E-TOWER
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