EXAMPLE m The liquid overflow from the system in Example 11 containing 0.09 troy ounces per ton gold was returned to the centrifuge under the conditions of Example 11 except that the centrifuge speed was increased to 300 RPM. The products from the centrifuge were as follows in Table III. TABLE 111 Nozzle %Total %Total Ratio Gold Solids Gold2Solids H (retained) 15.08 11.60 121.30 G (retained) 5.78 4.45 121.30 F-B (retained) 6.85 6.85 1:1.00 H-B 27.18 27.46 120.99 Overflow 34.20 38.00 L:ore processing equipment,0.90.Insufficient solids were present in the centrifuge to indicate beneficiation in the nozzle discharge. However, the centrifuge residues in proximity to nozzles H and G indicated a 30 per cent beneficiation. No beneficiation was evident in the residues at ...view middle of the document...
Also, the feed impeller can be centrally located at the bowl end remote from the wide end. Centrifugal force created by rotation of the centrifuge substantially overcomes the effects of gravity and centrifuge disposition is therefore not critical. The location of the feed impeller at the bowl narrow end remote from the wide end can provide the advantages of increasing centrifugal forces with reduced longitudinal slurry flow velocities as the wide end of the bowl is reached such that the colloidal and near-colloidal solids remaining in the slurry obtain optimum effects from centrifugal forces with maximum retention time.
FIG. 6 illustrates such an embodiment of my invention in which the frusto-conical bowl is disposed with the wide end upwards. The bowl includes a base plate 141 and a cover plate 143 and is journaled for rotation in bearings 142, 144 and rotated by shelf 146 in a manner described with reference to my embodiment described in FlGS. l-4. Impeller 148 receives a slurry from feed conduit 150 and impels the slurry tangentially outwardly towards the periphery of the centrifuge. Nozzles 152, which are disposed circumferentially equispaced about the periphery of the bowl, are arranged in a plurality of axially spaced apart planes and each axial set of nozzles S, T, X, Y is separated from the adjacent set by a baffle 154. Baffle 156 functions as an overflow ring or weir and, in conjunction with the liquid discharge from nozzles 1S2, rate of rotation of the centrifuge and rate of slurry feed, controls the depth of liquid in the centrifuge bowl. The surface of the liquid is designated by numeral 158. Longitudinal vanes 160 angularly impel the liquid at substantially the centrifuge rotational speed.
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