Patent GB-1068296-A (GB)
Title: Method and apparatus for particle segregation
Inventor: BURDYN RALPH FRANCIS
IPC: E21B21/06
Filed: 1963-10-22
Abstract: 1,068,296. Centrifugal separators. MOBIL OIL CORPORATION. Oct. 22, 1963, No. 41718/63. Heading B2P. An apparatus for effecting selective particle segregation in a liquid mixture containing particles of varying densities and/or sizes comprises a stationary vessel 10 provided with a pressure-tight chamber 11 to which the mixture is fed through a conduit 12, a hollow cylinder 24 having a number of openings 25 and supported and rotated within the chamber by means of a rotary shaft 30 provided with openings 35 and with a conduit or bore 34 for withdrawing a portion of the mixture containing relatively light or fine particles from within the cylinder 24, and a conduit 14 for withdrawing another portion of the mixture containing relatively heavy or large particles from within the chamber 11 around the cylinder 24. The vessel 10 may be arranged horizontally or it may be inverted from the position shown. It is closed by a member 20 in which the shaft 30 is supported in ball bearings 43, 44 the shaft being driven through belt and pulley 52, 53 by an electric motor. Packing 50 and leakage drain holes 51 are provided. The shaft 30 may be formed integrally with the top of the cylinder 24 or it may extend through the bottom of the vessel 10. The openings 25 may be in the form of longitudinal slots or the cylinder 24 may be of sintered metal. The cylinder has secured to it a number of partitions 33 dividing the annular space around shaft 30 into a number of separate compartments. In a modification, the partitions are dispensed with. The apparatus may be used for the separation of solids of different densities and/or sizes contained in a liquid and the segregation of uranium isotopes, in suspenpension in a liquid. The operation of the apparatus is described in connection with the treatment of contaminated drilling fluids used in oil well drilling. The drilling fluid has the coarse cuttings removed therefrom by screening and is introduced into the chamber 11 where undesirable submicron clay particles have to be separated from the bulk of the drilling fluid and from barite particles (usually greater than 1 micron in diameter) which are used as weighting material for the drilling fluid. Once the chamber 11 is filled, the perforated cylinder 24 is rotated thereby establishing at its surface a cylindrical boundary layer in which the particles are subjeced to centrifugal force. At the same time the particles are subjected to an inwardly, radially acting force due to the flow of part of the fluid through the perforations 25 caused by the difference in pressure between the outside and the inside of the cylinder 24. The clay particles being of lower density are entrained with that part of the fluid inside the cylinder 24 through the perforations 25 and evacuated through the hollow shaft 30 and conduit 41 while the heavier barite particles, on which centrifugal action is greater, are repelled from the surface of the cylinder 24 and removed from with the remainder of balls of the fluid through the conduit 14. To avoid attaining too high a viscosity of the fluid containing the retained barite, water may be added to the drilling fluid prior to, or after, its introduction in the chamber 11.