GB494153A - A new or improved process for the separation from liquids of solids or other liquids - Google Patents

Abstract

494,153. Electrostatic separation of impurities from liquids. BIBBY & SONS, Ltd., J., STURTEVANT ENGINEERING CO., Ltd., IBISON, A., and WAGNER, H. W. April 16, 1937, No. 10903. [Class 72] A process for separating from a liquid solid or liquid impurities contained in the liquid which are not precipitated, or are only slowly precipitated, if the liquid with the suspended particles of impurities is subjected to an electrostatic discharge, consists in adding to the liquid a loading material of such a nature that its particles coalesce with the particles of the impurities, and the liquid so treated is then subjected to an electrostatic discharge whereby the suspended particles are precipitated. The loading material may be liquid or solid. To lower the viscosity of the liquid treated the temperature may be raised or a liquid of lower viscosity added. The electrodes may be spaced about one and a half inches apart and a voltage between about 4,000 to 20,000 applied. The electric circuit may be interrupted or the current reversed or scrapers provided in order to remove the impurities from the electrodes. In cleaning lubricating oil from diesel engines about 6-10 per cent and preferably about 10 per cent of " activated earth " is added. The oil is heated to between 85 and 100‹ F. The voltage is 5,000. Again in the case of oil from oil-immersed electric switch gear about 10 per cent of " activated earth " is used. The voltage is 5,000 with electrode spacing one and a half inches and the temperature about 70‹ F. For the removal of lecithin from soya bean oil the loading material may be 0'5 to 1À0 per cent by weight of a dilute solution (33‹ Twaddell) of neutral sodium silicate, or 1 per cent by weight of a 10 per cent aqueous solution of ammonia, or 0À25 per cent of a 5 per cent aqueous solution of the wetting agent known under the Registered Trade Mark " Perminal." The potential difference used is 10,000 volts. In one form the apparatus used comprises an open metal tank 1 rectangular in plan and its floor shaped to form two hoppers 2 each fitted with a discharge valve. Suspended in the tank are the metal plates 4 which together with the tank form the earthed collecting electrodes. A second series of plates 5 are suspended between the other plates and insulated from them. The corners of both sets of plates are rounded. A pipe 9 introduces the liquid and another pipe 10 removes the liquid when purified. The impurities fall into the hoppers and are removed through the valves. The plates are of different length so that a line joining their lower edges follows the contour of the floor and are arranged so that the path of the liquid defined by them is a zigzag (Fig. 3). In a modified system the central plate may extend to the bottom of the tank and to the walls so that the liquid flows over its top edge. Liquid may be preheated in a header tank by means of electric heaters outside this tank and the treating chamber itself may have external heaters. The polarities of the electrodes may be reversed so that the impurities collect on the plates 5.