Patent GB-501656-A (GB)
Title: Improvement in method of, and apparatus for, isolating minerals
IPC: B03B5/36
Filed: 1937-08-31
Abstract: 501,656. Wet separating. DU PONT DE NEMOURS & CO., E. I. Aug. 31, 1937, No. 23777. Convention date, Aug. 31, 1936. [Class 82 (ii)] [Also in Groups I and III] Minerals and gangue, e.g. coal and slate, are separated in a liquid immiscible with water und of intermediate specific gravity ; the separated fractions are withdrawn and scrubbed with water to remove separating liquid, and the wash water is separated, e.g. in one or more settling tanks, into a sludgy constituent and a liquid constituent, the liquid constituent being returned to the scrubbing step, and the sludgy constituent being treated, e.g. by further settling and distillation, to isolate the separating liquid. The mineral and gangue may'be wetted prior to the separating operation and the separating liquid'may be, for example, a halogenated hydrocarbon or mixtures of such substances with one another or with diluents such as kerosene, benzene, and naphthalene, or it may be for example mercury or antimony bromide. A long list of suitable organic compounds is given. The plant as shown in the Key Figure comprises a separating section 3 containing the separating liquid which is preferably covered with a layer of water into which the material is introduced, the construction and operation of this section being as described in Specification 501,658 ; a scrubbing section 4 as described in Specification 501,657 comprising screens on which adhering separating liquid is washed from the separated particles which are then discharged by conveyers in the casings 5 ; and means for recovering the washing water and the separating liquid. The separating and scrubbing sections are preferably hermetically sealed to prevent the escape of vapour. A preliminary separation of the liquid and sludge passing through the screens in section 4 is effected, as described in Specification 501,657, by means of a riffle plate and a settling chamber disposed below the screens, from which the liquids with the finest solids in suspension pass to a settling tank 6 from which clarified water is returned to the sprays in section 4. The sludge from the screens. 4 and the tank 6 passes to a separator 7 in which it settles in three layers; the upper, mainly water, being returned to the tank 6, the middle, mainly separating liquid, being passed to a storage tank 964, and the bottom layer going to a distilling apparatus 8 from which water and separating liquid are distilled to a condenser 9, cooler 95, and separator 96. From the separator the separating liquid is passed either to the storage tank 964 for used separating liquid or to a tank 963 which is supplied with fresh liquid. The settling tank 6 which receives the liquids and light particles from the base of the scrubbing section through a pipe 458 has a top 61, Fig. 23, a tubular member 610 which receives the pipe 458 and has openings 612 above the water level, a sump 621 sloping to a valved discharge pipe 620, a rotary rake 626, an overflow weir 631 forming the inner edge of a sloping launder 630, and a circular channel 640 suspended from the top of the tank and having a lip 641 just below the level of the weir 631 and pipes 642 projecting downwardly. The channel 640 functions as a scum gutter. A supply 624 of water is provided for dislodging sludge from the bottom of the sump. The sludge &c. from the scrubbing section and from the-tank 6 is passed by a pipe 713, Fig. 25, terminating in a tubular member 714 into the settling tank 7 at the top of which is a circular weir 716 with an interior baffle plate 718 to form a vapour seal. A series of valved openings 719 are provided at intermediate levels in the tank, all connected to a pipe 721, and below these is a pipe 723 having a liquid-tight ball joint 725 and a portion 726 which can be raised or lowered by rack and pinion mechanism. The material in the tank separates into three layers, an upper layer mainly water, part of which overflows the weir and part of which can be removed by the valved openings 719, an intermediate layer mainly organic separating liquid which is removed by pumping through the adjustable pipe 726, and a lower layer of sludge which is finally passed with remaining liquid through the valve 741 with the aid of water jets 754. This mixture of sludge, organic liquid, and water passes into a still 8 having a steam jacket between the walls 81, 82 and at 84, and openings 85 through which steam can be injected into the contents of the still. The water vapour and organic vapour pass out at 88 and the remaining solids are then discharged through the valve 811 with the aid of water from pipes 821. The vapours pass to the condensers, cooler, and separator as above described. The Specification also describes the apparatus for testing the proportions of heavy and light particles in the separated portions as set out in Specification 501,657. A list is given of other minerals, besides coal and slate, which may be treated by the process.