GB789841A - A method and apparatus for compacting finely divided solids - Google Patents

Abstract

789,841. Forming pellets from finely divided solid material. DOW CORNING CORPORATION. Dec. 28, 1955 [Jan. 10, 1955], No. 37148/55. Class 87(2). [Also in Group XXX] A method of pelletising a finely divided solid, e.g. synthetic silica or carbon black comprises compressing the solid so that substantially all the air between the particles is expelled, subsequently compressing the solid to a bulk density of at least 4 pounds per cubic foot and thereafter tumbling the compressed solid for a time sufficient to form pellets which are substantially dust free. The material 10 to be pelleted or granulated is fed from a hopper 11 on to a lower conveyer 13. The front wall of the hopper is cut away at 14 and material passes through the opening and comes into contact with an upper conveyer 12. The conveyers move together over a support platform 42 and edge rollers 21 and runners 18 are arranged so that the edges of the upper conveyer are held against the lower conveyer, Fig. 4b, to prevent the escape of the material. The upper conveyer 12 is made of air-permeable material, e.g., canvas, and as it passes under rollers 22, 23 air is expelled from between the particles and escapes through the conveyer. The rollers 22, 23 also prevent billowing of the conveyer as it approaches squeeze rollers 43, 44, which also drive the conveyers. The de-aerating pressure may be applied by bars attached to the runners 18 at positions progressively nearer the support platform 42, or by a perforated plate 46, Fig. 4b, above the upper conveyer appropriately sloped, being rigidly or pivotally mounted and adjustable in the latter case. The edges of the upper conveyer 12 may be headed at 47 so as to be guided by the runners 18. The squeeze rollers 43, 44 should be of different diameters, e.g., the diameter of the lower roller 43 twice that of the upper roller 44, and their distance apart is adjustable, by means of a nut 40, for the material to be compressed to the required bulk density. Preferably at least one of the rollers is rubber coated. The compressed particles are removed from the conveyers by scrapers 24, 25 and fall through a shoot 26 into a tumbler 27. A roller 30 gives a better scraping angle to the upper conveyer and a roller 31 prevents it from flapping. The bearings for the idling roller 39 at the other end of the conveyer 12 are carried in posts 37 which are slidable and can be adjusted in position by screws 34, and the bearings for the idling roller of the lower conveyer are slidable in the frame and adjustable by screws 33 ; thus the tension of the conveyers is adjustable. Modifications are mentioned whereby the material is de-aerated by reciprocating one conveyer relatively to the other, and whereby the conveyers may be vertical.