GB1501620A - Cryogenic comminution - Google Patents

Abstract

1501620 Cryogenic comminution HENRY BALFOUR & CO Ltd 22 Oct 1975 [23 Oct 1974] 45934/74 Heading B2A Cryogenic comminution apparatus comprises a mill 2 fed by a right-angled V pair of tubes 3, 4 which include feed screws and serve as a cryogenic bath with controlled dwell time, either by varying speed or distance through the bath which is adjusted by varying the liquid level in the V-tubes. Material is initially broken up in a screw prebreaker 9 and delivered to a hopper 5 which feeds the tube 3. Cryogenic liquid {nitrogen) is maintained by a valve 20 and level controllers 21, 22. The tubes 3, 4 and mill 2 are mounted on insulating material. Ground material is conveyed via a conduit 25 to a receiver (not shown). Oversize is recycled via a conduit 27. Fines are separated at a separator 29. The temperature in the mill 2 is sensed by a sensor 32. Residence time in the bath 16 is adjusted by varying the speed of the conveyors 13, 14 in the tubes 3, 4. Pressure across the tubes 3, 4 is balanced by a duct 31, 31A. Tramp material e.g. wire reinforcement in tyres can be separated out if desired by means not shown. The level controllers 21, 22 control the static level prior to introduction of material and controller 22 the dynamic level when material is in transit. Each controller comprises a vertical capilliary tube 21B, Fig. 2, housed in a vertical limb 21A. The tube 21B is filled with a suitable gas via an inlet 37. Each tube has a bellows 21C controlling a switch 21D in an air or electrical line, and sensitive to pressure charges in the capillary tube. Thus when the level rises the vapour in the tube condenses resulting in a pressure drop so that the bellows 21C contact. The response time is reduced by passing relatively hot dry air or the like over the tube 21B.