GB1401493A - Grinding apparatus for vegetable or fibrous material - Google Patents

Abstract

1401493 Disc mills R B REINHALL 25 Sept 1972 [28 Sept 1971] 44148/72 Heading B2A A disc mill 18 comprises discs 22, 28 within a casing 20, a primary steam source to maintain superatmospheric pressure in the casing and a control valve 34 in the produce outlet 32 of the casing, which valve is controlled by a device 38, 40 sensing and acting in response to variations in pressure in the casing 20 caused by the introduction of secondary steam through a separate conduit 58. Raw material, e.g. wood chips is fed from a hopper 10 by a screw 12 into a pressurised receptacle 14 which is supplied with the primary steam at a pressure P 1 via a regulator 56. Material is supplied from the vessel 14 via a screw feeder 16 to the disc mill 18 which may include a fixed disc 22 and a rotating disc 28. Alternatively both discs may rotate or contrarotate, and may have the usual grooves/projections on their surfaces. The outlet 32 is connected via a conduit 50 to a steam separator 52. The secondary steam at a pressure P 2 is supplied to the casing 20 via a regulator 60 P 2 < P 1 . In operation, if valve34 tends to block with produce the mill pressure will rise to P 1 , actuating the regulator 38 and thus opening valve 34. The pressure then falls back to normal, i.e. P 2 . Should too much produce be discharged the corresponding fall in pressure is sensed and the valve closes until pressure P 2 is restored The secondary steam supply thus serves always to ensure a desired pressure at which discharge of produce is possible.