GB962410A - A method and a device for withdrawing a liquid from, or adding a liquid to, a fibre pulp - Google Patents

Abstract

962,410. Expressing liquid from or adding liquid to paper pulp. BILLERUDS A.B., and SVENSKA CELLULOSA A.B. Aug. 30, 1962 [Sept. 15, 1961], No. 33287/62. Heading D2A. A mass of fibre pulp is made to flow through a passage having perforated side walls under the action of a pressure difference between and applied at the ends of the passage and liquid is expelled from or introduced into the pulp through the perforations in the side walls according to the pressure difference across the walls. The fibre pulp, which must have a minimum concentration of 5% by weight and preferably at least 15%, forms a coherent column of pulp from which liquid may be expelled substantially without loss of fibre through the perforations. Counter pressure means are required at the end of the passage and may be provided by a constriction or bend in the passage, by a conically shaped member disposed at the outlet or by connecting the passage to a pressurised reaction vessel. As shown, filtered pulp of e.g. 15% concentration from a rotary filter 2 is supplied through tube 5 to a screwfeeder 6 and pulp pump 7 which causes a cylindrical column of pulp to flow through a perforated or foraminous strainer tube 8 surrounded by a jacket 9 into which liquid is expelled from the pulp. The discharge of liquid from the pulp is controlled by a valve 11. The concentrated pulp passes to a mixer 14 and is disintegrated therein to pass into a pressurised boiler 16 for digestion with soda solution. In a modification (Fig. 2 not shown) a plurality of strainer tubes each with pulp feeder and pump are connected in series and water for pulp-washing is added to the pulp entering the final stage while the liquid expelled from the strainer tube of that and of each stage is passed to the preceding stage inlet for further washing. In a further modification (Fig. 3 not shown) a plurality of strainer tubes are connected in series to form a tower and water for pulp washing or liquid for chemical treatment may be introduced through the perforations of one strainer tube and expelled through those of the following tube. In a further modification (Fig. 4 not shown) high pressure washing water is introduced at the point where the pulp is disintegrated to flow counter current to the pulp column the water being extracted through the strainer tube.