Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F1/00—Wet end of machines for making continuous webs of paper
  • D21F1/66—Pulp catching, de-watering, or recovering; Re-use of pulp-water
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
  • D21D5/00—Purification of the pulp suspension by mechanical means; Apparatus therefor
  • D21D5/26—De-aeration of paper stock

Definitions

• a suspension which may have a fibre content of 3 - 10 % or more, is diluted with about 10 parts of water per part of suspension from a conduit 18 and then passes a pump 2.
• This main flow subsequently passes a screen 3 (where coarser screened material is taken to a further screen 3' , from which screened-off material leaves the system via a conduit 17 and from which accepted fibres return to the conduit 18).
• the major portion of the diluted suspension which is the accept from the screen 3 continues to a hydrocyclone separator 4, from which the accept (which is the main portion) * continues to a deaerator 5 which may be one of the mentioned, known structures.
• the reject from the hydrocyclone separator 4 is taken via a pump 14 to a further hydrocyclone separator 4 1 , the accept of which is returned to the conduit 18 and the reject of which is further cleaned or separated in a third hydrocyclone separator 4" after having passed a pump 15.
• the refuse or discard from all three hydrocyclone installations leaves the system via the conduit 16.
• the suspension going to the deaerator 5 has now been cleaned from impurities (contraries) and is suitable for the production of paper or pulp semi-finished products after de- aeration has taken place.
• a pump 6 conveys the suspension to the head box 7 from which it is laid out on the wire in the schematically shown paper machine 8.
• the pump 6 is controlled e.g. by the pressure in the head box 7, via the indicated control line 22 and that with the aid of this control a minor, vari ⁇ able percentage of the flow to the pump 6 will be mixed, via the conduit 13, with the recirculating water intended for mixture in the conduit 18.
• the initial object of the invention is therefore to de- crease the number of deaerators in paper machines or the like, where the suspension is simultaneously supplied from two or several systems.
• a starting point of the invention i.s thereby the realization that it is not necessary to deaerate the sus ⁇ pension, which is purified, cleaned and ready for paper manu- facture, if it is instead ensured that the constituents there ⁇ of do not have too high an air content before dilution.
• the inventive concept is based on the circumstance that the three forms in which air may be present form "comir-unica- ting vessels" to a certain extent. This makes it possible to mix a smaller amount of air-containing suspension with a larg ⁇ er amount of extremely air-impoverished liquid, where a major portion of the dissolved air has also been removed. If these two are subsequently mixed well, the air which is free and that which is tied to the fibres in the minor portion of the suspension will substantially completely go over into dis ⁇ solved form in a state of equilibrium. In accordance with the invention it is then possible to eliminate deaeration of the suspension, if the dilution water is deaerated to a suffi- ciently high degree instead.
• a deaerator 25 in the white water stream 12 coming from the paper machine has been inserted in the embodiment instead.
• a pump 26 urges water therethrough, and to retain the advan ⁇ tage, e.g. described in the Swedish Patent Specification No. 224 271 with a definite pressure reference 11 to all parts of the plant there is a bypass conduit 27.
• the 'deaerator 25 must provid somewhat more effective deaeration than the deaerator 5 according to Figure 1, since it must eliminate not only free air present, but also a portio of the air dissolved in the water.
• the increased demands have here been compensated, at least partially, by deaeration takin place in substantially pure water instead of in a suspension.
• each of the screens 33, 33' ,33" with the respective associated hydrocyc ⁇ lone separator 4, 4 1 4" replaces the combination illustrated in Figure 2, of the series-coupled screens 3, 3 1 and hydro ⁇ cyclone separators 4, 4* 4", the latter being coupled in series and with a pump (14,15) between each hydrocyclone separator.
• hydrocyclone separator ' also and preferably designates a hydrocyclone separator unit having several hydrocyclone separators coupled in parallel.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Paper (AREA)
• Polymerisation Methods In General (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20345395

Family Applications (1)

Country Status (6)

Cited By (5)

Citations (4)

• 1981
  • 1981-12-30 SE SE8107851A patent/SE425808B/sv unknown
• 1982
  • 1982-12-14 WO PCT/SE1982/000426 patent/WO1983002293A1/en not_active Application Discontinuation
  • 1982-12-20 PT PT76007A patent/PT76007B/pt unknown
  • 1982-12-22 IT IT24912/82A patent/IT1153689B/it active
  • 1982-12-23 GR GR70167A patent/GR77817B/el unknown
  • 1982-12-28 PL PL23979982A patent/PL239799A1/xx unknown

Patent Citations (4)

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