EP1108084A1 - Tamisage de suspensions fibreuses - Google Patents

Tamisage de suspensions fibreuses

Info

Publication number
EP1108084A1
EP1108084A1 EP99930090A EP99930090A EP1108084A1 EP 1108084 A1 EP1108084 A1 EP 1108084A1 EP 99930090 A EP99930090 A EP 99930090A EP 99930090 A EP99930090 A EP 99930090A EP 1108084 A1 EP1108084 A1 EP 1108084A1
Authority
EP
European Patent Office
Prior art keywords
fraction
fibers
outlet
inlet
screen
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP99930090A
Other languages
German (de)
English (en)
Inventor
Börje FREDRIKSSON
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Valmet AB
Original Assignee
Valmet Fibertech AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Valmet Fibertech AB filed Critical Valmet Fibertech AB
Publication of EP1108084A1 publication Critical patent/EP1108084A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • 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
    • D21D5/02—Straining or screening the pulp

Definitions

  • This invention relates to separation of a fiber fraction from a liquid containing fibers and small particles.
  • the treatment is carried out in several steps, at which the process water is supplied and drained.
  • the papermaking pulp is transported as fiber suspension at a pulp concentration of 3 to 4 % from the pulp mill to the paper mill.
  • the process water in the paper mill thus, originates mainly from the pulp mill.
  • the surplus water from the papermaking is re-used later on at the pulpmaking. This implies that at the making of pulp and paper very great amounts of water are used which mainly circulate in the manufacturing process. From this complicated process results totally a small surplus of water, which must be cleaned before it can be discharged to the recipient.
  • Inreased re-circulation of water in the mill results in an increased build-up of contaminations in the process.
  • contaminations such as size lumps, particles of printing ink, ash and other matter (dispersed or solved) affect the process negatively. Even if it was possible to remove a large portion of the heavily contaminated process water, it is normally not defensible economically, because it often contains too many prime fibers.
  • Another object of the present invention is to increase the fiber separation efficiency of liquor screens in chemical pulp mills. These screens separate fibers from the waste liquor, before it is to be combusted. The separation efficiency of these screens is often much too low, especially in the case of short-fibrous hardwood pulps.
  • Fig. 1 is a flow chart showing an embodiment of the invention
  • Fig. 2 shows the effect of re-circulation of fibers according to the invention.
  • Fig. 1 The embodiment shown in Fig. 1 comprises a conventional screen means 1 with an inlet 2 and a first outlet 3 for a first fraction and a second outlet 4 for a second fraction. There is further a return line 5 with a central valve 6 between the second outlet 4 and inlet 2.
  • Fig. 1 the volume flow is indicated by the following definitions:
  • V c return flow
  • a liquid which can be process water containing fibers and contaminations, is fed as inject (Vj) through the inlet 2 to the screen means 1.
  • the liquid is allowed to flow along a screen member with screen apertures whereby a first fraction (V f - V r ) passes through the screen apertures and is taken out through the first outlet 3, and a second fraction (V r - V c ), which does not pass through the screen apertures, is taken out through the second outlet 4.
  • the first fraction (V f - V r ) contains mainly small particles in the form of dispersed contaminations and fine material from the papermaking pulp
  • the second fraction (V r - V c ) contains mainly long usable fibers.
  • the fiber concentration of the ingoing liquid is very low and thereafter increases along the screen member during the course of fractionation. This implies that the strength of the fiber network increases much along the screen member, from the inlet to the outlet for concentration fibers.
  • the energy supply from the rotor of the screen produces turbulence, which breaks up the weak fiber network at the beginning of the screening zone, which results in deteriorated separation of fibers.
  • the strength of the fiber network is much higher, because the fiber concentration has been multiplied, and the efficiency of the separation process is high.
  • the fiber network formed on the surface of the screen member due to the flocculation tendency of the fibers has a very important role in the separation mechanism. It is, thus, not only the apertures of the screen member which separate the fibers from the liquid.
  • the concentration of this fraction can be increased at the inlet end of the screen member.
  • the flow of the second fraction preferably is increased 2-5 times, and 50 - 80% of this fraction is recycled to the inlet.
  • the differences in concentration decrease strongly along the length of the screening zone with the help of the long fiber re-circulation according to the invention. This renders it possible to optimize the supplied de-flocculation energy along the screening zone so that the efficiency of the process increases, i.e. it is thereby possible to substantially decrease the share of long usable fibers in the first fraction.
  • An increased fiber concentration in the ingoing liquid increases the network formation in the ingoing fraction, and the probability that network forming fibers shall pass through the apertures of the screen barrier decreases.
  • Fig. 2 shows by means of a theoretical model based on mill data the effect of recirculation of a varying portion (V c ) of the second fraction (V r + N c ) to the inlet when the totally separated flow is 5 and 10 %, respectively.
  • the flow division (FS V/ V f ) is 0,05 and 0,10, respectively. It appears from Fig. 2, that it is possible to increase the efficiency of the recovery of usable fibers from about 80 % to about 90 % by using a re-circulation factor (CF) of 3-4.
  • the fiber concentration in the inlet has simultaneously trebled from 0,2 to 0,6.
  • the invention can also be used for increasing the efficiency of liquor screens in processes for the production of chemical pulp.
  • Liquor screens are used, for example, in a sulphate mill for recovering fibers from black liquor before its combustion.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Paper (AREA)
  • Separation Of Solids By Using Liquids Or Pneumatic Power (AREA)

Abstract

Cette invention concerne un procédé qui permet de séparer par tamisage une fraction fibreuse d'un liquide contenant des fibres ainsi que des particules de petite taille. La séparation se fait en faisant s'écouler le liquide entrant le long d'un élément tamis comportant des ouvertures de tamisage. L'écoulement se fait depuis une entrée (2) vers une première sortie (3) pour une première fraction passant à travers les ouvertures du tamis, et vers une seconde sortie (4) pour la seconde fraction ne passant pas à travers ces ouvertures. 50 à 80 % du débit de la seconde fraction sont renvoyés de la seconde sortie (4) vers l'entrée (2) afin d'accroître la concentration des fibres formant un réseau dans le liquide entrant.
EP99930090A 1998-08-26 1999-06-09 Tamisage de suspensions fibreuses Withdrawn EP1108084A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
SE9802870 1998-08-26
SE9802870A SE9802870L (sv) 1998-08-26 1998-08-26 Silning av fiberhaltiga suspensioner
PCT/SE1999/001003 WO2000012811A1 (fr) 1998-08-26 1999-06-09 Tamisage de suspensions fibreuses

Publications (1)

Publication Number Publication Date
EP1108084A1 true EP1108084A1 (fr) 2001-06-20

Family

ID=20412375

Family Applications (1)

Application Number Title Priority Date Filing Date
EP99930090A Withdrawn EP1108084A1 (fr) 1998-08-26 1999-06-09 Tamisage de suspensions fibreuses

Country Status (7)

Country Link
EP (1) EP1108084A1 (fr)
JP (1) JP2002523651A (fr)
AU (1) AU750899B2 (fr)
BR (1) BR9913254A (fr)
CA (1) CA2341535A1 (fr)
SE (1) SE9802870L (fr)
WO (1) WO2000012811A1 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6649068B2 (en) 2000-06-14 2003-11-18 Andritz Inc. Filtration of pulp mill liquids
DE10125975A1 (de) * 2001-05-29 2002-12-05 Voith Paper Patent Gmbh Verfahren zur Abscheidung von Anteilen aus einer Faserstoffsuspension

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE327328B (fr) * 1967-05-17 1970-08-17 G Holm
US4543181A (en) * 1982-12-16 1985-09-24 Kamyr, Inc. Medium consistency flat disk pressure screen
US4619761A (en) * 1984-12-20 1986-10-28 Koppers Company, Inc. Method for screening or fractionation
SE8701423L (sv) * 1987-04-06 1988-10-07 Kamyr Ab Foerfarande vid framstaellning av fiberhaltig massa med olika raamaterial
JP3065202B2 (ja) * 1993-10-20 2000-07-17 石川島播磨重工業株式会社 古紙パルプの選別方法および装置

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO0012811A1 *

Also Published As

Publication number Publication date
AU4669899A (en) 2000-03-21
WO2000012811A1 (fr) 2000-03-09
SE9802870D0 (sv) 1998-08-26
JP2002523651A (ja) 2002-07-30
CA2341535A1 (fr) 2000-03-09
AU750899B2 (en) 2002-08-01
BR9913254A (pt) 2001-05-22
SE9802870L (sv) 2000-02-27

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