WO1998018559A1 - Method and apparatus for treating pulp - Google Patents

Method and apparatus for treating pulp Download PDF

Info

Publication number
WO1998018559A1
WO1998018559A1 PCT/FI1997/000641 FI9700641W WO9818559A1 WO 1998018559 A1 WO1998018559 A1 WO 1998018559A1 FI 9700641 W FI9700641 W FI 9700641W WO 9818559 A1 WO9818559 A1 WO 9818559A1
Authority
WO
WIPO (PCT)
Prior art keywords
wall
fraction
vortex cleaner
fiber suspension
apertures
Prior art date
Application number
PCT/FI1997/000641
Other languages
French (fr)
Inventor
Simo Suortti
Kai Vilkko
Pentti Vikiö
Original Assignee
Ahlstrom Machinery Oy
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 Ahlstrom Machinery Oy filed Critical Ahlstrom Machinery Oy
Publication of WO1998018559A1 publication Critical patent/WO1998018559A1/en

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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
    • D21D5/18—Purification of the pulp suspension by mechanical means; Apparatus therefor with the aid of centrifugal force
    • D21D5/24—Purification of the pulp suspension by mechanical means; Apparatus therefor with the aid of centrifugal force in cyclones
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
    • B04C—APPARATUS USING FREE VORTEX FLOW, e.g. CYCLONES
    • B04C5/00—Apparatus in which the axial direction of the vortex is reversed
    • B04C5/08—Vortex chamber constructions
    • B04C5/085—Vortex chamber constructions with wear-resisting arrangements

Definitions

  • the present invention relates to a method of dividing a pulp fraction containing wearing components into an accepted fraction and a rejected fraction containing impurities in a vortex cleaner, in which the wearing impact of the abrasive components on the walls has been minimized
  • Vortex cleaners are commonly used for example in the pulp and paper industry in the cleaning of fiber suspensions
  • the function of the vortex cleaner is to separate sand and i other heavy fractions and tmpu ⁇ ty particles o ⁇ ginating from wood, such as bark from the fibei suspension and to reduce its sticks content
  • the fibei suspension to be cleaned is fed under pressure to a vortex cleaner Due to tangential feeding, the pulp assumes in the tapering screening cone a fast rotating movement which creates an increasing centrifugal force separating pulp suspension components of different specific gravity from each other While the pulp vortex proceeds in the tapering screening cone material of heavier specific gravity such as sand is slung to the wall of the screening cone
  • the heavier mate ⁇ al drifts along spiral paths toward a discharge opening in the tip of the screening cone
  • the heavier u impuimes in the pulp suspension have an abrasive impact on the walls of the vortex cleaner This abrasion wearing the walls is strongest in the end of the conical portion of the vo ⁇ ex cleaner having the shortest diameter
  • the grooves in the walls of the vortex cleaner caused by the abrasion may wear through Frequent and repeated replacement of the wearing parts of the vortex cleaner result in high apparatus costs and ⁇ possiblv interruptions in production
  • the aim of the present invention is to provide a method which is better than prior art methods of improving the wear resistance of a vortex cleaner used particularly in pulp and paper mills.
  • the pulp suspension is divided into an accepted fraction and a fraction containing impurity particles Suspension containing particles which wear out by abrasion is introduced tangentially into the vortex cleaner having a centrally located discharge duct for the accepted fraction and a partly conical portion serving as a discharge duct for the other fraction.
  • At least the conical portion has a double-wall structure.
  • inside an unperforated outer wall there is an inner wall having apertures. There is an open space between the outer wall and the inner wall.
  • pulp suspension fills the space between the unperforated outer wall and the inner wall. Then the pulp suspension and the impurity particles it contains serve as an insulation protecting the outer wall against wearing.
  • the pulp suspension is caused to form a uniform layer also onto the inner surface of the inner wall preferably by providing an adequate distance between the inner wall and the outer wall and a suitable form and open area of the apertures.
  • a uniform layer is formed when the distance of the inner wall from the outer wall is about 3 - 8 mm.
  • the apertures in the inner wall of the vortex cleaner preferably have a round or a slotlike form Most preferably they are round holes Preferably the holes have a diameter of 2 mm and an open area of over 15 %
  • the inner wall of the vortex clener is preferably made of steel or a corresponding material suitable for this purpose, by a pressure turning method which gives the cleaner a good smooth surface and a round form
  • the inner wall may be made of a perforated plate If the inner wall is manufactured by other methods than pressure turning the wall may be produced so that the apertures are made during the manufacturing process
  • the pulp layer protecting the outer wall of the vortex cleaner may be brought about also by some other kind of structures than an inner wall with apertures
  • elements may be mounted to the inner surface of the conical portion of the cleaner which stop the flow of pulp suspension in the vicinity of the inner surface of the cone
  • the invention provides remarkable advantages When a vortex cleaner is to give a good cleaning result its inner surface must be undamaged If the inner surface becomes uneven at some point, turbulence will be generated in the impurity layer flowing downward on the wall and a part of the impurities may end up in the accept flow travelling upwards With the invention, the wearing impact of the abrasive particles on the walls of a vortex cleaner may be minimized The walls will then remain smooth for a longer time This extends the efficient life of the vortex cleaners and reduces the need to replace the cleaners which gives a remarkable economic advantage
  • the invention will be described in detail below with reference to the accompanying drawings which illustrate a preferred embodiment of the invention
  • a vortex cleaner comprises a cylindrical portion (1) having a tangential feed duct (2) for pulp suspension and a centrally located discharge duct (3) for accepted fraction
  • a conical portion (4) of the cleaner serves as a discharge duct for rejected fraction
  • the conical portion of the vortex cleaner is formed of a unbroken outer wall (5) and of an inner wall (6) having apertures (7)
  • the apertures are round holes Due to the apertures in the inner wall, fibers fill the space (8) between the inner and the outer wall Then a uniform stationary fiber layer is formed which protects the wall from the wearing impact of the abrasive particles in a rapid rotating movement.
  • fibers fill the spaces (7) of the perforated wall and form a fiber layer also onto the surface (8) of the inner wall (6) facing the process This fiber layer protects the inner wall of the vortex cleaner against the wearing influence of the abrasive particles
  • the invention is applicable also in other kinds of processes in which solid, wearing impurity particles are separated from a li uid or a suspension

Abstract

The present invention relates to a method and an apparatus for dividing a pulp suspension into an accepted fraction and a rejected fraction containing impurity particles. According to the invention, a mixture of material containing components, which wear by abrasion, is introduced tangentially into a vortex cleaner having a centrally located discharge duct (3) for one fraction and a partly conical portion (4) serving as a discharge duct for the other fraction where at least the conical portion has a double-wall construction. According to the invention, there is inside an unbroken outer wall (6), an inner wall (6) having apertures (7), and an open space (8) between the outer wall and the inner wall.

Description

MF THOD AND APPARATUS FOR TREATING PULP
The present invention relates to a method of dividing a pulp fraction containing wearing components into an accepted fraction and a rejected fraction containing impurities in a vortex cleaner, in which the wearing impact of the abrasive components on the walls has been minimized
Vortex cleaners are commonly used for example in the pulp and paper industry in the cleaning of fiber suspensions The function of the vortex cleaner is to separate sand and i other heavy fractions and tmpuπty particles oπginating from wood, such as bark from the fibei suspension and to reduce its sticks content
The fibei suspension to be cleaned is fed under pressure to a vortex cleaner Due to tangential feeding, the pulp assumes in the tapering screening cone a fast rotating movement which creates an increasing centrifugal force separating pulp suspension components of different specific gravity from each other While the pulp vortex proceeds in the tapering screening cone material of heavier specific gravity such as sand is slung to the wall of the screening cone The heavier mateπal drifts along spiral paths toward a discharge opening in the tip of the screening cone The heavier u impuimes in the pulp suspension have an abrasive impact on the walls of the vortex cleaner This abrasion wearing the walls is strongest in the end of the conical portion of the voπex cleaner having the shortest diameter In the long run, the grooves in the walls of the vortex cleaner caused by the abrasion may wear through Frequent and repeated replacement of the wearing parts of the vortex cleaner result in high apparatus costs and ^ possiblv interruptions in production
Quick wearing through of vortex cleaners has been known for a long time A known method of coirecting this drawback is to provide the vortex cleaner with an outer shell Then there is a closed space between the screening cone and the outer shell into which "■><> the pulp in the vortex cleaner can erupt when the wall is worn through A double-wall stiuciure of this type has been disclosed in US patent no 4,278,534 In the application mentioned above, the vortex cleaner has been constructed to have an outer wall and inside that an unbroken inner lining. When the inner wall is worn through, pulp bursts into the space between the walls. Then the operation conditions of the vortex cleaner change compared with the situation when the inner wall is still unbroken Further, in this solution the wearing effect of the abrasive particles is directed maximally to the inner wall as there is no attempt to minimize it. Quick wearing out shortens the efficient life of a vortex cleaner.
The aim of the present invention is to provide a method which is better than prior art methods of improving the wear resistance of a vortex cleaner used particularly in pulp and paper mills. According to the invention, the pulp suspension is divided into an accepted fraction and a fraction containing impurity particles Suspension containing particles which wear out by abrasion is introduced tangentially into the vortex cleaner having a centrally located discharge duct for the accepted fraction and a partly conical portion serving as a discharge duct for the other fraction. At least the conical portion has a double-wall structure. According to the invention, inside an unperforated outer wall there is an inner wall having apertures. There is an open space between the outer wall and the inner wall.
According to the invention, due to the apertures in the inner wall, pulp suspension fills the space between the unperforated outer wall and the inner wall. Then the pulp suspension and the impurity particles it contains serve as an insulation protecting the outer wall against wearing.
According to an embodiment of the invention, the pulp suspension is caused to form a uniform layer also onto the inner surface of the inner wall preferably by providing an adequate distance between the inner wall and the outer wall and a suitable form and open area of the apertures. A uniform layer is formed when the distance of the inner wall from the outer wall is about 3 - 8 mm. Then the inner wall of the vortex cleaner, either, is not subjected to, for example, wear because a renewing almost stationary protecting laver is formed of pulp suspension onto the inner surfaces of the cleaner and the abrasive movement takes place between the stationary pulp layer and the flowing fibei suspension The inner wall serves then as a backing structure for the pulp suspension layer subjected to the wear
The apertures in the inner wall of the vortex cleaner preferably have a round or a slotlike form Most preferably they are round holes Preferably the holes have a diameter of 2 mm and an open area of over 15 %
The inner wall of the vortex clener is preferably made of steel or a corresponding material suitable for this purpose, by a pressure turning method which gives the cleaner a good smooth surface and a round form When the apertures of the inner wall are round holes the inner wall may be made of a perforated plate If the inner wall is manufactured by other methods than pressure turning the wall may be produced so that the apertures are made during the manufacturing process
The pulp layer protecting the outer wall of the vortex cleaner may be brought about also by some other kind of structures than an inner wall with apertures For example, elements may be mounted to the inner surface of the conical portion of the cleaner which stop the flow of pulp suspension in the vicinity of the inner surface of the cone
The invention provides remarkable advantages When a vortex cleaner is to give a good cleaning result its inner surface must be undamaged If the inner surface becomes uneven at some point, turbulence will be generated in the impurity layer flowing downward on the wall and a part of the impurities may end up in the accept flow travelling upwards With the invention, the wearing impact of the abrasive particles on the walls of a vortex cleaner may be minimized The walls will then remain smooth for a longer time This extends the efficient life of the vortex cleaners and reduces the need to replace the cleaners which gives a remarkable economic advantage The invention will be described in detail below with reference to the accompanying drawings which illustrate a preferred embodiment of the invention
As illustrated in Fig. 1 , a vortex cleaner comprises a cylindrical portion (1) having a tangential feed duct (2) for pulp suspension and a centrally located discharge duct (3) for accepted fraction A conical portion (4) of the cleaner serves as a discharge duct for rejected fraction
As illustrated in Fig. 2, in particular the conical portion of the vortex cleaner is formed of a unbroken outer wall (5) and of an inner wall (6) having apertures (7) In the embodiment illustrated by Fig 2, the apertures are round holes Due to the apertures in the inner wall, fibers fill the space (8) between the inner and the outer wall Then a uniform stationary fiber layer is formed which protects the wall from the wearing impact of the abrasive particles in a rapid rotating movement.
As illustrated in Fig. 3, fibers fill the spaces (7) of the perforated wall and form a fiber layer also onto the surface (8) of the inner wall (6) facing the process This fiber layer protects the inner wall of the vortex cleaner against the wearing influence of the abrasive particles
It should be noted that the examples described above in no way intend to limit the present invention They constitute only the most essential structural parts of the invention
In addition to the pulp and paper manufacturing industry, the invention is applicable also in other kinds of processes in which solid, wearing impurity particles are separated from a li uid or a suspension

Claims

We claim
1 A method of reducing the wearing of a vortex cleaner used for dividing a fiber suspension into an accepted fraction and a rejected fraction containing impurity particles when a mixture of material containing particles, which wear out by abrading, is introduced tangentially into a vortex cleaner having a centrally located discharge duct (3) tor one fraction and a partly conical portion (4) serving as a discharge duct for the other fraction, according to which method a protecting layer of mateπal is formed onto the inner surface of the vortex cleaner, characterized in that the protecting mateπal o lavei is formed of fiber suspension and located in a space (8) between an outer wall (5) and an inner wall (6) having perforations (7) of an at least double- wall portion
2 A method as claimed in claim 1 , characterized in that by means of the location of the inner wall (6) in respect to the outer wall (5), and the form and size of the apertures l ^ (7) in the inner wall (6), a uniform layer (9) is formed of fiber suspension also onto the inner surface of the inner wall which reduces the wearing effect directed to the inner wall
3 A method as claimed in claim 1 or 2, characterized in that the abrasive movement of 20 the flowing fiber suspension is received by the fiber suspension layer formed by means of the inner wall (6) whereby the wearing effect directed to the walls of the vortex cleaner is minimized and the inner wall serves as a supporting structure for this pulp layer receiving the wearing effect
2^ 4 An apparatus for diving a fiber suspension into an accepted fraction and a fraction containing impurity particles when a mixture of material containing abrasive particles is introduced tangentially into a vortex cleaner having a centrally located discharge duct ( 3 ) loi one f raction and partly conical portion
(4) serving as a discharge duct for the othei traction characterized in that at least the conical portion has a double-wall
"o structure toi med by an outer wall (5), an inner wall (6), apertures (7) in the inner wall, and a space (8) between the outer wall (5) and the inner wall (6) whereby a layer protecting the outer wall is formed of fiber suspension.
5. An apparatus as claimed in claim 4, characterized in that preferably the disctance of
? the inner wall (6) from the outer wall (5) is 3 - 8 mm.
6. An apparatus as claimed in claim 4, characterized in that the apertures (7) in the inner wall (6) preferably are elongated slots or round holes, whereby the holes of the inner wall preferably have a diameter of 2 mm and preferably an open area of over 15 0
7 An apparatus as claimed in claim 4, characterized in that the inner wall (6) of the vortex cleaner may be manufactured of a material suitable for this purpose, preferably of perforated steel plate by a pressure turning method. 5
8. An apparatus as claimed in claim 4, characterized in that the inner wall (6) of the vortex cleaner may be manufactured so that the apertures (7) are made during the manufacture of the wall.
PCT/FI1997/000641 1996-10-25 1997-10-23 Method and apparatus for treating pulp WO1998018559A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI964299 1996-10-25
FI964299A FI101725B1 (en) 1996-10-25 1996-10-25 Method and apparatus for handling pulp

Publications (1)

Publication Number Publication Date
WO1998018559A1 true WO1998018559A1 (en) 1998-05-07

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WO (1) WO1998018559A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1335064A1 (en) * 2002-02-08 2003-08-13 Voith Paper Patent GmbH Process for lining defibering apparatus for waste paper liable to wear
EP3165672A1 (en) * 2015-11-05 2017-05-10 Andritz Inc. Sand separator vessel and perforated replaceable insert

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2838173A1 (en) * 1978-09-01 1980-03-06 Temafa Textilmaschf Meissner CYCLONE SEPARATOR FOR SEPARATING HEAVY AND DUST PARTS MADE OF FIBER MATERIAL
US4278534A (en) * 1978-11-16 1981-07-14 Ab Celleco Method for separation of material mixtures, containing abrasive particles, in a hydrocyclone separator
US4280902A (en) * 1979-07-04 1981-07-28 Kamyr Aktiebolag Separation of dense impurities from a fluid

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2838173A1 (en) * 1978-09-01 1980-03-06 Temafa Textilmaschf Meissner CYCLONE SEPARATOR FOR SEPARATING HEAVY AND DUST PARTS MADE OF FIBER MATERIAL
US4278534A (en) * 1978-11-16 1981-07-14 Ab Celleco Method for separation of material mixtures, containing abrasive particles, in a hydrocyclone separator
US4280902A (en) * 1979-07-04 1981-07-28 Kamyr Aktiebolag Separation of dense impurities from a fluid

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1335064A1 (en) * 2002-02-08 2003-08-13 Voith Paper Patent GmbH Process for lining defibering apparatus for waste paper liable to wear
EP3165672A1 (en) * 2015-11-05 2017-05-10 Andritz Inc. Sand separator vessel and perforated replaceable insert

Also Published As

Publication number Publication date
FI964299A0 (en) 1996-10-25
FI964299A (en) 1998-04-26
FI101725B (en) 1998-08-14
FI101725B1 (en) 1998-08-14

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