EP0294832A2 - Appareil pour l'épuration de pâte - Google Patents

Appareil pour l'épuration de pâte Download PDF

Info

Publication number
EP0294832A2
EP0294832A2 EP88109280A EP88109280A EP0294832A2 EP 0294832 A2 EP0294832 A2 EP 0294832A2 EP 88109280 A EP88109280 A EP 88109280A EP 88109280 A EP88109280 A EP 88109280A EP 0294832 A2 EP0294832 A2 EP 0294832A2
Authority
EP
European Patent Office
Prior art keywords
grooves
screen
rotor
plane
perforations
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.)
Granted
Application number
EP88109280A
Other languages
German (de)
English (en)
Other versions
EP0294832A3 (en
EP0294832B1 (fr
Inventor
Frey Frejborg
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.)
Ahlstrom Corp
Original Assignee
Ahlstrom Corp
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
Priority claimed from US07/061,594 external-priority patent/US4880540A/en
Application filed by Ahlstrom Corp filed Critical Ahlstrom Corp
Publication of EP0294832A2 publication Critical patent/EP0294832A2/fr
Publication of EP0294832A3 publication Critical patent/EP0294832A3/en
Application granted granted Critical
Publication of EP0294832B1 publication Critical patent/EP0294832B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • D21D5/02—Straining or screening the pulp
    • D21D5/023—Stationary screen-drums
    • D21D5/026—Stationary screen-drums with rotating cleaning foils
    • 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
    • D21D5/16—Cylinders and plates for screens

Definitions

  • U.S. Serial No. 738,743 is the Continuation-in-Part of U.S. Serial No. 472,742, which was issued as U.S.P. 4,529,520.
  • the subject matter of U.S. Serial Nos. 472,742 and 738,743 is incorporated herein by reference.
  • the present application relates generally to apparatuses for screening fiber suspensions of consistency between 0.3% up to 6%, and in particular, to a screening apparatus for screening papermaking pulp containing wood portions and other undesirable particles of various sizes and types.
  • a pulp screening apparatus which comprises a vessel, a cylindrical screen within the vessel, a rotating element moving in the vicinity of the screen at a predetermined speed, an inlet for the unscreened pulp, an outlet for the accept screened pulp in the vessel, another outlet for the reject, in operative communication with the screen.
  • the rotating element has a contour surface with grooves formed of a first bottom plane parallel to the envelope surface of the screen, an inclined plane and a side plane.
  • the side plane is essentially perpendicular to the first bottom plane.
  • the inclined plane forms an angle between 30° - 60° with the first plane.
  • the upper plane is parallel to the first plane.
  • the screen is also provided with grooves.
  • pulp is produced by cooking wood which separates the wood into fibers. Due to the different properties of the wood even from the same tree, some of the fibers do not separate and are dispersed as fiber bundles usually called debris, shives or slivers which form the reject. There are also other impurities, such as bark, which must be removed.
  • the screen must separate the undesirable impurities and debris called the rejects from the accept portion. In order to avoid substantial losses of fibers which could be carried over together with the debris in the reject portion, it is necessary to remove the impurities efficiently and selectively.
  • the stock enters at the inlet end of the screening zone and travels in an angle along the screening surface with the acceptable portions of the stock passing through the screening surface and with the rejectable portions of the pulp traveling along the screening surface essentially in a spiral path and passing out of the screening zone at the reject end.
  • the liquid that accompanies the fibrous stock passes through the screening surface more easily than the fibers. Therefore, as the stock travels along the screening zone, it tends to crease in consistency which means that the fiber-to-water ratio is increased. If this ratio increases too much, the screening process will be slowed down or will be even interrupted. In order to prevent this slow-down or interruption, it has been common practice to add more water to the stock to replace some of the water which has passed through the screening surface so as to maintain a satisfactory screening consistency on the inlet side.
  • Another method used to maintain the screening consistency on the inlet side is to intentionally feed the apparatus with over-diluted stock so that the excess water at the inlet will be sufficient to allow for continuity of screening throughout the screening zone.
  • both methods of adding more water during the screening or initially over-diluting the stock have undesirable effects such as diminishing the capacity of the screen by the amount of water added.
  • Pulps of different consistencies require screens with different contours. Different contours are also required with pulp suspensions having different physical properties and for different applications.
  • An object of the present invention is to separate the long fibers from slives and debris efficiently and selectively.
  • Another object is to provide a screening apparatus which may be operated under smooth flow as well as under more turbulent flow conditions.
  • Still another object is to maintain the desired screening efficiency without adding water during the screening operation and without using initially an overly diluted stock.
  • a further object is to provide a screening apparatus which can operate at pulp feed consistencies between 0.3% up to 6%.
  • Still another object is to provide a rotor which may be used with a variety of contoured screens, for a variety of pulp suspensions, which may provide the pumping effect required with the low consistency suspensions and which may provide the turbulence required for higher consistency stocks.
  • the screening apparatus comprises a housing having an inlet for allowing fibrous stock to be introduced into the interior of the housing, an outlet for allowing the accepted screened stock to be removed from the housing, an outlet for the reject, a contoured screen within the housing, a rotor moving in the vicinity of the screen at a predetermined speed and forming together with the screen an annular screening chamber, the rotor having at least one partially contoured surface on the side facing screen and provided with a plurality of perforations along at least a portion of the length of the screening chamber to allow fibrous stock to be introduced into the screening chamber and to prevent the undesired debris of the stock from entering the chamber.
  • the pulp flows from the outside to the inside of the screen and the contoured surface of the screen is on the outside of the screen.
  • the screening apparatus includes a pressurized housing 1, a cylindrical screen 3 positioned within the housing, a rotor 4 mounted within the screen on the upper part of a rotatable, veritcal shaft 5.
  • the housing has an inlet 6 for allowing unscreened pulp suspension to be introduced into a chamber 7 in the upper part of the housing, an outlet 8 for accepted (screened) stock, a reject chamber 19 and an outlet 9 for rejected stock in the lower end.
  • a screening chamber 12 is formed between the cylindrical screen and the rotor.
  • Numeral 15 designates the accept chamber.
  • Numeral 2 designates a removable cover for the housing and numeral 11 designates a plate closing the upper end of the screening chamber.
  • the housing includes an additional structure 17 which, together with a flange 18, forms a partition between the second chamber and a third chamber 19 which is the reject chamber in the bottom part of the housing.
  • the stock inlet 6 communicates directly with the first chamber
  • the accept outlet 8 communicates directly with the second chamber
  • the reject outlet 9 communicates directly with the third chamber.
  • axial bars or foils 20 which extend along at least a portion of the length of the rotor are mounted on a support adjacent the inner surface of the rotor.
  • a plate 21 closes the lower end of the rotor. Openings 22 in the lower end of the rotor drum 23 provide communication between the space inside the rotor and the reject chamber.
  • the screen plate 3 has a contoured surface. According to one embodiment, shown in Fig. 2, the cylindrical screen plate has grooves 24 in the inlet surface. Also the outside and the inside surfaces of the rotor are contoured with grooves 25 and 26, but the rotor could have only one contour surface facing the screen. The contour surface is not necessarily continuous.
  • the grooves 25 on the screen side of the rotor are formed of a bottom plane 27 and two side planes 28 and 29.
  • the grooves 26 on the inlet side of the rotor are likewise formed by a bottom plane 30 and two side planes 31 and 32.
  • the bottom planes 27 and 30 are generally perpendicular to the side planes 32 and 29.
  • the side planes 28 and 31 are generally inclined with respect to the cylindrical outer and inner surfaces.
  • the angle ⁇ is formed between upper plane 33 and the inclined plane 28 and is in this embodiment between 5° and 60°.
  • the angle ⁇ is formed between the envelope surface 34 and side plane 31 and is between 10° and 60°.
  • the symbol H1 designates the distance between the bottom plane 27 and the upper plane 33 in the outer surface of the rotor and may be between 1/16 inch and 2 inches.
  • the symbol H2 designates the distance between the bottom plane 30 and the envelope surface 34 in the inlet side of the rotor and may be between 1/16 inch and 2 inches.
  • the symbols B1 and B2 designate the width of the bottom planes 27 and 30 in the outer and inner surface respectively of the rotor and may be as low as 1/8 inch and as long as 2 inches.
  • the rotor 23 has a plurality of perforations 35 extending along a portion (L in Fig. 1) of its axial length beginning from its upper end and a size allowing fibrous stock to pass through the rotor but preventing foreign objects of larger size than the inlet openings 36 of the perforations from entering the screening zone 12.
  • the inlet openings of the perforations are positioned in the bottom plane of the grooves 26 on the inlet side of the rotor and the discharge openings 37 are positioned either on the upper plane 33 of the outlet surface of the rotor or on the inclined plane 28 or on the bottom plane 27.
  • the perforations in the rotor are either cylindrical or preferably slotted in section.
  • the discharge opening of the perforations is preferably larger than the inlet opening.
  • the grooves as well as the perforations of the rotor are larger than the grooves and the perforations of the screen in the embodiment of Fig. 2 but this in not essential.
  • the rotor may also be constructed of profiled bars which, when assembled, form longitudinal openings therebetween which then constitute the perforations of the rotor.
  • the profiled bars may be represented by the dotted lines drawn through the openings of the rotor as shown in Fig. 2.
  • the inclined side plane on each surface of the rotor can be the leading side plane or the trailing plane of the groove in relation to the direction of the rotation of the rotor in the embodiment of Fig. 2.
  • the rotor may rotate in different directions, that is, clockwise as shown in Fig. 2, for high efficiency, or counterclockwise to achieve high capacity.
  • the grooves 25 and 26 may be located in relation to each other as shown in Fig. 2, that is the inclined planes being the downflow sides of the grooves. However, either or both of the grooves 25 and 26 may be formed so that the perpendicular planes 29, 32 are the downflow sides of the grooves. It is also possible that the grooves are so formed that every second groove has as its downflow side the inclined plane and the others have the perpendicular plane. Also it is possible to arrange the grooves in groups so that a certain group of grooves has as its downflow side the inclined planes and the next group of grooves the perpendicular planes.
  • pulp suspension is supplied to the first chamber 7 in the upper end of the apparatus through inlet 6 and flows into the rotor 4.
  • the fibrous stock flows through the perforations in the rotor to the screening chamber and particles larger than the perforations will not pass through the perforations of the rotor.
  • the large cross-sectional area of the rotor allows heavy foreign material to settle for rejection through the openings 22 at the lower end of the rotor and allows the pulp suspension to flow in an almost radial direction towards the inner surface of the rotor.
  • the stock which enters the screening chamber is set into circumferential motion by the rotor and subjected to high-intensity pulses and turbulence when flowing over essentially in a direction perpendicular to the grooves on the screen surface.
  • the angle between the direction of the grooves and the axial direction of the cylinder of the screen plate may be from 0° to 45°.
  • the acceptable fibers pass through the perforations in the screen to be collected in the chamber 15 surrounding the screen and are removed through the outlet 8 as accepted stock. Any stock not passing through the perforations of the rotor or the screen is collected in the chamber 19 in the lower end of the housing and is discharged through the outlet 9 as rejects.
  • the screening chamber 12 between the rotor and the screen can be as narrow as 1 mm and as large as 50 mm.
  • the screening chamber When the screening chamber is narrow, between 1 and 3 mm, an effective hydrodynamic interaction between the grooved surfaces of the rotor and the screen facing each other is achieved, and advantageous conditions for the screening are provided. This also permits the screen to efficiently handle stock of high consistency, up to 6%.
  • the groove in the screen is formed of a bottom plane 40 which is substantially parallel with the envelope surface 42 of the screen surface, an upstream side plane 44 as seen standing from the bottom of the groove and a downstream side plane 45.
  • the angle ⁇ between the envelope surface of the screen surface and the upstream side plane 44, or in other words between the plane tangenting the envelope surface of the screen surface close to this side plane and this side plane is approximately 90° and the angle ⁇ between the envelope surface of the screen surface and the downstream side plane 45 is 5° - 60°.
  • the angle is ⁇ 5° - 60° and the angle ⁇ is 90°.
  • the perforations of the screen plate are disposed on the bottom planes 40 of the grooves.
  • the grooves 52 are U-shaped, and both side planes 44 and 45 are substantially perpendicular to the envelope surface 42 of the screen surface.
  • the screen surface is undulant and both sides 44 and 45 of the grooves 52 are inclined with regard to the envelope surface 42 of the screen surface.
  • the surface of the rotor which does not face the screen is not necessarily grooved and it is not necessary that the entire surface of the rotor be grooved.
  • the inlet side of the rotor also may have a contour surface, for instance, the contour of the screen as shown in Figs. 3-8.
  • This example describes a typical screening apparatus with a cylindrical rotor having an outer diameter of 20 inches and a thickness of 3/8 inch.
  • Depth (H1 and H2) of grooves of the rotor 1/8 inch Width (B1 and B2) of bottom plane: 3/16 inch Angle ( ⁇ and ⁇ ) 50° Width of axial slots (36): 1/16 inch Circumferential spacing of grooves, that is the distance between consecutive grooves 26: 0.5 inch Width (W) of the screening chamber: 3/16 inch
  • the grooves have two side planes, a bottom plane and an upper plane, one side plane is perpendicular to the envelope surface of the screen and the other side plane is curved, convex or concave with respect to the envelope surface.
  • Fig. 8 the sides of the grooves have an inverted V-shape configuration.
  • Figs. 1 and 2 show an apparatus intended for outflow operation
  • the apparatus according to Fig. 9 may be readily adapted for inflow configuration according to which the pulp is fed into the outer surface of the rotor, goes through the perforations inwardly, flows into the screening chamber. Thereafter the accept portion passes through the finer perforations of the screen into the accept chamber and the remaining reject portion in the screening chamber moves towards the reject chamber. This operation is particularly advantageous when large dirt type particles are to be removed.
  • Another advantage of the apparatus according to the present invention is that it may be retrofitted and used with conventional screen housings, resulting in major capital savings.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Paper (AREA)
  • Combined Means For Separation Of Solids (AREA)
EP88109280A 1987-06-11 1988-06-10 Appareil pour l'épuration de pâte Expired - Lifetime EP0294832B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US61594 1979-07-30
US07/061,594 US4880540A (en) 1983-01-26 1987-06-11 Pulp screening apparatus

Publications (3)

Publication Number Publication Date
EP0294832A2 true EP0294832A2 (fr) 1988-12-14
EP0294832A3 EP0294832A3 (en) 1989-03-08
EP0294832B1 EP0294832B1 (fr) 1991-04-17

Family

ID=22036818

Family Applications (1)

Application Number Title Priority Date Filing Date
EP88109280A Expired - Lifetime EP0294832B1 (fr) 1987-06-11 1988-06-10 Appareil pour l'épuration de pâte

Country Status (5)

Country Link
EP (1) EP0294832B1 (fr)
BR (1) BR8807561A (fr)
DE (2) DE294832T1 (fr)
FI (1) FI882569A (fr)
WO (1) WO1988009843A1 (fr)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH03505759A (ja) * 1989-03-02 1991-12-12 エイ．アフルストロム　コーポレーション 繊維懸濁液を濃縮する方法及び装置
WO1996023930A1 (fr) * 1995-02-03 1996-08-08 Hermann Finckh Maschinenfabrik Gmbh & Co. Trieuse sous pression de suspensions de fibres et crible pour ces trieuses sous pression
WO1997002384A1 (fr) * 1995-07-03 1997-01-23 Sunds Defibrator Industries Ab Dispositif d'etancheite
ES2155410A1 (es) * 1999-08-24 2001-05-01 Perez Ernesto Pastor Depurador de pasta de papel.
WO2004046457A1 (fr) * 2002-11-19 2004-06-03 Advanced Fiber Technologies (Aft) Oy Procede et appareil de traitement d'une suspension fibreuse
USRE39940E1 (en) 1990-08-16 2007-12-18 Advanced Fiber Technologies (Aft) Trust Screen plates and methods of manufacture
US8297445B2 (en) 2007-11-14 2012-10-30 Filtration Fibrewall Inc. Screen basket
US8469198B2 (en) 2005-05-09 2013-06-25 Kadant Canada Corp. Screen basket with replaceable profiled bars

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU6713190A (en) * 1989-10-23 1991-05-16 Beloit Corporation Basket profile for screens
FI121794B (fi) * 2009-10-23 2011-04-15 Andritz Oy Laite kuitususpension käsittelemiseksi

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1070451A (en) * 1964-04-29 1967-06-01 Ingersoll Rand Canada Screening apparatus
GB1118646A (en) * 1965-03-30 1968-07-03 Ingersoll Rand Canada Screening apparatus
FR2193638A1 (fr) * 1972-07-24 1974-02-22 Nivoba Bv
US3939065A (en) * 1972-08-31 1976-02-17 Ahlfors S E E Screening device
FR2384889A1 (fr) * 1977-03-23 1978-10-20 Finckh Maschf Epurateur-trieur pour la separation de suspensions de fibres
EP0079811A1 (fr) * 1981-11-18 1983-05-25 E. + M. Lamort Société Anonyme dite: Perfectionnements aux épurateurs de pâte à papier et à leurs tamis
US4529520A (en) * 1983-01-26 1985-07-16 A. Ahlstrom Osakeyhtio Screen plate
EP0206975A2 (fr) * 1985-06-20 1986-12-30 Beloit Corporation Tamis à pression pour hautes consistances et procédé pour séparer la matière acceptée du refus

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3572928D1 (en) * 1984-12-25 1989-10-19 Mitsubishi Heavy Ind Ltd Pressure slit screen
FI77481C (fi) * 1985-05-29 1989-03-10 Ahlstroem Oy Sil.

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1070451A (en) * 1964-04-29 1967-06-01 Ingersoll Rand Canada Screening apparatus
GB1118646A (en) * 1965-03-30 1968-07-03 Ingersoll Rand Canada Screening apparatus
FR2193638A1 (fr) * 1972-07-24 1974-02-22 Nivoba Bv
US3939065A (en) * 1972-08-31 1976-02-17 Ahlfors S E E Screening device
FR2384889A1 (fr) * 1977-03-23 1978-10-20 Finckh Maschf Epurateur-trieur pour la separation de suspensions de fibres
EP0079811A1 (fr) * 1981-11-18 1983-05-25 E. + M. Lamort Société Anonyme dite: Perfectionnements aux épurateurs de pâte à papier et à leurs tamis
US4529520A (en) * 1983-01-26 1985-07-16 A. Ahlstrom Osakeyhtio Screen plate
EP0206975A2 (fr) * 1985-06-20 1986-12-30 Beloit Corporation Tamis à pression pour hautes consistances et procédé pour séparer la matière acceptée du refus

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH03505759A (ja) * 1989-03-02 1991-12-12 エイ．アフルストロム　コーポレーション 繊維懸濁液を濃縮する方法及び装置
USRE39940E1 (en) 1990-08-16 2007-12-18 Advanced Fiber Technologies (Aft) Trust Screen plates and methods of manufacture
WO1996023930A1 (fr) * 1995-02-03 1996-08-08 Hermann Finckh Maschinenfabrik Gmbh & Co. Trieuse sous pression de suspensions de fibres et crible pour ces trieuses sous pression
US6029825A (en) * 1995-02-03 2000-02-29 Hermann Finckh Maschinenfabrik Gmbh & Co. Pressure sorter for sorting fiber suspensions as well as screen for such a pressure sorter
WO1997002384A1 (fr) * 1995-07-03 1997-01-23 Sunds Defibrator Industries Ab Dispositif d'etancheite
AU691120B2 (en) * 1995-07-03 1998-05-07 Sunds Defibrator Industries Ab Sealing device
US6113104A (en) * 1995-07-03 2000-09-05 Valmet Fibertech Aktiebolag Sealing device
ES2155410A1 (es) * 1999-08-24 2001-05-01 Perez Ernesto Pastor Depurador de pasta de papel.
WO2004046457A1 (fr) * 2002-11-19 2004-06-03 Advanced Fiber Technologies (Aft) Oy Procede et appareil de traitement d'une suspension fibreuse
US8469198B2 (en) 2005-05-09 2013-06-25 Kadant Canada Corp. Screen basket with replaceable profiled bars
US8297445B2 (en) 2007-11-14 2012-10-30 Filtration Fibrewall Inc. Screen basket

Also Published As

Publication number Publication date
WO1988009843A1 (fr) 1988-12-15
FI882569A (fi) 1988-12-12
FI882569A0 (fi) 1988-06-01
DE3862433D1 (de) 1991-05-23
EP0294832A3 (en) 1989-03-08
BR8807561A (pt) 1990-04-17
EP0294832B1 (fr) 1991-04-17
DE294832T1 (de) 1989-07-13

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