AU683786B2 - Screening arrangement - Google Patents

Screening arrangement Download PDF

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Publication number
AU683786B2
AU683786B2 AU42747/96A AU4274796A AU683786B2 AU 683786 B2 AU683786 B2 AU 683786B2 AU 42747/96 A AU42747/96 A AU 42747/96A AU 4274796 A AU4274796 A AU 4274796A AU 683786 B2 AU683786 B2 AU 683786B2
Authority
AU
Australia
Prior art keywords
arrangement
housing
light impurities
upper portion
casing
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.)
Ceased
Application number
AU42747/96A
Other versions
AU4274796A (en
Inventor
Borje 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 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
Priority to JP35824092A priority Critical patent/JP3173199B2/en
Priority to JP36011192A priority patent/JP3206167B2/en
Priority to SE9404264A priority patent/SE504162C2/en
Priority to SE9404264 priority
Application filed by Valmet AB filed Critical Valmet AB
Priority to PCT/SE1995/001340 priority patent/WO1996017998A1/en
Publication of AU4274796A publication Critical patent/AU4274796A/en
Application granted granted Critical
Publication of AU683786B2 publication Critical patent/AU683786B2/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21DTREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
    • D21D5/00Purification of the pulp suspension by mechanical means; Apparatus therefor
    • D21D5/18Purification of the pulp suspension by mechanical means; Apparatus therefor with the aid of centrifugal force
    • D21D5/24Purification of the pulp suspension by mechanical means; Apparatus therefor with the aid of centrifugal force in cyclones
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B04CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
    • B04CAPPARATUS USING FREE VORTEX FLOW, e.g. CYCLONES
    • B04C7/00Apparatus not provided for in group B04C1/00, B04C3/00, or B04C5/00; Multiple arrangements not provided for in one of the groups B04C1/00, B04C3/00, or B04C5/00; Combinations of apparatus covered by two or more of the groups B04C1/00, B04C3/00, or B04C5/00
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B04CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
    • B04CAPPARATUS USING FREE VORTEX FLOW, e.g. CYCLONES
    • B04C9/00Combinations with other devices, e.g. fans, expansion chambers, diffusors, water locks
    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21DTREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
    • D21D5/00Purification of the pulp suspension by mechanical means; Apparatus therefor
    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21DTREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
    • D21D5/00Purification of the pulp suspension by mechanical means; Apparatus therefor
    • D21D5/02Straining or screening the pulp
    • D21D5/023Stationary screen-drums
    • D21D5/026Stationary screen-drums with rotating cleaning foils
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B04CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
    • B04CAPPARATUS USING FREE VORTEX FLOW, e.g. CYCLONES
    • B04C9/00Combinations with other devices, e.g. fans, expansion chambers, diffusors, water locks
    • B04C2009/005Combinations with other devices, e.g. fans, expansion chambers, diffusors, water locks with external rotors, e.g. impeller, ventilator, fan, blower, pump

Description

1 SCREENING ARRANGEMENT The invention relates to an arrangement for separating light impurities from pulp suspensions. Light impurities are understood to be particles or aggregates with lower density than water, for example plastic particles.

Aggregates are found, for example, at flotation where a heavy particle is bound to a gas, and the aggregate particle/bubble behaves like a light particle.

Heavy impurities in the pulp are separated in conventional screens by means of centrifugal force in separate scrap taps, while coarse fiber fractions and impurities are separated by a scxeen member whereby the pulp is divided into accept and reject.

Light impurities are more difficult to separate, especially at high pulp concentrations. The pulp concentration, however, is desired to be high, for example in order 20 to achieve a high production capacity and to avoid the transport of large liquid volumes in the screening system.

Light impurities, therefore, usually are separated in *separate devices, such as hydrocyclones. This requires not *:Go 080 25 only separate equipment, but also low concentrations, below in order to achieve a good effect. It is, therefore, a less attractive method to vortex clean the entire flow from S* a pulp line. It is, instead, possible to carry out pressure screening through very fine slits at highest possible concentration and thereafter to use vortex cleaner for separating the light impurities from the reject flow of the screens.

It is an object of the present invention, therefore, to provide an arrangement that reduces or avoids the aforesaid problems.

\\HELB0I\home$\Vicky\Kee \speci\42747 96.doc 18/08/97 IA According to a broad aspect of the present invention there is provided an arrangement for separating light impurities from pulp suspensions, for connecting to a casing of a fractionation device where the fiber network is broken up and the pulp is caused to rotate for enriching the light impurities, wherein the separation arrangement is designed with a rotationally symmetrical housing connected centrally to the upper portion of the casing through a passage, that an inlet for dilution liquid is connected tangentially to the housing, and that an outlet for the light impurities is located centrally at the top of the housing.

Preferably the housing consists of an upward diverging lower portion and a substantially cylindric upper portion, and the dilution liquid inlet is located in the passage between the lower and upper portion.

Preferably the division of the housing into a lower and upper portion is determined from a flow aspect of the 20 location of the dilution liquid inlet.

Preferably a valve is located in the outlet for controlling the discharge of light impurities.

*9* 25 Preferably a rotor axle with a rotor element extends through the passage from the casing of the fractionation I device into the housing to effect the rotation of the contents in the housing.

Preferably the rotor axle is provided with a screw thread for upward feeding.

9 In order that the invention may be more fully explained, a preferred embodiment will be described, by way of example, with reference to the accompanying drawings in which the figure is a view of a screening arrangement according to f mS I \\MELSOl\home$Wicky\Keep\speci\42747.96.doc 1t/08/97

II

lB the present invention in which a separation device is combined with a fractionation device in the form of a pulp screen.

to 7~

R

\\MrLBO1\home$\Vic',ty\Keep\speci% ;2747.96.doc 19/08/97 The arrangement shown comprises a pulp -creen with an airtight casing 1, which has an inlet 2 for inject and outlets 3 and, respectively, 4 for accept and, respectively, reject. A rotation symmetrical screening member 5 with vertical axle is located in the casing i. The pulp inlet 2, which preferably is tangential, communicates with the inside of the screening member 5 at the upper end thereof while the .reject outlet 4 communicates with the lower end of the screening member. The accept outlet 3 is connected to a space 6, which is located outside and extends about the screening member 5. In connection to the upper pprtion of the casing, a space with outlet 7 for heavy impurities, such as sand and scrap, is located.

A rotor 8 within the screening member 5 extends along the entire screening member. The rotor* is concentric with the-.screening member in sach a way that a screening zone 9 extending all about is formed between the rotor and screening member. The rotor 8 and screening member 5 can be cylindric or conic.

The rotor 8 preferably is provided with wing elements 10, which are intended to bring about pulsations in the pulp in the screening zone 9 in order to break up the fiber network and. to render it poss- :ible to divide the pulp into accept and reject.

A member 11 for the separation of light impurities is connected cebttrally to the upper portion of the casing I and communicates with the interior of the casing 1 via a passage 12. The said member is formed i :with a rotation symmetrical housing, which preferably comprises a conic upward diverging lower portion 13 and a substantially cylindric upper portion 14. In the transition between the lower and upper houso* a 9* ^\a e f.

a WO 96/17998 PCT/SE95/01340 ing portions 13, 14, an inlet 15 for dilution liquid is connected tangentially, and an outlet 16 for light impurities is located centrally at the top of the housing 11. In said outlet 16 a valve 17 is located, for example a sluice valve, for controlling the outflow from the member 11.

A rotor axle 18 can possibly be provided to extend from the casing 1 through the passage 12 upward in the housing 13,14, and a rotor element 19 with a carrier be attached to the axle 18 in the housing 13,14. The rotor axle 18 can be :ovided with a screw thread 20 for upward feeding. The rotor axle 18 preferably is driven by being attached to the rotor 8 of the fractionation device. The rotor element 19 preferably shall be located on the same height as the inlet 15 for dilution liquid so that correct flow geometry is obtained.

The rotor element supplies energy, which otherwise must have been supplied by the inlet rate and amount of dilution liquid. By using the rotor element, thus, the dilution amount supplied can be reduced at maintained separation effectiveness.

The pulp suspension is supplied through the inlet 3 in the casing 1 where it is caused to rotate due to the tangential supply and the rotation of the rotor 8. Scrap and other heavy impurities are collected in the space 7 by the effect of centrifugal force. The pulp is introduced into tht. screening zone 9 and moves axially downward to the reject outlet 4 while being simultaneously rotated. The accept passes thereby through the apertures of the screening member 5. The wing elements 10 bring about pulsations in the pulp which facilitate the division into accept and reject. The reject is discharged through the outlet 4.

Due to the rotation of the pulp in the casing 1, the,light impurities are collected centrally at the top of the casing. The location and design of the separation device 11 give rise to an upward directed flow centrally in the passage 12 at the same time as a downward directed return flow is caused in the outward portion of the passag 12.

auL. I P WO 96/17998 PCT/pSE95/013u 4 The light impurities are thereby moved up through the passage 12 to the member 11 where they are collected centrally upwardly. By tangential supply of dilution liquid through the' inlet 15 energy is supplied which drives the rotation and produces suitable flow conditions to enrich the impurities and promote the collection of light impurities centrally upwardly in the device 11. These impurities can thereby be taken out through the outlet 16. The discharge, which is controlled by a valve 17, can be continous or intermittent, depending on the amount of impurities. When the arrangemeht comprises a rotor axle 18 with a rotor: element 19, the rotation of the contents in the housing 13,14 is affected additionally in that the effect of the tangential dilution liquid supply is increased.

The flow rate through the passage 12 shall be low; of the magnitude 0,02 m/s. The conical design of the lower portion 13 of the device 11 promotes in this portion circulation, which is directed upward at the centre and downward along the conical walls, at the same time as there is a horizontal rotation movement.in the entire device 11. Owing to the location of the tangential inlet 15 for dilution liquid, an opposed circulation movement is caused in the upper portion 14, i.e. a movement directed downward at the centre and upward along the outer walls, Which results in a movement of the light i,mpurities toward the centre in this portion 14.

In the embodiment shown the separation device 11 for light impurities is shown connected to a type of screen arrangement, but it is obvious that also other types of fractionation means can be applied, for eample screens with rotating screen members and screens with other types of rotors. The screening can take place from the inside outward or from the outside inward through the screen member. The screening can also take place during the passage from above downward or from below upward through the screening zone. In all cases is common, that the pulp suspension shall be rotated in the upper portion of the casing of the fractionation device.

The invention, of course, is not restricted to the embodiments shown, but can be varied within the scope of the invention idea.

Claims (7)

1. An arrangement for separating light impurities from pulp suspensions, for connecting to a casing of a fractionation device where the fiber network is broken up and the pulp is caused to rotate for enriching the light impurities, wherein the separation arrangement is designed with a rotationally symmetrical housing connected centrally to the upper portion of the casing through a passage, that an inlet for dilution liquid is connected tangentially to the housing, and that an outlet for the light impurities is located centrally at the top of the housing.
2. An arrangement as claimed in claim 1, wherein the housing consists of an upward diverging lower portion and a substantially cylindric upper portion, and the dilution liquid inlet is located in the passage between the lowr and upper portion. 20
3. An arrangement as claimed in either claim 1 or 2, wherein the division of the housing into a lower and upper portion is determined from a flow aspect of the location of the dilution liquid inlet. 25
4. An arrangement as claimed in any one of the preceding claims, wherein a valve is located in the outlet for controlling the discharge of light impurities.
5. An arrangement as claimed in any one of the a, preceding claims, wherein a rotor axle with a rotor element extends through the passage from the casing of the fractionation device into the housing to effect the rotation of the contents in the housing.
6. An arrangement as claimed in claim 5, wherein the rotor axle is provided with a screw thread for upward S feeding. \\HELO1\home$\Vicky\Kee\sPeci\42747.96.doc 1810/97 I1P3iil-r 6-
7. An arrangement for separating light impurities from pulp suspensions substantially as hereinbefore described with reference to the accompanying drawings. Dated this 18th day of August 1997 SUNDS DEFIBRATOR INDUSTRIES AB By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent Attorns~ys of Australia 4 44e4 *4* 0* 4 S. 94 S a S S .9 4 4 J;i \MELB01\hog~29\Vicky\Keep\speci\4274 7 .9 6 .doc 18108/97
AU42747/96A 1992-11-16 1995-11-13 Screening arrangement Ceased AU683786B2 (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
JP35824092A JP3173199B2 (en) 1992-11-16 1992-12-26 Feedback processing condition correction device
JP36011192A JP3206167B2 (en) 1992-12-28 1992-12-28 Feedback processing condition correction device
SE9404264A SE504162C2 (en) 1994-12-07 1994-12-07 A screening device
SE9404264 1994-12-07
PCT/SE1995/001340 WO1996017998A1 (en) 1994-12-07 1995-11-13 Screening arrangement

Publications (2)

Publication Number Publication Date
AU4274796A AU4274796A (en) 1996-06-26
AU683786B2 true AU683786B2 (en) 1997-11-20

Family

ID=27341575

Family Applications (1)

Application Number Title Priority Date Filing Date
AU42747/96A Ceased AU683786B2 (en) 1992-11-16 1995-11-13 Screening arrangement

Country Status (1)

Country Link
AU (1) AU683786B2 (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4107033A (en) * 1976-03-20 1978-08-15 Hermann Finckh Maschinenfabrik Apparatus for cleaning fibrous suspensions of low stock consistency
GB2109260A (en) * 1981-10-13 1983-06-02 Voith Gmbh J M Sorting fibre suspensions

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4107033A (en) * 1976-03-20 1978-08-15 Hermann Finckh Maschinenfabrik Apparatus for cleaning fibrous suspensions of low stock consistency
GB2109260A (en) * 1981-10-13 1983-06-02 Voith Gmbh J M Sorting fibre suspensions

Also Published As

Publication number Publication date
AU4274796A (en) 1996-06-26

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