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Publication numberUS3589521 A
Publication typeGrant
Publication dateJun 29, 1971
Filing dateSep 13, 1968
Priority dateSep 15, 1967
Also published asDE1792528B1
Publication numberUS 3589521 A, US 3589521A, US-A-3589521, US3589521 A, US3589521A
InventorsJohan C F C Richter
Original AssigneeKamyr Ab
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Device for cleaning of screens in cellulose digesters
US 3589521 A
Abstract  available in
Images(2)
Previous page
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Claims  available in
Description  (OCR text may contain errors)

United States Patent Johan c. F. c. Richter [72] Inventor St. Jean Cap Ferrat, France (21] Appl, No. 759,632 [22] Filed Sept. i3, [968 [45] Patented June 29, 1971 [73] Assignee AktiebolagetKamyr Karlstad, Sweden [32] Priority Sept. 15, 1967 [33] France 12,729/67 [54] DEVICE FOR CLEANING 0F SCREENS IN CELLULOSE DIGESTERS 4 Claims, 4 Drawing Figs.

[52] U.S..Cl 210/411, 162/251,162/275,209/380,210/415 [51] Int. Cl B07b 1/50 [50] Field of Search... [62/272, 25l.48.60.274.275;210/4l5.411.4|2,395:209/380 [56] References Cited UNITED STATES PATENTS 3,434,920 3/1969 Green 162/251 X 3,360,907 1/1968 Clark et a1. 210/411 X FOREIGN PATENTS 146,907 7/1954 Sweden Primary ExaminerS. Leon Bashore Assistant Examiner-R. H. Tushin Att0rneyCushman, Darby and Cushman ABSTRACT: Screens inserted in the shell ofa continuous cellulose digester are cleaned by a liquid under high pressure pumped through a sector of the screen during the normal operation of the digester and while the rest of the sd for drawing off digesting liquor from the fibrous material in the digester. The cleaning liquid passes the screen in the opposite direction to the digesting liquor and works loose fibers wedged into the slits of the screen. On the pulp side of the screen the sector being cleaned is blinded off by a turning cover plate, and the space back of screen is divided into sector-shaped compartments. By means of valves a conduit for circulating cleaning liquid is connected to the space within the sealing edge of the cover plate and to the opposite compartment. By

'tuming the cover plate and adjusting the valves one screen PATENTEU JUN29|971 SHEET 2 OF 2 INVENTOR uunw crc 5cm.-

ATTORNEYS DEVICE FOR CLEANING F SCREENS IN CELLIUILOSE llItllGlES'lIlElRS The invention relates to a device for cleaning of screens inserted in containers for treatments, particularly digestion, of finely comminuted cellulosic material, and serving for straining off liquid from the cellulosic material. Particularly the invention relates to a screen-cleaning device of the kind comprising a movable cover plate arranged on the fiber material side of the screen, which cover plate has an edge surrounding and sealing off a portion of the face of said screen, a conduit for cleaning liquid being connected to the space between said screen part and said cover plate.

In a known device of said kind, as described in Swedish Pat. No. 146,907 liquid taken from the space behind the screen is forced back through the screen and is carried off together with particles worked loose from the screen apertures through the conduit connected to the cover plate. Thus, the screen is cleaned by a flow of liquid of the kind mixed with the cellu losic material, and also the possible fluid pressure is restricted.

The object of the present invention is to improve screencleaning devices of the above-mentioned kind so as to make them more efficient. A chamber back of the screen is divided up into compartments separated from each other and connected to individual conduits. Thereby the cleaning liquid flow can be made independent of the function of the screen and can take plate without disturbing the same. For instance, cleaning liquid may be forced through the screen with a considerably higher pressure than the pressure of the container, so that the force exerted by the cleaning liquid upon the particles clogging the screen apertures can be made greater than the force by which they have been wedged into the same during the previous screening period, and consequently said particles can be worked loose more easily. Furthermore, the cleaning liquid can be held separated from the liquid mixed with the cellulosic material, involving the possibility of using any suitable kind of cleaning liquid, e.g. a chemically active liquid, which dissolves heavily adhering deposits upon the screen and which is of such a kind that it should not be mixed into the liquid treating the cellulosic material. For instance, in screens used for drawing off dissolved reaction products from the fibrous material after a prehydrolysis step in a continuous cellulose digester, clogging deposits will often form in the screen apertures already after a few hours of operation and obviously it is a great advantage to be able to perform during the continuous operation of the digester, a dissolution of the deposits by means of a scavenging flow of sodium lye or similar caustic chemicals.

An embodiment of the device according to the invention will be more closely described herein below with reference to the accompanying drawings, in which FIG. 1 is a vertical sectional view of the screen according to the invention, FIG. 2 is a horizontal sectional view of the screen, FIG. 3 is an elevational view thereof taken from the right-hand side in FIG. l, and FIG. 4 is a vertical sectional view taken from the line lV-IV of FIG. ll.

Referring to FIGS. l and 2, the number 11 designates the cylindrical shell of an upright cylindrical cellulose digester adapted for carrying out continuous digester of cellulosic material, such as wood chips. At the level of the digester where the wood chips should be relieved of used liquor and reaction products, such as black liquor with an admixture of prehydrolysate, there are inserted in the digester shell a number of screens, only one thereof being shown in the drawings.

The shown screen is composed of a number of parallel, closely set vertical screen rods 13 and a screen chamber 15 back thereof. The latter is formed by a back wall 17 and a cylindrical flange 19 having a recess against which the screen rods rest with their ends and are held evenly spaced so that their sides facing the interior of the digester form a flat circular surface in which there are parallel slits of a suitable width for retaining the chips and letting the digesting liquor through. These screening rods and the chamber form a unit which is inserted in an annular flange 21 integral with the digester shell and is attached thereto by means of a flat annular flange 23 in such a position that said flat screen surface is flush with the digester wall 11 or somewhat retracted.

Approximately half of the screen surface at a time is covered by a half-circular cover plate 25 or eyelid" attached to a hollow shaft 27 extending centrally through the screen and its chamber. Said shaft is journaled in a central bearing sleeve 29 integral with the backwall 17 of the screen chamber and extending therefrom in the forward as well as in the backward direction. The shaft 27 is sealed to said bearing sleeve by means of a stuffing box 31. Attached to the backward end of the shaft is a handle 33 or other operating means whereby the shaft and the cover plate 25 attached thereto can be turned and set in any desired angular position. Normal positions are the position shown and the diametrically opposite position obtained by a turning movement of In both of said positions the straight edge 35 of the cover plate is vertical and parallel to the screen rods 13, so that the cover plate offers the least possible resistance to movement of the chips in the length direction of the digester and so that the exposed slits between the screen rods are swept in their entire lengths by the chips, a certain automatic cleaning effect being obtained.

The cover plate 25 is somewhat convex or domed inwardly but its straight edge 35 as well as its half-circular edge 37 fit closely to the screen so that a cavity 9 closed off from the digester is formed on the back side of the cover plate. Via the central bore 411 and radial bores 43 in the shaft 27 said cavity communicates with a space 45 in the bearing sleeve 29, which space is connected by means of a conduit 47 to a manifold 49 common to several screens. Such liquid as enters the cavity 39 from the screen chamber is let out in the described path.

By means of a diametrically extending vertical partition 51 (FIG. 4) the screen chamber 15 is divided upon into two compartments 53, 55, completely separated from each other. In each of the several screen units the left-hand compartment 53 communicates via a conduit 57 extending through the backwall 17, with a manifold 59, whereas the right-hand compartment of each screen communicates over a conduit 61 with a manifold 63. By means of a three-way valve 65 the manifold 59 can be connected either to a main discharge conduit 67 for extracted digesting liquor and/or to a scavenging liquid conduit 69. Similarly the manifold 63 can be connected by means of a three-way valve 71 either to the conduit 67 or the conduit 69. The two three-way valves should always connect the manifolds differently, and therefore they are preferably mechanically coupled so as to be reset simultaneously and in a fixed relation.

The conduit 69 is connected to the manifold 49 over a motor'driven pump 73, so that said pump can maintain a circulation of liquid which when the cover plate 25 takes the position shown runs in the loop 73, 69, 65, 59, 57, 53, 39, 41, 43, 45, 47, 49, 73. Cleaning liquid which may be strong sodium lye, is introduced into said loop from a supply tank 75. When the cleaning liquid has become too contaminated with dissolved impurities, it is drained through conduit 79 by opening valve 77. During said cleaning of one screen half the other can be used for withdrawing digesting liquor which is discharged through 55, 61, 63, 71, 67. After a while a shift is made by turning the cover plate 25 through 180 and resetting the three-way valves. The cleaning liquid passes from the pump 73 through 69, 71, 63, 61, 55, 39, 41, 43, 45, 47, 49 back to the pump, and simultaneously the withdrawn digesting liquor runs through 53, 57, 59, 65 to the draining conduit 67.

It is apparent apparent that the cleaning liquid will clean not only the screen proper but also all parts of the screen chamber back thereof and also the manifolds 49, 59, 63 as well as all conduits connected thereto and the three-way valves.

The shown embodiment is merely an example which may be modified in various respects within the scope of the invention as set forth in the following claims. Thus, in principle, it is possible to have the cover plate blind merely a small sector of the screen; then the screen chamber must be divided up into a greater number of chambers having a correspondingly smaller angular extension. Thus, if the cover plate forms a sector of 120, the screen chamber must be divided in three compartments by means of radial partitions.

On account of the independent scavenging system it is possible to use for the cleaning another liquid than the liquid mixed with the eellulosic material for treating the same, but obviously said latter liquid may also be used for the cleaning purpose here contemplated. In this case the invention offers the advantage that the cleaning can take place at a higher pressure than the pressure prevailing in the digester, because the cover plate seals off the pressure of the cleaning liquid. ln screens inserted in a container for treatment of pulp at a low temperature, the invention offers the possibility of cleaning the screens with heated liquid of one kind or another.

What I claim is:

1. Apparatus for cleaning of screens inserted in containers for treatment of finely comminuted eellulosic material and serving for drawing off liquid from the eellulosic material, said apparatus comprising: a cover plate covering a portion of the screen; means for moving the cover plate over the screen on the eellulosic material side thereof, said cover plate having an edge closely applied against the screen and surrounding a part of its surface and defining a cavity with said surface; a cleaning liquid discharge conduit extending through the cover plate and opening out into said cavity; means defining a chamber located on the opposite side of the screen from the cover plate; partition means dividing said chamber into separate compartments, said partition means having edges adjacent said screen opposite said cover plate which cooperate with the edge of said cover plate to maintain said cavity in communication with a given compartment, and a separate conduit connected to each compartment for delivery thereto a stream of cleaning liquid when said cavity is in communication with said given compartment whereby cleaning liquid will flow through said screen from said given compartment to said cavity and out through said discharge conduit.

2. Apparatus as in claim 1 wherein said screen is flat and circular, wherein said partition means extends diametrically of said screen to form two compartments, and wherein said cover plate is semicircular so that the edge thereof can be located, upon rotation of said cover plate, to cover the screen surface opposite either compartment and leave the rest of the screen surface exposed to the eellulosic material.

3. Apparatus as in claim 1 including valve means connected to said separate conduits, means connected to said valve means for supplying cleaning liquid under pressure, each valve means also connected to a main discharge conduit, said valve means operative such that with one valve in position to connect its associated compartment conduit with said cleaning liquid the other valves are positioned to connect their associated compartment conduits with said main discharge conduitv 4. Apparatus as in claim 1 including a supply tank of cleaning liquid, means for supplying said cleaning liquid under pressure from said supply tank to one of said separate conduits when the compartment associated with that separate conduit is covered by said cover plate whereby cleaning liquid flows through said one conduit into said compartment, then through said screen into said cavity and then through said cleaning liquid discharge conduit.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 35 95 Dated June 29, -97

Johan C.F.C. RICHTER Patent No.

Inventor(s) in the above-identified patent It is certified that error appears corrected as shown below:

and that said Letters Patent are hereby In the front page format, line 33:

"France" should read Sweden Signed and sealed this 7th day of March 1972.

EDWARD PLFLb'TCIflRJR.

Commissioner of Patents Abtesting Officer USCOMM'DC 60376-P69 FORM PO-OSO (\0-69} n u s covzmmzm vnmnuc OFFICE uses o-zss-su

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3360907 *Oct 17, 1963Jan 2, 1968Southwest Res InstApparatus for cleaning filters
US3434920 *Oct 7, 1965Mar 25, 1969Green Frank B KApparatus for continuous digesting
SE146907A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3755072 *Oct 23, 1970Aug 28, 1973Kamyr AbStrainer device for cellulose digester
US3971715 *Mar 10, 1975Jul 27, 1976Albert WehnerDevice for sieving, sorting, filtering and the like
US3979289 *Aug 23, 1974Sep 7, 1976Water Pollution Control CorporationFiltration method
US4167482 *Oct 6, 1977Sep 11, 1979Mueller HansFiltering method and apparatus
US4219420 *Feb 9, 1979Aug 26, 1980Chemap AgArrangement for and a process of filtering a contaminated medium
US4284120 *Apr 23, 1979Aug 18, 1981Gloeersen StigMethod and device for transfer of fiber materials transportable by liquids
US4995944 *Aug 9, 1990Feb 26, 1991Dearborn Chemical Company Ltd.Controlling deposits on paper machine felts using cationic polymer and cationic surfactant mixture
US5223097 *Jun 20, 1989Jun 29, 1993W. R. Grace AbMethod for controlling pitch on a paper-making machine
US5565061 *Jun 14, 1994Oct 15, 1996Salminen; ReijoMethod and apparatus for removing scales deposited on the strainer of a pulp digester
US5626720 *May 19, 1995May 6, 1997W.R. Grace & Co.-Conn.Method for controlling pitch on a papermaking machine
US6010013 *Feb 3, 1997Jan 4, 2000Meurer Industries, Inc.Universal method of and apparatus for screening debris
US6120647 *Jan 26, 1998Sep 19, 2000Ahlstrom Machinery Inc.Simplified liquid removal system for a cellulose pulp digester
US20020129911 *Oct 16, 2001Sep 19, 2002Marcoccia Bruno S.Process and configuration for providing external upflow/internal downflow in a continuous digester
WO1998033603A1 *Jan 20, 1998Aug 6, 1998Meurer Industries, Inc.Universal method of and apparatus for screening debris
Classifications
U.S. Classification210/411, 162/275, 209/380, 210/415, 162/251
International ClassificationD21C7/00, D21F1/32
Cooperative ClassificationD21C7/00, D21F1/32
European ClassificationD21F1/32, D21C7/00