US3886035A - Process for separating knots from pulp - Google Patents

Process for separating knots from pulp Download PDF

Info

Publication number
US3886035A
US3886035A US339759A US33975973A US3886035A US 3886035 A US3886035 A US 3886035A US 339759 A US339759 A US 339759A US 33975973 A US33975973 A US 33975973A US 3886035 A US3886035 A US 3886035A
Authority
US
United States
Prior art keywords
knots
wood chips
pulp
fibers
digester
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.)
Expired - Lifetime
Application number
US339759A
Other languages
English (en)
Inventor
Oliver A Laakso
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.)
Kamyr Inc
Original Assignee
Kamyr Inc
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 Kamyr Inc filed Critical Kamyr Inc
Priority to US339759A priority Critical patent/US3886035A/en
Priority to JP9482673A priority patent/JPS545004B2/ja
Priority to CA182,004A priority patent/CA987263A/en
Priority to SE7313951A priority patent/SE404209B/xx
Priority to FI3190/73A priority patent/FI56215C/fi
Priority to FR7341302A priority patent/FR2221577B1/fr
Priority to BR74214A priority patent/BR7400214D0/pt
Priority to US05/563,171 priority patent/US4000063A/en
Application granted granted Critical
Publication of US3886035A publication Critical patent/US3886035A/en
Priority to CA238,375A priority patent/CA1010406A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

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

  • ABSTRACT An improved system for the production of digested pulp from wood chips and knots which includes a separating apparatus, connected to the digester output, capable of separating knots from partially cooked wood chips and fibers at the digester pressure and consistency.
  • the separated fibers and fiber bundles pass to a refiner where the fiber bundles are mechanically reduced to fibers in a liquid environment at a high consistency and at the digester pressure.
  • the knots are then re-cycled to the digester or other processes.
  • the process of digesting wood chips comprises immersing the wood chips and knots in a digesting liquor under a pressure of from about 150-250 P816 in order to chemically reduce at least some of the wood chips to the constituent fibers.
  • the wood chips and knots are washed then with water in order to separate the partially reduced wood chips fibers and knots from the digesting liquor and to form a pulp having a solid consistency of about 10-15 percent.
  • Pulp cooking processes are well known in which a charge of wood chips which includes knots and other large impurities is subjected, in a digester, to a digesting liquor which chemically reduces most of the wood chips to their constituent fibers. Further, it is known to wash these fibers in the digester with water to remove at least a portion of the digesting liquor therefrom and to form a pulp of water, fibers, fiber bundles and knots. It is also known to remove the knots from said pulp in a separating apparatus and to feed the pulp to a refiner to mechanically break down those fiber bundles which had resisted the digesting liquid.
  • a recently developed digester is shown in the US. h No. to Laakso 3,298,899, issued Jan. I7, 1967.
  • This digester produces a pulp having a safe level of actlye digesting liquor, for example, 0.05 pounds of active dlgeslihg liquor per cubic foot of pulp and thus eliminates the need of water dilution for the refiners.
  • a pulp digesting system of a separating apparatus comprising a separating chamber, a screen comprising a plurality of closely spaced helically threaded intermeshing screws or peripherally contacting rolls having cooperating grooves, positioned vertically in the chamber, and dividing the chamber into inlet and outlet sections, a pulp supply inlet for supplying pressurized pulp from a digester into the inlet section of the chamber, means for rotating all of the screws or rolls in the same direction for feeding the pulp in cooperation with the pulp pressure through the screws or rolls to a pulp outlet and means for discharging the knots and other large impurities which do not pass through said screws or rolls from a knot outlet.
  • FIG. I is a schematic view showing a system for digesting pulp including the separating apparatus of this invention.
  • FIG. 2 is a front sectional view along the center line of the separating apparatus shown in FIG. 1',
  • FIG. 3 is a top view of the separating apparatus along the line 3-3 shown in FIG. 2;
  • FIG. 4 shows the grooved rolls which are shown in FIG. 2;
  • FIG. 5 is a view similar to FIG. 2 but showing another embodiment of the separator
  • FIG. 6 is a top view along the line 6-6 of FIG. 5;
  • FIG. 7 is a view of the separating apparatus shown in FIG. 5 showing the action of the screw threads
  • FIG. 8 is a sectional side view of FIG. 5 showing an optional feature.
  • FIG. 1 shows a portion of a plant for processing wood chips into pulp.
  • the wood chips which also include knots or the like, are introduced into a pre-impregnation vessel (not shown) where they are impregnated with the digesting liquor and then circulated via a pump (not shown) to digester 10 where most of the chips are reduced by the digesting liquor to their constituent fibers and washed with water to remove the digesting liquor.
  • a pump not shown
  • Continuous digesters of the type now in large scale use produce a relatively high density pulp containing from 8-l5 percent fiber solids.
  • This pulp usually includes a minor percentage of undigested particles, mostly knots, wh have to be removed to obtain a high quality pape P uct.
  • digesters with improved wash Cycles, sLl h as are described in the aforementioned patent produce pulp which contains very little active digesting Iiq for example, about 0.05 pounds per cubic foot. a thus this pulp may be passed directly to a refiner without a prior dilution to reduce the digesting liquor content to a safe level.
  • knots and relatively large, unreduced particles are removed without diluting the pulp by the separating apparatus 12.
  • the pulp issuing under pressure from digester which may be about 440 tons/day in volume is fed by the digester pressure of about lSO-ZSO psig to the separating apparatus via conduit 11 and a conventional consistency controller 13.
  • Separated knots, and the like are discharged from outlet 14 located at the bottom of the separating apparatus 12 at the volume of about 88 ton/day while the accepted pulp is discharged at outlet 16 at the volume of about 352 ton/day.
  • the pulp may be passed by conduit 18 to refiner 20 which is employed to mechanically remove any shives or fiber bundles which pass through the separating apparatus 12 with the pulp.
  • the refiner does not encounter knots or the like because these were removed upstream at the separating apparatus 12 and thus the effluent from the refiners is a clean pulp consisting almost solely of individual fibers which are capable of forming high grade pa per.
  • the pulp exiting from the refiner 20 is fed to a stock storage receptacle 22 through the stand pipe 21 where it is stored as base stock for use in the paper making process.
  • the combination of the pressure on the inlet side and the head pressure of the stand pipe 21 insures that the refiner always operates wet, i.e., that the refining action always takes place in a liquid state where forces applied to the edge of the fiber bundles are transferred by the incompressible liquid to all portions thereof.
  • a more efficient refining action is provided in addition to a more efficient separating action.
  • knots and the like and the small amount of rejected pulp which pass from the separating apparatus 12 through the outlet 14 are diluted by water from conduit 23 to a solids content less than 7 percent and generally about 1% percent.
  • This slurry of knots, water and some pulp is then fed to the conventional gravity knot ter 24 in which the pulp is fed through a screen while the knots are rejected and fall over a spillway,
  • the accepted pulp then passes from outlet 26 of knotter 24 to a standard thickener 28 where the pulp consistency is increased to about 6.5 percent solids content.
  • This thickened pulp next passes to the recycle tank 30 where it is stored prior to recycling.
  • pump 32 When it is desired to recycle the pulp, pump 32 is en ergized and the pulp is pumped through conduit 33 which joins conduit ll upstream of the consistency controller 13.
  • knots which are rejected by gravity knotter 24 pass through the outlet 34 of the knotter 24 and fall through conduit 36 into the knot storage tank 38 where they are stored at a solids content of about 3.5 percent prior to recycling.
  • the knots are recycled by pump 40 and conduit 41 to the digester 10.
  • the knots are usually broken down by the digesting liquor to their constituent fibers on a second through the digester.
  • the separating apparatus is divided into an inlet chamber 42 and an outlet chamber 44 by a circular ring of grooved rolls 46 as is best seen in FIGS. 2 and 3.
  • the pulp and knots enter from the conduit ll through the inlet 15 at the top of the separating apparatus 12 at a flow rate of about 1000 gpm or 440 tons/day.
  • Most of the pulp passes between the grooved rolls under the digester pressure of between lSO-ZSO psig which is transferred via conduit 11 (minus normal friction losses) to chamber 42 which is always kept completely full of liquid and pulp.
  • knots and that portion of pulp not passing through the grooved rolls 46 pass, under the combined force of gravity and digester pressure, to outlet 14 of the separating apparatus 12 and are expelled therefrom.
  • the accepted pulp enters the annular outlet chamber 44 which surrounds the ring of rolls and is forced therefrom, out through outlet 16 under the pressure of fresh pulp which continually enters this area.
  • each grooved roll 46 contact each other at their peripheries.
  • Each grooved roll contains a plurality of square cut grooves 48 which are separated by ridges.
  • the grooves are disposed at an angle of about 20 percent with respect to the horizontal plane.
  • the rolls 46 are so arranged that the grooves 48 of adjacent rolls 46 are in register with ridges which define the grooves of the adjacent rolls.
  • the pattern of grooves 48 at the point of contact between adjacent rolls 46 will change from the pattern shown at A in FIG, 4 to that shown at B and then back that shown at A. It is therefore seen that the grooved rolls 46, during rotation, produce an oscillatory motion at the face of the rolls which keeps the plurality of rolls from being clogged by a film of knots while the grooves 48 provide access for pulp to enter the outlet chamber and the rotary movement of the rolls 46 helps to draw pulp through the grooves.
  • the rolls are powered, for example, by a standard 30 hp electric motor 50 and which is connected to an input shaft 54.
  • a bevel gear 56 is attached to the end of the input shaft 54 and this gear is in meshing engagement with the ring gear 58 which is mounted upon shaft 60 to transfer power to said ring gear.
  • the gear 62 mounted upon the shaft 60 is the gear 62 which, in turn, transfers power to the gear 64 mounted upon the main drive shaft 66.
  • the main drive shaft 66 powers one of the rolls 46 through coupling 68, and packing ring 70.
  • Shaft 66 like all the other shafts 76 discussed below, is journallcd by conventional roller bearings 77 and all the rolls 46 are similarly journalled by bearings 79.
  • the shaft 66 also has mounted thereupon a gear 72 which is in meshing engagement with the bull gear 74.
  • the bull gear 74 is mounted for rotation about the axis of the inlet 15 and inlet chamber 42 of the separating apparatus [2.
  • the bull gear 74 also is in meshing engagement with a plurality of gears 73 which are similar to gear 72.
  • the other gears 73 are, in turn. mounted upon journalled stub shafts 76 which are each connected through separate coupling means 78 and separate packing rings 86 to separate rolls 46. In all, there are about 20 such rolls and they are arranged on a ring having the inlet axis as its axis, but more or less may be used depending on the size of rolls 46 and the capacity of separator 12.
  • the above described drive system provides an efficient way to rotate all the rolls 46 in a common direction since no motion is lost in chain or pulley drives.
  • the circular arrangement of the rolls provides for a maximum separating surface within the area of the separating apparatus.
  • the pulp enters the inlet chamber 93 ofthe separating apparatus 12 through inlet 15 from the conduit 11 at about [000 gpm, here the pulp is deflected by the baffle 194 from a vertically downward to a horizontal path and encounters the plurality of intermeshing screws 96 which are disposed in a semicircle.
  • the screws divide inlet chamber 93 from outlet chamber 98.
  • Most of the pulp passes through the screws 96 by means discussed in detail below at a rate of about 850 gpm while all the knots and some pulp pass out through the knot outlet 14 at a rate of about l50 gpm.
  • the accepted pulp leaves the separating apparatus 12 by the pulp outlet 14.
  • a mechanical agitator 100 ofa generally windshield wiper" type shape is oscillated by motor 102 and transmission ]03 to cause the agitator blade 104 to continually sweep to the area adjacent the screws to thereby avoid a knot build-up thereupon.
  • the screws 96 are each mounted on separate shafts 106 and the tops of these shafts protrude outwardly from the separating apparatus 12' through packing means 108 while the bottoms of the shafts are rotatabiy mounted in bearings 110 (shown in FIG. 8).
  • a verti cally disposed central drive shaft 112 is also provided and connected to the other shafts by chains 114 which rotate all the screws 96 in a common direction.
  • the central shaft is powered by a motor (not shown) which rotates shaft 17 and the chain 19.
  • the shafts are rotated at the speed of between 75 and 150 rpm.
  • inlet 15 and outlet 14 are secured by means of flanges 124 and 125, respectively, and the outlet 16 is welded to the separating apparatus 12'.
  • the entire separating apparatus may be disassembled without disconnecting the outlet flanges.
  • the pulp is pushed through the interstices between the rotating screws by the digester pressure of inlet chamber 93 while the knots are carried downward by the screws.
  • the rotating screw threads help to feed the pulp through the interstices between the intermeshing screws by providing a surface which continuously moves from the inlet to the outlet section.
  • the surface also moves continuously from the outlet to the inlet sections as well, but when a point P upon the screw thread begins to rotate back into the inlet section, the higher pressure existing in the inlet section strips the pulp from the thread thus freeing it to receive a new load of pulp in the inlet section.
  • the relatively small pressure drop across the row of screws which may be approximately 10 psia aids the operation of the separating apparatus 12 and 12 Moreover, the degree of intermeshing between adjacent screws may be varied from a minimum overlap when the outer diameter of the screws just touch to a maximum overlay in which the pressure drop across the screws becomes excessive due to the limitation of the area through which the pulp may flow.
  • the grooved rolls could be replaced with meshing screws as described with respect to the second embodiment.
  • knots may be passed directly to other process equipment where they can be used as the base stock in a process for making, for example. corrugated cardboard boxes.
  • a method for digesting wood chips and knots comprising:
  • step c) The method as recited in claim 1 further including the step of re-immersing the knots which have been separated in step c) in said digesting liquor to chemically reduce the knots to their constituent fibers.
  • step c The method as recited in claim 1 further including the steps of diluting the knots and fibers which have been separated from the partially reduced wood chips and fibers in step c) to a solids concentration less than 7 percent and then separating the knots from the fibers.
  • the method as recited in claim 4 further including the step of re-immersing the separated knots in the digesting liquor to chemically reduce the knots to their constituent fibers.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Paper (AREA)
US339759A 1973-03-12 1973-03-12 Process for separating knots from pulp Expired - Lifetime US3886035A (en)

Priority Applications (9)

Application Number Priority Date Filing Date Title
US339759A US3886035A (en) 1973-03-12 1973-03-12 Process for separating knots from pulp
JP9482673A JPS545004B2 (it) 1973-03-12 1973-08-22
CA182,004A CA987263A (en) 1973-03-12 1973-09-26 Inclined or vertical rotating grooved-rollers for separating knots from pulp
FI3190/73A FI56215C (fi) 1973-03-12 1973-10-15 Foerfarande foer kokning av traespaonor och kvistar samt apparat foer tillaempning av detta foerfarande
SE7313951A SE404209B (sv) 1973-03-12 1973-10-15 Forfaringssett och apparat for separering av knutar fran kokt treflis
FR7341302A FR2221577B1 (it) 1973-03-12 1973-11-20
BR74214A BR7400214D0 (pt) 1973-03-12 1974-01-14 Aparelho aperfeicaodo para separar nos e outras grandes particulas nao-digeridas de cavacas e fibras de madeira parcialmente digeridas e respectivo processo aperfeicoado
US05/563,171 US4000063A (en) 1973-03-12 1975-03-28 Apparatus for separating knots from pulp
CA238,375A CA1010406A (en) 1973-03-12 1975-10-27 Process for separating knots from pulp

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US339759A US3886035A (en) 1973-03-12 1973-03-12 Process for separating knots from pulp

Related Child Applications (1)

Application Number Title Priority Date Filing Date
US05/563,171 Division US4000063A (en) 1973-03-12 1975-03-28 Apparatus for separating knots from pulp

Publications (1)

Publication Number Publication Date
US3886035A true US3886035A (en) 1975-05-27

Family

ID=23330457

Family Applications (1)

Application Number Title Priority Date Filing Date
US339759A Expired - Lifetime US3886035A (en) 1973-03-12 1973-03-12 Process for separating knots from pulp

Country Status (7)

Country Link
US (1) US3886035A (it)
JP (1) JPS545004B2 (it)
BR (1) BR7400214D0 (it)
CA (1) CA987263A (it)
FI (1) FI56215C (it)
FR (1) FR2221577B1 (it)
SE (1) SE404209B (it)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4014736A (en) * 1974-12-17 1977-03-29 The Ontario Paper Company Limited Process for treating a slurry of cellulosic material
US4046621A (en) * 1974-12-17 1977-09-06 The Ontario Paper Company Limited Process for treating a slurry of cellulosic material
US4230524A (en) * 1977-07-08 1980-10-28 Borregaard A/S Method for the production of unbleached sulphite cellulose or bleached cellulose from a defibrated knot pulp
US4466862A (en) * 1981-03-23 1984-08-21 International Paper Company Method for screening, separating, and removing fiber bundles, lumps, knots and foreign matter from aqueous dispersions used in forming non-woven fabrics by wet-laying
USRE32182E (en) * 1981-03-23 1986-06-17 International Paper Co. Method for screening, separating, and removing fiber bundles, lumps, knots and foreign matter from aqueous dispersions used in forming non-woven fabrics by wet-laying
WO1995023257A1 (en) * 1994-02-23 1995-08-31 Kvaerner Pulping Technologies Ab Recycling of knots in a continuous process for cooking chemical pulp
US20030116661A1 (en) * 2001-12-10 2003-06-26 Samuel Schabel Method of regulating sorting systems and a sorting system suitable for carrying out this method
US20070045157A1 (en) * 2005-08-29 2007-03-01 Kajzer Wieslaw C Recovery of pin chips from a chip washing reject stream
WO2011102760A1 (en) * 2010-02-17 2011-08-25 Metso Paper Sweden Ab Method and system for recycling of rejects in a process for cooking chemical pulp
US9580864B2 (en) * 2011-08-30 2017-02-28 Valmet Ab Kraft cooking method using polysulfide cooking liquor

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2846941A1 (de) * 1977-11-09 1979-10-04 Rader Int Ab Vorrichtung zur groessenaufteilung von korn- oder stueckfoermigem material

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US553945A (en) * 1896-02-04 Paper pulp
US1275299A (en) * 1918-05-06 1918-08-13 Adam Pellerin Bull-screen cleaner.
US2707905A (en) * 1953-04-01 1955-05-10 Wilfred F Mathewson Pulp screen
US3219187A (en) * 1961-06-16 1965-11-23 Kamyr Ab Apparatus for the classification of finely divided materials

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US553945A (en) * 1896-02-04 Paper pulp
US1275299A (en) * 1918-05-06 1918-08-13 Adam Pellerin Bull-screen cleaner.
US2707905A (en) * 1953-04-01 1955-05-10 Wilfred F Mathewson Pulp screen
US3219187A (en) * 1961-06-16 1965-11-23 Kamyr Ab Apparatus for the classification of finely divided materials

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4014736A (en) * 1974-12-17 1977-03-29 The Ontario Paper Company Limited Process for treating a slurry of cellulosic material
US4046621A (en) * 1974-12-17 1977-09-06 The Ontario Paper Company Limited Process for treating a slurry of cellulosic material
US4230524A (en) * 1977-07-08 1980-10-28 Borregaard A/S Method for the production of unbleached sulphite cellulose or bleached cellulose from a defibrated knot pulp
US4466862A (en) * 1981-03-23 1984-08-21 International Paper Company Method for screening, separating, and removing fiber bundles, lumps, knots and foreign matter from aqueous dispersions used in forming non-woven fabrics by wet-laying
USRE32182E (en) * 1981-03-23 1986-06-17 International Paper Co. Method for screening, separating, and removing fiber bundles, lumps, knots and foreign matter from aqueous dispersions used in forming non-woven fabrics by wet-laying
WO1995023257A1 (en) * 1994-02-23 1995-08-31 Kvaerner Pulping Technologies Ab Recycling of knots in a continuous process for cooking chemical pulp
US5672245A (en) * 1994-02-23 1997-09-30 Kvaerner Pulping Technologies Aktiebolag Recycling of knots in a continuous process for cooking chemical pulp
US20030116661A1 (en) * 2001-12-10 2003-06-26 Samuel Schabel Method of regulating sorting systems and a sorting system suitable for carrying out this method
US7083049B2 (en) * 2001-12-10 2006-08-01 Voith Paper Patent Gmbh Method of regulating sorting systems and a sorting system suitable for carrying out this method
US20070045157A1 (en) * 2005-08-29 2007-03-01 Kajzer Wieslaw C Recovery of pin chips from a chip washing reject stream
WO2011102760A1 (en) * 2010-02-17 2011-08-25 Metso Paper Sweden Ab Method and system for recycling of rejects in a process for cooking chemical pulp
US9580864B2 (en) * 2011-08-30 2017-02-28 Valmet Ab Kraft cooking method using polysulfide cooking liquor

Also Published As

Publication number Publication date
FI56215C (fi) 1979-12-10
SE404209B (sv) 1978-09-25
FR2221577A1 (it) 1974-10-11
JPS545004B2 (it) 1979-03-13
JPS49117705A (it) 1974-11-11
FR2221577B1 (it) 1979-10-19
CA987263A (en) 1976-04-13
FI56215B (fi) 1979-08-31
BR7400214D0 (pt) 1974-11-05

Similar Documents

Publication Publication Date Title
CN104711880B (zh) 一种化学机械浆制浆工艺
US3886035A (en) Process for separating knots from pulp
US3814246A (en) Method for centrifugally removing liquid from a mixture
CN105696393B (zh) 一种湿强废纸再利用化学机械制浆方法
CN105544264B (zh) 湿强废纸再利用化学机械制浆系统
US4324612A (en) Process for the preparation of groundwood pulp
CA2503619A1 (en) Method and device for handling cellulose pulp
US4619736A (en) Apparatus for defiberizing, screening and pumping cellulose pulp or recycled paper
EP0856079B1 (en) Supply of washing liquid in a fractionating multi-stage washer
US3245868A (en) Continuous process for the recovery of paper broke containing a wet strength resin
US4207139A (en) Method for producing groundwood pulp
US4288288A (en) Apparatus for mixing chemicals into pulp at a refiner inlet
US2641164A (en) Method for processing fibrous pulp
CN204039825U (zh) 一种湿强废纸回收再利用化学机械制浆系统
US4002528A (en) Apparatus for processing pulp
US4000063A (en) Apparatus for separating knots from pulp
US2791503A (en) Process for producing semichemical pulp
CN101838943B (zh) 一种节子节能环保制浆方法及设备
US1960106A (en) Method and apparatus for reconditioning paper stock
CN208562978U (zh) 一种废纸制浆的预处理装置
US1936697A (en) Paper manufacture
CN104514167A (zh) 转鼓式水力碎解机
US3499528A (en) Pressurized knotter screen
US2977274A (en) Digestion of pulp
CN105648817B (zh) 一种湿强废纸回收再利用制浆系统