US3578554A - Method for common digestion of two differently pre-treated fractions of wood chips - Google Patents

Method for common digestion of two differently pre-treated fractions of wood chips Download PDF

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Publication number
US3578554A
US3578554A US760486A US3578554DA US3578554A US 3578554 A US3578554 A US 3578554A US 760486 A US760486 A US 760486A US 3578554D A US3578554D A US 3578554DA US 3578554 A US3578554 A US 3578554A
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Prior art keywords
chips
digester
fraction
steaming
fractions
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Expired - Lifetime
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US760486A
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English (en)
Inventor
Johan C F C Richter
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Metso Fiber Karlstad AB
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Kamyr AB
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/22—Other features of pulping processes

Definitions

  • the pre-treatrnent of the coarser fraction consists in steaming and thorough impregnation With digesting liquor, and the pre-treatment of the finer fraction consists in merely steaming or steaming and impregnation during a shorter time.
  • the two fractions are conveyed to the digester top in different ways, the coarser chips being suspended in circulating liquid, and the finer chips may be blown by steam, preferably steam later used for heating the digester to digesting temperature.
  • the invention relates to digestion of wood chips in a continuous cellulose digester.
  • said difficulties are obviated thereby that the charge of chips is divided by screening into a larger fraction of coarser particles and a smaller fraction of finer particles and that said fractions after separate pre-treatment and separate transportation up to the digester top are mixed and digested in common.
  • a pre-treatment adapted to the respective particle size the subsequent digestion can take place in common in a single digester with comparatively good result.
  • the coarser chips fraction is steamed and impregnated with digesting liquor by immersion therein, whereas the finer chips fraction is steamed and possibly mixed with digesting liquor in a separate operation.
  • the advantage is gained that the coarser chips fraction can be pumped into the digester by the use of circulating liquid which, due to the risk of clogging the screens would not be possible if the finer particles were admixed thereto, whereas the finer chips fraction is easy to convey to the digester top by blowing With steam.
  • the finer chips fraction is easy to convey to the digester top by blowing With steam.
  • A designates generally an upright cylindrical cellulose digester adapted for continuous downwardly directed feed of the fibrous material
  • B and C designate two devices connected in parallel to the digester and adapted for pre-treatment and supply of chips thereto.
  • the pre-treatment device B is provided for a finer fraction of the hewn chips available in the cellulose mill in question, which fraction is obtained by screening and to which may be admixed sawdust in a percentage of about 15 percent as a maximum.
  • Said fiber material is introduced into a hopper 11, from which it is transferred via a rotary low-pressure feeder valve 13 into a steaming vessel 15, in which the chips are steamed by low-pressure steam, supplied through the conduit 19, while being stirred by the conveying screw 17.
  • the cylindrical steaming vessel is substantially horizontal but may be somewhat inclined so that its output end towards which the chips are moved by the conveying screw 17, is located at a somewhat higher level than the input end.
  • a small quantity of digesting liquor supplied through the conduit 21 may be introduced into the steaming vessel in order to have the chips impregnated, at least superficially, with said liquor.
  • the liquor forms a pool at the charging end of the steaming vessel, and the chips are immersed into said pool before they are raised by the feeding screw 17.
  • the chips are carried through a high-pressure feeder valve 23 and a standpipe 25 up to the digester top.
  • the steaming vessel is located at ground level, whereas the digester top is situated at a level of several tens of meters above ground, power being required for the chips transportation.
  • the chips are conveyed by a flow of steam, high-pressure steam from conduit 27 being supplied not only to the high-pressure feeder valve 23 in order to flush out its chips-filled pockets, but also via a branch conduit 29 to the lower end of the standpipe 25 in a required quantity controlled by the valve 31.
  • the pre-treatment device C is provided for the coarser fraction of the wood chips obtained during the screening thereof. Said fraction is introduced into a hopper 33 and discharged by a rotary feeder valve 35 into the top of an upright cylindrical vessel 37 adapted for a combined steaming and impregnating treatment of the chips.
  • the upper part of said vessel is maintained filled with low-pressure steam supplied through the conduit 19 and the lower part thereof is maintained filledto a predetermined level with such digesting liquor, for instance sulphate liquor, as should be used for digestion of the fiber material in the continuous digester A and taken from the conduit 21.
  • digesting liquor for instance sulphate liquor
  • the chips then move as a solid column continuously down below the surface level in the vessel, the chips particles being impregnated with digesting liquor by absorption.
  • the mixture of chips and digesting liquor is discharged at the bottom end of the vessel by means of a motor-driven rotary scraper 41 and is transferred to the top of the digester A by means of a conveying device operating with circulating liquid and comprising a high-pressure feeder valve 43 of known construction, a screening device 45 located near the digester top and two conduits 47, 49 extending therebetween.
  • Small batches of the chips-liquor-mixture are successively introduced into the pockets of the rotary feeder valve when said pockets are in the vertical position, a corresponding amount of liquor being reurned by means of the pump 51 through the conduit 53 to the vessel 37.
  • the pockets When the pockets have been turned to their horizontal position, they form part of a circulation loop under high pressure and the chips-liquor-batch therein is fed through the conduit 47 to the screening device 45 by the action of the pump 55 which is supplied with liquor drawn otf the chips through a screen 57 in the device 45 and returned through the conduit 49.
  • the pump maintains a circulating liquid flow by which the chips are carried from the bottom of the vessel 37 to the top of the digester A.
  • a feeding screw 59 By means of a feeding screw 59 the chips are lifted above the liquor level in the device 45 and are dropped through the outlet 61 into the uppermost steam-filled space of the digester.
  • the conduit 25 Also connected to said space is the conduit 25 which supplies the high-pressure steam required for a first digesting treatment in steam phase and also the finer wood material carried therewith.
  • said material will be mixed with the coarser material in connection with the charging of the digester.
  • the digester may be of any previously known design. According to the drawing there follows upon the steam phase digesting step a digesting step in liquid phase comprising circulation and heating of the digesting liquor in a heat exchanger 63. In the lower part of the digester the pulp is washed by liquid supplied at the digester bottom through the conduit 65 and heated at a somewhat higher level by circulation through a heat exchanger 67. Said liquid is then driven upwardly in counter-current to the downwardly moving chips column and is finally discharged together with black liquor through a sieve girdle 69 inserted in the digester shell, and transferred to the two blow tanks 71, 73 connected in series.
  • the steam released due to the pressure drop in the first tank 71 flows through the conduit 75 to the vessel 37 and is used therein for the steaming of the chips.
  • the digested and preliminary washed pulp is discharged from the dige ter by means of a rotary scraper 77 and departs through the throttling device 79 and the conduit 81.
  • the invention provides the possibility of pretreating the two chips fractions in mutually different ways and so that the best possible final result is obtained after the common digestion of the two fractions.
  • the finer material into which the digesting liquor penetrates more easily can be 4 pre-impregnated with digesting liquor during a much shorter time than the coarser material, or is not pre-impregnated at all, because the former is more easily digested or will get a sufiicient contact with the digesting liquor after its introduction into the digester.
  • the duration and the temperature of the steaming operation of the two chips kinds can be chosen differently and adapted to the degree of comminution of the material.
  • a method for digesting a charge of wood chips in a continuous cellulosic digester comprising the steps of:

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  • Paper (AREA)
US760486A 1967-09-18 1968-09-18 Method for common digestion of two differently pre-treated fractions of wood chips Expired - Lifetime US3578554A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SE12803/67A SE305582B (sv) 1967-09-18 1967-09-18

Publications (1)

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US3578554A true US3578554A (en) 1971-05-11

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Family Applications (1)

Application Number Title Priority Date Filing Date
US760486A Expired - Lifetime US3578554A (en) 1967-09-18 1968-09-18 Method for common digestion of two differently pre-treated fractions of wood chips

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US (1) US3578554A (sv)
BR (1) BR6802420D0 (sv)
DE (1) DE1792540C2 (sv)
FI (1) FI47390C (sv)
FR (1) FR1583131A (sv)
NO (1) NO120660B (sv)
SE (1) SE305582B (sv)

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3830689A (en) * 1968-11-19 1974-08-20 Metsaluton Selluloosa Oy Separate impregnation and common digestion of different wooden raw materials
US4096027A (en) * 1976-02-19 1978-06-20 Kamyr Inc. System for presteaming wood chips at or near atmospheric pressure with minimum displacement of air
US4123318A (en) * 1976-06-29 1978-10-31 Kamyr, Inc. Three-vessel treatment system
US4152197A (en) * 1974-09-23 1979-05-01 Mo Och Domsjo Ab Process for preparing high-yield cellulose pulps by vapor phase pulping an unpulped portion of lignocellulosic material and a partially chemically pulped portion
US4599138A (en) * 1977-05-02 1986-07-08 Mooch Domsjo Aktiebolag Process for pretreating particulate lignocellulosic material to remove heavy metals
WO1986006769A1 (en) * 1985-05-06 1986-11-20 Sunds Defibrator Aktiebolag Manufacture of mechanical pulp
US5213662A (en) * 1991-08-14 1993-05-25 Kamyr, Inc. Treatment of chips with high temperature black liquor to reduce black liquor viscosity
US5679217A (en) * 1994-02-10 1997-10-21 Kvaerner Pulping Ab Method and apparatus for optimizing the liquor-to-wood ratio during the production of paper pulp
US5795438A (en) * 1996-11-04 1998-08-18 Ahlstrom Machinery Inc. Method and apparatus for feeding multiple digesters
US5882477A (en) * 1997-02-10 1999-03-16 Ahlstrom Machinery, Inc. Continuous digester with a low temperature gas-phase
US6336573B1 (en) 1998-04-06 2002-01-08 Andritz-Ahlstrom Inc. Hopper, or bin, screw feeder construction controlling discharge velocity profile
US20020129911A1 (en) * 2000-10-16 2002-09-19 Marcoccia Bruno S. Process and configuration for providing external upflow/internal downflow in a continuous digester
US20050061464A1 (en) * 2001-05-04 2005-03-24 Vidar Snekkenes Feeding arrangement for feeding of chips to chip bins
US20130098569A1 (en) * 2011-04-08 2013-04-25 Pec-Tech Engineering And Construction Pte Ltd Method and system for efficient production of dissolving pulp in a kraft mill producing paper grade pulp with a continuous type digester

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2948336A (en) * 1955-06-06 1960-08-09 Pandia Inc Continuous digester

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3830689A (en) * 1968-11-19 1974-08-20 Metsaluton Selluloosa Oy Separate impregnation and common digestion of different wooden raw materials
US4152197A (en) * 1974-09-23 1979-05-01 Mo Och Domsjo Ab Process for preparing high-yield cellulose pulps by vapor phase pulping an unpulped portion of lignocellulosic material and a partially chemically pulped portion
US4096027A (en) * 1976-02-19 1978-06-20 Kamyr Inc. System for presteaming wood chips at or near atmospheric pressure with minimum displacement of air
US4123318A (en) * 1976-06-29 1978-10-31 Kamyr, Inc. Three-vessel treatment system
US4599138A (en) * 1977-05-02 1986-07-08 Mooch Domsjo Aktiebolag Process for pretreating particulate lignocellulosic material to remove heavy metals
WO1986006769A1 (en) * 1985-05-06 1986-11-20 Sunds Defibrator Aktiebolag Manufacture of mechanical pulp
US5213662A (en) * 1991-08-14 1993-05-25 Kamyr, Inc. Treatment of chips with high temperature black liquor to reduce black liquor viscosity
US5679217A (en) * 1994-02-10 1997-10-21 Kvaerner Pulping Ab Method and apparatus for optimizing the liquor-to-wood ratio during the production of paper pulp
US5795438A (en) * 1996-11-04 1998-08-18 Ahlstrom Machinery Inc. Method and apparatus for feeding multiple digesters
US5882477A (en) * 1997-02-10 1999-03-16 Ahlstrom Machinery, Inc. Continuous digester with a low temperature gas-phase
US6336573B1 (en) 1998-04-06 2002-01-08 Andritz-Ahlstrom Inc. Hopper, or bin, screw feeder construction controlling discharge velocity profile
US20020129911A1 (en) * 2000-10-16 2002-09-19 Marcoccia Bruno S. Process and configuration for providing external upflow/internal downflow in a continuous digester
US20050061464A1 (en) * 2001-05-04 2005-03-24 Vidar Snekkenes Feeding arrangement for feeding of chips to chip bins
US7229524B2 (en) 2001-05-04 2007-06-12 Metso Fiber Karlstad Ab Feeding arrangement for feeding of chips to chip bins
US20130098569A1 (en) * 2011-04-08 2013-04-25 Pec-Tech Engineering And Construction Pte Ltd Method and system for efficient production of dissolving pulp in a kraft mill producing paper grade pulp with a continuous type digester
US8951388B2 (en) * 2011-04-08 2015-02-10 Pec-Tech Engineering And Construction Pte Ltd Method and system for efficient production of dissolving pulp in a kraft mill producing paper grade pulp with a continuous type digester
US9574302B2 (en) * 2011-04-08 2017-02-21 Rge Pte Ltd Method and system for efficient production of dissolving pulp in a kraft mill producing paper grade pulp with a continuous type digester

Also Published As

Publication number Publication date
DE1792540B1 (de) 1972-05-31
FI47390B (sv) 1973-07-31
BR6802420D0 (pt) 1973-06-07
FI47390C (sv) 1973-11-12
FR1583131A (sv) 1969-10-17
NO120660B (sv) 1970-11-16
SE305582B (sv) 1968-10-28
DE1792540C2 (de) 1973-01-04

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