US3007839A - Method and plant for continuous cellulose digestion - Google Patents

Method and plant for continuous cellulose digestion Download PDF

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Publication number
US3007839A
US3007839A US825764A US82576459A US3007839A US 3007839 A US3007839 A US 3007839A US 825764 A US825764 A US 825764A US 82576459 A US82576459 A US 82576459A US 3007839 A US3007839 A US 3007839A
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Prior art keywords
digester
outlet
fiber material
digesting
liquid
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US825764A
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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
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/02—Washing ; Displacing cooking or pulp-treating liquors contained in the pulp by fluids, e.g. wash water or other pulp-treating agents
    • 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

  • the present invention relates to a method and a plant or apparatus for the liberation of cellulosic fiber material by its digestion with digesting liquor at a raised pressure and a raised temperature in a continuous digester.
  • the object of the invention is to improve the pulp quality, in methods and plants, as referred to, by decreasing the possibility of a chemical attack during the discharge of the pulp from the digester; and the essential characterizing feature of the invention resides in that a part of the digesting liquor is withdrawn from the fiber material immediately before the same passes out through the digester outlet and in that this withdrawn digesting liquor is replaced by a weaker liquid which then accompanics the fiber material out through the digester outlet.
  • this weaker liquid consists of digesting liquor diluted by washwater and taken from a device for washing the digested fiber material, e. g., a Wash filter, disposed downstream from the digester.
  • liquid is of a temperature considerably digesting temperature and accordingly, in the digester outlet, the fiber material will desirably be mixed with a liquid which in comparison to the aforesaid withdrawn digesting liquor is weaker as to its content of chemicals as well as being cooler and, therefore, less detrimental than the digesting liquor in two respects.
  • a withdrawn digesting liquor fracthe replacement lower than the first such withdrawn fraction, being of high temperature, it is possible by lowering the pressure to obtain low-pressure steam which advantageously may be used for steaming or preheating the fiber material supplied to the digester; whereas the second withdrawn fraction, which is at too low a temperature for satisfactorily giving off usable steam, may be used for other heating purposes.
  • the numeral 11 designates a steam vessel in which wood chips or other comminuted cellulosic fiber materials supplied through a low-pressure charging apparatus 15, are heated by low pressure steam supplied through conduit 17, while the material is stirred and conveyed towards the outlet end of the steaming vessel by means of conveyer screw 19.
  • a desired superatmospheric pressure preferably about 1 atmosphere gauge, is maintained in vessel 11 as by means of an automatic control valve 21.
  • a suitable digesting liquor for instance sodium lye
  • the mixture of chips and lye is transferred by means of a high-pressure charging apparatus 23 from the vessel 11 into a loop of circulating lye flushing the chips to the upper end of a standing cylindrical digester 25, as indicated.
  • the chips are fed downwardly into the digester as by means of a motor-driven screw conveyer 27, and a large part of the lye is withdrawn through a cylindrical sieve 29 and by means of pump 31 is pumped through a heat exchanger 33, where it is heated. From there, the lye is returned to the charging apparatus 23 and carries chips charged into the same, with it to the digester.
  • a further heating of the mixture of chips and lye is eifected by means of a circulation system comprising two sieve girdles 35, 37 in the digester wall, a pump 39, a heat exchanger 41 and a return conduit 43 extending centrally in the digester and discharging, at about the center of the digester, the circulating lye taken out from the sieve girdles and heated in the heat exchanger 41.
  • the lye is heated to a temperature of approximately C.
  • the sieve girdles 35, 37 may be of the type disclosed in Patent No. 2,695,232, and the disclosure of that patent is hereby incorporated herein by reference.
  • a conventional valve 35a is shown for connecting the sieve girdles 35, 37 individually, or one at a time, to the pump 39, as indicated, .and also as suggested in the aforesaid patent.
  • a hydraulic pressure of the order of 10 atmosphere gauge is maintained in the digester.
  • a reaction with the digesting liquor takes place, as is understood, so that the fiber material is completely digested when it reaches the lower end of the digester.
  • the material is fed down into a centrally located outlet 45 as by means of a motor-driven scraping or stirring device 47.
  • a throttling device 49 Inserted in the conduit connected to the digester outlet is a throttling device 49 by means of which the material is conveyed into a blow tank 44 in which atmospheric pressure or a low superatmospheric pressure is maintained.
  • the steam given off due to the pressure drop escapes through an outlet 46, whereas the pulp is discharged through a bottom outlet 48 and is carried through a conduit connected there to, and in which a valve 50 controlled by the level of the blow tank is inserted, to the pulp vat. 52 of a conventional rotary suction filter.
  • the valve 50 may be of the type disclosed in Swedish Patent 137,071.
  • Part of the filtrate which consists of digesting liquor diluted with washwater is collected in a container 60 from which it is returned through a conduit 51 to the digester to be used therein in accordance with the invention and in a manner to be described in more detail hereinafter.
  • a sieve girdle consisting of a perforated or slitted cylindrical sieve plate 53 arranged flush with the cylindrical wall of the digester, as disclosed in the aforesaid U.S. patent.
  • a space 55 for collection of sieved-off or withdrawn digesting liquor is arranged in a widened part of the digester wall exterior of said sieve plate.
  • Said collecting space is shown as being connected by means of a conduit 57 to a steam separating device 59, preferably made as a cyclone, with the conduit 57 opening tangentially thereinto, as is understood.
  • the upper steam outlet of cyclone 59 is shown as being connected through the conduit 17 to the steaming vessel 11, and therefore, a comparatively low superatmospheric pressure is maintained in the cylone 59.
  • a comparatively low superatmospheric pressure is maintained in the cylone 59.
  • a second similar sieve girdle 68 Adjacent to and below the sieve girdle 53, a second similar sieve girdle 68 is shown as being inserted in the digester wall.
  • the space 70 for collecting digesting liquor'in back of the sieve 68 is separated or hydraulically isolated from the space 55 and is shown as being connected by means of a conduit 72 to a second steam separating device which also preferably is made as a cyclone 74 having a tangential inlet of the conduit72.
  • the steam outlet of the cyclone 74 is connected to a condenser 76 in which the steam formed in the cyclone 74 is condensed and used, for instance, for producing warm water or for some other heating purpose, such as preheating the digesting liquor supplied to the digester through the conduit 22.
  • the digesting liquor discharged through the'bottom outlet of cyclone 74 is delivered by means of a pump 78 through a valve 80 controlled by the liquid level of the cyclone and through the conduit 82 to a plant for recovery of the chemicals of the digesting liquor.
  • the cyclone 74 can be shut-off by means of the valves 84, 86 when there is no need to take steam out of the digesting liquor flowing through the conduit 72, or'when the liquor temperature is so low that the steam given off is of practically no value.
  • said fraction of the digesting liquor can be carried to a container 92 from which it is pumped directly into the conduit82, valve 80 also being controlled by the liquid level in container 92, as indicated.
  • the cyclone 74 can be omitted from the apparatus.
  • valves 94 and 6 Shown as being inserted in the conduits 57 and 72 are conventional valves 94 and 6, respectively, which are suitably controlled in known manner by the quantity of liquid flowing thereto in such a manner as to maintain said quantity at a desired value.
  • the digesting liquor taken out through the sieve girdles 53, 68 is replaced by liquid taken from the container 60 by the conduit 51 and pumped into the digester by means of a high pressure pump 65.
  • a vertically etxending conduit 67 which penetrates the digester wall close to the upper end of the digester, as shown, and runs concentrically within the tube 43, preferably being suspended along the vertical center line or axis of the digester and having an open lower end at about the level of the sieve :girdle 53.
  • the lower end of tube 67 is perforated, as shown.
  • Liquid pumped in through conduit 67 is distributed from the lower end thereof in the digester radially in all directions and displaces a corresponding quantity of digesting liquor.
  • the washing liquid supplied by tube 67 reaches the digester wall and consequently the digesting liquor taken out from the sieve girdle 68 is diluted or partially diluted and forms a second but diluted lye fraction of a reduced temperature.
  • the replacement liquid can be suppliedto the digester through a fluid distribution system or arrangement connected to the pump 65 and opening into the space between the sievegirdle 63-and the scraping and stirring device 47.
  • a fluid distribution system or arrangement is shown in the drawing as comprising an annular tube or fluid conduit 69 which is connected to a number of branch tubes 71 distributed around the digester and penetrating its wall, as indicated, with tube 69 being connected to the outlet of pump 65.
  • the tubes 71 have orifices which are radially or somewhat tangentially disposed in the same direction relative to the digester wall and situated at some distance from the digester wall, as indicated.
  • the quantity of liquid supplied through this system may be in excess of the quantity of digesting liquid withdrawn from the digester so that the pulp at the digester bottom will be diluted to a lower consistency, thereby facilitating its discharge through the outlet 45 and the throttle device 49.
  • the sieve girdles 53, 68 may be divided either along an axial plane or a transverse plane, only parts thereof being used at any given time and the connected parts being shifted periodically.
  • the replacement liquid can be more or less pure water and the heat content of the withdrawn or sieved-off liquid can be utilized for purposes other than those mentioned above.
  • the replacement liquid referred to, may be supplied through an axial tube connected to the center of the rotary scraper 47 at the bottom of the digester. In case the amount of replacement liquid obtainable from the vessel 60 does not suffice for effecting a desired degree of cooling at the outlet end of the digester, an additional amount may be recirculated through a branch line connecting conduit 82 to conduit 51.
  • a method of liberating cellulosic fiber material by digestion thereof with a digesting liquor at a raised pressure and a raised temperature in a continuous digester having an inlet and an outlet said method being characterized in introducing a weaker liquid centrally in said digester flowing outwardly and axially downwardly with said digesting liquor to displace at least a part of the same from the fiber material, withdrawing the displaced liquor from the digester immediately before the fiber material passes out through the outlet of the digester, some of the withdrawn digesting liquor being undiluted while some of it is diluted by said weaker liquid, simultaneously and separately collecting said diluted and undiluted withdrawn fractions, and discharging said fiber material through said outlet together with at least a portion of said weaker liquid, at least a portion of said weaker liquid having previously to passed through the digester outlet together with fiber material.
  • Apparatus of the character described for continuously digesting cellulosic fiber material comprising: an upright cylindrical digester vessel having an upper inlet and a bottom outlet; means for delivering fibrous material and digesting liquor to said digester vessel through said inlet; means for washing the fibrous material downstream of said digester vessel; means for conveying fibrous material from said digester vessel outlet to said Washing means; agitating means arranged in said digester vessel upstream from and adjacent to said bottom outlet; means for conveying a mixture of digesting liquor and Wash Water from said washing means back to said digester vessel, said last-mentioned means including a conduit having an outlet and extending axially downwardly along the central region of the digester vessel, said conduit constructed and arranged to introduce the mixture of Wash water and digesting liquid outwardly and axially downwardly into said vessel; first means for Withdrawing substantially undiluted digesting liquor from said vessel disposed adjacent said conduit outlet but above the efiective path of fluid flow therefrom; and second means disposed adjacent to and below said conduit outlet for simultaneously withdrawing
  • conduit outlet is constructed and arranged to provide a substantially conical dispersion of said Wash water and digester liquid.
  • Apparatus defined in claim 3 including a steam separating device operatively connected to said first means, said device being at a lower pressure than said digester whereby steam is given ofi therein, and means for conveying this steam given oil? in said separating device to preheat the fibrous material being delivered to said digester.
  • Apparatus defined in claim 5 including a second steam separating device operatively connected to said second means to recover the low quality steam from the diluted digesting liquid recovered therefrom.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
US825764A 1958-07-09 1959-07-08 Method and plant for continuous cellulose digestion Expired - Lifetime US3007839A (en)

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SE3007839X 1958-07-09

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DE (1) DE1262116B (de)
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Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3158533A (en) * 1962-09-21 1964-11-24 Improved Machinery Inc Continuous pulping extraction apparatus
US3243341A (en) * 1961-11-20 1966-03-29 Improved Machinery Inc Continuous pulping apparatus
US3298899A (en) * 1962-03-03 1967-01-17 Kamyr Ab Method and arrangement for washing and cooling at the outlet end of a continuous cellulose digester
US3313677A (en) * 1962-03-30 1967-04-11 Black Clawson Co Two-stage continuous digestion with removal of liquor in first stage and recirculation of liquor in second stage
US3313678A (en) * 1962-02-14 1967-04-11 Svenska Cellulose Aktiebolaget Bleaching of cellulose pulp in towers in completely filled and closed system
US3332836A (en) * 1964-08-28 1967-07-25 American Defibrator Continuous impregnation and digestion apparatus for the production of wood pulp
US3515631A (en) * 1965-07-14 1970-06-02 Curt Fredrick Rosenblad Method and system for flushing sulphite pulp digesters
US3874996A (en) * 1973-04-02 1975-04-01 Sterling Drug Inc Chip feeder for high pressure pulping system
US4028171A (en) * 1974-07-05 1977-06-07 Kamyr Aktiebolag Method for continuous treatment of fiber material in a vertical array
US4033811A (en) * 1975-06-09 1977-07-05 Stig Gloersen Method and apparatus for filling of fiber material and liquid to steam phase in treatment vessel
US4061193A (en) * 1975-09-15 1977-12-06 Kamyr, Inc. Method and apparatus for digesting cellulose material without screening digesting liquid withdrawn through the digester top
US4078964A (en) * 1973-12-10 1978-03-14 Kamyr Ab Method and apparatus for filling a pressure treatment vessel with a fiber material and liquid mixture
US4212705A (en) * 1978-05-22 1980-07-15 Babington William M Jr Apparatus for recovering high pressure steam from a blow tank
US5766418A (en) * 1996-09-13 1998-06-16 Ahlstrom Machinery Inc. Handling fibrous material used to produce cellulose pulp
US5795438A (en) * 1996-11-04 1998-08-18 Ahlstrom Machinery Inc. Method and apparatus for feeding multiple digesters
US5985096A (en) * 1997-09-23 1999-11-16 Ahlstrom Machinery Inc. Vertical pulping digester having substantially constant diameter
US20020129911A1 (en) * 2000-10-16 2002-09-19 Marcoccia Bruno S. Process and configuration for providing external upflow/internal downflow in a continuous digester
EP3129546A4 (de) * 2014-04-07 2017-11-15 Stora Enso Oyj Verfahren zum aufschluss von cellulosefasermaterial in einem kontinuierlichen faulbehälter
US11162218B1 (en) 2020-09-30 2021-11-02 Robert Clayton Biomass pulp digester

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3434920A (en) * 1965-10-07 1969-03-25 Frank B K Green Apparatus for continuous digesting
CH602963A5 (de) * 1975-11-19 1978-08-15 Sulzer Ag

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2360779A (en) * 1940-07-31 1944-10-17 Int Paper Co Method of screening and washing paper pulp
US2695232A (en) * 1950-07-08 1954-11-23 Kamyr Ab Apparatus for heating and controlling the temperature of a continuously operating cellulose digester
US2876098A (en) * 1956-01-11 1959-03-03 Hans Werner Meyer Process of and apparatus for the continuous manufacture of cellulose or hemicellulose from cellulosic fibrous materials
US2920697A (en) * 1953-03-28 1960-01-12 Braunschweigische Maschb Ansta Apparatus for the production of cellulose

Family Cites Families (10)

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Publication number Priority date Publication date Assignee Title
DE322270C (de) * 1918-05-11 1920-06-23 Waldhof Zellstoff Fab Verfahren zum Entleeren von Zellstoffkochern
DE527206C (de) * 1929-08-11 1931-06-15 Knut Madsen Strand Zellstoffkocher
US1914073A (en) * 1931-02-06 1933-06-13 Brobeck Arnold Method for the digestion of materials containing cellulose
DE945972C (de) * 1941-11-22 1956-07-19 Rosenblads Patenter Ab Verfahren und Vorrichtung zum Entlaugen von Zellstoff
DE868695C (de) * 1943-10-10 1953-02-26 Kamyr Ab Vorrichtung zum Beschicken von Zellstoffkochern unter Druck
DE897948C (de) * 1951-12-21 1953-11-26 Kamyr Ab Verfahren und Vorrichtung zum kontinuierlichen Aufschliessen von Faserstoffen
DE1010819B (de) * 1953-07-13 1957-06-19 Aschaffenburger Zellstoffwerke Verfahren zur Entleerung von Sulfitzellstoffkochern
US2769710A (en) * 1954-01-12 1956-11-06 Cellulose Dev Corp Ltd Process for the continuous treatment of vegetable fibers
DE1017016B (de) * 1955-01-31 1957-10-03 Meyer Hans Vorrichtung zur fortlaufenden Entnahme von aufgeschlossenem Faserstoff aus Kontinuierlich betriebenen Zellstoffkochern
US2870009A (en) * 1955-06-15 1959-01-20 Kamyr Ab Method and apparatus for the separation of liquids from cellulosic pulp

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2360779A (en) * 1940-07-31 1944-10-17 Int Paper Co Method of screening and washing paper pulp
US2695232A (en) * 1950-07-08 1954-11-23 Kamyr Ab Apparatus for heating and controlling the temperature of a continuously operating cellulose digester
US2920697A (en) * 1953-03-28 1960-01-12 Braunschweigische Maschb Ansta Apparatus for the production of cellulose
US2876098A (en) * 1956-01-11 1959-03-03 Hans Werner Meyer Process of and apparatus for the continuous manufacture of cellulose or hemicellulose from cellulosic fibrous materials

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3243341A (en) * 1961-11-20 1966-03-29 Improved Machinery Inc Continuous pulping apparatus
US3313678A (en) * 1962-02-14 1967-04-11 Svenska Cellulose Aktiebolaget Bleaching of cellulose pulp in towers in completely filled and closed system
US3298899A (en) * 1962-03-03 1967-01-17 Kamyr Ab Method and arrangement for washing and cooling at the outlet end of a continuous cellulose digester
US3313677A (en) * 1962-03-30 1967-04-11 Black Clawson Co Two-stage continuous digestion with removal of liquor in first stage and recirculation of liquor in second stage
US3158533A (en) * 1962-09-21 1964-11-24 Improved Machinery Inc Continuous pulping extraction apparatus
US3332836A (en) * 1964-08-28 1967-07-25 American Defibrator Continuous impregnation and digestion apparatus for the production of wood pulp
US3515631A (en) * 1965-07-14 1970-06-02 Curt Fredrick Rosenblad Method and system for flushing sulphite pulp digesters
US3874996A (en) * 1973-04-02 1975-04-01 Sterling Drug Inc Chip feeder for high pressure pulping system
US4078964A (en) * 1973-12-10 1978-03-14 Kamyr Ab Method and apparatus for filling a pressure treatment vessel with a fiber material and liquid mixture
US4028171A (en) * 1974-07-05 1977-06-07 Kamyr Aktiebolag Method for continuous treatment of fiber material in a vertical array
US4033811A (en) * 1975-06-09 1977-07-05 Stig Gloersen Method and apparatus for filling of fiber material and liquid to steam phase in treatment vessel
US4061193A (en) * 1975-09-15 1977-12-06 Kamyr, Inc. Method and apparatus for digesting cellulose material without screening digesting liquid withdrawn through the digester top
US4212705A (en) * 1978-05-22 1980-07-15 Babington William M Jr Apparatus for recovering high pressure steam from a blow tank
US5766418A (en) * 1996-09-13 1998-06-16 Ahlstrom Machinery Inc. Handling fibrous material used to produce cellulose pulp
US5795438A (en) * 1996-11-04 1998-08-18 Ahlstrom Machinery Inc. Method and apparatus for feeding multiple digesters
US5985096A (en) * 1997-09-23 1999-11-16 Ahlstrom Machinery Inc. Vertical pulping digester having substantially constant diameter
US20020129911A1 (en) * 2000-10-16 2002-09-19 Marcoccia Bruno S. Process and configuration for providing external upflow/internal downflow in a continuous digester
EP3129546A4 (de) * 2014-04-07 2017-11-15 Stora Enso Oyj Verfahren zum aufschluss von cellulosefasermaterial in einem kontinuierlichen faulbehälter
US11162218B1 (en) 2020-09-30 2021-11-02 Robert Clayton Biomass pulp digester

Also Published As

Publication number Publication date
DE1262116B (de) 1968-02-29
FR1229425A (fr) 1960-09-07

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