US3832276A - Delignification and bleaching of a cellulose pulp slurry with oxygen - Google Patents

Delignification and bleaching of a cellulose pulp slurry with oxygen Download PDF

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Publication number
US3832276A
US3832276A US00338862A US33886273A US3832276A US 3832276 A US3832276 A US 3832276A US 00338862 A US00338862 A US 00338862A US 33886273 A US33886273 A US 33886273A US 3832276 A US3832276 A US 3832276A
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pulp
slurry
oxygen
bleaching
tower
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US00338862A
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English (en)
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S Roymoulik
K Brown
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International Paper Co
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International Paper Co
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Publication date
Application filed by International Paper Co filed Critical International Paper Co
Priority to US00338862A priority Critical patent/US3832276A/en
Priority to CA192,339A priority patent/CA1007807A/en
Priority to AU66023/74A priority patent/AU489486B2/en
Priority to ZA00741287A priority patent/ZA741287B/xx
Priority to GB921874A priority patent/GB1445276A/en
Priority to BR1573/74A priority patent/BR7401573D0/pt
Priority to FI649/74A priority patent/FI59434C/fi
Priority to NO740795A priority patent/NO144930C/no
Priority to SE7402968A priority patent/SE397983B/xx
Priority to IT67618/74A priority patent/IT1011546B/it
Priority to DE2410934A priority patent/DE2410934C2/de
Priority to JP49026701A priority patent/JPS5747798B2/ja
Priority to FR7407858A priority patent/FR2220620B1/fr
Priority to PH15590*A priority patent/PH10177A/en
Application granted granted Critical
Publication of US3832276A publication Critical patent/US3832276A/en
Priority to AR20291975D priority patent/AR202919A1/es
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/1068—Bleaching ; Apparatus therefor with O2

Definitions

  • an object of the present invention to provide a commercial low cost continuous process for the delignication and bleaching of wood pulp.
  • FIG. 1 is a ow diagram illustrating one embodiment of the present invention
  • FIG. 2 is a flow diagram illustrating another embodiment of the present invention.
  • lFIG. 3 is a graph in which viscosity of the bleached pulp is plotted versus its Kappa No. where pressure is held constant throughout delignification and bleaching with oxygen as against gradually reducing the pressure during the delignification and bleaching with oxygen, as in the present invention.
  • the aqueous bleaching solution can be readily regenerated by adding additional sodium hydroxide or other alkaline agent and recycled. Consequently, unconsumed reagents are reused in this continuous process and ecological contamination is eliminated.
  • an alkaline aqueous pulp of low consistency such as less than about by Weight of wood pulp, preferably between about 2 to 6%, and most desirably between about 3 and 4%, is employed.
  • Sufficient alkali is introduced to elevate the pH of the pulp to between about 9 and 14, and preferably between about 11.5 and 12.5.
  • sodium hydroxide it is usually desirable that about 1 to 10 grams per liter are employed, or to constitute between about 0.1% and 1.0% by weight of the pulp slurry.
  • the alkaline pulp is desirably mixed with oxygen in a high-shear mixing device so that no large bubbles exceeding about 1/16 of an inch in diameter are present.
  • substantially no undissolved oxygen gas is present in the pulp.
  • oxygen is introduced in an amount of between about 0.1 and 4% by weight of aqueous pulp, with amounts of about 0.2 to 0.8% being preferred for softwood, and between about 0.2 and 0.4% by weight giving best results for hardwood pulp.
  • Any undissolved bubbles of oxygen of substantial size are to be avoided, since they cause channeling to disrupt the upward flow of pulp through the bleaching tower, thereby causing non-uniform bleaching, which is highly undesirable. Also larger bubbles tend to agglomerate and this is to be avoided. Any undissolved bubbles should be so nely dispersed as to avoid any substantial agglomeration.
  • Any undissolved oxygen such as bubbles exceeding about V16 inch in diameter, are vented from the system before the oxygenated pulp is introduced into the bleaching tower.
  • the distribution of oxygen through the pulp is desirably achieved through any high-speed, high-shear mixing device or gas absorber.
  • any high-shear mixing device or gas absorber are the Lightening In-line mixer or Line-Blender of Mixing Equipment Co. Inc.
  • any high-shear mixer may be employed.
  • the alkaline aqueous pulp may be briefly subjected to a high pressure oxygen pretreatment before introducing the pulp into the bleaching tower.
  • a high pressure oxygen pretreatment of up to 300 p.s.i.g., or preferably 2 to 10 atmospheres, are desirable. This pretreatment is done briefly in small volume pressure apparatus which does not add substantially to the cost of the apparatus employed.
  • reaction temperature of the aqueous pulp be about 70 to 120 C., with about 90 to 110 C. preferred.
  • reaction temperatures substantially in excess of 100 C. are employed, some means of providing pressure are required.
  • maximum reaction temperatures to be employed will be somewhat dependent on the height of the bleaching tower or initial pressure employed. Desirably the temperature should not exceed the boiling point of the pulp slurry at the pressure involved.
  • the pressure on the aqueous alkaline pulp is gradually reduced by a diferential of at least about one atmosphere, with a maximum differential being about 10 atmospheres.
  • This differential in pressure during the bleaching operation may be represented by the height of the bleaching tower, although any means for gradually and constantly reducing the pressure during treatment may be employed.
  • a 300 foot bleaching tower provides an initial pressure of about 135 p.s.i.g. and a 40 foot bleaching tower provides an initial pressure of about 17 p.s.i.g. It is desirable that a bleaching tower be employed which is not higher than about 300 feet with the minimum height being about 40 feet.
  • the residence time of the aqueous pulp in the bleaching tower may vary depending upon the pressure on the system and on the degree of bleaching required for the particular pulp employed. Some pulps require more drastic bleaching treatment than others, Generally speaking, from about 5 to 120 minutes is suflicient. With a higher initial pressure provided by a higher tower, the time can be reduced to a period of from about 1 minute to 60 minutes. With a 40 foot tower, providing a pressure differential of roughly about one atmosphere, about 30 to 60 minutes, preferably about 40 minutes is satisfactory.
  • the bleaching tower 8 may be one of the pre-existing towers which have been conventional in the paper industry for ybleaching by chlorination. These towers are relatively inexpensive since they require no high pressure specifications and are therefore easily constructed.
  • a pulp slurry of the desired consistency is produced by mixing in make-up tank 1 sufficient pulp, sodium hydroxide or other alkaline agent, such as ammonia, sodium carbonate, etc., and desirably, recycled bleach liquor transferred from stream 2. This recycled liquor is introduced so as to economically reuse the alkaline values of the bleach liquor.
  • Pump 3 carries the alkaline pulp of desired consistency into oxygenator or mixer 4, which is a chamber having a high-speed, high-shear mixing device, such as a Lightnin Mixer, to incorporate and disperse oxygen into the alkaline pulp.
  • oxygen can rst be mixed with the warm alkaline spent liquor stream 2 as shown at 2a in FIG. 1 and recovered at the make-up tank.
  • the oxygenated pulp is then carried to heat exchanger 5 where steam is employed to elevate the temperature to the desired value.
  • the heated alkaline oxygenated pulp is then optionally subjected momentarily to a pre-pressurizing chamber 6 where the pressure is momentarily elevated in that chamber, using oxygen, for a brief period of time. Any undissolved, undispersed oxygen is then removed from the liquid by vent 7 and thereafter the vented oxygenated alkaline pulp is introduced into the bottom of bleaching tower 8.
  • the flow of the alkaline oxygenated pulp is upward through the tower, as shown, with suflicient retention time to permit the desired bleaching and delignification to take place. Agitation of the pulp slurry in the tower is to be avoided.
  • the initial pressure and differential in pressure during the bleaching treatment is determined by the height of the tower 8.
  • the effluent from the tower is then carried though pipe 9 to washer 10.
  • the residual warm alkaline liquor recovered at the first washer is collected in container 11 and part of it is returned through pipe 2 to pulp make-up tank 1. Another part is returned to washer 10.
  • the pulp from washer 10 is then carried through conduit 13 to second washer 14 where wash water is applied and the washed pulp is then carried to succeeding stages of bleaching, such as represented by chlorine dioxide treatments.
  • the effluent is collected in container 15 from which a portion is used for brown stock washing and the remainder carried through conduit 16 .to be used in washing the pulp in iirst washer 10.
  • FIG. 2 differs from that of FIG. 1 in that the pre-pressurizing chamber 6 of FIG. 1 is eliminated.
  • the oxygenator 4 of FIG. 2 has an in-line Lightnin Mixer or other high-shear mixer having the facility of readily dispersing oxygen throughout the pulp.
  • FIG. 3 represents a graph plotting the pulp viscosity versus the Kappa Nos. for two runs, one of which employed constantly decreasing pressure during bleaching in accordance with the present invention (represented by the circled points) (representing a decline of pressure from 40 p.s.i.g. to zero p.s.i.g.) compared with constant pressure (represented by points encompassed by squares) in which the pressure was maintained constantly at 40 p.s.i.g. As shown in FIG. 3, the two curves are represented by straight lines.
  • Viscosity represents a measurement of the average degree of polymerization of the cellulose in the pulp sample, i.e., the average chain length of the cellulose.
  • decreases in viscosity values represent the extent of depolymerization or degradation caused by the bleaching process. Excessive degradation is to be avoided since it provides undesirable physical properties in any paper made from t-he pulp.
  • Kappa No. is determined by the potassium permanganate consumed by a sample of pulp and represents a measurement of its retained lignin content. The higher the Kappa No., the less bleached and delignitied is the pulp. By comparing Kappa Nos. of samples before and after bleaching treatment, one can obtain an evaluation of the extent of delignication which has taken place.
  • the present invention employing gradual reduction in pressure during bleaching and delignification, produces less pulp shrinkage for the same degree of bleaching and delignilication than does oxygen bleaching conducted at constant pressure. This means that there is less damage to the cellulose and hemicellulose as represented by reduced loss of bleached pulp. This is a consequence of the fact that the process of the present invention is more selective in lignin removal than is oxygen bleaching conducted at constant pressure. As a consequence, the process of the present invention is more economical than a similar process conducted at constant pressure.
  • Example 1 Employing apparatus illusrtaated by FIG. 1 of the appended drawing, except that no high pressure pre-retention chamber 6 was employed, several pulp slurries having a consistency of 2 or 3% by weight of pulp, in which the pulp was slurried using 0.1 normal sodium hydroxide, were subjected to the process of the invention.
  • the pulp slurry was heated to boiling.
  • Oxygen gas was mixed with the heated slurry and pressurized to 40 p.s.i.g. and vigorosuly agitated in the oxygenator 4, equipped with a highshear propeller, during a residence time of about 5 minutes.
  • Example 2 Employing the apparatus system of FIG. 2, wood pulp was slurried with 0.1N sodium hydroxide to a pH of 11.5 and a consistency of approximately 3% and the slurry heated to a temperature of about C.
  • Oxygen was mixed through oxygenator 4 equipped with Lightening -In-line propeller-equipped mixer Model No. 4LB ⁇ C operating at a velocity of 1700 r.p.m. to finely divide the oxygen in the slurried pulp. Residual undispersed and undissolved oxygen was vented at vent 7.
  • the oxygenated alkaline pulp was then introduced near the bottom of bleaching tower 8, comprising a tower 84 feet tall providing a static pressure at the bottom of approximately 36 p.s.i.g.
  • the slurry was permitted to ow slowly upward through the tower without any agitation to provide a retention time of approximately 42 minutes. Throughout the operation no bubbles of oxygen were seen to escape at the top of the slurry.
  • Table 2 The results are shown in Table 2 below:
  • Example 3 Apparatus illustrated by FIG. l of the appended drawings, both with and without the use of the chamber 6, was employed.
  • the pulp slurry was heated to boiling at atmospheric pressure.
  • Oxygen gas was mixed with the heated slurry and pressurized to 40 p.s.i.g. and vigorously agitated in the oxygenator 4, equipped with a high-shear propellar, during a residence time of about 5 minutes.
  • the slurry was subjected to a pressure of oxygen of about 100 p.s.i.g. for a short time of one minute to 30 minutes. Excess undissolved and undispersed oxygen was vented through the vent 7.
  • the oxygenated pulp slurry was then introduced into bleaching tower 8 which was approximately 90 to feet high.
  • the slurry was permitted to rise lWithout agitation so that it had a residence time in the tower of approximately 60 minutes.
  • the pressure head on the slurry decreased from 7 about 40 p.s.i.g. to atmospheric. No bubbles of oxygen were seen to rise out of the top of the slurry in the tower. No depolymerization protector was employed. The results are shown in Table 3 below:
  • Example 4 The procedure of Example 1 was repeated, employing a pulp slurry consistency of 3% by weight of pulp using two samples of hardwood kraft pulp and softwood kraft pulp, The results obtained are set forth in Table 4 below:
  • Oxygen bleached Hardwood kraft
  • a continuous method of bleaching and delignifying cellulose pulp which does not require the use of a cellulose depolymerization protective agent, which method comprises preparing a cellulose pulp slurry comprised of an alkaline aqueous suspension of a pulp having a reaction temperature of between about 70 and 120 C., a consistency of from about 2% to about 10% by weight, and having a pH of between about 9 and 14, dissolving and intimately dispersing oxygen into said slurry so that no agglomerated bubbles are formed and the oxygenated cellulose pulp slurry has substantially no bubbles exceeding about 1/16 inch in diameter, continuously introducing said slurry into a vessel, subjecting the slurry in said vessel to an initial pressure of less than about 135 p.s.i.g. and thereafter gradually reducing that pressure, without subjecting the slurry to any substantial agitation, so that there is a pressure gradient of between about 1 and 10 atmospheres between the initial pressure and nal pressure, and continuously withdrawin-g treated slurry from said vessel.
  • a continuous method of bleaching and delignifying cellulose pulp which does not require the use of a cellulose depolymerization protective agent, which method comprises preparing a cellulose pulp slurry comprised of an alkaline aqueous suspension of a pulp having a reaction temperature of between about 70 and 120 C., a consistency of from about 2% to about 10% by weight, and having a pH of between about 9 and 14, dissolving and intimately dispersing oxygen into said slurry so' that no agglomerated bubbles are formed and the'oxygenated cellulose pulp slurry has substantially no bubbles exceeding about 1/16 inch in diameter, continuously introducing said slurry into the lower region of a vertically elongated tower, subjecting the slurry in said tower to an initial pressure of less than about 135 p.s.i.g and flowing said slurry upwardly through said tower without any substantial agitation while maintaining a pressure gradient of 10 between 1 and l0 atmospheres between the point of introduction of said slurry into said tower and the point of withdrawal

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
  • Cereal-Derived Products (AREA)
  • Coloring Foods And Improving Nutritive Qualities (AREA)
US00338862A 1973-03-07 1973-03-07 Delignification and bleaching of a cellulose pulp slurry with oxygen Expired - Lifetime US3832276A (en)

Priority Applications (15)

Application Number Priority Date Filing Date Title
US00338862A US3832276A (en) 1973-03-07 1973-03-07 Delignification and bleaching of a cellulose pulp slurry with oxygen
CA192,339A CA1007807A (en) 1973-03-07 1974-02-12 Delignification and bleaching of wood pulp with oxygen
AU66023/74A AU489486B2 (en) 1973-03-07 1974-02-26 Delignification and bleaching of woodpulp with oxygen
ZA00741287A ZA741287B (en) 1973-03-07 1974-02-27 Delignification and bleaching of wood pulp with oxygen
GB921874A GB1445276A (en) 1973-03-07 1974-02-28 Delignification and bleaching of wood pulp with oxygen
FI649/74A FI59434C (fi) 1973-03-07 1974-03-05 Delignifiering och blekning av cellulosa med syre
BR1573/74A BR7401573D0 (pt) 1973-03-07 1974-03-05 Processo continuo de alvejamento e deslignificacao de polpa de celulose
SE7402968A SE397983B (sv) 1973-03-07 1974-03-06 Alkalisk syrgasbehandling av cellulosamassa varvid massan utsettes for gradvis trycksenkning
NO740795A NO144930C (no) 1973-03-07 1974-03-06 Fremgangsmaate til kontinuerlig blekning og delignifisering av cellulosemasse under anvendelse av oksygen
IT67618/74A IT1011546B (it) 1973-03-07 1974-03-07 Procedimento di delignificazione e sbianca di polpa di legno median te ossigeno
DE2410934A DE2410934C2 (de) 1973-03-07 1974-03-07 Kontinuierliches Verfahren zum Bleichen und Entfernen von Lignin aus Zellstoff
JP49026701A JPS5747798B2 (fr) 1973-03-07 1974-03-07
FR7407858A FR2220620B1 (fr) 1973-03-07 1974-03-07
PH15590*A PH10177A (en) 1973-03-07 1974-03-07 Delignification and bleaching of wood pulp with oxygen
AR20291975D AR202919A1 (es) 1973-03-07 1975-01-01 Metodo continuo de blanquear y deslignificar pasta de celulosa

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US00338862A US3832276A (en) 1973-03-07 1973-03-07 Delignification and bleaching of a cellulose pulp slurry with oxygen

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US (1) US3832276A (fr)
JP (1) JPS5747798B2 (fr)
AR (1) AR202919A1 (fr)
BR (1) BR7401573D0 (fr)
CA (1) CA1007807A (fr)
DE (1) DE2410934C2 (fr)
FI (1) FI59434C (fr)
FR (1) FR2220620B1 (fr)
GB (1) GB1445276A (fr)
IT (1) IT1011546B (fr)
NO (1) NO144930C (fr)
PH (1) PH10177A (fr)
SE (1) SE397983B (fr)
ZA (1) ZA741287B (fr)

Cited By (47)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3951733A (en) * 1974-11-06 1976-04-20 International Paper Company Delignification and bleaching of wood pulp with oxygen
US4002526A (en) * 1975-10-10 1977-01-11 International Paper Company Oxygen-alkali delignification of low consistency wood pulp
US4089737A (en) * 1974-02-18 1978-05-16 Toyo Pulp Company, Ltd. Delignification of cellulosic material with an alkaline aqueous medium containing oxygen dissolved therein
US4115186A (en) * 1973-05-30 1978-09-19 A. Ahlstrom Osakeyhtio Process for bleaching cellulose pulp with molecular oxygen
US4155806A (en) * 1974-05-16 1979-05-22 Skogsagarnas Industri Aktiebolag Method for continuous alkaline delignification of lignocellulose material in two or more steps, the final of which with oxygen
US4198266A (en) * 1977-10-12 1980-04-15 Airco, Inc. Oxygen delignification of wood pulp
US4209359A (en) * 1978-10-23 1980-06-24 International Paper Company Process for removing residual oxygen from oxygen-bleached pulp
US4216054A (en) * 1977-09-26 1980-08-05 Weyerhaeuser Company Low-consistency ozone delignification
US4227964A (en) * 1976-12-01 1980-10-14 Kerr Allan J Method of treating lignocellulosic or cellulosic pulp to promote the kinking of pulp fibres and/or to improve paper tear strength
US4259150A (en) * 1978-12-18 1981-03-31 Kamyr Inc. Plural stage mixing and thickening oxygen bleaching process
US4294654A (en) * 1980-03-21 1981-10-13 International Paper Company Delignification and bleaching of lignocellulosic pulp via photo-oxygenation
US4295926A (en) * 1979-06-15 1981-10-20 Weyerhaeuser Company Method and apparatus for treating pulp with oxygen
US4295925A (en) * 1979-06-15 1981-10-20 Weyerhaeuser Company Treating pulp with oxygen
US4295927A (en) * 1979-06-15 1981-10-20 Weyerhaeuser Company Method and apparatus for treating pulp with oxygen and storing the treated pulp
WO1983000816A1 (fr) * 1981-09-04 1983-03-17 Weyerhaeuser Co Procede et dispositif de melange de pulpe avec de l'oxygene
WO1983000887A1 (fr) * 1981-09-04 1983-03-17 Weyerhaeuser Co Procede de traitement de pulpe par une pluralite d'etages a oxygene
US4384920A (en) * 1981-04-06 1983-05-24 The Black Clawson Company Method and apparatus for oxygen delignification
US4419184A (en) * 1980-08-26 1983-12-06 Kamyr Ab Method for control of chemicals during gas treatment of suspensions
US4451332A (en) * 1979-05-11 1984-05-29 Sca Development Aktiebolag Method for delignification of ligno-cellulose containing fiber material with an alkali-oxygen extraction stage
US4568420A (en) * 1984-12-03 1986-02-04 International Paper Company Multi-stage bleaching process including an enhanced oxidative extraction stage
WO1986005708A1 (fr) * 1985-04-01 1986-10-09 Weyerhaeuser Company Reservoir de desaeration et procede d'utilisation dudit reservoir
US4684442A (en) * 1984-03-29 1987-08-04 Weyerhaeuser Company Oxygen reactor deaeration tank and system
US4756798A (en) * 1984-06-15 1988-07-12 Air Liquide Process for bleaching a mechanical pulp with hydrogen peroxide
US4840703A (en) * 1984-11-08 1989-06-20 Rauma-Repola Oy Method for controlling an oxygen bleaching
US4886577A (en) * 1985-05-03 1989-12-12 Kamyr, Inc. Method and apparatus for mixing oxygen gas with medium consistency pulp in a pump discharge
US4978426A (en) * 1987-02-24 1990-12-18 Westvaco Corporation Production of high strength linerboard with oxygen and alkali
WO1991000386A1 (fr) * 1989-06-30 1991-01-10 Nekoosa Papers, Inc. Procede de blanchiment de pate a papier kraft avec un melange d'oxygene et de peroxyde
US5085734A (en) * 1989-02-15 1992-02-04 Union Camp Patent Holding, Inc. Methods of high consistency oxygen delignification using a low consistency alkali pretreatment
US5164043A (en) * 1990-05-17 1992-11-17 Union Camp Patent Holding, Inc. Environmentally improved process for bleaching lignocellulosic materials with ozone
US5164044A (en) * 1990-05-17 1992-11-17 Union Camp Patent Holding, Inc. Environmentally improved process for bleaching lignocellulosic materials with ozone
US5173153A (en) * 1991-01-03 1992-12-22 Union Camp Patent Holding, Inc. Process for enhanced oxygen delignification using high consistency and a split alkali addition
US5174861A (en) * 1990-10-26 1992-12-29 Union Camp Patent Holdings, Inc. Method of bleaching high consistency pulp with ozone
US5181989A (en) * 1990-10-26 1993-01-26 Union Camp Patent Holdings, Inc. Reactor for bleaching high consistency pulp with ozone
US5188708A (en) * 1989-02-15 1993-02-23 Union Camp Patent Holding, Inc. Process for high consistency oxygen delignification followed by ozone relignification
US5211811A (en) * 1989-02-15 1993-05-18 Union Camp Patent Holding, Inc. Process for high consistency oxygen delignification of alkaline treated pulp followed by ozone delignification
US5217574A (en) * 1989-02-15 1993-06-08 Union Camp Patent Holdings Inc. Process for oxygen delignifying high consistency pulp by removing and recycling pressate from alkaline pulp
US5266160A (en) * 1989-05-10 1993-11-30 Kamyr, Inc. Method of an apparatus for treating pulp
WO1994025669A1 (fr) * 1993-04-29 1994-11-10 Ingersoll-Rand Company Procede de blanchiment de pate cellulosique a etages multiples
US5387317A (en) * 1993-01-28 1995-02-07 The Mead Corporation Oxygen/ozone/peracetic aicd delignification and bleaching of cellulosic pulps
US5409570A (en) * 1989-02-15 1995-04-25 Union Camp Patent Holding, Inc. Process for ozone bleaching of oxygen delignified pulp while conveying the pulp through a reaction zone
US5451296A (en) * 1991-05-24 1995-09-19 Union Camp Patent Holding, Inc. Two stage pulp bleaching reactor
US5472572A (en) * 1990-10-26 1995-12-05 Union Camp Patent Holding, Inc. Reactor for bleaching high consistency pulp with ozone
US5520783A (en) * 1990-10-26 1996-05-28 Union Camp Patent Holding, Inc. Apparatus for bleaching high consistency pulp with ozone
US5525195A (en) * 1989-02-15 1996-06-11 Union Camp Patent Holding, Inc. Process for high consistency delignification using a low consistency alkali pretreatment
US5554259A (en) * 1993-10-01 1996-09-10 Union Camp Patent Holdings, Inc. Reduction of salt scale precipitation by control of process stream Ph and salt concentration
US5755926A (en) * 1992-02-24 1998-05-26 Kimberly-Clark Worldwide, Inc. Integrated pulping process of waste paper yielding tissue-grade paper fibers
US20050203291A1 (en) * 2004-03-11 2005-09-15 Rayonier Products And Financial Services Company Process for manufacturing high purity xylose

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FI67241B (fi) * 1981-06-10 1984-10-31 Aga Ab Saett foer blekning av cellulosahaltiga material
DE3207157C1 (de) * 1982-02-27 1983-06-09 Degussa Ag, 6000 Frankfurt Verfahren zur Herstellung von halbgebleichten Zellstoffen

Cited By (52)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4115186A (en) * 1973-05-30 1978-09-19 A. Ahlstrom Osakeyhtio Process for bleaching cellulose pulp with molecular oxygen
US4089737A (en) * 1974-02-18 1978-05-16 Toyo Pulp Company, Ltd. Delignification of cellulosic material with an alkaline aqueous medium containing oxygen dissolved therein
US4155806A (en) * 1974-05-16 1979-05-22 Skogsagarnas Industri Aktiebolag Method for continuous alkaline delignification of lignocellulose material in two or more steps, the final of which with oxygen
US3951733A (en) * 1974-11-06 1976-04-20 International Paper Company Delignification and bleaching of wood pulp with oxygen
US4002526A (en) * 1975-10-10 1977-01-11 International Paper Company Oxygen-alkali delignification of low consistency wood pulp
US4227964A (en) * 1976-12-01 1980-10-14 Kerr Allan J Method of treating lignocellulosic or cellulosic pulp to promote the kinking of pulp fibres and/or to improve paper tear strength
US4216054A (en) * 1977-09-26 1980-08-05 Weyerhaeuser Company Low-consistency ozone delignification
US4198266A (en) * 1977-10-12 1980-04-15 Airco, Inc. Oxygen delignification of wood pulp
US4209359A (en) * 1978-10-23 1980-06-24 International Paper Company Process for removing residual oxygen from oxygen-bleached pulp
US4259150A (en) * 1978-12-18 1981-03-31 Kamyr Inc. Plural stage mixing and thickening oxygen bleaching process
US4451332A (en) * 1979-05-11 1984-05-29 Sca Development Aktiebolag Method for delignification of ligno-cellulose containing fiber material with an alkali-oxygen extraction stage
US4295925A (en) * 1979-06-15 1981-10-20 Weyerhaeuser Company Treating pulp with oxygen
US4295927A (en) * 1979-06-15 1981-10-20 Weyerhaeuser Company Method and apparatus for treating pulp with oxygen and storing the treated pulp
US4295926A (en) * 1979-06-15 1981-10-20 Weyerhaeuser Company Method and apparatus for treating pulp with oxygen
US4294654A (en) * 1980-03-21 1981-10-13 International Paper Company Delignification and bleaching of lignocellulosic pulp via photo-oxygenation
US4419184A (en) * 1980-08-26 1983-12-06 Kamyr Ab Method for control of chemicals during gas treatment of suspensions
US4384920A (en) * 1981-04-06 1983-05-24 The Black Clawson Company Method and apparatus for oxygen delignification
WO1983000816A1 (fr) * 1981-09-04 1983-03-17 Weyerhaeuser Co Procede et dispositif de melange de pulpe avec de l'oxygene
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CA1007807A (en) 1977-04-05
SE397983B (sv) 1977-11-28
NO144930B (no) 1981-08-31
IT1011546B (it) 1977-02-10
NO740795L (no) 1974-09-10
AU6602374A (en) 1975-08-28
JPS5747798B2 (fr) 1982-10-12
PH10177A (en) 1976-09-16
JPS5024503A (fr) 1975-03-15
FR2220620A1 (fr) 1974-10-04
DE2410934A1 (de) 1974-09-19
GB1445276A (en) 1976-08-11
FI59434B (fi) 1981-04-30
FI59434C (fi) 1983-07-04
BR7401573D0 (pt) 1974-11-05
NO144930C (no) 1981-12-09
DE2410934C2 (de) 1983-12-01
ZA741287B (en) 1975-02-26
AR202919A1 (es) 1975-07-31
FR2220620B1 (fr) 1978-04-21

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