EP0106609A1 - Vorrichtung und Verfahren zur Sauerstoffextraktion von Pulpe niedriger Konsistenz - Google Patents

Vorrichtung und Verfahren zur Sauerstoffextraktion von Pulpe niedriger Konsistenz Download PDF

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Publication number
EP0106609A1
EP0106609A1 EP83305945A EP83305945A EP0106609A1 EP 0106609 A1 EP0106609 A1 EP 0106609A1 EP 83305945 A EP83305945 A EP 83305945A EP 83305945 A EP83305945 A EP 83305945A EP 0106609 A1 EP0106609 A1 EP 0106609A1
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EP
European Patent Office
Prior art keywords
pulp
oxygen
vessel
shaft
mixing
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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.)
Withdrawn
Application number
EP83305945A
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English (en)
French (fr)
Inventor
Larry D. Markham
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.)
Black Clawson Co
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Black Clawson Co
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Filing date
Publication date
Application filed by Black Clawson Co filed Critical Black Clawson Co
Publication of EP0106609A1 publication Critical patent/EP0106609A1/de
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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

  • This invention relates to a process and apparatus for delignifying pulp in the presence of oxygen and more particularly to a process and apparatus for oxygen extraction of lower consistency pulps using a vertical upflow reactor provided with at least one radially extending mixing element.
  • Oxygen delignification of high consistency pulp has not been generally accepted as the solution to the pulp industries pollution problems for several reasons. It is known that because the pulp used in these processes does not contain a high amount of water, it is difficult to control the reaction temperature of the oxygen delignification system. Consequently, overheating of the pulp and pulp degradation can occur, and if conditions are appropriate combustion of the pulp can occur. Furthermore, special equipment is required to carry out the process which is relatively expensive. For example, special dewatering is required to obtain the higher consistencies and an expensive and elaborate reaction vessel is often used to treat the pulp.
  • Richter U.S. Patent No. 3,963,561 of 1976 and U.S. Patent No. 4,093,511 of 1978 discloses an apparatus wherein a pulp-oxygen emulsion is moved upwardly through an open ended funnel-shaped body in a pressurized reactor and then cascades downwardly through a ring-shaped chamber.
  • Sherman U.S. Patent No. 4,161,421 of 1979 discloses a pressurized vessel provided with a plurality of vertical tubular reaction columns access to which is selectively controlled to more carefully control the pulp retention time and to prevent channeling.
  • Roymoulik et al U.S. Patent No. 3,832,276 of 1974
  • Phillips U.S. Patent No. 3,951,733 of 1976 disclose delignification of low consistency pulp (2-10% consistency) by flowing it upwardly through a reaction vessel without agitation wherein the non-dissolved oxygen content of the pulp is minimized to prevent agglomerated bubbles from forming and channeling through the reaction mixture.
  • high shear mixers are used to disperse or emulsify oxygen gas in the pulp prior to its being introduced into the reactors.
  • One example of such a high shear mixer is Bentvelzen et al (U.S. Patent No. 4,295,925).
  • This has several disadvantages.
  • High shear mixers require considerable horsepower to achieve an adequate dispersion of oxygen gas.
  • high shear mixing in the presence of oxygen and alkali at high temperatures can result in damage to the pulp fiber which reduces the pulp strength.
  • a further disadvantage of the foregoing systems is that high intensity dispersion of oxygen gas in the pulp can sometimes result in a foamy condition which reduces washing efficiency as the dissolved solids are washed from the fiber subsequent to delignification.
  • the principal object of the present invention is to provide a process and an apparatus for oxygen extraction of lower consistency pulps, for example, pulps having from approximately 3-20% solids content.
  • a further object of the present invention is to provide a process and apparatus for the oxygen extraction of lower consistency pulps wherein it is not necessary to subject the pulp to intensive mixing which tends to damage the pulp.
  • Another object of the present invention is to provide an oxygen extraction system which entails a comparatively low capital outlay.
  • pulp and alkaline chemicals are introduced into the lower portion of the reaction vessel, flow upwardly within the vessel, and are gently stirred by the at least one mixing element as the pulp reacts with an oxygen containing gas.
  • the gas may be directly introduced into the lower portion of the reaction vessel (for example by using a sparger) or the gas may be mixed inline with the pulp prior to its introduction to the reaction vessel.
  • the oxygen extraction system of the present invention is typically used in combination with other conventional treatments.
  • the oxygen extraction system of the present invention is preferably used in a bleaching sequence in which the pulp is previously chlorinated. Chlorinated pulps have been found to be reactive with oxygen under mild conditions so that the lignin is readily extracted from the pulp in the oxygen extraction stage and bleaching to high brightness can be accomplished with relatively small dosages of other bleaching chemicals such as chlorine dioxide or sodium hypochlorite. It has also been found desirable to after-treat the pulp in a caustic extraction tower following the oxygen treatment.
  • Oxygen may be introduced into the lower portion of the reaction vessel, but it is preferred to mix oxygen or an oxygen-containing gas with the pulp immediately prior to its introduction into the reaction vessel.
  • the pulp and oxygen containing gas are pre-mixed inline using a low intensity motionless mixer, diffuser, injector, or the like.
  • the oxygen gas may only partially dissolve in the aqueous medium at the bottom of the reaction vessel, but as the gas bubbles and pulp move up through the vessel, the gentle mixing action of the rotating mixing element or elements causes the remaining gas to dissolve.
  • the presence of large gas bubbles of a size up to 1.3cm (0.5 inches) diameter is not detrimental.
  • intensive mixing to form a gas-pulp emulsion is not required or used in the present invention.
  • a plurality of horizontally extending mixing elements are utilized and may be spaced evenly or unevenly along the vertical mixing shaft. In some cases it is desirable that there be a higher number of mixing elements per unit length in the lower portions of the reaction vessel near the pulp inlet.
  • the mixing elements may be simply horizontal sections of pipe mounted on the shaft or more sophisticated design elements may be used such as paddles of various configurations, ribbon flight screws, modified ribbon flight screws, and the like.
  • the mixing elements need not extend along the entire length of the reaction vessel but may be located adjacent the inlet of the vessel to promote initial mixing of the pulp and oxygen gas.
  • anti-rotation means such as a plurality of spline bars are vertically mounted on the inside walls of the reaction vessel. To prevent gas channeling along the bars, the bars are interrupted along the length of the vessel.
  • the invention apparatus is useful for oxygen extraction of lower consistency pulps, for example, pulps having from approximately 3 to 20% by weight solids and is preferably used for pulps of about 6 to 15% consistency.
  • fibrous materials can be treated in the present invention including kraft pulp, sulfite pulp, semi-chemical pulp, chemi-mechanical pulp, and mechanical pulps.
  • Wood pulps or agricultural fiber pulps can be treated in the process. Especially suitable are pulps which have been chlorinated.
  • Figure 1 illustrates one example of an oxygen extraction system in accordance with the present invention wherein oxidation extraction is carried out in a vertical reaction vessel 10 provided with a rotating shaft 30 which carries a plurality of mixing elements 32.
  • the extraction vessel 10 may be pressurized or the pressure differential established by the height of the vessel may be sufficient for the reaction.
  • Pulp at from 3-20%, and preferably 6-15%, consistency is introduced into reaction vessel 10 by pump 12.
  • a centrifugal pump be utilized for pulp consistencies up to 6%.
  • a thick stock pump be utilized for pulp consistencies greater than 6%.
  • pump 12 may be a Cloverotor pump available from the Impco Division of Ingersoll-Rand Co., Nashua, New Hampshire, a thick stock pump manufactured by Warren Pumps, Inc., Warren, Massachusetts, or any other type of thick stock or high density pump known in the industry.
  • steam Prior to introducing the pulp into thick stock pump 12, steam may be injected into the pulp via line 14. Steam may be mixed by a conventional single shaft or double shaft mixer. The steam aids in expelling excess air from the pulp and also raises the temperature of the pulp somewhat. Additionally, a portion of the total amount of the charge of alkaline material may be added prior to the introduction of the pulp into the thick stock pump 12 via line 15. A convenient point of addition is at the discharge of the pulp from a washer.
  • the alkaline material serves to lubricate the pulp for easier pumping as well as to insure that the pulp will have an alkaline pH when it enters the reaction vessel 10. To minimize pulp degradation, however, it is sometimes preferred to add part or all of the alkaline charge downstream of pump 12 at line 17.
  • the alkali is added immediately upstream of the inline mixer 19.
  • Various inline mixers can be used in the present invention. However, the use of mixers which generate high shear forces should be avoided.
  • One example of a suitable mixer is a Komax triple action motionless mixer manufactured by Komax Systems, Inc., Long Beach, California.
  • the total alkaline material charge will amount to approximately 0.5 to 20% by weight calculated as Na 2 0 of the moisture free pulp.
  • alkaline materials suitable for use in the invention include sodium hydroxide, sodium carbonate, sodium borate compounds, ammonia, kraft white liquor, oxidized kraft white liquor, kraft green liquor, and mixtures thereof although other known alkaline pulping liquors may also be used.
  • Oxygen may be introduced to the pulp slurry by line 20 upstream of the pulp inlet 18 located near the bottom of the reaction vessel.
  • oxygen may be introduced directly into the bottom of the vessel 10 by line 22 through a sparging device 24.
  • an inline- motionless mixer 26 may be inserted into the pipe section between line 20 and the vertical reaction vessel 10 to disperse the oxygen in the pulp slurry.
  • the oxygen gas may be pre-dispersed in a liquid using a venturi type mixer, motionless mixer, injector, or diffuser, and this dispersion can be added to the pulp through line 20 or 22.
  • a liquid which can be used for this purpose is the filtrate collected downstream upon washing the oxygen treated pulp.
  • the oxygen may be mixed with an alkaline liquid containing part or all of the alkali requirement for carrying out the delignification reaction.
  • the reaction vessel 10 is preferably cylindrical having a length to diameter ratio of at least 3 to 1. Lower ratios may result in channeling of gas or pulp up through the reactor.
  • a vertical shaft 30 which carries a plurality of horizontally extending mixing elements 32 is coaxially mounted within the vessel 10.
  • the mixing elements may be simply horizontal sections of pipe mounted through the vertical shaft 30 or more sophisticated design elements could be used such as paddles of various configurations and ribbon flight screws. It is not necessary that the mixing elements be evenly spaced along the shaft 30. In some cases, it is desirable to have a larger number of elements per unit length of shaft in the bottom portion of the vessel near the pulp inlet 18 as shown in shaft portion 33.
  • Shaft 30 is rotated by drive means D.
  • the speed of rotation is generally between 0.5 and 500 rpm, but speeds of 5 to 50 rpm are preferred. This gentle agitation has been found to provide adequate mixing of pulp with oxygen without the deleterious effects that high shear mixers cause.
  • the speed of rotation of the shaft is coordinated with other reaction conditions including the reaction temperature and pressure to provide a suitable retention time to achieve the desired degree of delignification for the particular pulp treated. Generally suitable retention times range from approximately 5 seconds to three hours and preferably between 10 seconds and 30 minutes.
  • the temperature of the delignification reaction can vary over a very wide range but typically ranges from approximately 50 to 160°C.
  • Use of protector chemicals such as magnesium carbonate, magnesium hydroxide and magnesium sulfate are generally not required but may be desirable in some instances. These chemicals may be added to the pulp upstream of vessel 10 when they are used.
  • the pressure in the reaction vessel is typically between 1.0 and 20.7 bars (15 and 300 psi (Gauge)) and preferably between 1.4 and 6.9 bars (20 and 100 psi (Gauge)).
  • the solubility of oxygen is higher at higher reaction pressures and, therefore, higher pressures are desired where a high degree of delignification must be achieved.
  • a valve 34 may be located at the discharge end 36 of the vessel to control the reaction pressure. In other cases, especially where a low degree of delignification is required, the top of the vessel may be open to the atmosphere.
  • Air is generally not used as the oxygen containing gas because of its relatively low oxygen content and because extraneous gases become entrained in the pulp which is detrimental for washing. Typically oxygen having a purity of 90 to 99.9% is used.
  • the oxygen dosage on the pulp ranges from approximately 0.1 to 15% and preferably 0.4 to 4% by weight oven dry pulp.
  • the vessel 10 is preferably operated so that no separate gas phase exists at the top of the vessel. Rather, it is preferred that the process be carried out with vessel 10 completely filled with the pulp suspension. If any excess gas does exist at the top of vessel 10 it will easily separate from the pulp and will not be in the form of tiny bubbles which create foam or interfere with subsequent washing of the pulp.
  • the treated pulp is discharged from the reaction vessel through outlet 38. From outlet 38, the pulp may be directed to a storage or retention tank or to additional treatments such as a caustic extraction tower. Alternatively, the pulp may be conveyed to a tank for dilution prior to washing.
  • FIG. 2 illustrates an embodiment of the invention wherein the invention apparatus is used in combination with a chlorination tower and a caustic extraction tower.
  • a feed pulp is fed by line 40 to a chlorination tower 41 where the pulp is bleached and chlorinated in a conventional manner.
  • the chlorinated pulp product is thereafter washed and fed to the invention apparatus 42 in a manner similar to Figure 1.
  • Steam may be added to the chlorinated pulp by line l4 and the pulp may be pre-treated with an alkaline liquor by line 15, but it is also possible to add the total alkali charge downstream of pump 12 through line 17 using an inline motionless mixer 19.
  • a thick stock pump 12 pumps the pulp to the bottom of the oxygen extraction tower 42.
  • Oxygen gas is added to the pulp by line 44 immediately upstream of a conventional inline mixing device 46 whereafter the pulp is introduced into the bottom of tower 42 at inlet 48.
  • the oxygen extraction tower 42 is equipped with a vertical shaft 50 having mounted thereon a plurality of radially extending mixing elements 52.
  • the mixing elements may be simply horizontal sections of pipe mounted on shaft 50 or they may be more elaborate configurations as discussed above. In Figure 2, the number of mixing elements 52 in the vicinity of the inlet 48 is greater per unit length than in the upper portion 54 of the tower.
  • the shaft 50 is rotated by a drive means D at the rotational velocities previously indicated.
  • a plurality of anti-rotation means 56 are provided on the inside walls of the tower 42.
  • the anti-rotation means illustrated in Fig. 2 are spline bars, typically one-half inch to one inch wide strips of metal, which are mounted vertically on the inside wall of the tower 42. These spline bars act to slow the rotation of the pulp. To prevent the oxygen-containing gas from channeling up the spline bars 56, the bars are interrupted and staggered along the inside surface of the tower.
  • the anti-rotation means may take other forms than the illustrated spline bars, for example, horizontal pegs or baffles may be mounted on the inside of the tower.
  • the pulp is discharged through outlet 58 which feeds a valved line 60 from which the pulp is conveyed to a caustic extraction tower 62.
  • Extraction tower 62 is constructed in a conventional manner. The tower may be of the type in which the pulp is introduced from the top and flows downwardly. Following caustic extraction the pulp is washed at 64 and discharged for further treatment or use.
  • Fig. 3 in which like elements are represented by like reference numerals, illustrates: an embodiment of the invention in which shaft 30 extends only partially along the length of vertical reaction vessel 10.
  • Shaft 30 carries on it a ribbon flight mixing screw 70 which provides gentle agitation to the pulp to provide adequate mixing.
  • ribbon flight mixing screw 70 which provides gentle agitation to the pulp to provide adequate mixing.
  • mixing elements including mixing screws having modified flights, paddles, and the like may also be utilized in the practice of the present invention.
  • Figs. 4 and 5 illustrate yet another embodiment of the invention in which the generally horizontally extending mixing elements 32 are linked together by vertical reinforcing bars 72 which add mechanical strength to the mixing elements.
  • Vertical spline bars 56 are again provided to slow the rotational movement of the pulp.
  • Reaction vessel 10 is also illustrated having a modified base structure extending angularly upward to meet the sidewalls of the vessel. The mixture of pulp and oxygen is fed to the vessel through line 18 as previously described. Oxygen can alternatively be added through line 23.
  • a KAPPA 14.2 hardwood kraft pulp was treated with chlorine at 25°C for thirty minutes at a 3.5% pulp consistency by mixing the pulp and water containing chlorine in a container.
  • the chlorine dosage was 3% based on oven dry pulp.
  • the pulp was then washed and treated with a 2.0% sodium hydroxide dosage at 80°C and at a 15% pulp consistency.
  • the treatment with sodium hydroxide was carried out in a reaction vessel equipped with a shaft passing along the length of the vessel. The shaft was equipped with radial mixing paddles.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Medicines Containing Plant Substances (AREA)
  • Paper (AREA)
EP83305945A 1982-09-30 1983-09-30 Vorrichtung und Verfahren zur Sauerstoffextraktion von Pulpe niedriger Konsistenz Withdrawn EP0106609A1 (de)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US43144082A 1982-09-30 1982-09-30
US431440 1982-09-30
US50168283A 1983-06-06 1983-06-06
US501682 1990-03-29

Publications (1)

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EP0106609A1 true EP0106609A1 (de) 1984-04-25

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EP83305945A Withdrawn EP0106609A1 (de) 1982-09-30 1983-09-30 Vorrichtung und Verfahren zur Sauerstoffextraktion von Pulpe niedriger Konsistenz

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EP (1) EP0106609A1 (de)
AU (1) AU1730083A (de)
BR (1) BR8305362A (de)
FI (1) FI833513A (de)
NO (1) NO832898L (de)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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
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
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

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2516447A (en) * 1947-02-24 1950-07-25 Elmer R Burling Method and apparatus for chemical treatment
US2772138A (en) * 1952-12-31 1956-11-27 Hercules Powder Co Ltd Continuous bleaching process
US3951733A (en) * 1974-11-06 1976-04-20 International Paper Company Delignification and bleaching of wood pulp with oxygen
US3992248A (en) * 1969-05-19 1976-11-16 Stadler Hurter Limited Continuous feeding system for treatment towers
JPS52132101A (en) * 1976-04-30 1977-11-05 Toyo Pulp Co Ltd Process and apparatus for treating cellulose material
US4209359A (en) * 1978-10-23 1980-06-24 International Paper Company Process for removing residual oxygen from oxygen-bleached pulp

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2516447A (en) * 1947-02-24 1950-07-25 Elmer R Burling Method and apparatus for chemical treatment
US2772138A (en) * 1952-12-31 1956-11-27 Hercules Powder Co Ltd Continuous bleaching process
US3992248A (en) * 1969-05-19 1976-11-16 Stadler Hurter Limited Continuous feeding system for treatment towers
US3951733A (en) * 1974-11-06 1976-04-20 International Paper Company Delignification and bleaching of wood pulp with oxygen
JPS52132101A (en) * 1976-04-30 1977-11-05 Toyo Pulp Co Ltd Process and apparatus for treating cellulose material
US4209359A (en) * 1978-10-23 1980-06-24 International Paper Company Process for removing residual oxygen from oxygen-bleached pulp

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
ABSTR. BULL. OF INST. OF PAPER CHEM., vol. 50, no. 3, September 1979, page 309, abstract no. 2848, Appleton, Wisc. (US) & JP - A - 77 132 101 (05-11-1977) *
TAPPI J. TECHN. ASS. PULP PAPER IND., vol. 63, no. 4, April 1980, Atlanta, GA (US) *
TAPPI J. TECHN. ASS. PULP PAPER IND., vol. 64, no. 8, August 1981, Atlanta, GA (US) *

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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
US5525195A (en) * 1989-02-15 1996-06-11 Union Camp Patent Holding, Inc. Process for high consistency delignification using a low consistency alkali pretreatment
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
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
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
US5164043A (en) * 1990-05-17 1992-11-17 Union Camp Patent Holding, Inc. Environmentally improved process for bleaching lignocellulosic materials with ozone
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
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
US5863389A (en) * 1990-10-26 1999-01-26 Union Camp Patent Holding, Inc. Pulp bleaching reactor for dispersing high consistency pulp into a gaseous bleaching agent containing 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
US5451296A (en) * 1991-05-24 1995-09-19 Union Camp Patent Holding, Inc. Two stage pulp bleaching reactor

Also Published As

Publication number Publication date
NO832898L (no) 1984-04-02
AU1730083A (en) 1984-04-05
FI833513A0 (fi) 1983-09-29
FI833513A (fi) 1984-03-31
BR8305362A (pt) 1984-05-08

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