EP0520140A1 - Blanchiment par ozone-extraction alcaline sans lavage intermédiaire - Google Patents

Blanchiment par ozone-extraction alcaline sans lavage intermédiaire Download PDF

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Publication number
EP0520140A1
EP0520140A1 EP92103706A EP92103706A EP0520140A1 EP 0520140 A1 EP0520140 A1 EP 0520140A1 EP 92103706 A EP92103706 A EP 92103706A EP 92103706 A EP92103706 A EP 92103706A EP 0520140 A1 EP0520140 A1 EP 0520140A1
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EP
European Patent Office
Prior art keywords
stage
pulp
bleaching
washing
ozonation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP92103706A
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German (de)
English (en)
Inventor
Jian Ridge Center Jiang
Brain Ridge Center Greenwood
Joseph R. Ridge Center Phillips
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Kamyr Inc
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Kamyr Inc
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Application filed by Kamyr Inc filed Critical Kamyr Inc
Publication of EP0520140A1 publication Critical patent/EP0520140A1/fr
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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
    • D21C9/1057—Multistage, with compounds cited in more than one sub-group D21C9/10, D21C9/12, D21C9/16
    • 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
    • D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
    • D21C9/153—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications with ozone

Definitions

  • an ozone bleaching (Z) stage is generally followed by an alkaline extraction (E) stage, with inter-stage washing.
  • Inter-stage washing has conventionally been considered necessary in order to remove ozonated lignin products so as to decrease alkali consumption in the subsequent E stage.
  • PZE peroxide reinforced alkaline extraction stage
  • a single (ZE) stage is provided, without washing between the ozonation and alkaline extraction. It has been found according to the invention that when such a stage is utilized higher pulp brightness can be obtained for a given amount of chemical, and there is decreased color and decreased COD discharge in the E stage effluent.
  • the increase in brightness is typically about 2-8 percentage points (ISO), and a lower kappa number is achieved, compared to exactly the same treatment only with washing between ozonation and alkali extraction.
  • the single (ZE) stage according to the invention is in fact substantially equivalent to the two stage sequence ZEpo, yet is simpler and more economical to operate.
  • the invention also relates to a method of bleaching cellulose chemical pulp in multiple stages, providing a (ZE)P(ZE)P or (ZE)D(ZE)D bleaching sequence.
  • a pretreatment step is provided before the first (ZE) stage, which pretreatment may be an oxygen stage, a C/D stage, an acid washing stage, or a nitrogen dioxide stage.
  • the use of an oxygen delignification stage is particularly desirable.
  • the bleaching sequence includes not more than five stages. With an O(ZE)P(ZE)P sequence, it is capable of achieving a brightness of significantly greater than 90 ISO. Normally there is between stage washing in the practice of the invention.
  • the method of bleaching according to the invention is also quite flexible. Ozonation can take place either at high consistency (about 25-50%), medium consistency (about 6-18%), or low consistency (about 3% or less). If ozonation takes place at high or medium consistency, caustic, typically with some water, is added directly to the pulp discharged from the ozonation treatment. The consistency of the pulp is adjusted to medium consistency range by the amount of water added, either separately, or in solution with the caustic. Where low consistency ozonation takes place, the pulp is dewatered before alkaline extraction.
  • a multi-stage bleaching apparatus having separate and distinct stages, for bleaching cellulose pulp.
  • the apparatus comprises: In a first stage, means for subjecting the pulp to treatment with ozone at acidic conditions, immediately followed -- without any washing -- by alkaline extraction. In a second stage, means for effecting peroxide or chlorine dioxide bleaching of the pulp. In a third stage, means for subjecting the pulp to treatment with ozone at acidic conditions, immediately followed -- without any washing -- by alkaline extraction. And, in a fourth stage, means for effecting peroxide or chlorine dioixde bleaching of the pulp.
  • the inter-stage washing normally provided between ozone bleaching and alkaline extraction stages is eliminated to provide a single (ZE) stage comprising both ozonation (typically under acidic conditions, e.g. at about pH 2-4), and alkaline extraction (e.g. at about pH 10-13).
  • the single (ZE) stage provides improved brightness and other pulp properties compared to conventional ozone bleaching followed by alkaline extraction with between stage washing, in fact providing an enhancement substantially equivalent to the two stage sequence ZEpo, yet being simpler and more economical.
  • the ozonation/extraction stage according to the invention can employ high (greater than 25%), medium (about 6-18%), and low (less than about 3%) pulp consistency during the ozone bleaching phase.
  • FIGURE 1 schematically illustrates a (ZE) stage according to the invention when the pulp being fed to the mixer 10 is high or medium consistency.
  • Ozone is added to the pulp in the mixer 10, and after a short period of time is allowed for ozonation to take place, alkali is added at 11 either in a conduit 12, or in a vessel 13.
  • alkali is added at 11 either in a conduit 12, or in a vessel 13.
  • water can be added in a line 14; or the water may be added merely in the form of a more dilute caustic in line 11.
  • the pulp is maintained in the reactor 13 a conventional length of time for alkaline extraction, and then is discharged in line 15, typically to be washed before a subsequent bleaching stage.
  • the mixer 10 and reactor 13 are only exemplary structures.
  • a tumbling device may alternately be utilized, as may be conventional ozone and alkaline extraction treatment devices.
  • FIGURE 2 schematically illustrates apparatus similar to that in FIGURE 1 only for the situation when the pulp being fed to the mixer 17 is of low consistency (e.g. about 3% or less).
  • the pulp passes to a conventional dewaterer 18, and only after the pulp has been concentrated to medium consistency is alkali added in line 19 either to the conduit 20, or to the vessel 21, with the treated pulp being discharged from the vessel 21 in conduit 22 after an appropriate alkali extraction time.
  • the filtrate in line 23 from the dewaterer 18 -- or a portion thereof -- can be used to dilute the pulp prior to the ozonation (e.g. prior to mixer 17) in actual mill practice.
  • a decreased color and COD discharge in the E-stage effluent is also expected in actual practice as a side benefit from the (ZE) stage.
  • the decrease in color and COD should be comparable to that achieved by converting an E to an Eo stage.
  • FIGURE 2 An example of a low consistency (see FIGURE 2) ozone bleaching O(ZE) sequence compared to a prior art OZE sequence will now be described:
  • Ozonation was carried out at 1.0% pulp consistency in a 10-liter glass reactor at 20-50°C.
  • the pulp slurry was stirred vigorously with a Waring blender mounted at the bottom of the reactor.
  • the ozone gas was introduced into the slurry in the center of the reactor, about 0.5 inch above the blender blades to effect uniform mixing and adequate contact between the ozone gas and the pulp.
  • the ozone gas was shut off and the slurry was further stirred for about 10-30 min.
  • the slurry was then dewatered to about 15% consistency.
  • the dewatered pulp was immediately subjected to alkaline extraction with 1-2% NaOH at 60-70°C for about 60 minutes.
  • a washing stage was performed after dewatering prior to an alkaline extraction stage.
  • the (ZE) single stage according to the invention is best utilized in a four or five stage bleaching sequence with peroxide.
  • a bleaching sequence is illustrated in FIGURE 3.
  • chemical pulp e.g. kraft, sulfite, sodium, or like pulp
  • the discharged pulp in line 27 may optionally be washed in washer 28, and then fed to the first (ZE) stage 29, which typically will be one of the structures schematically illustrated in FIGURES 1 and 2 (or described with respect to these FIGURES), depending upon the concentration of the pulp.
  • the pre-treatment stage 25 preferably is an oxygen delignification stage, which is practiced at typical oxygen conditions of time, temperature, consistency, chemical charge, and pH.
  • pretreatment stages also may be provided.
  • a chlorine/chlorine dioxide (C/D) stage such as described in U.S. patent 4,959,124, prior to the (ZE) stage 29, or a nitrogen dioxide pretreatment stage, or an acid washing stage (e.g. where the pH of the wash water is adjusted to 2-3 with sulfuric acid, with the temperature maintained at about 20-60°C, for about 30-60 minutes) to remove heavy metal ions.
  • the pulp is fed in a conduit preferably to a conventional washer 30, and then from there to a conventional peroxide or chlorine dioxide reactor 31.
  • a conventional peroxide or chlorine dioxide reactor 31 From the conventional peroxide or chlorine dioxide reactor 31 the pulp is optionally fed to another washer 32 which removes the bleach chemical and other products, then to a second (ZE) stage 33. From the stage 33 the pulp is fed to the washer 34 and then to the second peroxide or chlorine dioxide stage 35.
  • the bleached pulp discharged in line 36 typically has enhanced brightness (e.g. greater than 90 ISO) compared to pulp produced in exactly the same way if the six stage sequence ZEPZEP, or the four stage sequence ZEPP, is utilized given the same total ozone and peroxide or (chlorine dioxide) dosage.
  • the (ZE) stage was conducted as described above in EXAMPLE I, and after the pulp from the first (ZE) stage was washed it was bleached with 1.0-2.0% peroxide, 0.05% MgSO4 (as Mg), and 0.2-1.0% NaOH at 10% consistency, 70°C, for 180 minutes in a lab reactor. After washing the (ZE) second stage was practiced in the same manner as the first stage, and then after washing the second peroxide stage was practiced in the same manner as the first peroxide stage.
  • the ZE two stage bleaching sequences were conducted identically to those described with respect to EXAMPLE I, and the peroxide stages were identical to those described earlier in this example. It was found that the bleached pulp according to the invention had 2-5 percentage points higher pulp brightness and a 5-10% reduction in both effluent color and COD loads as compared to the prior art sequence (with washing between the Z and E stages).

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
EP92103706A 1991-06-28 1992-03-04 Blanchiment par ozone-extraction alcaline sans lavage intermédiaire Withdrawn EP0520140A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US72178091A 1991-06-28 1991-06-28
US721780 1996-09-25

Publications (1)

Publication Number Publication Date
EP0520140A1 true EP0520140A1 (fr) 1992-12-30

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ID=24899279

Family Applications (1)

Application Number Title Priority Date Filing Date
EP92103706A Withdrawn EP0520140A1 (fr) 1991-06-28 1992-03-04 Blanchiment par ozone-extraction alcaline sans lavage intermédiaire

Country Status (7)

Country Link
EP (1) EP0520140A1 (fr)
AU (1) AU1282692A (fr)
BR (1) BR9202472A (fr)
FI (1) FI922945A (fr)
MX (1) MX9203191A (fr)
NO (1) NO922526L (fr)
ZA (1) ZA921843B (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5368688A (en) * 1992-07-08 1994-11-29 Sumitomo Heavy Industries, Ltd. Method for bleaching pulp with ozone with successive steps of lower consistency
US5520783A (en) * 1990-10-26 1996-05-28 Union Camp Patent Holding, Inc. Apparatus for bleaching high consistency pulp with ozone

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2265908A1 (en) * 1970-12-21 1975-10-24 Scott Paper Co Kraft pulp bleaching and recovery process - using alkali extraction effluents in subsequent bleaching steps
CA1112813A (fr) * 1978-04-06 1981-11-24 Arthur W. Kempf Separation des matieres fibreuses traitees a l'ozone
CA1178756A (fr) * 1981-06-29 1984-12-04 Shyam S. Bhattacharjee Blanchiment de pate kraft a l'ozone, precede d'une extraction alcaline

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2265908A1 (en) * 1970-12-21 1975-10-24 Scott Paper Co Kraft pulp bleaching and recovery process - using alkali extraction effluents in subsequent bleaching steps
CA1112813A (fr) * 1978-04-06 1981-11-24 Arthur W. Kempf Separation des matieres fibreuses traitees a l'ozone
CA1178756A (fr) * 1981-06-29 1984-12-04 Shyam S. Bhattacharjee Blanchiment de pate kraft a l'ozone, precede d'une extraction alcaline

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
ABSTRACT BULLETIN OF THE INSTITUTE OF PAPER CHEMISTRY vol. 55, no. 6, December 1984, APPLETON US page 705 RUTKOWSKI, J. 'Use of ozone in bleaching kraft pulp.' *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5520783A (en) * 1990-10-26 1996-05-28 Union Camp Patent Holding, Inc. Apparatus for bleaching high consistency pulp with ozone
US5368688A (en) * 1992-07-08 1994-11-29 Sumitomo Heavy Industries, Ltd. Method for bleaching pulp with ozone with successive steps of lower consistency

Also Published As

Publication number Publication date
BR9202472A (pt) 1993-02-09
FI922945A0 (fi) 1992-06-25
NO922526D0 (no) 1992-06-26
NO922526L (no) 1992-12-29
FI922945A (fi) 1992-12-29
ZA921843B (en) 1992-12-30
MX9203191A (es) 1992-12-01
AU1282692A (en) 1993-01-07

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