EP0155928B1 - Hydrosulfitbleichen von mechanischer Pulpe - Google Patents

Hydrosulfitbleichen von mechanischer Pulpe Download PDF

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Publication number
EP0155928B1
EP0155928B1 EP85890055A EP85890055A EP0155928B1 EP 0155928 B1 EP0155928 B1 EP 0155928B1 EP 85890055 A EP85890055 A EP 85890055A EP 85890055 A EP85890055 A EP 85890055A EP 0155928 B1 EP0155928 B1 EP 0155928B1
Authority
EP
European Patent Office
Prior art keywords
pulp
pump
bleaching
hydrosulfite
practiced
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.)
Expired
Application number
EP85890055A
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English (en)
French (fr)
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EP0155928A1 (de
Inventor
Louis Otto Torregrossa
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.)
Kamyr Inc
Original Assignee
Kamyr Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Kamyr Inc filed Critical Kamyr Inc
Priority to AT85890055T priority Critical patent/ATE38258T1/de
Publication of EP0155928A1 publication Critical patent/EP0155928A1/de
Application granted granted Critical
Publication of EP0155928B1 publication Critical patent/EP0155928B1/de
Expired legal-status Critical Current

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Classifications

    • 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
    • D21D5/26—De-aeration of paper stock
    • 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
    • D21C9/1084—Bleaching ; Apparatus therefor with reducing compounds
    • D21C9/1089—Bleaching ; Apparatus therefor with reducing compounds with dithionites

Definitions

  • the invention relates to a method of treating a mechanical pulp with hydrosulfite bleaching chemical which (b) is added to the mechanical pulp, substantially free of entrained air, whereupon (c) the pulp is retained at predetermined pH and temperature conditions for a predetermined period of time to effect bleaching thereof.
  • hydrosulfite such as sodium hydrosulfite or zinc hydrosulfite.
  • hydrosulfite bleaching can achieve the desired decoloration of the mechanical pulp, there are a number of drawbacks associated with its use. Hydrosulfite is oxidized extremely rapidly by air, therefore the entrainment of air in the pulp can negate the bleaching effects of the hydrosulfite. This makes hydrosulfite impractical for use with mechanical pulps having a consistency of much greater than 4% since as the consistency rises the pulp tends to entrain air.
  • it is desirable to effect bleaching at the same consistency as for other processing of the pulp e.g. 5-25%, preferably 8-15%), although successive diluting and thickening stages are to be avoided because of the equipment costs and energy expense associated therewith.
  • a method of bleaching mechanically-disintegrated wood pulp in accordance with the prior art portion of claim 1 is disclosed by US-A-2 707 146 comprising continuously feeding a watersoluble polyphosphate, in aqueous solution substantially free of entrained air, into a continuously moving stream of mechanically-disintegrated wood pulp, substantially free of entrained air.
  • the polyphosphate is fed to the pulp at a point not substantially later than that at which the hydrosulfite is fed to the pulp.
  • the mixture of pulp and bleaching chemicals is subjected to vigorous agitation and propulsion, thereby forcing the mixture along a confined, airtight path, including a vertical fluid way, as a streamline, plug flow, until the desired bleaching takes place.
  • the consistency of the pulp to be treated may range up to the point where satisfactory mixing is not feasible, e.g. up to 10% or even 15%, by weight, the actual range of consistency for which good results easily can be achieved is between about 2% and 5%.
  • a method of treating mechanical pulp that allows reductive bleaching of the pulp in an effective manner at pulp consistencies of about 5-25%, and preferably 8-15%, during the entire treating procedure.
  • Simultaneous pumping and degassing of the mechanical pulp is preferably accomplished utilizing a fluidizing centrifugal pump.
  • Mixing of the mechanical pulp with an effective charge of hydrosulfite bleaching chemical preferably is accomplished in a fluidizing mixer, with the hydrosulfite bleaching chemical including sequestering, chelating, and buffering agents.
  • Atypical charge is 0,5-1,5% hydrosulfite.
  • oxidation of the reductive bleaching agent is avoided, a minimal amount of equipment is utilized, and the processing can be done at the desired consistency range of 8-15%.
  • the mixer may be eliminated, and the hydrosulfite added directly to the fluidizing pump.
  • the chemical may be added to the discharge, or the suction, of the pump.
  • the method according to the present invention is applicable to mechanical pulps. That term, as commonly used in the industry and as used in the instant specification and claims, encompasses refiner mechanical pulps (RMP), chemimechanical pulps (CMP), thermomechanical pulps (TMP), chemithermomechanical pulps (CTMP), and stone groundwood pulps.
  • RMP refiner mechanical pulps
  • CMP chemimechanical pulps
  • TMP thermomechanical pulps
  • CMP chemithermomechanical pulps
  • stone groundwood pulps stone groundwood pulps.
  • the mechanical pulp is produced utilizing any desired conventional technique, and then is fed by line 11 to a storage tower 12 or the like. According to the present invention it is preferable to mount a fluidizing centrifugal pump 13 at the bottom of the storage tower 12, to draw the mechanical pump downwardly therefrom.
  • the pulp typically has a consistency of about 5-25 percent, and a consistency of 8-15 percent is preferred.
  • the fluidizing centrifugal pump 13, and an apparatus and method for controlling the head therefrom, are illustrated and described in Applicant's FR-A-2479 870.
  • the pump 13, as illustrated in Figure 2 may comprise an inlet channel 14, a rotor 15 including a plurality of axially extending blades 16 having an interior opening 17 therebetween, and impeller blades 18.
  • the blades 18 rotate in a spiral housing section 19, and gas can pass through openings 21, 22 from the housing section 19 to a gas chamber 20, the gas chamber 20 being connected up to a gas discharge line 23.
  • Pulp passes from the pump 13 into the discharge line 25, with a throttling valve 26 disposed therein.
  • the head of the pump 13 is controlled, by adjusting the throttling valve 26 in a manner explained in the aforementioned FR-A-2479 870 so that a variety of heads within a wide range may be achieved.
  • the valve 26 preferably is controlled, according to the present invention, so that the pump head is maximized, to thereby maximize the degassing action of the pump (i.e. maximizing the amount of air withdrawn through conduit 23).
  • the pulp is immediately passed to a mixer 28.
  • the pulp must be passed to the mixer 28 so that substantially no air introduction occurs, and the mixer 28 must effect mixing without air introduction.
  • hydrosulfite bleaching chemical is added from line 29 to the mixer, and is thoroughly mixed with the pulp.
  • the mixer 28 preferably comprises a fluidizing mixer such as shown in U.S. Patents 4,093,506 and 4,339,206.
  • hydrosulfite bleaching chemical added to provide an effective charge will vary depending upon the properties of the mechanical pulp, the amount of bleaching desired, etc. Typically, however, the sodium hydrosulfite or zinc hydrosulfite would be added so that the total charge was about 0.5-1.5 percent. Buffering, sequestering, and/or chelating agents, such as sodium tripolyphophate and sodium diethylenet- riaminepetaacetate, are also preferably added with the hydrosulfite.
  • the pulp After mixing of the hydrosulfite bleaching chemical into the pulp using mixer 28, the pulp, still at the same consistency (i.e. 5-25 percent), is retained at predetermined pH and temperature conditions for a predetermined period of time to effect the desired bleaching.
  • This retention may be merely in conduits passing the pulp onto a further processing station, or may be in a vessel particularly designed for that purpose, such as a conventional up-flow bleaching tower 31.
  • Typical, although not limiting, conditions are: pH, about 4.5-6.5; temperature, about 35-80°C; retention time, about 0.25-2 hours.
  • the bleaching action can be effectively controlled, and the desired amount of bleaching chemical can be added to effect the desired bleaching.
  • the degassing action is accomplished, according to the present invention, in a simple and effective manner, and with a minimum amount of equipment.
  • the pulp at a consistency of between 5-25 percent, and preferably 8-15 percent, is withdrawn from storage tower 12, simultaneously pumped and degassed by fluidizing centrifugal pump 13, the head of which is controlled by valve 26 to maximize degassing action, immediately passed to fluidizing mixer 28 at which the hydrosulfite bleaching chemical is added via line 29, and subsequently passed to a conventional retention tower 31, or the like, where it is retained at predetermined pH and temperature conditions for a predetermined period of time to effect desired bleaching.
  • the hydrosulfite bleaching chemical is added through line 33 directly to the discharge of the pump 13.
  • the pulp has been effectively degassed, and when the bleaching chemical is added through a nozzle, or like other introduction structure, due to the turbulence of the pulp at that point, it will become intermixed with the pulp, and effective bleaching will occur.
  • the pump 13 is shown with the axis of rotation of the rotor thereof horizontal. This merely illustrates ° that the present invention may be practiced irrespective of the orientation (e.g., horizontal or vertical) of the pump rotor.
  • the hydrosulfite bleaching chemical is added via line 35 at the suction of the pump 13. Again, introduction can be accomplished utilizing a suitable nozzle, or the like. While the pulp is not completely degassed at this position, adding the bleaching chemical at the suction provides for complete intermixing of the bleaching chemical with the pulp as it is pumped by the pump 13, and the time from chemical addition at the suction side of the pump, to effective degassing by the pump, is short enough that under most circumstances entrained air will not significantly negate the bleaching effects of the hydrosulfite. However, if entrained air does negate such effects for a particular pulp, then the embodiments of FIGURES 1 and 3 will be utilized instead of the embodiment of FIGURE 4.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
  • Detergent Compositions (AREA)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
  • Catalysts (AREA)
  • Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)

Claims (8)

1. Verfahren zum Behandeln einer mechanischen Pulpe mit Hydrosulfit-Bleichchemikalien, die (b) der im wesentlichen von mitgeführter Luft freien mechanischen Pulpe zugesetzt werden, wonach (c) die Pulpe zum Bewirken des Bleichens derselben während einer vorbestimmten Zeitspanne unter vorbestimmten Bedingungen von pH-Wert und Temperatur gehalten wird, gekennzeichnet durch (a) gleichzeitiges Pumpen und im wesentlichen vollständiges Entgasen der mechanischen Pulpe bei einer Konsistenz von etwa 8-15% und (b) unmittelbar anschließendes Vermischen der eine Konsistenz von etwa 8-15% aufweisenden mechanischen Pulpe ohne wesentliches Einführen von Luft mit einer wirksamen Menge von Hydrosulfit-Bleichchemikalien, gefolgt von Schritt (c), wobei die Konsistenz von 8-15% während des gesamten Behandlungsvorganges aufrechterhalten wird.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die im Schritt (b) zugesetzten Hydrosulfit-Bleichchemikalien Puffersubstanzen, Chelatbildner und Sequestrierungsmittel enthalten und daß der Schritt (b) durch Zusetzen einer hinreichenden Menge von Hydrosulfit-Bleichchemikalien ausgeführt wird, so daß die Hydrosulfit-Bleichchemikalien etwa 0,5-1,5% ausmachen.
3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß der Schritt (c) durch Aufrechterhalten eines pH-Wertes von etwa 4,5-6,5 und einer Temperatur von etwa 35-80°C ausgeführt wird, wobei die vorbestimmte Zeitspanne etwa 0,25-2 h beträgt.
4. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß der Schritt (a) unter Verwendung einer Fluidisierungspumpe und Regelung des Förderdruckes der Pumpe durch Drosseln des Pulpenausstoßes der Pumpe ausgeführt wird.
5. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß der Schritt (b) unmittelbar anschließend an den Schritt (a) ausgeführt wird und daß der Schritt (a) unter Verwendung einer Fluidisierungspumpe und der Schritt (b) unter Verwendung eines gesonderten und von der Pumpe unterschiedlichen Fluidisierungsmischers ausgeführt werden.
6. Verfahren nach Anspruch 5, dadurch gekennzeichnet, daß der Schritt (c) durch Zuführen der Pulpe nach deren Durchgang durch den Fluidisierungsmischer an eine Steigstrom-Bleichkolonne ausgeführt wird.
7. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß die Schritte (a) und (b) unter Verwendung einer Fluidisierungspumpe ausgeführt werden, wobei die Chemikalien am Auslaß der Pumpe zugesetzt werden.
8. Verfahren nach einem der Ansprüche 1 bis 7, dadurch gekennzeichnet, daß die mechanische Pulpe CTMP, TMP, CMP und/oder Holzschliff ist.
EP85890055A 1984-03-05 1985-03-04 Hydrosulfitbleichen von mechanischer Pulpe Expired EP0155928B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT85890055T ATE38258T1 (de) 1984-03-05 1985-03-04 Hydrosulfitbleichen von mechanischer pulpe.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US58593884A 1984-03-05 1984-03-05
US585938 1984-03-05

Publications (2)

Publication Number Publication Date
EP0155928A1 EP0155928A1 (de) 1985-09-25
EP0155928B1 true EP0155928B1 (de) 1988-10-26

Family

ID=24343611

Family Applications (1)

Application Number Title Priority Date Filing Date
EP85890055A Expired EP0155928B1 (de) 1984-03-05 1985-03-04 Hydrosulfitbleichen von mechanischer Pulpe

Country Status (7)

Country Link
EP (1) EP0155928B1 (de)
JP (1) JPS60209088A (de)
AT (1) ATE38258T1 (de)
BR (1) BR8500938A (de)
DE (1) DE3565870D1 (de)
FI (1) FI77905C (de)
NO (1) NO164310C (de)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ATE164895T1 (de) * 1988-02-26 1998-04-15 Ahlstroem Oy Verfahren und vorrichtung zum behandeln von faserbrei
US4877368A (en) * 1988-11-08 1989-10-31 A. Ahlstrom Corporation Fluidizing centrifugal pump
FI94440C (fi) * 1990-08-14 1995-09-11 Ahlstroem Oy Menetelmä ja -laitteisto ilmaa ja/tai kaasua sisältävä nesteen tai kuitususpension käsittelemiseksi sekä kaasua erottavan massapumpun käytöt
SE513790C2 (sv) * 1999-03-08 2000-11-06 Mo Och Domsjoe Ab Blekning av mekanisk massa med reducerande blekmedel
CA2432459A1 (en) 2002-06-28 2003-12-28 Rohm And Haas Company Method for brightening pulp with hydrosulfite solutions

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2071307A (en) * 1936-08-11 1937-02-16 Great Western Electro Chemical Co Bleaching
US2707146A (en) * 1951-08-08 1955-04-26 Scott Paper Co Method of bleaching mechanically disintegrated wood pulp
US2963395A (en) * 1958-03-31 1960-12-06 Crown Zellerbach Corp Process of bleaching lignocellulosic pulps
US3313678A (en) * 1962-02-14 1967-04-11 Svenska Cellulose Aktiebolaget Bleaching of cellulose pulp in towers in completely filled and closed system
US4030969A (en) * 1972-06-13 1977-06-21 Defibrator Ab Method of dispersing a bleaching agent into a stream of fibrous cellulosic pulp material in a throttling nozzle
SE389351B (sv) * 1975-03-14 1976-11-01 Kamyr Ab Sett och anordning for fordelning och inblandning av gas och/eller vetska i massasuspensioner av hog koncentration.
US4435193A (en) * 1980-04-07 1984-03-06 Kamyr Ab Controlling operation of a centrifugal pump
US4410337A (en) * 1980-04-07 1983-10-18 A. Ahlstrom Osakeyhtio Method and an apparatus for separating a gas from a fibre suspension

Also Published As

Publication number Publication date
NO164310C (no) 1990-09-19
ATE38258T1 (de) 1988-11-15
DE3565870D1 (en) 1988-12-01
FI850854A0 (fi) 1985-03-01
BR8500938A (pt) 1985-10-22
FI850854L (fi) 1985-09-06
NO850720L (no) 1985-09-06
FI77905C (fi) 1989-05-10
FI77905B (fi) 1989-01-31
NO164310B (no) 1990-06-11
JPS60209088A (ja) 1985-10-21
EP0155928A1 (de) 1985-09-25

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