EP0434662B1 - Procédé pour blanchir des matières cellulosiques et installation pour la mise en oeuvre de ce procédé - Google Patents

Procédé pour blanchir des matières cellulosiques et installation pour la mise en oeuvre de ce procédé Download PDF

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Publication number
EP0434662B1
EP0434662B1 EP90890325A EP90890325A EP0434662B1 EP 0434662 B1 EP0434662 B1 EP 0434662B1 EP 90890325 A EP90890325 A EP 90890325A EP 90890325 A EP90890325 A EP 90890325A EP 0434662 B1 EP0434662 B1 EP 0434662B1
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EP
European Patent Office
Prior art keywords
ozone
bleaching
absorption column
strong water
pulp
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 - Lifetime
Application number
EP90890325A
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German (de)
English (en)
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EP0434662A1 (fr
Inventor
Karl Dr. Schwarzl
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.)
Schmidding-Werke Wilhelm Schmidding & Co GmbH
Original Assignee
Schmidding-Werke Wilhelm Schmidding & Co GmbH
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Publication of EP0434662B1 publication Critical patent/EP0434662B1/fr
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Classifications

    • 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

  • the invention relates to a method for bleaching cellulose-containing materials, in particular cellulose, by means of ozone and to a plant for carrying out the method.
  • ozone is an excellent bleach for pulp. So from FR-A-1 441 787 an ozone bleaching is known, wherein ozone-containing gas, which comes from an ozonizer and contains 2.5 to 18 mg O3 per liter, saturated with water vapor and then brought into contact with the pulp to be bleached .
  • the pulp to be bleached is first brought to high consistencies of over 25% and then exposed to the gaseous ozone in flake form.
  • the pulp is placed in a reaction vessel through which an ozone-containing gas flows. The pulp is then washed in order to separate the undesired degradation products that are formed during bleaching.
  • This method has the disadvantage that separate facilities have to be created for the thickening and for the dilution of the pulp.
  • the pulp is bleached unevenly because the pulp flakes have a high consistency.
  • Another method is to bleach pulp at low consistencies of around 3% (low consistency method).
  • Gas containing ozone is passed through a pulp slurry. Because of the large dilution, the process requires the handling of large amounts of liquid and, on an industrial scale, a correspondingly high outlay on equipment.
  • the invention aims to avoid these disadvantages and has as its object to provide an improved method for bleaching cellulose-containing materials, in particular cellulose, by means of ozone.
  • the materials suspended in an aqueous medium contain a solution of ozone in an aqueous medium (strong water) with a content of 30 to 300 gO3, preferably 100 to 150 gO3 per m3 of aqueous medium, is fed under pressure and mixed with the former medium in a mixing device (5), whereupon the mixture is passed through a reaction vessel (7), the bleached material is separated from the bleaching liquor, and any present Residual ozone is destroyed, and the process according to the invention can also be carried out continuously.
  • an aqueous medium strong water
  • ozone is thus first dissolved in an aqueous medium, a concentrated ozone solution being obtained which is referred to as heavy water and which is mixed under pressure with the suspension of the material to be bleached.
  • the ozone-containing gas used being one which contains at least 100 g of ozone / Nm3 of oxygen and where The ozone solution and the remaining oxygen are withdrawn from the column and the remaining oxygen is dried and recycled to produce ozone-containing gas.
  • a preferred embodiment of the process according to the invention is characterized in that an overpressure between 5 and 10 bar is provided in the absorption column, and an overpressure between 2 and 5 bar is provided in the mixing device and in the reaction vessel, the overpressure in the absorption column being higher than in the mixing device and is set in the reaction vessel.
  • the bleaching process according to the invention is best carried out at a temperature below 60 ° C., preferably between 25 and 40 ° C.
  • a further embodiment of the process according to the invention is characterized in that a part of the bleaching liquor is pretreated with ozone after the bleached material has been separated off and is returned to the absorption column for the production of heavy water.
  • the process according to the invention has the advantage that cellulose-containing materials with a higher consistency than is possible with the low consistency process can be bleached, the consistency being up to 15% without a noticeable loss in bleaching quality.
  • the bleach can be used much better, since the required amount of ozone can be calculated precisely.
  • the low-consistency process by which ozone is passed in gaseous form through the pulp slurry inevitably leads to loss of ozone.
  • the invention also relates to a plant for carrying out the method according to the invention, with a device for producing a cellulose suspension, at least one bleaching tower as a reaction vessel, a device for generating an ozone-containing gas, filters, pumps and lines for connecting the plant parts, and is characterized in that the device for generating ozone is connected in terms of line to an absorption column for producing strong water, a mixing device is provided for mixing the pulp suspension with the strong water, the mixing device being connected to the absorption column via a strong water line, and a bleaching tower for receiving the mixture of pulp suspension and heavy water is provided, the absorption column, mixing device and bleaching tower being equipped with devices for generating and adjusting an overpressure.
  • the bleaching tower can be connected to a filter for separating the bleached pulp from the bleaching liquor, which filter is a bleaching liquor line for recycling used Has bleaching liquor in the device for producing the pulp suspension.
  • the bleaching liquor line is expediently connected via a branch to the absorption column, in which branch a heat exchanger is provided, which heat exchanger is also connected to the heavy water line in order to enable heat transfer from the bleaching liquor to the heavy water.
  • Another embodiment of the system according to the invention is characterized in that the absorption column is connected to a return line to the ozone generator in order to return undissolved oxygen from the absorption column to the ozone generator, a dryer preferably being present in the return line.
  • the absorption column 2 is connected via the high-pressure water line 4 via the heat exchanger 22 and the valve 23 to the mixer 5, which in turn is connected to the lower end of a bleaching tower 7 via the feed line 6.
  • an ozone line 8 leads to the residual ozone destroyer 9 and a discharge line 10 via a pump 11 to a filter 12 which is connected to a filter 14 via the bleach liquor line 13.
  • a branch 13a leads from the bleaching liquor line 13 via the heat exchanger 22 to the return water pretreatment 25, which in turn is connected to the top of the absorption column 2 via the return water line 15 and the heat exchanger 24, with supply and discharge lines 24a, 24b for the heat transfer medium is.
  • the method according to the invention is carried out by first filtering e.g. a pulp with a consistency between 10 and 15% is prepared. This pulp is transported by the pump 16 through the pulp line 17 into the mixer 5, where it is intimately mixed with strong water to form a solution with a consistency of between 2 and 5%.
  • the heavy water is formed in the absorption column 2 by return water, which is fed from the return water pretreatment 25 via the return water line 15 into the head of the absorption column 2, having previously been brought to the temperature required for the production of heavy water in the heat exchanger 24 and is treated with ozone-containing gas at an overpressure of up to 8 bar.
  • This gas is produced in the ozone generator 1 from oxygen, contains over 100 g O3 / Nm3 O2 and is introduced in the ozone line 18 from the ozone generator 1 into the lower end of the absorption column 2. Unreacted gas can be fed to the ozone generator 1 via the return line 19 after it has passed the dryer 3.
  • the return line 19 opens into the oxygen line 20, via which the ozone generator 1 is supplied with oxygen.
  • the ozone content of the heavy water can be adjusted between 30 and 300 g O3 / m3 water by a suitable choice of pressure and temperature conditions.
  • the heavy water is removed from the lower end of the absorption column 2 and fed to the mixer 5 via the valve 23 via the heavy water line 4.
  • the valve 23 reduces the pressure, which is between 5 and 10 bar in the heavy water line, so that it is between 2 and 5 bar in the mixer 5 and in the bleaching tower 7.
  • the pulp / heavy water mixture is then introduced into the lower end of the bleaching tower 7 and transported to its upper end over a period of approximately 20 minutes. During this time, the pulp actually bleaches.
  • Any excess ozone present at the head of the bleaching tower 7 can be fed to the residual ozone destroyer 9 via the ozone line 8.
  • the bleached pulp is also applied at the head of the bleaching tower 7 and introduced by the pump 11 through the discharge line 10 into the filter 12 for separating the bleached pulp from the bleaching liquor.
  • the removal of the bleached pulp is indicated at 21.
  • the bleaching liquor can be fed back into the filter 14 to adjust the consistency for further pulp to be bleached.
  • it can also be used for the production of strong water, although it must be pretreated with ozone before being introduced into the absorption column 2. This possible use is indicated in the drawing by the branch line 13a, the return water pretreatment 25 and the return water line 15.
  • the ozone for pretreatment is taken from the ozone line 18.
  • a heat exchanger 22 is expediently provided in the branch line 13a in order to be able to recover heat from the bleaching liquor (approx. 50 ° C.). With this heat, the heavy water in the heavy water line 4 is tempered, preferably to a temperature of about 46 ° C.
  • the process according to the invention can also be carried out with several successive bleaching stages.
  • at least one further bleaching tower is connected downstream of the bleaching tower 7.
  • the pulp suspension is expediently thickened.
  • a pretreated pulp with a consistency of 12% was treated with an amount of 2 kg of ozone per ton of pulp.
  • the ozone solution strong water
  • the ozone solution was mixed into the pulp suspension in a mixer prior to entering the upward bleaching tower.
  • the mixture with the pulp resulted in an ozone concentration of 61.86 g / m3.
  • the initially rapid ozone consumption and the hydrostatic pressure in the bleaching vessel prevented the ozone from rapidly degassing in the initial phase of the bleaching, so that there was no breakdown through the amount of pulp to be bleached.
  • a pre-treated pulp with a consistency of 14% was treated with 4 kg of ozone per ton of pulp.
  • the consistency during bleaching was 2%.
  • the strong water contained 93.3g O3 / m3.
  • the overpressure in the bleaching tower was 4 bar.
  • the treatment with ozone reduced the kappa number by 2 units and also achieved a whiteness gain of 5 points.
  • a pre-treated pulp with a consistency of 14% was bleached with 10 kg of ozone per ton of pulp. In this case, the bleaching was done in two stages.
  • the pulp was brought to a consistency of 2% by adding the ozone solution. After bleaching for 20 minutes in an upward tower under pressure, the suspension was thickened to 5%. Subsequently, the ozone solution was mixed in again to a consistency of 2%. The concentration of the ozone solution was 137.2g O3 / m3.
  • the second bleaching stage was also carried out in a bleaching tower working under pressure. In both cases the bleaching time was 20 minutes. In this case a kappa reduction of 7 units could be achieved with a whiteness increase of 6 points.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
  • Polysaccharides And Polysaccharide Derivatives (AREA)
  • General Preparation And Processing Of Foods (AREA)
  • Detergent Compositions (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Claims (10)

  1. Procédé de blanchiment des matériaux cellulosiques, en particulier de la pâte, au moyen de l'ozone, caractérisé en ce qu'aux matériaux suspendus dans un milieu aqueux est alimentée sous pression une solution de l'ozone dans un milieu aqueux (eau riche) ayant une teneur de 30 à 300 g O₃, de préférence 100 à 150 g O₃, par m³ du milieu aqueux et est mélangée avec le premier milieu dans un moyen de mélange (5), puis le mélange est conduit à travers un réacteur (7), le matériau blanchi est séparé du bain de blanchiment et de l'ozone résiduelle éventuellement présente est détruite.
  2. Procédé selon la revendication 1, caractérisé en ce que la solution de l'ozone (eau riche) est produite dans une colonne d'absorption (2) dans laquelle un milieu aqueux est traité sous pression par un gaz ozonique, cependant qu'un gaz contenant au moins de 100 g O₃/Nm³ de l'oxygène est utilisé comme gaz ozonique, la solution de l'ozone et l'oxygène résiduel sont évacués de la colonne (2) et l'oxygène résiduel est séché et récyclé à la production du gaz ozonique.
  3. Procédé selon la revendication 2, caractérisé en ce que dans la colonne d'absorption (2) une surpression entre 5 et 10 bar, et dans le moyen de mélange (5) ainsi que dans le réacteur (7) une surpression entre 2 et 5 bar sont maintenues, la surpression dans la colonne d'absorption (2) étant ajustée à être supérieure à celle dans le moyen de mélange (5) et dans le réacteur (7).
  4. Procédé selon l'une ou plusieurs des revendications 1 à 3, caractérisé en ce que le procédé est réalisé en continu.
  5. Procédé selon l'une ou plusieurs des revendications 1 à 4, caractérisé en ce que la température pendant la réaction est maintenue inférieure à 60°C, de préférence entre 25 et 40°C.
  6. Procédé selon l'une ou plusieurs des revendications 1 à 5, caractérisé en ce qu'une part du bain de blanchiment, après la séparation du matériau blanchi, est traitée avec de l'ozone et est récyclée à la colonne d'absorption (2) pour produire de l'eau riche.
  7. Installation pour la mise en oeuvre du procédé selon l'une ou plusieurs des revendications 1 à 6, comportant un moyen de production d'une suspension de pâte (14), au moins une tour de blanchiment (7) en tant que réacteur, un moyen de production d'un gaz ozonique (1), des filtres, des pompes, et des conduits de connection des éléments d'installation, caractérisée en ce que le moyen de production de l'ozone (1) est relié au point de vue conduite à une colonne d'absorption (2) pour produire de l'eau riche, un moyen de mélange (5) est prévu pour mélanger la suspension de pâte avec l'eau riche, ledit moyen de mélange (5) étant relié à la colonne d'absorption (2) par un conduit d'eau riche (4), et une tour de blanchiment (7) est prévue à reçevoir ledit mélange de suspension de pâte et de l'eau riche, la colonne d'absorption (2), le moyen de mélange (5) et la tour de blanchiment (7) étant équipés de moyens à générer et ajuster une surpression.
  8. Installation selon la revendication 7, caractérisée en ce que la tour de blanchiment (7) est reliée par un conduit d'évacuation (10) à un filtre (12) pour séparer la pâte blanchie du bain de blanchiment, ledit filtre (12) comprenant un conduit de bain de blanchiment (13) pour recycler au moyen de production de solution de pâte (14) du bain de blanchiment usé.
  9. Installation selon la revendication 8, caractérisée en ce que le conduit de bain de blanchiment (13) est relié au point de vue conduite à la colonne d'absorption (2) par un branchement (13a) dans lequel il y a prévu un échangeur de chaleur (22) qui est connecté également au conduit d'eau riche (4) en vue d'effectuer le transfer de chaleur du bain de blanchiment à l'eau riche.
  10. Installation selon l'une ou plusieurs des revendications 7 à 9, caractérisée en ce que la colonne d'absorption (2) est relié au générateur d'ozone (1) par un conduit de rétour (19) pour recycler de l'oxygène non solué de la colonne d'absorption (2) au générateur de l'ozone (1), un sécheur (3) étant de préférence prévu dans le conduit de retour (19).
EP90890325A 1989-12-22 1990-12-17 Procédé pour blanchir des matières cellulosiques et installation pour la mise en oeuvre de ce procédé Expired - Lifetime EP0434662B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AT2927/89 1989-12-22
AT0292789A AT393701B (de) 1989-12-22 1989-12-22 Verfahren zum bleichen von cellulosehaeltigen materialien sowie anlage zur durchfuehrung des verfahrens

Publications (2)

Publication Number Publication Date
EP0434662A1 EP0434662A1 (fr) 1991-06-26
EP0434662B1 true EP0434662B1 (fr) 1994-09-21

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Application Number Title Priority Date Filing Date
EP90890325A Expired - Lifetime EP0434662B1 (fr) 1989-12-22 1990-12-17 Procédé pour blanchir des matières cellulosiques et installation pour la mise en oeuvre de ce procédé

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US (1) US5133946A (fr)
EP (1) EP0434662B1 (fr)
AT (2) AT393701B (fr)
DE (1) DE59007258D1 (fr)

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT395445B (de) * 1991-05-02 1992-12-28 Voest Alpine Ind Anlagen Verfahren zum bleichen von cellulosehaeltigem material
NO912449L (no) * 1991-06-24 1992-12-28 Norske Stats Oljeselskap Flyttbar plattform til havs.
ZA924351B (en) * 1991-06-27 1993-03-31 Ahlstroem Oy Ozone bleaching process
AT400154B (de) * 1991-12-23 1995-10-25 Voest Alpine Ind Anlagen Verfahren zum bleichen cellulosehältiger materialien
US6231718B1 (en) * 1992-02-28 2001-05-15 International Paper Company Two phase ozone and oxygen pulp treatment
US5364505A (en) * 1992-12-07 1994-11-15 Kamyr, Inc. Pressurized ozone pulp delignification reactor and a compressor for supplying ozone to the reactor
SE500616C2 (sv) * 1993-06-08 1994-07-25 Kvaerner Pulping Tech Blekning av kemisk massa med peroxid vid övertryck
US5645687A (en) * 1995-07-10 1997-07-08 Champion International Corporation Process for manufacturing bleached pulp with reduced chloride production
KR101255873B1 (ko) * 2005-07-07 2013-04-17 엠케이에스 인스트루먼츠, 인코포레이티드 멀티 챔버 툴을 위한 오존 시스템

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2812861A (en) * 1954-02-09 1957-11-12 Maryland Lab Inc Means for ozone treatment of liquids
US2864757A (en) * 1956-02-17 1958-12-16 Air Reduction Ozone concentration and dilution
FR1441787A (fr) * 1965-04-30 1966-06-10 Progil Procédé de blanchiment des pâtes à papier
CA902861A (en) * 1969-11-27 1972-06-20 Pulp And Paper Research Institute Of Canada Bleaching of cellulosic 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
US3951733A (en) * 1974-11-06 1976-04-20 International Paper Company Delignification and bleaching of wood pulp with oxygen
US4310384A (en) * 1979-01-11 1982-01-12 Weyerhaeuser Company Reducing chemical transfer between treatment stages
JPS6048444B2 (ja) * 1981-06-05 1985-10-28 三菱電機株式会社 間欠オゾン供給装置
AT380496B (de) * 1984-06-27 1986-05-26 Steyrermuehl Papier Verfahren und reaktor zur delignifizierung von zellstoff mit sauerstoff
US4816229A (en) * 1986-07-09 1989-03-28 American Ozone Technology, Inc. Ozone apparatus
US4902381A (en) * 1988-12-09 1990-02-20 Kamyr, Inc. Method of bleaching pulp with ozone-chlorine mixtures

Also Published As

Publication number Publication date
AT393701B (de) 1991-12-10
ATE111989T1 (de) 1994-10-15
EP0434662A1 (fr) 1991-06-26
US5133946A (en) 1992-07-28
ATA292789A (de) 1991-05-15
DE59007258D1 (de) 1994-10-27

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