[go: up one dir, main page]

WO1999027179A1 - Procede de blanchiment de cellulose dans un systeme ferme au moyen d'acide de caro - Google Patents

Procede de blanchiment de cellulose dans un systeme ferme au moyen d'acide de caro Download PDF

Info

Publication number
WO1999027179A1
WO1999027179A1 PCT/SE1998/002117 SE9802117W WO9927179A1 WO 1999027179 A1 WO1999027179 A1 WO 1999027179A1 SE 9802117 W SE9802117 W SE 9802117W WO 9927179 A1 WO9927179 A1 WO 9927179A1
Authority
WO
WIPO (PCT)
Prior art keywords
acid
caro
bleaching
sulphur
cellulose
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.)
Ceased
Application number
PCT/SE1998/002117
Other languages
English (en)
Inventor
Erik Bengtsson
Peter BJÖRKLUND
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.)
Metso Fiber Karlstad AB
Original Assignee
Kvaerner Pulping AB
Kvaerner Pulping Technologies AB
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 Kvaerner Pulping AB, Kvaerner Pulping Technologies AB filed Critical Kvaerner Pulping AB
Priority to AU13581/99A priority Critical patent/AU1358199A/en
Publication of WO1999027179A1 publication Critical patent/WO1999027179A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

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
    • D21C9/16—Bleaching ; Apparatus therefor with per compounds
    • D21C9/166—Bleaching ; Apparatus therefor with per compounds with peracids
    • 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
    • D21C11/00—Regeneration of pulp liquors or effluent waste waters
    • D21C11/06—Treatment of pulp gases; Recovery of the heat content of the gases; Treatment of gases arising from various sources in pulp and paper mills; Regeneration of gaseous SO2, e.g. arising from liquors containing sulfur compounds

Definitions

  • the present invention relates to the bleaching of cellulose with Caro's acid in a system which is closed or partially closed with respect to the bleaching, the digestion of the cellulose and the recovery of the chemicals.
  • the method is distinguished by the fact that it comprises one or more bleaching stages using Caro's acid.
  • the new bleaching agents which have begun to be used are mainly peracetic acid, peroxysulphuric acid
  • both peracetic acid and Caro' s acid are unstable chemicals, it is advantageous to produce these in situ in part of the plant, so that storage and transport can be avoided.
  • the peracetic acid is an expensive chemical, for which reason Caro's acid is preferred.
  • Caro's acid and the acetic acid are easy to produce in situ, but since Caro's acid is produced from sulphuric acid and hydrogen peroxide, large quantities of sulphur have to be added to the bleaching process. Since both the bleaching process and the digestion and recovery process must as far as possible be closed, then, when Caro's acid is used, the sulphur content in the system will increase.
  • a method for bleaching cellulose in a closed or partially closed system in one or more stages using Caro's acid which method is characterized in that the production of Caro's acid is included in the closed or partially closed system.
  • the sulphuric acid needed for producing Caro's acid can be produced from uncondensed gases rich in sulphur, as is described in French Patent 9303831.
  • sulphur-containing and uncondensable gases from the evaporation of waste liquor and from cellulose digestion and/or from heat treatment of the thick liquor in a superconcentrator represent the source of sulphur needed for producing Caro's acid.
  • the bleaching stage with Caro's acid can also include an addition of peracetic acid which can, for example, represent half the acid mixture.
  • totally oxidized white liquor is preferably used according to the invention.
  • the totally oxidized white liquor can be produced, for example, by any one of the methods which are described in US Patents 5 382 322, 5 500 085 and 5 439 556. In this way, a balanced level of sulphur and sodium is achieved in the closed system.
  • an advantageous bleaching sequence comprising Caro's acid is one which is characterized by the stages OP-CAQ-PO, where 0 stands for oxygen, P for hydrogen peroxide, CA for
  • the invention involves bleaching cellulose in a closed system using Caro's acid in at least one bleaching stage, Caro's acid being produced in situ with preservation of the sulphur balance in the system.
  • Cellulose is produced according to one of the known methods by means of wood chips being cooked in an alkaline liquid, after which the released cellulose is filtered off from the cooking liquid or waste liquor.
  • the unbleached cellulose is then subjected to a bleaching procedure while the waste liquor is evaporated in a number of so-called effects for concentrating the waste liquor which, in the concentrated state, i.e. with a high dry substance content, is combusted in a soda recovery unit for generating thermal energy and managing the chemicals in melted form.
  • the waste liquor also contains, in addition to dissolved lignin, a large quantity of sulphur and sodium compounds, mainly in the form of sodium sulphide and sodium hydroxide.
  • vapour also contains sulphur compounds in the form of hydrogen sulphide, mercaptans and the like.
  • the amount of sulphur which can come from these evaporation stages can be somewhere in the region of up to 3 kg of sulphur per tonne of pulp produced.
  • this amount of sulphur can be dealt with by means of the sulphur-rich vapour being combusted so that sulphur dioxide is obtained with a concentration of about 1% by volume in the waste gas.
  • the sulphur dioxide is combusted to sulphur trioxide.
  • This mixture of sulphur trioxide and water is then conducted into a tower with circulating 60% strength sulphuric acid.
  • the S0 3 gas is absorbed and forms sulphuric acid which is incorporated in the circulating acid and removed continuously from the plant.
  • the concentration of the circulating acid is regulated with the aid of the temperature and possible addition of water.
  • the pure, sulphur-free waste gas is allowed into the atmosphere after passing through an aerosol separator.
  • the 60% strength sulphuric acid is then concentrated to a concentration in the region of 93% by weight, which is a suitable concentration for production of Caro's acid.
  • the amount of sulphur which is available from the evaporation plant amounts to somewhere in the region of 3 kg of sulphur per tonne of pulp. However, this is not sufficient to permit production of a sufficient amount of Caro's acid, for which reason a further source of sulphur must be used.
  • This source consists of sulphur from a further heat treatment of thick liquor, for example in a so-called superconcentrator .
  • the vapour which develops in such a superconcentrator is very much richer in sulphur and represents somewhere in the region of 5 - 10 kilos of sulphur per tonne of pulp.
  • vapour richer in sulphur
  • vapour from the evaporation plant By subjecting this vapour, richer in sulphur, to the same processes as the vapour from the evaporation plant or combining it with the latter, it is possible to achieve a combined amount of sulphur of 8 - 13 kg per tonne of pulp. This is a sufficient amount for the sulphur balance in the system to be maintained upon total closure and optimum use of Caro's acid.
  • the bleaching and cooking stages are included in a completely closed system, the metals which are dissolved out from the wood will gradually accumulate. Some of the metals are undesirable in bleaching because they cause disintegration of active bleaching chemicals, for example hydrogen peroxide, and can even degrade the cellulose fibres. According to the invention, it may therefore be expedient to make the system partially closed by tapping off some of the circulating liquid to the outlet, with some of the undesired metals then disappearing. However, in this case it is necessary to replace the sulphur with, for example, bought-in sulphuric acid, and the sodium with, for example, bought-in NaOH.
  • the system can be made completely closed without accumulation of the metals originating from the wood. This is because these can be made to precipitate on the cellulose in an alkaline medium. It is therefore possible to raise the pH at the end of the acidic Caro's acid stage without separating the acidic liquid from the cellulose, which is done at present in order to save alkali. The metals then follow the cellulose out of the system.
  • Caro's acid is produced in a known manner by reaction between hydrogen peroxide and sulphuric acid, with Caro's acid and water being obtained. The reaction between these reactants is not complete and the equilibrium is displaced in favour of the final Caro's acid if the reactants have a high concentration. To obtain a high conversion of hydrogen peroxide, which is the most expensive raw material, an excess of sulphuric acid is used.
  • Caro's acid can be used in one or more stages in the bleaching sequence. Since it disintegrates and loses oxygen at pH values higher than 6, the most suitable initial pH value is 4 - 6, which drops to about 3 at the end of the stage. Liquor should be added to control the final pH value since the natural final pH value in an unbuffered Caro's solution is about 1.5 - 2.0. The optimum pH value in bleaching is about 5 - 6 and the temperature can be kept fairly high, between 70 and 90°C. Since Caro's acid bleaches in approximately the same way as peracetic acid, these acids can be mixed in a bleaching stage and used in preferably similar quantities. After the acid bleaching stage with Caro's acid, a basic hydrogen peroxide stage may be appropriate.
  • the invention can be implemented in various bleaching methods. It is possible to have one or more stages with Caro's acid.
  • An example of complete bleaching comprising this acid stage consists of the sequences OP-CAQ-PO. This means that the pulp is first bleached in a known manner in a stage which is dominated by oxygen with admixed hydrogen peroxide, followed by the stage with Caro's acid, and finally a stage with peroxide and oxygen where the peroxide predominates .
  • the system according to the present invention gives a low bleaching chemicals cost and it is suitable for all installations for cellulose production. It also allows different bleaching sequences to be used.

Landscapes

  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Polysaccharides And Polysaccharide Derivatives (AREA)
  • Paper (AREA)

Abstract

Cette invention se rapporte à un procédé servant au blanchiment de cellulose dans un système fermé en une ou plusieurs étapes au moyen d'acide de Caro. Ce procédé se caractérise en ce que, pour maintenir l'équilibre entre le soufre et le sodium, la production de l'acide de Caro et celle de l'acide sulfurique nécessaire pour produire cet acide sont incluses dans le système fermé en question.
PCT/SE1998/002117 1997-11-24 1998-11-23 Procede de blanchiment de cellulose dans un systeme ferme au moyen d'acide de caro Ceased WO1999027179A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU13581/99A AU1358199A (en) 1997-11-24 1998-11-23 Method for bleaching cellulose in a closed system using caro's acid

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9704298A SE9704298L (sv) 1997-11-24 1997-11-24 Förfarande vid blekning av cellulosa i ett slutet system under användning av Caro´s syra
SE9704298-0 1997-11-24

Publications (1)

Publication Number Publication Date
WO1999027179A1 true WO1999027179A1 (fr) 1999-06-03

Family

ID=20409088

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1998/002117 Ceased WO1999027179A1 (fr) 1997-11-24 1998-11-23 Procede de blanchiment de cellulose dans un systeme ferme au moyen d'acide de caro

Country Status (3)

Country Link
AU (1) AU1358199A (fr)
SE (1) SE9704298L (fr)
WO (1) WO1999027179A1 (fr)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1992015752A1 (fr) * 1991-03-11 1992-09-17 Interox International S.A. Procede pour le blanchiment d'une pate a papier chimique et application de ce procede au blanchiment d'une pate kraft
WO1993006297A1 (fr) * 1991-09-17 1993-04-01 Mo Och Domsjö Aktiebolag Procede de blanchiment de pate a l'ozone
US5246543A (en) * 1989-08-18 1993-09-21 Degussa Corporation Process for bleaching and delignification of lignocellulosic materials
FR2690934A1 (fr) * 1992-04-01 1993-11-12 Tampella Power Oy Procédé de récupération et de réutilisation du soufre dans la fabrication de pâte chimique au sulfate.
WO1994006964A1 (fr) * 1992-09-21 1994-03-31 North Carolina State University Procede de production d'une solution oxydante de peracide melange, et procedes de traitement de substrats a l'aide de cette solution

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5246543A (en) * 1989-08-18 1993-09-21 Degussa Corporation Process for bleaching and delignification of lignocellulosic materials
WO1992015752A1 (fr) * 1991-03-11 1992-09-17 Interox International S.A. Procede pour le blanchiment d'une pate a papier chimique et application de ce procede au blanchiment d'une pate kraft
WO1993006297A1 (fr) * 1991-09-17 1993-04-01 Mo Och Domsjö Aktiebolag Procede de blanchiment de pate a l'ozone
FR2690934A1 (fr) * 1992-04-01 1993-11-12 Tampella Power Oy Procédé de récupération et de réutilisation du soufre dans la fabrication de pâte chimique au sulfate.
WO1994006964A1 (fr) * 1992-09-21 1994-03-31 North Carolina State University Procede de production d'une solution oxydante de peracide melange, et procedes de traitement de substrats a l'aide de cette solution

Also Published As

Publication number Publication date
SE9704298D0 (sv) 1997-11-24
AU1358199A (en) 1999-06-15
SE9704298L (sv) 1999-05-25

Similar Documents

Publication Publication Date Title
US4053352A (en) Method for producing oxidized white liquor
JPH07506637A (ja) 塩素を含む化学物質を使用しないでパルプを漂白するためのプロセス
JP2796477B2 (ja) パルプ工場における白液選択酸化法と酸化白液の製法ならびに酸化反応系操作の制御法
FI75883B (fi) Foerfarande foer framstaellning av koklut.
US6143130A (en) Polysulfide pulping process
EP0617747B2 (fr) Methode d'elaboration de liqueur de digestion
FI96973B (fi) Menetelmä halogeeniorgaanisten yhdisteiden vähentämiseksi valkaisujätevesissä
EP0670000B1 (fr) Procede pour l'acidification de savon au moyen d'une solution de bisulfite de sodium
JPH06505063A (ja) ケミカルペーパーパルプをさらす方法及びこの方法のクラフトパルプのさらしへの適用
US2772240A (en) Method of treating residual liquors obtained in the manufacture of pulp by the sulphate cellulose process
WO1999027179A1 (fr) Procede de blanchiment de cellulose dans un systeme ferme au moyen d'acide de caro
US4334956A (en) Method of reutilizing kraft spent liquor
JP4205855B2 (ja) ポリサルファイドパルプ化プロセス
JPH06341082A (ja) 硫酸ナトリウム及び／又は炭酸ナトリウム含有物質の処理方法
AU651462B2 (en) Bleaching and delignification of pulp
CA1043516A (fr) Procede d'obtention d'une liqueur blanche oxydee
AU657003B2 (en) Ozone bleaching of pulp
EP0091457B1 (fr) Procede de traitement au polysulfure dans une reduction alcaline de pulpe d'un materiau de lignocellulose
US1795756A (en) Production of chemical pulp
FI116074B3 (fi) Rikin kierrätys sulfaattiselluprosessissa
NO144236B (no) Veske, saerlig skoleveske.
US5993601A (en) Process for producing polysulphide by means of oxidizing sulphide in spent liquors from kraft cellulose cooking
US1860570A (en) Manufacture of pulp, etc.
US1870944A (en) Production of pulp, etc.
JPH08311790A (ja) ポリサルファイド蒸解液の製造方法

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AU BR CA ID NO US

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): AT BE CH CY DE DK ES FI FR GB GR IE IT LU MC NL PT SE

121 Ep: the epo has been informed by wipo that ep was designated in this application
DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
122 Ep: pct application non-entry in european phase
NENP Non-entry into the national phase

Ref country code: CA