WO1995032331A1 - Impregnation sulfuree de copeaux pour procede alcalin de trituration - Google Patents

Impregnation sulfuree de copeaux pour procede alcalin de trituration Download PDF

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Publication number
WO1995032331A1
WO1995032331A1 PCT/SE1995/000573 SE9500573W WO9532331A1 WO 1995032331 A1 WO1995032331 A1 WO 1995032331A1 SE 9500573 W SE9500573 W SE 9500573W WO 9532331 A1 WO9532331 A1 WO 9532331A1
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WO
WIPO (PCT)
Prior art keywords
liquor
digestion
chips
impregnation
digester
Prior art date
Application number
PCT/SE1995/000573
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English (en)
Inventor
Nils Mannbro
Original Assignee
Nils Mannbro
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 Nils Mannbro filed Critical Nils Mannbro
Publication of WO1995032331A1 publication Critical patent/WO1995032331A1/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
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/02—Pulping cellulose-containing materials with inorganic bases or alkaline reacting compounds, e.g. sulfate processes
    • D21C3/022—Pulping cellulose-containing materials with inorganic bases or alkaline reacting compounds, e.g. sulfate processes in presence of S-containing compounds
    • 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
    • D21C1/00—Pretreatment of the finely-divided materials before digesting
    • D21C1/06—Pretreatment of the finely-divided materials before digesting with alkaline reacting compounds

Definitions

  • BL Black liquor
  • white liquor white liquor
  • the present invention refers to kraft pulp cooking of wood chips and also applies to versions using sulphidic alkaline cooking liquors enhanced by various additions, such as polysulphide (PS) , sulphite, anthra- quinone, methanol and others.
  • PS polysulphide
  • Normal cooking yield of pulp i.e. brown stock (BS)
  • BS brown stock
  • Bleached soft wood pulp was produced at an average yield of 45% before environmental regulations required extended cooking which decreases bleached yield to about 42% or lower.
  • Inclusion of PS in cooking liquor can give a pulp increment of 10-15% (on ordinary pulp) from a given quantity of wood but would require means to prevent emission of acidic and/or odorous sulphur compounds from BL processing.
  • Too advan ⁇ ced yield increase of bleached pulp produces some non- desirable paper qualities, such as lower opacity and tear strength approaching that of (acid) sulphite pulp.
  • DW Digester washing comprising displacement in digester of ex-digestion liquor to be distinguished from pre ⁇ viously known displacement of BL (black liquor) from 5 BS (brown stock) to recovery plant
  • BL Black liquor at pertinent concentration passed to 0 recovery plant for regeneration of WL alkali. Optional recycling of some portion of BL to digestion
  • BL+Aq Regular BL at some dilution reclaimed from pulp and passed to recovery plant
  • Aq+ ⁇ DL Major portion of washing medium and dilute minor proportion of DL from pulp to recovery plant
  • reduction or reduction degree refers to sulphur equiva- lents present as percentage of sulphide to total sulphur.
  • reduction declines in the course of digestion to a major extent by dispropor- tioning reactions and is at its lowest level in evapora- ted BL. The highest level is reached in (by reductive combustion of BL recovered) soda product prior to its dissolving in green liquor preparation.
  • reduction declines down to about 85% when soda smelt is dissolved in green liquor and then in recausticizing plants of past design, depending on how well various forms of catalytic metals and contact to air oxygen are avoided.
  • oxidation degree is related to oxidation of BL sulphide to produce more stable thiosulphate and prevent losses of sulphur compounds in non-condensable gases and is cal ⁇ culated as percentage on sulphide in non-oxidized BL.
  • Brown stock refers to fully washed pulp, discharged from digester and sometimes called “unbleached pulp”.
  • digester stock Incompletely washed or non-washed pulp is, according to prevailing technique, obtained together with black liquor (BL) .
  • black liquor black liquor
  • hot stock refers to suspen ⁇ sion prior to the last washer in a series of washers delivering brown stock for bleaching. Novel features of this invention necessitate that digested chips prior to defibering into a suspension are designated digester stock.
  • Scheme I of Figure 1 exhibits regular batch cooking with steaming (S) at digester chip filling, followed by charge of WL and BL filling to prescribed ratio liquor/wood. This ratio is in general 3/1 to 4/1, but may be lower, about 2/1, when vapour phase cooking is applied on parti- 0 cularly impregnated chips. Temperature rising schedule comprises initial phase impregnation, followed by, often stepwise, increase to maximum temperature. Appropriate combination of cooking variables is performed by means of the H-factor according to Vroom, formulated on kinetical 5 grounds.
  • Scheme II shows reclaiming of BL directly from batch digester stock by in-digester displacement (DW) and flushing stock with temperate filtrate from brown stock washing (SE patent 139 301, Mannbro, N.V.).
  • DW in-digester displacement
  • SE patent 139 301 Mannbro, N.V.
  • Progress is rapidly made for modified cooking systems based on in- digester displacement of BL of which a portion is re ⁇ cycled for impregnation of chips to be digested by injec- tion of WL.
  • This type of modified cooking facilitates extended delignification to low kappa number, although the yield of pulp in percentage calculated on wood, decreases.
  • 5. an increase is proposed of not only sulphidity but also actual concentration of sulphide in the impregnation liquor, which may produce a gain in yield by 0.5-1%.
  • Scheme III refers to continuous cooking. For clarity, 0 directions of liquor flows through the material in the digester are omitted from the scheme. Presumably at most mills WL is still charged, wholly or to a major part, to impregnation liquor circulation. However, presumably in regard to sulphide-concentration and consequences on 5 sulphidity at modified WL alkali distribution, some recirculation of diluted BL from DW (indicated by hatched line) is considered elsewhere (SE patent application 8804578-6, Backlund, A.). Another but straight counter- current system employs total recycling of BL for impreg- 0 nation (SE patent application 9001783-1, Richter,
  • Scheme IV shows particular recycling of ex-digestion 5 liquor (DL) to the impregnation stage.
  • the hemicellulose recycling increases somewhat pulp yield (SE patent from application 2823/66, Croon, Dillen and Noreus) .
  • all WL is also charged to the impregnation stage and all BL is reclaimed from DW diluted by Aq from brown stock washing.
  • the patent discloses addition of separately prepared polysulphide solution for stabilizing hemicellu- lose in impregnation of softwood and birch chips. The latter gave a particularly increased yield of bleached pulp.
  • the present invention is a.
  • Non-withdrawn DL is as residual DL ( ⁇ DL) reclaimed from brown stock wash ⁇ ing (W) of digester stock and is hereby diluted by an ex ⁇ tensively larger volume of Aq.
  • ⁇ DL residual DL
  • W brown stock wash ⁇ ing
  • Continuous digesters of type Ka yr feature split charge of white liquor and application of zones for concurrent and counter-current flows, as regards movement of liquor relative to the fibrous material, as well as zones where
  • a volume of sulphidic white liquor determined by its concentration of hydroxide (effective alkali) , is added to the impregnated chips and considered together with alkali in recycling DL in reac- tion with chips.
  • the resulting sulphide equilibrium concentration is utilized by the recycled fraction reac ⁇ ted with feed of chips to the impregnation stage (I) .
  • 0_ indicates addition of oxygen or oxygen containing gas to sulphidic impregnation liquor reacting with chips. This relates to an alternative oxidative conversion of sulphide to partial formation of poly ⁇ sulphide as dealt with further on.
  • I-V washing medium (Aq) is often used, compri- sing effluent filtrate from alkaline oxygen delignifica- tion stage in an effluent-free brown stock treatment system between digestion and O-stage (US patent 3,830,688, Mannbro, N.V. - Validity confirmed by owner's request for re-examination) .
  • O-stage filtrate is commonly used for displacement of BL from brown stock and is then included in BL passed to alkali regeneration plant. Effluent-free operation is facilitated when carry-over with washed brown stock is derived from ex-digestion liquor (DL) rather than from black liquor (BL) .
  • Alkali required in the O-stage is mostly prepared by WL oxida ⁇ tion using oxygen containing gas to such an extent that reduction degree approaches zero. Regeneration of alkali free from almost any sulphur compounds is being developed and such alkali may also be used for final stage cooking and extraction stages of the bleaching sequence.
  • heating of liquor for continuous cooking at a constant temperature although it is now applied to extended delignification at relatively maintained temperature and alkalinity in a zone of continuous digester previously used for displacement washing.
  • the DW zone of Scheme V 0 improves the extended delignification because of the early removal from the impregnation stage of BL solids.
  • extended cooking referred to methods for bringing down brown stock kappa prior to oxidative bleaching, in order to avoid or reduce formation of 5 organic chlorine compounds in bleach plant effluent. When this has been accomplished, the new issue now reduces costs for oxygen based bleaching agents, such as peroxi ⁇ de.
  • Scheme V is instrumental in fulfilling this aim, although separate combustion of bleachery filtrate in- eluded in the final filtrate (Aq+ ⁇ DL) facilitates hand ⁇ ling of chlorine compounds.
  • the impregnation stage (I) shown in Scheme V is not limited to physical impregnation of liquor in the voids of the material but comprises chemical reactions signifi ⁇ cant to the initial phase of cooking.
  • three phases can usually be distinguished: 1) initial phase, 2) bulk delignification and 3) final delignification.
  • Initial impregnation is optionally performed in a digester vessel or separate vessels are used as an alternative.
  • Impregnation for batch cooking is preferably performed in each digester. Continuous cooking has developed into use of a separate zone or vessel for impregnation and sometimes an additional vessel for the initial phase.
  • impregna ⁇ tion may be performed by addition of H_S according to known methods. Oxidation of sulphidic compounds prevents their emission to atmosphere and polysulphide can be produced, as dealt with further on.
  • Digestion heat economy is favoured by the direct charge 0 of ex-digestion liquor (DL) to impregnated chips which join with hot white liquor (WL) .
  • Less steam is required for heating because resulting cooking liquor is not subjected to dilution by washing medium (Aq) which, as far as volume balance of digester system allows, is 5 passed directly to plant for concentration, evaporation and alkali regeneration.
  • the cooking mixture of chips and new cooking liquor will have a temperature that, besides any pre-warming and 0 steaming of chips, depends on the withdrawal of heat with BL from the impregnation stage which derives from diges ⁇ tion.
  • BL heat can be directly utilized for multiple effect evaporation or optionally flashed for steaming of chips.
  • thin liquor of washing medium (Aq+ ⁇ DL) is 5 sufficiently free from chloride forming substance, it may be mixed with black liquor for common evaporation.
  • Some versions of batch cooking are designed for pre-warming of chips by some used displacement liquor.
  • this liquor could be subjected to separate pre-evaporation, i.a. to thermo-compression evaporation within the limits for acceptable boiling point rise.
  • Mechanical compression can possibly be gas turbine powered.
  • Impregnation in the presence of polysulphide is practiced according to various methods.
  • sulphide supplied as Na_S in white liquor (WL) contributed to delignification of increment PS pulp at given kappa number and denoted as a threshold effect.
  • anthraquinone was introduced as a delignifica ⁇ tion accelerating agent while PS stabilizes hemicellulose and their combination is considered to give synergistic effect and the addition should be made for long residence in the digestion system by avoiding dilution, which otherwise is caused by a washing medium.
  • Hemicellulose stabilization is, as is well-known, attai ⁇ ned by reacting polysulphide (PS) according to Scheme IV.
  • PS polysulphide
  • Scheme IV Separately prepared PS, either from elemental sulphur or PS essentially deriving from sulphide, is used. Elimina ⁇ tion of particular sulphur compounds to generate PS is developed according to other methods.
  • oxidation of sulphidic liquor or mixture of liquors by oxygen contai ⁇ ning gas and in the presence of chips proved simple and satisfactorily efficient.
  • the kraft process produces fundamentally white liquor (WL) at a high reduction degree to form cooking liquor of high delignification efficiency which, however, is more or less lost by any 5.
  • prior PS oxidation of WL sulphide as such or as a cooking liquor component.
  • the present invention features application of ex-diges ⁇ tion liquor (DL) for impregnation of chips which, in 0 turn, can be combined with oxidative PS reaction with no harm attaching to the reduction degree and sulphidic values contributed by fresh white liquor (WL) .
  • Alkali remaining in ex-digestion liquor (DL) is utilized for BL forming reactions with wood and at a pertinent temperatu- 5 re after partial ex-liquor recycling determined by the ratio volume of cooking liquor/wood required at the digestion stage.
  • Black liquor viscosity during evaporation is primarily 0 related to its alkalinity, and some addition of alkali, during or after impregnation, could be justified. Alter ⁇ natively, the viscosity may be lowered by pressure hea ⁇ ting of the black liquor, whereby, in some cases, sulphi ⁇ dic gaseous compounds are expelled. These techniques are currently being practiced for evaporation of up to 80-85% solids on total liquor.
  • Sulphidic impregnation according to the invention may, in its PS version, use air in agitators such as at screw feeding of chips through certain horizontal or inclined digester tubes of known design. These are also suitable for flow of air or oxygen containing vapour through the connecting chip steaming stage. Low concentration of oxidizing agent but still almost closed system is accomplished by injection of concentrated oxygen and optional degassing to some combustion stage. For safety reasons, it is important that turpentine and volatile combustibles from wood and vapour condensate are treated separately from oxygen. Sulphur compounds present in odorous process gases are, according to certain publica ⁇ tions (Teder and Tormund, Svensk Papperstidning 1983, R 198) , reacted by polysulphide. The possible use of vapour from oxidized BL for steaming of chips without odour emission is noted.
  • Bleached softwood kraft pulp was produced by typical Kamyr-type impregnation and MCC (Modified Continuous Cooking) to brown stock kappa number 25 and oxygen delig- nification to kappa number 18, followed by bleaching according to the sequence (C+D) (E0)D for brightness 90% ISO.
  • C+D oxygen delig- nification
  • E0 brightness 90% ISO.
  • C+D oxygen delig- nification
  • E0 brightness 90% ISO.
  • To reduce pollution from the mill effluent trials were performed to evaluate lowering the kappa number of stock from oxygen delignification stage to 14. This, according to parallel laboratory measurements, decreased the yield of bleached pulp from 43 to 42% on wood and viscosity from 900 to 830 dm 3/kg.
  • investigations within the frame of the present invention were performed by labora- tory cooking and bleaching, simulating mill conditions after installation of impregnation stage using ex-diges ⁇ tion liquor as follows:
  • Each series comprised a succession of 5 recycling batch cooks simulating equilibrium at MCC continuous cooking.
  • the following results were obtained: a) at brown stock kappa 20 and kappa 12 after oxygen delignification, bleached pulp was obtained at a yield of 42% on wood and viscosity 890 dm 3/kg, b) at brown stock kappa 18 and kappa 12 after oxygen delignification, the yield of bleached pulp was 44% and the viscosity was 980 dm 3/kg.
  • TEF process again allows a total environmental concept for brown stock kappa number about 35 and bleaching with efficient chemicals.
  • These chemicals particularly elemental oxygen and chlo ⁇ rine, are being manufactured at low energy demand and the pulp is produced at a bleached pulp yield of up to 45% or, according to the PS version, with 48% or higher within the limits for potential paper strength.

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  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Paper (AREA)

Abstract

L'invention concerne un procédé de délignification par étapes des fibres de lignocellulose par lessivage avec une lessive alcaline sulfurée, comportant la cuisson selon le procédé kraft des copeaux de bois avec une lessive fraîche. Cette dernière est répartie pendant la cuisson. La lessive issue de la cuisson est extraite de la pâte du lessiveur, avec peu ou pas de dilution, par n'importe quel milieu de lavage de la pâte brune et acheminée par canalisations à l'étage d'imprégnation initiale des copeaux. Le rendement de la pâte et les valeurs de viscosité s'en trouvent ainsi améliorés et peuvent l'être encore davantage par du polysulfure qui stabilise les glucides. Une telle réaction avec du polysulfure est produite par oxydation in situ. Au degré de réduction atteint par imprégnation, la lessive noire est acheminée jusqu'à l'installation de récupération tandis qu'une partie de la lessive issue de la cuisson, à son degré de réduction initiale, est recyclée directement conjointement avec le matériau imprégné. Séparément de l'extraction de la lessive issue de la cuisson, la lessive contenant le milieu de lavage est éliminée et acheminée vers des étapes de concentration et de combustion qui sont prévues éventuellement après mélange avec la lessive noire.
PCT/SE1995/000573 1994-05-24 1995-05-22 Impregnation sulfuree de copeaux pour procede alcalin de trituration WO1995032331A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9401769A SE9401769L (sv) 1994-05-24 1994-05-24 Flisimpregnering vid pappersmassakokning med sulfidiskt alkali
SE9401769-6 1994-05-24

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5885414A (en) * 1997-08-18 1999-03-23 Kvaerner Pulping Ab Method of producing pulp with high alkali cooking in the last cooking stage
EP1245721A4 (fr) * 1999-06-15 2002-10-09 Kawasaki Kasei Chemicals Procede de cuisson pour pate a papier
WO2003002813A3 (fr) * 2001-06-29 2003-03-20 Voith Paper Fiber Systems Gmbh Procede de delignification de matieres premieres lignocellulosiques
WO2004104293A1 (fr) * 2003-05-21 2004-12-02 Voith Paper Fiber Systems Gmbh & Co. Kg Procede de delignification de materiaux bruts lignocellulosiques
WO2006037858A1 (fr) * 2004-10-04 2006-04-13 Metso Paper, Inc. Procede et dispositif de preparation d'une pate a papier
EP1797235A1 (fr) * 2004-10-04 2007-06-20 Metso Paper, Inc. Procede alcalin ameliore et systeme de fabrication de pate a papier
WO2011138633A1 (fr) * 2010-05-04 2011-11-10 Bahia Specialty Cellulose Sa Procédé et système pour le traitement de pâte à papier en utilisant l'extraction alcaline à froid avec la réutilisation du filtrat alcalin
US8535480B2 (en) 2010-05-06 2013-09-17 Bahia Specialty Cellulose Sa Method and system for pulp processing using cold caustic extraction with alkaline filtrate reuse

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4595455A (en) * 1973-11-23 1986-06-17 Mannbro Systems Handelsbolag Method for controlling batch alkaline pulp digestion in combination with continuous alkaline oxygen delignification
US5053108A (en) * 1989-06-28 1991-10-01 Kamyr Ab High sulfidity cook for paper pulp using black liquor sulfonization of steamed chips
EP0527294A1 (fr) * 1991-08-14 1993-02-17 Kamyr, Inc. Traitement des copeaux de bois avec de la liqueur noire

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4595455A (en) * 1973-11-23 1986-06-17 Mannbro Systems Handelsbolag Method for controlling batch alkaline pulp digestion in combination with continuous alkaline oxygen delignification
US5053108A (en) * 1989-06-28 1991-10-01 Kamyr Ab High sulfidity cook for paper pulp using black liquor sulfonization of steamed chips
EP0527294A1 (fr) * 1991-08-14 1993-02-17 Kamyr, Inc. Traitement des copeaux de bois avec de la liqueur noire

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5885414A (en) * 1997-08-18 1999-03-23 Kvaerner Pulping Ab Method of producing pulp with high alkali cooking in the last cooking stage
EP1245721A4 (fr) * 1999-06-15 2002-10-09 Kawasaki Kasei Chemicals Procede de cuisson pour pate a papier
US7056418B2 (en) 1999-06-15 2006-06-06 Kawasaki Kasei Chemicals Ltd. Cooking method for pulp
WO2003002813A3 (fr) * 2001-06-29 2003-03-20 Voith Paper Fiber Systems Gmbh Procede de delignification de matieres premieres lignocellulosiques
WO2004104293A1 (fr) * 2003-05-21 2004-12-02 Voith Paper Fiber Systems Gmbh & Co. Kg Procede de delignification de materiaux bruts lignocellulosiques
WO2006037858A1 (fr) * 2004-10-04 2006-04-13 Metso Paper, Inc. Procede et dispositif de preparation d'une pate a papier
WO2006037857A1 (fr) * 2004-10-04 2006-04-13 Metso Paper, Inc. Procede et dispositif pour preparer de la pate cellulosique
EP1797235A1 (fr) * 2004-10-04 2007-06-20 Metso Paper, Inc. Procede alcalin ameliore et systeme de fabrication de pate a papier
EP1797235A4 (fr) * 2004-10-04 2010-10-06 Metso Paper Inc Procede alcalin ameliore et systeme de fabrication de pate a papier
WO2011138633A1 (fr) * 2010-05-04 2011-11-10 Bahia Specialty Cellulose Sa Procédé et système pour le traitement de pâte à papier en utilisant l'extraction alcaline à froid avec la réutilisation du filtrat alcalin
US8535480B2 (en) 2010-05-06 2013-09-17 Bahia Specialty Cellulose Sa Method and system for pulp processing using cold caustic extraction with alkaline filtrate reuse
US8734612B2 (en) 2010-05-06 2014-05-27 Bahia Specialty Cellulose Method and system for high alpha dissolving pulp production

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Publication number Publication date
SE9401769D0 (sv) 1994-05-24
SE9401769L (sv) 1995-11-25

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