NO130776B - - Google Patents

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NO130776B
NO130776B NO04803/69A NO480369A NO130776B NO 130776 B NO130776 B NO 130776B NO 04803/69 A NO04803/69 A NO 04803/69A NO 480369 A NO480369 A NO 480369A NO 130776 B NO130776 B NO 130776B
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pulp
chlorine
bleaching
mass
treatment
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NO04803/69A
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Norwegian (no)
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NO130776C (en
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I Croon
S Dillen
S Noreus
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Mo Och Domsjoe Ab
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    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21CPRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00After-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
    • D21C9/10Bleaching ; Apparatus therefor
    • D21C9/1057Multistage, with compounds cited in more than one sub-group D21C9/10, D21C9/12, D21C9/16
    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21CPRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00After-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
    • D21C9/10Bleaching ; Apparatus therefor
    • D21C9/12Bleaching ; Apparatus therefor with halogens or halogen-containing compounds
    • D21C9/14Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites
    • D21C9/144Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites with ClO2/Cl2 and other bleaching agents in a multistage process

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)

Description

Fremgangsmåte til fremstilling av bleket Procedure for producing the bleach

cellulosemasse. cellulose pulp.

Foreliggende oppfinnelse vedrører fremstilling av blekede cellulosemasser, f.eks. sulfatmasse, sulfittmasse eller halvkjemisk masse, ved partiell avlignifisering med oksygenholdig gass under alkaliske betingelser og derpå følgende fortsatt avlignifisering med klorholdig blekemiddel. The present invention relates to the production of bleached cellulose pulps, e.g. sulphate pulp, sulphite pulp or semi-chemical pulp, by partial delignification with oxygen-containing gas under alkaline conditions and then continued delignification with chlorine-containing bleach.

Ved bleking av cellulosemasser oppnådd ved kjemisk oppslutning av tre eller andre lignocellulosematerialer, benyttes vanligvis kon-tinuerlige flertrinnsprosesser. Por sulfatmasser, som er forholdsvis vanskelige å bleke, anvendes ofte en behandling i seks trinn, som kan betegnes C-E-H-D-E-D. De forskjellige bokstavene tilsvarer behandlingstrinn ifølge det nedenfor angitte: C: Klorering. Utføres normalt med relativt lav masse-konsistens: 1 - 4 % s lav temperatur: 5° - 25°C, behandlingstid: 1/2-2 timer. Klortilsetningen varierer avhengig av den ublekede massens egenskaper; normalt onskes dog så stor tilsetning at et lite overskudd, ca. 0.1 - 6.5 % av massevekten, gjenstår, ved behandlingstidens slutt. When bleaching cellulose masses obtained by chemical digestion of wood or other lignocellulosic materials, continuous multi-stage processes are usually used. Por sulfate masses, which are relatively difficult to bleach, often use a treatment in six stages, which can be designated C-E-H-D-E-D. The different letters correspond to treatment steps as indicated below: C: Chlorination. Normally carried out with a relatively low mass consistency: 1 - 4 % s low temperature: 5° - 25°C, treatment time: 1/2-2 hours. The addition of chlorine varies depending on the properties of the unbleached pulp; normally, however, such a large addition is desired that a small surplus, approx. 0.1 - 6.5% of the mass weight remains at the end of the treatment period.

E: Alkalibehandling (alkalisk ekstraksjon). Utfores ved relativt hoy massekonsistens, normalt 4. - 18 % (ved anvendelse av presser for avvanning opp til 30$)) temperatur 25° - 80°C (i forbindelse med såkalt varmeforedling for fremstilling av masse med hpyt alfacelluioseinnhold anvendes hoyere temperatur på opp til 130°C); behandlingstiden varierer fra meget kort, noen minutter (noytraliser-ingstrinn) opp til 4 - 5 timer. Alkalitilsetningen varierer avhengig av massens egenskaper og den massekvalitet .som onskes fremstilt, for papirmasser onskes i alminnelighet ved- behandlingens slutt en pH-verdi i området 8 - 12.5, vanligvis ca. 11. E: Alkali treatment (alkaline extraction). Carried out at a relatively high pulp consistency, normally 4. - 18% (when using presses for dewatering up to 30$)) temperature 25° - 80°C (in connection with so-called heat processing for the production of pulp with a high alpha cellulose content, a higher temperature of up to to 130°C); the treatment time varies from very short, a few minutes (neutralisation step) up to 4 - 5 hours. The addition of alkali varies depending on the properties of the pulp and the desired pulp quality, for paper pulps a pH value in the range of 8 - 12.5 is generally desired at the end of the treatment, usually approx. 11.

H: Hypoklorittbehandling utfores med natrium- eller kal-siumhypokloritt.ved massekonsistenser tilsvarende de ved alkalibehandling benyttede, dvs. 4 - 18$, temperatur 25° - 6,0°C-, behandlingstid fra 1 time og over dette, normalt 2-4 timer. Hypoklorittilsetningen varierer med massetype og betingelsene forovrig fra meget lave tilsetninger, 0.2$ opp til flere prosent. (Prosentangivelsene angår vekten av den ekvivalente mengde klor angitt i forhold til vekten av den torre massen). Normalt sokes oppnådd et lite gjenværende overskudd, ca. 0.1$ av massevekten, ved behandlingens slutt. Fordi -hypokloritt ved pH-verdier omkring og like under noytralitetspunktet er kraftig nedbrytende på cellulosen, tilsettes normalt såkalt overskuddsalkali, hvilket som regel utgjores av en vektmengde NaOH på opp til mellom 10 og 100$ av hypoklorittilsetningen (beregnet som ekvivalent mengde klor). Hensikten er at pH-verdien ved behandlingens slutt skal være H: Hypochlorite treatment is carried out with sodium or calcium hypochlorite. With mass consistencies corresponding to those used for alkali treatment, i.e. 4 - 18$, temperature 25° - 6.0°C-, treatment time from 1 hour and above, normally 2-4 hours. The hypochlorite addition varies with the pulp type and the conditions otherwise, from very low additions, 0.2$ up to several percent. (The percentages relate to the weight of the equivalent amount of chlorine stated in relation to the weight of the dry mass). Normally, a small remaining surplus is achieved, approx. 0.1$ of the mass weight, at the end of the treatment. Because -hypochlorite at pH values around and just below the neutrality point is strongly degrading the cellulose, so-called excess alkali is normally added, which is usually made up of a weight amount of NaOH of up to between 10 and 100$ of the hypochlorite addition (calculated as an equivalent amount of chlorine). The purpose is that the pH value at the end of the treatment should be

>8.5 vanligvis 10-11. >8.5 usually 10-11.

D: Klordioksydbehandling. Denne utfores i prinsippet ved samme massekonsistens som hypoklorittbehandlingen, i praksis dog ved D: Chlorine dioxide treatment. In principle, this is carried out with the same mass consistency as the hypochlorite treatment, but in practice with

noe lavere konsistens fordi klordioksydopplosningen oppnåes i mer for-tynnet form enn hypoklorittopplosningen, nemlig 4 - 15$- Temperaturen er 50° - 90°C, vanligvis ca. 70°C. Behandlingstiden er minst 2 timer, vanligvis 3-5 timer. Den tilsatte mengde klordioksyd varierer fra 0.5 opp til 2 - 3 $ av massevekten, i visse tilfeller til og med mer (også i dette.tilfelle angår prosentangivelsene vekten av den fra ok-sydasjonssynspunkt ekvivalente mengde klor). Normalt onskes oppnådd et lite overskudd ved behandlingens slutt. Disse forskjellige behandlingstrinn arrangeres stundom også i andre kombinasjoner, f.eks. C-E-C-E-H-D-E-D somewhat lower consistency because the chlorine dioxide solution is obtained in a more diluted form than the hypochlorite solution, namely 4 - 15% - The temperature is 50° - 90°C, usually approx. 70°C. The treatment time is at least 2 hours, usually 3-5 hours. The added amount of chlorine dioxide varies from 0.5 up to 2 - 3 $ of the mass weight, in certain cases even more (also in this case, the percentages relate to the weight of the equivalent amount of chlorine from the point of view of oxidation). Normally, a small profit is desired at the end of the treatment. These different treatment steps are sometimes also arranged in other combinations, e.g. C-E-C-E-H-D-E-D

C-E-H-C-H-D-E-D C-E-H-C-H-D-E-D

C-H-E-D-E-D C-H-E-D-E-D

C-E-D-E-D C-E-D-E-D

I prinsippet kan det sies at de innledende bleketrinn, spesielt den forste kloreringen fmed etterfølgende alkalibehandling), In principle, it can be said that the initial bleaching steps, especially the first chlorination with subsequent alkali treatment),

mer er beregnet for avlignifisering enn bleking. For masser som er vanskelige å avlignifisere, dvs. spesielt sulfatmasser, er imidlertid et kloreringstrinn utilstrekkelig for.avlignifisering og av denne grunn foretas en kompletterende avlignif isering i en ytterligere kl-or-ering i et hypokloritt- eller-klordioksydtrinn. more is intended for delignification than bleaching. However, for pulps that are difficult to delignify, i.e. sulfate pulps in particular, a chlorination step is insufficient for delignification and for this reason a complementary delignification is carried out in a further chlorination in a hypochlorite or chlorine dioxide step.

Blekingen innebærer kjemisk at ligninet ved oksydasjon nedbrytes og overfores til vann- eller alkaliopploselig form. Det oksydasjonsmiddel som hovedsakelig anvendes for dette formål er elementært klor som har en god avlignifiseringsevne og som er billigere enn de alternative kjemikaliene, dvs. hypokloritt, klordioksyd, natri-umperoksyd og andre perforbindelser. Klor som avlignifiseringsmiddel har imidlertid den ulempe at det restlignin som ikke kan fjernes, mis-farves, og derfor blekingen ikke sluttlig gjennomføres med bare klor, Bleaching chemically means that the lignin is broken down by oxidation and transferred to a water- or alkali-soluble form. The oxidizing agent that is mainly used for this purpose is elemental chlorine, which has a good delignifying ability and which is cheaper than the alternative chemicals, i.e. hypochlorite, chlorine dioxide, sodium peroxide and other compounds. However, chlorine as a delignifying agent has the disadvantage that the residual lignin that cannot be removed is discoloured, and therefore the bleaching is not finally carried out with only chlorine,

men hypokloritt og/eller klordioksyd må benyttes for komplettering av blekingen. Hvis omkostningene for bleking av,massen skal senkes, er det nærliggende å prove å finne et oksydasjonsmiddel som er billigere enn klor. Et slikt er elementært oksygen. Det har temmelig lenge vært kjent at oksygen under alkaliske betingelser har evne til å oksy-dere lignin, hvorved dette delvis opploses og det gjenværende ligninet blir lysere. For å oppnå en hurtig reaksjon mellom det celluloseholdige materiale og den tilforte oksygengassen (respektive luften) bor oksygenets partialtrykk ved behandlingens begynnelse være minst 1 at-mosfære. Lavere trykk kan dog forekomme. Vanligvis er et oksygen-gasstrykk på 2 - 12 atmosfærer foretrukket. Hoyere trykk kan benyttes, men dette stiller hoyere krav til reaksjonsapparaturen. Ved lav temperatur, f.eks. 50°C, skjer reaksjonene langsomt,og av denne grunn kreves store reaksjonsbeholdere. For at korte reaksjonstider skal oppnåes, utfores behandlingen normalt ved en temperatur på 80° - 130°C, fortrinnsvis ved 90° - 110°C. Konsentrasjonen av cellulcssholdig materiale kan varieres innen vide grenser uten at reaksjonen påvirkes ugunstig, f.eks. mellom 3 og 45%- Det har imidlertid vist seg at behandlingen ved lave massekonsentrasjoner, 10 - 15/» > medforer at det må benyttes en reaksjonsapparatur der massen onirores kraftig for at en but hypochlorite and/or chlorine dioxide must be used to complete the bleaching. If the costs for bleaching the pulp are to be lowered, it is obvious to try to find an oxidizing agent that is cheaper than chlorine. One such is elemental oxygen. It has been known for quite some time that oxygen under alkaline conditions has the ability to oxidize lignin, whereby this is partially dissolved and the remaining lignin becomes lighter. In order to achieve a rapid reaction between the cellulose-containing material and the supplied oxygen gas (respectively the air), the partial pressure of the oxygen at the beginning of the treatment must be at least 1 atmosphere. However, lower pressures may occur. Generally, an oxygen gas pressure of 2 - 12 atmospheres is preferred. Higher pressures can be used, but this places higher demands on the reaction equipment. At low temperature, e.g. 50°C, the reactions take place slowly, and for this reason large reaction vessels are required. In order to achieve short reaction times, the treatment is normally carried out at a temperature of 80° - 130°C, preferably at 90° - 110°C. The concentration of cellulose-containing material can be varied within wide limits without the reaction being adversely affected, e.g. between 3 and 45%- It has, however, been shown that the treatment at low mass concentrations, 10 - 15/»>, means that a reaction apparatus must be used in which the mass is heated strongly so that a

tilfredsstillende avlignifisering skal kunne oppnås. Hvis derimot høyere massekonsentrasjon benyttes, kreves ikke noen omrøring av massen. Ved høy massekonsentrasjon bør massen rives opp mekanisk etter eller i forbindelse med tilføringen av kjemikaliene. Den for proses-sen nødvendige alkalimengde avhenger av hvor meget lignin og hemicellulose som ønskes fjernet. satisfactory delignification must be achieved. If, on the other hand, a higher mass concentration is used, no stirring of the mass is required. In the case of a high mass concentration, the mass should be torn up mechanically after or in connection with the addition of the chemicals. The amount of alkali required for the process depends on how much lignin and hemicellulose is desired to be removed.

Vanligvis ligger alkalitilsetningen beregnet som NaOH, ved 0,5 _ 10.% beregnet på det tilførte celluloseholdige materialets vekt. Tilsetningen innen det noe høyere intervall 7 - 12%, er aktu-elt bare når det ved behandlingen ønskes utløst store mengder lignin og/eller hemicellulose. Ved masser med lavt lignininnhold benyttes tilsetninger på 0,5 - 1%, hvorved det skal bemerkes at utløsningen av hemicellulose minsker med minsket alkalitilsetning. Usually, the alkali addition, calculated as NaOH, is at 0.5 - 10.% calculated on the weight of the cellulose-containing material added. The addition within the somewhat higher interval of 7 - 12% is relevant only when it is desired to release large amounts of lignin and/or hemicellulose during the treatment. For pulps with a low lignin content, additions of 0.5 - 1% are used, whereby it should be noted that the release of hemicellulose decreases with reduced alkali addition.

Oksygen-alkaliprosessens selektivitet med hensyn til ligninutløsning forbedres betydelig hvis en inhibitor for oksygenets reaksjon med massens karbohydrater, f.eks. magnesiumforbindelser, tilsettes. The selectivity of the oxygen-alkali process with regard to lignin release is significantly improved if an inhibitor for the reaction of oxygen with the carbohydrates of the mass, e.g. magnesium compounds, are added.

Oksygengassbleking ifølge det ovenfor beskrevne, er imidlertid forbundet med den ulempe at den også i nærvær av magnesiumforbindelser gir en altfor kraftig nedbrytning av massen med ikke ønsket viskositetsnedsettelse som følge. Oxygen gas bleaching according to the above is, however, associated with the disadvantage that, even in the presence of magnesium compounds, it results in an excessively strong breakdown of the mass with an undesired reduction in viscosity as a result.

Foreliggende oppfinnelse har til formål å eliminere de ovenfor nevnte ulemper. Således er det tilveiebragt en fremgangsmåte til fremstilling av bleket cellulosemasse ved partiell avlignifisering med oksygenholdig gass under alkaliske betingelser og derpå følgende fortsatt avlignifisering med klorholdig blekemiddel, og denne fremgangsmåte er kjennetegnet ved en kombinasjon av følgende trekk: at klorblekingen utføres med en blanding av klor og klordioksyd inneholdende 2-50% klordioksyd (beregnet som i oksydasjonshenseende ekvivalent mengde klor). og under følgende i og for seg kjente betingelser: temperatur 30-70°C, tid 0,5-5 timer, massekonsistens minst 2%, fortrinnsvis 3-15 %, og veo. at massen etter denne fortsatte avlignifisering underkastes ytterligere minst et behandlingstrinn,- hvorved alkaliske betingelser råder, for ut-løsning av klorert lignin. The purpose of the present invention is to eliminate the above-mentioned disadvantages. Thus, a method has been provided for the production of bleached cellulose pulp by partial delignification with oxygen-containing gas under alkaline conditions and subsequent continued delignification with chlorine-containing bleach, and this method is characterized by a combination of the following features: that the chlorine bleaching is carried out with a mixture of chlorine and chlorine dioxide containing 2-50% chlorine dioxide (calculated as an equivalent amount of chlorine in terms of oxidation). and under the following per se known conditions: temperature 30-70°C, time 0.5-5 hours, pulp consistency at least 2%, preferably 3-15%, and veo. that, after this continued delignification, the pulp is further subjected to at least one treatment step, whereby alkaline conditions prevail, for the release of chlorinated lignin.

Ved anvendelse av det ifølge oppfinnelsen foreslåtte klor/klordioksydtrinn med forholdsvis drastiske betingelser under ferdigblek-.irige:m-etter:rtfksyvge^ lignifisering av massen under betingelser som er meget skånsomme med hensyn til massens viskositet. Den meget gode avlignifiseringen medforer at massen etter alkalibehandling og et klordioksydtrinn, oppnår lyshets- og viskositetsdata som er helt sammenlignbare med de for konvensjonelt bleket masse når blekingen av denne utfores -i seks trinn. Denne reduksjon av trinnantallet er av meget stor okonomisk betydning fordi omkostningene ved et bleketrinn i en moderne massefabrikk når opp til vel 2 millioner kroner, hvortil kommer drifts- og vedlikeholds-omkostninger. When using the chlorine/chlorine dioxide step proposed according to the invention with relatively drastic conditions under pre-bleached lignification of the mass under conditions that are very gentle with regard to the viscosity of the mass. The very good delignification means that the pulp, after alkali treatment and a chlorine dioxide step, achieves lightness and viscosity data that are completely comparable to those for conventionally bleached pulp when the bleaching is carried out -in six stages. This reduction in the number of steps is of very great economic importance because the costs of a bleaching step in a modern pulp factory reach well over NOK 2 million, to which are added operating and maintenance costs.

Ved anvendelse av et 5_trinns blekeskjerna for oksygen-alkalibehandlet masse, dvs. med ytterligere en alkalibehandling og et klordioksydtrinn, oppnås masser som i kombinasjon har en så hcy lyshet og hoy viskositet at denne vanskelig kan oppnåes ved konvensjonell bleking. Massens ettergulningstendens er dessuten ytterst lav. Fra et blekekjeniikaliesynspunkt innebærer bleking ifolge oppfinnelsen av oksygen-alkalibehandlet masse med C/D-trinn og ett eller to klordioksydtrinn med mellomliggende alkalibehandlinger, besparelser sammen-lignet med konvensjonell bleking av en størrelsesorder, på 14 kroner/ tonn torr masse. When using a 5-stage bleaching core for oxygen-alkali treated pulp, i.e. with an additional alkali treatment and a chlorine dioxide step, pulps are obtained which in combination have such a high brightness and high viscosity that this can hardly be achieved by conventional bleaching. The pulp's subsequent yellowing tendency is also extremely low. From a bleaching technology point of view, bleaching according to the invention of oxygen-alkali-treated pulp with C/D stage and one or two chlorine dioxide stages with intermediate alkali treatments involves savings compared to conventional bleaching of an order of magnitude, of NOK 14/tonne dry pulp.

Eksempel 1 Example 1

Ubleket furusulfatmasse ble benyttet ved forsokefc. Massen hadde folgende analysedata: Unbleached pine sulphate pulp was used in trials. The mass had the following analytical data:

Massen samt en tilsetning av 1 vektprosent MgCOc beregnet på masse og en vannopplosning av NaOH inneholdende 6.4 g/l NaOH, ble grundig blandet ved 3% massekonsentrasjon. Deretter ble massen avvannet i en sentrifuge slik at det ble oppnådd en massekonsentrasjon på 24$. The pulp and an addition of 1% by weight MgCOc calculated on pulp and a water solution of NaOH containing 6.4 g/l NaOH were thoroughly mixed at 3% pulp concentration. The mass was then dewatered in a centrifuge so that a mass concentration of 24$ was obtained.

Massen ble behandlet i en pinneriver slik Pt en luftig masse ble oppnådd. Denne massen ble anbragt i en trykkbeholder, som ble oppvarmet med direkte damp til 100°C. Trykkbeholderen ble forbundet med en oksygentilforsel og trykket innstilt på 8 kp/cm-. Etter 15 minutters reaksjonstid ble massen vasket med vann. Massen hadde da folgende analyseverdier: The mass was processed in a stick grater so that an airy mass was obtained. This mass was placed in a pressure vessel, which was heated with direct steam to 100°C. The pressure vessel was connected to an oxygen supply and the pressure set at 8 kp/cm-. After a 15-minute reaction time, the mass was washed with water. The pulp then had the following analysis values:

Denne massen ble ferdigbleket ifolge folgende blekeskjerna: This mass was finished bleaching according to the following bleaching core:

Den oksygen-alkalibehandlede massen ble også ferdigbleket ifolge folgende blekeskjerna: The oxygen-alkali treated pulp was also finished bleaching according to the following bleaching core:

Samme utgangsmasse ble også benyttet for bleking med det konvensjonelle blekeskjema C-E-H-D-E-D uten forutgående oksygen-alkali-behandl ing av massen. Massen ble bleket ifolge folgende betingelser: The same starting mass was also used for bleaching with the conventional bleaching scheme C-E-H-D-E-D without prior oxygen-alkali treatment of the mass. The pulp was bleached according to the following conditions:

Folgende analysedata ble oppnådd for massene som var bleket på de forskjellige måtene som angitt ovenfor: The following analytical data were obtained for the pulps bleached in the various ways indicated above:

Det fremgår således .at det overraskende nok har vært mulig ifolge oppfinnelsen å oppnå gode lyshetsverdier ved anvendelse av bare tre bleketrinn etter oksygen-alkalitrinnet. Den etter oksygengassoe-handlingen utforte bleking har derved blitt utfort med et spesielt C/D-trinn hvis gode avlignifiserende og blekende evne gjor at' bare et klordioksydtrinn er nodvendig etter alkaliekstraksjonen for at et hoyt lyshetsnivå skal oppnås. Ved konvensjonell bleking av sulfatmasse kreves seks trinn for å oppnå tilsvarende resultater. Den i den andre kolonne i tabellen viste blekesekvens gir videre en kombinasjon av lyshetsnivå og viskositet, som i dag er uoppnåelig ved hjelp av konvensjonelle blekefremgangsmåter. It thus appears that, surprisingly enough, it has been possible according to the invention to achieve good lightness values by using only three bleaching steps after the oxygen-alkali step. The bleaching carried out after the oxygen gas operation has thereby been carried out with a special C/D step whose good delignifying and bleaching ability means that only a chlorine dioxide step is necessary after the alkali extraction for a high level of brightness to be achieved. In conventional bleaching of sulphate pulp, six steps are required to achieve similar results. The bleaching sequence shown in the second column of the table further provides a combination of lightness level and viscosity, which is currently unattainable using conventional bleaching methods.

Eksempel 2 Example 2

Ubleket furusulfatrnasse ble' benyttet ved forsoket. Massen hadde folgende analysedata: Unbleached pine sulphate pulp was used in the experiment. The mass had the following analytical data:

Massen ble behandlet ifolge eksempel 1, men ved benyttelse av luft istedenfor oksygengass. The pulp was treated according to example 1, but using air instead of oxygen gas.

Folgende analysedata ble oppnådd for vasket masse: The following analysis data were obtained for washed pulp:

Denne massen ble ferdigbleket ifolge folgende blekeskjerna: This mass was finished bleaching according to the following bleaching core:

Folgende analysedata ble oppnådd for massen: The following analytical data were obtained for the pulp:

Det fremgår således at anvendelsen av luft istedenfor oksygengass ved oksygengass-alkalitrinnet også har gitt en kraftig redusering av massens kappatall, hvilket dog er mindre enn hvis ren oksygengass benyttes. Det er imidlertid mulig å kompensere denne for-ringede avlignifisering ved en skjerping av betingelsene i det etter-følgende C/D-trinnet. En hevning av temperaturen i C/D-trinnet medforer at hoyere kjemikaliemengder kan forbrukes i lopet av en viss tid. I eksemplet har reaksjonstiden kunnet minskes til 1 time sammen-lignet med 3 timer som ble benyttet i eksempel 1, til tross for en vesentlig okning av blekekjemikaliemengden i eksempel 2. Denne kraf-tige behandling i C/D-trinnet gjor det mulig å oppnå hoye lysheter med bare tre blekietrinn etter en luft-alkalibehandling. It thus appears that the use of air instead of oxygen gas in the oxygen gas-alkali stage has also resulted in a strong reduction in the kappa number of the mass, which is however less than if pure oxygen gas is used. However, it is possible to compensate for this deteriorated delignification by tightening the conditions in the subsequent C/D step. An increase in the temperature in the C/D stage means that higher amounts of chemicals can be consumed over a certain period of time. In the example, the reaction time could be reduced to 1 hour compared to the 3 hours used in example 1, despite a substantial increase in the amount of bleaching chemicals in example 2. This powerful treatment in the C/D step makes it possible to achieve high lightness with only three bleaching steps after an air-alkali treatment.

Eksempel 3 Example 3

Ubleket gransulfittviskosemasse ble benyttet ved forsoket. Massen hadde folgende analysedata: Unbleached spruce sulphite viscose pulp was used in the experiment. The mass had the following analysis data:

Massen og en vannopplosning av NaOH inneholdende 3-1 g/l The mass and a water solution of NaOH containing 3-1 g/l

NaOH ble godt blandet ved 6% massekonsentrasjon. Deretter ble massen avvannet i en sentrifuge slik at det ble oppnådd en massekonsentrasjon på 30$. NaOH was well mixed at 6% mass concentration. The mass was then dewatered in a centrifuge so that a mass concentration of 30% was achieved.

Massen ble behandlet i en pinneriver slik at det ble oppnådd en luftig masse. Denne masse ble anbragt i en trykkbeholder som ble oppvarmet med direkte damp til 80°C. Trykkbeholderen ble forbundet nved et lufttilforselsror og trykket innstilt på 4 kp/cm . Etter 30 minutters reaksjonstid ble massen vasket med vann. The mass was processed in a stick grater so that an airy mass was obtained. This mass was placed in a pressure vessel which was heated with direct steam to 80°C. The pressure vessel was connected by an air supply pipe and the pressure set at 4 kp/cm. After a 30-minute reaction time, the mass was washed with water.

Massen hadde da folgende analyseverdier: The pulp then had the following analysis values:

Massen ble ferdigbleket ifolge folgende blekeskj erna : The pulp was finished bleaching according to the following bleaching methods:

Masse som ikke ble oksygengassbehandlet, ble også bleket ifolge skjema C-E-D-H ifolge folgende betingelser: Masses that were not treated with oxygen gas were also bleached according to form C-E-D-H according to the following conditions:

Folgende analysedata ble oppnådd for massene: The following analytical data were obtained for the masses:

Det fremgår således at. det ved bleking av viskosemasse ifølge oppfinnelsen er mulig å fremstille en masse med lavt ekstrakt-innhold og forøvrig med analysedata som helt kan sammenlignes med konvensjonelt bleket masse. Blekeomkostningene kan reduseres med ca. 7 kroner/tonn masse ved bleking ifølge oppfinnelsen. It thus appears that. by bleaching viscose pulp according to the invention, it is possible to produce a pulp with a low extract content and otherwise with analysis data that is completely comparable to conventionally bleached pulp. Bleaching costs can be reduced by approx. NOK 7/tonne pulp when bleaching according to the invention.

Claims (2)

1. Fremgangsmåte til fremstilling av bleket cellulosemasse ved partis-il avlignifisering med oksygenholdig gass .under alkaliske betingelser og derpå følgende fortsatt avlignifisering med klorholdig blekemiddel, karakterisert ved en kombinasjon av følgende trekk: at klorblekingen utføres med en blanding av klor og klordioksyd inneholdende' 2-50% klordioksyd (beregnet som i oksydasjonshenseende ekvivalent mengde klor), og under følgende i og for seg kjente betingelser: temperatur 30-70°C, tid 0,5-5 timer, massekonsistens minst 2%, fortrinnsvis 3-15%, og ved at massen etter denne fortsatte avlignifisering underkastes ytterligere minst et behandlingstrinn, hvorved alkaliske betingelser råder, for utløsning av klorert lignin.1. Process for the production of bleached cellulose pulp by partial delignification with oxygen-containing gas under alkaline conditions and subsequent continued delignification with chlorine-containing bleach, characterized by a combination of the following features: that the chlorine bleaching is carried out with a mixture of chlorine and chlorine dioxide containing' 2 -50% chlorine dioxide (calculated as an equivalent amount of chlorine in terms of oxidation), and under the following conditions known in and of themselves: temperature 30-70°C, time 0.5-5 hours, mass consistency at least 2%, preferably 3-15%, and in that, after this continued delignification, the pulp is further subjected to at least one treatment step, whereby alkaline conditions prevail, for the release of chlorinated lignin. 2. Fremgangsmåte ifølge krav 1, karakterisert-ved at hypokloritt som i og for seg kjent tilsettes i det alkaliske behandlingstrinnet etter C/D-trinnet.2. Method according to claim 1, characterized in that hypochlorite, which is known per se, is added in the alkaline treatment step after the C/D step.
NO4803/69A 1968-12-05 1969-12-04 NO130776C (en)

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CA897361A (en) * 1969-12-19 1972-04-11 E. Mallett Samuel Oxygen bleaching process
GB1449828A (en) * 1973-04-26 1976-09-15 Canadian Ind Oxygen pulping process
US4338158A (en) * 1976-04-09 1982-07-06 Weyerhaeuser Company Pulping in the presence of a protector
US4199399A (en) * 1976-04-19 1980-04-22 Process Evaluation & Development Corp. Method for preparing bagasse dissolving pulps and producing rayon having a degree of polymerization of at least 800 therefrom
FI55878C (en) * 1976-04-28 1979-10-10 Ahlstroem Oy FOERFARANDE FOER BEHANDLING AV LIGNOCELLULOSAMATERIAL MED KLOR
CA1079457A (en) * 1976-09-13 1980-06-17 Robert C. Eckert Manganic ion bleaching process
US4410397A (en) * 1978-04-07 1983-10-18 International Paper Company Delignification and bleaching process and solution for lignocellulosic pulp with peroxide in the presence of metal additives
EP0211945A4 (en) * 1985-02-14 1987-07-06 Edward Francis Elton Method and apparatus for alkaline delignification of lignocellulosic fibrous materials.
US4806203A (en) * 1985-02-14 1989-02-21 Elton Edward F Method for alkaline delignification of lignocellulosic fibrous material at a consistency which is raised during reaction
US5173153A (en) * 1991-01-03 1992-12-22 Union Camp Patent Holding, Inc. Process for enhanced oxygen delignification using high consistency and a split alkali addition
US5409570A (en) * 1989-02-15 1995-04-25 Union Camp Patent Holding, Inc. Process for ozone bleaching of oxygen delignified pulp while conveying the pulp through a reaction zone
US5217574A (en) * 1989-02-15 1993-06-08 Union Camp Patent Holdings Inc. Process for oxygen delignifying high consistency pulp by removing and recycling pressate from alkaline pulp
US5085734A (en) * 1989-02-15 1992-02-04 Union Camp Patent Holding, Inc. Methods of high consistency oxygen delignification using a low consistency alkali pretreatment
US5525195A (en) * 1989-02-15 1996-06-11 Union Camp Patent Holding, Inc. Process for high consistency delignification using a low consistency alkali pretreatment
US5211811A (en) * 1989-02-15 1993-05-18 Union Camp Patent Holding, Inc. Process for high consistency oxygen delignification of alkaline treated pulp followed by ozone delignification
US5188708A (en) * 1989-02-15 1993-02-23 Union Camp Patent Holding, Inc. Process for high consistency oxygen delignification followed by ozone relignification
US5164044A (en) * 1990-05-17 1992-11-17 Union Camp Patent Holding, Inc. Environmentally improved process for bleaching lignocellulosic materials with ozone
US5164043A (en) * 1990-05-17 1992-11-17 Union Camp Patent Holding, Inc. Environmentally improved process for bleaching lignocellulosic materials with ozone
US5441603A (en) * 1990-05-17 1995-08-15 Union Camp Patent Holding, Inc. Method for chelation of pulp prior to ozone delignification
CA2069447C (en) * 1991-04-18 1996-08-27 Bruce F. Griggs Pulp alkali addition process for high consistency oxygen delignification
US5554259A (en) * 1993-10-01 1996-09-10 Union Camp Patent Holdings, Inc. Reduction of salt scale precipitation by control of process stream Ph and salt concentration
WO2002099186A1 (en) * 2001-06-06 2002-12-12 Kvaerner Pulping Ab Reduction of organically bound chlorine formed in chlorine dioxide bleaching

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US2147618A (en) * 1936-04-01 1939-02-14 West Virginia Pulp & Paper Com Method of bleaching pulp
NL134770C (en) * 1963-07-12
FR1404605A (en) * 1964-05-22 1965-07-02 Air Liquide Improvement in delignification of chemical cellulose pulps

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NO130776C (en) 1975-02-05
US3652388A (en) 1972-03-28
SE334286B (en) 1971-04-19
DE1959118B2 (en) 1973-08-02
FI45573B (en) 1972-04-04
AT292443B (en) 1971-08-25
DE1959118A1 (en) 1970-06-11
FI45573C (en) 1972-07-10
BR6914755D0 (en) 1973-01-18

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