EP2606175B1 - Verfahren zur beseitigung von hexenuronsäuren - Google Patents

Verfahren zur beseitigung von hexenuronsäuren Download PDF

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Publication number
EP2606175B1
EP2606175B1 EP11770836.2A EP11770836A EP2606175B1 EP 2606175 B1 EP2606175 B1 EP 2606175B1 EP 11770836 A EP11770836 A EP 11770836A EP 2606175 B1 EP2606175 B1 EP 2606175B1
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Prior art keywords
pulp
acid
oxygen
perbenzoic acid
stage
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English (en)
French (fr)
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EP2606175A1 (de
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Pedro Fardim
Malin Ekroos
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Abo Akademi University
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Abo Akademi University
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    • 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
    • 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

Definitions

  • the present invention relates to a method for removing hexenuronic acids from pulp according to preambles of the enclosed claims.
  • Wood comprises several different components: cellulose; hemicelluloses, such as xylan; lignin and extractives.
  • cellulose hemicelluloses, such as xylan
  • lignin and extractives a group of hemicelluloses, such as xylan
  • hemicelluloses such as xylan
  • extractives lignin and extractives.
  • the process of kraft pulping comprises alkaline cooking and bleaching, and it begins with wood handling where wood is debarked and made into chips.
  • the chips are screened so fine material and oversized chips are eliminated.
  • the chips are then fed to a digester where they first are treated with steam and then with cooking liquid, while the temperature is raised to the desired cooking temperature.
  • desired rate of delignification is achieved, cooking is interrupted and the content in the digester is moved to a blow tank and onwards to a screener.
  • After the pulp is screened it is washed several times and pumped to the following delignification stage, i.e. bleaching.
  • the cooking chemicals are recovered in the chemical recovery plant.
  • the main target for chemical pulping process is delignification in order to liberate the fibres without harming them.
  • Alkaline delignification occurring during cooking is alkaline hydrolyses of phenol ether bonds that make lignin soluble.
  • Phenols are weak acids that dissociate in alkali environment (pH> 10).
  • the lignin will be partly demethylated by nucleophilic attack of sulfide ions on methoxyl groups in lignin.
  • Bleaching of the obtained pulp comprises typically a number of discrete steps or stages.
  • oxygen delignification which may occur either as pre-bleaching or bleaching step, more lignin is dissolved and washed away. This is also the case in the different following bleaching stages; peroxide bleaching, ozone bleaching and chlorine dioxide bleaching.
  • Oxygen delignification occurring in pre-bleaching or bleaching step may comprise only one stage, but usually the process is carried out in a two-stage system with or without washing between the stages.
  • oxygen delignification system the cooked pulp is washed in the filtrate from the post-oxygen washer before it is charged with NaOH or oxidized white liquor.
  • the pulp is preheated in a low-pressured steam mixer before it is transferred by a medium consistency pump to the high-shear, medium-consistency mixer. Oxygen is added to the mixer and the oxygen delignification process begins.
  • the first stage after oxygen delignification may be a delignification stage using chlorine dioxide to dissolve lignin.
  • the typical following alkaline extraction stage (EOP) stage is an alkaline extraction stage enhanced with the oxidizing agents: oxygen and peroxide.
  • HexAs are consumed by chlorine in the chlorine dioxide stage by forming unchlorinated and chlorinated dicarboxylic acids. The HexAs thus consume bleaching chemicals and also increase brightness reversion of fully bleached pulps.
  • the HexAs also bind heavy metal ions and increase the problems with non-process elements (NPEs) which will lead to an increase in deposits in the bleaching stages. This is why it is in interest to remove these components from the pulp before the bleaching stages. In that case a lower chemical batch can be used in each delignification or bleaching stage and higher brightness stability can be achieved.
  • NPEs non-process elements
  • HexAs consume potassium permanganate that is one of the reactants used in the kappa number analysis. Permanganate reacts with carbon-carbon double bonds in the lignin structure but HexAs also contribute to the consumption because of its carbon-carbon double bond.
  • the hot acid stage (A-stage, at pH 3, temperatures of 50-90 °C and retention time of 1-3 hours), that is disclosed in US 6,776,876 and the hot chlorine dioxide bleaching (at temperatures 60-90 °C) disclosed in WO 2008/044988 are two methods to eliminate HexAs that are used today. Both these methods leave residual HexAs in the pulp, increase the retention time in the bleaching lines, increase the costs of effluent treatment, reduce the amount of charged groups on the fibre surface and reduce the fibre strength properties.
  • WO 92/13993 discloses bleaching of lignocellulosic material with activated oxygen, where chemical pulp contains reactants able to generate dioxirane within the pulp.
  • An object of the present invention is to minimise or even totally eliminate the problems and/or disadvantages existing in the prior art.
  • An object of the invention is to provide a method for eliminating hexenuronic acids (HexA) more efficiently from the lignocellulosic pulp after chemical cooking.
  • HexA hexenuronic acids
  • Another object is to lower the production and capital costs for the chemical, such as kraft, pulp mills while at the same time providing a pulp that is at least as useable as when manufactured in a traditional manner.
  • a yet further object of the invention is to provide a method enabling the development of new pulp products with enhanced optical and mechanical properties.
  • a typical method for removing hexenuronic acids from pulp comprises
  • Typical pulp according to the present invention is obtainable by the method of this invention.
  • the method for removing hexenuronic acids from a cellulosic pulp during a pulping process comprises an oxygen treatment stage, which is carried out in the presence at least one perbenzoic acid.
  • the oxygen treatment stage of a pulping process refers in this application to a stage which can also be called oxygen bleaching stage or oxygen delignification stage. This stage is thus different from the chlorine dioxide treatment stage and from the alkaline extraction stage. In the oxygen treatment stage oxygen is added to the pulp under alkaline conditions.
  • the oxygen treatment stage may also be a pre-bleaching stage, occurring after the cooking of the pulp and before actual bleaching stage, or the oxygen treatment stage may be part of the bleaching sequence.
  • Some advantages of the present invention are a time gain in the overall process, since there is no need for a separate stage for removing HexAs, therefore no need for a supplemental retention time.
  • the present method can also be implemented in existing installations without the need for any specialised equipment. Most importantly, the method allows the manufacture of pulps having improved characteristics compared to prior art methods.
  • the pulp produced by the present invention shows an increase of at least 25 %, typically 30 % in tensile stiffness index, an increase of at least 25 %, typically 30 % in tensile strength index, and/or an increase of at least 20 %, typically 25 %.
  • the water retention value of the pulp produced according to the present invention is decreased typically at least 6 %, more typically 10 %, compared to pulp of similar origin produced by using conventional prior art methods.
  • An improved brightness value may be achieved for the pulp according to the present invention after oxygen bleaching in comparison with similar pulp bleached by using conventional oxygen bleaching.
  • an increase of ISO brightness of at least 10 points may be achieved when the amount of perbenzoic acid used is about 150 kg/ton of pulp.
  • the pulp treated according to the present invention may comprise fibres originating either from hardwood or softwood, and it can be obtained in any suitable manner.
  • the present invention is also suitable for treating pulps obtained by pulping or fiberising of non-wood material, such as bamboo, sugar cane bagasse, hemp, wheat or rice straw.
  • the at least one perbenzoic acid is selected from the group consisting of perbenzoic acids, salts of perbenzoic acids, derivatives or precursors of perbenzoic acids and mixtures thereof.
  • perbenzoic acid as such at least in the solid form, is quite unstable. Therefore, its derivatives are preferred, and it is believed that the nature of derivative group does not have any or only minor influence on the activity of the compound and thus on the present invention.
  • Salts of perbenzoic acid, both inorganic and organic, may be used in the present invention. For example, sodium or potassium salt of perbenzoic acid may be used.
  • the at least one perbenzoic acid is perbenzoic acid, sodium salt of perbenzoic acid, metachloroperoxybenzoic acid, 4-tert-butylperbenzoic acid, 4-methylperbenzoic acid or 4-methoxyperbenzoic acid.
  • Some useful perbenzoic acids are 4-cyanoperbenzoic acid, 3-tert-butylperbenzoic acid, 2-tert-butylperbenzoic acid, 4-nitroperbenzoic acid, 4-fluoroperbenzoic acid, 3-chloroperbenzoic acid, 2,4-dichloroperbenzoic acid, 4-chloroperbenzoic acid, 2-methylperbenzoic acid, 3-methylperbenzoic acid, 3,4,5-trimethoxyperbenzoic acid, monoperphthalic acid and 1-pernaphthoic acid. Particularly preferred are 4-tert-butylperbenzoic acid, 3-chloroperbenzoic acid, 4-methylperbenzoic acid and 4-methoxyperbenzoic acid.
  • Some useful perbenzoic acid precursors are benzoic acid, phthalic anhydride, substituted and unsubstituted benzoyl oxybenzene sulfonates, N-benzoyl succinimide, tetrabenzoyl ethylene diamine, N-acylated lactam, tetraacetyl ethylene diamine, lactose octaacetate and 4-trimethyl ammonium methyl derivative of benzoyl oxybenzene sulfonate.
  • the amount of perbenzoic acid used and/or present in the oxygen treatment stage can be for example 1-500 kg/ton of cellulosic pulp, according to one embodiment 1-300 kg/ton of cellulosic pulp.
  • the amount depends on the type of pulp (for example on the origin of the cellulose), as different pulps contain different amounts of HexAs.
  • the amount is given as calculated to pure active perbenzoic acid.
  • derivatives, salts or precursors of perbenzoic acid are used, the added amounts should be calculated and converted as pure perbenzoic acid.
  • the at least one perbenzoic acid, salt of perbenzoic acid, derivative or precursor of perbenzoic acid or a mixture thereof is added to the oxygen treatment stage in a form selected from the group consisting of powder, solution, slurry or suspension.
  • the perbenzoic acid is added in the form of powder or slurry, which had been found to be the optimal form in order to achieve a rapid and effective mixing of the components in the oxygen treatment stage.
  • the at least one perbenzoic acid, salt of perbenzoic acid, derivative or precursor of perbenzoic acid or a mixture thereof can be added before or during the oxygen treatment stage.
  • the oxygen treatment stage is carried out in a system comprising two or more discrete steps with or without washing between the steps, the at least one perbenzoic acid, salt of perbenzoic acid, derivative or precursor of perbenzoic acid or a mixture thereof may be added during the first or the following step, or to all of the steps of the oxygen treatment stage. The addition may thus be done in the first, second and/or the following treatment vessels, tanks or reactors of the oxygen treatment stage.
  • the oxygen treatment stage may be a pre-bleaching stage or it is a treatment stage incorporated into the bleaching sequence.
  • the at least one perbenzoic acid, salt of perbenzoic acid, derivative or precursor of perbenzoic acid or a mixture thereof may be added to the pulp during the alkaline extraction stage when oxygen is added to the pulp.
  • the general conditions of the oxygen treatment stage can be as follows: the alkali dosage is 10-30 kg/ton of pulp, the temperature 80-120 °C, the retention time is 20-120 minutes, the dosage of magnesium sulphate 1-4 kg/ton of pulp and the oxygen pressure is 50-100 psi.
  • the present invention yet further relates to the use of a perbenzoic acid for removing hexenuronic acids from a cellulosic pulp. This use preferably occurs during an oxygen treatment stage of a pre-bleaching or bleaching process.
  • the pulp used for these examples was a eucalyptus pulp from Fibria and-Stora Enso pulp mill Veracel in Brazil. The pulp was collected from the last washing stage before oxygen delignification and properly washed at the pulp mill in Brazil before shipping it.
  • the perbenzoic acid derivative used was metachloroperoxybenzoic acid (mCPBA), in the form of powder. Also sodium hydroxide (NaOH) and magnesium sulfate (MgSO 4 ) were used as traditionally in the oxygen treatment stage.
  • mCPBA metachloroperoxybenzoic acid
  • NaOH sodium hydroxide
  • MgSO 4 magnesium sulfate
  • the initial pulp in the oxygen delignification stage was an unbleached kraft pulp.
  • Oxygen pressure, heat, alkali, magnesium sulfate (MgSO 4 ) arid different charges of m CPBA (presented in table 5 above) was applied in the oxygen delignification stage. After oxygen bleaching the pulp was washed with water.
  • the pulp was then mixed with the Quantum set to manual in order to adjust the temperature to the desired 100 °C.
  • the chemicals were added to the reactor. Some more preheated water was also added, in order to dilute the pulp consistency to about 10 %.
  • the reactor was closed carefully and the oxygen valve was opened.
  • the temperature was set once again in order to have it as close to 100 °C as possible. Also the pressure was adjusted to be precisely 6 bars during the delignification sequence.
  • the Quantum mixer was set to automatic and the settings were adjusted to 10 seconds of mixing every second minute for a reaction time of 60 minutes.
  • the pulp was placed in a container and distilled water was added. The mixture was then filtered in a Buchner-funnel. Water was added until the filtrate was clear. The pulp was then centrifuged in order to increase the dry content, placed in a plastic bag and stored in a refrigerator.
  • D 0 initial chlorine dioxide step
  • EOP oxygen and peroxide reinforced alkali extraction step
  • D chlorine dioxide step
  • Pulps selected for these bleaching sequence trials were the reference pulp (without any additional m CPBA), the pulp with a m CPBA charge of 75 kg/ton and the pulp with a m CPBA charge of 150 kg/ton.
  • the parameters used in the different bleaching steps are presented in Table 4 below. Table 4 The parameters used in the different bleaching steps.
  • One plastic bag at a time was prepared by weighing the right amount of pulp, adding the right amount of ClO 2 and water. The pH was also adjusted with 1 M H 2 SO 4 . The amounts used are presented in Table 5 below. The plastic bag was then placed in a water bath with the temperature adjusted to 70 °C, and left there for 15 minutes. Table 5 The amounts used in D 0 stage. Do Unit Ref.
  • the plastic bag was removed from the water bath and opened.
  • the pulp was immediately put in a Buchner-funnel equipped with a wire.
  • the chlorine residues were measured from the filtrate and used to calculate the chlorine consumption.
  • Warm water was added to clean the pulp and in a last step, cold water was added in order to cool down the pulp.
  • the pulp was transferred to a centrifuge bag and centrifuged in order to increase the dry content of the pulp.
  • the residue chlorine was determined after the bleaching operation. This was done by mixing 10 ml 1 M potassium iodide solution, 5 ml 2M sulfuric acid, 50 ml of the filtrate from the bleaching operation and a few drops of starch solution. The mixture was titrated with a 0.01 M sodium thiosulfate solution, and the consumption was noted as a (ml).
  • Kappa number, viscosity, brightness and HexA content were analyzed for each pulp.
  • the oxygen and peroxide reinforced alkali extraction stage was carried out in a quantum mixer.
  • concentration of the hydrogen peroxide, H 2 O 2 was determined. 10 ml of the H 2 O 2 -solution, 10 ml 1M potassium iodide solution, 5 ml 2M sulfuric acid and about 5 drops 15 % ammonium molybdate solution was mixed and titrated with 0.2M sodium thiosulfate solution. The sodium thiosulfate consumption was noted as e and the H 2 O 2 -concentration was calculated according to the equation below.
  • H 2 O 2 g / l 0.34 ⁇ e
  • EOP Unit Reference 75 kg m CPBA/ton 150 kg m CPBA/ton m pulp dry G 100.00 80.00 80.00 H 2 O 2 kg/t 8.00 8.00 8.00 H 2 O 2 ml 95.24 76.19 76.19 Consistency % 8.00 8.00 8.00 Total G 1250.00 1000.00 1000.00 Water ml 828.98 654.07 667.35
  • the quantum mixer was filled with water and preheated until the temperature of the water was the desired 75 °C.
  • the weighted pulp was preheated in a microwave and the added water in a Teflon-covered pot.
  • the preheated pulp, water and the right H 2 O 2 amount was mixed in a big glass beaker.
  • the pH was adjusted by adding a few drops of NaOH.
  • the quantum mixer was emptied and water residues were removed.
  • the mixture was transferred from the glass beaker to the quantum reactor and the lid was carefully closed.
  • the pulp inside the reactor was mixed with the quantum set on manually to the desired temperature before oxygen was applied.
  • the pressure was now adjusted to 2.8 bar.
  • the quantum was set to automatic and the reaction time was 70 minutes.
  • Kappa number, viscosity, HexA content and brightness were determined for each pulp.
  • the D-stage was carried out exactly the same way as the D 0 -stage, except that the reaction time was 200 minutes instead of 15 minutes.
  • Table 7 below the different amounts of pulp, ClO 2 and water for each pulp are presented. Table 7 The amounts used in D-stage.
  • D Unit Reference 75 kg m CPBA/ton 150 kg m CPBA/ton m pulp dry g 56.94 37.15 34.09 Active Cl kg/ton 15.78 15.78 15.78 ClO 2 ml 105.58 68.89 63.44 Consistency % 8.00 8.00 8.00 Total g 711.75 464.38 427.63 Water ml 412.10 267.61 250.50
  • the pulp was analyzed for kappa number, viscosity, HexA content and brightness.
  • the pulps were analysed as follows. Kappa number was analysed according to the standard SCAN -C 1:00, in force on July 2010, viscosity according to the standard SCAN-CM 15:99, in force on July 2010, water retention value according to the standard SCAN-C 62:00, in force on July 2010 and brightness according to the standard SCAN-CM 11:9, in force on July 2010. Other analyses performed on the pulps were HexA content analysis and total anionic group analysis.
  • the pulp was freeze dried in order to measure the HexA content.
  • a hydrolysis solution consisting of 22 mmol/l of mercuric chloride (0.6 %) (HgCl 2 ) and sodium acetate (CH 3 COONa ⁇ 3H 2 O) was prepared for the HexA content analysis.
  • the anionic groups in the pulp were determined by methylene blue sorption.
  • a 60 mM barbital buffer mother solution was prepared by dissolving pure 5-5 diethyl barbituric acid in deionized water. Sodium hydroxide (NaOH) was added to promote the dissolution of the 5-5 diethyl barbituric acid.
  • a 0.4 mM methylene blue solution was prepared by dissolving methylene blue powder in deionized water with the addition of 10 ml barbital buffer mother solution.
  • a calibration curve was made by diluting the 0.4 mM methylene blue solution at a ratio of 25:250 by using a 0.6 mM buffer barbital solution as a solvent.
  • oven dry pulp About 50 mg of oven dry pulp was measured and transferred to a 100 ml mixing flask. Different volumes of the methylene blue solution were added to the flasks and the reaction time was 15 minutes under continuous stirring at 500 rpm. The mixtures were then filtered in a sintered glass filter. Each sample was diluted 25 times, including the blank, with the 0.6 mM barbital buffer solution. The solutions were then analyzed in a UV-visual spectroscopy at 664 nm. The solution without pulp was used as a blank.
  • m CPBA Seven different charges of m CPBA were tested in the first experiments to eliminate HexAs from the pulp.
  • m CPBA was added as powder.
  • a reference pulp was also made by adding only NaOH and MgSO 4 to the oxygen delignification stage. The effect on kappa number, viscosity, water retention value, brightness, HexA-content and anionic groups will be discussed below.
  • Total anionic groups were determined for each pulp by methylene blue adsorption followed by UV-measurements.
  • the WRV is also affected by anionic groups; the more anionic groups the higher WRV.
  • a drop in WRV can be recognized.
  • the brightness of the pulps was measured as mentioned above and the results are shown in Figure 4 , as percentage. It can be seen that the brightness slightly increases with smaller amounts of m CPBA and that a more notable increase can be achieved with higher loads of m CPBA.
  • the HexA-content was measured as explained above and the results can be seen from Figure 5 as ⁇ mol of HexA per g of the material.
  • the effect of smaller amounts of m CPBA on the amount of HexAs is minimal, but the effect improves exponentially at higher loads.
  • the viscosity of the pulp treated with benzoic acid was about 1300 ml/g, whereas for a pulp treated with the same amount of perbenzoic acid the viscosity about 930 ml/g.
  • the water retention value of the pulp treated with benzoic acid was 1.52 compared to 1.39 for the pulp treated with m CPBA.
  • Figures 6-10 show the effect of the form of the m CPBA added to the process, the powder form being on the left and the solution form on the right.
  • the first group (on the left) shows the effect at a load of 25.0 kg/ton and the second group on the right the effect of a load of 75.0 kg/ton.
  • Figure 6 shows the effect on Kappa number
  • Figure 7 the effect on viscosity
  • Figure 8 the effect on water retention value
  • Figure 9 the effect on brightness
  • Figure 10 the effect on the amount of HexAs.
  • Figures 11-14 show the results of Kappa number ( Figure 11 ), viscosity ( Figure 12 ), brightness ( Figure 13 ) and the amount of HexAs ( Figure 14 ) for the samples that were subjected to the complete bleaching sequence.
  • the reference sample in each group the reference sample is on the left, the sample treated with 75.0 kg of m CPBA/ton of pulp in the middle and the sample treated with 150.0 kg of m CPBA/ton of pulp on the right.

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Claims (9)

  1. Verfahren zum Entfernen von Hexenuronsäuren aus Zellstoff, das Verfahren umfasst:
    - Gewinnung des Zellstoffs durch chemischen Aufschluss,
    - Behandlung des gewonnenen Zellstoffs unter Verwendung eines weiteren Entlignifizierungs-Prozesses, der eine Sauerstoff-Behandlungsstufe umfasst, welche eine Sauerstoffbleichstufe, Sauerstoff-Entlignifizierungsstufe oder Sauerstoff-Vorbleichstufe ist, wobei dem Zellstoff Sauerstoff unter alkalischen Bedingungen zugesetzt wird,
    - Ausführen der Sauerstoff-Behandlungsstufe in Gegenwart von mindestens einer Perbenzoesäure, wobei die Menge an verwendeter Perbenzoesäure 1-500 kg/t Zellstoff ist.
  2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass die mindestens eine Perbenzoesäure ausgewählt ist aus der Gruppe, bestehend aus Perbenzoesäuren; Salzen der Perbenzoesäuren; Vorstufen der Perbenzoesäuren, ausgewählt aus Benzoesäure, Phthalsäureanhydrid, substituierten oder nicht substituierten Benzoyloxybenzensulfonaten, N-Benzoylsuccinimid, Tetrabenzoylethylendiamin, N-acyliertem Lactam, Tetraacetylethylendiamin, Laktoseoctaacetat und 4-Trimethylammoniummethyl-Derivat des Benzoyloxybenzensulfonats; und Mischungen davon.
  3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass die mindestens eine Perbenzoesäure Perbenzoesäure, das Natriumsalz der Perbenzoesäure, Metachlorperoxybenzoesäure, 4-tert-Butylperbenzoesäure, 4-Methylperbenzoesäure oder 4-Methoxyperbenzoesäure ist.
  4. Verfahren nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass die Menge an verwendeter Perbenzoesäure 1-300 kg/t Zellstoff ist.
  5. Verfahren nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass die mindestens eine Perbenzoesäure, das Salz der Perbenzoesäure, das Derivat oder die Vorstufe der Perbenzoesäure oder eine Mischung davon dem Zellstoff in Form von ausgewählt aus der Gruppe, bestehend aus Pulver, Lösung, Aufschlämmung und Suspension zugesetzt wird.
  6. Verfahren nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass die mindestens eine Perbenzoesäure, das Salz der Perbenzoesäure, das Derivat oder die Vorstufe der Perbenzoesäure oder eine Mischung davon vor der Sauerstoff-Behandlungsstufe zugesetzt wird.
  7. Verfahren nach einem der vorstehenden Ansprüche 1-5, dadurch gekennzeichnet, dass die mindestens eine Perbenzoesäure, das Salz der Perbenzoesäure, das Derivat oder die Vorstufe der Perbenzoesäure oder eine Mischung davon während der Sauerstoff-Behandlungsstufe zugesetzt wird.
  8. Verfahren nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass während der Sauerstoff-Behandlungsstufe die Alkalidosierung 10-30 kg/t Zellstoff beträgt, die Temperatur 80-120°C ist, die Retentionszeit 20-120 Minuten, die Dosierung von Magnesiumsulfat 1-4 kg/t Zellstoff und der Sauerstoffdruck 50-100 psi beträgt.
  9. Verfahren nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass die Sauerstoff-Behandlungsstufe eine Vorbleichstufe oder eine Behandlungsstufe ist, die in die Bleichsequenz integriert ist.
EP11770836.2A 2010-08-18 2011-08-18 Verfahren zur beseitigung von hexenuronsäuren Not-in-force EP2606175B1 (de)

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FI20105862A FI20105862A0 (fi) 2010-08-18 2010-08-18 Menetelmä hekseeniuronihappojen poistamiseksi
PCT/FI2011/050721 WO2012022840A1 (en) 2010-08-18 2011-08-18 Method for removing hexenuronic acids

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EP2606175A1 EP2606175A1 (de) 2013-06-26
EP2606175B1 true EP2606175B1 (de) 2016-04-20

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BR (1) BR112013003758B1 (de)
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WO (1) WO2012022840A1 (de)

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US6776876B1 (en) 1994-10-13 2004-08-17 Andritz Oy Method of treating cellulosic pulp to remove hexenuronic acid
DE102005005016A1 (de) * 2005-02-03 2006-08-10 Basf Ag Polymere hydrophobe Aminonitrilquats zur Bleichaktivierung
RU2380466C1 (ru) * 2005-12-02 2010-01-27 Акцо Нобель Н.В. Способ получения целлюлозы с высоким содержанием альфа-целлюлозы
ES2403371T3 (es) 2006-10-11 2013-05-17 Akzo Nobel N.V. Blanqueo de pasta papelera

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FI20105862A0 (fi) 2010-08-18
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EP2606175A1 (de) 2013-06-26
WO2012022840A1 (en) 2012-02-23

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