EP0351330A1 - Process for manufacturing bleached chemithermomechanical pulps - Google Patents
Process for manufacturing bleached chemithermomechanical pulps Download PDFInfo
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- EP0351330A1 EP0351330A1 EP19890420245 EP89420245A EP0351330A1 EP 0351330 A1 EP0351330 A1 EP 0351330A1 EP 19890420245 EP19890420245 EP 19890420245 EP 89420245 A EP89420245 A EP 89420245A EP 0351330 A1 EP0351330 A1 EP 0351330A1
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- Prior art keywords
- bleaching
- treatment
- pulp
- bleached
- dough
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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
- D21C3/00—Pulping cellulose-containing materials
- D21C3/04—Pulping cellulose-containing materials with acids, acid salts or acid anhydrides
- D21C3/06—Pulping cellulose-containing materials with acids, acid salts or acid anhydrides sulfur dioxide; sulfurous acid; bisulfites sulfites
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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
- D21C9/16—Bleaching ; Apparatus therefor with per compounds
- D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides
Definitions
- the invention relates to the manufacture of bleached chemothermal-mechanical pulps.
- chemothermal mechanical pulps designated in all that follows by CTMP pastes, is meant the pastes which result from the application to a lignocellulosic material, generally wood in the form of chips, of a treatment using one or more chemical agents combined with heating and mechanical defibration operations.
- CTMP pastes are of certain industrial interest because they achieve an interesting compromise between mechanical and chemical pulps themselves.
- the treatment can take place before, during or after defibration.
- treatment is meant here and in all that follows, the operation during which the lignocellulosic material is present with a sulfite, in practice sodium sulfite Na2SO3, or a bisulfite, in practice sodium bisulfite NaHSO3, or more generally a mixture of sulfur dioxide SO2 and sodium hydroxide NaOH, at a temperature equal to or higher than 100 ° C., under saturated steam pressure, said sulfite, bisulfite or mixture being indifferently designated by sulfite in all following.
- the treatment includes, where appropriate, a conventional impregnation of the lignocellulosic material using a solution of the selected reagents.
- the temperature at which the treatment is carried out generally does not exceed 200 ° C. and is preferably between approximately 120 ° C. and 160 ° C.
- the treatment medium has an initial pH generally chosen preferably between 6 and 12.5.
- the consistency, concentration by weight of paste expressed in the dry state in the medium is, in the treatment, for example between 10% and 40%, most often between 15% and 30%.
- the duration of the treatment depends on the choice of other parameters but generally does not exceed 1 hour.
- the amount of sulfite is for example between about 0.1% and 10%, most often between 0.5% and 3%, the percentages being given by weight relative to the weight of the lignocellulosic material considered at the dry state, as will be the case, unless otherwise specified or evident, for the percentages of material in all that follows.
- Chemical agents can be used in the treatment at the same time as the sulphite, such as for example complexing or sequestering agents such as diethylenetriaminepentaacetic acid (DTPA) or ethylenetriaminetetraacetic acid (EDTA) used in the form of sodium salts in an amount generally between approximately 0.1% and 1%.
- complexing or sequestering agents such as diethylenetriaminepentaacetic acid (DTPA) or ethylenetriaminetetraacetic acid (EDTA) used in the form of sodium salts in an amount generally between approximately 0.1% and 1%.
- CTMP pasta for example to the work of James P. CASEY, PULP & PAPER CHEMISTRY & CHEMICAL TECHNOLOGY, 3rd edition, vol.I, 1980, in particular pages 241-245, 213-219-229, to the work PULP & PAPER MANUFACTURE, VOL. 2, 1987 - MECHANICAL PULPING -, in particular chapters VIII D and XI, or even to the patent of the United States of America n ° 4718980 in particular figure 1 .
- bleached CTMP pulps here the CTMP pulps defined above, after they have been bleached using hydrogen peroxide H2O2 in an alkaline medium.
- the dough before being bleached with hydrogen peroxide, must be as far as possible free of chemical agent (s) such as sulphite ions, which it is known that they must cause consumption of H2O2 harmful to money laundering as indicated for example by H. KRUGER, HUSUSS, TAPPI PROCEEDINGS, 1982 INTERNATIONAL SULFITE PULPING CONFERENCE, 143-148.
- chemical agent such as sulphite ions
- the dough is carefully washed before being bleached, and this washing is conventionally carried out, for example by virtue of a repeated or not a sequence of dilution and reconcentration of the dough.
- Reconcentrating the whitening dough to a consistency at least equal to approximately 10%, starting from values which are very low, is an operation which the known technique requires not only to effectively eliminate the chemical agent or agents considered to be undesirable in bleaching. but also so that the hydrogen peroxide, in the very absence of these compounds, has a satisfactory effectiveness.
- the whitening of the CTMP pulp using hydrogen peroxide in an alkaline medium is usually carried out by using an amount of hydrogen peroxide of between approximately 0.5% and 10%, in the presence of approximately 1% to 6 % of a sodium silicate solution of density 1.33, at a pH between about 9 and 11, at a temperature between about 40 ° C and 100 ° C for about 0.5 to 2 hours, with a consistency included between about 10% and 30%.
- the bleaching bath can contain additives such as mainly one or more sequestering or complexing agents, such as for example DTPA, in an amount generally between approximately 0.1% and 1%.
- the dough After bleaching the dough is preferably treated with an acid such as SO2 to stabilize its whiteness, before being diluted with water to a very low consistency, for example of the order of 1%, to allow its transfer, storage and use in stationery.
- an acid such as SO2
- aqueous effluents coming mainly from washing operations, classification, separation of the final dilution water before or during the manufacture of the paper, depending on whether or not this manufacture is integrated into the manufacture of pulp, which contain practically no more sulphite but a still high pollutant load, are necessarily recycled and serve in particular as a pulp washing agent to remove the sulphite before bleaching with hydrogen peroxide.
- the present invention makes it possible to avoid the above drawbacks of the known industrial technique for manufacturing bleached CTMP pastes, without the white level of these pastes being felt, on the contrary.
- a process for manufacturing bleached CTMP pulps which comprises a treatment in which the lignocellulosic material is present with the sulphite at a temperature equal to or greater than 100 ° C. under saturated steam pressure, and a bleaching using hydrogen peroxide in an alkaline medium, characterized in that solid or liquid material is not removed from the pulp from the start of said treatment until the end of said bleaching.
- the reducing agent is most often chosen from thiourea dioxide or formamidinesulfinic acid, sodium hydrolsulfite or dithionite, or sodium borohydride.
- the amount of reducing agent used can vary depending on the nature thereof. It is generally understood, for the first two cited between about 0.1% and 5% and between about 0.01% and 0.5% for the third that is conveniently used in the form of an aqueous solution as for example the solution containing 12% by weight of sodium borohydride and marketed under the name of BOROL® by the company VENTRON Corporation.
- the invention finds all its interest in practice when it is aimed at obtaining CTMP pulps bleached to a high degree of white, for example 80 ° and more when it is measured in the usual way today at the length d wave of 457 nm with magnesium oxide as a reference standard using the spectrophotometer of the General Electric or Elrepho type.
- the amount of sulfite expressed as SO2 is then preferably between approximately 0.5% and 3% and the amount of hydrogen peroxide preferably between 3% and 10%, most often between 4% and 6%.
- Another object of the invention is a method according to the invention in which the bleached CTMP pulp is refined directly at the outlet of the bleaching. This refining is carried out at atmospheric pressure.
- the invention is therefore also a process for manufacturing bleached CTMP doughs, according to what has already been presented of said invention, characterized in that the bleached CTMP dough is refined directly after bleaching and therefore in that it is not removed from solid or liquid matter from the dough from the start of treatment until the end of refining after bleaching.
- the classification can thus be carried out on bleached and refined pulp. Dilute with clear industrial water and recycle the classification refusals to the bleached pulp refiner is then done without inconvenience.
- the method of the invention in which there is no need to reheat the dough, makes it possible to dispense with a supply of calories from a source external to the system provided that the conservation of the calories of the system is sufficiently well ensured .
- the process of the invention compared to known techniques, therefore saves mechanical as well as thermal energy.
- the invention applies to softwoods or softwoods, such as hardwoods or hardwoods.
- the wood shavings are conveyed from the feed hopper 101 to 102, a chamber for preheating the shavings with steam introduced by 103, from which they come out to pass with the solution of the reagents introduced by 104, into the refiner 105 then into the cyclone 106 from which water vapor is separated by 107.
- the dough passes through the latency zone 108 before being intimately mixed with the bleaching reagents supplied by 109, to be bleached in the bleaching tower 110.
- the bleached pulp leaving 110 is directly brought into the refiner at atmospheric pressure 111 from which it leaves to be classified in 112 after dilution by clear industrial water introduced by 113.
- Refusals of classification sufficiently reconcentrated, are refined separately (circuit not shown) or recycled by 114 at the entrance of the refiner 111.
- the dough is acidified ée in a known manner and sent to storage 115 and / or to the manufacture of paper by 116.
- the means indexed with 2 in hundred correspond in structure and in function to those of FIG. 1 indexed with 1 in hundred.
- the additional means 217 is a thickening equipment, for reconcentrating the dough between its classification in 212 and its bleaching in 210.
- the aqueous effluent collected from 217 by 218 contributes to forming the clear industrial water which is introduced par 213 to serve as a paste washing agent.
- - by DTPA is designated an aqueous solution at 40% by weight of sodium salt of diethylenetriaminepentaacetic acid and the amount of DTPA is that of this solution
- - by washing is designated the operation combining dilution and pressing of the dough
- - sodium borohydride is applied in the form of BOROL® and the quantity indicated is that of this presentation
- - by silicate is designated an aqueous solution of sodium silicate with a density equal to 1.33
- - the degree of white is measured at the wavelength of 457 nm with magnesium oxide as a reference standard using a spectrophotometer of ELREPHO type manufactured by KARL ZEISS.
- Softwood shavings are refined under saturated steam pressure at 120 ° C with 2.75% Na2SO2 to yield a paste with a white degree of 57 °.
- This paste is bleached, without removing any liquid or solid material, using H2O2: 5%, NaOH: 2%, silicate: 4%, DTPA: 0.5%, for 2 hours at 90 ° C at a consistency of 15%.
- the bleached pulp obtained has a white degree of 77.9 °.
- the dough is washed by dilution to a consistency of 1.25% using industrial white water taken from an industrial plant with reconcentration by pressing up to a consistency of 20% so that 95% of the sulphite is removed before adding the bleaching reagents in aqueous solution, its degree of white after bleaching is 77.4 °. It is therefore lower than that achieved by conforming to the invention.
- a mechanical softwood pulp pulp, the degree of white of which is equal to 53.7 ° is subjected to a pressure treatment of saturated steam at 120 ° C with 2.75% Na2SO3 and 0.5% of DTPA for 30 minutes at a consistency of 20%, before being bleached directly, without elimination of solid or liquid material, as in Example 1.
- the bleached pulp obtained has a degree of white equal to 78.7 °
- the dough is bleached after washing with industrial white water as in Example 1, its degree of white is 78.6 ° and is still lower, at most equal to that achieved by operating according to the invention.
- Example 2 and the comparison which it includes, is repeated with the difference that 1% of BOROL® is present with the sulfite.
- the degree of white of the bleached pulp is equal to 82.2 ° while it is only 80.9 ° in the comparison.
- the degree of white of the bleached pulp is only 1 ° higher than that achieved by proceeding according to the invention.
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Abstract
Description
L'invention concerne la fabrication de pâtes chimicothermomécaniques blanchies.The invention relates to the manufacture of bleached chemothermal-mechanical pulps.
Par pâtes chimicothermomécaniques, désignées dans tout ce qui suit par pâtes CTMP, on entend les pâtes qui résultent de l'application à une matière lignocellulosique, généralement le bois sous forme de copeaux, d'un traitement à l'aide d'un ou plusieurs agents chimiques combiné à des opérations de chauffage et de défibrage mécanique.By chemothermal mechanical pulps, designated in all that follows by CTMP pastes, is meant the pastes which result from the application to a lignocellulosic material, generally wood in the form of chips, of a treatment using one or more chemical agents combined with heating and mechanical defibration operations.
Les pâtes CTMP sont d'un intérêt industriel certain car elles réalisent un compromis intéressant entre les pâtes mécaniques et les pâtes chimiques proprement dites.CTMP pastes are of certain industrial interest because they achieve an interesting compromise between mechanical and chemical pulps themselves.
Par exemple, elles sont obtenues avec un rendement, poids de pâte à l'état sec par rapport au poids de matière de départ à l'état sec, généralement supérieur à 85 %, le plus souvent au moins égal à 90 %, qui les rend en cela très proches des pâtes d'origine purement mécanique.For example, they are obtained with a yield, weight of dough in the dry state relative to the weight of starting material in the dry state, generally greater than 85%, most often at least equal to 90%, which makes this very close to purely mechanical pasta.
Dans la combinaison chauffage, traitement, défibrage, évoquée plus haut, le traitement peut avoir lieu avant, pendant ou après le défibrage.In the combination of heating, treatment and defibration, mentioned above, the treatment can take place before, during or after defibration.
Par traitement on entend ici et dans tout ce qui suit, l'opération au cours de laquelle la matière lignocellulosique est présente avec un sulfite, en pratique le sulfite de sodium Na₂SO₃, ou un bisulfite, en pratique le bisulfite de sodium NaHSO₃, ou plus généralement un mélange de dioxyde de soufre SO₂ et d'hydroxyde de sodium NaOH, à une température égale ou supérieure à 100°C, sous pression de vapeur d'eau saturée, lesdits sulfite, bisulfite ou mélange étant indifféremment désignés par sulfite dans tout ce qui suit. Le traitement comprend le cas échéant une imprégnation classique de la matière lignocellulosique à l'aide d'une solution des réactifs choisis.By treatment is meant here and in all that follows, the operation during which the lignocellulosic material is present with a sulfite, in practice sodium sulfite Na₂SO₃, or a bisulfite, in practice sodium bisulfite NaHSO₃, or more generally a mixture of sulfur dioxide SO₂ and sodium hydroxide NaOH, at a temperature equal to or higher than 100 ° C., under saturated steam pressure, said sulfite, bisulfite or mixture being indifferently designated by sulfite in all following. The treatment includes, where appropriate, a conventional impregnation of the lignocellulosic material using a solution of the selected reagents.
La température à laquelle est réalisé le traitement n'excède généralement pas 200°C et est préférablement comprise entre environ 120°C et 160°C.The temperature at which the treatment is carried out generally does not exceed 200 ° C. and is preferably between approximately 120 ° C. and 160 ° C.
Le milieu de traitement a un pH initial généralement choisi de préférence entre 6 et 12,5.The treatment medium has an initial pH generally chosen preferably between 6 and 12.5.
La consistance, concentration pondérale en pâte exprimée à l'état sec dans le milieu, est, dans le traitement, comprise par exemple entre 10 % et 40 %, le plus souvent entre 15 % et 30 %.The consistency, concentration by weight of paste expressed in the dry state in the medium, is, in the treatment, for example between 10% and 40%, most often between 15% and 30%.
La durée du traitement dépend du choix des autres paramètres mais n'excède généralement pas 1 heure.The duration of the treatment depends on the choice of other parameters but generally does not exceed 1 hour.
Exprimée en SO₂, la quantité de sulfite est comprise par exemple entre environ 0,1 % et 10 %, le plus souvent entre 0,5 % et 3 %, les pourcentages étant donnés en poids par rapport au poids de la matière lignocellulosique considérée à l'état sec, comme ce sera le cas, sauf précision ou évidence, pour les pourcentages de matière dans tout ce qui suit.Expressed as SO₂, the amount of sulfite is for example between about 0.1% and 10%, most often between 0.5% and 3%, the percentages being given by weight relative to the weight of the lignocellulosic material considered at the dry state, as will be the case, unless otherwise specified or evident, for the percentages of material in all that follows.
Des agents chimiques peuvent être employés dans le traitement en même temps que le sulfite, comme par exemple des agents complexants ou séquestrants tels que les acides diéthylènetriaminepentaacétique (DTPA) ou éthylènetriaminetétraacétique (EDTA) employés sous forme de sels de sodium en quantité généralement comprise entre environ 0,1 % et 1 %.Chemical agents can be used in the treatment at the same time as the sulphite, such as for example complexing or sequestering agents such as diethylenetriaminepentaacetic acid (DTPA) or ethylenetriaminetetraacetic acid (EDTA) used in the form of sodium salts in an amount generally between approximately 0.1% and 1%.
La combinaison, comme dit plus haut, du traitement avec les opérations de chauffage et de raffinage se conclut généralement en pratique par deux opérations de raffinage successives pour rendre la pâte utilisable de façon sûre dans l'industrie papetière.The combination, as said above, of the treatment with the heating and refining operations generally ends in practice with two successive refining operations in order to make the pulp usable in a safe manner in the paper industry.
On peut se reporter pour ce qui concerne l'obtention de pâtes CTMP par exemple à l'ouvrage de James P. CASEY, PULP & PAPER CHEMISTRY & CHEMICAL TECHNOLOGY, 3ème edition, vol.I, 1980, en particulier pages 241-245, 213-219-229, à l'ouvrage PULP & PAPER MANUFACTURE, VOL.2, 1987 - MECHANICAL PULPING -, en particulier chapitres VIII D et XI, ou encore au brevet des Etats Unis d'Amérique n°4718980 en particulier figure 1.One can refer for what concerns obtaining CTMP pasta for example to the work of James P. CASEY, PULP & PAPER CHEMISTRY & CHEMICAL TECHNOLOGY, 3rd edition, vol.I, 1980, in particular pages 241-245, 213-219-229, to the work PULP & PAPER MANUFACTURE, VOL. 2, 1987 - MECHANICAL PULPING -, in particular chapters VIII D and XI, or even to the patent of the United States of America n ° 4718980 in particular figure 1 .
Par pâtes CTMP blanchies on entend ici les pâtes CTMP définies ci-dessus, après qu'elles aient été blanchies à l'aide de peroxyde d'hydrogène H₂O₂ en milieu alcalin.By bleached CTMP pulps is meant here the CTMP pulps defined above, after they have been bleached using hydrogen peroxide H₂O₂ in an alkaline medium.
Dans la technique connue de fabrication de pâtes CTMP blanchies la pâte, avant d'être blanchie à l'aide du peroxyde d'hydrogène, doit être le mieux possible débarassée de ou des agents chimiques tels que les ions sulfite, dont on sait qu'il doivent provoquer une consommation de H₂O₂ nuisible au blanchiment comme le signalent par exemple H. KRUGER, H.U.SUSS, TAPPI PROCEEDINGS, 1982 INTERNATIONAL SULFITE PULPING CONFERENCE, 143-148.In the known technique for manufacturing bleached CTMP doughs, the dough, before being bleached with hydrogen peroxide, must be as far as possible free of chemical agent (s) such as sulphite ions, which it is known that they must cause consumption of H₂O₂ harmful to money laundering as indicated for example by H. KRUGER, HUSUSS, TAPPI PROCEEDINGS, 1982 INTERNATIONAL SULFITE PULPING CONFERENCE, 143-148.
En pratique la pâte est soigneusement lavée avant d'être blanchie et ce lavage est classiquement effectué par exemple grâce à une séquence répétée ou non de dilution et de reconcentration de la pâte.In practice, the dough is carefully washed before being bleached, and this washing is conventionally carried out, for example by virtue of a repeated or not a sequence of dilution and reconcentration of the dough.
Lorsqu'une opération de classage de la pâte raffinée est effectuée, ce qui est pratiquement le cas général, la dilution doit amener la consistance à des valeurs comprises dans des limites aussi faibles que 0,5 % à 2 % environ. On pourra se reporter en ce qui concerne le lavage et le classage à l'ouvrage de James P. CASEY déjà cité, pages 228-231, 363-365,447-452 ou à l'ouvrage déjà cité aussi PULP & PAPER MANUFACTURE - en particulier chapitres XIII - XVIII.When a classification operation of the refined pulp is carried out, which is practically the general case, the dilution must bring the consistency to values comprised within limits as low as 0.5% to 2% approximately. For washing and classification, reference may be made to the work by James P. CASEY already cited, pages 228-231, 363-365,447-452 or to the work already cited also PULP & PAPER MANUFACTURE - in particular chapters XIII - XVIII.
Reconcentrer la pâte à blanchir à une consistance au moins égale à 10 % environ, à partir de valeurs qui sont très faibles est une opération que la technique connue exige non seulement pour éliminer de façon efficace le ou les agents chimiques tenus pour indésirables dans le blanchiment mais aussi pour que le peroxyde d'hydrogène, en l'absence même de ces composés, ait une efficacité satisfaisante.Reconcentrating the whitening dough to a consistency at least equal to approximately 10%, starting from values which are very low, is an operation which the known technique requires not only to effectively eliminate the chemical agent or agents considered to be undesirable in bleaching. but also so that the hydrogen peroxide, in the very absence of these compounds, has a satisfactory effectiveness.
Le blanchiment de la pâte CTMP à l'aide de peroxyde d'hydrogène en milieu alcalin est réalisé usuellement en engageant une quantité de peroxyde d'hydrogène comprise entre environ 0,5 % et 10 %, en présence d'environ 1 % à 6 % d'une solution de silicate de sodium de densité 1,33, à pH compris entre environ 9 et 11, à une température comprise entre environ 40°C et 100°C durant environ 0,5 à 2 heures, avec une consistance comprise entre environ 10 % et 30 %. Le bain de blanchiment peut contenir des additifs comme principalement un ou plusieurs agents séquestrants ou complexants, comme par exemple le DTPA, en quantité généralement comprise entre environ 0,1 % et 1 %.The whitening of the CTMP pulp using hydrogen peroxide in an alkaline medium is usually carried out by using an amount of hydrogen peroxide of between approximately 0.5% and 10%, in the presence of approximately 1% to 6 % of a sodium silicate solution of density 1.33, at a pH between about 9 and 11, at a temperature between about 40 ° C and 100 ° C for about 0.5 to 2 hours, with a consistency included between about 10% and 30%. The bleaching bath can contain additives such as mainly one or more sequestering or complexing agents, such as for example DTPA, in an amount generally between approximately 0.1% and 1%.
Après blanchiment la pâte est de préférence traitée par un acide comme par exemple SO₂ pour stabiliser sa blancheur, avant d'être diluée à l'eau à une consistance très faible, par exemple de l'ordre de 1 %, pour permettre son transfert, son stockage et son utilisation en papeterie.After bleaching the dough is preferably treated with an acid such as SO₂ to stabilize its whiteness, before being diluted with water to a very low consistency, for example of the order of 1%, to allow its transfer, storage and use in stationery.
La technique actuelle de fabrication de pâtes CTMP blanchie décrite ci-avant et considérée en liaison avec la fabrication du papier présente des inconvénients importants sur le plan de l'économie et/ou sur celui de la pollution :
. la production d'une quantité très importante d'effluents aqueux, environ 100 tonnes par tonne de papier,
. la reconcentration nécessaire de la pâte avant blanchiment, qui implique l'usage d'un appareillage coûteux, filtre pour pâte ou presse par exemple, au moyen duquel il reste malgré tout difficile d'atteindre une consistance élevée dont il est connu qu'elle favorise l'action du peroxyde d'hydrogène.The current technique for manufacturing bleached CTMP pulp described above and considered in connection with the manufacture of paper has significant drawbacks in terms of economy and / or pollution:
. the production of a very large quantity of aqueous effluents, around 100 tonnes per tonne of paper,
. the necessary reconcentration of the pulp before bleaching, which involves the use of an expensive apparatus, filter for pulp or press for example, by means of which it remains nevertheless difficult to achieve a high consistency which it is known that it favors the action of hydrogen peroxide.
Les effluents aqueux, provenant essentiellement des opérations de lavage, de classage, de séparation de l'eau de dilution finale avant ou pendant la fabrication du papier selon que cette fabrication est intégrée ou non à la fabrication de pâte, qui ne renferment pratiquement plus de sulfite mais une charge polluante encore élevée, sont nécessairement recyclés et servent en particulier d'agent de lavage de la pâte pour en éliminer le sulfite avant le blanchiment par le peroxyde d'hydrogène.The aqueous effluents, coming mainly from washing operations, classification, separation of the final dilution water before or during the manufacture of the paper, depending on whether or not this manufacture is integrated into the manufacture of pulp, which contain practically no more sulphite but a still high pollutant load, are necessarily recycled and serve in particular as a pulp washing agent to remove the sulphite before bleaching with hydrogen peroxide.
Ces effluents aqueux sont désignés dans tout ce qui suit par eau claire industrielle.These aqueous effluents are designated in all that follows by industrial clear water.
Malgré le lavage efficace de la pâte à l'aide de cette eau claire industrielle, le niveau de blanc de la pâte CTMP blanchie qui est fabriquée reste sensiblement inférieur à celui que permettrait d'atteindre l'usage d'eau d'origine naturelle déminéralisée et non recyclée, usage malheureusement non envisageable déjà du seul point de vue économique.Despite the effective washing of the pulp using this clear industrial water, the white level of the bleached CTMP pulp which is produced remains significantly lower than that which would be achieved by using water of demineralized natural origin. and not recycled, unfortunately unfortunately not possible to use only from an economic point of view.
La présente invention permet d'éviter les inconvénients ci-dessus de la technique industrielle connue pour fabriquer des pâtes CTMP blanchies, sans que le niveau de blanc de ces pâtes s'en ressente, au contraire.The present invention makes it possible to avoid the above drawbacks of the known industrial technique for manufacturing bleached CTMP pastes, without the white level of these pastes being felt, on the contrary.
Elle est basée sur la constatation inattendue qu'un niveau de blanc au moins égal à celui atteint en opérant selon la technique industrielle connue est obtenu lorsque la pâte n'est pas débarassée avant blanchiment du ou des agents chimiques tenus pour nuire au blanchiment à l'aide de peroxyde d'hydrogène.It is based on the unexpected observation that a white level at least equal to that reached by operating according to known industrial technique is obtained when the dough is not removed before bleaching of the agent (s) chemicals believed to interfere with bleaching using hydrogen peroxide.
Elle consiste d'abord en un procédé de fabrication de pâtes CTMP blanchies qui comprend un traitement dans lequel la matière lignocellulosique est présente avec le sulfite à une température égale ou supérieure à 100°C sous pression de vapeur d'eau saturée, et un blanchiment à l'aide de peroxyde d'hydrogène en milieu alcalin, caractérisé en ce qu'il n'est pas éliminé de matière solide ou liquide de la pâte depuis le début dudit traitement jusqu'à la fin dudit blanchiment.It consists first of all in a process for manufacturing bleached CTMP pulps which comprises a treatment in which the lignocellulosic material is present with the sulphite at a temperature equal to or greater than 100 ° C. under saturated steam pressure, and a bleaching using hydrogen peroxide in an alkaline medium, characterized in that solid or liquid material is not removed from the pulp from the start of said treatment until the end of said bleaching.
Tout ce qui a été énoncé plus avant s'applique à la définition de l'invention, à l'exception de ce qui, après raffinage, touche, en amont du blanchiment, aux opérations de lavage, de classage et de reconcentration de la pâte qui n'ont plus lieu. Lorsque le traitement est effectué pendant l'opération de raffinage, un temps de latence d'une durée comprise entre environ 5 et 30 minutes à la température de sortie du raffineur permet l'achèvement du traitement.All that has been stated above applies to the definition of the invention, with the exception of what, after refining, affects, prior to bleaching, washing operations, classification and reconcentration of the dough. which no longer take place. When the treatment is carried out during the refining operation, a lag time of between 5 and 30 minutes at the outlet temperature of the refiner allows the completion of the treatment.
Seule la vapeur d'eau, par exemple à la sortie d'une opération de défibrage, peut être séparée de la pâte entre le début du traitement et la fin du blanchiment, par exemple de façon connue dans un cyclone.Only water vapor, for example at the end of a defibering operation, can be separated from the dough between the start of the treatment and the end of bleaching, for example in a known manner in a cyclone.
Il a été trouvé que l'avantage procuré par le procédé de l'invention est encore observé et est même accru de façon surprenante, quand un agent chimique plus électronégatif que l'ion sulfite SO₃-- et désigné dans tout ce qui suit par réducteur agit en même temps que le sulfite dans le traitement. C'est même alors le mode préféré de réalisation du traitement dans le procédé de l'invention.It has been found that the advantage obtained by the process of the invention is still observed and is even surprisingly increased, when a chemical agent more electronegative than the sulphite ion SO₃ - and designated in all that follows by reducing agent acts at the same time as sulfite in the treatment. It is even then the preferred embodiment of the treatment in the method of the invention.
Le réducteur est choisi le plus souvent parmi le dioxyde de thiourée ou acide formamidinesulfinique, l'hydrolsulfite de sodium ou dithionite, ou le borohydrure de sodium.The reducing agent is most often chosen from thiourea dioxide or formamidinesulfinic acid, sodium hydrolsulfite or dithionite, or sodium borohydride.
La quantité de réducteur mis en oeuvre peut varier selon la nature de celle-ci. Elle est en général comprise, pour les deux premiers cités entre environ 0,1 % et 5 % et entre environ 0,01 % et 0,5 % pour le troisième que est commodément utilisé sous forme d'une solution aqueuse comme par exemple la solution renfermant 12 % en poids de borohydrure de sodium et commercialisée sous le nom de BOROL® par la société VENTRON Corporation.The amount of reducing agent used can vary depending on the nature thereof. It is generally understood, for the first two cited between about 0.1% and 5% and between about 0.01% and 0.5% for the third that is conveniently used in the form of an aqueous solution as for example the solution containing 12% by weight of sodium borohydride and marketed under the name of BOROL® by the company VENTRON Corporation.
L'invention trouve tout son intérêt dans la pratique lorsqu'est visée l'obtention de pâtes CTMP blanchies jusqu'à un haut degré de blanc, par exemple 80° et plus quand il est mesuré de façon aujourd'hui usuelle à la longueur d'onde de 457 nm avec l'oxyde de magnésium comme standard de référence à l'aide du spectrophotomètre de type General Electric ou Elrepho. La quantité de sulfite exprimée en SO₂ est alors comprise de préférence entre environ 0,5 % et 3 % et la quantité de peroxyde d'hydrogène comprise de préférence entre 3 % et 10 %, le plus souvent entre 4 % et 6 %.The invention finds all its interest in practice when it is aimed at obtaining CTMP pulps bleached to a high degree of white, for example 80 ° and more when it is measured in the usual way today at the length d wave of 457 nm with magnesium oxide as a reference standard using the spectrophotometer of the General Electric or Elrepho type. The amount of sulfite expressed as SO₂ is then preferably between approximately 0.5% and 3% and the amount of hydrogen peroxide preferably between 3% and 10%, most often between 4% and 6%.
Un autre objet de l'invention est un procédé selon l'invention dans lequel la pâte CTMP blanchie est raffinée directement à la sortie du blanchiment. Ce raffinage est réalisé à pression atmosphérique. L'avantage rapporté par le brevet des Etats Unis d'Amérique n°4718980 dans le cas uniquement des pâtes mécaniques et des pâtes thermomécaniques est ainsi conservé dans le cas des pâtes CTMP blanchies sans avoir alors à procéder à un épaississement de la pâte.Another object of the invention is a method according to the invention in which the bleached CTMP pulp is refined directly at the outlet of the bleaching. This refining is carried out at atmospheric pressure. The advantage reported by the patent of the United States of America n ° 4718980 in the case only of mechanical doughs and thermomechanical doughs is thus preserved in the case of bleached CTMP doughs without then having to carry out a thickening of the dough.
L'invention est donc aussi un procédé de fabrication de pâtes CTMP blanchies, selon ce qui a déjà été présenté de ladite invention, caractérisé en ce que la pâte CTMP blanchie est raffinée directement après blanchiment et donc en ce qu'il n'est pas éliminé de matière solide ou liquide de la pâte depuis le début du traitement jusqu'à la fin du raffinage aprés blanchiment.The invention is therefore also a process for manufacturing bleached CTMP doughs, according to what has already been presented of said invention, characterized in that the bleached CTMP dough is refined directly after bleaching and therefore in that it is not removed from solid or liquid matter from the dough from the start of treatment until the end of refining after bleaching.
Le classage peut êre ainsi réalisé sur de la pâte blanchie et raffinée. Diluer à l'aide d'eau claire industrielle et recycler les refus de classage au raffineur de pâte blanchie se fait alors sans inconvénient.The classification can thus be carried out on bleached and refined pulp. Dilute with clear industrial water and recycle the classification refusals to the bleached pulp refiner is then done without inconvenience.
Le procédé de l'invention, dans lequel il n'y a pas à réchauffer la pâte, permet de se dispenser d'un apport de calories provenant d'une source extérieure au système pourvu que la conservation des calories du système soit suffisamment bien assurée.The method of the invention, in which there is no need to reheat the dough, makes it possible to dispense with a supply of calories from a source external to the system provided that the conservation of the calories of the system is sufficiently well ensured .
Le procédé de l'invention, par rapport aux techniques connues, économise donc de l'énergie mécanique aussi bien que thermique.The process of the invention, compared to known techniques, therefore saves mechanical as well as thermal energy.
L'invention s'applique aux bois tendres ou bois de résineux, comme aux bois durs ou bois de feuillus.The invention applies to softwoods or softwoods, such as hardwoods or hardwoods.
Les différentes opérations s'enchaînant selon l'invention sont réalisées chacune dans des équipements conventionnels quant à leur structure et à leur fonction respectives.
- La figure 1 est un schéma d'une suite de telles opérations selon un mode qu'on peut tenir pour préféré.
- La figure 2 est un schéma qui illustre un exemple de la technique connue telle qu'elle est communément adoptée.
- FIG. 1 is a diagram of a series of such operations according to a mode which can be considered to be preferred.
- Figure 2 is a diagram illustrating an example of the known technique as it is commonly adopted.
En se référant à la figure 1 : les copeaux de bois, habituellement lavés, sont convoyés de la trémie d'alimentation 101 à 102, chambre de préchauffage des copeaux à la vapeur d'eau introduite par 103, d'où ils sortent pour passer avec la solution des réactifs introduite par 104, dans le raffineur 105 puis dans le cyclone 106 d'où de la vapeur d'eau est séparée par 107. A la sortie de 106 la pâte passe par la zone de latence 108 avant d'être intimement mélangée avec les réactifs de blanchiment amenés par 109, pour être blanchie dans la tour de blanchiment 110. La pâte blanchie sortant de 110 est directement amenée dans le raffineur à pression atmosphérique 111 d'où elle sort pour être classée en 112 après dilution par de l'eau claire industrielle introduite par 113. Les refus de classage, suffisamment reconcentrés, sont raffinés séparément (circuit non schématisé) ou recyclés par 114 à l'entrée du raffineur 111. Après 112 la pâte est acidifiée de manière connue et envoyée dans le stockage 115 et/ou à la fabrication du papier par 116.Referring to FIG. 1: the wood shavings, usually washed, are conveyed from the
En se référant à la figure 2, les moyens indicés avec 2 en centaine correspondent en structure et en fonction à ceux de la figure 1 indicés avec 1 en centaine. Le moyen supplémentaire 217 est un équipement d'épaississement, de reconcentration de la pâte entre son classage en 212 et son blanchiment dans 210. L'effluent aqueux recueilli de 217 par 218 contribue à former l'eau claire industrielle qui est introduite par 213 pour servir d'agent de lavage de la pâte.Referring to FIG. 2, the means indexed with 2 in hundred correspond in structure and in function to those of FIG. 1 indexed with 1 in hundred. The additional means 217 is a thickening equipment, for reconcentrating the dough between its classification in 212 and its bleaching in 210. The aqueous effluent collected from 217 by 218 contributes to forming the clear industrial water which is introduced par 213 to serve as a paste washing agent.
Les exemple suivants sont donnés à titre indicatif mais non limitatif pour illustrer l'invention et juger de son intérêt.The following examples are given as an indication but not limiting to illustrate the invention and to judge its interest.
Dans ces exemple :
- les quantités, comme cela a déjà été signalé, sont exprimées en % en poids par rapport à la matière lignocellulosique prise à l'état sec, sauf précision,
- par DTPA est désignée une solution aqueuse à 40 % en poids de sel de sodium de l'acide diéthylènetriaminepentaacétique et la quantité de DTPA est celle de cette solution,
- par lavage est désignée l'opération combinant dilution et pressage de la pâte,
- le borohydrure de sodium est appliqué sous forme de BOROL® et la quantité indiquée est celle de cette présentation,
- par silicate est désignée une solution aqueuse de silicate de sodium de densité égale à 1,33,
- le degré de blanc est mesuré à la longueur d'onde de 457 nm avec l'oxyde de magnésium comme standard de référence à l'aide d'un spectrophotomètre de type ELREPHO fabriqué par KARL ZEISS.In these example:
- the quantities, as already mentioned, are expressed in% by weight relative to the lignocellulosic material taken in the dry state, unless otherwise specified,
- by DTPA is designated an aqueous solution at 40% by weight of sodium salt of diethylenetriaminepentaacetic acid and the amount of DTPA is that of this solution,
- by washing is designated the operation combining dilution and pressing of the dough,
- sodium borohydride is applied in the form of BOROL® and the quantity indicated is that of this presentation,
- by silicate is designated an aqueous solution of sodium silicate with a density equal to 1.33,
- the degree of white is measured at the wavelength of 457 nm with magnesium oxide as a reference standard using a spectrophotometer of ELREPHO type manufactured by KARL ZEISS.
Des copeaux de bois de résineux sont raffinés sous pression de vapeur d'eau saturée, à 120°C avec 2,75 % de Na₂SO₃ pour conduire à une pâte dont le degré de blanc est égal à 57°.Softwood shavings are refined under saturated steam pressure at 120 ° C with 2.75% Na₂SO₂ to yield a paste with a white degree of 57 °.
Cette pâte est blanchie, sans qu'il en soit éliminé de matière liquide ou solide, à l'aide de H₂O₂ : 5 %, NaOH : 2 %, silicate : 4 %, DTPA : 0,5 %, pendant 2 heures à 90°C à une consistance de 15 %.This paste is bleached, without removing any liquid or solid material, using H₂O₂: 5%, NaOH: 2%, silicate: 4%, DTPA: 0.5%, for 2 hours at 90 ° C at a consistency of 15%.
La pâte blanchie obtenue a un degré de blanc de 77,9°.The bleached pulp obtained has a white degree of 77.9 °.
Si, avant d'être blanchie dans les conditions ci-dessus la pâte est lavée par dilution à une consistance de 1,25 % à l'aide d'une eau blanche industrielle prélevée dans une installation industrielle à reconcentration par pressage jusqu'à une consistance de 20 % de sorte que 95 % du sulfite soit éliminé avant ajout des réactifs de blanchiment en solution aqueuse, son degré de blanc après blanchiment est de 77,4°. Il est donc inférieur à celui atteint en se conformant à l'invention.If, before being bleached under the above conditions, the dough is washed by dilution to a consistency of 1.25% using industrial white water taken from an industrial plant with reconcentration by pressing up to a consistency of 20% so that 95% of the sulphite is removed before adding the bleaching reagents in aqueous solution, its degree of white after bleaching is 77.4 °. It is therefore lower than that achieved by conforming to the invention.
Lorsque le lavage ci-dessus est réalisé à l'aide d'eau pure déminéralisée à la place d'eau blanche industrielle, le degré de blanc de la pâte blanchie, admis pour être le plus élevé possible dans les conditions de blanchiment adoptées, est supérieur seulement de 1,5° à celui atteint en procédant selon l'invention.When the above washing is carried out using pure demineralized water in place of industrial white water, the degree of whiteness of the bleached pulp, admitted to be as high as possible under the bleaching conditions adopted, is only 1.5 ° higher than that achieved by proceeding according to the invention.
Une pâte mécanique de meule de bois de résineux, dont le degré de blanc est égal à 53,7° subit un traitement sous pression de vapeur d'eau saturée à 120°C avec 2,75 % de Na₂SO₃ et 0,5 % de DTPA pendant 30 minutes à une consistance de 20 %, avant d'être blanchie directement, sans élimination de matière solide ou liquide, comme dans l'exemple 1.A mechanical softwood pulp pulp, the degree of white of which is equal to 53.7 ° is subjected to a pressure treatment of saturated steam at 120 ° C with 2.75% Na₂SO₃ and 0.5% of DTPA for 30 minutes at a consistency of 20%, before being bleached directly, without elimination of solid or liquid material, as in Example 1.
La pâte blanchie obtenue a un degré de blanc égal à 78,7°The bleached pulp obtained has a degree of white equal to 78.7 °
Si la pâte est blanchie après lavage au moyen d'eau blanche industrielle comme dans l'exemple 1 son degré de blanc est de 78,6° et est encore inférieur, au plus égal à celui atteint en opérant selon l'invention.If the dough is bleached after washing with industrial white water as in Example 1, its degree of white is 78.6 ° and is still lower, at most equal to that achieved by operating according to the invention.
L'exemple 2 et la comparaison qu'il inclut, est répété à la différence près que 1 % de BOROL® est présent avec le sulfite.Example 2 and the comparison which it includes, is repeated with the difference that 1% of BOROL® is present with the sulfite.
En procédant selon l'invention, le degré de blanc de la pâte blanchie est égal à 82,2° tandis qu'il n'est que de 80,9° dans la comparaison.By proceeding according to the invention, the degree of white of the bleached pulp is equal to 82.2 ° while it is only 80.9 ° in the comparison.
Lorsque, dans cette dernière, de l'eau pure déminéralisée est employée à la place de l'eau blanche industrielle, le degré de blanc de la pâte blanchie n'est supérieur que de 1° à celui atteint en procédant selon l'invention.When, in the latter, demineralized pure water is used in place of industrial white water, the degree of white of the bleached pulp is only 1 ° higher than that achieved by proceeding according to the invention.
Claims (10)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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FR8809703A FR2634233B1 (en) | 1988-07-12 | 1988-07-12 | PROCESS FOR PRODUCING BLANCHED CHEMICOTHERMOMECHANICAL PASTES |
FR8809703 | 1988-07-12 |
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EP0351330A1 true EP0351330A1 (en) | 1990-01-17 |
EP0351330B1 EP0351330B1 (en) | 1998-09-30 |
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EP89420245A Expired - Lifetime EP0351330B1 (en) | 1988-07-12 | 1989-07-06 | Process for manufacturing bleached chemithermomechanical pulps |
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EP (1) | EP0351330B1 (en) |
JP (1) | JPH0268377A (en) |
AT (1) | ATE171741T1 (en) |
AU (1) | AU616541B2 (en) |
CA (1) | CA1335406C (en) |
DE (2) | DE351330T1 (en) |
ES (1) | ES2012324T3 (en) |
FI (1) | FI96522C (en) |
FR (1) | FR2634233B1 (en) |
NO (1) | NO176726C (en) |
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PT (1) | PT91128B (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0509905A1 (en) * | 1991-04-17 | 1992-10-21 | Elf Atochem S.A. | Process for producing high yield bleached pulp |
EP1258559A1 (en) * | 2001-05-09 | 2002-11-20 | Rohm And Haas Company | Method for brightening mechanical pulps |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2615874B1 (en) * | 1987-05-25 | 1992-02-21 | Atochem | PROCESS FOR THE PREPARATION OF CHEMICOTHERMOMECHANICAL PASTES |
JP4501329B2 (en) * | 2002-03-29 | 2010-07-14 | 日本製紙株式会社 | Coated paper for gravure printing |
WO2008129048A1 (en) * | 2007-04-24 | 2008-10-30 | Basf Se | Method for the production of bleached wood particles and wood materials ranging from light-toned to white |
US20100224333A1 (en) * | 2009-03-09 | 2010-09-09 | Prasad Duggirala | Method and chemical composition to improve efficiency of mechanical pulp |
US9932709B2 (en) | 2013-03-15 | 2018-04-03 | Ecolab Usa Inc. | Processes and compositions for brightness improvement in paper production |
EP2924166A1 (en) * | 2014-03-25 | 2015-09-30 | Basf Se | Method for the manufacture of bleached wood fibre |
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FR2615874B1 (en) * | 1987-05-25 | 1992-02-21 | Atochem | PROCESS FOR THE PREPARATION OF CHEMICOTHERMOMECHANICAL PASTES |
SE460124B (en) * | 1988-09-14 | 1989-09-11 | Sunds Defibrator | SET FOR PREPARATION OF CHEMICAL MECHANICAL MASS OF LEAVES |
-
1988
- 1988-07-12 FR FR8809703A patent/FR2634233B1/en not_active Expired - Fee Related
-
1989
- 1989-07-06 DE DE198989420245T patent/DE351330T1/en active Pending
- 1989-07-06 NO NO892805A patent/NO176726C/en unknown
- 1989-07-06 EP EP89420245A patent/EP0351330B1/en not_active Expired - Lifetime
- 1989-07-06 DE DE68928822T patent/DE68928822T2/en not_active Expired - Fee Related
- 1989-07-06 AT AT89420245T patent/ATE171741T1/en not_active IP Right Cessation
- 1989-07-06 ES ES89420245T patent/ES2012324T3/en not_active Expired - Lifetime
- 1989-07-11 PT PT91128A patent/PT91128B/en not_active IP Right Cessation
- 1989-07-11 AU AU37999/89A patent/AU616541B2/en not_active Ceased
- 1989-07-11 CA CA000605392A patent/CA1335406C/en not_active Expired - Fee Related
- 1989-07-11 NZ NZ229902A patent/NZ229902A/en unknown
- 1989-07-11 FI FI893372A patent/FI96522C/en not_active IP Right Cessation
- 1989-07-12 JP JP1180113A patent/JPH0268377A/en active Granted
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FR1389308A (en) * | 1964-02-17 | 1965-02-12 | Fmc Corp | High gloss cellulose pastes |
FR2389712A1 (en) * | 1977-05-02 | 1978-12-01 | Mo Och Domsjoe Ab | |
EP0172135A1 (en) * | 1984-07-17 | 1986-02-19 | Rudy Vit | Method, process and apparatus for converting wood, wood residue, vegetable fibre and biomass into pulp |
US4718980A (en) * | 1985-12-30 | 1988-01-12 | Weyerhaeuser Company | Interstage treatment of mechanical pulp |
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Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
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EP0509905A1 (en) * | 1991-04-17 | 1992-10-21 | Elf Atochem S.A. | Process for producing high yield bleached pulp |
FR2675518A1 (en) * | 1991-04-17 | 1992-10-23 | Atochem | PROCESS FOR THE PREPARATION OF HIGH - PERFORMANCE PAPER PULP AND WHITENING FROM WOOD CHIPS. |
EP1258559A1 (en) * | 2001-05-09 | 2002-11-20 | Rohm And Haas Company | Method for brightening mechanical pulps |
Also Published As
Publication number | Publication date |
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CA1335406C (en) | 1995-05-02 |
DE351330T1 (en) | 1990-06-13 |
NO892805D0 (en) | 1989-07-06 |
FI893372A0 (en) | 1989-07-11 |
FI96522C (en) | 1996-07-10 |
NO176726B (en) | 1995-02-06 |
AU616541B2 (en) | 1991-10-31 |
AU3799989A (en) | 1990-01-18 |
ATE171741T1 (en) | 1998-10-15 |
FR2634233B1 (en) | 1995-04-14 |
NZ229902A (en) | 1991-09-25 |
FR2634233A1 (en) | 1990-01-19 |
JPH0250236B2 (en) | 1990-11-01 |
NO176726C (en) | 1995-05-16 |
DE68928822T2 (en) | 1999-05-27 |
PT91128A (en) | 1990-02-08 |
EP0351330B1 (en) | 1998-09-30 |
FI893372A (en) | 1990-01-13 |
FI96522B (en) | 1996-03-29 |
DE68928822D1 (en) | 1998-11-05 |
JPH0268377A (en) | 1990-03-07 |
PT91128B (en) | 1994-12-30 |
ES2012324T3 (en) | 1998-11-16 |
ES2012324A4 (en) | 1990-03-16 |
NO892805L (en) | 1990-01-15 |
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