EP0180529A1 - Process for preparing chemical wood pulps with a view to bleaching - Google Patents
Process for preparing chemical wood pulps with a view to bleaching Download PDFInfo
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- EP0180529A1 EP0180529A1 EP85420187A EP85420187A EP0180529A1 EP 0180529 A1 EP0180529 A1 EP 0180529A1 EP 85420187 A EP85420187 A EP 85420187A EP 85420187 A EP85420187 A EP 85420187A EP 0180529 A1 EP0180529 A1 EP 0180529A1
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- European Patent Office
- Prior art keywords
- chlorine
- pretreatment
- pulp
- oxygen
- bleaching
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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
- D21C9/12—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds
- D21C9/14—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites
- D21C9/144—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites with ClO2/Cl2 and other bleaching agents in a multistage process
Definitions
- the invention relates to a process for preparing chemical pulp for bleaching.
- delignification is an operation which consists in removing the maximum of the lignin contained in the fibers. To remove residual lignin and / or degraded by this treatment, the dough must be prepared for the actual bleaching.
- a second type of process consists in treating the dough by means of oxygen in an alkaline medium.
- this process makes it possible to recycle the effluents, on the other hand, in practice, one hardly exceeds a lignin extraction rate close to 50%, in order to avoid oxidation and therefore the degradation of the cellulose by l 'oxygen. (see TAPPI-June 1981 Vol.64 N ° 6- pages 91 et seq.).
- the invention overcomes these drawbacks. It relates to an improved process for the preparation for bleaching by means of a compound containing active chlorine then by means of a compound containing oxygen, which is more economical to use, and which makes it possible to achieve improved delignification rate and whiteness.
- chlorine pretreatment inhibits the degradation that normally occurs during peroxide bleaching.
- the method according to the invention makes it possible to achieve an excellent degree of pre-bleaching without, however, degrading the cellulose.
- the chlorine concentration must be between 0.8 and 1.5% by weight of the weight of the pulp.
- the temperature of the chlorine pretreatment were less than 50 ° C., this would pose problems from a practical point of view, in particular for using the recycling effluents which are at least at this temperature. Similarly, if this temperature exceeds 100 ° C, it would be necessary to use special devices and a supply of calories, which would make the pretreatment difficult to carry out.
- the temperature of this chlorine pretreatment must be between 70 and 90 ° C. If the temperature exceeds 90 ° C, there is a tendency to degrade the cellulose without appreciably improving the pre-bleaching. If this temperature is below 70 ° C, the treatment loses its effectiveness.
- the method according to the invention essentially resides in a particular selection of the operating conditions of a known method of treatment in several phases, one with chlorine, the other using an oxygenated compound. Thanks to this selection in the operating conditions, this pre-bleaching unexpectedly ensures the protection of the cellulose while by allowing the recycling of effluents after treatment with the oxygen compound.
- the chlorination stage being carried out hot, the recycling of these effluents containing very little chlorides in the washing of the unbleached pulp does not in fact pose any problem.
- the method according to the invention has overcome this prejudice because one could not expect that by using a similar but different chlorine concentration on a paste having a particular consistency and at an appropriate temperature, the degradation phenomena are more observed caused by both chlorination and oxidation by the oxygenated compound.
- the levels of reagents indicated will be expressed in percent (%) by weight relative to the weight of the paste counted in dry.
- a witness is produced by operating in the following manner.
- the Kappa index is reduced to 14.0 and the DP to 1400.
- Example 2 The same kraft pulp is used as in Example 1. The latter is treated, before the oxygen treatment, with 1% of chlorine gas, at 70 ° C., for ten minutes, the pulp concentration being 10%.
- Example 1 After washing, the oxygen treatment is carried out with a 3% sodium hydroxide solution, the other conditions remaining those of Example 1.
- the ⁇ Kappa index obtained is 9.7 and the DP, instead of falling at 128 as in Example 1, remains at 1350.
- the degree of polymerization of the cellulose remains at a good level, which allows the mechanical properties of the pulp to be preserved.
- Example 2 is repeated by simply modifying the temperature of the pretreatment with chlorine which is por 90 ° C.
- the Kappa index obtained is 8.5 and the DP of 1450.
- Example 2 is repeated, increasing the soda level to 4% during the oxygen treatment.
- the Kappa index obtained is 7.9 and the DP only drops to 1300.
- the Kappa indices obtained in Examples 3 and 4 are of the same level as those obtained by the conventional chlorosodation process (CE) in which approximately 6% chlorine is used.
- Example 2 is repeated while removing the oxygen.
- Example 5 the use of oxygen has been described as an agent for the delignification treatment. It is also possible to use other oxygenated compounds, such as hydrogen peroxide.
- the kraft paste from Example 1 (Kappa number 30, DP 1600) is delignified under the following conditions.
- the Kappa index is reduced to 17.1 and the DP to 1250.
- Example 6 is repeated, subjecting the dough to a pretreatment with chlorine under the following conditions:
- the method according to the invention requires a low consumption of reagent.
- CE chlorosodation
- the comparison with the conventional treatment of chlorosodation (CE) shows that practically identical performance, the chlorine level used in the process according to the invention represents only a quarter, even a sixth of that of this treatment (CE).
- the oxygen consumption in the process according to the invention (2 to 3% maximum) is significant, but the cost of this consumption is low compared to the savings made on chlorine, so that the economic balance of the process is largely positive.
- the delignification process according to the invention is applicable to any type of chemical pulp regardless of the starting plant (softwood or hardwood, annual plants, etc.).
Abstract
Description
L'invention concerne un procédé pour la préparation de pâtes papetières chimiques en vue de leur blanchiment.The invention relates to a process for preparing chemical pulp for bleaching.
Comme on le sait, la délignification est une opération qui consiste à enlever le maximum de la lignine contenue dans les fibres. Pour enlever la lignine résiduelle et/ou dégradée par ce traitement, il faut préparer la pâte en vue du blanchiment proprement dit.As we know, delignification is an operation which consists in removing the maximum of the lignin contained in the fibers. To remove residual lignin and / or degraded by this treatment, the dough must be prepared for the actual bleaching.
A ce jour, essentiellement, trois types de procédés ont été proposés.To date, essentially, three types of process have been proposed.
Dans un premier type de procédé, on a suggéré de traiter la pâte par du chlore. Ce procédé ne permet pas malheureusement de recycler les effluents dans les circuits de l'usine, du fait de leur teneur élevée en chlorures. En outre, l'augmentation de la température du traitement par le chlore, inévitable en cas de recyclage intensif, provoquerait une dégradation important de la cellulose (voir la publication "Pulp and Paper Magazine of Canada, Juin 1974 - Vol.75 N° 6 - pages 67 et suivantes).In a first type of process, it was suggested to treat the dough with chlorine. Unfortunately, this process does not make it possible to recycle the effluents in the factory circuits, due to their high chloride content. In addition, the increase in the temperature of the chlorine treatment, inevitable in the case of intensive recycling, would cause significant degradation of the cellulose (see the publication "Pulp and Paper Magazine of Canada, June 1974 - Vol.75 N ° 6 - pages 67 and following).
Un second type de procédé consiste à traiter la pâte au moyen d'oxygène en milieu alcalin. Toutefois, si ce procédé permet de recycler les effluents, en revanche, en pratique, on ne dépasse guère un taux d'extraction de la lignine voisin de 50 %, afin d'éviter l'oxydation et donc la dégradation de la cellulose par l'oxygène. (voir TAPPI-Juin 1981 Vol.64 N° 6- pages 91 et suivantes).A second type of process consists in treating the dough by means of oxygen in an alkaline medium. However, if this process makes it possible to recycle the effluents, on the other hand, in practice, one hardly exceeds a lignin extraction rate close to 50%, in order to avoid oxidation and therefore the degradation of the cellulose by l 'oxygen. (see TAPPI-June 1981 Vol.64 N ° 6- pages 91 et seq.).
Dans un troisième type de procédé, on a suggéré de traiter La pâte au moyen de peroxydes, notamment de peroxyde d'hydrogène. Toutefois, en pratique, ce procédé n'est efficace qu'à des températures supérieures à l00°Ç, notamment au voisinage de 120°C. Malheureusement comme on le sait, par ces conditions de température, on provoque une dégradation importante de la pâte.In a third type of process, it has been suggested to treat the dough with peroxides, in particular hydrogen peroxide. However, in practice, this process is only effective at temperatures above 100 ° C., in particular in the vicinity of 120 ° C. Unfortunately as is known, by these temperature conditions, a significant degradation of the dough is caused.
Dans le brevet français FR-A-2 018 562, on a proposé de traiter la pâte tout d'abord à l'aide d'une suspension aqueuse de chlore, puis ensuite avec de l'oxygène gazeux en milieu alcalin à une pression supérieure à la pression atmosphérique. Dans une forme de réalisation avantageuse, la pâte traitée en suspension aqueuse a une consistance comprise entre 3 et 6 %, à une température ambiante, avec 2 à 8 % de chlore actif en poids par rapport à la pâte, notamment sous forme d'hypochlorite, puis à traiter cette suspension aqueuse à une consistance de 3 à 12 % avec de l'oxygène, notamment sous forme peroxyde en milieu alcalin à une pression d'au moins deux bars. On obtient ainsi une pâte conduisant à de bonnes caractéristiques papetières. Malheureusement, du fait de la grande quantité d'hypochlorite introduite, les effluents ne peuvent pas être recyclés. De la sorte, ce procédé ne s'est guère développé.In French patent FR-A-2,018,562, it has been proposed to treat the paste firstly with an aqueous suspension of chlorine, then then with gaseous oxygen in an alkaline medium at a higher pressure. at atmospheric pressure. In an advantageous embodiment, the pulp treated in aqueous suspension has a consistency of between 3 and 6%, at room temperature, with 2 to 8% of active chlorine by weight relative to the pulp, in particular in the form of hypochlorite. , then treating this aqueous suspension at a consistency of 3 to 12% with oxygen, especially in peroxide form in an alkaline medium at a pressure of at least two bars. A paste is thus obtained leading to good papermaking characteristics. Unfortunately, due to the large quantity of hypochlorite introduced, the effluents cannot be recycled. In this way, this process has hardly developed.
Bref, toutes les solutions proposées jusqu'à ce jour pour préparer les pâtes papetières chimiques en vue de leur blanchiment présentent l'inconvénient soit d'entraîner une dégradation importante de la cellulose, soit de ne pas permettre le recyclage des effluents sauf à faire appel à des stades additionnels de traitement.In short, all of the solutions proposed to date for preparing chemical pulp for bleaching have the disadvantage either of causing significant degradation of the cellulose, or of not allowing the recycling of the effluents unless recourse is had to at additional stages of treatment.
L'invention pallie ces inconvénients. Elle vise un procédé perfectionné pour la préparation en vue du blanchiment au moyen d'un composé contenant du chlore actif puis au moyen d'un composé contenant de l'oxygène, qui soit plus économique à mettre en oeuvre, et qui permette d'atteindre un taux de délignification et une blancheur améliorés.The invention overcomes these drawbacks. It relates to an improved process for the preparation for bleaching by means of a compound containing active chlorine then by means of a compound containing oxygen, which is more economical to use, and which makes it possible to achieve improved delignification rate and whiteness.
Ce procédé de traitement des pâtes papetières chimiques en plusieurs stades, du type dans lequel ladite pâte est traitée tout d'abord par du chlore actif puis ensuite au moyen d'un composé oxygéné, se caractérise en ce que le traitement au chlore actif est effectué :
- - à une température comprise entre 50 et 100°C, de préférence entre 70 et 80°C ;
- - sur une pâte dont la consistance est comprise entre 5 et 15 %, de préférence entre 8 et 12 % ;
- - et enfin, à une concentration en chlore actif comprise entre 0,5 et 2 %, de préférence au voisinage de 1 à 1,5 % en poids par rapport au poids de la pâte.
- - at a temperature between 50 and 100 ° C, preferably between 70 and 80 ° C;
- - On a dough whose consistency is between 5 and 15%, preferably between 8 and 12%;
- - And finally, at an active chlorine concentration between 0.5 and 2%, preferably in the vicinity of 1 to 1.5% by weight relative to the weight of the paste.
Ainsi, le choix de ces conditions opératoires spécifiques permet, de manière tout à fait inattendue, de pouvoir recycler les effluents, ce que ne permettait pas les traitements proposés jusqu'alors tout en obtenant d'aussi bons résultats de blancheur et sans dégrader la cellulose.Thus, the choice of these specific operating conditions makes it possible, quite unexpectedly, to be able to recycle the effluents, which the treatments hitherto proposed did not allow while obtaining such good whiteness results and without degrading the cellulose. .
Avantageusement, en pratique :
- - le prétraitement au chlore actif est effectué par du chlore gazeux pendant une durée comprise entre cinq et trente minutes, de préférence entre dix et vingt minutes ;
- - le traitement ultérieur à l'oxygène est effectué par du peroxyde d'hydrogène à une température supérieure à 100°C, avantageusement voisine de 120°C.
- the pretreatment with active chlorine is carried out with chlorine gas for a period of between five and thirty minutes, preferably between ten and twenty minutes;
- the subsequent treatment with oxygen is carried out with hydrogen peroxide at a temperature above 100 ° C., advantageously close to 120 ° C.
Ainsi, le prétraitement au chlore inhibe la dégradation qui se produit normalement lors du blanchiment au peroxyde. Ainsi, de manière tout à fait inattendue, le procédé selon l'invention permet d'atteindre un excellent degré de préblanchiment sans toutefois dégrader la cellulose.Thus, chlorine pretreatment inhibits the degradation that normally occurs during peroxide bleaching. Thus, quite unexpectedly, the method according to the invention makes it possible to achieve an excellent degree of pre-bleaching without, however, degrading the cellulose.
On a observé que si la concentration en chlore était inférieure à 0,5 % en poids du poids de la pâte, l'effet inhibiteur devenait insuffisant. De même, si cette concentration excédait 1,5 %, cela entraînerait une consommation inutile de chlore et surtout une plus grande difficulté du recyclage des effluents. Comme déjà dit, en pratique, la concentration en chlore doit être comprise entre 0,8 et 1,5 % en poids du poids de la pâte.It was observed that if the chlorine concentration was less than 0.5% by weight of the weight of the pulp, the inhibitory effect became insufficient. Likewise, if this concentration exceeded 1.5%, this would lead to an unnecessary consumption of chlorine and above all a greater difficulty in recycling effluents. As already said, in practice, the chlorine concentration must be between 0.8 and 1.5% by weight of the weight of the pulp.
De même, si la température du prétraitement au chlore était inférieure à 50°C, cela poserait des problèmes sur le plan pratique, notamment pour faire appel aux effluents de recyclage qui se trouvent au moins à cette température. De même, si cette température excédait 100°C, il faudrait faire appel à des appareils spéciaux et à un apport de calories, ce qui rendrait le prétraitement difficile à réaliser.Likewise, if the temperature of the chlorine pretreatment were less than 50 ° C., this would pose problems from a practical point of view, in particular for using the recycling effluents which are at least at this temperature. Similarly, if this temperature exceeds 100 ° C, it would be necessary to use special devices and a supply of calories, which would make the pretreatment difficult to carry out.
Comme déjà dit, avantageusement en pratique, la température de ce prétraitement au chlore doit être comprise entre 70 et 90°C. Si la température dépasse 90°C, on a tendance à dégrader la cellulose sans améliorer notablement le préblanchiment. Si cette température est inférieure à 70°C, le traitement perd de son efficacité.As already said, advantageously in practice, the temperature of this chlorine pretreatment must be between 70 and 90 ° C. If the temperature exceeds 90 ° C, there is a tendency to degrade the cellulose without appreciably improving the pre-bleaching. If this temperature is below 70 ° C, the treatment loses its effectiveness.
En ce qui concerne la consistance .de la pâte, on a observé que si cette consistance était inférieure à 5%, cela entraînerait la manipulation d'une grande quantité d'eau, ce qui rendrait peu économique le recyclage des effluents. De même, si la consistance était supérieure à 15 %, la manipulation de la pâte deviendrait plus difficile.With regard to the consistency of the pulp, it has been observed that if this consistency was less than 5%, this would involve the handling of a large amount of water, which would make the recycling of effluents uneconomical. Likewise, if the consistency was more than 15%, handling the dough would become more difficult.
Comme déjà dit, le procédé selon l'invention réside essentiellement dans une sélection particulière des conditions opératoires d'un procédé connu de traitement en plusieurs phases, l'une au chlore, l'autre à l'aide d'un composé oxygéné. Grâce à cette sélection dans les conditions opératoires, ce préblanchiment assure de manière inattendue la protection de la cellulose tout en permettant le recyclage des effluents après le traitement par le composé oxygène. Le stade de chloration étant réalisé à chaud, le recyclage de ces effluents contenant très peu de chlorures au lavage de la pâte écrue, ne pose en effet aucun problème.As already said, the method according to the invention essentially resides in a particular selection of the operating conditions of a known method of treatment in several phases, one with chlorine, the other using an oxygenated compound. Thanks to this selection in the operating conditions, this pre-bleaching unexpectedly ensures the protection of the cellulose while by allowing the recycling of effluents after treatment with the oxygen compound. The chlorination stage being carried out hot, the recycling of these effluents containing very little chlorides in the washing of the unbleached pulp does not in fact pose any problem.
Le brevet FR-A-2 018 562 déjà cité, qui enseignait le traitement en deux phases au moyen tout d'abord d'une suspension aqueuse de chlore et ensuite au moyen d'oxygène gazeux en milieu alcalin, faisait appel à des quantités de chlore importantes, d'au moins 2 %, ce qui rendait le recyclage des effluents impossible.De plus, l'augmentation de la température de la chloration qui en résulterait entraînerait une dégradation de'la cellulose. De la sorte,il fallait opérer à froid.The patent FR-A-2 018 562 already cited, which taught the treatment in two phases using first of all an aqueous suspension of chlorine and then by means of gaseous oxygen in an alkaline medium, used quantities of significant chlorine content of at least 2%, which made recycling of effluents impossible; moreover, the resulting increase in the temperature of chlorination would lead to degradation of the cellulose. In this way, it was necessary to operate cold.
Le procédé selon l'invention a vaincu ce préjugé car on ne pouvait s'attendre à ce qu'en utilisant une concentration en chlore voisine mais différente sur une pâte ayant une consistance particulière et à une température appropriée, on observe plus les phénomènes de dégradation provoqués à la fois par la chloration et l'oxydation par le composé oxygéné.The method according to the invention has overcome this prejudice because one could not expect that by using a similar but different chlorine concentration on a paste having a particular consistency and at an appropriate temperature, the degradation phenomena are more observed caused by both chlorination and oxidation by the oxygenated compound.
La manière dont l'invention peut être réalisée et les avantages qui en découlent ressortiront mieux des exemples de réalisation qui suivent, donnés à titre indicatif mais non limitatif.The manner in which the invention can be implemented and the advantages which result therefrom will emerge more clearly from the following exemplary embodiments, given by way of indication but not limiting.
Dans la suite, les taux de réactifs indiqués seront exprimés en pour cent (%) en poids par rapport au poids de la pâte comptée en sec.In the following, the levels of reagents indicated will be expressed in percent (%) by weight relative to the weight of the paste counted in dry.
On réalise un témoin en opérant de la manière suivante.A witness is produced by operating in the following manner.
On traite une pâte kraft commerciale, de bois résineux d'indice Kappa 30 (norme NF-T-12018) dont le degré de polymérisation de la cellulose (DP) est de 1600 (TAPPI-T-230 of 76) par de l'oxygène en milieu alcalin dans les conditions conventionnelles et industrielles suivantes :
- 0,5 % de sulfate de magnésium ont été introduits comme protecteur de la cellulose.
- 0.5% of magnesium sulfate was introduced as a protector for cellulose.
Après lavage dans des conditions usuelles, l'indice Kappa est ramené à 14,0 et le DP à 1400.After washing under usual conditions, the Kappa index is reduced to 14.0 and the DP to 1400.
Comme on le sait, on ne peut augmenter l'action délignifiante de l'oxygène sans dégrader parallèlement la cellulose. Ainsi, si au lieu d'utiliser 2 % de soude, on en utilisait 3, puis 4 %, l'indice Kappa tomberait respectivement à 12,1, puis à 10,2 et le DP chuterait parallèlement à 1280, puis 1130.As is known, one cannot increase the delignifying action of oxygen without at the same time degrading the cellulose. Thus, if instead of using 2% soda, we used 3, then 4%, the Kappa index would fall respectively to 12.1, then to 10.2 and the DP would drop in parallel to 1280, then 1130.
On utilise la même pâte kraft qu'à l'exemple 1. On traite celle-ci, préalablement au traitement à l'oxygène, par 1 % de chlore gazeux, à 70°C,pendant dix minutes, la concentration en pâte étant de 10 %.The same kraft pulp is used as in Example 1. The latter is treated, before the oxygen treatment, with 1% of chlorine gas, at 70 ° C., for ten minutes, the pulp concentration being 10%.
Après lavage, le traitement à l'oxygène est réalisé avec une solution de soude à 3 %, les autres conditions restant celles de l'exemple 1. L'indice\Kappa obtenu est de 9,7 et le DP, au lieu de chuter à 128 comme à l'exemple 1, se maintient à 1350.After washing, the oxygen treatment is carried out with a 3% sodium hydroxide solution, the other conditions remaining those of Example 1. The \ Kappa index obtained is 9.7 and the DP, instead of falling at 128 as in Example 1, remains at 1350.
Ainsi, bien que la délignification obtenue soit plus importante (indice Kappa inférieur), le degré de polymérisation de la cellulose reste à un bon niveau, ce qui permet de conserver les propriétés mécaniques de la pâte.Thus, although the delignification obtained is greater (lower Kappa index), the degree of polymerization of the cellulose remains at a good level, which allows the mechanical properties of the pulp to be preserved.
On répète l'exemple 2 en modifiant simplement la température du prétraitement par le chlore qui est portée à 90°C. L'indice Kappa obtenu est de 8,5 et le DP de 1450.Example 2 is repeated by simply modifying the temperature of the pretreatment with chlorine which is por 90 ° C. The Kappa index obtained is 8.5 and the DP of 1450.
Cet exemple illustre parfaitement l'effet favorable de l'augmentation de la température du prétraitement.This example perfectly illustrates the favorable effect of increasing the temperature of the pretreatment.
On répète l'exemple 2 en augmentant à 4 % le taux de soude lors du traitement à l'oxygène.Example 2 is repeated, increasing the soda level to 4% during the oxygen treatment.
L'indice Kappa obtenu est de 7,9 et le DP chute seulement à 1300.The Kappa index obtained is 7.9 and the DP only drops to 1300.
A titre indicatif, les indices Kappa obtenus dans les exemples 3 et 4 sont du même niveau que ceux obtenus par le procédé conventionnel de chlorosodation (CE) dans lequel on utilise environ 6 % de chlore.As an indication, the Kappa indices obtained in Examples 3 and 4 are of the same level as those obtained by the conventional chlorosodation process (CE) in which approximately 6% chlorine is used.
On répète l'exemple 2 en supprimant l'oxygène.Example 2 is repeated while removing the oxygen.
L'indice Kappa initialement de 30, au lieu d'être ramené à 9,7 comme dans l'exemple 2, est seulement de 24.The Kappa index initially of 30, instead of being reduced to 9.7 as in Example 2, is only 24.
Cela illustre parfaitement l'action délignifiante de l'oxygène dans le procédé selon l'invention.This perfectly illustrates the delignifying action of oxygen in the process according to the invention.
Dans l'exemple 5, on a décrit l'utilisation de l'oxygène comme agent du traitement de délignification. On peut également utiliser d'autres composés oxygénés, tels que le peroxyde d'hydrogène.In Example 5, the use of oxygen has been described as an agent for the delignification treatment. It is also possible to use other oxygenated compounds, such as hydrogen peroxide.
On délignifie la pâte kraft de l'exemple 1 (indice Kappa 30, DP 1600) dans les conditions suivantes.
Après lavage, l'indice Kappa est ramené à 17,1 et le DP à 1250.After washing, the Kappa index is reduced to 17.1 and the DP to 1250.
On répète l'exemple 6 en faisant subir à la -pâte un prétraitement par le chlore dans les conditions suivantes :
Après le traitement au peroxyde dans les mêmes conditions qu'à l'exemple 6, l'indice Kappa est ramené à 13 au lieu de 17,1 mais le DP ne chute qu'à 1470 au lieu de 1250.After the peroxide treatment under the same conditions as in Example 6, the Kappa index is reduced to 13 instead of 17.1 but the PD only drops to 1470 instead of 1250.
Ces deux exemples 6 et 7 illustrent également,parfaitement l'effet favorable du prétraitement au chlore sur l'efficacité de la délignification et sur sa sélectivité.These two examples 6 and 7 also illustrate perfectly the favorable effect of the chlorine pretreatment on the efficiency of delignification and on its selectivity.
Les résultats de ces exemples 1 à 7 sont rassemblés par commodité dans le tableau annexé.The results of these examples 1 to 7 are collated for convenience in the appended table.
Si l'on examine ce tableau, notamment les valeurs obtenues par les procédés connus, c'est-à-dire dans lesquels on effectue un traitement à l'oxygène (exemple 1) ou un traitement au chlore (exemple 5), on voit nettement le progrés réalisé par l'invention (exemples 2,3 et 4). En effet, il est bien connu que le traitement délignifiant à l'oxygène et le traitement par le chlore à chaud sont deux traitements qui dégradent la cellulose.Il n'était donc nullement évident qu'en combinant ces deux traitements connus séparément et dans des conditions particulières,la délignification par l'oxygène deviendrait aussi sélective, puisqu'elle ne toucherait que la lignine sans provoquer de dépolymérisation de la cellulose. En d'autres termes, il est surprenant que la combinaison de deux traitements connus pour dégrader la cellulose conduisent à une opération qui non seulement ne dégrade pas la cellulose, mais améliore la délignification.If we examine this table, in particular the values obtained by known methods, that is to say in which an oxygen treatment is carried out (example 1) or a chlorine treatment (example 5), we see clearly the progress made by the invention (examples 2, 3 and 4). Indeed, it is well known that the oxygen-delignifying treatment and the hot chlorine treatment are two treatments which degrade cellulose. It was therefore by no means obvious that by combining these two known treatments separately and in Under specific conditions, delignification by oxygen would also become selective, since it would only affect lignin without causing depolymerization of the cellulose. In other words, it is surprising that the combination of two known treatments for degrading cellulose leads to an operation which not only does not degrade the cellulose, but improves the deligni fication.
En outre, le procédé selon l'invention nécessite une faible consommation de réactif. En effet, la comparaison avec le traitement conventionnel de chlorosodation (CE) (voir publication "Pulp and Paper Magazine of Canada" Juin 1974, vol. 75 N° 6, pages 67 et suivantes, rappelée dans le préambule), montre qu'à performances pratiquement identiques, le taux de chlore utilisé dans le procédé selon l'invention ne représente que le quart, voire le sixième de celui de ce traitement (CE). Certes, la consommation d'oxygène dans le procédé selon l'invention (2 à 3 % maximum) est notable, mais le coût de cette consommation est faible par rapport à l'économie réalisée sur le chlore, de sorte que le bilan économique du procédé est largement positif.In addition, the method according to the invention requires a low consumption of reagent. Indeed, the comparison with the conventional treatment of chlorosodation (CE) (see publication "Pulp and Paper Magazine of Canada" June 1974, vol. 75 N ° 6, pages 67 and following, recalled in the preamble), shows that practically identical performance, the chlorine level used in the process according to the invention represents only a quarter, even a sixth of that of this treatment (CE). Admittedly, the oxygen consumption in the process according to the invention (2 to 3% maximum) is significant, but the cost of this consumption is low compared to the savings made on chlorine, so that the economic balance of the process is largely positive.
D'autres avantages du procédé selon l'invention proviennent de ce que l'on utilise de très faibles quantités de chlore. La-quantité de produits organiques chlorés formés lors du prétraitement par le chlore est donc très faible, ce qui réduit considérablement le problème de la pollution posé par ces produits dont le caractère mutagène est connu. Par ailleurs, le taux de chlorures dans l'effluent de chloration ou de délignification par l'oxygène est également très faible, ce qui permet d'envisager favorablement le recyclage de ces effluents dans les circuits de régénération. Il en résulte donc une réduction importante de la pollution aqueuse provoquée par les effluents de blanchiment, réduction supérieure à celle qu'autorise la délignification conventionnelle à l'oxygène.Other advantages of the process according to the invention come from the fact that very small amounts of chlorine are used. The quantity of chlorinated organic products formed during the pretreatment with chlorine is therefore very low, which considerably reduces the problem of pollution posed by these products, the mutagenic nature of which is known. Furthermore, the level of chlorides in the chlorination or oxygen delignification effluent is also very low, which makes it possible to envisage favorably the recycling of these effluents in the regeneration circuits. This therefore results in a significant reduction in the aqueous pollution caused by the bleaching effluents, a reduction greater than that authorized by conventional oxygen delignification.
Le procédé de délignification selon l'invention est applicable à tout type de pâte chimique papetière quel que soit le végétal de départ (bois résineux ou feuillus, plantes annuelles, etc.).
Claims (7)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT85420187T ATE35433T1 (en) | 1984-10-25 | 1985-10-22 | METHODS OF PREPARING CHEMICAL WOOD PULP FOR BLEACHING. |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8416518A FR2572431B1 (en) | 1984-10-25 | 1984-10-25 | PROCESS FOR THE PREPARATION OF CHEMICAL PAPER PULP FOR BLEACHING. |
| FR8416518 | 1984-10-25 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| EP0180529A1 true EP0180529A1 (en) | 1986-05-07 |
| EP0180529B1 EP0180529B1 (en) | 1988-06-29 |
| EP0180529B2 EP0180529B2 (en) | 1992-04-08 |
Family
ID=9309092
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP85420187A Expired - Lifetime EP0180529B2 (en) | 1984-10-25 | 1985-10-22 | Process for preparing chemical wood pulps with a view to bleaching |
Country Status (9)
| Country | Link |
|---|---|
| EP (1) | EP0180529B2 (en) |
| JP (1) | JPS61102495A (en) |
| AT (1) | ATE35433T1 (en) |
| AU (1) | AU576394B2 (en) |
| CA (1) | CA1273755A (en) |
| DE (2) | DE3563548D1 (en) |
| ES (1) | ES8606557A1 (en) |
| FI (1) | FI82726C (en) |
| FR (1) | FR2572431B1 (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2018562A1 (en) * | 1968-09-20 | 1970-05-29 | Canadian Ind | |
| FR2322235A1 (en) * | 1975-08-30 | 1977-03-25 | Degussa | WHITENING ATTACK OF CELLULOSE WITH SIGNIFICANT REDUCTION IN THE QUANTITY OF CHLORINE USED |
| US4402788A (en) * | 1982-04-26 | 1983-09-06 | Champion International Corporation | Process for bleaching wood pulp with hydrogen peroxide |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1544216A (en) * | 1921-08-11 | 1925-06-30 | Donald J Campbell | Molding apparatus |
| JPS51102103A (en) * | 1975-03-05 | 1976-09-09 | Nippon Parupu Kogyo Kk | Ryusanenhoparupuno hyohakuhoho |
-
1984
- 1984-10-25 FR FR8416518A patent/FR2572431B1/en not_active Expired
-
1985
- 1985-10-22 DE DE8585420187T patent/DE3563548D1/en not_active Expired
- 1985-10-22 AT AT85420187T patent/ATE35433T1/en not_active IP Right Cessation
- 1985-10-22 EP EP85420187A patent/EP0180529B2/en not_active Expired - Lifetime
- 1985-10-22 DE DE198585420187T patent/DE180529T1/en active Pending
- 1985-10-23 FI FI854148A patent/FI82726C/en not_active IP Right Cessation
- 1985-10-24 ES ES548166A patent/ES8606557A1/en not_active Expired
- 1985-10-24 CA CA000493708A patent/CA1273755A/en not_active Expired - Lifetime
- 1985-10-25 AU AU49108/85A patent/AU576394B2/en not_active Ceased
- 1985-10-25 JP JP60239261A patent/JPS61102495A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2018562A1 (en) * | 1968-09-20 | 1970-05-29 | Canadian Ind | |
| FR2322235A1 (en) * | 1975-08-30 | 1977-03-25 | Degussa | WHITENING ATTACK OF CELLULOSE WITH SIGNIFICANT REDUCTION IN THE QUANTITY OF CHLORINE USED |
| US4402788A (en) * | 1982-04-26 | 1983-09-06 | Champion International Corporation | Process for bleaching wood pulp with hydrogen peroxide |
Also Published As
| Publication number | Publication date |
|---|---|
| CA1273755A (en) | 1990-09-11 |
| ES548166A0 (en) | 1986-04-01 |
| ES8606557A1 (en) | 1986-04-01 |
| FI854148L (en) | 1986-04-26 |
| FI82726C (en) | 1991-04-10 |
| FR2572431A1 (en) | 1986-05-02 |
| AU576394B2 (en) | 1988-08-25 |
| AU4910885A (en) | 1986-05-29 |
| FI82726B (en) | 1990-12-31 |
| EP0180529B1 (en) | 1988-06-29 |
| DE3563548D1 (en) | 1988-08-04 |
| EP0180529B2 (en) | 1992-04-08 |
| DE180529T1 (en) | 1986-12-18 |
| FI854148A0 (en) | 1985-10-23 |
| JPS61102495A (en) | 1986-05-21 |
| ATE35433T1 (en) | 1988-07-15 |
| FR2572431B1 (en) | 1987-12-04 |
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