EP0091457B1 - Procede de traitement au polysulfure dans une reduction alcaline de pulpe d'un materiau de lignocellulose - Google Patents

Procede de traitement au polysulfure dans une reduction alcaline de pulpe d'un materiau de lignocellulose Download PDF

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Publication number
EP0091457B1
EP0091457B1 EP82903084A EP82903084A EP0091457B1 EP 0091457 B1 EP0091457 B1 EP 0091457B1 EP 82903084 A EP82903084 A EP 82903084A EP 82903084 A EP82903084 A EP 82903084A EP 0091457 B1 EP0091457 B1 EP 0091457B1
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EP
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Prior art keywords
liquor
digestion
polysulphide
chips
white
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EP82903084A
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German (de)
English (en)
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EP0091457A1 (fr
Inventor
Nils V Mannbro
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Individual
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Priority to AT82903084T priority Critical patent/ATE24556T1/de
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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
    • D21C11/00—Regeneration of pulp liquors or effluent waste waters
    • D21C11/0057—Oxidation of liquors, e.g. in order to reduce the losses of sulfur compounds, followed by evaporation or combustion if the liquor in question is a black liquor
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/02—Pulping cellulose-containing materials with inorganic bases or alkaline reacting compounds, e.g. sulfate processes
    • D21C3/022—Pulping cellulose-containing materials with inorganic bases or alkaline reacting compounds, e.g. sulfate processes in presence of S-containing compounds

Definitions

  • Berthier also dealt with the subject of recovering sulphur dioxide in flue gas from combustion of black liquor in furnaces for recovery of sulphide-containing soda smelt.
  • the sulphur dioxide is then converted with hydrogen sulphide orginating from the smelt for generating elementary sulphur.
  • Union Camp Corporation discloses in Swedish patent application No. 72 03993-6 (publication No. 381 691) a method invented by Barker. Chips are impregnated with white liquor, and then black liquor is added. The sulphide of the liquor mixture is oxidized to polysulphide by means of a gas containing gaseous oxygen. The delignification of the wood then takes place with the entire volume of liquor and chips. After the delignification black liquor is recovered from the pulp in a conventional washing step which means that the portion of black liquor that is not recycled to the digestion plant for the polysulphide oxidation is conveyed from the pulp washing to the evaporation and combustion stages.
  • Norwegian patent No. 142 408 describes a method of treatment of cellulose material comprising certain stages such as a pretreatment stage, a digestion (delignification) stage, and stages for processing black liquor to regenerate white liquor hydroxide.
  • the black liquor is withdrawn from digested raw material and a portion of this black liquor is passed outside the digester to the raw material in the pretreatment stage.
  • the black liquor charged to the digestion step is often of the same kind as that conveyed from the pulp wash to the evaporation plant.
  • the total recovered black liquor volume from the pulp wash is 4 a 5 m 3 per ton of wood, and thus only one fourth of the black liquor substance is as indicated above recycled to the digestion stage.
  • only about one fourth of the monosulphide present in the digestion stage would, at the most, be available for oxidation of black liquor to polysulphide according to known technique.
  • polysulphide is reverted to monosulphide during the digestion. Sulphide absorbed from the liquor by the wood as organic compounds is solubilized towards the end of the digestion stage and some sulphide is split off. Thio-sulphate generated by non-desired reactions during the preparation of polysulphide may revert partially to monosulphide in the digestion stage.
  • the present invention relates to a method of preparing polysulphide of practically the whole volume of the used digestion liquor or black liquor, respectively, from the preceding digestion, the white liquor then being completely or partially charged to the lignocellulose material or pulp being delignified.
  • Recovered black liquor is not diverted directly from the pulp to the stages of alkali regeneration, i.e. evaporation and combustion steps, but from stages for pretreatment of the wood chips to said alkali generation steps.
  • Polysulphide treatment of wood chips can be carried out batchwise or continuously when connected to batch digestion. In continuous digestion only continuous pre-treatment should be of interest.
  • polysulphide treatment liquor is circulated through the chips via an external pipe system and oxygen is injected immediately before the liquor enters the treatment vessel. Since according to the invention ultimate black liquor is recovered after the polysulphide reaction with chips, other liquors used in the digester liquor circulation system subsequently to the polysulphide stage are referred to as digestion liquor or spent digestion liquor or just spent liquor.
  • a digestion method preferred for the invention is the digestion method described in Swedish patent No. 73 15894-1 (publication No. 381 897).
  • the present invention is applicable in general for such an operation of a cooking liquor system for multiple digesters, irrespective of the presence of a possible subsequent bleaching.
  • Sulphide- carrying white liquor is thus dosed to digestion liquor containing black liquor components and which cooking liquor being circulated through a multiple of digesters with various contents of partially delignified wood or pulp, respectively.
  • a digester filled with fresh wood chips is charged with digestion liquor and then shut off from the common cooking liquor circulation system of the digesters.
  • a mixture temperature of wood chips and digestion liquor is arrived at, and a rapid consumption of the alkali of the black liquor takes place.
  • oxygen or oxygen containing gas is injected and conveyed through the content of the digester, preferably into circulating liquor, whereby the generation of polysulphide will be at maximum. This takes place when about half of the sum of monosulphide and reactable organic sulphide compounds has been converted. If the oxidization is continued the polysulphide is oxidized further to thiosulphate.
  • Black liquor is successively reused according to the invention and the carbohydrate components of the wood react directly with the generated polysulphide. Therefore it is not purposeful to perform analyses of separate liquor samples afterwards.
  • a measure of the efficiency of the polysulphide generation is obtained by relating the increase of the yield of cellulose in the pulp to the content of the liquor of the polysulphide stage of 1) total amount of sulphur in various sulphur compounds of black liquor solids present in digestion liquor and 2) sodium. These substances have to a large extent passed previous digestion stages while a minor portion thereof may have been immediately transferred from white liquor charged to digestion liquor.
  • the wood chips rapidly absorb or consume, respectively, the content of hydroxide of the digestion liquor.
  • the pH of the spent - digestion liquor is lowered and during the polysulphide oxidation pH is further decreased.
  • the yield gain is improved as compared to that normally obtained by polysulphide reaction alone. The comparison is based on pulps of the same degree of delignification from the same lot of wood chips.
  • the invention features an additive yield-increasing effect from hydrogen sulphide and polysulphide.
  • hydrogen sulphide gas may be expelled from black liquor that is depleted of hydroxide, and the gas is then recirculated to the liquor system of the digester.
  • Thio-sulphate reacts only to a small extent with the chips and will consequently be removed with the black liquor to be generated to monosulphide in white liquor.
  • the concentration of oxidizable sulphur compounds in the surrounding black liquor decreases in the course of reaction of the various sulphides with wood. Approximately between 1/5 and 1/2 of the reacted sulphide compounds accompany the wood to the subsequent digestion stage in which they are re-dissolved in digestion liquor. They will recirculate according to a liquor volume equilibrium in the digester system which, according to the invention, is determined by the reactions of digestion liquor and black liquor, respectively, with charged wood material. This equilibrium is governed by the fact that black liquor which is subjected to regeneration of its chemicals is first utilized for polysulphide reactions with the chips. The known methods, however, utilize only the fraction of black liquor required for subsequent digestion.
  • the method was modified in such a way that white and black liquor was first charged to the wood chips.
  • the mixed liquor was circulated through the batch of chips and simultaneously air was supplied into the digester from below for one hour. During this period the temperature dropped to about 80°C.
  • the capacity of the digestion plant was reduced to 85% of normal in spite of the fact that the maximum digestion temperature was raised from 170 to 176°C and the charge of white liquor was increased to 190 kg of EA per ton of wood.
  • the charge of black liquor was consequently reduced to about 1.1 m 3 whereby the liquor mixture contained of white liquor.
  • the available amount of sulphide was equivalent to per ton of wood.
  • the generation of polysulphide could not be determined by analysis of the liquor mixture, due to its instantaneous reaction with the chips.
  • the pulp was alkali-oxygen delignified.
  • the amount of oxy-pulp increased by 1% as calculated on the obtained pulp from the same quantity of wood as according to Example 1.
  • the batch digestion plant was equipped with a digestion liquor accumulator as described in Swedish patent No. 7315894-1 (publication No. 381 897). Used liquor in the form of digestion liquor from the liquor accumulator was introduced after filling the digesters with chips. Each digester was completely filled with liquor and finally the same pressure was reached as that in the digestion liquor accumulator.
  • Oxygen containing gas was introduced from a gas circulation system through nozzles in the bottom zone of the digester while the liquor was circulated through the digester content. Gas and some foam were removed at the top and recirculated. The consumed volume of oxygen was replaced by concentrated oxygen.
  • the circulating gas contained about 25% by volume of O2 which was favourable with regard to even generation of polysulphide during the period of 30 minutes devoted thereto.
  • the temperature was kept at about 120°C.
  • the digester content was exposed to two hydrostatic pressure changes, and after that a gas relief.
  • a surplus volume of black liquor was withdrawn from the digester to the chemical regeneration plant and the surplus derived from the volumes added to the liquor accumulator by supply of white liquor, wood moisture and washing liquid, etc.
  • Samples of wood chips drained of black liquor and samples of surrounding black liquor were analysed with regard to their content of sulphur compounds. The result showed that 20 kg more sulphur in various compounds per ton of wood was taken up by the chips than what corresponded to the concentration of surrounding black liquor.
  • the sulphur in the polysulphide is released from the wood and again forms monosulphide which together with monosulphide of the recirculated black liquor is again reacted with new wood to polysulphide.
  • thiosulphate is enriched which only to a small extent reacts with the wood but can to some extent revert to sulphide via reactions in which a number of other sulphur compounds participate.
  • Sulphur compounds which do not affect the pulp yield were gradually passed to the chemical generation plant with the removed black liquor which also contained a certain amount of polysulphide and regenerable sulphide.
  • Polysulphide treatment according to the invention produced pulp which was bleached more easily than conventional pulp to the target brightness of 92 SCAN. Therefore more delignification could be transferred from digestion to the oxy-stage. Thus it was found advantageous to adjust to the maximum digestion temperature down to 170°C that was used in conventional digestion and reduce the charge of EA to 160 kg per ton of wood.
  • Chlorine dioxide for pulp bleaching was produced electrolytically with supply of hydrochloric acid.
  • Sodium hydroxide liquor for bleaching was regenerated according to Swedish patent No. 6909674-1 (publication No. 360129).
  • the polysulphide reaction of the chips can be carried out with spent digestion liquor, i.e. in the digestion used liquor, and consisting of

Claims (7)

1. Procédé de traitement au polysulfure d'un matériau de lignocellulose dans la production de pulpe alcaline par digestion de la matière, de préférence des copeaux de bois, avec une liqueur de digestion préparée à partir d'une liqueur blanche contenant du sulfure, dans lequel
A) on produit le polysulfure par oxydation d'une liqueur contenant du monosulfure dans une étape de prétraitement en présence de matériau de lignocellulose nouvellement chargé par réaction avec de l'oxygène ou un mélange gazeux contenant de l'oxygène;
B) dans une étape ultérieure on charge le matériau que l'on a fait réagir avec du polysulfure pour accroître le rendement de cellulose délignifiée, avec de la liqueur blanche fraîche aux fins de délignification avec la liqueur de digestion;
C) on retire de ladite étape la liqueur contenant du monosulfure qui a été utilisée dans une étape ultérieure de délignification avec sa teneur en substance dissoute à partir du matériau, et on la fait réagir selon A).
D) on obtient la liqueur usée contenant du monosulfure selon C) à partir d'un groupe connu de procédés de digestion comprenant la digestion continue ainsi que discontinue du matériau pendant l'injection de liqueur blanche avec soit injection en succession de liqueur blanche pendant la digestion, soit charge initiale traditionnelle de liqueur blanche pour digestion et enlèvement à partir de la pulpe formée de la liqueur de digestion usée sous la forme d'une liqueur noire, caractérisé en ce que
a) on fait réagir le matériau avec un volume de liqueur usée dans l'étape de prétraitement avec fourniture d'oxygène et recyclage en continu de tout mélange gazeux, ledit volume étant maintenu pendant la réaction avec le matériau en excès par rapport au volume qui reste avec le matériau prétraité et on l'inclut dans une étape ultérieure de délignification;
b) on retire l'excès de liqueur provenant de la réaction du polysulfure a) pour le diriger vers une unité de régénération d'hydroxyde dans la liqueur blanche, ledit excès de liqueur comprenant de préférence une liqueur noire que l'on transporte vers une unité d'évaporation et de combustion;
c) on retire l'excès de liqueur selon b) du matériau nouvellement chargé, dont la demande en hydroxyde est partiellement satisfaite par le teneur en hydroxyde de l'excès de liqueur et compensant ainsi partiellement la consommation d'hydroxyde de la liqueur réactionnelle qui reste avec le matériau soumis à une étape ultérieure de délignification, où le polysulfure est retransformé en monosulfure;
d) on fait recirculer la plus grande partie du monosulfure formé dans l'étape de délignification sous forme de liqueur de digestion usée vers l'étape de prétraitement selon a).
2. Procédé selon la revendication 1, dans lequel la digestion de la pulpe s'effectue de façon discontinue, caractérisé en ce qu'on charge la liqueur blanche vers et/ou pendant la digestion des copeaux que l'on a fait réagir avec le polysulfure, la liqueur usée chargée dans l'étape a) contenant les produits réactionnels de la mise en pulpe de la liqueur blanche.
3. Procédé selon la revendication 1, dans lequel la digestion de la pulpe est conduite de façon continue, caractérisé en ce qu'on charge la plus grande partie ou la totalité de la liqueur blanche après avoir enlevé la liqueur noire des copeaux lorsque les copeaux traités, avec la liqueur noire-polysulfure qui y est incluse ou qui y adhère, on atteint la zone de digestion du digesteur à contre-courant avec la liqueur de digestion qui s'écoule librement et la liqueur noire respectivement.
4. Procédé selon l'une quelconque des revendications 1-3, caractérisé en ce qu'on charge une fraction de liqueur blanche ayant une faible teneur en sulfure vers l'étape de digestion, tandis qu'une fraction de liqueur blanche à haute teneur en sulfure ou respectivement de liqueur de sulfure, séparée pendant la production de la liqueur blanche à faible teneur en sulfure, et chargée dans la liqueur usée qui contient une liqueur noire formant des solides, et laquelle liqueur usée est recyclée pour la production de polysulfure.
5. Procédé selon la revendication 4, caractérisé en ce qu'on charge la liqueur blanche enrichie en sulfure après avoir enlevé la liqueur noire des copeaux soumis à une première oxydation au polysulfure, une seconde oxydation étant conduite après l'addition de liqueur enrichie en sulfure et le mélange liquoreux oxydé étant ensuite transporté vers l'étape de digestion avec les copeaux.
6. Procédé selon la revendication 1, caractérisé en ce que la base de la liqueur usée pour l'étape a) est autant que possible consommée par les composants acides des copeaux, et en ce que la liqueur vidée de base ainsi formée est enlevée et transportée vers une unité de régéneration de base.
7. Procédé selon la revendication 1, caractérisé en ce qu'on prépare le polysulfure dans la liqueur blanche avant de la charger dans les copeaux, de préférence soit en ajoutant du soufre élémentaire, soit par oxydation de la liqueur blanche au moyen d'oxygène ou d'un mélange gazeux contenant de l'oxygène.
EP82903084A 1981-10-21 1982-10-13 Procede de traitement au polysulfure dans une reduction alcaline de pulpe d'un materiau de lignocellulose Expired EP0091457B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT82903084T ATE24556T1 (de) 1981-10-21 1982-10-13 Verfahren zur polysulfidbehandlung im alkalischen pulpverfahren von lignocellulosematerial.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8106203 1981-10-21
SE8106203A SE8106203L (sv) 1981-10-21 1981-10-21 Sett for polysulfidbehandling av lignocellulosamaterial vid alkalisk massaframstellning

Publications (2)

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EP0091457A1 EP0091457A1 (fr) 1983-10-19
EP0091457B1 true EP0091457B1 (fr) 1986-12-30

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EP82903084A Expired EP0091457B1 (fr) 1981-10-21 1982-10-13 Procede de traitement au polysulfure dans une reduction alcaline de pulpe d'un materiau de lignocellulose

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EP (1) EP0091457B1 (fr)
AT (1) ATE24556T1 (fr)
DE (1) DE3274887D1 (fr)
SE (1) SE8106203L (fr)
WO (1) WO1983001469A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FI122841B (fi) * 2004-10-04 2012-07-31 Metso Paper Inc Menetelmä ja laitteisto selluloosamassan valmistamiseksi
US8940129B2 (en) * 2010-12-30 2015-01-27 Uop Llc Process for reducing one or more insoluble solids in a black liquor
SE538792C2 (en) 2015-02-06 2016-11-29 Stora Enso Oyj Apparatus and method for component assembly

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FI40677B (fr) * 1961-05-27 1968-12-31 Papirind Forskningsinst
NO123511C (fr) * 1966-05-14 1976-07-22 Domtar Ltd
US3567572A (en) * 1967-09-06 1971-03-02 Pulp Paper Res Inst Polysulfide liquor impregnation of lignocellulose materials in a multistage pulping process
US3723242A (en) * 1971-04-01 1973-03-27 Union Camp Corp Oxidation of sulfide pulping liquor to form polysulfide liquor in situ
NO142408C (no) * 1972-04-11 1980-08-20 Rosenlew Ab Oy W Fremgangsmaate ved alkalisk cellulosekoking.
CA1013903A (en) * 1973-06-04 1977-07-19 Union Camp Corporation Method of pulping with polysulfide

Also Published As

Publication number Publication date
SE8106203L (sv) 1983-04-22
EP0091457A1 (fr) 1983-10-19
DE3274887D1 (en) 1987-02-05
ATE24556T1 (de) 1987-01-15
WO1983001469A1 (fr) 1983-04-28

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