WO1994024362A1 - Procede continu de cuisson d'une pate - Google Patents

Procede continu de cuisson d'une pate Download PDF

Info

Publication number
WO1994024362A1
WO1994024362A1 PCT/SE1994/000248 SE9400248W WO9424362A1 WO 1994024362 A1 WO1994024362 A1 WO 1994024362A1 SE 9400248 W SE9400248 W SE 9400248W WO 9424362 A1 WO9424362 A1 WO 9424362A1
Authority
WO
WIPO (PCT)
Prior art keywords
digester
temperature
cooking
pressure
fibre material
Prior art date
Application number
PCT/SE1994/000248
Other languages
English (en)
Inventor
Sven-Erik Olsson
Stig Andtbacka
Finn Jacobsen
Åke BACKLUND
Johanna Svanberg
Original Assignee
Kamyr Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from SE9301284A external-priority patent/SE501848C2/sv
Application filed by Kamyr Ab filed Critical Kamyr Ab
Publication of WO1994024362A1 publication Critical patent/WO1994024362A1/fr

Links

Classifications

    • 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
    • D21C7/00—Digesters
    • D21C7/14—Means for circulating the lye
    • 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
    • D21C3/22—Other features of pulping processes
    • D21C3/24—Continuous processes
    • 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
    • D21C9/02—Washing ; Displacing cooking or pulp-treating liquors contained in the pulp by fluids, e.g. wash water or other pulp-treating agents
    • D21C9/04—Washing ; Displacing cooking or pulp-treating liquors contained in the pulp by fluids, e.g. wash water or other pulp-treating agents in diffusers ; Washing of pulp of fluid consistency without substantially thickening

Definitions

  • the pulp industry is therefore seeking methods which permit bleaching of pulp without using these chemicals.
  • the lignox method (see SE-A 8902058) can be mentioned, in which, inter alia, bleaching is carried out with hydrogen peroxide.
  • Ozone is another bleaching chemical of interest which is also being used to an increasing extent. It is thus possible, using such bleaching chemicals, to achieve the brightnesses which are demanded for marketed pulp, i.e. 89 ISO and higher, without using chlorine-containing bleaching agents.
  • the invention relates to an arrangement, which is advantageous from the point of view of equipment, for effecting a cooking in accordance with the new method, in particular with regard to digesters built according to an older principle, and consisting of an upper cocurrent cooking zone and a lower countercurrent washing zone.
  • a first such problem is the difficulty of efficiently reaching and maintaining the temperature in the lower part of the digester, i.e. that part which is normally utilized for washing.
  • a related problem is that, in order to be able to maintain the high temperature in the digester in the preferred case, the pulp must be taken out of the digester at a temperature exceeding +100°C, implying that, if a blowing off to atmospheric pressure were to take place, a disintegration of an explosive nature would be obtained in direct connection with this, with consequent negative effect on the pulp quality.
  • a pressurized washing apparatus be connected directly after the digester and that the pulp be conducted to this washing apparatus without any real diminution in pressure taking place. Moderate lowering of the pressure does not take place until after the pressurized wash, when the temperature and alkali content of the pulp have been lowered to a level such that the lowering of pressure consequently has little or no negative effect on the quality of the pulp.
  • a washing apparatus of this type can advantageously comprise a pressure diffuser, in which case the advantage is also gained that the hot and pressurized draw-off from this pressure diffuser can be used as washing liquid in the high-heat zone. This provides significantly increased heat economy while at the same time resulting in reduced pumping energy and decreasing the need for heat exchangers of cumbersome size.
  • FIG 1 isothermal cooking and so-called modified conventional cooking (MCC) are compared in three diagrams.
  • Figure 2 shows a diagram which describes the degree of delignification and the viscosity (the viscosity is normally considered to indicate the strength properties of the pulp)
  • Figure 3 shows how, in a preferred manner using a pressure diffuser, an existing digester can be converted so that it can be operated in accordance with the novel process.
  • the first figure shows three diagrams which compare different results obtained in association with isothermal cooking and modified conventional cooking (MCC) .
  • MCC modified conventional cooking
  • Figure 2 demonstrates that the method according to the invention makes it possible to reach very low kappa numbers, while retaining good pulp strength (viscosity of about 1000) , after oxygen delignification.
  • so-called environmentally-friendly bleaching chemicals such as peroxide and ozone, can be employed in subsequent bleaching stages without the risk of the strength being too low to permit bleaching up to the brightness level, and consequently also the purity level, demanded by the market.
  • FIG 3 shows the lower part of a digester 1, which is intended to symbolize an existing digester shell.
  • the digester is of the type which has an upper cocurrent part and a lower countercurrent part.
  • full cooking temperature i.e. about 162°C for hardwood and about 168°C for softwood
  • the countercurrent part which is principally a washing zone
  • the temperature is normally about 135°C on a level with and above the lower screen.
  • the countercurrent zone of the digester will be referred to as a cooking zone even if it is to be considered, in accordance with conventional operation, as a washing zone.
  • Liquid is supplied to the lower part of the digester through an inflow arrangement 4 mounted in the vicinity of the bottom IA of the digester.
  • This liquid consists, in the first instance, of washing liquid from a washing apparatus in a later stage.
  • the liquid can contain fresh alkali (white liquor) , which is added here in this loop and/or in the draw-off from the lower screen cincture (IB) .
  • the cooked pulp is collected via a conduit from the bottom of the digester.
  • a central pipe 5A is fed from the lower screen arrangement IB of the digester via a first heat exchanger 6A.
  • the central pipe opens out on a level with the latter screen arrangement in the digester.
  • the cooking liquid thereafter flows in a countercurrent manner up towards the draw-off screens ID.
  • the draw-off from this middle screen arrangement ID of the digester is taken off via a conduit 2 for further treatment.
  • FIG 3 additionally shows that, in accordance with a preferred embodiment, a pressure diffuser 7 has been arranged alongside the digester 1.
  • the pulp which is fed out from the bottom of the digester is conducted via conduit 8, without any real fall in pressure (preferably less than 1 bar, for example about 0.5 bar) to the said pressure diffuser 7.
  • This implies that the pressure in the pressure diffuser will correspond to that in the digester, i.e. somewhere between 10 and 20 bar in the bottom region.
  • the liquid which is drawn off from the pressure diffuser is led back to the digester 1 via a conduit 9.
  • the washing liquid 3 (expediently obtained from subsequent stages) , which is fed into the pressure diffuser 7, should have a temperature which is well below +100%C in order to be able to obtain a pulp from the pressure diffuser 7, in conduit 11, which has a temperature below +100°C (expediently at a consistency of about 10%) in order thereafter to be able to cold blow the pulp, thereby ensuring that the pulp retains its high quality.
  • the pulp leaving the digester should have a temperature exceeding +100°C, expediently a temperature of between +105°C and +115°C. It is furthermore desirable that about a third of the heating requirement comes about in the lower zone of the digester (the so-called high-heat zone) .
  • the liquid 9, which is drawn off from the pressure diffuser will have a temperature of about +100°C or somewhat higher, depending on the exact temperature flow prevailing. If necessary, therefore, this liquid should be heated somewhat in a heat exchanger 10 in order to ensure that its temperature is at the optimum, preferably +100°C-+110°C, before it is supplied to the lower part of the digester.
  • the liquid which, in this connection, is drawn off through the lower screen assembly IB of the digester is conveyed, via a central pipe 5A, back to the digester 1.
  • this liquid In connection with this liquid being returned, it is heated in a heat exchanger 6A so that the digester is maintained at essentially the same temperature level in all three zones.
  • the temperature of the chip column does not differ by more than 2°C between that part which is located at the upper end of the lower screen assembly IB and that part which is located in the highest cooking zone. In an embodiment which is even more preferred, it does not differ by more than 1°C between these two levels.
  • washing liquid at 70° is supplied to the pressure diffuser.
  • a buffer 12 can be used between the pressure diffuser 7 and the digester 1 for the draw-off from the respective washing liquids to these two units. Accordingly, a buffer 12 of this type must be pressurized.
  • a further vessel for example a tower of the type which is used for storing pulp, in which vessel a further delignification takes place, can be arranged between the digester and the pressure diffuser.
  • a pressure-regulating device is expediently arranged prior to this second delignification vessel, with the aid of which device a suitable pressure drop is controlled, principally with a view to regulating the feeding of the pulp in an optimal manner.
  • Further alkali is preferably added directly after such a pressure-regulating device.
  • some form of influx and mixing device for example an MC mixer
  • the pressure drop through the pressure-regulating device should be at least about 3 bar.
  • the pressure drop from this second vessel to the pressurized washing apparatus should be as small as possible, i.e. preferably less than 1 bar.
  • an existing digester of the MCC type can also be arranged in accordance with the invention, where, therefore, the digester has a top cocurrent part, a middle, principally countercurrent, part, and a bottom countercurrent part, with a part of the cooking liquid being added to the said bottom countercurrent part, the so-called high-heat zone.
  • a digester of the so-called hydraulic type having a lower temperature in the top part (the impregnation zone) , can also advantageously be arranged in accordance with the invention for cooking in a so-called isothermal manner in accordance with the invention.
  • the method can be used in conjunction with all types of cooking liquid, even if the method is principally intended for producing sulphate pulp.
  • the invention is not limited to the exemplifying temperature levels given above; however, in this context, it applies that the average temperature level in the digester should preferably exceed +150°C but be less than +165°C, and preferably be between 150-155°C for hardwood and between 160-165°C for softwood, and, additionally, that the mean temperature in the cooking zone/zones should preferably be about +151°C ⁇ 1°C, when the wood is hardwood, and, respectively, that the mean temperature in the digester should be +159°C ⁇ 1°C, when the wood is softwood.
  • new digesters can also, naturally, be arranged with screen arrangements and procedural steps in accordance with the invention.

Landscapes

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

Abstract

La présente invention concerne la cuisson de matériau fibreux dans un cuiseur vertical (1) en continu, sous pression et température élevées. Le matériau fibreux et le liquide de cuisson sont introduits par le haut du cuiseur, la liqueur de cuisson usée est soutirée depuis au moins un agencement d'écran du cuiseur (1D) entre le haut et le bas du cuiseur et le matériau fibreux est évacué par le bas du cuiseur. Il est possible de maintenir la température dans la zone de cuisson immédiatement au-dessus de l'agencement d'écran du cuiseur (1B) sensiblement au même niveau que celui de la zone ou zones de cuisson restantes du cuiseur.
PCT/SE1994/000248 1993-04-20 1994-03-22 Procede continu de cuisson d'une pate WO1994024362A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9301284-7 1993-04-20
SE9301284A SE501848C2 (sv) 1992-11-18 1993-04-20 Metod att koka massa kontinuerligt vid konstant temperatur

Publications (1)

Publication Number Publication Date
WO1994024362A1 true WO1994024362A1 (fr) 1994-10-27

Family

ID=20389614

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1994/000248 WO1994024362A1 (fr) 1993-04-20 1994-03-22 Procede continu de cuisson d'une pate

Country Status (1)

Country Link
WO (1) WO1994024362A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6605180B2 (en) * 2000-11-03 2003-08-12 Vidar Snekkenes Process for continuous cooking of pulp
US6699357B2 (en) * 2000-11-03 2004-03-02 Kvaerner Pulping Ab Process for continuous cooking of pulp
WO2010110724A1 (fr) * 2009-03-26 2010-09-30 Metso Fiber Karlstad Ab Procédé et agencement de lavage après cuisson complète dans un lessiveur en continu pour la production de pulpe de cellulose

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4123318A (en) * 1976-06-29 1978-10-31 Kamyr, Inc. Three-vessel treatment system
EP0476230A2 (fr) * 1990-09-17 1992-03-25 Kamyr, Inc. Cuisson kraft complète avec lessive blanche ajoutée à la circulation de lavage

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4123318A (en) * 1976-06-29 1978-10-31 Kamyr, Inc. Three-vessel treatment system
EP0476230A2 (fr) * 1990-09-17 1992-03-25 Kamyr, Inc. Cuisson kraft complète avec lessive blanche ajoutée à la circulation de lavage

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6605180B2 (en) * 2000-11-03 2003-08-12 Vidar Snekkenes Process for continuous cooking of pulp
US6699357B2 (en) * 2000-11-03 2004-03-02 Kvaerner Pulping Ab Process for continuous cooking of pulp
WO2010110724A1 (fr) * 2009-03-26 2010-09-30 Metso Fiber Karlstad Ab Procédé et agencement de lavage après cuisson complète dans un lessiveur en continu pour la production de pulpe de cellulose
CN102365405A (zh) * 2009-03-26 2012-02-29 美卓造纸机械(瑞典)公司 在生产纤维素纸浆的连续蒸煮器中完成蒸煮后进行洗涤的方法和装置

Similar Documents

Publication Publication Date Title
EP0673453B1 (fr) Procede de cuisson en continu de pate cellulosique
NO147801B (no) Fremgangsmaate til kontinuerlig blekning og delignifisering av cellulosemasse med oksygen
EP1268924B1 (fr) Procede permettant d'eviter une degradation mecanique de pate
US5919337A (en) Method of continuously isothermally cooking of pulp
JPH10331085A (ja) 低温気相連続蒸解カンおよびその使用方法
CA2570997A1 (fr) Procede pour diminuer l'entartrage des systemes lessiveurs
US20040089431A1 (en) Method for alkaline batch cooking of fiber material
WO1995009945A1 (fr) Procede de traitement de pate a papier chimique dans lequel on n'utilise pas de produits chimiques contenant du chlore
WO1994024362A1 (fr) Procede continu de cuisson d'une pate
US6221207B1 (en) Oxygen delignification of pulp in two stages with low pressure steam heating between stages
US20050087315A1 (en) Low consistency oxygen delignification process
US6113742A (en) Digester having screening arrangement for isothermal cooking of fibrous material
SE525773C2 (sv) Metod och arrangemang för syrgasdelignifiering av cellulosamassa med pH-reglering i slutfasen
US3272691A (en) Apparatus for continuously chlorinating pulp including automatic control of the degree of chlorination
FI91896C (fi) Menetelmä happivalkaisun yhteydessä
US20010050152A1 (en) Oxygen delignification of pulp in two stages
SE524896C2 (sv) Blekning av cellulosamassa med klordioxid i två faser med uppvärmning mellan faserna
US20040089430A1 (en) Method for alkaline cooking of fiber material
Hart et al. Medium consistency oxygen delignification performed with a controlled cavitation reactor
Ryszard et al. StatOx [TM], The Low Energy Oxygen Delignification System
NO870562L (no) Fremgangsmaate for fremstilling av masse av plante- og/eller trefibre og egnet som raastoff for blant annet papir, papp eller fiberplater.

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): CN