WO2016087717A1 - Évacuation de matière à partir d'un digesteur en discontinu - Google Patents

Évacuation de matière à partir d'un digesteur en discontinu Download PDF

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Publication number
WO2016087717A1
WO2016087717A1 PCT/FI2015/050845 FI2015050845W WO2016087717A1 WO 2016087717 A1 WO2016087717 A1 WO 2016087717A1 FI 2015050845 W FI2015050845 W FI 2015050845W WO 2016087717 A1 WO2016087717 A1 WO 2016087717A1
Authority
WO
WIPO (PCT)
Prior art keywords
digester
cone
outlet opening
nozzles
base
Prior art date
Application number
PCT/FI2015/050845
Other languages
English (en)
Inventor
Lasse Hernesniemi
Henri KESSELI
Original Assignee
Andritz Oy
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
Application filed by Andritz Oy filed Critical Andritz Oy
Priority to EP15820554.2A priority Critical patent/EP3227492A1/fr
Publication of WO2016087717A1 publication Critical patent/WO2016087717A1/fr

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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
    • D21C7/08—Discharge devices

Definitions

  • the present invention provides systems for improving the flow of a discharge stage of a batch digester used in chemical pulping.
  • a digester reactor vessel is filled with wood chips and steam is added to pressurize and heat the chips. Warm black liquor is fed in to the digester. The black liquor impregnates the chips. After impregnation, black liquor is removed from the digester reactor vessel and returned to an accumulator vessel. Thereafter, the digester reactor vessel is filled with hot black and white liquors to be used to cook the chips. The chips in the digester are cooked for a predetermined time and temperature to form pulp. After cooking, filtrate liquid is pumped into the digester reactor vessel to displace the hot liquor which is removed from the vessel. The pulp and filtrate form a slurry which is discharged from the digester reactor vessel and pumped under pressure to a blow tank.
  • a novel solution has been developed for equalizing the discharge flow from a batch digester.
  • a purpose of the invention is to provide as wide and versatile a solution as possible for the problems limiting this aim. The purpose is achieved such that the apparatus defined in the preamble of the independent claims is implemented as defined in the characterizing part of the claims. Preferred embodiments of the invention may correspond to the dependent claims.
  • a batch digester for treating comminuted lignocellulosic fibrous material comprises an inlet for introducing comminuted lignocellulosic fibrous material, a circular cylindrical wall portion, an outlet opening for discharging treated comminuted lignocellulosic fibrous material, and a hemispherical bottom wall portion between said circular cylindrical wall portion and the outlet opening.
  • a stationary flow diverter having a form of a double cone and being supported by supporting legs is arranged above the outlet opening of the digester for preventing direct vertical pulp flow to the outlet.
  • the double cone diverter comprises a first cone having a base and extending upwardly from the base, and a second cone having said base common with said first cone, and extending downwardly.
  • the diverter is supported to the bottom of the digester by means of supporting legs for preventing the generation of turbulence.
  • the supporting legs are arranged to function as vortex-breakers.
  • the cone base has a diameter, which is longer than the outlet opening diameter.
  • the apexes of the cones are located on the vertical central axis of the digester.
  • the vertex angle of the first cone is 70 degrees or less, typically 50-70 degrees.
  • the vertex angle of the second cone is 80-120 degrees, typically 90-1 10 degrees.
  • a plurality of upper dilution nozzles are arranged in the periphery of the digester wall at an elevational level between the apex of the first cone and the upper ends of the supporting legs in the vertical direction.
  • the feeding of dilution liquid is directed essentially to the vicinity of the walls of the digester so that the upper nozzles are directed to feed dilution liquid downwards to the fibrous material in the bottom portion.
  • a plurality of lower dilution nozzles is arranged at a level below the cone base and above the digester outlet in the vertical direction.
  • the lower nozzles are directed to feed dilution liquid towards the outlet.
  • the upper and lower nozzles are typically evenly spaced about the periphery of the digester wall.
  • the upper ends of the supporting legs are typically connected to an upper part of the second cone of the diverter.
  • the lower ends of the supporting legs engage on the inside of the bottom wall of the digester, and the legs have a height so that the upper ends of the legs are located higher than the lower dilution nozzles, but lower than the upper dilution nozzles.
  • the modification moves the central pulp flow into the dilution area, improves pulp movement on the side of the digester wall and forces dilution liquid to meet pulp in the bottom of digester.
  • Fig. 1 is a schematic side view of a bottom section of a batch digester illustrating one embodiment of the present invention. Detailed description of the invention
  • Fig. 1 shows the basic diagram of a bottom section of a batch digester 10 with dilution nozzles and a double cone with supporting legs.
  • the digester 10 has a circular cylindrical wall portion 12 and a hemispherical bottom 1 1 .
  • the bottom has an outlet opening 13 for discharging fibrous material, such as pulp, from the digester.
  • the outlet opening has a diameter L1 .
  • a vertical central axis 23 of the digester typically passes through the center of the outlet opening 13.
  • the hemispherical bottom section is provided with a stationary flow diverter 14, which has a form of a double cone 15.
  • the diverter is arranged above the outlet opening 13 for preventing a direct vertical pulp flow downward to the outlet.
  • the double cone 15 comprises a first cone 16 having a base 18 and extending upwardly from the base, and a second cone 17 having said base common with said first cone, and extending downwardly.
  • Apex 21 is at the upper end of the first cone 16, and the cone expands out to meet the expanded portion of the lower cone 17, referred to as second cone, thus the double cone has apexes at opposite ends.
  • the double cone can be manufactured in one piece or the two cones can be attached, e.g. by welding, together.
  • the diameter of the diverter is at its largest.
  • the largest diameter L2 of the double cone 15, i.e. the diameter of the cone base 18, is longer than the outlet diameter L1 so that the direct vertical pulp flow downward to the outlet opening is prevented.
  • the diameter of the diverter shall not be too long so that there is enough space for the flow between the diverter and the bottom wall.
  • the double cone diverter 14 is supported to the bottom of the digester by means of supporting legs 19.
  • the supporting legs are arranged to function as vortex-breakers for preventing the generation of turbulence.
  • the upper ends of the supporting legs are typically attached to an upper part of the second cone 17 of the diverter.
  • the apexes 21 and 20 of the essentially right cones 16 and 17 are located on the vertical central axis 23 of the digester.
  • the cones 16, 17 have a central axis coinciding with the central axis 23 of the digester.
  • the vertex angle Z of the first cone 16 is 70 degrees or less, typically 50-70 degrees.
  • the vertex angle D of the second cone 17 which is inverted with respect to the first cone is 80-120 degrees, typically 90-1 10 degrees.
  • the first cone 16 is higher than the second cone 17.
  • a plurality of upper dilution nozzles 25 is arranged in the periphery of the digester wall at an elevational level between the apex 21 of the first cone 16 and the upper ends of the supporting legs 19 in the vertical direction.
  • upper nozzles are disposed in the cylindrical wall portion at a level 22 or above, which is located above the point where the hemispherical bottom area starts. Then a problem is that dilution liquid tends to flow upward and pulp is thickening in the bottom, which prevents uniform material flow through the outlet 13.
  • the upper nozzles 25 according to the new arrangement are disposed at a lower level than in known batch digesters in which the upper nozzles are located at the level 22 or above.
  • the upper nozzles 25 are directed so that dilution liquid flows mainly downward in the vicinity of the digester wall to the fibrous material in the bottom. Thus the dilution liquid meets the pulp in the bottom of the digester and does not flow upward.
  • a plurality of lower dilution nozzles 24 is arranged at a level below the cone base 18 and above the outlet opening 13 in the vertical direction.
  • the lower nozzles 24 are directed to feed dilution liquid towards the outlet opening.
  • the lower dilution nozzles must be pointed to the outlet flange of the digester to avoid turbulence above the bottom outlet and liquor flow upward.
  • each supporting leg 19 is typically attached to an upper part of the second cone 17 of the diverter.
  • the attachment may be direct or by means of a spacer ring.
  • the supporting legs have a height y (26) extending from the lowest point to the uppermost point thereof. The height of the legs is such that the upper ends of the legs are located higher than the lower dilution nozzles 24, but lower than the upper dilution nozzles 25.
  • the supporting legs have to be designed so that they are sufficiently strong to bear the weight of the material column in the digester.
  • pulp With the properly located upper nozzles and the double cone, pulp will be forced into the bottom dilution zone of the digester. These modifications are ensuring that dilution liquid and pulp flow meet before the digester outlet connection. More homogenous pulp consistency (and temperature) decreases pump out time of the digester, reduces dilution volume and reduces mass of "dry pulp cakes" during an emptying sequence of the digestion process. It also improves the production capacity of the digester plant.
  • a modeled discharge process of the batch digester showed that the upper dilution liquid flows almost totally downstream towards the digester outlet. Thus it is reducing the area of the thickened pulp in the hemispherical bottom. It was also discovered that the digester flow field is a very straightforward through-flow. Flow paths of fibers do not show any weighting (bias) by cross-section and the flow field higher in the digester (above the diverter) almost resembles plug flow.
  • a modeled discharge process in a prior art digester in which the upper nozzles are located at the level 22 and the bottom has no double cone, shows that the upper dilution liquid flows upward. Then pulp is thickening in the spherical bottom, which prevents uniform outflow.
  • Diluted pulp-liquor mixture tends to find the shortest route towards the bottom outlet along the centerline, right in the beginning of the discharging sequence, leaving the outer walls of the digester bottom filled with continuously thickening pulp. This "doughnut" of thick pulp must then be removed using excessive amount of dilution liquor in the end of the discharging sequence. Formation of a thick pulp layer on bottom walls is specific for the round-bottomed digesters.
  • the above mentioned problems are thus solved in connection with discharge from a batch digester. In this arrangement the even discharge consistency has been obtained without the use of moving, such as rotating, mechanical discharge means.

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  • Paper (AREA)

Abstract

La présente invention concerne un digesteur en discontinu pour traiter une matière fibreuse lignocellulosique broyée. Le digesteur comprend une entrée pour introduire une matière fibreuse lignocellulosique broyée, une partie paroi cylindrique circulaire, une ouverture de sortie pour évacuer la matière fibreuse lignocellulosique broyée traitée, et une partie paroi inférieure hémisphérique entre ladite partie paroi cylindrique circulaire et la sortie. Le digesteur comprend également un déflecteur fixe disposé dans la partie inférieure au-dessus de l'ouverture de sortie. Le déflecteur comprend un premier cône ayant une base et s'étendant vers le haut à partir de la base, et un second cône ayant ladite base commune avec ledit premier cône, et s'étendant vers le bas, ledit déflecteur étant supporté par des pattes de support, qui viennent en prise avec l'intérieur de la paroi inférieure et sont disposées autour de la sortie. Une pluralité de buses de dilution supérieures sont agencées à la périphérie de la paroi du digesteur à un niveau de hauteur entre le sommet du premier cône et les pattes de support, et une pluralité de buses de dilution inférieures sont agencées à la périphérie de la paroi du digesteur verticalement en dessous des buses supérieures.
PCT/FI2015/050845 2014-12-05 2015-12-02 Évacuation de matière à partir d'un digesteur en discontinu WO2016087717A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP15820554.2A EP3227492A1 (fr) 2014-12-05 2015-12-02 Évacuation de matière à partir d'un digesteur en discontinu

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI20146070 2014-12-05
FI20146070A FI20146070A (fi) 2014-12-05 2014-12-05 Materiaalin poistaminen eräkeittimestä

Publications (1)

Publication Number Publication Date
WO2016087717A1 true WO2016087717A1 (fr) 2016-06-09

Family

ID=55071051

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI2015/050845 WO2016087717A1 (fr) 2014-12-05 2015-12-02 Évacuation de matière à partir d'un digesteur en discontinu

Country Status (3)

Country Link
EP (1) EP3227492A1 (fr)
FI (1) FI20146070A (fr)
WO (1) WO2016087717A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE2150679A1 (en) * 2021-05-28 2022-11-29 Valmet Oy Treatment vessel having reduced outlet end diameter

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5116475A (en) 1989-10-17 1992-05-26 Sunds Defibrator Industries Aktiebolag Method for discharging a digester
EP0573892A1 (fr) * 1992-06-08 1993-12-15 Air Products And Chemicals, Inc. Système de réacteur pour le traitement de pâte de cellulose
US6280575B1 (en) * 1998-05-29 2001-08-28 Andritz-Ahlstrom Inc. Frusto-conical outlet for a cellulose material treatment vessel
US20030111200A1 (en) * 2001-08-02 2003-06-19 Prough James Robert System and method for improving the movement and discharge of material from vessels
WO2004072363A1 (fr) * 2003-02-12 2004-08-26 Sulzer Pumpen Ag Dispositif et procede destines au traitement de la pate a papier et procede destine a la modernisation d'un reservoir de stockage de pate a papier
WO2012102650A1 (fr) * 2011-01-25 2012-08-02 Metso Paper Sweden Ab Digesteur en continu à racloir inférieur équipé d'ouvertures de drainage

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5116475A (en) 1989-10-17 1992-05-26 Sunds Defibrator Industries Aktiebolag Method for discharging a digester
EP0573892A1 (fr) * 1992-06-08 1993-12-15 Air Products And Chemicals, Inc. Système de réacteur pour le traitement de pâte de cellulose
US6280575B1 (en) * 1998-05-29 2001-08-28 Andritz-Ahlstrom Inc. Frusto-conical outlet for a cellulose material treatment vessel
US20030111200A1 (en) * 2001-08-02 2003-06-19 Prough James Robert System and method for improving the movement and discharge of material from vessels
WO2004072363A1 (fr) * 2003-02-12 2004-08-26 Sulzer Pumpen Ag Dispositif et procede destines au traitement de la pate a papier et procede destine a la modernisation d'un reservoir de stockage de pate a papier
WO2012102650A1 (fr) * 2011-01-25 2012-08-02 Metso Paper Sweden Ab Digesteur en continu à racloir inférieur équipé d'ouvertures de drainage

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
"Papermaking Science and Technology", vol. 6A, 1999, CHEMICAL PULPING, BOOK, pages: 501 - 506

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE2150679A1 (en) * 2021-05-28 2022-11-29 Valmet Oy Treatment vessel having reduced outlet end diameter
WO2022250602A1 (fr) * 2021-05-28 2022-12-01 Valmet Ab Cuve de traitement à diamètre d'extrémité de sortie réduit
SE545646C2 (en) * 2021-05-28 2023-11-21 Valmet Oy Treatment vessel having reduced outlet end diameter

Also Published As

Publication number Publication date
FI20146070A (fi) 2016-06-06
EP3227492A1 (fr) 2017-10-11

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