WO2011053203A1 - Procédé et dispositif de traitement à la vapeur et d'imprégnation de copeaux de bois dans une cuve à écoulement descendant - Google Patents

Procédé et dispositif de traitement à la vapeur et d'imprégnation de copeaux de bois dans une cuve à écoulement descendant Download PDF

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Publication number
WO2011053203A1
WO2011053203A1 PCT/SE2009/051228 SE2009051228W WO2011053203A1 WO 2011053203 A1 WO2011053203 A1 WO 2011053203A1 SE 2009051228 W SE2009051228 W SE 2009051228W WO 2011053203 A1 WO2011053203 A1 WO 2011053203A1
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WO
WIPO (PCT)
Prior art keywords
vessel
chips
liquid level
baffles
volume
Prior art date
Application number
PCT/SE2009/051228
Other languages
English (en)
Inventor
Jonas SAETHERÅSEN
Anders Samuelsson
Fredrik Wilgotsson
Per Nyström
Original Assignee
Metso Paper Sweden 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
Application filed by Metso Paper Sweden Ab filed Critical Metso Paper Sweden Ab
Priority to PCT/SE2009/051228 priority Critical patent/WO2011053203A1/fr
Publication of WO2011053203A1 publication Critical patent/WO2011053203A1/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
    • 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
    • D21C1/00—Pretreatment of the finely-divided materials before digesting
    • D21C1/02—Pretreatment of the finely-divided materials before digesting with water or steam

Definitions

  • the present invention concerns a method and an arrangement for steaming and impregnating wood chips, during the manufacture of chemical pulp in a continuous process, using a down flow vessel where chips are descending down the vessel in a plug flow and where treated chips are continuously fed out at the bottom of the vessel, said vessel having an upper volume of chips above a liquid level established in the vessel, said upper volume having a height of at least 2-5 meter, and said vessel having a lower volume of chips below the liquid level, and where steam and impregnation liquid is supplied to the vessel, according to the preamble of claim 1 and claim 2.
  • a down flow vessel where chips are descending down the vessel in a plug flow and where treated chips are continuously fed out at the bottom of the vessel, said vessel having an upper volume of chips above a liquid level established in the vessel, said upper volume having a height of at least 2-5 meter, and said vessel having a lower volume of chips below the liquid level, and where steam and impregnation liquid is supplied to the vessel, according to the preamble of claim 1 and claim 2.
  • a system is shown in US 5.635.025 in which the chips are fed without prior steaming to a vessel in the form of a combined chip bin, impregnation vessel and chip chute. Steaming of the chips takes place here, the chips lying above the fluid level, and a simple addition of impregnation fluid takes place trough the vessel wall below the liquid level.
  • a further such system is revealed in US 6.280.567, in which the chips are fed without prior steaming to an atmospheric impregnation vessel in which the chips are heated by the addition of warm black liquor that maintains a temperature around 130-140 C.
  • the added impregnation liquid is added via nozzles in a manner similar to what is shown in US 2.803. 540, i.e. using supply nozzles penetrating the wall of the vessel.
  • the principle object of the invention is to obtain an improved method and arrangement for steaming and impregnating wood chips, during the manufacture of chemical pulp in a continuous process, using a down flow vessel where chips are descending down the vessel in a plug flow and where treated chips are continuously fed out at the bottom of the vessel, said vessel having an upper volume of chips above a liquid level established in the vessel, said upper volume having a height of at least 3-5 meter, and said vessel having a lower volume of chips below the liquid level, and where steam and impregnation liquid is supplied to the vessel.
  • a specific objective is to enable the greatest possible downward thrust from the chip pile established above the liquid level, allowing this thrust force to push the steamed chips downwardly into the liquid volume, which liquid volume impose a wet-steaming effect on the chips displacing any residual air bound in the chips, but first when this wet-steaming effect has been obtained at a certain depth into the impregnation liquid is a plug holding force applied against the descending plug flow now being immersed in the impregnation liquid.
  • Another specific objective is to establish a non disturbed dense packed chip pile above the liquid level, which chip pile is to be steamed by the hot impregnation liquids being added into the chip pile.
  • a compacted chip pile is beneficial for establishment of a even and thorough steaming effect over the entire cross section of the chip pile.
  • the dense packed chip pile also enables establishment of a temperature gradient upwards in the chip pile, such that a so called “cold top” control of the chip pile is possible. "Cold top” control avoids continuous blow-trough of hot steam in evacuated gases and associated losses in energy in the chip steaming process.
  • the invention can advantageously be used when cooking hard wood and softwood wood chips, bagasse and other annual plants.
  • Figure 1 shows an impregnation vessel according to state of the art
  • Figure 2 shows a detail of a first embodiment of the invention
  • Figure 3 shows a detail of a second embodiment of the invention
  • Figure 4 shows a detail of a third embodiment of the invention
  • Figure 5 shows a detail of a fourth embodiment of the invention
  • Figure 6 shows a detail of a fifth embodiment of the invention
  • treatment liquor one kind of treatment liquor that is intended to be added to the entire chip flow in the treatment vessel.
  • This treatment liquor could comprise only of spent cooking liquor, i.e. black liquor, from a subsequent digester, but could also be a mixture of two or more of following liquids;
  • treatment liquid will also be used, and by this is meant the treatment liquid established in or withdrawn from the vessel, which besides partially used treatment liquor also contains chip moisture or any other organic or inorganic content dissolved from the chips.
  • treatment vessel will also be used, and by this is meant any kind of treatment vessel used for treating chips in either form of delignification or impregnation state, i.e. the vessel could be an atmospheric combined steaming and treatment vessel like IMPBIN.
  • crushed cellulose material will be used, which preferably could be in form of wood chips, but also more fragmented wood material such as sawdust or pin chips, all obtained from either hardwood or softwood or annual plants.
  • FIG. 1 A prior art arrangement for the impregnation of chips during the manufacture of chemical pulp is shown in Figure 1 .
  • this arrangement corresponds to the IMPBIN concept sold by Metso, including the method of wet- steaming chips in a substantially atmospheric pressure ( ⁇ 0,5 bar, i.e. not a pressure vessel).
  • the arrangement comprises an essentially cylindrical impregnation vessel 30 arranged vertically into which unsteamed chips Ch are continuously fed into the top of the impregnation vessel via feed means, in the form of a small chip buffer 1 without steaming and a chute feed (preferably a sluice feeder) 2.
  • the chips that are fed into the impregnation vessel are thus unheated chips that normally have the same temperature as the ambient temperature.
  • the pressure in the vessel can be adjusted as necessary through a control valve 31 arranged in a valve line 4 at the top of the impregnation vessel, possibly also in combination with control of the steam ST via input lines 5.
  • this valve line When atmospheric pressure is to be established, this valve line may open out directly to the atmosphere. It is preferable that a pressure is established at the level of atmospheric pressure, or a slight deficit pressure by the outlet 4 of magnitude -0.5 bar (-50 kPa), or a slight excess pressure of magnitude up to 0. 5 bar (50 kPa).
  • SW_AI R squeeze air
  • the impregnated chips are continuously fed out via output means, here in the form of an outlet 1 0, with a bottom scraper 20 driven by a motor 22 via shaft 21 .
  • the level of the chips, CH_LEV, above the level of the liquid, LIQ_LEV, should preferably be at least 2 meters and preferably at least 5 meters when impregnating wood chips, or an equivalent retention time of the chips in the upper volume exceeding 1 0 minutes.
  • the chip level is monitored by any suitable chip level meter means, and the output from such level meter controls the inlet feed rate of chips, here visualized as a valve V C H in the feed line for chips.
  • a corresponding increase in the height HO towards the upper part of the range is preferably established.
  • a corresponding decrease in the height towards the lower part of the range is preferably established.
  • the actual mini mum height established in this range 2-5 meters is also depending upon the temperature of the chips being fed into the vessel, as colder chips during winter operation may need more retention time in the steaming phase in the chip pile. This minimum height is important in order to provide an optimal passage of the chips in an even plug flow through the vessel, and establishment of a positive thrust force, indicated by F-marked arrow, on the chips that reach the liquid level and still may have some buoyancy effect left.
  • steaming with fresh steam can be essentially avoided if hot black liquor, typically spent cooking liquor from digester at cooking temperature in the range 130-150 degrees C, is added as the impregnation liquid, which black liquor during pressure release emits all the steam necessary. Fresh steam is thus not necessarily added to the chips that lie on top of the fluid level established by the impregnation fluid during normal steady-state operation.
  • the invention can also be applied even if softwood with lower density is used as raw material, giving a markedly reduced need for steaming, that is, a reduced addition of fresh steam.
  • the chips that lie above the fluid level established by the impregnation fluid can be heated by the addition of external steam ST such that a temperature of the chips approach 60-100° C in the chip pile before the chips reach the fluid level that has been established by the treatment liquor.
  • the treatment liquor added via supply pipe or pipes, here a common central pipe 7a can also be established as a mixture from totally separate sources, that is, not from one common flow of black liquor.
  • the added liquor may also contain a wash filtrate.
  • the liquid level is monitored by any suitable liquid level meter means, and the output from such level meter controls the inlet valve V L i in the feed line for the impregnation liquors added.
  • the chips immersed in the lower volume below the liquid level should have a sufficient retention time for a thorough impregnation, preferably such that said lower volume has a height H1 of at least 2-5 meter, or an equivalent retention time of the chips in the lower volume exceeding 1 0 minutes
  • the treatment liquor added can also be a mixture of black liquor and an additive amount of fresh cooking chemicals, i.e. white liquor, with the object of establishing alkali profiles that are necessary for the process.
  • a rapid initial consumption of alkali normally takes place, simply in order to neutralize the wood acidity, while it is desired to keep the final residual alkali after the impregnation stage at a certain level.
  • the needed amount of additional alkali is mostly dependent on the level of wood acidity being released during steaming in the chip volume above the liquid level, and thus dependent on type of wood being treated (softwood or hardwood).
  • the vessel may be equipped without or with extraction screens 6 to allow liquid extraction (to recovery REC) early in the process.
  • FIG 2 is a detail view of a first embodiment of the invention.
  • a ring shaped conical baffle 25a located a distance H3 below the liquid level, LIQ_LEV.
  • the baffles 25a protrudes towards the center of the vessel at a distance D1 being in the range 5-20% and preferably 10% of the interior diameter of the vessel at the positions of the baffles.
  • this distance D1 could thus preferably lie in the range 20 to 80 centimeter and preferably correspond to 40 centimeter.
  • this first embodiment there is a withdrawal screen 6 at or close to the liquid level LIQ_LEV.
  • Spent treatment liquid is withdrawn from this screen 6, typically to recovery REC, via conventional chambers arranged outside of the screen 6.
  • a step-out SO is in a conventional manner established below the screen section, and the baffle 25a I located at a distance D2 below the step-out SO.
  • the upwardly directed face of the baffles 25a are sloping downwardly from the wall of the vessel, and preferably with an inclination angle a in the range 5-30 degrees, and preferably about 10 degrees.
  • the baffle 25a have a continuous ring formed shape around the interior circumference of the vessel, and could preferably be built by a single deflection plate, leaving a void beneath the deflection plate.
  • the baffle 25a will thus introduce a plug holding force applied against the descending plug flow at a location at the distance H3 below the liquid level in said vessel such that a minimum free and unobstructed plug flow in the first volume above the liquid level is established which unobstructed plug flow is established at a distance exceeding 2-5 meter above the liquid level, said distance depending on the type of wood being steamed, i.e. specific weight thereof, and the steaming effect in the chip pile above the liquid level.
  • FIG 3 is a second alternative embodiment shown but without a withdrawal screen. As there are no screen section, the baffle is arranged closer to the liquid level LIQ_LEV, such that the distance H3 equals the distance D2. The distance D2 is given by the expansion effect on the chip pile after a step-out.
  • the chip pile expansion is indicated by the hashed line PE on the right hand side in figure 3.
  • FIG 4 is a third alternative embodiment shown but without a withdrawal screen or step-out.
  • the baffle is arranged even closer to the liquid level LIQ_LEV, such that the distance H3 equals the distance D2.
  • the distance H3 is typically exceeding 0,2 meter, but less than 1 meter, if located in a vessel without a step out SO at the liquid level according to the embodiment shown in figure 4.
  • the chip plug normally expands to the full vessel diameter, following the hashed line PE on the right hand side in figure 3, some 80-100 centimeter below the step out, indicated by the distance D2.
  • the effect of this expansion could be observed on the interior wall below step-outs in installed digesters during shut-down, as the polishing effect from the chip pile on the interior wall is fully developed first at a distance some 80-100 centimeter below the step out.
  • this distance may typically lie in the range 0,2 to 1 meter, i.e. the indicated distance D2 in figure 4, and 1 -2 meter if a step out SO is located above in the liquid volume i.e. the indicated distance D2 plus the height of the screen section 6 in total corresponding to H3 in figures 2-3.
  • FIG 5 is a fourth alternative embodiment shown but where the baffles 25 are made from a plurality of individual baffle segments 25b located around the inner circumference of the vessel wall. In this embodiment the baffle segments 25b are all located at the same horizontal plane. All other details are corresponding to the embodiment shown in figure 2.
  • FIG 6 is a fifth alternative embodiment shown but where the ring shaped baffle 25a according figure 2 is complemented by a second lower ring shaped baffle 25c at a distance H4 below the first upper shaped baffle 25a.
  • the distance D3 may typically lie in the range 0,2 to 1 meter below the step out generated by the first upper baffle 25a, such that the chip plug could expand to the full vessel diameter below the step out established by the first upper baffle 25a.
  • baffle segments 25d located around the inner circumference of the vessel wall above the liquid level. This additional baffle segments 25d used for supplying steam or hot treatment liquor at the periphery of the vessel, besides offering an additional load reduction on the bottom scraper.

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Abstract

L'invention concerne un procédé et un dispositif de traitement à la vapeur et d'imprégnation de copeaux de bois dans une cuve unique à écoulement descendant. On établit un premier volume supérieur de copeaux au-dessus d'un niveau de liquide (LIQ_LEV) dans la cuve, le traitement à la vapeur ayant lieu, ledit volume supérieur ayant une hauteur (H1) d'au moins 2 à 5 mètres. On établit un second volume inférieur de copeaux en dessous du niveau de liquide, une imprégnation ayant lieu, ledit volume inférieur ayant une hauteur (H1) d'au moins 2 à 5 mètres. Afin de réduire la demande de couple sur le racleur inférieur, on applique des forces de maintien de bouchon contre l'écoulement de bouchon descendant à une distance (H3) en dessous du niveau de liquide de moins de 20 % de la hauteur (H1) dudit volume inférieur, de telle sorte qu'on établit un écoulement minimal et non obstrué de bouchon libre dans le premier volume, lequel écoulement piston non obstrué est établi à une distance verticale dans ladite cuve excédant 2 à 5 mètres au-dessus du niveau de liquide.
PCT/SE2009/051228 2009-10-28 2009-10-28 Procédé et dispositif de traitement à la vapeur et d'imprégnation de copeaux de bois dans une cuve à écoulement descendant WO2011053203A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/SE2009/051228 WO2011053203A1 (fr) 2009-10-28 2009-10-28 Procédé et dispositif de traitement à la vapeur et d'imprégnation de copeaux de bois dans une cuve à écoulement descendant

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/SE2009/051228 WO2011053203A1 (fr) 2009-10-28 2009-10-28 Procédé et dispositif de traitement à la vapeur et d'imprégnation de copeaux de bois dans une cuve à écoulement descendant

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WO2011053203A1 true WO2011053203A1 (fr) 2011-05-05

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PCT/SE2009/051228 WO2011053203A1 (fr) 2009-10-28 2009-10-28 Procédé et dispositif de traitement à la vapeur et d'imprégnation de copeaux de bois dans une cuve à écoulement descendant

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5454490A (en) * 1993-10-01 1995-10-03 Kamyr, Inc. Conical insets for chip bin
US5635025A (en) * 1994-12-05 1997-06-03 Ahlstrom Machinery Inc. Digester system containing a single vessel serving as all of a chip bin, steaming vessel, and chip chute
US6280569B1 (en) * 1998-10-15 2001-08-28 Andritz-Ahlstrom Inc. Compression rings for column relief in continuous cooking vessels
WO2006006934A1 (fr) * 2004-07-15 2006-01-19 Kvaerner Pulping Ab Procede et dispositif d'impregnation de copeaux

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5454490A (en) * 1993-10-01 1995-10-03 Kamyr, Inc. Conical insets for chip bin
US5635025A (en) * 1994-12-05 1997-06-03 Ahlstrom Machinery Inc. Digester system containing a single vessel serving as all of a chip bin, steaming vessel, and chip chute
US6280569B1 (en) * 1998-10-15 2001-08-28 Andritz-Ahlstrom Inc. Compression rings for column relief in continuous cooking vessels
WO2006006934A1 (fr) * 2004-07-15 2006-01-19 Kvaerner Pulping Ab Procede et dispositif d'impregnation de copeaux

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