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WO1999001606A1 - Procede et dispositif de traitement de la vapeur produite dans un processus de raffinage de fibres - Google Patents

Procede et dispositif de traitement de la vapeur produite dans un processus de raffinage de fibres Download PDF

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Publication number
WO1999001606A1
WO1999001606A1 PCT/FI1998/000568 FI9800568W WO9901606A1 WO 1999001606 A1 WO1999001606 A1 WO 1999001606A1 FI 9800568 W FI9800568 W FI 9800568W WO 9901606 A1 WO9901606 A1 WO 9901606A1
Authority
WO
WIPO (PCT)
Prior art keywords
steam
fiber
dryer
heat exchanging
fibers
Prior art date
Legal status (The legal status 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 status listed.)
Ceased
Application number
PCT/FI1998/000568
Other languages
English (en)
Finnish (fi)
Inventor
Pentti Juhola
Arvi Artamo
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rinheat Oy
Original Assignee
Rinheat 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 Rinheat Oy filed Critical Rinheat Oy
Publication of WO1999001606A1 publication Critical patent/WO1999001606A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
    • D21B1/00—Fibrous raw materials or their mechanical treatment
    • D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
    • D21B1/12—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by wet methods, by the use of steam
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F1/00—Wet end of machines for making continuous webs of paper
    • D21F1/04—Head boxes of cylinder machines

Definitions

  • the invention relates to a method for the treatment of steam that is generated in the process of defibering mechanically defibered wood pulp, which steam is used for removing the pulp from the defibrator, in order to facilitate the recovery of heat energy in said steam, simultaneously enabling the elimination of environmentally harmful emissions of organic compounds evaporated from the wood during defibration.
  • the method is suited for use in the production of pulp for manufacturing medium density fiberboard (MDF), and the recovered energy is used for preheating air for drying.
  • MDF medium density fiberboard
  • a further objective of the invention is a device for the utilization of said process.
  • the wood used as raw material in the production of medium density fiberboard is first defibered into fibers or fiber bundles of desired size.
  • the defibering usually is carried out at a pressure of 5...12 bar and a temperature of 150...180 °C.
  • the humidity in the wood is vaporized due to the large frictional heat generated, and additionally steam may be fed into the process, on the one hand to soften the lignin and on the other hand for conveying the material in the transfer ducts.
  • a binder resin is added to the fiber stream as well as required additives, whereafter the fiber stream and the steam are blown into the dryer at great velocity.
  • the dryer is usually a so-called pneumatic dryer, wherein the drying takes place by means of hot air, blown through the drying duct and simultaneously carrying the material to be dried through the drying duct.
  • the dryer ends in one or several separating cyclones, where the fibers are separated from the drying air, which is directed out of the dryer.
  • the amount of air used for drying fiber is substantial, typically about 20 m 3 per kg of dry material.
  • Volatile organic compounds (VOC) evaporating together with the water vapor represent a substantial environmental emission, as they leave the cyclones in their entirety with the exhaust air. Removal of these from air streams of this magnitude would involve investments out of proportion. Disclosure of the invention
  • a method according to claim 1 has been invented, providing a substantial improvement in the energy economy of a defibering/drying process, simultaneously eliminating the air emis- sions of organic compounds (VOC) originating from the wood raw material.
  • the invention may be practiced using a device according to claim 10.
  • a separation device which may be a cyclone or another separation device suitable for the purpose, the fibers are separated from the flow of steam.
  • the fibers are directed to the dryer and the steam to a heat exchanging device.
  • the pressure of the separation device is, according to the invention, equal to or preferably somewhat lower than the dryer pressure.
  • the dryer pressure is the pressure in the drying duct essentially at the point of entrance of fibers into the dryer.
  • the pressure difference between the separation device and the dryer is adjusted to allow a minor flow of air from the dryer into the separation device, not disturbing the fibers moving by gravity into the drying duct.
  • the steam is wholly or partly condensed, and the liberated heat is transferred to an appropriate gas or liquid stream, primarily for utilization.
  • said heat is used for preheating the flow of drying air fed to the dryer.
  • the heat exchanging surfaces on the steam side can be washed during operation, simultaneously neutralizing the discharged condensate stream.
  • the noncondensable organic compounds that have entered the heat exchanging device with the water vapor represent a source of VOC emissions.
  • they may be conveyed from the heat exchanging device to incineration or recovery.
  • they are burned in the boiler or hot air generator connected to the dryer.
  • a split device is preferably installed, providing the option of directing part of the steam/fiber stream from the defibrator directly into the drying duct according to prior art practice.
  • the separation device may be a cyclone, whereby its efficiency can be controlled by adjusting the back pressure of its upper discharge connection. It may also be another device or apparatus for removal of solids from a gas phase, for example a device based on centrifugal force and provided with rotating parts. Preferably, the separation device is connected to the drying duct without a lock arrangement.
  • the invention provides for recovery of a very significant amount of the heat of the transfer steam, which would, according to the prior art, leave the process into the surrounding air with the drying gases. In addition, the VOC emissions are eliminated.
  • the invention is evident from the enclosed drawing, depicting the drying section of a plant producing raw material for medium density fiberboard.
  • the basic raw material e.g. wood chips
  • Defibrator 1 represents the last stage of the defibrating apparatus.
  • a split device 2 is provided to enable direction of the fiber/steam flow to startup cyclone 3 during the startup phase, or forward to the drying process.
  • the glue and resin components required for fiberboard production are fed to the process stream as a water emulsion through dosage device 4 into duct 5.
  • a split device 6 Following dosage de- vice 4 is a split device 6, to provide for direction of the fiber/steam flow either directly into the dryer 7, or to a separation device which in the figure is represented by cyclone 8.
  • Cyclone 8 is equipped with a mechanical scraper 9, to ensure that fiber does not stick, clogging the cyclone.
  • the fiber stream separated at the lower part of cyclone 8 is directed into the dryer 7, where the entrance point for the fiber 10 has the form of a venturi to ensure good mixing of the fiber into the drying air.
  • the steam flow separated from cyclone 8 is directed through duct 11 into heat exchanging equipment 12, in which steam condenses and which is used to preheat the air streams for providing drying air in the dryer 7 and for supporting the combustion in hot air generator 13.
  • the condensate which is acid due to raw material components carried over in the steam, exits at the bottom into a wash and neutralization circuit 10, circulated by pump 15.
  • Base is dosed into this circuit from reservoir 16 by means of pump 17, and neutralized condensate leaves the circuit through pipe 18.
  • the solution circulates to rinse the heat transfer surfaces of the heat transfer device.
  • the circuit is further provided with a filter 19.
  • Preferably, sodium hydroxide is used as a base.
  • the noncondensable gases comprising organic compounds and residual humidity in addition to air, is directed via control valve 20 into the combustion chamber 21 of hot air generator 13.
  • the control valve 20 is used to adjust the steam side pressure of heat recovery device 12 in order to optimize the separation efficiency of cyclone 8.
  • the flow of preheated air may additionally be controlled by throttling branch duct 22. If the amount of drying air is not sufficient for condensing the whole amount of separated steam, the air flow through the heat exchanger is increased, and the surplus air is expelled through branch 22 according to the figure, or is directed for use as drying air in another drying stage.
  • the air flow preheated in heat exchanger 8 is directed to hot air generator 13, and the air leaving that unit is used to dry the fiber stream leaving cyclone 8 in drying duct 7.
  • the fibers are separated from the drying air stream in a known manner in product cyclone assembly 23.

Landscapes

  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Mechanical Engineering (AREA)
  • Paper (AREA)
  • Drying Of Solid Materials (AREA)

Abstract

Selon ce procédé, la vapeur produite lors du défibrage de pâte mécanique vapeur, qui est utilisée pour transférer les fibres du défibrateur vers le processus de déshydratation, est séparée de la vapeur des fibres, pour que l'on puisse utiliser l'énergie qu'elle contient. Cette énergie thermique est de préférence employée pour chauffer l'air alimentant le processus de déshydratation. En même temps, on empêche les composés organiques volatils contenus dans cette vapeur de se disperser dans l'environnement.
PCT/FI1998/000568 1997-07-03 1998-07-03 Procede et dispositif de traitement de la vapeur produite dans un processus de raffinage de fibres Ceased WO1999001606A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI972847 1997-07-03
FI972847A FI972847A0 (fi) 1997-07-03 1997-07-03 Foerfarande foer hantering av aonga i en fibreringsprocess

Publications (1)

Publication Number Publication Date
WO1999001606A1 true WO1999001606A1 (fr) 1999-01-14

Family

ID=8549189

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI1998/000568 Ceased WO1999001606A1 (fr) 1997-07-03 1998-07-03 Procede et dispositif de traitement de la vapeur produite dans un processus de raffinage de fibres

Country Status (2)

Country Link
FI (1) FI972847A0 (fr)
WO (1) WO1999001606A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001003804A1 (fr) * 1999-07-12 2001-01-18 Rinheat Oy Procede et dispositif permettant de separer des fibres d'un flux de vapeur
CN102489448A (zh) * 2011-12-16 2012-06-13 北京中诺德瑞工业科技有限公司 一种用于干法制浆的风选设备及其在干法制浆中的用途

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE415493B (sv) * 1977-06-06 1980-10-06 Sca Development Ab Sett att mojliggora utnyttjande av anga som utvecklas vid raffinering av fibermaterial
US4710268A (en) * 1985-06-24 1987-12-01 Kamyr Ab Method for regulating the pressure of blow-through discharge steam from a reboiler of process steam produced during production of mechanical pulp

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE415493B (sv) * 1977-06-06 1980-10-06 Sca Development Ab Sett att mojliggora utnyttjande av anga som utvecklas vid raffinering av fibermaterial
US4710268A (en) * 1985-06-24 1987-12-01 Kamyr Ab Method for regulating the pressure of blow-through discharge steam from a reboiler of process steam produced during production of mechanical pulp

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
APPITA, Volume 34, No. 2, Sept. 1980, OLOF JEPPSON et al., "Energy Savings in a Swedish Market TMP Mill", pages 135-137. *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001003804A1 (fr) * 1999-07-12 2001-01-18 Rinheat Oy Procede et dispositif permettant de separer des fibres d'un flux de vapeur
CN102489448A (zh) * 2011-12-16 2012-06-13 北京中诺德瑞工业科技有限公司 一种用于干法制浆的风选设备及其在干法制浆中的用途

Also Published As

Publication number Publication date
FI972847A0 (fi) 1997-07-03

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