EP0103577B1 - Process of producing fiberboard according to the wet method - Google Patents

Process of producing fiberboard according to the wet method Download PDF

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Publication number
EP0103577B1
EP0103577B1 EP19820903275 EP82903275A EP0103577B1 EP 0103577 B1 EP0103577 B1 EP 0103577B1 EP 19820903275 EP19820903275 EP 19820903275 EP 82903275 A EP82903275 A EP 82903275A EP 0103577 B1 EP0103577 B1 EP 0103577B1
Authority
EP
European Patent Office
Prior art keywords
chips
water
pulp
impregnation
backwater
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.)
Expired
Application number
EP19820903275
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0103577A1 (en
Inventor
Ove Danielsson
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.)
Valmet AB
Original Assignee
Sunds Defibrator 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 Sunds Defibrator AB filed Critical Sunds Defibrator AB
Publication of EP0103577A1 publication Critical patent/EP0103577A1/en
Application granted granted Critical
Publication of EP0103577B1 publication Critical patent/EP0103577B1/en
Expired legal-status Critical Current

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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
    • D21F1/66—Pulp catching, de-watering, or recovering; Re-use of pulp-water
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21J—FIBREBOARD; MANUFACTURE OF ARTICLES FROM CELLULOSIC FIBROUS SUSPENSIONS OR FROM PAPIER-MACHE
    • D21J1/00—Fibreboard

Definitions

  • This invention relates to a process for producing fiberboard according to the wet method in a closed backwater system, in which process chips of lignocellulose-containing material are preheated in an atmosphere of saturated steam at increased temperature and under increased pressure and thereupon defibrated under atmospheric or increased pressure, the defibrated material is suspended in backwater so as to obtain a pulp suspension for formation of wet sheets which are liberated from water by compression under supply of heat, the water squeezed out being returned to the suspension step (US-A-4 012 279).
  • the lignocellulose-containing material which may consist of any kind of annual or perennial plants, such as coniferous or hardwood, straw or bagasse, etc., is usually prior to the defibration step disintegrated to suitable piece size such as chips or chaff.
  • chips which for the sake of simplicity hereinafter generally shall be referred to as "chips"
  • chips are disintegrated and treated mechanically, defibrated into pulp at increased temperature and under increased pressure in an atmosphere of steam.
  • the temperature can be kept between 125 and 200°C depending on the type of starting material, pulp quality and supplied grinding energy.
  • the defibration is usually performed in disc grinders of various types, such as machines equipped with grinding members for single or double rotation.
  • the temperature during the defibration is in most cases kept in the range between 150 and 170°C and corresponding steam pressure.
  • the grinding energy may vary between 100 and 300 KWh per ton, but is usually about 200 KWh per ton, of bone dry material, when wood chips are defibrated and ground finally in one step.
  • the defibration is performed at a temperature of 170°C and coniferous wood is used as the starting material, about 8 percent of the dry substance of the wood are dissolved by hydrolysis as polysaccarides of varying composition in the water contained in the chips and escapes partly into the backwater and partly into the finished fiberboard. This results in that in a thoroughly closed backwater system the fiberboard units when subjected to hot pressing become dark-coloured and even can get dark spots, and also show a tendency to stick to the press plates.
  • the main object of the invention is to provide a novel process to reduce the content of released organic substance in the backwater in the production of pulp for fiberboard and this object is attained by the process being characterized therein that the pulp obtained by the defibration is dewatered and that the aqueous solution obtained thereby of organic substance released in the defibration step is returned into the process by impregnation of the chips prior to the defibration of the same.
  • the entering chips are impregnated with an aqueous solution of substance released during the defibration and thereafter defibrated at 170°C, the dissolved substance in bound practically completely in the pulp and cannot be removed by washing with water.
  • the conversion of the dissolved substance to insoluble state is effected probably by cooperation of several processes of chemical as well as physical nature.
  • the released substance consists substantially of polysaccarides, which can undergo both polymerisation and condensation processes and converted to substances difficult to dissolve in water. It is also possible that the polysaccarides are absorbed so firmly into and onto the fiber walls that they cannot be dissolved out by means of water.
  • so much squeezed-out solution is obtained usually as to render necessary evaporation to that volume which the chips are capable to absorb.
  • Evaporation of the squeezed-out solution can be effected in any known method of evaporation, but should suitably be done at reduced pressure in order to avoid trouble due to incrustation, or by evaporation of heated aqueous solution with air, the water then escaping as an air-steam mixture.
  • the entering chips are conveyed by means of a conveyor 10 to a steaming vessel 12 wherein they are moistened with steam which is drawn off through pipe 14 from a cyclone 16 belonging to a later part of the plant.
  • the moist chips are discharged into a screw press 18 where water is squeezed out mechanically and drained off through pipe 20 to a vessel 22 situated below.
  • the plug of chips compressed in the screw press 18 is forced into an impregnation vessel 24 where it is allowed to expand and absorb aqueous solution containing released substance of polysaccarides etc., which aqueous solution has been obtained by mechanical dewatering of the pulp in a later step in the plant and been conveyed to the impregnation vessel 24 via pipe 26.
  • a feed screw 28 Through a feed screw 28 the chips are fed into preheater 30 which is subjected to steam pressure and to which steam is fed from a pipe 32, from which pipe a branch pipe 32a opens into the steaming vessel 12.
  • the chips heated by means of steam are conveyed through screw feeder 34 into a defibrator 36 with motor 38 and are ground to pulp.
  • the finished pulp in which the organic substance supplied during the impregnation in the vessel 24 was changed into insoluble state, is blown through a blowduct 40 to the cyclone 16.
  • the pulp is fed from the cyclone 16 by means of screw conveyor 46 to receptacle 48, which is equipped with a stirring device.
  • a pipe 42 from the vessel 22 leads to the receptacle 48, through which pipe drained-off wood water from the vessel 22 is supplied to the receptacle by means of pump 44.
  • the pulp is fed from the receptacle 48 via chute 50 down into high pressure screw press 52, wherein the pulp is dewatered mechanically.
  • the aqueous solution obtained thereby of organic substance released in the defibration step is drained off from the screw press 52 via pipe 54 to vessel 56, from which it is pumped by means of pump 58 via pipe 60 through a heat exchanger 62 to a cooling tower 64, where part of the water is evaporated.
  • the heating in the preheater 62 is performed with steam which is drawn off from the cyclone 16 via pipe 14a and which leaves the preheater via conduit 66. Part of the water thus is evaporated in the tower 64 as a steam-air mixture, the air being supplied by means of fan 68.
  • the evaporated solution is pumped by means of a pump 70 through the pipe 26 into the impregnation vessel 24 for impregnation of a new charge of fresh chips, as described earlier.
  • the incoming chips of coniferous wood which are assumed to amount per hour to 8 000 kg dry substance +8 000 kg of water, are fed into the steaming vessel 12, and simultaneously 1 295 kg of steam are supplied through the pipe 14, whereupon the chips holding 100 percent of moisture, calculated on dry chips, are conveyed down into the screw press 18, where they are dewatered to a dry content of 55 percent, calculated on moist chips.
  • Pulp from the cyclone is fed by the screw 46 into the receptacle 48, into which at the same time 3 380 kg of wood water from the vessel 22 are conducted by means of the pump 44 and the pipe 42.
  • From the receptacle 48 equipped with a device 'for thorough stirring the pulp flows down into the high pressre screw press 52 and is dewatered to 55 percent dry substance.
  • 10 400 kg of water with 400 kg of soluble substance from a total 640 kg of substance released from the chips flow down into the vessel 56. 245 kg of dissolved substance remain in the pulp. This quantity of dissolved substance is caused to remain in the fiberboard in order that all released material shall be rendered harmless.
  • the backwater may be permitted to hold 245 kg of dissolved substance per 5 200 kg of water or 4.5 percent.
  • the solution flowing down into the vessel 56 comprises 10 400 kg of water +400 kg of released substance, this is more than the chips normally are capable to absorb, a quantity which usually does not exceed 8 000 kg of water per 8 000 kg of chips dry substance. Therefore, 2 400 kg of water must be evaporated in the tower 64, which is effected by preheating of the solution. The preheating is done with steam coming from the cyclone 16 through the pipe 14a.
  • the whole quantity of released wood substance can be rendered harmless in such a way that 400 kg are bound within the pulp during the defibration and 245 kg are bound in the fiberboard. 5 200 kg of water evaporated in the hot press are replaced by supply of water to the backwater cycle. Any discharge of backwater need not be done, and the content of 4.5 percent of dissolved organic substance in the backwater is kept at a sufficiently low level to avoid any discoloration of the fiberboard units in the hot pressing operation. Furthermore, all squeezed-out wood water has been rendered harmless.

Landscapes

  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Mechanical Engineering (AREA)
  • Paper (AREA)
  • Dry Formation Of Fiberboard And The Like (AREA)
  • Stringed Musical Instruments (AREA)
EP19820903275 1981-10-28 1982-10-28 Process of producing fiberboard according to the wet method Expired EP0103577B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8106369A SE428813B (sv) 1981-10-28 1981-10-28 Sett for framstellning av fiberskivor enligt den vata metoden
SE8106369 1981-10-28

Publications (2)

Publication Number Publication Date
EP0103577A1 EP0103577A1 (en) 1984-03-28
EP0103577B1 true EP0103577B1 (en) 1985-09-18

Family

ID=20344907

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19820903275 Expired EP0103577B1 (en) 1981-10-28 1982-10-28 Process of producing fiberboard according to the wet method

Country Status (7)

Country Link
EP (1) EP0103577B1 (fi)
JP (1) JPS58501825A (fi)
DE (1) DE3266424D1 (fi)
FI (1) FI71804C (fi)
NO (1) NO154316B (fi)
SE (1) SE428813B (fi)
WO (1) WO1983001637A1 (fi)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3802489C2 (de) * 1988-01-28 1997-12-18 Schwaebische Huettenwerke Gmbh Einrichtung zum Konditionieren von Schüttgut wie Spänen oder Schnitzeln
AT394741B (de) * 1991-03-08 1992-06-10 Sprout Waldron & Co Ag Verfahren zur herstellung von produkten aus lignozellulosefasern

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE341322B (fi) * 1968-04-02 1971-12-20 Defibrator Ab
SE7317565L (fi) * 1973-12-28 1975-06-30 Selander Stig Daniel

Also Published As

Publication number Publication date
DE3266424D1 (en) 1985-10-24
FI834308A0 (fi) 1983-11-24
FI71804C (fi) 1987-02-09
SE8106369L (sv) 1983-04-29
FI834308A (fi) 1983-11-24
SE428813B (sv) 1983-07-25
WO1983001637A1 (en) 1983-05-11
NO832354L (no) 1983-06-28
EP0103577A1 (en) 1984-03-28
FI71804B (fi) 1986-10-31
JPS58501825A (ja) 1983-10-27
NO154316B (no) 1986-05-20

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