Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
  • B27N1/00—Pretreatment of moulding material
  • B27N1/003—Pretreatment of moulding material for reducing formaldehyde gas emission
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
  • B27N3/00—Manufacture of substantially flat articles, e.g. boards, from particles or fibres
  • B27N3/007—Manufacture of substantially flat articles, e.g. boards, from particles or fibres and at least partly composed of recycled material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
  • B27N1/00—Pretreatment of moulding material

Definitions

• the invention relates to a process for the recovery of chips and fibers from wood materials and wood material containing materials glued with urea-formaldehyde binders or with other hydrolyzable or chemically digestible binders according to the preamble of the main claim.
• Such a method is known from DE 42 24 629 A1.
• the wood-based material waste is exposed to the action of steam at high temperatures between 120 and 180 ° C. and the resulting high pressures of 2 to 11 bar.
• the wood materials are broken into small fragments in a pre-treatment step and any metal parts that may be present are separated.
• Modified urea binders are used in the gluing of the chips produced by this method. Due to the shredding of the material to be treated into small fragments, the chips are severely mechanically damaged in addition to the temperature load. H. shortened. Coatings and other non-chip components are also difficult to separate due to the strong pre-comminution after the steam treatment.
• Another method is e.g. B. boiling in an excess of water and the associated dissolution of urea-formaldehyde resin bonded chipboard and medium-density MDF.
• This process is energy and cost intensive.
• the energy consumption is v. a. greatly increased by boiling the excess water.
• the chips are boiled out and thereby change their properties unfavorably.
• the swellability increases due to the removal of wood components, while the technological properties of the chips deteriorate.
• the binder is removed from the chips and can no longer have a positive effect on re-gluing. The resulting wastewater problem and the cost of drying the chips or fibers are considerable.
• DE 42 01 201 A1 discloses a process for recycling wood-based materials and waste. According to this method, new, finished semi-finished products or finished products are produced from wood-based material remnants after corresponding mechanical processing thereof.
• the object of the present invention is to provide a method for the recovery of chips and fibers from pieces of wood material which is environmentally friendly and economically feasible.
• this process is intended to recover high-quality chip and fiber material (secondary chips or secondary fibers).
• wood material pieces are impregnated with an impregnating or impregnating solution and pre-swollen until they have absorbed at least 50% of their own weight in impregnating solution.
• the impregnated wood material pieces are heated to 80 ° C heated to 120 ° C until the bond of chips and fibers is dissolved by the influence of the impregnation solution and the temperature, ie the glue compounds are destroyed chemically by hydrolysis and mechanically by swelling.
• the amount of impregnation solution and the impregnation process taken up by the wood material pieces are dimensioned or adjusted such that, on the one hand, a complete solution of the wood materials takes place in the specified temperature range, but on the other hand, after the digestion, there is no longer any free catchable liquid, so that so there is no solution to dispose of.
• the method according to the invention is a combination of chemical, thermal and mechanical process steps. These make it possible to digest the wood material pieces with comparatively mild digestion parameters and thereby to recover chips and fibers in undamaged or even tempered form. This procedure is possible through the use of the impregnation solution with which the material is impregnated or soaked without any cooking liquor or waste water remaining after the digestion.
• the secondary chips and secondary fibers can be produced with little financial and technical effort and can be made with and without the addition of fresh chips or fresh fibers in conventional production plants to new wood-based materials such as. B. chipboard and fibreboard.
• the wood-based materials produced in this way have comparable or even better properties than wood-based materials made from fresh material. This applies to both the technological properties and the formaldehyde emission.
• the secondary chips and fibers can be processed with conventional binders. Binder consumption is not increased. It can even be reduced by the process.
• the process is carried out in such a way that impregnating solution is added to the wood material pieces, in such an amount that after the wood material pieces have completely absorbed the solution have absorbed at least 50% of their own weight in impregnation solution.
• it is important to mix or stir the wood material pieces so that the existing solution is absorbed evenly by all wood material pieces. This can also be achieved with a rotating container.
• Another embodiment of the method provides that an excess of impregnation solution is added to the wood material pieces, so that the wood material is completely covered by the liquid. After the pieces of wood have absorbed at least 50% of their own weight in liquid, the remaining liquid is drained off. It can be used as an impregnation solution for the digestion of other wood-based materials.
• the treated wood material pieces ie soaked with impregnation solution
• the wood-based material pieces are heated to a temperature in the range between 80 and 120 ° C.
• the hydrolysis of the glue compounds takes place under the influence of temperature and the action of the impregnation solution.
• a variant of the method provides that the impregnation process already takes place in the digestion tank and that the temperature is applied after the liquid material has been completely absorbed by the wood material pieces or after the excess impregnation solution has been drained off.
• the temperature can be applied either under pressure (in the pressure-tightly closed digestion tank) or without pressure. The pressure level depends on the set temperature.
• the duration of the digestion is about 1 to 60 minutes.
• the digestion is accelerated by higher temperatures, a higher proportion of impregnation solution and a high acid content of the impregnation solution, while it is slowed down by lower temperatures, a lower proportion of impregnation solution and a basic setting of the impregnation solution.
• the amount of pressure used during the heating begins at normal pressure and should be with a view to the most gentle digestion expediently do not go over two bar overpressure.
• the temperature should also not be above 120 ° C with a view to digestion which is as gentle as possible and nevertheless rapid.
• the impregnation process is to be accelerated, it is advantageous if it takes place under negative pressure (after evacuating the impregnating container) or at an overpressure above normal pressure.
• a vacuum treatment applying a negative pressure of, for example, 150 mbar (absolute) to the impregnation tank) of the wood-based materials allows the air contained therein to escape. At normal pressure, this hinders the penetration of the impregnation solution and would make it impossible to open up, in particular, flat, coated wood-based materials without negative pressure.
• the cavities filled with air make up approximately 30 to 70% of the volume of the wood-based material. Overpressure also facilitates rapid penetration of the impregnation solution into the wood material pieces.
• the impregnation process takes place with a combination of negative and positive pressure, it is accelerated compared to the course at normal pressure. Heating the impregnation solution or the wood-based material during or before the impregnation has the same effect.
• the impregnation solution can be heated in an energy-saving manner by the heat which arises when the digestion container is degassed, or when it is discharged from the digestion container or when the digestion material is sorted.
• the digestion material can be heated by the heat generated during the exhaust or discharge from the digestion tank.
• Another procedural procedure * provides that the wood material residues are filled together with the impregnation solution into a rotating digestion tank or equipped with a mixer or agitator (the amount of the impregnation solution added being such that none after the impregnation and the digestion) free, drainable impregnation solution or waste liquor is more to be disposed of) and the digestion tank is heated to a temperature between 80 and 120 ° C.
• the mechanical process of destroying the glue connections by swelling and the chemical decomposition by hydrolysis take place simultaneously. Ie the wood material pieces are simultaneously exposed to the influence of the impregnation solution and the temperature (and pressure).
• the wood-based composite After the digestion, the wood-based composite is completely dissolved.
• the chips and fibers as well as the coatings, solid wood parts, edge materials, metals and other non-chip and fiber components are detached from one another and can be sorted by sieving, air separation, a combination of both, or a new separation process, in particular ⁇ in particular, the chip and fiber fraction can be easily separated, since the chips or fibers are much smaller than, for example, the coatings, which are still the size of the pre-broken wood materials.
• the chips and fibers After digestion, the chips and fibers have a moisture content that corresponds to that of fresh forest wood or even lies below it.
• the increased temperature of the chips after digestion has an advantageous effect on their drying.
• the recovered chip material can be separated in the usual way or also dried with fresh chips or fibers. Chip and fiber boards can be produced from the recovered chips and fibers without the addition of fresh chips or fibers with unmodified commercially available binders, which have the same or even better properties than the starting material. This applies to both the technological properties and the formaldehyde emission.
• An absorption of 80% of the weight of the wood-based materials in impregnation solution is particularly favorable for a particularly fast and complete digestion.
• the absorption of the impregnation solution can be temperature (ambient temperature) and normal pressure.
• the absorption can be accelerated, for example, by a vacuum treatment preceding the impregnation and / or a pressure swing treatment and / or a temperature increase in the impregnation solution and / or heating of the digestion material.
• the size of the wood materials to be broken down is advantageously in the range of an average edge length of at least 10 to 20 cm, which is achieved by a slowly rotating, commercially available primary crusher.
• This size contributes to the chips and fibers being only slightly damaged. Only a few chips and fibers are damaged in the edge area, since the material breaks here mainly in the glue joint due to the special, slowly rotating roller of the primary crusher.
• the coatings and other non-chip and fiber components are changed only slightly in size, so that they can be easily separated after digestion, since they are then much larger than the chips or fibers.
• the use of such large pieces of wood material is possible because the impregnation treatment precedes the material to such an extent that it is permeated with impregnation solution everywhere and so chemical and hydrolytic destruction of the binder can take place everywhere due to the action of heat.
• the use of the impregnation solution opens up numerous possibilities for controlling the digestion and especially the digestion result.
• the chips and fibers can even be coated with the composition of the impregnation solution, ie, due to the impregnation and / or the digestion, they can have better chemical and physical properties than fresh chips.
• chipboard and medium-density fibreboard from old furniture in particular have relatively high formaldehyde emissions and contents, it makes sense to add urea, ammonia or urea or ammonia which release or other formaldehyde-binding, formaldehyde-inhibiting or formaldehyde-destroying chemicals to the impregnation solution.
• the formaldehyde concentration released in the waste air and drying air after digestion is reduced or avoided entirely.
• the addition of acids also has an advantageous effect if the chips or fibers thus recovered are used to produce materials onto which coatings are applied which have an acid-curing adhesive system.
• the adhesive system could be simplified and the application of the coating would also be accelerated.
• the digestion process is also accelerated by adding acid to the impregnation solution.
• the addition of oxidizing or reducing agents is also advantageous. This can on the one hand destroy formaldehyde released, on the other hand z. B. by the addition of peroxides urea can be reactivated to a certain extent.
• Another advantageous embodiment with regard to the composition of the impregnation solution is also the addition of binders such as. B. urea-formaldehyde resins or binder additives such. B.
• paraffins for impregnation solution This has a positive effect on the reduction in formaldehyde or on the subsequent swelling and water absorption of the secondary chips and fibers, and further gluing of the recovered chips and fibers after digestion can be dispensed with in whole or in part. In addition, the chips and fibers do not need to be dried as much for further processing into plates. If the recovered chips are to be processed into fibers for the manufacture of fiberboard, the addition of lignin-softening chemicals such as methanol, sulfites or ammonia is sensible in order to save energy in the later fiber production.
• a standard impregnation solution will contain approx. 0.5 to 3% urea, and approx. 0.1 to 1% ammonia or approx. 0.5% sodium hydroxide solution (dissolved in water). Due to the chemicals contained in the impregnation solution, no wood digestion (delignification) is brought about as in the production of cellulose.
• the digestion can also be influenced positively by adding chemicals to the digestion container during the digestion. So z. B. formaldehyde released by gassing ozone.
• the digestion is carried out with a controlled temperature profile. This can be such that the temperature is brought to a higher temperature level at the beginning of the digestion and there is a falling temperature towards the end of the digestion. Another, non-constant temperature profile is also possible.
• Old furniture, production remnants and scrap which contain chipboard and / or MDF or other wood materials, are broken into pieces with an edge length of 10 to 20 cm by means of a commercially available primary crusher (e.g. primary crusher from Pallmann or Maier).
• primary crusher e.g. primary crusher from Pallmann or Maier
• an optimum bulk density mass per volume
• the chips and fibers as well as the coatings and edge materials are only mechanically damaged to a small extent.
• Metal, plastic and solid wood parts do not have to be separated.
• Chipboard and MDF or other wood materials can be broken down separately or mixed.
• the pre-broken wood material parts are filled into a standing or rotating digestion / pressure vessel.
• a bulk density of about 350 to 400 kg / m 3 is achieved .
• the pressure vessel is closed and evacuated, so that a negative pressure of 150 to 200 mbar (absolutely) sets.
• the length of time until this vacuum is set depends on the technology used.
• the impregnation solution now added can penetrate the wood-based materials in a short time. This penetration time is about 5 to 15 minutes with chipboard and depends on the type of wood material, the negative pressure, the composition of the impregnation solution and its temperature.
• the impregnation solution consists of water, urea and sodium hydroxide solution.
• the wood material pieces are exposed to this solution until they have absorbed at least 50% of their own weight corresponding to a liquor ratio (ratio of wood materials to impregnation solution after the impregnation process has ended) of 1: 0.5.
• a liquor ratio ratio of wood materials to impregnation solution after the impregnation process has ended
• the digestion container is then closed again and heated to 110 ° C. for about 20 minutes. The heating takes place in a relatively short time due to the free spaces between the plate pieces. After this treatment, the chips or fibers are again in their original geometric shape.
• the coatings and edge materials as well as other undesired constituents have been removed and can be separated from the chip or fiber fraction by a subsequent screening or air separation or a combination of both.
• the residue can be sorted further, e.g. B. in Vollhoiz, plastic and metal parts. These can be processed further, used thermally to generate electricity or energy or disposed of in some other way.
• Metals can e.g. B. separated by magnets or metal detectors. Plastics and wooden parts are sorted and separated by NIR spectroscopic or other methods.
• Example 1 the digestion material and impregnation solution are already filled in the desired liquor ratio into a rotating digestion tank or a digestion tank equipped with a stirrer or mixer.
• D ' ⁇ .- means that there is a maximum of as much impregnation solution in the digestion tank as the digestion material can hold.
• the impregnation solution is mixed and evenly taken up by rotating the digestion tank or the agitator or mixer.
• the digestion container can be heated from the beginning, ie immediately after being closed.
• the impregnation takes place in a different container than the digestion container and the finished impregnated wood material pieces are filled into the digestion container so that the temperature can be applied directly.
• the impregnation solution is at a temperature higher than ambient, preferably 60 to 80 ° C.
• the impregnating solution contains formaldehyde-binding, formaldehyde-inhibiting or formaldehyde-destroying chemicals, such as e.g. Urea ammonia or urea or ammonia-releasing substances are added.
• impregnating solution bases such.
• Tables 1 and 2 provide an overview of the properties of boards made from recovered chip material. Show it:
• Table Properties of a laboratory chipboard made from recovered chip material, the furniture chipboard (production 1993) from which the chips were recovered (after the coating had been removed) and a laboratory chipboard made from chipboard of the furniture chipboard manufacturer was produced.
• Fig. 1 a plant for the digestion of chipboard and wood material residues according to the invention is shown schematically.
• the process sequence is shown schematically in FIG.
• Wood material remnants are placed on a primary crusher 2 by a wheel loader 1 or a gripping excavator or another suitable device.
• the pre-crusher 2 breaks the wood materials into flat pieces with an edge length of on average 10 to 20 cm.
• the pre-broken material is then conveyed into the digestion container 3 via a suitable conveying device 17.
• the digestion container 3 also has the function of an impregnation container. After the digestion container 3 is filled, it is closed airtight. The air contained in the digestion tank 3 and the wood materials is sucked off via a vacuum pump 9 until a negative pressure of about 150 to 200 mbar (absolute) has been reached.
• the impregnation solution is now fed from the preparation container 4 for impregnation solution via a line 15 into the digestion container 3 until the wood materials are completely covered by the latter.
• Normal pressure is now set again in the digestion tank 3. Overpressure could also be applied to accelerate the penetration of the impregnation solution. Impregnation at normal pressure is also possible.
• the preparation container 4 for the impregnation solution has an agitator 5 and a feed for chemicals 6 and a feed line for water 7.
• the excess impregnation solution is drained from the digestion tank 3 back into the preparation tank 4 via a line 10.
• the digestion container 3 is closed again in a pressure-tight manner and is now heated by means of a heat source 8 via the outer surface or by direct supply of heat by hot air, steam or another gaseous heat transfer medium. For example, a temperature of 110 ° C. is produced for 20 minutes in the digestion tank 3.
• the heat supply is then ended and the digestion tank 3 is emptied by a discharge device 16.
• the digestion container could also be emptied through an opening in the lower region which extends over the entire width.
• the digested material is fed into a silo 11 or another suitable storage container. From there it is continuously fed to a screening machine 12.
• chips or fibers are separated from coatings, solid wood parts, edge materials and other non-chip components.
• the separated chips or fibers are now fed to further processing 14.
• the separated other constituents can now be sorted further or compacted by means of a press 13 in order to reduce the volume.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Wood Science & Technology (AREA)
• Forests & Forestry (AREA)
• Dry Formation Of Fiberboard And The Like (AREA)
• Chemical And Physical Treatments For Wood And The Like (AREA)
• Debarking, Splitting, And Disintegration Of Timber (AREA)
• Processing Of Solid Wastes (AREA)

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• 1995
  • 1995-03-14 DE DE59500559T patent/DE59500559D1/de not_active Expired - Lifetime
  • 1995-03-14 CA CA002162894A patent/CA2162894C/fr not_active Expired - Fee Related
  • 1995-03-14 JP JP52378295A patent/JP3609414B2/ja not_active Expired - Fee Related
  • 1995-03-14 DK DK95913030T patent/DK0697941T4/da active
  • 1995-03-14 AT AT95913030T patent/ATE157298T1/de active
  • 1995-03-14 US US08/553,245 patent/US5804035A/en not_active Expired - Fee Related
  • 1995-03-14 ES ES95913030T patent/ES2107311T5/es not_active Expired - Lifetime
  • 1995-03-14 KR KR1019950705107A patent/KR100353308B1/ko not_active Expired - Fee Related
  • 1995-03-14 DE DE19509152A patent/DE19509152A1/de not_active Withdrawn
  • 1995-03-14 WO PCT/DE1995/000360 patent/WO1995024998A1/fr not_active Ceased
  • 1995-03-14 EP EP95913030A patent/EP0697941B2/fr not_active Expired - Lifetime
• 1997
  • 1997-10-20 GR GR970402731T patent/GR3025090T3/el unknown

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