Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B25/00—Details of general application not covered by group F26B21/00 or F26B23/00
  • F26B25/008—Seals, locks, e.g. gas barriers or air curtains, for drying enclosures
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B15/00—Machines or apparatus for drying objects with progressive movement; Machines or apparatus with progressive movement for drying batches of material in compact form
  • F26B15/10—Machines or apparatus for drying objects with progressive movement; Machines or apparatus with progressive movement for drying batches of material in compact form with movement in a path composed of one or more straight lines, e.g. compound, the movement being in alternate horizontal and vertical directions
  • F26B15/12—Machines or apparatus for drying objects with progressive movement; Machines or apparatus with progressive movement for drying batches of material in compact form with movement in a path composed of one or more straight lines, e.g. compound, the movement being in alternate horizontal and vertical directions the lines being all horizontal or slightly inclined
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B15/00—Machines or apparatus for drying objects with progressive movement; Machines or apparatus with progressive movement for drying batches of material in compact form
  • F26B15/10—Machines or apparatus for drying objects with progressive movement; Machines or apparatus with progressive movement for drying batches of material in compact form with movement in a path composed of one or more straight lines, e.g. compound, the movement being in alternate horizontal and vertical directions
  • F26B15/12—Machines or apparatus for drying objects with progressive movement; Machines or apparatus with progressive movement for drying batches of material in compact form with movement in a path composed of one or more straight lines, e.g. compound, the movement being in alternate horizontal and vertical directions the lines being all horizontal or slightly inclined
  • F26B15/122—Machines or apparatus for drying objects with progressive movement; Machines or apparatus with progressive movement for drying batches of material in compact form with movement in a path composed of one or more straight lines, e.g. compound, the movement being in alternate horizontal and vertical directions the lines being all horizontal or slightly inclined the objects or batches of material being carried by transversely moving rollers or rods which may rotate
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B21/00—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects
  • F26B21/02—Circulating air or gases in closed cycles, e.g. wholly within the drying enclosure
  • F26B21/04—Circulating air or gases in closed cycles, e.g. wholly within the drying enclosure partly outside the drying enclosure
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B3/00—Drying solid materials or objects by processes involving the application of heat
  • F26B3/02—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air
  • F26B3/04—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour circulating over or surrounding the materials or objects to be dried
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B2210/00—Drying processes and machines for solid objects characterised by the specific requirements of the drying good
  • F26B2210/14—Veneer, i.e. wood in thin sheets

Definitions

• the invention relates to a dryer for drying veneer panels according to the preamble of patent claim 1.
• the dryer according to the invention is intended in particular for drying veneer panels; However, the dryer according to the invention can also be used for drying any board such as hardboard, plywood or wallboard and the like.
• the term "veneers” is always used below; however, all the other boards mentioned above can also be dried by means of the veneer dryer instead of the veneers.
• the veneers Before the veneers are brought into the veneer dryer, they are first transported to a drying line as a stack with the help of forklifts after peeling.
• the veneers are separated at a loading device of the veneer dryer, placed on transport rollers and distributed to different floors with the help of a swiveling device, for example.
• the individual veneers are then transported into and through the dryer by chain-driven rollers.
• a screen belt can also be used instead of rollers.
• the dryer is divided into sections or zones along its length.
• Each of the sections has its own heating - usually a thermal oil or steam-heated register - as well as a circulating air fan.
• heated circulating air for drying the veneers is distributed over the individual levels and across the width of the transport rollers and, after passing through the nozzles, flows out of the box onto the veneers, whereby impingement drying of the veneers is achieved.
• the veneers dried in this way leave the dryer at the dryer outlet.
• Such a veneer dryer is known, for example, from DE 34 05 754 A1 or from WO 2005/047793 A1.
• the necessary fresh air enters the dryer via a dryer inlet and outlet;
• the dryer has openings in its end walls for the inlet and outlet of the veneers and the means of transport.
• Some dryers still have additional lateral fresh air connections.
• dryers that have so-called “sealing fields" at the outlet and inlet. These are partitioned off areas where occasionally escaping vapors can be extracted with the help of one or more fans.
• a controller is to be provided in order to keep the pressure within an outlet-side cooling section of a veneer dryer at a level that is greater than the pressure in the upstream drying chamber.
• Operating the cooling section at a slightly higher pressure is intended to prevent leakage of exhaust gases from the drying chamber into the cooling section, using automatic control to maintain the required pressure difference between the cooling section and the drying chamber pressure.
• the dryer known from GB 340 510 A is not equipped with nozzle boxes, but has a single chamber which extends over the entire length of the drying device of the dryer and in which there is a longitudinal air flow.
• a positive static pressure inside the dryer with respect to atmospheric pressure while at the inlet end of the dryer there will be a negative static pressure.
• the overpressure there is a risk at the outlet end that vapors and wood ingredients will escape from the dryer.
• the condensate can also contain organic acids. In areas of the dryer where overpressure prevails, these can penetrate the insulation through leaks in the inner skin and damage the metal outer skin of the dryer and the support structure through condensation and corrosion. The latter can corrode in such a way as a result of constant exposure to such acidic and resinous vapors and vapors that it is even necessary to shut down the dryer.
• the condensed substances form combustible deposits on the walls of the dryer or on parts inside, which can catch fire. This is a well-known problem, particularly at the dryer outlet, where it often leads to fires. However, the cooling fields and the chimneys there are also affected if vapors from the dryer get there and condense there.
• a dryer manufacturer makes the outer skin of its dryers from stainless steel; Apparently, this is intended to mitigate the corrosion caused by condensing substances in the wood.
• stainless steel results in considerable additional costs; moreover, this measure only affects the outer skin of the dryer.
• the object of the invention is therefore to provide a dryer which does not have the disadvantages of the prior art described above.
• the dryer is operated completely with the exception of the sealing sections that are preferably attached at the inlet and at the outlet, which is generated in each zone via at least one exhaust air fan. Due to the negative pressure then acting everywhere, dryer air can no longer escape to the outside and lead to the problems described there. Rather, the dryer air is sucked out of the dryer for each zone and preferably fed to a filter system before the air is released into the open air.
• the negative pressure is then, for example, approx. - 500 to - 800 Pa, while in veneer dryers according to the prior art, values of around -50 to 0 Pa are usual for the sections of the drying room and in places even overpressures of 200 to 800 Pa are possible; at these points, drying gases can escape from the dryer in the event of leaks in dryers according to the prior art and lead to the problems described above.
• the dryer is equipped with a special, heated sealing chamber as a sealing section, at least at the outlet.
• a sealing section can also be provided at the entrance.
• the negative pressure can preferably be set individually for each section and determined by the extraction capacity of the respective fan.
• a pressure drop between the individual sections of the dryer is avoided, with at most the sections on the inlet and outlet sides being operated at lower absolute pressures than the sections between them.
• the sealing section which is provided in particular at the outlet of the dryer, but can also be used on the inlet side and is intended as a heated sealing chamber, is preferably not vented, as is usual with conventional dryers, but is subjected to hot air (100 °C to 200 °C) via a fan and a heating device .
• the sealing chamber is operated with a slight overpressure or with a lower vacuum to a downstream cooling section in the conveying direction. This prevents colder cooling air from lowering the air temperature in the chamber.
• sealing chamber as a sealing section at the dryer inlet is also advantageous if the occurrence of wood constituents is to be expected at this point due to the climate control.
• nozzle boxes are preferably used for this purpose, as are generally used in dryers, as is known, for example, from WO 03/025484 A1.
• the sealing of each section towards the outlet of the dried veneers is constructed as follows: by installing a chain seal to minimize the air flow through the front opening for the transport chains ; by a brush seal, e.g. with a fabric insert between the first or last transport roller and the end walls of the dryer, and by closable openings, e.g. by adjustable flaps, or another closable opening in the end and/or side walls of the sections of the dryer in order to To be able to set the climate in the dryer in a targeted manner.
• the hot air applied sealing panel and the chain seal are particularly advantageous elements of the present invention.
• Fig. 1 is a schematic plan view of an inventive
• Fig. 2 is a section with a variety of nozzle boxes for drying
• Fig. 3a, b seals for sealing transport chains on the end walls of the sections and 4a, b the transport of the veneers in the area of the end faces of the sections and seals.
• a veneer dryer 1 (FIG. 1) has, for example, a conveyor device that extends over the entire length of the drying system shown in FIG.
• the flow direction is illustrated by an arrow A.
• a plurality of sections 3 are arranged one behind the other in the direction of passage of the arrow A, starting behind an entry zone 2, for example up to twenty sections, all of which are operated at substantially the same temperature; behind a section 4 follows a sealing field 5, which is operated at a slight overpressure, for example 10 to 30 Pa above normal pressure or ambient air pressure, and a cooling area 7, which consists of three sections 8.
• the number of sections 3, 4 is usually between five and twenty-five.
• Each of the sections 3 to 8 has its own housing.
• the sections 3, 4 each have partitions 9, via which they connect to one another, and have, for example, 2 to 2.5 m in length.
• the pressure inside is significantly lower than the ambient normal air pressure, as stated above, in order to prevent vapors, solvent vapors and the like from evaporating and particles condensing therefrom from settling out of the veneers.
• Each section 3, 4, 5 is equipped with or is connected to a device for generating dry air.
• the sections 3, 4 each have a circulating air fan 10 (Fig. 1, 2) for generating a
• each section 3, 4 is provided with a device for discharging the heated air saturated with moisture and solvents from section 3, 4, the vapors.
• This device is either an exhaust air fan assigned to each individual section 3, 4 or a central exhaust air and extraction system, through each section 3, 4 individually or at least a plurality of sections 3, 4 combined into groups, vented and the vapors extracted.
• FIG. 1 According to the embodiment shown in FIG. 1, three groups of sections 3, 4 arranged one behind the other are combined, the vapors of which are discharged in groups together via lines 12, 13 and 14 to a central exhaust air valve 15 and from there to a chimney 16.
• Each of the lines 12 to 14 is equipped with a throttle valve 17 in order to be able to control or regulate the amount of air sucked off.
• the sealing panel 5 is also connected to a heating device 18, through which warm air supplied via an air supply valve 19 is introduced into the sealing panel 5 under slight overpressure.
• Three cooling zones 20 are arranged downstream of the sealing field 5 .
• each section 3, 4 is equipped with its own exhaust air fan or other means for extracting vapors, which is designed in a manner known to those skilled in the art such that vapors are extracted over the length of all sections in accordance with the desired drying profile.
• each of the sections 3, 4 air flows from a circulating air fan 10 (Fig. 2), the flow direction of which is indicated by an arrow B, to the heating device 11 and is heated there.
• the air is guided into a pressure chamber 21 by the heating device 11 .
• the pressure chamber 21 serves to evenly distribute the air to the individual floors of a drying room 23 equipped with nozzle boxes 22.
• the air is pressed into the nozzle boxes 22, from which it is discharged via perforated nozzles which are arranged on the top and bottom of the nozzle boxes 22 , is blown perpendicularly onto the veneers, which pass through the drying space 23 between the nozzle boxes 22.
• the veneers lie on support rollers and are conveyed by means of a transport device (not explained in detail here) perpendicularly to the viewing plane of FIG.
• the idlers are between and slightly above the nozzle boxes 22 so that the drying air flows between the support rollers onto the veneers.
• the width of the pressure chamber 21 is larger in relation to the width of the suction chamber 25.
• a part of the drying air is extracted by means of the exhaust air chimney, so that the air pressure inside each of the sections 3, 4 can be reduced by up to 300 Pa. Simultaneously sucking off the substances contained in the drying air prevents them from being able to settle on the inner walls of sections 3, 4 or other places. In this way, any corrosion is avoided.
• the exhaust air is preferably sucked out of the suction space of the first fan 10 .
• the drying air extracted by the fan 25 is preferably passed through a filter system (not shown here) in which corrosive components of the drying air are selectively separated out so that the cleaned drying air can be fed back into the system where this is necessary.
• An adjustable flap 26 is arranged on the front side of those sections 3, 4 whose neighboring section should or can have a different negative pressure, in order to set the air pressure, the temperature and the moisture content and/or other parameters inside the respective section 3, 4 to be able to
• sealing plates 30 , 31 are provided, which are additionally equipped with elastic sealing lips or sealing lamellae 32 towards the chain 28 .
• pairs of rollers 33, 37 and 34, 38 (FIG. 4a) are used, between which the veneers 36 are passed.
• sealing devices 39, 40 are provided, which are each connected to the rollers 34 and 38 on the bottom and top of the veneers 36, respectively, cooperating to prevent the ingress of air into the respective one of the sections 4 to 6 through the open slot 41, the area of a front outer wall 42 being present.
• the sealing devices 39 comprise, for example, a large number of bristles 43 formed, for example, from animal hair or from metal wire, or lamellae, which consist, for example, of rubber or plastic.
• the bristles 43 are bundled together by a carrier 44 which is preferably attached to the inside of the outer wall 42 .
• the measures provided according to the invention to maintain a significant negative pressure in the sections 3, 4 can be implemented in all types of veneer driers, for example in the veneer drier already mentioned at the outset, which is disclosed in WO 03/025484 A1, or in the WO 2005/047793 A1 known veneer dryer, which discloses a loop-shaped guidance of the veneers between two conveyor belts.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Microbiology (AREA)
• Drying Of Solid Materials (AREA)
• Chemical And Physical Treatments For Wood And The Like (AREA)
• Veneer Processing And Manufacture Of Plywood (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=77104008

Family Applications (1)

Country Status (10)

Families Citing this family (1)

Family Cites Families (13)

• 2020
  • 2020-07-23 DE DE102020004455.7A patent/DE102020004455A1/de active Pending
• 2021
  • 2021-07-23 WO PCT/EP2021/025283 patent/WO2022017649A1/de active Application Filing
  • 2021-07-23 CN CN202180059524.6A patent/CN116157641A/zh active Pending
  • 2021-07-23 KR KR1020237006210A patent/KR20230043161A/ko unknown
  • 2021-07-23 US US18/017,230 patent/US20230296318A1/en active Pending
  • 2021-07-23 BR BR112023000912A patent/BR112023000912A2/pt unknown
  • 2021-07-23 CA CA3186483A patent/CA3186483A1/en active Pending
  • 2021-07-23 JP JP2023502971A patent/JP2023534486A/ja active Pending
  • 2021-07-23 EP EP21746643.2A patent/EP4185825A1/de active Pending
• 2023
  • 2023-01-20 CL CL2023000207A patent/CL2023000207A1/es unknown

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