Installation and method for producing a fiberboard

Abstract

The invention relates to a method for producing a fiberboard, in which method fibers and vapor form a first mixture which is supplied to a dryer (4) via a blow line (3). The invention is characterized in that, downstream of a refiner (2) and upstream of the entry into the dryer (4), further fibers are fed (5) into the blow line (3) according to a jet-pump principle. The invention also relates to an installation for producing a fiberboard and allows for an advantageous thorough mixing of the fibers and the further fibers.

Description

[0001] PLANT AND METHOD FOR PRODUCING A FIBERBOARD

[0002] The invention relates to a method for producing a fiberboard, in particular an MDF or HDF board, wherein lignocellulosic material, e.g. annual plants or wood, e.g. in the form of wood chips or wood sawdust, is cooked in a cooker and then defibrated into fibers in a refiner, wherein the fibers form a first mixture with steam, which exits the refiner at a first pressure and is fed to a dryer via a blow line. The invention also relates to a plant for producing a fiberboard, in particular an MDF or HDF board, comprising a cooker for cooking lignocellulosic fiber material, e.g. annual plants or wood, a refiner for defibrating the material into fibers, and a dryer for drying the fibers, wherein the refiner and the dryer are connected via a blow line.

[0003] In the production of fiberboard, particularly MDF boards, the fiber is blown out of the refiner together with steam as a first mixture at a first pressure in a dry process and fed through the blow line to the pressureless, i.e., atmospherically operated, dryer. Gluing of the fibers, particularly the wood fibers, takes place in the blow line. Such an arrangement is known to the person skilled in the art, for example, from EP3027806 A1, wherein a device for continuously discharging steam and a device for gluing are disclosed between the refiner and the dryer.

[0004] WO 2021176326 A1 discloses a method for producing chipboard, MDF or HDF boards, comprising the step of recycling chipboard, MDF and / or HDF board material, wherein the recycled chips and / or the recycled wood fibers are provided as starting material in a production process for chipboard, MDF or HDF boards - preferably in a dry production process.

[0005] WO 2023031763 A1 discloses a method for producing a wood fiberboard, wherein recycled wood fiberboards are converted into recycled wood fibers; and wherein the recycled wood fibers are fed as starting material to a production line—preferably in a dry production process—for the production of wood fiberboards. DE 202016101394 U1 discloses a jet pump for loosening and separating wood fibers, wherein the wood fibers are fed to the jet pump via a suction nozzle; and the wood fibers encounter a propellant at the outlet of a propellant nozzle arranged in the jet pump and are accelerated by this propellant.

[0006] There is an increasing aim to add additional fibers to the manufacturing process, e.g. fibers recycled from MDF or HDF boards or alternative fibers, e.g. from annual plants. One option is to mix the additional fibers with the fibers, particularly the fresh wood fibers, and feed the mixture as an input material into the conventional manufacturing process. Alternatively, the additional fibers can be added directly to the dryer. Both variants are based on the idea of ​​adding the additional fibers to the manufacturing process without pressure, which is very easy to implement. Conversely, direct addition into an overpressure area, e.g. the refiner, is not recommended, as this is technically and energetically difficult and a high pressure difference must be overcome.Adding the fibers under pressure can make things even more difficult, as the process may not be sufficiently pressure-tight, resulting in incorrect flow and even system downtime. Generally, these options do not provide adequate mixing of the fibers and the other fibers.

[0007] The aim of the invention is a system or process in which additional fibers can be safely and efficiently introduced into the process or system. A further aim of the invention is to achieve thorough mixing of the fibers and the additional fibers.

[0008] This is achieved according to the invention in that further fibers are fed into the blow line after the refiner and before entry into the dryer. The further fibers advantageously comprise chips and / or recycled fibers from recycled fiberboard, in particular particle board, MDF and / or HDF fiberboard, or alternative fibers, e.g. from annual plants, and are optimally suited for the re-production of a fiberboard, in particular an MDF or HDF board. The further fibers therefore advantageously also originate from a lignocellulosic fiber material. Surprisingly, it has been found that the introduction of further fibers according to the invention allows, on the one hand, very good mixing of the fibers and the other fibers, since high velocities and advantageous turbulence are formed in the blow line.On the other hand, the introduction of the additional fibers into the blow line is advantageous because the additional fibers are not degraded, shortened, etc. between the feed and the dryer and, in particular, are not boiled or ground.

[0009] A method has proven particularly advantageous in which the feed into the blow line takes place at a second pressure, and the second pressure is closer to the pressure of the dryer than to the first pressure. When the feed is made at a pressure closer to the pressure of the dryer, which is typically operated at atmospheric pressure, than to the first pressure, a large part of the first pressure has already been converted into kinetic energy, i.e. the flow of the first mixture of steam and fibers takes place at a correspondingly high speed. On the other hand, feeding in at such a second pressure is advantageous because the further fibers only have to be brought to a correspondingly lower pressure level compared to the first pressure. Advantageously, the first pressure is in particular between 4 and 10 bar g, the second pressure in particular a maximum of 3 bar g, preferably a maximum of 2.0 bar g and particularly preferably a maximum of 0.5 bar g.

[0010] According to the process according to the invention, the additional fibers form a second mixture with steam and / or air and are fed to the feed via a second blow line. The feeding of the second mixture results in particularly effective mixing with the first mixture and, in particular, in better mixing than if the additional fibers were fed in alone, e.g., through a rotary valve. The routing of the additional fibers in the separate second blow line also allows for separate addition of chemicals, explicitly tailored to the requirements of the additional fibers. At low second pressures, in particular up to a maximum of 0.2 bar g, it can be technically expedient to introduce the second mixture as a mixture of additional fibers and air.

[0011] According to the invention, the second mixture is fed in according to a jet pump principle, with the first mixture being fed to a mixing chamber as the driving medium and the second mixture as the suction medium. Surprisingly, the momentum of the first mixture acting as the driving medium in a mixing chamber of a jet pump can be used to draw the second mixture into the mixing chamber as the suction medium. The first mixture of fibers and steam is fed to the mixing chamber via the blow line, and the second mixture of further fibers and steam and / or air is fed to the mixing chamber via the second blow line. This not only achieves energy-efficient feeding, but also allows the mixing chamber of the jet pump arrangement to ensure excellent mixing of the first and second mixtures.

[0012] In a first, particularly advantageous embodiment of the method, the pressure of the second mixture is increased before feeding via a pressure increasing means, wherein the mixture of further fibers and steam and / or air is fed to the pressure increasing means.

[0013] In an alternative, advantageous embodiment of the method, the pressure of the steam and / or the air is increased via a pressure increasing means before the second mixture is formed, then the further fibers are mixed into the steam and / or the air and the second mixture is fed to the feed via the second blow line.

[0014] In both cases, the pressure booster can be passive, i.e., a mixer for admixing compressed air or pressurized steam, or active, i.e., a blower, fan, compressor, etc. The use of a blower or fan is recommended for a second mixture of additional fibers and air, although blowers or fans only allow a slight pressure increase of, in particular, a maximum of 0.2 bar g.

[0015] In both cases, the additional fibers can be added using a refiner, a fluffer, a rotary valve, a screw conveyor or similar.

[0016] A process is particularly advantageous in which the fibers are subjected to gluing after the refiner, and the additional fibers are fed in after the gluing of the fibers. This ensures a sufficient residence time of the fibers between the gluing and the dryer. To glue the fibers, the glue and air and / or steam are fed, in particular, to a two-component nozzle, thereby achieving advantageous atomization of the glue and efficient glue application. A process in which the additional fibers are glued before the feed is also advantageous. This is advantageous when the amount of the second mixture increases in relation to the amount of the first mixture. Gluing the fibers of the first mixture alone, in the sense of "over-gluing," is then no longer effective or does not meet the quality requirements. Gluing the fibers before the feed can, for example, take place in the second blow line, e.g.via the above-mentioned two-component nozzle, and allows for controlled and specific gluing of the other fibers in the second mixture. Alternatively, gluing can also take place during the addition of the other fibers to the second blow line, for example, in the refiner, fluffer, rotary valve, screw, or similar.

[0017] Equally advantageous is a process in which a portion of the steam is separated from the first mixture after the refiner and before the feed, and the remaining fibers are fed to the feed together with this portion of steam. After this separation, the first mixture then still comprises the fibers as well as a smaller amount of steam and is fed to the feed. The portion of steam separated from the blow line advantageously forms the second mixture together with the remaining fibers and is also fed to the feed via the second blow line. This allows for particularly efficient steam utilization.

[0018] The invention also relates to a plant for producing a fiberboard, in particular an MDF or HDF board, comprising a cooker for cooking lignocellulosic fiber material, e.g. annual plants or wood, e.g. in the form of wood chips or wood sawdust, a refiner for defibrating the fiber material into fibers, and a dryer for drying the fibers, wherein the refiner and the dryer are connected via a blow line. According to the invention, a feed means for feeding further fibers into the blow line is arranged between the refiner and the dryer. As already explained with regard to the method according to the invention, this arrangement allows efficient and very good mixing of the fibers and the other fibers, wherein degradation of the other fibers is avoided.

[0019] According to a favorable design of the plant, the feed means is arranged such that, during operation, the feed into the blow line occurs at a pressure of the blow line, and the pressure is closer to the dryer pressure than to the refiner pressure. This allows the first blend to be fed in at a correspondingly high velocity, with a comparatively small pressure increase being sufficient to feed the additional fibers.

[0020] In the inventive design of the system, the feed means is designed as a jet pump and comprises a mixing chamber, wherein the

[0021] The feed means is connected, on the one hand, to the refiner via the blow line and, on the other hand, to a second blow line designed to provide the additional fibers, and a first mixture of steam and fibers can be fed to the mixing chamber via the blow line as the driving medium, and a second mixture of steam and / or air and additional fibers can be fed as the suction medium via the second blow line. The momentum of the first mixture can thus be used to suck the second mixture into the mixing chamber of the jet pump, whereby efficient and excellent mixing of the first and second mixtures is achieved. The mixture later entering the dryer, comprising the fibers and the additional fibers, is virtually homogeneous.

[0022] A system is particularly advantageous in which the feed means is designed as a cyclone, the cyclone comprises an inlet, a dip tube, a conical region and an outlet, the blow line is connected to the dip tube or forms this and the first mixture can be fed to the feed means via the dip tube, the second mixture can be fed to the feed means via the inlet in a circumferential direction via the second blow line, the dip tube extends into the conical region and the mixing chamber is formed in the conical region between a dip tube outlet and the outlet. In this case, the dip tube can comprise a nozzle in the region of the dip tube outlet or be designed as a nozzle in order to further accelerate the first mixture before it enters the mixing chamber. The design of the feed means as a cyclone overall allows a simple integration of a jet pump into the blow line.By introducing the second mixture through the inlet and in the circumferential direction of the cyclone, the second mixture is evenly distributed over the circumference of the cyclone and, in particular, is fed evenly over the circumference to the mixing area, which in turn leads to very good mixing of the first mixture and the second mixture in the mixing area. According to a particularly advantageous embodiment, in order to regulate the amount of second mixture that can be introduced into the mixing chamber, the dip tube outlet can be positioned relative to the outlet, in particular along an axial direction of the mixing chamber or cyclone. The axial positioning of the dip tube outlet relative to the outlet or the conical area can be achieved by simply moving the dip tube or the blow line. In this way, the open annular cross-section between the conical area and the dip tube can be effectively influenced orand consequently the amount of second mixture introduced into the mixing chamber.

[0023] In a further embodiment of the system, a pressure booster is arranged on the second blow line to increase the pressure of the second mixture, or alternatively, the pressure booster is arranged upstream of a mixing device for the additional fibers on the second blow line. The pressure booster can be actively designed as a blower, fan, compressor, etc., or passively designed, i.e., as a mixer for mixing compressed air or pressurized steam. The additional fibers are mixed, for example, via a refiner, a fluffer, a rotary valve, a screw, or similar.

[0024] Equally advantageous is a system in which a first gluing device for gluing the fibers is arranged in the blow line after the refiner and before the feed means, and optionally a second gluing device for gluing the other fibers is arranged in the second blow line upstream of the feed means.

[0025] A particularly advantageous system is one in which a separator for separating a portion of the steam from the first mixture is arranged in the blow line between the refiner and the feed means. The separated portion of the steam can be fed to the feed means together with the additional fibers. Downstream of the separator, the first mixture still comprises the fibers and a smaller amount of steam and is fed to the feed means via the blow line. The portion of the steam separated from the blow line advantageously forms the second mixture together with the additional fibers and is fed to the feed means via the second blow line.

[0026] The invention will now be described by way of example with reference to the drawings.

[0027] Fig. 1 shows a machine for producing a fiberboard, in particular an MDF or HDF board, according to the prior art. Fig. 2 shows a machine according to the invention for producing a fiberboard, in particular an MDF or HDF board.

[0028] Fig. 3 shows a feed means according to the invention, wherein the feed means is designed as a cyclone.

[0029] Fig. 4 shows a further machine according to the invention for producing a fiberboard, in particular an MDF or HDF board.

[0030] Fig. 1 shows a machine for producing a fiberboard, in particular an MDF or HDF board, according to the prior art, wherein fiber material, in particular wood, is fed from a digester 1 to a refiner 2 for defibration of the fiber material. The defibrated fiber material forms a first mixture with steam in the refiner, which is fed from the refiner 2 via a blow line 3 to a dryer 4. It is also known from the prior art that the defibrated material, in particular wood, can be glued in the blow line between the refiner 2 and the dryer 4 (not shown).

[0031] Fig. 2 shows a machine according to the invention for producing a fiberboard, in particular an MDF or HDF board. Again, fiber material, in particular wood, e.g. in the form of wood chips or wood sawdust, is fed from a digester 1 to a refiner 2 for defibration of the fiber material. In the refiner, the defibrated fiber material forms a first mixture with steam, which exits from the refiner 2 at a first pressure and is fed to a dryer 4 via a blow line 3. According to the invention, further fibers are fed 5 into the blow line 3 via a feed means 11 downstream of the refiner 2 and upstream of the dryer 4. Advantageously, the feed 5 takes place closer to the dryer 4 than to the refiner 2, whereby the feed 5 takes place at a pressure that is closer to the pressure of the dryer 4 than to the refiner 2. Typically, the refiner pressure, i.e. the first pressure, is between 4 and 10 bar g.It is advantageous to position the feed means such that the further fibers are fed into the blow line at a pressure of maximum 3 bar g, preferably maximum 2.0 bar g, and particularly preferably maximum 0.5 bar g. The defibrated fiber material can be glued in a first gluing device 9, wherein the first gluing device 9 is arranged upstream of the feed 5 or between the refiner 2 and the feed means 11. The feed means 11 is connected to the refiner 2 and the dryer 4 via the blow line 3, wherein a second mixture of further fibers and steam and / or air is fed to the feed means 11 via a second blow line 6. The feed 5 in the feed means 11 advantageously takes place according to a jet pump principle, wherein the first mixture is fed to a mixing chamber 7 as the driving medium and the second mixture as the suction medium.The pressure of the second mixture can be increased before the feed 5 via a pressure increasing means 8. It is possible to pass the mixture of further fibers and steam and / or air through the pressure increasing means 8 and to increase the pressure of the mixture before the feed 5, whereby an admixture 18 of the further fibers to the steam and / or the air takes place upstream of the pressure increasing means 8. Alternatively, before the second mixture is formed, only the steam and / or the air can be passed through the pressure increasing means 8, with the admixture 18 of the further fibers to the steam and / or the air only taking place afterwards, i.e. downstream of the pressure increasing means 8. Optionally, a second gluing device 10 for gluing the further fibers in the second mixture is arranged on the second blow line 6.

[0032] Fig. 3 shows the feed means according to the invention, designed as a cyclone. The feed means 11 is configured as a cyclone 12 and forms a jet pump. The cyclone 12 comprises an inlet 13, a dip tube 14, a conical region 15, and an outlet 16. The blow line 3 is connected to the dip tube 14 or forms it, and the first mixture is fed to the cyclone 12 via the blow line 3 or the dip tube 14. The second mixture is fed to the cyclone 12 in a circumferential direction via the inlet 13. The axis of the dip tube essentially defines the axial direction of the cyclone. The circumferential direction of the cyclone is understood to be concentric to the axial direction. The dip tube 14 extends into the conical region 15 of the cyclone 12, wherein a mixing chamber 7 is formed in the conical region 15 between a dip tube outlet 17 and the outlet 16.Similar to a jet pump, the first mixture of steam and fibers is fed into the mixing chamber 7 as the propellant, and the second mixture of steam and / or air and additional fibers is fed into the mixing chamber 7 as the suction medium. Advantageously, the immersion tube outlet 17 is positionable relative to the outlet 16, particularly along the axial direction of the cyclone or the mixing chamber 7. This allows for control of the amount of the second mixture introduced into the mixing chamber 7.

[0033] Fig. 4 shows a further machine according to the invention for producing a fiberboard, which differs from the machine shown in Fig. 2 by the presence of a separator 19. The separator 19 is arranged in the blow line 3 between the refiner 2 and the feed means 11. The separator 19 is advantageously designed as a cyclone, wherein the first mixture is fed to the cyclone via an inlet and a portion of the steam of the first mixture is discharged via a dip tube of the cyclone. The separated portion of the steam is fed together with the other fibers to the feed means 11 via the second blow line 6, wherein the separated portion of the steam can be guided via a pressure increasing means 8 and the other fibers are fed to the steam upstream 18 or downstream 18 of the pressure increasing means 8. Optionally, the second mixture can be gluing before the feed 5.After the separator 19, the first mixture still contains the fibers and a correspondingly reduced amount of steam and is fed to the feed means 11 via the blow line 3. Gluing 9 can optionally be applied between the separator 19 and the feed means 11. The use of the separator 19 allows for particularly efficient use of the steam.

[0034] The present invention offers numerous advantages. It allows for effective—because thorough—mixing of the fibers with the other fibers. It also allows for efficient—because energetically advantageous—mixing, since the energy content or momentum of the first mixture is utilized in the blow line.

[0035] Reference symbol

[0036] 1 cooker

[0037] 2 refiners

[0038] 3 Blow line

[0039] 4 dryers

[0040] 5 Feed-in

[0041] 6 Second blow line

[0042] 7 Mixing chamber 8 Pressure booster

[0043] 9 Gluing of the fibers

[0044] 10 Gluing the other fibers

[0045] 11 Feed medium 12 Cyclone

[0046] 13 Entrance

[0047] 14 Immersion tube

[0048] 15 Conical area

[0049] 16 Outlet 17 Dip tube outlet

[0050] 18 Admixture

[0051] 19 separators

Claims

Patent claims 1 . Method for producing a fiberboard, in particular an MDF or HDF board, wherein lignocellulosic fiber material, e.g. annual plants or wood, e.g. in the form of wood chips or wood sawdust, is cooked in a cooker (1), then defibrated into fibers in a refiner (2), wherein the fibers form a first mixture with steam, which exits the refiner (2) at a first pressure and is fed to a dryer (4) via a blow line (3), wherein after the refiner (2) and before entering the dryer (4), further fibers are fed (5) into the blow line (3), the further fibers form a second mixture with steam and / or air and are fed to the feed (5) via a second blow line (6), characterized in that the feed (5) takes place according to a jet pump principle, wherein the first mixture is fed to a mixing chamber (7) as a driving medium and the second mixture as a suction medium.

2. Method according to claim 1, wherein the feed (5) into the blow line (3) takes place at a second pressure, and the second pressure is closer to the pressure of the dryer (4) than to the first pressure and wherein the first pressure is in particular between 4 and 10 bar g, the second pressure is in particular a maximum of 3 bar g, preferably a maximum of 2.0 bar g and particularly preferably a maximum of 0.5 bar g.

3. Method according to one of claims 1 to 2, wherein an increase in the pressure of the second mixture in the second blow line (6) takes place before the feed (5) via a pressure increasing means (8) or alternatively before the formation of the second mixture the pressure of the steam and / or the air is increased via a pressure increasing means (8), then the further fibers are mixed with the steam and / or the air and the second mixture is fed to the feed (5) via the second blow line (6).

4. Method according to one of claims 1 to 3, wherein the fibers are subjected to gluing (9) after the refiner (2) and the feeding (5) of the further fibers takes place after the gluing (9) of the fibers, wherein optionally a gluing (10) of the further fibers takes place before the feeding (5).

5. A method according to any one of claims 1 to 4, wherein after the refiner (2) and before the feed (5) from the first mixture a part of the steam is separated and the remaining fibers are fed together with the part of the steam into the feed.

6. Plant for producing a fiberboard, in particular an MDF or HDF board, comprising a cooker (1) for cooking lignocellulosic fiber material, e.g. annual plants or wood, e.g.in the form of wood chips or wood sawdust, a refiner (2) for defibrating the fiber material into fibers, a dryer (4) for drying the fibers, wherein the refiner (2) and the dryer (4) are connected via a blow line (3), wherein a feed means (11) for feeding (5) further fibers into the blow line (3) is arranged between the refiner (2) and the dryer (4), characterized in that the feed means (11) is designed as a jet pump and comprises a mixing chamber (7), the feed means (11) is connected on the one hand via the blow line (3) to the refiner (2) and on the other hand to a second blow line (6) designed to provide the further fibers, wherein a first mixture of steam and fibers as a driving medium is supplied to the mixing chamber (7) via the blow line (3) and a second mixture of steam and / or air and further fibers as a suction medium is supplied via the second blow line (6). can be supplied.

7. Plant according to claim 6, wherein the feed means (11) is arranged such that, in operation, the feed (5) into the blow line (3) takes place at a pressure of the blow line (3), and the pressure is closer to the pressure of the dryer (4) than to the pressure of the refiner (2).

8. Plant according to one of claims 6 to 7, wherein the feed means (11) is designed as a cyclone (12), the cyclone (12) comprises an inlet (13), a dip tube (14), a conical region (15) and an outlet (16), the blow line (3) is connected to the dip tube (14) or forms this and the first mixture can be fed to the feed means (11) via the dip tube (14), the second mixture can be fed to the feed means (11) in a circumferential direction via the inlet (13), the dip tube (14) extends into the conical region (15) and the mixing chamber (7) is formed in the conical region (15) between a dip tube outlet (17) and the outlet (16).

9. Plant according to claim 8, wherein for regulating the quantity of the second mixture that can be introduced into the mixing chamber (7), the immersion tube outlet (17) is arranged relative to the outlet (16), in particular along an axial direction of the mixing chamber (7).

10. Plant according to one of claims 6 to 9, wherein a pressure increasing means (8) for increasing the pressure of the second mixture is arranged on the second blow line (6) or alternatively the pressure increasing means (8) is arranged upstream of an admixture of the recycled fibers on the second blow line (6).

11. Plant according to one of claims 6 to 10, wherein after the refiner (2) and before the feed means (11) a first gluing device (9) for gluing the fibers in the blow line (3) and optionally in the second blow line (6) upstream of the feed means (11) a second gluing device (10) for gluing the further fibers is arranged.

12. Plant according to one of claims 6 to 11, wherein a separator (19) for separating a part of the steam of the first mixture is arranged in the blow line (3) between the refiner (2) and the feed means (11), wherein the separated part of the steam can be fed to the feed means together with the further fibers.

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