Method for finely screening waste wood-based materials

Abstract

The present disclosure relates to a method of recovering waste wood-based material, the method comprising: collecting waste wood-based material resulting from sawing and / or machining wood-based material; separating the waste wood-based material by particle size by sieving the waste wood-based material via at least one first sieve (3) to separate a first portion of the particles from the waste wood-based material without pre-grinding the waste wood-based material wherein the at least one first sieve has pores having a pore width of 3000 [mu] m or less; subsequently sieving the remaining portion of the waste wood-based material via at least one second sieve (4) to separate a second portion of the particles from the waste wood-based material wherein the at least one second sieve has pores having a pore width exceeding 50 [mu] m; and wherein a third portion of the particles is formed from the particles from the waste wood-based material passing through the at least one second screen.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to a method for fine screening and recycling of waste material resulting from machining and / or sawing of wood-based materials. Background Art

[0002] When wood-based products are produced, waste is generated, for example, in the form of sawdust and off-cut material. Production waste can be generated when machining wood-based materials, for example by cutting, milling, sanding, planing, etc. Production waste in the form of sawdust and / or removed wood or particles can result from all types of wood machining.

[0003] In the modern production of building panels, such as floor panels and furniture panels, waste material is generated when sawing the boards into individual panels, when sanding the surfaces, when machining bevels, tongues and grooves, etc. If floor panels or furniture panels are to be provided with a mechanical locking system for locking in the horizontal and vertical direction, several machining steps may be performed, such as cutting, milling, and finishing the surfaces to the desired shape.

[0004] To maintain a safe and healthy working environment, all material removed during the woodworking process (e.g. in the form of sawdust, wood particles, wood fibers, chips or large pieces) must be collected, for example by conveying it into a container via a suction hose. In certain circumstances, fine sawdust can cause a dust explosion.

[0005] Waste can be burned. However, it is desirable to recycle materials, particularly when producing products that include wood particles or wood fiber. Including waste in the production process when making new products is beneficial in many ways, including environmentally. Waste can replace virgin wood fiber or any other type of filler in production.

[0006] However, the wide particle size distribution in the waste (ranging from particles 50 μm or less in size to wood fibers 100 mm or more in length) has made it difficult to simply replace existing raw materials with the waste in the production process. One attempt has been to grind the waste into particles with a narrower particle size distribution in order to replace existing fillers in the production process. However, this grinding process is energy-intensive. In some processes, the waste is dried after grinding to reduce its moisture content and then sieved to the desired particle size distribution. This may be a common procedure when the material is sieved through finer holes (e.g., holes less than 400 μm) in a sieve element. Summary of the Invention

[0007] It is an object of at least embodiments of the present disclosure to provide improvements over the above-described techniques and known technologies.

[0008] According to a first aspect of the present disclosure, a method for finely screening waste wood-based materials is provided. The method may include:

[0009] Collection of waste wood-based materials resulting from sawing and / or machining of wood-based materials;

[0010] separating the waste wood-based material by particle size by screening the waste wood-based material through at least one first screening element to separate a first portion of particles from the waste wood-based material, wherein the at least one first screening element has holes having a hole width of 3000 μm or less;

[0011] subsequently screening the remaining portion of the waste wood-based material by screening via at least one second screening element to separate a second portion of particles from the waste wood-based material, wherein the at least one second screening element has pores with a pore width exceeding 50 μm, and

[0012] Wherein a third portion of particles is formed from particles from waste wood based material passing through said at least one second screening element.

[0013] Fine screening in the present disclosure refers to fine screening by removing undesirable particles from the waste wood-based material. These particles may be undesirable due to their size, e.g., to remove coarse particles and / or fine particles, and / or undesirable due to their shape, e.g., to remove particles having an undesirable shape.

[0014] Such fine screening at least improves the processability and handling of the remaining waste wood-based material, for example in a subsequent process for recycling the waste wood-based material.

[0015] The first portion of particles is formed by particles that have not passed through the at least one first screening element.

[0016] The second portion of particles is formed by particles that have not passed through the at least one second screening element.

[0017] The third portion of particles is formed by particles that pass through the at least one first sifting element and the at least one second sifting element.

[0018] The pore width of at least one first sieve element may exceed the pore width of at least one second sieve element.

[0019] The method may be performed in a single screening device comprising the at least one screening element and the at least one second screening element.

[0020] The waste wood-based material is screened by the at least one screening element and the at least second screening element without intermediate processes such as drying.

[0021] When discussing drying herein, drying is defined or considered to be an active process / processing step, rather than a side effect of another process step such as grinding.

[0022] Separation of the waste wood based material may be performed without prior grinding. Screening allows providing particles having a desired particle size distribution from the waste wood based material without the need to grind all of the waste wood based material to the desired particle size distribution.

[0023] The waste wood based material may not be ground prior to screening.The waste wood based material may not be machined prior to screening.

[0024] The sieving of the waste wood-based material may be performed without grinding the waste wood-based material in advance. The sieving of the waste wood-based material may be performed without drying the waste wood-based material in advance.

[0025] The size of the fibers and / or particles forming the waste wood-based material remains substantially unaffected prior to screening.

[0026] The size of the fibers and / or particles forming the waste wood-based material remains substantially unaffected during the separation process.

[0027] The first portion of the granules may be a coarse fraction of the granules. Another term that can be used for the first portion of the granules is an oversize fraction of the granules. The second portion of the granules may be a useful fraction of the granules. Another term that can be used for the second portion of the granules is a useful fraction of the granules. The third portion of the granules may be a fine fraction of the granules. Another term that can be used for the third portion of the granules is a dust fraction of the granules.

[0028] The second portion of particles can be used in a subsequent process for producing building panels, or can be used in a subsequent process to form a portion of a building panel. The second portion of particles can be used without further processing, such as grinding or drying. Thus, waste wood-based materials can be recycled into new products. This method is intended to remove coarse and / or fine particles that may be difficult to handle in subsequent processes.

[0029] Screening the remaining portion of the waste wood-based material refers to screening the waste wood-based material that has passed through the at least one first screening element. The waste wood-based material that has passed through the at least one first screening element is fed to the at least one second screening element, for example, by gravity. The waste wood-based material that has passed through the at least one first screening element and the at least one second screening element forms a third portion of particles.

[0030] Waste wood-based materials can be formed when wood-based materials are sawn, machined (e.g., planed, cut, milled, and finished). Waste wood-based materials can be in the form of sawdust, particles, and / or fibers. Wood-based materials can be wood-based boards, such as MDF, HDF, OSB, particle boards. Wood-based materials can include solid wood and / or wood veneer. Wood-based materials can contain components other than wood, such as binders, additives, fillers, such as organic and inorganic fillers, paper materials (e.g., in the case of laminates).

[0031] The second portion of particles from waste wood-based material can be used as raw material in a method for producing a building panel or a portion of a building panel. In the method for producing a building panel or a portion of a building panel, the second portion of particles from waste wood-based material can replace virgin raw material, such as virgin wood fibers or virgin wood particles.

[0032] The waste wood-based material may be screened without prior drying. The waste wood-based material may be undried before screening. The moisture content may be at least 3%. The moisture content may be defined as the mass before drying minus the mass after drying divided by the mass after drying.

[0033] The average particle size of the second portion of particles from the waste wood based material may be smaller than the average particle size of the first portion of particles.The average particle size of the second portion of particles from the waste wood based material may exceed the average particle size of the third portion of particles.

[0034] In the sieve analysis as described in the "Example 2: Method Description of Sieve Analysis" section of this disclosure, at least 60 wt.% of the particles of the second portion of particles from waste wood based material may have a size / particle size in the range of 100-400 μm.

[0035] In the sieve analysis as described in the "Example 2: Method Description of Sieve Analysis" section of this disclosure, at least 60 wt.% of the particles of the first portion of particles from waste wood-based material may have a particle size exceeding 400 μm.

[0036] As described in the sieve analysis of the “Example 2: Method Description of Sieve Analysis” section of this disclosure, at least 60 wt.% of the particles of the third portion of particles from waste wood-based material may have a particle size of less than 100 μm.

[0037] The hole width of the holes of the at least one second sieve member may be smaller than the hole width of the holes of the at least one first sieve member.

[0038] The at least one first screening element may include a group of first screening elements, wherein the number of screening elements in the group of first screening elements may be 1 to 3.

[0039] The at least one first screening element may be arranged at a non-zero angle relative to the horizontal. If a set of first screening elements is provided, the at least one first screening element may be arranged at a non-zero angle relative to the horizontal.

[0040] The at least second screening element may include a group of second screening elements, wherein the number of screening elements in the group of second screening elements may be 1 to 3.

[0041] The at least second screening element may be arranged at a non-zero angle relative to the horizontal.If a set of second screening elements is provided, at least one of the second screening elements may be arranged at a non-zero angle relative to the horizontal.

[0042] The aperture width of each screen in the first set of screens may exceed the aperture width of each screen in the second set of screens.

[0043] The at least one first sieve may have pores with a pore width in the range of 450 μm to 3000 μm. If the at least one first sieve comprises a group of first sieves, each first sieve may have pores with a pore width in the range of 450 μm to 3000 μm.

[0044] The at least one second sieve may have pores with a pore width in the range of 50 to 600 μm or 50 to 400 μm. If the at least one second sieve comprises a group of second sieves, each second sieve may have pores with a pore width in the range of 50 to 400 μm.

[0045] The at least one first sieve element or the sieve elements of the group of first sieve elements may have pores with a pore width in the range of 450 μm to 3000 μm. The at least one second sieve element or the sieve elements of the group of second sieve elements may have pores with a pore width in the range of 50 μm to 600 μm.

[0046] The pores of the at least one first sieve element or the sieve elements in the group of first sieve elements may be larger than the pores of the at least one second sieve element or the sieve elements in the group of second sieve elements. For example, if the pores of the second sieve element are 600 μm, the pores of the first sieve element are at least within the range of greater than 600 μm (excluding 600 μm) but less than or equal to 3000 μm.

[0047] At least one of the first and / or second screening elements may comprise a chain arranged on at least one of the first and / or second screening elements. If a set of first screening elements is provided, at least one of the first screening elements may comprise a chain. If a set of second screening elements is provided, at least one of the second screening elements may comprise a chain.

[0048] At least one of the first and / or second screening elements may be vibrating. If a set of first screening elements is provided, at least one of the first screening elements may be vibrating. If a set of second screening elements is provided, at least one of the second screening elements may be vibrating.

[0049] At least one of the first and / or second screening elements can be vibrated with a stroke of 1.5-8 mm, for example 2-4 mm or 7-8 mm. If a set of first screening elements is provided, at least one of the first screening elements can be vibrated with a stroke of 7-8 mm. If a set of second screening elements is provided, at least one of the second screening elements can be vibrated with a stroke of 7-8 mm.

[0050] The method may further comprise grinding a first portion of particles from the waste wood-based material after screening. The first portion of particles are oversized particles that may be ground to reduce the particle size.

[0051] After being ground, the first portion of the particles may be treated / processed according to the methods disclosed above.

[0052] After being ground, the first portion of the particles can be separated by sieving, for example, according to the methods disclosed above.

[0053] After being ground, the first portion of the particles may be mixed with waste wood-based material.

[0054] The method may further comprise compacting a third portion of the particles from the waste wood-based material into pellets after screening. The third portion of the particles is fine particles that can be compacted into pellet fuel.

[0055] The second portion of particles from waste wood based material may be used in a process for producing a building panel or board, or in a process for producing a part of a building panel or board.

[0056] The second portion of particles from waste wood based material may be material in a subsequent method step, for example in a step for producing a building panel or board, or in a step for producing a part of a building panel or board.

[0057] The method or a subsequent method may further comprise applying a binder and particles from the second portion of particles to a substrate; and applying heat and pressure to the particles, binder and substrate to form a building panel or a portion of a building panel.

[0058] The method or a subsequent method may further comprise applying a wood veneer layer over the binder and particles from the second portion of particles before applying the heat and pressure, wherein after applying the heat and pressure the particles, binder and wood veneer layer form a surface layer of the building panel.

[0059] According to a second aspect, there is provided a method for recycling waste wood-based material. The method comprises: applying particles of a second portion of the particles obtained by the method according to the first aspect and a binder to a substrate; and applying heat and pressure to the particles, binder and substrate to form a building panel or a portion of a building panel.

[0060] The method may further comprise applying a wood veneer layer over the particles and the binder before applying the heat and pressure, wherein after applying the heat and pressure, the particles, binder and wood veneer layer form a surface layer of the building panel.

[0061] According to a third aspect, there is provided a building panel comprising a surface layer arranged on a substrate, wherein the surface layer comprises a binder and particles from a second portion of particles of waste wood based material obtained from the method according to the first aspect.

[0062] The surface layer may include a wood veneer layer disposed on a sub-layer formed from particles from the second portion of particles and a binder. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The present disclosure will be described in more detail, by way of examples, with reference to the accompanying drawings, in which embodiments of the disclosure are shown.

[0064] Figure 1 A cross-sectional view of a screening device according to a first example is schematically shown.

[0065] Figure 2 A portion of an example screen is shown in greater detail.

[0066] Figure 3 A portion of an example screening element provided with a chain is shown.

[0067] Figure 4 A cross-sectional view of an example of a particle or fiber is shown.

[0068] Figure 5 A cross-sectional view of a screening device according to a second example is schematically shown.

[0069] Figure 6 An example of a method of producing building panels is shown.

[0070] Figure 7 An embodiment of a process for separating waste wood-based materials is shown. DETAILED DESCRIPTION

[0071] Figure 1 A cross-sectional view of an example of a screening device 1 is shown. Figure 1 The screening device or screener comprises a first screening element 3 and a second screening element 4 .

[0072] The first screening element 3 is at a non-zero angle relative to the horizontal plane HP. The first screening element 3 may be at an angle of 5-60° relative to the horizontal plane HP. The first screening element 3 may have a planar extension that may extend in a plane at a non-zero angle relative to the horizontal plane HP. The first screening element 3 may be at an angle of less than 90° relative to the horizontal plane HP, for example, not vertical.

[0073] The second screening element 4 is at a non-zero angle relative to the horizontal plane HP. The second screening element 4 can be at an angle of 5-60° relative to the horizontal plane HP. The second screening element 4 can have a planar extension that can extend in a plane at a non-zero angle relative to the horizontal plane HP. The second screening element 4 can be at an angle of less than 90° relative to the horizontal plane HP, for example, not vertical.

[0074] The first screening element 3 and the second screening element 4 may not be parallel.

[0075] The first screening element 3 and / or the second screening element 4 may be moved in a vibratory manner during the screening process.The first screening element 3 and the second screening element 4 may be connected to one or more vibrator motors 8 configured thereto.

[0076] The first sieve element 3 and / or the second sieve element 4 can be moved with a stroke of 1.5-8 mm, for example 2-4 mm or 7-8 mm.

[0077] The first screening element 3 and / or the second screening element 4 can be moved during screening, for example, by vibrating motion. The direction of movement of the first screening element 3 can be at a non-zero angle relative to the horizontal plane HP, for example, at an angle of 5-60° relative to the horizontal plane HP. The direction of movement of the second screening element 4 can be at a non-zero angle relative to the horizontal plane HP, for example, at an angle of 5-60° relative to the horizontal plane HP.

[0078] like Figure 3 As shown, the first screening element 3 and / or the second screening element 4 can be provided with one or more chains 9. Chains 9 can be arranged on the first screening element 3 and / or the second screening element 4. At least one end of chain 9 can be attached to at least one edge of a frame surrounding the first screening element 3 and / or the second screening element 4. Chains 9 are suitable for cleaning the screening elements 3 and 4 during screening due to the vibrating movement of the screening elements 3 and 4. This at least reduces the risk of so-called clogging.

[0079] The chain 9 may be made of metal, such as steel, or a polymer material, such as a thermoplastic material, for example polyamide.

[0080] Any of the screening elements, namely the first screening element 3 and the second screening element 4, can be Figure 2 The type shown in more detail in FIG. The screening element may also be referred to as a screen cloth. The screening element may be in the form of a mesh. The mesh may be formed from wires 11 such as metal wire or plastic wire. The metal wire may be made of stainless steel.

[0081] The openings between adjacent wires define apertures 12 or meshes. Apertures 12 may have a rectangular shape, such as a substantially square shape. Thus, for a square aperture 12 with equal sides, all sides have the same aperture width AW. In the case of apertures that do not have equal sides, the aperture width AW is defined in the width direction, and the aperture length is defined in the length direction, where the aperture length exceeds the aperture width.

[0082] The holes 12 may have a uniform / consistent hole width. In various other examples, the hole widths between the holes 12 may be different.

[0083] The screening device 1 is used in the process of separating waste wood-based materials according to particle size. The waste wood-based materials may be formed when sawing and / or machining the wood-based materials. Machining may include planing, cutting, milling, and finishing of the wood-based materials. The waste wood-based materials formed by machining and sawing may have a variety of sizes, ranging from sawdust to larger particles and / or fibers. The larger particles and fibers may have a size of several millimeters, for example, 1-100 mm.

[0084] When producing building panels, such as floor panels, wall panels and furniture panels, waste can be generated when dividing a board by sawing it into individual boards and when machining the mechanical locking system by sawing, cutting, milling and finishing its elements, such as locking surfaces, grooves, tongues, recesses, etc. Even more waste can be generated when bevels, grooves and decorative elements are machined in the building panels.

[0085] Waste is formed by material that has been machined during the production process. In the case of building panels, the material is typically wood-based. The wood-based material can be a wood-based board, such as MDF, HDF, OSB, particle board. Boards such as MDF, HDF, OSB, particle board are often used as boards in building panels. Such boards can also be referred to as the core of the building panel. When forming a mechanical locking system, the board can be machined. In various other examples, the wood-based material can include solid wood and / or wood veneer, such as building panels or boards that are machined to have a solid wood surface or a wood veneer surface. The wood-based material can include components other than wood, such as binders, additives or paper materials, as in the case of machined laminates. Waste formed by machined boards such as MDF, HDF, OSB, particle board can also contain binders.

[0086] Machining refers to any process other than crushing and grinding of waste wood-based materials.

[0087] For example, waste wood-based materials must be removed from manufacturing facilities due to health and safety concerns.

[0088] Instead of burning the waste wood based material, the waste wood based material can be recycled into the production process. The waste wood based material can be used as raw material in a process for producing a building panel or board or a part of a building panel or board. Due to the changes in size, grinding of waste wood based material has previously been used to reduce the size changes of the waste wood based material. However, grinding is an energy consuming process, wherein the major part of the energy consumed is not used to break the bonds to achieve the required size reduction. The energy used to break the bonds to achieve the required size reduction is very small (<1%) relative to the total energy input in the grinding process, as described in the following document: Handbook of Powder and Technology, 2nd edition, Chapman and Hall, edited by Muhammad E. Fayed and Lambert Otten, 1997. Therefore, grinding particles to achieve size reduction is inefficient considering the energy consumption.

[0089] In the present disclosure, the waste wood-based materials are separated by size by screening. The screening of the waste wood-based materials can be performed without pre-grinding the waste wood-based materials. The screening of the waste wood-based materials can be performed without pre-drying the waste wood-based materials.

[0090] However, it is not excluded that the material may have been dried before becoming waste and / or that the material may have been ground before becoming waste. For example, wood boards may have been dried and then formed into the core of a building panel. As another example, the fibers forming a wood fiber substrate, such as HDF, may have been ground before forming the wood fiber substrate. However, machining building panels such as wood boards or wood fiber substrates may generate waste wood-based materials that can be screened according to the present disclosure without prior drying and / or prior grinding.

[0091] Sizing is performed to improve the processability of the material, thereby allowing the waste wood-based material to be recycled in a process for producing building panels or parts of building panels and allowing the waste wood-based material to be recycled with a high yield. Improved processability is intended to mean a higher yield per unit of input material, for example by reducing the number of production stops.

[0092] It is known that large differences in particle size can lead to difficulties during production. Branched particles, curved particles and / or irregularly shaped particles can also lead to processability problems during production.

[0093] In addition, large particles, with Figure 4 Particles that are elongated and / or branched, curved, irregularly shaped, or otherwise have high surface area may be difficult to process and handle due to mechanical interlocking and steric hindrance. Mechanical interconnection and steric hindrance of particles may lead to bridging in production equipment, resulting in maintenance stops and reduced material yield.

[0094] Large particles, particles with elongated shapes and / or branched, curved, irregular shapes or otherwise having high surface area have difficulty passing through screens, even if the screen hole width exceeds the particle size due to their irregular shape.

[0095] Fine particles can cause blockages in production equipment. Combined problems related to bridging and blockages can also occur, with bridging leading to blockages.

[0096] By screening the particles into at least three different fractions, the above problems are at least reduced, thereby allowing the recycling of waste wood-based materials in an efficient manner.

[0097] In the present disclosure, the waste wood-based material may be gathered or collected while the wood-based material is being machined. The waste wood-based material may be stored prior to further machining. The waste wood-based material may be from the same production site where the waste wood-based material will be used as a raw material, or may be from a different source.

[0098] like Figure 1 As shown, a batch of waste wood-based materials may be delivered to the inlet 2 of the screening device 1. The waste wood-based materials may be unprocessed before being separated in the screening device 1. The waste wood-based materials may not be dried before being separated in the screening device 1. When entering the screening device 1, the wood-based materials may have a moisture content of 3% or higher.

[0099] Waste wood-based material is fed to the first screening element 3. A portion of the wood-based material has a size that does not allow particles or fibers of the waste wood-based material to pass through the holes 12 of the first screening element 3. The portion of the waste wood-based material that does not pass through the holes 12 of the first screening element 3 forms a first portion of particles. The first portion of particles leaves the screening device 1 via the first outlet 5.

[0100] In one example, the first sieve 3 has a pore width AW of 3000 μm or less. The first sieve 3 may have a pore width AW in the range of 450 μm to 3000 μm.

[0101] A consequence of the non-zero angle of the first sifting element 3, or any sifting element in the present disclosure, relative to the horizontal plane is that particles that are able to pass through the holes in the first sifting element 3 have a particle size that is smaller than the hole width. Due to the inclination of the first sifting element 3, it is more likely that the actual holes through which particles can pass are smaller than if the first sifting element 3 were arranged parallel to the horizontal plane HP.

[0102] In the sieve analysis as described in the “Example 2: Method Description of Sieve Analysis” section of this disclosure, the first portion of particles, ie, at least 60% of the particles that do not pass through the first sieve 3 , may have a particle size exceeding 400 μm.

[0103] When particle 10 strikes first sieving element 3 or second sieving element 4, particle 10 can be oriented so that particle 10 can pass through sieving element, even if the length of particle 10 exceeds the size of hole 12. Particle 10 can be oriented so that its length direction is substantially perpendicular to the plane of sieving element. In this orientation, the maximum width of particle 10 determines whether particle 10 can pass through the hole of sieving element. Figure 4 Particles having an elongated shape are shown, with their length in the length direction L exceeding their width in the width direction W.

[0104] The first portion of particles may be collected in a container (not shown), for example downstream of the first outlet 5. Further processing of the first portion of particles will be described below. The first portion of particles may be considered to be an oversized portion of waste wood-based material.

[0105] The remaining portion of the waste wood-based material fed into the screening device 1 is fed to the second screening element 4. Figure 1 As shown, the remaining portion of the waste wood-based material falls by gravity onto the second screening element 4. The remaining portion of the waste wood-based material is formed by particles of the waste wood-based material that have passed through the first screening element 3.

[0106] A portion of the remaining portion of the waste wood-based material has a size that does not allow particles or fibers of the waste wood-based material to pass through the holes 12 of the second screening element 4. The portion of the waste wood-based material that does not pass through the holes 12 of the second screening element 4 forms a second portion of particles. The second portion of particles leaves the screening device 1 via the second outlet 6.

[0107] Second sieve element 4 has holes with a hole width AW that is smaller than the hole width AW of first sieve element 3 .

[0108] In one example, the second sieve 4 has a pore width AW of more than 50 μm, such as more than 100 μm, such as more than 150 μm. The second sieve 4 may have a pore width AW in the range of 50 μm to 450 μm, such as in the range of 150-400 μm.

[0109] As a result of the non-zero angle of the second sifting element 4, or any sifting element, relative to the horizontal plane HP, the particles that are able to pass through the holes in the second sifting element 4 have a particle size that is smaller than the width of the hole. Due to the inclination of the second sifting element 4, it is more likely that the actual holes that particles are able to pass through are smaller than if the second sifting element 4 were arranged parallel to the horizontal plane HP.

[0110] In the sieve analysis as described in the “Example 2: Method Description of Sieve Analysis” section of this disclosure, the second portion of the particles, i.e., at least 60% of the particles that have passed through the first sieve 3 but not the second sieve 4, may have a particle size in the range of 100-400 μm.

[0111] The second portion of particles may be collected in a container (not shown), for example downstream of the second outlet 6. Further processing of the second portion of particles will be described below. The second portion of particles may be considered as a useful portion of waste wood-based material.

[0112] The particles that pass through the second screening element 4 form a third portion of the particles. The third portion of the particles can be considered as a fine fraction of the particles.

[0113] In the sieve analysis as described in the “Example 2: Method Description of Sieve Analysis” section of this disclosure, the third portion of particles, ie, at least 60% of the particles having passed through the second sieve 4 , may have a particle size of less than 100 μm.

[0114] A third portion of the particles leaves the screening device via a third outlet 7, for example below the second screening element 4. The third portion of the particles may be collected in a container (not shown), for example downstream of the third outlet 7. Further processing of the third portion of the particles will be described below.

[0115] In another example of the screening device 1 ′, the first screening element comprises more than one first screening element, such as a group of first screening elements, and the second screening element comprises more than one second screening element, such as a group of second screening elements. Figure 5 Such a screening device 1 ′ is shown in FIG.

[0116] The above description with reference to the first sieve element 3 and the second sieve element 4 applies to at least one of the first sieve elements and at least one of the second sieve elements, respectively.

[0117] Figure 5 The screening device 1' shown in the example of FIG comprises a set of first screening elements and a set of second screening elements. The set of first screening elements comprises first screening elements 3a, 3b, 3c. The set of second screening elements comprises second screening elements 4a, 4b.

[0118] The hole width of the holes of the screen elements 3a, 3b, 3c of the first group of screen elements exceeds the hole width of the holes of the screen elements 4a, 4b of the second group of screen elements.

[0119] As previously referenced Figure 1 As described, the screening device 1 ′ may include an inlet 2 , a vibration motor 8 configured to vibrate the set of first screening elements 3 a , 3 b , 3 c and the set of second screening elements 4 a , 4 b , and a plurality of outlets 5 , 6 .

[0120] As previously referred Figure 2 As described above, the first screening elements 3a, 3b, 3c and the second screening elements 4a, 4b may be provided with reference Figure 3 A chain of the type described.

[0121] Each of the screening elements 3a, 3b, 3c, 4a, 4b of the first and second groups may be Figure 2 The type of description.

[0122] The above-described type of waste wood-based material is fed to the inlet 2 of the screening device 1'. The waste wood-based material may be unprocessed before being separated in the screening device 1'. The waste wood-based material may be undried before being separated in the screening device 1'. When entering the screening device 1', the wood-based material may have a moisture content of 3% or more.

[0123] Waste wood-based material is fed into a first set of sieve elements 3a, 3b, and 3c. The waste wood-based material is fed into the upper first sieve element 3a. The upper first sieve element 3a may have pores with an aperture width AW exceeding the aperture widths of any other sieve elements in the first set of sieve elements and any sieve elements in the second set of sieve elements. In one example, the upper first sieve element 3a may have pores with an aperture width AW in the range of 1000 μm to 3000 μm, for example, approximately 2000 μm. Particles that do not pass through the upper first sieve element 3a are directed to the first outlet 5a.

[0124] The particles that pass through the upper first sieve 3a, i.e., the remaining portion of the waste wood-based material, are fed, for example, by gravity, to the middle first sieve 3b. The middle first sieve 3b may have pores with a pore width AW exceeding the pore width AW of the lower first sieve 3a. The pore width of the middle first sieve 3b may be smaller than the pore width of the upper first sieve 3a. In one example, the middle first sieve 3b may have pores with a pore width in the range of 500 μm to 900 μm, for example, approximately 720 μm. Particles that do not pass through the upper middle sieve 3b are directed to the second outlet 5b.

[0125] Particles that pass through the upper first sieve 3a and the middle first sieve 3b are fed to the lower first sieve 3c, for example, by gravity. The lower first sieve 3c may have pores with a smaller pore width than the pore widths of the upper first sieve 3a and the middle first sieve 3b. In one example, the lower first sieve 3c may have pores with a pore width in the range of 450 μm to 500 μm, for example, approximately 450 μm. Particles that do not pass through the lower middle sieve 3c are directed to the third outlet 5c.

[0126] The particles that do not pass through any of the first set of sieves, ie, the upper first sieve 3a, the middle first sieve 3b and the lower first sieve 3c, form a first portion of particles. The first outlet 5a, the second outlet 5b and the third outlet 5 merge into the first portion of outlets 5.

[0127] In the sieve analysis as described in the “Example 2: Method Description of Sieve Analysis” section of this disclosure, the first portion of the particles, i.e., at least 60% of the particles that did not pass through the first sieve element 3 or the first group of sieve elements 3a, 3b, 3c, may have a particle size exceeding 400 μm.

[0128] The first portion of particles may be collected in a container (not shown), for example downstream of the first portion outlet 5. Further processing of the first portion of particles will be described below. The first portion of particles may be considered to be an oversized portion of waste wood-based material.

[0129] The particles passing through the upper first sieve 3a, the middle first sieve 3b and the lower first sieve 3c are fed to the second set of sieves 4a, 4b, for example by gravity.

[0130] The second set of screening elements includes an upper second screening element 4a and a lower second screening element 4b.

[0131] Particles that pass through the set of first sieve elements 3a, 3b, and 3c are fed to upper second sieve element 4a. The pore width of upper second sieve element 4a exceeds the pore width of lower second sieve element 4b. The pore width of upper second sieve element 4a is smaller than the pore width of any sieve element in the first set of sieve elements. In one example, upper second sieve element 4a may have pores with a pore width in the range of 315 μm to 380 μm. Particles that do not pass through upper second sieve element 4a are directed to fourth outlet 6a.

[0132] Particles that pass through upper second sieve 4a are fed to lower second sieve 4b, for example, by gravity. The pore width of lower second sieve 4b is smaller than the pore width of upper second sieve 4b. In one example, lower second sieve 4b may have pores with a pore width in the range of 50 μm to 300 μm, for example, in the range of 50 μm to 200 μm. Particles that do not pass through lower second sieve 4b are directed to fifth outlet 6b.

[0133] The particles that have not passed through the upper second sieve 4a or the lower second sieve 4b form the second portion of the particles. The fourth outlet 6a and the fifth outlet 6b merge into the second portion of the outlet 6.

[0134] In the sieve analysis described in the "Example 2: Description of the Sieve Analysis Method" section of this disclosure, the second portion of particles, i.e., at least 60% of the particles that have passed through the first set of sieve elements 3a, 3b, 3c but not the second set of sieve elements 4a, 4b, may have a particle size of 100-400 μm. This second portion of particles may be collected in a container (not shown). Further processing of this second portion of particles will be described below. This second portion of particles may be considered a useful portion of the waste wood-based material.

[0135] The particles that pass through the upper second sifting element 4a and the lower second sifting element 4b form a third portion of the particles. The third portion of the particles can be considered as a fine portion of the particles.

[0136] In the sieve analysis as described in the “Example 2: Method Description of Sieve Analysis” section of this disclosure, the third portion of the particles, i.e., at least 60% of the particles having passed through the upper second sieve 4a and the lower second sieve 4b, may have a particle size of less than 100 μm.

[0137] A third portion of the granules leaves the screening device through the fines outlet 7. The third portion of the granules may be collected in a container (not shown), for example downstream of the fines outlet 7. Further processing of the third portion of the granules will be described below.

[0138] At least one of the first set of screening elements 3a, 3b, 3c can be tilted relative to the horizontal plane HP. Figure 5 In the example shown, all screening elements of the first set of screening elements 3a, 3b, 3c are inclined.

[0139] At least one of the second set of screening elements 4a, 4b can be tilted relative to the horizontal plane HP. Figure 5 In the example shown, all screen elements of the second set of screen elements 4a, 4b are inclined.

[0140] The first portion, which may be considered an oversized portion, may be further processed to reduce the size of the particles and / or fibers of the first portion. The first portion of particles may be ground after screening. This may reduce the size of the particles. After grinding, the first portion of particles may be separated again in a screening device 1 ′ to separate them according to particle size. The first portion of particles may be collected with unscreened waste wood-based material or stored separately from the waste wood-based material.

[0141] The second part of the particles, which may be considered as a useful part, may be used as a feedstock or raw material in a method of producing the building panel 210 or a part of the building panel 210, such as Figure 6 As shown. Thus, waste wood-based materials can be recycled into new products, such as building panels or parts of building panels. The second portion 120 of particles comprises particles derived from the second portion of particles obtained from the waste wood-based materials. The second portion of particles can be applied to the first surface 211 of the core 201, for example, by spreading using a spreading device 220. The core 201 can be a wood-based material, such as MDF, HDF, particle board, a veneer core, etc. The second portion 120 of particles can be applied directly to the first surface 211 of the core 201. The second portion 120 of particles can be applied together with the virgin fiber material or in place of all other virgin fiber material.

[0142] The second portion 120 of particles may be mixed with the binder 203, or the binder 203 may be applied separately from the second portion 120 of particles. For example, the binder 203 may be applied before applying the second portion 120 of particles, or applied to the second portion 120 of particles. Figure 6 In the example shown, a binder 203 is mixed with the second portion 120 of particles. The binder 203 can be a thermoplastic binder or a thermosetting binder. The thermosetting binder can be an amino resin, such as melamine formaldehyde or urea formaldehyde resin, or a combination thereof.

[0143] The second part 120 of particles may be formed as a sublayer or as part of a sublayer arranged on the first surface 211 of the core 201. The second part 120 of particles and the binder 203 may together form the sublayer. The sublayer may be intended to be formed as a surface layer or part of a surface layer of the building panel 210. The wood veneer layer 202 may be arranged on the sublayer, which Figure 6 In another example, the second portion 120 of particles together with the binder 203 is formed as a surface layer of the building panel 210 .

[0144] The second portion 120 of particles may also be applied to a second surface 212 of the core 201 (not shown) opposite the first surface 211 of the core 201. The second portion 120 of particles applied to the second surface 212 of the core 201 may form a balancing layer (not shown) or part of a balancing layer, optionally together with a binder of the type described above.

[0145] The core 201, the second portion 120 of particles applied to the first surface 211 of the core 201 and / or the second surface 212 of the core 201, and the binder 203 are pressed together by applying heat and pressure. If a wood veneer layer 202 is included, the core 201, the sublayer disposed on the first surface 211 of the core 201, the sublayer comprising the second portion 120 of particles and the binder 203, and the wood veneer layer 202 disposed on the sublayer are pressed together by applying heat and pressure. The heat and pressure may be applied in a static or continuous pressing device 230.

[0146] Pressing may include applying a pressure of at least 10 bar and a temperature of at least 130°C for a pressing time of at least 10 seconds. The applied pressure may be in the range of 10-80 bar. The pressure may be applied for 10-90 seconds. The temperature may be 130-235°C.

[0147] A second portion 120 of particles may be arranged on the second surface 212 of the core 201 , optionally with a binder 203 of the type described above.

[0148] After pressing, a building panel 210 is provided, wherein the second portion 120 of particles forms a surface layer together with the binder 203 or forms part of a surface layer by forming a sublayer on which the wood veneer layer 202 is arranged.

[0149] Particles from the second portion of particles may also be included in the process of forming the core.

[0150] The third portion of the particles, which can be considered as the fine particle fraction, can be compacted into pellets. Such pellets can be used for combustion as a particulate fuel.

[0151] The method and subsequent methods and processes are Figure 7 The process is shown in FIG. Step 100 includes collecting waste wood-based materials, as described above with reference to Figure 1 and 5 Step 101 includes screening the waste wood-based material by the first screening element 3 or the first group of screening elements 3a, 3b, 3c, such as Figure 1 and 5 The particles that do not pass through the first screening element 3 or the first group of screening elements 3a, 3b, 3c form the first part of the particles. Figure 7 The first portion 110 of the particles may be ground, as shown in FIG. Figure 7 400 in the figure, and thereafter the process can be entered again, collected and / or stored in step 100, and thereafter screened again in step 101.

[0152] In step 102, the particles that have passed through the first sieve 3 or the first set of sieves 3a, 3b, 3c are then sieved by the second sieve 4 or the second set of sieves 4a, 4b, as described above with reference to Figure 1 and 5 The particles that do not pass through the second screening element 4 or the second group of screening elements 4a, 4b form the second part of the particles. Figure 7 Indicated by 120 .

[0153] The second portion 120 of particles may be used to form a raw material or feedstock, such as a filler, in a subsequent process shown in step 200. In step 200, the second portion of particles may be used to form a building panel or a portion of a building panel, as described above with reference to Figure 6 As stated.

[0154] In step 102, the particles passing through the second screening element 4 or the second set of screening elements 4a, 4b form a third portion of the particles, which is Figure 7 130. In a subsequent step 300, the third portion of the particles can be compacted into pellets. Such pellets can be used as pellet fuel. Alternatively or in addition, the third portion of the particles can be burned.

[0155] It is envisaged that there are numerous modifications to the embodiments described herein which still fall within the scope of the present disclosure as defined by the appended claims.For example, it is envisaged that more than one wear resistant foil may be arranged on a core for forming a building panel.

[0156] Example 1A: Screened waste wood-based material as raw material

[0157] Waste wood-based material was collected in the form of sawn and profiled waste from wood-based panels with a veneer surface layer. The waste wood-based material was not processed / treated prior to screening. The waste wood-based material was not ground or dried prior to screening. Two fiber samples were produced from the wood-based waste using two different production technologies.

[0158] Sample 1 was produced by passing the entire waste wood stream through a hammer mill and screening the output through a 300 μm drum screen. All particles that passed through the screen were considered the useful fraction (the second fraction of particles), and particles that did not pass through the screen were considered the coarse fraction (the first fraction of particles). The amount of material in each fraction was estimated and is shown in Table 1.

[0159] Table 1: Amount of each part of Sample 1

[0160]

[0161] Sample 2 was produced by sieving waste wood-based material in a sieving device having a first set of sieving elements including sieving elements A, B and C, and a second set of sieving elements including sieving elements D and E, according to Table 2 below.

[0162] The five screening elements are angled at non-zero angles relative to the horizontal and vertical planes. The material is fed into the top of the downwardly inclined screening elements so that it is fed forward through the elements by gravity and the vibrations of the screening element motor, which has a stroke length of 7.5 mm. The screening settings are described in Table 2, and the yield of each section is given in Table 3.

[0163] Table 2: Screening settings for product sample 2

[0164] data The obtained part Screening element width 0.5m Feed speed 1128kg / min Hole width of screening element A 2000μm Part 1 (rough) Hole width of screening element B 720μm Part 1 (rough) Hole width of screening element C 450μm Part 1 (rough) Hole width of screening element D 315μm Part 2 (useful) Hole width of screening element E 200μm Part 2 (useful) 0μm Part 3 (small)

[0165] Particles that do not pass through sieve A, sieve B, or sieve C form the first fraction of particles, the coarse fraction. Particles that do not pass through sieve D or E form the second fraction of particles, the useful fraction. Particles that pass through all of sieves A, B, C, D, and E form the third fraction of particles, the fine fraction.

[0166] The amount of material in each portion was measured according to Table 3.

[0167]

[0168] Samples 1 and 2 were then blended with melamine formaldehyde resin and inorganic filler according to the formulations shown in Table 2. Six 600 kg batches of each blend were produced and placed in large bags. The formulations are shown in Table 4 below.

[0169] Table 4: Formulations made from fiber materials 1, 2, and 3

[0170] Fiber Type Fiber (wt%) MF resin (wt%) Inorganic filler (%) Blend 1 Sample 1 45 47.5 7.5 Blend 2 Sample 2 45 47.5 7.5

[0171] The blends were then discharged one by one from the big bags into an air conveying system, which transported the material for discharge to a spreading device, which spread the blend onto the HDF board. The number of flowability-related errors was calculated for each blend type. The error types counted were:

[0172] - Emission issues where material is bridging in the big bag, preventing it from entering the air conveying system.

[0173] -Conveying problems where material forms a blockage in the air conveying line instead of flowing through the line.

[0174] -Spreading problems, such as material getting stuck or bridging in the spreader, preventing it from spreading onto the board.

[0175] The results are shown in Table 5.

[0176] Table 5: Results for the number of flow-related processability issues.

[0177] Test materials Number of batches run during the trial The number of liquidity-related errors Blend 1 6 7 Blend 2 6 0

[0178] It can be seen that when the fines are excluded from the useful fraction as in Sample 2, there is a clear improvement in processability (the ability to complete processing steps without flow issues), with Blend 1 made from Fiber Type 1 showing the worst processability and Blend 2 made from Fiber Type 2 showing the best processability.

[0179] In Sample 1, the entire waste wood stream was passed through the mill, and it is clear that before grinding, approximately 35% of the feed was already in a suitable useful fraction (according to the screening results in Table 3). When grinding, the already suitable useful fraction runs the risk of being reduced in size to a fine fraction (according to the screening results in Table 3, it was already 18.5% before grinding), which results in poor processing performance. Therefore, screening the waste wood stream is a much more reasonable operation than grinding.

[0180] In a further step, the coarse fraction from the screening can be fed through a mill and passed through a screening operation again to optimize the yield of high-quality, highly processable fiber material.

[0181] Example 1B: Screened waste wood-based material as raw material

[0182] Waste wood based material in the form of sawn and profiled waste from wood based panels having a veneer surface layer was collected. The waste wood based material was not processed / treated prior to screening. The waste wood based material was not ground and dried prior to screening. A fiber sample was made from the wood based waste and compared to the material in Example 1A. The purpose of this example was to show that this material, similar to Sample 2 in Example 1A, can be sieved at different stroke lengths and maintain performance within the second section, wherein the material sieved at a stroke length of 3.0 mm showed approximately the same purity and yield as Sample 2 in Example 1A sieved at a stroke length of 7.5 mm.

[0183] According to Table 6 below, the samples were produced by sieving waste wood-based material in a sieving device having a first set of sieving elements including sieving elements A, B and C, and a second set of sieving elements including sieving elements D and E.

[0184] The five screens were angled at nonzero angles relative to the horizontal and vertical planes. The material was fed into the top of the downwardly inclined screens so that it was fed forward through the screens by gravity and the vibrations of the screen motors, which had a stroke length of 3.0 mm. The screening settings are described in Table 6, and the yields for each section are given in Table 7.

[0185] Table 6: Screening settings for production sample 2.

[0186] data The obtained part Screening element width 0.5m Feed speed 828kg / min Width of hole A of screening element 2000μm Part 1 (rough) Width of hole B of screening element 720μm Part 1 (rough) Screening element C hole width 450μm Part 1 (rough) Screening element D hole width 315μm Part 2 (useful) Screening element E hole width 200μm Part 2 (useful) 0μm Part 3 (Details)

[0187] Particles that do not pass through sieve A, sieve B, or sieve C form the first fraction of particles, the coarse fraction. Particles that do not pass through sieve D or E form the second fraction of particles, the useful fraction. Particles that pass through all of sieves A, B, C, D, and E form the third fraction of particles, the fine fraction.

[0188] The amount of material in each portion was measured according to Table 7.

[0189] Table 7: Amount of each portion of Sample 2.

[0190]

[0191] As can be seen in Table 7, the material was screened without any of the screen elements being substantially empty, indicating that the screen elements were functional at 3.0 mm and that there was no material blockage on any of the screen elements. Material blockage would be accounted for when any of the screen elements exceeded 30% of the weight distribution. It will be appreciated that the distribution on all of the screen elements was similar to that of Sample 2 from Example 1A. This distribution, combined with the high purity of the second fraction (useful fraction), meaning that at least 60% by weight of the particles were in the 100-400 μm range, is considered to be close to that of Sample 2 from Example 1A and that it would exhibit substantially the same properties during production. Therefore, the purity of the useful fraction was measured by blending the two second fractions together and sampling and analyzing according to the method described in Example 2.

[0192] Table 8: Useful parts

[0193] Analytical sieve (μm) Useful part (wt.%) 0 14,4 Pollutants (fine) 50 13,9 Pollutants (fine) 100 35,3 Correct part 150 24,4 Correct part 200 7,9 Correct part 250 3,3 Correct part 300 0,8 Correct part

[0194] As can be seen in Table 8, the purity of the useful fraction (the sum of the correct fractions) was 71.7%, and therefore, it can be considered close to that of Sample 2 from Example 1A. Through this experiment, it was determined that this material, similar to Sample 2 in Example 1A, could be sieved at different stroke lengths and maintain performance in the second fraction, with the material sieved at a stroke length of 3.0 mm exhibiting approximately the same purity and yield as Sample 2 in Example 1A sieved at a stroke length of 7.5 mm.

[0195] Example 2: Description of the method for sieving analysis

[0196] All particle size measurements were performed using the following equipment and the following setup:

[0197] Model Name: Fritsch Analysette 3PRO

[0198] Stroke length: 1.8mm

[0199] Screening diameter: 200mm

[0200] Screening element distance = 50mm

[0201] The pore sizes of each sieve element are (from bottom to top): 50 μm, 100 μm, 150 μm, 200 μm, 250 μm and 300 μm.

[0202] Sieving particle size: 0-50μm, 50-100μm, 100-150μm, 150-200μm, 200-250μm, 250-300μm and >300μm

[0203] Number of balls / number of screening pieces: 5

[0204] ball: Rubber (No. 31.0180.15)

[0205] Material input: 50 grams

[0206] Screening time: 20 minutes

[0207] After sieving 50 grams of material, weigh the material on and below each sieve and calculate the weight percentage of each fraction. Material that passes through the 50 μm sieve is classified as 0-50 μm, material that passes through the 100 μm sieve but not the 50 μm sieve is classified as 50-100 μm, and so on.

[0208] Project Section

[0209] 1. A method for finely screening waste wood-based materials, the method comprising:

[0210] Collection of waste wood-based materials resulting from sawing and / or machining of wood-based materials;

[0211] separating the waste wood-based material by particle size by screening the waste wood-based material through at least one first screening element to separate a first portion of particles from the waste wood-based material, wherein the at least one first screening element has a hole width of 3000 μm or less;

[0212] subsequently sieving the waste wood-based material having passed through the at least one first sieving element through at least one second sieving element to separate a second portion of particles from the waste wood-based material, wherein the at least one second sieving element has a hole width of more than 50 μm, and

[0213] Wherein a third portion of particles is formed from particles from waste wood based material passing through said at least one second screening element.

[0214] 2. The method according to item 1, wherein the separation of the waste wood-based materials according to particle size by screening is performed without prior grinding.

[0215] 3. The method according to item 1 or 2, wherein the second part of the particles is used as material in a method for producing a building panel or a part of a building panel.

[0216] 4. The method according to any of the preceding items, wherein the average particle size of the second portion of the particles is smaller than the average particle size of the first portion of the particles and exceeds the average particle size of the third portion of the particles.

[0217] 5. The method according to any of the preceding items, wherein the pore width of the at least one second sieve element is smaller than the pore width of the at least one first sieve element.

[0218] 6. Method according to any of the preceding items, wherein the at least one first screening element is at a non-zero angle relative to the horizontal.

[0219] 7. The method according to any of the preceding items, wherein the at least one first screen element comprises a group of first screen elements, wherein at least one of the first screen elements is at a non-zero angle relative to the horizontal.

[0220] 8. Method according to any of the preceding items, wherein the at least one second screening element is at a non-zero angle relative to the horizontal.

[0221] 9. The method according to any of the preceding items, wherein the at least one second screen element comprises a group of second screen elements, wherein at least one of the second screen elements is at a non-zero angle relative to the horizontal.

[0222] 10. The method according to any of the preceding items, wherein at least 60% of the particles of the second portion of particles have a particle size in the range of 100-400 μm.

[0223] 11. The method according to any of the preceding items, wherein the waste wood-based material is not dried before screening.

[0224] 12. The method according to any of the preceding items, wherein the waste wood-based material has a moisture content of at least 3% before screening.

[0225] 13. The method according to any of the preceding items, further comprising grinding the first portion of the particles.

[0226] 14. The method according to any of the preceding items, further comprising compacting the third portion of particles into pellets.

[0227] 15. The method according to any of the preceding items, further comprising: applying a binder and particles from the second portion of particles to a substrate; and pressing the particles, the binder and the substrate to form a building panel or a part of a building panel.

[0228] 16. The method of item 15, further comprising applying a wood veneer layer over the particles and the binder before pressing, wherein after pressing, the particles, the binder and the wood veneer layer form a surface layer of the building panel.

[0229] 17. The method according to any of the preceding items, wherein the at least one first sieve element has a pore width in the range of 450 μm to 3000 μm, for example in the range of 720 μm to 3000 μm, for example in the range of 1000 μm to 3000 μm, for example in the range of 1500 μm to 2500 μm.

[0230] 18. A method according to any of the preceding items, wherein the at least one first sieve element comprises a group of first sieve elements, wherein each first sieve element has a pore width in the range of 450 μm to 3000 μm, for example in the range of 720 μm to 3000 μm, for example in the range of 1000 μm to 3000 μm, for example in the range of 1500 μm to 2500 μm.

[0231] 19. The method according to any of the preceding items, wherein the at least one second sieve element has a pore width in the range of 50 μm to 600 μm, for example in the range of 50 μm to 450 μm, for example in the range of 50 μm to 400 μm.

[0232] 20. The method according to any of the preceding items, wherein the at least one second sieve element comprises a group of second sieve elements, wherein each second sieve element has a pore width in the range of 50 μm to 600 μm, for example in the range of 50 μm to 450 μm, for example in the range of 50 μm to 400 μm.

[0233] 21. The method according to any of the preceding items, wherein the at least one second sieve element comprises a set of second sieve elements, wherein each second sieve element has a pore width in the range of 150 μm to 450 μm.

[0234] 22. Method according to any of the preceding items, wherein the at least one first and / or second screening element comprises a chain arranged on the at least one first and / or second screening element.

[0235] 23. Method according to any of the preceding items, wherein the at least one first and / or second screening element is vibrating.

[0236] 24. The method according to item 23, wherein the at least one first and / or second screening element is vibrated with a stroke of 1.5-8 mm, such as 2-4 mm or 7-8 mm.

[0237] 25. The method according to any of the preceding items, wherein the first portion of particles is formed by particles that have not passed through the at least one first sieving element.

[0238] 26. Method according to any of the preceding items, wherein the second portion of particles is formed by particles that have not passed through the at least one second screening element.

[0239] 27. The method according to any of the preceding items, wherein the third portion of particles is formed by particles passing through the at least one first sifting element and the at least one second sifting element.

[0240] 28. The method according to any of the preceding items, wherein the pore width of the at least one sieve element exceeds the pore width of the at least one second sieve element.

[0241] 29. A method for recycling waste wood-based materials, the method comprising:

[0242] Collection of waste wood-based materials resulting from sawing and / or machining of wood-based materials;

[0243] separating the waste wood-based materials within the range of an oversized particle fraction, a fine particle fraction, and a recyclable particle fraction by particle size by screening the waste wood-based materials through one or more first screening members having a hole width of 3000 μm or less to separate the oversized particle fraction;

[0244] subsequently sieving the remaining wood-based material through one or more second sieving elements having a pore width of at least 50 μm to separate out the reusable particle fraction, wherein the fine particle fraction is formed by the particles that have passed through the one or more second sieving elements,

[0245] Therein the reusable particle portion forms raw material in a process for producing building panels.

[0246] 30. A method for recycling waste wood-based materials, the method comprising:

[0247] Collection of waste wood-based materials resulting from sawing and / or machining of wood-based materials;

[0248] separating the waste wood-based material by screening the waste wood-based material by particle size through at least one first screening element (3; 3a, 3b, 3c) to separate a first portion of particles from the waste wood-based material, wherein the at least one first screening element (3; 3a, 3b, 3c) has holes (12) with an hole width (AW) of 3000 μm or less;

[0249] The remaining portion of the waste wood-based material is subsequently screened via at least one second screening element (4; 4a, 4b) to separate a second portion of particles from the waste wood-based material, wherein the at least one second screening element (4; 4a, 4b) has holes (12) with an hole width (AW) exceeding 50 μm, and

[0250] wherein a third portion of particles is formed by particles from waste wood-based material passing through said at least one second screening element (4; 4a, 4b),

[0251] Wherein a second portion of the particles forms a raw material in a process for producing building panels.

[0252] 31. The method according to item 30, wherein the separation is carried out without prior grinding.

[0253] 32. The method according to item 30 or 31, wherein the separation is carried out without prior drying.

[0254] 33. A method for recycling waste wood-based materials, the method comprising:

[0255] Collection of waste wood-based materials resulting from sawing and / or machining of wood-based materials;

[0256] separating the waste wood-based material by screening the waste wood-based material by particle size through at least one first screening element (3; 3a, 3b, 3c) to separate a first portion of particles from the waste wood-based material, wherein the at least one first screening element (3; 3a, 3b, 3c) has holes (12) with an hole width (AW) of 3000 μm or less;

[0257] The remaining portion of the waste wood-based material is subsequently screened via at least one second screening element (4; 4a, 4b) to separate a second portion of particles from the waste wood-based material, wherein the at least one second screening element (4; 4a, 4b) has holes (12) with an hole width (AW) exceeding 50 μm, and

[0258] wherein a third portion of particles is formed by particles from waste wood-based material passing through said at least one second screening element (4; 4a, 4b);

[0259] applying a binder and particles from the second portion of particles to a substrate; and

[0260] The particles, the binder and the substrate are pressed to form a building panel or a part of a building panel.

[0261] 34. The method according to item 33, wherein the separation is carried out without prior grinding.

[0262] 35. The method according to item 33 or 34, wherein the separation is carried out without prior drying.

[0263] 36. A method of producing a building panel, the method comprising:

[0264] applying a binder and particles from the second portion of particles according to any of the preceding items to a substrate;

[0265] Heat and pressure are applied to the binder and the second portion of particles to form a layer attached to the substrate.

[0266] 37. The method of item 36 further comprises applying a wood veneer layer over the binder and the particles before applying heat and pressure, wherein after applying heat and pressure, the binder and the particles form a sublayer disposed between the substrate and the wood veneer layer.

[0267] 38. A building panel comprising a surface layer arranged on a substrate, wherein the surface layer comprises a binder and particles from a second portion of particles of waste wood based material, the second portion of particles being obtained by the method according to any of the preceding items.

[0268] 39. The building panel according to item 38, wherein the surface layer comprises a wood veneer layer arranged on a laminate formed of a binder and particles from the second portion of particles, the laminate being arranged between the substrate and the wood-based material.

Claims

1. A method for finely screening waste wood-based materials, the method comprising: Collection of waste wood-based materials resulting from sawing and / or machining of wood-based materials; In the case where the waste wood-based material has not been ground in advance, the waste wood-based material is passed through at least one first screening element (3; 3a, 3b, 3c) screening the waste wood-based material to separate the waste wood-based material by particle size to separate a first portion of particles from the waste wood-based material, wherein the at least one first screening element (3; 3a, 3b, 3c) having pores (12) with an pore width (AW) of 3000 μm or less; subsequently screening the remaining portion of the waste wood-based material via at least one second screening element (4; 4a, 4b) to separate a second portion of particles from the waste wood-based material, wherein the at least one second screening element (4; 4a, 4b) has holes (12) with an hole width (AW) exceeding 50 μm; and wherein a third portion of particles is formed by particles from waste wood-based material passing through said at least one second screening element (4; 4a, 4b).

2. The method according to claim 1, further comprising using the second portion of the particles as raw material in a method of producing a building panel (210) or a part of a building panel (210).

3. The method according to claim 1 or 2, wherein: The average particle size of the second portion of the particles is smaller than the average particle size of the first portion of the particles and larger than the average particle size of the third portion of the particles.

4. A method according to any one of the preceding claims, wherein The hole width (AW) of the at least one second sieve element (4; 4a, 4b) is smaller than the hole width (AW) of the at least one first sieve element (3; 3a, 3b, 3c).

5. A method according to any one of the preceding claims, wherein The at least one first screening element (3; 3a, 3b, 3c) is arranged at a non-zero angle relative to the horizontal.

6. A method according to any one of the preceding claims, wherein The at least one second screening element (4; 4a, 4b) is arranged at a non-zero angle relative to the horizontal.

7. A method according to any one of the preceding claims, wherein At least 60% of the particles of the second portion of particles have a particle size in the range of 100 μm to 400 μm.

8. A method according to any one of the preceding claims, wherein The waste wood-based materials were not dried before screening.

9. The method of any one of the preceding claims, further comprising grinding the first portion of the granules after sieving.

10. The method of any one of the preceding claims, further comprising compacting the third portion of particles into pellets after screening.

11. A method according to any one of the preceding claims, wherein The at least one first sieve element comprises a group of first sieve elements (3a, 3b, 3c), wherein each first sieve element (3a, 3b, 3c) has holes (12) with a hole width (AW) in the range of 450 μm to 3000 μm.

12. A method according to any one of the preceding claims, wherein The at least one second sieve element comprises a group of second sieve elements (4a, 4b), wherein each second sieve element (4a, 4b) has holes (12) with a hole width (AW) in the range of 50 μm to 600 μm or in the range of 50 μm to 400 μm.

13. A method according to any one of the preceding claims, wherein The at least one first screening element and / or the at least one second screening element comprises a chain (9) arranged on the at least one first screening element and / or the at least one second screening element.

14. A method according to any one of the preceding claims, wherein The at least one first screening element and / or the at least one second screening element are vibrating.

15. The method according to claim 14, wherein The at least one first screening element and / or the at least one second screening element vibrates with a stroke of 1.5-8 mm, for example 2-4 mm or 7-8 mm.

16. A method for recycling waste wood-based materials, the method comprising: applying a binder and particles from a second portion of particles to a substrate (201), wherein the second portion of particles is obtained by the method according to any one of claims 1 to 15; and The particles, the binder and the substrate are heated and pressurized to form a building panel (210) or a portion of a building panel (210).

17. The method according to claim 16, further comprising: A wood veneer layer (202) is applied over the particles and the binder before heating and pressurizing, wherein after heating and pressurizing, the particles, the binder and the wood veneer layer form a surface layer of the building panel (210).

18. A building panel (210) comprising a surface layer arranged on a substrate, wherein The surface layer comprises a binder and particles from a second portion of particles, wherein the second portion of particles is obtained by a method according to any one of claims 1-15.

19. The building panels according to claim 18, wherein The surface layer comprises a wood veneer layer disposed on a sub-layer, wherein the sub-layer is formed from the binder and particles from the second portion of particles.

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