Method and system for recovering wood particles from bark-containing wood-based feedstock

Abstract

A method for recovering wood particles from a bark-containing wood-based feedstock is disclosed. Additionally, a system for recovering wood particles from a bark-containing wood-based feedstock is disclosed. Also disclosed are products comprising wood particles formed using the disclosed method. Finally, uses of the wood particles formed in the disclosed method are disclosed.

Description

[Technical field]

[0001] The present disclosure relates to a method for recovering wood particles from a bark-containing wood-based feedstock. Additionally, the present disclosure relates to a system for recovering wood particles from a bark-containing wood-based feedstock. Also, the present disclosure relates to products comprising wood particles formed using the method of the present disclosure. Finally, the present disclosure relates to uses of the wood particles formed in the method according to the present disclosure. [Background technology]

[0002] Before being used in various processes, wood-based raw materials, i.e. logs, need to be debarked in order to produce raw materials that contain as little undesirable material as possible, such as bark. Debarking in a commercial environment is usually performed using various mechanical debarking machines that peel or remove a certain thickness of material from the surface of the log. A drawback of mechanical debarking is that the layer removed from the log will contain wood in addition to the bark, which can lead to a significant loss of valuable wood raw material if the wood contained in the bark fragments is not recovered. Summary of the Invention [Means for solving the problem]

[0003] A method for recovering wood particles from a bark-containing wood-based feedstock is disclosed. The method comprises: a) providing a bark-containing wood-based feedstock; b) sieving the bark-containing wood-based feedstock to separate wood particles from bark particles; c) collecting the wood particles to form a wood stream and a sieved bark-containing wood-based feedstock; may include.

[0004] Disclosed are articles of manufacture that include the wood particles produced by the disclosed methods.

[0005] Uses of the wood particles formed using the disclosed methods or the disclosed products are disclosed.

[0006] A system for sieving a bark-containing wood-based feedstock to recover wood particles contained therein is disclosed. The system may comprise at least one sieving means for separating the bark particles from the wood particles to form a wood stream and a sieved bark-containing wood-based feedstock.

[0007] The accompanying drawings are included to provide a further understanding of the embodiments, and are incorporated in and constitute a part of this specification, and illustrate various embodiments. [Brief description of the drawings]

[0008] [Figure 1] 1 is a flow chart of one embodiment of a method for recovering wood particles from a bark-containing wood-based feedstock. [Diagram 2] 1 is a flow chart of one embodiment of a method for recovering wood particles from a bark-containing wood-based feedstock. [Diagram 3] FIG. 1 shows the classification and sorting of wood chips according to the SCAN-CM 40:01 method. [Figure 4] FIG. 1 shows bark chips formed during mechanical debarking of beech and ash. [Diagram 5] FIG. 2 shows the thickness of beech bark as a function of wood diameter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A method for recovering wood particles from a bark-containing wood-based feedstock is disclosed, the method comprising the step of sieving the wood-based feedstock.

[0010] In one embodiment, the method comprises: a) providing a bark-containing wood-based feedstock; b) sieving the bark-containing wood-based feedstock using at least one sieving means to separate wood particles from bark particles; c) collecting the wood particles to form a wood stream; may include.

[0011] In one embodiment, a method includes recovering wood particles from a bark-containing wood-based feedstock, the method comprising: a) providing a bark-containing wood-based feedstock; b) sieving the bark-containing wood-based feedstock to separate wood particles from bark particles; c) collecting the wood particles to form a wood stream and a sieved bark-containing wood-based feedstock; Includes.

[0012] In one embodiment, a method for recovering wood particles from a bark-containing wood-based feedstock comprises: d) sieving the sieved bark-containing wood-based feedstock to form a second wood stream and a second sieved bark-containing wood-based feedstock; e) combining the wood stream with a second wood stream to form a combined wood stream. Includes.

[0013] In one embodiment, a method includes recovering wood particles from a bark-containing wood-based feedstock, the method comprising: a) providing a bark-containing wood-based feedstock; b) sieving the bark-containing wood-based feedstock to separate wood particles from bark particles; c) collecting the wood particles to form a wood stream and a sieved bark-containing wood-based feedstock; d) sieving the sieved bark-containing wood-based feedstock to form a second wood stream and a second sieved bark-containing wood-based feedstock; e) combining the wood stream with a second wood stream to form a combined wood stream. Includes.

[0014] The step of preparing a) wood-based feedstock may include subjecting the wood-based raw material to a mechanical treatment selected from debarking, chipping, splitting, cutting, beating, crushing, crushing, splitting, sieving, and / or washing the wood-based raw material to form the wood-based feedstock. In a particular embodiment, the step of preparing a) wood-based feedstock may include subjecting the wood-based raw material to a mechanical treatment selected from debarking and / or chipping. In a particular embodiment, the wood-based raw material may be a wood log, a wood stump, a wood block, or any combination thereof. In one embodiment, the wood-based raw material is a log. During the mechanical treatment, for example, the wood log may be debarked and / or wood chips may be formed.

[0015] In certain embodiments, the bark-containing wood-based feedstock is separated into recovered wood particles and bark particles.

[0016] In one embodiment, the bark-containing wood-based feedstock is formed by debarking a wood-based raw material to form a bark-containing wood-based feedstock and a debarked wood-based raw material. In one embodiment, the bark-containing wood-based feedstock is formed by debarking a log to form a bark-containing wood-based feedstock and a debarked log. In one embodiment, the debarked wood-based raw material is a debarked log.

[0017] The step of providing a wood-based feedstock may include purchasing a wood-based feedstock. The purchased wood-based feedstock may include a purchased bark-containing wood-based feedstock derived from a wood-based raw material.

[0018] In a particular embodiment, the wood-based raw material is a hardwood, a softwood, or any combination thereof. The wood-based raw material or wood-based feedstock may be derived from, for example, pine, poplar, beech, aspen, spruce, eucalyptus, ash, or birch. The wood-based raw material or wood-based feedstock may also be any combination or mixture thereof. The wood-based raw material or wood-based feedstock may be a hardwood. The hardwood may be selected from the group consisting of beech, birch, ash, oak, maple, chestnut, willow, poplar, and any combination or mixture thereof.

[0019] In certain embodiments, the wood-based raw material may be logs. In certain embodiments, the logs may have a length of 0.5-8 m, 1-6 m, or 2-4 m. In certain embodiments, the logs of the wood-based raw material may have an average diameter of 10-80 cm, or 20-60 cm.

[0020] In certain embodiments, the recovered wood particles are oversize wood chips and / or overthick wood chips as designated by SCAN-CM 40:01. In certain embodiments, the bark particles are large accept chips, small accept chips, pin chips, and / or fines as designated by SCAN-CM 40:01.

[0021] Standard SCAN-CM 40:01 (revised 2001) describes a procedure for sorting wood chips, in which a sample of wood chips is placed on the top sieve of a stack of five sieve trays and a fines tray (see FIG. 3). The sieves have holes or slots of specified dimensions and the stack is maintained in reciprocating motion. After a specified time, sieving is stopped and the resulting six grades are weighed separately. The size of each grade is its mass, expressed as a percentage of the total mass of all six grades.

[0022] Surprisingly, the inventors have discovered that it is possible to separate bark particles contained in a bark-containing wood-based feedstock from the wood particles by sieving the bark-containing wood-based feedstock using a suitable arrangement of sieving means.

[0023] As used herein, the term "screening means" refers to a means for screening wood-based feedstock based on particle size. Non-limiting examples of screens are plate screens, disc screens, hole screens, groove screens, bar groove screens, and wire groove screens.

[0024] As known to those skilled in the art, a plate sieve comprises a flat plate-like surface in which holes or apertures are made. The shape of the holes or apertures of the plate sieve plates may be, for example, circular, square, elliptical, rhomboidal, or triangular. The size and shape of the holes or apertures should be selected according to the size of the particles to be sieved. A disc sieve comprises a series of axially driven assemblies including contoured discs mounted at equal intervals. The discs of one axis alternate with the discs of the adjacent axis, creating openings or slots between the discs and between the axes. The rotating discs move the material through the sieve, and the material is sieved according to the size of the slots. In certain embodiments, the slot sieve comprises slots through which particles of a desired size, width, and / or length can pass. In certain embodiments, the slot sieve may be a bar slot sieve, in which the slots are constructed using metal bars or rods. In certain embodiments, the slot sieve may be a wire slot sieve, in which the slots are constructed using metal wires.

[0025] In certain embodiments, at least one sieving is performed using a disk screen, a plate screen, or a groove screen. In certain embodiments, the groove screen may be a rod groove screen or a wire groove screen.

[0026] In certain embodiments, the size of the holes in a plate sieve may be defined according to the size of the particles that are to be retained on the sieve. As a non-limiting example, if the hole size (or diameter) is defined as about 45 mm, particles larger than about 45 mm will be retained on the sieve and particles smaller than about 45 mm will be allowed to pass through the holes in the sieve regardless of the shape of the holes. In certain embodiments, the hole size may be between 40 mm and 50 mm, between 43 mm and 48 mm, or about 45 mm.

[0027] A person skilled in the art will be able to select the size and shape of the holes in the plate sieve based on the size and shape of the bark particles, which is determined case by case for different combinations of bark remover and wood type. Figure 4 shows examples of the shape of bark particles formed by bark removal of ash and beech. Figure 3 a) is ash bark, the particles or chips of which are more rounded and thicker. Figure 3 b) is beech bark, the particles or chips of which are plate-like and thinner.

[0028] In one embodiment, the sieve used to sieve the bark-containing wood-based feedstock allows substantially all bark particles to pass through the sieve. In one embodiment, the sieve used to sieve the bark-containing wood-based feedstock allows at least 95% of the bark particles to pass through the sieve. In one embodiment, the sieved bark-containing wood-based feedstock comprises at least 95% by weight of the bark particles from the bark-containing wood-based feedstock. In one embodiment, the second sieved bark-containing wood-based feedstock comprises at least 95% by weight of the bark particles from the bark-containing wood-based feedstock. In a particular embodiment, the size of the holes in the board sieve is selected to be about 110-120% of the maximum dimension of the bark particles. The size of the bark particles can be easily determined by measuring them from the bark-containing wood-based feedstock to be sieved.

[0029] In one embodiment, the recovered wood particles contain less than 5%, less than 3%, less than 1%, less than 0.5%, or less than 0.25% bark by weight of the recovered wood particles after separation from the bark particles.

[0030] In one embodiment, the bark particles comprise less than 50% wood by weight of the bark fragments after separation from the wood particles.

[0031] In one embodiment, sieving of the bark-containing wood-based feedstock is carried out by passing the bark-containing wood-based feedstock through a series of sieves or sieving means selected such that the particles retained in the sieves are successively smaller than the particles retained in the previous sieve. In one embodiment, sieving of the bark-containing wood-based feedstock is carried out by passing the bark-containing wood-based feedstock through a series of sieves or sieving means selected such that the particles retained in the sieves are successively smaller than the particles retained in the previous sieve.

[0032] In one embodiment, the sieving includes using a plate sieve, a groove sieve, and / or a disk sieve. In certain embodiments, the sieving is performed using one sieving means, two sieving means, or three sieving means. In certain embodiments, the sieving is performed using at least one sieving means.

[0033] In one embodiment, in the method according to the present disclosure, the sieving in b) comprises at least one sieving.

[0034] In one embodiment, the method according to the present disclosure includes at least a first screening and a second screening performed after the first screening.

[0035] In certain embodiments, one or more screening means may be arranged in series to allow screening of the bark-containing wood-based feedstock in two or more successive screening steps. In one embodiment, one or more screening means may be arranged vertically, such that a first screening means is above a second screening means. In one embodiment, one or more screening means may be arranged horizontally, such that product screened by the first screening means is conveyed from the first screening means to the second screening means, for example, using a conveyor belt, a screw, or other similar means known to those skilled in the art.

[0036] In one embodiment, wood loss in the bark removal process is less than 10% by weight, less than 8% by weight, less than 6% by weight, less than 4% by weight, less than 3% by weight, less than 2% by weight, or less than 1% by weight, relative to the total wood content in the wood-based raw material before mechanical treatment.

[0037] In one embodiment, the barker is a knife barker, a drum barker, or a rotary barker.

[0038] Disclosed are products comprising wood particles produced by the methods of the present disclosure. In one embodiment, a wood stream comprises wood particles formed in the methods of the present disclosure.

[0039] Uses of wood particles formed by the disclosed method or products including wood particles formed by the disclosed method are disclosed. Products including wood particles produced by the disclosed method can be used in any suitable application known to those skilled in the art. Non-limiting examples of suitable applications are for the production of pulp, for the production of paper, for the production of bioethanol, and for the production of other chemicals or intermediates. In one embodiment, the recovered wood particles may be returned upstream in the processing of wood-based raw materials, such as being fed to a chipping process. As will be readily apparent to those skilled in the art, some applications may require additional treatment or processing steps to make the wood particles suitable for further use.

[0040] A system for sieving a bark-containing wood-based feedstock to recover wood particles contained therein is disclosed. In one embodiment, the system according to the present disclosure comprises at least one sieving means for separating the wood particles from the bark particles to form a wood stream and a sieved bark-containing wood-based feedstock.

[0041] In one embodiment, the system comprises a first screening means for separating wood particles from bark particles to form a wood stream and a screened bark-containing wood-based feedstock.

[0042] In one embodiment, the system comprises a second screening means for screening the sieved bark-containing wood-based feedstock to form a second wood stream and a second sieved bark-containing wood-based feedstock.

[0043] In one embodiment, the system comprises a first sieving means for separating wood particles from bark particles to form a wood stream and a sieved bark-containing wood-based feedstock, and a second sieving means for sieving the sieved bark-containing wood-based feedstock to form a second wood stream and a second sieved bark-containing wood-based feedstock.

[0044] In one embodiment, the system for screening bark-containing wood-based feedstock comprises a screening means having groove openings adjusted to about 120% of the maximum dimension of the bark particles to separate the bark particles from the wood particles. In one embodiment, the system for screening bark-containing wood-based feedstock comprises one screening means having groove openings adjusted to about 110-120% of the maximum thickness of the bark to separate the bark particles from the wood particles. In one embodiment, the groove size of at least one screening means may be about 110% of the thickness of the bark.

[0045] In one embodiment, wood-based feedstock is formed upon debarking of wood-based raw materials including logs, stumps, blocks, branches, or any combination thereof.

[0046] In one embodiment, the system for sieving bark-containing wood-based feedstock comprises a plate sieve. The plate sieve has holes with a size of 40 mm to 50 mm, 43 mm to 48 mm, or about 45 mm. In particular embodiments, the shape of the holes or openings of the plate sieve may be, for example, circular, square, oval, rhomboid, diamond, or triangular. In one embodiment, the system comprises a groove sieve. The groove sieve may have a groove size of 8 mm or less. In one embodiment, the system comprises a disc sieve. In particular embodiments, the disc sieve may have a groove size of 8 x 45 mm or less. The size of the holes or grooves may be selected or adjusted depending on the thickness of the bark of the wood-based raw material. To separate wood particles from the bark-containing wood-based feedstock, the groove size must be larger than the thickness of the bark.

[0047] In one embodiment, the system comprises screening means having a slot or hole size adjusted according to a dimension such as the thickness of the bark of the bark-containing wood-based feedstock.

[0048] In certain embodiments, the system comprises at least one sieving means. In certain embodiments, the system according to the present disclosure comprises at least one plate sieve and at least one additional sieving means.

[0049] In one embodiment, the system comprises a first screening means having a groove or hole size adjusted to the size of the bark particles so that all the bark particles pass through the holes, and a second screening means having a groove or hole size selected according to the thickness of the bark in the wood-based raw material or bark-containing wood-based feedstock. As a non-limiting example, a hole size of about 45 mm can be mentioned for diamond-shaped holes with sides extending to about 45 mm.

[0050] The bark thickness can be determined, for example, by measuring the thickness of a representative number of bark pieces collected from a bark-containing wood-based feedstock. Once the thickness is measured, the groove size is selected according to the thickest bark piece. In certain examples, the bark thickness may also be estimated based on the diameter of the logs of the wood-based raw material. As a non-limiting example, FIG. 5 shows the relationship between log diameter and bark thickness for beech. As will be apparent to one skilled in the art, the bark thickness should be determined on a case-by-case basis.

[0051] In one embodiment, the system comprises a first screening means having a groove or hole size of about 110-120% of the maximum dimension of the bark particles, and a second screening means having a groove or hole size adjusted according to the thickness of the bark in the wood-based raw material or bark-containing wood-based feedstock. In one embodiment, the first screening means comprises a plate screen having holes of a size of about 110-120% of the maximum dimension of the bark particles, and the second screening means comprises a groove screen disposed below the first plate screen and having rods configured to have a groove size adjusted according to the thickness of the bark in the wood-based raw material or bark-containing wood-based feedstock.

[0052] In certain embodiments, the first sieving means comprises a sieve having holes of size between 40 mm and 50 mm, between 43 mm and 48 mm, or about 45 mm. In certain embodiments, the second sieving means comprises a grooved sieve having rods disposed below the sieving means and configured to have a groove size of about 7 mm or about 8 mm.

[0053] In a particular embodiment, the second screening means comprises a screen having a groove size or hole size adjusted according to the thickness of the bark in the wood-based raw material or bark-containing wood-based feedstock. In a particular embodiment, the second screening means comprises a groove screen arranged below the first plate screen and having rods configured to have a groove size adjusted according to the thickness of the bark in the wood-based raw material or bark-containing wood-based feedstock. In a particular embodiment, the second screening means comprises a groove screen arranged below the screening means and having rods configured to have a groove size of about 7 mm or about 8 mm.

[0054] In one embodiment, the first sieving means comprises a sieve having holes of size 40 mm to 50 mm, 43 mm to 48 mm, or about 45 mm, and the second sieving means comprises a grooved sieve positioned below the sieving means and having rods configured to have a groove size of about 7 mm or about 8 mm.

[0055] In one embodiment, the first screening means comprises a screen having a hole size of 40mm to 50mm, 43mm to 48mm or about 45mm, and the second screening means comprises a screen having a groove size or hole size adjusted according to the thickness of the bark in the wood-based raw material or bark-containing wood-based feedstock. In one embodiment, the first screening means comprises a plate screen having holes of a size of 40mm to 50mm, 43mm to 48mm or about 45mm, and the second screening means comprises a groove screen arranged below the first plate screen and having rods configured to have a groove size adjusted according to the thickness of the bark in the wood-based raw material or bark-containing wood-based feedstock. In one embodiment, the first sieving means comprises a sieve having holes of size 40 mm to 50 mm, 43 mm to 48 mm, or about 45 mm, and the second sieving means comprises a grooved sieve positioned below the sieving means and having rods configured to have a groove size of about 7 mm or about 8 mm.

[0056] In certain embodiments, one or more screening means may be arranged in series to allow screening of the bark-containing wood-based feedstock in two or more successive screening steps. In one embodiment, one or more screening means may be arranged vertically, such that a first screening means is above a second screening means. In one embodiment, one or more screening means may be arranged horizontally, such that product screened by the first screening means is conveyed from the first screening means to the second screening means, for example, using a conveyor belt, a screw, or other similar means known to those skilled in the art.

[0057] In one embodiment, the second screening means is located after or below the first screening means.

[0058] In one embodiment, the first screening means comprises a screen with a hole size of about 45x45mm and the second screening means comprises a second screen with a groove or hole size adjusted according to the dimensions of the bark particles in the wood-based raw material. In one embodiment, the first screening means comprises a plate screen with holes with a size of 40mm-50mm, 43mm-48mm or about 45mm and the second screening means comprises a groove screen with rods arranged below or after the first plate screen and with a groove size adjusted according to the thickness of the bark in the wood-based raw material. In one embodiment, the first sieving means comprises a plate sieve having holes of size 40mm to 50mm, 43mm to 48mm, or about 45mm, and the second sieving means comprises a grooved sieve arranged below or after the first plate sieve and having bars or wires configured to have a groove size of about 7mm or about 8mm. In one embodiment, the first sieving means comprises a disk sieve having holes of size 40mm to 50mm, 43mm to 48mm, or about 45mm, and the second sieving means comprises a grooved sieve arranged below or after the first plate sieve and having bars or wires configured to have a groove size of about 7mm or about 8mm.

[0059] In one embodiment, the first screening means is a plate screen having holes of about 45 mm size and the second screening means disposed below the plate screen is a groove screen having bars or wires configured to have a groove size adjusted according to the bark thickness of the wood-based feedstock.

[0060] In one embodiment of the system according to the present disclosure, the purpose of the first sieving means is to separate thin, long stick-like wood particles from the bark-containing wood-based feedstock to form a sieved bark-containing wood-based feedstock, while at the same time the first sieving will also separate thick stick-like wood particles and other large wood particles from the bark-containing wood-based feedstock.

[0061] Thus, the wood particles are retained in the first sieve and the sieved wood-based feedstock comprises bark and smaller wood particles. If a second sieving means is placed below or after the first sieving means, the purpose of the second sieving means is to separate the remaining wood particles from the sieved bark-containing wood-based feedstock. The wood particles separated from the bark-containing wood-based feedstock in both sieves may then be merged to form wood particle fragments. Since the bark-containing wood-based feedstock will also contain wood particles of similar size to or smaller than the bark particles, the sieved bark-containing wood-based feedstock and / or the second sieved bark-containing wood-based feedstock will also contain some small wood particles.

[0062] A flow chart of one embodiment of a method for recovering wood particles from a bark-containing wood-based feedstock is shown in Figure 1. In the embodiment of Figure 1, a bark-containing wood-based feedstock is provided (a) and screened (b) by a screening means. During screening, the wood particles are separated from the bark particles and the wood particles are recovered (c).

[0063] In a particular embodiment, the second screening means, which is placed after or below the first screening means, may be a disc screen, groove screen or board screen having rods configured with groove sizes adjusted according to the bark thickness of the wood-based feedstock.

[0064] Figure 2 shows a flow chart of one embodiment of a method for recovering wood particles from a bark-containing wood-based feedstock. In the embodiment of Figure 2, a provided bark-containing wood-based feedstock (a) is screened by two successive screening means (b). In the first screening, the bark particles are separated to form a screened bark-containing wood-based feedstock. In the second screening, the screened bark-containing wood-based feedstock is screened to separate the wood particles from the bark particles and the wood particles are recovered (c).

[0065] The methods described herein have the enhanced utility of increasing the overall yield of wood from wood-based raw materials after bark removal, thereby reducing wood losses in the bark removal process.

[0066] Real-life examples Reference will now be made in detail to various embodiments.

[0067] The following description discloses some embodiments in detail to enable a person skilled in the art to utilize the embodiments based on the present disclosure. Not all steps or features of the embodiments are discussed in detail because many steps or features are believed to be obvious to a person skilled in the art based on the present specification.

[0068] "Example 1" Beech bark Beech logs with a diameter of about 20-40 cm were debarked in a rotary debarker. The bulk density of the recovered bark fragments was about 241 kg / m when uncompressed. 3 , about 326 kg / m when compressed by hand 3 It was.

[0069] The bark fragments recovered from the bark removal were sieved using a sieving setup according to FIG. 3, and the resulting fragments were analyzed for wood and bark content. [Table 1]

[0070] As can be seen here, for beech wood (20-40 cm diameter), the total amount of wood recovered from the bark by debarking in the first two fragments was about 50%. This wood may be combined with the wood from the debarked logs for further use.

[0071] "Example 2" Ash bark Ash logs with a diameter of approximately 20 cm were debarked in a rotary debarker. The bulk density of the recovered bark fragments was approximately 292 kg / m when uncompressed. 3 , about 409 kg / m when compressed by hand 3 It was.

[0072] The bark fragments recovered from the bark removal were sieved using a sieving setup according to FIG. 3, and the resulting fragments were analyzed for wood and bark content. [Table 2]

[0073] As can be seen here, for ash wood (20 cm diameter), the total amount of wood recovered in the first two fragments was about 27%. This wood may be combined with the wood from the debarked logs for further use.

[0074] The examples show that by sieving it is possible to recover a significant amount of wood particles from the bark after debarking. Thus, the loss of wood material can be reduced and wood procurement can be reduced, leading to environmental benefits. The recovered wood particles are pure and free of bark and can be sent to various processes that utilize such pure wood particles.

[0075] It is obvious to those skilled in the art that with the advancement of technology, the basic concept can be implemented in various ways. Therefore, the embodiments are not limited to the above examples, but can vary within the scope of the claims.

[0076] The above described embodiments may be used in any combination with each other. Some of the embodiments may be combined together to form further embodiments. The method, product, or system disclosed herein may include at least one of the above described embodiments. It will be understood that the benefits and advantages described above may relate to one embodiment or to several embodiments. The embodiments are not limited to those that solve any or all of the problems mentioned, nor are they limited to those that have any or all of the benefits and advantages mentioned. Furthermore, it will be understood that a reference to "an" or "an" item refers to one or more of that item. The term "comprising" is used herein to mean including the following feature or act without excluding the presence of one or more additional features or acts.

Claims

1. 1. A method for recovering wood particles from a bark-containing wood-based feedstock, comprising: a) providing said bark-containing wood-based feedstock; b) sieving the bark-containing wood-based feedstock to separate wood particles from bark particles; c) collecting the wood particles to form a wood stream and a sieved bark-containing wood-based feedstock; A method comprising:

2. d) sieving the sieved bark-containing wood-based feedstock to form a second wood stream and a second sieved bark-containing wood-based feedstock; e) combining said wood stream with said second wood stream to form a combined wood stream; The method of claim 1 , comprising:

3. 3. The method of claim 1 or 2, wherein the bark-containing wood-based feedstock is formed by debarking a wood-based raw material to form a bark-containing wood-based feedstock and a debarked wood-based raw material.

4. 3. The method of claim 1 or 2, wherein the sieving in b) comprises at least one sieving.

5. 3. The method according to claim 1 or 2, wherein the sieving in b) comprises at least a first sieving and a second sieving performed after the first sieving.

6. 3. The method of claim 1 or 2, wherein the sieved bark-containing wood-based feedstock comprises at least 95% by weight of bark particles from the bark-containing wood-based feedstock.

7. 3. The method according to claim 1 or 2, wherein the at least one sieving is carried out using a disc sieve, a plate sieve or a grooved sieve.

8. 3. The method of claim 1 or 2, wherein the wood-based feedstock is hardwood, softwood, or any combination thereof.

9. 3. The method according to claim 1 or 2, wherein the wood-based raw material is a log.

10. The method of claim 1 or 2, wherein the logs have a length of 0.5 to 8 m, 1 to 6 m, or 2 to 4 m.

11. 3. The method of claim 1 or 2, wherein the recovered wood particles are oversize wood chips and / or overthick wood chips as designated by SCAN-CM 40:

01.

12. 3. The method of claim 1 or 2, wherein the bark particles are large accept chips, small accept chips, pin chips, and / or fines as designated by SCAN-CM 40:

01.

13. 3. The method of claim 1 or 2, wherein the recovered wood particles contain less than 5%, less than 3%, less than 1%, less than 0.5%, or less than 0.25% bark by weight of the recovered wood particles after separation from the bark particles.

14. 3. The method of claim 1 or 2, wherein the sieving of the bark-containing wood-based feedstock is carried out by passing the bark-containing wood-based feedstock through a series of sieves or sieving means selected so that the particles retained in each sieve are successively smaller than the particles retained in the previous sieve.

15. 3. The method of claim 1 or 2, wherein the debarker is a knife debarker, a drum debarker, or a rotary debarker.

16. 10. An article of manufacture comprising wood particles produced by the method of claim 1.

17. 17. Use of wood particles formed using the method of claim 1 or 2, or the product of claim 16.

18. A system for sieving bark-containing wood-based feedstock to recover wood particles contained therein, the system comprising at least one sieving means for separating the wood particles from the bark particles to form a wood stream and a sieved bark-containing wood-based feedstock.

19. 20. The system of claim 18, comprising a first screening means for separating the bark wood particles from the wood bark particles to form a wood stream and a screened bark-containing wood-based feedstock.

20. 20. The system of claim 19, comprising a second screening means for screening the screened bark-containing wood-based feedstock to form a second wood stream and a second screened bark-containing wood-based feedstock.

21. 21. The system according to any one of claims 18 to 20, comprising at least one screening means having openings adjusted to about 120% of the largest dimension of the bark particles of the wood-based raw material to separate the bark particles from the wood particles.

22. 21. The system of any one of claims 18 to 20, wherein the wood-based feedstock is formed in the debarking of wood-based raw materials including logs, stumps, blocks, branches, or any combination thereof.

23. 21. The system of any one of claims 18 to 20, wherein the first sieving means comprises a sieve having a hole size of between 40mm and 50mm, between 43mm and 48mm, or about 45mm.

24. 21. The system of claim 20, wherein the second screening means comprises a screen having a groove or hole size adjusted according to the thickness of the bark of the wood-based feedstock.

25. 21. The system of claim 20, wherein the second screening means is located after or below the first screening means.

26. 21. The system of any one of claims 18 to 20, wherein the first screening means is a plate screen having holes of about 45 mm in size, and the second screening means arranged below the plate screen is a grooved screen having rods or wires configured to have groove sizes adjusted according to the thickness of the bark of the wood-based feedstock.

Images