Abstract
Recycled fibers are produced from MDF or HDF containing material, for instance for use in MDF or HDF production by steaming (2) the MDF or HDF containing material for a predetermined time to obtain steamed material, subjecting the steamed material to a pulping process (3) to obtain a slurry, screening (4a, 4b) the slurry to remove oversize particles to obtain a screened slurry, dewatering (5) the screened slurry to obtain dewatered fibers and refining or fluffing (6) the dewatered fibers to obtain said recycled fibers. A method for producing MDF or HDF boards using such recycled fibers is also provided. Corresponding systems for producing recycled fibers and producing MDF or HDF boards are also provided.
Claims
1-21. (canceled)
22. A method for producing recycled fibers from MDF or HDF containing material comprising the steps of: receiving MDF or HDF containing material; steaming the received MDF or HDF containing material for a predetermined time to obtain treated material; subjecting the treated material to a pulping process to obtain a slurry; screening the slurry to remove oversize particles to obtain a screened slurry; dewatering the screened slurry to obtain dewatered fibers; and refining or fluffing the dewatered fibers to obtain recycled fibers.
23. The method of claim 22 wherein the MDF or HDF containing material is provided in the form of chips having an area of less than 10,000 mm2.
24. The method of claim 22 further comprising the step of providing the MDF or HDF containing material by reducing the size of an MDF or HDF containing object into chips.
25. The method of claim 22 wherein the step of steaming the MDF or HDF containing material with water or steam is done as pre-steaming before the pulping process or by introducing steam or hot water directly to the pulping process.
26. The method of claim 22 wherein the step of steaming the MDF or HDF containing material is carried out by introducing steam or hot water having a temperature between 60 and 105° C. for 5-20 min.
27. The method of claim 22 wherein the predetermined time is 5-20 minutes.
28. The method of claim 22 where the step of steaming the MDF or HDF containing material is carried out with water or steam having a temperature between 95-105° C.
29. The method of claim 22 where the step of steaming the MDF or HDF containing material is carried out with steam of at least 90% consistency.
30. The method of claim 22 where the step of subjecting the treated MDF or HDF containing material to the pulping process is carried out at 60-90° C.
31. The method of claim 22 where the step of subjecting the treated MDF or HDF containing material to the pulping process is performed at a consistency of 2-8%.
32. The method of claim 22 wherein the step of screening the slurry to remove oversize particles further comprises: using a coarse screen to remove oversize particles from the slurry; and using a fine screen to remove smaller particles from the slurry, wherein the coarse screen has larger perforations than the fine screen.
33. The method of claim 22 wherein the step of dewatering the screened slurry to obtain dewatered fibers is carried out to a consistency of at least 30%.
34. The method of claim 22 wherein the step of dewatering the screened slurry to obtain dewatered fibers is carried out to a consistency of about 50%.
35. The method of claim 22 wherein the step of refining or fluffing the dewatered fibers comprises using a refiner having a fillings gap of 2-8 mm.
36. The method of claim 22 wherein the step of refining or fluffing the dewatered fibers to obtain said recycled fibers, comprises using a fluffer having a gap of 3-5 mm.
37. The method of claim 22 further comprising: coating the recycled fibers with at least one binding agent; drying the coated recycled fibers; and forming MDF or HDF sheets using the dried fibers.
38. The method of claim 37 further comprising: providing new biomass fibers from biomass material; coating the new biomass fibers with a binding agent; drying the coated new biomass fibers; and mixing the coated new biomass fibers with the recycled fibers before the coating step, or after the coating step, or after the drying step, such that the coated new biomass fibers and recycled fibers are both fed to the step of forming MDF or HDF sheets.
39. The method of claim 38 wherein the step of coating the recycled fibers with a binding agent is carried out using a blowline, in which said binding agent is injected.
40. A system for producing recycled fibers from recycled MDF or HDF material, said system comprising: a source of MDF or HDF containing material; a steaming apparatus provided with an inlet for receiving MDF or HDF containing material from the source of MDF or HDF containing material, and at least one steam inlet connected to a source of steam; a pulping apparatus connected to an outlet of said steaming apparatus and being configured to subject the steamed material to a pulping process to provide a slurry; a screening system connected to an outlet of the pulping apparatus and being configured to remove oversize particles from the slurry; a dewatering apparatus connected to an outlet of the screening system and being configured to dewater the slurry, and a refiner or fluffer connected to an outlet of said dewatering apparatus and being configured to refine the dewatered slurry to produce recycled fibers.
41. The system of claim 40 further comprising: a coating apparatus configured to coat the recycled fibers with at least one binding agent; a dryer configured to dry the coated recycled fibers, and an MDF or HDF sheet forming line connected to the dryer and being configured to produce MDF or HDF sheets using dried coated recycled fibers.
42. A system for producing recycled fibers from recycled MDF or HDF material, said system comprising: a source of MDF or HDF containing material; a pre-steaming device connected to receive MDF or HDF containing material from the source of MDF or HDF containing material, and subject it to steaming; a pulping apparatus connected to an outlet of the pre-steaming device and being configured to subject the steamed material to a pulping process to provide a slurry; a screening system connected to an outlet of said pulping apparatus and being configured to remove oversize particles from said slurry; a dewatering apparatus connected to an outlet of said screening system and being configured to dewater the slurry; and a refiner or fluffer connected to an outlet of said dewatering apparatus and being configured to refine the dewatered slurry to produce said recycled fibers.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Above discussed and other aspects of the present invention will now be described in more detail using the appended drawings, which show presently preferred embodiments of the invention.
[0028] FIGS. 1A-1B show flowcharts of embodiments of the method according to the first aspect of the invention.
[0029] FIG. 2 shows a flowchart of an embodiment of the method according to the second aspect of the invention.
[0030] FIG. 3 shows a schematic illustration of an embodiment of a system according to the third aspect of the invention.
[0031] FIG. 4 shows a schematic illustration of an embodiment of a system according to the fourth aspect of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] FIG. 1A shows a flowchart of an embodiment of the method according to the first aspect of the invention. The method comprises reducing 1 the size of one or more provided MDF or HDF containing objects into chips having an area of less than 10,000 mm.sup.2, preferably less than 3,600 mm.sup.2, for instance 40×40 mm, and having a thickness substantially less than their length/width. The reducing step is optional, since the MDF/HDF containing object may alternatively have been reduced in size to chips beforehand, such that pre-produced chips are provided to the steaming 2. The chips are steamed 2 for a predetermined time, preferably 5-20 minutes, preferably at atmospheric conditions with 100° C. steam, to obtain steamed material. The steaming can be done as pre-steaming before the pulping process in the pulping apparatus or by introducing steam or hot water directly to the pulping process in the pulping apparatus at the pulping consistency. The steaming is preferably carried out at 90% consistency or more. The steamed material is thereafter subjected to a pulping process 3, preferably at a temperature of 60-90° C. and at a consistency of about 4%, to obtain a slurry. The slurry is thereafter screened using a fine screening system 4b, optionally with a preceding coarse screening 4a, to remove oversize and undesired particles. The screened slurry is thereafter dewatered 5 to a consistency of at least 30%, preferably around 50%. The dewatered material is refined/fluffed 6 to obtain recycled fibers. The recycled fibers may optionally be coated 7 with at least one binding agent as part of the method. Between the pulping process 3 and the screening system 4a, 4b optionally a high consistency cleaning (HCC) stage 3b in a high consistency cleaning (HCC) device 3b can be located.
[0033] FIG. 1B is a flowchart of an embodiment of the method according to the first aspect of the invention and corresponds to the embodiment of the method as above referring to FIG. 1A but the steaming 2 has been omitted and the steaming is done by introducing steam S or hot water from a steam or hot water source S directly to the pulping process 3 in the pulping apparatus at the pulping consistency. The method comprises reducing 1 the size of one or more provided MDF or HDF containing objects into chips having an area of less than 10,000 mm.sup.2, preferably less than 3,600 mm.sup.2, for instance 40×40 mm, and having a thickness substantially less than their length/width. The reducing step is optional, since the MDF/HDF containing object may alternatively have been reduced in size to chips beforehand, such that pre-produced chips are provided. The steaming is done by introducing steam S or hot water from a steam or hot water source S directly to the pulping process 3 in the pulping apparatus at the pulping consistency. The material is subjected to a pulping process 3, preferably at a temperature of 60-90° C. and at a consistency of about 4%, to obtain a slurry. The slurry is thereafter screened using a fine screening system 4b, optionally with a preceding coarse screening 4a, to remove oversize and undesired particles. The screened slurry is thereafter dewatered 5 to a consistency of at least 30%, preferably around 50%. The dewatered material is refined/fluffed 6 to obtain recycled fibers. The recycled fibers may optionally be coated 7 with at least one binding agent as part of the method. Between the pulping process 3 and the screening system 4a, 4b optionally a high consistency cleaning (HCC) stage 3b in a high consistency cleaning (HCC) device 3b can be located.
[0034] FIG. 2 shows a flowchart of an embodiment of the method according to the second aspect of the invention. The method comprises the same method steps 1-6 as shown in FIG. 1 and explained above. The method further comprises a coating step 9, which is similar to the coating 7 in FIG. 1 in that at least one binding agent such as resin and wax is added, except that new biomass fibers may be provided 8 and optionally be mixed 14 with the recycled fibers. The new biomass fibers may be produced from biomass such as tree material, bagasse, straw or any other type of biomass suitable to be used as basis for MDF/HDF production. The process steps involved in producing the new biomass fibers are well known to the person skilled in the art and will not be described in further detail herein. The coated fibers are thereafter dried 10, and after said drying, fed to an MDF or HDF sheet forming line 11. As indicated by the dotted arrows in the figure, the new biomass fibers may alternatively be subjected to a separate coating step 12 and be mixed 15 with the recycled fibers after coating 9 or may be subjected to separate coating and drying steps 12, 13, and be mixed 16 with the recycled fibers after the drying step 10. The process steps involved in MDF or HDF sheet forming are well known to the person skilled in the art and will not be described in further detail here.
[0035] FIG. 3 shows a schematic illustration of an embodiment of a system according to the third aspect of the invention. The system comprises an optional size reduction apparatus 20, for instance a hammermill, and a steaming apparatus 21 being an atmospheric steamer provided with an inlet for said MDF or HDF containing material and at least one steam inlet connected to a source of low-pressure steam to provide steam to said material. A pulping apparatus 22 is connected to an outlet of the steaming apparatus 21 and is configured to subject the steamed material to a pulping process to provide a slurry. An optional coarse screening system 23a is connected to an outlet of the pulping apparatus 22 and is configured to remove oversize particles from the slurry. A fine screening system 23b is connected to an outlet of the coarse screening system 23a or (in embodiments without a coarse screen) to the pulping apparatus 22 and is configured to remove smaller particles from the slurry. The coarse screen has holes with a diameter of 2-5 mm. The fine screen has slots having a width of 0.2-0.9 mm or holes having a diameter of 1-4 mm. The outlet of the fine screening system is connected to an optional pulp tank 24 in which the slurry may be stored prior to being fed to a dewatering apparatus 25, which is a screw press or similar. The water pressed out from the dewatering apparatus may be fed to an optional water tank 27 from which it is recycled for use in the pulping apparatus. An atmospheric refiner 26 is connected to an outlet of the dewatering apparatus 25 and is configured to refine the dewatered slurry to produce said recycled fibers. The refiner has a fillings gap of 3-5 mm, preferably about 4 mm. Between the pulping apparatus 22 and the screening system 23a, 23b optionally a high consistency cleaning (HCC) stage 3b in a high consistency cleaning (HCC) device 33 can be located.
[0036] FIG. 4 shows a schematic illustration of an embodiment of a system according to the fourth aspect of the invention. The system comprises the same devices and screening systems 20-27 as shown in FIG. 3 and described above. The outlet of the refiner 26 is connected to a blowline 29, in which at least one binding agent is injected/sprayed to coat the recycled fibers while being conveyed to a dryer 210, being of a conventional type as used in MDF/HDF production lines. The outlet of the dryer 210 is connected to an MDF or HDF sheet forming line 211. Optionally, new biomass fibers may be provided such that the MDF or HDF sheets are formed from a combination of new and recycled fibers. In FIG. 4, new biomass fibers are illustrated as being provided in the form of new biomass chips which are fed to a refiner/defibrator 28 for size reduction/refining. In other embodiments, the system may furthermore comprise devices such as a debarker, chipper, screen and chip washer involved in the production of producing the biomass chips fed to the refiner 28. In yet other embodiments, the refiner 28 is omitted, and new biomass fibers are supplied directly, for instance from a tank containing previously produced fibers. As illustrated in the figure, the new fibers may be added together with the recycled fibers to an inlet of the blowline 29 such that the new and recycled fibers are coated/blown and dried together. Alternatively, the new biomass fibers may be fed to a separate (optional) blowline 212 and be fed together with the recycled fibers to the dryer 210 or may be fed to a separate (optional) dryer 213 and be mixed with the recycled fibers after drying by being fed together to the MDF or HDF sheet forming line 211. The devices and screening systems comprised in an MDF or HDF sheet forming line 211 are well known to the person skilled in the art and will not be described in further detail here.
[0037] The description above and the appended drawings are to be considered as non-limiting examples of the invention. The person skilled in the art realizes that several changes and modifications may be made within the scope of the invention.
[0038] For example, the MDF or HDF containing material does not necessarily need to be furniture, flooring or raw board reject, but may be any type of object or material comprising MDF or HDF. Furthermore, the MDF or HDF containing material does not necessarily need to be provided as chips in the literal sense thereof but may have any form or size as long as said form or size allows the steam to effectively treat the material. Furthermore, the described residence times, temperatures and consistencies are only exemplary, and may need to be varied outside the proposed ranges depending on the content and size of the provided raw material.
