GB2527544A

GB2527544A - A method of processing waste material to produce various wood products

Info

Publication number: GB2527544A
Application number: GB1411256.9A
Authority: GB
Inventors: Mark Christensen
Original assignee: RELIAGEN Ltd
Current assignee: RELIAGEN Ltd
Priority date: 2014-06-25
Filing date: 2014-06-25
Publication date: 2015-12-30
Anticipated expiration: 2034-06-25
Also published as: GB2527544B; GB201411256D0

Abstract

A method of processing waste for recovering of various wood products comprises receiving waste material 10, shredding 30 the waste material, removing at least some metallic objects from the shredded waste material 40, 50, mechanically separating the waste material into at least three size fractions 60, mechanically sorting at least one of the at least three size fractions using near infrared spectroscopy 160 to separate it into at least two streams with one stream comprising substantially only wood products and one stream comprising treated wood products and mechanically sorting the stream comprising substantially only wood products using x-ray fluorescence and/or x-ray transmission 170 to separate it into two streams with one stream comprising substantially only grade "A" wood products and the other stream comprising treated wood products. The various grades of wood may be used for fuel pellet manufacture. Ideally, the undersize size fraction is subjected to air separation and the largest fraction is subjected to shredding.

Description

A method of processing waste material to produce various wood products The present invention relates generaUv to a method of processing waste, a fuel product, a waste processing plant, and a computer program.

With regard to the term "waste" this may be understood as relating to mixed, substantially solid and substantially non-hazardous waste from domestic, commercial and/or industrial sources.

Tt is known to process waste in order to extract useful materials for further uses (i.e. the materials are recycled possibly for onward further processing/manufacturing into different products) and also sometimes for the purpose of producing a fuel product. Such fuel products may be burnt in conventional or purpose built power generation facilities and may he a fuel substitute for, or used in addition to, existing fuels such as coal, hiomass etc. It is desirable for the fuel product to exclude hazardous materials such as chemicals. The fuel product may be considered to be a refined fuel product.

Other products of the waste processing may be timber of various grades for uses such as the manufacture of engineered wood products and animal bedding. Metals rilay also be rccovcrcd and rccyclcd from the waste material.

Wood products may be categorised as follows: Grade "A" -natural wood, un-treated wood, un-painted wood; Grade "B" -natural wood which has been treated, such as painted wood; Grade "C" -man made wood products, such as chipboard, _MDIç oriental strand board (OSB), plywood. engineered wood products; Grade "D" -Any type of wood (natural or man-made) with toaic trealments such as CCA. Creosote, Lindane.

The terms "wood" and "timber" are used interchangeably herein.

Due to regulations relating to emissions from such processes, and from the resultant products themselves, being regularly changed and generally tightened in relation to the limits on certain elements and/or compounds being released into the environment it is desirable to have a process which meets and possibly exceeds the requirenien of these regulations. The present invention provides not only a process which meets this target hut also allows for further adjustnient and modification to keep pace with regulatoty and commercial pressures.

In a first aspect. the invention provides a method of processing waste material to produce vanous woid products comprising the steps of: (a) receiving waste matenal; @i) shredding the waste material; (c) removing at least some metallic objects from the shredded waste matenal; (ci) mechanically separating the waste. material into at least three size fractions; (e) mechanically sorting at least one of the at least three size fractions using near-infrared spectroscopy to separate it into at least two streams, one stream comprising substantially only wood products and one stream comprising treated wood products; (f mechanically sorting the stream comprising substantially only wood products using x-ray fluorescence and/or x-ray transmission to separate it into tvo streams, one stream comprising suhstantaally only grade "iy wood products and one stream comprising treated wood products.

Tn this way, grade "A" wood may be recovered fir re-use from mixed waste.

One of the other of the three size fractions may he returned to the shredding step Qi). For instance, the oversize may be returned to the shredding step to reduce its size. the oversize may be regarded as having at least one dimension greater than approxunatcly 50 to 1 5otrnji, rjiorc particularly grcatcr than I O0rrun. Alternatively, the oversize may be regarded as greater than 60mm.

the waste material may be washed after having been shredded in step b) and before mechanically separating the waste material into at least three size fractions in step (d).

At least one of the at least three size fractions may have at least some metallic objects removed from it before being separated into Iwo streams by an air separator.

One stream may he mechanically separated into an undersize product and an oversize product; the oversize product may be mechanically sorted using near-infrared spectroscopy to separate it into at least three streams, one stream comprising metallic objects, one stream comprising wood dust, and one stream cotnpnsing any of ceramic, stone arid porcelain.

A fourth stream may be produced comprising wood dust and other materials, tins stream may be separated by x-ray transmission and/or x-ray fluorescence into substantially only wood dust and a mixture of \vood dust and metallic objects/metal conipounds.

The \v2iste material may he sorted by hand prior to shredding in step (h) to remove at least some non-wood materials and at least some grade "D" timber.

The stream comprising treated wood products in steps (e and (t) may be mechanically sorted using near-infrared spectroscopy and/or x-ray transmission and/or x-ray fluorescence to separate it into two streams, one stream compnsing grade "B" wood products and one. stream comprising grade. "C" wood products.

Alternatively, the stream comprising treated wood products in steps (e) and ( may be mechanically sorted using near-infrared spectroscopy and/or x-ray transmission and/or x-ray fluorescence to separate it into three streams, one stream comprising grade "B" xvood products, one stream comprising grade "C" wood products, and one streani comprising grade "13" products.

The wood dust may he formed into any one or more of hriquettes, pellets and logs.

The method may further comprise the step of washing and/or drying the grade CC A" wood product of step (f.

The method may further comprise the step of pelletizing the grade "A" wood realised in step (f. A pelletiser may be employed to achieve this. Non-grade "A" wood iderititied and/or sortcd using the riethod may also be pellenzed and/or used as a fuel product.

the air separator may be a cyclone or a levitation sifter or an air classifier, the air separator may act to separate material on the basis of weight or density. in this regard a levitation sifter may comprise a vibrating screen deck substantially enclosed in a chamber with a negative pressure beneath the deck and a cross-wind applied above the deck. In use, the materials are bounced into the air above the deck wirh some particles passing through the deck and others being hlo\vn across above the deck. The device may he able to sort materials by density and/or weight.

The removal of metallic objects discussed herein includes either or both ferrous and non-ferrous objects and may he effected by using one or more metallic separators.

The separators may entploy magnets and/or an induced current. Non-ferrous metals may include brass and aluminium.

A vibratory feeder may be used to move the size fraction to the ncar-infrared spectroscopy in step (e.

In a second aspect, the invention provides a ffiel product manufactured using the method of the first aspect.

Tn a third aspect, the invention provides a waste processing plant operable according to the method of the first aspect.

Tn a fourth aspect. the invention provides a computer program comprising computer program code means adapted to operate and/or control plant required to perform the method of the first aspect when said program is run on a computer.

Various grades of timber may be recovered in using the method of the first aspect.

One of the at least three size fractions created in step (d) may be split into turo streanis of waste material prior to each stream being mechanically sorted in step (e. For instance, a flow splitter may split the size fraction so as to spread the load between more than one piece of near-infrared spectroscopy equipment.

The size fraction may be split into two or more streams each for processing by a 1 5 separate piece of near-infrared spectroscopy sorting equipment.

The products comprising metallic objects, separated by the near infrared spectroscopy sorter may be added back to the waste processing stream at any point.

For iristancc, it could bc added irrirriediately upstream of the shredding stage.

Altenutively, or additionally, the metallic objects and wood products comprising metillic objects collected front the near infrared sorters described herein may be shredded before being added to the waste stream immediately downstream of the initial shredding stage in step b).

One of the at least three size fractions created in step (d) may have a size range ofess than 10 to 20mm. one of the at east three size fractions may have a size range of less than 30 to 100 and greater than or equal to 10 to 20mm. In one embodiment this last size fraction may have a size range of less than 50mm to greater than or equal to to 30mm. One of the three size fractions may have a size range of equal to or greater than 50 to 100mm. Alternative size ranges are contemplated. If a fourth size fraction is produced it may have a size range of less than 50 and greater than or equal to 10 to 20mm.

The size ranges may be selected dependent on the type of near infrared speetroscopic sorting equipment employed. More than one type of such equipment may he employed at different or the same stages throughout the process.

Means other than a vibratory feeder for moving one of the three size fractions are contemplated such as the use of conveyors.

The method may further comprise the step of reducing the size of at least some of the untreated grade "A" wood produced in step (f. For instance a hammer-mill may he used to further reduce the untreated wood to have a size less than 5mm. Less than 3mm is also contemplated.

Any pellets create.d using the. method may have dimensions of approximately 3 to 6mm by 10mm and may be approximately cylindrical in shape.

The method may further comprise the step of using a person to observe and remove oversize and non-\vood objects by hand from the size fraction having a size less than 10 to 20mm. A conveyor "picking-belt" may be used in this connection. this may occur prior to shredding in step (h).

This method contains the steps necessary for making various wood products, including a fuel product. however it does not describe other processes for dealing with all of the other waste streams derived during the process. Accordingly, the method may include other steps as discussed below and as claimed herein. For instance, the method may further comprise the step of separating the metals into various types of metal, arid/or tlic furtlcr reduction in size of tlc treated wood for furtlcr proccssirig thereof.

Any reference to metal separation may use a magnetic and/or electro-magnetic separator. Non-ferrous metals may be separated using an eddy-current magnet.

The near infrared spectroscopy sorting equipment used in the method may rely on air jets to eject identified items from its conveyor belt. Equally, an X-ray optical sorter may rely on air jets to eject identified items from its conveyor belt.

It is to he understood that the steps of the method do not necessarily have to he performed in the sequence disclosed and that at least some of the steps may he repeated and/or performed at other stages within the process.

The processes described herein have been designed in order to ensure that the products described herein will he of such specification and commercial quality as to be capable of satisfying the relevant legal criteria laid down by the European Court of Justice and the Court of Appeal in England for a "completely recovered" or "end of waste" product. Those criteria are that: (a) the fuel is a distinct and marketable product, (b) the fuel can he used in exactly the same \vay as an ordinary fuel, and (c) the use of the processed fuel in the particular intended applications must not require any greater 2) environmental protection precautions nor result in any greater impact on the environment or human health than those applying to the use of the relevant virgin fossil fuel in the same application.

The above and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawing, which illustrates, by way of example, the principles of the invention. Ihis description is given for the sake of example only, without limiting the scope of the invention. The reference figures quoted below refer to the attached drawing.

Figure 1 is a flowchart of one \vay in \vhich the invention may be put into effect.

The present invention will be described with respect to particular embodiments and with reference to a drawing hut the invention is not limited thereto hut only by the claims. The drawing described is only schematic and is non-limiting.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking (Jr in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circurristarices arid that the erribodiiiierits of tile invention described herein arc capable of operation in other sequences than described or illustrated herein.

Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein.

It is to he noticed that the term "comprising", used in the claims, should not he interpreted as being restricted to the means listed thereafter; it does riot exclude other elements or steps. It is thus to he interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B. a Similarly, it is to he noticed that the term "connected", used in the description, should not be interpreted as being restricted to direct connections only. Thus, the scope of the expression "a device: connected to a device B" should not be limited to devices or systems wherein an output of device A is directly connected to an input of device B. It means that there exists a path between an output of A and an input of B which may be a path including other devices or means. "Connected" may mean that tvo or more elements are either in direct physical or electrical contact, or that vo or more elements are not in direct contact with each other but yet still co-operate or interact with each other.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection \vith the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all 1 5 referring to the same embodiment, hut may refer to different embodiments.

Furthemore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this

disclosure, in uric or rriorc crnbodirricrits.

Similarly it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure. or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. Ihis method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

Furthermore, \vhile some embodiments described herein include some, but not other, features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would he understood by those skilled in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

Tn the description provided herein, numerous specific details arc set forth.

Tjowever, it is understood that embodiments of the invention may be practised without these specific details. Tn other instances, well-known methods, structures and techniques have, not be.en shown in de.tuil in orde.r not to obscure an unde.rstanding of

this description.

The invention will now he described by a detailed description of several embodiments of the invention, it is clear that other embodiments of the invention can be configured according to the knowledge of persons skilled in the art without departing from the true spirit or technical teaching of the invention, the invention being limited only by the terms of the appended claims.

The overall process of waste processing is shown in Figure 1. As explained already, not all of the elements are crucial to its effectiveness and other arrangements and features may be included as required.

The waste is received 10 and passed along a picking belt 20 fnr removal of at least some non-tin-flier materials by hand. the waste then passes to a shredder 30 to rcducc thc ovcrall si/c of each object within the waste.

A Rawlings shredder may be used to reduce the size of the waste. The shredder may use blades to slice and cut the objects, rather than a tearing and smashing process such as occurs in ball mills, flail mills and the like.

the waste is then passed under a magnet 40 to remove any ferrous materials.

Any ferrous materials are collected, possibly for further processing.

The waste material is then passed to a non-ferrous metal removal stage 30 where metals such as aluminium and brass are removed by an induced current process. Any non-ferrous metals recovered are stored possibly for further processing.

The waste material is then conveyed to a series of screen decks 60 for separation into various size ranges. in the particular example the rangesare <10 to 20mm, (10 to 20) to (50 to ioomm) and >50 to 100mm.

The <H to 20mm is referred to as "undersize" 80 and is collected for further processing. Tn this regard, the undersize 80 may be washed and/or dried before passing through ferrous metal removal equipment too and non-ferrous metal removal equipment ito. the undersize is then sent to an air separator t20 where it is split into relatively light weight (or relatively lo\v density) material and relatively heavy weight (or relatively high density) material. The former will comprise paper and cardboard and the like. The latter is sent to a screen 130 where the resulting <3 to <5mm size 15 termed c1i/d 140.

The fraction which is greater than 3 to 5mm (i.e. approximately >3 to 5mm to 10mm is passed to another near infrared spectroscopy sorting device 210 where it is separated into four streams. One comprises ceramics, stone and porcelain 230, one conipnses clean wood dust 220, one compnses metallic objects (possibly alloys) 200, and one is passed to another set of x-ray transmission and/or x-ray fluorescence sorters to remove metallic objects and wood products comprising metallic (and/or non-wood) objects.

The oversize 70 from the initial screen decks 60 is sent back to the shredder 30 for further size reduction.

The middle size fraction from the screen decks 60 passes via a vibratory feeder iSO which in turn feeds a near infrared N1R) spectroscopy sorting device 160 which removes materials/objects comprising metals. These are collected 200 with materials comprising metals identified by the near infrared spectroscopy sorting device 210 dcscribcd abovc. Ihc N lIt sorter may also identify and isolatc trcatcd wood products (grade "B"). The remaining waste is passed to an x-ray transmission and/or x-ray fluorescence sorter which may rely on optical sorting and/or fluorescent sorting to identify and separate grade "A" wood products 180 from non-grade "A" wood products 190.

it is to be understood that the resultant non-grade "A" wood products may be sent to at least one or more NIR and/or x-ray transmission and/or x-ray fluorescence sorters for further processing to separate grade "B", and possibly grade "C' and grade "D" products therefromn.

The grade "A" product may he densified for the production of pellets and briquettes and the like.

The screen sizes and the ranges of dimensions stated herein may be adjusted to suit the moisture content of the waste material and to optimnise the efficiency (in terms of material identification and separation) and throughput of the process.

Claims

(Turns 1. A method of proces5i1g waste matenal to produce vanous wood products comprising the steps of: (a) receiving waste material; (b) shredding the. waste material; (c) removing at least some metallic objects from the shredded waste material; (d) mechanically separating the waste material into at least three size fractions; (e) mechanically sorting at least one of the at least three size fractions using near-infrared spectroscopy to separate it into at least tvo streams, one stream comprising substantially only wood produc and one steam comprising treated (t) mechanically sorting the stream comprising substantially only wood products using x-ray fluorescence and/or x-ray transmission to separate it into two streams, one steam comprising substantially only grade "A" wood products and one steam comprising treated wood products.
2. Ihe rietiiod of claim I, wherein oric of the other of the at least three size fractions is returned to the shredding step (h).
3. the method of either one of claims 1 and 2, wherein the waste material is washed after having been shredded in step b) and before mechanically separating the waste material into at least three size fractions in step (d).
4. The method of any one of claims 1 to 3, wherein at least one of the at least three size fractions has at least some metallic objects removed from it before being separated into Iwo streams by an air separator.
5. The method of claim 4, wherein one stream is mechanically separated into an undersize product and an oversize product; the oversize product being mechanically sorted using near-inFrared spectroscopy to separate it into at least three steams, one steam comprising metallic objec, one stream comprising wood dust, and one steam comprising any of ceramic, stone and porcelain.
6. The method of claim 4. wherein a fR)urth stream is produced comprising wood dust and other materials, this stream being separated by x-ray transmission and/or x-ray fluorescence into substantially only wcod dust and a mixture of
7. the method of any preceding claim, wherein the waste material is sorted by hand prior to shredding iii step (h) in claim 1 to ren-iove at least some non-wood materials.
8. The method of any preceding claim, wherein the stream comprising treated wood products in steps (e) and (F) in claim I is mechanically sorted using near-infrared spectroscopy and/or x-ray transmission and/or x-ray fluorescence to separate it into tvo streams, one stream comprising grade "B" wood products and one streani comprising grade "C" wood products.
9. The method of any one of claim I to 7, wherein the stream comprising treated wood products in steps (e) and (F) in claim I is mechanically sorted using near-infrared spectroscopy and/or x-ray transmission and/or x-ray fluorescence to separate it into tliree strcarris, one stream corriprisimig gradc B" wood products, one stream comprising grade "C" wood products, and one stream comprising grade "D" products.10. the method of claim 5 or any one of claims 6 to 9, when directly or indirectly dependent on claim 5, wherein the wood dust is formed into any one or more of briquettes, pellets and logs.ii. The method of any preceding claim, further comprising the step of washing and/or drying the grade "A" wood product of step (0 in claim 1.12. the method of any preceding claim, further comprising the step of pelletizing the grade "A" wood realised in step (0 in china t.13. the method of claim 4, or any claim directly or indirectly dependent on claim 4, wherein the air separator is a cyclone or a levitatlon sifter. Ii14. A fuel product manufbctured using the method of any preceding claim.15. A waste processing plant operable according to any of the methods of claims 1 to 13.16. A computer program comprising computer program code means adapted to operate and/or control plant required to perform the methods of any of claims 1 to 13 when said program is run on a computer.17. A method of processing waste material to produce a fuel pellet substantially as hereinhefore described with reference to the accompanying drawing.18. A waste processing patft substantially as hereinbefore described with reference to the accompanying drawing.