GB2465202A

GB2465202A - Method and apparatus for comminuting particle and fibre board

Info

Publication number: GB2465202A
Application number: GB0820583A
Authority: GB
Inventors: Donald Charles Blair
Original assignee: AQUABLAST Ltd
Current assignee: AQUABLAST Ltd
Priority date: 2008-11-10
Filing date: 2008-11-10
Publication date: 2010-05-12
Also published as: GB0820583D0

Abstract

A method of and apparatus for reducing waste particle board, fibreboard and the like to constituent materials for recycling comprises feedstock conveyors 22, 23 for introducing sections of waste wood materials to a series of high-pressure water jets 25, 26, 27 which break the adhesive bonds holding wood particulate or wood fibre within a matrix. The apparatus may also comprise a press and a dryer unit to remove water from the wood fiber after comminution and programmable control means for the water jets.

Description

METHOD OF AND APPARATUS FOR REDUCTION OF PARTICLE

BOARD AND MEDIUM-DENSITY FIBREBOARI) FOR RECYCLING

Field of the Invention

The present invention relates to a method of and apparatus for reducing particle board and medium-density fibreboard into components for re-use and recycling.

The invention is directed particularly to a method of and apparatus for obtaining commercially valuable materials from particle board and medium-density fibreboard generated as off-cuts during manufacture or for the recycling of furniture, kitchen units and wall panels, which ordinarily would be dumped, and ** 10 to do so in an economically efficient and substantially environmentally-friendly

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manner.

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The method and apparatus as described hereinbelow are directed primarily with reference to the recovery of wood fibres and wood particulates from medium-density fibreboard (MDF), particle board, chip-board and plood used generally ***.* * 15 in the construction industry and in the manufacture of furniture and kitchen units.

It will be appreciated by the skilled addressee that the invention may be applied to any composite material comprising particulates bound in an adhesive matrix such as a urea-aldehyde adhesive (commonly urea-formaldehyde).

Background to the Invention

Particle board and fibreboard is formed from woOd particulates and fibres bonded by an adhesive. It is used predominantly in furniture manufacture as it is easy to work and can be coated using a number of finishes.

In the manufacture of articles using particle board and fibreboard (particularly medium-density fibreboard) between 15% and 20% of materials go to waste, either as machined material, off-cuts or dust. This material currently is disposed of to landfill.

At the end of the product cycle or when furniture is replaced, it tends to be dumped rather than re-used. In domestic kitchens, for example, an existing chip-board or MDF (medium-density fibreboard) kitchen will be one of the first modifications made to an existing property. Additionally, it is not uncommon for home-owners to replace a kitchen within an eight year period of the installation of an earlier kitchen. The turnaround in MDF articles means that there is a significant amount of MDF being replaced in the domestic market alone, and most of the replaced material finds its way to landfill.

Economically, it is now no longer a viable option to dispose of particle board and fibreboard to landfill due to the associated disposal costs. There are also environmental considerations to be made. * . SI..

There are well-established problems associated with the volume of material ear- * marked for disposal in the construction industry, of which particle board arid I.....

* fibreboard is a factor, the most significant problem being the space these materials occupy in landfill sites. The scarcity of available landfill space and the associated *: 20 costs of disposal now means that, in certain jurisdictions, the use of landfill sites as a disposal option is no longer viable.

Within the last twenty years, and more particularly within the last decade, there has been a considerable upsurge in interest from commercial undertakings and impetus from government bodies to seek environmentally-friendly solutions to problems such as the disposal of certain waste materials. More particularly, the costs associated with disposal has lead to research into the recycling and re-use of particle board and fibreboard, particularly MDF.

Numerous solutions to the problem of particle board and fibreboard recycling have been proposed in the past. In one arrangement (Japanese Patent Publication

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No. JP 2004130549) waste material in the form of chips is used as a core material within a multi-ply material. Other methods of re-use include the crushing of wood based materials which are subsequently mixed with concrete such as in United States Patent Publication No. US 2004175449.

Included amongst the disadvantages of the above solutions are the physical reduction of the wood particle sizes and the integrity of the wood fibres recovered.

Accordingly, the amount of recycled material used in the production of fresh material is small, as little as 1% recycled material in many instances.

To recover substantially undamaged wood particle and wood fibres it is necessary to break down the adhesive used to bind these materials. Commonly, the adhesive used is a resin, usually urea-formaldehyde.

At present, there are three main approaches used to release wood particles and wood fibres from resin bonded materials. The first method involves soaking the material and subsequently applying heat and pressure to break the adhesive bonds.

.... 15 This is a time-consuming and costly procedure which makes it a non-viable solution commercially. The second method includes the use of acoustic radiation * to interfere with the adhesive bonds but again involves the pre-soaking of the **.S.

* material and the penetration of the acoustic radiation is known to be limited. To *:*. date no known commercial realisation of this technology has been achieved. The * .... 20 third method uses microwave radiation to break the urea-formaldehyde bonds and enhance swelling of the waste material feedstock within an acceptable time frame.

Unfortunately, to have sufficient processing capacity to deal with useful amounts of waste feedstock, the loading and unloading of a microwave chamber (or cavity) and the provision of sufficiently large chambers still presents a challenge.

Additionally, the energy consumption negates the potential savings and environmental efficiency of the recovery of the target material.

Many of the above solutions have now been discredited as environmentally unsafe or too expensive to implement.

With the increased interest in recovered wood particles and fibre from MDF a number of commercial avenues are available for recovered wood particles and wood fibres. Recovered wood particles can, where of sufficiently large size, be reused in the production of fresh particle board. Additionally, biodegradable packing material may be produced using recovered wood particles. Reclaimed wood fibre from MDF is often used in insulation products and provides an environmentally friendly alternative to glass fibre. Furtherniore, the fibre may be used in the production of new products when combined with other materials including, for example, plastic composites which may be used in numerous different fields including uPVC replacement materials and vehicle interiors.

It is a primary object of the present invention to provide a method of reducing particle board and fibreboard which obviates the disadvantages associated with the prior art and seeks to maximise the extraction of commercially viable materials therefrom in an economically efficient and substantially * : :* 15 environmentally-friendly manner. S...

It is a particular object of the present invention to obviate the disadvantages associated with methods including the pre-soaking of waste materials or the use of S.....

* high-energy means to reduce adhesive bonding of wood particles of fibres. S... * S

*: .: An additional object of the invention is to provide apparatus to implement the * ..: 20 method of the invention and to extract commercially viable materials from waste particle board and medium-density fibreboard.

Summary of the Invention

Accordingly, the present invention provides a method of reducing waste particle board and fibreboard to useable constituent materials, the method comprising: feeding substantially planer sections of waste wood based material feedstock towards a plurality of high-pressure water jets; exposing the feedstock to the jets to mechanically separate wood particles or wood fibres from a bonded matrix of like material; and continuously feeding new material towards the jets as exposed feedstock is eroded.

The method further includes the separation of wood particle or wood fibre from effluent water generated during the reduction of feedstock, the method comprising; pumping wood particle or wood fibre slurry to a separation tank to extract a majority of effluent water: feeding wet particle or fibre to a press, where further water is extracted; conveying, from a damp material accumulator, a batch of damp wood particle or fibre; and feeding the damp material into a dryer unit. * ** * * *

:.:. Advantageously, the method further includes screening dry wood particles to size. ****

* * Preferably, the method additionally comprises: * ** S... * S

positioning waste wood material feedstock in a conveying means to *. 5 expose the feedstock to a pressurised water jet; *5*55* * S moving the jet along a leading edge portion of the feedstock so as to expose raw feedstock material to the directed jet; rotating an array of nozzles comprising the jet across said leading edge portion of the feedstock to enhance a cutting action; moving the nozzle with respect to the leading edge portion of the feedstock material; and moving the material feedstock so as to optimise the position of the nozzle with respect to the leading edge portion thereof, whereby the feedstock material is disintegrated into a slurry of water, wood particulate or wood fibre, reduced adhesive arid surface material, if present.

Surface material may include paints, foils, surface veneers and laminates.

Conveniently, a slurry of wood particulate or wood fibre is collected and conveyed to further processing stations.

At one further processing station, additional materials and excess water are separated from the target wood particulate or fibre materials, the wet particulate or fibre is then washed before being conveyed to a press where further water is extracted.

The present invention also provides an apparatus for reducing waste particle board and fibreboard, to useable constituent materials, the apparatus comprising: * : :* feeding means for introducing substantially planar sections of waste wood based feedstock material into the apparatus; * S..

high-pressure water jet means; S..... * .

*: 15 programmable control means for positioning the water jet means; * : * means for moving the feedstock material with respect to the water jet means to expose a feedstock surface to one or more jets; and means for continuously feeding new waste material towards the jets as exposed feedstock is eroded.

The apparatus further comprises means for separating wood particulate or wood fibre from effluent water generated during the reduction of waste wood products, the apparatus comprising: a separation tank to extract a majority of effluent water from a wood particulate or wood fibre slurry presented thereto; a press where further water is extracted from wet particulate or fibre from the separation tank; and a damp material accumulator from which there is conveyed a batch of damp material for feeding to a dryer unit.

Conveniently, the apparatus includes a means for collecting and conveying a slurry of wood materials downstream to a particulate or fibre processing station.

Brief Description of the Drawings

The invention will now be described more particularly with reference to the accompanying drawings which show, by way of example only, one construction of an apparatus for reducing waste particle board and fibreboard, including means for eroding the introduced wood materials and plant for the dewatering and drying of wood particulate or wood fibre, in accordance with the invention. In the *:*::* drawings: *... * S * 55*

Figure 1 comprises a perspective view of a first feedstock processing station for :: 15 handling substantially elongate rectangular sections of particle board and fibreboard; *5 S * S S * Figure 2 is a perspective view of a second feedstock processing station for S.....

* S handling substantially planar (including irregularly shaped) sections of particle board and fibreboard; and Figure 3 is a schematic perspective view of the plant for the dewatering and drying of wood particles and wood fibres extracted from waste wood products.

Detailed Description of the Drawiigs

In the present description, the terms "upstream" and "downstream" should be regarded with respect to the drawings only and relate to the processing and conveyance of particle board, fibreboard and constituent materials taken therefrom. In this arrangement, "upstream" represents the source of material to be processed and "downstream" towards an accumulation point for further processing, storage or dispatch.

Referring now to the drawings, and initially to Figure 1, an accumulated and sorted stock of either particle board or fibreboard is presented for reducing into constituent components. Where convenient or the stock material allows, sections of stock may be pre-cut into elongate sections for convenient processing. At a first processing station 10, an elongate section of material M is secured or otherwise guided for feeding past at least one high-pressure water jet nozzle 12, which is adapted under microprocessor control to scan across the width of the presented section and adjust to the required scan width. Using a rotating nozzle 12 comprising an array of high-pressure jet outlets, the leading edge of the section is eroded using high-pressure water (and optionally cutting grit) supplied via an ultra-high pressure compressor (not shown). Using edge-detecting sensors, the nozzle 12 is passed over the leading edge until it is totally eroded by the action of * * 15 the water. The material is then progressed stepwise towards the nozzle until a leading edge detector indicates that sufficient material is available for action, and S...

the nozzle is moved to a start position at one side of the presented section and the cycle is re-commenced. In this way the section is reduced and the wood material *: slurry thus produced is collected in a chute C for conveying the slurry to a material recovery station, as described in detail hereinbelow. S* * SS * *e

Figure 2 shows a second particle board or fibreboard processing station 20 comprising a pair of oppositely rotating conveyor belts 22, at least one of which is driven, to convey planar feedstock P from an accumulated and sorted stock of particle board or fibreboard. The planar feedstock P is fed to the conveyor 22 either manually or by a gravity feed mechanism. The rubberised belts 23 of the * conveyor 22 grip the feedstock as it is presented in a stepwise manner to a plurality of high-pressure water jet nozzles 25, 26, 27. In the illustrated arrangement, first and second nozzles 25, 26 scan the upper and lower planar surfaces under microprocessor control so that the width of the planar feedstock is subjected to water jets of sufficient force to break down the particle-to-particle and fibre bonds. A third nozzle 27 scans across the leading edge of the presented feedstock P under microprocessor control so that as the leading edge is eroded by the water jets, the feedstock is advanced by the conveyor 22. Proximity detectors adjacent the third nozzle 27 or nozzle independent edge-detecting sensors (not shown), again under microprocessor control, detect the position of the leading edge of the feedstock P and to progress it when said leading edge is eroded.

Each of the nozzles 25, 26, 27 (and the nozzle 12 illustrated in the first embodiment) comprise an array of high-pressure water jets adapted to rotate to enhance their cutting action.

The water and wood material (wood particulate and wood fibre) falls into a collection chute C and is conveyed as a slurry of wood particulate, wood fibre, reduced adhesive and any surface finish material that may be present, towards the material recovery station.

Referring now to Figure 3, downstream of the processing stations 10, 20 there is provided a material recovery station 30 for dewatering, drying and recovering *: *: :* wood particulate and/or wood fibre. The plant comprises a separation tank 31 into *: :: :* 15 which a slurry of effluent water and wood particulate or wood fibre (hereinafter "wood pulp") is fed. Using a weir and trap system (although other systems are S.....

* : equally good) excess water is extracted and drained off, ideally for filtering and S.....

* treating for re-use.

S * . .

: The wet wood pulp is pumped or otherwise conveyed to a filter belt press 32 where further water is extracted and the now merely damp pulp is accumulated in a storage vessel 34 to be fed batchwise into a rotary dryer 35 via a feed-screw 36.

Hot air is circulated through the rotary dryer 35 via hot air inlet 37 and outlet 38 paths. Ideally, hot air is taken from the ultra-high pressure compressor so as to utilise this source more effectively. Drying wood pulp is agitated within the dryer by helical blades 39 disposed therein. To unload the dryer, it is rotated in the opposite direction to that used to load and dry the wood pulp. The dried pulp is then optionally sorted batchwise and/or fed into storage containers (not shown).

It will of course be understood that the invention is not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the appended claims. * ** * * * * ** **** * * *.. * *

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Claims

CLAIMS: 1. A method of reducing waste particle board and fibreboard to useable constituent materials, the method comprising: feeding substantially planar sections of waste wood based material feedstock towards a plurality of high-pressure water jets; exposing the feedstock to the jets to mechanically separate wood particles or wood fibres from a bonded matrix of like material; and continuously feeding new material towards the jets as exposed feedstock is eroded.
2. A method as claimed in Claim 1 which includes the separation of wood particle or wood fibre from effluent water generated during the reduction of feedstock. * .* * S * * *.

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3. The method as claimed in Claim 2, the method including: ** pumping a wood particle or wood fibre slurry to a separation tank to :" 15 extract a majority of effluent water; *. . feeding wet particle or fibre to a press, where further water is extracted; **.** * S conveying, from a damp material accumulated, a batch of damp wood, particle or fibre; and feeding the damp material into a dryer unit.
4. A method as claimed in any one of the preceding claims, the method including: positioning waste wood material feedstock into a conveying means to expose the feedstock to a pressurised water jet; moving the jet along the leading edge portion of the feedstock so as to expose raw feedstock material to the directed jet; rotating an array of nozzles comprising the jet across said leading edge portion of the feedstock to enhance a cutting action; moving the nozzle with respect to the leading edge portion of the feedstock material; and moving the feedstock material so as to optimise the position of the nozzle with respect to the leading edge portion thereof whereby the feedstock material is disintegrated into a slurry of water, wood particle or wood fibre, reduced adhesive and surface material, if present.
5. The method as claimed in any one of Claims 2 to 4 in which the method includes: separating effluent water and additional materials from the target wood particulate or fibre materials; * .S washing the target materials; and ***. * *conveying the target materials to a press where further water is extracted.

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6. An apparatus for reducing waste particle board and fibreboard to useable *: * constituent materials, the apparatus comprising: feeding means for introducing substantially planar sections of waste wood-based feedstock material into the apparatus; high-pressure water jet means; programmable control means for positioning the water jet means; means for moving the feedstock material with respect to the water et means to expose a feedstock surface to one or more jets; and means for continuously feeding new waste material towards the jets as exposed feedstock material is eroded.
7. The apparatus as claimed in Claim 6 in which the apparatus includes a means for separating wood particulate or wood fibre from effluent water generated during the reduction of waste wood products.
8. The apparatus as claimed in Claim 7, in which the means for separating wood particulate or wood fibre from effluent water includes; a separation tank to extract a majority of effluent water from a wood particulate or wood fibre slurry presented thereto; a press where further water is extracted from wet particulate or fibre from the separation tank; and a damp material accumulator from which there is conveyed a batch of damp material for feeding to a dryer unit.
9. The apparatus as claimed in any one of Claims 6 to 8, in which the * *. apparatus includes means for collecting and conveying a slurry of wood materials * downstream to a particulate or fibre processing station. **** * * **, *
10. A method of reducing waste particle board and fibreboard substantially as * ***** * herein described with reference to the accompanying drawings.I..... * S*
11. An apparatus for reducing waste particle board and fibreboard substantially as herein described with reference to and as shown in the accompany I.....* * drawings.