GB2436083A

GB2436083A - A process for recycling timber products

Info

Publication number: GB2436083A
Application number: GB0605278A
Authority: GB
Inventors: Fergal Martin Conroy; Deborah Philomena Conroy
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-03-15
Filing date: 2006-03-15
Publication date: 2007-09-19
Anticipated expiration: 2026-03-15
Also published as: GB0605278D0; GB2436083B

Abstract

This invention relates to a process for recycling timber products in a recycling plant 1. The timber products are soaked in situ in the hold 53 of a delivery truck 51 as they enter the recycling plant before being placed on a stock pile 11 in an elevated area in the recycling plant. The water and any grit washed from the timber in the stock pile are allowed to gravity flow through the recycling plant to a settling tank 33. The water and the grit are separated in the settling tank and a further filtration tank 35. The water may then be pumped out through a pipe network into an adjacent pasture 41 or reused in the soaking of timber products entering into the recycling plant. The timber products are then passed to a slow crusher 13 then a fast crusher 15, and metals of varying sizes are removed before the crushed timber products are graded according to size. The process allows for the timber products to be washed before being allowed to enter the crushing equipment, and furthermore allows for collection of debris from the timber in a simple manner without requiring expensive equipment to do so.

Description

"A Process for Recycling Timber Products"

Introduction

This invention relates to a process for recycling timber products in a recycling plant and in particular to a process for recycling timber products in a simple and efficient manner that allows for improved yields to be obtained from the recycling process.

Over the last number of years, due to increased public awareness in the harmful effects of waste on the environment, numerous recycling projects have been:. :.

undertaken around the world. Many governments have introduced regulatory provisions to ensure that recyclable waste is handled in the most environmentally friendly manner possible. Furthermore, many companies have themselves * is introduced better recycling practices in order to improve their public image as well as to minimise their costs and in some cases avoid hefty penalties imposed on them for ----v--dumping waste. Some of the most successful recycling programmes introduced to: date have been concentrated around wood and timber products in general. These products may be recycled and transformed into other consumer goods and items with relative ease. Therefore, it is attractive for individuals and companies with large amounts of waste timber products to have them recycled rather than sending them to landfill. There are however numerous problems with the various known methods of recycling timber products.

Typically, recycling of timber products involves grinding the timber products down into a uniform particle size and thereafter using the reduced particle sized product for a different purpose or carrng out further treatment steps such as producing a pulp from the wood particles. One problem with grinding timber products is that the grinding has a tendency to create a lot of dust and debris that may become airborne and travel significant distances in the open air. This in itself is considered to be a pollutant and must be controlled in order to prevent a recycling company from incurring large penalties for polluting the environment. In particular, wood dust has a tendency to travel significant distances when airborne which may cause difficulties for individuals with respiratory difficulties in the vicinity of the recycling plant.

Furthermore, the dirt and dust kicked up by the known methods have a tendency to cause disputes with neighbouring premises due to the levels of dirt created.

Another problem with the known methods of recycling is that the steps of grinding used in these methods is relatively crude. It is not uncommon for a recycling plant to take in a load of material, that may come from a construction site or the like, that includes cementitious materials and metallic objects and other debris other than timber products in the load. Typically, with the known methods of recycling timber products, these non-timber materials have to be removed by hand in order to prevent these alien materials from entering the grinder and potentially damaging the grinder.

If these objects are not removed they may cause damage to the grinder or may blunt:. :: the blades of the grinding device which is highly disadvantageous. Furthermore, one of the greatest problems encountered by recyclers of timber products is caused by dirt on the debris or attached to the timber. This dirt attached to the debris or dirt: . . attached to the timber products may over time clog up the grinder which thereafter will require cleaning and down-time in which the grinder may not be used. This -----.

reduces the total production time available to the recycling plant thereby reducing * : productivity as well as profitability. Furthermore, if this dirt should get into the equipment such as a conveyor, the dirt can cause the conveyor to rip and fail, thereby further increasing the cost of recycling the timber to the company, which in turn further reduces profit and productivity.

Another problem with the known recycling processes is that the timber products are ground for a specific purpose and then sold for that purpose. For example, it may be desirable to grind the timber products up for sale as fuel in incinerators. In such a case, the timber product is crushed into as small a particle size as possible for use in large scale incinerators. In other circumstances the wood will be shaven into larger sized particles for use as bedding in stables and the like. Depending on the size of the product produced it is possible to achieve a greater return for the recycled good.

For example, high quality wood shavings for stables obtain a much higher premium than low grade fuel for incinerators. However, up until now the known processes of recycling timber products, although they produce a number of different sized products, have tended to provide only one end product thereby either wasting more valuable product when it is sold as part of a less expensive end product or devaluing an expensive end product that is considered to be of lower quality as it contains additional non-standard particle size material. For example, grinding timber products will result in an end product of a variety of different sizes. If the end product is to be sold as fuel, the larger shavings are sold as fuel along with smaller sized particles which is a waste, as the true market value of the larger sized particles is far in excess of that for the smaller sized particles and accordingly the best price for the product is not being achieved. Therefore an opportunity cost is incurred by the recycling plants operators by not been able to separate the various different products that are produced and obtain the best possible price for each product. In order to separate the goods or provide goods of high value more elaborate processes have to be introduced such as plaining the timber products in specially adapted machines in order to provide wood shavings of a particular size suitable for use in stabling. Again, this will increase the cost of recycling the timber products which is highly undesirable due to the relatively tight margins in this industry.

Therefore, it is an object of the present invention to provide a process for recycling *. S...

timber products that overcomes at least some of these difficulties that is both simple *: :: . and efficient to operate but at the same time improves the productivity and yield from the timber recycling plant.

Statements of Invention

According to the invention there is provided a process for recycling timber products in a recycling plant comprising the steps of: receiving the timber products in a hold of a delivery truck at the recycling plant; soaking the timber products with water, in situ in the hold of the delivery truck; dumping the soaked timber products on a timber stock pile in an elevated area in the recycling plant and allowing the water and any grit washed from the timber products to gravity flow through the recycling plant from the timber stock pile in the elevated area to a collection area of the recycling plant having a settling tank; allowing the water and grit to settle in the settling tank and thereafter removing any settled grit particles from the settling tank; passing the remaining settled water from the settling tank to a filtration tank and removing any further unsettled grit particles from the water in the filtration tank and filtering further impurities from the water in the filtration tank; pumping the filtered water from the filtration tank along a subterranean pipe network to a plurality of points in an adjacent pasture; * S delivering the soaked timber products from the stock pile to a slow crusher and coarsely grinding the soaked timber products before placing the ------. S...

coarsely ground timber products onto a transfer conveyor; * : : : : passing the transfer conveyor with coarsely ground timber products thereon beneath a magnetic conveyor and removing any large metallic objects from the coarsely ground timber products; delivering the coarsely ground timber products from the transfer conveyor to a fast crusher in which the coarsely ground timber products are more finely ground and thereafter placing the finely ground timber products onto a second transfer conveyor; passing the second transfer conveyor beneath a second magnetic conveyor and removing any further small metallic objects from the coarsely ground timber products before placing the finely ground timber products in a hopper; passing the finely ground timber products from the hopper to a screening unit having at least one graded screen and separating the finely ground timber products into a plurality of graded timber products for subsequent distribution.

By having such a process the productivity of the recycling plant will be significantly improved. The timber products will be soaked whilst they are still in the hold of the delivery truck. This helps to wash any loose debris or dirt off the timber while it is still in the truck. Accordingly, this dirt and debris will not be able to get into the grinding equipment and potentially cause it to fail. The timber products are then dumped onto a timber stock pile which is located in an elevated site in the recycling plant. This allows the water and the grit washed from the timber products to be washed away from the timber products to a collection area where the water may be treated for re-use or subsequent distribution. This is achieved without the need for pumps or other equipment to remove the water from the timber stock pile. The impurities are removed from the water and these impurities may be sent to dry-fill or disposed of by another method if necessary while the water is pumped into an adjacent pasture, thereby returning back into the environment. This process is ---.

seen as particularly useful as the amount of dirt and grit which accompanies the timber products for grinding is significantly reduced before the timber products enter any of the crushing devices. Therefore, maintenance of the crushing devices is significantly reduced and these crushing devices will be able to operate far more efficiently than was heretofore the case. Furthermore, this is a very environmentally friendly way of reducing the amount of dirt and debris in the timber products. In addition to this, the water and grit will naturally flow away from the timber products when they are on the timber stockpile which is very useful and inexpensive to perform.

Furthermore, by soaking the timber products in this manner the timber will naturally soak up a significant amount of water as it will be effectively held in a bath in the hold of the delivery truck, in this way, the timber products will not cause as much dust when being ground as was heretofore the case. This significantly reduces the amount of airborne dust which is carried off in the atmosphere to surrounding areas thereby obviating the possibility of legal suits or disputes with neighbours.

Furthermore, by incorporating a slow crusher followed by a fast crusher, a more crude crushing step may be first performed which will allow the large timber products to be broken down into smaller sizes as well as allowing any large foreign metallic objects to be removed from the crudely crushed timber products. In this way, more sensitive crushing machinery and blades will not be blunted by contacting with very large metallic objects. The metallic objects may be removed before a finer grinding step is carried out to grind the coarsely ground material into smaller particles that are of greater commercial value. Again smaller magnetic objects such as nails and the like may be removed at this stage by passing the finely ground timber products under a magnetic conveyor so that a more valuable end product may be produced. Furthermore, the metallic objects removed after both the coarsely grinding step and the fine grinding step may be recycled themselves for scrap metal or other purposes. Finally, the finely ground timber products in various different sizes may then be passed to a screening unit which will separate the finely ground timber products into a number of different sizes, hence different valued commodities may be subsequently sold for the true commercial worth of each product rather than selling a product with numerous disparate particle sizes. This helps to further increase the profitability and efficiency of the recycling plant. . : : : In another embodiment of the invention there is provided a process for recycling timber products in which the step of soaking the timber products further comprises spraying the timber products from a position above the hold of the delivery truck until the hold of the delivery truck begins to overflow. This is seen as particularly useful as once the hold of the delivery truck begins to overflow, all of the wood contained in the delivery truck will be immersed in water thereby ensuring that the wood is thoroughly soaked before it is passed to a crusher.

In one embodiment of the invention there is provided a process for recycling timber products in which the step of soaking the timber products further comprises spraying the timber products from a position above the delivery truck at a flow rate in the order of 500 litres/minute. By soaking the timber products with a spray of a flow rate in the order of 500 Iitres/ minute, the majority of debris and dirt will be washed from the timber products thereby preventing any dirt from inhibiting operation of the grinding devices.

In a further embodiment of the invention there is provided a process for recycling timber products in which the timber products are sprayed for a period of between I and 10 minutes.

In another embodiment of the invention there is provided a process for recycling timber products in which the process further comprises the step of soaking the timber products sufficiently so that the finely ground timber products have a water content in the order of 15% by weight after being finely ground. By soaking the timber products so that the finely ground timber products have a water content in the order of 15% by weight, the finely ground timber products do not have a tendency to become airborne and travel. Furthermore, the smaller particles with this water content will also have a tendency to separate more easily from the larger products thereby ensuring more comprehensive separation of goods. * * * *

In another embodiment of the invention there is provided a process for recycling *..* timber products in which the process further comprises having the slow crusher ----.

located in an elevated area in the recycling plant and allowing any water removed from the timber products during the coarsely grinding step to gravity flow from the slow crusher to the settling tank in the collection area of the recycling plant.

In a further embodiment of the invention there is provided a process for recycling timber products in which the process further comprises having the fast crusher located in an elevated area in the recycling plant and allowing any water removed from the timber products during the finely grinding step to gravity flow from the fast crusher to the settling tank in the collection area of the recycling plant.

In another embodiment of the invention there is provided a process for recycling timber products in which the step of pumping the filtered water from the filtration tank along a subterranean pipe network to a plurality of points in an adjacent pasture further comprises pumping the filtered water along a pipe network having a plurality of elongate distribution pipes, each of which is embedded in a gravel channel, each elongate distribution pipe in the pipe network having a plurality of discharge apertures spaced along its length. This is seen as particularly useful as the filtered water will be distributed throughout the entire pasture in a simple manner. The water will be able to soak into the ground in the pasture more easily and will evaporate over time more efficiently. Furthermore, a gravel channel will ensure that the subterranean pipes do not become clogged with earth and other similar materials.

In another embodiment of the invention there is provided a process for recycling timber products in which the discharge apertures are evenly spaced along the length of the elongate distribution pipes. Again this ensures that the water will be distributed evenly throughout the pasture in a simple manner.

In a further embodiment of the invention there is provided a process for recycling timber products in which there is provided a water tank for supplying water to spray the timber products in the hold of the delivery truck, the water tank having means for monitoring the volume of water in the water tank and on the volume of water in the water tank falling below a predetermined level, the process further comprises the step of pumping filtered water from the filtration tank to the water tank to ------.. **S.

replenish the supply of water in the water tank until the volume of water exceeds the predetermined level. This is seen as particularly useful as the filtered water may be reused to spray further timber products that are brought into the recycling plant. In this way, the water may be reused again and again and new water will not have to be acquired. Again, this is a very environmentally friendly way of handling the process.

In another embodiment of the invention there is provided a process for recycling timber products in which the step of separating the finely ground timber products into a plurality of graded timber products for subsequent distribution further comprises passing the ground timber products over a graded screen having a plurality of apertures therein of a predetermined size. This is seen as a particularly simple way of separating the ground timber products into a number of different sizes. Preferably, the ground timber products may be passed over the graded screens, each graded screen having a plurality of apertures therein of a predetermined size, the aperture size of the screens increasing in size relative to the previous screen in relation to the direction of travel of the timber products along the screens. Preferably, the graded screen comprises a reticulated wire mesh. By passing the ground timber products over a plurality of graded screens each of the screens may be provided with different sized apertures to allow through passage of the timber product of a particular size. By increasing the size of the apertures in the screens relative to the direction of travel of the timber product over the screens, the smallest particulate material may be removed from the timber product first of all and so on until the largest particulate timber products above a certain size remain.

This may be done gradually so that different sized timber products of different particulate size may be separated from each other and therefore the best price for each product may be obtained, thereby significantly increasing profitability.

In another embodiment of the invention there is provided a process for recycling timber products in which the process further comprises the steps of separating the finely ground timber products into timber products of three distinct sizes, 0-13mm, 14-50mm and 51 to 60mm. This is seen as particularly useful as the smallest most finest timber product of 0-13mm may be used for boiler fuel, a low yield product.

The next size 14-50mm may be a more valuable product which may be used in ---i..

board manufacture and similar industries where the largest size product, 51mm - 60mm, is the most valuable product of all and may be used for lining stables as well as dry paddocks in fields and this is a very valuable and relatively inexpensive product to produce. In this way, the timber products may be separated into specific sized products that allow for the best price to be obtained for each product.

In another embodiment of the invention there is provided a process for recycling timber products in which the slow crusher comprises a rotating drum having a plurality of blades arranged about its surface and spaced circumferentially and axially from each other, the blades co-operating with complimentary fingers mounted internal the slow crusher as the drum rotates.

In another embodiment of the invention there is provided a process for recycling timber products in which the fast crusher further comprises a rotating drum having a plurality of flails arranged on the outer surface thereof.

In another embodiment of the invention there is provided a process for recycling timber products in which the process further comprises the step of storing the -10 -metallic objects removed from the coarsely ground timber products in a storage container for further recycling.

In another embodiment of the invention there is provided a process for recycling timber products in which the process further comprises the step of storing the metallic objects removed from the finely ground timber products in another storage container for further recycling.

In another embodiment of the invention there is provided a process for recycling timber products in which the process further comprises the initial step of weighing the dry weight of the timber products as they are brought into the recycling plant.

The company depositing the recyclable wood products may be charged by weight for all items delivered to the recycling plant thereby providing a further stream of revenue for the recycling plant. In this way, the operator of the recycling plant is obtaining a fee for receiving the goods for recycling as well as an additional fee for transforming those products into consumer items. Ideally, the process further -----.-.

comprises the intermediate step of weighing the unladen weight of the delivery truck as it exits the recycling plant. In this way, an accurate estimation of the dry weight of the wood may be achieved in a simple and efficient manner.

In a further embodiment of the invention there is provided a process for recycling timber products in which the process further comprises the additional step of sending any grit removed from the settling tank or the filtration tank to dry fill. This is seen as useful particularly in the case where the particular material may contain hazardous materials such as asbestos and the like that has been used in the building trade and may be attached to the timber products that have been brought into the recycling plant.

Detailed descriDtion of the Invention The invention will now be more clearly understood from the following description of some embodiments thereof given by way of example only, with reference to the accompanying drawings in which:- -11 -Fig. 1 is a diagrammatic representation of a recycling plant in which the process for recycling timber products according to the invention is carried out.

Fig. 2 is a more detailed view of part of the recycling plant shown in Fig. 1, Fig. 3 is a perspective view of the soaking unit for use in the process according to the invention, Fig. 4 is a perspective view of a crushing and screening apparatus used in the process according to the invention, Fig. 5 is a more detailed perspective view of the crushing apparatus shown inFig.4, : Fig. 6 is a more detailed perspective view of the screening apparatus used in the process according to the invention.

Referring to the drawings and initially to Fig. 1 thereof, there is shown a recycling plant, indicated generally by the reference numeral 1 comprising a wood treatment area 3 and a water treatment area 5. The wood treatment area 3 comprises a weighbridge 7, a soaking unit 9, a timber stockpile 11, a slow crusher 13, a fast crusher 15, a pair of transfer conveyors 17, 19, a pair of magnetic conveyors 21, 23, arranged above and substantially orthogonal to the transfer conveyors 17, 19 respectively, a hopper 25 and a screening unit 27. The timber stockpile 11, the slow crusher 13, the fast crusher 15, the hopper 25 and the screening unit 27 are located in elevated positions in the recycling plant so that water may flow from those elevated positions to the water treatment area 5.

The water treatment area 5 further comprises a collection area 31 having a settling tank 33, a filtration tank 35, a pump 37 and a subterranean pipe network 39 situated in a pasture 41 adjacent the timber product recycling plant. The subterranean pipe network 39 further comprises a plurality of elongate distribution pipes 43, 45 and 47, each of which is embedded in a gravel channel (not shown) in -12 -pasture 41. Each of the elongate distribution pipes 43, 45 and 47 is provided with a plurality of discharge apertures (not shown) spaced along their length to allow through passage of water pumped through the subterranean pipe network 39 from the filtration tank 35.

In use, a truck 51 with timber products in the hold 53 of the delivery truck for recycling enters the recycling plant and is weighed on the weighbridge 7 in order to calculate the dry weight of the timber products in the truck. The truck 51 is then advanced to the soaking unit 9 where water is sprayed onto the timber product in the hold 53 of the truck at a rate of 500 litres per minute for between 1 and 10 minutes. Once the water begins to overflow from the hold 53 of the delivery truck 51 the water supply is turned off. The thoroughly soaked wood products are then driven in the delivery truck 51 to the stockpile 11 where the timber products are dumped on the timber stockpile 11. Water and grit washed from the timber products during the soaking stage are allowed to flow under gravity through the recycling plant wood treatment area 3 to the settlement area 31 of the water treatment area 5 where the water and grit are gathered in a settling tank 33. Once settled, the settled grit is removed from the settling tank 33 and the settled water is * pumped into the filtration tank 35 where further grit and further contaminants are removed from the settled water. The grit may then be removed and sent to landfill.

The filtered water is then pumped from the filtration tank through the pipe network 39 by the pump 37 along the distribution pipes 43, 45 and 47 and water escapes from the distributions pipes through apertures (not shown) formed along the length of the distribution pipes 43, 45 and 47 into the surrounding soil and the pasture 41.

At the same time, timber is taken from the timber products stockpile using a suitable gripping device, in this case a caterpillar tracked loader 55 with gripping arm 81 is used to transport timber products from the timber stockpile 11 to the slow crusher 13. The timber products are coarsely ground in the slow crusher 13 whereafter they are placed onto a transfer conveyor 17 that travels underneath a magnetic conveyor 21 which removes any large pieces of metal from the coarsely crushed timber product. The large pieces of metal are then deposited in a storage bin 57 for further recycling or sale as scrap. The coarsely crushed timber material is then delivered by the transport conveyor 17 to the fast conveyor 15 where the -13 -coarsely crushed material is more finely ground into smaller particular sizes. From there, the finely ground timber product is placed onto a second transfer conveyor 19 where the finely ground timber product is first led under the second magnetic conveyor 23 so that smaller metallic objects freed by the fast crusher are removed from the finely ground timber product and deposited in a suitable hopper 59. The finely ground timber products are then led along the second transfer conveyor 19 to a hopper 25, from which they are passed to a screening unit 27. In the screening unit 27, the timber products are passed along a number of screens (not shown) and separated into various different sizes of particulate timber product materials before being gathered in stockpiles 65, 67 and 69 of similarly sized timber products. Referring to Fig. 2 of the drawings, there is shown an enlarged view of

the wood treatment area 3 shown in Fig. 1 where it can be seen that the screening unit 21 is itself on caterpillar tracks 61 so that the screening unit may be moved about the recycling plant if and when needed. A loading truck 63 is used to transport the stockpiles of different particulate materials 65, 67and 69 for subsequent distribution "* as well as keeping the stockpiles 11, 65, 67 and 69 in order. *1*** Referring now to Fig. 3 of the drawings there is shown a more detailed view of the soaking unit 9 for use in the process according to the invention. The soaking unit 9 further comprises a water tank 71 and a pumping unit 73. The pumping unit 73 pumps water from the water tank 71 to a series of spray nozzles 75 arranged on a canopy 77 located directly above the hold 53 of a delivery truck 51. In use, a delivery truck 51 with timber products in the hold 53 thereof is driven underneath the canopy 77 and water is pumped from the water tank 71 through the spray nozzles 75 into the hold 53 of the delivery truck 51 on top of the timber products therein. When the water begins to overflow from the hold 53, the timber products in the hold will be fully soaked and the water supply may be turned off. The soaked timber products are then transported to the timber stockpile (not shown) and dumped thereon.

Referring now to Figs. 4 to 6 inclusive of the drawings there is shown a more detailed view of the slow crusher 13, the fast crusher 15 and the screening unit 27.

In use, the caterpillar tracked loader 55 with gripping arm 81, grips soaked timber -14 -products from the timber stockpile (not shown). These timber products are then deposited by the loader 55 into the slow crusher 13. The slow crusher 13 comprises a rotating drum 83 having a plurality of blades 85 arranged about its surface, spaced circumferentially and axially from each other about the rotating drum. The blades 85 co-operate with complimentary fingers 87 mounted internal the slow crusher as the rotating drum rotates. Therefore, timber products are crushed between the blades 85 and the fingers 87 of the slow crusher as the drum 83 rotates. This coarsely grinds the timber products and detaches any large metallic objects from the coarsely ground timber products. At the same time, the timber products and large metallic objects are pushed towards the transfer conveyor 17. When on the transfer conveyor 17, the coarsely crushed timber products pass underneath a magnetic conveyor 21 which is arranged above and substantially orthogonal to the direction of travel of the transfer conveyor 17 and the magnetic conveyor 21 removes any large pieces of metallic material from the coarsely chopped timber products and deposits them in a hopper 57. The coarsely chopped timber product is then transferred to the fast crusher 15 which in turn --.

comprises a rotating drum 91 having a plurality of flails 93 arranged in an outer *.S.

surface thereof. The coarsely ground timber product progresses through the fast crusher 15 towards the flails 93 and is finely ground by the flails. The finely ground * timber product is then passed on to a second transfer conveyor 19 and is passed underneath a magnetic conveyor 23 which is arranged above and substantially orthogonal to the direction of travel of the transfer conveyor 19 where any smaller pieces of metallic material are removed from the finely ground timber product and deposited in a hopper 59.

The finely ground timber product is then advanced along the conveyor 19 to a hopper 25 of the screening unit. From the hopper 25, the finely ground timber product is moved along an enclosed conveyor 92 of the screening unit 27 and then dropped upon a series of graded screens 95a, 95b. The graded screens 95a, 95b are provided with apertures therein and the aperture sizes of the screens increases in size relative to the previous screen in the direction of travel of the timber products as they move along the screens. In other words, the first graded screen that the finely ground timber products encounter will have the smallest aperture size and the next graded screen that the timber products encounter will have a -15 -larger aperture size and so on depending on the number of different graded sizes of timber products that are required. The first graded screen 95a has a reticulated wire mesh with apertures of approximately 13mm in diameter. The next reticulated wire mesh graded screen 95b has apertures of approximately 50mm in diameter.

As the finely ground timber product passes over the screens 95a and 95b the product of a very fine composition under 13mm in length will pass through the first reticulated mesh graded screen 95a and will be transported away on a conveyor 97 to a stockpile (not shown). Any particles larger than 13mm will pass over the reticulated mesh 95a and on to the reticulated mesh graded screen 95b. Any particles under 50mm and greater than 13mm will pass through the graded mesh 95b and these are then transported off by conveyor 99 to a second stockpile (not shown). Finally, any materials greater than 50mm will not pass through either reticulated mesh 95a or 95b and will be deposited into hopper 101 and thereafter transported away by conveyor 103 to a third stockpile (not shown). An observation platform 105 is provided to allow inspection and repair if necessary as well as to allow unclogging any of the reticulated mesh screens.

It will be appreciated that by using the process according to the present invention, all of the timber products will be thoroughly soaked in the soaking unit 9.

Therefore, when the materials are placed on the timber stockpile 11, excess water and grit will flow from the timber stockpile to the collection area 31 where it may be stored in a settling tank 33. However, the timber product on the stockpile will still remain moist. When the timber product is introduced into the slow crusher and the fast crusher respectively the timber will still be relatively wet and moist and therefore the dust from the timber wilt not have a tendency to become airborne as it will be significantly heavier than dry dust. Furthermore, this also aids the grouping of the smaller particles of material and they will have less of a tendency to stick to the larger particles and therefore may be more easily separated from the larger particles in due course. Furthermore, it will also be appreciated that by using the reticulated mesh screens, the different sizes of timber products may be easily separated and graded in a simple and efficient manner and different separate dedicated equipment does not have to be used in order to separate the various different sizes of timber products apart. In addition to this, various different sizes of timber product may be produced at the same time and more labour intensive hand -16 -operated devices do not have to be incorporated simply to fulfil an order for a particular size of product as they are being produced simultaneously. A further advantage is that the best price may be achieved for each of the graded products.

This is seen as a particularly advantageous aspect of the invention.

Furthermore, it will be understood that water from the filtration tank need not necessarily always be pumped into the surrounding pasture. Although this is seen as a very efficient way of disposing of the water in an environmentally friendly manner that is in accordance with all good practices in recycling facilities, it is envisaged that water that has been through the filtration process may also be returned to the water tank 71 of the soaking unit 9. The water tank is preferably provided with means such as a ball cock internal the water tank to determine when the level of water in the water tank is becoming low. When this is sensed, water is then pumped from the filtration tank 35 up to the watering tank 71 until there is sufficient water in the watering tank that may be used to soak the next batch of timber products received at the recycling plant. This is particularly efficient and allows for the recycling of the water used for cleaning the timber products.

Furthermore, in the embodiment shown there are provided three separate pipes arranged branching out from the pump 37, however, it will be appreciated that any number of pipes and any separate configuration of pipes may be used to the same effect. What is important is that the pipes are evenly distributed throughout the pasture to allow good dispersion of the water through the distribution pipes into the pasture for subsequent transfer to the environment.

In the specification the terms "comprise, comprises, comprised and comprising" or any variation thereof and the terms "include, includes, included and including" are all deemed to be totally interchangeable and they should all be afforded the widest possible interpretation.

The invention is not limited to the embodiments hereinbefore described but may be varied in both construction and detail within the scope of the claims.

Claims

-17 -Claims 1. A process for recycling timber products in a recycling

plant comprising the steps of: receiving the timber products in a hold of a delivery truck at the recycling plant; soaking the timber products with water, in situ in the hold of the delivery truck; dumping the soaked timber products on a timber stock pile in an elevated area in the recycling plant and allowing the water and any grit washed from the timber products to gravity flow through the recycling plant from the timber stock pile in the elevated area to a collection area of the recycling plant having a settling tank; allowing the water and grit to settle in the settling tank and thereafter.. *...

removing any settled grit particles from the settling tank;

..CLME: passing the remaining settled water from the settling tank to a filtration tank and removing any further unsettled grit particles from the water in the filtration tank and filtering further impurities from the water in the filtration tank; pumping the filtered water from the filtration tank along a subterranean pipe network to a plurality of points in an adjacent pasture; delivering the soaked timber products from the stock pile to a slow crusher and coarsely grinding the soaked timber products before placing the coarsely ground timber products onto a transfer conveyor; -18 -passing the transfer conveyor with coarsely ground timber products thereon beneath a magnetic conveyor and removing any large metallic objects from the coarsely ground timber products; delivering the coarsely ground timber products from the transfer conveyor to a fast crusher in which the coarsely ground timber products are more finely ground and thereafter placing the finely ground timber products onto a second transfer conveyor; passing the second transfer conveyor beneath a second magnetic conveyor and removing any further small metallic objects from the coarsely ground timber products before placing the finely ground timber products in a hopper; passing the finely ground timber products from the hopper to a screening unit having at least one graded screen and separating the finely ground timber products into a plurality of graded timber S 5

S

products for subsequent distribution.

2. A process for recycling timber products as claimed in claim 1 in which the step of soaking the timber products further comprises spraying the timber products from a position above the hold of the delivery truck until the hold of the delivery truck begins to overflow.

3. A process for recycling timber products as claimed in claim 1 or 2 in which the step of soaking the timber products further comprises spraying the timber products from a position above the delivery truck at a flow rate in the order of 500 litres/minute.

4. A process for recycling timber products as claimed in claim 3 in which the timber products are sprayed for a period of between 1 and 10 minutes.

5. A process for recycling timber products as claimed in any preceding claim in which the process further comprises the step of soaking the timber products -19 -sufficiently so that the finely ground timber products have a water content in the order of 15% after being finely ground.

6. A process for recycling timber products as claimed in any preceding claim in which the process further comprises having the slow crusher located in an elevated area in the recycling plant and allowing any water removed from the timber products during the coarsely grinding step to gravity flow from the slow crusher to the settling tank in the collection area of the recycling plant.

7. A process for recycling timber products as claimed in any preceding claim in which the process further comprises having the fast crusher located in an elevated area in the recycling plant and allowing any water removed from the timber products during the finely grinding step to gravity flow from the fast crusher to the settling tank in the collection area of the recycling plant.

8. A process for recycling timber products as claimed in any preceding claim in which the step of pumping the filtered water from the filtration tank along a *.se I..

subterranean pipe network to a plurality of points in an adjacent pasture further comprises pumping the filtered water along a pipe network having a plurality of elongate distribution pipes, each of which is embedded in a gravel channel, each elongate distribution pipe in the pipe network having a plurality of discharge apertures spaced along its length.

9. A process for recycling timber products as claimed in claim 8 in which the discharge apertures are evenly spaced along the length of the elongate distribution pipes.

10. A process for recycling timber products as claimed in any preceding claim in which there is provided a water tank for supplying water to spray the timber products in the hold of the delivery truck, the water tank having means for monitoring the volume of water in the water tank and on the volume of water in the water tank falling below a predetermined level, the process further comprises the step of pumping filtered water from the filtration tank to the water tank to replenish the supply of water in the water tank until the volume -20 -of water exceeds the predetermined level.

11. A process for recycling timber products as claimed in any preceding claim in which the step of separating the finely ground timber products into a plurality of graded timber products for subsequent distribution further comprises passing the ground timber products over a graded screen having a plurality of apertures therein of a predetermined size.

12. A process for recycling timber products as claimed in claim 11 in which the step of separating the finely ground timber products into a plurality of graded timber products for subsequent distribution further comprises.-.* *..

passing the ground timber products over a plurality of graded screens, each s graded screen having a plurality of apertures therein of a predetermined size, the aperture size of the screens increasing in size relative to the previous screen in relation to the direction of travel of the timber products.** . along the screens. OS.. *s.. * S *

13. A process for recycling timber products as claimed in claim 11 or 12 in which the graded screen further comprises a reticulated wire mesh.

14. A process for recycling timber products as claimed in any preceding claim in which the process further comprises the steps of separating the finely ground timber products into timber products of three distinct sizes, 0-13mm, 14-50mm and 51 to 60mm.

15. A process for recycling timber products as claimed in any preceding claim in which the slow crusher comprises a rotating drum having a plurality of blades arranged about its surface and spaced circumferentially and axially from each other, the blades co-operating with complimentary fingers mounted internal the slow crusher as the drum rotates.

16. A process for recycling timber products as claimed in any preceding claim in which the fast crusher further comprises a rotating drum having a plurality of flails arranged on the outer surface thereof.

-21 - 17. A process for recycling timber products as claimed in any preceding claim in which the process further comprises the step of storing the metallic objects removed from the coarsely ground timber products in a storage container for further recycling.

18. A process for recycling timber products as claimed in any preceding claim in which the process further comprises the step of storing the metallic objects removed from the finely ground timber products in another storage container for further recycling. *. : . SI. *

19. A process for recycling timber products as claimed in any preceding claim in * which the process further comprises the initial step of weighing the dry weight of the timber products as they are brought into the recycling plant. * . I..)

20. A process for recycling timber products as claimed in claim 19 in which the SSS.

process further comprises the intermediate step of weighing the unladen * S S weight of the delivery truck as it exits the recycling plant. 1 21. A process for recycling timber products as claimed in any preceding claim in which the process further comprises the additional step of sending any grit removed from the settling tank or the filtration tank to dry fill.

22. A process for recycling timber products substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.