GB2466215A

GB2466215A - Wet recyclable material processing

Info

Publication number: GB2466215A
Application number: GB0822686A
Authority: GB
Inventors: Martin Sheahan Snr; Martin Sheahan Jnr
Original assignee: MBL IP
Current assignee: MBL IP
Priority date: 2008-12-12
Filing date: 2008-12-12
Publication date: 2010-06-16
Also published as: GB0822686D0

Abstract

A solids or wet separating trommel 40 has three sets of differently sized apertures, a first set in the region of 60mm or less, a second set in the region of 180mm or less, and a third set in the region of 180mm of more for the graded separation of wastes of different sizes. The trommel 40 may be employed specifically in the separation of pre-shredded household waste sacks, and their contents, possibly as part of a broader, multi-step separation process, which may employ other separation techniques. This broader system may also feature an inclined conveyor 32 which raise the waste up as it enters the system.

Description

Wet Recyclable Material Processing

Field of the Invention

The present invention relates to waste recycling and in particular to the recycling of wet domestic waste. Further, the invention relates to the recycling of wet commercial/industrial waste.

Background to the Invention

Recycling of domestic waste has become a very large industry in recent years, that demands as much waste as possible is recycled. Recycling is getting more important as it is now accepted that landfill is not the environmentally preferred method of handling waste and due to fact that landfill is very expensive.

It is desirable to turn normal domestic waste into products such as RDF (Refuse Derived Fuel) which is used as a replacement for fossil fuels. Recycling also allows the recovery of steel and aluminium which is then sold and used in the production of new products, it also allows for the removal of plastics which are then sent to be recycled and so reducing the demand on crude oil in the plastics industry. Recycling also allows for the recovery of organic material such as grass cuttings, potatoes, carrots etc. This material can then be processed into compost which can be used for landfill capping and land remediation, as this material is extremely fertile it is an ideal replacement for chemically produced fertilisers. The term wet domestic waste' in this specification encompasses all these forms of waste.

For efficient recycling it is necessary to provide a process to separate out the waste into different materials for subsequent recycling. It is known, for example, from PCI Patent Specification No. NO 00/45966 (CP Manufacturing Inc.) to produce a disc screening apparatus for separating mixed recyclable materials of varying sizes and shapes. It is particularly directed to assisting in the recycling of solid waste materials similar to those used in the present invention. However, this particular apparatus is used more for the separation of the larger pieces of material from each other. Ihe emphasis is entirely on the separation of, for example, paper, magazines, aluminium containers, and the like. US Patent Publication No. US 2001/0004059A1 (Davis) shows another example of such screening apparatus.

Korean patent publication number KR20060090202 (Kwang Jin Engineering Co. Ltd.) discloses a trommel system for separating recyclable material using a plurality of different sized openings in combination with a hopper having a vibrating member. However a problem with this process is that the separating process for the recycling is not very efficient.

Another problem with waste recycling is that it is difficult to control the flow of waste on the conveyor that feeds the trommel. Waste can regularly overflow or jam the trommel and/or conveyor meaning that the process must be stopped. PCI patent publication number W02004/012866 (Wastec Limited) discloses a method and system for separating waste material, however this suffers from poor design for separation of the materials to be recycled.

There is therefore a need to provide a recycling process to separate out the recyclable materials from domestic waste and to control the flow of waste material during the recycling process. There is also a need to ensure that an even load is supplied to the trommel to prevent jamming during the recycling process.

Summary of the Invention

According to the present invention there is provided, as set out in the appended claims, a process of recycling wet domestic waste materials comprising the steps of: receiving domestic waste and shredding the waste to reduce the particle size of the material to be recycled; conveying the shredded waste material on a steel conveyor, wherein a first section of the steel conveyor is level with a floor and a second section of the conveyor is inclined at a substantially 45 degree angle to the floor to provide a vertical drop of approximately 1.8 meters and a third section of the conveyor levels off at an elevated height from the floor; positioning an optical sensor at said third section of the conveyor, that controls the speed of the conveyor to regulate the throughput of waste material on the third part of the conveyor; conveying the waste material from the third section of the steel conveyor onto a rubber conveyor, positioned at substantially 90 degrees to the steel conveyor, in the horizontal, to allow for removal of non-recyclable material by hand; delivering the recyclable material to a constantly rotating single trommel, said trommel comprising a large steel cylinder having three different size perforations, on a sloped conveyor trommel floor wherein said trommel further comprises: a first set of perforations, dimensioned below 60mm, allow any organic, steel and aluminium waste material or the like below 60mm, to fall through and drops onto a vertical conveyor, a second set of perforations in the trommel remove any material below 180mm to be recycled, mostly made up of paper, plastic and the like and conveyed to a wind shifter to remove the paper and plastic, a third set of perforations greater than 180mm to remove the remaining material for further processing and recycling; composting the organic material; recycling the removed steel and aluminium; and baling the removed paper and plastic material to provide a Refuse Derived Fuel (RDF) The conveyor system of the present invention advantageously allows for an even flow of waste material into the trommel.

By elevating the waste material to a height of approximately 1.8meters, or over, allows the waste to travel at an optimum throughput. The incline on the conveyor system, inclined at 45 degrees to the floor, ensures that larger waste or excess waste material falls backwards down the conveyor, relative to the direction of the conveyor, and will only be conveyed to the third section during periods when little or no waste material is on the first and/or second sections of the conveyor. In addition the use of the optical sensor in combination with the conveyor system advantageously regulates the flow of the waste material to prevent the conveyor and trommel from jamming. The design and dimensions of the trommel perforations around the whole circumference of the single trommel maximises the efficiency of the recycling process.

Suitably, the process provides the step of positioning a set of variable teeth at the mouth of said single trommel, said teeth mounted along the inner circumference of the trommel mouth to shred the waste as the waste enters the trommel to further reduce the particle size of the material to be recycled. The rotating set of teeth at the mouth of the trommel ensures that all waste bags entering the trommel are shredded to increase the efficiency of the recycling process.

Suitably, the process provides the step of positioning a set of counter rotating teeth at the mouth of said trommel, rotating in the opposite direction to the trommel, to shred the waste to further reduce the particle size of the material to be recycled. The counter rotating teeth at the mouth of the trommel ensures that all waste bags entering the trommel are shredded to increase the efficiency of the recycling process.

Ideally, the invention comprises the further step of separating the organic, steel and aluminium waste material, or the like, below 60mm by passing the waste material through a magnet that removes any steel from the waste and subsequently passing the waste through an eddiecurrent separator, which applies a charge to the aluminium, and allows a magnet to remove the aluminium to provide organic material for composting.

Preferably, the wind shifter is adapted to drop waste material from one conveyor to another which is approximately 90 degrees to it, such that as the material drops air is blown up from underneath to separate light paper and plastic through ducts and into a silo for baling.

The remaining material can enter a second eddiecurrent separator which removes any aluminium or steel present.

Ideally, a walking floor is provided for receiving recycled waste, said floor consisting of steel grates that independently move such that waste can move in either direction, and adapted to drop the recycled waste into a compactor for subsequent processing. The walking floor advantageously improves the efficiency of the recycling process.

Preferably, the removed steel and aluminium are dropped onto two separate conveyors and are separately dropped onto the walking floor.

In another embodiment the invention provides the further step of conveying the waste material to a conventional trommel comprising only a single set of perforations in the trommel, said perforations are dimensioned to be less than 65mm such that any remaining organic material will be removed for composting.

Ideally, at least one conveyor is fitted with a load cell, said load cell comprising weighing the conveyors when there is no material on a conveyor and then continuously weighing the conveyors during operation, to determine handling capacity and recycling recovery rates.

Suitably, the process is controlled using a computerised system, wherein the system allows the operator to stop individual conveyors and adjust the speeds of individual parts of the plant.

Brief Description of the Drawings

The invention will he more clearly understood from the following description of an embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which:-Figure 1 shows main processing area for receiving waste at the start of the recycling process; Figure 2 illustrates a shredding apparatus for shredding the material to be recycled; Figure 3 illustrates a conveyor, according to one aspect of the invention; Figure 4 illustrates a trommel according to a further aspect of the invention; Figure 5 shows where different recycled waste can be deposited; Figure 6 illustrates a windshifter according to a third aspect of the present invention; Figure 7 illustrates who the recycled waste is compacted; Figure 8 illustrates a walking floor according to a fourth aspect of the invention; and Figure 9 illustrates a second trommel in the process according to the invention.

Detailed Description of the Drawings

Referring now to the drawings, Figure 1 shows waste 1 entering the facility in bin trucks, skip trucks and/or articulated trucks 2. All of this material is then weighed over a weighbridge 3, for example an Avery Berkel' weighbridge. From here the trucks 2 move into the main processing area where the waste material 1 to be recycled is then tipped onto the floor 4.

The waste material 1 is then handled by a loading shovel 5, and loaded into a shredder 20, as shown in Figure 2. The shredder reduces the size of the larger material and also rips open many of the refuse bags. The shredder 20 has variable shafts, which allows the process to vary the particle size of the material depending on the makeup of the material to be recycled. A shredder 22 is positioned at a right angle to counter rotating pairs of shredders 21 and 23 to shred the waste material.

Referring now to Figure 3 there is illustrated a conveyor system according to the invention, indicated generally by the reference numeral 30. After being shredded the shredded material is then dropped onto a steel slat conveyor. The conveyor is made of steel, as opposed to rubber, due to the large amount of material to be recycled. The first part or section 31 of this conveyor is level with the floor, but the second part 32 of the conveyor is inclined at a substantially 45 degree angle to the floor to provide a vertical drop of approximately six foot (1.8 meters) . A third part or section 33 of the conveyor levels off at an elevated height from the floor and is provided with an optical sensor 34 that controls the speed of the conveyor in response to the throughput of the waste material. The optical sensor 34 can advantageously automatically slow down or speed up the conveyor depending on the amount of waste material detected on the third section 33 of the conveyor system to ensure maximum efficiency.

From here the waste material drops onto a rubber conveyor which is running substantially at 90 degrees to the first conveyor. This rubber conveyor 35 transports the material to a pre-pick station, where at least one operator can remove any objects by hand that should not be in the waste, such as batteries and the like. The waste material removed by hand is dropped onto a ramp and is stored in a storage bin for subsequent disposal. The bulk of the waste then continues along the conveyor and again turns 90 degrees before entering a trommel system 40, as shown in Figure 4.

The new trommel design, according to the invention, indicated generally by the reference numeral 40, comprises a large steel cylinder 41 with three different sized sets of perforations 42, 43 & 44. A set large steel teeth 45 positioned at the mouth of the trommel 41 rip open any bags of waste material that are not already ripped open. This is an important aspect of the recycling process. The steel teeth 45 can be bolted to the inner circumference of the trommel mouth, and rotates as the trommel 41 is rotated.

The steel teeth 45 can be of variable size. A further set of teeth can be provided to counter rotate in the opposite direction to the trommel 41 to further increase the efficiency of the ripping process. The extra set of teeth prevents the trommel from jamming.

The waste material moves through the trommel as it is on a slight slope and is constantly rotating. The first set of perforations 42 allow any material below 60mm to fall through. This waste is normally made up of organics and small pieces of steel and aluminium such as bottle caps.

This fraction of material falls through the perforations and drops onto a conveyor 46, from here it goes to a vertical conveyor 47 that brings the material up approximately 15 meters and passes it onto another conveyor. The purpose of this is to allow the material to be transported over the weighbridge. Once the material has passed over the weighbridge it passes through a magnet, for example an Andrin' magnet that removes any steel from the waste. The material then passes through an Andrin' eddiecurrent separator, which applies a charge to the aluminium and allows a magnet to remove it. The material has then had all of the steel and aluminium removed and as a result is mostly organic material. The organic material is conveyed to a storage location 50 and can be used for composting, while the steel and aluminium is recycled at a separate location 51, as shown in Figure 5.

Referring again to Figure 4 a second set of perforations 43 in the trommel 41 remove any material below 180mm to be recycled. This material is mostly made up of paper, plastic, cans and other general waste. Once the material passes through the perforations it is dropped onto a conveyor 48, as shown in Figure 6. Figure 6 shows the material passing through a wind shifter 60a, 60b. The wind shifter 60a, 60b is specifically designed to operate on the basis of dropping material from one conveyor to another which is at 90 degrees to it, as the material drops air is blown up from underneath, this air will blow all of the light paper and plastic through ducts and into a silo 61a, 61b. The remainder of the material travels along the conveyor and it next passes through a magnet 62a, 62b. The magnet 62a, 62b will remove all of the steel. An important aspect of the wind shifter design is the provision of an adjustable mechanical flap 63a, 63b that can be adjusted to regulate the wind flow to ensure only light paper and plastic is blown into the silo 61a, 61b.

The material then passes through another windshifter 60b, which will remove any remaining plastic and paper 61b, the remaining material then enters an eddiecurrent separator 62b which removes the aluminium, thus all of the aluminium cans are removed. The steel and aluminium are then dropped onto two separate conveyors and are dropped in a storage area to be recycled. While the remainder of the waste drops onto a conveyor going 90 degrees, before again dropping 90 degrees to an angled conveyor which carries the waste out of the processing area, from here the material drops onto a walking floor.

Referring to Figure 7 the walking floor 70 is made up of steel grates that independently move and so can move the waste in either direction, this drops the waste into one of two pierce' compactors. The waste can then be compacted into 40 foot containers for transport, for example up to 25 tonnes of waste can be compacted into a single container.

At the end of the trommel 41, all of the material that is left is over 180mm, this material drops onto a conveyor through a third set of perforations 44 greater than 180mm before passing through another windshifter. The windshifter removes all of the light paper and plastic and sends it to a silo. The waste then passes through a magnet, which removes all of the steel and sends it to the storage area 80 illustrated in Figure 8. The remaining waste then joins the waste line and ends up in a container. This waste that is in these containers then goes to be reprocessed to remove any remaining recyclable material. This involves the containers tipping the load in the reprocessing area. This material is then loaded onto a walking floor, for example, using a fixed crane. The material then enters another trommel 90 comprising only a single set of perforations 91 in the trommel and a plurality of teeth 92, as illustrated in Figure 9. The perforations are dimensioned to be 65mm.

This means that any remaining organic material will be removed and can then be composted. The material that is over 65mm will pass through the trommel before turning 90 degrees and travelling up along an angled conveyor and dropping onto a picking line. The picking line has at least one operator working on it who can pick off plastic, cardboard and any other valuable material. This material is then dropped into bunkers under the picking line while the waste continues on along the line before coming to another windshifter which will remove paper and plastic and store them in a silo, the remaining waste can then either he dropped directly into a compactor, or can be sent back into the plant depending on the amount of recyclable material remaining.

The material that is picked off on the picking line and dropped into one of six bunkers and can then stored for baling. Once one bunker is full, the operator sets up the baler for that material, the bunker door then opens and the material is conveyed to one of the two balers. This material is then shipped to be recycled. All of the material that is collected by the windshifters is stored in silos, these silos feed into a baler machine. The baler machine can produce bales weighing between 750 and 800kg, these bales are then conveyed to a crosswrap' wrapper, where the bales are wrapped in plastic before being removed by a teleporter and then stored for shipment. These bales are known as RDF (Refuse Derived Fuel) and due to the large paper and plastic content have a high calorific value and are used as a replacement for fossil fuel in cement kilns and power stations.

It will be appreciated that the above process is controlled by one operator in a control room using a fully computerised system which allows the operator to stop individual conveyors and adjust the speeds of individual parts of the plant. The operator also knows exactly what the plant has processed at any one time as six conveyors are fitted with load cells, these work by weighing the conveyors when there is nothing on them and then continuously weighing them as the plant is in operation, this allows them to know what the plant is handling and also the recovery rates.

The process allows for over 80% recycling of all domestic and commercial waste from going landfill, by using the conveyor system and trommel to implement the present invention. The process allows to turn normal waste into products such as RDF (Refuse Derived Fuel) which is used as a replacement for fossil fuels. The process allows the recovery of steel and aluminium which is then sold and used in the production of new products, it also allows for the removal of plastics which are then sent to be recycled and so reducing the demand on crude oil in the plastics industry. The facility also allows for the recovery of organic material for composting.

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