IE83764B1 - Waste treatment process - Google Patents

Abstract

ABSTRACT A waste material processing plant is provided which comprises various stations, namely, an intake station (2), a separation station (3), a combined paper and plastics baling station (4), a treatment station (6), a screening and agitation (7), a compost preparation station (8) and a fuel preparation (9). In the process according to the invention, the waste is separated into large plastics and residual material. After the larger materials have been removed and baled, the rest of the material is delivered to a further station where the material is agitated and separated so that the smaller cohesive and the softer, less cohesive material, is separated from the more cohesive material. Then, the materials, so separated, are screened with further agitation so as to remove all the softer compostible, less stmcturally cohesive material which is then ready for composting .

Description

introduction The present invention relates to waste recycling and in particular to the recycling of domestic waste, including the waste of people service industries such as hotels, restaurants, and so on. Further, the invention relates to the recycling of industrial waste. which is not produced by the industrial process per se but is incidental thereto, which comprises packing materials, namely, wood, plastics, paper, cardboard and indeed food as a waste product of food producers and of the canteens etc. of such operations. Almost all of these waste materials are biodegradable except plastics but, for example, certain of the waste materials take some considerable time to degrade unless they have been prior treated. Generally the waste being recycled is a mixture of many materials. Thus the term “domestic waste” in this specification encompasses all these forms of waste.

It is known, for example, from PCT Patent Specification No. WO 00/45966 (CP Manufacturing lnc.) 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. The emphasis is entirely on the separation of, for example, paper, magazines, aluminium containers, and the like. US Patent Specification No. 2001/O0O4059A1 (Davis) shows another example of such screening apparatus. US Patent Specification No. 5901856 (Brantley et al) shows a further device for separating office paper and computer printouts from cardboard waste material.

Heretofore, little attention has been paid to the separation of compostible materials from domestic waste. One of the major objects of the present invention is not just simply to provide a way of separating paper, plastics and for example, glass and tin cans, butto separate compostible materials that can be usefully used.

The present invention is directed towards providing an improved process for the recycling of such mixed waste materials, namely, paper, plastics and other materials, as defined above so as to separate, not just larger recyclable material, but also to produce a product suitable for composting.

Statements_m‘JmLen1ian According to the invention, there is provided a process for recycling domestic waste materials, namely, paper, plastics and other material as hereinbefore defined, comprising:- receiving the waste; separating the waste in an initial station into large paper, large plastics and residual material; removing the paper; baling the paper for recycling in a paper production plant; removing the plastics material; , baling the plastics material for recycling in a plastics material production plant; delivering the residual material between a pair of counter-rotating spaced- apart shafts each carrying a plurality of radially and circumferentially arranged hammer-like projecting flails, dimensioned so that a flail on, one shaft rotates in the space between two flails on the other shaft, the action of the flails causing the separation of the softer materials from the structurally more cohesive material, while shredding the larger structurally more cohesive material coarsely; screening and further agitating the shredded residual material so as to remove the structurally cohesive material above a predetermined size; baling the larger removed material for subsequent use as a fuel; and sending the other materials for composting.

The major advantage of this invention is that the majority of the softer materials from domestic waste are retrieved for composting by a process of abrading, separating and screening. Because of the nature of the original waste material, the compost produced is of a high grade.

Ideally, the material for composting has a particle size less than 40mm. Preferably, the screening further comprises agitating the materials while rotary screening to further separate the softer materials from the structurally cohesive materials within the screen, as the smaller materials are delivered through the screen. in one embodiment of the invention, subsequent to screening the structurally softer waste material, the waste material is further crushed and separated prior to composting. ideally, the shafts are rotated in one direction, stopped and then rotated in the opposite direction after a predetermined time. Subsequent to screening, the structurally softer waste material, the waste material is further crushed and separated prior to composting. in the process according to the invention, as the material progresses through the process, ferrous metal forming part of the waste material is removed by magnets arranged"above the material as it is conveyed through the plant. Also, a metal detector is provided to detect the presence of non-ferrous metals and those ferrous metals not previously removed, and in which detection of metal causes stopping of the plant until the metal is removed.

Ideally, after composting, the composted material is screened to remove un- composted waste material. um”: .I. “II I.

The invention will be 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:- Fig. 1 is a plan diagrammatic layout of a waste recycling plant according to the invention, Fig. 2 is a side view of the plant, Figs. 3 to 9 are enlarged side views of portion of the plant illustrated in Fig. 2, Fig. 10 is a detailed end view of portion of a treatment station according to the invention, Fig._, 11 is a plan view of portion of the equipment used in the treatment station, and Figs. 12 and 13 are enlarged side views of portion of the plant.

Referring to the drawings and initially to Figs. 1 and 2, there is illustrated in outline a waste material processing plant, indicated generally by the reference numeral 1. The waste material processing plant 1 comprises various stations, all indicated generally by reference numerals, namely, an intake station 2, a separation station 3, a combined paper and plastics baling station 4, a treatment station 6, a screening and agitation station 7, a compost preparation station 8,and a fuel preparation station 9.

A certain amount of the equipment and stations are conventional, however, they are described for completeness.

Various pieces of mechanical loading equipment such as shovels, grabs, and so on, as well as trucks and vehicles, are illustrated but are not identified as there is no need to. Refuse is identified generally by the reference numeral 10 and various letters in brackets are used to indicate changes in the composition of the waste, for example separation into paper and plastics material.

Referring specifically to Figs. 3 and 4, the intake station 2 comprises a pair of intake hoppers 11 and 12, each of which is sited below ground level and each has an intake conveyor 13 and 14 respectively which in turn feeds take—otf conveyors 15 and 16.

Referring-now to Figs. 5 and 6, the conveyors 15 and 16 feed further conveyors 17 in the separation station 3 above which is mounted a magnet 18. The conveyor 16 is connected to three conveyors, namely, a large paper take-off conveyor 25, a large plastics take-off conveyor 26 and a residual waste conveyor 27. In this separation station 3, the larger paper waste is delivered onto the conveyor 25 and the larger plastic waste is delivered onto the conveyor 26 from which it is delivered respectively into a paper storage bin 28 and a plastics material storage bin 29. Take-off elevators and 36 respectively feed the combined paper and plastics ballng station 4.

Referring now to Fig. 7, there is illustrated the paper ballng station 4 which is identical in construction to the plastics ballng station 5 and comprises an intake chute 37 feeding a baler, indicated generally by the reference numeral 40 which in turn feeds plastic bales 10a onto a take-off conveyor 41. The baler 40 is essentially a roller conveyor 42, a moveable end plate 43, inwardly moveable sidecompaction plates 44 and a top compaction plate 45, all operated by pneumatic rams 46. Each side compaction plate 44 carried an inwardly directed plate not shown which projects approximately halfway across the spacing between the two plates 44 so that when the plates 44 are pushed together, they meet to form a rectangular space.

The ballng station is used to compress both the large plastics material and the large paper material. As required one or other of the materials is delivered on the conveyor where it is delivered down the intake chute 37 into the ballng machine 40 where the plates 44 are retracted and material is allowed fall down the chute 37. Then the plates 44 are pushed inwards to compact the material inwardly and they are then further compacted by the end plate 43 to form a rectangular bale. It is then delivered along the conveyor 42 by pushing the plate 43 towards the top compaction plate 45.

The bale is further compressed by the top compaction plate 45. This compressed bale 10a is then delivered from the conveyor 42 onto the conveyor 41 where it is delivered to the bale tying machine 50.

Referring to Fig. 8, the bales 10a are delivered along the conveyor 41 to a bale tying machine 50 where the tied paper bales 10b are available for removal and subsequent recycling in a paper or cardboard manufacturing plant or in a plastics recycling plant.

Referring to Fig. 9, there is illustrated in more detail the treatment station 6, screening and agitation station 7 and compost preparation station 8. The waste 10c which is all the smaller waste material and not the easily identifiable large pieces of plastics and cardboard, effectively the residual waste material, is delivered from the conveyor 27 to a stock_pile 28 from which it is delivered to the treatment station 6.

Referring to Figs. 10 and 11, the treatment station 6 comprises a hopper 51 mounting separator bars 52 above a pair of spaced-apart augers 53. Also mounted within the hopper 51 are a pair of opposed shafts 55 (illustrated in more detail in Fig. 11) carrying a drum 56 on the outer periphery of which are mounted a plurality of radially and circumferentially arranged hammer-like projecting flails 57. It will be noted that the flails 57 are so dimensioned that a flail on one shaft 55 rotates on the space between two flails 57 on the other shaft 55. Motors 58 are provided to drive the shafts 55 in contra rotation. Mounted on the bottom of the hopper 51 is a conveyor 60 above which is mounted a further magnet arrangement 61. The conveyor 60 in turn feeds a further conveyor 62 which transfers waste material from the treatment station 6 to the screening and agitation station 7, illustrated in more detail in Fig. 12.

The screening and agitation station 7 comprises two rotary screens 65 carrying an outer metal mesh screen cloth having two take—off conveyors, namely, a take—off conveyor 66 and a further take-off conveyor 67 mounted respectively at an exit 68 for the screens 65 and beneath the screen 65 respectively.

The take-off conveyor 67 in turn feeds the compost preparation station 8 which comprises a storage hopper 70 fed by the conveyor 67. The storage hopper 70 in turn feeds to a conveyor 71, a hopper 72, again mounting counter-rotating flails 73 which in turn feeds a take—off conveyor 75 which feeds a compost stockpile 76 (see Fig. 9).

The conveyor 66 feeds the fuel preparation station 9 which comprises a compactor, a baling machine and tying machine (not shown, as they are similar to the baling machines and tying machines already illustrated).

There is also provided metal detectors for non-ferrous metals which will stop the operation of the plant where they are detected. These are not shown in the drawings but it will be appreciated that they can be relatively easily fitted and arranged throughout the plant.

In operation, waste of the type hereinbefore defined is delivered to the intake station 2 and into one or other of the hoppers 11 and 12 and then up the conveyors 13 and 14 and then to the separation station 3 where the larger pieces of paper and cardboard are removed, as are the larger pieces of plastics material. This is a relatively crude sorting of the materials. The object is to remove as much of the larger plastics material and the large paper materials so that they can be easily recycled the suitable plants. It should be noted that effectively this is where most waste separation stations and operations cease. In other words, after most of the large waste material has been removed and the remainder of the waste material is almost considered not to be worth recycling. However, with the present invention, the purpose is to remove that material that can be composted because by removing the material that can be composted, not alone is there less material being incinerated but the material that is being incinerated is a composite material that can be usefully used as fuel, while the remainder of the material, even more importantly, is composted into soil which can be usefully used. The particular domestic waste material would not contain any material that would be likely to be harmful to humans or animals and thus the composted material that can be obtained from such domestic waste material is material that can be used and spread on land immediately, which land can be used for edible crops. Even if it is decided not to spread it on land for immediate use in crop growing, it can be spread on land and then the land can have, for example, trees and the like grown thereon so that at some future date, the soil will be free for the growing of edible crops. it cannot be overemphasised how important this is. Additionally, it will be further appreciated that once material has been composted in the form of friable soil-like material, it is relatively easy, by screening and other known processes, to separate those materials that have not composted from it. Indeed, there are many machines already available that will assist in this separation.

The residual waste material is then delivered out the conveyor 27 to the treatment station 6 where the waste material is delivered between the augers 53 down onto the contra- rotating flails 57 where the material which now contains some paper and plastics and possibly wood and other materials, together with a considerable amount of softer, i.e. less structurally cohesive material, which is then further separated from the structurally cohesive material by the flails, which flails will break up inevitably some of the structurally cohesive material but will only do this coarsely. The intention here is not to break up the structurally cohesive materials, so much as to separate the softer compostible materials from the other materials. Effectively, the flails scrape and separate the softer material from the structurally cohesive material. This softer or less structurally cohesive material is the material that will naturally form good compost. The flails therefore, while doing a certain amount of breaking up of the material, act more as abraders, scrapers and separators, than as shredders or crushers. While it is accepted that, for example, paper is compostible and is more likely to be broken by the flails than plastics material, the general object here is to produce as much of the softer material as possible and separate it from the structurally more cohesivelmaterial. in any event, it is preferable to recycle paper and cardboard materials than to compost them.

The material is then delivered out and onto the conveyor 62 where it is delivered to the screening and agitation station 7. In the rotary screen 65, the waste material is further agitated and the softer less cohesive material will be delivered out through the screen onto the conveyor 67. The harder and more cohesive material above a certain size, in this embodiment, 40 mm as the screen cloth used is 40 mm mesh, will be delivered out the conveyor 66 for subsequent compression and baling for use as fuel. However, a major proportion of the material is now delivered out the conveyor 67 to the bin 72 where it is further treated to make those structurally cohesive materials that have been carried with the softer materials, to break and shred them as far as possible. Thus, there is delivered out the conveyor 75 a considerable amount of soft compostible material, together with material, some of which is structurally cohesive and compostible such as paper, while other, such as plastics, is not. This then forms a basic raw material for composting either, for example, in a wormery or may be simply delivered into storage where suitable treatment can take place. it will be appreciated that with the present invention, firstly by using a relatively crude sorting process, ensures that a considerable amount of materials are recycled and used in paper and plastics manufacturing plants. Further, a considerable amount of the material which is softer and which can be used for composting is recycled for composting and only that material which cannot be easily separated for recycling is used as fuel. At the same time when used as fuel, the materials according to the present invention provide relatively cohesive material and can be used in commercial plants for the generating of electricity. The separation that is carried out in accordance with the invention provides a relatively cohesive fuel material which is useful. it is not just simply waste material that has to be incinerated. Thus, with the present invention, relatively small amounts of the waste material are incinerated and even those are incinerated in a productive way.

It is envisaged that it will not always be necessary to further break up the material after it has been delivered out of the rotary screen. it is envisaged that, for example, in the rotary screen, the materials may be washed to further remove any softer materials which adhere to the structurally more cohesive materials that may be delivered out for fuel. However, the general agitation in the screen and the previous operation of the treatment station, ensures that most of the structurally cohesive material is relatively “clean” in the sense that it does not have other materials adhering thereto. The purpose of the present invention is to reduce the need for landfill and to further provide a compost material which can be spread over landfills or can be used directly for horticultural purposes.

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

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

Claims (1)

1. CLAIMS 1. A process for recycling domestic waste materials, namely, paper, plastics and other material as hereinbefore defined, comprising:- receiving the waste; separating the waste in an initial station into large paper, large plastics and residual material; removing the paper; baling the paper for recycling in a paper production plant; removing the plastics material; baling the plastics material for recycling in a plastics material production plant; _ delivering the residual material between a pair of counter-rotating spaced- apart shafts each carrying a plurality of radially and circumferentially arranged hammer-like projecting flails, dimensioned so that a flail on one shaft rotates in the space between two flails on the other shaft, the action of the flalls causing the separation of the softer materials from the structurally more cohesive material, while shredding the larger structurally more cohesive material coarsely; screening and further agitating the shredded residual material so as to remove the structurally cohesive material above a predetermined size; baling the larger removed material for subsequent use as a fuel; and sending the other materials for composting. 10. A process as claimed in claim 1, in which the material for composting has a particle size less than 40mm. A process as claimed in claim 1 or 2, in which the screening further comprises agitating the materials while rotary screening to further separate the softer materials from the structurally cohesive materials within the screen, as the smaller materials are delivered through the screen. A process as claimed in claim 3, in which subsequent to screening the structurally softer waste material, the waste material is further crushed and separated prior to composting. A process as claimed in any preceding claim, in which the shafts are rotated in one direction, stopped and then rotated in the opposite direction after a predetermined time. A process as claimed in claim 5, in which subsequent to screening the structurally softer waste material, the waste material is further crushed and separated prior to composting. ' A process as claimed in any preceding claim, in which, as the material progresses through the process, ferrous metal forming part of the waste material is removed by magnets arranged above the material as it is conveyed through the plant. A process as claimed in any preceding claim, in which a metal detector is provided to detect the presence of non-ferrous metals and those ferrous metals not previously removed, and in which detection of metal causes stopping of the plant until the metal is removed. A process as claimed in any preceding claim, in which, after composting, the composted material is screened to remove un-composted waste material. A process for recycling domestic waste material substantially as described herein, with reference to and as illustrated in the accompanying drawings.