WO1997000143A1

WO1997000143A1 - A waste recycling process and apparatus

Info

Publication number: WO1997000143A1
Application number: PCT/AU1996/000367
Authority: WO
Inventors: Michael Gerard Stephen Walsh; Peter William Holbut
Original assignee: Petemic Technology Pty. Ltd.
Priority date: 1995-06-19
Filing date: 1996-06-19
Publication date: 1997-01-03
Also published as: AU667659B3

Abstract

A waste recycling process and apparatus involves basically four elements, firstly the waste selection means shown generally at (10), this is followed by the waste reducing means shown generally at (11), a mixer and binder stage shown generally at (12) and a compacting and heating stage shown generally at (13).

Description

A WASTE RECYCLING PROCESS AND APPARATUS

TECHNICAL FIELD OF THE INVENTION THIS INVENTION relates to a waste recycling process and apparatus and in particular but not limited to a waste recycling process and apparatus for producing useful products from domestic garbage.

BACKGROUND ART Disposal of domestic waste has become an ongoing problem and it would be desirable to provide a process and apparatus for taking domestic waste that would otherwise be disposed of in a land fill and recycle that domestic waste by processing it into a useable building material.

It is therefore an object of the present invention to provide a process and apparatus for producing a useable product from domestic waste.

OUTLINE OF THE INVENTION With the above object in mind, the present invention provides a waste recycling process comprising the steps of:-

(a) selecting non-toxic domestic waste to be processed;

(b) reducing the selected waste to a mass of finely divided particles of predetermined character;

(c) mixing a predetermined quantity of the finely divided particles with a predetermined quantity of binder to provide a mixture; and

(d) compacting the mixture while simultaneously or subsequently supplying heat to reduce water content and compact the mixture to produce a relatively dense particulate product suitable for use as a building material, road base or moulding material for production of bricks, tiles or the like.

The present invention also provides an apparatus for waste recycling comprising a waste selection means, a waste reducer for reducing waste delivered thereto from the waste selection means to provide a mass of finely divided particles of predetermined character, a mixer for mixing the finely divided particles with a binder and means for compacting and drying the mixture.

The waste selection means can be any suitable means for separating waste that can be recycled by other means. Typically, raw waste can include iron based wastes and other recyclables including PTFE bottles and aluminium cans and therefore the waste selection means typically includes an automated magnetic sorting means to eliminate iron based wastes from the raw waste. The waste selection means typically also includes means for removing other recyclables including PTFE bottles and aluminium cans and this typically comprises a manual sort of the raw waste on a conveyor or the like.

The waste selection means typically produces waste which is predominantly waste packaging and other solid domestic wastes.

The waste reducer typically takes the selected waste and reduces it to a size most suitable for providing an intimate blend between the finely divided particles and the binder. This can typically take place by employing a cutting or shredding process so there is provided a finely divided particulate mass similar to sawdust in character and having a particle size of .5mm to 1 mm. The reducer typically comprises a pulveriser or a number of pulverisers to reduce the particle size in stages, each pulveriser having an associated screen whereby particles that do not pass through the screen are recycled to the pulveriser for reprocessing.

The mixing and binding stage typically involves the use of an agitator where any binder, typically a clay based binder which can include cementitious material or other refractory material is added to coat the particles in the mass. Typically, the binder is preferably finely divided clay introduced in dry form in proportion of about 1 part binder to 1 part reduced waste.

The means for compacting and drying typically includes a pan palletiser, the palletiser forming an aggregate sized according to demand, the aggregate can be sundried or dried by employing a heat gradient over relatively short time period. Typically, the heat gradient involves initial heat applied at a temperature of about 500°C to a final heat applied at a temperature of about 1500°C. Most preferably, the heat gradient is a two or three stage process. In the two stage process an inlet temperature of about 500° C ± 200°C and an outlet temperature of about 1300°C ± 200°C can be employed. In a typical three stage heating process, firstly at a temperature of around 630°C for a first time period, to a temperature of 1050°C for a second time period and a final drying stage at 1250°C. Subsequently, the pellets are transferred to a recovery stage where they are held at a temperature of about 1 50°C to provide slow cooling. Typically, they are held within the range of 120°C to 180°C for a predetermined time period. The result of this process provides a ceramic-like material that can be used as is or reprocessed by crushing or otherwise for storage purposes and then later used as a road base aggregate, fill, or base for production of moulded or extruded building products.

DESCRIPTION OF THE DRAWINGS In order that the present invention can be more readily understood and be put into practical effect, reference will now be made to the accompanying drawings which illustrate one preferred embodiment of the present invention and wherein:-

Figures 1 A and 1 B form a flow diagram illustrating a process and apparatus according to the present invention;

Figures 2A and 2B form a block diagram illustrating a control system for the apparatus described in relation to Figure 1 ; and

Figures 3 to 14 are schematic diagrams illustrating typical apparatus according to a preferred form of the present invention.

Referring to the drawings and initially to Figures 1 A and 1 B, there is illustrated in flow chart form a waste recycling process and apparatus according to the present invention.

The apparatus and process involves basically four elements, firstly the waste selection means shown generally at 10, this is followed by the waste reducing means shown generally at 1 1 , a mixer and binder stage shown generally at 12 and a compacting and heating stage shown generally at 13. The waste selection means typically involves the use of a weighbridge where a waste vehicle is weighed prior to emptying its contents into a hopper 1 5.

The raw garbage in hopper 15 travels through an initial crusher 24 to iron sorter

16 where iron based metal products are magnetically sorted and automatically removed from the raw garbage stream. At this stage, or prior to this stage, manual sorting can be undertaken and other recyclable wastes also retrieved.

Building rubble once weighed will be held in stockpile before being crushed.

The selected waste then moves onto a first pulveriser 1 7 where the waste is reduced, a screen 18 is used and oversized particles are returned to the pulveriser 17. The particles from the screen 18 are pulverised in a second pulveriser 19 and then screened at 20. Oversized particles are returned to the second pulveriser or to the first pulveriser for further reduction. The weighbridge 21 then receives the finely reduced and screened garbage and this can be in the form of a weighing hopper.

The binding and mixing stage 12 includes a binding station 22 and, a mixer 23. At the binding station, finely reduced recycled building rubble including cementitious material and clay is introduced in dry form in proportion of about 1 part of binder to 1 part of the finely divided garbage measured out of the weighbridge at 21 . This dry mixture is then incorporated into the mixer at 23 and at this stage, grey water can be introduced in a proportion of about 10% to 20% by weight where the moisture content is controlled to provide a mixture of generally plastic consistency suitable for the next stage. In the illustrated embodiment, the compacting and drying phase illustrated at 13 involves the use of a pan palletiser 25 where the mixture is treated to form an aggregate which is then delivered to a revolving tumbler 27 to further separate and initiate drying of the particles before entering kiln 28. The kiln 28 has an inlet temperature of around 630°C and an outlet temperature of 1250°C. In the illustrated embodiment, the kiln is typically configured with a spiral path conveyor to reduce the length of the kiln and has two or three temperature regions with a central temperature region of about 1 150°C in the three region embodiment.

After kiln 28, the basic processing of the garbage has been completed producing an aggregate of ceramic-like particles and these are then despatched to a recovery bay at 29 where they are held at a temperature of 120°C to 180°C to provide a slow cooling. The aggregate can then be delivered to storage bays at 31 for later dispatch and use in road bases or as aggregate in production of building materials. As will be appreciated from the foregoing description in relation to Figures

1 A and 1 B, the process according to the present invention involves an initial selection of waste to be processed at 10, a subsequent reduction of the wastes at 1 1 , subsequently mixing a predetermined quantity of the wastes at 12 with a binder and then compacting and drying at 13.

The process and apparatus is controlled using a main computer system so that there is generally continuous processing of garbage at a rate of 20 to 30 tonnes of garbage per hour. Figures 2A and 2B illustrate in schematic block diagram the control system for the process and apparatus depicted in Figures 1 A and 1 B.

The system includes a main process controller 32 having three workstations 33, 34 and 35 as shown enabling operators to control the apparatus depicted in Figures 1 A and 1 B.

Referring now to Figures 3 to 14, there is illustrated in more detail but in schematic form typical apparatus suitable for use in the process of the present invention.

Figure 3 illustrates a weighbridge 14. Figure 4 illustrates a garbage hopper 15 and in this case, the garbage hopper communicates with an endless belt conveyor 36 having a manual sort region shown generally at 37 so that PTFE bottles and other recyclables including aluminium cans and so forth can be manually removed from the garbage as it leaves the hopper 15.

The conveyor 36 is shown in Figure 5 entering the iron based metal sorter 16 and this magnetic sorter typically involves a rotating periodically energised electromagnetic arrangement to extract iron based materials from the garbage stream onto an exit conveyor 38 whereas the rest of the garbage leaves on a conveyor 39. The conveyor 39 then carries the garbage into the first pulveriser 1 7 which operates in conjunction with the primary screen 18. The pulveriser includes a hammermill type arrangement shown generally at 40 and a return conveyor at 41 . Oversized particles are screened out using the screen 18 and these are returned upstream of the hammermill 40. Particles despatched downstream on conveyor 42, in this case are sized in the range of 1 mm to 2mm, according to the screen 18. The arrangement of Figure 6 is generally repeated with pulveriser 19 and screen 20 although with a further reduction in particle size so that the garbage is finely divided to a size of approximately .5mm to 1 mm providing a general consistency like that of sawdust. This is then delivered as shown in Figure 7 to a weighbin at 43 where predetermined amounts of finely divided garbage are despatched along conveyor 44 to a binder station 22 where a binder is dispensed from a silo 45 at a predetermined rate onto a conveyor 46. The conveyor 46 is in the form of a tubulator or generally curved conveyor and thereby delivers the garbage and binder to a mixer 23 which in this case includes revolving agitator 47 mounted on bearings 48 and 49 which monitors moisture level in the mixture and delivers the mixture out along conveyor 51 as a generally plastic granular material which is then delivered to the pan palletiser 25 along the conveyor 51 . This produces an aggregate which is then despatched onto the revolving tumbler 27 or if the revolving tumbler 27 is omitted directly to the kiln 28.

The still plastic material travels along the conveyors 60 or 64 to the kiln 28. The kiln 28 in this embodiment is a three stage kiln having a spiral path that the aggregate follows through where it is subjected to a heat gradient from a low entrance temperature to a high exit temperature. In the illustrated embodiment at stage 65, the aggregate is subjected to a temperature of around 630°C, at an intermediate stage 66 a temperature of around 1050°C, and at a final stage at 67, a temperature of around 1250°C is used. The aggregate which exits the kiln on conveyor 68 is hard dried, ceramic-like. This is then cooled slowly using a recovery bay arrangement shown generally at 29 where the conveyor 68 holds the aggregate at a temperature of 120°C to 180°C until sufficiently cool that it can be discharged along conveyor 69. The path length through the recovery bay and therefore the time in the recovery bay can be controlled using a spiral conveyor as in the case of the kiln 28. As illustrated in Figures 1 A and 1 B, the cooled aggregate can be used directly or further reduced in a crusher 30 as shown in Figure 14 where a mill 70 dispenses the crushed material onto a conveyor 71 where it can be delivered to storage bays for later use as aggregate or in the construction of other building materials. Many variations are possible for example, the heating can be in the two stage kiln typically at 350°C - 650°C in the first stage and 900°C-1200°C in the second stage. It will be appreciated that whilst the above has been given by way of illustrative example of the present invention, many variations and modifications thereto will be apparent to those skilled in the art without departing from the broad ambit and scope of the invention as set forth in the appended claims.

Claims

1 . A waste recycling process comprising the steps of:-

(a) Selecting non-toxic domestic waste to be processed;

(b) reducing the waste to a mass of finely divided particles of pre¬ determined character;

(c) mixing a pre-determined quantity of finely divided particles with a pre-determined quantity of binder to provide a mixture; and

(d) compacting the mixture while simultaneously or subsequently supplying heat to reduce water content and compact the mixture to produce a relatively dense aggregate suitable for use as a building material, road base or moulding material for production of bricks, tiles or the like.

2. The waste recycling process according to claim 1 wherein the waste selecting step includes separating waste that can be recycled by other means.

3. The waste recycling process according to claim 1 or 2 wherein the waste includes predominantly waste packaging and other solid domestic waste.

4. The waste recycling process according to any one of claims 1 to 3 wherein the waste includes iron-based wastes and other recyclables.

5. The waste recycling process according to claim 4 wherein said other recyclables include PTFE bottles and aluminium cans.

6. The waste recycling process according to claim 4 or 5 wherein the waste selecting step includes automated magnetic sorting for eliminating the iron based wastes from raw waste, and/or sorting procedure for removing said other recyclables.

7. The waste recycling process according to claim 6 wherein said sorting procedure comprises a manual sorting of the raw waste on a conveyor belt or the like.

8. The waste recycling process according to any one of claims 1 to 7 wherein in the waste reducing step the selected waste is reduced to a size suitable for providing an intimate blend between the finely divided particles and the binder.

9. The waste recycling process according to claim 8 wherein the waste reducing step includes a cutting or shredding process for providing a finely divided particulate mass.

10. The waste recycling process according to claim 9 wherein the particulate mass is similar to sawdust in character.

1 1 . The waste recycling process according to any one of claims 8 to 10 wherein the particles or particulate mass has a particulate size of .5mm to 1 mm.

12. The waste recycling process according to any one of claims 8 to 1 1 wherein a pulverising process is employed for reducing the selected waste.

13. The waste recycling process according to claim 12 wherein the pulverising process reducing the particulate size in stages.

14. The waste recycling process according to claim 12 or 1 3 wherein a screening process is employed for screening pulverised particles and particles which fail to pass the screening process are recycled to the pulverising process for reprocessing.

1 5. The waste recycling process according to any one or claims 1 to 14 wherein the mixing and binding step includes an agitating process in which a binder is added for coating the particles or particulate mass.

16. The waste recycling process according to claim 15 wherein the binder is a clay based binder including cementitious material or other refractory material.

1 7. The waste recycling process according to claim 16 wherein the clay based binder is finely divided and introduced in proportion of about 1 part binder to 1 part reduced waste.

18. The waste recycling process according to any one of claims 1 to 1 7 wherein the compacting and drying step includes a pelletising process for forming an aggregate sized according to demand.

19. The waste recycling process according to any one of claims 1 to 18 wherein the compacting and drying step includes a heating process for drying the mixture.

20. The waste recycling process according to claim 19 wherein the heating process comprising sundrying or employing a heat gradient over relatively short time period.

21 . The waste recycling process according to claim 20 wherein the heat gradient having a initial heat applied at a temperature of about 300°C to 700°C and a final temperature of about 1 100°C to 1500°C.

22. The waste recycling process according to claim 21 wherein the initial temperature is about 500°C and the final temperature is about 1500°C.

23. The waste recycling process according to claim 21 or 22 wherein the heat gradient is a two or three stage process.

24. The waste recycling process according to claim 23 wherein the heat gradient is a three stage process having an initial temperature of about 630°C for a first time period, an intermediate temperature of about 1050°C for a second time period and a final temperature of about 1250°C.

25. The waste recycling process according to any one of claims 1 to 24 wherein the recycling process including a recovery step where the aggregate is subject to slow cooling by maintaining the aggregate at a predetermined lower temperature for a predetermined period of time.

26. The waste recycling process according to claim 25 wherein said predetermined temperature is about 120°C to 180°C.

27. The waste recycling process according to claim 26 wherein said predetermined temperature is about 150°C.

28. The waste recycling process according to any one of claims 1 to 27 wherein the aggregate is a ceramic-like material suitable for use as is or reprocessed by crushing or otherwise, as a road base aggregated, fill or base for production of moulded or extruded building material.

29. An apparatus for waste recycling comprising a waste selection means, a waste reducer for reducing waste delivered thereto from the waste selection means to provide a mass of finely divided particles of predetermined character, a mixer for mixing the finely divided particles with a binder and means for compacting and drying the mixture.

30. The apparatus according to claim 29 wherein the waste selection means including a crusher means for crushing waste.

31 . The apparatus according to claim 29 or 30 wherein the waste selection means includes means for separating waste that can be recycled by other means.

32. The apparatus according to claim 31 wherein the separating means includes an automated magnetic sorting means for eliminating iron based wastes from raw waste.

33. The apparatus according to any one of claims 29 to 32 wherein the apparatus including transfer means for transferring waste between different means of the apparatus.

34. The apparatus according to any one of claims 29 to 33 wherein the waste reducer including pulverising means for reducing waste to the divided particles of predetermined character.

35. The apparatus according to claim 34 wherein the pulverising means comprising a single pulveriser or a plurality of pulverisers.

36. The apparatus according to claim 35 wherein the or each pulveriser is associated with a screening means, and particles which fail to pass the screen means are returned to the associated or preceding pulveriser for reprocessing.

37. The apparatus according to any one of claims 29 to 36 wherein binding means is provided for binding the finely divided particles with the binder, prior to mixing in the mixer.

38. The apparatus according to any one of claims 29 to 37 wherein the compacting means including a pelletising means of forming the mixture into a aggregate having a predetermined size.

39. The apparatus according to claim 38 wherein the pelletising means is a pan palletiser.

40. The apparatus according to any one of claims 29 to 39 wherein the drying means include a first dryer for initial drying of the mixture or aggregate at a temperature of 300°C to 700°C.

41 . The apparatus according to claim 40 wherein the first dryer is a tumbler dryer.

42. The apparatus according to claim 40 or 41 wherein the drying means including a second dryer for drying the mixture at a temperature of about 1 100°C to 1500°C.

43. The apparatus according to claim 42 wherein the second dryer is a kiln.

44. The apparatus according to claim 43 wherein the kiln having a spiral path conveyor.

45. The apparatus according to claim 43 or 44 wherein the kiln having two or more temperature regions.

46. The apparatus according to any one or claims 29 to 45 wherein the apparatus including a recovery means for providing slow cooling to the mixture or aggregate from the drying means.

47. The apparatus according to claim 46 wherein slow cooling is provided by maintaining the mixture or aggregate at a temperature of 120°C to 180°C.

48. The process according to any of claims 1 to 28 employing the apparatus according to anyone of claims 29 to 47.

49. The invention according to any one of claims 1 to 48 wherein a processor means is provided for controlling the steps/means so that there is generally continuous processing of waste.

50. A waste recycling process substantially as described with references to the drawings.

51 . An apparatus for waste recycling substantially as described with references to the drawings.