GB2489254A

GB2489254A - An autoclave for processing domestic and municipal waste

Info

Publication number: GB2489254A
Application number: GB1104812.1A
Authority: GB
Inventors: Simon Gareth Kilvington Rose; John Chenery
Original assignee: WINGCROSS ENGINEERING Ltd
Current assignee: WINGCROSS ENGINEERING Ltd
Priority date: 2011-03-22
Filing date: 2011-03-22
Publication date: 2012-09-26
Also published as: GB201104812D0

Abstract

A waste processing facility 48 for domestic and municipal waste comprises at least one autoclave wherein the autoclave 10 comprises an elongate body (11: fig 1) and the body is arranged to rotate with an axis of rotation (22; fig 1) which is non parallel with the elongate dimension of the body such that the ends of the elongate body rotate around the axis of rotation, the axis of rotation being arranged such that the plane of rotation of each end comprises a vertical component. The autoclave has tumbling or â end over endâ rotational motion. The facility may further comprise a conveyor 54. An apparatus for breaking down domestic and municipal waste comprises autoclave with a treatment body, waste steam exit and waste outlet with filter and a means to clean the filter by delivering a pulse of compressed fluid, such as air or steam or water, through the outlet towards the body.

Description

A Waste Processing Facility for Domestic and Municipal Waste, Use of an Autoclave for Breaking Down Domestic/Municipal Waste, an Apparatus for Breaking Down Domestic/Municipal Waste, and a Method for Breaking Down Domestic/Municipal Waste The invention relates to a waste processing facility for domestic/municipal waste, use of an autoclave for breaking down domestic/municipal waste, an apparatus for breaking down domestic/municipal waste, and a method for breaking down domestic/municipal waste.

A known autoclave for breaking down domestic/municipal waste has a vessel body which is elongate with rounded ends, and is generally known and hereinafter referred to as a "cigar-shaped" autoclave. The autoclave comprises a body for holding waste to be broken down and a flight inside the body. In use, the flight is rotated to excite the waste. In combination with heat and pressure, the excitation of the contents causes the waste to break down. The cigar-shaped autoclave is arranged so that the axis of rotation of the flight is coincident with the longitudinal axis of the autoclave and between 0° to around 30° to the horizontal. Such cigar-shaped autoclaves have been used in domestic/municipal waste processing facilities for around twenty years.

However, in use, waste, such as textiles, can become wrapped around the flight and needs to be removed to ensure continued efficient function of the autoclave.

Removal of any material wrapped around the flight is time consuming. Further, the known autoclave can only be filled to about 30% to 40% capacity, as a result of the complexity of filling and emptying the body, requiring conveyors which extend into the body, and because that capacity allows flights to operate effectively.

A further known autoclave comprises an elongate vessel, which is pivoted about a central axis perpendicular to the elongate dimension, such that the body rotates end over end. This type of autoclave is hereinafter referred to as a "tumbling autoclave". Tumbling autoclaves have not been used for domestic or municipal waste.

Tumbling autoclaves were used until the 1960s for breaking down fibre-based materials such as paper and textiles. In use, the body is rotated end over end, and this excites the waste and, in combination with heat and pressure, the excitation causes the fibre-based materials to break down. DE749028 from 1942 discloses a tumbling autoclave.

According to a first aspect of the present invention, there is provided use of an autoclave for breaking down domestic/municipal waste, the autoclave comprising a body which is elongate, the body being arranged to rotate with an axis of rotation which is non-parallel with the elongate dimension of the body, such that the ends of the elongate body rotate around the axis of rotation, the axis of rotation being arranged such that the plane of rotation of each end comprises a vertical component.

Preferably, the axis of rotation of the body is substantially perpendicular to the elongate dimension of the body and the use comprises rotating the body such that it rotates end over end and the planes of rotation of the ends are substantially coincident and preferably substantially vertical.

At the time the present invention was made, it was the generally accepted view that cigar-shaped autoclaves should be used for breaking down domestic/municipal waste and that they provided the best results.

Domestic/municipal waste can comprise many different materials, including materials such as metals and ceramics which are considerably tougher and less porous than fibre-based materials such as paper and textiles, and hence are more difficult to break down. Tumbling autoclaves had previously only been used for fibre-based materials or soft materials like rubber, a quite different and limited technical area.

However, the inventors of the present invention have found surprisingly that the prejudice against tumbling autoclaves is not well founded, and tumbling autoclaves can in fact be used to satisfactorily break down domestic/municipal waste.

The non-obviousness of the present invention is reinforced by the fact that the use of tumbling autoclaves for breaking down fibre-based materials has been known since at least 1910. Cigar-shaped autoclaves have been used in breaking down domestic/municipal waste for about twenty years, and the wrapping of material around the flight has been a long-recognised problem. The inventors have answered a long felt want by adopting a non-obvious solution to the problem.

According to a second aspect of the present invention there is provided a method of breaking down domestic/municipal waste, the method comprising the steps of: placing domestic/municipal waste in an autoclave with a body which is elongate, the body being arranged to rotate with an axis of rotation which is non-parallel with the elongate dimension of the body, such that the ends of the body rotate around the axis of rotation, the axis of rotation being arranged such that the plane of rotation of each end comprises a vertical component; and rotating the body about its axis of rotation.

According to a further aspect of the invention there is provided a waste processing facility for domestic and/or municipal waste, the facility including at least one autoclave, the or at least one autoclave comprising a body which is elongate, the body being arranged to rotate with an axis of rotation which is non-parallel with the elongate dimension of the body, such that the ends of the elongate body rotate around the axis of rotation, the axis of rotation being arranged such that the plane of rotation of each end comprises a vertical component.

Preferably, the axis of rotation of the body is substantially perpendicular to the elongate dimension of the body and rotating the body is arranged to be rotated end over end with the planes of rotation of the ends substantially coincident and preferably substantially vertical.

According to a further aspect of the invention there is provided a waste processing facility for domestic and/or municipal waste, the facility including at least one autoclave, the or at least one autoclave being elongate and arranged to rotate by tumbling end over end.

The or each tumbling autoclave preferably has a door at one end through which waste for treatment can be introduced, and treated waste can be tipped out.

The facility preferably includes a conveyor to convey waste into the or each tumbling autoclave and may include a conveyor to convey waste from each tumbling autoclave.

Preferably the facility includes a plurality of autoclaves and preferably all of the autoclaves are tumbling autoclaves.

According to another aspect of the present invention there is provided an apparatus for breaking down domestic/municipal waste, the apparatus comprising an autoclave with a body for treatment of waste at elevated temperature and pressure, the apparatus further comprising an outlet to allow exit of waste steam from the body, the outlet comprising a filter to filter out waste particles, the apparatus further comprising means to clean the filter by delivering through the outlet a pulse of compressed fluid such as air or steam, or a pulse of liquid such as water, towards the body.

The pulse through the outlet towards the body results in detachment of waste particles attached to the filter, so that the filter can be cleared, thus allowing more efficient flow of waste steam through the outlet.

Preferably, the means to clean the filter comprises a first delivery means to deliver a pulse of a compressed fluid or a pulse of liquid and a second delivery means to deliver a pulse of compressed fluid or pulse of liquid which is different from that of the first means.

Preferably, the first delivery means is arranged to deliver a pulse of air and the second delivery means is arranged to deliver a pulse of one of steam and water.

Preferably, the apparatus further comprises a monitoring device to monitor the flow of waste steam through the outlet, the means to clean the filter being arrange to operate when the monitored flow drops below a first threshold of flow level. Clearing of the filter can therefore be carried out automatically, without the need for an operator to monitor flow.

Preferably, the means to clean the filter is arranged to deliver further pulses until the flow monitored by the monitoring device exceeds a threshold flow level, the second threshold flow level being at least as high as the first threshold flow volume level and preferably higher than the first threshold flow level. Therefore, pulses are delivered until the flow level is at an acceptable level again.

Preferably, the apparatus further includes means to monitor the pressure in the autoclave body, the means to deliver a pulse being arranged to operate to deliver a pulse only if the pressure in the body of the autoclave is below a threshold pressure level. This prevents pressure pulses being applied if they would increase the pressure in the body of the autoclave to an undesirably high level.

According to a fourth aspect of the present invention there is provided a method of operating an autoclave, the autoclave comprising a body for treatment of waste at elevated temperature and pressure, the autoclave further comprising an outlet to allow exit of waste steam from the body, the outlet comprising a filter to filter out waste particles, the method comprising the steps of delivering through the outlet a pulse of compressed fluid such as air or steam, or a pulse of liquid, such as water, towards the body, to clean the filter.

Preferably, the step of delivering a pulse is carried out whilst the autoclave is being operated to break down waste. The efficiency of the process is therefore increased, as it is not necessary to continue an autoclaving operation with a below optimal waste steam outlet, or to stop autoclaving activity in order to clean the filter.

The method may further comprise the step of monitoring flow through the outlet, the step of delivering a pulse being carried out if the monitored flow drops below a first threshold flow level. After an initial pulse has been delivered, the method may comprise a further step of monitoring the flow, the steps of delivering a pulse and monitoring the flow being alternated until the flow returns above a second threshold flow level, the second threshold flow level being at least as high as and preferably higher than the first threshold flow level.

Preferably, the method further comprises the step of monitoring the pressure in the autoclave body, the step of delivering a pulse being only carried out if the pressure in the body of the autoclave is below a threshold pressure level.

According to a fifth aspect of the present invention there is provided a method of emptying an autoclave body through an opening in the autoclave body, the body being movable so that waste can be emptied through the opening under the influence of gravity, the autoclave comprising an inlet to the body, the inlet being connectable to pressure providing means, the method comprising the step of: when the autoclave body is arranged such that waste can be emptied through the opening under the influence of gravity, applying through the inlet a pulse of compressed fluid such as air or steam, or a pulse of liquid, such as water, towards the body to aid emptying.

The application of pressure provides a simple and efficient way of ensuring the body of the autoclave is efficiently emptied.

In use, for breaking down waste, the inlet may act as an outlet for waste steam.

Thus, only one opening performing the function of both said inlet and outlet needs to be provided, increasing the simplicity of the autoclave.

An embodiment of the present invention will now be described with reference to the Figures, in which: Fig. 1 shows a view from the side of a tumbling autoclave; Fig. 2 shows a view from above of the autoclave of Fig. 1; Fig. 3 shows a view from the side of the autoclave of Fig. 1 arranged in use on axle supports; Fig. 4 is a view of a waste processing unit in a recycling facility; and, Fig. 5 is a schematic diagram of the autoclave of Fig. 1 and the outlet of the autoclave.

Figures 1 to 5 illustrate a tumbling autoclave 10. The autoclave 10 comprises a body 11 which is elongate. The body 11 comprises three sections, a central cylindrical section 12, a hemispherical section 13 extending from one end 14 of the cylindrical section 12, and a frustoconical section 15 extending from the other end 16 of the cylindrical section 12. The frustoconical section 15 tapers inwardly away from the cylindrical section 12. The hemispherical section 13 defines one end 17 of the body 11 and the frustoconical section 15 defines the other end 18 of the body 11. The frustoconical section 15 defines an opening which can be closed by means of a door 19. The body 11 is about 10 m long and about 5 m in diameter and has an internal capacity of about 145 m3. The autoclave 10 is made of steel.

The autoclave 10 includes two stub axles 20. Each axle 20 extends from the body 11 at a position which is the mid point of the length of the cylindrical section 12. The axles 20 are diametrically opposed, such that they are aligned with and define an axis of rotation 22 of the autoclave 10.

As shown in Fig. 3, each axle 20 is rotatably connected to an axle support 24.

One of the axle supports 24 is connected to drive means 26. The height of each axle support is approximately half of the length of the body 11. The axle supports 24 are positioned on the edge of a recess 28, such that the body 11 extends into the recess 28.

Fig. 4 shows a waste processing unit 48 in a recycling facility. Waste 50 arrives at the waste processing unit 48 and is shunted, for example by a bulldozer 52, on to one of a number of inclined conveyors 54. Each inclined conveyor 54 leads to a tumbling autoclave 10. The inclined conveyor 54 conveys waste on to a horizontal conveyor 56. With the autoclave body 11 arranged in the upright position with the door 19 uppermost, the door 19 is opened, and the horizontal conveyor 56 transports waste 50 so that it drops from the conveyor 56 through the opening 21 in the top of the autoclave body 11. The body 11 can be filled to 80 to 85% full, a much higher capacity than the known cigar shaped autoclaves. The door 19 is then hinged closed and locked and the autoclave 10 is rotated on the axles 20 by the drive means 26 causing rotation of the body 11 about the horizontal rotation axis 22. The body 11 thus rotates end over end, which causes excitation of the waste inside the autoclave 10. At the same time as the body 11 is rotated, the pressure and temperature inside the body 11 are increased.

Once the waste has been broken down the body 11 can be arranged with its end 18 downmost, so that when the door 19 is opened the contents of the body 11 fall out under the influence of gravity. The waste will fall out on to a horizontal conveyor 58 which may carry the waste to a series of further conveyors 60 to convey the processed waste to the recycling unit of the facility for sorting and recycling.

As shown in Fig. 5, the autoclave is provided with high pressure steam via an inlet 29, which is in fluid connection with the body 11 to allow steam to flow into the body 11. The inlet 29 is a pipe, and is positioned so that it is coincident with and located inside one of the axles 20. The autoclave 10 further includes an outlet 30, which is in fluid connection with the body 11, to allow the exit of steam from the body 11. The outlet 30 is a pipe. The outlet 30 is positioned so that it is coincident with and located inside one of the axles 20. The inlet 29 and outlet 30 allow the steam inside the body 11 to be continually refreshed. The outlet 30 is connected to a condensate line 31 which transfers the waste team.

The pipe 30 includes a filter 32 to remove any particles of waste which may be transported with the waste steam. A flow meter 34 is included in the pipe 30 to monitor the flow rate of steam from the body 11. The outlet 30, as well as being connected to the condensate line 31, is also fluidly connected via pipes 33, 35 to a high pressure water/steam generator and pump 36 and an air compressor 37 and air tank 38, respectively. The air compressor 37 and the pump 36 are arranged to provide pulses of high pressure air or steamlwater, respectively. Flow of air along pipe 33 towards the body 11 is controlled by valve 40. Flow of steamlwater along the pipe 35 towards the body 11 is controlled by valve 42. A pressure sensor 344 is provided inside the body 11 to measure the pressure inside the body 11. The pressure sensor 44 and the monitoring device 34 are connected to a control unit 45. The control unit 45 controls the air compressor 37, pump 36, and valves 40, 42.

In use, the filter 32 may become blocked as it traps waste transported in the steam. This will result in a decreased ability of the outlet 30 to transfer waste steam from the body 11 along the condensate line 31. As the filter 32 becomes blocked, the flow rate of steam through the outlet 30, as measured by the monitoring device 34, will be reduced. When a flow rate below a threshold flow rate value is detected by the monitoring device 34, the control unit operates either the air compressor 37 or the pump 36. The appropriate valve 40, 42 is opened by the control unit for a short period of time, such that a pressure pulse of air or water steam is produced which travels through the outlet 30, in a direction towards the body 11 of the autoclave 10. As the pressure pulse travels through the filter 32, it acts to unblock the filter 32. Further pressure pulses are applied until the monitoring device 34 detects a flow rate which is greater than a second threshold flow rate value, the second threshold flow rate value being higher than the first threshold flow rate value. If the pressure sensor 44 detects a pressure inside the body 11 which is higher than a threshold pressure, the plc? unit will not allow pressure pulses to be produced. This prevents the pressure inside the body 11 being increased to an undesirably high level by any pressure pulses provided by the pump 36, or the air compressor 37.

When the body 11 is being emptied, the opening to the body 11 may become blocked by waste. Pressure pulses can be provided in the same manner as when the filter 32 requires unlocking. This increases the pressure inside the body 11, so that the waste is forced out of the opening.

The recycling facility might include five to twenty autoclaves 10, or more or fewer, as desired.

In the above embodiment, the outlet 30 is used to provide pressure pulses to clear the filter 32 and to help force waste out of the opening of the body 11. However, a separate inlet could be provided to increase pressure in the body 11 to force waste out of the body 11, and the pressure may be provided by the same pump 36 and compressor 37 or a different pump/compressor.

In the above embodiment high pressure steam, water or air can be used to unblock the filter 32. Alternatively, only one of steam, water or air may be available for use, or the type of medium, i.e. water, air or steam, used could be varied depending on the action being undertaken, i.e. whether the pressure is being used to unblock the filter 32 or to force waste out of the autoclave 10.

In the above embodiment, flow rate is used to monitor the flow of waste steam through the outlet 30. However, other parameters could be measured instead, for example, flow volume or pressure.

Claims

Claims 1. A waste processing facility for processing domestic and municipal waste, the facility including at least one autoclave, the or at least one autoclave comprising a body which is elongate, the body being arranged to rotate with an axis of rotation which is non-parallel with the elongate dimension of the body, such that the ends of the elongate body rotate around the axis of rotation, the axis of rotation being arranged such that the plane of rotation of each end comprises a vertical component.
2. A waste processing facihty as claimed in claim 1, wherein the axis of rotation of the body is substantially perpendicular to the elongate dimension of the body and the body is arranged to be rotated end over end with the planes of rotation of the ends substantially coincident.
3. A waste processing facility as claimed in claim 2, wherein the planes of rotation are substantially vertical.
4. A waste processing facility as claimed in claim 1, 2 or 3, wherein the or each tumbling autoclave has a door at one end through which waste for treatment can be introduced and treated waste can be tipped out.
5. A waste processing facility as claimed in any preceding claim, wherein the facility includes a conveyor to convey waste into the or each tumbling autoclave.
6. A waste processing facility as claimed in any preceding claim, wherein the facility includes a conveyor to convey waste from the or each tumbling autoclave.
7. A waste processing facility as claimed in any preceding claim, wherein the facility includes a plurality of autoclaves.
8. A waste processing facility as claimed in claim 7, wherein all of the autoclaves are tumbling autoclaves.
9. Use of an autoclave for breaking down domestic/municipal waste, the autoclave having a body which is elongate, the body being arranged to rotate with an axis of rotation which is non-parallel with the elongate dimension of the body, such that the ends of the elongate body rotate around the axis of rotation, the axis of rotation being arranged such that the plane of rotation of each end comprises a vertical component.
10. The use of an autoclave according to claim 9, wherein the axis of rotation of the body is substantially perpendicular to the elongate dimension of the body and the use comprises rotating the body, such that it rotates end over end and the planes of rotation of the ends are substantially coincident.
11. The use as claimed in claim 10, wherein the planes of rotation of the ends of the body are substantially vertical.
12. A method of breaking down domestic/municipal waste, the method comprising the steps of: placing domestic/municipal waste in an autoclave with an elongate body, the body being arranged to rotate with an axis of rotation which is non-parallel with the elongate dimension of the body, such that the ends of the body rotate around the axis of rotation, the axis of rotation being arranged such that plane of rotation of each end comprises a vertical component; and rotating the body about its axis of rotation.
13. A method as claimed in claim 12, wherein the method includes rotating the body end over end such that the axis of rotation of the body is substantially perpendicular to the elongate dimension of the body and the planes of rotation of the ends of the body are substantially coincident.
14. A method as claimed in claim 13, wherein the planes of rotation of the ends of the body are substantially vertical.
15. A method as claimed in claim 12, 13 or 14, wherein the body of the autoclave has a door at one end,
16. A method as claimed in claim 15, wherein the method includes introducing waste into the autoclave by arranging the body with the door facing upwards, opening the door and dropping waste into the body.
17. A method as claimed in claim 15 or claim 16, wherein the method includes emptying the autoclave by rotating the body so that the door faccs downwards and opening the door.
18. An apparatus for breaking down domestic/municipal waste, the apparatus comprising an autoclave with a body for treatment of waste at elevated temperature and pressure, the apparatus further comprising an outlet to allow exit of waste steam from the body, the outlet comprising a filter to filter out waste particles, the apparatus further comprising means to clean the filter by delivering through the outlet a pulse of compressed fluid, such as air or steam, or a pulse of liquid such as water, towards the body.
19. An apparatus according to claim 18, wherein the means to clean the filter comprises a first delivery means to deliver a pulse of a compressed fluid or a pulse of liquid, and a second delivery means to deliver a pulse of compressed fluid or pulse of liquid which is different from that of the first means.
20. An apparatus according to claim 19, wherein the first delivery is arranged to deliver a pulse of air and the second delivery means is arranged to deliver a pulse of onc of steam and water.
21. An apparatus according to claim 18, claim 19 or claim 20, wherein the apparatus further comprises a monitoring device to monitor the flow of waste steam through the outlet, the means to clean the filter being arranged to operate when the monitored flow drops below a first threshold flow level.
22. An apparatus according to claim 21, wherein the means to clean the filter is arranged to deliver further pulses until the flow monitored by the monitoring device exceeds a second threshold flow level, the second threshold flow level being at least as high as and preferably higher than the first threshold flow level.
23. An apparatus according to any of claims 18 to 22, wherein the apparatus further includes means to monitor the pressure in the autoclave body, the means to deliver a pulse being arranged to operate to deliver a pulse only if the pressure in the body of the autoclave is below a threshold pressure level.
24. An apparatus according to any of claims 18 to 23, the autoclave having a body which is elongate, the body being arranged to rotate with an axis of rotation which is non-parallel with the elongate dimension, such that the ends of the body rotate around the axis of rotation, the axis of rotation arranged such that plane of rotation of each end comprises a vertical component.
25. The apparatus of claim 24, wherein the outlet extends from the body along the axis of rotation of the body.
26. An apparatus according to claim 25, wherein the body comprises at least one axle for rotation of the body about the axis of rotation, the outlet extending through the axle.
27. An apparatus according to claim 26, wherein the outlet is concentric with the axle.
28. The apparatus of any of claims 18 to 27, comprising a plurality of said autoclaves.
29. A method of operating an autoclave, the autoclave comprising a body for treatment of waste at elevated temperature and pressure, the autoclave further comprising an outlet to allow exit of waste steam from the body, the outlet comprising a filter to filter out waste particles, the method comprising the step of: delivering through the outlet a pulse of compressed fluid, such as air or steam, or a pulse of liquid, such as water, towards the body to clean the filter.
30. A method according to claim 29, wherein the step of delivering a pulse is carried out whilst the autoclave is being operated to break down waste.
31. A method according to claim 29 or claim 30, wherein the method further comprises the step of monitoring flow through the outlet, and the step of delivering a pulse is carried out if the monitored flow drops below a first threshold flow level.
32. A method according to claim 31, wherein after an initial pulse has been delivered, the method comprises a further step of monitoring the flow, the steps of delivering a pulse and monitoring the flow being alternated until the flow returns above a second threshold flow level, the second threshold flow level being at least as high as and preferably higher than the first threshold flow level.
33. A method according to any of claims 29 to 32, wherein the method further comprises the step of monitoring the pressure in the autoclave body, and the step of delivering a pulse is only carried out if the pressure in the body of the autoclave is below a threshold pressure level.
34. A method of emptying an autoclave body through an opening in the autoclave body, the body being movable so that waste can be emptied through the opening under the influence of gravity, the autoclave comprising an inlet to the body, the inlet being connectable to pressure providing means the method comprising the steps of: when the autoclave body is arranged such that waste can be emptied through the opening under the influence of gravity, applying through the inlet a pulse of fluid such as compressed air or steam, or a pulse of liquid, such as water towards the body to aid emptying.
35. The method of claim 34, wherein, during autoclaving, the inlet acts as an outlet for waste steam.
36. The use of an autoclave for breaking down domestic/municipal waste substantially as described herein with reference to the accompanying drawings.
37. An apparatus substantially as described herein with reference to the accompanying drawings.
38. A method of operating an autoclave substantially as described herein with reference to the accompanying drawings.
39. A method of emptying an autoclave body substantially as described herein with reference to the accompanying drawings.
40. A waste processing unit substantially as described herein with reference to the accompanying drawings.