GB2421688A

GB2421688A - Waste treatment apparatus

Info

Publication number: GB2421688A
Application number: GB0425686A
Authority: GB
Inventors: William F Murphy; William E G Cooper; Paul Anthony Burrows
Original assignee: Estech Europe Ltd
Current assignee: Estech Europe Ltd
Priority date: 2004-11-23
Filing date: 2004-11-23
Publication date: 2006-07-05
Anticipated expiration: 2024-11-23
Also published as: GB2421688B; GB0425686D0

Abstract

A waste treatment apparatus 10 comprising a plurality of autoclaves 11, waste supply apparatus 12 to supply waste material to the autoclaves 11 and a discharge apparatus 13 to receive treated waste from the autoclaves, the autoclaves 11 being rotatable between a first position to receive the waste material, a second position to treat waste material, and a third position to discharge treated waste material. The autoclaves 11 may be rotatable about a horizontal axis so that they are upright when in the first position, generally horizontal in the second position and directed downwardly for discharge. The autoclaves 11 may also be rotatable about their longitudinal axes when in the second position. The waste supply apparatus 12 may include a moveable loading arm 12a which supplies waste material to the autoclaves 11 in turn. Steam is supplied at a high temperature and pressure and the autoclave 11 may be rotated to agitate the waste material during treatment.

Description

PATENTS ACT 1977 Al1189GB-R4j Title: Waste Treatment Apparatus

Description of Invention

This invention relates to a waste treatment apparatus.

It is known to process municipal and household waste, and also some commercial waste and industrial waste which can be included in municipal waste, by treating the waste material in an autoclave. The waste material is introduced into an autoclave which is a closed pressure vessel, and is subjected to saturated steam at an appropriate pressure and temperature, typically of at least 3 bar and above 130 C. By processing the waste material under these conditions for a sufficient period of time, the waste material is sterilised making it safe to handle. Advantageously, organic material within the waste material, such as fibres, plant matters, paper and the like is broken down to form a mass of small cellulose particles. During the processing, labels and printing on metal waste, glass and plastic bottles are removed and any plastic items such as bottles reduce in size. The resulting material can be easily sorted to remove recyclable items, the cellulose particles may be used in a variety of different - applications, and the remaining fraction which is sent to a landfill will be less than about 20% of the original mass of waste materials. The process of treating waste material in an autoclave has thus many advantages.

Some disadvantages of the method are known. The supply of heated and pressurised steam to the autoclave requires a great deal of energy, particularly over a sustained period. Further, the autoclave itself is large and consequently heavy piece of equipment: a typical autoclave able to take 20 tons of waste will be 20 meters long by 3 meters in diameter. The autoclave is typically pivotally mounted and is raised to receive waste and are lowered during the treatment process and to permit removal of the treated waste from the autoclave. This requires an appropriately powerful lifting mechanism which must be able to support the autoclave and resist substantial sideways forces as a result of the rotation of the autoclave. In addition, the long treatment period requires that waste is treated in batches over relatively long periods.

An aim of the present invention is to provide a new or improved waste treatment apparatus.

According to the present invention, we provide a waste treatment apparatus comprising a plurality of autoclaves, a waste supply apparatus to supply waste material to the autoclaves and a discharge apparatus to receive treated waste from the autoclaves, the autoclaves being rotatable between first position to receive the waste material, a second position to treat the waste material, and a third position to discharge treated waste material.

The autoclaves may be rotatable about a first generally horizontal axis between the first position and the third position.

Each autoclave may be generally upright when in the first position, generally horizontal in the second position and directed downwardly when in the third position.

Each autoclave may be rotatable about a longitudinal axis when in the second position.

The discharge apparatus and the waste supply apparatus may be laterally offset.

The waste supply apparatus may comprise a moveable loading arm operable to supply waste material to a selected one of the autoclaves.

The discharge apparatus may comprise a conveyor belt to receive treated waste material from each autoclave when the autoclave is in the third position.

The autoclaves may be successively loaded, operated to treat the waste material and discharged in sequence such that at least one autoclave is being loaded, one autoclave is performing a waste treatment operation and one autoclave is discharged at a given time.

The waste treatment operation may have a pressurising stage when steam under pressure is supplied to the autoclave, a treatment stage in which the waste is treated and a depressurising stage in which steam is released from the autoclave.

The waste treatment apparatus may comprise a steam supply network wherein steam released from one autoclave in a depressurising stage may be supplied to another autoclave in a pressurising stage.

Each autoclave may have a capacity of about 10 cubic metres.

The number of autoclaves may be a multiple of three.

Each of the autoclaves may comprise a mouth part, and wherein a door may close the mouth part when the autoclave is in the second position.

The door may be moved linearly to close the mouth.

The door may be provided with a steam supply joint to supply steam to the autoclave.

Each autoclave may have a collar part comprising a channel to receive steam from the steam supply joint.

Each autoclave may have a plurality of steam outlet pipes located internally of the autoclave, wherein steam supply pipe is connected to a channel in the collar part.

The steam outlet pipes may be supported on base plates such that the pipes are located inwardly of the walls of the autoclave to act to lift the waste during treatment.

The invention will now be described by way of example only with reference to the accompanying drawings wherein: Figure 1 is a plan view of a waste treatment apparatus embodying the invention, Figure 2 is a side view of the waste treatment apparatus of Figure 1, Figure 3 is a view of one of the autoclaves of the waste treatment apparatus of Figure 1 on a larger scale, Figure 4 is a sectional of line 4-4 of Figure 3, Figure 5 is a sectional of line 5-5 of Figure 3, Figure 6 is a view of a part of the autoclave of Figure 5 on a larger scale, Figure 7 is a view of another part of the autoclave of Figure 5 on a larger scale, Figure 8 is a view of the neck and door of the autoclave of Figure 3 in an open position.

Figure 9 is a section through a steam joint for the autoclave of Figure 3, Figure 10 is a diagram of a steam distribution system for use with the apparatus of Figure 1, and Figure 11 is a diagranimatic illustration of the sequence of operation of the waste treatment apparatus of Figure 1.

Returning now to Figure 1, a waste treatment apparatus embodying the present invention is as shown in plan view at 10. The waste treatment apparatus comprises a plurality of autoclaves 11, shown at Al, A2, A3, A4, A5 and A6. The apparatus 10 further comprises a waste supply apparatus generally illustrated at 12 and a discharge apparatus generally illustrated at 13. As shown in Fjgure 2, the waste supply apparatus 12 and the discharge apparatus 13 are laterally offset in a horizontal direction to ensure segregation of incoming "dirty" untreated waste material and outgoing "clean" treated waste material.

Each of the autoclaves 11 are each rotatable about a generally horizontal axes which is located at or near the centre of gravity of the autoclave when it is loaded with waste material to allow for easy rotation of the autoclave. Each autoclave 11 is rotatable between a first, generally upright position illustrated in dashed outline at 14 in Figure 2, a second position shown at 15 in Figure 1, and a third, downwardly inclined position shown at 16 in Figure 2 to discharge treated waste material onto the discharge apparatus 13. In the second position, the autoclave 11 may be generally horizontal or preferably, as shown in Figure 3, may be slightly inclined to the horizontal as shown by line H-H.

To describe the autoclaves 11 in more detail with reference to Figures 3 to 7, each autoclave comprises a part spherical end part 20, a generally cylindrical middle part 21, and a frusto-conical neck part 22 which ends in a steam supply part 23. Each autoclave 11 in the present example is relatively small for a waste treatment autoclave, with a capacity of about 10 cubic metres, corresponding to about 2.0 tonnes of waste, to allow for relatively quick treatment of waste material in the autoclave 11 and to allow easier handling and rotation of the autoclave 11. A drive mechanism for the autoclave 11 is shown at 25 in Figure 3, and comprises a pair of toothed tracks 26 attached to the cylindrical middle part 21. A drive carriage 27 supports the autoclave 11 via bearings generally shown at 28. A gear drive mechanism 28 in mesh with the toothed tracks 26 allows for rotation of the autoclave 11 about a longitudinal axis Y-Y when in the second position. A tilt drive can be is at 30 is operable to rotate the carriage 27 and hence the autoclave 11 between the first, second and third positions.

To close the autoclave 11 to permit pressurisation and supply of steam, a door 31 is provided. The door 31 engages the collar 23 when the autoclave 11 is in its second position, and is moved in a generally linQar direction as shown at A by a suitable hydraulic support, generally shown in Figure 8. The door 31 is supported on a ring clamp attachment generally shown at 3 1, supported on arms 3 lb which are moveable in a linear direction by hydraulic rams generally illustrated at 3 ic. The ring clamp is operable to support the door and locate it in position in engagement with the collar 23, and may either be disengaged from the door 31 during the treatment phase of operation, or may be provided with a suitable rotary connection such that the door 31 is supported by and rotatable relative to the ring clamp 3 la. The rotary joints generally shown at 50 is mounted and moveable with the door 31 as discussed herein. A simple linear motion to open and close the door 31 is simpler than providing a hinge support for the door and attached services. To hold the door 31 in a closed position, the neck part 23 has rotating cam locks 32 which are received in recesses 33 in a skirt 34 of the door 31.

Each autoclave 11 has internal steam outlet pipes 36 disposed within and running along its length. The pipes 36 as shown in cross-section in Figure 6 are generally triangular in cross-section, and are welded to base plates 37 welded to the interior wall of the autoclave 11 in a sacrificial maimer for easy repair and replacement. The pipes 36 have nozzles 38 to release steam into the interior of the autoclave 11. The pipes 36 project inwardly of the walls of the autoclave 11 to act to lift the waste material in the autoclave 11 when the autoclave 11 is rotated to agitate the waste material.

Although as discussed above the autoclave 10 may be rotated to a generally horizontal position in the treatment phase, it would be preferable to incline the autoclave slightly upwards during treatment so that the waste material is retained towards the rear of the autoclave. This would help to ensure that the material is thoroughly agitated by the pipes 36 and also reduce spilling of material when the door 30 is opened after treatment.

To supply steam to the steam outlet pipes 38, the neck collar 23 is provided with channels 39. The channels 39 are connected to the steam outlet pipes 36 by connection pipes 40, which are connected to the channels 39 via an internal ring 41 located next to the neck collar 23, for easy removal and repair.

The door 31 is provided with internal channels 42 which, when the door is in its closed position, are in flow communication with the internal channels 39 of the neck 23. The door also has a vent channel 43 to permit air and steam to be vented from the interior of the autoclave 11. The air vent channel 43 is protected by a mesh cover 44 to prevent waste material entering and potentially blocking the vent channel 43. Such a door configuration may advantageous also be used when an autoclave is provided with two doors, such as that autoclave shown in our co-pending application entitled Autoclave'.

In operation, when the door 31 is in place and clamped to the autoclave 11 and the autoclave 11 is rotating, the door 31 will rotate with the autoclave.

To supply steam to the interior of the autoclave 11, a rotating steam joint is provided, generally shown at 50 in Figure 9. The steam supply joint comprises a fixed outer case 51 having a first part 52 and a second part 53 bolted together.

Received within the casing 51 is an air vent pipe 54 which is fixedly connected at one end 55 to the door 43, and at its other end is supported within the second part 52 by a rotating joint generally illustrated at 56. The vent pipe 54 includes a flange 57 which engages seals generally shown at 58 to provide a sliding seal and support the vent pipe 54. A spring mechanism 59 maintains the seal 58 and flange 57 in engagement. The interior of the pipe 54 is in flow communication with a vent connection 60 provided as part of the second part 52. To provide for supply of steam to the autoclave, a steam supply pipe 61 is shown fixedly engaged at one end 62 with the door 31 and concentric with the vent pipe 54.

The other end 63 of the steam supply pipe 61 is supported by a sleeve 64 of the second part 53 of the casing 50. Seals 65 provide a rotating seal and support between the steam supply pipe 61 and support the part 64. The second part 63 further defines an annular channel 66 which is in flow communication with the steam supply pipe 61 and supplied with steam through an appropriate inlet 67.

An appropriate steam supply apparatus is provided connected to the inlet 67 and vent 60 of each of the autoclaves 11 to supply steam thereto and receive vented air and vapour from each of the autoclaves 11. Alternatively, a steam joint with lost motion may be used as disclosed in our co-pending application entitled Autoclave'.

The steam supply apparatus is generally shown in Figure 10, and shows a boiler operable to generate steam for supply to the autoclaves. In the present example, the boiler 100 has an operating pressure of 14 bar and a pressure reduction valve 101 is provided to supply steam at a pressure of 5 bar to the autoclave. Connected to the valve 101 are supply ducts 1 02a, 1 02b, 1 02c, 102d, 102e, 102f for connection to autoclaves Al to A6. For clarity, oniy the connection to the first autoclave via duct 1 02a is shown. Steam is supplied through a second valve 103 and third valve 104 to supply steam to the rotating joint and the door 31 to supply pressure to the first autoclave. A fourth valve 105 is provided and connected to the steam recovery manifold 106. Each autoclave is similarly connected to the steam recovery manifold so that the steam from one autoclave may be supplied to the next autoclave via a transfer valve 107. A condensor connection valve shown at 109 is also operable to connect the outlet to a condensor manifold shown at 110. The system Figure 10 thus permits pressure to be released from a first autoclave Al by connecting it to the next autoclave A4 until the pressure is equalised or almost equalised.

The valve 105 can then be closed and valve 109 opened to condense the remaining steam within the first autoclave and bring it down to ambient pressure or any other desired pressure. The pressure in the next autoclave A4 is then increased further to its working pressure by supplying steam from the boiler 100.

With reference to Figure 11, the waste treatment apparatus 10 is operated as follows. At step 90, the mobile loading arm l2a of the waste supply apparatus 12 is moved to the first autoclave 11 and begins to fill that autoclave with waste material to be treated. The autoclave 11 is then rotated to its second position, the door 31 is closed and treatment of the waste material begins with a pressurising phase shown at 91. In the phase, in the present example, the pressure within the autoclave is raised to about 5 bar and the autoclave is supplied with steam temperature of about 130 C. The waste material is then treated at high temperature and pressure during a treatment stage 92, during which the autoclave 11 is rotated about is longitudinal axis to agitate the waste material to ensure that it is all reached by the steam. During a depressurisation stage 93, the pressure is then released from within the autoclave 11, advantageously for use in pressurising another autoclave as discussed below, then passed to a condenser and then remaining steam is extracted using an air ejector. At a discharge stage 94, the door 91 is released and the autoclave 11 is rotated to its third, downwardly inclined position to discharge the treated waste to the discharge apparatus 13. As the steam supply pipes 36 are arranged in a helical pattern the loading stage 90 and discharge stage 94 can be facilitated by rotating the autoclave 11 about its longitudinal axis X - X. As illustrated by Figure 9 each of the autoclave 11 go through this process in turn, such that when the first autoclave Al has been loaded the mobile loading arm 12 then moves onto the second autoclave A2 to begin to load that autoclave whilst the first autoclave Al begins its pressurisation stage 91. Once the second autoclave A2 is loaded, it then begins its pressurisation stage 91 and the mobile loading arm 12a moves onto the third autoclave A3. By selection of the appropriate cycle length, it will be apparent that the waste treatment apparatus 10 will be operating effectively continuously. In the example of Figure 1, one of the autoclaves A6 is being supplied with waste material, one of the autoclaves Al is discharging treated waste material, two of the autoclaves A3, A4 are in the treatment stage of treating the waste within each of the autoclaves 11, one autoclave AS is in its pressurisation phase 91 and one of the autocaves A2 is in the depressurisation stage 93. Once treated waste material has been discharged from an autoclave in the discharge stage 94, the autoclave 11 is then rotated to its first, loading position and the mobile loading arm 1 2 is moved to that autoclave to supply it with waste material to be treated in the next cycle.

Advantageously, it can be seen from Figure 11 that one of the autoclaves 11 will be discharging steam at discharge stage 94 at the same time as another one of the autoclaves 11 is being pressurised, in the pressurisation stage 91. By provision of an appropriate steam supply apparatus (not shown) steam may be routed from the de-pressurising autoclave 11 to the pressurising autoclave 91 as illustrated by arrows 95. The step effectively reuses some of the steam from each autoclave at the end of the treatment cycle, and thus reduces the amount of energy needed to supply steam under pressure. By using a series of relatively small autoclaves, the entire treatment cycle can be kept a relatively short cycle length to permit near-continuous operation as shown in Figure 9 and allows each individual autoclave 11 to be lighter and more easily manoeuvred. The waste treatment apparatus is appropriately modular so that the capacity can be increased simply by adding additional autoclaves 11 as required. In the cycle as envisaged in Figure 11, six autoclaves are used and it is appropriate that the autoclaves are a multiple of three, but it will be apparent that other autoclaves may be varied as desired depending on the exact cycle time.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

Claims 1. A waste treatment apparatus comprising a plurality of

autoclaves, a waste supply apparatus to supply waste material to the autoclaves and a discharge apparatus to receive treated waste from the autoclaves, the autoclaves being rotatable between a first position to receive the waste material, a second position to treat waste material, and a third position to discharge treated waste material.
2. A waste treatment apparatus according to claim 1 wherein the autoclaves are rotatable about a generally horizontal axis between the first position and the third position.
3. A waste treatment apparatus according to claim 2 wherein each autoclave is generally upright when in the first position, generally horizontal in the second position and directed downwardly when in the third position.
4. A waste treatment apparatus according to any one of the preceding claims wherein each autoclave is rotatable about a longitudinal axis when in the second position.
5. A waste treatment apparatus according to any one of the preceding claims wherein the discharge apparatus and the waste supply apparatus are laterally offset.
6. A waste treatment apparatus according to any one of the preceding claims wherein the waste supply apparatus comprises a moveable loading arm operable to supply waste material to a selected one of the autoclaves.
7. A waste treatment apparatus according any one of the preceding claims wherein the discharge apparatus comprises a conveyor belt to receive treated waste material from each autoclave when the autoclave is in the third position.
8. A waste treatment apparatus according any one of the preceding claims wherein the autoclaves are successively loaded, operated to treat the waste material and discharged in sequence such that at least one autoclave is being loaded, one autoclave is waste treatment operation and one autoclave is discharged at a given time.
9. A waste treatment apparatus according to claim 8 wherein the waste treatment operation has a pressurising stage when steam under pressure is supplied to the autoclave, a treatment stage in which the waste is treated and a depressurising stage in which steam is released from the autoclave.
10. A waste treatment apparatus according to claim 9 comprising a steam supply network wherein steam released from one autoclave in a depressurising stage is supplied to another autoclave in a pressurising stage.
11. A waste treatment apparatus according to any one of the preceding claims wherein each autoclave has a capacity of about 10 cubic metres.
12. A waste treatment apparatus according to any one of the preceding claims wherein the number of autoclaves is a multiple of three.
13. A waste treatment apparatus according to any one of the preceding claims wherein each of the autoclaves comprises a mouth part, and wherein a door closes the mouth part when the autoclave is in the second position.
14. A waste treatment apparatus according to claim 13 wherein the door is moved linearly to close the mouth.
15. An autoclave according to claim 13 or claim 14 wherein the door is provided with a steam supply joint to supply steam to the autoclave.
16. A waste treatment apparatus according to claim 15 wherein each autoclave has a neck part comprising a channel to receive steam from the steam supply joint.
17. A waste treatment apparatus according to claim 16 wherein each autoclave has a plurality of steam outlet pipes located internally of the autoclave, wherein each steam supply pipe is connected to a channel in the neck part.
18. A waste treatment apparatus according to claim 17 wherein the steam outlet pipes are supported on base plates such that the pipes are located inwardly of the walls of the autoclave to act to lift the waste during treatment.
19. A waste treatment apparatus substantially hereinbefore described with reference to and as shown in the accompanying drawings.
20. Any novel feature or novel combination of features described herein and/or in the accompanying drawings.