GB2561846A

GB2561846A - Waste treatment apparatus and method

Info

Publication number: GB2561846A
Application number: GB1706486.6A
Authority: GB
Inventors: Spencer Nik; Jouhara Hussam
Original assignee: MANIK VENTURES Ltd
Current assignee: MANIK VENTURES Ltd
Priority date: 2017-04-24
Filing date: 2017-04-24
Publication date: 2018-10-31
Also published as: GB201706486D0

Abstract

A waste treatment apparatus comprising a heat treatment chamber 200, a basket 300 for receiving waste to be treated, a piston 100 moveable within the chamber and moveable into and out of the basket, a heat source 210 for the chamber suitable for elevating the temperature of the chamber and a control apparatus adapted to activate the heat source and to move the piston. The piston improves the arrangement and/or compression of the waste within the chamber. The basket may be movable within the chamber wherein the piston and basket are provided with corresponding engagement portions which form a selectable connection between each other so that the piston directs movement of the basket. The chamber may comprise one or more heat conductive pins 208. The piston may further comprise a sensor such as a pressure transducer, current meter or displacement sensor which is connected to the control apparatus. A method of operation comprises receiving waste material in the basket, elevating the temperature of the chamber and lowering the piston from an initial position to either a pre-determine position or one based upon a signal received from a pressure sensor.

Description

(54) Title of the Invention: Waste treatment apparatus and method Abstract Title: Waste treatment apparatus and method (57) A waste treatment apparatus comprising a heat treatment chamber 200, a basket 300 for receiving waste to be treated, a piston 100 moveable within the chamber and moveable into and out of the basket, a heat source 210 for the chamber suitable for elevating the temperature of the chamber and a control apparatus adapted to activate the heat source and to move the piston. The piston improves the arrangement and/or compression of the waste within the chamber. The basket may be movable within the chamber wherein the piston and basket are provided with corresponding engagement portions which form a selectable connection between each other so that the piston directs movement of the basket. The chamber may comprise one or more heat conductive pins 208. The piston may further comprise a sensor such as a pressure transducer, current meter or displacement sensor which is connected to the control apparatus. A method of operation comprises receiving waste material in the basket, elevating the temperature of the chamber and lowering the piston from an initial position to either a predetermine position or one based upon a signal received from a pressure sensor.

FIG. 7

100 100 / 6

2/6

122

FIG.

I—I LL ο

3/6

104 ¹⁰⁶

FIG. 5 FIG.

4/6

200

100

202

208

202

300

FIG. 7

5/6

400

420 oo d

cn d

6/6

116

FIG. 10

-1Waste treatment apparatus and method

FIELD OF THE INVENTION

The present invention relates to a domestic waste treatment apparatus, in which heat 10 energy can be released from waste material produced in the domestic environment, by way of heat treatment or other appropriate means.

BACKGROUND ART

Our earlier patent application W02015/104400 disclosed a chamber for domestic use, which provides heat treatment (such as by pyrolysis) of domestic waste.

SUMMARY OF THE INVENTION

The present invention relates to an improved waste treatment apparatus and method.

Accordingly, a first aspect of the present invention is directed to a waste treatment apparatus comprising a heat treatment chamber, a basket for receiving waste to be treated, a piston moveable within the chamber and moveable into and out of the basket, a heat source for the chamber suitable for elevating the temperature of the chamber and a control apparatus adapted to activate the heat source and to move the piston.

Furthermore, the basket may be moveable within the chamber.

The chamber may have one or more heat-conductive pins extending from an interior wall into the interior of the chamber. The presence and arrangement of such pins provides for a more uniform temperature distribution in the chamber (described in more detail in our earlier

-2application W02015/104400), but presents a challenge in arranging waste material optimally within the chamber. Preferably, waste material can be arranged around and between any heat-conductive pins. Movement of the piston within the chamber, and optionally relative to the basket so that the piston may be moved at least partially into the basket, is aimed at arranging or compressing waste material being treated so that it so far as possible lies within a region of the chamber most suitable for heat treatment, for example arranged around and between any heat-conducting pins; and thus allows for improved efficiency of heat treatment of waste material.

For the purposes of this disclosure, the terms up, upwards and so on and their converses down, downwards and so on refer to substantially those orientations when the apparatus is installed and set up for use. While the apparatus will usually be oriented when set up for use so that the piston and basket move substantially vertically within the chamber, it is envisaged that the invention will be capable of operating similarly effectively in other configurations and orientations.

Also for the purposes of this disclosure, the term piston is intended to mean an arrangement in which a head part is moveable within an enclosure in order to transfer a force from a piston head to material within the enclosure. In this case the enclosure is, it will be clear to the skilled reader, the heat treatment chamber. However, in the present invention the piston and its enclosure need not be in a sealed relationship. Indeed in the present invention a specific size and shape of the piston in relation to the chamber is not essential. For example, the chamber may have a quadrilateral cross-section and the piston may have a circular crosssection, or vice-versa, without affecting the functionality of the apparatus of the invention.

The piston may comprise a piston head and a piston rod.

The piston may be provided with a force sensor which is in turn connected to the control apparatus. A force sensor can detect resistance to movement of the piston, for example provided by waste being treated. Domestic waste may comprise a range of different materials in different forms such as differently sized pieces of waste material, and it is desirable for the present treatment apparatus to be useable with many different waste materials and forms thereof. Thus, as the piston is moved downwards into the basket to compress and/or arrange the waste material being treated it may encounter material which is resistant to compression. The force sensor may provide a suitable signal to the control

-3apparatus. In turn, the control apparatus may alter the movement of the piston; for example by ceasing downward movement of the piston and then moving the piston upwards back towards an initial position. The ability for the apparatus to detect resistance to movement of the piston is important, for example to avoid damage to the apparatus itself.

The force sensor may be located in a lower region of the piston head, preferably at substantially the bottom of the piston head. The force sensor may comprise a pressure transducer, such as a semiconductor or piezoelectric pressure sensor for example. Alternatively, an approximation of force could be derived indirectly. For example, electrical current drawn by an electric motor driving the piston head may vary in dependence on physical resistance to movement of the piston head. For example, physical resistance to downward movement of the piston head may result in an increase in current drawn by such a motor. Thus, the force sensor of the present invention may comprise a current meter connected to the control apparatus and to a drive means, such as a first drive means described below. Such a force sensor may include calibration means.

As the temperature is elevated, the characteristics of some or all of the material of the waste being treated may change. For example, some plastics material may soften or even melt as the temperature rises, depending on the particular material or materials concerned and the temperature. Furthermore, when the temperature is elevated, water present in the waste being treated may be driven out in the form of water vapour. Thus, as the temperature rises (or even as a result of a rearrangement or compression of waste material resulting from a previous movement of the piston) resistance to movement of the piston may change. Preferably, therefore, the piston may be moved upwards and downwards within the chamber and/or relative to the basket more than once during a treatment cycle. Such a plurality of piston movements may improve the arrangement and/or compression of waste material within the chamber.

The waste treatment apparatus may comprise a displacement sensor to provide the control apparatus with information regarding a displacement of the piston from a predetermined initial position. A cycle of upwards and downwards movements of the piston may be terminated by the control apparatus when the piston reaches a pre-determined final displacement from its initial position. Such a pre-determined final displacement may represent a preferred lowermost position for the piston. The pre-determined final displacement may also

-4be limited by the arrangement of the apparatus. The piston head may be provided with one or more openings for accommodating at least a portion of heat-conductive pins. Thus, the extent to which the piston may be lowered with respect to the apparatus may be limited by the extent to which the heat-conductive pins may be accommodated by the piston head.

The piston and basket may be provided with corresponding engagement portions, to form a selectable connection between each other. Such engagement portions allow movement of the piston to direct movement of the basket, for example to raise or lower it or to agitate it. This provides an advantage over previously-suggested raising and/or lowering means in that the connection between the piston and basket can be strong and the mechanism itself is long-lasting and able to withstand temperatures in the chamber. The selectable connection is an important feature because the ability to select between relative movement of the piston and basket and movement of the piston and basket in concert with each other allows for those elements to be used to optimise the arrangement of waste material within the chamber across a range of waste material characteristics. In one conceivable scenario, waste material may be made up of relatively small pieces which may simply arrange themselves under gravity between and around heat-conductive pins, when the basket is lowered into the chamber, without any further action needed.

However in an alternative conceivable scenario, waste material may be made up of large and/or irregularly sized pieces. In that case, one or more pieces of waste material may be arranged in the basket so that they prevent other pieces of waste material from being arranged optimally. In such a case, the ability of the piston to move relative to and into the basket may provide means for rearranging pieces of waste material. Furthermore, repeated cycles of insertion and withdrawal may provide agitation to waste material and thus encourage it to become arranged within the chamber better for efficient heat treatment.

Agitation (such as a relatively small, rapid raising and lowering action) may also be provided when the piston and basket are connected to each other, an agitating movement of the piston thus providing a corresponding agitation of the basket.

Agitation may be provided during and/or after heat treatment and/or after combustion.

Agitation after combustion may encourage any ash left behind as a result of the combustion to fall into a portion of the chamber below the basket, for subsequent removal from the

-5chamber. To aid this, the basket may be provided with suitable openings or perforations or be constructed in a way to leave suitable openings and the like.

The basket may be provided with more than one suitable engagement portion so that a connection with the piston may be formed at more than one vertical point of the basket.

The corresponding engagement portions may comprise at least one bolt and corresponding socket. For example, the piston head may be provided with a bolt and the basket with a corresponding socket. Two or more sets of corresponding engagement portions may be provided approximately evenly spaced around the piston head or basket, as appropriate. The engagement portions selectively form a connection (or release a connection) by extending a bolt into (or withdrawing a bolt from) a socket.

The or each bolt may be extended and/or withdrawn by a suitable mechanism. One possible mechanism envisaged may be a spring provided on a bolt to bias that bolt to the withdrawn position; a corresponding cam may provide an extending force to overcome the bias of the spring to extend the bolt for engagement with a corresponding socket. Other suitable mechanisms may provide for suitable extension and withdrawal of the or each bolt without the need for a spring. The mechanism for extension and/or withdrawal of the or each bolt may comprise a drive shaft connected in turn to a motor.

The heat treatment chamber may be provided with a valve to optionally allow controlled ingress of air from outside the chamber. The valve may be connected to the control apparatus.

The piston rod may comprise a rod with a screwthread on its external surface, sometimes referred to as a lead screw. The piston head may be moved with respect to the chamber - for example up or down - by an action which rotates the rod within a suitable corresponding threaded component.

At least a portion of the rod may be arranged to extend beyond an inner wall of the chamber, to provide a means for driving the rod and thus providing for raising and lowering of the piston within the chamber. For example, a portion of the rod extending beyond the inner wall of the chamber may engage with a nut located towards the top of the apparatus and fixed with respect to at least the inner wall of the chamber.

-6The rod may comprise two or more connecting segments, each with dimensions suitable so that a segment may fit circumferentially inside another segment. Such an arrangement may be similar to the action of a telescope, so that the rod can be extended or shortened by extending or withdrawing one or more segments within another segment. Segments may be moved axially in relation to one another by the presence of a protrusion from an inner surface of a segment which can engage with a screwthread on an outer surface of a neighbouring segment.

The apparatus may be provided with a first drive means to rotate to the rod. Such rotation in turn provides for raising and lowering ofthe piston head as described above. The first drive means may comprise a motor, such as an electric motor. The first drive means may further comprise a gearing arrangement, such as a worm gear arrangement.

The displacement sensor may comprise an optical beam generator and sensor, for example. Alternatively, the displacement sensor may comprise an arrangement by which the first drive means is monitored by the control apparatus to provide information as to the position ofthe piston within the chamber. For example, depending on the gearing ofthe first drive means, a certain number of rotations provided to the rod could be used to calculate the displacement ofthe piston from a known starting position.

The drive shaft of the mechanism for extending and/or withdrawing the one or more bolts ofthe engagement portion may be coaxial with the rod. The drive shaft may be arranged substantially within the rod, but mechanically independent of it, so that the rod and the drive shaft may be driven independent of each other. Alternatively, the drive shaft and rod may be separate (i.e. non-coaxial) mechanisms.

The drive shaft may comprise one or more connecting segments. Connecting segments may fit circumferentially one another. Such an arrangement may be similar to the action of a telescope, so that the drive shaft can be extended or shortened as the piston rod extends or shortens. Segments ofthe drive shaft may further comprise engagement portions to transmit a rotational force between adjacent segments.

The apparatus may be provided with a second drive means to rotate to the drive shaft.

Such rotation in turn provides for operation of the extension and/or withdrawal of the engagement bolt or bolts as described above, for example by rotating a cam. The second

-7drive means may comprise a motor, such as an electric motor. The second drive means may further comprise a gearing arrangement, such as a worm gear arrangement.

The first and second drive means may be operable independently of each other.

The piston may be provided with a feed pipe. The piston may be provided with a 5 nozzle. The feed pipe may provide water to the nozzle for providing a spray or jet of water to a lower surface of the piston head. Such water may provide for washing of the lower surface of the piston head or to dislodge any ash and/or other residue from locations beneath the lower surface of the piston head. Such water may also cool parts of the apparatus, for example after heat treatment has been completed. The nozzle may be connected to the control apparatus, so that a supply of water through the nozzle may be controlled.

The feed pipe may be arranged eccentrically with respect to the piston head, thus resisting unwanted rotation of the piston head in use.

The apparatus may be provided with an upper opening in a wall for receiving and removing the basket. The upper opening may be a door, openable only when conditions within the apparatus are suitable.

The apparatus may be provided with a lower opening in a wall for removal of ash and/or other material which may be left within the chamber after heat treatment. The lower opening may be a door, openable only when conditions within the apparatus are suitable.

The apparatus may be provided with an engineer's opening in a wall for providing 20 access to parts of the apparatus.

A second aspect of the present invention is directed to a method of treatment of waste material in a heat treatment chamber comprising the steps of:

- receiving waste material in a basket;

- elevating the temperature in the treatment chamber to a pre-determined 25 temperature;

- during or after temperature elevation lowering a piston from a pre-determined initial position into the basket until either a pre-determined final displacement is reached or a signal is received from a pressure sensor indicating resistance by waste material;

-8- raising the piston towards the initial position;

- optionally repeating the lowering and raising steps of the piston during heat treatment;

- allowing the temperature in the treatment chamber to fall.

The pre-determined temperature is selected by its suitability for the heat treatment concerned. For example, for pyrolysis a temperature in a range of approximately 250 to 350 °C is suitable but other pre-determined temperatures may be suitable, and other temperatures may be suitable for other heat treatment modes.

As the temperature rises towards the pre-determined temperature, some of the waste material may soften or melt or otherwise become less rigid or structurally integral. Furthermore, water present in the waste material to be treated may be driven out as the temperature rises. Such changes are likely to aid the arrangement and/or compaction of that waste material within the chamber. If changes take place in the characteristics of waste material, it may become easier to arrange and/or compact the material by lowering the piston.

For example, some plastics materials may soften or melt at a temperature above a usual room temperature (room temperature often being estimated at around 20 to 25 °C).

The method may comprise a drying step in which the temperature in the treatment chamber is elevated to a pre-determined drying temperature lower than the pre-determined temperature.

The method may further comprise the step of connecting the piston and basket together.

The method may further comprise the step of disconnecting the piston and basket from each other.

The method may further comprise the step of raising or lowering the piston while the 25 piston is connected to the basket to raise or lower the basket.

The method may further comprise the step of agitating the piston to cause agitation of the basket.

The method may further comprise the step of providing a signal to a control apparatus.

-9The method may further comprise the step of receiving a signal from a control apparatus.

The method may further comprise a cancellation step, in which if certain predetermined conditions are met the method is cancelled, the piston is raised to its initial position and the temperature in the chamber is allowed to fall.

The pre-determined conditions may include a pre-determined threshold being met by a force sensor or a pre-determined time having elapsed with the piston unable to reach a predetermined maximum displacement from an initial position.

The method may additionally comprise the step of initiating combustion of material 10 within the chamber. Preferably, combustion takes place after the basket has been raised into the upper position. Thus, material present in the basket after pyrolysis - especially combustible material - is generally located away from heat-conducting pins. This is preferred because any flames or localised high temperatures which may result from combustion are less likely to cause damage or sooting of such pins if combustion takes place away from them.

Preferably, combustion takes place after temperature has been elevated to the predetermined temperature.

Combustion may be initiated by the introduction of oxygen into the chamber, thus providing suitable conditions for combustion in addition to the elevated temperature already provided within the chamber.

Thus, the method may further comprise the step of opening a valve to allow controlled ingress of air from outside the chamber.

The method may further comprise the step of activating a nozzle to provide a flow of water to the piston, for removal of ash or char from the piston.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described by way of example, with reference to the accompanying figures in which;

-10Figure 1 shows a side view of a piston embodying the present invention;

Figure 2 shows a section of the piston of Figure 1;

Figure 3 shows a simplified section of an upper part of a piston head embodying the present invention;

Figure 4 shows in perspective a disassembled upper part of a piston head embodying the present invention;

Figure 5 shows an alternative view of the disassembled upper part of Figure 4; and

Figure 6 shows in perspective a second casing element of a piston head embodying the present invention;

Figure 7 shows a section of an apparatus embodying the present invention;

Figure 8 shows one embodiment of a piston rod for use in the present invention, with certain other parts of the apparatus;

Figure 9 shows a section of the embodiment of Figure 8; and

Figure 10 shows a section of a piston head for use in the present invention with an example of a suitable cam.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Figure 1 shows a piston 100 having a piston head 102 which is formed of an upper part 104 and a lower part 106 joined together, the piston head 102 is connected to a piston rod 108. Extending below the lower part 106 is a nozzle 110. The nozzle 110 is connected within the piston head 102 to a feed conduit 112 and can be connected to an outside source of water (not shown). Extending outwards from the upper part 104 of the piston head 102 is a bolt 114.

Figure 2 shows the same features as described with reference to Figure 1, further showing a cam arrangement 116 for extending or withdrawing the bolt 114. Nut and bolt arrangements 118 provide a connection between the upper part 104 and the lower part 106

-11of the piston head 102. Nut and bolt arrangements 118 pass through openings 120 in the upper part 104 ofthe piston head 102. The lower part 106 ofthe piston head 102 is provided with openings 122. Openings 122 may be sized to accommodate part of a heat-conducting pin (not shown).

Figure 3 shows a simplified section of the upper part 104 of the piston head 102, in which bolts 114 extend outwards from the upper part 104. Inner ends of the bolts 114 are sprung and in contact with a cam arrangement 116. In use, the cam arrangement can urge the bolts 114 to extend beyond the circumference of the upper part 104 or can allow the bolts 114 to be withdrawn within the circumference ofthe upper part 104. The sprung arrangement may assist this action but other mechanical means for such extension and withdrawal are also envisaged.

Figure 4 shows a disassembled upper part 104 ofthe piston head, in which openings 120 allow for nut and bolt arrangements (not shown) to connect the upper part 104 with a lower part ofthe piston head (not shown). Further openings 124 allow for bolts (not shown). A yet further opening 126 is provided for a feed conduit (not shown) and a further opening still 128 is provided for connection to a cam arrangement. Each of the openings 120, 124, 126, 128 is provided with a sleeve to accommodate the item intended to be inserted into the respective opening. Figure 5 shows another view of the same upper part 104 as shown in Figure 4.

Figure 6 shows a disassembled lower part 106 of the piston head, which has an opening 126 provided for a feed conduit and nozzle (not shown). Openings 122 provide accommodation for part of heat-conducting pins (not shown). Each ofthe openings 126,122 are provided with a sleeve.

Figure 7 shows an apparatus for waste treatment embodying the present invention. A chamber 200 is enclosed by side walls 202, a base 204 and a top 206. Within the chamber 200 is arranged a piston 100 and a basket 300. Heat-conducting pins 208 extend upright from a heating element 210 towards the base 204 ofthe chamber. Valve 212 provides a controlled connection to the environment outside the chamber 200, for example for the provision of air ingress into the chamber 200. Valve 214 may provide for a controlled connection with other apparatus which may be used in conjunction with the present apparatus. The chamber 200 may also be provided with other openings (not shown) as described above.

-12In use, waste material may be introduced into the basket 300. The basket 300 may be positioned so that that it overlays the heat-conducting pins 208 and thus some of the waste material may be arranged around and between the heat-conducting pins 208. The piston 100 may be brought down within the chamber 200. Depending on the location and arrangement of the waste material within the basket 300, the piston 100 may be brought down towards the basket 300 or partially into the basket 300. The maximum possible descent of the piston 100 is defined by openings 122 within the piston 100, and the lowest possible position for the piston 100 at any particular time will be defined by that maximum possible descent and the position and arrangement of any waste material, as previously described.

The piston 100 may be lowered and raised within the chamber 200 and into the basket 300 until the piston 100 can reach the position of maximum possible descent.

Furthermore, the piston 100 may be provided with engagement means for selectable connection with the basket 300. Such engagement means are reflected in the presentlydescribed embodiment as sockets 302 which are arranged to accept corresponding bolts (not shown in Figure 7) of the piston 100. Thus, the piston 100 may move the basket 300 when the piston 100 and the basket 300 are connected together. As described above, such movement may be to raise and/or lower the basket 300 within the chamber 200 or it may be to agitate the basket 300.

Turning to Figures 8 and 9, a piston rod 400 is provided in interconnected segments 402, 404 and 406. Segment 402 is arranged at one end of the piston rod 400, away from the piston head 100. Segment 404 is arranged to be connected to segment 402 towards one end and to segment 406 towards the other end. Segment 406 is arranged at the other end of the piston rod 400, nearest the piston head 100. For the purpose of the description of Figures 8 and 9, the region nearest the piston head 100 will be described using terms such as lower and the region furthest away from the piston head 100 will be described using terms such as upper. The segments 402, 404 and 406 are each provided with a screwthread on their respective outer surfaces. The screwthreads provided are correspondingly handed with regard to the screwthread on the adjacent segment, respectively. In other words, if the upper segment 402 has a left-handed thread then the central segment 404 will also have a lefthanded thread and the lower segment 406 will also have a left-handed thread, or vice-versa. The inside surface of segment 402, in the region of a lower end of the segment, is provided

-13with at least one protrusion 408. The protrusion 408 may take the form of a pin or more than one pin or a continuous lip or edge. Similarly, the inside surface of segment 404, in the region of a lower end of the segment, is provided with at least one protrusion 410. A similar arrangement may be used in the first drive means 500 to provide for axial movement.

In use, a rotational force applied to segment 402 is likely to be transmitted to segment 404 as a rotational force. As the adjacent segments have screwthreads which are oppositely handed to each other, some of the rotational force may be translated into an axial force due to the interaction of the protrusions 408, 410 and the screwthreads. Thus, a shortening or lengthening of the length of the piston rod 400 can be achieved by applying a suitable rotational force to the upper segment. The segments 402, 404 and 406 are sized to fit within each other, similar in form to a telescope. In this way the piston head 100 can be raised or lowered within the apparatus of this invention. Similarly, the first drive means 500 can raise or lower the piston rod 400 itself.

Within the piston rod 400 can be provided a drive shaft 420 for providing rotational force to a cam 116. In turn, the cam 116 may operate one or more bolts (not shown) of a selectable connection means. The drive shaft 420 may have a similar arrangement to that of the piston rod 400, or may be a simplified arrangement led by the shortening or lengthening of the piston rod 400.

In Figure 10, there is shown a section of a portion of piston head showing a cam 116 mechanism. It will be clear to the reader that for the purposes of clarity in showing the cam 116, various features of the piston head are not shown, but will be present in embodiments of a piston head in use. The cam 116 in this example has a toothed pinion 602 which is in turn connected to a drive shaft (not shown), the pinion 602 being engaged with corresponding toothed racks 604. The racks 604 are each moveable in one dimension within a guide (not shown). Each rack 604 is in turn linked to a bolt 114. In use, a rotation of a drive shaft can cause a rotation of the toothed pinion 602. Engagement of the corresponding teeth on the pinion 602 and the racks 604 can cause linear movement of the racks 604 and, in turn, the bolts 114. Rotation of the pinion 602 may thus extend or withdraw bolts 114. The bolts 114 may extend beyond the circumference of the piston head, via openings 124.

It will of course be understood that many variations may be made to the abovedescribed embodiment without departing from the scope of the present invention.

Claims

1. A waste treatment apparatus comprising a heat treatment chamber, a basket for receiving waste to be treated, a piston moveable within the chamber and moveable into and out of the basket, a heat source for the chamber suitable for elevating the temperature of the chamber and a control apparatus adapted to activate the heat source and to move the piston.

2. A waste treatment apparatus according to claim 1 in which the basket is moveable within the chamber.

3. A waste treatment apparatus according to claim 1 or claim 2 in which the chamber has one or more heat-conductive pins extending from an interior wall into the interior of the chamber.

4. A waste treatment apparatus according to any preceding claim in which the piston is provided with a force sensor connected to the control apparatus.

5. A waste treatment apparatus according to claim 4 in which the force sensor comprises a pressure transducer.

6. A waste treatment apparatus according to claim 4 in which the force sensor comprises a current meter connected to the control apparatus.

7. A waste treatment apparatus according to any preceding claim comprising a displacement sensor.

8. A waste treatment apparatus according to any preceding claim in which the piston is provided with one or more openings.

9. A waste treatment apparatus according to any preceding claim in which the piston and basket are provided with corresponding engagement portions, to form a selectable connection between each other.

10. A waste treatment apparatus according to claim 9 in which the basket is provided with more than one suitable engagement portion so that a connection with the piston may be formed at more than one vertical point of the basket.

-1511. A waste treatment apparatus according to claim 9 or 10 in which the corresponding engagement portions are a bolt and socket, respectively.

12. A waste treatment apparatus according to claim 11 in which the bolt is extended or withdrawn by a cam.

13. A waste treatment apparatus according to any preceding claim in which the heat treatment chamber is provided with a valve to control ingress of air from outside the chamber.

14. A waste treatment apparatus according to any preceding claim in which the piston comprises a piston head and a piston rod.

15. A waste treatment apparatus according to claim 14 in which the piston rod comprises a rod with a screwthread on its external surface.

16. A waste treatment apparatus according to claim 15 in which the rod comprises two or more corresponding segments extendable axially with respect to one another.

17. A waste treatment apparatus according to any one of claims 14 to 16 in which a first drive means is provided to rotate the piston rod.

18. A waste treatment apparatus according to any one of claims 9 to 17 in which a second drive means is provided to form the selectable connection between the piston and basket.

19. A waste treatment apparatus according to any preceding claim in which the piston is provided with a feed pipe and a nozzle.

20. A method of treatment of waste material in a heat treatment chamber comprising the steps of:

- receiving waste material in a basket;

- elevating the temperature in the treatment chamber to a pre-determined temperature;

-16- during or after temperature elevation lowering a piston from a pre-determined initial position into the basket until either a pre-determined final displacement is reached or a signal is received from a pressure sensor indicating resistance by waste material;

- raising the piston towards the initial position;

- allowing the temperature in the treatment chamber to fall.

21. A method according to claim 20 further comprising a drying step in which the temperature in the treatment chamber is elevated to a pre-determined drying temperature lower than the pre-determined temperature.

22. A method according to claim 20 or claim 21 further comprising the step of connecting the piston and basket together.

23. A method according to claim 22 further comprising the step of disconnecting the piston and basket from each other.

24. A method according to any of claims 20 to 23 further comprising the step of raising or lowering the piston while the piston is connected to the basket to raise or lower the basket.

25. A method according to any of claims 20 to 24 further comprising the step of agitating the piston to cause agitation of the basket.

26. A method according to any of claims 20 to 25 further comprising the step of providing a signal to a control apparatus.

27. A method according to any of claims 20 to 26 further comprising the step of receiving a signal from a control apparatus.

28. A method according to any of claims 20 to 27 further comprising a cancellation step, in which if certain pre-determined conditions are met the method is cancelled, the piston is raised to its initial position and the temperature in the chamber is allowed to fall.

-1729. A method according to claim 28 in which the pre-determined conditions are selected from: a pre-determined threshold being met by a force sensor; or a pre-determined time having elapsed with the piston unable to reach a pre-determined maximum displacement from an initial position.

5 30. A method according to any of claims 20 to 29 further comprising the step of initiating combustion of material within the chamber.

31. A method according to claim 30 in which combustion is initiated by opening a valve to allow controlled ingress of air into the chamber.

32. A method according to any of claims 20 to 31 further comprising the step of 10 activating a nozzle to provide a flow of water to the piston, for removal of ash or char from the piston.

33. A method according to any of claims 20 to 32 in which the pre-determined temperature is approximately 250 to 350 °C.

34. A method according to any of claims 20 to 33, applied to the apparatus of any 15 of claims 1 to 19.

-18Intellectual

Property

Office

Application No: GB1706486.6 Examiner: Miss Elizabeth Price