WASTE PROCESSING APPARATUS

Abstract

A pyrolyser may include a rotary kiln configured to pyrolyse feedstock material received therein. The pyrolyser may also include a heating vessel surrounding the rotary kiln and defining a heating chamber for hot gases. The pyrolyser may further include an agitator disposed within the heating chamber. The agitator may be configured to agitate the hot gases. The agitator may be rotatable with the rotary kiln.

Claims

1-13. (canceled)

14. A pyrolyser comprising: a rotary kiln configured to pyrolyse feedstock material received therein; a heating vessel surrounding said rotary kiln and defining a heating chamber for hot gases; and an agitator disposed within said heating chamber, wherein said agitator is configured to agitate said hot gases, and wherein said agitator is rotatable with said rotary kiln.

15. The pyrolyser of claim 14, wherein said agitator is fixed with respect to said rotary kiln.

16. The pyrolyser of claim 14, wherein said agitator is mounted to an outer surface of said rotary kiln.

17. The pyrolyser of claim 14, wherein said agitator is configured to propel said hot gases over an outer surface of said rotary kiln.

18. The pyrolyser of claim 14, wherein said agitator comprises at least one flight.

19. The pyrolyser of claim 14, wherein said agitator comprises at least one fin.

20. The pyrolyser of claim 14, wherein said agitator comprises a plurality of agitator elements, and wherein an arrangement of said plurality of agitator elements is configured to cause said hot gases within said heating chamber to flow between said plurality of agitator elements.

21. The pyrolyser of claim 14, wherein said agitator is configured to convey particulate material along a floor of said heating vessel.

22. The pyrolyser of claim 21, wherein a floor of said heating vessel defines a particulate outlet opening, and wherein said agitator is configured to convey particulate material along said floor towards said particulate outlet opening.

23. The pyrolyser of claim 14, wherein said heating chamber is substantially cylindrical.

24. The pyrolyser of claim 14, wherein said feedstock material includes a plastic material selected from a group consisting of polyurethane and polystyrene.

25. A waste processing apparatus comprising: an oxidiser configured to combust combustible gas to produce hot gas; and a pyrolyser configured to receive said hot gas from said oxidiser, wherein said pyrolyser includes: a rotary kiln configured to pyrolyse feedstock material received therein; a heating vessel surrounding said rotary kiln and defining a heating chamber for hot gases; and an agitator disposed within said heating chamber, wherein said agitator is configured to agitate said hot gases, and wherein said agitator is rotatable with said rotary kiln.

26. The waste processing apparatus of claim 25, wherein said agitator is fixed with respect to said rotary kiln.

27. The waste processing apparatus of claim 25, wherein said agitator is mounted to an outer surface of said rotary kiln.

28. The waste processing apparatus of claim 25, wherein said agitator is configured to propel said hot gases over an outer surface of said rotary kiln.

29. The waste processing apparatus of claim 25, wherein said agitator comprises at least one flight.

30. The waste processing apparatus of claim 25, wherein said agitator comprises at least one fin.

31. The waste processing apparatus of claim 25, wherein said agitator comprises a plurality of agitator elements, and wherein an arrangement of said plurality of agitator elements is configured to cause said hot gases within said heating chamber to flow between said plurality of agitator elements.

32. The waste processing apparatus of claim 25, wherein said agitator is configured to convey particulate material along a floor of said heating vessel.

33. The waste processing apparatus of claim 32, wherein a floor of said heating vessel defines a particulate outlet opening, and wherein said agitator is configured to convey particulate material along said floor towards said particulate outlet opening.

34. The waste processing apparatus of claim 25, wherein said heating chamber is substantially cylindrical.

35. The waste processing apparatus of claim 25, wherein said feedstock material includes a plastic material selected from a group consisting of polyurethane and polystyrene.

Description

[0027] The invention will now be described by reference to the following drawings, in which:

[0028] FIG. 1 schematically shows waste processing apparatus according to an embodiment of the invention; and

[0029] FIG. 2 shows a pyrolyser for the waste processing apparatus of FIG. 1.

[0030] FIG. 1 shows waste processing apparatus 100 comprising a feed assembly 200, a pyrolyser 300 including a rotary kiln or rotary pyrolysis tube 302 and a heating vessel 400, a gasifier 500 and an oxidiser 600.

[0031] In use, waste is received in the feed assembly 200 and conveyed into the rotary pyrolysis tube 302 of the pyrolyser 300 where it is decomposed under the action of heat to form pyrolysis char and pyrolysis gas. The rotary pyrolysis tube 302 is disposed within the heating chamber 404 of the heating vessel 400, and heat is transferred to the rotary pyrolysis tube 302 from hot gases received within the heating chamber 404. The pyrolysis char and pyrolysis gas exit the rotary pyrolysis tube 302 to enter the gasifier 500, where the pyrolysis char is gasified by the introduction of oxygen and/or steam to produce syngas and ash. The pyrolysis gas and syngas flow together from the gasifier 500 to the oxidiser 600, where the gas is combusted to produce hot gas. The hot gas is redirected to the heating chamber 404 of the heating vessel 400 to heat the rotary pyrolysis tube 302. The hot gas is then directed from the heating chamber 404 to a separate heat recovery unit, such as a steam turbine for power generation.

[0032] Ash formed in the gasifier and collected in the oxidiser and heating chamber is collected in an ash bin (not shown) of an ash collection unit by a number of ash ducts 702, 704. The ash duct 704 from the heating vessel 400 comprises a double flap valve to control the release of ash from the heating chamber 400

[0033] As shown in FIG. 2, the pyrolyser 300 comprises a static heating vessel 400 including a refractory-lined chamber wall 402 defining an internal heating chamber 404 which receives the rotary pyrolysis tube 302. The internal heating chamber 404 is generally cylindrical and is approximately double the diameter of the cylindrical outer surface the rotary pyrolysis tube 302.

[0034] The heating chamber 404 has an inlet 406 for receiving hot gas from the oxidiser 600 and an outlet 408 for discharging hot gas to a heat recovery system (not shown). The inlet 406 is formed in the lower portion of the chamber wall 402 towards the inlet end of the pyrolysis tube 302, and the outlet 408 is formed in the upper portion of the chamber wall 402 towards the outlet end of the pyrolysis tube 302. An ash outlet 410 is formed in the lower portion of the chamber wall towards the outlet end of the pyrolysis tube 302 for collecting particulate material that may build-up in the internal heating chamber 404.

[0035] The static heating vessel 400 also comprises a bearing assembly (not shown) outside of the heating chamber 404 and arranged to support the rotary pyrolysis tube 302 at both of its ends, and drive equipment 412 for causing the rotary pyrolysis tube 302 to rotate.

[0036] The rotary pyrolysis tube 302 comprises a stainless steel tube of substantially the same diameter as a feed duct 206 of the feed assembly that extends through the heating chamber 400. The pyrolysis tube 302 has an input end adjacent the feed assembly 200 and an outlet end adjacent the gasifier 500. An inlet rotary seal (FIG. 1) forms a seal between the feed assembly 200 and the inlet end of the pyrolysis tube 302 and between the inlet end of the pyrolysis tube and the static housing chamber 400. Further, an outlet rotary seal (FIG. 1) forms a seal between the heating chamber 400 and the outlet end of the pyrolysis tube 302 and between the outlet end of the pyrolysis tube and the gasifier 500.

[0037] The pyrolysis tube 302 is provided with a set of internal flights 308 and a gas agitator 310 in the form of a set of external flights 310.

[0038] The internal flights 308 are mounted to the inner cylindrical wall of the pyrolysis tube 302 and are provided to break-up waste received in the pyrolysis tube 302 and convey the waste along the length of the pyrolysis tube. The internal flights 308 comprise a number of helical sections joined together to form a continuous helix. In other embodiments the pyrolysis tube 302 may be provided with planar paddles in addition to the flights (i.e. discrete planar projections) in order to assist in the break-up of waste during pyrolysis.

[0039] The gas agitator 310 is mounted on the outer surface of the pyrolysis tube 302. In this embodiment the gas agitator 310 comprises external flights in the form of a continuous helix which is configured to accelerate hot gas over the outer surface of the pyrolysis tube 302. In other embodiments, gas agitator elements (such as a plurality of external flights) may be non-continuous so that gas can flow over the outer surface of the rotary pyrolysis tube 302 between the elements. In still further embodiments, the gas agitator 310 may comprise fins or paddles provided on the outer surface of the rotary pyrolysis tube 302, in addition or as an alternative to the helical flights, to accelerate the gas tangentially (i.e. circumferentially with respect to the rotational axis of the rotary pyrolysis tube) and/or axially along the rotary pyrolysis tube 302.

[0040] The external flights 310 extend towards the refractory-lined chamber wall 402 so that, in use, the flights 310 engage with any build-up of particulates settled on the floor of the heating chamber 404 (i.e. the inner surface of the lower portion of the heating chamber 404). Since the external flights 310 are helical, they are configured to drive the particulate material along the internal chamber towards the ash outlet 410 so that they can be removed from the heating chamber 404. In other embodiments, planar fins provided on the outer surface of the rotary pyrolysis tube 302 and angled with respect to a plane normal to the rotational axis of the rotary pyrolysis tube 302 may have the same effect of moving the particulate material towards the ash outlet.

[0041] In use, waste material is received in the inlet end of the pyrolysis tube 302 from a feed duct 206 of the feed assembly 200. As the pyrolysis tube 302 rotates, heat is transferred from hot gas received in the heating chamber 404 to the pyrolysis tube 302 through the outer surface of the pyrolysis tube 302 and through the external flights 310. This heat is transferred from the rotating pyrolysis tube 302 to the waste within the tube via the inner surface of the tube and the internal flights 308. The rotation of the internal flights 308 causes the waste material to break-up by continuously lifting the waste and allowing it to fall. In addition, the helical shape of the internal flights 308 cause the waste to gradually move through the pyrolysis tube from the inlet end to the outlet end of the tube 302.

[0042] Breaking up the waste material during pyrolysis increases the surface area of the waste exposed within the pyrolysis tube and therefore allows for efficient heat transfer from the pyrolysis tube to the waste. In particular, breaking up the waste material can allow the residence time of the waste within the pyrolysis tube to be reduced, and/or the temperature of the heating chamber to be reduced compared with previously considered designs.

[0043] As the rotary pyrolysis tube 302 rotates, the gas agitator 310 moves through the hot gas received in the heating chamber 404 of the heating vessel 400 from the oxidiser 600. The rotation of the gas agitator 310 locally accelerates at least the rotational component of the hot gas flow adjacent the surface of the rotary pyrolysis tube 302 so that the flow has a whirl component within the heating chamber 404 and so as to inhibit particulate material entrained in the hot gas flow from depositing on the surface of the rotary pyrolysis tube 302. The gas agitator 310 imparts energy into the flow to inhibit the deposition of the particulate material. The gas agitator 310 may increase the rotational velocity of the hot gas flow so that it has a tangential velocity of up to 5 m/s.

[0044] The gas agitator 310 also acts to increase the effective length of the flow path of the hot gas by introducing the whirl component into the flow. This has the compound effect of increasing the local gas flow velocity over the rotary pyrolysis tube 302 for efficient heat transfer, and promotes mixing of the hot gas in the heating chamber 404. Mixing the hot gas in the heat chamber 404 results in efficient heat transfer since it ensures homogeneous flow conditions and prevents portions of the flow from effectively passing straight through the heating chamber 404 without coming into contact with the rotary pyrolysis tube. In contrast, in the absence of the gas agitator 302 the hot gas flow may pass through the heating chamber 404 substantially axially, with only a small annular portion of the flow coming into contact with the rotary pyrolysis tube 302 for heat transfer therewith.

[0045] The hot gas received in the heating chamber 404 may have entrained particles, such as ash, from an upstream part of the waste processing apparatus 100. For example, the particles may originate from the input waste material, pyrolysis char, ash generated in the gasifier 500, or any of the above combusted in the oxidiser 600. The gas agitator 310 locally imparts additional energy into the hot gas to accelerate it, which prevents the entrained particles from depositing on the outer surface of the rotary pyrolysis tube 302. The gas agitator 310 therefore prevents a build-up of particles on the pyrolysis tube 310 which would reduce heat transfer efficiency between the hot gas and the pyrolysis tube (and the waste received therein).

[0046] In addition, the provision of the gas agitator 310 on the outer surface of the rotary pyrolysis tube 302 increases the effective surface area of the pyrolysis tube 302 for heat transfer. Accordingly, the gas agitator may result in more efficient heat transfer between the hot gas in the heating chamber 404 and the waste received in the pyrolysis tube 302.