WO2019113626A1

WO2019113626A1 - A pyrolysis plant

Info

Publication number: WO2019113626A1
Application number: PCT/AU2018/000257
Authority: WO
Inventors: Archibald Alexander KELLY
Original assignee: Tyre Takers Pty Ltd
Priority date: 2017-12-12
Filing date: 2018-12-12
Publication date: 2019-06-20

Abstract

A pyrolysis plant includes a pyrolytic reactor having a housing for a pyrolytic chamber into which raw material can be introduced to be subject to a pyrolytic process. A supply of substantially inert gas is connected to the reactor to supply the gas to the housing for lowering a temperature of the reactor after applying a pyrolytic process to the raw material. An eductor assembly is in fluid communication with the supply of the inert gas so that the supply of the inert gas can be directed through the eductor assembly to form a motive fluid for the eductor assembly. A gas extraction conduit has an inlet positioned in the pyrolytic chamber and an outlet in fluid communication with a draw inlet of the eductor assembly.

Description

A PYROLYSIS PLANT

FIELD

[0001 ] Various embodiments of a pyrolysis plant and a method of operating a pyrolysis plant are described herein.

BACKGROUND

[0002] Pyrolysis is used for the thermochemical decomposition of material at elevated temperatures in the absence of oxygen or any other halogen. It is a process that is used to produce various products such as charcoal, activated carbon, methanol, Coke from coal, syngas and biochar from biomass, oil from waste plastics, and various other purposes.

[0003] One of the by-products of pyrolysis is char or ash. This material can be extremely light and requires specialised handling processes to inhibit environmental pollution and loss of product. In various pyrolytic processes, the char is removed manually, for example, by opening a retort or oven and using labour or an auger-like mechanism to displace the char to a position in which it can be extracted from the retort. One of the issues with such forms of extraction is that opening the retort exposes an interior of the retort to oxygen. A temperature within the retort can be more than 100°C after a pyrolytic process. Char can combust in such an

environment. This is undesirable. A temperature within the retort needs to drop below a certain level, for example 65°C, before the retort can be opened. This is time- consuming.

[0004] Pyrolysis is used to reclaim useful materials from vehicle tyres. For example, European patent EP 1 163 092 B1 describes the production of carbon black through pyrolytic distillation of scrap tyres. The process includes feeding shredded vehicle tyres into a rotary kiln in which pyrolysis of the tyres takes place. The rotary kiln includes a rotatable feed cylinder that extends between a first end and a second end. A flight is formed in the feed cylinder to move the feed stock from the first end to the second end as it is heated. After pyrolysis, the tyre pieces are received in a rotatable trommel in which char and steel wire scrap are separated.

Also described is a discharge tube that is positioned to extend into the interior of the rotary kiln with a first end of the tube positioned within the rotary kiln and a second end of the tube connected to a supply of negative pressure. This serves to remove gases from within the rotary kiln for processing. [0005] Pyrolysis results in significant heat generation. In United States Patent Publication US 2009/0188649 A1 , there is described the use of Nitrogen as an inert carrier gas and as a means for regulating the temperatures generated during the pyrolytic processes.

[0006] The information provided in this background section is not intended to describe common general knowledge and is not intended to limit the scope of the summary or the appended claims.

SUMMARY

[0007] According to one aspect, there is provided a pyrolysis plant, which includes:

a pyrolytic reactor having a housing for a pyrolytic chamber into which raw material can be introduced to be subject to a pyrolytic process;

a supply of substantially inert gas connected to the reactor to supply the gas to the housing for lowering a temperature of the reactor after applying a pyrolytic process to the raw material;

an eductor assembly in fluid communication with the supply of the inert gas so that the supply of the inert gas can be directed through the eductor assembly to form a motive fluid for the eductor assembly; and

a gas extraction conduit having an inlet positioned in the pyrolytic chamber and an outlet in fluid communication with a draw inlet of the eductor assembly.

[0008] The pyrolytic reactor may be configured for carrying out a pyrolytic process on used car tyres.

[0009] The supply of substantially inert gas may be a supply of nitrogen.

[0010] The eductor assembly may include at least one eductor with an inlet in fluid communication with the supply of inert gas. The supply of inert gas may include a nitrogen supply conduit that is connected to a source of nitrogen, such as a nitrogen farm.

[001 1 ] The, or each, eductor may have an outlet that is in fluid communication with a nitrogen return conduit. Thus, gas with entrained char can be extracted from the pyrolytic chamber and directed into the nitrogen return conduit. [0012] The nitrogen return conduit may be connected to a separator to separate the char from the nitrogen. The separator may be a cyclone separator.

[0013] An inlet valve may be interposed between the inlet of the, or each, eductor and the supply of nitrogen. The inlet valve may be operable to supply nitrogen selectively to the, or each, eductor.

[0014] The pyrolysis plant may include a nitrogen supply manifold assembly in fluid communication with the housing of the pyrolytic reactor so that the nitrogen can be introduced into the housing to cool the reactor. An array of conduits may interconnect the nitrogen supply manifold assembly and the housing so that the supply of nitrogen is distributed about the reactor.

[0015] The conduits may be flexible. The nitrogen supply manifold assembly may be self-supporting or otherwise not connected to the housing so that vibration of the housing is accommodated by the flexible conduits.

[0016] A nitrogen recirculation conduit may be connected between the cyclone separator and the manifold assembly so that nitrogen can be recirculated back to the manifold assembly once the char is extracted from the nitrogen. Thus, nitrogen from the pyrolytic chamber can be used for cooling the manifold assembly or can be redirected to the pyrolytic chamber, when necessary.

[0017] A filtration assembly may be positioned in the nitrogen recirculation conduit to filter the nitrogen before the nitrogen is recirculated back to the manifold assembly. The filtration assembly may be a bag filtration assembly.

[0018] A manifold supply conduit may be connected between the nitrogen supply conduit and the, or each, inlet valve of the eductor(s) so that when the, or each, inlet valve is closed, nitrogen bypasses the eductor(s) to be supplied to the nitrogen supply manifold.

[0019] The nitrogen supply conduit may also be connected to a nitrogen storage arrangement, such as a nitrogen tank farm.

[0020] The gas extraction conduit may have an internal portion located in the pyrolysis chamber and an external portion that extends from the pyrolysis chamber. The internal portion may extend generally orthogonally with respect to the external portion. The internal portion may be connected to the external portion with a rotatable coupling so that the internal portion can rotate, together with the retort, relative to the external portion. The internal portion may include an elbow so that it has one section that is generally parallel with an axis of rotation of the retort and an inlet section that extends generally at right angles to the said one portion.

[0021 ] According to another aspect, there is provided a method of operation of a pyrolytic plant, the method including the steps of:

supplying a substantially inert gas to a housing of a pyrolytic reactor for lowering a temperature of the reactor after a pyrolytic process;

directing the inert gas into an eductor assembly having an inlet, an outlet and a draw inlet with the inert gas being displaced between the inlet and the outlet such that a pressure drop is established at the draw inlet, with the inert gas serving as a motive fluid for the eductor assembly; and

extracting gas, together with char, from the pyrolytic chamber using the pressure drop established at the draw inlet.

[0022] The step of introducing the substantially inert gas into the pyrolytic chamber may include the step of introducing nitrogen into the pyrolytic chamber.

[0023] The method may include the steps of directing gas and char extracted from the pyrolytic chamber to a separator for separating the char from the gas, and directing the gas back to the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 shows a partial layout of one example of a pyrolysis plant.

[0025] Figure 2 shows an eductor assembly and a gas and byproduct extraction assembly of the pyrolysis plant.

[0026] Figure 3 shows one view of an eductor assembly of the pyrolysis plant.

[0027] Figure 4 shows another view of the eductor assembly of figure 3.

[0028] Figure 5 shows an exploded side view of a char extraction assembly of the pyrolysis plant.

[0029] Figure 6 shows an internal view, from within a pyrolytic chamber, of the char extraction assembly of figure 5.

[0030] Figure 7 shows a layout of a char processing assembly and a nitrogen recovery assembly. [0031 ] Figure 8 shows a plan layout of the char processing assembly and nitrogen recovery assembly of figure 7.

[0032] Figure 9 shows a layout of a cyclone separator and a filter assembly of the pyrolysis plant.

[0033] Figure 10 shows a layout of an inert gas supply system for a reactor of the pyrolysis plant.

DETAILED DESCRIPTION

[0034] In figure 1 , reference numeral 10 generally indicates a partial layout of one example of a pyrolysis plant. The pyrolysis plant 10 is configured for carrying out a pyrolytic process on used car tyres to extract char and hydrocarbons from the used car tyres. Other raw materials can be processed, including those set out in the background of this specification.

[0035] The plant 10 includes a pyrolytic reactor 20 (figure 10). In this example, the reactor 20 is a rotary kiln reactor. Rotary kiln reactors are known for use in tyre pyrolysis. Other forms of pyrolytic reactors can be used. In this example, the kiln reactor 20 is suitable for carrying out a pyrolytic process on tyres. The kiln reactor 20 has a rotating reactor chamber or retort 21. The retort 21 is shown in dotted lines in figure 2 for ease of view. The rotating retort 21 is housed in a housing 22, in a conventional manner.

[0036] The plant 10 includes a flue or exhaust gas outlet arrangement 17.

[0037] The pyrolysis plant 10 includes an inert gas production plant for providing a supply of substantially inert gas to the reactor 20. For example, the plant 10 includes a nitrogen production plant 12 (figure 1 ). The production plant 12 supplies nitrogen to a nitrogen tank farm 14 that includes nitrogen receiving tanks 16.

[0038] Nitrogen is supplied to the housing 22 and the retort 21 via a nitrogen supply conduit 24. For example, a nitrogen supply manifold assembly 26 is connected to the housing 22 (figure 10) to supply an interior of the housing 22 with nitrogen to cool the retort 21 . A nitrogen inlet described below is connected to the nitrogen supply conduit 24 to establish a substantially inert environment within the retort for the pyrolytic process or to purge the retort 21.

[0039] An eductor assembly 18 is also connected to the nitrogen supply conduit 24 via a suitable valve mechanism so that nitrogen can pass through the eductor assembly 18, by operation of the valve mechanism. A nitrogen return conduit 30 is connected to an outlet of the eductor assembly 18.

[0040] A gas extraction conduit 36 is connected to a draw inlet of the eductor assembly 18 so that an outlet of the conduit 36 is in fluid communication with the draw inlet. The conduit 36 extends into the retort 21 . Thus, when nitrogen passes through the eductor assembly 18, nitrogen can be drawn from the retort 21. Char and ash can be entrained in the flow of nitrogen within the conduit 36 and out through the nitrogen return conduit 30.

[0041 ] A T-piece 51 (see figure 2, for example) is arranged in the nitrogen supply conduit 24, upstream of the eductor assemblies 18. A manifold supply conduit 50 interconnects the T-piece 51 and the nitrogen supply manifold assembly 26. Thus, when the eductor assemblies 18 are closed, nitrogen is supplied to the assembly 26, via the T-piece 51 and the supply conduit 50 for cooling the reactor 20.

[0042] The return conduit 30 is connected to a separator to separate the char from the nitrogen. The separator is a cyclone separator 32. A nitrogen outlet 33 of the cyclone separator 32 is connected to a filtration assembly 37 (figure 9). The filtration assembly 37 is connected to a nitrogen recirculation conduit 35, which, in turn, is connected to the manifold assembly 26 at valved connection points 39 (see figure 10) so that nitrogen can be recirculated back to the manifold assembly 26 for cooling the reactor 20.

[0043] In figure 1 , two nitrogen supply manifold assemblies 26 are shown. One or more such assemblies can be provided. In figure 1 , the rotary kiln reactors 20 have been omitted for clarity.

[0044] A separation column 34 is in fluid communication with each reactor 20 to process pyrolytic gases resulting from the pyrolytic process, in a conventional manner.

[0045] In operation, the retort is charged with the raw material. In this example, the raw material is used car tyres. It will readily be appreciated that other forms of raw material can be processed. A substantially inert gas in the form of the nitrogen is introduced into the retort 21 to establish an anaerobic environment within the retort 21 . Other inert gases also be used. [0046] The retort 21 is heated to a predetermined temperature for a

predetermined length of time, such that anaerobic, thermal decomposition of the raw material takes place.

[0047] The valve mechanism of the eductor assembly 18 is closed and nitrogen is supplied to the interior of the housing 22 via the nitrogen supply conduit 24, to cool the retort once thermal decomposition is complete. The valve mechanism of the eductor assembly 18 is opened when the retort is between about 80°C and 100°C. The inert gas, in this case nitrogen, with entrained char, in the retort 21 is drawn into the gas extraction conduit 36 because nitrogen flowing through the eductor assembly creates a pressure drop at the draw inlet of the eductor assembly 18.

[0048] The nitrogen and entrained char and ash in the nitrogen return conduit 30 is received in the cyclone 32. The cyclone 32 separates the char from the nitrogen. The char is fed to a grinder and stored in a storage bin for further use/processing.

[0049] The eductor assembly 18 and a byproduct extraction assembly 38 are shown in figure 2. Detail of the eductor assembly 18 is shown in figures 3 and 4.

[0050] The eductor assembly 18 includes two eductors 40. Each eductor 40 has an inlet connected to an inlet valve 42. Each inlet valve 42 is connected to a common inlet conduit 44. The inlet conduit 44 is in fluid communication with the nitrogen supply conduit 24, via the T-piece 51 , so that nitrogen can be supplied to the eductors 40 via the inlet valves 42.

[0051 ] The manifold supply conduit 50 (figures 1 , 2, 10) is connected between the nitrogen supply conduit 24 and the inlet conduit 44 via a T-piece 51 (figure 10). Thus, when the valves 42 are closed, nitrogen can be supplied to the nitrogen supply manifold assembly 26 via the manifold supply conduit 50. Appropriate operation of the valves 42 can determine whether nitrogen flows into the manifold assembly 26 for cooling the reactor 20 or flows through the eductors 40 to draw nitrogen and entrained char from the retort 21. For example, a temperature of the reactor can be monitored so that after a certain period of cooling, the valves can be operated so that the eductors 40 the control nitrogen and entrained char from the retort 21.

[0052] Each eductor 40 has an outlet connected to an outlet valve 46. Each outlet valve 46 is connected to a common outlet conduit 48 that is in fluid

communication with the nitrogen return conduit 30. [0053] Each eductor 40 has a draw inlet 52. Each of the draw inlets 52 is connected to the extraction conduit 36 via respective draw inlet valves 54.

[0054] As can be seen, each inlet valve 42 has an actuator 56 for control with a suitable controller, either manually or automatically. Each outlet valve 46 has an actuator 58 for control with a suitable controller, either manually or automatically. Each draw inlet valve 54 has an actuator 64 for control with a suitable controller, either manually or automatically.

[0055] An outlet conduit 60 of the separation column 34 is also shown in figures 3 and 4.

[0056] It will be appreciated that appropriate operation of the valves 42, 46 and 54 via the actuators 56, 58 and 64 can be used to control the flow of gas through the eductors 40 selectively to draw gas from the retort 21 or to supply the manifold assembly 26 with cooling nitrogen. Thus, subsequent to pyrolysis, the inlet valves 42 can be closed so that nitrogen cools the reactor 20. Once the reactor 20 is cooled, the inlet valves 42 are opened so that the resultant flow of nitrogen through the eductors 40 generates a suction at the draw inlets 52. The valves 54 can be opened so that nitrogen and entrained char, dust and ash pass through the assemblies 18 and into the nitrogen return conduit 30. This serves to cool the gas from the retort 21 to below a flashpoint for the char.

[0057] Figures 5 and 6 show the byproduct extraction assembly 38 in further detail.

[0058] The extraction assembly 38 includes a shroud 62. An internal portion 36.1 of the char extraction conduit extends into the shroud 62. An external portion 36.2 of the char extraction conduit extends into the shroud 62 (figure 6). The internal portion 36.1 is connected orthogonally to the external portion 36.2 via a rotatable T-piece coupling 65 that is positioned within the shroud 62.

[0059] The shroud 62 includes an inspection panel 63 that can be removed to provide access to an interior of the shroud 62.

[0060] The internal portion 36.1 is configured to rotate together with the retort. However, the byproduct extraction assembly 38 is static, together with the external portion 36.2 relative to the retort. For example, the internal portion 36.1 rotates together with an auger (not shown) that feeds byproduct, such as material containing hydrocarbons, towards the shroud 62, which is positioned at a product end of the reactor 20.

[0061 ] The internal portion 36.1 includes an axial section 43 connected to the external portion 36.2 via the rotatable T piece coupling 65. The internal portion 36.1 also includes a radial section 41 connected to the horizontal section with an elbow connector 66 so that the radial section 41 extends towards a wall 45 of the retort 21 (figure 2). An end opening 53 of the radial section 41 can receive the nitrogen with entrained char. The end opening 53 can be positioned proximate the wall 45 of the retort 21 .

[0062] A valve 68 is mounted in the external portion 36.2 (figure 5). The valve 68 includes an actuator 70 so that the valve 68 can be manually or automatically controlled. A T-piece 72 is mounted in the external portion 36.2, downstream of the valve 68. A bridging extraction conduit 74 is connected to the T-piece 72. Thus, when the valve 68 is closed, extraction of nitrogen and char from an adjacent reactor can take place via the bridging extraction conduit 74.

[0063] Nitrogen, char and ash and other by-products can be drawn into the extraction conduit 36 and can flow through the eductors 40 when the valves 42 and 54 are opened. The nitrogen and entrained char pass through the eductors 40 and into the nitrogen return conduit 34 via the outlet valves 46. The char is then removed from the nitrogen by the cyclone separator 32.

[0064] A flange 76 is mounted on the shroud 62. Figure 5 also shows an inlet 78 of the separation column 34. The inlet 78 has a flange 80. A valve 82 is mounted between the flanges 76, 78 via complementary flanges 84, 86. Thus, when the valve 82 is opened, pyrolytic gases can pass into the separation column 34. The valve 82 includes an actuator 88 for manual or automatic operation of the valve 82.

[0065] The internal portion 36.1 can serve to draw char from the retort 21 , via the eductor assembly 18, by suction. In that case, rotation of the retort 21 , together with the internal portion 36.1 facilitates extraction of the char from the retort 21 .

[0066] A nitrogen inlet 90 is mounted on the shroud 62 to supply nitrogen to the retort 21 via a retort supply conduit 92 (figures 1 and 10). A valve 94 is connected between the inlet 90 and the conduit 92 to control the supply of nitrogen to the retort. The valve 94 includes an actuator 96 for manual or automatic operation of the valve 94. [0067] In figures 7 and 8 there is shown a char processing assembly 100 and the tank farm 14 having the nitrogen receiving tanks 16. Figure 9 shows further detail of the assembly 100, namely the cyclone separator 32 and the filtration assembly 37, which can be a bag filtration assembly.

[0068] The nitrogen return conduit 30 is connected to an inlet 1 10 of the cyclone separator 32. As set out earlier, the nitrogen outlet 33 of the cyclone separator 32 is connected to the filtration assembly 37. A nitrogen outlet conduit 1 12 is connected between the outlet 33 and an inlet 108 of the bag filtration assembly 37. The bag filtration assembly 37 includes a bypass conduit 1 14. The bypass conduit 114 is connected between the nitrogen outlet conduit 1 12 and the nitrogen recirculation conduit 35. The inlet 108 and an outlet 1 16 of the filtration assembly 37 are connected to the conduits 112, 35, respectively with valves 1 18, 120. A valve 122 is positioned in the bypass conduit 1 14. The valves 118, 120, 122 have actuators so that the filtration assembly 37 can be bypassed, if necessary, for maintenance and cleaning.

[0069] The char processing assembly 100 includes a hopper 102 located below an outlet of the cyclone separator 32. The char separated from the nitrogen drops into the hopper and from there is fed into a char grinder 104. The char grinder 104 grinds the char which is then fed into a char bin 106 from which it can be extracted and processed further.

[0070] The tank farm 14 includes an outlet manifold 134. The outlet manifold 134 is connected to the nitrogen supply conduit 24. The manifold 134 includes valves 136 in fluid communication with respective tanks 16 and independently operable so that the tanks 16 can supply nitrogen separately depending on requirements.

[0071 ] The tank farm 14 includes an inlet manifold 138. The inlet manifold 138 is connected to an inlet conduit 140 that, in turn, is connected to the nitrogen plant 12. The manifold 138 includes valves 142 in fluid communication with respective tanks 16 and independently operable so that the tanks 16 can be supplied with nitrogen separately depending on requirements.

[0072] Figure 10 shows further detail of the manifold assembly 26. The manifold assembly 26 includes two end conduits 144. Each end conduit 144 extends over each end of the reactor 22, from one lower side of the reactor 22 to an opposite lower side. Two longitudinal conduits 146 are connected between the end conduits 122 on respective sides of the reactor 22. A three-way connector 148 is mounted in each P longitudinal conduit 146 and has three inlets in the form of two lower inlets and an upper inlet.

[0073] The manifold assembly 26 includes four intermediate conduits 150. One intermediate conduit 150 is connected between each respective end of the end conduits 144 and one respective lower inlet of the connector 148 on a corresponding side of the reactor 22.

[0074] The manifold supply conduit 50 is connected to two side conduits 132, via a T-piece 130 with a valve 131 . The two side conduits 132 are connected to two respective upper inlets of the three-way connectors 148. Thus, nitrogen can be supplied to the manifold assembly 26 to flow through the conduits 144, 146, 150. A T-Piece 154 is mounted in the supply conduit 50, downstream of the T-piece 51 . The retort supply conduit 92 is connected to the T-piece 51 via a valve 156. An actuator 158 is arranged on the valve 156 and is operable so that nitrogen can be directed into the retort 21 or the manifold 26 depending on operation of the actuator 158.

[0075] The conduits 144, 146, 150 are of steel and form a relatively rigid cage about the reactor 20. The conduits 144, 146, 150 are self-supporting in that they are not supported by the reactor 20. Thus, any vibration of the reactor 20 is not conveyed to the conduits 144, 146, 150. This helps to preserve the structural integrity of the manifold assembly 26 and associated components.

[0076] Flexible feed hoses 152 are connected between the longitudinal conduits 146 and the housing 22 of the reactor 20. The hoses 152 accommodate any vibration of the reactor 20 because of their flexibility.

[0077] The plant 10 provides a system of cooling the reactor 20 with a flow of nitrogen. The flow of nitrogen can also be used either to provide the necessary anaerobic environment within the reactor 20 or it can be used, via the adductor assemblies 18, to extract nitrogen and entrained char from the reactor 20. Thus, the necessary cooling fluid serves an extra purpose of extraction, as opposed to simply cooling the plant 10. It follows that it is possible to cool the reactor to a desired temperature and then immediately or expeditiously thereafter, to extract nitrogen and entrained char from the reactor 20, without opening the reactor 20. This facilitates the provision of a safe working environment because personnel are not exposed to heated product and potentially harmful char and other byproduct. Furthermore, the extract nitrogen and entrained char is separated into its independent constituents, allowing the nitrogen to be used again, either for cooling or for flooding the retort 21 prior to the pyrolytic process. Still further, once the entrained char reaches the separator 32, the nitrogen is cooled to a value below a flashpoint of the char. As a result, the char is not exposed to atmosphere at a temperature at or near a flashpoint of the char. It will be appreciated that this is achieved by the use of the adductor assemblies 18 which obviate the need for exposing the char to atmosphere at any temperature which could be close to a flashpoint of the char.

[0078] The appended claims are to be considered as incorporated into the above description.

[0079] Throughout the specification, including the claims, where the context permits, the term“comprising” and variants thereof such as“comprise” or “comprises” are to be interpreted as including the stated integer or integers without necessarily excluding any other integers.

[0080] It is to be understood that the terminology employed above is for description and should not be regarded as limiting. The described embodiments are intended to be illustrative of the invention, without limiting the scope thereof. The invention is capable of being practised with various modifications and additions as will readily occur to those skilled in the art.

[0081 ] When any number or range is described herein, unless clearly stated otherwise, that number or range is approximate. Recitation of ranges of values herein are intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value and each separate subrange defined by such separate values is incorporated into the specification as if it were individually recited herein.

[0082] Words indicating direction or orientation, such as“front”,“rear”,“back”, etc, are used for convenience. The inventor(s) envisages that various embodiments can be used in a non-operative configuration, such as when presented for sale. Thus, such words are to be regarded as illustrative in nature, and not as restrictive.

Claims

1. A pyrolysis plant, which includes:

2. The pyrolysis plant as claimed in claim 1 , in which the supply of substantially inert gas is a supply of nitrogen.

3. The pyrolysis plant as claimed in claim 1 , in which the eductor assembly includes at least one eductor with an inlet in fluid communication with the supply of inert gas.

4. The pyrolysis plant as claimed in claim 3, in which the supply of inert gas includes a nitrogen supply conduit that is connected to a source of nitrogen.

5. The pyrolysis plant as claimed in claim 4, in which the, or each, eductor has an outlet that is in fluid communication with a nitrogen return conduit so that gas with entrained char can be extracted from the pyrolytic chamber and directed into the nitrogen return conduit.

6. The pyrolysis plant as claimed in claim 5, in which nitrogen return conduit is connected to a separator to separate the char from the nitrogen.

7. The pyrolysis plant as claimed in claim 3, in which an inlet valve is interposed between the inlet of the, or each, eductor and the supply of nitrogen, the inlet valve being operable to supply nitrogen selectively to the, or each, eductor.

8. The pyrolysis plant as claimed in claim 7, in which a nitrogen supply manifold assembly is in fluid communication with the housing of the pyrolytic reactor and the nitrogen supply conduit.

9. The pyrolysis plant as claimed in claim 8, in which an array of conduits interconnects the nitrogen supply manifold assembly and the housing.

10. The pyrolysis plant as claimed in claim 9, in which the conduits are flexible, and the nitrogen supply manifold assembly is self-supporting or otherwise not connected to the housing so that vibration of the housing is accommodated by the flexible conduits.

11 . The pyrolysis plant as claimed in claim 8, in which a nitrogen recirculation conduit is connected between the separator and the manifold assembly so that nitrogen can be recirculated back to the manifold assembly once the char is extracted from the nitrogen.

12. The pyrolysis plant as claimed in claim 1 1 , in which a filtration assembly is positioned in the nitrogen recirculation conduit to filter the nitrogen before the nitrogen is recirculated back to the manifold assembly.

13. The pyrolysis plant as claimed in claim 8, in which a manifold supply conduit is connected between the nitrogen supply conduit and the, or each, inlet valve of the eductor(s) so that when the, or each, inlet valve is closed, nitrogen bypasses the eductor(s) to be supplied to the nitrogen supply manifold.

14. The pyrolysis plant as claimed in claim 1 , in which the gas extraction conduit has an internal portion located in the pyrolysis chamber and an external portion that extends from the pyrolysis chamber.

15. The pyrolysis plant as claimed in claim 14, in which the internal portion extends generally orthogonally with respect to the external portion.

16. The pyrolysis plant as claimed in claim 15, in which the internal portion is connected to the external portion with a rotatable coupling so that the internal portion can rotate, together with the retort, relative to the external portion.

17. The pyrolysis plant as claimed in claim 16, in which the internal portion includes an elbow so that it has an axial section that is generally parallel with an axis of rotation of the retort and a radial section that extends generally at right angles to the axial section.

18. A method of operation of a pyrolytic plant, the method including the steps of: supplying a substantially inert gas to a housing of a pyrolytic reactor for lowering a temperature of the reactor after a pyrolytic process;

19. The method as claimed in claim 18, in which the step of introducing the substantially inert gas into the pyrolytic chamber includes the step of introducing nitrogen into the pyrolytic chamber.

20. The method as claimed in claim 18, which includes the steps of directing gas and char extracted from the pyrolytic chamber to a separator for separating the char from the gas, and directing the gas back to the housing.