GB2536048A

GB2536048A - Advanced thermal treatment methods and apparatus

Info

Publication number: GB2536048A
Application number: GB1503769.0A
Authority: GB
Inventors: Michael Donegan Daniel
Original assignee: STANDARD GAS Ltd
Current assignee: STANDARD GAS Ltd
Priority date: 2015-03-05
Filing date: 2015-03-05
Publication date: 2016-09-07
Also published as: GB201503769D0

Abstract

A multi-stage pyrolysis system comprises a retort structure 26, 29 which rotates about an axis. Calorific material is fed into the retort structure 26,29 at an input end. There is a continuous path between the input end of the retort structure 26, 29 to the exit end 9 of a gas conduit 22. A heating system includes a section that heats the retort structure 26, 29 in a first zone at a first temperature and the gas conduit 22 in a second zone at a second temperature, the temperatures being sufficient for pyrolysis of the calorific material with the second temperature being higher than the first temperature. The retort structure 26, 29 may be enclosed in a thermally insulated housing (40, Fig. 4) and a pipe (28, Fig. 4) may extend along an external surface of the retort structure 26, 29 and may be connected between the output end of the retort structure 26, 29 and the gas conduit 22. A three stage pyrolysis method, heating system for heating a gas enclosure, and method of cracking hydrocarbons are also claimed

Description

Advanced Thermal Treatment Methods and Apparatus

Field of disclosure

100011 The present invention generally relates to pyrolysis methods and apparatus. Pyrolysis is used to destroy calorific waste and/or to produce gas therefrom. The destruction of calorific waste is desirable to avoid the need for environmental damage due to burial in landfill sites, or dumping at sea. However, some forms of destruction create gaseous pollution and/or carbon dioxide, leading to environmental damage and potentially increasing global warming.

Background

100021 Advanced Thermal Treatment (ATT) piimarily relates to technologies that employ pyrolysis or gasification. ATT is discussed in the Brief, entitled 'Advanced thermal treatment of municipal solid waste' produced by the Department for Environment, Food & Rural Affairs of the UK Government (https://www.gov. uk/govemment/publications/advanced-thermal-treatment-of-municipalsolid-was te). That Brief indicates a problem with conventional pyrolysis and gasification systems is tarring, in which the build up of tar can cause operational problems (for example, if tar build up causes blockages).

[0003] Pure pyrolysis is a process of thermochemical decomposition of material, in which oxygen is absent. If a small quantity of oxygen is present, the process is termed gasification. The amount of oxygen present in gasification is insufficient to allow combustion to occur. In the present application, unless otherwise specified, pyrolysis and gasification will have the same meaning.

[0004] In an ATT process, gas is released from a feed material or 'feedstock', leaving solid matter (char) as a by-product. The skilled person will understand that the term 'feedstock' as used throughout this description relates to any solid material having a calorific value. Feedstocks typically envisaged in this context are waste materials such as biomass, wood or paper, rubber tyres, plastics and polythene, or sewage solids. They also include low quality fossil fuels such as lignite or bituminous coals. The feedstock of ATT units for generating syngas may be most carbon-based materials with a calorific value.

For example, fossil fuels can be used. However, in conventional ATT units, the feedstock must be prepared before entering the unit, thus adding additional time and expense to the process.

100051 The released gas, termed synthetic gas or "Syngas" hereafter, can then be used as a fuel to generate heat or electricity. If carbonaceous material is used as the feedstock, the resulting solid residue ("char") is generally richer in carbon. That char also may he used as a secondary fuel source. Generally, conventional pyrolysis processes do not result in Syngas pure enough to be input into a generator. Instead, the Syngas must first be put through a rigorous cleaning (scrubbed) process, so that any remaining particulate matter and tar are removed from the Syngas. The retention of tar and oil is the consequence of insufficient temperature and dwell time.

100061 Those oils and tars can contain polycyclic aromatic hydrocarbons, PAHs, (also termed poly-aromatic hydrocarbons), which are organic pollutants that may be formed from incomplete combustion of carbonaceous material (such as wood, coal, oil etc). PAHs can be hazardous to human health, and can have toxic and/or carcinogenic properties. It is therefore preferable that gas exiting the pyrolysis system is free from oils and tars, and therefore from PAHs.

100071 PAHs usually have high melting points and boiling points. The boiling points may, for example, be 500°C or more For example, Picene (C22H14) has a boiling point of around 520°C and a melting point of around 365°C and Coronene (C24H12) has a boiling point of around 525°C and a melting point of around 440°C. Accordingly, thermochemical decomposition, or 'cracking'. PAHs requires very high temperatures and the PAHs are difficult to remove using a conventional pyrolysis process.

100081 In general in the prior art, feedstock is prepared before entering the pyrolysis unit. The feedstock is then heated in a low pressure atmosphere containing minimal oxygen. This process breaks down the feedstock into char and Syngas. The Syngas is then cleaned or scrubbed in order to remove any remaining particulate matter. The resulting scrubbed Syngas can be used, for example, to generate electricity by utilising the Syngas as fuel for a reciprocating generator engine or turbine.

100091 The feedstock of pyrolysis units for generating Syngas may be most carbon based materials with a calorific value. For example, fossil fuels can be used. However, in conventional pyrolysis units, the feedstock must be prepared before entering the unit, thus adding additional time and expense to the heat or electricity generation process. Moreover, in preparing the feedstock, certain material with a calorific value may be rejected as being non-compliant with a given pyrolysis unit. For example, certain feedstock materials may be difficult for some fuel specific pyrolysis technologies available to breakdown using thermal processes.

190101 Conventional pyrolysis units may include a secondary gasifier. For example, W02005/116524 describes plant equipment which includes two pyrolysis units. Char from the primary pyrolysis unit is used as fuel in the secondary pyrolysis unit.

[00111 W02005/116524 further describes an apparatus and process for converting carbonaceous or other material with calorific value into high quality gas preferably to fuel a reciprocating gas engine for the generation of elecnicity. Wet fuel enters the unit, whereupon it is dried. The dried fuel then is checked for size via a trammel. Correctly sized fuel passes through the trammel and oversized fuel goes onto the reject conveyer where it is delivered for shredding, after which the fuel may be the correctly sized. The correct sized dry fuel is then compacted, forming a cylindrical fuel plug and fed via a feed system, to avoid the ingress of air, into a gasifier provided with an internal vane configuration, which allows homogenous distribution of the feed material over a large area of a retort. This exposes the feed material to heat without the need for rapid tumbling and agitation. The gas released by the arrangement W02005/116524 is cooled and cleaned in a gas quench unit.

100121 It is known in the art that use of a CO2 atmosphere may improve the yield of Syngas produced from a pyrolysis process. "An Investigation into the Syngas Production From Municipal Solid Waste (MSW) Gasification Under Various Pressure and CO2 Concentration" (Kwon et al, presented at the 17th Annual North American Waste-toEnergy Conference 18-20 May 2009, Chantilly, Virginia, US, PrOC 17th Annual North American Waste-to-Energy Conference NAWTEC17, paper NAWTEC17-2351) discloses that CO, injection enables further char reduction, and produces a significantly higher proportion of CO. Additionally. CO2 injection reduces the levels of Polycyclic Aromatic Hydrocarbons (PAHs), which can be directly related to tar and coke formation during a gasification process [0013] The arrangement of W02005/116524 includes a main gasifier and a secondary gasifier. The main gasifier is a rotary kiln consisting of a rotating, slightly inclined metal shell or tube which transports fuel along its length. The exhaust gas from the secondary gasifier external to the kiln heats the tube.

[0014] WO 2009/133341 relates to improvements to a gasifier. Internal vanes are attached to the rotating vessel or retort, and constructed in such a way that the feedstock falls initially onto the inner surface of the vanes nearest the longitudinal axis. The feedstock then falls through gaps between the vanes to reach outer chambers of the rotating vessel. The vanes allow homogeneous distribution of the feed material over an increased surface area of the retort whilst providing heating gas to an increased surface area extending into the retort interior.

Means for solving the problem [0015] The inventors have devised novel and inventive pyrolysis apparatus and techniques. A broad description will be given of specific aspects of the invention. Preferred features of the specific aspects are set out in the dependent claims.

100161 Claim 1 provides a multi-stage pyrolysis apparatus in accordance with one aspect of the present invention. Calorific material entering the pyrolysis unit of the present aspect will have an increased dwell time in comparison to known pyrolysis units of similar size. Accordingly, the size of a pyrolysis unit may be reduced without negatively affecting the quality and volume of Syngas produced. Moreover, the reduction in size of the pyrolysis unit allows a pyrolysis unit that can be transported via road, rail, sea, or air. Additionally the present aspect allows for the take-off of the latent heat, which is available at various points of the technology (for example, the exhaust, heat from the Syngas as it is cooled, and heat from the exhaust and water jacket of the reciprocating engine). Advantageously, on a 3 tonnes per hour unit this additional energy capture would total in the order of 6 MWt. Additionally, the one heating source may be used to heat multiple components of the same pyrolysis unit. Therefore, less conventional fuel is required to perform multiple pyrolysis processes.

[0017] A further aspect of the present invention is a rotahle pyrolysis retort structure at least part of which is constructed of copper sheets explosively welded to a nickel alloy framework. A retort of the present aspect allows the retort to have the characteristics of both copper and nickel alloy. Specifically, the retort of the present aspect of the invention has the thermal conductivity characteristics of copper sheet along with the high temperature strength of a nickel alloy framework. Such construction provides improved thermal conductivity through the retort structure due to the high thermal conductivity of copper (which is of the order of 30 times that of Nickel alloys), whilst maintaining high temperature strength via the nickel alloy frame, which has the mechanical strength lacked by the copper at elevated pyrolysis temperatures.

[0018] Accordingly, as the thermal conductivity through the retort is higher, there is a lower temperature drop between the outside (which is where heat is applied) and the inside (which is where pyrolysis occurs), so that a lower temperature can be applied to the retort structure in order to heat a calorific material to a temperature sufficient for pyrolysis throughout a retort structure of the present aspect, or a shorter dwell time (and hence higher volume throughput of waste material and higher generation rate of syngas) can be achieved for the same temperature.

[0019] Advantageously, the one heating system may be used to heat multiple components of the same pyrolysis unit.

[0020] Additionally, performing one pyrolysis process at a temperature higher than another pyrolysis process allows particulate matter from one pyrolysis process to be further broken down. Preferably, the second temperature is sufficient to crack tars and oils. Accordingly, Syngas produced by the method requires a reduced amount of cleaning.

[0021] Advantageously, the present invention can reduce the amount of waste going to landfill, and convert waste into useful end products. For example, in the varying quantities available the char is used as a secondary fuel for the heating system.

[0022] More advantageously, aspects of the present invention comply with legal requirements of various countries for the incineration of waste. For example, Directive 2000/76/EC of the European Parliament and of the Council of 4 December 2000 on the incineration of waste (the Waste Incineration Directive, or WID) requires that certain conditions are met pertaining to the temperature and length of time a combustion must take place. The controllable exhaust allows the present invention to exceed those conditions.

[0023] Waste processed by the present invention can be converted into Syngas and vitrified slag. The Syngas can then be used to produce electricity (as described above) and the vitrified slag can be used in the construction industry. The process redirects waste from landfill; also an existing landfill site may be mined to provide feedstock. Moreover, the amount of recyclable waste being used as feedstock can be reduced as the present invention is capable of processing a vast range of feedstock as the process is not fuel specific. Additionally, it is an object of the present invention to be capable of processing hazardous waste, by utilising corrosion resistant materials.

[0024] Additionally, some aspects of the present invention are able to deal more effectively than conventional pyrolysis apparatus and techniques with the hydrocarbons associated with the retention of tar and oil thereby obviating the need for an oil refinery.

100251 One aspect of the present invention relates to an efficient multi-stage pure pyrolysis unit in which a single heating unit may be used to process a source material to generate heat for the process. This primary fuel is a calorific solid waste, and a secondary fuel (in the form of the resultant char created by the initial pyrolysis process) is used to fuel the heating unit, and thus improve the overall efficiency by reducing dependency on fossil fuels. A minimal amount of diesel, liquid petroleum gas (LPG) or gas may be required in a start-up situation, however, after this, the unit may use the resultant char as a secondary form of fuel. Other calorific waste based materials are used as a primary fuel to provide the requisite fuel for the heating process, as the resultant char return is insufficient in both its volume (these volumes vary in relation to feed stock types) and calorific value to provide the heat required to complete the pyrolysis process.

[0026] Preferred embodiments relate to a low Nox (Nitrogen Oxide), and W1Dcompliant, pyrolysis unit which performs pyrolysis in three separate stages, designed so as to significantly increase the dwell time of both the exhaust and resultant Syngas within the process. The preferred embodiment utilises CO, introduced in controlled volumes into the process and this, together with the increased dwell time, more effectively deals with the hydrocarbons associated with the retention of tars and oils, thereby increasing both the volume of Syngas produced and its quality. The first embodiment. does not require the Syngas produced by the process to be recycled for use as fuel to provide the requisite heat (though this is possible in a second embodiment).

[0027] The heat provided for the process is preferably fromcalorific waste (of a homogenous consistency) with the resultant char generated by the process being utilised as a secondary fuel source. The use of this fuel type enables the correct energy balance within the process to be maintained. The volumes of the resultant char would sometimes be insufficient for use as the primary fuel because feed stock types can produce both varying and minimal volumes of char. Additionally, in some cases it may be desired to sell the char as a fuel product for use elsewhere.

[0028] In a first embodiment, each stage of the pyrolysis process takes place within the same highly insulated compact housing which could easily be transported by road, rail, sea or air.

[0029] In a second embodiment, a further heat source is provided which is arranged to further heat the gas produced by the pyrolysis process described above to an even higher temperature, at which Nox is removed. Preferably, a portion of the additional heat produced by this further heat source is recovered, very preferably from both the Syngas and the exhaust gas from the further heat source.

100301 At this point it may be mentioned that removal of Nox by reburning is described in for example Smoot et al "Nox control through reburning". Progress in Energy and Combustion Science, Vol 24 Issue 5 Oct 1995, pp385-408.

[0031] In this second embodiment, preferably, there are thus three stages of pyrolysis treatment in the process of Syngas production: firstly, in the retort at a first temperature; secondly, in the system of pipes at a second, higher temperature; and thirdly, in the array of pipes (gas conduit). As the gas at each stage is progressively more free of long-chain hydrocarbons (waxes, oils and tars) the gas channels can be made progressively smaller at each stage, which in turn makes it easier to achieve higher gas temperatures for a given gas flow rate, and improves the thermal efficiency of the process.

Brief description of the drawings

100321 Various embodiments and aspects of the present invention are described without limitation below, with reference to the accompanying figures in which: 100331 Figure] is a plan view from above of one aspect of a pyrolysis unit according to a first preferred embodiment.

[0034] Figure 2 is a sectional end elevation of an aspect of the pyrolysis unit of Figure 1 on line A-A thereof.

[0035] Figure 3 is a sectional side elevation of an aspect of that pyrolysis unit on line E-E of figure 1 showing the heating system.

[0036] Figure 4 is a sectional end elevation of an aspect of that pyrolysis unit on line CC of figure 1.

[0037] Figure 5 is a side elevation of an aspect of that pyrolysis unit on line B-B of figure 1 showing the retort structure, retort housing and the heating duct.

[0038] Figure 6 is an elevated perspective view of an aspect of that pyrolysis unit. [0039] Figure 7 is a level perspective view of an aspect of that pyrolysis unit.

[0040] Figure 8 is perspective view with a cut-away section showing the inner and outer retort of an aspect of the retort structure of the pyrolysis unit of the first embodiment.

[0041] Figure 9 is a flow diagram of an aspect of the first embodiment showing a process of taking feedstock and converting it into usable products.

[0042] Figure 10 is a side elevation of the retort structure showing the nickel alloy framework and copper plating of one aspect of the first embodiment.

[0043] Figure 11 corresponds to Figure 1 and shows a plan view from above of one aspect of a pyrolysis unit according to a second embodiment.

[0044] Figure 12 is an exploded schematic isometric view of the main elements of the second embodiment.

[0045] Figure 13 corresponds to Figure 3 and shows a sectional side elevation of an aspect of the pyrolysis unit of Figure 11 on line E-E thereof showing the heating system.

[0046] Figure 14 corresponds to Figure 4 and shows a sectional end elevation of an aspect of the pyrolysis unit of Figure 11 on line C-C thereof [0047] Figure 15 corresponds to Figure 5 and shows a sectional side elevation of an aspect of the pyrolysis unit of Figure 11 on line B-B thereof.

[0048] Figure 16 is a perspective view from above of the embodiment of Figure 11.

100491 Figure 17 is an exploded sectional perspective view of part of the embodiment of Figure 11 to illustrate the cracking process.

[0050] Figure 18 corresponds to Figure 8 and is perspective view with a cut-away section showing the inner and outer retort of an aspect of the retort structure of the pyrolysis unit of the first embodiment.

100511 Figure 19 is a schematic block diagram illustrating the operation of the embodiment of Figure 11.

100521 Figure 20 corresponds to Figure 10 and is a side elevation of the retort structure of Figure 11 showing the nickel alloy framework and copper plating of one aspect of the second embodiment.

100531 Figure 21 is a sectional view of the retort of Figure 20 along a line A-A thereof, showing the vanes present therein.

100541 Figure 22 is a sectional end elevation of a pyrolysis apparatus according to an aspect.

[0055] Figure 22 is a section side elevation of a pyrolysis apparatus according to that aspect.

[0056] Figure 24 is a section side elevation of a healing system including a gas enclosure of an aspect.

100571 Figures 25a-c show plan views of various aspects of an aspect. [0058] Figure 26a shows a perspective view of a spiral insert [0059] Figure 26b shows a perspective view of a tube having a cut-away showing the spiral insert of figure 26a.

[0060] Figure 27a shows a plan view of a series of gas enclosures within a thermally insulated chamber.

[0061] Figure 27b shows a plan view of a series of gas enclosures each with a respective thermally insulated chamber.

[0062] Figure 28 shows a plan view of an Advance Thermal Treatment (pyrolysis or gasification) apparatus including a series of gas enclosures according to an aspect.

[0063] Figure 29 shows a gas coil.

[0064] Figure 301s a schematic side view of the pyrolysis or gasification system according to a first group of preferred aspects relating to a multiple retort system.

[00651 Figure 31 is a sectional end elevation of a first pyrolysis or gasification apparatus according to the first group of preferred aspects relating to a multiple retort system.

[0066] Figure 32 is a section side elevation of a part of the first group of preferred aspects relating to a multiple retort system.

[0067] Figure 33 is a section side elevation of a part of the first group of preferred aspects relating to a multiple retort system.

[0068] Figure 34 is a schematic plan view of the pyrolysis or gasification system according to the first group of preferred aspects relating to a multiple retort system.

[0069] Figure 35 is a schematic side view of the pyrolysis or gasification system according to a second group of preferred aspects relating to a multiple retort system.

100701 Figure 36 is a schematic plan view of the pyrolysis or gasification system according to the second group of preferred aspects relating to a multiple retort system.

[0071] Figure 37 is a representative end view of three pyrolysis or gasification retorts in accordance with an aspect of the second group of preferred aspects relating to a multiple retort system.

[0072] Figure 38 is a sectional end elevation of a pyrolysis unit according to a first preferred embodiment relating to the Temperature Profile in an ATT unit.

[0073] Figure 39 is a sectional end elevation of a pyrolysis unit according to the first preferred embodiment relating to the temperature profile in an ATT unit.

[0074] Figure 40 is a graph showing time against temperature for carbonaceous material/gas according to the first group of preferred aspects relating to the temperature profile in an ATT unit.

[0075] Figure 41 is an exploded schematic isometric view of the main elements of a second group of preferred aspects relating to the temperature profile in an ATT unit.

[00761 Figure 42 is a sectional end elevation of a pyrolysis unit according to the second group of preferred aspects relating to the temperature profile in an ATT unit.

[0077] Figure 43 is a sectional end elevation of a pyrolysis unit according to the second group of preferred aspects relating to the temperature profile in an ATT unit.

[0078] Figure 44 is a graph showing time against temperature for carbonaceous material/gas according to the second group of preferred aspects relating to the temperature profile in an ATT unit.

[00791 Figure 45 is an exploded sectional perspective view of part of the second group of preferred aspects relating to the temperature profile in an ATT unit.

[0080] Figure 46 is a sectional side view of an aspect of the pyrolysis apparatus according to a group of preferred aspects relating to a flat pyrolysis surface.

[0081] Figure 47 is a perspective view of an aspect of the pyrolysis apparatus according to the group of preferred aspects relating to a flat pyrolysis surface.

[0082] Figure 48is a perspective side view of a second end of the pyrolysis apparatus according to the group of preferred aspects relating to a flat pyrolysis surface.

[00831 Figure 49is a perspective side view of a first end of the pyrolysis apparatus according to the group of preferred aspects relating to a flat pyrolysis surface.

[0084] Figure 50a shows a single link from the chain drive of an aspect of the group of preferred aspects relating to a flat pyrolysis surface.

[0085] Figure 506 shows a two joined links from the chain drive of an aspect of the group of preferred aspects relating to a flat pyrolysis surface.

[0086] Figure 51 is a perspective view of an aspect of the pyrolysis apparatus according to a second group of preferred aspects relating to a flat pyrolysis surface.

Detailed description of a first preferred embodiment [0087] The following description relates to Advanced Thermal Treatment (ATT) of feedstock. Specific examples of ATT include pyrolysis and gasification. In the present application, unless otherwise specified, pyrolysis and gasification will have the same meaning. Further, it will be understood that the description of an ATT apparatus may equally relate to a gasification apparatus or a pyrolysis apparatus. Similarly, the description of an ATT method or process may equally relate to a gasification method or process, or a pyrolysis method or process.

[0088] The pyrolysis unit of the first preferred embodiment will now be described in detail on the assumption that the start-up process has already taken place.

100891 With reference to figures 1 and 5, the pyrolysis unit includes a pyrolysis retort feed I to allow feedstock to enter the pyrolysis unit. The retort feed 1 is shaped to funnel feedstock into a substantially vertical feed pipe 3. An airlock 2, which may he a double action airlock, is located toward the top of the feed pipe 3, but below the retort feed I. The airlock 2 is designed to maintain a positive pressure inside the feed pipe 3, thereby preventing air entering the feedpipe 3.

[0090] The double action airlock of this embodiment comprises first and second hydraulically actuated blades 2a, 2b (not shown) in series in the feed pipe, each capable of closing the pipe and acting additionally as safety barriers to the environment under control of an electronic control unit (not shown but indicated herein as 100). Feedstock falls onto the first 2a. When the second 2h is closed, the first 2a opens to admit the feedstock. When the first 2a doses again, the second opens to allow the feedstock into the apparatus. At no time are both open. Both may be closed together, to provide a double safety barrier.

[0091] A side feed airlock 4 is located toward the bottom of the feed pipe 3. The feed pipe 3 may include a CO2 feed supply 8, which may allow CO2 to enter the feed pipe 3, between the double action airlock 2 and the side feed airlock 4, in controlled volumes. The bottom of the feed pipe 3 is connected to a substantially horizontal pipe 27, which includes an auger 37 for transporting the feedstock toward a rotable retort structure. The auger 37 for transporting the feedstock to the retort structure is of nickel alloy and is driven by a motor 6. The diameter of the auger 37 is 12 inches (0.3m). The feed system in the present embodiment enables fuel of a homogeneous consistency (of a specific size) to flow freely in, which facilitates the first stage of pyrolysis within the retort taking place more efficiently.

[0092] A portion of the substantially horizontal pipe 27 may be located within the retort structure. The portion located within the retort structure may have a perforated section within the retort structure to allow feedstock to exit the pipe 27 through the perforations to exit the substantially horizontal pipe 27 over a wider area as shown in Figure 5. Alternatively, the feedstock can exit the substantially horizontal pipe 27 via an exit end of the substantially horizontal pipe 27. As shown in figures 4, 5 and 8, the retort structure includes an inner retort 29. The inner retort has holes in its surface to allow feedstock to pass from the inner retort 29 to an outer retort 26. The outer retort has a larger cross-sectional diameter than the inner retort thereby forming an annular cavity between the two. The inner retort 29 and the outer retort 26 are coaxial, with the inner retort 29 being located substantially within the outer retort 26 and both are substantially hollow and cylindrical in shape. The inner retort 29 carries outward-facing vanes 31a and the outer retort 26 carries inward-facing vanes 31b, which act as in the above described prior art to increase the dwell time of the char. The structure of the vanes 31 is discussed in greater detail below.

100931 The inner 29 and the outer retort 26 rotate around a common substantially horizontal axis. The common axis extending through the centre of the circular cross-section of the inner and outer retorts. The horizontal pipe 27 is positioned to allow feedstock to enter a first end of the retort structure, and is preferably positioned to allow feedstock to enter the inner retort 29.

[0094] Within the retort structure cavity, a first pyrolysis process takes place. The airlock 2 and the side feed airlock 4 prevent, or substantially prevent, air and other ambient gases from entering the retort structure. Accordingly, the first pyrolysis process may be considered a pure pyrolysis process in a CO2 atmosphere.

[0095] The retort structure is inclined at an angle to aid throughput of feedstock. In one aspect of the present invention, the angle of inclination is 1/10. In another aspect of the present invention, the angle of inclination may be varied utilising a software driven control system within the control unit 100 (not shown). For example, the angle of inclination is controlled hydraulically via a hydraulic arrangement such as a hydraulic piston. An adjustable inclination angle allows the dwell time (or, viewed differently, the transit speed or mass flow) of feedstock within the retort structure to be adjusted (advanced or retarded), thus allowing more varied feedstock materials to be processed whilst optimising the process of carbonisation. The incline of the retort structure is such that the input end is higher than the output end. It will be understood that although the axis has previously been described as substantially horizontal, the angle of inclination will cause the axis to incline along with the retort structure.

[0096] Additionally, the retort structure is resistant to toxic materials and acidic erosion. Accordingly, the present pyrolysis unit is capable of processing hazardous materials and industrial waste.

100971 As mentioned above, the inner and outer retort structures rotate around a common axis. The rotations are driven by a retort drive motor 20 via drive gear 35). Preferably the retort drive motor 20 is capable of alternating its direction of rotation under control of the control device 100. In other words, the rotations need not limited to either a clockwise rotation or a counter clockwise rotation. Preferably, a given number of rotations in one direction are followed by a number of rotations in the opposite direction. For example, four clockwise rotations could be followed by a single counter clockwise rotation. Such alternation of the rotation direction prevents feedstock, char and tar from bulking or forming a bridge between the surface of the inner retort 29 and the outer retort 26. Accordingly, the time between cleaning the retort structure may be increased, and maintenance costs reduced.

[0098] In one aspect of the present invention, the inner and outer retort structures 26, 29 are at least partially constructed from copper. Copper is conventionally considered too soft for use in a rotating retort designed for pyrolysis temperatures. However, with regard to figure 10, in the present arrangement the outer retort structure 26 is made from a nickel alloy cylindrical rectangular grid structure 26a with heavy copper cylindrical plate 26b explosively welded on the inside of that structure.

[0099] The process of explosively welding metals requires two concentric cylindrical shells (copper inside nickel) to be placed a small distance apart, and then brought together at a speed below the speed of sound within those materials by controlled a explosion. The pressure at the interface between the two metals must be greater than the yield strength of the metals. In this way, the metals deform plastically, and explosive welding occurs. Explosive (or explosion) welding (or bonding) was first described in US 3140539 (Holtzman) and may be carried out by High Energy Metals, Inc. of Sequim, Washington USA or Dynamic Materials Corporation of Boulder, Colorado, US.

[00100] Having welded the two shells together, an array of nickel alloy rectangles are milled off the surface of the underlying copper plate 26b, to leave the cylindrical rectangular grid structure 26a in place.

[00101] The advantages of explosive welding include retaining the qualities of the parent metals (e.g. nickel alloy and copper). In the present arrangement, a retort is formed that provides the high temperature strength of the nickel alloy structure with the conductivity of the copper plates. The two materials have close thermal coefficients of expansion so the retort can withstand high temperatures, and an explosive welded joint results in no electrolytic action across the Ni/Cu interface.

[00102] In conventional retort structures, a high temperature applied to one location of the retort structure by a heating system would not necessarily be transferred throughout the retort structure, and therefore to the feedstock, due to the low conductivity of the construction materials. There are thus temperature gradients within the retort: firstly, along its length from the point where die heating system is coupled to the retort, and secondly, radially from the outside of the retort where the heat is applied to the inside where the feedstock is located. The faster the transit speed of material through the retort, the steeper the radial temperature gradient across the retort and hence the higher the temperature which must be applied by the heating system in order to reach a given pyrolysis temperature of the feedstock. Using the high thermal conductivity of copper allows the present aspect of the invention to efficiently equalise temperature applied to the retort structure throughout the entire retort structure. Accordingly, the temperature applied to the outside of the retort structure by the heating system does not have to be as great in order to transfer a sufficient temperature for pyrolysis to the feedstock.

[00103] The use of copper for the retort structure also improves the local heat distribution within the retort structure, and therefore reduces temperature variation across the retort structure. This, in turn, lowers the onset of "hotspots" along the surface of the retort structure beneath the points where the relatively cool feedstock sits. In addition to these advantages, the pyrolysis process in the retort structure may be further improved. For example, the gas produced may include Syngas combined with particulate matter and tar. Conventional units may send this gas to be cleaned or purified.

[00104] Referring again to figures 4, 5, and 8, the retort structure is located within a thermally insulated retort housing 40. The thermally insulated retort housing 40 is preferably a cuboid, but it will be understood that other shapes are within the scope of the invention. A cuboid retort housing 40 allows for ease of construction, and transport. A cuboid shape may also help the rigidity of the multi-stage pyrolysis unit. The atmosphere within the retort structure is isolated from the atmosphere inside the retort housing 40, but external to the retort structure. In this embodiment, the pyrolysis unit, including at least the retort housing 40 and the retort structure, forms a rigid, compound unit capable of being inclined as a single unit via a hydraulic arrangement, such as a pair of hydraulic pistons adjacent the input end of the unit pivoting the unit around a pivot axle adjacent the discharge end. To aid rigidity, the pyrolysis unit may comprise a steel outer shell lined with refractory ceramic bricks.

1001051 In the accompanying figures, the substantially horizontal pipe 27 enters the retort housing 40 via an airtight housing 5 Accordingly, the atmosphere within the retort housing may only escape via the exhausts 7. Alternatively, the substantially horizontal pipe 27 may be located within the retort housing 40, and the feed pipe 3 may enter the retort housing 40 via an airtight housing 5 located on surface of the retort housing 40.

[00106] Also within the housing 40 is a system of piping 28, preferably located proximate to the exterior surface of the outer retort 26 as shown in figures 1, and 6-8. The system of piping 28 extending generally parallel to the common axis, and horizontally along the length of the retort structure. The system of piping 28 has a cross-sectional diameter much smaller than the retort structure, for example four inches (approximately 10cm). The system of piping 28 in this embodiment is made out of nickel alloy.

[00107] The system of piping 28 is connected to the output end of the retort structure so that a continuous path is formed between the retort structure and the system of piping 28 for gas exiting the retort structure.

1001081 The system of piping 28 consists of a series of parallel straight sections connected by curved sections, so as to follow a generally cylindrical shape wrapped around the retort, forming a continuous path for gas to travel along. The atmosphere within the system of piping 28 is isolated from the atmosphere inside the retort housing 40 and outside the retort.

[00109] The piping 28 may be a single pipe or a plurality of pipes. If the system of piping is a plurality of pipes each following a generally cyclindical shape wrapped around the retort. Each of the plurality of pipes can converge into a single connection to the output of the retort structure.

[00110] The system of piping 28 is located close to the external surface of the outer retort 26 so as to benefit from residual heat from the retort structure. Preferably, the gas enters the system of piping 28 at a point higher than the gas exits the system of piping 28.

[00111] Thus, the total length of the system of piping 28, including each of the straight sections and the curved sections, is many times the length of the retort structure. Such a total length increases the time gas will spend in the system of piping 28 and therefore the proportion of longer-chain hydrocarbons (associated with tar and oil retention) and particulate matter still mixed with the gas being thermochemically broken down will be increased.

1001121 The use of the system of piping 28 allows the feedstock and resultant gas/particulate matter mix to remain at a temperature sufficient for pyrolysis for a longer time. Conventional pyrolysis units use an elongated retort to achieve the same effect. Accordingly, one aspect of the present invention may use a retort structure of reduced length without loss of performance. Further, the heat required is lower since the piping 28 is co-located with the retort and heated from the same source.

1001131 Referring to figure 5, at a second (discharge or exit) end of the of the retort structure, opposite to the first end, beyond cyclone furnace gas diffuser plate 38 a retort exit pipe 33 is located to allow a mixture of gas and particulate matter to exit the retort structure. The retort exit pipe 33 extends out of the retort structure along the common axis. A holed section of the exit pipe 33 has holes throughout the surface of the exit pipe located above a substantially vertically-extending char pipe 36. Char falling through the holes in the holed section falls into the char pipe 36 via an airlock 39. Further, the holes allow the mixture of gas and particulate matter to rise through a gas duct 19. One end of the gas duct 19 is located above and proximate to the holed section, whereas the other end is positioned to allow gas passing through the gas duct 19 to enter the system of piping 28. Gas may be impelled to travel through the system of piping 28 by a syngasgas booster fan 18. An access hatch 34 allows maintenance access.

1001141 Within the system of piping 28, a second pyrolysis process takes place. Preferably, the second pyrolysis process is undertaken in the absence, or near absence, of oxygen. Accordingly, the second pyrolysis process may also be a pure pyrolysis process.

[00115] Referring to figure 2, the exit of the system of piping 28 is connected to a first end of a high temperature Syngas outlet 9. The second end of the high temperature Syngas outlet 9 is connected to a pressure storage chamber, including a compressor, 10. The compressor 10 is further connected to a high-pressure exchange coil 12. Preferably, the exchange coil 12 has a diameter less than that of the system of piping 28.

[00116] Referring again to figure 4, the high pressure exchange coil 12 is connected to an input end of narrow gas conduit 22, which is at least partially located within a main furnace heat duct 15. Preferably, the narrow gas conduit 22 has a diameter the same as, or substantially the same as, the exchange coil 12. This may be two and a half inches (approximately 6.3cm). Preferably, the at least partial section of the gas conduit 22 located within the heat duct 15 forms a helix.

[00117] The temperature within the heat duct is sufficient to heat the narrow gas conduit 22 in which a third pyrolysis process can take place. Preferably, the narrow gas conduit 22 is raised to a temperature greater than the temperature within the retort housing 40. More preferably, the temperature of the narrow gas conduit 22 is sufficient to thermochemically break down tar that may be within the narrow gas conduit 22. By utilising such a high temperature, the Syngas exiting the multi-stage pyrolysis unit is sufficiently clean to be directly input into a turbine or generator, for example, to generate electricity following a minimum amount of gas clean up.

[00118] An output end of the gas conduit 9, opposed to the input end of the gas conduit 22, may form a Syngas outlet 9, which may be connected to another piece of machinery, such as a generator. Alternatively, the Syngas outlet may be connected to a storage vessel such as a gasometer, following a minimum amount of gas clean up.

[00119] The multi-stage pyrolysis unit of one aspect of the present embodiment can use a single heat source to perform three distinct pyrolysis processes. Moreover, the innovative arrangement of components in the present aspect allows the size of the pyrolysis unit to be reduced. For example, a multi-stage pyrolysis unit of the present aspect, which is rated a 6-tonne unit, can be less than 4.8 meters in width. Accordingly, such a unit can be transported easily via road, rail, sea or air.

[00120] The heating system for the pyrolysis unit will now be described in detail. In general, the heating system comprises at least one heat source and a heating duct to transfer heat from the heat source to the interior of the thermally insulated retort housing. The heating system may comprise additional heat sources. It will be understood by those skilled in the art, that multiple heated areas may be supplied by a single heating source. In this embodiment the heating system, the retort structure and the retort housing 40 may be inclined together as a single, compound unit by hydraulic rams under control of the control unit 100.

[00121] A furnace feed 13 is connected to a combustion control unit 21. The combustion control unit 21 is also connected to the combustion zone of a main furnace 17. The main furnace may be a cyclone furnace. In one aspect of the present invention, the main furnace may be gravitationally fed. Dampers are provided to allow the temperature in the retort chamber 40 to be maintained at a constant level.

[00122] The heat duct 15 is attached to the main furnace 17. Alternatively, instead of the heat duct being 15 being attached to the main furnace 17, a secondary furnace 16 may be attached to the main furnace 17. If a secondary furnace 16 is used, the heat duct 15 will be attached to the secondary furnace 16.

[00123] The heat duct 15 is connected to the thermally insulated retort housing so that heated gas from the furnace may enter the thermally insulated retort housing, thus heating the system of piping 28 and the retort structure.

[00124] It has previously been described how a char pipe 36 is located near, and below, the holed section of the exit pipe. Below the open, bottom end of the char pipe 36 is a conveyor 23. The conveyor 23 is capable of transporting char that has fallen from the char pipe 36 to the base of a hopper feed 14. The hopper feed 14 transports the char from the conveyor 23 to be deposited in the furnace feed 13. The hopper may include a vertical auger to help the transport of the char and waste.

[00125] hi this way, char from the retort structure may be used as a secondary fuel in the heating system. The heating system may operate using char from the retort structure, supplemented by a top up fuel. The top up fuel may be a fossil fuel, feedstock or any other material with a calorific value, such as waste material. For example, the waste material may comprise 10-20% of the fuel used to operate the heating system. In this way, the energy (or calorific) content of the heating system may be increased. Conventional pyrolysis units do not use waste material in such a manner because of Nox. Preferred aspects of the present invention allow waste materials to be used as fuel in the furnace, whilst remaining WID compliant. In a further aspect of the present invention, the requirements of the W1D can be met and exceeded by the structure of the exhaust 7, which allows the exhaust gas to be kept at approximately 850°C for approximately 4 seconds.

[00126] It will be understood that the heating system may be fuelled by char from the retort structure alone.

1001271 Heated gas exiting the main furnace 17 and the secondary furnace 16 enters the heat duct 15 and travels toward the retort housing 40. The heated gas then enters the retort housing 40, whereupon the system of piping 28 and the retort structure are heated.

[00128] The heating system can operate at between 1250°C and 1600°C. Those temperatures are capable of heating the retort structure and the system of piping 28 to between 800°C and 1000°C (for example, 850°C), and the gas conduit 22 to between 1000°C and 1300°C (for example, 1200°C).

[00129] The temperature of the retort structure is therefore capable of thermochemically breaking down (-cracking") feedstock placed within. The gas leaving the feedstock upon being broken down is then directed toward the system of piping 28, whereupon it is thennochemically broken down further. The further broken down gas is then compressed and directed toward the gas conduit 22. The at least partial section of the gas conduit 22 located within the heat duct 15 being heated to between 1000°C and 1300°C is capable of cracking any residual tars and oils contained in the gas.

1001301 In an aspect of the present invention, a pyrolysis unit performs pyrolysis at three distinct stages. The first stage is inside the retort structure, the second stage is with the system of piping 28, and the third stage is within the gas conduit 22. It is to he understood that the temperature at each of those stages is not necessarily consistent, and it is preferable that at least one of the stages involves pyrolysis at a higher temperature than the other two. The period of time the gas spends in any or all of the three stages of pyrolysis is referred to as the "dwell time".

[00131] This three-stage pyrolysis process allows a greater volume and higher quality of Syngas to be released from a given amount of feedstock, thus improving the efficiency of the system. Using the resultant char from the retort structure as secondary fuel for the heating system lowers the requirement for fossil fuels, and accordingly the present arrangement is more efficient in terms of conventional fuel usage. Additionally, the reduction in use of fossil fuels has environmental advantages.

[00132] The path of the feedstock will now be described with reference to figures 1-5.

[00133] When the feedstock undergoes the first pyrolysis process inside the retort structure, it produces char and gas. The char then follows one path whilst the gas follows a separate path. It will be understood that although the paths are described as separate, they may interconnect at certain points.

1001341 Feedstock enters the retort feed 1, passes the double action airlock 2, and falls through the feed pipe 3. The double action airlock 2 minimises or prevents air entering the retort structure, thereby allowing a pure-pyrolysis process to occur. The feedstock passes through the side feed airlock 4 and is transported via a substantially horizontal pipe 27 into the inner retort 29. The retort structure may be variably inclined so as to speed up, or slow down, the rate at which the feedstock passes through the retort structure. In other words, the dwell time of the feedstock inside the retort structure may be adjusted by tilting the retort structure.

[00135] As mentioned above, the retort structure rotates around the common axis of the inner retort 29 and the outer retort 26. This rotation helps to physically breakdown the feedstock. The retort being able to rotate and counter-rotate further prevents the feedstock forming a bridge between the surfaces of the retort structure or the vanes thereon.

[00136] The atmosphere inside the retort may be rich in CO, supplied by the CO2 feed supply 8. It is known in the art that such a CO, rich environment (in controlled volumes) provides an increased yield of Syngas at a higher quality for a given feedstock during a pyrolysis process. This process also potentially facilitates the use of a greenhouse gas in a way which is less harmful to the environment.

[00137] The temperature of the retort structure is sufficient to thermochemically break down the feedstock into gas and char. The retort structure is preferably made at least in part from Copper to improve the thermal conduction of the retort structure. Preferably the retort structure is made at least in part from a nickel alloy to improve the strength of the retort structure.

[00138] Inside the retort structure the gas path and the char path diverge. The gas path will be now be described, followed by the char path.

[00139] The gas exiting the retort structure via the retort exit pipe is Syngas combined with some particulate matter. The particulate matter may comprise particulate char, droplets of tar or other matter not completely broken down in the pyrolysis process which occurs in the retort structure.

[00140] The mixture of Syngas and particulate matter is introduced into the system of piping 28 sunounding the retort structure via the retort exit pipe and the gas duct 19. The system of piping 28 is at a sufficient temperature to allow the mixture to undergo a second pyrolysis process. The system of piping 28 may be of a length approximately nine times the length of the retort structure in order to maintain the mixture of Syngas and particulate matter at a temperature sufficient for a pyrolysis process to occur, for a significant length of time.

[00141] The mixture of Syngas and particulate matter exiting the system of piping 28 has an increased proportion of Syngas compared to the levels entering the system of piping 28. The residual particulate matter may include oils and tar. The residual particulate matter still present in the mixture generally cannot be broken down further by the temperatures in the retort structure or the system of piping 28. Conventional pyrolysis units would either dispose of the residual particulate matter or, if the residual particulate matter contains oils and tars, send them to a refinery for further processing. Conventional pyrolysis units remove the oils and tars via a quenching and/or cleaning process, for example, passing the gas exiting the conventional pyrolysis unit through a quenching spray.

[00142] The mixture of Syngas and residual particulate matter exits the system of piping 28 and is compressed inside compressor 10. The compressed mixture is then sent through a gas conduit 22 that preferably includes a helical section. At least part of the gas conduit 22 is located within the heat duct 15; preferably at least part of the gas conduit includes the helical section.

[00143] The temperature within the heat duct 15 is substantially higher than the temperature within the retort structure. The temperature within the gas coil is sufficient to crack the remaining oils and tars still present in the gas mixture. For example, the temperature inside the heat duct 15 may be sufficient to raise the temperature of the section of the narrow gas conduit 22 to between 1000°C-1300°C (for example, 1200°C), whereas the temperature inside the retort housing may be sufficient to raise the temperature of the retort structure to between 800°C-1000°C. hi this embodiment, the temperature of the retort structure is approximately 850°C.

[00144] By raising the temperature of the narrow gas conduit 22 to between 1000°C-1300°C, the yield of Syn2as is improved, and the requirement for a refinery for oils and tars is removed. Advantageously, the temperature within the heat duct 15 can be adjusted by controlling the temperature of the heating system. For example, as shown in figures 1 and 3, a furnace control 21 under control of the control unit 100 may be attached to the main furnace 17 in order to adjust the temperature at which the heating system operates. Such temperature adjustment allows the composition of the gas exiting the unit to be controlled. This process further controls the cracking of oils and tars within the gas conduit 22. For example, the methane content may be adjusted.

[00145] Syngas exiting the gas conduit 22, and subsequently the pyrolysis unit, is capable of being fed directly into a turbine. The turbine may then create electricity. Alternatively, the Syngas exiting the pyrolysis unit may be fed into a storage container for transport to another facility or device following a minimum amount of gas clean up.

[00146] As will be appreciated from the above description, three distinct pyrolysis processes are applied to the feedstock. The first process occurs in the retort structure, the second in the system of piping 28 and the third in the gas conduit 22. The yield of Syngas for a given amount and type of feedstock is increased by the use of the three-stage pyrolysis process. Further, having one of the stages at a temperature greater than the temperature of the other two stages means the Syngas exiting the pyrolysis unit is cleaner than prior pyrolysis units without the need for designated scrubbers to clean the gas. Further, the gas is clean enough to be directly fed into a turbine following a minimum amount of gas clean up. Additionally, oils may be broken down without the need for an additional refinery.

[00147] The char path will now be described with regard to figures 1-5. It will be noted that whilst the gas path operates in a substantially oxygen free environment, the char path can be exposed to air.

[00148] After exiting the retort structure via the retort exit pipe, the char falls through the char pipe 36 and onto the conveyor 23. The conveyor transports the char to the base of hopper feed 14 which, in turn, transports the char to the top of the hopper feed 14. An auger (not shown) may be included in the hopper feed 14 to accomplish such transport. From the top of the hopper feed 14 the char is deposited within furnace feed 13. The char entering the furnace feed 13 may be mixed with additional fuel, such as fossil fuels, or other feedstock. Alternatively, the char may enter the furnace feed 13 alone. Tt will be understood that, although a gravitational feed has been herein described, other methods of feeding the furnace with char and/or additional fuel are within the scope of the present invention.

[00149] With specific reference to figure 3, after passing through the furnace feed 13, the char enters the heating system. The heating system can operate at a temperature of approximately 1600°C. The temperature inside the heating system is sufficient to burn the char, which becomes hot gas and slag. The hot gas is directed toward the heat duct 15. The slag is directed toward a slag tap 11.

1001501 The slag is periodically removed and forms a vitreous solid which can be used in the construction industry.

1001511 Referring now to figure 4, the hot gas passes heat duct diffuser 32 and travels along the heat duct 15 and heats the external surface oldie helical section of the narrow gas conduit 22. It will be understood that hot gas within the heat duct 15 cannot enter the narrow gas conduit 22.

1001521 After heating the narrow gas conduit 22, the hot gas is input into interior of the thermally insulated retort housing 40. Inside the retort housing 40, the hot gas heats the system of piping 28 and the retort structure to between 800°C and 1000°C. In this embodiment, the system of piping 28 and the retort structure are at 850°C during operation.

1001531 The hot gas can exit the retort housing 40 via the exhaust 7. It is within the scope of the present invention to include more than one exhaust 7. The exhaust 7 preferably includes a flexible joint and/or a restrictive throat so that the exhaust is controllable. Such control allows the multi-stage pyrolysis unit of an aspect of the present invention to comply with varying official regulations in a number of countries.

1001541 Figure 9 shows a simplified flow diagram of the method of processing feedstock in a further aspect of the present embodiment, including the gas path, and the char path.

1001551 At step Si, the feedstock may be prepared in advance of entry into the pyrolysis unit as with conventional pyrolysis units. It will be understood that step S1 is not necessary with the presentemboditnent. At step S2 the feedstock can be held in the retort feed 1 above the airlock 2 in order to regulate the amount of feedstock entering the retort structure. At step S3, the air lock 2 holds the feedpipe 3 at a positive pressure in relation to atmosphere so that feedstock may enter the feedpipe 3, air is prevented from entering feedpipe 3.

1001561 At step S4 the feedstock enters the retort structure, and undergoes the first pyrolysis process. The gas path moves to step 55, whereas the char path moves to step S12. At step S5, the mixture of gas and particulate matter exiting the retort structure is put through the system of piping 28, before being pressurised in the compressor 10 and sent through the narrow gas conduit 22 at step S6. When the mixture is at step S6 the hot exhaust gas from the cyclonic combustor at step Sll directly heats the narrow gas conduit 22. At step S7, the gas exiting the narrow gas conduit 22 may be cleaned up further using conventional cleaning and/or quenching processes. Often, and desirably, step S7 is not necessary as the multi-stage pyrolysis process produces Syngas clean enough to enter a generator directly, following a minimum amount of gas clean up. Specifically, one of the multiple pyrolysis stages is at a temperature significantly greater than the remaining stages, and accordingly tars and oils that would not be broken down by conventional pyrolysis units are cracked and therefore removed.

1001571 Steps 58, 59, and 510 provide possible destinations for the Syngas exiting the multi-stage pyrolysis unit of certain aspects of the present embodiment which are not limited to those destinations. In step S8 the Syngas is sent to a storage unit, possibly for transport to a different location. In step 59, the Syngas is input into a reciprocating gas engine. The Syngas could first be entered into a storage unit before being input into the gas engine. The gas engine may be used to power a generator, as in step SD, or may be used in another manner not specified in this description.

Detailed description of a second preferred embodiment [00158] In this embodiment, to the extent they are not discussed below, features having the same reference numbers as in the first embodiment are as described above and need no further explanation.

[00159] Referring to Figures II and 12, in this embodiment, an additional, higher temperature, stage is provided in which nitrous oxide (Nox) is removed. In this embodiment, a second beat source is therefore provided. Accordingly, in this embodiment, after the gaseous output of the primary furnace has passed through the system of piping 28 wrapped around the outer retort 26 the pipes 28 extend on to manifolds 44 in a second section 50 (see Figure 17).

[00160] The pipes 22 in this embodiment are above, and aligned with the axis of, the retort structure. The array of pipes is a parallel array of pipes of two and a half inch (approximately 6.3cm) diameter. Providing a parallel array enables the use of relatively narrow diameter pipes whilst maintaining a high gas flow rate. The chamber 15 in this embodiment extends above and along the length of the retort.

[00161] As best seen in Figure 16, each pipe of the array 22 follows a serpentine path in the vertical plane, passing through three U-bends to execute 4 longitudinal traverses through the chamber 15.

[00162] The paths taken by combustion gases in this embodiment are most clearly seen in Figure 12. Hot combustion gas is generated in the furnace 16 by burning char as described above, and fed to the chamber 15, which is at around 1200C. Here, it contacts the array of parallel pipes 22 and heats the gas therein, cracking the hydrocarbon content. The combustion gas is cooled thereby and passes downwards through ducts into the retort chamber 40 to heat the retort at a temperature of around 850C.

[00163] The combustion gas used to heat the retort chamber 40 passes, as shown in Figure 15, through exhaust vent 7 to a Nox burnout chamber 142, aligned with but separated from the chamber 15 by a divider wall (through which the pipes 22 pass).

[00164] Beside and below this burnout chamber 142 lies a furnace 141, heating the chamber 142 to an even higher temperature of 1250C-1300C at which any Nox is removed from the combustion gases used to heat the retort chamber 40. The furnace 141 burns a portion of the syn2as previously produced by the apparatus of the embodiment. At startup, if no stored syngas is available, hydrogen may be used.

[00165] The thermal energy from the hot gases circulating in the Nox burnout chamber 142 (consisting of gas from the retort chamber 40 and gas from the furnace 141) is recovered by supplying these to a first heat recovery steam generator (HRSG) 45a, of conventional type, in which the gas is passed via pipes through a boiler to generate steam used to drive a steam turbine 150. The cooled combustion gases are then vented to the atmosphere via a stack 52. The steam turbine 150 is used to drive a first electrical generator 154a to generate electricity, part of which is employed to provide power to the apparatus itself and part of which is provided for other purposes such as supply to industrial or domestic consumers. Thus, all combustion gases produced are contained within the airtight housing of the apparatus until Nox and other harmful traces have been burned out, after which they can be vented to the stack.

[00166] The operation of the retort is as described in the first embodiment. The inner radius of the outer retort 26 is approximately 0.71m, and the inner radius of the inner retort is approximately 0.43m, leaving a gap of around 0.25-0.3m between the inside of the outer retort 26 and the outside of the inner retort 29. A pair of nickel alloy or stainless steel end-caps mount the cylindrical wall of the outer retort to the retort drive gear 35 at one end and a bearing at the other end. The outer retort 26 therefore supports its own weight, and undergoes periodic torsional loads as it is driven to rotate in alternate rotational senses by the motor 20, which loads are borne by the nickel framework.

[00167] The cylindrical wall of the inner retort 29 is mounted within the outer retort at the end-caps, and by bracing stainless steel dividers along its length. As the cylindrical wall of the inner retort 29 does not take any of the torsional or gravitational load, it does not require the same strength as the outer retort and it can therefore be made more cheaply of copper without nickel reinforcement. Likewise, the vanes 31 carried on both retorts can be made of copper alone.

[00168] Typically, in use, when the temperature outside the retort is maintained around 850C, the temperature inside the inner retort 29 will be around 700C due to cooling by newly input feedstock. The feedstock then falls through the holes or slots in the portion of the wall of the inner retort 29 (best seen in Figures 5 and 8) which is currently at the bottom, into the space between the two retorts. where its dwell time is increased by the vanes 31, until it can fall back into the inner retort 29 and so on along the length of the retort.

[00169] As best seen in Figure 21, the vanes 31 are T-shaped in cross-section, each made up of a fin running longitudinally along the retort surface, with a plate at its outer end. The symmetrical cross-section allows the retort to operate in the same manner regardless of the rotational direction. The further ends of the vanes projecting inwards from the outer retort and those projecting outwards from the inner retort lie on approximately the same cylindrical surface. Thus, when charred solid matter falls out from an outer vane it will fall into an inner vane and vice versa.

1001701 The syngas entering the pipes 22 traverses the dwell chamber 15 at 1200C along the first U-shaped section of pipe. It then alternately traverses the burnout chamber 42 and the dwell chamber 15 on successive U-shaped pipe sections, encountering temperatures of 1250C and 1200C. As with the combustion gases, any Nox is burned out in burnout chamber 42. Additionally, the high temperatures further crack oils and tars, which are found to be entirely removed.

1001711 Finally, it exits the array of pipes 22 into a manifold feeding a wide diameter pipe, via which it passes to a second heat recovery steam generator (HRSG) 451), in which it is passed via pipes through a boiler to generate steam used to drive the steam turbine 50. After being thus cooled, it is passed to a scrubber 62 of conventional type which extracts impurities such as water vapour, metals, and other impurities and dust.

[00172] The scrubbed gas then passes through a hydrogen separator 164 of conventional type which separates out hydrogen for use as a fuel for one or both of the cyclone furnaces. Finally. CO, is extracted by a CO, separator 166 of conventional type. The extracted CO, is recycled to the air lock 2.

[00173] The syngas (consisting of ethane, methane, and other relatively short hydrocarbons as well as some CO) is then passed to a gasometer 68, and (via the gasometer or if the latter is empty, directly) to a gas turbine engine 70 driving a second electrical generator 154b. The engine may be a General Electric (GE) Jensbacher engine, which burns gases such as ethane and methane, without too much hydrogen content. The stored syngas not thus used to generate electricity can be sold as a fuel, and vice versa.

[00174] It may be helpful at this point to recap some of the features of the second embodiment. Waste material is gasified, and the resulting gas is treated at three progressively increasing temperatures: the temperature in the retort (700-750C), the temperature in the system of piping surrounding the retort (850C) and the temperatures in the dwell chamber (1200C) and burnout chamber (1250-1300C). As NO2 is burned out, the combustion gases can be vented after heat is recovered therefrom. The diameters of the pipes used are chosen to be smaller at the higher temperatures so as to minimise the temperature drop within the pipes and hence increase the transit speed achievable. Heat is recovered from the hot syngas generated and then after removal of hydrogen and CO, it is used to generate electricity, and also stored for supply to gas customers. The syngas (and/or hydrogen recovered therefrom) are used as fuels within the apparatus.

[00175] It will be apparent that the apparatus has a number of advantages. Firstly, the apparatus operates to destroy solid waste materials which would otherwise cause environmental damage. Pyrolysis in a carbon dioxide atmosphere without oxygen creates a genuine pure pyrolysis environment, different from and cleaner than prior waste incineration and gasification systems. The units can be run on all carbonaceous products including biomass, municipal solid waste, hazardous waste, tyres, sewage etc while complying with all regulations and requirements currently in force.

[00176] Secondly, it produces from them a number of useful end-products. As solids, vitreous slag may be used as a building material. The char which is produced may be used as a fuel in the apparatus itself as described above. However, additionally, if the wood content of the waste feedstock is high, the char makes a clean, charcoal-like fuel which can be sold for use instead of fossil fuels, as briquettes or as tonified pellets (for which see Anna Austin "Glorified, Tonified & Cofired", Biomass Power & Thermal, September 2011 pp29-33).

[00177] As gases, hydrogen and syngas are both useful fuels. Although syngas produced according to the embodiments may in some cases have a different calorific content to natural gas, it can be used as a substitute with appropriate modifications, and is clean enough to run a reciprocating engine or gas turbine, producing emissions that are the same or less than that given by natural gas. If the syngas produced by the embodiments is being sold as a fuel, the calorific content of the syngas can be controlled by maintaining an appropriate mixture of waste feedstock materials. The calorific values of various types of solid waste are well known, but a convenient table is found at http://www.pyromex.com/waste%20types/values asc.htm. ha general, dried sewage and some agricultural materials such as hay have lower energy content by weight, and plastics have higher energy contents by a factor of 2-3.

[00178] The heat recovered is used to generate electricity which can be used to power the apparatus itself, supplied to co-located equipment such as waste comminution machinery, and/or sold to electricity supply companies or directly to consumers. if electrical generation is the main use of the apparatus, the electrical output is maintained by controlling the volume flow of feedstock into and through the apparatus (by varying the input rate into the apparatus and the inclination of the apparatus). By design the units are able to be flexible in their power output and emission control, which has been previously unattainable, allowing instant peaking power control by simply controlling the feedstock input.

[00179] The units of preferred embodiments can be installed extremely quickly and can be dismantled and moved to an alternative location just as easily. They are capable of high outputs of energy from a relatively small and compact unit which meets all current environmental issues and requirements and also solves the problems of the long standing tar and PAH issues by using high gas temperatures and variable dwell times Other aspects, embodiments and modifications [00180] The terms "horizontal" and "vertical" herein are with reference to the main axes of the apparatus. It is understood that the entire apparatus is, in use, inclined to the horizontal plane and hence "horizontal" and "vertical" herein are not used by reference to the Earth's surface. Whether or not used in conjunction with the word "substantially", "horizontal" and "vertical" herein are intended to imply, respectively, "more horizontal than vertical" and "more vertical than horizontal" rather than as terms of geometrical precision.

[00181] Although carbon dioxide has been described as a suitable atmosphere for pyrolysis, other reducing or non-oxidising gases could be used.

1001821 In the preceding embodiments, the heat source is a cyclone furnace. However, a person skilled in the art would understand that other types of heat source could be as efficient. Although char has been described as the fuel for the furnace and syngas for the furnace 41, either or both furnaces could run off either or both fuel sources, supplemented by feedstock, hydrogen or other fuels.

ASPECTS RELATING TO A SPIRAL OR HELICAL GAS PATTI

[00183] In accordance with the some aspects, there is provided a pyrolysis apparatus having a heating system adapted to heat a gas enclosure, wherein a gas path within the heated enclosure is helical or spherical. In accordance with some aspects, there is also provided a method of cracking hydrocarbons comprising heating a gaseous mixture, containing hydrocarbons, that is travelling around an axis of the gas enclosure.

1001841 A helical or spherical gas path enables heavier particulates within a gas to be impelled toward the wall of the gas enclosure. When the gas enclosure is heated, the heavier particulates move closer to the heated wall of the gas enclosure, thereby experiencing a greater heat transfer. Some of the heavier particulates will move into physical contact with the heated wall of the gas enclosure, thereby experiencing conductive heat transfer. Heavier particulates are therefore more easily broken down. For example, when the gaseous mixture is syngas mixed with oils, tars and/or PAHs, the syngas oils, tars and/or PAHs, being heavier, will be impelled toward the heated wall of the gas enclosure. Accordingly, syngas produced by the method requires a reduced amount of cleaning.

[00185] In some aspects, the gas enclosure is a tube having a spiral insert. This minimises the space required to centrifuge the gaseous mixture. The tube having a spiral insert may replace that already exists, and is already in a location where it will be heated, within a pyrolysis or gasification (ATT) apparatus.

[00186] In some aspects, the gas enclosure includes a frustoconical shell having a gas input pipe connected thereto, the input pipe being inclined at a radius of the gas enclosure. Advantageously, the heavier particles are impelled toward the wall of the gas enclosure by the centripetal force and gravity. Further, heavy particulates that cannot be broken down can be readily removed. In some aspects, the gas enclosure includes an extension portion having parallel, or substantially parallel, walls extending from a widest circumference of the frustoconical shell. The extension portion is simpler to manufacture than the frustoconical shell, and can increase the dwell time within the gas enclosure. In some aspects, the frustoconical shell has a smaller diameter end positioned below a larger diameter end. Heavy particulates that cannot be broken down can accumulate at the smaller diameter for ease of removal.

[00187] In some aspects, wherein the gas enclosure is a coiled tube.

[00188] In some aspects, the apparatus comprises a pyrolysis unit having pyrolysis region and a gas exit passage, wherein the gas enclosure is coupled to the gas exit passage. Gas from the pyrolysis region may therefore enter the gas enclosure. The gas retains some of the heat applied during a pyrolysis process in the pyrolysis region, thereby improving the efficiency of the pyrolysis apparatus.

[00189] In some aspects, the heating system is adapted to heat the pyrolysis region. Including a heating system that heats both the gas enclosure and the pyrolysis region improves the efficiency of the pyrolysis system. In some aspects, the gas enclosure is located within the heating system. The gas enclosure is therefore located in a hotter location than the pyrolysis region, meaning that particulates that remain within a gaseous mixture that results from a pyrolysis process in the pyrolysis region are more likely to be cracked in the gas enclosure.

[00190] In some aspects, the pyrolysis apparatus comprises a second gas enclosure, wherein a gas path within the second heated enclosure is helical or spherical and a gas output of the first gas enclosure is connected to a gas input of the second gas enclosure. Including more than one gas enclosure having a helical or spherical gas path increases the dwell time of the gaseous mixture. Additionally, heat transfer to the heavier particulates will be conductive for longer.

[00191] In some aspects, the heating system comprises a thermally insulated chamber and one or more heat sources arranged to heat the inside of the thermally insulated chamber.

[00192] In some aspects, the heating system comprises a plurality of heating units, wherein each heating unit comprises a thermally insulated chamber and a heat source arranged to heat the inside of the thermally insulated chamber. Temperature of gas enclosures within each of the heating systems can therefore be controlled separately.

[00193] In some aspects, the gas enclosure is within the thermally insulated chamber.

[00194] In some aspects, the thermally insulated chamber has an exit aperture through one wall, and the gas enclosure is positioned between the heat source and the exit aperture. Heated air from the heat source will directly impinge on the gas enclosure before leaving the thermally insulated chamber.

[00195] hi some aspects, the heating system is adapted to heat an exterior surface of the gas enclosure.

[00196] hi some aspects, the gaseous mixture follows a spiral or helical path about said axis. Following a spiral or helical gas path about an axis ensures particulates are in contact with the heated wall of a gas enclosure for a prolonged period of time.

[00197] Some aspects comprise pyrolysing a feedstock to create the gaseous mixture.

[00198] Some aspects comprise using a single heating system to pyrolyse the feedstock and to heat said gaseous mixture.

[00199] Advantageously, the present aspects can reduce the scrubbing (cleaning) required to produce usable syngas.

[00200] In some aspects, a gaseous mixture resulting from the pyrolysis or gasification of feedstock can follow a spherical or helical path, at least in part.

[00201] For the purposes of this document, the terms 'helix' and 'helical' are used to denote a helix or a spiral unless otherwise specified. The heated enclosure could be a heated pipe, tube or system of piping, or a heated conc.

1002021 The heated enclosure (gas enclosure) 17 containing a helical gas path is particularly of use for processing a gaseous mixture that results from an ATT process in an ATT unit 50. If that ATT process is not efficient, the gaseous mixture may contain tars, oils and PAHs in addition to syngas. That gaseous mixture can be directed through the heated enclosure 17, in which hydrocarbons are cracked. Within the heated enclosure 17, the gaseous mixture is forced into a spiral or helical path, thereby giving rise to a centrifugal force.

[00203] The magnitude of centrifugal force is given by the following equation: F = mv2 where F is the centrifugal force, m is the mass of a particle, v is the tangential velocity of the particle, and r is the radius of curvature.

1002041 It will be appreciated that the particles of tars, oils and PAHs will be more massive than the syngas particles. As shown by the above equation, those more massive particles experience a greater centrifugal force, are more likely to be moved into contact with the wall of the enclosure, whereupon they experience conductive heat transfer from the hottest portion of the enclosure. As conductive heat transfer is more efficient than convective or radiative heat transfer, the particles in contact with the enclosure wall are more likely to be pyrolysed that particles more remote from the enclosure wall. Additionally, the centrifugal force keeps the heavier particles in contact with the enclosure wall, thereby increasing the length of time in which the heavier particles experience conductive heating. Even where particles merely approach, and do not contact, the wall, there will be a temperature profile such that the zone closer to the wall will be hotter, so that in general, the heavier (and more in need of cracking) the particles are, the more heat they are exposed to. By centrifuging the gaseous mixture in this manner, the heavier particles within the gas are more likely to be broken down (i.e. cracked or pyrolysed), and therefore fewer particulates remain in the gaseous mixture.

1002051 The enclosure wall may be heated by any mechanism that achieves a temperature sufficient for an ATT process. In the preferred aspects related to a spiral or helical gas path, for example, a burner blows heated air onto the enclosure wall.

[00206] Some implementations of the above concept are described below. Frustoconical Shell 1002071 In a preferred aspects related to a spiral or helical gas path, as shown in Fig. 24, the heated enclosure (gas enclosure) 17 includes a frustoconical shell 41 with a first opening 42 having a first radius being positioned lower a second opening 43 having a second radius, with the first radius being smaller than the second radius. Gas is inserted into the frustoconical shell 41 at an oblique angle to the diameter of the shell. The gas therefore spirals within the shell (i.e. the gas generally follows a helical path) 41, and the particles within the gas experience centrifugal force, which causes those particles to move away from the axis and toward the wall of the frustoconical shell 41.

[00208] The gas may enter the heated enclosure (gas enclosure) 17 in any manner, as shown in Figs. 25a-c, as long as the gas enters the heated enclosure 17 at an angle inclined to a radius of the heated enclosure 17. In other words, if the frustoconical axis 41 is aligned with a Z-axis, gas enters the frustoconical shell 41 at an oblique angle when considering only the X and Y components. This does not limit the Z-componcnt of the gas entry angle. For example, gas may enter the frustoconical shell 41 by a pipe 44 that is attached to the shell 41, such that gas is not directed directly toward the axis of the frustoconical shell 41. As the gas is not directed along a radial line of the heated enclosure 17, it is caused to follow a gas path about an axis of that heated enclosure 17, thereby giving rise to a centrifugal force.

1002091 In some variations of this aspect, an extension portion 46 extends from the widest circumference of a frustoconical portion. The extension portion 46 has parallel, or substantially parallel, walls. It will be appreciated that the cross section of the extension portion 46 will be the same as the cross section of the second opening 43. In the example shown in Fig. 24, the gas obliquely enters the extension portion 46 above the frustoconical portion.

[00210] The gas initially follows a spiral path in the extension portion 46. Heavier particulates in the gas fall, under gravity, into the frustoconical portion, whereas hot gas generally rises through the extension portion 46 to exit the enclosure through the exit aperture.

[00211] As the heavier particulates fall through the frustoconical portion. gravity and the centrifugal force impel those particulates toward the wall of the frustoconical portion. The time spent in contact with the heated enclosure wall is therefore increased for the heavier particulates, which require the most energy to breakdown. Heavy particulates that are not broken down by in the frustoconical portion fall through the waste aperture 47 at the bottom of the enclosure, thereby preventing build up of unwanted residual particulates within a piping system. This reduces the chances of blockages within a piping system and reducing the amount of cleaning and scrubbing required for syngas exiting the pyrolysis apparatus.

1002121 hi the arrangement shown in Fig. 24, a frustoconical shell is included as part of a heating system, which comprises a thermally insulated chamber 15 and a heat source 51 provided to heat the inside of the thermally insulated chamber 15. For example, an ATT unit in an ATT apparatus is heated by an external heating system 52, with an external heating system 52 comprising at least one heating unit. In some aspects, a heating system 52 comprises three heating units.

[00213] In Figs. 24 and 25a-c, the frustoconical shell 41 is shown as having a circular cross-section. It will be appreciated, however, that other cross-sections, such as an oval or an ellipse, could also be adopted as long as the cross-section includes a surface that causes gas to flow around an axis of curvature. Sharp corners are preferably avoided to minimise turbulence in the gas path.

Heated Tube with a Spiral Insert 1002141 hi another aspect, as shown in Figs. 25a and 25b, the heated enclosure (gas enclosure) 17 is a tube (or pipe) 48, and the helical gas path may be created by spiral insert 49 within the tube 48. Preferably. the spiral insert 49 is fixedly attached to the inside of the tube 48 such that the spiral insert 49 does not rotate with respect to the tube 48.

[00215] The gas cannot flow along the centre of the centre of the tube 48 due to the spiral insert 49 and instead flows in a helical path. Under the centrifugal force, the particles within the gas move toward the tube wall. The particles with greater mass (i.e. the more massive particles) experience a larger centrifugal force than the particles with a lesser mass. The more massive particles are therefore more likely to come into physical contact with the tube wall, and experience a conductive heat transfer.

[00216] The edge of the spiral insert 49 may be connected to the enclosure wall, thereby placing the spiral insert 49 in conductive thermal contact with the enclosure wall. In this arrangement, the spiral insert will be heated by conduction with the tube wall, and can assist in conductive heat transfer to the particles within the gas.

[00217] The spiral insert 49 may be located within a tube (or pipe) 49 downstream, in the gas path, of the retort 50 in an ATT apparatus, in which the tube 49 and the retort 50 are heated by the same heat source 51. In such an arrangement, the tube 49 and the retort 50 are preferably located within the same thermally insulated housing 40. This makes efficient use of a heat source 51 for a pyrolysis retort. Alternatively, the tube 49 may be placed within a thermally insulated chamber separate from the thermally insulated housing. The tube 49 may also he used in place of the frustoconical shell of the preferred aspects related to a spiral or helical gas path.

Coiled Tube 1002181 hi an aspect, the enclosure is a coiled tube (coiled pipe). The gas is caused to flow around the coiled tube, thereby flowing in a spiral path. Heavier particles are urged towards the wall portion on the outside of the spiral. In some aspects related to a spiral or helical gas path, the coiled tube may be used in place of the frustoconical shell of the preferred aspects related to a spiral or helical gas path. Alternatively, the gas coil can be located downstream, in the gas path, of the retort 50 in an ATT apparatus.

Serial Gas Enclosures [00219] Figs. 27a and 27b show aspects in which three gas enclosures 17 are provided in series. It will be appreciated that more gas enclosures 17 may be added, or two gas enclosures 17 may be used, as long as there is a plurality of gas enclosures 17. In Fig. 24, the gas enclosures 17 are shown as frustoconical shells 41, but other gas enclosures 17, such as a tube with a spiral insert or a gas coil, may be used. Additionally, each gas enclosure 17 may be different. For example, the first gas enclosure may be a gas coil and the second may include a frustoconical shell.

[00220] Fig. 27a shows an arrangement in which the gas enclosures 17 are all provided in a single thermally insulated chamber 15. Three heat sources 51 are shown, although any number of heat source 51 can provided (even a single heat source). The heat sources 51 heat the inside of the thermally insulated chamber 15, and thereby also heat the gas enclosures 15.

[00221] Gas enters the input of the first gas enclosure, and follows a spiral or helical gas path around an axis of that first gas enclosure before exiting the first gas enclosure. The input of the second gas enclosure is connected to the output of the first gas enclosure. The gas then follows a second spiral or helical gas path in the second heated enclosure. The output of the second enclosure, in Figs. 27a and 27b, is connected to the input of the third gas enclosure, in which the gas follows a third spiral or helical path.

[00222] Providing multiple gas enclosures (heated enclosures) 17 allows the dwell time for the gas to be increased. For example, the dwell time in the first gas enclosure 17 may be 2 seconds. If the other gas enclosures are the same as the first gas enclosure, the dwell time will be 2 seconds multiplied by the number of gas enclosures (heated enclosures). Accordingly, there is a greater chance of cracking (pyrolysing or gasifying) hydrocarbons in the gas.

[00223] The arrangement of Fig. 27b comprises three units, each including a gas enclosure 17, a thermally insulated chamber 15 and a heat source 51. The arrangement of Fig. 27b may be, for example, the heating system of an ATT apparatus, wherein each unit is a heating unit of that ATT apparatus. It will be appreciated that more heat source 51s can be provided for each chamber as appropriate. Further, more than three units may be provided, or two units may be provided.

[00224] As each gas enclosure 17 of Fig. 27b has an associated thermally insulated housing, and heat source 51, the temperature of each of the gas enclosures can be more carefully controlled.

1002251 As the residual hydrocarbons that remain in the within the gaseous mixture after the first heated enclosure are likely to be more difficult to break down, more energy (higher temperatures) will he useful in the second heated enclosure. Accordingly, in some aspects, the gaseous mixture first enters the heated enclosure of the coolest heating unit, and is then directed to the heated enclosure of the second coolest heating unit, and so forth until the gaseous mixture reaches the heated enclosure of the hottest heating unit.

[00226] In some aspects, two (or more) consecutive gas enclosures 17 may be at the same temperature to increase the dwell time. This provides an increased dwell time at a temperature hot enough for a pyrolysis process to occur. Any particulates (hydrocarbons) that remain after that extended dwell time may be subjected to a relatively high temperature in a later gaseous enclosure. In an example, the first and second gas enclosures may be at 1250°C whereas the third gas enclosure may be at 1500°C.

1002271 Having the temperature of the gas enclosure increase from the first to the last gas enclosure provides a more efficient system, as the highest temperatures are provided to the final gas enclosure in which a higher proportion of hydrocarbons remaining in the gas will be difficult to break down.

Preferred arrangement in an Advanced Thermal Treatment Apparatus [00228] Figs. 22 and 28 show an ATT apparatus incorporating gas enclosures (heated enclosures) 17 containing a helical gas path. That ATT apparatus includes both a frutoconical shell 41 within a heating unit and a heated tube having a spiral insert. It will be appreciated, however, that other aspects related to a spiral or helical gas path may omit the frustoconical shell 41 within a heating unit or the heated tube having a spiral insert. A preferred ATT apparatus related to aspects related to a spiral or helical gas path is described below.

1002291 With reference to Figs. 22, 23 and 28, the Advanced Thermal Treatment apparatus includes a retort feed 1 to allow feedstock to enter an ATT unit 50. The ATT unit 50 in Figs. 22 and 23 is shown as a cylindrical retort (or 'kiln') 50. however, any ATT unit 50 having a pyrolysis region can be used. For example, in the retort 50 shown in Figs. 22 and 23, a burner 51 directs heated air toward the surface of the retort 50, thereby creating a pyrolysis region in the retort as the temperature of the retort surface rises.

[00230] The retort feed 1 is shaped to direct feedstock into a substantially vertical feed pipe 3. One or more airlocks 4 can he provided in the feed pipe 3, below the retort feed 1, to prevent air entering the ATT retort. The one or more airlocks 4 may be arranged to maintain a positive pressure inside the feed pipe 3, thereby preventing air entering the feed pipe 3.

[00231] The feed pipe 3 may include a CO, feed supply 8, to allow CO2 to enter the feed pipe 3. Where two airlocks are provided, the CO, may enter the feed pipe 3 between the two airlocks. Further airlocks may be provided in addition to the two airlocks. The bottom of the feed pipe 3 is connected to a substantially horizontal pipe 27 for transporting the feedstock toward the ATT retort 50.

[00232] In some aspects, the horizontal pipe includes an auger 37 for transporting the feedstock to the retort 50. The auger 37 may be constructed from nickel alloy and is driven by a motor 6. In some aspects, the diameter of the auger 37 is 12 inches (0.3m).

[00233] A portion of the substantially horizontal pipe 27 may be located within the retort 50. The portion located within the retort 50 may have a perforated section to allow feedstock to exit the pipe 27 through the perforations, thereby dispersing the feedstock over a wider area within the retort 50. Alternatively, the feedstock can exit the substantially horizontal pipe 27 via an exit end of the substantially horizontal pipe 27. Preferably, the retort 50 is coaxial with the feed pipe 3, and the retort is rotable about the common axis. The rotating action of the retort 50 helps to mechanically break down the feedstock, therefore exposing a larger surface area of the feedstock to the heated atmosphere within the retort 50. In this manner, feedstock can be processed more efficiently.

[00234] Within the retort 50, the feedstock undergoes an Advanced Thermal Treatment (ATT) process (i.e. a pyrolysis or gasification process). The one or more airlocks prevent, or substantially prevent, air and other ambient gases from entering the retort 50. Accordingly, the first ATT process may be considered a pure pyrolysis process.

[00235] Referring again to Figs. 22 and 28, the retort 50 (retort or kiln in Figs. 22 and 28) is located within a thermally insulated retort housing 40. The atmosphere within the retort 50 is isolated from the atmosphere that is inside the retort housing 40 but external to the retort SO. The retort SO is heated to a temperature sufficient for a first ATT process to occur.

[00236] In the first ATT process, the feedstock within the retort 50 is converted into a gaseous mixture, comprising syngas, and char. Due to inefficiencies in the process, such as insufficient temperature or dwell time being applied to the feedstock, the gaseous mixture also includes residual particulates such as oil and tar particles, and PAHs. Conventionally, therefore, the gas produced by an ATT unit 50 would need to be scrubbed (cleaned) before use. In the preferred aspect related to a spiral or helical gas path, the gas from the ATT unit 50 is directed through one or more heated enclosures, in which the gas follows a helical gas path.

[00237] In the preferred aspect related to a spiral or helical gas path, the first gas enclosure (heated enclosure) is located within the insulated housing 40 and is therefore heated by the same heating system 52 as the retort 50. The first gas enclosure is a tube 48 with a spiral insert 49, the tube 48 having a narrower diameter than the retort 50. For example, the tube 48 may be part of the system of piping 28 that connects the retort 29 to a second heated enclosure 41 within the heating system 52.

1002381 Due to the narrower diameter, heat transfer to the middle of the tube 48 by radiation and convection will be greater than heat transfer to the middle of the retort. Accordingly, the average temperature within the tube 48 will be higher than the average temperature of the retort 50. Additionally, due to the centrifugal force that results from the helical gas path, particles within the gaseous mixture are impelled toward the wall of the tube 48. A second ATT process, which includes conductive heating for heavier particles, takes place within the tube 48.

[00239] In the preferred aspect related to a spiral or helical gas path, the second heated enclosure is located downstream of the tube 48. The second heated enclosure is shown in Fig. 22 as a frustoconical shell 41 having an extension portion 46. The gas enters the extension portion 46, above the frustoconical shell 41, at an oblique angle (i.e. at an angle inclined to the radius of the frustoconical shell), resulting in a helical path for the gaseous mixture. In the preferred aspects related to a spiral or helical gas path, the frustoconical shell 41 is located within a thermally insulated chamber 15 of the heating system 52.

[00240] In some aspects, one or more heat sources 51 may heat the inside of the thermally insulated housing 15. In other aspects, a heating system 52 comprises a plurality of heatin2 units as described earlier. Each heating unit comprises a thermally insulated housing 15 and a heat source 51. A heating system 52 of the preferred aspects related to a spiral or helical gas path includes a plurality of heating units that comprise frustoconical shells 41.

[00241] As shown in Figs. 22 and 24, the thermally insulated chamber 15 includes an exit aperture through one wall. Preferably, the one wall is opposite the heat source 51 such that air heated by the heat source 51 can exit the thermally insulated chamber 15 via the exit aperture. When deployed as part of an ATT apparatus, the exit aperture is arranged so as to direct heated air from the heat source 51 onto an ATT unit (retort) 50. For example, gas heated by the heat source 51 can exit the thermally insulated chamber 15 through the exit aperture and thereafter heat the ATT unit 50. In the arrangement shown in Fig. 22, the exit aperture leads to the inside of the thermally insulated housing 40. The exit aperture may lead directly to the inside of the thermally insulated housing 40, as shown in Fig. 22, or may lead to an insulated passageway, which then leads to the inside of the thermally insulated housing 40. The insulated passageway may be of any cross-section, such as a square cross-section or a circular cross-section.

[00242] In the arrangement shown in Figs. 22 and 24, the heat source 51 is a burner and is located outside the thermally insulated chamber 15. A duct, which penetrates the thermally insulated chamber 15 connects the burner 51 to the thermally insulated chamber 15 so as to provide heated air into the thermally insulated chamber 15. The thermally insulated chamber 15 is sealed around the duct in the arrangement of Figs. 22 and 24.

[00243] Figs. 22 and 23 shows an arrangement in which the gas enclosure (heated enclosure) 17 includes a frustoconical shell 41, but it will be appreciated that other heated enclosures 17 in which gas follows a helical path are contemplated. It is preferred that the heated enclosure 17 is positioned in the path of the heated air from the burner 51. The heated enclosure 17 is therefore positioned in one of the hottest locations within the ATT system, thereby improving the chance of breaking down any residual particulates in the gaseous mixture within the gas enclosure 17.

[00244] In some aspects, the heating system 52 comprises a plurality of heating units. Preferably, the heating units are spaced along the length of the ATT unit. The heating units may be at different temperatures. In the preferred aspects related to a spiral or helical gas path, the heating unit nearest the feedstock input hopper 1 is the hottest. As the feedstock is the coldest on entry into the retort 50, the retort 50 will be coldest near the feedstock input hopper 1. Accordingly, it is advantageous to locate the hottest heating unit proximate the feedstock input hopper end of the retort SO in order to minimise any potential temperature gradient along the length of the retort 50.

[00245] Where a heating system 52 comprises a plurality of heating units, the gaseous mixture may exit the heated enclosure located within a first heating unit, and be directed to a heated enclosure located within a second heating unit, and so forth.

[00246] The amount of residual particles (oils, tars and PAHs) within the gaseous mixture will reduce at each gas enclosure 17 at least due to the additional dwell time. Additionally, where multiple heating units are provided, the gas enclosures 17 may be at different temperatures, allowing cracking of hydrocarbons within the gaseous enclosures to be controlled.

[00247] As shown in Fig. 28, the gaseous mixture first enters a gas enclosure 17 within a first heating unit located furthest from the feedstock input end of the ATT unit 50, before being directed to another gas enclosure 17 within a second heating unit located closer to the feedstock input end of the ATT unit 50. Finally, the gaseous mixture is directed toward the gas enclosure within the third heating unit closest to the feedstock input end of the ATT unit 50. The gas enclosure 17 in each of the first to third heating units has a 2 second dwell time in the preferred aspects related to a spiral or helical gas path.

However, other gas enclosures may be used that have different dwell times.

1002481 The temperature of the gas enclosures (heated enclosures) 17 within the first two heating units is between 1100°C and 1300°C. The temperature of the gas enclosure (heated enclosure) 17 within the third heating unit (closest to the feedstock input end of the ATT unit) is between 1300°C and 1600°C. To account for the temperature, the heated enclosure within the third heating unit is made of Titanium or a Titanium-alloy, whereas the heated enclosures within the first and second heating units maybe a cheaper material such as Nickel or a Nickel-alloy.

ASPECTS RELATING TO A MULTIPLE RETORT SYSTEM

[00249] One issue with many conventional ATT systems is the inability to completely crack some materials. The syngas exiting those ATT systems therefore contains particulates, such as tars and oils, that must be removed from the syngas before the syngas can be used.

[00250] To account for those particulates, a process involving super critical water process can be used. A fluid may be described as 'super critical' when its temperature and pressure exceed its critical point. For water, the critical point is at 374°C and 221 bar (22.1 MPa). Above that pressure and temperature water enters a super critical state in which the miscibility of organic substances is increased. This effect can be used to destroy pollutants, such as polycyclic hydrocarbons. It is thought that the increased miscibility of organic substances in supercritical water is due to the reduced effect of hydrogen bonding ("Supercritical Water-A Medium for Chemistry" -Shaw, R.W.; Thomas, B.B.; Antony, A.C.; Charles, A.E.; Franck, E.U. -ChentEng.News 1991, Dec 23, 26.).

[00251] US4113446 relates to the conversion of solid or liquid organic materials into high energy gas using supercritical water. The use of a hydrogenation catalyst during such conversion can result in increased conversion of the organic materials into high energy gas.

[00252] US5780518 relates to the use of superheated steam for the pyrolysis of the waste material. Superheated steam, amounting to between 18 and 110 percent of the mass of the rubber waste, is used as the heat carrier. High temperature water vapour goes from a steam generator to a reactor to pyrolyse rubber tires.

[00253] US2009/0206007 discusses a process by which coal is converted into hydrocarbons using a supercritical water process, involving two stages: a first stage in which carbonaceous material is reacted with supercritical water at above 850K to produce a first supercritical fluid reaction mixture comprising hydrocarbon compounds; and a second stage in which hydrocarbon compounds are extracted from coal mixed with at least a portion of the first supercritical fluid at a temperature within a range of from the supercritical temperature of water to about 695K. Char from the second stage is finely divided and may be used outside the process.

[00254] In conventional arrangements, however, energy must be expended in order to create the supercritical water or super heated steam, thereby leading to an inefficiency in the system.

1002551 According to the present aspects there is provided a system for pyrolysis or gasification having a first pyrolysis or gasification unit connected to a second pyrolysis or gasification unit by a hermetically sealed gas path. Advantageously, heated gaseous mixture from the first pyrolysis or gasification unit can enter the second pyrolysis or gasification due to the hermetically sealed gas path, thus inputting a heat source into the interior of the second pyrolysis or gasification unit. According to the present aspects, there is provided a method for pyrolysis or gasification, characterised in that gas resulting from a first pyrolysis or gasification process in a first pyrolysis or gasification process unit undergoes a second pyrolysis or gasification process in a second pyrolysis or gasification process unit.

1002561 A pyrolysis or gasification (ATT) process occurring in the second pyrolysis or gasification therefore requires less heat from external heat sources. Additionally. the heat of the gaseous mixture exiting the first pyrolysis or gasification unit is used in the second pyrolysis or gasification unit, rather than undergoing a heat recovery operation. Accordingly, the pyrolysis or gasification system of the present aspects is more efficient than conventional systems.

[00257] In some aspects, the second pyrolysis or gasification unit is a rotable retort. The hermetically sealed gas path connects to the second pyrolysis or gasification unit through a bearing of the retort. The heated gaseous mixture from the first pyrolysis or gasification unit is therefore input near the axis of the second pyrolysis or gasification unit. Conventionally, when a pyrolysis or gasification retort is only heated externally, a cool region is located near the axis due to the drop off in radiative and convective heat transfer from the surface of the retort as the axis is approached. By inputting the heated gaseous mixture at or near the axis of the second pyrolysis or gasification retort, such cool regions can be avoided.

1002581 In some aspects, the first pyrolysis or gasification unit is a rotable retort.

[00259] In some aspects, the hermetically sealed gas path is connected to a perforated gas input pipe inside the second pyrolysis or gasification unit. Gas is directed along a hermetically sealed path from the first pyrolysis or gasification unit to the second pyrolysis or gasification unit. This helps to disperse the gaseous mixture from the first pyrolysis or gasification unit over a larger portion of the second pyrolysis or gasification unit.

[00260] Some aspects comprise a first thermally insulated housing enclosing the first pyrolysis or gasification unit and a second thermally insulated housing enclosing the second pyrolysis or gasification unit. Preferably, an exhaust duct connects the first thermally insulated housing to the second thermally insulated housing, the exhaust duct being adapted to direct exhaust from the interior of the first thermally insulated housing to the interior of the second thermally insulated housing. Exhaust from a first heating system associated with the first pyrolysis or gasification process unit heats the second pyrolysis or gasification process unit.

[00261] Hot air used to heat the first pyrolysis or gasification unit is therefore also used to heat the second pyrolysis or gasification unit rather than venting to atmosphere or being sent through a heat recovery system. This improves the efficiency of the pyrolysis or gasification system as a whole as the second pyrolysis or gasification unit requires less additional heat to provide a pyrolysis or gasification process.

1002621 Some aspects comprise a first heating system adapted to heat the interior of the first thermally insulated housing and a second heating system adapted to heat the interior of the second thermally insulated housing. A second heating system associated with the second pyrolysis or gasification process unit heats the second pyrolysis or gasification process unit.

[00263] In some aspects, the thermal conductivity of the second pyrolysis or gasification unit is higher than the thermal conductivity of the first pyrolysis or gasification unit. As many hydrocarbons will have been cracked in the first pyrolysis or gasification unit (i.e. many oils, tars and PA H s will have been pyrolysed or gasified), more heat will be required to crack the remaining hydrocarbons. A higher thermal conductivity allows more heat to be transferred along the surface of the second pyrolysis or gasification unit, thereby reducing the onset of 'hotspots' on the retort and improving the heat distribution across the retort.

[00264] Some aspects comprise a thermally insulated housing enclosing the first pyrolysis or gasification unit, the second pyrolysis or gasification unit and the hermetically sealed gas path. Both pyrolysis or gasification units can therefore benefit from all external heat sources.

[00265] In some aspects, the gas resulting from the first pyrolysis or gasification process includes a moisture content. Preferably, the pressure and temperature in the second pyrolysis unit are sufficient that the moisture content becomes superheated steam. Preferably, the pressure and temperature in the second pyrolysis unit are sufficient that the moisture content is in a supercritical state. Superheated steam and water in a supercritical state are both advantageous for cracking hydrocarbons. Conventionally, a separate steam generator is required, which is inefficient in terms of energy used to heat the water. Using a first pyrolysis or gasification process to create superheated steam or supercritical water removes the need for that additional steam generator. As a result, heat used to create the superheated steam or supercritical water is also used in the second pyrolysis or gasification process. In some aspects, wet feedstock having a moisture content of 20%-30% by weight is input into the first pyrolysis or gasification process unit.

[00266] A first aspect relating to a multiple retort system generally relates to the use of a first ATT unit 50 connected to a second ATT unit 53 by a hermetically sealed gas path.

1002671 An enclosed gas path leads from the first ATT unit 50 into the second ATT unit 53. A gaseous mixture created in the first ATT unit 50 is fed into the second ATT unit 53 through a hermetically sealed gas path. The gaseous mixture includes syngas, particulates such as oils and tars, and, if the feedstock has a moisture content, water. In the preferred aspect related to a multiple retort system, a first ATT process occurs in the first ATT unit 50. The resulting gaseous mixture is then directed, through the hermetically sealed gas path, into the second ATT unit 53, in which a second ATT process occurs. When more than two ATT units are provided, a hermetically sealed path is provided from the exit of the first ATT unit 50 to the exit of the second ATT unit 53.

[00268] If the initial feedstock had moisture content, and therefore the gaseous mixture contains water, that second ATT process is carried out in the presence of super heated steam or super critical water. Accordingly, remaining organic substances are more readily dissolved than in the first ATT process, or in a conventional ATT system, and residual tars and PAHs can be more readily broken down. As a result, the syngas exiting the second All unit 53 is cleaner than conventional ATT systems. Advantageously, the present aspect does not require a separate, dedicated, steam generator. Instead, feedstock, having a moisture content, undergoes a first ATT process in a first ATT unit. The resulting gaseous mixture is then directed toward a second ATT unit wherein a second ATT process occurs in the presence of superheated steam, or supercritical water depending on the temperature and pressure of the water within the gaseous mixture from the first ATT unit.

1002691 Feedstock for the present aspects may include any material with a calorific value. Advantageously, there is no requirement to pre-treat the feedstock other than to ensure it physically fits into the ATT system. Accordingly, feedstock having a moisture content may be used with the present ATT system. For example, feedstock having a moisture content of 20%-30% by weight can be processed by the ATT system without the need to first dry the feedstock, as would be the case in a conventional ATT system. In some arrangements, a moisture content of as little as 10% by weight is used. It is to be noted that the anangement described herein is able to process treated (e.g. dried) feedstock in addition to untreated (e.g. wet) feedstock.

1002701 As the first ATT unit 50, the hermetically sealed path and the second ATT unit 53 form an enclosed volume, water in the gaseous mixture resulting from the first ATT process can reach superheated temperatures (i.e. the water may be above 100"C). Further, the increase in the temperature of the water within an enclosed volume additionally results in an increase in pressure. As the temperature in the ATT system is sufficient for pyrolysis/gasification, the temperature of the water in the gaseous mixture, in some aspects related to a multiple retort system, can exceed 374°C (i.e. the critical temperature of water). Additionally, the increase in pressure can cause the pressure of the water within the gaseous mixture to exceed 22.1MPa (i.e. the critical pressure of water). In that event, the water reaches a supercritical state. This diameter and length of the piping leading from the first ATT unit 50 to the second ATT unit 53 can be chosen to cause the water within the gaseous mixture to enter a super critical state. For example, the smaller the diameter, the greater the increase in pressure within the piping.

[00271] In some aspects, a compressor is provided downstream of the first ATT unit 50, and upstream of the second ATT unit 53, to ensure that water entering the second ATT unit 53 from the first ATT unit 50 is pressurised sufficiently to be in a supercritical state.

[00272] The gaseous mixture is directed, via the hermitically sealed path into the second ATT unit 53. In the second ATT unit 53, a second ATT process occurs.

First ATT Apparatus [00273] The first ATT apparatus comprises a first ATT unit 50, a first thermally insulated housing 40 and a first heating system 52. In general, any pyrolysis and/or gasification unit having a pyrolysis region may be used as a first ATT unit 50. In a preferred aspect related to a multiple retort system, the first ATT unit 50 is a rotable cylindrical retort.

[00274] Referring to figure 30, feedstock enters the first ATT unit 50 at a first end via a feedstock input pipe 3. Preferably, the feedstock input pipe 3 includes an airlock 2 to regulate the amount air entering the first ATT unit 50. In some aspects, the feedstock input pipe 3 includes a CO, feed supply 8 to introduce CO, (carbon dioxide) between the airlock 2 and the retort. The CO2 in the feedstock input pipe 3 may be at a greater pressure than atmosphere, thereby minimising the amount of air entering the first ATT unit 50. As discussed in "An Investigation into the Syngas Production From Municipal Solid Waste (MSW) Gasification Under Various Pressure and CO, Concentration" (Kwon et al, presented at the It" Annual North American Waste-to-Energy Conference 18-20 May 2009, Chantilly, Virginia, US, Proc 17th Annual North Ammican Waste-toEnergy Conference NAWTEC17, paper NAWTEC17-2351). CO2 injection enables char reduction and produces a significantly higher proportion of CO. Additionally, CO, injection reduces the levels of Polycyclic Aromatic Hydrocarbons (PAHs), which can be directly related to tar and coke formation during an advanced thermal treatment (gasification or pyrolysis) process.

[00275] In the arrangement of Fig. 32, the first ATT unit 50 includes an inner retort 29. The inner retort 29 has holes in its surface to allow feedstock to pass from the inner retort 29 to an outer retort 26. The outer retort 26 has a larger cross-sectional diameter than the inner retort 29 thereby forming an annular cavity between the two. The inner retort 29 and the outer retort 26 are coaxial, with the inner retort 29 being located substantially within the outer retort 26 and both are substantially hollow and cylindrical in shape. The inner retort 29 may be rotated relative to the outer retort 26 by a drive motor 6. The inner retort 29 carries outward-facing vanes and the outer retort 26 carries inward-facing vanes, which act as in the above described prior art to increase the dwell time of the feedstock and char, and to mechanically break solid matter into smaller portions.

[00276] A retort exit opening is located at a second (discharge or exit) end, opposed to the first end, of the first ATT unit 50 to allow a gaseous mixture to exit the retort structure 50. The gaseous mixture contains syngas but, if the ATT process in the first ATT unit 50 is not efficient, can also contain comprising tars, oils and PAHs. Additionally, if the feedstock included a moisture content, the gas mixture will include water vapour. The retort exit opening is connected to inter unit piping 56 that connects to the input end of a second ATT unit 53, thereby fanning a hermetically sealed gas path between the first and second ATT units. In some aspects, the inter unit piping may be connected to the first ATT unit 50 via another system of piping, or other device, such as a booster fan to impel the gaseous mixture along the inter unit piping 56 or a compressor to increase the pressure of the gaseous mixture before it is input into the inter unit piping 56.

[00277] The interior of the first thermally insulated housing 40 is heated by a first heating system 52. That first heating system comprises at least one heat source 51. As shown in figure 31, the heat source 51 directs heated air into the interior of the thermally insulated housing 40, but the interior of the retort 50 is isolated from the remaining interior of the thermally insulated housing 40.

[00278] In the preferred aspect related to a multiple retort system, as shown in figure 34, the first heating system 52 comprises three heat sources 51 external to a first thermally insulated housing 40, and spaced along the length of the first ATT unit 50. In some aspects, the heating sources 51 comprise burners. The heating sources 51 may be at different temperatures. In the preferred aspect related to a multiple retort system, the heat source 51 nearest the feedstock input hopper 1 is the hottest. As the feedstock is the coldest on entry into the retort 50, the retort 50 will be coldest near the feedstock input hopper 1. Accordingly, it is advantageous to locate the hottest heat source 51 proximate the feedstock input hopper end of the retort 50 in order to minimise any potential temperature gradient along the length of the retort 50.

[00279] The first thermally insulated chamber 40 includes an exhaust pipe 7. As the heat source 51 provides more heated air to the interior of the first thermally insulated housing 40, exhaust is emitted. In the preferred aspect related to a multiple retort system, as shown in figures 30 and 34, the exhaust is directed from the exhaust pipe 7 of the first thermally insulated housing 40 to the interior of the second thermally insulated housing 1040 by an exhaust duct 59. Accordingly, air heated by the heat sources 51 of the first ATT unit 50 is used to heat the second ATT unit 53. The heat sources 57 of the second ATT apparatus do not, therefore, need to provide as much heat as the heat sources 51 of the first ATT apparatus. The heat sources 57 of the second ATT apparatus may, in some aspects, be 'top-up' heat sources.

Second ATT Apparatus [00280] The inter unit piping 56 is connected to an input pipe 54 to the second ATT unit 53. In the preferred aspect related to a multiple retort system, the second ATT unit 53 is a cylindrical retort. The second ATT unit 53 is similar to the first ATT unit 50, and corresponding elements are not repeated.

[00281] The gaseous mixture from the first ATT unit 50 passes through the hermetically sealed gas path (inter unit piping 56 and input pipe 54) and enters the second ATT unit 53 through a bearing 55 of the second ATT unit 53. In the arrangement shown in figures 30 and 34, for example, an input tube 54, connected to the inter unit piping 56, extends into the second ATT unit 53. The gaseous mixture is therefore directed into the centre of the second ATT unit 53.

[00282] In the preferred aspect related to a multiple retort system, inter unit piping 56 is connected to the input tube 54, which may also be connected to a feedstock input pipe 103 of the second ATT unit 53, and contain an auger 1037. That input tube 54 may be a perforated tube. The input tube 54 therefore functions similarly to the substantially horizontal pipe 27 of the first ATT unit 50, albeit with input tube also housing gaseous mixture from the first ATT unit 50. Similarly to the first ATT unit 50, the feedstock input pipe 103 of the second ATT unit 53 may include an airlock 102, a CO2 input pipe 108 and a feed hopper 101.

[00283] The feedstock for the second ATT unit 53 may be different from the feedstock for the first ATT unit 50. For example, whereas feedstock for the first ATT unit 50 may be largely untreated (other than to ensure it is physically the correct size to fit in the ATT unit 50), feedstock for the second ATT unit 53 may be pre-sorted or dried to improve the quality of syngas exiting the second ATT unit 53. In other aspects, the same feedstock can be used in both the first ATT unit 50 and the second ATT unit 53.

[00284] Conventionally, a heated retort is only heated from the outside. This creates a temperature gradient, where the greatest temperature is at the surface of the retort and the lowest temperature is toward the axis of the retort. This leads to a cooler area toward the axis of the retort, where the temperature may not be sufficient for an ATT process despite the average temperature of a retort being sufficiently high to pyrolyse or gasify feedstock. Advantageously, the gaseous mixture in the preferred aspect related to a multiple retort system acts as a heat source along the axis of the second ATT unit 53, thereby raising the lowest temperature of the temperature gradient. As a result, the average temperature inside the second ATT unit 53 is higher and there is an increased probability of gas at the centre of the retort 53 being broken down.

[00285] If the feedstock input into the first ATT unit 50 contained moisture, the gaseous mixture also includes superheated steam, or super critical water. Accordingly, the ATT process in the second ATT unit 53 takes place in the presence of superheated steam or super critical water, thereby increasing the production of high energy gases (such as methane), whilst reducing the amount of char. Additionally, organic matter, including volatile organic compounds (VOCs), can be converted into syngas.

1002861 It will be appreciated that, in other aspects related to a multiple retort system, the second ATT unit 53 is not a cylinder, but a heated gaseous mixture from a first ATT unit 50 may still enter the second ATT unit 53 raising the average temperature therein.

[00287] The second ATT unit 53 is constructed from a different material than the first ATT unit 50 in some aspects. For example, in some aspects, courser material is used as feedstock for the first ATT unit 50 that the second ATT unit 53. The material used to construct the first ATT unit 50 must therefore be more durable than the material used to construct the second ATT unit.

[00288] The second ATT unit 53 may he constructed of a material having higher thermal conductivity than the material used to construct the first ATT unit 50. Less heat is therefore required to produce a pyrolysis process in the second ATT unit 53. When the exhaust from the first thermally insulated housing 40 is directed to the interior of the second thermally insulated housing 1040, as shown in figure 30, the heat sources 57 of the second ATT apparatus are used to 'top-up' the heating provided by the exhaust from the first thermally insulated housing 40 (i.e. the heat sources operate at a reduced capacity), thereby creating a more efficient ATT system as a whole. For example, in some aspects the first heating system 52 can provide air heated to between 1100°C and 1600°C. The exhaust directed to the second ATT apparatus can be at temperature of 800°C to 900°C. If the second ATT unit 53 has a higher thermal conductivity, the temperature of the exhaust from the first ATT apparatus may be sufficient to heat second ATT unit 52 such that the interior of the second ATT unit is at a temperature sufficient for an ATT process (pyrolysis or gasification process). The second heating system 58 can be used to provide additional heat to supplement that provided by the exhaust.

[00289] In the arrangement shown in figure 34, the number of heat sources 51 in the first heating system 52 and the number of heat sources 57 in the second heating system 58 is shown as being the same for illustrative purposes. In some aspects, the second heating system 58 has fewer heat sources 57 than the first heating system 52.

[00290] The number of heating units in the first and second heating systems does not have to be the same. For example, the second heating system may contain more heating units if it is desirable that the second ATT unit 53 operates at a higher temperature than the first ATT unit 50.

Second aspect relating to a mulitple retort system [00291] In the first aspect related to a multiple retort system, two ATT units (pyrolysis or gasification units) were provided. In the second aspect related to a multiple retort system, more than two ATT units are provided. Figures 35 and 36 show an arrangement having a third ATT apparatus, including a third ATT unit 60, a third thermally insulated housing 2040, and a third heating system 63. The third heating system 63 is shown as having three heat sources 61, but one or more heat sources 61 may be provided.

[00292] The first and second ATT apparatuses of the second aspect related to a multiple retort system are the same as the first and second ATT apparatuses of the first aspect related to a multiple retort system. It will be noted, however, that an exhaust pipe 107 of the second ATT apparatus (not shown in figures 30 and 34) is connected to a second exhaust duct 64 to direct exhaust from the second ATT apparatus to the interior of the third thermally insulated housing 2040. Second inter unit piping 66 connects the second ATT unit 53 to the input pipe 2054 to the third ATT unit 60. Accordingly, the hermetically sealed gas path extends from the first ATT unit 50 to the third ATT unit 60.

[00293] It will be appreciated that still further ATT units can be provided. For example, an arrangement with four ATT units is envisaged. Further exhaust ducts and inter unit piping is provided for the ATT apparatuses that include those still further ATT units. It will be appreciated that the hermetically sealed gas path will extend from the first ATT unit to the final ATT unit.

[00294] In some arrangements, the size of the ATT units may increase from the first ATT unit to the last ATT unit. Figure 37 shows an arrangement in which the diameter of three consecutive cylindrical retorts increases from the first to the third retort. An initial pyrolysis process occurs in the first retort 50 which can create a gaseous mixture with a temperature of between 350°C and 1000°C (preferably in the range 900°C to 1000°C). That gaseous mixture is then provided to middle of the second retort 53. Accordingly, heat is transferred into the second retort 53 from two directions; firstly, the surface of the retort 53 is externally heated by the heating system 58 and the exhaust from the first ATT apparatus via the exhaust duct 59 and, secondly, from the gaseous mixture input from the first retort 50. The diameter of the second retort may therefore be increased in size without having a cooler region, in which the temperature is not sufficient for an ATT process, inside the second retort 53 that conventionally occurs from only externally heating a retort.

[00295] When a third retort 60 is provided, as shown in figures 35 and 36, the diameter of the third retort 60 may be larger than the diameter of the second retort 53, as shown in figure 37. The gaseous mixture entering the third retort 60 has now been heated in the first and second retorts. The temperature of the gaseous mixture entering the third retort 60 will, on average, be higher than the temperature of the gaseous mixture entering the second retort 53. Accordingly, the temperature provided by the gaseous mixture near the axis of the third retort 60 is greater, meaning the diameter of the third retort 60, which is also externally heated by the third heating system 62, can be larger than the diameter of the second retort 53 without having the cooler region, in which the temperature is not sufficient for an ATT process, inside the third retort 60.

[00296] The hermetically sealed gas path may include a portion located proximate to the exterior surface, and extending along the length, of the first ATT unit 50. For example, when the first ATT unit 50 is a rotable retort, a system of piping 28 may extend from the second end of the first ATT unit 50, and along the length of the first ATT unit 50. In some aspects, the system of piping 28 may include several pipes extending along the length of the first ATT unit 50, or one pipe that extends along the length of the first ATT unit 50 several times. As the system of piping 28 has a smaller cross section than the first ATT unit 50, the average temperature within the system of piping 28 is higher than the average temperature in the first ATT unit 50. Accordingly, a further ATT process may occur within the system of piping 28 proximate to the exterior surface of the ATT unit. Additionally, if the hermetically sealed gas path extends along the length of the first ATT unit 50 several times, the dwell time of the gaseous mixture in the system of piping 28 is increased, thereby increasing the chances of hydrocarbons cracking, which results in a reduction of PAHs, tars and oils.

[00297] In an alternative aspect, the first and second ATT units may be located within the same thermally insulated housing 40, together with the hermetically sealed gas path, to reduce the number of heating units required to heat both the first and second ATT units.

[00298] If the first and second ATT units are located within a single thermally insulated housing 40, a single heating system 52 may be used to heat both ATT units.

ASPECTS RELATING TO TIIE TEMPERATURE PROFILE IN AN ATT UNIT

[00299] In accordance with the present aspect, there is provided a pyrolysis method comprising applying heat from a heat source to a first region to cause a first pyrolysis process, the first pyrolysis process resulting in a gaseous mixture; applying heat from the heat source to a second region to cause a second pyrolysis process, the second pyrolysis process being applied to the gaseous mixture; wherein the second region is located closer to the heat source than the first region.

1003001 In accordance with the present aspect, there is provided a gasification method comprising applying heat from a heat source to a first region to cause a first gasification process resulting in a gaseous mixture; applying heat from the heat source to a second region to cause a second gasification process to the gaseous mixture; wherein the second region is located closer to the heat source than the first region.

[00301] In accordance with the present aspect, there is provided a pyrolysis apparatus comprising a first region; a second region; and a heat source being positioned such that, when operated the heat source heats the first region to cause a first pyrolysis process, the first pyrolysis process resulting in a gaseous mixture, and the heat source heats the second region to cause a second pyrolysis process, the second pyrolysis process being applied to the gaseous mixture; wherein the second region is located closer to the heat source than the first region.

[00302] In accordance with the present aspect, there is provided a gasification apparatus comprising a first region; a second region; and a heat source being positioned such that, when operated the heat source heats the first region to cause a first gasification process, the first gasification process resulting in a gaseous mixture, and the heat source heats the second region to cause a second gasification process, the second gasification process being applied to the gaseous mixture; wherein the second region is located closer to the heat source than the first region.

[00303] Due to the proximity to the heat source, the second regions will be hotter than the first regions. The pyrolysis and gasification processes that occur in the second region act on a gaseous mixture that has already undergone a first ATT process. Accordingly, the hydrocarbons remaining in the gaseous mixture will be more difficult to break down, and therefore require a higher temperature. The present aspect is therefore advantageous, as thermal energy in the second regions is not absorbed by hydrocarbons that are relatively easy to breakdown, and the heat is instead absorbed by hydrocarbons that are relatively difficult to breakdown, and therefore require higher temperatures to breakdown. Further, as the differing temperatures are provided by the same heat source, the aspect provides a more efficient ATT apparatus and method.

[00304] Some aspects comprise applying heat from the heat source to a third region to cause a third pyrolysis process, the third pyrolysis process being applied to the gaseous mixture; wherein the third region is located closer to the heat source than the first region and the second region is located closer to the heat source than the third region. The third region may be longer than the first region and the second region. During operation of the ATT apparatus, the dwell time in the third region is longer than the dwell time in the first region and longer than the dwell time in the second region. A longer dwell time increases the chances of hydrocarbons cracking as heat is applied to the hydrocarbons for longer. This further reduces the proportion of hydrocarbons that are relatively easy to break down before the gaseous mixture enters the second, hotter, region.

[00305] Some aspect comprise applying heat from the heat source to a third region to cause a third gasification process, the third gasification process being applied to the gaseous mixture; wherein the third region is located closer to the heat source than the first region and the second region is located closer to the heat source than the third region.

[00306] In sonic aspects, the first region is a rotable retort and the second region is a gas enclosure, wherein the gas enclosure is located proximate the heat source.

[00307] Sonic aspects comprise a heating system including the heat source and a thermally insulated chamber. In some aspects, the second region is located within the thermally insulated chamber.

[00308] The present aspect generally relates to multiple ATT stages using a single heating system. Some aspects include two ATT stages. A first ATT stage is used to convert feedstock into a gaseous mixture and char. A second ATT stage occurs at a significantly higher average temperature to reduce the amount of residual oils, tars and PAHs in the gaseous mixture. Each of the first and second ATT stages are heated by the same heating system. It will be appreciated that, in other aspects, the aspect is not limited to two ATT stages, and three or more ATT stages are possible.

Fir, t preferred aspect [00309] Referring to figures 38 and 39, an ATT apparatus comprises at least an ATT unit 50 located within a thermally insulated housing 40, and a heating system 52 for heating the interior of the thermally insulated housing 40.

[00310] The ATT unit 50 in figures 38 and 39 is shown as a cylindrical retort (or 'kiln') 50, however, any ATT unit 50 having a pyrolysis or gasification region can be used. For example, in the retort 50 shown in Figs. 38 and 39, a burner 51 directs heated air toward the surface of the retort 50, thereby creating a pyrolysis region in the retort as the temperature of the retort surface rises. As shown in figure 38, the first ATT unit 50 includes an inner retort 29. The inner retort 29 has holes in its surface to allow feedstock to pass from the inner retort 29 to an outer retort 26. The outer retort 26 has a larger cross-sectional diameter than the inner retort 29 thereby forming an annular cavity between the two. The inner retort 29 and the outer retort 26 are coaxial, with the inner retort 29 being located substantially within the outer retort 26 and both are substantially hollow and cylindrical in shape. The inner retort 29 may be rotated relative to the outer retort 26 by a drive motor 6. The inner retort 29 carries outward-facing vanes and the outer retort 26 carries inward-facing vanes, which act as in the above described prior art to increase the dwell time of the feedstock and char, and to mechanically break solid matter into smaller portions.

[00311] The heating system 52 comprises at least one a heat source 51 and, in some aspects, a thermally insulated chamber 15. The heating system 51 may comprises a plurality of heat sources 51. For example, in some aspects, the heating system comprises three heat sources external to a thermally insulated housing 40, and spaced along the length of an ATT unit 50.

[00312] In some aspects, the heating sources 51 are burners that emit hot air into the inside of a thermally insulated chamber 15. As shown in figures 38 and 39, the thermally insulated chamber 15 has an exit aperture leading to the inside of a thermally insulated housing 40 in which the ATT unit 50 is located; with the atmosphere inside the ATT unit 50 being isolated from the atmosphere inside the thermally insulated housing 40 but external to the ATT unit 50. In other aspects, the thermally insulated chamber IS may be omitted from the heating unit, and the heat source 51 may directly heat the inside of the thermally insulated housing 40.

1003131 The preferred heating system 52 can operate at between 1250°C and 1600°C. Those temperatures are capable of heating the ATT unit 50 and the system of piping 28 to between 800°C and 1000°C (for example, 850°C, and the gas enclosure 17, 22 to between 1000°C and 1300°C (for example, 1200°C). The ATT unit 50 therefore forms a first pyrolysis or gasification region. It will be appreciated that in an arrangement having more than one heat source 51, the heat sources 51 may be at different temperatures, although each heat source 51 can operate within the temperature range of 1250°C to 1600°C.

[00314] When more than one heat source 51 is provided in the heating system 52, the heat source 51 nearest the feedstock input hopper 1 is the hottest. As the feedstock is the coldest on entry into the retort 50, the retort 50 will be coldest near the feedstock input hopper 1. Accordingly, it is advantageous to locate the hottest heat source 51 proximate the feedstock input hopper end of the retort 50 in order to minimise any potential temperature gradient along the length of the retort 50, and also to avoid inefficient use of the burners. Further, reducing the operating temperature of a heat source 51 requires less fuel. For example, the heat source 51 nearest the feedstock input hopper 1 may be at 1500°C, and the other two heat sources 51 operate at 1250°C.

1003151 Some aspects include a gas enclosure 17, 22 hermetically connected to the ATT unit 50. The gas enclosure 17, 22 is preferably located in the thermally insulated chamber 15 of the heating system 52. Preferably, the gas enclosure 17, 22 is located between the heat source (burner) 51 and an exit aperture leading to the interior of the thermally insulated housing 40 of the ATT unit 50. As the heat source 51 heats the inside of the thermally insulated housing 40, therefore, it also heats the gas enclosure 17, 22. In some aspects, the gas enclosure 17, 22 can be located proximate the heat source 51 such that the gas enclosure 17, 22 is at approximately the same temperature as the heat source 51. Hence, the gas enclosure 17, 22 can operate in a temperature range of 1250°C to 1600°C. Accordingly, the gas enclosure 17, 22 forms a second pyrolysis or gasification region.

1003161 The gas enclosure 17, 22 is connected to a syngas extraction pipe (not shown) to allow gaseous mixture to be collected once it has passed through each of the ATT stages. At this point, the gaseous mixture will include a higher percentage of syngas than a conventional ATT apparatus. If additional cleaning is required, the gaseous mixture can be fed into a wide diameter pipe, via which it passes to a second heat recovery steam generator (HRSG) 45, in which it is passed via pipes through a boiler to generate steam used to drive the steam turbine, as shown in figure 41. After being thus cooled, it is passed to a scrubber of conventional type which extracts impuiities such as water vapour, metals, and other impurities and dust.

[00317] The scrubbed gas then passes through a hydrogen separator of conventional type which separates out hydrogen for use as a fuel for one or both of the cyclone furnaces. Finally, CO, is extracted by a CO-, separator of conventional type. The extracted CO, is recycled to the air lock.

[00318] The syngas (consisting of ethane, methane, and other relatively short hydrocarbons as well as some CO) is then passed to a gasometer, and (via the gasometer or if the latter is empty, directly) to a gas turbine engine driving a second electrical generator. The engine may be a General Electric (GE) Jensbacher engine, which burns gases such as ethane and methane, without too much hydrogen content. The stored syngas not thus used to generate electricity can be sold as a fuel, and vice versa.

First ATT Stage [00319] A first pyrolysis or gasification (ATT) process occurs at the first stage 72.

[00320] At the first ATT stage 71, feedstock is converted into a gaseous mixture and char in the ATT unit 50. The ATT unit 50 may be any pyrolysis or gasification device, such as a rotable retort or an upright static retort. In the preferred arrangement, the ATT unit 50 is a rotable retort 50. However, it will be appreciated that the rotable retort may be substituted for other ATT units.

[00321] hi the first ATT stage 71, feedstock is broken down into a gaseous mixture and char. The gaseous mixture contains syngas, but will also contain residual particulates (such as oils, tars and PAHs). The gaseous mixture is then directed toward the system of piping 28. In some aspects, where the ATT unit 50 is a rotable retort 50, the gaseous mixture exits the ATT unit 50 at a gas exit aperture, which is connected to a system of piping 28. The gaseous mixture may be impelled to travel through the system of piping 28 by a booster fan 18.

[00322] The temperature inside the retort 50 depends on a number of factors, such as the material from which the retort 50 is constructed, the size (diameter and length) of the retort 50, the heat from the heating system 52, and the amount/type of feedstock. In some aspects, temperature in the retort 50 is in the range 450°C to 750°C. More preferably, the temperature in the retort 50 is in the range 700°C to 750°C.

Second ATT stage [00323] A second pyrolysis or gasification (ATT) process occurs at the second stage 73.

[00324] The second ATT stage 73 occurs within the gas enclosure 17, 22, and is at a higher temperature than either the first ATT stage 71. To achieve this, the gas vessel is located closer to the heat source than the system of piping 28 or the ATT unit 50. Preferably, the gas enclosure 17, 22 is located in the heating system 52. In aspects where a thermally insulated chamber 15 is provided, the gas enclosure 17, 22 may be located within that chamber 15. For example, the gas enclosure 17, 22 may be located between a heat source 51 and an exit aperture.

1003251 In some aspects, the gas enclosure 17, 22 is a gas conduit 22, having a diameter far less than the retort 50. In some aspects, the gas conduit has a diameter of between 5 and 10 cm (for example, 6.3 cm or 2.5 inches). As shown in figure 38, for example, the gas conduit 22 may be located in a thermally insulated chamber 15 and heated by the heat source 51. The gas conduit 22 is located closer to the heat source than the system of piping 28 or the ATT unit 50. Accordingly, the gas conduit 22 experiences higher temperatures from the heat source 51 than either the system of piping 28 or the ATT unit 50.

1003261 When the surface of an enclosure is externally heated, a cool region forms near the centre due to the drop off in radiative and convective heat transfer from the surface. In a cylinder, the cool region generally forms at or near the axis of the cylinder. If the same heating is applied to a cylinder with smaller diameter, the average temperature inside the smaller diameter cylinder will be greater than in a larger diameter cylinder due to that drop off in radiative and convective heat transfer.

1003271 In the gas conduit 22, however, due to the higher temperature and the smaller diameter, the average temperature within the gas conduit 22 will be higher than within either the system of piping 28 or the ATT unit 50. The temperature of the gas conduit 22 can be between 1000°C and 1600°C, for example at 1250°C or 1500°C.

1003281 In other aspects, the gas enclosure may be another type of gas vessel 17 located proximate the heat source 51. As shown in figure 39, a gas vessel 17, which may be a box, for example, is located near a heat source 51. Such aspects therefore utilize the high temperatures associated with the proximity of the gas vessel to the heat source 51, rather than the combination of the higher temperatures and the small diameter of a gas conduit 22.

1003291 The intended temperature for the gas enclosure 17, 22 will have an effect on the construction material. The gas enclosure 17, 22 can be made out of nickel alloy or stainless steel for most temperatures within the above ranges. However, an enclosure 17, 22 designed to operate at temperatures between 1500°C and 1600°C would preferably be made of titanium or an alloy thereof.

Temperature Profile [00330] As desciibed above, multiple ATT stages can be heated by a single heating system 52, with those ATT stages at different temperatures. As shown in figure 40, the temperature applied to feedstock/a gaseous mixture increases with each successive stage. In this regard, the first ATT stage 71 is at the lowest temperature, whereas the second (final) ATT stage 73 is at the highest temperature.

[00331] It is noteworthy that the gas path flows in the opposite direction to the heated air from a heat source 51. For example, the heated air from the heat source 51 will be hottest when it is initially emitted (i.e. at the heat source 51), and coolest when it leaves the thermally insulated housing 40 of the ATT apparatus (i.e. the heated air cools as it moves away from the heat source 51). The gaseous mixture, on the other hand, follows a gas path that is generally directed toward the heat source 51. Accordingly, the hottest ATT stage 73 is at the end of the gas path. In this way, hydrocarbons that are relatively easy to break down are not present in the gaseous mixture when the gaseous mixture is at the hottest stage (i.e. the final ATT stage). Accordingly, thermal energy in the hottest stage is not absorbed by hydrocarbons that are relatively easy to breakdown, and the heat is instead absorbed by hydrocarbons that are relatively difficult to breakdown, and therefore require higher temperatures to breakdown.

luSec nd Preferred Aspect 1003321 The first group of aspects includes a first and a second ATT stage. The second group of aspects additionally includes a third ATT stage in between the first and the second ATT stage from the first group of aspects.

1003331 Referring to figures 42, 43 and 45, in the second group of aspects, the ATT apparatus of the first group of aspects includes a system of piping 28 connected in between the gas exit aperture of the ATT unit 50 and the gas enclosure 17, 22 of the first group of aspects. A gaseous mixture resulting from the first ATT process in the ATT unit therefore travels along the system of piping 28 before entering the gas enclosure 17, 22.

[00334] The system of piping 28 extends along the length of the ATT unit 50 and comprises a plurality of straight lengths with curved connecting portions in between. Each of the straight lengths is positioned parallel, or substantially parallel, with the axis of the ATT unit 50. Thus, the total length of the system of piping 28, including each of the straight portions and the curved connecting portions, is many times the length of the ATT unit 50. The dwell time for a gaseous mixture within the system of piping 28 is therefore longer than the dwell time inside the ATT unit 50.

[00335] The system of piping 28 is located within the thermally insulated housing 40 along with the ATT unit 50. As shown in figures 42 and 43, both the rotable retort 50 and the system of piping 28 are heated by the same heating system 52. The temperature applied to the rotable retort 50 and the system of piping 28 will therefore be approximately the same.

[00336] When the ATT unit 50 is a rotable retort, the diameter of the system of piping 28 will be smaller than the diameter of the retort 50. In some aspects the system of piping 28 has a diameter of 10cm, whereas a retort 50 may have a diameter of between 1.4m and 2m. Due to the smaller diameter, the average temperature in the system of piping 28 will therefore be greater than die average temperature in the retort 50. Accordingly, the system of piping 28 forms a third ATT region, in which a third ATT process occurs on a gaseous mixture resulting from the first ATT process in the ATT unit 50.

[00337] In some aspects, as shown in figure 42, the system of piping 28 is at least in part closer to the heat source 51 than the rotable retort 50. Having the system of piping 28 surrounding die retort 50, as shown in figure 42, allows the system of piping 28 to be heated by the hot air from the heat source 51 as that hot air circulates around the retort 50 inside the thermally insulated housing 40.

1003381 In other aspects, the entirety of the system of piping 28 is closer to the heat source 51 than the rotable retort 50, thereby placing die system of piping 28 at a higher temperature than the rotable retort 50.

[00339] In some aspects, as shown in figure 43, the system of piping 28 is further from the heat source 51 than the rotable retort 50. This can make manufacturing and maintenance simpler by making the system of piping 28 more accessible.

Third ATT stage 1003401 A third pyrolysis or gasification (ATT) process occurs at the third stage 72.

1003411 The third ATT stage 72 occurs in a system of piping 28, which has a smaller diameter than the rotable retort (ATT unit). For example, the system of piping 28 in some aspects has a diameter of 10cm, whereas a retort 50 may have a diameter of between 1.4m and 2m.

1003421 As the system of piping 28 and the ATT unit 50 are heated externally, the interior of those vessels is heated by convection and radiation from a heated wall of the respective vessel. Hence, the temperature inside the system of piping 28 and the ATT unit 50 has an inverse relationship with the distance from the respective vessel's walls.

[00343] In the preferred aspect, both the rotable retort 50 and the system of piping 28 are heated by the same heating system 52. The temperature applied to the rotable retort 50 and the system of piping 28 will therefore be approximately the same. As the system of piping 28 has a smaller diameter than the rotable retort (ATT unit) 50, however, the temperature at the centre of the system of piping 28 is greater than the temperature at the centre of the ATT unit 50, and the average temperature of the third ATT stage 72 is greater than the average temperature of the first ATT stage 71, but less than the average temperature of the second ATT stage 73. This can be seen in figures 42 and 43.

[00344] Preferably, the system of piping 28 has a cross-sectional diameter much smaller than the retort structure, for example four inches (approximately 10cm). The system of piping 28. in some aspects, is made out of nickel alloy, although other materials, such as stainless steel and titanium can be used depending on circumstances.

1003451 More advantageously, the system of piping 28 in the preferred aspect is many times the length of the ATT unit, and so the dwell time of the gaseous mixture is increased, as seen in figures 42 and 45. Accordingly, the longer-chain hydrocarbons (associated with tar and oil retention) and/or other residual particulates in the gaseous mixture are more likely to be broken down.

[00346] Subsequent to the third ATT stage 72, the gaseous mixture is directed toward a gas enclosure 17, 22 located proximate or within the heating system 52. In the preferred arrangement, the end of the system of piping 28 that is not attached to the gas exit aperture is connected to the gas enclosure 17, 22, which is within the heating system 52.

[00347] The temperature within the system of piping 28 will depend on. for example. the diameter of the system of piping 28, the heat supplied from the heating system 52, and the temperature of the gaseous mixture from the ATT unit 50. It is envisaged, however, that the temperature within the system of piping 28 is in the range 700°C to 1000°C. Preferably, the temperature within the system of piping 28 is in the range 850°C to 1000°C.

Temperature profile 1003481 Referring to figure 44, the temperature profile of the second group of aspects includes an additional step to account for the third ATT stage 72. The third stage 72 is preferably longer than the first and second stages, thereby providing a longer dwell.

[00349] It will he appreciated that a more efficient ATT method and apparatus can he achieved without each of the ATT stages mentioned in the preferred aspect. For example, the gaseous mixture may be directed from the ATT unit 50 to the gas enclosure 17,22 without first entering a system of piping 28, thereby omitting the second ATT stage. The ATT apparatus will still, however, apply the first ATT process and the, hotter, third ATT process using the same heating system. Accordingly, a greater proportion of hydrocarbons will be broken down in comparison to a conventional system where simply a gasification or pyrolysis apparatus is heated by a heating system.

ASPECTS RELATING TO A FLAT PYROLYSIS SURFACE

[00350] The present group of aspects aims to improve the efficiency of the pyrolysis process. The present inventors propose to do so by increasing the surface area of the retort for contacting the feedstock.

[00351] In the above prior art, the feedstock will still be impelled, by gravity, to the bottom of the retort where the feedstock will pile up. When the feedstock piles in this manner, it reduces the surface area available for heating. Additionally, the feedstock toward the centre of the pile will be insulated. Accordingly, heating efficiency is reduced. Providing vanes may help disperse the feedstock over a greater proportion of the interior surface of the retort. However, the feedstock will still collect where the vanes meet the interior surface. Moreover, the feedstock will not remain in contact with the interior surface of the retort during an entire revolution of the retort.

[00352] An aspect is a pyrolysis structure at least part of which is constructed of a flat sheet of high thermal conductivity material explosively welded to a high temperature strength framework. The high thermal conductivity material is preferably a non-transition metal, very preferably relatively pure copper (but alternatively silver). The high temperature strength framework may be made from a nickel alloy.

[00353] The structure of the present aspect thus has the thermal conductivity characteristics of copper (which is of the order of 30 times that of Nickel alloys) along with the high temperature strength of a nickel alloy framework, which has the mechanical strength lacked by the copper at elevated pyrolysis temperatures.

[00354] Although the thermal coefficients of expansion of the high thermal conductivity material sheets may differ from those of the high temperature strength framework, which would lead to differential expansion stresses as the structure is heated and cooled in use over a range of several hundred degrees, and despite a hostile environment which includes steam, gases, tars and unknown contaminants, the explosive welding process has been found to maintain a reliable join. Explosive (or explosion) welding (or bonding) was first described in US3140539 (Holtzman).

[00355] Accordingly, as the thermal conductivity through the structure is higher, there is a lower temperature drop between the outside (which is where heat is applied) and the inside (which is where pyrolysis occurs), so that a lower temperature can be applied to the structure in order to heat a calorific material to a temperature sufficient for pyrolysis, or a shorter dwell time (and hence higher volume throughput of waste material and higher generation rate of syngas) can be achieved for the same temperature.

[00356] In conventional stainless steel or nickel alloy retort structures, a high temperature applied to one location of the retort structure by a heating system would not necessarily be transferred throughout the retort structure, and therefore to the feedstock, due to the low conductivity of the construction materials. There are thus temperature gradients within the retort: firstly, along its length from the point where the heating system is coupled to the retort, and secondly, radially from the outside of the retort where the heat is applied to the inside where the feedstock is located. The faster the transit speed of material through the retort, the steeper the radial temperature gradient across the retort and hence the higher the temperature which must be applied by the heating system in order to reach a given pyrolysis temperature of the feedstock. Not all of the large amount of applied heat required can readily be recovered, reducing the thermal efficiency of the process.

[00357]However, the materials with the highest thermal conductivity -relatively pure copper, silver and (to a lesser extent) gold -cannot be used because their mechanical strength at the high temperatures required for pyrolysis is too low, and/or their creep and/or fatigue resistance is insufficient, for long-term use with solid waste materials. Attempts to strengthen these materials by alloying reduce their thermal conductivity to varying degrees, with the very additives which most improve the strength tend also to most degrade the thermal conductivity. Silver, for example, dissolves well in copper and thus degrades conductivity less than other elements, but offers relatively little improvement in strength.

[00358] Strengthening by modifying the microstructure would be ineffective because pyrolysis takes place typically above the annealing temperature of copper (around 400 degrees Kelvin). Thus, to the inventors' knowledge, copper has hitherto not been used as a pyrolysis surface.

[00359] Using the high thermal conductivity of copper allows the present aspect of the group of aspects to efficiently equalise temperature applied to the retort structure throughout the entire retort structure. Accordingly, the temperature applied to the outside of the retort structure by the heating system does not have to be as great in order to transfer a sufficient temperature for pyrolysis to the feedstock.

[00360] The use of copper also improves the local heat distribution within the retort structure, and therefore reduces temperature variation across the retort structure. This, in turn, lowers the onset of -hotspots" along the surface of the retort structure beneath the points where the relatively cool feedstock sits. In addition to these advantages, the pyrolysis process in the retort structure may be further improved. For example, the gas produced may include Syngas combined with particulate matter and tar. Conventional units may send this gas to be cleaned or purified.

[00361] Advantageously, the present group of aspects can reduce the amount of waste going to landfill, and convert waste into useful end products. For example, char produced may be useful as a secondary fuel for the heating system.

[00362] Waste processed by the present group of aspects can be converted into Syngas and vitrified slag. The Syngas can then be used to produce electricity (as described above) and the vitrified slag can be used in the construction industry. The process redirects waste from landfill; also an existing landfill site may be mined to provide feedstock. Moreover, the amount of recyclable waste being used as feedstock can be reduced as the present group of aspects is capable of processing a vast range of feedstock as the process is not fuel specific. Additionally, it is an object of the present group of aspects to be capable of processing hazardous waste, by utilising corrosion resistant materials.

[00363] Additionally, some aspects of the present group of aspects are able to deal more effectively than conventional pyrolysis apparatus and techniques with the hydrocarbons associated with the retention of tar and oil thereby obviating the need for an oil refinery.

[00364]The heat provided for the process is preferably from calorific waste (of a homogenous consistency) with the resultant char generated by the process being utilised as a secondary fuel source. The use of this fuel type enables the correct energy balance within the process to be maintained. The volumes of the resultant char would sometimes be insufficient for use as the primary fuel because feed stock types can produce both varying and minimal volumes of char. Additionally, in some cases it may be desired to sell the char as a fuel product for use elsewhere.

1003651 A pyrolysis apparatus 1 according to a preferred group of aspects of the present invention is shown in Fig. 46, and comprises a chain drive 4 to transport feedstock from one end of a first heating chamber 2 to a second end, opposed to the first end, of a first heating chamber 2. The chain drive 4 is located below an upper heating plate (first thermally conducting plate) 5, and surrounds a lower heating plate (second thermally conducting plate) 6. The chain drive 4 is described in more detail below.

[00366] A second heating chamber 3 is atmospherically separated from the first heating chamber 2 by the upper heating plate 5. This can be seen in Fig. 47. The first and second heating chambers 2, 3 being sealed so as to prevent, or substantially prevent, gas from travelling from one chamber 2, 3 to the other 2, 3. Both the first heating chamber 2 and the second heating chamber 3 may be contained within a single insulated housing 7.

First Heating Chamber 1003671 One horizontal face of the first heating chamber 2 is defined, at least in part, by the upper heating plate 5. A lower heating plate 6. being longer than the upper heating plate 5, is positioned within the first heating chamber 2 parallel to the upper heating plate 5. The upper and lower heating plates 5,6 arc placed 10 inches (25cm) apart or less (for example, 8 inches or 20 cm), defining a heated area therebetween. The heater zone above and below the upper heating plate 5 may be termed a primary heat zone 23.

[00368] A chain drive 4 is positioned around the lower heating plate 6, such that a portion of the chain drive 4 is within the heated area. The portion of the chain drive 4 within the heating area is located closer to the lower heating plate 6 than the upper heating plate 5.

[003691 An input section is positioned to deliver feedstock onto the chain drive 4. The chain drive 4 is operable to transport feedstock through the heated area, and away from the input section.

1003701 In use, the upper and the lower heating plates 5, 6 may reach 900°C or above. Typically, the upper and the lower plates 5, 6 arc at 850°C during operation. Due to the proximity of the upper and lower plates 5. 6, the heated area therebetween is at a temperature similar to the temperature of the heating plates 5, 6 themselves. Accordingly, the heated area between the upper and lower heating plates 5, 6 may be at 800"C-900t. It will be appreciated that a temperature gradient will exist between the plates, and that direct contact with feedstock will create a cooler area on a heating plate, even if only temporarily.

[00371] As the feedstock is moved away from the input section it is dragged along the lower heating plate 6 and is heated by the heating plate 6 mostly through conduction, although some convection and radiation from the lower heating plate 6 will also occur. The feedstock is also heated by the upper heating plate 5 by convection and radiation. The heated feedstock eventually pyrolyscs whilst in contact with the lower heating plate 6, and releases gas. The released gas may be a combination of syngas, particulate matter and tar. This pyrolysis of the initial feedstock can be considered a first pyrolysis process.

[00372] The gas is initially released within the heated area between the upper and lower plates 5, 6. Whilst within the heated area, the released gas may be further pyrolyscd, which may be considered as a second pyrolysis process. The second pyrolysis process reduces the amount of particulate matter and tars within the gas to leave a cleaner gas. In this regard, it is advantageous to extend use an elongated heated area so as to increase the dwell time, thus increasing the effect of the second pyrolysis process.

[00373] The gas released within the heated area moves away from the input section toward a primary gas collection zone 24. This can be due to a positive pressure gradient in the first heating chamber, and may be aided by a fan or blower if necessary. At the primary gas collection zone 24, the gas exits the area between the upper and lower plates 5, 6. Due to the high temperature, the gas then rises, and any chars and tars fall into a char and tar collection zone 17.

[00374] When the gas leaves the heated area between the upper and lower heating plates 5, 6, it is directed toward an array of pipes 8. In some aspects, the entrance to the array of pipes 8 is located higher than the upper heating plate 5 so that when the hot gas leaves the heated area between the upper and lower heating plates 5, 6, it rises toward the entrance of the array of pipes 8. The gas then enters the array of pipes (due to the pressure gradient if appropriate) and exits the first heating chamber 2.

Second Heating Chamber [00375] One horizontal face of the second heating chamber 3 is defined at least in part by the first thermally conducting plate (upper heating plate) 5. In this way, the heated atmosphere within the second heating chamber 3 will heat the first thermally conducting plate 5. In turn, the first thermally conducting plate 5 will then heat the interior of the first heating chamber 2.

[00376] With reference to Fig. 48, the ray of pipes 8 enters a first end of the second heating chamber 3 and extends toward a second end, opposed to the first end, of the second heating chamber 3. The array of pipes 8 is airtight with respect to the second heating chamber 3 such that gas from the firs( heating chamber 2 may travel within the array of pipes 8, but cannot otherwise permeate into the second heating chamber 3.

[00377] A first heat source 9 (for example, a burner or a cyclone furnace) is located near the first end of the second heating chamber 3, and heats the interior of the second heating chamber 3. Heated gas from first heat source 9 enters the second heating chamber 3 via an input port. The heated gas from the first heating source 9 may be directed toward a baffle 10 so as to minimise the temperature gradient on the array of pipes 8. The temperature of the heated gas may be between 1400-1600°C although, typically, temperatures of 1200-1250°C are sufficient. It may be appreciated that the firs( heat source 9 can reside within the second heating chamber 3 without departing from the present invention. However, locating the first heat source 9 outside the second heating chamber 3 provides simpler access for maintenance.

1003781 The heated gas from the first heat source 9 is directed from the first end of the second heating chamber 3 toward the second end of the second heating chamber 3, thereby heating the entire of the second heating chamber 3. In some aspects, a fan is used to assist through flow of the heated gas. The path of the heated gas is depicted with arrows within the second heating chamber 3 in Fig. 46.

1003791 It will be understood that the temperature of the series of pipes 8 is dependent on the temperature of gas exiting the first heating source 9. If the first heating source 9 provides gas at 1250°C, the syngas within the array of pipes 8 will be at approximately 1200°C near the first end of the second heating chamber 3.

[00380] As the syngas moves away from the first end of the second heating chamber 3, the temperature will drop. In order to reduce the temperature gradient along the array of pipes S. subsidiary heat sources 9a may be placed along the array of pipes 8, within the second heating chamber 3. In Fig. 46, three subsidiary heat sources 9a are shown, but it will be understood by those skilled in the art that any number of subsidiary heat sources 9a may be used.

[00381] With the interior of the second chamber 3 being heated, the upper heating plate 5 separating the first and second heating chambers 2, 3 will also be heated. Typically, the upper heating plate 5 operates at 850°C.

[00382] The second end of the second heating chamber is a Nox (nitrous oxide) burnout zone, wherein a second heat source is used to mitigate the drop off in temperature from the first end of the second heating chamber. The Nox burnout zone is described in more detail below.

[00383] At the end of the Nox burnout zone, the heated gas from the heat sources 9, 11 is passed to a heat recovery steam generator, thus further improving the efficiency of the pyrolysis device (in terms of calorific value in compared to useable energy out). The heat recovery is described in more detail below.

Array of pipes [00384] When a pipe is heated from the outside, there is a temperature gradient toward the centre of the pipe. To limit the effect of that temperature gradient, the present group of aspects uses an array of pipes 8 to transport the gas through the second heating chamber 3. Accordingly, the syngas produced in the first heating chamber 2 is provided a sealed path from the first pyrolysis stage, until the syngas exits the pyrolysis device 1. Additionally the syngas within the array of pipes 8 will still benefit from the high temperatures within the second heating chamber 3.

[00385] The array of pipes 8 consists of an input end and an exit end 8'. Preferably, the exit end of the array of pipes 8 is external to the second heating chamber 3.

[00386] The array of pipes 8 generally comprises a plurality of small diameter (6.3 cm) pipes. The input end of the array of pipes 8 may comprise such a plurality of small diameter pipes, or may comprise a single pipe that then splits into the plurality of small diameter pipes. The small diameter of the pipes reduces the temperature drop-off caused by the thermal gradient within the pipes. This allows the temperature within the array of pipes 8 to be kept at a temperature closer to the temperature of the atmosphere within the second heating chamber 3.

[00387] At the exit end, the plurality of small diameter pipes are combined into a single exit pipe 8'. The single exit pipe 8' of the array of pipes 8 leads to a heat recovery area to improve the efficiency of the pyrolysis system. The heat recovery is described in more detail below.

Feedstock Input Zone [00388] As seen in Figs. 46 and 49, the feedstock input zone 21 is located toward the first end of the first heating chamber, and is designed to deliver feedstock onto the chain drive 4 above the lower heating plate 6.

[00389] The feedstock input zone comprises a feed hopper 14 positioned above an airlock 15. The airlock 15 comprises two heavy duty (HD) knife valves 16', 16". In the present group of aspects, the HD knife valves 16', 16" are tungsten knife valves able to exert 150psi (10.3bar) of pressure, and are located one above the other. This may be considered as a gravity-fed input zone.

[00390] Carbon Dioxide (CO2) may be injected into the airlock, to improve char reduction. The CO2 can also create a positive pressure at the first end of the first heating chamber. This will cause gasses within the first heating chamber to move away from the feedstock input zone 21 and toward a primary gas collection zone 24.

[00391] When the feed hopper 14 is first filled, it is assumed that both HD knife valves 16', 16" are closed. Feedstock is placed in the hopper 14 and collects against the first HD knife valve 16'. When the feedstock is to be admitted into the first heating chamber 2, the first HD knife valve 16' opens, and the feedstock falls onto the second HD knife valve 16". The first HD knife valve 16' then closes. The pressure that can be exerted by the first HD knife valve 16' is sufficient to cut through any feedstock that would otherwise prevent an airtight seal. Hence, the present group of aspects reduces the chances of gas escaping through the airlock 16.

1003921 When the first HD knife valve 16' is fully closed, the second HD knife valve 16" opens to allow the feedstock to fall into the first heating chamber 2. The second HD knife valve 16" is then closed, after which the first HD knife valve 16' may be opened, and the process repeated.

[00393] When both knife valves 16'. 16" are closed with the feedstock therebetween, carbon dioxide (CO2) can be introduced into the airlock 15. This allows the pyrolysis within the pyrolysis device to take place in a CO2 atmosphere. Additionally, this creates an area of high-pressure in between the two knife valves 16', 16". Advantageously, when the second knife valve 16" is opened, the positive pressure from within the airlock will resist gas from inside the first heating chamber from entering airlock. Hence, the amount of syngas escaping the pyrolysis device can be reduced.

[00394] As shown in Figs. 46 and 49, at the bottom of the primary feed zone 21, the feedstock passes through the lower knife valve 16' of the airlock 15, and into the first heating chamber 2. When the feedstock falls into the first heating chamber 2, it will fall onto the lower heating plate 6. In the preferred group of aspects, the means for impelling the feedstock (transport means) is a chain drive 4 surrounding the lower heating plate 6. Accordingly, in this group of aspects, the feedstock will fall onto the chain drive 4 as well as the lower heating plate 6. With other means for impelling, the feedstock may fall directly onto the lower heating plate 6.

NoX burn out zone [00395] In this group of aspects, the second end of the second heating chamber 3 is defined as a Nox burn out zone 22 as shown in Figs. 46 and 49. A second heating source 11 is positioned closer to the second end of the second heating chamber 3 than the first heating source 9. Generally, the second heating source 11 will be located near the second end of the secondary heating chamber 3.

[00396] Heated gas from the second heating source 11 enters the second heating chamber 3 via an input port. The heated gas of the second heating source 11 is sufficient to raise the temperature of the gas within the array of pipes 8 to 1000°C or more. By raising the temperature in such a manner, the NoX in the syngas may be removed. The removal of Nox by rebuming is described in, for example, Smoot et al "Nox control through rebuming", Progress in Energy and Combustion Science, Vol 24 Issue 5 Oct 1995, pp385-408.

Chain Drive 1003971 The chain drive 4 comprises a plurality of links 12 formed into a continuous loop. The first end of a first link is connected to an end of a second link; a second end of the first link is connected to an end of a third link and so forth.

[00398] With reference to Fig. 50a, the links comprise two generally planar, elongated side portions 12a placed parallel with each other. A rod 12b connects an end of the two side portions 12a, and another rod 12b connects the opposite end of the two side portions 12a. When taking a plan view of the link the two side portions and the two rods generally define a rectangular gap 12c.

[00399] As shown in Fig. 50b, a rod 12b can be shared between two neighbouring finks 12, 12', such that one rod 12b pivatobly connects the elongated side portions 12a of one link 12 to the elongated side portions 12a' of the neighbouring link 12'. This can then he repeated, with one rod 12b being shared between two links 12, until a continuous loop (chain drive) is formed. The length of the chain drive can be increased by including more links 12 [00400] To increase the width of the chain drive 4, two or more of the above described chain drives 4 can be connected side by side. For example, a rod 12b may span the width of two links 12, so as to connect two links 12 side by side. In such an arrangement, one elongate side 12a can be shared between the two links 12 [00401] The chain drive 4, having an inside and an outside, is spread over two or more rollers 13. If more than two rollers 13 arc used, at least one 13' of those rollers 13 may he located on the outside of the chain drive. In this way, the chain drive 4 will be made to bend in multiple directions to account for the position of the rollers 13. If the chain drive 4 is made to bend in this manner, tars and chars that are attached to the chain drive 4 have an increased chance of becoming detached, thus reducing maintenance requirements. The process of removing the detached char and tar from the first heating chamber 2 described below.

[00402] The chain drive 4 of this group of aspects is driven by a motor, which is controlled by a controller (not shown). The motor is located outside the first heating chamber 2 and outside the housing 7 for ease of maintenance. A drive shaft penetrates the housing and first heating chamber 2 so as to actuate the chain drive 4.

[00403] Generally, insulating around a larger moving part can become problematic. For example, the shaft around which a conventional rotary retort rotates must increase in diameter as the size of the retort increases (to support the weight, and to allow more feedstock to be entered into the retort). Requiring only a drive shaft to penetrate the housing 7 and first heating chamber 2 allows the pyrolysis device 1 to be better insulated, and thus more efficient, than a conventional pyrolysis device. Further, it allows for greater scalability as one size drive shaft can be used for many sizes of chain drive 4.

[00404] The motor is arranged so that, the chain drive 4 may he actuated in a forward direction, to carry feedstock away from the input zone, or in a reverse direction, to carry feedstock toward the input zone. Being able to move the chain drive 4 in such a manner allows some waste material stuck to the chain drive 4 or one of the heating plates 5, 6 to be un-stuck without needing to open the first heating chamber 2. Accordingly, maintenance may be simplified.

1004051 The speed of the motor is adjustable by the controller. Accordingly, the dwell time of the feedstock within the heated area may be increased. The speed of the motor may be adjusted in response to feedback from sensors around the pyrolysis device I. For example, if a larger proportion of chars and tars are removed through a char collection zone 17, the motor may be slowed to increase dwell time. Similarly, if the syngas has a greater than expected amount of particulates, the dwell time could be increased by adjusting the motor speed.

Char and Tar Removal [00406] As best seen in Fig. 48, once the tars and chars are detached from the chain drive 4 and the heating plates 5, 6, they are directed toward a primary char collection zone 17 located toward the second end of the first heating chamber 2. Those chars and tars may be termed 'waste', as they are not pyrolysed.

1004071 The primary char collection zone 17 allows the waste to gravitationally collect in a recess. An airlock (not shown) is located beneath the recess to allow the chars and tars to be removed from the first heating chamber whilst preventing gas, and heat, from escaping from the first heating chamber. The airlock may comprise two or more tungsten knife valves (not shown). Similarly to the knife valves of the feedstock input zone, the knife valves of the primary tar collection zone 17 are able to exert 150 psi (10.3 bar) of pressure so as to avoid the waste preventing the knife valves from fully closing.

Operation is similar to the airlock 15 of the feedstock input zone.

[004081 The waste exiting the first heating chamber 2 can then he sorted, so as to remove metals. The remaining waste can be turned into vitrified slag for use in the construction industry. The chars can be used to power the heat. sources 9, 9a, 11. Accordingly, even material that was not pyrolysed is still of use.

[004091 In the preferred group of aspects, a secondary char removal zone 17' is located at the first end of the first heating chamber 2. Although the majority of chars and tars will be removed with the primary char removal zone 17, some chars and tars may remain stuck to the chain drive 14 after passing over the primary char collection zone 17. Such chars and tars may then become unstuck as they pass around the roller 13 toward the first end of the first heating chamber 2.

[004101 Similarly to the primary char removal zone 17, the secondary char removal zone 17' includes and airlock to prevent, or substantially prevent, syngas within the primary heating chamber 2 from exiting the pyrolysis device I. The airlocks will also limit the ingress of the air surrounding the pyrolysis device I. That air would otherwise cool the inside of the first heating chamber 2, reducing the efficiency of the pyrolysis device 1.

Upper and Lower Heating Plates [004111 The present group of aspects uses planar or substantially planar heating plates to pyrolysc a feedstock. Such sheets are used in place of a conventional retort. A conventional retort becomes less efficient as it increases in size due to the thernaal gradient within the retort. By using planar heating plates, the present group of aspects overcomes such limitations in scalability.

[004121 The upper and lower heating plates 5, 6 can be of any length and width and still fall within the scope of the scope of the present invention. In the preferred group of aspects, the lower heating plate 6 is 32 It (9.75m) long and 6 It (1.8m) wide. The upper heating plate 5 will be shorter than the lower heating plate to allow feedstock to fall from the hopper 14 directly onto the chain drive 4 and remain above the lower heating plate 6. The upper heating plate 5 is 6 ft wide in the preferred group of aspects.

[00413] As previously described, the upper heating plate 5 is heated as primary heat source 9 heats the second heating chamber 3. In the preferred group of aspects, the lower heating plate 6 is positioned 8 inches (20cm) below die upper heating plate 5. Due to this close proximity, the lower heating plate 6 is heated by the upper heating plate 5 via convection and radiation. The lower heating plate 6 will be at approximately the same temperature as the upper heating plate 5.

[00414] The heating plates are constructed at least in part from copper. Conventionally copper has been too malleable at high temperatures to be a viable material for constructing the heating portions of a pyrolysis. However, in the present group of aspects copper is explosively welded to a nickel or stainless steel frame. This provides a structure that. remains rigid at the high operating temperatures required for pyrolysis, whilst maintaining the thermal conductivity of the copper. Explosive welding is described in US3140539 to Holtzman.

1004151 Multiple panels of copper may be explosively welded onto a nickel or stainless steel frame to allow for heating plates of various dimensions. For example, 4 copper sheets measuring 8 ft by 6 ft (2.44m by 1.83m) can be used to create a heating plate 32 ft (9.75m) long by 6ft (1.8m) wide. Alternatively, the same 4 copper sheets may be used to create a heating plate measuring 16ft (4.88m) by 12ft (3.6m). It is generally preferable to use heating plates that are significantly longer than they are wide (for example, 5 times as long as they are wide), as this increases the dwell time of the feedstock, and resulting syngas, in the heated area between the upper and lower heating plates 5, 6. A longer dwell time will provide a more complete pyrolysis process.

[00416] By constructing the heating plates 5, 6 from copper in such a manner, temperature gradients can be reduced across the heating plates 5, 6. Accordingly, the onset of "hot spots" and "cool spots" on the heating plates 5, 6 in the present group of aspects is reduced, thereby more evenly heating the feedstock.

[00417] In the preferred group of aspects, the copper sheets are explosively welded to a 310-grade stainless steel frame. The coefficient of thermal expansion (CTE) of copper is 16.5 ppm/oC, and the CTE of 310-grade stainless steel is 14.4 ppin/oC (it will be appreciated that the CTE may vary depending on the temperature range). Selecting materials with similar CTEs minimises stress and strain resulting from heating the heating plate 5,6.

Heat Recovery [00418] An exit 8' of the array of pipes 8 provides a path for the syngas into a manifold feeding a wide diameter pipe, via which it passes to a heat recovery steam generator (HRSG), in which it is passed via pipes through a boiler to generate steam used to drive the steam turbine. After being thus cooled, it is passed to a scrubber of conventional type which extracts impurities and dust.

[00419] The scrubbed gas then passes through a hydrogen separator of conventional type which separates out hydrogen for use as a fuel for one or both of the cyclone furnaces. Finally, CO2 is extracted by a CO2 separator of conventional type. The extracted CO2 is recycled to the air lock 15.

[00420] The syngas (consisting of ethane, methane, and other relatively short hydrocarbons as well as some CO) may then be passed to a gasometer and (via the gasometer or if the latter is empty, directly) to a gas turbine engine driving an electrical generator. The stored syngas not thus used to generate electricity can be sold as a fuel, and vice versa.

1004211 Similarly, the gas within the second heating chamber but not inside the array of pipes 8 is directed, via an exhaust 20, to a heat recovery stage.

Alternate Aspects [00422] In an alternative aspect, the chain drive 4 is replaced by a conveyor belt 18. This can be seen in Fig. 51. The feedstock is placed on the conveyor belt 18 and transported beneath the upper heating plate 6. The upper heating plate 6 is at a temperature sufficient to pyrolise the feedstock. Particulate matter is also pyrolised by the heat emitted from the upper heating plate 6. In this aspect, the lower heating plate 5 may be removed, thus reducing manufacturing cost and complexity.

[00423] The conveyor belt 18 may be constructed using bonded copper. The feedstock will thus be heated by conduction when being transported through the heated area. Vanes 19 may protrude from the conveyor belt 18 to aid movement of the feedstock. The vanes 19 may be made of copper, which will provide an increased surface area for heating the feedstock.

1004241 In an aspect, the chain drive is replaced with a jigging conveyor. The motor produces reciprocating motion on the lower heating plate, thereby transporting the feedstock away from the input section, and through the heated area. Advantageously, this removes the need for a separate means to transport the feedstock through the heated area. The jigging conveyor may be made of copper explosively welded to a nickel or stainless steel frame, as with the lower heating plate.

[00425] In an aspect, secondary heat sources 9b for the first heating chamber 2 are placed below and proximate to the lower heating plate 5. A plurality of secondary heat sources 9b can be positioned from the first end of the first heating chamber 2 to the second end of the first heating chamber 2. The secondary heat sources heat the lower healing plate 5, which offsets the reduction in temperature caused by contact with the feedstock.

Providing a plurality of second heat sources 9b along the length of the first heating chamber 2 will limit the onset of hotspots and cool spots on the lower heating plate 5.

OTT TER ASPECTS

1004261 Although aspects related to multiple retort systems and spherical and helical gas paths have been described separately, it is not intended that such aspects are mutually exclusive. For example, any of the ATT apparatus of the aspects related to multiple retort systems may include a gas enclsure of the aspects related to spherical and helical gas paths. In some examples, the first ATT apparatus of the aspects related to multiple retort systems includes a gas enclosure including a frustoconical shell located within the heating system of the first ATT apparatus. In some examples, the second ATT apparatus of the aspects related to multiple retort systems includes a gas enclosure including a frustoconical shell located within the heating system of the first ATT apparatus.

[00427] In the preceding embodiments and aspects, a cylindrical rotating retort has been described. However, in other embodiments and aspects, different shapes could be adopted. For example, the cross-section does not need to be constant along the entire length of the retort -it could flare or narrow downwards.

[00428] Likewise, whilst a circular cross-section is convenient to manufacture, non-circular cross-sections could be used; an elliptical cross-section increases the dwell time on some parts of the retort which may be useful in some cases. Many other cross-sections could be used, though sharp corners might tend to trap material. The rotation employed might likewise be provided using elliptical gears or other means to vary the rotational speed within each rotation, so as to control the dwell time on different sectors of the retort.

[00429] Whilst rotation, unidirectional or bidirectional, has been described, it would be possible to turn the retort through less than an entire turn before reversing it -in other words, to apply a rotational oscillation. In this case, the retort does not need to be enclosed but could be a concave, for example semicircular, surface.

[00430] Other aspects which might be used with the present invention are described in our co-pending applications incorporated in their entirety by reference, filed the same day as the present application and with the following titles and attorney references: * J0548260B "Pyrolysis Methods and Apparatus" * .1101182GB "Pyrolysis or Gasification Apparatus and Method" * J102464GB "Pyrolysis Retort Methods and Apparatus" * J102465GB -Temperature Profile in an Advanced Thermal Treatment Apparatus and Method" * J102466GB -Advanced Thermal Treatment Apparatus" [00431] A person skilled in the art would understand that various types of heat source and fuels therefor could be used, in addition to those described above and in the co-pending applications mentioned above.

[00432] Many other variants and embodiments will be apparent to the skilled reader, all of which are intended to fall within the scope of the invention whether or not covered by the claims as filed. Protection is sought for any and all novel subject matter and combinations thereof disclosed herein.

Claims

Claims 1. A multi-stage pyrolysis apparatus to convert calorific material into gas, the apparatus comprising: a heating system, including a heating section; a retort structure having an input end, through which calorific material can enter the retort structure, and an output end, the retort structure being rotatable about an axis through the input end and the output end: and a gas conduit, the gas conduit having an exit through which gas can exit the gas conduit; wherein, the retort structure and the gas conduit are so connected as to form a continuous path capable of transferring gas from the input end of the retort structure to the exit of the gas conduit; and the heating section is capable of heating the retort structure and the gas conduit to a temperature sufficient for pyrolysis of the calorific material.
2. The apparatus of claim 1, wherein the retort structure is enclosed within a thermally insulated retort housing.
3. The apparatus of claim 2, further comprising a pipe for gas to pass therethough, wherein the pipe is enclosed within the thermally insulated retort housing, said pipe connected at one end to the output end of the retort structure and connected at another end to the gas conduit.
4. The apparatus of claim 3 herein the pipe extends along an external surface of the retort structure.
5. The apparatus of any of claims 3 to 4 herein the pipe follows a serpentine path around the retort structure.
6. The apparatus of any of claims 2 to 5, wherein the heating system further comprises a heat duct capable of transferring heated gas from the heating section to the interior of the thermally insulated retort housing.
7. The apparatus of claim 6, wherein the gas conduit is at least partially located within the heat duct.
8. The apparatus of claim 1, further comprising: a retort feedpipe connected to the input end of the retort structure, wherein the feedpipe includes an airlock which allows feedstock to enter the retort structure but prevents air from entering the retort structure, and wherein the feedpipe may control the amount of feedstock entering the retort structure.
9. The apparatus of claim 8, wherein the airlock maintains a positive pressure within the feedpipe.
10. The apparatus of claim 8, further comprising a gas feed connected to the feedpipe between the airlock and the retort structure to supply a reducing gas such as Carbon Dioxide to the feedpipe.
11. The apparatus of any preceding claim, wherein the heating section is adapted to heat the interior of the gas conduit to a greater temperature than the interior of the retort structure.
12. The apparatus of claim 11, wherein the temperature of the gas conduit is sufficient to crack tars and oils.
13. The apparatus of any preceding claim, wherein the heating system is capable of heating the gas conduit to 1200°C.
14. The apparatus of any preceding claim, wherein the retort structure is at least partially constructed from copper.
15. The apparatus of any preceding claim including a retort housing, in which is located the retort structure having an input end, through which calorific material can enter the retort structure, wherein the pyrolysis apparatus, including the retort housing and the retort structure, is capable of being variably inclined to create a gradient away from the input end.
16. The apparatus of claim 15, wherein the variable incline of the pyrolysis apparatus is provided by a hydraulic arrangement.
17. The apparatus of claim 14, in which the heating system is capable of being inclined along with the pyrolysis apparatus.
18. The apparatus of any preceding claim further comprising a reversible drive train capable of alternating the direction of rotation of the retort structure.
19. A pyrolysis apparatus constructed of sheets of a high thermal conductivity metal such as copper explosively welded to a framework of a high temperature strength metal such as nickel alloy or stainless steel.
20. The apparatus of claim 19, wherein the pyrolysis apparatus is a rotable pyrolysis retort.
21. The apparatus of claim 20 comprising co-rotating inner and outer bodies, a first of said bodies comprising said sheets of said high thermal conductivity metal such as copper explosively welded to a framework of said high temperature strength metal.
22. The apparatus of claim 21 in which said first body is said outer body.
23. The apparatus of claim 19 or 21 in which said second body consists of sheets of a high thermal conductivity metal such as copper.
24. The apparatus of claim 19 in which the inner body contains holes to allow particulate material to pass therethrough.
25. The apparatus of claim 19 in which the inner and outer bodies carry vanes to retain particulate material.
26. The apparatus of claim 24 in which the vanes are symmetrical so that the retort apparatus can be rotated in either sense.
27. The apparatus of claim 25 in which the vanes have a T-shaped cross-section.
28. A method of converting calorific solid material into gas in a pyrolysis apparatus, the method comprising: applying a first pyrolysis process within a thermally insulated housing at a first temperature with the calorific solid material adjacent. a high thermal conductivity metal construction; applying a second pyrolysis process at a second temperature, substantially higher than said first, within piping co-located in said thermally insulated housing; applying a third pyrolysis process at a third temperature substantially higher than said second temperature; and recovering from said gas heat applied in said third pyrolysis process.
29. The method of claim 28, wherein the second temperature is approximately 850°C.
30. The method of claim 28, wherein the third temperature is approximately 1200-1300°C.
31. The method of any of claims 28-30, wherein the high thermal conductivity metal construction is a retort.
32. A multi-stage pyrolysis apparatus to convert calorific material into gas, the apparatus comprising: a heating system including a heating section and a heating duct; a retort structure having an input end, through which calorific material can enter the retort structure, and an output end, the retort structure being rotable about an axis through the input end and the output end; and a gas conduit at least partially located within the heat duct, the gas conduit having an exit through which gas can exit the gas conduit; wherein, the retort structure and the gas conduit are so connected as to form a continuous path capable of transferring gas from the input end of the retort structure to the exit of the gas conduit; and the heating section is capable of heating the retort structure to a first temperature in a first zone, and the gas conduit to a second temperature in a second zone, the second temperature being substantially greater than the first temperature.
33. The apparatus of claim 32, in which: the gas conduit comprises a plurality of parallel pipes and the heating section is arranged to heat the gas conduit to a temperature sufficient to break down Nox.
34. The apparatus of claim 32 or claim 33, in which: the heating section comprises a first burner and a second burner, and further comprising a path routing combustion gas from the first burner to the second zone.
35. The apparatus of any of claims 32 to 34, further comprising: a heat recovery system for recovering the heat applied by the second burner in the second zone.
36. A pyrolysis apparatus having a heating system adapted to heat a first gas enclosure, wherein a gas path within the heated enclosure is helical or spherical.
37. A method of cracking hydrocarbons comprising heating a gaseous mixture, containing hydrocarbons, that is travelling around an axis of the gas enclosure.
38. A system for pyrolysis or gasification having a first pyrolysis or gasification unit connected to a second pyrolysis or gasification unit by a hermetically sealed gas path.
39. A method for pyrolysis or gasification, characterised in that gas resulting from a first pyrolysis or gasification process in a first pyrolysis or gasification unit undergoes a second pyrolysis or gasification process in a second pyrolysis or gasification unit.
40. A pyrolysis method comprising: applying heat from a heat source to a first region to cause a first pyrolysis process, the first pyrolysis process resulting in a gaseous mixture; applying heat from the heat source to a second region to cause a second pyrolysis process, the second pyrolysis process being applied to the gaseous mixture; wherein the second region is located closer to the heat source than the first region.
41. A gasification method comprising: applying heat from a heat. source to a first region to cause a first gasification process resulting in a gaseous mixture; applying heat from the heat source to a second region to cause a second gasification process to the gaseous mixture; wherein the second region is located closer to the heat source than the first region.
42. A pyrolysis apparatus comprising: a first region; a second pyrolysis region; and a heat source being positioned such that, when operated the heat source heats the first region to cause a first pyrolysis process, the first pyrolysis process resulting in a gaseous mixture, and the heat source heats the second region to cause a second pyrolysis process, the second pyrolysis process being applied to the gaseous mixture; wherein the second region is located closer to the heat source than the first region.
43. A gasification apparatus comprising: a first region; a second pyrolysis region; and a heat source being positioned such that, when operated the heat source heats the first region to cause a first gasification process the first gasification process resulting in a gaseous mixture, and the heat source heats the second region to cause a second gasification process, the second gasification process being applied to the gaseous mixture; wherein the second region is located closer to the heat source than the first region.
44. A pyrolysis apparatus comprising: i. a first heating chamber having a first thermally conducting plate as at least a portion of one side, the first heating chamber containing a second theimally conducting plate; and ii. a second heating chamber having the first thermally conducting plate as at least a portion of one side, the second heating chamber containing a first heating means; wherein the first heating chamber and the second heating chamber are atmospherically isolated from each other.
45. A pyrolysis apparatus comprising: a first static planar thermally conducting plate having a first face and a second face; transport means for transporting feedstock along the first face of the first static planar thermally conducting plate; and iii. first heating means for heating the second face of the first static planar thermally conducting plate to a temperature sufficient to pyrolyse the feedstock.
46. A pyrolysis apparatus comprising: a. a static thermally conducting surface adapted to heat feedstock to a temperature sufficient for pyrolysis; and b. transport means for transporting feedstock in contact with the thermally conducting surface.
47. A pyrolysis apparatus comprising: i. a first heating chamber having a first thermally conducting plate as at least a portion of onc side, the first heating chamber containing a second thermally conducting plate; and ii. a second heating chamber having the first thermally conducting plate as at least a portion of one side, the second heating chamber containing a first heating means; wherein the first heating chamber and the second heating chamber arc atmospherically isolated from each other.
48. A pyrolysis method comprising steps of: i. perfoiming a first pyrolysis process in a first heating chamber, the first pyrolysis process being performed on feedstock between a first thermally conducting plate and a second thermally conducting plate; ii. performing a second pyrolysis process in an array of pipes within a second heating chamber, iii. wherein the first heating chamber and the second heating chamber are atmospherically isolated from each other, and the first thermally conducting plate forms at least a portion of a wall of the first heating chamber and at least a portion of a wall of the second heating chamber.