Waste Processing

Abstract

M&C PB 143543WO 22 31524653-1-abhimani ABSTRACT An apparatus and method for processing organic materials is provided comprising an elongate process tube (22) having an inlet for receiving the material and an outlet for processed material. A gas conveying system fluidically conveys the material through the processing tube, The gas conveying system comprises a supply of conveying gas which is a hot pressurised inert gas, connected to the processing tube (22) at its inlet end. A control system is configured to control the supply of the pressurised inert gas to the processing tube (22) so as to convey a batch of material through the tube (22) whilst simultaneously heating said it to cause the organic matter therein to gasify to produce process. The processing tube (22) has a plurality of sections, each separated by a closure (44), and the gas conveying means conveys the material from one section to the next.

Description

The present invention relates to improvements in the processing of materials having an organic component. In particular the method relates to improvements in the processing of such materials in a semi continuous process.

The batch processing and the continuous processing of materials to gasify them or pyrolyse them to produce synthesis gas is known in the art.

One known continuous method is the use of conveying ovens, these systems uses a mesh belt conveyor to transport materials for treatment through an oven. Hot gasses are passed through the material on the belt as it passes through the oven. A problem with this method is that the depth of materials on the belt limits the process. The materials are stacked which reduces efficiency as the hot gases do not come in to contact with the materials that are enclosed within the stack of materials on the mesh. It is advantageous for efficient processing of the material that all the surfaces of the materials being treated are exposed to the hot gases. Also there is no agitation of the material being treated and conveyor belt life is usually short.

Another known continuous method is the use of rotating kilns. In this method a large kiln is inclined to the horizontal so that material fed or charged into the kiln at its highest end travels towards the lowest end, where it is discharged, under the influence of gravity. The kiln is rotated so that material within the kiln is agitated and a flow of hot gases is provided to heat up the material as it travels through the kiln. One problem with this method is that there are a large number of moving parts, in particular the fact that the whole kiln rotates is a source of constant wear and possible failure, especially in relation to the rotating seals at either end which much seal across a wide range of temperatures. A further problem is that these ovens commonly take up a large amount of space in comparison to their throughput of material.

It is a further problem with continuous processes that their processing parameters are usually set to a very stable level so that the material passing therethrough can be guaranteed to be fully processed. This can create problems if there are large variations in the material that is required to be processed, for example the water content.

Entrained flow furnaces in which small particles of organic matter are entrained in a hot gas flow which is passed through a furnace are known, for example from Japanese patent application JP2009256490.

It is also known to dry waste, or example municipal waste by heating it by passing a flow of ht gas over or through it. Examples of such prior art is disclosed in Japanese patent application JP9042836, in PCT publication WO2010/027138, and European application EP0031939.

It is the purpose of the present invention to provide an improved method and apparatus for processing material having an organic component.

According to a first aspect of the invention there is provided an apparatus for processing material such as organically coated waste and organic materials including biomass, industrial waste, municipal solid waste and sludge; the apparatus comprising: an elongate process tube having an inlet for receiving the material and an outlet for processed material; a gas conveying system for fluidically conveying said material through said processing tube, said conveying system comprising a supply of conveying gas, comprising hot pressurised inert gas, connected to said processing tube at its inlet end; and a control system configured to control the supply of said pressurised inert gas to said processing tube so as to convey a batch of said material through said tube simultaneously heating said material to cause any organic matter therein to gasify to produce process gas, wherein the processing tube comprises a plurality of sections, each separated by a closure, and the gas conveying means is configured to convey the material from one section to the next.

By processing in this manner essentially a continuous batch process is affected. This gives the flexibility of modifying processing parameters associated with batch processing together with the benefits of continuous process, e.g. better throughput of material, no interbatch downtime etc.

Preferably the apparatus further comprises separation means for extracting the process gas from the processing tube.

Preferably the gas conveying means includes a conveying gas inlet associated with each section for the supply of conveying gas to move the material therein into the next section. Preferably each section of the processing tube has a process gas outlet towards its downstream end.

By breaking the process down into sections of tube the parameters for each section can be independently monitored, e.g. fluid extraction/addition (see below). Furthermore as hot conveying gas is introduced at each stage the greater the number of sections the greater the heat input from the conveying gas.

The apparatus may comprise a conveying gas compressor for increasing the pressure of the conveying gas and expansion of the conveying gas moves the material in the processing tube.

The conveying gas compressor may comprise a compression chamber having a piston therein for receiving said conveying gas and an actuator for moving said piston in said chamber to compress the gas therein. Preferably the compression chamber is sized such that one stroke of the piston in the chamber expels sufficient conveying gas to convey material from one section of the processing tube to another.

In one preferred arrangement each section of the processing tube has a compressor associated with it. In an alternative arrangement the apparatus may be provided with one central compressor and the gas may be directed to the required sections of the processing tube by valve means.

The apparatus may comprise a fluid outlet in each section of the tube for draining fluid therefrom. The apparatus may also include a fluid inlet in the conveying gas inlet conduit of each section for feeding the drained fluid into said conveying gas. As the hot conveying gas is at an elevated temperature, in the region of several hundreds of degrees, the fluid will vaporise when it is added to the conveying gas, the expansion in volume as it vaporises will slightly drop the temperature of the gas but will boost its pressure, thereby assisting in conveying the material along the tube.

In a preferred arrangement the apparatus further comprises a thermal treatment chamber for thermally treating the process gas produced by the apparatus by heating it so as to breakdown any volatile organic compounds therein. Preferably an outlet conduit is provided from the thermal treatment chamber for supplying hot process gas therefrom to the processing tube for use as said conveying gas.

The apparatus may comprise: a feed hopper for receiving and temporarily storing material to be processed, and a secondary hopper fed by the feed hopper wherein the secondary hopper is connected to the processing tube by a valve and wherein the secondary hopper has a conveying gas inlet at an upper end thereof. In this way batches can continuously be gated through the secondary hopper, from the first hopper, and introduced into the process.

The apparatus may be provided with sensors to sense the quality of the process gas and: if the sensed quality does not meet a predetermined criteria, the apparatus may be controlled to re-circulate the process gas through the processing tube as conveying gas and, if it does meet the predetermined criteria at least some of the process gas may be extracted for storage or direct use.

The interior surface of the processing tube may be provided with fixed agitators to promote the tumbling of material within said tube as it is conveyed therethrough.

According to a second aspect of the invention there is provided a method for processing material such as organically coated waste and organic materials including biomass, industrial waste, municipal solid waste and sludge; the method comprising: providing an elongate process tube having an inlet for receiving the material and an outlet for processed material; providing a gas conveying system for fluidically conveying said material through said processing tube, said conveying system comprising a supply of hot pressurised inert gas connected to said processing tube at its inlet end; and controlling the supply of said pressurised inert gas to said processing tube so as to convey a batch of said material through said tube thereby heating said material to cause any organic matter therein to gasify to produce process gas, the processing tube further comprising a plurality of sections, each separated by a closure, each section having a conveying gas inlet associated therewith for the supply of conveying gas; and wherein the method further comprises controlling the supply of conveying gas so as to convey the material from one section to the next.

Preferably the method further comprises separating the process gas from the processing tube.

Preferably the method comprises compressing the conveying gas to increase its pressure and wherein expansion of the conveying gas moves the material in the processing tube.

The method may comprise draining fluid from each section of the tube via a fluid outlet therein. The fluid drained from the tube may then be supplied into the conveying gas upstream of the conveying tube. The temperature of the conveying gas is sufficient to vaporise the fluid added thereto, thereby increasing the pressure of said conveying gas.

The method preferably comprises heating the process gases in a thermal treatment chamber to thermally breakdown any volatile organic compounds therein. The hot process gas may then be supplied from the thermal treatment chamber to the processing tube for use as said conveying gas.

In one embodiment the method comprises: providing a feed hopper for receiving and temporarily storing material to be processed; providing a secondary hopper fed by the feed hopper wherein the secondary hopper is connected to the processing tube by a valve; providing a conveying gas inlet at an upper end of the secondary hopper; feeding a batch of material to be processed from the feed hopper to the secondary hopper; passing gas through the conveying gas inlet and opening the valve such that the batch of material is conveyed from the secondary hopper into the processing tube.

Preferably each section of the processing tube is provided with a process gas outlet towards its downstream end for the extraction of the process gas via said process gas outlets.

The method may include sensing the quality of the process gas and: if it does not meet a predetermined criteria, recirculating the process gas through the processing tube and, if it does meet the predetermined criteria extracting at least a part of the process gasses for storage or direct use.

The method may comprise providing a waste material silo downstream of the processing tube and collecting the inert fully processed material in the silo.

The method may comprise agitating the material within the tube as it is conveyed therethrough.

Specific embodiments of the invention will now be described with reference to the drawings in which:

FIG. 1 is a schematic diagram of a first embodiment of the invention;

FIG. 2 is a schematic diagram of a second embodiment of the invention;

FIG. 3 is a schematic diagram of the invention;

FIG. 4 is a partially cut away section of a processing tube of an alternative embodiment, in accordance with the invention;

FIG. 5 is a cross section through a processing tube of an alternative embodiment, in accordance with the invention; and

FIG. 6 is a schematic diagram of an alternative embodiment of the invention.

Referring to FIG. 1 a feed hopper 1 is provided for the waste material to be loaded, which may be by conventional methods, for example conveyor, directly from a tipping truck or from a vehicle with a bucket loading capability.

The term ‘waste material’ is used throughout the following description and describes the material which is to be processed by the apparatus, and can take many different forms. It will be appreciated by the skilled person that the system could process any material containing a large percentage of organic matter.

A valve 3 is provided to allow the waste material 2 to be introduced into the secondary hopper 4 in a metered amount based on volume or weight.

The initial introduction of the waste material into the process tube can be done using existing pneumatic conveying methods, which are known in the art, but to describe it briefly, when valve 3 is opened, valve 8 remains closed and the hopper is allowed to vent air out of the hopper at a position local to valve 8 and also at the top of the hopper at a position local to valve 3 as the waste material falls through the valve 3 and fills the secondary hopper, allowing the air to escape.

A compressed air supply is connected to the secondary hopper via conduit 10 so as to push the waste material into the process tube 22 by allowing compressed air to enter at position 10 when valve 8 is opened and valve 3 is closed. Although this part of the system charging may be performed using conventional pneumatic means as described, it will be appreciated that this loading part, may be, achieved by using the hot process gas as the conveying gas, as described herein below for the general movement of the waste material through the system, instead of normal compressed air.

The basis of operation of this invention is that waste material is conveyed from entry point to exit point through the processing tube by the hot gas used in the gasification process itself. In doing so the gas applies a pressure to the waste material in order to cause conveying movement and therefore agitation by default of its movement. In doing so the waste material in part or bulk is subjected to exposure to the hot process gas thereby causing its gasification. The gasification process creates a process gas which contains carbon monoxide (CO) and hydrogen (H₂), which is commonly referred to as syngas.

The waste material is moved through the process apparatus, not by compressed air in the conventional method, but by a pressurised supply of hot process gas from the gasification process.

Typically at locations along the process tube the hot gas is entered under pressure from one of a proposed number of compression chambers 21, each of which is mounted adjacent to a section length of process tube and is connected to the hot process gas inlet duct 19. The sections are separated by valves 44 into a plurality of discreet chambers.

In one of a number of preferred embodiments, typically a chamber 21 is provided which houses a piston 20 which is movable in the direction of the arrows 13 and 14 in a working stroke and which may be actuated by conventional means, for example by connection to a hydraulic cylinder 15.

When the piston 20 is actuated to travel in the direction of arrow 13 the valve 11 and 17 are closed on the chamber 21 whilst valves 12 and 16 are open thus allowing hot gas 53 from the inlet duct 18 piped from the larger duct 19 to be compressed under the movement of the piston 20 to a suitable pressure required to cause the gas to be forced out through the valve 12 and duct 10 and into the secondary hopper 4 causing the waste material 2A to have a pressure applied to it so that it is forced to move through valve 8 and commence the journey through the process tube 22.

Whilst the piston is moving in the direction of arrow 13, valve 16 is open and allows the continuous unrestricted flow of hot gas from the duct 18 to be maintained and thus there is no pressure drop in the hot gas flow 53 in the duct 19.

As the secondary hopper fills with waste material 2A then valve 5 and 7 are open to allow trapped air to escape through duct 6 and join the outlet gas duct 47.

The valves 5 and 7 are closed prior to the secondary chamber 4 being filled with pressurised hot gas through the duct 10.

As the volume is filled freely by the gas 53 behind the piston then at the end of the stroke of the piston 20 the valves 11 and 17 are opened and valves 12 and 16 are closed, allowing the free space in the chamber to continue to fill with hot inlet gas 53 through valve 17 from duct 18 behind the piston as it moves in the direction of arrow 14 forcing pressurised hot gas to travel through the valve 11 and pressurise the next batch of material 2A already loaded in the secondary hopper 4. In this way both stroke directions of the piston are utilised.

The size of the chamber 21 is calculated such that enough volume of hot gas can be compressed by the piston in a single stroke, to cause the waste material to be conveyed through the process tube in a metered increment by effectively pressurising a slug of waste material in a conventional manner to existing pneumatic conveying methods. The technique is known widely in the conveying industry and various terms exist such as dense phase, lean phase and pulse phase, but the salient point is that the proposed apparatus uses the process hot gas to convey whilst also causing gasification. The use of hot gas therefore has a dual purpose, to move the material in increments through the process tube 22 and to heat the material so as to cause it to become gasified.

The process is incremental and so a number of chambers typical to the chamber 21 are mounted at appropriate length intervals adjacent and along the length of the process tube 22 at suitably timed intervals to create continuous, or semi continuous conveying of the waste material, for example there may be a residency time of the material in each section prior to it being conveyed to the following section.

Typically as the previous described function is taking place then the same function is performed by a number of chambers along the process tube length 22.

For example, at the same time as the piston 20 moves in the direction of arrow 13 then the piston 31 is actuated by a suitable means 32 whilst valves 25 and 24 are closed then valves 23 and 26 remain open whilst the piston 31 moves in the direction of arrow 29. Again hot gas is pressurised in the chamber 30 and forced through the valve 23 and duct 9 and into the process tube 22 at a position in front of the previous slug of waste material 2B. As the piston 31 moves in the direction of arrow 29 the chamber 30 continues to fill as valve 26 is open and hot gas 53 passes unrestricted from the duct 27.

Similar to previously described, the piston 31 returns in the direction as shown by the arrow 28 and valves 23 and 26 closes whilst valves 25 and 24 open allowing continuation of the process cycle.

A valve 44 typically seals each section of process tube 22 along the length and the valves may be selectively operated in sequence with the chambers to effect the conveying of the material through the system by gas conveying.

The process is repeated for as many sections as required and the waste material is conveyed typically in slugs depicted by 2B, 2C, 2D etc. In operation the operation will typically be sequenced so that material in a downstream chamber is first conveyed out of that chamber before the upstream material is conveyed into that chamber.

The gas from the process within the process tube 22 is expelled through valves 45, located in each tube section, and out through the conduits 46 into the main outlet process gas duct 47 for the gasification process. Some of the process gasses are also allowed to pass through the end of the process tube and into the collection silo 48 at the end of the process tube, where it can escape through valve 51 and duct 52 into the main outlet duct 47. A valve 50 is provided in the bottom of the silo to enable the inert processed material to be removed therefrom.

The process waste 49, which is fully processed and is inert, is captured from the end of the process tube 22 and collected in the silo 48 which can be emptied through a valve 50.

It may be appreciated that the explanation of exact timing of the chamber actuations and location of hot process gas entry need not be strictly complied with as depicted in the accompanying FIG. 1 which is intended to be a schematic representation of the system.

Although shown as a continuous straight process tube 22 it will be appreciated that the process does not have to be a continuous length but could be a number of stage sections where the waste material can be traversed to and from one stage section to the next. Alternatively the process tube 22 can be arranged in a number of stages in a circular arrangement to allow the waste material to pass continuously around the loop sections and then emptied via a suitable exit valve and silo once gasification is complete, but either of these arrangements would make the process more akin to a batch system.

Referring again to the Figures the initial zones of the process tube 22 may have a facility to allow much higher compression of the waste material 2C and 2D for example such that any H₂O or fluid may be squeezed out of the waste material and drained via the collection point 57 in each of the process tube sections, stored and subsequently used at any point in the gasification phase by controlled means. In particular water extracted in the earlier phases, where there is an excess of H₂O in the material, a may be reintroduced into the system in the later stages of the process tube 22 by which stage the majority of the moisture has been used and there is a shortage of moisture for the gasification process.

It may be appreciated that H₂O collected from the initial compression stages at valves 57 described above, can be added to the hot gas entry at any of the zones via the inlet valves 56 to cause pressurisation to help with heat transfer and hot gas (syngas) penetration through the waste material surface in the process tube. In particular the hot gas will vaporise the water as it is added and the increased volume of the liquid to gas phase change will cause a pressure increase in the process gas as it is added, thereby accelerating the gas into the processing tube 22 and assisting in conveying the material therein.

After each section a process check will be made of the process gas being extracted from that section giving the status of gas quality (chemical composition and temperature) and if the overall quality is good then the gas is qualified as process gas, and is allowed to pass through ducts 46 and into the outlet gas duct 47, and if the quality is poor then it will need reconditioning prior to using it in the next zone. In this case the gas will be re circulated via the exit pipes 54 and entered into the hot gas inlet ducts 27 via the valves 55 or any other suitable location. In this manner the process gas being extracted from the system via the conduit 47 can be controlled so that it is of a high quality. This ability to recycle the gas in individual sections of the apparatus gives the flexibility of a batch operating system and the gas conveying from one section to another gives the benefit of continuous operation. The apparatus therefore can operate in a continuous manner but is very adaptable at handling different waste products having different calorific values and different organic and moisture contents.

The pressure and temperature of the hot gas on entry to the sections via the inlets can be controlled to be higher in the later zone stages to collect CO and H₂ and break larger hydrocarbon molecules (CxHy).

With reference to FIG. 2 the system shown functions in the same manner as that shown in FIG. 1 except for the variation described below where a single pressurised tank 61 may be mounted remote from the process tube 22 above or below ground level. The tank is pressurised by a single compressor 62 which may be of the type described with reference to FIG. 1 or may be any other type of high temperature compressor.

As described previously, a recirculation loop can be provided to each section and a process check will be made giving the status of process gas overall quality and if the overall quality is good then the process gas passes through ducts 46 and into the outlet gas duct 47 and if the quality is poor then it can be re circulated via the exit pipes 54 and entered into the hot gas inlet duct via the valves 55 or any other more suitable location. It will be appreciated that in this arrangement the gas that is re-circulated is re-circulated into all of the sections as opposed to only the section from which it originated, as with the example of FIG. 1.

The process tube 22 also can be situated above or below ground level typically and if the tube is mounted below ground level then the compressed hot gas can be stored in a single pressurised tank 61, above or below ground, to feed all of the process tube zones, each of which can be selected for actuation in sequence via the relevant control valves 60. In the example of FIG. 1 if the process tube 22 is situated below ground then the compressors, which have moving parts and are therefore more likely to require maintenance, are situated above ground, or at least in an easily accessible position to facilitate maintenance. Furthermore the valves 44 that control the movement of waste from one section to another will each have an actuator to control them which is likewise also preferably situated above ground or at least in a readily accessible location.

Also as described previously it may be appreciated that H₂O collected from the initial compression stages at valves 57 described previously, can be added to the hot process gas entry at any of the zones via the inlet valves 56 to cause pressurisation and to help with heat transfer and hot gas (syngas) penetration through the waste material surface in the process tube.

As the waste material reduces in volume as it travels through the process tube (due to the continuous gasification), the last section zones can reduce in cross section or the mode of operation adjusted to give a higher flow to support less mass but higher density material transportation.

The movement speed of the waste material as it is conveyed through the process tube 22 can be proportional to the waste material requirements to process and gasify the organic matter therein and can be speeded up or slowed down accordingly by controlling one or more of, valve timings, compressor actuator operation and the introduction of H₂O into the process tube sections.

Referring now to both embodiments, raised portions of suitable form and size are mounted inside the process tube 22 along its length to cause the waste material 2C, 2D etc. to tumble and reform and allow the material to be opened up and aerated as it is forced through the process tube. Such raised details 63 are depicted in FIG. 2 but are omitted from FIG. 1 for clarity.

The process tube 22 interior walls may have rifling or a cut spiraled groove cut along its length to force the material to move away from the centre in addition to shaped fins 63 mounted within the process tube 22 to counteract the waste movement and push the material towards the centre of the tube. These features can be used individually or together, for example in alternation to move the material radially within the tube leading to a greater agitation and mixing, which leads to a better gas penetration and hence higher gasification rate.

Referring to FIG. 3, the system is shown in combination with a thermal oxidiser 65 in which process gas exiting the process tube 22 is thermally treated. The process gas is brought up to a temperature in excess of 800° C. for a period of around two minutes so as to break down long chain hydrocarbons and VOC's therein. This is done in a reduced oxygen environment so as to prevent combustion of the process gasses. Heat may be provided by means of a burner 66 in which a substantially stoichiometric mixture of fuel, for example natural gas or syngas, and oxygen are combusted. Some of the hot gasses from the thermal oxidiser 65 are used as the conveying gas to both move the material through the process tube 22 and to heat it. It will be appreciated that some details of the system shown in FIGS. 1 and 2, for example the compression of the gas and valving are omitted from FIG. 3 for clarity.

In addition to the heat supplied by the hot process gases additional means of heating 64 the process tube sections may be provided in order to control the individual zone temperatures and assist with the gasification process. These may be any known heating means, for example electrical, or may use system heat, for example they may circulate hot gasses from the thermal oxidiser 65 via recirculation conduits (not shown). This assists in ensuring a finer control of the process chamber temperature throughout the process, in particular it allows for fine control of the temperature in each section, thereby leading to a better control of the syngas quality of the process gas.

As described above the quality of the gas being produced can be monitored. If the gas is of low quality then it can either be sent to a separate chamber for conditioning, or alternatively can be cycled through the thermal processing chamber 65 and recirculated through the process tube until it reaches a desired quality. Once the system is producing high quality process gas (syngas) this can be removed from the system for use 68, or storage for later use, for example to drive a syngas generator.

During some stages of the process where the temperature is in particular ranges both carbon and coke can be formed in the apparatus. During the carbon and coke period the process tube sections, or the material therein, may be vibrated at the resonant frequency of the coke particulates to separate the cokes from the metal components, and intensify the gasification process of the harder to gasify coke components. The vibration may be created by back and forth pressure pulsing at the later stages to create cycling of the pressure, this may for example be achieved through the compressors or alternative vibration means (which may comprise a pressure wave generator or mechanical vibrators) may be used. This step will only be used at the later stage once most of the gasification process is completed, and only harder particulates are left, which will be mixed with or coating the metal fines.

Sensors for eddy currents and magnetic devices 67 may be fitted to agitate the waste dust in the later process tube stages to force the movement of the particles in a desired direction. These devices will be added to enable finer control over the gasification process toward the end of the process tubes when coke, ferrous, and non-ferrous matter are left from the gasification process. This agitation has a similar effect as the mechanical vibration in that it can help separate the coke and carbon from the metal and expose more of its surface area to the heat, thereby assisting its gasification.

The movement of the material between the various process tube sections will be fully controlled by controller 74 having a control algorithm that evaluates the status of the waste and process gas by receiving signals of process parameters from various sensors that measure the syngas quality over the various pipe zones, and other process parameters, for example temperature. Although not shown it will be appreciated that the controller will be connected to the various valves and sensors of the system to receive information relating to the operating parameters, and for sending control signals to the various valves, actuators and heaters to operate the system. Based on the status of the waste, the pressure, and syngas quality is changed. Furthermore, based on the condition of the waste and the rate of the gasification, the waste movement speed (residence time in each process tube section) can be controlled. This gives an additional degree of freedom to the gasification process, and allows the waste to be fully gasified, or converted to coke, before entering the final pipe sections in which the coke is then gasified.

With reference to FIGS. 4 and 5 the process tube 22 may be constructed such to have an outer skin 69 and an inner skin 70 which may serve to support the waste material within the confines of the inner skin 70 whilst allowing the inlet of the hot process gas to pass into the inner processing tube 71, from the void 72 between the inner and outer skin, at certain sections of the process tube 22 to aid a more effective waste degradation during gasification. Alternatively, or in combination, the waste material may be supported within the confines of the inner skin whilst allowing the hot process gas to pass out of the confines of the inner process tube 71 into the void 73 between the inner and outer tube construction at certain zone sections of the process tube 22 to aid a more effective waste degradation during gasification. It may be appreciated that the tube sections may take many cross sectional forms in a number of combinations that differ from those shown such as a round inner tube and a square outer tube for example.

Referring to FIG. 6 a variation of the apparatus of FIG. 3 is shown. In this embodiment there are two thermal oxidisers 65 and two outlet gas ducts 47. Each outlet gas duct 47 is connected to the conduits 46 by valves 74, 75. The quality of the process gas passing through the conduits 46 can be determined and depending on the quality either the valve 74 or the valve 75 can be opened to allow the process gas to pass through one outlet gas duct 47 or the other. In use low quality process gas, which does not meet predetermined criteria, will be routed through one outlet gas duct 47 and thermal oxidiser 65, which will treat the gas and re-circulate it back through the process tube 22 as conveying gas. Process gas above a certain quality will be routed through the other outlet gas duct and thermal oxidiser this oxidiser will thermally treat the gas and then the gas can either be re-circulated to the process tube 22 or can be output for storage or direct use, for example in a syngas engine to produce electricity. Although shown with all stages of the process tube 22 connected to both outlet ducts 47, a variation is to only connect the outlets of some of the sections of the processing tube 22 to one outlet duct or the other. It may be that for the material being processed it is known that the process gas from the first few stages will never reach the required quality as in these stages there are large amounts of volatiles and water vapour produced and the gasification is only just starting. Accordingly it may be appropriate that the outlet from these stages is always routed to one of the thermal oxidisers. In contrast the process gas in the last few stages, especially if the material has decomposed to carbons and cokes, will be high grade process gas and may always be routed to the other thermal oxidiser for treatment downstream storage or use. In the central stages where the process gas will shift in quality depending on the process parameters and the material being processed it may be appropriate to connect the conduits 46 to both conduits and control its flow with valves 74, 75 as described above in dependence on gas quality. An alternative arrangement not shown in the figures may be to use a single thermal oxidiser and to combust the lower quality process gas in the burner by mixing it with the fuel prior to injection.

Claims

1. Apparatus for processing material such as organically coated waste and organic materials including biomass, industrial waste, municipal solid waste and sludge; the apparatus comprising:

an elongate process tube having an inlet for receiving the material and an outlet for processed material;

a gas conveying system for fluidically conveying said material through said processing tube, said conveying system comprising a supply of conveying gas, comprising hot pressurised inert gas, connected to said processing tube at its inlet end; and

a control system configured to control the supply of said pressurised inert gas to said processing tube so as to convey a batch of said material through said tube simultaneously heating said material to cause any organic matter therein to gasify to produce process gas wherein

the processing tube comprises a plurality of sections, each separated by a valve, and wherein the gas conveying system is configured to convey the material from one section to the next.

2. The apparatus of claim 1 further comprising a separator configured to extract the process gas from the processing tube.

3. The apparatus of claim 1 wherein the gas conveying system includes a conveying gas inlet associated with each section for the supply of conveying gas to move the material therein into the next section.

4. The apparatus of claim 1 further comprising a conveying gas compressor for increasing the pressure of the conveying gas and wherein expansion of the conveying gas moves the material in the processing tube.

5. The apparatus of claim 4 wherein the conveying gas compressor comprises a compression chamber having a piston therein for receiving said conveying gas and an actuator for moving said piston in said chamber to compress the gas therein.

6. The apparatus of claim 5 wherein the compression chamber is sized such that one stroke of the piston in the chamber expels sufficient conveying gas to convey material from one section of the processing tube to be to another.

7. The apparatus of claim 4 wherein each section of the processing tube has a compressor associated with it.

8. The apparatus of claim 1 further comprising a fluid outlet in each section of the tube for draining fluid therefrom.

9. The apparatus of claim 5 further comprising a fluid outlet in each section of the tube for draining fluid therefrom and a fluid inlet in the conveying gas inlet conduit of each section for feeding fluid into said conveying gas.

10. The apparatus of claim 1 further comprising at least one thermal treatment chamber for thermally treating the process gas produced by the apparatus by heating it so as to breakdown any volatile organic compounds therein.

11. The apparatus of claim 10 further comprising an outlet conduit from at least one thermal treatment chamber for supplying hot process gas therefrom to the processing tube for use as said conveying gas.

12. The apparatus of claim 1 further comprising: a feed hopper for receiving and temporarily storing material to be processed, and a secondary hopper fed by the feed hopper wherein the secondary hopper is connected to the processing tube by a valve and wherein the secondary hopper has a conveying gas inlet at an upper end thereof.

13. The apparatus of claim 1 wherein each section of the processing tube has a process gas outlet towards its downstream end.

14. The apparatus of claim 1 further comprising sensors to sense the quality of the process gas and: if it does not meet a predetermined criteria, recirculating the process gas through the processing tube and, if it does meet the predetermined criteria extracting at least a part of the process gasses for storage or direct use.

15. The apparatus of claim 1 wherein the interior surface of the processing tube is provided with fixed agitators to promote the tumbling of material within said tube as it is conveyed therethrough.

16. A method for processing material such as organically coated waste and organic materials including biomass, industrial waste, municipal solid waste and sludge; the method comprising:

providing an elongate process tube having an inlet for receiving the material and an outlet for processed material;

providing a gas conveying system for fluidically conveying said material through said processing tube, said conveying system comprising a supply of hot pressurised inert gas connected to said processing tube at its inlet end; and

controlling the supply of said pressurised inert gas to said processing tube so as to convey a batch of said material through said tube thereby heating said material to cause any organic matter therein to gasify to produce process gas wherein

the processing tube comprises a plurality of sections, each separated by a valve, each section having a conveying gas inlet associated therewith for the supply of conveying gas; the method further comprising controlling the supply of conveying gas so as to convey the material from one section to the next.

17. The method of claim 16 further comprising separating the process gas from the processing tube.

18. The method of claim 17 further comprising compressing the conveying gas to increase its pressure and wherein expansion of the conveying gas moves the material in the processing tube.

19. The method of claims 16 further comprising draining fluid from each section of the tube via a fluid outlet therein.

20. The method of claim 19 further comprising supplying fluid drained from the tube into the conveying gas upstream of the processing tube.

21. The method of claim 20 wherein the temperature of the conveying gas is sufficient to vaporise the fluid added thereto, thereby increasing the pressure of said conveying gas.

22. The method of claims 16 further comprising heating the process gases in a thermal treatment chamber to thermally breakdown any volatile organic compounds therein.

23. The method of claim 22 further comprising supplying hot process gas from the thermal treatment chamber to the processing tube for use as said conveying gas.

24. The method of claims 16 further comprising: providing a feed hopper for receiving and temporarily storing material to be processed; providing a secondary hopper fed by the feed hopper wherein the secondary hopper is connected to the processing tube by a valve; providing a conveying gas inlet at an upper end of the secondary hopper; feeding a batch of material to be processed from the feed hopper to the secondary hopper; passing gas through the conveying gas inlet and opening the valve such that the batch of material is conveyed from the secondary hopper into the processing tube.

25. The method of claims 16 further comprising providing each section of the processing tube with a process gas outlet towards its downstream end and extracting process gas via said process gas outlets.

26. The method of claims 16 further comprising sensing the quality of the process gas and: if it does not meet a predetermined criteria, recirculating the process gas through the processing tube and, if it does meet the predetermined criteria extracting at least a part of the process gasses for storage or direct use.

27. The method of claims 16 further comprising providing a waste material silo downstream of the processing tube for collecting the inert fully processed material.

28. The method of claims 16 further comprising agitating said material within the tube as it is conveyed there through.

29. The method of claim 16 further comprising heating the process gases from initial sections of the processing tube in a first thermal treatment chamber, to thermally breakdown any volatile organic compounds therein, and recycling the treated gas as conveying gas.

30. The method of claim 29 further comprising heating the process gases from final sections of the processing tube in a second thermal treatment chamber, to thermally breakdown any volatile organic compounds therein.

31. The method of claim 16 further comprising determining the quality of the process gas and: if the process gas is below a predetermined quality threshold, passing the process gas through a first thermal treatment chamber to heat the gas so as to thermally breakdown any volatile organic compounds therein, and recycling the treated gas as conveying gas; and if the process gas is above a predetermined quality threshold, passing the process gas through a second thermal treatment chamber to heat the gas so as to thermally breakdown any volatile organic compounds therein.