Abstract:
The invention provides an apparatus for processing material such as organically coated waste and organic materials including biomass, industrial waste, municipal solid waste and sludge, comprising a processing chamber ( 2 ) for processing said material at an elevated temperature to produce syngas and a combustion chamber ( 4 ) having at least one burner therein for combusting syngas released by processing of said material. A conduit means ( 18 ) is provided between said combustion chamber and said processing chamber for carrying hot exhaust gasses from the combustion chamber ( 4 ) to said processing chamber ( 2 ) and at last one mirror ( 24 ) is arranged to reflect and concentrate sunlight thereby to cause the temperature within said processing chamber ( 2 ) to be raised. The apparatus also includes a syngas reservoir ( 66 ). A storage conduit ( 62 ) is provided for carrying syngas into said syngas reservoir ( 66 ) and a syngas feed line ( 68 ) is provided for feeding syngas from said reservoir to said combustion chamber ( 4 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to International Application No. PCT/GB2010/002178 filed on Nov. 26, 2010, which claims priority to Great Britain Patent Application No. 0921266.3 filed on Dec. 4, 2009. 
     
    
     STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT 
       [0002]    Not Applicable 
       BACKGROUND OF THE INVENTION 
       [0003]    This invention relates to gasification systems, in particular to gasification systems for waste. 
         [0004]    Thermal gasification of waste products by the pyrolysis under controlled conditions is a known process used to disseminate waste and to produce synthetic gas (syngas) therefrom which can then be used for the production of energy in known ways. Accordingly energy can be recovered from organic matter within waste. 
         [0005]    One problem associated with such processes is that to provide the heat for the pyrolysis to occur currently necessitates the use of natural gas burners. The natural gas is needed to start the system and bring the waste material up to its pyrolysis temperature and then to provide a constant burner in which the syngas can be combusted. 
         [0006]    The use of natural gas in waste gasification systems removes some of the environmental benefits of recovering energy from waste organic matter and can somewhat offset any advantages gained. 
       SUMMARY OF THE INVENTION 
       [0007]    It is the purpose of the present invention to provide an improved system for processing organic waste. 
         [0008]    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, comprising: a processing chamber for processing said material at an elevated temperature, in an oxygen deficient environment, to produce syngas; a combustion chamber having at least one burner therein for combusting syngas released by processing of said material; a conduit means between said combustion chamber and said processing chamber for carrying hot exhaust gasses from the combustion chamber to said processing chamber; and at last one mirror arranged to reflect and concentrate sunlight thereby to cause the temperature within said processing chamber to be raised. 
         [0009]    The invention may further include: a syngas reservoir; a storage conduit for carrying syngas into said syngas reservoir; and a syngas feed line for feeding syngas from said reservoir to said combustion chamber. 
         [0010]    The storage conduit and feed line may comprise sections of a conduit between said processing chamber and said combustion chamber such that the syngas reservoir is inline in said conduit. Alternatively the reservoir can be located offline and the storage conduit and feed line connect the reservoir to the processing chamber and combustion chamber respectively, and may optionally branch from the a conduit between said processing chamber and said combustion chamber, accordingly a syngas reservoir bypass conduit is provided for the flow of syngas from the processing chamber to the combustion chamber without passing through the syngas reservoir. 
         [0011]    Preferably a first control valve to control the flow of gas from the processing chamber into the syngas reservoir and a second valve to control the flow of combustion chamber exhaust gas into said processing chamber are provided. 
         [0012]    The apparatus therefore can be configured to direct excess syngas into a storage reservoir. This has several benefits including the provision of a smaller combustion chamber. As, when used for batch processing of organic waste the syngas produced is not a steady flow but rather ramps up at the start of the process and ramps down at the end of the process the combustion chamber must be dimensioned to meet maximum demand. By providing a syngas reservoir to which some of the syngas can be diverted the consumption of syngas in the combustion chamber can be balanced over the cycle. Further advantages of the reservoir are detailed below. 
         [0013]    The apparatus according may further comprise a second mirror for reflecting sunlight onto a second heat absorbent surface adjacent said reservoir bypass conduit do as to pre heat said syngas passing through said bypass conduit prior to combustion in said combustion chamber. By raising the syngas temperature prior to its combustion in the combustion chamber less external energy is needed during the combustion process. In a preferred arrangement the apparatus comprises a combustion tower housing said combustion chamber and the second heat absorbent surface comprises an external surface of said combustion tower. 
         [0014]    Preferably the apparatus according to any preceding claim further comprising a fossil fuel feed line to said burner capable of maintaining a burner pilot and/or, in the absence of sufficient syngas and/or solar heat, providing sufficient fossil fuel for combustion in said burner so as to, in use, create sufficient heat for the oxidation of any syngas entering said combustion chamber. 
         [0015]    In one arrangement the invention further comprises at least one external heat absorbent surface associated therewith and said at last one mirror is arranged to reflect and concentrate sunlight onto said heat absorbing surface, said heat absorbent surface comprising a heat absorbent external layer and a first gas heating conduit adjacent said heat absorbent layer for receiving combustion chamber exhaust gas, said first gas heating conduit in fluid communication with said processing chamber such that, in use, combustion chamber exhaust gas passing adjacent said heat absorbent surface is heated by said reflected sunlight and flows into said process chamber so as to raise the temperature therein. 
         [0016]    By heating a gas that is then carried into the processing chamber greater control of the processing chamber environment can be obtained as the gas flow can be increased or decreased to alter its residency time in the first gas heating conduit so as to alter the temperature of said gas entering said processing chamber. 
         [0017]    Preferably there is an insulating layer adjacent said gas first heating conduit and separated from said absorbent layer thereby; and a bypass valve operable to either direct exhaust gas from said combustion chamber through said first gas heating conduit or direct exhaust gas from said combustion chamber through a gas heating conduit bypass; wherein said gas heating conduit bypass is separated from said heat absorbent surface by an insulating layer. 
         [0018]    In this manner, when sunlight is available to heat the absorbent surface the exhaust gasses from the combustion chamber can pass through the first gas heating conduit to become heated and when no, or minimal, sunlight is available, for example at night time, the hot exhaust gasses from the combustion chamber can bypass the absorbent surface so as to avoid heat loss therefrom, thereby ensuring the maximum amount of the heat from the combustion chamber exhaust gas enters the processing chamber to heat it. 
         [0019]    In a preferred embodiment the processing chamber is movable and the heat absorbent surface forms an external surface of said movable processing chamber. 
         [0020]    The external surface of the first and/or second heat absorbing surface may have a surface texture thereon so as to increase its surface area. Although beneficial in fixed arrangements this is especially beneficial in arrangements wherein the processing chamber moves, e.g rotates or pivots, during operation as it maximises, at any one time, the surface area exposed to the reflected sunlight and reduces the need for the mirrors to track the movement of the processing chamber. Preferably the internal surface of the first and/or second heating conduit has a surface texture thereon to induce turbulence in gas flow therethrough thereby increasing heat exchange with said heat absorbent surface. 
         [0021]    The apparatus may further comprise a further at least one mirror for reflecting and concentrating sunlight directly into said combustion chamber so as to raise the temperature within said combustion chamber. 
         [0022]    By reflecting concentrated solar energy directly into the combustion chamber solar energy can be directly used to raise the syngas temperature to the required 850° plus that is needed for the combustion of syngas to reduce harmful emissions. The use of direct solar heating for this process has the further added advantage that it is easier to provide the required residency period of two seconds at the elevated temperature for the syngas to oxidize as when using the combustion of syngas with the aid of a natural gas burner. Since the addition of the natural gas, and oxidant to burn the natural gas, in the combustion chamber will increase the total volume of gas to be burned inside the combustion chamber a larger combustion chamber is needed to accommodate and combust this extra volume. Then elimination, or at worst minimisation, of the natural gas needed hence reduces the volume of the combustion chamber needed to achieve the required residency time. 
         [0023]    By reflecting concentrated solar energy directly into the combustion chamber solar energy can be directly used to raise the syngas temperature to the required 850° plus that is needed for the combustion of syngas to reduce harmful emissions. The use of direct solar heating for this process has the further added advantage that it is easier to provide the required residency period of two seconds at the elevated temperature for the syngas to oxidize as when using the combustion of syngas with the aid of a natural gas burner. Since the addition of the natural gas, and oxidant to burn the natural gas, in the combustion chamber will increase the total volume of gas to be burned inside the combustion chamber a larger combustion chamber is needed to accommodate and combust this extra volume. Then elimination, or at worst minimisation, of the natural gas needed hence reduces the volume of the combustion chamber needed to achieve the required residency time. 
         [0024]    In a preferred arrangement a conduit between said processing chamber and said combustion chamber is arranged to direct syngas into said combustion chamber burner. In this manner, when syngas is available it can be burned in the burner in place of fossil fuel to reduce the fossil fuel needed or, where solar heating is used in the combustion chamber, the syngas can be burned in the burner when there is insufficient solar energy available to raise the combustion chamber to the required combustion temperature. 
         [0025]    The apparatus preferably comprises a combustion chamber exhaust gas outlet for supplying hot exhaust gas to a means of converting heat to electrical energy. 
         [0026]    According to a second aspect of the invention there is provided a method of processing organic waste comprising: placing said organic waste in a processing chamber; reflecting sunlight from a plurality of mirrored surfaces onto a heat absorbent surface so as to raise the temperature within said processing chamber so as to cause the organic waste material to gassify and produce synthetic gas; withdrawing said synthetic gas from said processing chamber and passing it into a combustion chamber where its temperature is raised to sufficient temperature to so as to destroy any volatile organic compounds (VOC&#39;s) therein; and re-circulating at least a portion of the combustion chamber exhaust gas back into said processing chamber. 
         [0027]    Preferably the method includes: diverting at least a portion of said withdrawn syngas into a storage reservoir; and passing the remainder of the syngas into a combustion chamber. The method may also comprise feeding syngas from said storage reservoir to said combustion chamber. Preferably heat from said recycled combustion chamber exhaust gas makes up any shortfall in thermal input from reflected sunlight. 
         [0028]    In this method a portion of the syngas created during sunlight processing cycles is diverted and stored for use as a fuel during the night time (or periods of low solar energy) processing cycle, i.e. the solar energy is converted into chemical energy and is stored in the form of a syngas for use during night time processing cycles where it is converted from chemical energy to thermal energy to drive the processing of the organic waste. In this manner the size of the combustion chamber can be balanced to the combined night time/daytime processing cycle needs 
         [0029]    The temperature of the syngas in the combustion chamber may be raised in the presence of oxygen to a sufficient temperature to oxidise said synthetic gas. 
         [0030]    The method may comprising introducing fossil fuel into a burner within the combustion chamber to produce a flow of hot combustion chamber exhaust gas sufficient to compensate for any shortfall in reflected sunlight used for heating said processing chamber. Preferably the method also comprises: controlling the flow of syngas diverted into the reservoir; controlling the flow of syngas from the reservoir into the combustion chamber; and controlling the flow of combustion chamber exhaust gas into the processing chamber; so as to maximise the solar energy used by the process and minimise the fossil fuel burnt in the burner. 
         [0031]    Benefits of the method reflect those described in relation to the apparatus 
         [0032]    The method may comprise: during sunlight hours, following the method as described above and; during night time hours, introducing syngas from said syngas reservoir into a burner within said combustion chamber so as to: a) create sufficient hot exhaust gas to heat said processing chamber to the required temperature for the gasification of the organic waste therein; and b) raise the temperature within the combustion chamber to a sufficient temperature to destroy any VOC&#39;s therein and/or oxidise therein syngas produced in and received from said processing chamber. 
         [0033]    In this manner solar energy is used when available to provide heating for the process chamber and optionally pre-heating of the syngas prior to combustion and heating the syngas in the combustion chamber and, when not available, i.e. during a night time processing cycle using fossil fuels to provide the required thermal input to the system. It will be appreciated that the night time cycle may be run at any time when there is insufficient solar energy to provide the required heat and is not restricted to use during night time hours. 
         [0034]    During said night time hours the method may further comprise: if said syngas reservoir becomes depleted below a predetermined threshold, introducing fossil fuel into said burner in said combustion chamber in sufficient quantities to: a) create sufficient hot exhaust gas to heat said processing chamber to the required temperature for the gasification of the organic waste therein; and b) raise the temperature within the combustion chamber to a sufficient temperature to destroy and VOC&#39;s therein oxidise therein syngas produced in and received from said processing chamber. 
         [0035]    During Daylight hours the method may further comprise: passing combustion chamber exhaust gas adjacent said heat absorbent surface to heat said exhaust gas with said reflected sunlight; and passing said heated gas into said process chamber so as to raise the temperature within said processing chamber. 
         [0036]    The method may further comprise: raising the temperature of said syngas prior to passing it into said combustion chamber by passing said syngas adjacent a second heat absorbent surface; and reflecting sunlight from a second at least one mirrored surface onto said second heat absorbent surface. 
         [0037]    The method may comprise reflecting and concentrating sunlight into said combustion chamber so as to directly heat gasses therein. Reflecting and concentrating sunlight into said combustion chamber may heat the gasses therein to a temperature at which in the presence of oxygen they oxidise. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0038]      FIGS. 1 and 2  show schematic diagrams of processes in accordance with the invention; 
           [0039]      FIG. 3  shows an apparatus for performing the process of  FIG. 2 ; 
           [0040]      FIG. 4  shows a further schematic diagram of a process in accordance with the invention; 
           [0041]      FIG. 5  shows an apparatus for performing the process of  FIG. 4 ; 
           [0042]      FIG. 6  shows a diagram of the heat exchange surfaces of the apparatus of  FIGS. 3 and 5 ; 
           [0043]      FIG. 7  shows a further schematic diagram of a process in accordance with the invention; and 
           [0044]      FIG. 8  shows an apparatus for performing the process of  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0045]    Referring to  FIG. 1  a diagram of an apparatus for processing organic waste is shown. The apparatus comprises a processing chamber  2  in which waste material containing organic substances is thermally treated. The processing chamber  2  may be of a known type which may include a through-process chamber in which a stream of waste material containing organic substances is continuously fed into one end and the char removed from the other or, alternatively, it may be used in a batch processing method wherein waste material is loaded in to the processing chamber  2 , is left therein for a period of time, and then is removed from the processing chamber  2 . The processing chamber  2  is preferably moved during use so as to expose all surfaces of the waste material therein such that they may be processed. Movement may include one or more of rotating or tipping the processing chamber. 
         [0046]    A combustion chamber  4  is connected to an outlet of the processing chamber  2  by conduit  6  which has a valve  8  therein. Conduit  6  carries syngas created by the processing of the organic waste material. The valve  8  may control one or both of the flow of syngas into the combustion chamber  4  and the back pressure within the processing chamber  2 . The combustion chamber  4  contains a burner, not shown, in which the syngas is combusted. 
         [0047]    Oxygen, or an Oxygen containing gas, for example compressed air, is injected into the combustion chamber  4  from supply  10 . Sufficient Oxygen, or Oxygen containing gas, is added to the combustion chamber to enable the full oxidation of Volatile Organic Compounds (VOC&#39;s) in the syngas combusting therein, although it will be appreciated that oxygen is not required to destroy the VOC&#39;s which may alternatively be heated in the absence of oxygen so as to cause them to break down. The combustion chamber  4  is maintained at a temperature in excess of 850° C. This temperature may be achieved either by the combustion of the syngas itself or alternatively, or in addition, by the combustion of a fossil fuel, in particular natural gas, which is supplied from source  12  through conduit  14  and is controlled by means of valve  16 . The burner may comprise an afterburner arrangement into which the syngas is introduced. 
         [0048]    An outlet conduit  18  withdraws a proportion of the hot combustion gasses from the combustion chamber  4  and passes these through a first gas heating conduit  20  and from there into the processing chamber  2 . The flow of hot exhaust gasses from the combustion chamber  4  into the first gas heating conduit is controlled by means of valve  22 . 
         [0049]    A solar reflector means  24  reflects sunlight onto an absorbent surface  26  of the first gas heating conduit  20 . 
         [0050]    The solar reflector means  24  comprises a mirror which focuses and concentrates the sunlight. The mirror may be any one of a number of known high temperature solar collectors for example it may include one or more parabolic troughs, parabolic dishes, Fresnel Reflectors or Linear Fresnel Reflectors. 
         [0051]    The concentrated sunlight imparts thermal energy into the gas passing through the first gas heating conduit  20  thereby increasing its temperature before it passes into the processing chamber  2 . The thermally heated exhaust gasses impart heat into the organic waste material in the processing chamber  2  causing it to pyrolysis and release synthetic gas. 
         [0052]    The amount of natural gas from source  12  that is combusted in the combustion chamber  4  will vary throughout the process cycle and will reduce as the amount of syngas produce from the combustion chamber  4  increases. 
         [0053]    A first gas heating conduit bypass  28  having a valve  30  therein allows the hot exhaust gasses taken from the combustion chamber  4  to bypass the first gas heating conduit  20 . This bypass would be used in times of low solar energy whereby passing the hot combustion chamber exhaust gas through the first gas heating conduit  20  would result in a heat loss from the absorbent surface thereof. In such conditions, bypassing the gas heating conduit  20  results in hotter gasses being inputted to the processing chamber  2 . 
         [0054]    When the bypass  28  is in use it is anticipated that a higher volume of natural gas would be burned within the combustion chamber  4  such that a larger volume of hot exhaust gasses are input into the combustion chamber  4  to compensate for their lower temperature due to the lack of additional solar thermal heating. 
         [0055]    Combustion chamber  4  has an outlet conduit  32  which takes the hot exhaust gasses not re-circulated back into the processing chamber  2  to an energy generation plant. The hot exhaust gasses may, for example, be used to create steam to power a steam turbine. 
         [0056]    The inclusion of the solar reflector  24  into the process reduces the volume of natural gas required to maintain the process thereby reducing the environmental impact associated with the use of fossil fuels. The flow rates of gas through the various valves is controlled so as to maintain a predetermined temperature and pressure within the processing chamber  2  in order to thermally decompose all the organic matter therein without melting the majority of the metal within the waste. However, metals with very low melting points, for example lead, may be melted within the process. 
         [0057]    Referring to  FIG. 2  a similar system to that of  FIG. 1  is shown. In addition, instead of the syngas leaving the processing chamber  2  via conduit  6  being fed directly into the combustion chamber  4 , it first passes through a second heating conduit  34  which has a second heat absorbent surface  36 . One or more solar reflectors  24  as described above reflect sunlight onto the heat absorbent surface of the second heating conduit  34  so as to heat the syngas from the processing chamber  2  prior to its introduction to the combustion chamber  4 . 
         [0058]    By heating the syngas to close to its combustion temperature prior to adding it into the combustion chamber  4  the amount of energy needed in the combustion chamber  4  to combust it at a temperature in excess of 850° C. is thereby reduced, further improving the efficiency of the system. 
         [0059]    While it is noted that the total amount of energy required to thermally decompose the organic material and to combust the syngas produced therefrom does not change, the source of a proportion of this energy, in the present invention, is provided by the solar reflectors and therefore a reduced reliance on fossil fuels from supply  12  is achieved. 
         [0060]    Referring to  FIG. 3  a diagram of an apparatus in accordance with the present invention is shown. The apparatus comprises a processing chamber  2  which is pivotally mounted on to processing chamber mounts  40  such that, in use, it can be pivoted thereon so as to cause any organic waste materials therein to pass from one side of the processing chamber  2  to the other. The processing chamber may be of the type described in published patent application WO 2006/100512. 
         [0061]    The conduit  6  connects an outlet of the processing chamber  2  to the combustion chamber  4  and an outlet conduit  18  connects the combustion tower  4  to the processing chamber  2 . 
         [0062]    A plurality of solar reflectors  24  reflect light from the sun  42  onto a heat absorbing surface  20  of the processing chamber and a heat absorbing surface  34  of the combustion chamber  4 . 
         [0063]    The solar reflectors are shown as parabolic mirrors which may be positioned via positioning means  44  to track the sun so as to reflect solar energy onto the heat absorbing surfaces  20 ,  34 . The combustion chamber  34  has a natural gas inlet and an Oxygen inlet, not shown. 
         [0064]    The outlet of the combustion chamber  4  has a valve block  46  which controls the proportion of the hot exhaust gasses from the combustion chamber  34  which are directed through conduit  18  to the processing chamber and through conduit  32  to a power generation means. In use the apparatus of  FIG. 3  are operated as described with reference to the system of  FIG. 2 . Further details of the heat absorbent panels  20 ,  34  are described below with reference to  FIG. 6 . 
         [0065]    Referring to  FIGS. 4 and 5  a schematic diagram and apparatus of a further embodiment of the invention are shown. The system is substantially similar to that shown in  FIGS. 2 and 3  except in so far as additional solar reflectors  48  are provided to reflect and concentrate sunlight from the sun  42  directly into the combustion chamber  4  so as to raise the temperature therein. The combustion chamber  4  comprises at least one substantially transparent section  50  through which the concentrated sunlight reflected by solar reflectors  48  can pass to enter the combustion chamber  4 . In use the syngas exits the processing chamber  2  via conduit  6  and its flow is controlled by valve  8 . The syngas then passes through the heat exchange panels  34  where it is heated by sunlight reflected by parabolic dishes  24  which reflect and concentrate sunlight onto the heat absorbent surface  36  of the panels  34 . The preheated syngas then enters the combustion chamber  4  where its temperature is increased to a combustion temperature in excess of 850° C. by concentrated sunlight reflected directly into the combustion chamber  4  by parabolic mirrors  48 . A supply of Oxygen, or Oxygen containing gas  10 , is supplied to the combustion chamber with the syngas in sufficient quantities for full oxidation of Volatile Organic Compounds (VOC&#39;s) within the syngas to occur within the combustion chamber. 
         [0066]    The combustion chamber  4  is also supplied with natural gas from a supply  12  through conduit  14 , the supply being controlled by valve  16 . At times when there is insufficient sunlight to power the combustion process within the combustion chamber  4  natural gas can be burnt in the combustion chamber  4  so as to increase the temperature therein. The remainder of the system operates substantially as described with reference to  FIGS. 2 and 3 . 
         [0067]    The system and apparatus shown in  FIGS. 4 and 5  maximise the use of available solar energy and can drastically reduce the amount of fossil fuels that are needed to be consumed to process organic waste material within the processing chamber  2 . Furthermore, the excess exhaust gasses from the combustion chamber  4  are used to power an electricity generating means resulting in a waste processing apparatus that transfers solar thermal energy into chemical potential energy within the processing chamber by processing organic waste and then combusts the chemical potential energy within combustion chamber  4  to produce thermal and kinetic energy in exhaust gasses passing through conduit  32  which can then be transferred into electrical potential energy. 
         [0068]    Accordingly, not only is waste material safely processed but as a by-product of the waste processing cycle electrical energy can be produced with the minimum reliance upon fossil fuels. 
         [0069]    It will be appreciated that the solar energy can only be used to power the processing of the waste materials during hours of sufficient sunlight. Accordingly, in a second mode of operation the system shown in any one of diagrams  1 , 2  and  4  can, during hours where there is not sufficient sunlight to provide the required thermal energy input, function solely on the thermal energy provided by the combustion or natural gas from source  12  within the combustion chamber. 
         [0070]    Referring to  FIG. 6  a schematic cross-section of heating panels  20 ,  34  of the invention is shown. The panels are shown in two modes of operation, a night time mode of operation and a daytime mode of operation. During the daytime mode of operation exhaust gasses from the combustion chamber  4  enter the heating panel  52  via conduit  18  and pass through a first gas heating conduit  20  which runs adjacent the absorbent surface  26 . Although not shown the heat absorbing surface  26  may have a corrugated or otherwise adapted external surface that increases its surface area. The use of an externally textured surface, for example a corrugated surface is especially beneficial when used with moving or rotating processing chambers as it ensures that there are always parts of the surface area which are perpendicular to the light reflected from the solar reflectors thereby enabling maximum heat absorbance. 
         [0071]    The internal surface  54  of the conduit  20  may contain a surface texture that encourages the turbulent flow of exhaust gasses through the conduit  20 . By inducing turbulent flow over the internal surface through which heat is absorbed, maximum heat transfer into the flowing gasses is obtained. The panel  52  may comprise a large flat conduit  20  or alternatively may comprise a plurality of smaller conduits arranged adjacent to one another substantially over the entire heat absorbent surface  26  of the panel  52 . 
         [0072]    After passing through the conduit  20  the heated exhaust gasses exit the panel  52  via outlet  56  and may thereafter directly enter the processing chamber  2 . In some arrangements the outlets surface  58  of the panel  52  may comprise an internal surface of the processing chamber  2 . 
         [0073]    During night time use valve  30  is opened and the exhaust gasses from the combustion chamber  4  flow therethrough. The conduit  28  through which the exhaust gasses flow bypasses the heat exchange surface  26  of the panel  52  and is separated therefrom via a layer of insulation  60 . During non-sunlight, or low sunlight hours the heat absorbent surface  26  will be at a lower temperature than the exhaust gasses entering the conduit  28  and therefore, without the thermal separation of the hot exhaust gasses from the heat absorbent surface  26  heat would be lost through the surface  26 . Having bypassed the first heating conduit  20  the hot exhaust gasses pass directly from the combustion chamber  4  through outlets  56  into the processing chamber  2 . Accordingly a heat absorbing panel may be provided that can be used to receive heat into gas passing therethrough during the hours in which solar energy is available and may thermally insulate exhaust gasses from combustion chamber  4  from the external environment when insufficient solar energy is available to affect heat. 
         [0074]    Referring to  FIGS. 7 and 8  a further embodiment of the invention is shown. The apparatus is substantially as described in relation to  FIGS. 4 and 5  except in so far as a storage conduit  62  with a control valve  64  therein branches off the conduit  6  which carries syngas from the processing chamber  2  to the combustion chamber  4  via heat exchange conduit  34 . The storage conduit  62  feeds into a syngas reservoir in which syngas can be stored. A syngas feed line  68  connects the syngas reservoir  66  to the combustion chamber  4 . The syngas feed line  68  has a valve  70  therein for controlling the feed of syngas from the syngas reservoir  66  into the combustion chamber  4 . The syngas feed line  68  may feed syngas from the reservoir  66  back into the conduit  6  so that it can travel therein to the combustion chamber  4  or, alternatively, the syngas feed line  68  may lead directly into the combustion chamber  4  without reconnecting with conduit  6 . 
         [0075]    In arrangements where the syngas feed line  68  leads back into conduit  6 , a valve, not shown, is positioned in conduit  6  between the junctions with the storage conduit  62  and the syngas feed line  68 . 
         [0076]    In use, syngas exiting the processing chamber  2  via conduit  6  may be directed such that a proportion of the syngas enters the combustion chamber for combustion therein and a proportion of the syngas produced is withdrawn from the conduit  6  and is stored in the syngas reservoir  66  via storage conduit  62 . 
         [0077]    As the processing chamber  2  is, in a preferred arrangement, a batch processing chamber the output level of syngas varies in relation to the treatment cycle. During the initial period of treatment a low production of syngas is achieved which increases to a maximum production rate of syngas toward the middle of the cycle and, towards the end of the cycle the syngas production rate decreases. The syngas reservoir  66  may act as a buffer to withdraw syngas from the system during times of maximum production and to return syngas to the system during times of lower production so as to even the flow of syngas to the combustion chamber  4  throughout the processing cycle. 
         [0078]    Alternatively, or in addition to evening the flow of syngas to the combustion chamber  4 , syngas drawn from the syngas reservoir  66  may be combusted at a higher or lower rate within a combustion chamber  4  to vary the temperature and flow rate of exhaust gas passing therefrom into the processing chamber  2 . In this manner, during the initial stages of the cycle where the organic waste material within the processing chamber  2  is at a relatively low temperature heat can be quickly supplied to the processing chamber to bring the temperature of the organic containing waste material up to its processing temperature. This heating is provided in two manners. Firstly by the rate of syngas and/or natural gas burnt within the combustion chamber and secondly by the amount of solar energy that can be reflected from the solar reflectors  24  on to the heating conduits  20  to increase the temperature of the exhaust gasses from combustion chamber  4 . Once the processing chamber  2  is at its processing temperature the volume of syngas from the reservoir  66  that is being combusted in the combustion chamber  4  can be decreased such that sufficient heat is maintained within the processing chamber  2  for the process to continue. 
         [0079]    Towards the end of the processing cycle, as the syngas production rate within the processing chamber  2  decreases, then additional syngas may be added into the combustion chamber  4  from the syngas reservoir  66  so as to maintain a high enough temperature and flow of exhaust gasses to maintain the production of electricity from the electricity producing means powered by the exhaust gasses supplied by conduit  32 . It is anticipated that during the middle period of the processing cycle, when maximum syngas is being produced from the processing chamber, that sufficient syngas will be produced to both power the combustion chamber and to allow for a proportion of the produced syngas to be withdrawn via storage conduit  62  to replenish syngas levels within the reservoir  66 . 
         [0080]    In a preferred method of operation the processing chamber  2  produces sufficient excess syngas during hours of sunlight such that a sufficient reserve can be stored within the reservoir  66  such that, at night time, when the solar energy is not available to power the system that a large portion, if not all, of the heating requirement of the combustion chamber  4  can be provided by the combustion therein of syngas from the syngas reservoir  66 , in combination with the syngas produced by the processing chamber  2 . In this manner, the system can be run during both the night time and daytime with a minimal need for the additional use of fossil fuels. Effectively, the syngas within the reservoir  66  is used to store the solar energy utilised within the process during sunlight hours for conversion back into thermal energy during night time hours. 
         [0081]    As will be appreciated the skilled person, various standard operating conditions are associated with the combustion of syngas, for example the temperature and residence time at which it is combusted in order to fully oxidise any VOCs therein and various exhaust gas treatment operations would be used in connection with the method and apparatus as described herein. 
         [0082]    It will further be appreciated by the skilled person that various combinations of the features of the embodiments may be utilised in combination with one another whilst remaining within the scope of the invention. For example, the syngas reservoir  66  described in relation to  FIGS. 7 and 8  may be used with the system as described in  FIGS. 1 to 3 .