Combustion apparatus

Abstract

A combustion apparatus 10 for combustion of particulate combustible material comprises a combustion portion 60 which defines an internal combustion chamber (12, Fig. 4) and an outlet portion 100. A fi

Description

FIELD The present disclosure relates to a combustion system. Aspects of the disclosure relate to a combustion apparatus, to a combustion system, and to a method of combusting combustible material. BACKGROUND Combustion of particulate materials occurs in various industries including power generation, manufacturing, and waste management. Cyclone combustors are a type of combustion system that utilizes a high-speed rotating airflow to enhance the mixing of fuel and air, thereby improving combustion efficiency. These systems are particularly effective for burning particulate materials due to their ability to handle a wide range of combustible materials of different particle sizes and compositions. However, there are challenges to be overcome for cyclone combustors, such as incomplete combustion, inefficient energy conversion, and maintenance. It is an aim of the present invention to address one or more of the disadvantages associated with the prior art. SUMMARY The present teachings provide a combustion apparatus, a combustion system, and a method according to the appended claims. A first aspect of the teachings provides a combustion apparatus for combustion of particulate combustible material. The combustion apparatus comprises: a combustion portion which defines an internal combustion chamber; and an outlet portion comprising a first end coupled to an open end of the combustion portion and a second end which defines an exhaust gas outlet. The combustion portion comprises one or more inlets for input of combustible material and air to the internal combustion chamber. The outlet portion comprises a combustion residue outlet positioned between the first and second ends of the outlet portion for output of combustion residue from the combustion apparatus. It is desirable for as much combustion residue (i.e., material which is leftover after a combustion process) to be removed from the combustion apparatus as possible. In particular, increasing the proportion of combustion residue that is removed through a combustion residue outlet decreases the proportion of combustion residue that remains inside the internal combustion chamber. As a result, this increases the amount of time the combustion apparatus can be used for before manual cleaning of the combustion residue has to take place (e.g., by disassembling the combustion apparatus and scraping out the combustion residue). It has been found that positioning the residue outlet in an outlet portion coupled to an open end of the combustion portion increases the proportion of combustion residue which is captured in the combustion residue outlet in comparison to alternatives (e.g., configurations in which the combustion residue outlet is provided within the internal combustion chamber proximal to a closed end of the internal combustion chamber). In addition, such a configuration in which the combustion residue outlet is located in the outlet portion may facilitate easier cleaning of the combustion portion (e.g., by sliding out a portion of the combustion portion, without having to disconnect a combustion residue removal device, such as an outlet auger, from the combustion residue outlet). Optionally, the one or more inlets are arranged to create a swirling flow of air within the internal combustion chamber when a flow of air is supplied through the one or more inlets. Such a swirling flow of air or "vortex" may facilitate an effective combustion process within the internal combustion chamber, particularly for particulate combustible material which can be directed away from the respective inlet by the swirling flow. In addition, such a swirling flow of air may facilitate directing combustion residue towards the combustion residue outlet (i.e., by urging the combustion residue radially outwards under centrifugal force). Optionally, the combustion portion comprises a combustible material inlet for input of combustible material to the internal combustion chamber and one or more air inlets for input of air to the internal combustion chamber. Optionally, the combustible material inlet is separate to the one or more air inlets. Optionally, the one or more air inlets are arranged to create a swirling flow of air within the internal combustion chamber when a flow of air is supplied through the one or more air inlets. Optionally, the outlet portion has a length which extends between the first and second ends of the outlet portion, wherein the combustion residue outlet comprises an axial dimension extending in a direction parallel to the length of the outlet portion. Optionally, the axial dimension is in a range of about 5% to about 60% of the length of the outlet portion, optionally in a range of about 5% to about 30% of the length of the outlet portion. An axial dimension in such a range may increase the proportion of combustion residue which is captured in the combustion residue outlet. Optionally, the combustion residue outlet comprises a circumferential dimension extending along a circumference of the outlet portion. Optionally, the circumferential dimension is in a range of about 5% to about 50% of the circumference; optionally in a range of about 10% to 30% of the circumference. A circumferential dimension in such a range may increase the proportion of combustion residue which is captured in the combustion residue outlet. Optionally, the combustion residue outlet defines an aperture through an internal surface of the outlet portion. Optionally, the internal surface of the outlet portion comprises an outlet groove extending circumferentially from the combustion residue outlet along at least a portion of a circumference of the internal surface. Such an outlet groove is configured to capture combustion residue which is urged along the internal surface (e.g., by a swirling flow of air), and to direct the captured combustion residue towards the combustion residue outlet. In this context, the term "circumferentially" will be understood to mean generally along a circumference of the internal surface, but not necessarily exactly circumferentially. In other words, a plane through the outlet groove may not be exactly perpendicular to a longitudinal axis of the combustion apparatus. Optionally, the outlet groove extends only partially along the circumference of the internal surface. By extending only partially along the circumference of the internal surface, less material (e.g., refractory material) has to be removed from the outlet portion than would be required for a complete circumferential groove. Optionally, the one or more inlets are arranged to create a swirling flow of air within the internal combustion chamber and the outlet portion when a flow of air is supplied through the one or more inlets, wherein the outlet groove extends along a side of the internal surface which is upstream of the combustion residue outlet with respect to the swirling flow of air. By having the outlet groove provided on an upstream side of the combustion residue outlet with respect to the swirling flow of air, the swirling flow of air is configured to guide combustion residue captured in the outlet groove along the outlet groove to the combustion residue outlet, which thereby increases the proportion of combustion residue which is output through the combustion residue outlet. Optionally, the outlet groove extends circumferentially along a range of about 5% to about 50% of the circumference of the internal surface. Optionally, the circumferential dimension of the combustion residue outlet and the outlet groove collectively extend over a range of about 25% to 75% of the circumference of the outlet portion. It will be understood that in embodiments where the circumferential dimension of the combustion residue outlet is greater, more combustion residue may be captured in the combustion residue outlet and thus the outlet groove may extend over a smaller proportion of the circumference of the internal surface (and vice versa). Optionally, the outlet groove comprises an axial dimension in a direction parallel to a length of the outlet portion. Optionally, the axial dimension of the outlet groove tapers inwards towards the combustion residue outlet along a circumferential dimension of the outlet groove. In other words, the outlet groove may be wider in the axial dimension at portions of the outlet groove which are further from the combustion residue outlet, and narrower in the axial dimension at portions of the outlet groove which are closer to the combustion residue outlet. In this way, the outlet groove may act as a funnel, capturing combustion residue from a wider area and channelling it down to a narrower combustion residue outlet. Optionally, the combustion residue outlet defines an aperture through a lower end of the outlet portion. Positioning the combustion residue outlet at lower end facilitates better output of combustion residue (e.g., due to the assistance of gravity). In addition, such a positioning allows combustion residue to be removed from underneath the combustion residue outlet (e.g., using an outlet auger). Optionally, the combustion residue outlet is arranged to be lower than or level with a lower end of the internal combustion chamber. This may improve removal of combustion residue through the combustion residue outlet. Optionally, the outlet portion comprises an internal diameter wherein, at the first end of the outlet portion, the internal diameter of the outlet portion is greater than or equal to the diameter of the internal combustion chamber. In other words, there is no upwards step between the internal combustion chamber and the outlet portion which could act as a barrier for combustion residue reaching the combustion residue outlet. Put another way, this ensures that the lower end of the outlet portion is at or below the lower end of the combustion portion, and thereby limits build-up of combustion residue inside the internal combustion chamber. Optionally, an internal diameter of the outlet portion decreases from the first end of the outlet portion to the combustion residue outlet. Optionally, the internal diameter of the outlet portion gradually decreases from the first end of the outlet portion to the combustion residue outlet. Such a decrease in the internal diameter leads to a narrowing area for an exhaust flow through the outlet portion, which may urge combustion residue entrained in the exhaust flow towards the internal surface of the outlet portion and thus towards the combustion residue outlet. This may be particularly beneficial when the exhaust flow is a swirling flow of air, because the combination of a narrowing area and centrifugal forces may urge combustion residue radially outwards towards the combustion residue outlet. In addition, the decreasing internal diameter of the outlet portion between the first and second ends facilitates connection to downstream exhaust pipework at the second end which is narrower than the internal combustion chamber. Optionally, the outlet portion has an oblique frustoconical shape. Optionally, the oblique frustoconical shape has a lower side which is arranged substantially horizontally. An oblique frustoconical shape may be particularly beneficial for urging combustion residue towards the combustion residue outlet. Optionally, the combustion portion has a length defined between a first end and a second end of the combustion portion. Optionally, the length of the combustion portion is in a range of about 0.5m to about 3m, optionally in a range of about 0.75m to about 2.5m, optionally in a range of about lm to about 2m, optionally in a range of about 1.25m to about 1.5m. Optionally, the length of the combustion portion is less than a diameter (e.g. an external diameter or an internal diameter) of the combustion portion. Optionally, the diameter of the combustion portion is in a range of about 0.5m to 3m, optionally in a range of about lm to about 2.5m, optionally in a range of about 1.5m to about 2.25m. Optionally, the diameter of the internal combustion chamber is in a range of about 0.5m to about 3m, optionally in a range of about lm to about 2.5m, optionally in a range of about 1.25m to about 2m. Optionally, the outlet portion has a length defined between the first and second ends of the outlet portion. Optionally, the length of the outlet portion is in a range of about 0.75m to 3m, optionally in a range of about Im to 2m, optionally in a range of about 1.25m to about 1.75m. Optionally, the length of the outlet portion is less than a maximum diameter of the outlet portion. Optionally, the maximum diameter of the outlet portion is in a range of about 0.5m to 3m, optionally in a range of about lm to about 2.5m, optionally in a range of about 1.5m to about 2.25m. Optionally, the length of the outlet portion is greater than the length of the combustion portion. Optionally, the length of the outlet portion is equal to the length of the combustion portion. Optionally, the length of the combustion portion is greater than the length of the outlet portion. Optionally, the collective length of the combustion portion and the outlet portion is greater than a diameter of the combustion portion. Optionally, the collective length of the combustion portion and the outlet portion is greater than a diameter of the internal combustion chamber (i.e., an internal diameter of the combustion portion). Optionally, the collective length of the combustion portion and the outlet portion is in a range of about 1.5m to about 6m, optionally in a range of about 2m to about 5m, optionally in a range of about 2.5m to about 4m. Optionally, the combustion apparatus further comprises a combustion residue removal device coupled to the combustion residue outlet in order to convey combustion residue away from the combustion residue outlet. This allows a continuous removal of combustion residue through the combustion residue outlet. Optionally, the combustion residue removal device comprises an outlet auger. This provides a simple means of removing combustion residue, which may be particularly useful for removing residue from particulate combustion material. Optionally, the outlet auger is supported by at least one outlet auger bearing. Optionally, the at least one outlet auger bearing is laterally spaced apart from the outlet portion and / or combustion portion (i.e., in a direction transverse to a longitudinal axis of the combustion apparatus). Optionally, the outlet auger bearing is laterally spaced apart from the outlet portion and / or combustion portion by a distance of at least 0.25m, optionally at least 0.5m, optionally at least 0.75m, optionally at least Im. This may protect the outlet auger bearing from heat generated in the combustion apparatus. Optionally, the outlet portion is releasably coupled to the combustion portion. This allows the internal combustion chamber and inside of the outlet portion to be accessed (e.g., for cleaning and / or replacement or regeneration of refractory material. Optionally, the combustion portion and / or outlet portion are lined with refractory material (e.g., having a metallic outer skin and an inner lining of refractory material). Optionally, the combustion apparatus further comprises an ignition device configured to provide an ignition source (e.g., flame, spark or other suitable ignition source) inside the internal combustion chamber. Optionally, the ignition device is provided outside of the internal combustion chamber. Optionally, the combustion apparatus has an ignition inlet through which the ignition source can be supplied from the ignition device to the internal combustion chamber. Optionally, the ignition inlet is a separate inlet to the one or more inlets for input of combustible material and air to the internal combustion chamber. A second aspect of the teachings provides a combustion apparatus for combustion of particulate combustible material. The combustion apparatus comprises a substantially cylindrical body which defines an internal combustion chamber. The substantially cylindrical body comprises: a first end through which combustible material can be input to the internal combustion chamber; a second end opposite the first end; and one or more air inlets provided through the substantially cylindrical body at a position between the first and second ends. The one or more air inlets are arranged to create a swirling flow of air inside the internal combustion chamber. The one or more air inlets are configured to direct at least a portion of the swirling flow of air towards the first end of the cylindrical body. By having the one or more air inlets configured to direct at least a portion of the swirling flow of air towards the first end of the cylindrical body (at which the combustible material is input), the swirling flow of air may interact with the combustible material to urge it away from the first end of the cylindrical body towards a centre of the internal combustion chamber. This may improve the combustion performance of the combustion apparatus. Optionally, the one or more air inlets are adjustable to vary a proportion of air flowing through the one or more air inlets that is directed towards the first end of the cylindrical body, and / or to vary an angle at which air flowing through the one or more air inlets is directed towards the first end of the cylindrical body. Such adjustment facilitates tuning the swirling flow of air for different particle sizes of combustible material which are input to the combustion chamber. For example, CFD analysis has shown that combustible material of smaller particle size is more likely to become stuck at the first end of the cylindrical body outside of a "fireball" within the swirling flow of air than combustible material of larger particle size. This may be because larger particles bounce off each other and / or a wall which closes the first end of the cylindrical body more easily and thus become entrained within the fireball inside the swirling flow of air. Therefore, it may be desirable to increase the proportion of air that is directed towards the first end of the cylindrical body and / or increase the angle at which air is directed towards the first end when the particle size of the combustible material is smaller. Optionally, each of the one or more air inlets defines a channel having an inlet axis extending through the cylindrical body and a diverter arranged at least partly within the channel. Optionally, the diverter is angled and / or curved relative to the inlet axis to direct air flowing along the channel towards the first end of the cylindrical body. Such a diverter provides a simple means of directing flow towards the first end of the cylindrical body. Optionally, the diverter comprises a plate which is arranged at an angle in a range of about 20 degrees to about 60 degrees to the inlet axis. Such a plate provides a simple construction for the diverter. In addition, such a range of angles has been found to direct the air to efficiently direct combustible material of different particle sizes towards the fireball within the swirling flow of air. Optionally, the channel comprises a lateral dimension extending in a direction perpendicular to the inlet axis, wherein the diverter comprises a width which partially overlaps the lateral dimension of the channel. Optionally, the width of the diverter overlaps about 15% to about 70% of the lateral dimension of the channel, optionally about 25% to about 60% of the lateral dimension of the channel. In other words, because the width partially overlaps the lateral dimension, some portions of the air flowing along the channel do not impact the diverter and are thus not directed towards the first end of the cylindrical body. This configuration has been found to direct the air to effectively direct combustible material of different particle sizes towards the fireball within the swirling flow of air. The lateral dimension of the channel and the width of the diverter may be defined in a direction which is parallel to a central axis of the internal combustion chamber (i.e., in a direction which is parallel to a length of the cylindrical body extending from the first end to the second end of the cylindrical body). Optionally, the position and / or orientation of the diverter is adjustable within the channel to vary a proportion of air flowing along the channel that is directed towards the first end of the cylindrical body, and / or to vary an angle at which air flowing along the channel is directed towards the first end of the cylindrical body. Adjusting the position and / or orientation of the diverter provides a simple means for varying the proportion and / or angle of air which is directed by the diverter. As mentioned above, such adjustment facilitates tuning the swirling flow of air for different particle sizes of combustible material which are input to the combustion chamber. For example, CFD analysis has shown that combustible material of smaller particle size is more likely to become stuck at the first end of the cylindrical body outside of a "fireball" within the swirling flow of air than combustible material of larger particle size. This may be because larger particles bounce off each other and / or a wall which closes the first end of the cylindrical body more easily and thus become entrained within the fireball inside the swirling flow of air. Therefore, it may be desirable to increase the proportion of air that is directed towards the first end of the cylindrical body and / or increase the angle at which air is directed towards the first end when the particle size of the combustible material is smaller. Optionally, the diverter is pivotally mounted in the channel such that an angle of the diverter relative to the inlet axis is adjustable, and / or wherein the diverter is slidably mounted in the channel such that a position of the diverter relative to the inlet axis is adjustable. Optionally, each of the one or more air inlets further comprises an actuator configured to change the position and / or orientation of the diverter. In other words, the position and / or orientation of the diverter can be changed without manual adjustment. This may facilitate automated adjustment of the diverter (e.g., using feedback control based on a measured particle size or other property). Optionally, the combustion apparatus further comprises a controller configured to determine a particle size of combustible material being input to the internal combustion chamber. Optionally, the controller is configured to control the actuator to adjust the diverter depending on the determined particle size. Optionally, the controller is configured to adjust the diverter to divert a greater proportion of air flowing along the channel towards the first end as the determined particle size decreases. Such a controller allows automated adjustment of the diverter to tune the swirling flow of air for different particle sizes. CFD analysis has shown that combustible material of smaller particle size is more likely to become stuck at the first end of the cylindrical body outside of a "fireball" within the swirling flow of air than combustible material of larger particle size. This may be because larger particles bounce off each other and / or a wall which closes the first end of the cylindrical body more easily and thus become entrained within the fireball inside the swirling flow of air. Therefore, by increasing the proportion of air that is directed towards the first end of the cylindrical body as the particle size decreases, better entrainment of combustible material within the fireball can be achieved. Optionally, the controller is configured to automatically determine the particle size (e.g., using a vision system and image processing, or an alternative particle size sensing arrangement). Alternatively, the particle size may be input to the controller manually by a user of the combustion apparatus. Optionally, the channel is defined by an elongate slot. Optionally, the elongate slot extends over at least 50% of the length of the cylindrical body, optionally at least 75% of the length of the cylindrical body. This facilitates input of air along the majority of the length of the cylindrical body. Optionally, the inlet axis of the channel is parallel to the first and second ends of the cylindrical body (i.e., orthogonal to a central axis of the internal combustion chamber). In alternative embodiments, the inlet axis of the channel is angled towards the first end of the cylindrical body in order to direct the swirling flow of air towards the first end of the cylindrical body. In such embodiments, the diverter may be omitted. In such embodiments, adjustability may be achieved by changing the angle of the entire channel relative to the first end of the cylindrical body. Optionally, each of the one or more air inlets is configured to direct air flowing through the air inlet in an approximately tangential direction along an internal wall of the internal combustion chamber to create the swirling flow of air. In other words, the inlet axis of the channel may be arranged approximately tangentially to the internal wall of the internal combustion chamber. Optionally, the one or more air inlets comprise a first air inlet located on a first side of the substantially cylindrical body, and a second air inlet located on a second side of the substantially cylindrical body opposite to the first side. Optionally, the first and second air inlets are configured to direct air into the internal combustion chamber in opposite directions to create the swirling flow of air. Optionally, the first and second air inlets are located opposite each other (e.g., in horizontal alignment with each other) and the first and second air inlets are angled in opposite directions (e.g., one of the first and second air inlets being angled upwards and the other of the first and second air inlets being angled downwards) to direct air into the internal combustion chamber in opposite directions. Optionally, the combustion apparatus further comprises an end body positioned at a first end of the cylindrical body. Optionally, the end body comprises a combustible material inlet. Optionally, the combustion apparatus further comprises an ignition device configured to provide an ignition source (e.g., flame, spark or other suitable ignition source) inside the internal combustion chamber. Optionally, the ignition device is provided outside of the internal combustion chamber. Optionally, the combustion apparatus has an ignition inlet through which the ignition source can be supplied from the ignition device to the internal combustion chamber. Optionally, the ignition inlet is a separate inlet to the one or more air inlets and / or the combustible material inlet. A third aspect of the teachings provides a combustion apparatus in accordance with both the first and second aspects of the teachings. Such a combustion apparatus benefits from the advantages of both the combustion residue outlet and one or more air inlets outlined above. A fourth aspect of the teachings provides a combustion system comprising: a combustion apparatus as disclosed herein; a combustible material supply apparatus for suppling combustible material to the combustion apparatus; and an air supply apparatus for supplying a flow of air to the combustion apparatus. Such a combustion system may benefit from the advantages of the combustion residue outlet and / or one or more air inlets outlined above. A fifth aspect of the teachings provides a combustion system for combustion of particulate combustible material. The combustion system comprises: a combustion apparatus defining an internal combustion chamber, the combustion apparatus having one or more air inlets for input of air to the internal combustion chamber; and an air supply apparatus for supplying a flow of air to the one or more air inlets. The air supply apparatus comprises a blower and one or more inlet pipes configured to connect the blower to the one or more air inlets. Each of the one or more inlet pipes extends upwards from the blower and then horizontally to the respective air inlet. Having one or more such inlet pipes allows the blower to be positioned below the one or more air inlets (e.g., on the ground) and spaced longitudinally from the one or more air inlets. This may facilitate positioning of the blower in a more convenient position spaced apart from the combustion apparatus. In addition, it has been found that, by directing air upwards first and then horizontally to the one or more air inlets, the flow of air can straighten out as it travels horizontally. This provides a more laminar flow through the respective air inlet, which may lead to better direction of air by the one or more air inlets and thus a better Further, as the one or more inlet pipes extend upwards first and then horizontally, a space below the horizontal portion of the one or more inlet pipes is provided (e.g., in comparison to alternatives where the inlet pipe is curved or angled upwards to the respective air inlet and thus provides an obstruction in this region). This provides better access underneath the one or more inlet pipes (e.g., for maintenance purposes). Optionally, the blower has a blower inlet which is configured to suck ambient air from the atmosphere surrounding the blower to be conveyed along the one or more inlet pipes. In other words, the blower inlet is an open inlet (i.e., is open to the atmosphere surrounding the blower). Put another way, the blower inlet is not connected to any pipe or ductwork upstream of the blower. This contrasts with alternative configurations in which the blower inlet is configured to suck air from another component of the combustion system (e.g., from inside a hopper of the combustible material supply apparatus), which may be more susceptible to build-up of dust or other material in the blower and / or inlet pipes. Optionally, the one or more air inlets are arranged to create a swirling flow of air within the internal combustion chamber when a flow of air is supplied through the one or more air inlets by the air supply apparatus. As outlined above, the structure of the one or more inlet pipes may provide a more laminar flow through the respective air inlets. This may be particularly beneficial when the one or more air inlets are arranged to create a swirling flow of air within the internal combustion chamber because the more laminar flow may facilitate better generation of the swirling flow of air. Optionally, the combustion system comprises a first air inlet arranged on a first side of the combustion apparatus and a second air inlet arranged on a second side of the combustion apparatus, opposite to the first side. Optionally, the air supply apparatus comprises a first inlet pipe configured to connect the blower to the first air inlet and a second inlet pipe configured to connect the blower to the second air inlet. Optionally, the first and second air inlets are configured to input air to the combustion chamber in opposite directions to create a swirling flow of air within the internal combustion chamber. Optionally, each of the one or more inlet pipes has a downstream portion coupled to the respective air inlet and an upstream portion connecting the blower and the downstream portion. Optionally, the downstream portion is arranged substantially horizontally. For example, the downstream portion may have an approximately equal height along a length of the downstream portion. Put another way, at least a majority of the downstream portion may be intersected by a horizontal plane. Optionally, the upstream portion is arranged substantially vertically. For example, at least a majority of the upstream portion may be intersected by a vertical plane. Optionally, the downstream portion is at least Im long, optionally at least 1.5m long, optionally at least 2m long, optionally at least 2.5m long. This facilitates better straightening of the flow of air along the downstream portion in comparison to shorter alternatives. Optionally, the downstream portion comprises a downstream straight section and a downstream elbow coupled between the downstream straight section and the respective air inlet. Optionally, the downstream portion comprises an expander which couples the downstream elbow to the respective air inlet. Optionally, the expander widens the flow of air prior to entering the respective air inlet. Optionally, the expander changes the cross-sectional shape of the inlet pipe from a circular cross-section to a rectangular crosssection. Optionally, the upstream portion comprises an upstream straight section, an intermediate elbow coupled between the upstream straight section and the downstream straight section, and an upstream elbow coupled between the upstream straight section and the blower. Optionally, the blower comprises a first blower outlet for coupling to the first inlet pipe and a second blower outlet for coupling to the second inlet pipe. Optionally, the first and second blower outlets are provided on different (e.g., opposite) sides of the blower. Optionally, the blower comprises a splitter portion configured to direct air towards the first and second blower outlets. Optionally, each of the one or more inlet pipes has a horizontal dimension and a vertical dimension between the blower and the respective air inlet. Optionally, the horizontal dimension is greater than the vertical dimension. Optionally, the horizontal dimension is at least 25% greater than the vertical dimension, optionally at least 50% greater than the vertical dimension, optionally at least 75% greater than the vertical dimension, optionally at least 100% greater than the vertical dimension. This facilitates better straightening of the flow of air before input to the one or more air inlets than in alternatives where the horizontal dimension is smaller. A sixth aspect of the teachings provides a combustion system comprising: a combustion apparatus which defines an internal combustion chamber; a combustible material supply apparatus for suppling combustible material to the combustion apparatus; and an air supply apparatus for supplying a flow of air to the combustion apparatus. The combustion system also comprises a rail arrangement for guiding movement of at least one portion of the combustion apparatus and / or combustion material supply apparatus and / or air supply apparatus between a first position corresponding to an assembled state of the combustion system and a second position corresponding to a disassembled state of the combustion system. Such a rail arrangement facilitates assembly and disassembly of the combustion system (e.g., for maintenance purposes). This may be particularly beneficial when a particular component requires regular disassembly (e.g., for cleaning internally). In addition, the rail arrangement may help to move heavy components which would otherwise need specialist tools (e.g., cranes, forklifts etc.). Further, the rail arrangement may provide a more accurate relative positioning of components during assembly (i.e., by constraining movement to a single direction defines by one or more rails of the rail arrangement). Optionally, the combustion system further comprises a lifting device which is configured to mount or dismount the at least one portion of the combustion apparatus and / or combustion material supply apparatus and / or air supply apparatus onto the rail arrangement. Such a lifting device may facilitate a more controlled movement of the apparatus on and off the rail arrangement. These benefits may be particularly useful when the apparatus is a combustion apparatus lined with refractory material due to the heavy weight of such material. Optionally the lifting device comprises a hydraulic jack. Optionally, the lifting device is movable in at least one direction. Optionally, the lifting device is movable along one or more lifting device rails. Alternatively, the lifting device may comprise one or more wheels. This may facilitate movement of the component which is lifted by the lifting device (e.g., to facilitate alignment with other components during assembly). Optionally, the lifting device comprises a first formation and the respective apparatus comprises a second formation configured to be engaged by the first formation to lift the respective apparatus with the lifting device. Optionally, the first formation is a male formation and the second formation is a female formation. This reduces the likelihood of disengagement of the lifting device and the respective apparatus during lifting. Optionally, the rail arrangement comprises one or more rails and a support arrangement for supporting at least one portion of the combustion apparatus and / or combustion material supply apparatus and / or air supply apparatus. Optionally, the support arrangement comprises one or more guide formations configured to slidingly engage the one or more rails to facilitate movement along the one or more rails. Such guide formations may facilitate controlled movement along the one or more rails. Optionally, the one or more guide formations comprise one or more linear motion bearings. Linear motion bearings reduce resistance and thereby facilitate easier movement along the one or more rails. This may be particularly beneficial for heavy components (e.g., a combustion apparatus lined with refractory material). Optionally, the one or more guide formations are provided at a lower end of support arrangement. Optionally, the at least one portion of the combustion apparatus and / or combustion material supply apparatus and / or air supply apparatus is arranged to rest on the support arrangement during movement along the one or more rails. Optionally, the lifting device is configured to raise and lower the at least one portion of the combustion apparatus and / or combustion material supply apparatus and / or air supply apparatus onto the support arrangement. Optionally, the support arrangement comprises a cradle, optionally a concave cradle. Such an arrangement provides a simple means of mounting / dismounting the respective component from the rail arrangement using the lifting device. Alternatively, the support arrangement may be fixed to the respective component (e.g., so that the support formation is raised / lowered onto the tracks by the lifting device). Optionally, the combustion system further comprises a movement actuator configured to drive movement of the at least one portion of the combustion apparatus and / or combustible material supply apparatus and / or air supply apparatus along the rail arrangement. Such a movement actuator provides an easier and more controlled movement along the rail arrangement. Optionally, the movement actuator comprises a manual linear screw actuator. A manual linear screw actuator may be operated by a user without an external power source (e.g., electrical, hydraulic, pneumatic). Optionally, the combustion system has a longitudinal axis, wherein the rail arrangement comprises one or more transverse rails which are configured to guide movement of at least one portion of the combustion apparatus and / or combustible material supply apparatus and / or air supply apparatus in a direction transverse to the longitudinal axis. Such one or more transverse rails facilitate transverse movement, which may be beneficial for sliding a component out sideways to gain access inside. Optionally, the one or more transverse rails comprise at least two transverse rails. Having at least two transverse rails provides improved guiding and support of the respective component on the rails. Optionally, the combustion apparatus comprises a substantially cylindrical body which defines the internal combustion chamber. Optionally, the internal combustion chamber has a central axis which is parallel to the longitudinal axis of the combustion system. Optionally, the one or more transverse rails are configured to guide movement of the substantially cylindrical body in the transverse direction. In this way, the cylindrical body can be slid out sideways (e.g., to gain access to the internal combustion chamber for cleaning and / or replacement or regeneration of refractory material). Optionally, the lifting device is configured to lift the cylindrical body. As mentioned above, the lifting device facilitates easier movement of the cylindrical body via the rail arrangement (e.g., by mounting or dismounting the cylindrical body on the rails, or by supporting the weight of the cylindrical body as it moves along the rails). Optionally, a lower end of the cylindrical body comprises a recess for engagement with the lifting device. Optionally, the support arrangement comprises a cradle having a shape which is complementary to a periphery of the cylindrical body (e.g., a convex cradle). Optionally, the lifting device is configured to raise and lower the cylindrical body onto the cradle. Optionally, the cradle comprises one or more guide formations configured to slidingly engage the one or more transverse rails to facilitate movement of the substantially cylindrical body along the one or more transverse rails. Optionally, the one or more guide formations comprise one or more linear motion bearings. Optionally, the one or more guide formations are provided at a lower end of the cradle. Optionally, the cylindrical body is releasably coupled to one or more adjacent components of the combustion system. Optionally, the cylindrical body and one or more adjacent components comprise complementary flanges which are bolted together. Such a releasably coupling facilitates easy disassembly (e.g., by unbolting the complementary flanges) for movement of the cylindrical body along the one or more transverse rails. Optionally, the combustion apparatus comprises an end body which is releasably coupled to a first end of the cylindrical body and / or an outlet portion which is releasably coupled to the second end of the cylindrical body. Optionally, the rail arrangement comprises one or more longitudinal rails which are configured to guide movement of the one or more adjacent components in a direction parallel to the central axis, in order to separate the cylindrical body and the one or more adjacent components. In other words, the one or more longitudinal rails are configured to guide movement of the one or more adjacent components in a direction which is orthogonal to the direction in which the cylindrical body is moved along the one or more transverse rails. This facilitates separation of the cylindrical body from the one or more adjacent components (i.e., provides a clearance) to facilitate easier transverse movement of the cylindrical body. Optionally, the one or more longitudinal rails comprise at least two longitudinal rails. Optionally, the combustion system has a longitudinal axis, and the rail arrangement comprises one or more longitudinal rails which are configured to guide movement of the combustion apparatus and / or combustible material supply apparatus and / or air supply apparatus in a direction parallel to the longitudinal axis. Such one or more longitudinal rails facilitate longitudinal movement, which may be beneficial for separating different components which are joined end to end. Optionally, the one or more longitudinal rails comprise at least two longitudinal rails. Having at least two longitudinal rails provides improved guiding and support of the respective component on the rails. Optionally, the combustible material supply apparatus and / or air supply apparatus are at least partly mounted on a support base. Optionally, the support base is configured to move along the one or more longitudinal rails. Such a support base provides a simple means of moving a group of different components together in a longitudinal direction. Optionally, the combustion system further comprises a movement actuator to drive movement of the support base along the one or more longitudinal rails. Such a movement actuator provides an easier and more controlled movement along the rail arrangement. Optionally, the movement actuator comprises a manual linear screw actuator. A manual linear screw actuator may be operated by a user without an external power source (e.g., electrical, hydraulic, pneumatic). Optionally, the support base comprises one or more guide formations configured to slidingly engage the one or more longitudinal rails to facilitate movement of the support base along the one or more longitudinal rails. Optionally, the one or more guide formations comprise one or more linear motion bearings. Optionally, the one or more guide formations are provided at a lower end of the support base. A seventh aspect of the teachings provides a combustion system in accordance with the fifth and sixth aspects of the teachings. Such a combustion system benefits from the advantages of the combustion systems and / or combustion apparatuses outlined above. An eighth aspect of the teachings provides a combustion system in accordance with the fourth aspect of the teachings and the fifth and / or sixth aspects of the teachings. Such a combustion system benefits from the advantages of the combustion systems and / or combustion apparatuses outlined above. A ninth aspect of the teachings provides a method of combusting combustible material with a combustion system according to the fourth aspect and / or fifth aspect and / or sixth aspect and / or seventh aspect and / or eighth aspect of the teachings. The method comprises: loading combustible material into the combustible material supply apparatus; operating the combustible material supply apparatus and air supply apparatus to simultaneously provide a mixture of combustible material and air in the internal combustion chamber; and combusting the combustible material inside the internal combustion chamber. Such a method uses a combustion system disclosed herein, and thereby benefits from the advantages of the combustion systems outlined above. It will be appreciated that any feature of any of the aspects of the teachings outlined above may be combined with any compatible features of any of the other aspects of the teachings above. For the sake of brevity, not all combinations are explicitly recited above. BRIEF DESCRIPTION OF DRAWINGS Embodiments will now be described by way of example only with reference to the accompanying figures, in which: Figures 1 and 2 are perspective views of a combustion system according to an embodiment; Figures 3 and 4 are side cross-sectional views through the combustion system of Figures 1 and 2; Figure 5 is a lateral cross-sectional view through the combustion system of Figures 1 to 4; Figure 6 is a plan cross-sectional view through the combustion system of Figures 1 to 5; Figure 7 is an exploded side cross-sectional view of a combustion apparatus of the combustion system of Figures 1 to 6; Figure 8 is a perspective cross-sectional view of the combustion apparatus of Figure 7; Figures 9 and 10 are perspective views of an outlet portion of the combustion apparatus of Figures 7 and 8; Figure 11 is a side cross-sectional view of the outlet portion of Figures 9 and 10; Figure 12 is an enlarged lateral cross-sectional view through an air inlet of the combustion system of Figures 1 to 11; Figure 13 is a perspective view of a cylindrical body of a combustion apparatus of the combustion system of Figures 1 to 12; Figure 14A is a schematic view of an air inlet of the combustion apparatus of Figures 1 to 13 viewed in a direction parallel to an inlet axis of the air inlet; Figure 14B is a schematic view of the air inlet of Figure 14A viewed in a direction perpendicular to the inlet axis; Figure 15 is a side cross-sectional view of a portion of the combustion system of Figures 1 to 14B in an assembled state; Figure 16 is a side cross-sectional view of the portion of the combustion system of Figure 15 in a disassembled state; Figure 17 is a cross-sectional view through a rail arrangement of the combustion system of Figures 1 to 16; and Figure 18 is a flow chart of a method of combusting combustible material, according to an embodiment of the invention. DETAILED DESCRIPTION In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of various embodiments and the teachings. However, those skilled in the art will understand that: the present teachings may be practiced without these specific details or with known equivalents of these specific details; that the present teachings are not limited to the described embodiments; and, that the present teachings may be practiced in a variety of alternative embodiments. It will also be appreciated that well known methods, procedures, components, and systems may not have been described in detail. With reference to Figures 1 to 6, a combustion system according to an embodiment is indicated at 1. The combustion system 1 includes: a combustion apparatus 10 which defines an internal combustion chamber 12; a combustible material supply apparatus 200 for supplying combustible material (e.g., particulate combustible material) to the combustion apparatus 10; and an air supply apparatus 300 for supplying a flow of air 302 to the combustion apparatus 10. In the illustrated embodiment, the combustion apparatus 10 has one or more inlets 14A, 14B, 16 for input of combustible material and air to the internal combustion chamber 12. In particular, the combustion apparatus 10 has one or more air inlets 14A, 14B for input of air to the internal combustion chamber 12 (e.g., via the air supply apparatus 300), and a combustible material inlet 16 for input of combustible material to the internal combustion chamber 12 (e.g., via the combustible material supply apparatus 200). In alternative embodiments, the one or more air inlets 14A, 14B and combustible material inlet 16 may be combined so that each of the one or more inlets 14A, 14B, 16 inputs both air and combustible material to the internal combustion chamber 12. In the illustrated embodiment, the combustion apparatus 10 includes an ignition device 18 configured to provide an ignition source (e.g., flame, spark or other suitable ignition source) inside the internal combustion chamber 12. The ignition device 18 may be any device which is suitable for supplying an ignition source (e.g., flame, spark or other suitable ignition source). The ignition device 18 may be powered by a different energy source to the combustible material (e.g., a flammable gas, or electrical energy). In the illustrated embodiment, the ignition device 18 is provided outside of the internal combustion chamber 12. The combustion apparatus 10 has an ignition inlet 20 through which the ignition source can be supplied from the ignition device 18 to the internal combustion chamber 12. In the illustrated embodiment, the ignition inlet 20 is a separate inlet to the one or more inlets 14A, 14B, 16 for input of combustible material and air to the internal combustion chamber 12. In the illustrated embodiment, the combustion apparatus 10 also has an exhaust gas outlet 22 for connection to downstream exhaust pipework. The combustion apparatus 10 also has a combustion residue outlet 24. The combustion residue outlet 24 allows combustion residue which is leftover after the combustion process inside the internal combustion chamber 12 to be removed from the combustion apparatus 10. During use, combustible material (e.g., particulate combustible material) and air are input simultaneously to the internal combustion chamber 12. As will be described in more detail below, in the illustrated embodiment, the one or more air inlets 14A, 14B are arranged to create a swirling flow of air 26 or "vortex" within the internal combustion chamber 12 when a flow of air is supplied through the one or more air inlets (e.g., by the air supply apparatus 300). The swirling flow of air 26 is illustrated by the arrows inside the internal combustion chamber 12 on Figure 5. The swirling flow of air 26 facilitates formation of a "fireball" inside the swirling flow of air, which is supplied by the combustible material which is input to the internal combustion chamber 12 and air within the swirling flow of air 26 which is sucked into the fireball. The combustible material input to the internal combustion chamber 12 may be directed by the swirling flow of air 26 towards the "fireball" inside the internal combustion chamber 12. Such a combustion apparatus 10 may be referred to as a "cyclone combustion apparatus" or a "cyclone combustor". To initiate combustion of the mixture of air and combustible material within the internal combustion chamber 12, the ignition device 18 is activated to supply the ignition source. Once combustion is established, the ignition device 18 may be deactivated. In other words, once combustion is established the combustion process may be self-sustained by the supply of air and combustible material to the internal combustion chamber 12. Exhaust gases produced during the combustion process may be expelled through the exhaust gas outlet 22. Similarly, combustion residue which is produced following the combustion process may be removed from the internal combustion chamber 12 through the combustion residue outlet 24. Referring now to Figures 7 to 11, the illustrated combustion apparatus 10 includes: a combustion portion 60 which defines the internal combustion chamber 12, and an outlet portion 100 coupled to the combustion portion 60. The combustion portion 60 includes the one or more air inlets 14A, 14B. The combustion portion 60 also includes the combustible material inlet 16 and the ignition inlet 20. In the illustrated embodiment, the combustion portion 60 and outlet portion 100 are both lined with refractory material 28. For example, the combustion portion 60 and outlet portion 100 may each have a metallic outer skin and an inner lining of refractory material 28. Any suitable type of refractory material 28 may be used. In the illustrated embodiment, the combustion portion has a substantially cylindrical body 62. In this context, "substantially cylindrical" will be understood to mean a hollow and round body of approximately circular cross-section. The substantially cylindrical body 62 may be straight (i.e., of constant cross-sectional diameter along a central axis C of the substantially cylindrical body 62), bilged (i.e., having a larger cross-sectional diameter towards a centre of the substantially cylindrical body 62), or have any other slight variations in cross-sectional diameter along the central axis C of the substantially cylindrical body 62. Hereafter, the substantially cylindrical body 62 may be referred to as a "cylindrical body". The illustrated combustion portion 60 also has an end body 64 coupled to a first end 66 of the cylindrical body 62. In the illustrated embodiment, the end body 64 is releasably coupled to the cylindrical body 62 (e.g. via complementary flanges 70 on the cylindrical body 62 and the end body 64 which are bolted together). In alternative embodiments, the end body 64 and cylindrical body 62 are fixedly attached (e.g., via welding) and / or integrally formed. In the illustrated embodiment, the end body 64 is substantially disc shaped. However, the end body 64 may be of any other shape suitable for closing the first end 66 of the cylindrical body 62 (e.g., a concave or convex shape). In the illustrated embodiment, the combustible material inlet 16 and ignition inlet 20 are provided in the end body 64. The one or more air inlets 14A, 14B are provided in the cylindrical body 62 at a position between the first end 66 and a second end 68 of the cylindrical body 62. The outlet portion 100 is coupled to an open end of the combustion portion 60. In particular, the outlet portion is coupled to the second end 68 of the cylindrical body 62 of the combustion portion 60 (i.e., the second end 68 of the cylindrical body 62 defines the open end of the combustion portion 60). In the illustrated embodiment, the outlet portion 100 is releasably coupled to the combustion portion (e.g., via bolting adjacent flanges 70 on the cylindrical body 62 and outlet portion 100). In alternative embodiments, the outlet portion 100 and cylindrical body 62 are fixedly attached (e.g., via welding) and / or integrally formed. The outlet portion 100 extends from a first end 102 proximal the combustion portion 60 to a second end 104 distal the combustion portion 60. In the illustrated embodiment, the second end 104 of the outlet portion 100 defines the exhaust gas outlet 22. As best illustrated in Figure 7, the exhaust gas outlet 22 has a cross-sectional dimension 106 which is less than a diameter 72 of the internal combustion chamber 12 (e.g., less than an internal diameter of the cylindrical body 62). In the illustrated embodiment, the combustion residue outlet 24 is provided in the outlet portion 100, positioned between the first and second ends 102, 104 of the outlet portion 100. However, in alternative embodiments the combustion residue outlet 24 may be provided within the combustion portion 60 (e.g., through a lower end of the cylindrical body 62). It will be understood that, due to the vortex created inside the internal combustion chamber 12, a mixture of exhaust gas and combustion residue will enter the outlet portion 100 in a swirling flow 26 which urges the combustion residue radially outwards and through the combustion residue outlet 24. As best illustrated in Figure 11, the outlet portion 100 has a length 108 which extends between the first and second ends 102, 104 of the outlet portion 100. The combustion residue outlet 24 has an axial dimension 110 extending in a direction parallel to the length 108 of the outlet portion 100. The axial dimension 110 may be in a range of about 5% to about 60% of the length 108 of the outlet portion 100, e.g., in a range of about 5% to about 30% of the length 108 of the outlet portion 100. For example, in the illustrated embodiment the axial dimension 110 is approximately 7% of the length 108 of the outlet portion 100. In some embodiments, the axial dimension 110 may be a greater proportion of the length 108 of the outlet portion 100 than in the illustrated embodiment, which may increase the amount of combustion residue that can be removed through the combustion residue outlet 24. As best illustrated in Figure 9, the combustion residue outlet 24 has a circumferential dimension 112 extending along a circumference of the outlet portion 100. As will be described in more detail below, the illustrated outlet portion 100 has a varying cross-sectional diameter (and thus varying circumference) along its length 108. However, in this context, the term "circumference" will be understood to mean a circumference of the outlet portion 100 at the longitudinal position of the combustion residue outlet 24. The circumferential dimension 112 may be in a range of about 5% to about 50% of the circumference of the outlet portion 100, e.g., in a range of about 10% to 30% of the circumference of the outlet portion 100. For example, in the illustrated embodiment the circumferential dimension 112 is approximately 10% of the circumference of the outlet portion 100. In some embodiments, the circumferential dimension 112 may be a greater proportion of the circumference of the outlet portion 100 than in the illustrated embodiment, which may increase the amount of combustion residue that can be removed through the combustion residue outlet 24. The combustion residue outlet 24 defines an aperture through an internal surface 114 of the outlet portion 100. In the illustrated embodiment, the internal surface 114 of the outlet portion 100 has an outlet groove 116 extending circumferentially from the combustion residue outlet 24 along at least a portion of the circumference of the internal surface 114. In this context, the term "circumferentially" will be understood to mean generally along a circumference of the internal surface, but not necessarily exactly circumferentially. In other words, a plane through the outlet groove 116 may not be exactly perpendicular to a longitudinal axis Lof the combustion apparatus 10. The outlet groove 116 is configured to capture combustion residue which is urged along the internal surface 114 by the swirling exhaust gas flow, and to direct the captured combustion residue towards the combustion residue outlet 24. In the illustrated embodiment, the outlet groove 116 extends only partially along the circumference of the internal surface 114. In particular, the outlet groove 116 extends along a side of the internal surface 114 which is upstream of the combustion residue outlet 24 with respect to a swirling direction of exhaust gas through the outlet portion 100. For example, in the illustrated embodiment the combustion apparatus 10 is configured so that exhaust gases swirl through the outlet portion 100 in a clockwise direction (when looking from the first end 102 towards the second end 104 of the outlet portion). The outlet groove 116 extends from the combustion residue outlet 24 in an anti-clockwise direction over part of the circumference of the internal surface 114. In embodiments where air is configured to swirl in the opposite direction, the outlet groove 116 may extend along the opposite side of the internal surface 114 to that illustrated. The outlet groove 116 may extend circumferentially along a range of about 5% to about 50% of the circumference of the internal surface 114 of the outlet portion 100. For example, in the illustrated embodiment the outlet groove 116 extends circumferentially along a range of about 45% of the circumference of the internal surface 114 of the outlet portion 100. It will be understood that in embodiments where the circumferential dimension 112 of the combustion residue outlet 24 is greater, more combustion residue may be captured in the combustion residue outlet 24 and thus the outlet groove 116 may extend circumferentially over a smaller proportion of the circumference of the internal surface 114 (and vice versa). For example, if the circumferential dimension 112 of the combustion residue outlet 24 increased to around 30% of the circumference of the internal surface 114 of the outlet portion 100, the outlet groove 116 may only extend over approximately 25% of the internal surface 114 of the outlet portion 100. The circumferential dimension 112 of the combustion residue outlet and the outlet groove may collectively extend over a range of about 25% to 75% of the circumference of the outlet portion 100. The outlet groove 112 has an axial dimension 118 in a direction parallel to the length 108 of the outlet portion 100. As best shown in Figure 11, the axial dimension 118 of the illustrated outlet groove 116 is approximately constant at a lower portion of the outlet groove 116 (e.g., similar to the axial dimension 110 of the combustion residue outlet 24), and narrows towards an upper end of the outlet groove 116. However, in other embodiments the axial dimension 118 of the outlet groove 116 tapers inwards towards the combustion residue outlet 24 along a circumferential dimension 120 of the outlet groove 116, as indicated by the dashed line on Figure 11. In other words, the outlet groove 116 may be wider in the axial dimension 118 at portions of the outlet groove 116 which are further from the combustion residue outlet 24, and narrower in the axial dimension 118 at portions of the outlet groove 116 which are closer to the combustion residue outlet 24. In this way, the outlet groove 116 may act as a funnel, capturing combustion residue from a wider area and channelling it down to a narrower combustion residue outlet 24. In other embodiments, the axial dimension 118 of the outlet groove 116 is constant along the entire length of the outlet groove 116. In the illustrated embodiment, the combustion residue outlet 24 is provided in a lower end 122 of the outlet portion 100. In this way, combustion residue may also be urged towards the combustion residue outlet 24 under the force of gravity, in addition to the swirling air flow. In addition, this allows combustion residue to be removed from underneath the combustion residue outlet 24 (e.g., using an outlet auger, as explained in more detail below). In the illustrated embodiment, the combustion residue outlet 24 is lower than a lower end 74 of the internal combustion chamber 12. In particular, there is a downwards step from the internal combustion chamber 12 to a lower end 124 of the internal surface 114 of the outlet portion 100, and the lower end 124 of the internal surface 114 of the outlet portion 100 is substantially flat when viewed in longitudinal cross-section (as illustrated in Figure 11). This may reduce build-up of combustion residue inside the internal combustion chamber 12. In other embodiments, the lower end 124 of the internal surface 114 of the outlet portion 100 may slope upwards after the downwards step towards the combustion residue outlet 24. In such embodiments, the combustion residue outlet 24 may not be lower than the lower end 74 of the internal combustion chamber 12. However, it will be understood that by stepping down and then gradually slowing upwards, there is less chance of combustion residue building up in the internal combustion chamber 12 than if there was an upwards step to the combustion residue outlet 24. In the illustrated embodiment, the downwards step from the lower end 74 of the internal combustion chamber 12 to the lower end 124 of the internal surface 114 of the outlet portion 100 is achieved by having an internal diameter 126 at the first end 102 of the outlet portion 100 greater than the diameter 72 of the internal combustion chamber 12 (i.e., so that, at the first end 102 of the outlet portion 100, the internal surface 114 of the outlet portion 100 is outboard of the internal combustion chamber 12 in all radial directions with respect to the combustion chamber axis C). However, it will be understood that in other configurations it may only be a lower region of the internal surface 114 of the outlet portion 100 which is radially outboard of the internal combustion chamber 12. In other embodiments, the internal diameter 126 at the first end 102 of the outlet portion 100 may be equal to the diameter 72 of the internal combustion chamber 12 (i.e., so that the internal surfaces of the combustion portion 60 and outlet portion 100 are substantially flush). In the illustrated embodiment, a cross-sectional dimension 128 of the outlet portion 100 decreases from the first end 102 to the second end 104 of the outlet portion 100 (i.e. along the length 108 of the outlet portion 100). In particular, the cross-sectional dimension 128 gradually (e.g., linearly) decreases from the first end 102 to the second end 104 of the outlet portion 100. In the illustrated embodiment, the internal diameter 126 of the outlet portion 100 decreases from the first end 102 of the outlet portion 100 to the combustion residue outlet 24. In particular, the internal diameter 126 of the outlet portion 100 gradually decreases from the first end 102 of the outlet portion 100 to the combustion residue outlet 24. In this way, the swirling flow of exhaust gas and combustion residue in the outlet portion 100 is forced through a decreasing area which increases the likelihood of combustion residue being urged radially outwards through the combustion residue outlet 24. As best illustrated in Figures 9 to 11, the outlet portion 100 has an oblique frustoconical shape 130 (i.e., defining a frustrum of an oblique cone). In particular, the outlet portion 100 defines a frustrum of an oblique cone having a vertex 132 positioned in line with a periphery of a base 134 of the cone (illustrated as a dot-dash line on Figure 11). Put another way, in a vertical cross-section taken through a horizontal axis of the outlet portion 100 (as illustrated in Figure 11), one side 136 of the oblique frustoconical shape 130 is perpendicular to the base 134 of the oblique frustoconical shape 130. In the illustrated embodiment, the oblique frustoconical shape 130 has a lower side 136 which is arranged substantially horizontally. In other words, the lower side 136 is arranged parallel to the central axis C of the internal combustion chamber 12. In the illustrated embodiment, the lower side 136 of the oblique frustoconical shape 130 defines the lower end 122 of the outlet portion 100. It will be understood that, because the oblique frustoconical shape 130 has a lower side 136 which is arranged substantially horizontally, the upper side 138 (i.e., opposite side) of the oblique frustoconical shape 130 is arranged at an angle to the horizontal. The intermediate surfaces 140 defined between the lower and upper sides 136, 138 define varying angles so that portions of the intermediate surfaces 140 which are closer to the lower side 136 are less angled relative to the horizontal, whereas portions of the intermediate surfaces 140 which are closer to the upper side 138 are more angled relative to the horizontal. As best illustrated in Figures 3, 4 and 9, the combustion apparatus 10 further comprises a combustion residue removal device 30 coupled to the combustion residue outlet 24 in order to convey combustion residue away from the combustion residue outlet 24. This allows a continuous removal of combustion residue through the combustion residue outlet 24. In the illustrated embodiment, the combustion residue removal device 30 is an outlet auger. The outlet auger 30 conveys combustion residue transversely away from the combustion residue outlet 24 to a combustion residue chute 32. A bin or other receptacle may be placed underneath the combustion residue chute 32 to receive the combustion residue from the outlet auger 30. The outlet auger 30 may be supported by at least one outlet auger bearing 31. For example, an outlet auger bearing 31 is illustrated in Figure 9 at a distal end of the outlet auger 30. The outlet auger bearing 31 is laterally spaced apart from the outlet portion 100, and thus laterally spaced from the combustion portion 60, (i.e., in a direction transverse to the longitudinal axis L of the combustion apparatus 10). The outlet auger bearing 31 may be laterally spaced apart from the outlet portion 100, for example, by a distance of at least 0.25m, e.g. at least 0.5m, e.g., at least 0.75m, e.g. at least Im. This may protect the outlet auger bearing 31 from heat generated in the combustion apparatus 10. Although not clearly illustrated in the figures, the outlet auger 30 may be supported at another position by a second outlet auger bearing 31. The second outlet auger bearing 31 may be laterally spaced from the outlet portion 100 (e.g., spaced from an opposite side of the outlet portion 100 to the first outlet auger bearing). The combustion portion 60 has a length 86 which extends from the end body 64 to the second end 68 of the cylindrical body 62. The length 86 of the combustion portion 60 may be in a range of about 0.5m to about 3m, e.g., in a range of about 0.75m to about 2.5m, e.g., in a range of about Im to about 2m, e.g., in a range of about 1.25m to about 1.5m. For example, in the illustrated embodiment the length 86 of the combustion portion is approximately 1.3m. In the illustrated embodiment, the length 86 of the combustion portion 60 is less than a diameter (e.g. an external diameter 88 or an internal diameter 72) of the combustion portion 60. For example, the external diameter 88 of the combustion portion 60 may be in a range of about 0.5m to 3m, e.g., in a range of about Im to about 2.5m, e.g., in a range of about 1.5m to about 2.25m. The diameter 72 of the internal combustion chamber 12 may be in a range of about 0.5m to about 3m, e.g., in a range of about Im to about 2.5m, e.g., in a range of about 1.25m to about 2m. For example, in the illustrated embodiment the internal combustion chamber 12 has a diameter 72 of approximately 1.5m. The length 108 of the outlet portion 100 may be in a range of about 0.75m to 3m, optionally in a range of about lm to 2m, optionally in a range of about 1.25m to about 1.75m. For example, in the illustrated embodiment the length 108 of the outlet portion 100 is approximately 1.5m. In the illustrated embodiment, the length 108 of the outlet portion 100 is less than a maximum diameter 142 of the outlet portion 100. The maximum diameter 142 of the outlet portion 100 may be in a range of about 0.5m to 3m, optionally in a range of about lm to about 2.5m, optionally in a range of about 1.5m to about 2.25m. For example, in the illustrated embodiment the maximum diameter 142 of the outlet portion 100 is approximately 1.95m. As will be apparent from the values given above, in the illustrated embodiment the length 108 of the outlet portion 100 is greater than the length 86 of the combustion portion 60. However, in other embodiments, the lengths 86, 108 of the combustion portion 60 and outlet portion 100 may be equal, or the length 86 of the combustion portion 60 may be greater than the length 108 of the outlet portion 100. In the illustrated embodiment, the collective length of the combustion portion 60 and the outlet portion 100 (i.e., the sum of the respective lengths 86, 108) is greater than the external diameter 88 of the combustion portion 60 and the internal diameter 72 of the internal combustion chamber 12. The collective length of the combustion portion 60 and the outlet portion 100 may be in a range of about 1.5m to about 6m, e.g., in a range of about 2m to about 5m, e.g., in a range of about 2.5m to about 4m. For example, in the illustrated embodiment the collective length is approximately 2.8m. Referring now to Figures 5 and 12 to 14B, the one or more air inlets 14A, 14B of the combustion apparatus 10 are described in more detail. As mentioned briefly above, the one or more air inlets 14A, 14B are arranged to create a swirling flow of air 26 inside the internal combustion chamber 12. In particular, each of the one or more air inlets 14A, 14B is configured to direct air flowing through the air inlet 14A, 14B in an approximately tangential direction along an internal wall 76 of the internal combustion chamber 12 to create the swirling flow of air 26 (as best illustrated in Figure 5). In the illustrated embodiment, the one or more air inlets 14A, 14B include a first air inlet 14A located on a first side 78 of the cylindrical body 62, and a second air inlet 14B located on a second side 80 of the substantially cylindrical body 62 opposite to the first side 78. The first and second air inlets 14A, 14 are configured to direct air into the internal combustion chamber 12 in opposite directions to create the swirling flow of air 26 (as best illustrated in Figure 5). In the illustrated embodiment, the first and second air inlets 14A, 14B are located opposite each other (e.g., in horizontal alignment with each other) and the first and second air inlets 14A, 14B are angled in opposite directions (e.g., one of the first and second air inlets 14A, 14B being angled upwards and the other of the first and second air inlets 14A, 14B being angled downwards) to direct air into the internal combustion chamber 12 in opposite directions. In the illustrated embodiment, the air inlets 14A, 14B are configured to direct at least a portion of the swirling flow of air 26 towards the first end 66 of the cylindrical body 62. By having the air inlets 14A, 14B configured to direct at least a portion of the swirling flow of air 26 towards the first end 66 of the cylindrical body 62 (at which the combustible material is input), the swirling flow of air 26 may interact with the combustible material to urge it away from the first end 66 of the cylindrical body 62 towards a centre of the internal combustion chamber 12 (i.e., towards the fireball inside the swirling flow of air 26). This may improve the combustion performance of the combustion apparatus 10. Each of the air inlets 14A, 14B defines a channel 34 having an inlet axis 36 extending through the cylindrical body 62. In the illustrated embodiment, the inlet axis 36 of the channel 34 is parallel to the first and second ends 66, 68 of the cylindrical body 62 (i.e., orthogonal to the central axis C of the internal combustion chamber 12). The channels 34 extend through the refractory material 28 of the cylindrical body 62. In Figure 13, the refractory material 28 has been omitted to show the shape of the channel 34 more clearly. As best illustrated in Figure 5, the inlet axis 36 is arranged approximately tangentially to the internal wall 76 of the internal combustion chamber 12, to induce the swirling flow of air 26. In the illustrated embodiment, the channel 34 defines an elongate slot. The elongate slot may extend over at least 50% of a length 82 of the cylindrical body 62 (extending between the first and second ends 66, 68 of the cylindrical body 62). For example, the elongate slot may extend over at least 75% of the length 82 of the cylindrical body 62. This facilitates input of air along the majority of the length 82 of the cylindrical body 62. However, in other embodiments, the channel 34 has any other suitable configuration. Each of the air inlets 14A, 14B also has a diverter 38 arranged within the channel 34. The diverter 38 is illustrated schematically as a dashed line on Figures 12 and 13. In the illustrated embodiment, the diverter 38 is a plate which is angled relative to the inlet axis 36 to direct air flowing along the channel 34 towards the first end 66 of the cylindrical body 12. In other embodiments, the diverter 38 may be curved relative to the inlet axis 36 to achieve a similar effect. The diverter 38 may be arranged at an angle in a range of about 20 degrees to about 60 degrees to the inlet axis 36. For example, in Figure 14B the diverter 38 is shown in solid lines at an angle of about 45 degrees to the inlet axis 36, and in dashed lines at angles of about 20 and 60 degrees to the inlet axis 36. As best illustrated in Figure 14A, the channel 34 has a lateral dimension 40 extending in a direction perpendicular to the inlet axis 36. The diverter 38 has a width 42 which partially overlaps the lateral dimension 40 of the channel 34. The lateral dimension 40 of the channel 34 and the width 42 of the diverter 38 are defined in a direction which is parallel to the central axis C of the internal combustion chamber 12 (i.e., in a direction which is parallel to the length 82 of the cylindrical body 12. The width 42 of the diverter 38 may overlap about 15% to about 70% of the lateral dimension 40 of the channel 34, e.g., 25% to about 60% of the lateral dimension 40 of the channel 34. For example, in Figure 14A, the width 42 of the diverter 38 overlaps approximately 40% of the lateral dimension 40 of the channel 34. It will be understood that, because the width 42 of the diverter 38 partially overlaps the lateral dimension 40 of the channel 34, some portions of the air flowing along the channel 34 do not impact the diverter 38 and are thus not directed towards the first end 66 of the cylindrical body 12. This configuration has been found to direct the air to effectively direct combustible material of different particle sizes towards the fireball within the swirling flow of air 26. In some embodiments, the air inlets 14A, 14B are adjustable to vary a proportion of air flowing through the air inlets 14A, 14B that is directed towards the first end 66 of the cylindrical body 12, and / or to vary an angle at which air flowing through the air inlets 14A, 14B is directed towards the first end 66 of the cylindrical body 12. Such adjustment facilitates tuning the swirling flow of air 26 for different particle sizes of combustible material which are input to the internal combustion chamber 12. For example, CFD analysis has shown that combustible material of smaller particle size is more likely to become stuck at the first end 66 of the cylindrical body 12 outside of the fireball within the swirling flow of air 26 than combustible material of larger particle size. This may be because larger particles bounce off each other and / or a wall which closes the first end 66 of the cylindrical body 12 (i.e., the end body 64) more easily and thus become entrained within the fireball inside the swirling flow of air 26. Therefore, it may be desirable to increase the proportion of air that is directed towards the first end 66 of the cylindrical body 12 and / or increase the angle at which air is directed towards the first end 66 when the particle size of the combustible material is smaller. To achieve this adjustment, the position and / or orientation of the diverter 38 may be adjustable within the channel 34. For example, in Figures 14A and 14B the diverter 38 is pivotally mounted in the channel 34 (i.e., at a pivot axis 44) such that an angle of the diverter 38 relative to the inlet axis 36 is adjustable. For example, the diverter 38 may be pivoted between the three positions illustrated in Figure 14B. The air inlet 14A, 14B illustrated in Figure 14A also has an actuator 46 configured to change the orientation of the diverter 38. The actuator 46 may be any suitable actuator (e.g., a rotary actuator such as a stepper motor, or a linear actuator coupled to a crank arm). In some embodiments, the diverter 38 is slidably mounted in the channel 34 such that a position of the diverter 38 relative to the inlet axis 36 is adjustable. In such embodiments, an alternative actuator may be provided. In Figure 14A, a controller 48 is indicated schematically. The controller 48 may be configured to determine a particle size of combustible material being input to the internal combustion chamber 12, and to control the actuator 46 to adjust the diverter 38 depending on the determined particle size. For example, the controller 48 may be configured to adjust the diverter 38 to divert a greater proportion of air flowing along the channel 34 towards the first end 66 as the determined particle size decreases. The controller 48 may be configured to automatically determine the particle size (e.g., using a particle size sensing apparatus 50, such as a vision system with image processing). Alternatively, the particle size may be input to the controller 48 manually by a user of the combustion apparatus 10. In some embodiments, the inlet axis 36 of the channel 34 is angled towards the first end 66 of the cylindrical body 62 in order to direct the swirling flow of air 26 towards the first end 66 of the cylindrical body 62. In such embodiments, the diverter 38 may be omitted. In such embodiments, adjustability may be achieved by changing the angle of the entire channel 34 relative to the first end 66 of the cylindrical body 62. Referring again to Figures 1 to 6, the air supply apparatus 300 will be described in more detail. The air supply apparatus 300 has a blower 304 and one or more inlet pipes 306A, 306B configured to connect the blower 304 to the one or more air inlets 14A, 14B. The blower 304 has a blower inlet 305 which is configured to suck ambient air from the atmosphere surrounding the blower 304 to be conveyed along the one or more inlet pipes 306A, 306B. In other words, the blower inlet 305 is an open inlet (i.e., is open to the atmosphere surrounding the blower 304). Put another way, the blower inlet 305 is not connected to any pipe or ductwork upstream of the blower 304. This contrasts with alternative configurations in which the blower inlet 305 is configured to suck air from another component of the combustion system 10 (e.g., from inside a hopper 202 of the combustible material supply apparatus 200). In the illustrated embodiment, because there are first and second air inlets 14A, 14B arranged on first and second sides 78, 80 of the combustion apparatus 10, there is a first inlet pipe 306A configured to connect the blower 304 to the first air inlet 14A and a second inlet pipe 306B configured to connect the blower 304 to the second air inlet 14B. The flow of air 302 along the first and second inlets pipes 306A, 306B is shown by the arrows illustrated on Figures 5 and 6. As will be described in more detail below, each of the first and second inlet pipes 306A, 306B extends upwards from the blower 304 and then horizontally to the respective air inlet 14A, 14B. In particular, each of the first and second inlet pipes 306A, 306B has a downstream portion 308 coupled to the respective air inlet 14A, 14B, and an upstream portion 310 connecting the blower 304 and the downstream portion 308. In the illustrated embodiment, the downstream portion 308 is arranged substantially horizontally, and the upstream portion 310 is arranged substantially vertically. The downstream portion 308 may be at least Im long, e.g., at least 1.5m long, e.g., at least 2m long, e.g., at least 2.5m long. For example, in the illustrated embodiment, the downstream portion 308 is approximately 3m long. In the illustrated embodiment, the downstream portion 308 has a downstream straight section 312 and a downstream elbow 314 coupled between the downstream straight section 312 and the respective air inlet 14A, 14B. As best illustrated in Figures 1, 2 and 6, the downstream portion 308 also has an expander 316 which connects the downstream elbow 314 to the respective air inlet 14A, 14B. The expander 316 widens the flow of air 302 prior to entering the respective air inlet 14A, 14B. In addition, the expander 316 changes the cross-sectional shape of the inlet pipe 306A, 306B from a circular crosssection to a rectangular cross-section. In this way, the expander 316 helps to guide the flow of air 302 into the respective air inlet 14A, 14B which, as outlined above, is a channel 34 in the form of an elongate slot. In the illustrated embodiment, the upstream portion 310 has an upstream straight section 318, an intermediate elbow 320 coupled between the upstream straight section 318 and the downstream straight section 312, and an upstream elbow 322 coupled between the upstream straight section 318 and the blower 304. In the illustrated embodiment, the blower 304 has a first blower outlet 324A for coupling to the first inlet pipe 306A and a second blower outlet 324B for coupling to the second inlet pipe 306B. The first and second blower outlets 324A, 324B are provided on different (e.g., opposite) sides of the blower 304. This facilitates a more direct path to the first and second air inlets 14A, 14B on opposite sides 78, 80 of the combustion apparatus 10. As best illustrated in Figure 2, the blower 304 has a splitter portion 326 configured to direct air towards the first and second blower outlets 324A, 324B. In the illustrated embodiment, the splitter portion 326 is an approximately Y-shaped duct. In the illustrated embodiment, each of the first and second inlet pipes 306A, 306B has a horizontal dimension 328 between the blower 304 and the respective air inlet 14A, 14B (illustrated on Figure 6). In the illustrated embodiment, the horizontal dimension 328 is approximately 3.5m (as measured from a centre of the respective blower outlet 324A, 324B to a centre of the respective air inlet 14A, 14B). In other embodiments, the horizontal dimension 328 may differ (e.g., in a range of 0.5m to 10m, e.g., in a range of 2m to 6m). Each of the first and second inlet pipes 306A, 306B also has a vertical dimension 330 between the blower 304 and the respective air inlet 14A, 14B (illustrated on Figure 5). In the illustrated embodiment, the vertical dimension 330 is approximately 1.25m (as measured from a centre of the respective blower outlet 324A, 324B to a centre of the respective air inlet 14A, 14B). In other embodiments, the vertical dimension 330 may differ (e.g., in a range of 0.25m to 4m, e.g., in a range of 0.5m to 2m). As outlined above, the horizontal dimension 328 is greater than the vertical dimension 330. In some embodiments, the horizontal dimension 328 is at least 25% greater than the vertical dimension 330, optionally at least 50% greater than the vertical dimension 330, optionally at least 75% greater than the vertical dimension 330, optionally at least 100% greater than the vertical dimension 330. In the illustrated embodiment, each of the first and second inlet pipes 306A, 306B has an approximately constant internal pipe diameter 332 (illustrated on Figure 6) between the blower outlets 324A, 324B and the expanders 316. However, it will be understood that in other embodiments the internal pipe diameter 332 may vary along the length of the first and second inlet pipes 306A, 306B (e.g., between different sections and elbows 312, 314 318, 320, 322, and / or within the same section or elbow 312, 314, 318, 320, 322). Referring now to Figures 1 to 5, 13 and 15 to 17, the combustion system 1 includes a rail arrangement 400 for guiding movement of at least a portion of the combustion apparatus 10 and / or combustible material supply apparatus 200 and / or air supply apparatus 300 between a first position corresponding to an assembled state of the combustion system 1 and a second position corresponding to a disassembled state of the combustion system 1. The rail arrangement 400 facilitates assembly and disassembly of the combustion system 1 (e.g., for maintenance purposes). This may be particularly beneficial when a particular component requires regular disassembly (e.g., for cleaning internally). In addition, the rail arrangement 400 may help to move heavy components which would otherwise need specialist tools (e.g., cranes, forklifts etc.). Further, the rail arrangement 400 may provide a more accurate relative positioning of components during assembly (i.e., by constraining movement to a single direction defined by one or more rails of the rail arrangement 400). The combustion system 1 has a longitudinal axis L (illustrated on Figure 6). The longitudinal axis L is parallel to the central axis C of the internal combustion chamber 12 defined by the cylindrical body 62. In the illustrated embodiment, the rail arrangement 400 has one or more transverse rails 402 which are configured to guide movement of a portion of the combustion apparatus 10 in a transverse direction Dt which is transverse (e.g., orthogonal) to the longitudinal axis L. In particular, the one or more transverse rails 402 are configured to guide movement of the substantially cylindrical body 62 of the combustion portion 60 of the combustion apparatus 10 in the transverse direction Dt. In the illustrated embodiment, there are two transverse rails 402. In other embodiments there are other numbers of transverse rails 402 (e.g., 1, 3 or greater than 3 transverse rails 402). The transverse rails 402 allow the cylindrical body 62 to be slid out sideways from the adjacent components of the combustion apparatus 10. For example, the cylindrical body 62 can be moved from an assembled position in which it is adjacent to the outlet portion 100 and end body 64 (as illustrated towards the left-hand side of Figure 1) to a disassembled position in which it is separated from the outlet portion 100 and end body 64 (as illustrated towards the right-hand side of Figure 1). The disassembled position permits access to the internal combustion chamber 12, e.g., for cleaning and / or replacement or regeneration of refractory material 28. It will be understood that, in order to permit movement of the cylindrical body 62 on the transverse rails 402, the releasable coupling between the cylindrical body 62 and adjacent components must be released. In particular, the bolts between the flanges 70 on the cylindrical body 62 and on the end body 64 and outlet portion 100 must be released. As best illustrated in Figure 5, the combustion system 1 includes a lifting device 404. In the illustrated embodiment, the lifting device 404 is a hydraulic jack (e.g., a manually actuated hydraulic jack). In other embodiments, the lifting device 404 may be an alternative device (e.g., a hydraulic or pneumatic cylinder). The lifting device 404 may be used to mount or dismount the cylindrical body 62 onto the rail arrangement 400. In the illustrated embodiment, the rail arrangement 400 includes a support arrangement 405 for supporting the cylindrical body 62 as it moves along the transverse rails 402. In the illustrated embodiment, the support arrangement 405 is a cradle having a shape which is complementary to a periphery of the cylindrical body 62 (e.g., a convex cradle). The lifting device 404 is configured to raise and lower the cylindrical body 62 onto the cradle 405. In particular, during assembly the cylindrical body 62 rests on the cradle 405 and is moved along the transverse rails 402 until it is in horizontal alignment with the end body 64 and outlet portion 100. The lifting device 404 then raises the cylindrical body 62 from the cradle 405 to put the cylindrical body 62 in vertical alignment with the end body 64 and outlet portion 100. This facilitates coupling of the cylindrical body 62, end body 64 and outlet portion 100 by bolting the adjacent flanges 70. During disassembly (e.g., for maintenance purposes), the lifting device 404 may be used to lower the cylindrical body 62 onto the cradle 405 for movement along the transverse rails 402. Alternatively, or additionally, the lifting device 404 may be used to support a weight of the cylindrical body 62 during movement along the transverse rails 402. This may reduce the resistance between the cylindrical body 62 and the transverse rails 402 and thereby facilitate easier sliding of the cylindrical body 62. This may also reduce the structural requirements of the transverse rails 402. This may be particularly beneficial in view of the heavy weight of the cylindrical body 62 due to the relatively thick refractory material lining 28. As illustrated in Figure 17, the lifting device 404 has a first formation 406 and the cylindrical body 62 has a second formation 408 configured to be engaged by the first formation 406 to lift the cylindrical body 62 with the lifting device 404. In the illustrated embodiment, the first formation 406 is a male formation and the second formation 408 is a female formation. In particular, the first formation 406 is a projection and the second formation 408 is a recess in a lower end 84 of the cylindrical body 62. In the illustrated embodiment, the lifting device 404 is movable in at least one direction. In particular, the lifting device 404 is movable along one or more lifting device rails 407. The lifting device rails 407 extend longitudinally (i.e. perpendicular to the transverse rails 402). In this way, once the cylindrical body 62 is lifted from the cradle 405 by the lifting device 404, the lifting device 404 can be moved longitudinally to facilitate alignment with adjacent components (i.e., the end body 64 and outlet portion 100). The lifting device 404 includes one or more guide formations 410 (as described below with reference to Figure 17) to move along the one or more lifting device rails 407. Alternatively, the lifting device 404 may comprise one or more wheels. This may facilitate movement of the component which is lifted by the lifting device (e.g., to facilitate alignment with other components during assembly). As best illustrated in Figure 17, cradle 405 which receives the cylindrical body 62 has one or more guide formations 410 configured to slidingly engage the transverse rails 402 to facilitate movement of the cylindrical body 62 along the transverse rails 402. In particular, there is at least one guide formation 410 for each transverse rail 402 (e.g., at least two guide formations 410 for each transverse rail 402). In the illustrated embodiment, the guide formations 410 are provided at a lower end of the cradle 405. The guide formations 410 may be linear motion bearings to facilitate movement along the transverse rails 402. Such linear motion bearings reduce resistance and thereby facilitate easier movement along the transverse rails 402. This may be particularly beneficial in view of the heavy weight of the cylindrical body 62 due to the relatively thick refractory material lining 28. As best illustrated in Figures 15 and 16, the rail arrangement 400 has one or more longitudinal rails 412 which are configured to guide movement of one or more components adjacent to the cylindrical body 62 in a longitudinal direction Di parallel to the longitudinal axis L, in order to separate the cylindrical body 62 and the one or more adjacent components. Put another way, the one or more longitudinal rails 412 are configured to guide movement of the one or more adjacent components in a longitudinal direction Di which is orthogonal to the transverse direction Dt in which the cylindrical body 62 is moved along the one or more transverse rails 402. This facilitates separation of the cylindrical body 62 from the one or more adjacent components (i.e., provides a clearance) to facilitate easier transverse movement of the cylindrical body 62. The one or more longitudinal rails 412 may include at least two longitudinal rails 412. In the illustrated embodiment, the one or more longitudinal rails 412 are configured to guide movement of the combustible material supply apparatus 200, the blower 304 of the air supply apparatus 300, and the end body 64 of the combustion apparatus 10 between an assembled position (as illustrated in Figure 15) and a disassembled position (as illustrated in Figure 16). In the illustrated embodiment, the combustible material supply apparatus 200 and the air supply apparatus 300 are supported by a support arrangement which moves along the longitudinal rails 412. In particular, the combustible material supply apparatus 200 and the air supply apparatus 300 are at least partly mounted on a support base 414 which is configured to move along the longitudinal rails 412. In the illustrated embodiment, the combustible material supply apparatus 200 and the blower 304 of the air supply apparatus 300 are mounted to the support base 414. The end body 64 of the combustion apparatus 10 is also mounted indirectly to the support base 414 via a vertical support wall 416. In this way, all of the components mounted to the support base 414 (whether directly or indirectly) can move together along the longitudinal rails 412. Although not shown in detail, a lower end 418 of the support base 414 includes a plurality of guide formations 410, similar to the guide formations 410 of the cradle 405 illustrated in Figure 17. In the illustrated embodiment, the combustion system 1 includes a movement actuator 420 to drive movement of the support base 414 along the longitudinal rails 412. In particular, the movement actuator 420 is a manual linear screw actuator. The manual linear screw actuator includes a wheel 422 coupled to the vertical support wall 416. Turning of the wheel 422 causes rotation of a screw 424, which is received in a thread on a fixed post 426. In this way, as the as the wheel 422 is turned, the engagement of the screw 424 with the thread of the fixed post 426 causes linear movement of the screw 424 and thus linear movement of the vertical support wall 416, support base 414, and components 304, 200, 64 mounted thereon. In alternative embodiments, the movement actuator 420 may be of any other suitable configuration (e.g., a hydraulic cylinder). In the illustrated embodiment, the combustible material supply apparatus 200 includes a hopper 202 for receiving combustible material (e.g., particulate combustible material). The combustible material supply apparatus 200 also includes a combustible material supply pipe 204 connecting the hopper 202 to the combustible material inlet 16 of the combustion apparatus 10. The combustible material supply pipe 204 includes an inlet auger 206 configured to convey the combustible material along the combustible material supply pipe 204. In the illustrated embodiment, the combustible material supply apparatus 200 includes an agitation device 208 inside the hopper 202. The agitation device 208 is configured to break up clumps of combustible material into smaller particles to facilitate easy movement via the inlet auger 206 and / or better mixing with the swirling flow of air 26 within the internal combustion chamber 12. In the illustrated embodiment, the agitation device 208 includes a pair of rotating shafts 210 each having a plurality of blades 212 for breaking up the combustible material. Each shaft 210 is driven in rotation by a motor 214 (e.g., an electric motor). In other embodiments, the agitation device 208 may have a single rotating shaft 210, or more than two rotating shafts 210. In other embodiments, the agitation device 208 is an alternative device (e.g., a vibration device instead of a rotating shaft 210 with blades 212). Referring now to Figure 18, a method of combusting combustible material with the combustion system 1 of Figures 1 to 17 is indicated as a flow chart. The method includes: loading combustible material into the combustible material supply apparatus 200; operating the combustible material supply apparatus 200 and air supply apparatus 300 to simultaneously provide a mixture of combustible material and air in the internal combustion chamber 12; and combusting the combustible material inside the internal combustion chamber 12 (e.g., via actuation of the ignition device 18). The one or more embodiments are described above by way of example only and it will be appreciated that the variations are possible without departing from the scope of protection afforded by the appended claims. For example, In some embodiments, the combustion apparatus 10 may have one or more common inlets for input of both air and combustible material through the common inlet to the internal combustion chamber 12. In some embodiments, the outlet portion 100 may be omitted. In such embodiments, the combustion residue outlet 24 may be provided through the cylindrical body 62. In some embodiments, the combustion residue outlet 24 may be moved from the outlet portion 100 to the combustion portion 60. In such embodiments, the outlet portion 100 may still be present and may still have the same oblique frustoconical shape, or another shape. In some embodiments, a movement actuator (e.g., a linear screw actuator) may be provided to move the cylindrical body 62 along the transverse rails 402. In some embodiments, a lifting device 404 may be provided to raise or lower a component other than the cylindrical body 62 onto the rail arrangement 400 and / or to support a weight of the component as it moves along the rails 42, 412. In some embodiments, the air inlets 14A, 14B are not configured to direct the swirling flow of air 26 towards the first end 66 of the cylindrical body 62, In some embodiments, the inlet pipes 306A, 306B have a different configuration (e.g., extending horizontally from the blower 204 and then upwards to the respective air inlet 14A, 14B, or extending at an angle to the horizontal and vertical). In some embodiments, the rail arrangement 400 may be omitted entirely. In some embodiments, the rail arrangement 400 includes only one of the transverse rails 402 or longitudinal rails 412. It should also be noted that whilst the appended claims set out particular combinations of features described above, the scope of the present disclosure is not limited to the particular combinations hereafter claimed, but instead extends to encompass any combination of features herein disclosed.

Claims

1. A combustion apparatus for combustion of particulate combustible material, the combustion apparatus comprising:a combustion portion which defines an internal combustion chamber; andan outlet portion comprising a first end coupled to an open end of the combustion portion and a second end which defines an exhaust gas outlet;wherein the combustion portion comprises one or more inlets for input of combustible material and air to the internal combustion chamber;wherein the outlet portion comprises a combustion residue outlet positioned between the first and second ends of the outlet portion for output of combustion residue from the combustion apparatus.

2. The combustion apparatus of claim 1, wherein the one or more inlets are arranged to create a swirling flow of air within the internal combustion chamber when a flow of air is supplied through the one or more inlets.

3. The combustion apparatus of claim 1 or 2, wherein the outlet portion has a length which extends between the first and second ends of the outlet portion, wherein the combustion residue outlet comprises an axial dimension extending in a direction parallel to the length of the outlet portion, and wherein the axial dimension is in a range of about 5% to about 60% of the length of the outlet portion, optionally in a range of about 5% to about 30% of the length of the outlet portion.

4. The combustion apparatus of any of claims 1 to 3, wherein the combustion residue outlet comprises a circumferential dimension extending along a circumference of the outlet portion, wherein the circumferential dimension is in a range of about 5% to about 50% of the circumference; optionally in a range of about 10% to 30% of the circumference.

5. The combustion apparatus of any preceding claim, wherein the combustion residue outlet defines an aperture through an internal surface of the outlet portion, wherein the internal surface of the outlet portion comprises an outlet groove extending circumferentially from the combustion residue outlet along at least a portion of a circumference of the internal surface.

6. The combustion apparatus of claim 5, wherein the outlet groove extends only partially along the circumference of the internal surface; optionally, wherein the one or more inlets are arranged to create a swirling flow of air within the internal combustionchamber and the outlet portion when a flow of air is supplied through the one or more inlets and wherein the outlet groove extends along a side of the internal surface which is upstream of the combustion residue outlet with respect to the swirling flow of air; and / or optionally, wherein the outlet groove extends circumferentially along a range of about 5% to about 50% of the circumference of the internal surface.

7. The combustion apparatus of claim 5 or 6, wherein the outlet groove comprises an axial dimension in a direction parallel to a length of the outlet portion, wherein the axial dimension of the outlet groove tapers inwards towards the combustion residue outlet along a circumferential dimension of the outlet groove.

8. The combustion apparatus of any preceding claim, wherein the combustion residue outlet defines an aperture through a lower end of the outlet portion.

9. The combustion apparatus of claim 8, wherein the combustion residue outlet is arranged to be lower than or level with a lower end of the internal combustion chamber.

10. The combustion apparatus of claim 8 or 9, wherein the outlet portion comprises an internal diameter and wherein, at the first end of the outlet portion, the internal diameter of the outlet portion is greater than or equal to the diameter of the internal combustion chamber.

11. The combustion apparatus of any preceding claim, wherein an internal diameter of the outlet portion decreases from the first end of the outlet portion to the combustion residue outlet; optionally, wherein the internal diameter of the outlet portion gradually decreases from the first end of the outlet portion to the combustion residue outlet; optionally, wherein the outlet portion has an oblique frustoconical shape; optionally, wherein the oblique frustoconical shape has a lower side which is arranged substantially horizontally.

12. A combustion apparatus for combustion of particulate combustible material, the combustion apparatus comprising a substantially cylindrical body which defines an internal combustion chamber, wherein the substantially cylindrical body comprises:a first end through which combustible material can be input to the internal combustion chamber;a second end opposite the first end; andone or more air inlets provided through the substantially cylindrical body at a position between the first and second ends;wherein the one or more air inlets are arranged to create a swirling flow of air inside the internal combustion chamber; andwherein the one or more air inlets are configured to direct at least a portion of the swirling flow of air towards the first end of the cylindrical body.

13. The combustion apparatus of claim 12, wherein the one or more air inlets are adjustable to vary a proportion of air flowing through the one or more air inlets that is directed towards the first end of the cylindrical body, and / or to vary an angle at which air flowing through the one or more air inlets is directed towards the first end of the cylindrical body.

14. The combustion apparatus of claim 12 or 12, wherein each of the one or more air inlets defines a channel having an inlet axis extending through the cylindrical body and a diverter arranged at least partly within the channel, wherein the diverter is angled and / or curved relative to the inlet axis to direct air flowing along the channel towards the first end of the cylindrical body.

15. The combustion apparatus of claim 14, wherein the diverter comprises a plate which is arranged at an angle in a range of about 20 degrees to about 60 degrees to the inlet axis.

16. The combustion apparatus of claim 14 or 15, wherein the channel comprises a lateral dimension extending in a direction perpendicular to the inlet axis, wherein the diverter comprises a width which partially overlaps the lateral dimension of the channel; optionally, wherein the width of the diverter overlaps about 15% to about 70% of the lateral dimension of the channel, optionally about 25% to about 60% of the lateral dimension of the channel.

17. The combustion apparatus of claim 14, 15 or 16, wherein the position and / or orientation of the diverter is adjustable within the channel to vary a proportion of air flowing along the channel that is directed towards the first end of the cylindrical body, and / or to vary an angle at which air flowing along the channel is directed towards the first end of the cylindrical body.

18. The combustion apparatus of claim 17, wherein the diverter is pivotally mounted in the channel such that an angle of the diverter relative to the inlet axis is adjustable, and / or wherein the diverter is slidably mounted in the channel such that a position of the diverter relative to the inlet axis is adjustable.

19. The combustion apparatus of claim 17 or 18, wherein each of the one or more air inlets further comprises an actuator configured to change the position and / or orientation of the diverter.

20. The combustion apparatus of claim 19, further comprising a controller configured to determine a particle size of combustible material being input to the internal combustion chamber, and to control the actuator to adjust the diverter depending on the determined particle size; optionally, wherein the controller is configured to adjust the diverter to divert a greater proportion of air flowing along the channel towards the first end as the determined particle size decreases.

21. The combustion apparatus of any of claims 12 to 20, wherein each of the one or more air inlets is configured to direct air flowing through the air inlet in an approximately tangential direction along an internal wall of the internal combustion chamber to create the swirling flow of air.

22. A combustion apparatus in accordance with any of claims 1 to 11 and any of claims 12 to 21.

23. A combustion system comprising:the combustion apparatus of any of claims 1 to 11 and / or 12 to 21;a combustible material supply apparatus for suppling combustible material to the combustion apparatus; andan air supply apparatus for supplying a flow of air to the combustion apparatus.

24. A combustion system for combustion of particulate combustible material, the combustion system comprising:a combustion apparatus defining an internal combustion chamber, the combustion apparatus having one or more air inlets for input of air to the internal combustion chamber; andan air supply apparatus for supplying a flow of air to the one or more air inlets;wherein the air supply apparatus comprises a blower and one or more inlet pipes configured to connect the blower to the one or more air inlets;wherein each of the one or more inlet pipes extends upwards from the blower and then horizontally to the respective air inlet.

25. The combustion system of claim 24, wherein the one or more air inlets are arranged to create a swirling flow of air within the internal combustion chamber when a flow of air is supplied through the one or more air inlets by the air supply apparatus.

26. The combustion system of claim 24 or 25, comprising a first air inlet arranged on a first side of the combustion apparatus, a second air inlet arranged on a second side of the combustion apparatus opposite to the first side, a first inlet pipe configured to connect the blower to the first air inlet and a second inlet pipe configured to connect the blower to the second air inlet; optionally, wherein the first and second air inlets are configured to input air to the combustion chamber in opposite directions to create a swirling flow of air within the internal combustion chamber.

27. The combustion system of claims 24, 25 or 26, wherein each of the one or more inlet pipes has a downstream portion coupled to the respective air inlet and an upstream portion connecting the blower and the downstream portion, wherein the downstream portion is arranged substantially horizontally; optionally, wherein the upstream portion is arranged substantially vertically.

28. The combustion system of claim 27, wherein the downstream portion is at least Im long, optionally at least 1.5m long, optionally at least 2m long, optionally at least 2.5m long.

29. The combustion system of any of claims 24 to 28, wherein each of the one or more inlet pipes has a horizontal dimension and a vertical dimension between the blower and the respective air inlet, wherein the horizontal dimension is greater than the vertical dimension; optionally, wherein the horizontal dimension is at least 25% greater than the vertical dimension, optionally at least 50% greater than the vertical dimension, optionally at least 75% greater than the vertical dimension, optionally at least 100% greater than the vertical dimension.

30. A combustion system comprising:a combustion apparatus which defines an internal combustion chamber;a combustible material supply apparatus for suppling combustible material to the combustion apparatus;an air supply apparatus for supplying a flow of air to the combustion apparatus; anda rail arrangement for guiding movement of at least one portion of the combustion apparatus and / or combustion material supply apparatus and / or air supply apparatusbetween a first position corresponding to an assembled state of the combustion system and a second position corresponding to a disassembled state of the combustion system.

31. The combustion system of claim 30, further comprising a lifting device which is configured to mount or dismount the at least one portion of the combustion apparatus and / or combustion material supply apparatus and / or air supply apparatus onto the rail arrangement; optionally wherein the lifting device comprises a hydraulic jack.

32. The combustion system of claim 30 or 31, wherein the rail arrangement comprises one or more rails and a support arrangement for supporting at least one portion of the combustion apparatus and / or combustion material supply apparatus and / or air supply apparatus, wherein the support arrangement comprises one or more guide formations configured to slidingly engage the one or more rails to facilitate movement along the one or more rails; optionally, wherein the one or more guide formations comprise one or more linear motion bearings; and / or optionally, wherein the one or more guide formations are provided at a lower end of support arrangement.

33. The combustion system of claim 31 and 32, wherein the at least one portion of the combustion apparatus and / or combustion material supply apparatus and / or air supply apparatus is arranged to rest on the support arrangement during movement along the one or more rails, and the lifting device is configured to raise and lower the at least one portion of the combustion apparatus and / or combustion material supply apparatus and / or air supply apparatus onto the support arrangement; optionally, wherein the support arrangement comprises a cradle; optionally a concave cradle.

34. The combustion system of any of claims 30 to 33, further comprising a movement actuator configured to drive movement of the at least one portion of the combustion apparatus and / or combustible material supply apparatus and / or air supply apparatus along the rail arrangement; optionally, wherein the movement actuator comprises a manual linear screw actuator.

35. The combustion system of any of claims 30 to 34, wherein the combustion system has a longitudinal axis, and wherein the rail arrangement comprises one or more transverse rails which are configured to guide movement of at least one portion of the combustion apparatus and / or combustible material supply apparatus and / or air supply apparatus in a direction transverse to the longitudinal axis; optionally, wherein the one or more transverse rails comprise at least two transverse rails.

36. The combustion system of claim 35, wherein the combustion apparatus comprises a substantially cylindrical body which defines the internal combustion chamber, wherein the internal combustion chamber has a central axis which is parallel to the longitudinal axis of the combustion system, and wherein the one or more transverse rails are configured to guide movement of the substantially cylindrical body in the transverse direction; optionally, wherein the combustion system is in accordance with claim 30 or 32 and the lifting device is configured to lift the cylindrical body; optionally, wherein a lower end of the cylindrical body comprises a recess for engagement with the lifting device.

37. The combustion system of claim 36, wherein the cylindrical body is releasably coupled to one or more adjacent components of the combustion system; optionally, wherein the cylindrical body and one or more adjacent components comprise complementary flanges which are bolted together.

38. The combustion system of claim 37, wherein the rail arrangement comprises one or more longitudinal rails which are configured to guide movement of the one or more adjacent components in a direction parallel to the central axis, in order to separate the cylindrical body and the one or more adjacent components; optionally wherein the one or more longitudinal rails comprise at least two longitudinal rails.

39. The combustion system of any of claims 30 to 37, wherein the combustion system has a longitudinal axis, and wherein the rail arrangement comprises one or more longitudinal rails which are configured to guide movement of the combustion apparatus and / or combustible material supply apparatus and / or air supply apparatus in a direction parallel to the longitudinal axis; optionally, wherein the one or more longitudinal rails comprise at least two longitudinal rails.

40. The combustion system of claim 39, wherein the combustible material supply apparatus and / or air supply apparatus are at least partly mounted on a support base, wherein the support base is configured to move along the one or more longitudinal rails; optionally, further comprising a movement actuator to drive movement of the support base along the one or more longitudinal rails; optionally wherein the movement actuator comprises a manual linear screw actuator.

41. A combustion system in accordance with:any of claims 24 to 29 and any of claims 30 to 40; and / orclaim 23 and any of claims 24 to 29 and / or any of claims 30 to 40.

42. A method of combusting combustible material with the combustion system of any of claims 23 to 40, the method comprising:loading combustible material into the combustible material supply apparatus;operating the combustible material supply apparatus and air supply apparatus to 5 simultaneously provide a mixture of combustible material and air in the internal combustion chamber; andcombusting the combustible material inside the internal combustion chamber.Application No: GB2413739.0 Examiner: Dr Rhys WilliamsClaims searched: 1-11 &22, 23, 41, 42 in part Date of search: 27 February 2025Patents Act 1977: Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular relevance X 1-6, 8-10, 23 &42 JP S6370015 A (DAIDO STEEL CO LTD) Note air / particulate inlet 3 into combustion chamber, exhaust gas outlet 4, and combustion residue outlet 5. X 1-6, 8-10, 23 &42 JPH10227435 A (MITSUBISHI HEAVY IND LTD) Note matter inlet 2 and air inlet 3 into combustion chamber, exhaust gas outlet 11, and combustion residue outlet 8. X 1-4, 8-10, 23 &42 JP H02126005 A (MITSUBISHI HEAVY IND LTD) Note air / particulate matter inlet 3 into combustion chamber 1, exhaust gas outlet 8, and combustion residue outlet 6. X 1-4, 8-10, 23 &42 US 5858033 A (HIRAYAMA et al.) See Fig. 9 with gas / particulate inlet 142, air inlets 134, combustion chamber 140, exhaust gas outlet 154, and combustion residue outlet 152. v A 1-4, 8-10, 23 &42 JP H08303745 A (CHUBU ELECTRIC POWER) Note combustion chamber 1 with air / particulate matter inlet 4, exhaust gas outlet 9, and combustion residue outlet 6. X 1-4, 8-10, 23 &42 JP 2016176683 A (KOBELCO ECO SOLUTIONS CO LTD) Note combustion chamber 22, with exhaust gas outlet 26, and combustion residue outlet 20b.Categories:X Document indicating lack of novelty or inventive step A Document indicating technological background and / or state of the art. Y Document indicating lack of inventive step if p Document published on or after the declared priority date but combined with one or more other documents of same category. before the filing date of this invention. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:Search of GB. EP, WO &US patent documents classified in the following areas of the UKCX :Worldwide search of patent documents classified in the following areas of the IPC F23G; F23JThe following online and other databases have been used in the preparation of this search reportSEARCH-PATENTInternational Classification:Subclass Subgroup Valid From F23G 0005 / 32 01 / 01 / 2006 F23J 0001 / 00 01 / 01 / 2006 F23J 0003 / 00 01 / 01 / 2006Application No: GB2413739.0Examiner: Dr Rhys WilliamsClaims searched: 12-21 &22, 23 in partDate of search: 9 July 2025Patents Act 1977Further Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular relevance v A 12, 13,22 &23 US 2013 / 0101944 Al (SUPANDI IRHARSUDI) See Figs. 1, 2, 5, 7, paragraphs [0029], [0032], [0035] &claim 8.Categories:X Document indicating lack of novelty or inventive step A Document indicating technological background and / or state of the art. Y Document indicating lack of inventive step if P Document published on or after the declared priority date but combined with one or more other documents of same category. before the filing date of this invention. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:International Classification:Subclass Subgroup Valid From F23G 0005 / 32 01 / 01 / 2006 F23J 0001 / 00 01 / 01 / 2006 F23J Template-------- 0003 / 00 01 / 01 / 2006Application No: GB2413739.0Examiner: Dr Rhys WilliamsClaims searched: 24-29 &41, 42 in partDate of search: 9 July 2025Patents Act 1977Further Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular relevance v A 24-29,41 &42 CN 116592343 A (UNIV HEFEI TECHNOLOGY) Note blower 3 and air supply pipe 301 in Fig.

1. X 24-29,41 &42 CN 102425776 A (SHIXING FUYI BOILER MFG CO LTD) Note blower 43 and air pipe 47 in Fig.

1. v A 24-29,41 &42 JP 2022127943 A (ELCOM KK) Note blower 201 and air passage 202 in Fig.

1. X 24-29,41 &42 WO 2005 / 026617 Al (YAMANE NOUBOKUJO INC) Note blower 22 and air inlet pipe 20 in Figs. 1 &3. X 24-29,41 &42 CN 218510897 U (HENAN NENGXIN ENVIRONMENTAL PROTECTION TECH CO LTD) Note blower 2 and air distribution pipe 3 in Fig.

1. X 24, 27-29, 41 &42 CN 219674245 U (HENAN TIANCHEN XIN YU AN ENVIRONMENTAL PROTECTION TECH RESEARCH INSTITUTE CO LTD) Note fan 56 and air inlet pipe 55 in Fig. 1.Categories:X Document indicating lack of novelty or inventive step A Document indicating technological background and or state of the art. Y Document indicating lack of inventive step if combined with one or more other documents of same category. P Document published on or after the declared priority date but before the filing date of this invention. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:International Classification:Subclass Subgroup Valid From F23G 0005 / 32 01 / 01 / 2006 F23J 0001 / 00 01 / 01 / 2006 F23J Template-------- 0003 / 00 01 / 01 / 2006Application No: GB2413739.0Examiner: Dr Rhys WilliamsClaims searched: 30-40 &41, 42 in partDate of search: 9 July 2025Patents Act 1977Further Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular relevance v A 30, 32, 34, 35, 39,41 & 42 US 2018 / 0202687 Al (LUCAS et al.) See Figs. 1, 2, paragraphs [0006] - [0008], [0020], [0027], claim 13.Categories:X Document indicating lack of novelty or inventive step A Document indicating technological background and / or state of the art. Y Document indicating lack of inventive step if combined with one or more other documents of same category'. P Document published on or after the declared priority date but before the filing date of this invention. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:International Classification:Subclass Subgroup Valid From F23G 0005 / 32 01 / 01 / 2006 F23J 0001 / 00 01 / 01 / 2006 F23J Template-------- 0003 / 00 01 / 01 / 2006

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