A biomass burner and a method of burning biomass in the form of solid particulate fuel

Abstract

Food and organic waste have long been costly and problematic to dispose of as a waste material, despite such waste material having a relatively high potential energy. All industrial treatment routes involve collection and transportation of the raw waste material. Domestic composting and subsequent local disposal as composted material might be carried out for some waste, but this is known to attract pests and vermin. Small-scale aerobic digesters have been developed to produce a stable substrate that can be used as a fuel for biomass burners; however, efficient combustion in such burners is difficult to achieve, and has been hitherto impossible without the co-burning of wood chips / pellets. The present invention provides a biomass burner that uses a primary oxygen feed (13) and gas distributor (15) to fluidize solid particulate fuel (17) within a primary combustion zone (11), whereby solid particulate fuel being conveyed to the primary combustion zone (11) is heated by such combustion, resulting in gasification prior to introduction into the primary combustion zone (11). A duct (27) conveys the combustible gas (25) from the gasification to a secondary combustion zone (29) where a secondary oxygen feed allows total combustion thereof.

Description

A BIOMASS BURNER AND A METHOD OF BURNING BIOMASS IN THE FORM OF SOLID PARTICULATE FUEL

[0001] The present invention relates generally to a biomass burner and a method of burning biomass in the form of solid particulate fuel and finds particular, although not exclusive, utility in energy-from-food-waste systems.

[0002] Food and organic waste have long been costly and problematic to dispose of as a waste material, despite such waste material having a relatively high potential energy. Traditionally, disposing in landfill results in generating methane gas, which has resulted in countries increasingly banning this disposal route.

[0003] Various industrial routes are known for the recovery of usable energy from such waste material, including large-scale composting (such as windrow composting), anaerobic digestion (in which resultant gasses are extracted and used for energy generation), liquification of the waste into a slurry for biological treatment and then disposal into waste water treatment systems, and incineration. Nevertheless, all of these treatment routes involve collection and transportation of the raw waste material and the associated energy and environmental impact of this. In addition, windrow composting involves the use of large areas of land for the process, the resultant sludge from anaerobic digestion requires consequent disposal (land spreading and / or reintroduction back into the animal food chain, e,g. pig food, has been outlawed in many countries following BSC, CJD and other pathogenic problems), and disposal into waste water treatment systems attracts a high disposal fee (for example, by the Mogden Formula applied by local water utility companies in the UK, if biological oxygen demand loading is found to be significant) and has already been banned in Scotland and is due to be banned in England and Wales soon.

[0004] To avoid the associated energy and environmental impact of collection and transportation of the raw waste material, domestic composting and subsequent local disposal as composted material might be carried out for some waste, but this is known to attract pests and vermin.

[0005] Small-scale aerobic digesters have been developed to produce a stable substrate that can be used as a fuel for biomass burners. However, efficient combustion in such burners is difficult to achieve, and has been hitherto impossible without the co-burning of wood chips / pellets. Thus, it can be seen that there is a need for small to medium scale on-site processing of food waste (secondary biomass) to usable energy that does not require the addition of primary biomass (biomass harvested directly for energy).

[0006] According to a first aspect of the present invention, there is provided a biomass burner for burning a solid particulate fuel, the biomass burner comprising: a fuel feed channel configured to convey a solid particulate fuel to a primary combustion zone; a primary oxygen feed configured to convey oxygen to the primary combustion zone; a gas distributor connected to the primary oxygen feed, the gas distributor configured to fluidize the solid particulate fuel within the primary combustion zone; wherein the fuel feed channel is located adjacent to the primary combustion zone such that, in use, solid particulate fuel therein is heated by combustion within the primary combustion zone, resulting in gasification of the solid particulate fuel within the feed channel to produce combustible gas, prior to introduction into the primary combustion zone; a duct configured to convey the combustible gas from the fuel feed channel to a secondary combustion zone; and a secondary oxygen feed configured to convey oxygen to the secondary combustion zone, so as to combust the combustible gas.

[0007] In this way, enough oxygen can be supplied to the primary combustion zone to ensure total combustion of the solid particulate fuel, as otherwise the oxygen-to-fuel ratio in the primary combustion zone would be too low. That is, oxygen supplied via the primary oxygen feed burns a non-gasified remnant of the solid particulate fuel, and oxygen supplied via the secondary air feed burns the combustible gas. In particular, continuous combustion of conditioned digestate material may be achieved without the need for additive primary biomass.

[0008] Biomass for use in the burner may be derived from organic waste, in particular food waste. The solid particulate fuel may comprise such processed biomass.

[0009] The primary combustion zone may be substantially annular in cross section. The fuel feed channel may have a substantially circular horizontal cross-section. The primary combustion zone may surround a radial periphery of the fuel feed channel.

[0010] The fuel feed channel may have an upper periphery over which the solid particulate fuel may fall into the primary combustion zone.

[0011] The fuel feed channel may comprise a vertical channel for conveying the solid particulate fuel up wards therethrough. The fuel feed channel may be configured to be under-stoked such that solid particulate fuel supplied to a lower (first) end thereof causes solid particulate fuel within the fuel feed channel to be expelled from an upper (second) end thereof, opposing the lower (first) end.

[0012] The fuel feed channel may be provided with paddles therein, for stirring the solid particular fuel to encourage movement up through the fuel feed channel. The paddles may be mounted on a rotating shaft. The rotating shaft may be configured to rotate with the fuel feed channel. The rotating shaft may be mounted centrally and / or vertically within the fuel feed channel. The paddles may comprise elongate members, for example bars or rods. In alternative arrangements, the paddles may form a vertical screw conveyer about the rotating shaft.

[0013] A rotating arm may be provided adjacent to the upper periphery, for instance in contact with or spaced from the upper periphery. The rotating arm may be configured to rotate about a central shaft, for example the rotating shaft. In this way, rotation of the rotating arm pushes solid particulate fuel over the upper periphery (e.g. the upper (second) end) of the fuel feed channel. The rotating arm may comprise a metering blade.

[0014] At least one (for example only one, two or more) horizontal screw conveyer may be provided to supply the solid particulate fuel to a lower end of the fuel feed channel. Pressure provided by the horizontal screw conveyor(s) may be sufficient to push solid particulate fuel within the fuel feed channel upwardly out of the upper end of the fuel feed channel.

[0015] The speed of the screw conveyor(s) and / or rotating arm may be controlled automatically such that a predefined amount of solid particulate fuel is metered into the primary combustion zone within a predefined period.

[0016] The primary oxygen feed may comprise a primary air feed; that is, it may be configured to convey air to the primary combustion zone.

[0017] The gas distributor may comprise an air distributor, for example a distributor plate. The distributor plate may comprise an annular ring sealing a bottom of the primary combustion zone such that solid particulate fuel cannot pass therebelow. The primary oxygen feed may convey oxygen up through the distributer plate from below. The distributor plate may comprise a plurality of holes therein. The holes may be sized to prevent the solid particulate fuel from passing therethrough.

[0018] The gas distributor may be configured such that, with a predefined flow-rate of gas from the primary oxygen feed, solid particulate fuel within the primary combustion zone is fluidized. The primary combustion zone may be provided with a non-combustible fluidized bed medium therein, to balance and distribute air flow evenly. The fluidized bed medium may comprise particulate matter, for example grit, but more preferably ceramic balls.

[0019] The burner may comprise an ignition device configured to ignite combustion of the solid particulate fuel within the primary combustion zone. The ignition device may comprise one or more ignition glow plugs and / or one or more ignition oxygen feeds (e.g. ignition air feeds).

[0020] The primary combustion zone may be annular, such that it surrounds the exterior of the fuel feed channel. The fuel feed channel may comprise a peripheral wall. The peripheral wall may comprise metal. In this way, heat can be effectively conveyed between the primary combustion zone and the fuel feed channel.

[0021] As the fuel feed channel is separated from the primary oxygen feed by a peripheral wall, the solid particulate fuel within the fuel feed channel is heated substantially in the absence of oxygen (or at least in the presence of limited oxygen).

[0022] Thus, some or all of the following processes may occur to the solid particulate fuel: dehydration (production of gaseous water), pyrolysis (volatile gasses are released), combustion (producing carbon monoxide and / or carbon dioxide), and gasification (steam and carbon dioxide react with char to produce carbon monoxide and hydrogen). The combustible gas may therefore include volatile gasses, carbon monoxide, and molecular hydrogen.

[0023] The burner may comprise a flue configured to convey hot gas away from the primary combustion zone. The duct may comprise the flue; that is, the flue may be configured to convey the combustible gas from the fuel feed channel to the secondary combustion zone. In particular, the flue may be configured to mix the combustible gas with the hot gas.

[0024] The secondary oxygen feed may comprise a secondary air feed, in a similar manner to the primary oxygen feed discussed above.

[0025] The burner may be provided with insulation on an exterior surface thereof. The secondary oxygen feed may be configured to pass around the flue such that the oxygen is pre-heated before reaching the secondary combustion zone. In particular, the secondary oxygen feed may be configured to pass between the flue and the insulation.

[0026] The burner may be provided with a heat-exchange gas channel beneath the insulation, for instance between the insulation and the flue. The heat-exchange gas channel may allow the heating of gas for subsequent use elsewhere. Gas may be blown into the channel by a pump and / or fan. The pump and / or fan may comprise a variable-speed fan, such that the temperature of gas extracted from the heat-exchange gas channel may be controlled. The gas extracted from the heat-exchange gas channel may be used to pre-heat other components of the system (e.g. the solid particulate fuel, one or more of the oxygen feeds, an anaerobic digester, air, water, steam, etc.).

[0027] The secondary combustion zone may be located within the flue. The flue may terminate with an exhaust outlet.

[0028] However, in preferred embodiments, a filter (such as a cyclone filter) may be provided between the secondary combustion zone and the exhaust outlet. In this way, particulates may be removed from the exhaust gas prior to emission. The filter may be provided with an ash capture box for collecting the particulates removed by the cyclone filter system. An ash screw conveyer may be provided in (e.g. a base of) the ash capture box to remove the ash build up.

[0029] The biomass burner may be configured to carry out combustion at temperature of at least 700 degrees centigrade, more particularly at least 800 degrees centigrade.

[0030] The or each oxygen feed may be provided by a pump and / or fan.

[0031] According to a second aspect of the present invention, there is provided a food waste processing system, comprising: an aerobic digester configured to convert food waste into solid particulate fuel; and the biomass burner according to the first aspect, further configured to receive the solid particulate fuel from the aerobic digester.

[0032] In this way, food waste can be directly processed at the source.

[0033] According to a third aspect of the present invention, there is provided a generator system, comprising: the biomass burner according to the first aspect; and a heat converter configured to convert heat produced by the biomass burner into usable energy.

[0034] In this way, energy from the biomass can be directly converted into a usable form.

[0035] The term heat converter is used herein to refer to any system that converts heat to usable energy, and in particular a device that does a certain amount of net positive work. The usable energy may comprise mechanical / kinetic energy, which can then be used to do mechanical work; however, in alternative arrangements, the usable energy may comprise electrical energy.

[0036] The heat converter may comprise a heat engine such as a Stirling engine. The term heat engine is used to refer to any system that converts heat to usable energy, irrespective of whether it operates in a thermodynamic cycle or not; and in particular a device that does a certain amount of net positive work as a result of heat transfer from a high-temperature body to a low-temperature body. The usable energy may comprise mechanical energy, which can then be used to do mechanical work.

[0037] The generator system may further comprise an electrical generator, and the kinetic energy may be used to drive the electrical generator to generate electricity. The generator may have an output power of approximately 20kW.

[0038] The heat converter may comprise a thermoelectric generator.

[0039] The generator system may further comprise a filter, similar to that described above, such as a cyclone filter, configured and / or arranged to filter particulates from exhaust gases from the biomass burner, for instance before passage of the exhaust gases to the heat converter.

[0040] The generator system may further comprise a heat exchanger configured to extract heat from the exhaust gases (for example after use by the heat converter, or potentially before) to pre-heat other components of the system (e.g. the solid particulate fuel, one or more of the oxygen feeds, the anaerobic digester, air, water, steam, etc.).

[0041] However, in alternative arrangements, where no generator system is used, a heat exchanger may be used to extract heat from the exhaust gases (for example after use by the heat converter) to pre-heat other components of the system (e.g. the solid particulate fuel, one or more of the oxygen feeds, the anaerobic digester, air, water, steam, etc.).

[0042] According to a fourth aspect of the present invention, there is provided an energy-from-food waste system, comprising: an aerobic digester configured to convert food waste into solid particulate fuel; the biomass burner according to the first aspect, further configured to receive the solid particulate fuel from the aerobic digester; and a heat converter configured to convert heat produced by the biomass burner into usable energy.

[0043] In this way, the system may provide an integrated package that can be located on a client site and left to run on a self-contained and fully automated basis.

[0044] According to a fifth aspect of the present invention, there is provided a method of burning biomass in the form of solid particulate fuel, the method comprising the steps of: providing a biomass burner according to the first aspect; conveying a solid particulate fuel through the fuel feed channel to the primary combustion zone; conveying oxygen through the primary oxygen feed to the primary combustion zone; fluidizing the solid particulate fuel within the primary combustion zone by passing oxygen through the gas distributor from the primary oxygen feed; combusting solid particulate fuel within the primary combustion zone; heating solid particulate fuel within the fuel feed channel with heat from said combusting within the primary combustion zone, resulting in gasification of the heated solid particulate fuel within the fuel feed channel to produce combustible gas, prior to introduction into the primary combustion zone; conveying the combustible gas through the duct from the fuel feed channel to the secondary combustion zone; and conveying oxygen through the secondary oxygen feed to the secondary combustion zone, so as to combust the combustible gas.

[0045] In this way, food waste can be burned without the need for additive primary biomass. In particular, the food waste can be burned in the absence of primary biomass. In the context of the present application, primary biomass means biomass harvested directly for energy, or biomass in the form of residues and waste. Primary biomass may comprise wood, wood residues, wood pellets, herbaceous plants, bioethanol, biodiesel, biogas, etc.

[0046] The above and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. This description is given for the sake of example only, without limiting the scope of the invention. The reference figures quoted below refer to the attached drawings.

[0047] is a cross-sectional view of a biomass burner.

[0048] is a system diagram of an energy-from-food-waste system.

[0049] is a flow diagram of a method of burning biomass.

[0050] The present invention will be described with respect to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. Each drawing may not include all of the features of the invention and therefore should not necessarily be considered to be an embodiment of the invention. In the drawings, the size of some of the elements may be exaggerated and not drawn to scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.

[0051] Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that operation is capable in other sequences than described or illustrated herein. Likewise, method steps described or claimed in a particular sequence may be understood to operate in a different sequence.

[0052] Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that operation is capable in other orientations than described or illustrated herein.

[0053] It is to be noticed that the term “comprising”, used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression “a device comprising means A and B” should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

[0054] Similarly, it is to be noticed that the term “connected”, used in the description, should not be interpreted as being restricted to direct connections only. Thus, the scope of the expression “a device A connected to a device B” should not be limited to devices or systems wherein an output of device A is directly connected to an input of device B. It means that there exists a path between an output of A and an input of B which may be a path including other devices or means. “Connected” may mean that two or more elements are either in direct physical or electrical contact, or that two or more elements are not in direct contact with each other but yet still co-operate or interact with each other. For instance, wireless connectivity is contemplated.

[0055] Reference throughout this specification to “an embodiment” or “an aspect” means that a particular feature, structure or characteristic described in connection with the embodiment or aspect is included in at least one embodiment or aspect of the present invention. Thus, appearances of the phrases “in one embodiment”, “in an embodiment”, or “in an aspect” in various places throughout this specification are not necessarily all referring to the same embodiment or aspect, but may refer to different embodiments or aspects. Furthermore, the particular features, structures or characteristics of any one embodiment or aspect of the invention may be combined in any suitable manner with any other particular feature, structure or characteristic of another embodiment or aspect of the invention, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments or aspects.

[0056] Similarly, it should be appreciated that in the description various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Moreover, the description of any individual drawing or aspect should not necessarily be considered to be an embodiment of the invention. Rather, as the following claims reflect, inventive aspects lie in fewer than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

[0057] Furthermore, while some embodiments described herein include some features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form yet further embodiments, as will be understood by those skilled in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

[0058] In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practised without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

[0059] In the discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, coupled with an indication that one of said values is more highly preferred than the other, is to be construed as an implied statement that each intermediate value of said parameter, lying between the more preferred and the less preferred of said alternatives, is itself preferred to said less preferred value and also to each value lying between said less preferred value and said intermediate value.

[0060] The use of the term “at least one” may mean only one in certain circumstances. The use of the term “any” may mean “all” and / or “each” in certain circumstances.

[0061] The principles of the invention will now be described by a detailed description of at least one drawing relating to exemplary features. It is clear that other arrangements can be configured according to the knowledge of persons skilled in the art without departing from the underlying concept or technical teaching, the invention being limited only by the terms of the appended claims.

[0062] is a cross-sectional view of a biomass burner having two horizontal screw conveyers 1 arranged to supply a solid particulate fuel (not shown) to a lower end of a fuel feed channel 3. The fuel feed channel under-stoked such that solid particulate fuel that is supplied to the lower end by the horizontal screw conveyors 1 causes solid particulate fuel (not shown) within the fuel feed channel 3 to be expelled from an upper end thereof. Paddles 5 within the fuel feed channel 3 are mounted on a central shaft 7 such that when they are rotated they stir the solid particular fuel to encourage passage of the solid particulate fuel within the fuel feed channel 3 to move upwards in response to pressure from below.

[0063] A rotating arm 9 is located adjacent to the upper periphery of the fuel feed channel 3 and is mounted on the central shaft 7 to rotate therewith. The rotating arm 9 pushes solid particulate fuel (not shown) that has been expelled from the upper end of the fuel feed channel 3 to be pushed into an annular primary combustion zone 11 surrounding the radial periphery of the fuel feed channel 3.

[0064] A primary air feed 13 is provided at a lower end of the primary combustion zone 11 beneath a gas distributor plate 15. The gas distributor plate 15 comprises a plurality of holes sized to prevent solid particulate fuel 17 within the primary burning region 11 from passing therethrough. The distributor plate 15 is configured such that, with a predefined flow-rate of gas conveyed from the primary air feed 13 through the distributor plate from below, the solid particulate fuel 17 within the primary combustion zone 11 is fluidized.

[0065] A pair of ignition glow plugs 19 are provided on either side of the primary combustion zone 11, each provided with a respective ignition air feed 21.

[0066] Heat produced in the primary combustion zone 11 passes through a peripheral wall 23 of the fuel feed channel 3 to heat the solid particulate fuel therein, resulting in gasification of the solid particulate fuel within the feed channel to produce combustible gas 25.

[0067] A flue 27 conveys the combustible gas 25 from the fuel feed channel 3, and hot gasses from the primary combustion zone 11, to a secondary combustion zone 29.

[0068] A secondary air feed 31 conveys oxygen to the secondary combustion zone 29, via an annular pre-heating chamber 33 so as to combust the combustible gas 25 in the secondary combustion zone 29.

[0069] Exhaust gases 35 leave the flue via an exhaust outlet 37.

[0070] The biomass burner is provided with an insulated outer-sleeve 39 up through the bottom of which solid particulate fuel is conveyed, through the sides of which the primary air feed 13, ignition air feeds 21 and secondary air feed 31 enter, and up through the top of which the exhaust outlet 37 is located.

[0071] is a system diagram of an energy-from-food-waste system comprising an aerobic digester 41 configured to convert food waste into solid particulate fuel, a biomass burner 43 configured to receive the solid particulate fuel from the aerobic digester, a Stirling engine 45 configured to convert heat produced by the biomass burner into kinetic energy, and an electrical generator 47 configured to convert the kinetic energy from the Stirling engine into electricity.

[0072] is a flow diagram of a method of burning biomass in which solid particulate fuel is conveyed through a fuel feed channel to a primary combustion zone 51, oxygen is conveyed through a primary oxygen feed to the primary combustion zone 53, the solid particulate fuel is fluidized within the primary combustion zone by passing oxygen through a gas distributor from the primary oxygen feed 55, the solid particulate fuel is combusted within the primary combustion zone 57, the solid particulate fuel within the fuel feed channel is heated by the combusting within the primary combustion zone 59, the heated solid particulate fuel within the fuel feed channel is gasified to produce combustible gas 61, the combustible gas is conveyed through a flue from the fuel feed channel to a secondary combustion zone, together with hot gas from the primary combustion zone 63, oxygen is conveyed through a secondary oxygen feed to the secondary combustion zone 65, and the combustible gas is combusted in the secondary combustion zone 67.

Claims

A biomass burner for burning a solid particulate fuel, the biomass burner comprising:a fuel feed channel configured to convey a solid particulate fuel to a primary combustion zone;a primary oxygen feed configured to convey oxygen to the primary combustion zone;a gas distributor connected to the primary oxygen feed, the gas distributor configured to fluidize the solid particulate fuel within the primary combustion zone;wherein the fuel feed channel is located adjacent to the primary combustion zone such that, in use, solid particulate fuel therein is heated by combustion within the primary combustion zone, resulting in gasification of the solid particulate fuel within the feed channel to produce combustible gas, prior to introduction into the primary combustion zone;a duct configured to convey the combustible gas from the fuel feed channel to a secondary combustion zone; anda secondary oxygen feed configured to convey oxygen to the secondary combustion zone, so as to combust the combustible gas.The biomass burner of claim 1, wherein the primary combustion zone surrounds a radial periphery of the fuel feed channel.The biomass burner of claim 1 or claim 2, wherein the fuel feed channel is configured to be under-stoked such that solid particulate fuel supplied to a lower (first) end thereof causes solid particulate fuel within the fuel feed channel to be expelled from an upper (second) end thereof, opposing the lower (first) end.The biomass burner of any preceding claim, further comprising paddles within the fuel feed channel for stirring the solid particular fuel.The biomass burner of any preceding claim, further comprising a rotating arm located adjacent to the upper periphery, and configured to rotate about a central shaft.The biomass burner of any preceding claim, further comprising at least one horizontal screw conveyer arranged to supply the solid particulate fuel to a lower end of the fuel feed channel.The biomass burner of any preceding claim, further comprising a gas distributor may comprise a distributor plate configured such that, with a predefined flow-rate of gas conveyed from the primary oxygen feed through the distributor plate from below, the solid particulate fuel within the primary combustion zone is fluidized.The biomass burner of any preceding claim, further comprising an ignition device configured to ignite combustion of the solid particulate fuel within the primary combustion zone.The biomass burner of any preceding claim, further comprising a flue configured to convey hot gas away from the primary combustion zone, and wherein the duct may comprise the flue.The biomass burner of any preceding claim, wherein the secondary oxygen feed is configured to pass around the flue such that the oxygen is pre-heated before reaching the secondary combustion zone.A food waste processing system, comprising:an aerobic digester configured to convert food waste into solid particulate fuel; andthe biomass burner according to any preceding claim, further configured to receive the solid particulate fuel from the aerobic digester.A generator system, comprising:the biomass burner according to any one of claims 1 to 10; anda heat converter configured to convert heat produced by the biomass burner into usable energy.An energy-from-food waste system, comprising:an aerobic digester configured to convert food waste into solid particulate fuel;the biomass burner according to any one of claims 1 to 10, further configured to receive the solid particulate fuel from the aerobic digester; anda heat converter configured to convert heat produced by the biomass burner into usable energy.A method of burning biomass in the form of solid particulate fuel, the method comprising the steps of:providing a biomass burner according to any one of claims 1 to 10;conveying a solid particulate fuel through the fuel feed channel to the primary combustion zone;conveying oxygen through the primary oxygen feed to the primary combustion zone;fluidizing the solid particulate fuel within the primary combustion zone by passing oxygen through the gas distributor from the primary oxygen feed;combusting solid particulate fuel within the primary combustion zone;heating solid particulate fuel within the fuel feed channel with heat from said combusting within the primary combustion zone, resulting in gasification of the heated solid particulate fuel within the fuel feed channel to produce combustible gas, prior to introduction into the primary combustion zone;conveying the combustible gas through the duct from the fuel feed channel to the secondary combustion zone; andconveying oxygen through the secondary oxygen feed to the secondary combustion zone, so as to combust the combustible gas.

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