Field of the Invention

[0001] The present invention relates to an apparatus for combusting recyclable or waste material.

Background to the Invention

[0002] The generation of waste is a great burden to society and infrastructure. Governments are being required to manage both domestic and commercial waste on massive scales in a manner that is sustainable over the long term. The task of dealing with the vast variety of materials in an efficient manner is therefore a challenging one.

[0003] One of the main problems when handling domestic and commercial waste materials is the generation of toxic and/or hazardous compounds which originate from the materials themselves and/or residual compounds contained within the waste. Initial processing of these materials liberates these compounds and can facilitate secondary reactions which produce further harmful compounds. This problem is exemplified when handling waste construction industry fibre board. During the initial processing the fibre board is particulated, thereby exposing the harmful adhesives and preservatives contained within the board products.

[0004] Conventional management schemes involve deposition within landfill sites. This is not sustainable in the long term and has environmental consequences. Other schemes involve large scale incineration to generate electricity, but this often leads to large emissions of harmful gases.

[0005] GB2517980 describes a burner which attempts to solve the above problems. The burner comprises a cylindrical combustion chamber where burning waste material is blown around the inside of the chamber before exiting an exhaust. Unfortunately the device described in GB2517980 does not provide enough residence time for the material within the chamber. Complete combustion is therefore not always brought about. [0006] There has now been developed an apparatus for combusting recyclable or waste material which overcomes or substantially mitigates the above- mentioned and/or disadvantages associated with the prior art.

Summary of the Invention

[0007] In a first aspect of the invention there is provided an apparatus for combusting recyclable or waste material, the apparatus comprising a cylindrical combustion chamber, the chamber comprising a first inlet in a side wall, the first inlet in communication with a blower, an ignition means, and a source of recyclable or waste material, and an outlet in a first end wall, the outlet being positioned on a longitudinal central axis of the chamber, wherein the longitudinal axis of the first inlet is offset from the central axis of the chamber, the first inlet is proximal the first end wall and the outlet comprises a portion which extends inwards of the first end wall a distance greater than the distance between the first inlet and the first end wall.

[0008] The apparatus according to the invention is advantageous primarily because the blower forces in large amounts of air into the apparatus therefore resulting in large amounts of oxidation of the waste or recyclable material during the combustion process. The material to be burnt is also entrained with the air before it enters the chamber, so it is fully mixed in the first inlet with air. The blower forces the materials to circulate within the chamber and this not only completely mixes the waste or recyclable material, but forces the heavier less combusted elements towards the inside of the chamber wall. The heavier less combusted material is prevented from escaping by the portion of the outlet which extends inwards of the first end wall. This forces the heavier less combusted material into the rotating air stream set up within the chamber by the blower. Having also the first inlet proximal the first end wall and at a distance from the first end wall which is less than the length of the inwards portion of the outlet, greatly increases the residence time for the waste or recyclable material within the apparatus. This all makes for an extremely efficient combustion process with surprisingly high combustion temperatures and pressures. Due to the high temperatures created in use, most toxic and/or harmful materials which would otherwise be released from waste or recyclable materials during processing are eliminated. As a result, only gases exit the apparatus through the outlet and no particulate matter. Therefore the apparatus can be used to combust waste or recyclable materials which are otherwise hazardous to dispose of.

[0009] The apparatus according to the invention may be adapted for the combustion of any type of recyclable or waste material, such as domestic or commercial waste, but is particularly advantageous in relation to the combustion of timber or timber composite materials, such as fibre-board.

[0010] The combustion chamber is preferably formed with a side wall and two opposing ends. The chamber can be formed from any non-combustible material capable of withstanding the combustion temperatures generated in use. Preferably the chamber is formed from steel or the like. The combustion chamber can comprise a refractory lining capable of protecting the chamber from the high temperatures generated in use. Preferably the chamber is manufactured with a lining of non-combustible material. The non-combustible lining material preferably comprises a heat resistant cement, ceramic, asbestos, or the like. The combustion chamber can also comprise an insulation layer. Preferably the insulation layer comprises a layer of inert gas, a layer of air, or a layer of insulation material. The combustion chamber generally comprises a longitudinal central axis, one or more side walls and two opposing end walls. Preferably the walls of the chamber are welded or otherwise sealed together.

[0011] The first inlet in a side wall of the chamber preferably comprises an opening. The blower preferably comprises a fan or turbine or the like. Preferably, air or the like is blown by the blower into the chamber via the first inlet. The blower can be attached directly to the outside of the chamber over the opening. In such an embodiment, the blower defines a passageway for air into the chamber from the blower. The blower can also be attached to the outside of the chamber via a housing positioned over the opening. In such an embodiment, the housing defines a passageway for air into the chamber from the blower. The blower preferably comprises a damper or the like to control the flow of air or the like into the chamber. [0012] The ignition means preferably comprises a fuel and a lighter capable of being combined and activated when the ignition means is switched on. The ignition means preferably comprises a fuel and a lighter capable of being de- combined and deactivated when the ignition means is switched off. The fuel preferably comprises a flammable or inflammable liquid, solid or gas. The lighter preferably comprises a heating element, a spark generator, pilot light, flame or the like. The ignition means preferably generates primary combustion products when it is switched on. The primary combustion products can be anything that initiates combustion of the recyclable or waste material. Preferably the primary combustion products are any of combustion gases, heat, and/or a flame. The ignition means can be integral with the blower. In a further embodiment, the ignition means preferably comprises a secondary device in communication with the passage way defined by the blower. The blower preferably blows air over the ignition means. The air or the like which is blown by the blower into the chamber via the first inlet, is preferably in communication with the ignition means before it enters the chamber.

[0013] The first inlet is in communication with a source of recyclable or waste material. The source of recyclable or waste material can be a storage vessel, such as a hopper or the like. The storage vessel is preferably capable of being filled or topped up either manually or by machine. The source of recyclable or waste material can also be a recycling or waste disposal plant or the like. The source of recyclable or waste material may comprise a conveyor for conveying the recyclable or waste material to the chamber via the first inlet. The conveyor is preferably a screw conveyor, such as an auger or the like, or a linear conveyor such as a conveyor belt or the like.

[0014] The outlet preferably comprises an opening in an end wall of the chamber. Preferably the opening defines a passageway for the exit of combustion products, which are exhaust gases only, from the chamber. An exhaust may be attached to the outlet and extend externally of the chamber. The exhaust preferably comprises a tubular member formed from any non-combustible material capable of withstanding the combustion temperatures in use. Prefera- bly the exhaust is lined with refractory material, such as that described above. The exhaust communicates the combustion products (gases) away from the chamber.

[0015] In a preferred embodiment the apparatus is connected to a secondary device. The secondary device preferably utilises the energy produced by the apparatus. The secondary device preferably comprises a heat exchanger, a turbine, or a smelting plant. The heat exchanger can be connected to the source of waste or recyclable material in order to dry the material in use before it enters the chamber. The heat exchanger can for example be a heat exchanger for a conventional hot water heating system or for a power station.

[0016] In a further preferred embodiment the walls of the chamber comprise a heat exchanger.

[0017] Preferably the longitudinal axis of the first inlet is directed away from the central axis of the chamber. The longitudinal axis of the first inlet can also be substantially tangential with the side wall of the chamber.

[0018] In use, the ignition means is switched on and the primary combustion products of the ignition means are preferably blown into the chamber via the first inlet by the air or the like from the blower. Recyclable or waste material is preferably delivered into the chamber from the source by the conveyor via the first inlet. The recyclable or waste material is preferably ignited by contact with the primary combustion products of the ignition means. The action of the air or the like from the blower within the chamber preferably forces the recyclable or waste material and/or the primary combustion products to circulate around the inside of the chamber. In a preferred embodiment, the circulation of material within the chamber is in a substantially uniform direction. The circulation of material within the inside of the chamber is preferably around the longitudinal axis of the chamber. The action of the primary combustion products on the recyclable or waste material preferably causes the recyclable or waste material to ignite and combust. Combusted material preferably exits the chamber through the outlet. Once combustion of the recyclable or waste material has begun, preferably the ignition means is switched off. Further recyclable or waste material is preferably fed into the chamber via the first inlet. In this way preferably the resultant combustion is self-sustaining.

[0019] A preferred embodiment of the invention will now be described in greater detail, by way of illustration only, with reference to the accompanying drawings.

Brief Description of the Drawings

[0020] Figure 1 is an aerial cross sectional view of an embodiment of an apparatus according to the invention.

[0021] Figure 2 is a rear end view of an embodiment of the apparatus. Detailed Description of the Illustrated Embodiment

[0022] Figure 1 shows an aerial cross sectional view of an embodiment of an apparatus according to the invention. The apparatus is generally designated 10 and comprises a cylindrical chamber 20 which has a longitudinal central axis X- X, and a circular cross section. The chamber 20 is made of steel. The chamber 20 has a tubular side wall which is welded to the first end wall 22. A second end wall 24, which is opposite the first end wall 22, is mounted on hinges to the side wall and held closed on the end of chamber by bolts (not shown). In this way, the chamber is sealed, but can be opened up for maintenance or cleaning.

[0023] In the cylindrical side wall of the chamber 20 there is a first inlet 30. The first inlet 30 is arranged proximal the first end wall 22 of the chamber 20. The first inlet 30 is arranged at the side of the chamber 20 as shown in figure 1 aerial view, but it has a longitudinal axis which crosses below the central longitudinal axis X-X of the chamber 20. Thus the first inlet 30 is mounted substantially tangential to the chamber 20. The first inlet 30 is connected to a blower 32, suitably a centrifugal fan having a rotatable vane in its inlet to enable the air flow to be controlled. Between the blower 32 and the chamber 20 is an igniter 34. Also between the blower 32 and the chamber 20 there is connected an auger 36. The auger 36 joins with the first inlet 30 in a T configuration. The auger 36 is connected to the base of a steel hopper 42 in which is contained a supply of waste or recyclable material. The auger 42 is driven by a motor 44. In the first end wall 22 of the chamber 20 there is an outlet 50. The outlet 50 has connected to it a steel exhaust 52 which is mounted to the external portion of the outlet 50. The outlet 50 has an internal portion 54 which extends into the chamber 20. The outlet comprises a steel tube which is welded into the first end wall 22. The internal portion 54 of the outlet 50 has a length A. Length A is greater than length B, which is the distance from the inside of first end wall 22 to the side of the first inlet 30. This is important, as when material is introduced into the chamber 20 it is not immediately blown outwards of the outlet 50. The internal portion 54 also further keeps the material within the chamber 20 for longer, thereby increasing retention time, which increases the temperatures and pressure generated and therein the amount of combustion.

[0024] The chamber 20 comprises a refractory lining 26 which is capable of withstanding the temperatures generated inside the chamber. The lining 26 is refractory cement which is fabricated to adhere to the inside of the chamber. The outlet 50 and the exhaust 52 are also lined with a lining of refractory cement (not shown).

[0025] In use the hopper 42 (in Figure 1 ) is filled with recyclable or waste material. The igniter 34 and the blower 32 are then switched on. The igniter 34 in the illustrated embodiment is a diesel oil burner. Combustion products from burning the oil are forced into the chamber 20 through the inlet 30 by the air from the blower 32. At the same time, the auger motor 44 is switched on and the auger 36 then transfers the recyclable or waste material in the hopper 42 into the lower part of the chamber 20 via the first inlet 30. The recyclable or waste material and the primary combustion products are forced to rotate around the inside of the chamber 20 in the direction generally shown by the arrows in Figure 2. The direction of rotation is around the axis X-X. The recyclable or waste material begins to combust. Heavy non-combusted material is pushed by centrifugal force to the outside of field of rotation (i.e. close to the refractory lining 26), whilst completely burnt material is found closer to the axis X-X. In use a gradient of particle weight is set up from the central longitudinal axis to the walls of the chamber 20. The gradient is generally heavier less combusted materials away from the longitudinal axis of the chamber, and lighter more combusted materials towards the longitudinal axis of the chamber. The air from the blower not only blows the materials around the chamber, but forces them to mix completely. The air also supplies excess oxygen for complete oxidation of the recyclable or waste material during the combustion process.

[0026] Recyclable or waste material continues to be fed into the chamber 20 and after a time the igniter 34 is turned off, and the apparatus 10 continues to combust the recyclable or waste material in a self-sustaining manner (i.e. with no additional combustion means applied). At this point the only input into the chamber 20 is air from the blower 32 and recyclable or waste material from the auger 36. The combustion products, which are gases only due to the efficiency of the invention, exit the chamber 20 through the outlet 50. The exhaust 52 carries the combustion products a safe distance away. Temperatures in excess of 2000°C have been reached during operation of the apparatus according to the invention and it has been estimated that if the apparatus was connected to a power station, burning 10 tonnes per hour of waste material would produce enough high pressure super-heated steam to drive a 10 megaWatt generator.

[0027] A principle advantage of the present invention as described above is that the residence time for the combusting material within the chamber is greatly increased from that experienced in the prior art. This leads to greater temperatures and pressures and thereby a more efficient combustion process. The residence time is increased because of the combination of the following features: the first inlet 30 being arranged proximal the first end wall 22, which is where the outlet 50 is and the outlet 50 having an internal portion 54, which extends into the chamber a greater distance than the distance between the first end wall 22 and the first inlet 34. Therefore non combusted or less combusted material does not simply flow straight out of the outlet but is forced into the main part of the chamber 20 continually. This increases the temperature and pressure of the combustions process within the chamber. Only the gaseous combustion products can escape the chamber 20, as these are the only products which are light enough to reside on the central axis X-X which is where the outlet is. The solid waste continues to be burnt until it is light enough to reach the central axis.

[0028] Proximal the second end wall 24 there is a second inlet 60. This is also shown in Figure 2. The second inlet is connected to a blower 62. As with the first inlet 30, the second inlet 60 is on the side of the chamber (the same side as the first inlet), and is arranged tangentially in the lower half of the chamber. The blower 62 is of smaller capacity than then blower 32. In use of the apparatus, certain types of waste materials can give rise to residues in the combustion chamber that require additional measures to remove. For example, materials such as medium density fibreboard (MDF) and chipboard contain resins that bond the fibres together. While most of the resin will be combusted, there is a possibility of a build-up of some material around the periphery of the chamber. The blower 62, blowing material around the second end wall 24 serves to prevent residue from settling on the inside of the second end wall 24.

[0029] Also proximate the second end wall 24 but at the bottom of the chamber 24 is a second outlet 70. The second outlet comprises a small opening in the lowermost part of the cylindrical wall of the chamber 20. Mounted around the opening is an inverted funnel 72, which is in communication with a second auger 74. The auger 74 is driven by an electric motor 76 through a reduction gearbox 78, and is angled slightly upwardly. In use of the apparatus the other type of residue which can be associated with waste wood products, for example, is metallic or glass particles which are too heavy to be carried out of the chamber with the combustion gases and are non combustable, instead tending to fall to the lowermost part of the chamber. These particles will collect in the second inlet and are extracted by the auger 74. The slight upwards angle of the auger 74 means that it remains filled with the particles, thereby providing a gas- tight and heat-resisting seal. To further ensure a gas tight and heat resistant seal, small sections of the blades of the auger 74 in the region of the base of the funnel 72 have been removed. In use of the apparatus, when the particles fall into the auger they form a moveable plug within the auger 74 and this further prevents hot gasses from escaping through the second outlet 70. The removed particles are deposited from the upper end of the auger 74.