SOLID FUEL

Abstract: A carbonaceous product (12), e.g. containing anthracites fines, is supplied to a mixer (15) in which it is mixed with a dispersing or deflocculating agent, a fibre material in fine fibrous form, and water; the resultant mixture is fed to a pelletiser (16) and a drier (17). The dispersing or deflocculating agent is a lignosulphate, and the fibre material comprises paper, especially waste paper.

Description: Solid Fuel The present invention relates to a solid fuel, for example a reactive fuel which is equivalent to charcoal, and to a method of manufacture thereof. Millions of tons of hardwood trees are felled each year for the production of charcoal. The method of production involves carbonisation of the wood to drive off tars and resins which creates enormous pollution problems in the form of smoke into the atmosphere. It takes five tons of hardwood to make one ton of charcoal. The charcoal is predominantly used for cooking and heating in third world countries, but also as a leisure activity in the developed countries. Therefore the pressures on the rain forests in these regions is an ongoing problem due to population growth, which must inevitably have an impact on the rain forests and therefore the environment globally. Depleting the rain forests leads to climatical changes, soil erosion and the silting up of rivers, all of which have contributed to major disasters in the past. There are already known various charcoal substitutes generally known as charcoal or barbecue briquettes. However these fuels suffer from one or more disadvantages. For example, most charcoal or barbecue briquettes contain charcoal and are therefore also contributing to the depletion of the rain forest. Some known charcoal substitutes contain significant amounts of binders, and possibly also chemical lighting agents. These binders and lighting aids create gases and smoke which contaminate food and the vicinity of the cooking or heating appliance. Commonly used binders in conventional charcoal and barbecue briquettes are starches, which because of the sugar content of such binders make the fuel prone to biodegradation, leading to fungal growth, and causing a lot of smoke during ignition and burning. Other known charcoal substitutes containing or not containing charcoal, are produced by making use c- a carbonisation process, which is just as polluting as the production of charcoal itself. The present invention seeks to overcome or reduce one or more of the above disadvantages. According to a first aspect of the present invention there is provided a solid fuel comprising a mixture of particles of at least one carbonaceous product, a dispersing or deflocculating agent, and a fibre material in fine fibrous form. An advantage of the above fuel is that it has excellent combustion properties. It is believed that the dispersing or deflocculating agent serves to expand the fuel product to separate the carbonaceous particles, while the individual fibres of the fibre material serve to bridge the cracks produced, so as to prevent the fuel product breaking up. This enables fuels such as anthracite to be employed, which in their original form can only safely be burnt in enclosed chambers such as furnaces. The fuel need not contain a binder and is not highly compacted. The particulate carbonaceous product is preferably anthracite fines, but it may alternatively or additionally comprise semi-anthracite, steam coal, bituminous coal , brown coal, coke, petroleum coke, charcoal and/or lignite. The dispersing or deflocculating agent is preferably a lignosulphonate, e.g a fractionated sodium salt of oxylignin. Alternatively, any other suitable dispersing or deflocculating agent may be used. The fibre material may be combustible or non- combustible. It preferably comprises paper especially waste paper. It may alternatively or additionally comprise cardboard, carton, sawdust, wood shavings, bagasse, straw, peat, cotton, man-made fibres or natural cellulosic material. Metal or ceramic material in fine fibrous form may alternatively or additionally be incorporated. The fibre material is preferably in the form of individual fibres; fibre clumps are not as effective at bridging the cracks to stop the fuel product falling apart. The carbonaceous products may constitute 5% to 95% by weight of the mixture, and preferably 7% to 55% by weight of the mixture. The anthracite preferably comprises 90% to 100% by weight of the carbonaceous products. The fibrous products may constitute at least 40% by weight of the remainder of the mixture, preferably 50% to substantially 100% by weight of the remainder of the mixture. An alkaline material, such as lime or cement, is also preferably incorporated since this tends to neutralise any possible sulphur dioxide emissions by converting them to stable calcium sulphates which remain in the ash. The fuel may also contain an additional binding agent and/or water. In certain cases the dispersing or deflocculating agent simultaneously serves as a binding agent. The fuel may further contain a water-proofing agent, and/or a chemical lighting aid commonly referred to in the barbecue trade as quick light or instant light barbecue. According to a second aspect of the present invention there is provided a method of manufacturing a solid fuel comprising mixing particles of at least one carbonaceous product, a dispersing or deflocculating agent, a fibre material in fine fibrous form, and a liquid, forming the mixture into a pellet and drying the pellet to remove at least a substantial part of the liquid. The pellet may be a briquette, an ovoid, a block, or log - or ball-shaped, or of any other suitable shape. The liquid is preferably water. According to a third aspect of the present invention, there is provided apparatus for manufacturing a solid fuel comprising means supplying particles of at least one carbonaceous product to a mixer which also receives a dispersing or deflocculating agent, a fibre material in fine fibrous form, and a liquid, means connected to the outlet of the mixer for forming the mixture into pellets, and drying means connected to the outlet of the pelletising means for supplying dried pellets. Means may also be provided for supplying a waterproofing agent to the mixer. The mixer and the pelletiser my be combined. Pelletising may be achieved by an extrusion, pan rolling, ring-roll, stamp press or any other suitable compacting, briquetting or moulding process. Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawing, which is a schematic diagram indicating the various steps in the manufacture of the fuel. Referring to the drawing, apparatus 10 comprises a hopper 11 which receives anthracite fines 12 from a conveyor or a vehicle. The output from hopper 11 is fed to a screener 14 and then to a mixer or tumbler 15. Here the anthracite fines, most of which is below lmm in size, is mixed with a lignosulphonate dispersing agent, water, paper material, an alkaline material, ε. binding agent and/or a plasticiser or lubricant. The preferred dispersing agent is a fractionated sodium salt of oxylignin which is sugar free. A preferred plasticiser is a hydroxyethylcellulose such as Natrosol. Within mixer 15 the abrasive action of the fine particles on the paper material in water has a pulping action, and the paper is reduced to fine fibres. After thorough mixing the product is fed to an extruder 16 from which it emerges in briquette form to be passed to a drier 17. Drier 17 blows hot air over the fuel to dry it preferably to 4 to 6% final water content. The dried briquettes 18 are then passed to a stockpile 19 or are packed in a packing plant 20. In its final form the fuel product 18 comprises the anthracite particles spaced apart from each other by a few microns in a matrix of aqueous dispersing agent. Compacted anthracite is hard to ignite, but the fuel product 18 is easy to ignite. In a preferred form, the final fuel product is porous which further increases its combustibility. Preferred compositions of the fuel expressed as parts by weight of the product before drying are as follows: Anthracite fines 30 to 99.9, preferably 97.5 lignosulphonate 0.1 to 5 , preferably 0.5 water 5 to 300 , preferably 15 to 40 and most preferably 27 paper fibre 0 to 15 , preferably 2 binder/plasticiser 0 to 15 , preferably 0.25 alkaline material 0 to 3 , preferably 1.5 The above described fuel has a number of advantages. In particular it burns without producing smoke or odour; thus pollution is substantially reduced since its manufacture is also pollution-free. It is easy to ignite, burns for a long time and is made from relatively cheap materials. Its production process is clean and simple and there is no health hazard to operating staff. There are no external emissions during manufacture, standard machinery is used in the manufacturing process, and the plant can operate continuously and is simple to control. The fuel may be suitable for outdoor use, e.g. for barbecues, or for indoor use in grates or boilers, whether domestic or industrial. Blast furnace use may also be possible. The fuel is especially suitable for barbecue use because it: 1. Is ready to cook in 10 mins, depending on the ignition means. 2. Will burn freely in any barbecue appliance. 3. Is clean to handle. 4. Is smokeless. 5. Has no smell whether burning or not burning. 6. Has ash, which unlike charcoal, is heavy and does not fly onto food. i 7. Burns longer than conventional barbecue briquettes. 8. Does not contain any toxic agents. 9. Is cheaper to produce than any other smokeless barbecue fuel. Various modifications may be made to the above described embodiment. In particular the dispersing agent, during drying of the fuel, may develop binding properties so that the separate binding agent may be omitted. The fibrous paper material may comprise waste paper, cardboard and/or carton. It may be replaced or supplemented by cotton, man-made fibres, or natural cellulosic material and/or a ceramic material. Other possible materials are sawdust, wood shavings, straw and peat. Alternatively or in addition fine metal fibres may be incorporated which have the advantages of further strengthening the fuel, increasing its storage life, and producing good heat conduction through the fuel thus ensuring quick drying and quick ignition. The anthracite fines may be supplemented or replaced by another ground down coal product such as semi anthracite, bituminous coal, coke, petroleum coke, and/or lignite. Charcoal can also be incorporated if desired. As described the paper material is fed straight into mixer 15. In modifications some or all of the paper may be first shredded in a shredder 26 and/or pulped in a pulping machine 27. In an alternative method of manufacture, the mixture emerging from mixer 15 is fed to a pan roller 22. Here the fuel is rolled into suitably-sized balls before being passed to drier 17. In another modification, the output of mixer 15 is fed to a moulding machine 23 such as a ring roll press and then to drier 17. In a further modification, the output of mixer 15 is placed in moulds and left to dry out naturally, thus avoiding the cost of expensive drying apparatus. Any suitable compaction machine can be used instead of devices 16, 22, 23 for example a stamp press, a pelletiser or an injection moulding machine. In modifications, suitable fuels may be provided in which the fibre material is not in individual fibre form. Also in certain mixtures a dispersing or deflocculating agent may not be required.

Claims: Claims 1. A solid fuel comprising a mixture of particles of at least one carbonaceous product (12), a dispersing or deflocculating agent, and a fibre material in fine fibrous form. 2. A solid fuel according to claim 1, wherein the carbonaceous product (12) comprises anthracite fires. 3. A solid fuel according to claim 1 or 2, wherein the carbonaceous product (12) comprises a fine coal product comprising semi-anthracite steam coal, bituminous coal, brown coal, coke, petroleum coke, charcoal and/or ligmite. 4. A solid fuel according to any preceding claim wherein the dispersing or deflocculating agent comprises a lignosulphonate. 5. A solid fuel according to any preceding Claim wherein the fibre material comprises paper in fine fibrous form. 6. A solid fuel according to any preceding claim wherein the fibre material comprises, in fine fibrous form cardboard, carton, sawdust, wood shavings, bagasse straw, peat cotton, man-made fibres, natural cellulosic material, metal and/or ceramic material. 7. A method of manufacturing a solid fuel comprising mixing particles of at least one carbonaceous product (12), a dispersing or deflocculating agent, a fibre material in fine fibrous form, and a liquid, forming the mixture into a pellet and drying the pellet to remove at least a substantial part of the liquid. 8. A method according to claim 7, wherein, during mixing, said particles abrade said fibre material into its fine fibrous form. 9. A method according to claim 7 or 8 wherein, before mixing, said fibre material is subjected to a shredding, pulping or other process for reducing it, at least partially, to its fine fibrous form. 10. Apparatus for manufacturing a solid fuel comprising means (11,14) supplying particles of at least one carbonaceous product (12) to a mixer (15) which also receives a dispersing or deflocculating agent, a fibre material in fine fibrous form, and a liquid, means (16) connected to the outlet of the mixer (15) for forming the mixture into pellets, and drying means (17) connected to the outlet of the pelletising means (16) for supplying dried pellets (18).

Inventors: DARBY WILLIAM FREDERICK, DARBY, WILLIAM, FREDERICK
Applicants: DARBY WILLIAM FREDERICK, DARBY, WILLIAM, FREDERICK
Application year: 1992
Main classification: C10L5
IPC codes: C10L5