Method for pellet combustion, combustible pellet, and combustion furnace

Abstract

To provide a pellet of biomass fuel that is difficult to heat internally due to being compacted.SOLUTION: The pellet for fuel comprises a combustible layer formed of an organic material mixed with metal scraps and a heat-up layer provided in layers on the combustible layer. The heat-up layer is formed of an organic material as a binder including metal scraps. The metal is heated by induction heating by passing a magnetic flux through the metal by using a high-frequency induction device, and the organic material is directly heated. Thereby, the temperature of the pellet rapidly rises, and the pellet is directly charged into a combustion furnace to improve combustion efficiency.

Description

[Technical field]

[0001] The present invention relates to a pellet combustion method, combustion pellets, and a combustion furnace that improve the combustion efficiency in a combustion furnace for biomass or the like. [Background technology]

[0002] A household food waste biomass compost pellet manufacturing machine as described in Patent Document 1 has been known. This household food waste biomass compost pellet manufacturing machine can produce biomass pellets for fuel and fertilizer as needed, and is environmentally friendly. In this manufacturing machine, high pressure is generated by a commercially available 10-ton manual jack-up, and a steel container and base are used to withstand the pressure. Biomass compost is manually pushed into a biomass billet, which is then compressed and extruded directly from the die hole blades to produce pellets. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Utility Model Registration No. 3160328 Summary of the Invention [Problem to be solved by the invention]

[0004] In normal biomass pellets produced by the above-mentioned manufacturing machine, internal combustion tends to be slow. This is because the raw material is compressed at high pressure during pellet production, making it difficult for air to enter the inside of the pellet. As a result, it takes time for combustion to progress to the center of the pellet, and the combustion time tends to be long. The present invention has been made to solve this problem. [Means for solving the problem]

[0005] The pellet combustion method according to the present invention involves subjecting pellets formed from an organic material mixed with metal chips to high-frequency induction heating to heat them from the inside.

[0006] The heat accelerating pellet according to the present invention comprises a combustible layer made of edible or other organic material as a base material, The heat-up layer is made of metal chips and a combustible layer made of edible or other organic materials as a base material, and a heat-up layer made of a metal plate is formed in layers. The combustible layer of the base material can be mixed with chips.

[0007] Furthermore, the combustion furnace of the present invention has a high-frequency induction device for performing high-frequency induction heating on the pellets formed from the organic material mixed with the metal chips. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing a pellet according to a first embodiment of the present invention. [Diagram 2] FIG. 1 is a schematic diagram showing a pellet according to a first embodiment of the present invention. [Diagram 3] FIG. 11 is an explanatory diagram showing a pellet according to another embodiment. [Figure 4] FIG. 1 is a configuration diagram showing a structure of a combustion furnace according to a first embodiment of the present invention. [Diagram 5] FIG. 5 is a partially enlarged view of FIG. [Figure 6] FIG. 11 is a configuration diagram showing a heating and drying device according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (Embodiment 1) The main material of the pellets is made of one or a mixture of discarded food, processing residues, other edible materials, thinned wood, wood chips, plant waste, cardboard, shredded waste, etc. In particular, organic materials such as edible materials and food waste for which no treatment method has been established at present are preferable.

[0010] The edible materials include fruits, vegetables, meat, and other food ingredients. Edible pellets are made in the following steps. First, edible materials are collected. The waste to be collected includes leftovers, defective products from the food manufacturing process, and expired food generated by restaurants, supermarkets, food factories, etc. Next, the collected edible materials are separated. Foreign objects such as impurities and plastics, as well as non-edible food waste, are removed.

[0011] The separated edible material is pre-processed by drying, crushing, sorting, etc. This adjusts the moisture content, particle size, and quality required for pelletization. In this state, the edible material becomes powder or chip-like, and is in a state that can be easily molded. When mixing multiple materials, the pre-processed powder or chips are mixed with the powder or chips of the required material depending on the required function to be produced.

[0012] The edible powder or chips are then mixed with metal shavings, either from the process described below or after pretreatment.

[0013] Next, the pre-processed edible material is fed into a pelletizer to be turned into pellets. In the pelletizer, the edible material is compressed under high temperature and pressure and formed into pellets. The formed pellets are either left to cool or cooled in a cooling machine to complete the final product. The binder used in pelletizing may be a component inherent in the material itself, or it may be added separately as a binder. The shape of the pellets can vary, including hollow cylinders, but more details will be given later.

[0014] After the pellets are formed, they are inspected for quality, including moisture content, particle size, hardness, density, and calorific value.

[0015] Thinning materials, wood chips, plant waste, cardboard, and shredded waste can also be processed into powder of a specified size through pre-processing, and then pelletized in the same way as the edible materials mentioned above.

[0016] [Chips] Metal chips generated in metal processing are generated by steel processing such as cutting, milling, drilling, and pressing. Aluminum chips generated when processing aluminum tend to be lighter and elongated compared to steel. Stainless steel chips generated when processing stainless steel tend to be harder and elongated compared to steel. Other metal chips such as titanium, nickel, brass, zinc, lead, and copper can also be used. Reusing metal chips allows for low-cost procurement and reduces the processing burden and environmental impact.

[0017] It is preferable to pre-process the chips to a specified size. For processing, a shredder, a hammer mill, ballast, etc. are used. A shredder can cut the chips into small pieces. A hammer mill hits the chips with a hammer to break them into small pieces. This is effective for brittle metals, etc. A ballast is used to further break down the chips into smaller pieces by putting them into ballast and rubbing them together in a rotating cylinder. Breaking the chips into smaller pieces makes them easier to mix with edible materials, etc. Also, the chips are distributed evenly.

[0018] The edible powder and the cutting chip powder are mixed using a mixer that uses a rotating shaft or blade to stir the mixture, or a mixer that uses a rotating cylindrical container.

[0019] The pellets are preferably shaped as follows: One example of the pellet shape is a cylinder. For example, the length is about 10 mm to 30 mm, and the diameter is about 6 mm to 8 mm. The pellets may also be spherical. The diameter of the pellets may be about 6 mm to 8 mm. The dimensions should not be too large or too small so that a uniform amount of heat is generated during combustion. The pellets may also be polygonal. For example, they may be hexagonal or octagonal.

[0020] Furthermore, it may be in a plate shape that allows easy combustion all the way to the inside. As long as it has a flat or curved plate-shaped portion, it may be corrugated, U-shaped, or macaroni-shaped. It may also be spring-shaped, scrubbing-pad-shaped, or box-shaped. In particular, in the case of a macaroni shape, it is possible to maintain space inside even if pellets are placed in layers, making it easier for oxygen to be supplied during combustion. An example of a plate shape will be described later.

[0021] The same effect can be obtained with a corrugated, U-shaped, spring-like, scrubbing-brush-like, box-like, etc. In other words, it is preferable that the pellets are hollow (including those having a partially open portion) or curved, long thread-like (spring, scrubbing brush, etc.) so that spaces can be easily formed even when the pellets overlap when a large number of pellets are added.

[0022] The machines used to manufacture pellets can be pellet presses, which compress the raw materials at a certain pressure to form fuel pellets. These machines vary in compression force, production volume, type of raw materials, shape, size, etc. Also, the manufacture of pellets requires conditions such as high pressure and high temperature.

[0023] For example, biomass combustion furnaces using the pellets of the present invention include the following. The pellets of the present invention can be used in fixed-bed combustion furnaces. This fixed-bed combustion furnace is a type in which fuel is fixed to the hearth and air is sent onto the hearth to burn it, and since it has high combustion efficiency and generates little exhaust gas, it is an environmentally friendly combustion method. Furthermore, the pellets of the present invention can be used in fluidized-bed combustion furnaces. This is a type in which fuel is put onto a fluidized bed and mixed with air in the furnace and burned, which has high combustion efficiency and few restrictions on the type of fuel. Furthermore, the pellets of the present invention can be used in mixed combustion furnaces. This is a type in which biomass fuel and fossil fuel are mixed and burned, and since it has improved combustion efficiency and power generation efficiency, it is suitable for use in large facilities such as power plants.

[0024] [Plate pellets] FIG. 1 is a schematic diagram showing a pellet according to the first embodiment of the present invention. An example of the distribution of chips when the pellet is formed into a plate shape is shown below. When performing high-frequency induction, it is preferable to distribute the chips in layers to facilitate high-frequency induction heating. If the chips are in layers, they may be concentrated on the surface of the pellet, or may be formed inside to form a path for inducing a magnetic field. By forming the pellet in a flat plate shape, it is easy to form a chip layer when forming a mold.

[0025] The plate-shaped pellet 100 has a structure in which a combustible layer 1 and a chip layer 2 are layered. In manufacturing, a certain amount of chips are first placed in a mold, and edible material is placed on top of it. In this state, heating and pressurization are performed in the same manner as above to form a temperature-raising layer 2 made of chips on one side of the combustible layer 1 of the plate-shaped body. The temperature-raising layer 2 is adjusted to a density where the chips come into contact with each other. By bringing the chips into contact with each other, magnetic lines of force can easily pass through. Fine edible material may be mixed as a binder for the chips to bond them together. The temperature-raising layer 2 may be formed only from the chips, or may be formed by mixing a certain amount of edible material with the chips. As shown in FIG. 2, if the temperature-raising layer 2 is to be formed on both sides, the chips are first placed in the mold after edible material has been placed therein.

[0026] The average particle size of the chips is preferably 1 mm or more and 3 mm or less. With a particle size of this order, the chip layer can be regarded as roughly a metal plate, improving heat generation efficiency. The density of the temperature-rising layer 2 should be about 7:3 in volume ratio of edible material to chips. The shape of the chips varies depending on the processing, but a shape that allows easy contact with each other is preferable. In the case of flake-like chips, the density needs to be adjusted so that they come into contact with each other. If the chips are spring-shaped or spiral-shaped, it is sufficient if they are held in an entangled state.

[0027] The plate thickness is 5 mm to 10 mm, and the surface has a temperature-raising layer 2 of 1 mm to 3 mm. It can also be provided on both sides. When provided on both sides, it is convenient because there is no need to check the direction when feeding the plate into a conveyor or the like.

[0028] Furthermore, the formation of the temperature-raising layer 2 on the surface improves the slippage on the surface of the loader. The surface of the loader is made of a material such as glass through which magnetic field lines do not pass, and since this surface is smooth, the slippage is improved by the temperature-raising layer 2 that forms fine irregularities on the surface. This makes it possible to heat the loader while heating it with the loader described below.

[0029] 3 is an explanatory diagram showing a pellet according to another embodiment. In this pellet, the temperature-raising layer 2 is reusable. Reuse here refers to a method of reusing the shape of the temperature-raising layer 2 as is and attaching a new combustible layer 1 to it. The temperature-raising layer 2 of the pellet 150 shown in Figs. (a) and (b) is made of a metal plate-like body, and a protrusion 2a is formed on one side of the plate-like body in one direction. The protrusion 2a also functions as a heat transfer fin, and eddy currents are generated on the surface of the protrusion 2a, causing it to heat up.

[0030] The plan view of the temperature-rising layer 2 is shown in Fig. 2(b). It is preferable to use this temperature-rising layer 2 formed by melting and shaping the chips. The precision of the shaping does not have to be high. The chips may be packed into a mold having the shape of the temperature-rising layer 2 and compressed to form it. When heated, the temperature may be set to a temperature lower than the melting point of the chips, at which the atoms of adjacent chips bond together, and the shape may be maintained.

[0031] In this state, the pellets 150 are placed in a mold, edible material is poured in from above, and compressed. As a result, the edible material enters between the protrusions 2a and acts as an anchor to fix the combustible layer 1 to the temperature-raising layer 2 (as shown in FIG. 3(a)). By placing the pellets in this state in the combustion device described below, an electric current flows through the temperature-raising layer 2, which heats it and heats the combustible layer 1 that it comes into contact with.

[0032] Furthermore, the above-mentioned protrusions 2a may be cylindrical. A cross-sectional view of the pellet 160 in this case is shown in Fig. 1(c). A large number of cylinders are formed in an array (see Fig. 1(d)). Even with this configuration, the combustible layer 1 is easily fixed to the temperature-raising layer 2.

[0033] Furthermore, in another pellet 170, as shown in FIG. 1(f), the temperature-raising layer 2 may be a metal plate with many holes 2b formed therein. When edible material is layered on the plate-shaped temperature-raising layer 2, the edible material enters the holes 2b and is fixed by the anchor effect (see FIG. 1(e)). In this configuration, oxygen is supplied through the holes, improving the combustion efficiency of the combustible layer 1. The holes 2b may be formed as a large number of relatively small holes such as punched metal, or may be formed as a small number of larger holes.

[0034] Furthermore, like pellets 180 shown in Fig. 2(g), edible material may be placed and fixed to the temperature-raising layer 2 in Fig. 2(a). Making the whole into a plate-like body of uniform dimensions is suitable for transportation and automation, but it takes time to form. For this reason, if the edible material is placed like a paste and attached to the temperature-raising layer 2 in a manner that engages with the protrusions 2a, it becomes easier to manufacture.

[0035] In the above pellets 150 to 180, the combustible layer is burned away after combustion and the temperature rising layer remains, so the temperature rising layer can be removed from the heating device and reused. When reusing, the edible material is re-bonded as described above to form pellets.

[0036] In addition, multiple holes may be formed in the temperature-raising layer 2 of the pellets having the configurations shown in Fig. 3(a) to (d) and (g). In this case, oxygen is easily supplied from the holes, improving the combustion efficiency. The pellets can also be used for induction heating, and can also be directly put into a combustion furnace.

[0037] [Combustion equipment] FIG. 4 is a configuration diagram showing the structure of the combustion furnace according to the first embodiment of the present invention. This combustion furnace 50 has a structure in which an induction heating device 90 is provided on a loader arranged between the storage and the boiler. As shown in FIG. 5, the loader 51 of the induction heating device is composed of a coil that passes high-frequency alternating current and a power source that supplies current to the coil. When a high-frequency current is passed through the coil of the induction heating device, a magnetic flux is generated, an electromotive force is generated on the surface of the chips, an eddy current is generated, and Joule heat is generated due to the resistance of the metal. The metal contained in the pellets moving through the loader 51 is rapidly heated by the induction heating device to promote combustion from the inside. The floor part of the loader 51 is made of a material that is not easily affected by high-frequency current, such as glass. The main body 61 is provided with a blower 70. The incinerator 50 is provided with a power generation device. A tank 62 is connected to the main body 61, and a pipe 63 extending from the tank 62 is connected to a turbine 64, and the rotation of the turbine 64 rotates the generator 65 to generate electricity.

[0038] As a pellet transport device, a loader 51 is structured to push the pellets forward while holding them at a position in the coil for a certain period of time in order to heat them. A piston 52 for pushing is provided at the end of the loader 51. A plate 53 for pushing is provided at the tip of the piston shaft. Since the pellets 100 dropped from a hopper 54 are located in front of the plate 53, the plate 53 pushes out the pellets 100 one by one. The pushed out pellets 100 are transported to a heating position of the coil 91. The floor of the heating position is made of a material such as glass. The pellets 100 are heated at this heating position and then transported into the furnace.

[0039] By providing an induction heating device in the loader 51, a high-frequency magnetic flux reaches the pellets 100 at close range, making it easier to heat the chips contained in the pellets 100. High-frequency heating is performed at a temperature below which metal does not melt and above the temperature at which edible material starts to burn. The temperature at which edible material starts to burn is about 200 degrees. The melting point of metal varies depending on the base material and added elements, but in the case of aluminum, it is about 660 degrees. For this reason, a temperature slightly higher than the temperature at which edible material burns is preferable. Specifically, it is adjusted to be in the range of 200 to 300 degrees.

[0040] In the case of pellets 100 made of non-edible materials such as wood chips, the temperature should be adjusted to be slightly higher than the temperature at which the material begins to burn.

[0041] Also, induction heating devices may be provided around and at the bottom of the main body of the combustion furnace 50. When pellets 100 are placed in the main body, the metal contained in the pellets 100 is rapidly heated by induction heating in addition to the internal heat, causing the pellets to burn from the inside.

[0042] In addition to heating by high-frequency induction, in the case of the pellets 100 of the present invention, the inside of the combustion furnace becomes very hot, heating the chips on the surface of the pellets. This promotes the combustion of the surface, and at the same time, the chips inside are exposed and heated, encouraging the combustion of the surrounding edible matter. Furthermore, the unburned chips accumulate and retain heat, heating the pellets 100. The heated chips are stirred by a stirrer in the combustion furnace and mixed with the pellets put into the furnace, promoting heating.

[0043] If the grain size of the metal is large, it can be captured by a net, so it is removed together with the ash when cleaning the combustion passage and separated by a sieve. The separated chips can be reused for the next pellets. This eliminates the need for pre-processing, and reduces the manufacturing cost of the pellets 100.

[0044] Since the plate-shaped pellets need to stay on the loader 51 for a certain period of time, they can be sent in a batch manner. In this case, the pellets are placed on a tray for transporting the pellets, and the tray is placed on the upper surface of the coil that generates high-frequency induction. The tray is preferably made of glass, which is non-conductive and heat-resistant. The pellets that have been induction-heated on the tray are transported together with the tray into the combustion furnace of the heating device and placed in the furnace. In addition, the pellets on the loader may be transported by generating traveling waves on the surface of the loader 51 using an ultrasonic generating element such as a piezoelectric element provided on the back of the loader. In the case of the batch manner, the coil is positioned on the underside of the tray, and the pellets are transferred to the combustion furnace every certain heating time.

[0045] (Embodiment 2) In the present invention, sludge can be dried and pelletized. Sludge contains a lot of water, so it takes time for the water inside to evaporate when it is dried. By mixing the sludge with cuttings and heating the cuttings by high-frequency induction, the sludge and its interior can be heated to a high temperature. Sludge from which some moisture has been removed is preferable. As mud is a non-conductive material, high-frequency induction acts on the metal cuttings inside, heating the cuttings. This heat heats the surrounding mud, accelerating the evaporation of the water.

[0046] 6, the sludge heating and drying device 200 is composed of a relatively flat tray 201 and an induction heating device 202 arranged below the tray 201. The induction heating device 202 is the same as that in the above-mentioned embodiment 1. The surface of the tray 201 is composed of a material, such as glass, through which magnetic lines of force cannot pass.

[0047] The sludge dried in the heating and drying device 200 is formed into pellets since it can be burned. The forming into pellets is performed in the same manner as in the first embodiment. Sewage sludge, industrial sludge, and agricultural sludge are suitable as sludge to be mixed with the cuttings. Sewage sludge is sludge generated by biological or physical treatment in a sewage treatment plant, and contains organic matter, microorganisms, solid impurities, and the like. In order to make it possible to reuse the sewage sludge, it is necessary to dry the sludge. Metal cuttings are used for this drying. Sewage sludge containing cuttings can be used as building materials by forming it after drying. By forming it into bricks containing metal, the heat storage effect can be increased. In addition, for energy utilization, the sludge is formed into pellets after drying to be used as biomass fuel.

[0048] Industrial sludge is sludge generated from industrial processes, and is industrial waste from industries such as construction sites, metal processing, chemical production, and oil refining. It includes waste from the production process and processing equipment in factories and manufacturing facilities. Construction sludge requires improvement such as dehydration and drying, so it is dehydrated and dried by nine-frequency induction heating of mixed metal cuttings, and reused as soil material.

[0049] Agricultural sludge is a waste material derived from animals and plants that is generated mainly in relation to livestock farming and agricultural work, and is therefore suitable for pelletization as fuel. In addition, since it is derived from natural materials, it may be used as a building material for buildings that use natural materials.

[0050] In this heating and drying furnace 200, sludge is placed in a tray 201 and mixed with a predetermined amount of metal chips, which are then heated by an induction heater 202. This heats the chips from around them, causing the moisture in the sludge to evaporate. When the moisture content falls below a certain level, the sludge is formed into an appropriate shape and made into pellets, which are then burned in a combustion furnace. According to the present invention, the sludge can be dried and made into pellets in a short time, making it possible to efficiently treat the sludge. [Explanation of symbols]

[0051] 100 Plate pellets 1 flammable layer 2 Chip layer

Claims

1. A pellet combustion method in which pellets made from organic material mixed with metal cuttings are heated from the inside by high-frequency induction heating.

2. A combustible layer made of edible or other organic materials; a heated layer containing metal chips; Heat-promoting pellets formed in layers.

3. A combustible layer made of edible or other organic materials; A temperature rising layer made of a metal plate; Heating pellets formed in layers.

4. A combustion furnace equipped with a high-frequency induction device that performs high-frequency induction heating on pellets made from organic material mixed with metal cuttings.

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