Combustion device and method for producing rice husk charcoal

Abstract

To provide a combustion device that can solve at least one of the problems in the prior art. [Solution] A combustion device comprising an outer cylinder with a bottom plate open at one end, an inner cylinder housed within the outer cylinder, a top plate extending radially from the outer peripheral surface of the inner cylinder to the inner peripheral surface of the outer cylinder and sealing the gap between the inner cylinder and the outer cylinder, and a first opening that can be opened and closed and is provided in the outer cylinder above the center position in the height direction, and the inner cylinder is configured to allow gas to flow between it and the outer cylinder.

Description

[Technical Field]

[0001] The present disclosure relates to a combustion device and a method for producing rice husk charcoal. [Background technology]

[0002] Patent Document 1 describes a combustion appliance that includes "an outer tube that serves as a combustor, a middle plate that is supported inside the outer tube and has a notch that allows a gap to be formed between the inner surface of the outer tube, a middle tube that is inserted into the hole in the middle plate, a plurality of small holes opened in the middle tube, and a trivet or mesh that is placed on either the middle tube and / or the outer tube." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-25361 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 discloses a method for filling the space between the outer and inner tubes of a combustion appliance with rice husks and burning them in a "smoking-roasting" manner to carbonize them. However, the inventors' investigations revealed that when using the combustion appliance described in Patent Document 1, the rice husks burn and generate a combustion flame inside the inner tube, or a vertical combustion flame along the outer tube from the notch in the middle plate, which not only makes it impossible to produce smoked charcoal but also poses safety issues, such as exposing the user to sudden rising combustion flames. Furthermore, the combustion appliance described in Patent Document 1 has the problem that it is difficult to add rice husks. When attempting to add rice husks through the notch in the middle plate, rice husks that have accumulated on the top of the middle plate ignite, generating a combustion flame, or a combustion flame along the outer tube as soon as they are added. The present disclosure solves at least one of the problems in the prior art described above. [Means for solving the problem]

[0005] The first combustion device of the present disclosure includes an outer cylinder having a bottom plate with one end open; The combustion device comprises an inner cylinder housed within the outer cylinder, a top plate extending radially from the outer peripheral surface of the inner cylinder to the inner peripheral surface of the outer cylinder and sealing the gap between the inner cylinder and the outer cylinder, and a first opening that can be opened and closed and is provided in the outer cylinder above the center position in the height direction, and the inner cylinder is configured to allow gas to flow between it and the outer cylinder. [Effects of the Invention]

[0006] The present disclosure solves at least one of the problems in the above-mentioned conventional techniques. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a perspective view of one embodiment of a combustion device of the present disclosure; FIG. [Figure 2] 1 is an exploded view of one embodiment of a combustion device of the present disclosure. FIG. [Figure 3] FIG. 2 is a perspective view of the combustion device with the upper stage removed. [Figure 4] FIG. 4 is a perspective view of the combustion device in a state where the top plate is further removed from the state shown in FIG. 3. [Figure 5] FIG. 5 is a perspective view of the combustion device in the state shown in FIG. 4 with the middle outer cylinder removed. [Figure 6] 1A and 1B are a side view and a plan view of an inner cylinder. [Figure 7] This is an exploded view of the lower part. [Figure 8] FIG. [Figure 9] FIG. 4 is an enlarged view of the dashed line portion in FIG. 3. [Figure 10] 10 is an image showing a conventional combustor with the feathered pot removed during combustion. [Figure 11] FIG. 10 is a diagram showing a state in which the feathered rice cooker is removed during combustion using the combustion device, and additional fuel is added through the first opening. DETAILED DESCRIPTION OF THE INVENTION

[0008] The first combustion device of the present disclosure is a combustion device comprising: an outer cylinder with a bottom plate open at one end; an inner cylinder housed within the outer cylinder; a top plate extending radially from the outer peripheral surface of the inner cylinder to the inner peripheral surface of the outer cylinder and sealing the gap between the inner cylinder and the outer cylinder; and a first opening that can be opened and closed and is provided in the outer cylinder above the center position in the height direction, wherein the inner cylinder is configured to allow gas to flow between it and the outer cylinder.

[0009] In one form of usage, the first combustion device is first placed between the outer and inner tubes in powdered or granular fuel, such as rice husks, wood chips, or bran, and then a heat source (such as firewood) is placed inside the inner tube. The heat source then heats the fuel between the outer and inner tubes, generating flammable gas. The generated flammable gas is guided into the inner tube, preventing it from flowing upward through the outer tube by the top plate that seals the gap between the outer and inner tubes. As a result, the flammable gas from the fuel stably functions as a combustion device (heating), and because combustion is the combustion of gas within the inner tube, the fuel in the outer tube does not directly ignite, allowing the carbonization process to proceed safely. In other words, with only a small amount of heat source input at the beginning, two excellent functions can be achieved: continuous heat generation from the fuel and the production of charcoal from the fuel.

[0010] The outer cylinder has a first opening that can be opened and closed, and additional fuel can be added through this first opening during combustion to maintain a continuous combustion state. In this case, the heat source is only added initially, and once the combustion of the flammable gas has started, the combustion continues by simply adding the fuel (which will later become charcoal) without the need for additional heat source.

[0011] Conventional burners, such as those described in Patent Document 1, are called "kudo" (rice bran stoves). They initially heat a large amount of fuel using a heat source, extracting and burning flammable gases, and utilize the heat for cooking. However, due to their structure, it was difficult to add fuel sequentially during combustion. If a pot or kettle were removed during combustion in an attempt to forcefully add fuel, flames would instantly erupt from the opening, creating a dangerous situation. In contrast, the first combustion device allows for safe addition of fuel through the first opening. Even if the first opening is opened and flammable gas temporarily escapes from the first opening, the structural distance between the inner and outer cylinders minimizes the risk of a combustion flame erupting from the first opening or the fuel igniting. Furthermore, rapid closure of the first opening maintains combustion stability and safety. Thus, the first combustion device effectively solves the problems of the prior art by enabling both efficient and safe continuous fuel combustion and the production of charcoal by smoky roasting of the fuel.

[0012] The second combustion device of the present disclosure is a combustion device that is the same as the first combustion device, but includes a fixed plate having a second opening, a movable plate that slides relative to the fixed plate and has a third opening, and an operating unit for operating the movable plate, and is configured so that by operating the operating unit, the third opening can be positioned relative to the second opening and a through hole formed by communication between the second opening and the third opening can be adjusted.

[0013] According to the second combustion device, the through-holes can be adjusted, allowing for efficient discharge of ash and smoked charcoal generated after combustion. This structure prevents combustion residues from remaining inside the device and reducing combustion efficiency, and allows users to easily perform discharge operations. Furthermore, the device is equipped with an operating unit that slides the movable plate, making discharge operations easier and improving maintainability. Furthermore, adjusting the opening and closing of the through-holes makes it easier to manage the progress of combustion and the carbonization process, enabling efficient smoked charcoal production.

[0014] A third combustion device of the present disclosure is a combustion device in which, in the second combustion device, the inner cylinder has a vent hole for the flow of the gas, and the vent hole is provided below the center position in the height direction of the inner cylinder.

[0015] According to the third combustion device, by providing a vent below the center of the inner tube, the combustion flame is concentrated in the lower part of the inner tube, stabilizing combustion control and suppressing the flame from escaping from the first opening, allowing for efficient carbonization from below. This configuration makes the addition of fuel and the discharge of char more efficient. That is, fuel is introduced through an inlet located at the top, and carbonization is advanced in stages using the heat of the combustion flame and combustible gases, with the final discharge from below, making the combustion and carbonization processes more efficient. The third combustion device can easily be configured as a system in which fuel is introduced from above and carbonized and discharged from below, enabling both stable continuous combustion and charcoal production to be achieved efficiently and reliably.

[0016] A fourth combustion device of the present disclosure is the third combustion device, wherein the inner cylinder has a lower end spaced apart from the bottom plate, and a gap is formed between the lower end and the bottom plate.

[0017] According to the fourth combustion device, the lower end of the inner tube is separated from the bottom plate, forming a gap, which allows the ash and charcoal generated after combustion to efficiently move downward through the gap and be easily discharged. This gap allows for proper control of the combustion flame, stabilizing combustion within the inner tube and preventing unnecessary fire contact with the fuel undergoing carbonization within the outer tube. Furthermore, the discharge process through the gap prevents combustion residues from accumulating within the device, improving combustion efficiency. Furthermore, the structure allows the discharged ash and charcoal to be easily separated, improving efficiency and safety in achieving both combustion and charcoal production.

[0018] A fifth combustion device of the present disclosure is a combustion device configured as the fourth combustion device, wherein the second opening and the third opening have a shape that spreads radially outward from a point near the center of the outer cylinder, and the through holes also have a similar shape.

[0019] According to the fifth combustion device, the second and third openings have a radially expanding shape, which causes the through-holes to widen outward, making it difficult for the ash generated from the heat source in the inner tube to mix with the char generated between the outer and inner tubes and discharged through the through-holes. As a result, the quality of the char is improved and the ash is easily separated, resulting in more efficient discharge operations. Furthermore, the shape of the through-holes allows the discharged material to flow smoothly, reducing stagnation within the device and stabilizing the overall combustion process. Another advantage is improved ease of maintenance during discharge operations.

[0020] A sixth combustion device of the present disclosure is the combustion device according to the first combustion device, wherein the outer cylinder is extended above the top plate and includes a support part for supporting a heating container on the upper part.

[0021] According to the sixth combustion device, by extending the outer tube above the top plate and providing a support part for supporting the heating container at the top, the combustion device can be used as a heat source, making it possible to cook food, etc. This structure allows the combustion device to function not only as a charcoal production device, but also as a multi-purpose device that utilizes thermal energy. Furthermore, the support part stably holds the heating container, improving safety when cooking food, etc. In addition, the structure that separates the outer tube from the inner tube with the top plate prevents flammable gases from coming into direct contact with the heating container, allowing for clean heat supply.

[0022] A seventh combustion device of the present disclosure is the combustion device according to the first combustion device, wherein the outer cylinder and the inner cylinder are formed by combining flat plates and are configured to be disassembled.

[0023] According to the seventh combustion device, the outer and inner cylinders are formed by combining flat plates and have a disassembly structure, which makes cleaning and maintenance after use easy. Furthermore, since it can be disassembled and stored compactly, the space required for transportation and storage can be reduced. Furthermore, the disassembly structure makes it easy to replace or repair parts, which can extend the service life of the device.

[0024] The first method for producing rice husk charcoal disclosed herein is a method for producing rice husk charcoal, which includes: introducing solid fuel into the inner tube of any one of the first to seventh combustion devices; igniting the solid fuel; and storing rice husks in the space partitioned by the inner tube and the outer tube.

[0025] According to the first method for producing rice husk charcoal, a stable heat source is provided by igniting solid fuel placed in the inner tube, and by placing rice husks between the inner and outer tubes, the fuel in the outer tube is carbonized safely and efficiently. This method allows flammable gas to be guided into the inner tube by the top plate, preventing the rice husks in the outer tube from burning directly and achieving uniform carbonization. In addition, additional fuel can be added through the first opening, which can be opened and closed, even during the combustion process, enabling continuous charcoal production.

[0026] The second method for producing rice husk charcoal of the present disclosure is a method for producing rice husk charcoal that, in the first method for producing rice husk charcoal, includes, after ignition, pouring the rice husks into the space through the first opening.

[0027] According to the second method for producing rice husk charcoal, the process includes a step of adding additional rice husks through the first opening after ignition, making it possible to continuously carbonize the rice husks while replenishing fuel during the combustion process. This method ensures stable combustion within the inner tube, ensuring uniform carbonization of the additional rice husks. Furthermore, even if combustible gas temporarily leaks out through the first opening, the spacing and structure of the inner and outer tubes reduces the risk of the rice husks igniting during combustion. Furthermore, the first opening of the combustion device can be opened and closed quickly, improving safety and operability.

[0028] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. The specification exemplifies specific materials and methods for embodying the technical idea of ​​the disclosure. The technical idea of ​​the disclosure is not limited to the following specific examples. Various modifications can be made to the technical idea of ​​the disclosure within the scope of the matters described in the claims. In particular, it should be noted that the drawings are schematic and may differ from the actual product.

[0029] Fig. 1 is a perspective view of an embodiment of a combustion device of the present disclosure, and Fig. 2 is an exploded view.

[0030] The combustion device 100 uses powdered or granular organic matter such as rice husks, wood chips, and bran as fuel, and is capable of burning the combustible gases generated from the fuel while carbonizing the fuel itself to produce charcoal. Conventionally, combustors that use such fuels have been known as "rice bran stoves." However, compared to similar conventional combustors, the combustion device 100 is a new device that has higher combustion efficiency, allows for the addition of additional fuel during combustion, and can produce high-quality charcoal (smoked charcoal). The combustion device 100 uses a small amount of kindling, such as firewood or dead leaves, as a heat source, heats the fuel in a "smoking-grilling manner," producing flammable gases that are burned, and carbonizes the fuel to produce, for example, rice husk charcoal.

[0031] The size of the combustion device 100 is not particularly limited, but as an example, the overall height is preferably 300 mm to 1500 mm, and the width and depth are preferably 150 mm to 1000 mm. As a specific embodiment, the width is preferably 400 mm to 600 mm, the depth is 400 mm to 600 mm, and the height is preferably 500 mm to 1000 mm.

[0032] The combustion device 100 is configured to be assembled by combining multiple metal flat plates. Broadly speaking, the combustion device 100 is configured to have three vertical levels. In the following description, these will be referred to as the upper level 10, the middle level 20, and the lower level 40 from top to bottom. Of these, the middle level 20 has a double-cylinder structure divided into an outer cylinder 26 and an inner cylinder 32. In other words, the inner cylinder 32 is housed inside the outer cylinder 26.

[0033] The upper stage 10 is composed of a tubular portion 12 formed by combining four flat plates 12A, 12B, 12C, and 12D. The tubular portion 12 is placed on the middle stage 20. The upper stage 10 and the middle stage 20 are fixed to each other by an interlocking structure. The upper and lower ends of the upper stage 10 are open in the vertical direction. The upper stage 10 does not need to have a double-tubular structure and includes a tubular portion 12 having the same diameter as the outer tube 26 of the middle stage 20. In this example, the tubular portion 12 is rectangular, but it may also be cylindrical or polygonal. A rectangular or polygonal tube is preferable because it can be assembled by combining flat plates. The upper stage 10 functions as a support for placing a heating container such as a pot or kettle on top of the combustion device 100. As will be described in detail later, kindling such as firewood is placed inside the inner tube 32 of the middle stage 20 as a heat source. Depending on the size and length of the kindling, a portion of it may protrude from the middle section 20. In this case, the cylindrical section 12 of the upper section 10 surrounds it and extends even higher, making it easier to place cooking utensils on the cylindrical section 12. Note that the combustion device 100 does not necessarily have to have the upper section 10, and may be used with the upper section 10 removed.

[0034] Next, FIG. 3 is a perspective view of the combustion device 100 with the upper stage 10 removed, and FIG. 4 is a perspective view of the combustion device 100 with the top plate 24 further removed.

[0035] The middle stage 20 has a double-cylinder structure consisting of an outer cylinder 26 and an inner cylinder 32, and further includes a top plate 24 that extends radially from the outer peripheral surface of the inner cylinder 32 to the inner peripheral surface of the outer cylinder 26. The outer cylinder 26 includes a cylindrical main body, openings 28A, 28B (first openings) formed on the side of the main body, and flap hatches 30A, 30B that openably and closably cover the openings 28A, 28B.

[0036] The outer cylinder 26 is composed of four flat plates 26A, 26B, 26C, and 26D. Each of the four flat plates 26A, 26B, 26C, and 26D is fixed to the adjacent flat plate by an interlocking structure, forming a cylindrical shape. Notched openings 28A and 28B are provided from the upper end of the outer cylinder 26 toward the thickness. Flap hatches 30A and 30B are provided to cover the openings 28A and 28B. The flap hatches 30A and 30B are configured to be able to rotate about the lower edge to open and close the openings.

[0037] The openings 28A and 28B function as inlets for introducing fuel into the space between the outer cylinder 26 and the inner cylinder 32. The openings 28A and 28B are configured to be openable and closable by the flap hatches 30A and 30B. Therefore, the flap hatches 30A and 30B are opened as needed, and fuel is introduced into the space SP between the outer cylinder 26 and the inner cylinder 32 through the openings 28A and 28B. The positions of the openings 28A and 28B are not limited to the top of the outer cylinder 26 and may be provided in other locations. However, as described below, considering that carbonization of fuel progresses from the bottom of the middle stage 20, it is preferable for the openings 28A and 28B to be located higher up. Specifically, it is preferable for the openings 28A and 28B to be located above the center of the outer cylinder 26, and more preferably, directly below the top plate 24. In this example, the openings 28A and 28B are provided in pairs on opposing surfaces. However, the openings 28A and 28B may be provided on each surface, or only one opening may be provided on the outer cylinder 26. The number of openings 28A and 28B is not limited.

[0038] FIG. 5 is a perspective view of the combustion device 100 with the outer cylinder 26 of the middle stage 20 removed. FIG. 6 shows a side view and a plan view of the inner cylinder 32. The inner cylinder 32 is a cylindrical structure formed by combining four flat plates 32A, 32B, 32C, and 32D. The inner cylinder 32 is open at the top and bottom, and a vent 34 is provided at the bottom of the side for gas circulation inside and outside the inner cylinder 32. Two protrusions are provided at the bottom of the flat plates 32B and 32D, and these protrusions form the four legs of the inner cylinder 32. The inner cylinder 32 is installed upright in the center of the bottom plate 44 using the four legs. The bottom plate 44 and the bottom of the inner cylinder 32 are spaced apart by the length of these legs, leaving a gap between them. This gap is wider than the vent 34 and is adjusted to allow carbonized fuel to pass through.

[0039] Kindling, such as firewood, is placed inside the inner cylinder 32. Meanwhile, fuel is placed in the space SP between the inner cylinder 32 and the outer cylinder 26. The kindling burns inside the inner cylinder 32, but the fuel is isolated by the inner cylinder 32 and does not burn directly. When the kindling burns inside the inner cylinder 32, heat is transferred through the inner cylinder 32, and flammable gas is generated from the fuel. The flammable gas moves into the inner cylinder 32 through the vent 34 at the bottom of the inner cylinder 32 and burns within the inner cylinder 32. The space SP defined by the inner cylinder 32 and the outer cylinder 26 is closed at its top by the top plate 24, so the flammable gas is less likely to dissipate outside the space SP and is efficiently guided into the inner cylinder 32 for combustion. As described below, carbonized fuel can be discharged from the bottom plate 44 of the lower section 40. Therefore, in consideration of the flow of fuel and flammable gas, the vent 34 is preferably located below the center position in the height direction of the inner cylinder 32. With this configuration, the fuel introduced through the upper openings 28A and 28B is carbonized successively from the bottom in the height direction and is discharged from the bottom plate 44.

[0040] FIG. 7 is an exploded view of the lower tier 40, and FIG. 8 is a perspective view of the main body 42 of the lower tier 40. The lower tier 40 is formed by combining multiple flat plates 42A, 42B, 42C, 42D, 44A, 44B, etc., excluding the tray 54. The main body 42 of the lower tier 40 is shaped like a tray with legs on all four sides. The main body 42 is tubular and slightly larger in diameter than the outer tube 26 of the middle tier 20, and a bottom plate 44 with an opening 46 formed in its center is fitted into the main body 42. The bottom plate 44 has multiple fan-shaped openings 46 (second openings) formed in its center, radiating outward from the center of the bottom plate 44.

[0041] The opening 46 can be opened and closed by a movable plate 48. The movable plate 48 is composed of a disk-shaped main body 48A and an arm 48B extending radially from the outer periphery of the main body 48A. The disk-shaped main body 48A is provided with a plurality of fan-shaped openings 50 (third openings) spreading out from the center. The openings 46 provided in the bottom plate 44 and the openings 50 provided in the movable plate 48 have shapes corresponding to each other. The movable plate 48 is rotatably fixed to the center of the bottom plate 44 by a fulcrum member 52. With this configuration, when the arm 48B is operated to slide the movable plate 48, the openings 46 and 50 communicate with each other to form a through-hole TH, or the opening 46 is closed by the main body 48A of the movable plate 48.

[0042] Openings 46 and 50 are located in the center of the bottom plate 44. The area of ​​this opening is approximately the same as or larger than the opening of the inner cylinder 32 of the middle stage 20, which is placed relative to the center of the bottom plate 44. In the middle stage 20, the carbonized fuel in the space SP flows through the gap formed between the inner cylinder 32 and the bottom plate 44 toward the center of the inner cylinder 32 and falls onto the tray 54 through the through-hole TH opened by operating the arm 48B. This allows the carbonized fuel to be collected sequentially even during combustion, enabling continuous processing. Furthermore, the movable plate 48 is configured to be adjustable in opening and closing amount using a stepless sliding mechanism, so in addition to discharging the carbonized fuel, it is also possible to adjust the amount of air introduced and the degree of kindling combustion.

[0043] In the combustion device 100 configured as described above, flammable gas generated from the fuel efficiently moves from the enclosed space SP to the inner cylinder 32 and burns. Therefore, even if the flap hatches 30A, 30B of the middle stage 20 are opened during combustion, flammable gas leaks and flames rarely erupt from the openings 28A, 28B. This means that additional fuel can be added during fuel processing. Furthermore, carbonized fuel is sequentially discharged through the opening 46 in the bottom plate 44 via a gap at the bottom of the inner cylinder 32. Because the vent 34 of the inner cylinder 32 is located lower in the vertical direction, carbonization begins at the bottom of the middle stage 20, ensuring that carbonized fuel is reliably discharged from the bottom plate 44. A peephole 56 is provided in the lower stage 40, allowing visual observation of the progress of carbonization.

[0044] The combustion device 100 is formed by combining multiple flat plates. Figure 9 is an enlarged view of the dashed line portion in Figure 3. Each flat plate is provided with a hook 60 and a corresponding slit 62, and the combustion device 100 is assembled by engaging and combining these. The combustion device 100 can be used by placing the double-walled cylinder and top plate 24 of the middle tier 20 on the assembled lower tier 40. Furthermore, by placing the upper tier 10 on top of this, it can also be easily used for cooking.

[0045] When in use, the flap hatches 30A, 30B of the openings 28A, 28B are opened and fuel is poured in. Note that fuel may be previously stored between the outer cylinder 26 and the inner cylinder 32 during assembly. After the fuel is stored, kindling such as firewood or fallen leaves is poured into the inner cylinder 32 through the opening at the top of the upper section 10 or middle section 20 and ignited. At this time, it is preferable to adjust the combustion so that it starts as close to the bottom plate 44 as possible. Specifically, it is preferable to pour in the ignition agent and kindling and then adjust the opening of the through-hole TH in the bottom plate 44 to ignite it.

[0046] When the kindling is ignited, the fuel heats up, and over time, flammable gas enters the inner cylinder 32, starting combustion. In this state, there is no need to add more kindling. The combustion of the flammable gas alone further heats the fuel, and combustion continues. As flammable gas is generated, the fuel begins to carbonize from the bottom of the middle section 20. Check the progress of carbonization through the peephole 56, and if sufficient carbonization has occurred, adjust the opening of the through-hole TH in the bottom plate 44 to discharge the carbonized material. The process continues by opening the flap hatches 30A and 30B of the openings 28A and 28B and sequentially adding fuel.

[0047] In the combustion device 100 of the present disclosure, the space between the outer cylinder 26 and the inner cylinder 32 is closed by the top plate 24, so the flame does not rise to the outside, and additional fuel can be safely added through the openings 28A and 28B. Furthermore, by using rice husks as fuel, rice husk charcoal can be discharged from the bottom plate 44, so the combustion device 100 can also be used as a rice husk charcoal manufacturing device.

[0048] (Demonstration experiment) Next, a demonstration experiment using the combustion device 100 will be described. Rice was cooked using a conventional combustor "Nukakudo" and the combustion device 100 in a kamado (feathered rice cooker) to examine the combustion efficiency. The conventional "Nukakudo" has a simple double-cylinder structure, with both the inner and outer cylinders open at the top, and is used by placing rice husks between the outer and inner cylinders, putting a heat source such as firewood into the inner cylinder, and placing the kamado on top to cover the opening.

[0049] Differences in combustion state First, the combustion conditions were different between the two. In the conventional example, flames rose not only from the inner tube but also from the outer tube, resulting in the heating points being dispersed and the heat not being transmitted efficiently to the kamado. On the other hand, when using the combustion device 100, the combustion flame rose only within the inner tube, making it easier for the heat to be concentrated and for the heat to be transmitted efficiently to the kamado.

[0050] Differences in heat source requirements As mentioned above, in the conventional example, the combustion efficiency was poor and the heat was dispersed, so sufficient heat could not be obtained unless a large amount of heat source (firewood) was put into the inner cylinder. As a result, even though rice husks were used as fuel, the amount of firewood required to cook rice satisfactorily was almost the same as when cooking rice using only firewood as fuel. On the other hand, when using the combustion device 100, only the amount of firewood needed for initial kindling was needed, and thereafter the heat was maintained with only the rice husks. Furthermore, the heat could be easily adjusted by simply adding more rice husks as needed.

[0051] Differences in flammable gas emissions In the conventional example, the gas generated from the heated rice husks was discharged from many places throughout the combustor, resulting in low utilization efficiency of the combustible gas. On the other hand, when the combustion device 100 was used, the combustible gas was guided into the inner cylinder through the vent and was reliably used for combustion, resulting in high efficiency.

[0052] The results of the above demonstration experiments clearly confirmed the following problems with the conventional example. First, because flames were generated from sources other than the inner tube, the heat was not transmitted sufficiently to the kamado. Second, even when the amount of fuel and heat source input was increased, the result was not much different from cooking using firewood alone, and efficiency was low. Third, flammable gases from the rice husks were wasted, significantly reducing combustion efficiency.

[0053] On the other hand, according to the combustion device 100, by placing a top plate between the inner and outer tubes and adopting a sealed structure, combustion is efficiently limited to within the inner tube, eliminating the lack of heat power, and the combustible gas generated from the rice husks is also effectively utilized, thereby significantly improving combustion efficiency.

[0054] FIG. 10 is an image showing the state in which the feathered kettle is removed during combustion in a conventional combustor. As shown in FIG. 10, when the feathered kettle is removed, flames erupt from the inner and outer cylinders. On the other hand, FIG. 11 is a diagram showing the state in which the feathered kettle is similarly removed using combustion device 100, and additional fuel is added through the first opening. From FIG. 11, it can be seen that with combustion device 100, even when the feathered kettle is removed and the first opening is opened, the combustion flame is limited to the inner cylinder, and does not erupt widely outside or flow back through the first opening. [Explanation of symbols]

[0055] 100 Combustion equipment 10 Upper 20 middle row 24 Top plate 26 Outer cylinder 28A aperture 28B opening 30A Flap Hatch 30B flap hatch 32 Inner cylinder 34 Ventilation hole 40 Lower 44 Bottom plate 46 Aperture 48 Movable plate 50 aperture

Claims

1. an outer cylinder having a bottom plate with one end open; an inner cylinder housed within the outer cylinder; a top plate extending radially from an outer peripheral surface of the inner cylinder to an inner peripheral surface of the outer cylinder and sealing the gap between the inner cylinder and the outer cylinder; a first opening that is openable and closable and is provided in the outer cylinder above a center position in a height direction, A combustion device, wherein the inner cylinder is configured to allow gas to flow between the inner cylinder and the outer cylinder.

2. the bottom plate includes a fixed plate having a second opening; a movable plate that slides relative to the fixed plate and has a third opening; an operating unit for operating the movable plate, 2. The combustion device according to claim 1, wherein the third opening is positioned relative to the second opening by operating the operating portion, and a through hole formed by communication between the second opening and the third opening can be adjusted.

3. The combustion device according to claim 2 , wherein the inner cylinder includes a vent hole for allowing the gas to pass therethrough, the vent hole being provided below a center position in a height direction of the inner cylinder.

4. The combustion device according to claim 3 , wherein a lower end of the inner cylinder is disposed away from the bottom plate, and a gap is formed between the lower end and the bottom plate.

5. 5. The combustion device according to claim 4, wherein the second opening and the third opening have a shape that extends radially outward from a point near the center of the outer cylinder, and the through hole has a similar shape.

6. The combustion device according to claim 1 , wherein the outer cylinder is extended above the top plate and includes a support portion for supporting a heating vessel on an upper portion thereof.

7. The combustion device according to claim 1 , wherein the outer cylinder and the inner cylinder are formed by combining flat plates and are configured to be disassembled.

8. 8. A combustion device according to claim 1, further comprising: a combustion chamber for evacuating a fuel gas from the combustion chamber; igniting the solid fuel; and storing rice husks in the space partitioned by the inner cylinder and the outer cylinder.

9. The method for producing smoked rice husk charcoal according to claim 8, further comprising, after the ignition, introducing the rice husks into the space through the first opening.

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