Solid fuel stove

Abstract

To provide a solid fuel stove with a simple structure that produces a blue flame during combustion and enables clean and efficient combustion, and a method for using the solid fuel stove.SOLUTION: Provided are a solid fuel stove and a method for using the solid fuel stove, the solid fuel stove comprising: a body part having a bottom plate, a top plate, and side plates; a solid fuel storage part provided on a lower part inside the body part; a gas mixing chamber located on an upper part inside of the body part; a first air supply port provided on the lower part of the side plate of the body part; a second air supply port provided on the upper part of the side plate of the body part; and a flame port provided on the top plate.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a heating or cooking stove that uses solid fuel such as wood and is capable of reducing air pollution caused by exhaust gases. [Background technology]

[0002] Stoves (combustion appliances) are widely used for heating rooms and cooking. Gas fuels such as natural gas and LP gas, or liquid fuels such as kerosene, are often used as fuels, but these are fossil fuels that emit greenhouse gases when burned. On the other hand, solid fuels such as wood, while they emit greenhouse gases when burned, are considered carbon-neutral (do not increase or decrease the amount of greenhouse gases in the atmosphere) because they absorb greenhouse gases from the atmosphere through photosynthesis as the next generation of plants (wood) grows.

[0003] However, compared to stoves that burn gaseous or liquid fuels, stoves that burn solid fuels such as wood have difficulty achieving complete combustion, and some of the solid fuel remains in the exhaust gas in the form of carbon and polymers, which are unable to burn. The presence of these substances causes the flame to appear red to yellow. This results in the drawback of air pollution caused by exhaust gases. According to a report by the World Health Organization, indoor air pollutants in homes are estimated to cause approximately 3.2 million deaths worldwide each year. This makes the problem of air pollution caused by exhaust gases a serious one.

[0004] Furthermore, the fact that some of the fuel remains unburned means that some of the fuel's energy cannot be converted into thermal energy, which has the disadvantage of reducing thermal efficiency (= thermal energy obtained by combustion ÷ chemical energy contained in the fuel).According to a report by the Food and Agriculture Organization of the United Nations, approximately half of the wood produced in the world (approximately 2 billion cubic meters) is used as fuel such as firewood and charcoal, and from the perspective of curbing deforestation, it is also important to increase the thermal efficiency of stoves that burn solid fuels such as wood, and to obtain more thermal energy with less solid fuel consumption.

[0005] To avoid the drawback of air pollution caused by exhaust gases, when a stove that burns solid fuel such as wood is used indoors, it is necessary to install an exhaust device such as a chimney or a ventilation fan, but this increases the size of the equipment. At the same time, there is also the problem that the actual thermal efficiency is further reduced because the heat energy obtained by combustion is discarded to the outside through the exhaust device such as a chimney. Patent Document 1 describes a clean and efficient solid fuel stove with a combustion process that includes a combustion chamber for containing solid fuel and a blower assembly configured to provide an air flow that enters the combustion chamber during operation. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-14453 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the solid fuel stove described in Patent Document 1, the flame color during combustion is red to yellow, and combustion is not necessarily clean and efficient, and the structure is complicated because forced ventilation by a blower assembly is required. The problem to be solved by this invention is to provide a solid fuel stove that does not require a forced ventilation device, has a simple structure, and produces a blue flame during combustion, enabling clean and efficient combustion. [Means for solving the problem]

[0008] The present invention relates to a solid fuel stove (A) comprising a main body (1) having a bottom plate (1a), an openable top plate (1b) and side plates (1c), characterized in that the solid fuel stove (A) comprises a solid fuel storage section (2) on the lower inside of the main body (1), a gas mixing chamber (3) on the upper inside of the main body (1), a first air intake port (4) provided at a position above the bottom plate (1a) on the lower side of the side plate (1c) of the main body (1), a second air intake port (5) provided at the upper part of the side plate (1c) of the main body (1), and a flame opening (6) provided on the top plate (1b).

[0009] The present invention also provides a fuel supply step of opening the top plate (1b) of the solid fuel storage section (2) of the solid fuel stove (A) and pouring solid fuel into the solid fuel storage section (2) so that the solid fuel is in contact with the bottom plate (1a) and fills the solid fuel up to a height located between the first air inlet (4) and the second air inlet (5); an ignition step of igniting the surface of the top layer of the solid fuel with a spark; a solid fuel combustion step of burning the solid fuel from the top layer to a predetermined depth; a switching step of closing the top plate (1b) to form the gas mixing chamber (3); a gas mixing process in which the combustible gas is mixed with air flowing in from the second air inlet (5) in the gas mixing chamber (3) to form a premixed gas; a gas outflow process in which the premixed gas flows out from the flame nozzle (6) provided on the top plate (1b); and a gas combustion process in which the premixed gas flowing out from the flame nozzle (6) provided on the top plate (1b) is ignited and burned. [Effects of the Invention]

[0010] By using the solid fuel stove with a simple structure of the present invention, solid fuel such as wood can be used, and flammable gases can be generated by dry distillation and burned in a manner that is close to complete combustion. The flame has a blue color that has a soothing psychological effect, and there is almost no air pollution caused by carbon or polymer components in the exhaust gas, resulting in improved thermal efficiency. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view of a solid fuel stove according to the present invention; [Figure 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 3] 1 is a graph showing the color of the flame when burning wood pellets in a solid fuel stove of the present invention and a conventional stove, and when burning propane in a propane gas stove, in terms of the wavelength of light. [Figure 4] 1 is a graph showing the amount of soot generated in exhaust gas when wood pellets are burned in a solid fuel stove of the present invention and a conventional stove. [Figure 5] FIG. 2 is a conceptual diagram illustrating the solid fuel combustion process of the solid fuel stove of the present invention. [Figure 6] FIG. 1 is a conceptual diagram illustrating the dry distillation process of the solid fuel stove of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described. Note that these embodiments are merely examples shown for the convenience of explanation, and the present invention is not limited to these embodiments in any sense.

[0013] Figure 1 shows an overall perspective view of a solid fuel stove of the present invention. Referring to Figure 1 and Figure 2, which is a cross-sectional view taken along line AA in Figure 1, the solid fuel stove (A) of the present invention comprises a main body (1) having a bottom plate (1a), a top plate (1b), and a side plate (1c), a solid fuel storage section (2) located at the lower inside of the main body (1), a gas mixing chamber (3) located at the upper inside of the main body (1), a first air inlet (4) located at the lower part of the side plate (1c) of the main body (1), a second air inlet (5) located at the upper part of the side plate (1c) of the main body (1), and a flame opening (6) located in the top plate (1b).

[0014] Here, solid fuel refers to fuel other than gaseous fuel and liquid fuel, specifically biomass such as wood, bamboo, and rice husks, coal, waste plastic, waste tires, and powders and granules produced from these raw materials.

[0015] A stove is a heat-generating device that uses a combustion reaction and is primarily used for heating or cooking indoors or outdoors.

[0016] The main body (1) is made of metal or ceramic material and has a cylindrical or hollow triangular, square or polygonal prism shape, and any size is acceptable.

[0017] The bottom plate (1a) is a flat plate located below the packed solid fuel, with a zero or very short gap between it and the solid fuel. It does not necessarily require a grate, ash pan, or forced ventilation device such as a blower.

[0018] The top plate (1b) serves as a lid that conforms to the cross-sectional shape of the main body (1). It is attached to the upper opening of the main body (1) so as to be able to open and close, and is perforated with multiple flame holes (6) that are small compared to the area of ​​the top plate. Various shapes can be used for the top plate (1b), such as a flat plate, a dome shape, a cone shape, a pyramid shape, a truncated cone shape, and a multi-layer flat plate. The top plate (1b) plays a role in mixing flammable gas with air in the gas mixing chamber (3), which will be described later, to form a premixed gas.

[0019] The side plate (1c) forms the housing of the main body, and is cylindrical or has a hollow triangular, square or polygonal prism shape formed by combining flat plates.

[0020] The solid fuel storage section (2) is located in an area surrounded by a side plate (1c) above the bottom plate (1a), and the solid fuel is filled up to the height between the first air inlet (4) and the second air inlet (5).

[0021] The gas mixing chamber (3) is a space located in an area surrounded by side plates (1c) from the top of the solid fuel storage section (2) to the top plate (1b), and forms a premixed gas by mixing the combustible gas generated from the solid fuel with the air drawn in from the second air inlet (5).

[0022] The first air intake (4) is a plurality of holes drilled in the lower part of the side plate (1c) that are small compared to the area of ​​the side plate (1c), through which air from outside the main body (1) is drawn in, contributing to the supply of air to the solid fuel storage section (2).

[0023] The second air intakes (5) are small holes drilled in the upper part of the side plate (1c) compared to the area of ​​the side plate (1c), through which air from outside the main body (1) is drawn in and supplied into the gas mixing chamber (3), where it is mixed with the combustible gas, contributing to the formation of a premixed gas.

[0024] The flame ports (6) are small holes drilled in the top of the top plate (1b) compared to the area of ​​the top plate (1b), through which the purified premixed gas flows out. When the flowing premixed gas is ignited in the flame ports (6), it burns with a blue flame.

[0025] The first air inlet (4), the second air inlet (5) and the flame port (6) may be provided with shutters whose opening degree can be adjusted.

[0026] The method of using the solid fuel stove (A) of the present invention includes a fuel supply step of opening the top plate (1b) and pouring solid fuel into the solid fuel storage section (2) so that the solid fuel is in contact with the bottom plate (1a) and fills the solid fuel storage section (2) up to a height located between the first air inlet (4) and the second air inlet (5); an ignition step of igniting the surface of the solid fuel with a spark; a solid fuel combustion step of burning the surface layer of the solid fuel to a predetermined depth; and a cut step of closing the top plate (1b) to form the gas mixing chamber (3). a dry distillation process for generating combustible gas from the solid fuel with the top plate (1b) closed; a gas mixing process for mixing the combustible gas with air flowing in from the second air inlet (5) in the gas mixing chamber (3) to form a premixed gas; a gas outflow process for causing the premixed gas to flow out from the flame nozzle (6) provided on the top plate (1b); and a gas combustion process for igniting and burning the premixed gas flowing out from the flame nozzle (6) provided on the top plate (1b).

[0027] In the following description of this embodiment, the process up to the switching step will be referred to as the preparation stage for use, and the dry distillation step and thereafter will be referred to as the use stage.

[0028] Here, the fuel supply step is carried out for the purpose of supplying solid fuel, which serves as a heat source for the solid fuel stove (A), to the solid fuel storage section (2). The solid fuel needs to be supplied to the solid fuel storage section (2) so that the surface of the solid fuel stored in the solid fuel storage section (2) is higher than the first air inlet (4) and lower than the second air inlet (5). This is to cause the air from the first air inlet (4) to react with the solid fuel, and also to mix the flammable gas generated from the solid fuel with the air supplied from the second air inlet (5).

[0029] The ignition process is carried out in preparation for use of the solid fuel stove (A) in order to raise the temperature of the solid fuel surface to the combustion initiation temperature in order to start combustion on the solid fuel surface. Ignition can be achieved by using a pilot light on wood or paper, an ignition agent, a gas burner, a lighter, or a spark.

[0030] The solid fuel combustion process is carried out after the preparation stage for use of the solid fuel stove (A) to maintain the temperature of the fuel surface above the combustion temperature for a certain period of time in order to sufficiently promote combustion on the fuel surface. Means for promoting sufficient combustion include removing the top plate (1b), allowing a sufficient amount of air to be drawn in through the first air inlet (4), or providing an air duct on the upper side of the stove body (1) to increase the amount of air supplied to the fuel in the solid fuel storage section (2).

[0031] The phenomenon that occurs in this solid fuel combustion process is conceptually shown in Figure 5. When solid fuel (represented by CmHn) is supplied with sufficient oxygen (O2), it burns to produce carbon dioxide (CO2), water (H2O), and heat.

[0032] The switching process is carried out when the preparation stage for use of the solid fuel stove (A) is completed, by restricting the air supply to the solid fuel storage section (2), in order to transition the fuel combustion to dry distillation (incomplete combustion) and to form the gas mixing chamber (3) above the solid fuel storage section (2). Means for forming the gas mixing chamber (3) include restricting the amount of air supply by closing the top plate (1b) provided at the upper opening of the stove body (1) or by closing a valve to restrict the flow of air to the ventilation pipe provided on the side of the upper part of the stove body (1).

[0033] The carbonization process is carried out in the solid fuel storage section (2) to generate combustible gases, such as carbon monoxide, hydrogen, and various hydrocarbons, from the fuel. The first air inlet (4) must supply sufficient air to the solid fuel storage section (2) to partially continue the combustion of the fuel and to continue the carbonization process using the heat from the partial combustion, but not enough to completely burn the fuel. The opening area of ​​the first air inlet (4) can be adjusted using the adjustable shutter described above to allow adequate air intake. A conceptual diagram of the process is shown in Figure 6. Specifically, the combustion of solid fuel (represented by CmHn) with sufficient oxygen (O2) produces carbon dioxide (CO2), water (HO), and heat.

[0034] Figure 6 shows a conceptual diagram of the phenomena that occur during the carbonization process. Under conditions of limited oxygen (O2) supply during the carbonization process, the following main phenomena occur simultaneously: (1) the formation of a surface carbonized layer (C) due to the combustion of solid fuel (CmHn). (Note: The combustion of the surface of the solid fuel is terminated by limiting the oxygen supply.) (2) the continued combustion of solid fuel (CmHn) below the carbonized layer (C). (3) The formation of carbon monoxide (CO) and hydrogen (H2) due to an endothermic reduction reaction that occurs when the carbon (CO2) and water (H2O) generated in (2) pass through the carbonized layer. In reality, the formation of soot, tar, and low-molecular-weight or high-molecular-weight hydrocarbons also occurs simultaneously, but this is omitted for simplicity.

[0035] The gas mixing process is carried out in the gas mixing chamber (3) to mix the combustible gas obtained in the dry distillation process with the air flowing in through the second air inlet (5) to form a premixed gas (composed of carbon monoxide, hydrogen, various hydrocarbons, oxygen, and nitrogen). The second air inlets (5) must be appropriately sized and located in sufficient number to ensure that a sufficient amount of air is drawn in to form the premixed gas, accompanied by the rising air current of the combustible gas. The gas mixing chamber (3) must also have a certain volume to ensure sufficient mixing of the combustible gas and air. The opening area of ​​the second air inlet (5) can be adjusted using the adjustable shutter to ensure an appropriate amount of air is drawn in through the second air inlet (5).

[0036] In addition, the presence of the top plate (1b) prevents impurities (such as soot (carbon) and tar (high molecular weight hydrocarbons)) in the premixed gas in the gas mixing chamber (3) from escaping from the stove body through the flame port (6) and causing them to fall onto the solid fuel surface or adhere to the inner wall of the gas mixing chamber, which is thought to reduce the amount of impurities in the flammable gas escaping from the flame port (6). In order to adequately remove the impurities in this flammable gas purification process, the number and total area of ​​the openings in the flame port (6) through which the gas flows out must be appropriate for the area of ​​the top plate (1b). In addition, the opening area of ​​the flame port (6) can be adjusted using the adjustable shutter described above to reduce the amount of impurities.

[0037] The gas outlet process is carried out for the purpose of allowing the premixed gas, from which impurities have been removed in the gas purification process, to flow out from the flame port (6). In order to allow a sufficient amount of premixed gas to flow out in the subsequent combustion process to continue combustion, the number and total area of ​​the openings in the flame port (6) through which the gas flows out must be appropriate relative to the area of ​​the top plate (1b). Similarly, the opening area of ​​the flame port (6) can be adjusted using the adjustable shutter described above to allow an appropriate amount of premixed gas to flow out from the flame port (6).

[0038] The gas combustion process is carried out for the purpose of igniting the impurity-free premixed gas that has flowed out from the flame port (6) in the gas outflow process to form a flame. Ignition can be achieved by using a pilot light on wood or paper, an ignition agent, a gas burner, a lighter, a spark, or an electric heating wire. In order to achieve a blue flame and clean combustion in the gas combustion process, it is necessary that a sufficient amount of combustible gas is generated in the dry distillation process, that sufficient air is mixed in the gas mixing process, that impurities are sufficiently removed, and that a sufficient amount of combustible gas is discharged from the flame port (6) in the gas outflow process to continue combustion.

[0039] The solid fuel stove (A) of the present invention produces a blue flame by burning solid fuel, which can have psychological effects such as healing. Furthermore, since the exhaust gas contains almost no impurities such as soot or polymers, it improves the environmental friendliness around the stove, preventing health hazards caused by toxic substances such as soot and polymers contained in the exhaust gas when used for heating, and preventing soot from adhering to the bottom of pots when used for cooking. Furthermore, since the exhaust gas does not contain soot or polymers, a chimney is not required for indoor combustion, reducing equipment costs. Furthermore, heat that would previously have escaped outdoors can now be used for heating, improving thermal efficiency.

[0040] In addition, when using the solid fuel stove of the present invention, in order to maintain a clean environment near the stove, it is necessary to take appropriate measures, such as conducting the solid fuel combustion process, which is the preparation stage for use, outdoors or using a chimney or forced exhaust means to vent outdoors the toxic substances such as soot and polymers contained in the exhaust gases generated during the above process. [Example]

[0041] In an example of a solid fuel stove according to the present invention, a cylindrical steel side panel measuring 125 mm in diameter, 175 mm in height, and 1 mm in thickness was placed vertically, to which a steel bottom panel measuring 125 mm in diameter and 1 mm in thickness was welded, and then a steel top panel measuring 125 mm in diameter and 1 mm in thickness was placed over the body to seal it. 15 3 mm diameter holes were drilled at equal intervals around the circumference of the side panel at a height of 10 mm from the bottom panel to serve as primary air intakes, 30 5 mm diameter holes were drilled at equal intervals around the circumference of the side panel at a height of 145 mm from the bottom panel to serve as secondary air intakes, 24 5 mm diameter holes were drilled at equal intervals at a pitch circle diameter of 70 mm from the center of the top panel to serve as flame openings, and 30 5 mm diameter holes were drilled at equal intervals at a pitch circle diameter of 90 mm from the center of the top panel to serve as flame openings.

[0042] The stove's top was opened, and 1 liter of wood pellets was placed in the solid fuel compartment inside the stove. An ignition agent was placed on the surface of the fuel, and it was ignited with a gas burner. The stove was then left to stand for approximately 10 minutes. After that, the top was closed, and flammable gas flowed out from the flame opening. When the flammable gas was ignited with the gas burner, it began to burn, producing a blue flame. The combustion continued for approximately an hour and a half.

[0043] As shown in Figure 3, when the color of the flame was measured during this time using a spectrophotometer (PMA-11 manufactured by Hamamatsu Photonics K.K.), it was found that it contained almost no light of the red (640-770 nm), orange (590-640 nm), or yellow (550-590 nm) wavelengths, and showed a wavelength distribution shorter than the blue (430-490 nm) equivalent to that of clean-burning propane gas stoves commonly used in homes.

[0044] In addition, when stove exhaust gas was collected according to Method 5G, one of the particulate matter sampling methods specified in the United States Environmental Protection Agency (USEPA) stove certification system, and measured using a soot concentration meter (HT-1850 manufactured by Hodaka Co., Ltd.), it was found that the exhaust gas contained almost no soot or other impurities, except for the period immediately after the ignition of the combustible gas, as shown in Figure 4.

[0045] On the other hand, in conventional stoves such as those shown in Patent Document 1, when wood pellets are used as solid fuel, the flame color ranges from red to yellow. When the color of the flame during combustion in a commercially available stove was measured using a spectrophotometer (PMA-11 manufactured by Hamamatsu Photonics K.K.), it was found that the flame contained light with wavelengths of red (640 to 770 nm), orange (590 to 640 nm), and yellow (550 to 590 nm), which are completely different from those of clean-burning propane gas stoves typically used in homes.

[0046] Furthermore, when solid fuel was burned in the above-mentioned conventional stove, the exhaust gas from the stove was collected according to Method 5G, one of the particulate matter sampling methods specified in the stove certification system of the United States Environmental Protection Agency (USEPA), and measured using a soot concentration meter (HT-1850 manufactured by Hodaka Co., Ltd.). As shown in Figure 4, it was found that the exhaust gas contained large amounts of impurities such as soot, including immediately after the ignition of the combustible gas. [Explanation of symbols]

[0047] A. Solid fuel stove 1 Main body 1a Bottom plate 1b Top plate 1c side plate 2. Solid fuel storage section 3 Gas mixing chamber 4 First air supply port 5 Second air supply port 6 flame mouth 7 Fuel surface

Claims

1. A solid fuel stove comprising a main body (1) having a bottom plate (1a), an openable top plate (1b), and side plates (1c), A solid fuel storage section (2) is provided at the lower inside of the main body section (1), A gas mixing chamber (3) is provided at the top of the inside of the main body (1), a first air intake port (4) provided at a position above the bottom plate (1a) in the lower part of the side plate (1c) of the main body portion (1); a second air intake port (5) provided on the upper part of the side plate (1c) of the main body portion (1); and, A flame port (6) provided on the top plate (1b) A solid fuel stove (A) characterized by comprising:

2. a fuel supply step of opening the top plate (1b) of the solid fuel storage section (2) of the solid fuel stove (A) according to claim 1, and pouring solid fuel into the solid fuel storage section (2) so that the solid fuel is in contact with the bottom plate (1a) and fills the solid fuel up to a height located between the first air inlet (4) and the second air inlet (5); an ignition step of igniting the surface of the uppermost layer of the solid fuel with a spark; a solid fuel combustion step of burning the solid fuel from the top layer to a predetermined depth; a switching step of forming the gas mixing chamber (3) by closing the top plate (1b); a dry distillation step of generating a combustible gas from the solid fuel while the top plate (1b) is closed; a gas mixing step of mixing the combustible gas with air flowing in from the second air inlet (5) in the gas mixing chamber (3) to form a premixed gas; a gas outflow step in which the premixed gas flows out from the flame port (6) provided on the top plate (1b); a gas combustion step of igniting and burning the premixed gas flowing out from the flame port (6) provided on the top plate (1b); A method for using a solid fuel stove (A), comprising:

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