JP7696166B2 - Combustion furnace and combustion furnace system - Google Patents

Description

The present invention relates to a combustion furnace and a combustion furnace system that can suitably use waste-derived solid fuels such as RPF (refuse derived paper and plastics densified fuel, hereinafter referred to as RPF), which are made primarily from waste plastics and other materials.

Conventionally, small combustion furnaces include wood pellet stoves and firewood boilers that can burn large amounts of firewood for long periods of time, but as heating equipment for use in greenhouses and the like, they have issues with high fuel costs and insufficient heat output. Another issue with firewood-fired hot water boiler combustion furnaces is that combustion is not constant due to differences in the moisture content and tree species of the firewood itself, making stable combustion difficult. Furthermore, many commonly used combustion furnaces have used fossil fuels such as petroleum, but there is a demand for combustion furnaces that can use cheaper fuels to replace petroleum in order to address issues of reducing carbon dioxide emissions and cost savings.

As a result, waste-derived fuels have been attracting attention as a cheap, high-calorie fuel. Known examples of waste-derived fuels include RPF and RDF (Refuse Derived Fuel), which are made by crushing plastic waste from which as much chlorine-based plastic as possible has been removed, mixing this with paper and wood waste, and forming it into pellets or dumplings. In recent years, in order to realize a transition to a sustainable recycling-based society, there has been an active movement to use waste-derived fuels such as RPF as fuel, also from the perspective of utilizing waste plastics, and there is an increasing demand for the development of combustion furnaces that are small and simple in structure and capable of stable combustion for long periods of time.

However, when waste solid fuels such as RPF are burned in a typical combustion furnace, the combustion temperature is low at around 500 degrees, resulting in black smoke and an unpleasant odor. In addition, unburned and molten plastic adheres to the inside of the furnace, making it practically difficult to use RPF as fuel in a furnace that burns regular firewood. Furthermore, there is concern that dioxins may be generated when burning at low temperatures as described above, so it is necessary to burn at high temperatures of over 800 degrees. However, when burning at high temperatures in a conventional furnace, the ash accumulated inside the furnace melts and solidifies due to the high heat, reducing the volume inside the combustion chamber and impairing the flow of combustion air, making it impossible to burn stably for long periods of time.

The following Patent Document 1 discloses a hot air generating furnace that uses a rotary kiln system and uses solid waste fuel as fuel. It describes that the furnace is equipped with an air supply means that supplies re-combustion air to a storage hopper that stores the combustion ash of the solid fuel discharged from the kiln body and solid unburned fuel, and that the solid unburned fuel is combusted and decomposed into ash by the re-combustion air.

The following Patent Document 2 discloses an RPF combustion furnace. It is equipped with multiple primary combustion air outlets at the front lower part of the combustion furnace, and a secondary combustion air outlet pipe with multiple outlet holes near the rear upper part of the combustion furnace, and it is disclosed that primary fuel air is blown into the RPF to cause combustion, blowing the combustion flame and unburned powder to the back of the combustion chamber, and hot secondary combustion air is sprayed from above onto the unburned powder to cause complete combustion.

JP 2015-87047 A JP 2020-60317 A

The device disclosed in the above Patent Document 1 is a rotary kiln type, so a rotary mechanism is essential, making it difficult to make the device small and simplifying the structure. The device disclosed in the above Patent Document 2 has a structure that can be made small, but since high-pressure air is sent from the top of the combustion chamber to blow the solid fuel to the back of the combustion chamber, and then high-temperature secondary combustion air is blown onto the solid fuel to burn it, if the distance between the back of the combustion chamber and the ash storage section is short, the fuel may fly unburned to the ash storage section at the back of the combustion chamber, and unburned fuel may remain due to lack of oxygen. This is thought to occur because the raw material for RPF is waste, and the amount of combustion air flowing in cannot be adjusted to correspond to the change in combustion speed due to the difference in combustion heat value. Also, if the temperature of the combustion air sent into the combustion chamber does not reach the ignition temperature of the solid fuel, it will ignite after reaching the back of the combustion chamber, so the solid fuel will accumulate in the ash storage section at the back of the combustion chamber before it burns out, and ash will accumulate on top of it, which may also result in unburned fuel due to lack of oxygen.

The present invention was made in consideration of the above-mentioned circumstances, and aims to provide a combustion furnace and a combustion furnace system that can efficiently burn waste-derived fuel while having a simple structure.

In order to achieve the above object, the combustion furnace according to the present invention is a combustion furnace equipped with a combustion chamber that burns fuel and causes primary combustion, and a heat riser that causes secondary combustion, the combustion chamber and the heat riser are arranged in a generally L-shape and communicate with each other, the combustion chamber is provided with a heating pipe that is arranged in the combustion chamber and heats the air flowing therethrough to a temperature exceeding the ignition point of the fuel, the heating pipe has a hot air outlet from which the air heated in the combustion chamber blows out, and the air blowing out from the hot air outlet has a wind pressure that blows the fuel introduced into the combustion chamber from the front side to the heat riser arranged at the back side.

In order to achieve the above-mentioned object, the fuel furnace system of the present invention has a rocket stove structure equipped with a combustion chamber in which fuel is burned to cause primary combustion, and a heat riser in which secondary combustion is caused, and the combustion chamber is provided with a heating pipe arranged in the combustion chamber so that the air flowing therethrough is heated to a temperature exceeding the ignition point of the fuel, and the heating pipe has a hot air outlet from which the air heated in the combustion chamber is blown out, and the air blown out from the hot air outlet has a wind pressure that blows the fuel fed into the combustion chamber from the front side to the heat riser arranged in the back side, and is characterized by comprising: a combustion furnace; and a dust collector having a cyclone that uses an ascending air current to collect gas, fly ash, etc. generated in the heat riser and forcibly exhaust them.

The combustion furnace and combustion furnace system of the present invention are configured as described above, and therefore can efficiently burn waste-derived fuel while having a simple structure.

FIG. 1 is a schematic perspective view for explaining the configuration of a combustion furnace and a combustion furnace system according to an embodiment of the present invention. FIG. 2 is a block diagram for explaining the combustion furnace and the combustion furnace system shown in FIG. 1 . FIG. 2A is a schematic perspective view for explaining the interior of a combustion chamber of a combustion furnace, and FIG. 2B is a schematic view for further explaining the same combustion furnace, shown partially in cross section. FIG. 13 is a block diagram for explaining a modified example of the combustion furnace and the combustion furnace system according to the embodiment. 1A to 1C are diagrams for explaining an example of a combustion test, in which (a) is a photograph showing an example of the display unit of a controller of a combustion furnace system, (b) is a photograph of waste-derived fuel being put into a combustion chamber and being burned, and (c) is a photograph of the state after combustion. 1A to 1C are diagrams for explaining an example of a combustion test, in which (a) is a photograph showing the inside of the ash pond after the combustion test was completed, (b) is a photograph showing the state before the start of the combustion test, in which waste-derived fuel has been poured into the fuel hopper, and (c) is a photograph showing the state after the combustion test was completed.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, a combustion furnace 1 and a combustion furnace system 100, 100A according to the present embodiment will be described with reference to Figs. 1 to 4. The combustion furnace 1 shown here is a so-called rocket stove type combustion furnace. The combustion furnace 1 includes a combustion chamber 11 that burns fuel R to cause primary combustion, a heat riser 13 that causes secondary combustion, and the combustion chamber 11 and the heat riser 13 that are arranged in a generally L-shaped manner and communicate with each other. The combustion chamber 11 constitutes a burn tunnel that is arranged in a generally horizontal direction below the heat riser 13, and the heat riser 13 is a heat riser that is arranged in a generally vertical direction relative to the combustion chamber 11. As a result, when the flame and combustion gas generated in the combustion chamber 11 pass through the heat riser 13, a strong updraft is generated, and secondary combustion can be caused inside the heat riser. In the illustrated example, the combustion chamber 11 and the heat riser 13 are arranged in a generally L-shaped manner and communicate with each other, but the present invention is not limited to this, and the combustion furnace may be an approximately J-shaped combustion furnace with a fire opening to the combustion chamber at an upper position. In the illustrated example, the cross-sectional areas of the combustion chamber 11, heat riser 13, and exhaust pipe 4a are configured so that the combustion chamber 11 is larger, but this is not limited to this and they may all have approximately the same cross-sectional area, or, in order to increase combustion efficiency, the cross-sectional area of the heat riser 13 may be configured to be larger than that of the combustion chamber 11, and the cross-sectional area of the exhaust pipe 4a may be configured to be larger than that of the heat riser 13.

The fuel R used here is preferably RPF, which has been difficult to make into a fuel that burns stably until now. According to the combustion furnace 1 of this embodiment, RPF can be burned efficiently at a high temperature of 800 degrees or more, so there is no risk of unburned molten plastic adhering to the inside of the combustion chamber 11, and there is no risk of black smoke or unpleasant odors occurring during low-temperature combustion. As RPF, a commercially available fuel with low cost and high calorie content can be used, and RPF with a diameter of 8 mm or 40 mm is generally available, but either one is acceptable. In addition, the fuel R may be something other than RPF, and it may be used by mixing RPF with various wood materials described later, or it may be used as fuel R without mixing. Examples of wood materials include twigs, fallen leaves, firewood, logs, square timber, and waste building materials. In addition, waste wood chips for shiitake mushroom log cultivation, bamboo chips, crushed PET bottle fluff, wood-based sawdust briquettes, etc. used in the combustion test described later may be mixed with RPF, or they may be used as fuel R without mixing.

As shown in Figures 1 and 2, the combustion furnace 1 is equipped with a fuel hopper 2 that sends out fuel R into the combustion chamber 11 and stores the fuel R, a blower 3 that supplies air to the heating pipe 11c, a dust collector 4 that collects fly ash and dust contained in the secondary combustion air that has passed through the heat riser 13, an ash storage section 5 that is located below the cyclone 40 of the dust collector 4 and stores ash, and an exhaust blower 6 that exhausts the air purified by the cyclone 40 in addition to high-temperature combustion, thereby forming a combustion furnace system 100. The structure of the cyclone 40 is not particularly limited, and may be, for example, a centrifugal force type or a ventilation type.

The fuel hopper 2 is formed in a funnel shape with an inlet that opens at the top and gradually narrows toward the bottom, and is configured to store a large amount of fuel R, and a screw 21 is provided at the bottom to send the fuel R to the combustion furnace 1. The fuel hopper 2 has an inlet control unit 20 that can automatically control the amount of fuel R input, and the inlet control unit 30 has a CPU 20a that performs various controls and a screw starter unit 20b that rotates and starts the screw 21. The fuel hopper 2 and the combustion furnace 1 are connected by a fuel supply pipe 2a through which the fuel R flows, and the fuel R is input from the fuel inlet 11a through the fuel supply pipe 2a. The configuration for storing the fuel R is not limited to the example shown in the figure, and the means for transporting the fuel R is not limited to a screw 21 type conveyor, but may be a belt type conveyor.

The combustion furnace 1 is equipped with a temperature control unit 10, which is equipped with a CPU 10a that performs various controls, an operation unit 10b that operates the temperature setting, a display unit 10c that displays the temperature inside the combustion chamber 11, etc., and a temperature detection unit 10d that detects the temperature inside the combustion chamber 11, etc., and this temperature control unit 10 is electrically connected to the input control unit 20. Therefore, when the temperature inside the combustion chamber 11 is set to 800°C, for example, using the operation unit 10b of the temperature control unit 10, the input amount of fuel R is controlled according to this temperature setting. This allows automatic input of fuel R, making continuous combustion operation possible.

The combustion chamber 11 is equipped with a fuel inlet 11a, an opening/closing door 11b with a glass window, and a heating pipe 11c. The fuel inlet 11a is provided to open at the top of the combustion chamber 11, and is configured so that the fuel R carried through the fuel supply pipe 2a falls from above to a position surrounded by the heating pipe 11c as shown in FIG. 3(a). The opening/closing door 11b is attached so as to be freely opened and closed so as to cover the opening 11ba formed on the front side of the combustion chamber 11. The opening/closing door 11b is provided with a glass window, and the inside of the combustion chamber 11 can be seen through this glass window even when the opening/closing door 11b is closed. The heating pipe 11c is made of a metal material or the like, and is provided in the combustion chamber 11 as shown in FIG. 3(a) and FIG. 3(b). The heating pipe 11c is connected to the air supply pipe 3a that carries the air supplied from the blower 3, and is generally L-shaped in side view and generally rectangular in plan view, with a space in the center surrounded by the heating pipe 11c for introducing fuel R. In the illustrated example, the heating pipe 11c is shown as a rectangular hollow pipe, but is not limited to this and may be round.

The heating pipe 11c includes straight sections 11ca, 11ce arranged along the bottom 11e of the combustion chamber 11 from the fuel inlet 11a side toward the back of the combustion chamber 11, standing sections 11cb, 11cd formed in a roughly L-shape in side view toward the heat riser 13 side, a bridge section 11cc provided between the standing sections 11cb, 11cd, and a blowing section 11cf arranged opposite the bridge section 11cc and near the opening and closing door 11b. As shown in FIG. 3(a), the blowing section 11cf is provided with multiple hot air outlets 11d. The number of hot air outlets 11d is not limited to four as shown in the example, and is set according to the size of the combustion chamber 11, etc.

The heating pipe 11c may be formed by bending a single hollow pipe, and the end 11cg of the blowing portion 11cf abuts against the wall outer surface of the straight portion 11ca on the blowing pipe 3a side. Therefore, as shown by the arrow in Figure 3 (a), the air passing through the heating pipe 11c is first supplied from the blower 3 through the blowing pipe 3a, passes through the straight portion 11ca, passes through the upright portion 11cb, the bridge portion 11cc, and the upright portion 11cd, and then passes through the straight portion 11ce to reach the blowing portion 11cf. In other words, the air flows in a one-way direction, and the air that reaches the blowing portion 11cf has nowhere to go, so it is blown out from the hot air outlet 11d. The air passing through the heating pipe 11c before reaching the hot air outlet 11d is heated to a high temperature by the heat of combustion inside the combustion chamber 11, so when it is blown out from the hot air outlet 11d, it becomes hot air. By arranging the heating pipe 11c in the shape shown in FIG. 3(a) inside the combustion chamber 11 in this way, the air flowing through the heating pipe 11c can be heated to the same temperature as inside the combustion chamber 11. At this time, the air blown out from the hot air outlet 11d has a wind pressure that blows the fuel R input into the combustion chamber 11 from the front side to the heat riser 13 located at the back side of the combustion chamber 11. The wind pressure can be adjusted by the blower 3.

The shape and structure of the heating pipe 11c are not limited to the example shown in the figure, and may be, for example, serpentine or complex so as to heat the air sufficiently inside the combustion chamber 11. However, the shape shown in FIG. 3(a) etc. can sufficiently heat the air passing through the heating pipe 11c without impeding the introduction of fuel R, while maintaining the wind pressure and having a simple structure.

The rising position of the rising part 11cd of the heating pipe 11c is directly below the front position of the heat riser 13 in the illustrated example, but is not limited to this. For example, since the flow of the flame may change depending on the fuel R, it may be any position from the back of the heat riser 13 to the front part on the drawing. In short, it is important that the air blown out from the hot air outlet 11d is made into high-temperature hot air and has a wind pressure that blows the fuel R introduced into the combustion chamber 11 from the front side of the combustion chamber 11 to the heat riser 13 side arranged at the back side. With the above configuration, the fuel R introduced into the combustion chamber 11 is blown from the front side to the heat riser 13 side by the air blown out from the hot air outlet 11d, so that the fuel R can be burned efficiently while being blown to the back side of the combustion chamber 11. Moreover, the air blown out from the hot air outlet 11d is hot air heated in the combustion chamber 11, so it burns the fuel R quickly and directs the combustion flame and combustion ash to the heat riser 13 side, achieving a level of combustion close to complete combustion at a higher temperature and efficiency in the primary combustion stage. It is essential that the temperature of the air blown out from the heating pipe 11c is heated to or above the ignition temperature of the fuel R to promote primary combustion. For example, the ignition point (ignition temperature) of RPF is set to 200 to 230 degrees, and that of wood materials is set to 400 to 500 degrees, but the fuel furnace 1 can be temperature controlled at around 800 degrees, so the temperature of the air passing through the heating pipe 11c can be heated to a temperature that is sufficiently above the ignition point (ignition temperature).

The combustion furnace 1 further includes a heat riser 13 and a heat radiation tube 12. The heat riser 13 has a roughly cylindrical chimney structure, and the heat riser 13 is surrounded by a heat radiation tube 12 made of heat insulating material. This allows the heat riser 13 to be kept at a high temperature, and the chimney effect of the heat riser 13 generates an updraft. In this way, the combustion flame and combustion ash generated in the above-mentioned combustion chamber 11 can be promoted by the updraft caused by the draft effect of the heat riser 13 to promote secondary combustion of the fuel R. In addition, this updraft can quickly transport the fly ash to the cyclone 40 without storing it in the combustion chamber 11, so ash accumulation inside the combustion chamber 11 can be significantly suppressed (see Figure 5 (c)), and stable combustion can be achieved for a long time.

The heat riser 13 and the dust collector 4 are connected via an exhaust pipe 4a, and the dust collector 4 has a cyclone 40 that uses the rising air current to collect gas and fly ash generated in the heat riser 13 and forcibly exhaust them. And below the dust collector 4 is an ash storage section 5 that stores the collected ash and dust. Meanwhile, the dust collector 4 is also connected to an exhaust blower 6. The ash storage section 5 is provided in a position separated from the combustion chamber 11 and the heat riser 13, and the ash and dust are guided to the ash storage section 5 by the cyclone 40, and the air purified by the cyclone 40 is drawn to the exhaust blower 6, which exhausts it to the outside.

And, according to the combustion furnace system 100 configured as above, the fuel R fed from the fuel hopper 2 at a constant speed through the screw 21 is dropped into the combustion chamber 11, where it burns stably and the ash of the combustion residue is discharged smoothly and quickly from the combustion chamber 11, so that the generation of ash melting (clinker) can be suppressed. In addition, since the fuel R is burned at a level close to complete combustion, it is possible to perform stable combustion for a long time without emitting any foul odor or black smoke. Due to the recent global rise in fuel prices, places that require a heat source are struggling with the significant increase in fuel consumption costs, but by using RPF, which currently costs about 10 yen per unit, as fuel R, fuel consumption can be significantly reduced compared to kerosene fuel. In addition, the development of the combustion furnace 1 and the combustion furnace system 100 that realize long-term stable combustion of RPF, which was not possible with conventional small combustion furnaces, can greatly contribute to society and has an effective effect on the effective use of waste and the reduction of marine plastic pollution. In addition, a predetermined amount of fuel R can be automatically fed into the combustion furnace 1 to maintain the desired temperature, making it suitable for use in heating systems for homes and facilities, as well as in heating systems for greenhouse cultivation of agricultural plants.

In addition to the above-mentioned configuration of the combustion furnace system 100, a heat exchanger 8 and a water tank 9 are provided as shown in FIG. 4 to form the combustion furnace system 100A, which can be used to form a hot water boiler. In this case, if the cyclone 40 and the heat exchanger 8 are attached to the same water tank 9 as shown in FIG. 4, the hot water boiler can be made smaller, and the heat dissipated from the cyclone 40 can be efficiently taken in, improving the heat exchange capacity. In addition, in the combustion furnace system 100A of this embodiment, ash and dust discharged from the combustion chamber 11 are removed by the cyclone 40, and only the purified hot air can be sent to the heat exchanger 8, so that the inside of the heat exchanger 8 is less likely to become dirty, and maintenance work can be reduced.

Next, the combustion furnace 1 and the combustion furnace system 100 according to this embodiment will be further described with reference to Figures 5 and 6, including actual combustion tests performed using various fuels.

The above-mentioned Patent Document 2 was developed by the present inventor, and the combustion furnace of the above-mentioned Patent Document 2 adopts a structure in which a certain amount of fuel is automatically supplied into the combustion chamber, combustion air is sent to the supplied fuel and blown into the inner part of the combustion chamber, while hot air is injected from a secondary combustion air outlet pipe installed in the inner part of the combustion chamber, and combustion residues such as ash are sent to an ash storage section installed in the inner part of the combustion chamber. However, the results of combustion experiments using this combustion furnace showed that when the fuel was blown into the inner part of the combustion chamber and the high-temperature secondary combustion air was blown to the ash storage section, the distance between the inner part of the combustion chamber and the ash storage section was short, so the fuel flew unburned to the ash storage section in the inner part of the combustion chamber, and there were cases where unburned fuel remained due to a lack of oxygen. In addition, since the temperature of the combustion air sent to the fuel put into the combustion chamber does not reach the ignition temperature of the fuel, the fuel was ignited after reaching the inner part of the combustion chamber, and before the fuel burned out, it accumulated in the ash storage section in the inner part of the combustion chamber, and if ash accumulated on top of it, unburned fuel occurred due to a lack of oxygen. Therefore, the present inventor solved the problem 1. After the fuel is charged, it is ignited immediately, and after task 2. complete combustion occurs within the combustion chamber 11, task 3. Further development was carried out to improve the structure to quickly exhaust the combustion residue from the combustion chamber 11, resulting in the combustion furnace 1 and combustion furnace system 100 (100A) of this embodiment.

<Regarding issue 1>
First, in order to immediately ignite the fuel R after it is thrown into the combustion chamber 11, a heating pipe 11c is provided inside the combustion chamber 11, and air is sent through the air supply pipe 3a connected to the heating pipe 11c by the blower 3. The sent air is heated by the combustion heat inside the combustion chamber 11 while traveling through the straight portion 11ca, the upright portion 11cb, the bridging portion 11cc, the upright portion 11cb, and the straight portion 11ca of the heating pipe 11c, and by the time it reaches the hot air outlet 11d, the air temperature is sufficiently above the ignition point of the fuel, which is about 230 degrees, and the dropped fuel R is successfully ignited immediately by blowing the heated air over it (see FIG. 5(b)).

<Regarding issue 2>
In order to burn the fuel R in the combustion chamber 11 to a level that can be considered complete combustion, the structure of the combustion furnace 1 is designed to be that of a rocket stove. When the combustible gas remaining in the combustion chamber 11 passes through the inner tube of the heat riser 13 of the rocket stove, it rises and burns while being exposed to high temperatures, so we have succeeded in burning the fuel R sufficiently with almost no unburned residue (see Figure 5(c)).
<Regarding issue 3>
As a method for immediately discharging the combustion residue from the combustion chamber 11, high-temperature air that is sufficiently higher than the ignition temperature of the fuel is blown from the hot air outlet 11d onto the surface of the dropped fuel R, which generates combustible gas due to a thermal reaction from the outer surface of the fuel R, thereby efficiently combusting the fuel R. At this time, the waste plastic contained in the fuel R does not melt and becomes liquid, and since it burns quickly, the ash of the combustion residue does not melt, and is successfully discharged in a powder state quickly outside the combustion chamber 11 by the rising air current of the heat riser 13 and the negative pressure effect of the cyclone 40 and the exhaust fan 6 (see Figures 5(c) and 6(a)).

A wide variety of fuels were subjected to combustion tests for more than 12 consecutive hours in the combustion furnace 1 and the combustion furnace system 100 according to this embodiment, and the results are listed below.
<Combustion test using 8mm diameter RPF>
A combustion test was conducted using an 8 mm diameter RPF. Because it is small and pellet-shaped, it was easy to automatically feed it into the combustion chamber, and it ignited immediately after being dropped into the combustion chamber, allowing stable combustion. Figure 5 (a) shows the display when a combustion test was conducted using an 8 mm diameter RPF. The temperature in the combustion chamber reached 870.6°C and was able to be kept at around 860°C. Figure 5 (b) is a photograph taken during the combustion test. From this photograph, it can be seen that the fuel cannot be seen in front of the combustion chamber, but is being blown to the back and that a combustion flame is rising at the back of the combustion chamber. In this combustion test, 600 kg of RPF was used in a full fuel hopper (see Figure 6 (b)), and about 12 kg was consumed per hour, the amount of fuel fed at one time was about 50 g (about a handful), and continuous combustion for 50 hours was successful. Figure 6(c) is a photograph of the fuel hopper taken from above after 50 hours, and Figure 6(a) is a photograph of the ash discharged from the combustion test and accumulated in the ash storage area. Figure 6(a) shows that no unmelted plastic or other substances were found, and that the ash was collected in good condition. Figure 5(c) is a photograph of the state of the combustion chamber after the combustion test. This photograph shows that no unburned melted plastic was found adhering to the front or back of the combustion chamber.

<Combustion test using 40mm diameter RPF>
A combustion test was conducted using an RPF with a diameter of 40 mm. The 40 mm RPF was able to ignite immediately after being dropped into the combustion chamber and burn stably, just like the 8 mm RPF. In addition, some 40 mm RPFs contain glass wool, which is a non-combustible material, and this glass wool melts and remains in the combustion chamber, so it was found that it is preferable to use RPFs that do not contain such non-combustible materials.

<Combustion test using waste wood chips for shiitake mushroom cultivation>
A combustion test was conducted using waste wood chips from Shiitake log cultivation. The waste wood chips from Shiitake log cultivation were also able to ignite immediately after being dropped into the combustion chamber and burn stably. The waste wood chips from Shiitake log cultivation have a lower calorific value compared to RPF, but a lot of fuel is required to obtain the same amount of heat as RPF. In addition, because of their light specific gravity, they do not easily ride on the screw, so it was found that it is best to attach a vibrator to the fuel hopper and feed it while applying intermittent vibrations.

<Combustion test using bamboo chips>
A combustion test was conducted using bamboo chips. Bamboo chips also ignited immediately after being dropped into the combustion chamber and were able to burn stably. Bamboo chips have a higher calorific value than waste wood chips used for Shiitake mushroom cultivation, but more fuel is required to obtain the same amount of heat as RPF.

<Combustion test using crushed PET bottle fluff>
A combustion test was conducted using crushed PET bottle fluff. The crushed PET bottle fluff also ignited immediately after being dropped into the combustion chamber and burned stably. In the test of the crushed PET bottle fluff, the crushed PET bottle fluff was sprinkled with about 10% of waste edible oil and burned under the assumption that when edible oil is collected in a PET bottle, it is difficult to recycle it because the oil is attached to the PET bottle. In this case, the combustion was almost the same as that of RPF, and the amount of ash was very small.

<Combustion test using wood sawdust briquettes>
A combustion test was conducted using wood sawdust briquettes. Wood sawdust briquettes also ignited immediately after being dropped into the combustion chamber and burned stably. Like wood sawdust briquettes and bamboo chips, they have a higher calorific value than waste wood chips for mushroom cultivation, but more fuel is required to obtain the same amount of heat as RPF.

As described above, the configuration and aspects of the combustion furnace 1 and combustion furnace system 100 (100A) according to this embodiment are not limited to the above embodiment.

1 Combustion furnace 100, 100A Combustion furnace system 10 Temperature control unit 11 Combustion chamber 11a Fuel inlet 11b Opening and closing door 11c Heating pipe 11d Hot air outlet 12 Heat dissipation tube 13 Heat riser 2 Fuel hopper 3 Blower 4 Dust collector 5 Ash storage section 6 Exhaust blower
9 Water tank 8 Heat exchanger R Fuel

Claims (7)

A combustion furnace comprising a combustion chamber for burning fuel to cause primary combustion and a heat riser for causing secondary combustion, the combustion chamber and the heat riser being arranged in a generally L-shape and in communication with each other,
A heating pipe is provided in the combustion chamber so that air flowing through the combustion chamber is heated to a temperature exceeding an ignition point of fuel,
The heating pipe has a hot air outlet through which air heated in the combustion chamber is blown out,
A combustion furnace in which the air blown out from the hot air outlet has a wind pressure that blows the fuel fed into the combustion chamber from the front side toward the heat riser arranged at the back side. In claim 1,
The heating pipe is formed in a substantially rectangular shape in a plan view, and has an upright portion formed in a substantially L-shape in a side view. In claim 1 or 2,
A combustion furnace in which the fuel is RPF. A combustion furnace system having a rocket stove structure with a combustion chamber that burns fuel to cause primary combustion and a heat riser that causes secondary combustion, wherein a heating pipe is disposed within the combustion chamber so that the air flowing through the combustion chamber is heated to a temperature exceeding the ignition point of the fuel, wherein the heating pipe has a hot air outlet through which the air heated within the combustion chamber is blown out, and the air blown out from the hot air outlet has a wind pressure that blows the fuel fed into the combustion chamber from the front side to the heat riser side disposed at the back side, and wherein the combustion furnace system has a dust collector having a cyclone that uses an ascending air current to collect gas, fly ash, etc. generated within the heat riser and forcibly exhaust them. In claim 4,
The combustion furnace system is provided with an ash storage section below the dust collector for storing collected fly ash, etc. In claim 5,
The combustion furnace system further includes an exhaust fan that draws in the hot air that has passed through the dust collector and exhausts it to the outside. In claim 4,
The combustion furnace system further includes a hot water boiler having a heat exchanger that takes in hot air from the cyclone and a water storage tank.