Boiler lower hopper arching removal system

Abstract

To safely remove arching during operation of a combustion plant equipped with a boiler, without damaging the hopper below the boiler. [Solution] The removal system 1 includes a projectile launcher 22 that launches projectiles towards an arching formed by fly ash 21 that has fallen from the flue 5 into the boiler lower hopper 16 through an opening 23 formed in the wall surface of the boiler lower hopper 16, and a temperature sensor 26 that measures the temperature of the outer or inner surface of the boiler lower hopper 16 below the arching and near the hopper outlet 17, or the outer or inner surface of the falling fly ash transfer device 18 near the hopper outlet 17, or the outer or inner surface of the piping 28, and a pressure sensor 25 that measures the air pressure inside the falling fly ash transfer device 18, or either one or both. The control device 29 launches projectiles from the projectile launcher 22 during the operation of the combustion plant 2 based on the temperature information measured by the temperature sensor 26 or the air pressure information measured by the pressure sensor 25.

Description

Technical Field

[0001] The present invention relates to an arching removal system for a boiler lower hopper in a combustion plant equipped with a boiler.

Background Art

[0002] In facilities such as a cleaning plant that burns waste and generates electricity while equipped with a boiler, or a power plant that burns fuels such as coal, that is, in a combustion plant equipped with a boiler, in order to prevent fly ash in exhaust gas from adhering to heat transfer tubes arranged in a flue and reducing the heat conversion efficiency, the adhered fly ash has been removed by an ash removal device using steam or a pressure wave. Then, the removed fly ash (hereinafter referred to as "falling fly ash") falls into a hopper arranged below the boiler (hereinafter referred to as "boiler lower hopper"), and after that, it is discharged from a hopper discharge port formed below the boiler lower hopper and transferred from the boiler lower hopper to the outside of the combustion plant.

[0003] On the other hand, not limited to heat transfer tubes, fly ash adheres to the flue, and if this grows, it may affect the discharge of exhaust gas. Therefore, in order to remove fly ash adhering to the flue not limited to heat transfer tubes, as a type of ash removal device, an injection device that injects bullets made of non-metallic materials such as fly ash at the adhered fly ash has been developed. Examples of such injection devices include an injection device that injects bullets between two rotating bodies like a pitching machine (Patent Document 1), and an injection device that injects bullets using high-pressure gas such as compressed air (Patent Documents 2 and 3).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

[0005] Fallen fly ash ranges in size from fine particles to lumpy flakes, exhibiting a wide range of dimensions. When multiple lumpy flakes fall from the flue into the boiler hopper, arching can occur. If arching in the boiler hopper blocks the hopper outlet, the fallen fly ash cannot be transported out of the hopper. As a result, the flue narrows, potentially affecting exhaust gas discharge. Therefore, to remove arching and facilitate the discharge of fallen fly ash from the hopper outlet, it is conceivable to use the aforementioned injection device during combustion plant operation.

[0006] The location where arching occurs is near the hopper outlet, and its position is known. On the other hand, the exhaust gas is toxic to humans. Therefore, it is preferable to apply a technique that starts the injection device while the combustion plant is running without opening the door connecting the inside and outside of the flue, rather than a technique that opens the door, such as a manhole, connecting the inside and outside of the flue when the injection device is started, as described in Patent Documents 1 and 2.

[0007] However, if the launching mechanism is activated when the arching is not present, even non-metallic projectiles may damage the hopper below the boiler. Therefore, it is necessary to confirm that the arching has already formed and is maintaining its shape before activating the launching mechanism.

[0008] However, during combustion plant operation, the boiler hopper becomes a sealed space through which high-temperature exhaust gas flows, making it difficult to place an imaging device inside the boiler hopper to check the arching condition. Therefore, there has been a need for a system that can appropriately detect the arching condition inside the boiler hopper during combustion plant operation by other means and activate the injection device accordingly.

[0009] The present invention has been made in view of the above problems, and aims to provide a boiler-bottom hopper arching removal system that can safely remove arching that occurs in the boiler-bottom hopper without damaging the boiler-bottom hopper during operation of a combustion plant equipped with a boiler. [Means for solving the problem]

[0010] The arching removal system for the boiler hopper of the present invention is A boiler-bottom hopper is provided, in which exhaust gas containing fly ash from a combustion plant equipped with a boiler is drawn into an induced draft fan and flows through a flue, the fly ash adheres to heat transfer tubes arranged in the flue, and the fly ash that falls through the flue is discharged as fallen fly ash from the hopper outlet, A projectile launcher that launches projectiles, mainly composed of non-metallic materials, towards an arching formed by the falling fly ash near the hopper discharge port, through an opening formed in the wall of the hopper below the boiler, A fall ash transfer device is provided, wherein a fall ash inlet is connected to the hopper outlet either directly or indirectly by piping, and the fall ash introduced from the fall ash inlet is discharged from the fall ash outlet. A temperature sensor that measures the temperature of the outer or inner surface of the boiler lower hopper below the arching and near the hopper outlet, or the outer or inner surface of the falling fly ash transfer device near the hopper outlet, or the outer or inner surface of the piping, and a pressure sensor that measures the air pressure inside the boiler lower hopper below the arching and near the hopper outlet, or inside the falling fly ash transfer device near the hopper outlet, or inside the piping, either one or both of these, The system includes at least a control device that receives temperature information measured by the temperature sensor or air pressure information measured by the pressure sensor, and, based on the temperature information or air pressure information, causes the projectile to be launched from the projectile launcher during the operation of the combustion plant. The path of the projectile from the projectile launching device to the opening is kept airtight.

[0011] Furthermore, if the temperature sensor is not installed but the pressure sensor is installed, the control device will cause the projectile launcher to launch the projectile when the air pressure information indicates that the air pressure has increased from a negative pressure lower than atmospheric pressure toward atmospheric pressure and has been maintained for a first predetermined time. If the pressure sensor is not installed but the temperature sensor is installed, the control device will cause the projectile launcher to launch the projectile when the temperature information indicates that the temperature has changed from a high temperature to a low temperature below a predetermined temperature range and has been maintained for a second predetermined time. If both the pressure sensor and the temperature sensor are installed, the control device will cause the projectile launcher to launch the projectile when the air pressure information indicates that the air pressure has increased from a negative pressure toward atmospheric pressure and the temperature information indicates that the temperature has changed from a high temperature to a low temperature. [Effects of the Invention]

[0012] The boiler hopper arching removal system of the present invention fires a projectile at the arching when arching occurs and is maintained, based on temperature information from one or both of the installed temperature sensors or air pressure information from the pressure sensor. In other words, the projectile is not fired when arching does not occur, or when arching occurs but quickly disappears due to natural collapse or other means. Furthermore, the projectile is made mainly of non-metallic material. Therefore, it is unlikely that the projectile fired to remove the arching will damage the boiler hopper. Furthermore, the arching removal system for the boiler hopper of the present invention automatically ejects projectiles through a pre-formed opening in the wall of the boiler hopper during the operation of the combustion plant. In other words, there is no need to open doors such as manholes when ejecting projectiles. The path of the projectiles from the projectile ejection device to the opening is kept airtight, so there is no risk of adverse effects on the human body.

[0013] Therefore, according to the boiler lower hopper arching removal system of the present invention, arching that occurs in the boiler lower hopper can be safely removed without damaging the boiler lower hopper during the operation of a combustion plant equipped with a boiler. [Brief explanation of the drawing]

[0014] [Figure 1] It is a schematic configuration diagram of an arching removal system for a boiler lower hopper according to an embodiment. [Figure 2] It is a partial enlarged view showing an enlarged view of a portion of the boiler lower hopper surrounded by a dashed-dotted circle in FIG. 1. [Figure 3] It is an explanatory diagram showing a wall surface 16A provided with an opening in the boiler lower hopper. [Figure 4] It is a schematic configuration diagram of a modification of the arching removal system for a boiler lower hopper.

Mode for Carrying Out the Invention

[0015] Hereinafter, with reference to FIGS. 1 to 4, an arching removal system 1, 1' (hereinafter referred to as "removal systems 1, 1'") for a boiler lower hopper, which are embodiments and modifications of the present invention, will be described. In the drawings, for the sake of simplicity of explanation, a rectangular coordinate system based on the X-axis, Y-axis, and Z-axis will be used for explanation as appropriate. The embodiments and modifications are merely examples, and there is no intention to exclude various modifications and applications of technologies that are not explicitly stated. Except for the essential configurations of the present invention, each configuration of the embodiments and modifications can be selected or variously modified as necessary and implemented.

[0016] First, the combustion plant 2 to which the removal system 1 of the embodiment is applied will be described, and then each configuration of the removal system 1 and its control will be sequentially described.

[0017] Then, the combustion plant 2 to which the removal system 1 is applied will be described. The removal system 1 is applied to the combustion plant 2 equipped with a boiler. The combustion plant 2 generally includes a combustion device for burning fuel (such as waste and coal), a boiler for heat-exchanging the heat generated by the combustion (which may include heat transfer tubes arranged in the flue and an economizer as its components), a dust removal device such as a bag filter for removing dust from the exhaust gas containing fly ash generated by the combustion, and at least a chimney for discharging the dust-removed and purified exhaust gas into the atmosphere. Here, as an example, the combustion plant 2 will be described as a waste incinerator plant equipped with a boiler for power generation. However, the combustion plant 2 may be other combustion plants such as a thermal power plant or a chemical factory.

[0018] Using FIG. 1, the components of the waste incinerator plant, which is the combustion plant 2, will be sequentially described. The waste incinerator plant generally includes an incinerator 3 (including a hopper 10 for storing waste, a feeder 11 for pushing out the waste stored in the hopper 10 from below the hopper 10, a stoker 12 for incinerating the waste pushed out by the feeder 11 while conveying it, and at least a main ash chute 13 for discharging the main ash, which is the residue incinerated by the stoker 12), a flue 5 through which the exhaust gas generated by the incineration of waste in the incinerator 3 flows, a desuperheating tower 8 for cooling the exhaust gas, a bag filter 9 for removing the fly ash contained in the exhaust gas cooled by the desuperheating tower 8, a chimney 4 for discharging the exhaust gas dust-removed by the bag filter 9 into the atmosphere, and an induced draft fan 6 for attracting the exhaust gas in the flue 5 to the chimney 4. There are also waste incinerator plants that do not have a desuperheating tower 8. Note that the induced draft fan 6 is installed in the flue 5 between the bag filter 9 and the chimney 4. Also, the flue 5 is a conveyance path for conveying the exhaust gas generated in the incinerator 3 to the chimney 4 substantially airtightly, and is composed of a rectangular duct or the like. During the operation of the combustion plant 2, the induced draft fan 6 operates, so the inside of the incinerator 3 and the inside of the flue 5 are under a suction pressure by the induced draft fan 6 and become a negative pressure lower than the atmospheric pressure.

[0019] Then, as described later, heat transfer tubes 7 and economizers 14 are installed in flue 5 between the stoker 12 and the cooling tower 8. The economizers 14, like the heat transfer tubes 7, are devices that exchange heat from the exhaust gas and are installed in flue 5 between the third flue 5C and the cooling tower 8, as described later. Flue 5, located between the incinerator 3 and the economizer 14, includes at least a first flue 5A, a second flue 5B, and a third flue 5C, in order from upstream in terms of exhaust gas flow. The first flue 5A (labeled "1 pass" in Figure 1; sometimes referred to as "1 cavity") extends upward in the Z-axis direction (i.e., vertical direction) from directly above the stoker 12 of the incinerator 3. Then, at the upper end of the first flue 5A, it bends in the +X-axis direction (i.e., horizontal direction). The second flue 5B (labeled "2-pass" in Figure 1; sometimes referred to as "2-cavity") connects to the bend in the first flue 5A and extends adjacent to the first flue 5A in the Z-axis direction and downward. Then, at the lower end of the second flue 5B, it bends in the +X-axis direction. The third flue 5C (labeled "3-pass" in Figure 1; sometimes referred to as "3-cavity") connects to the bend in the second flue 5B and extends adjacent to the second flue 5B in the Z-axis direction and upward. Therefore, as shown by the black arrows in Figure 1, the exhaust gas flows from the stoker 12 upward through the first flue 5A, downward through the second flue 5B, and upward through the third flue 5C.

[0020] Here, in the first flue 5A, second flue 5B, and third flue 5C, the "pass" in "1 pass," "2 pass," and "3 pass" means "pass" in English. Similarly, the "cavity" in "1 cavity," "2 cavity," and "3 cavity" means "cavity" in English. In Figure 1, the first flue 5A, the second flue 5B, and the third flue 5C are arranged between the incinerator 3 and the economizer 14. However, a similar configuration can be repeated, for example, by placing a fourth flue with the same configuration as the second flue 5B between the third flue 5C and the economizer 14.

[0021] Within the third flue 5C, multiple heat transfer tubes 7 and an ash removal device 15 positioned between the heat transfer tubes 7 are installed. Each heat transfer tube 7 is a component of the boiler and exchanges heat with the exhaust gas flowing upward through the third flue 5C. The ash removal device 15 is a device that removes fly ash adhering to the heat transfer tubes 7 using steam, liquid, pressure waves, etc., and causes it to fall downward, thereby cleaning the heat transfer tubes 7. As the ash removal device 15, for example, known soot blowers, water spray devices, pressure wave generators (e.g., shock pulse generators, detonation wave generators) can be used.

[0022] When the ash removal device 15 is activated, the fly ash 21 that falls downward (hereinafter referred to as "falling fly ash") accumulates below the third flue 5C. Therefore, in order to smoothly discharge the accumulated falling fly ash 21 from the flue 5, the connection point between the second flue 5B and the third flue 5C is formed into a shape in which the horizontal surface area gradually decreases as it goes downwards, and this is designated as the boiler lower hopper 16. At the very bottom of the boiler hopper 16, a hopper outlet 17 is formed, which is an opening for discharging the accumulated fall fly ash 21 to the outside of the flue 5. Since the boiler hopper 16 has a shape in which the area of ​​the horizontal plane (i.e., the XY plane) gradually decreases as it goes downwards, the fall fly ash 21 slides down the wall of the boiler hopper 16 by gravity and is collected at the hopper outlet 17. The boiler hopper 16 can have any shape as long as the area of ​​the horizontal surface gradually decreases as it goes downwards. However, if the second flue 5B and the third flue 5C are rectangular ducts, forming the boiler hopper 16 into an inverted square pyramidal shape that is continuously connected to the walls of the second flue 5B and the third flue 5C and has a gradually decreasing horizontal surface area as it goes downwards allows for a smooth and continuous connection between the walls of the second flue 5B and the third flue 5C and the wall of the boiler hopper 16.

[0023] Therefore, in Figure 1, we will proceed assuming that the shape of the boiler hopper 16 is the inverted square pyramidal shape described above. Of the four walls of the inverted square pyramidal boiler hopper 16, the wall furthest upstream in terms of exhaust gas flow will be called the "front 16A", the wall furthest downstream will be called the "rear 16B", and the other two walls connecting the front 16A and rear 16B will be called the "sides" (not specifically numbered in Figure 1).

[0024] Next, we will briefly explain the overall configuration of the removal system 1 using Figures 1 to 3, and then explain each component of the removal system 1 in detail. First, let me briefly explain the overall configuration of the removal system 1. The removal system 1 includes the boiler lower hopper 16 mentioned above, an arching removal projectile ejector 22 (hereinafter referred to as "projectile ejector") which ejects arching removal projectiles (hereinafter referred to as "projectiles") made mainly of non-metallic material towards the arching formed by falling fly ash 21 near the hopper outlet 17 through an opening 23 formed in the wall surface of the boiler lower hopper 16, and a falling fly ash inlet 18A which is connected to the hopper outlet 17 directly or indirectly by piping 28, and a falling fly ash transfer device 18 which discharges the falling fly ash 21 introduced from the falling fly ash inlet 18A through the falling fly ash outlet 18B. Furthermore, the removal system 1 is equipped with either a pressure sensor 25 or a temperature sensor 26, or both. The pressure sensor 25 measures the air pressure inside the boiler lower hopper 16 below the arching and near the hopper outlet 17, or inside the falling fly ash transfer device 18 near the hopper outlet 17, or inside the piping 28. The temperature sensor 26 measures the temperature of the outer or inner surface of the boiler lower hopper 16 below the arching and near the hopper outlet 17, or the outer or inner surface of the falling fly ash transfer device 18 near the hopper outlet 17, or the outer or inner surface of the piping 28. Furthermore, the removal system 1 includes a control device 29 that receives temperature information measured by the temperature sensor 26 or air pressure information measured by the pressure sensor 25, and based on the temperature information or air pressure information, ejects projectiles from the projectile ejector device 22 while the combustion plant 2 is in operation.

[0025] As shown in Figure 2, the fallen fly ash 21 that falls into the boiler hopper 16 has a wide range of particle sizes and dimensions, from fine fly ash 21A to lumpy fly ash 21B. When multiple lumpy pieces of fallen fly ash 21B fall from the third flue 5C into the boiler hopper 16, arching may occur near and above the hopper outlet 17, where the fallen fly ash 21 covers and seals the hopper outlet 17. When arching occurs, the hopper outlet 17 is blocked, and the boiler hopper 16 is unable to discharge the fallen fly ash 21. As a result, as shown in Figure 2, there is a risk that the fallen fly ash 21, including fine fly ash 21A and lumpy fly ash 21B, will accumulate without being discharged from the boiler hopper 16. The removal system 1, which will be described in detail below, is a system that removes arching that has occurred in the boiler lower hopper 16 without damaging the boiler lower hopper 16.

[0026] The timing of the fall of lumpy fly ash 21B from the heat transfer tubes 7 to the boiler hopper 16 is mainly during the periodic startup of the ash removal device 15. At this time, multiple lumpy fly ash 21B do not fall simultaneously, but often fall separately at different times with some time differences. For this reason, the control device 29, which will be described later, includes a predetermined waiting period after detecting the occurrence of arching, in order to prevent the firing of projectiles when arching is not present.

[0027] Now, let's describe the components of the removal system 1. The projectile launcher 22 is a device that launches projectiles, mainly composed of non-metallic materials, through an opening 23 formed in the wall of the hopper 16 below the boiler, towards an arching formed by falling fly ash 21 near the hopper outlet 17. The projectile launcher 22 is controlled by the control device 29, which will be described in detail later. Non-metallic materials such as fly ash, clinker, concrete, ice, and dry ice can be used as the material for the projectile. Since the projectile is made of non-metallic material, there is no risk of damage to the wall of the boiler hopper 16 even if the projectile hits the wall. In addition, even if the projectile is mixed with the falling fly ash 21, it can be transported outside the combustion plant 2 and disposed of as is, so there is no need to separate the projectile from the falling fly ash 21 separately. However, if there are no problems with damage or separation, a small amount of metal powder may be mixed into the projectile to increase its hardness. The projectile launching device 22 itself can utilize known technologies. Therefore, the projectile launching device 22 can employ, for example, a projectile launching device that launches projectiles from between two rotating bodies, like a pitching machine (see Patent Document 1), or a projectile launching device that launches projectiles using high-pressure gas such as compressed air (see Patent Document 2 or Patent Document 3).

[0028] Here, as shown in Figures 2 and 3, it is preferable that the opening 23 be formed on the front surface 16A of the four walls of the boiler hopper 16. The reason for this is as follows: Since the ash removal device 15 and heat transfer tubes 7 are located in the third flue 5C and not in the second flue 5B, the falling fly ash 21 accumulates more on the rear surface 16B, which is located below the third flue 5C, than on the front surface 16A, which is located below the second flue 5B. Therefore, as shown in Figure 2, when viewed in the XZ plane, the falling fly ash 21 accumulates unevenly on the rear surface 16B. On the other hand, the falling fly ash 21 hardly accumulates on the front surface 16A. Therefore, when an opening 23 is formed, the front surface 16A is selected from the four walls of the boiler hopper 16 because it is least likely to be blocked by falling fly ash 21. However, as long as the opening 23 is not blocked by the falling fly ash 21, the opening 23 may be formed on either of the two sides of the four walls of the boiler hopper 16, depending on the design.

[0029] The projectile launcher 22 launches projectiles towards the arching through the opening 23. As shown in Figure 2, the arching occurs near and above the hopper outlet 17 located at the lowest point of the boiler lower hopper 16, so it is desirable to launch the projectiles from above downwards. In other words, impacting the arching with a projectile from above is effective in destroying the arching, i.e., removing it. Therefore, as shown in Figure 2, an injection tube 24, which is a curved tube composed of a straight section 24C and a horizontal section 24D, is installed. The straight section 24C is smoothly connected to the horizontal section 24D, one end 24A of the straight section 24C is connected to the opening 23, and the other end 24B of the horizontal section 24D is connected to the projectile ejection port of the projectile ejection device 22. In other words, at both ends of the injection tube 24, one end 24A is connected to the opening 23, and the other end 24B is connected to the projectile ejection port of the projectile ejection device 22. The connection between one end 24A and the opening 23 may be made by welding. The connection between the other end 24B and the ejection port of the projectile ejection device 22 may be made by a fixing method using bolts and nuts, or by welding.

[0030] In this case, the injection tube 24 is installed so that it does not pass through the opening 23, or in other words, so that a portion of the straight tube section 24C does not protrude into the boiler hopper 16. If a portion of the injection tube 24 protrudes into the boiler hopper 16, the exhaust gas is corrosive, and the protruding portion will corrode, eventually breaking or falling off, making it difficult to eject projectiles towards the arching. However, depending on the design and operating method, such as using a corrosion-resistant material for the injection tube 24 or increasing the maintenance frequency, a portion of the injection tube 24 may protrude into the boiler hopper 16.

[0031] Then, the straight pipe section 24C is positioned at an angle such that as it moves along the +X axis it is located in the -Z axis direction, aiming at the position where arching is expected to occur, so that the extension of its central axis coincides with the arching. In other words, in Figure 2, the straight pipe section 24C is positioned at an angle diagonally upward to the left. Here, the straight pipe section 24C is positioned at an angle of 30° to 85° from horizontal upward (in the +Z axis direction and -X axis direction) toward the extension direction of the injection tube 24 from the opening 23. Within this angle range, it is easy to accurately hit the arching with the projectile, and the force of the projectile ejected by gravity can be increased, so the arching can be effectively destroyed. Furthermore, when the removal system 1 is retrofitted to an existing combustion plant 2, there is the advantage that the projectile launcher 22 can be positioned within the aforementioned angular range without affecting the arrangement of other existing equipment. Furthermore, if we let "A" be the angle of the front surface 16A with respect to the horizontal (the X-axis direction in Figure 2), and "B" be the angle of the central axis of the straight pipe section 24C with respect to the horizontal, then the following inequality relationship holds between angles A and B. Angle 90° ≧ Angle A > Angle B

[0032] The horizontal section 24D is a straight tube whose central axis is substantially horizontal (substantially in the X-axis direction in Figure 2). However, the connection point between the horizontal section 24D and the straight tube section 24C is rounded to allow the projectile to move smoothly through the inside of the ejection tube 24. "Substantially horizontal" means that something is horizontal, or not strictly horizontal but can be considered horizontal. Here, the horizontal section 24D is positioned such that the central axis of the horizontal section 24D extending from the other end 24B to the straight pipe section 24C is horizontal or at an angle of 2° or less upward from the horizontal. Within this angle range, the other end 24B of the horizontal section 24D can be easily fixed to the projectile launcher 22, and it also has the advantage of preventing the projectile from rolling naturally towards the opening 23 before it is launched when the projectile launcher 22 is loaded with projectile.

[0033] In the above description, the injection tube 24 was described as a curved tube having both a straight section 24C and a horizontal section 24D. However, the injection tube 24 may consist of only one of either the straight section 24C or the horizontal section 24D. In this case, one end of the straight section 24C becomes one end 24A and the other end becomes the other end 24B, or one end of the horizontal section 24D becomes one end 24A and the other end becomes the other end 24B. For example, if the ejection tube 24 consists only of a horizontal section 24D, the projectile ejection device 22 is installed on the horizontal plane where the hopper outlet 17 of the boiler lower hopper 16 is located, and the projectile is ejected from almost directly beside the arching. Such a configuration may be designed if it is possible to destroy the arching. Furthermore, although the projectile launcher 22 is located outside the boiler hopper 16, the projectile's path from the launcher 22 through the launch tube 24 to the opening 23 is kept airtight. Therefore, during the operation of the combustion plant 2, exhaust gas will not leak out of the flue 5 through this path, and thus there is no risk of adverse effects on human health.

[0034] Next, I will explain the fall ash transfer device 18. The falling fly ash transfer device 18 is a device installed below the hopper outlet 17 of the boiler lower hopper 16, and is equipped with at least a falling fly ash inlet 18A and a falling fly ash outlet 18B. The fall fly ash inlet 18A is connected directly or indirectly by piping 28 to the hopper outlet 17 of the boiler lower hopper 16. Here, as an example, as shown in Figure 2, the hopper outlet 17 and the fall fly ash inlet 18A are indirectly and airtightly connected via piping 28. The fallen fly ash 21, which is discharged naturally by gravity from the hopper outlet 17, is introduced into the fall fly ash transfer device 18 from the fall fly ash inlet 18A, transferred to a designated location, and then discharged to the outside of the fall fly ash transfer device 18 from the fall fly ash outlet 18B. For this transfer, for example, a rotary valve 19 that scrapes off a predetermined amount of fall fly ash 21 introduced from the fall fly ash inlet 18A and transfers it, or a screw conveyor 20 that transports the fall fly ash 21 scraped off by the rotary valve 19 to the fall fly ash outlet 18B, may be used. In this case, the rotary valve 19 and the screw conveyor 20 are connected by a pipe 27 as shown in Figure 1, and the fall fly ash 21 may fall by gravity through the inside of the pipe 27 from the rotary valve 19 to the screw conveyor 20. However, the transport route from the fly ash inlet 18A to the fly ash outlet 18B is configured to be substantially airtight in order to obtain air pressure information from the pressure sensor 25 described later.

[0035] Furthermore, the fall ash transfer device 18 may simply be composed of piping such as a duct or chute with a fall ash inlet 18A at one end and a fall ash outlet 18B at the other end at the bottom, as shown in the fall ash transfer device 18' in the modified example described later, and the fall ash 21 may slide down the inside of the fall ash transfer device 18 by gravity. Furthermore, depending on the design, the piping may have a circular or rectangular cross-section (for example, a square).

[0036] Next, I will explain the pressure sensor 25 and the temperature sensor 26. The pressure sensor 25 is installed below the position where arching is expected, and measures the air pressure inside the boiler lower hopper 16 near the hopper outlet 17, or inside the fall fly ash transfer device 18 near the hopper outlet 17, or inside the piping 28, either continuously or periodically (for example, intermittently at short intervals of about 10 seconds), and transmits the measured air pressure information to the control device 29 described later in a time-series and continuous manner. Figure 1 shows, as an example, a configuration in which a pressure sensor 25 is installed in the piping 27 inside the fall ash transfer device 18 to obtain air pressure information. However, the pressure sensor 25 may be installed anywhere inside the fall ash transfer device 18, as long as it is not near the fall ash discharge port 18B of the fall ash transfer device 18. The temperature sensor 26 is installed below the position where arching is expected, and measures the temperature of the outer or inner surface of the boiler lower hopper 16 near the hopper outlet 17, or the outer or inner surface of the falling fly ash transfer device 18 near the hopper outlet 17, or the outer or inner surface of the piping 28, continuously or periodically (for example, intermittently at short intervals of about 10 seconds), and transmits the temperature information obtained from the measurement to the control device 29 described later in a time series and continuously. Figure 1 shows, as an example, a configuration in which a temperature sensor 26 is installed on the outer surface of a pipe 28 connecting a hopper outlet 17 and a fall fly ash inlet 18A to obtain temperature information from the outer surface.

[0037] Note that the "internal temperature" is not limited to the surface temperature of the inner wall surface where the temperature sensor 26 is installed, i.e., the temperature of the air or gas passing through that inner surface. The "external temperature" is the surface temperature of the outer wall surface itself where the temperature sensor 26 is installed, i.e., the temperature of the metal shell. When the temperature sensor 26 measures the "internal temperature," the response speed of temperature measurement is fast, but there is a risk of inaccurate temperature measurement due to factors such as the adhesion of fallen fly ash. On the other hand, when measuring the "external temperature," the response speed is slow, but the temperature can be measured accurately. Depending on the design, the temperature sensor 26 may measure either the "internal temperature" or the "external temperature," but in the following explanation, we will proceed assuming that the temperature sensor 26 measures the "external temperature."

[0038] Finally, let's describe the control device 29 and its control. The control device 29 receives air pressure information measured by the pressure sensor 25 or temperature information measured by the temperature sensor 26, and based on the air pressure information or temperature information, controls the projectile launcher 22 during the operation of the combustion plant 2 to automatically launch projectiles from the projectile launcher 22. Figure 1 illustrates a removal system 1 equipped with both a pressure sensor 25 and a temperature sensor 26. However, the removal system 1 may be equipped with both a pressure sensor 25 and a temperature sensor 26, or it may be equipped with only one of either the pressure sensor 25 or the temperature sensor 26. Therefore, the control of the projectile launcher 22 by the control device 29 will be explained by dividing it into the following cases: (1), (2), and (3).

[0039] (1) When the temperature sensor 26 is not installed and only the pressure sensor 25 is installed. (1-1) If the air pressure information received by the control device 29 indicates that the air pressure has increased from a negative pressure lower than atmospheric pressure toward atmospheric pressure, and that this increased air pressure has been maintained for a first predetermined time (for example, about 1 minute), the control device 29 will activate the projectile launcher 22 to launch the projectile. This is because it can be determined that arching has occurred that is unlikely to resolve on its own.

[0040] The reason for this is explained below. If arching does not occur in the boiler lower hopper 16, the inside of the flue 5 is under negative pressure. Therefore, the air inside the falling fly ash transfer device 18, specifically the air in the transfer path described above, flows from the falling fly ash outlet 18B, through the falling fly ash inlet 18A and the hopper outlet 17 in sequence, to the boiler lower hopper 16. In other words, air flows from the falling fly ash outlet 18B towards the inside of the flue 5. At this time, the air pressure measured by the pressure sensor 25 is a negative pressure lower than atmospheric pressure. On the other hand, when arching occurs, the air path is blocked, and the airflow from the fall ash outlet 18B into the flue 5 ceases. As a result, the air pressure measured by the pressure sensor 25 increases from a constant negative pressure towards atmospheric pressure, and eventually becomes the same atmospheric pressure as the air pressure at the fall ash outlet 18B. Therefore, if the air pressure information received by the control device 29 indicates an increase from a negative pressure lower than atmospheric pressure toward atmospheric pressure, it can be determined that arching has occurred. Furthermore, if the increased air pressure, for example, atmospheric pressure, is maintained thereafter for a first predetermined time (for example, 1 minute), it can be determined that arching has occurred that is unlikely to resolve naturally. If there are small through-holes in the resulting arching, the increased air pressure may not reach atmospheric pressure. Therefore, the increased air pressure is greater than the aforementioned constant negative pressure but less than or equal to atmospheric pressure.

[0041] Furthermore, when the air pressure information received by the control device 29 indicates an increase from a negative pressure lower than atmospheric pressure towards atmospheric pressure, the control device 29 does not immediately activate the projectile launcher 22 because, as mentioned above, multiple clumps of fly ash 21B often fall at different times with some time difference, so after arching occurs, the arching may resolve naturally as later-falling clumps of fly ash 21B may destroy the arching. If the projectile launcher 22 launches a projectile after the arching has naturally resolved, there is a risk of adverse effects such as damage to the boiler hopper 16. Therefore, when the air pressure information received by the control device 29 indicates that the increased air pressure has risen from a negative pressure lower than atmospheric pressure toward atmospheric pressure and has been maintained for a first predetermined time (for example, 1 minute), the control device 29 determines that the possibility of the arching naturally resolving is low and activates the projectile launcher 22 to launch a projectile.

[0042] Furthermore, if, despite the projectile being launched by the control in (1-1), there is no subsequent change in the air pressure information received by the control device 29 and the increased air pressure is maintained, the control device 29 will again measure the first predetermined time or a shorter predetermined time (for example, about 30 seconds) from the launch of the projectile and repeat the control in (1-1). This is because it can be determined that the arching was not destroyed by the projectile launched by the control in (1-1), that is, the arching could not be removed. In this case as well, the control device 29 determines whether or not the arching is maintained based on the air pressure information it receives for a predetermined time, or a shorter predetermined time. In other words, it observes the state of the arching for a predetermined time, or a shorter predetermined time. This is because the arching may not be immediately destroyed by the impact of the previously fired projectile, but may collapse after a short delay.

[0043] (1-2) If the air pressure information received by the control device 29 indicates that the negative pressure is maintained at the constant value, or that after increasing from the constant value negative pressure toward atmospheric pressure, it decreases again to the constant value negative pressure within the first predetermined time, the control device 29 will not cause the projectile launcher 22 to launch a projectile. In other words, the control device 29 will not activate the projectile launcher 22. In this case, it can be determined that arching did not occur, or that arching was temporarily formed but then resolved naturally, so there is no need to fire a projectile from the projectile launcher 22.

[0044] (2) When the pressure sensor 25 is not installed and only the temperature sensor 26 is installed. (2-1) If the temperature information received by the control device 29 indicates that the temperature has changed from a high temperature (e.g., 350°C) measured when arching is not occurring to a low temperature (e.g., 150°C) which has decreased by more than a predetermined temperature range (e.g., a temperature range of 200°C), and that the low temperature has been maintained for a second predetermined time (e.g., about 10 seconds), the control device 29 will activate the projectile launcher 22 to launch the projectile. This is because it can be determined that arching has occurred that is unlikely to resolve on its own.

[0045] The reason for this is explained below. The temperature of the exhaust gas flowing below the second flue 5B of the flue 5 is generally high, exceeding 700°C. Furthermore, if arching does not occur in the boiler hopper 16, the inside of flue 5 is under negative pressure, causing air to flow from the falling fly ash outlet 18B into flue 5. The heat from the exhaust gas is transferred along the surrounding walls of this airflow. This transferred heat is significantly reduced in temperature by the refractory material installed on the walls of the boiler hopper 16 before being transferred to the falling fly ash transfer device 18. As mentioned earlier, this example describes a case where the temperature sensor 26 measures the steel shell temperature. Therefore, although the temperature measured by the temperature sensor 26 is lower than the temperature of the exhaust gas flowing below the second flue 5B, it is still a high temperature (for example, 350°C). On the other hand, when arching occurs in the boiler hopper 16, the airflow is blocked, making it difficult for heat from the exhaust gas to be transferred to the surrounding walls. As a result, a large temperature difference of several hundred degrees or more occurs between the boiler hopper 16 side and the fall fly ash transfer device 18 side, with the arching as the boundary. Therefore, if the temperature information received by the control device 29 indicates that the temperature has changed from a high temperature (e.g., 350°C) to a low temperature (e.g., 150°C) that has decreased by more than a predetermined temperature range (e.g., a temperature range of 200°C), it can be determined that arching has occurred. Furthermore, if the low temperature is maintained for a second predetermined time (e.g., about 10 seconds), it can be determined that arching has occurred that is unlikely to resolve naturally.

[0046] Furthermore, the reason why the control device 29 does not immediately activate the projectile launcher 22 when the temperature information received by the control device 29 changes from a high temperature to a low temperature that has decreased by more than a predetermined temperature range is that, as mentioned above, multiple clumps of fly ash 21B often fall at different times with some time difference between them, so after arching occurs, the arching may resolve naturally as later clumps of fly ash 21B that fall further may break up the arching. Therefore, similar to the control described in (1-1), the arching behavior is observed for a second predetermined time (for example, about 10 seconds). Then, when the temperature information received by the control device 29 changes from a high temperature to a low temperature that has decreased by more than a predetermined temperature range, and the low temperature is maintained for a second predetermined time (for example, 10 seconds), the control device 29 determines that the possibility of the arching spontaneously resolving is low, and activates the projectile launcher 22 to launch the projectile.

[0047] Here, as described above, the first predetermined time in control (1) and the second predetermined time in control (2) are set appropriately according to the design of the combustion plant 2, but the second predetermined time may be smaller than the first predetermined time, i.e., "first predetermined time" > "second predetermined time". When arching occurs, the air pressure information changes immediately, but the temperature information changes more slowly than the air pressure information. Therefore, it can be considered that when the temperature information becomes low, arching has been maintained for a considerably longer period than in the case of air pressure information.

[0048] Furthermore, if, despite the projectile being launched by the control in (2-1), there is no subsequent change in the temperature information received by the control device 29 and the temperature remains low, the control device 29 will measure a third predetermined time (for example, about 30 seconds), which is longer than the second predetermined time (for example, about 10 seconds), from the launch of the projectile and repeat the control in (2-1). This is because it can be determined that the arching was not destroyed by the projectile launched by the control in (2-1), that is, the arching could not be eliminated. In this case as well, the control device 29 determines whether or not the arching is maintained based on the temperature information it receives for a third predetermined time. In other words, it observes the state of the arching for a third predetermined time. This is because the arching may not be immediately destroyed by the impact of the previously fired projectile, but may collapse after a short delay.

[0049] However, the third predetermined time is set to be longer than the second predetermined time. That is, "first predetermined time" ≥ "third predetermined time" > "second predetermined time". Because temperature changes take longer to transmit than air pressure changes, even if the arching is eliminated by the impact of the projectile, it takes time for the temperature measured by the temperature sensor 26 to change from low to high. For this reason, by setting the third predetermined time to be longer than the second predetermined time, the projectile is not fired while the arching has been eliminated.

[0050] (2-2) If the temperature information received by the control device 29 indicates that the temperature remains high, or that after the temperature has decreased from high to low by more than a predetermined temperature range, it has changed again from low to high within the second predetermined time, the control device 29 will not cause the projectile launcher 22 to launch a projectile. In other words, the control device 29 will not activate the projectile launcher 22. In this case, it can be determined that arching did not occur, or that arching was temporarily formed but then resolved naturally, so there is no need to fire a projectile from the projectile launcher 22.

[0051] (3) When both the pressure sensor 25 and the temperature sensor 26 are installed (3-1) When the air pressure information received by the control device 29 increases from a negative pressure lower than atmospheric pressure to atmospheric pressure, and the temperature information received by the control device 29 changes from a high temperature (e.g., 350°C) measured when arching is not occurring to a low temperature (e.g., 150°C) which has decreased by more than a predetermined temperature range (e.g., a temperature range of 200°C), the control device 29 activates the projectile launcher 22 to launch a projectile. This is because it can be determined that arching has occurred that is unlikely to resolve on its own.

[0052] The reason for this is explained below. As mentioned earlier, pressure changes are transmitted faster than temperature changes. Therefore, after the air pressure information received by the control device 29 changes from negative pressure to atmospheric pressure, the temperature information received by the control device 29 changes from high temperature to low temperature. Looking at this in terms of time, it can be considered that arching occurs when the air pressure information changes towards atmospheric pressure, and that arching is maintained until the temperature information changes to low temperature. Therefore, as in the case of control (1) or control (2), there is no need to wait for a predetermined time to see if arching is maintained. Therefore, when both the air pressure information and temperature information received by the control device 29 satisfy the predetermined conditions described above, the control device 29 determines that the possibility of the arching spontaneously resolving is low and immediately instructs the projectile launcher 22 to launch a projectile.

[0053] Furthermore, if, despite the projectile being launched by the control in (3-1), there is no subsequent change in the air pressure information and temperature information received by the control device 29, the control device 29 measures a fourth predetermined time (for example, about 1 minute) from the launch of the projectile and repeats the control in (3-1). This is because the arching may not be immediately destroyed by the previous impact of the projectile, but may collapse after a slight time delay. The fourth predetermined time may be set to be less than or equal to the first predetermined time and greater than or equal to the second predetermined time, i.e., "first predetermined time" ≥ "fourth predetermined time" ≥ "second predetermined time".

[0054] (3-2) If the air pressure information and temperature information received by the control device 29 do not meet the predetermined conditions described in (3-1), the control device 29 will not allow the projectile launcher 22 to launch a projectile. In other words, the control device 29 will not activate the projectile launcher 22. In this case, it can be determined that arching did not occur, or that arching was temporarily formed but then resolved naturally, so there is no need to fire a projectile from the projectile launcher 22.

[0055] According to the removal system 1 described above, even if arching occurs, if the arching resolves naturally within a predetermined time, no projectile will be fired. Therefore, a projectile mainly composed of non-metallic material can be reliably fired at existing arching to remove it, thus eliminating the risk of damaging the boiler hopper 16. Furthermore, since the projectile path from the projectile ejection device 22 to the opening 23 is kept airtight, and the projectile is automatically ejected from the opening 23 toward the arching to remove it while the combustion plant 2 is in operation, there is no need to open doors such as manholes connecting the inside and outside of the flue 5. Therefore, the removal system 1 can be operated safely without damaging human health.

[0056] Next, we will explain the modified removal system 1' using Figure 4. Except for the fact that the fall ash transfer device 18' of removal system 1' has a different configuration from the fall ash transfer device 18 of removal system 1 in the embodiment, and that removal system 1' does not have a temperature sensor 26 but only a pressure sensor 25, removal system 1' has the same configuration as removal system 1. Therefore, the same configuration and effects as removal system 1 will not be explained. In Figure 4, the pressure sensor 25 is shown as being installed in the boiler lower hopper 16, located below the arching and near the hopper outlet 17.

[0057] The falling fly ash transfer device 18' is a device installed below the hopper outlet 17 of the boiler lower hopper 16, similar to the falling fly ash transfer device 18, and is equipped with at least a falling fly ash inlet 18A' and a falling fly ash outlet 18B'. However, unlike the falling fly ash transfer device 18, the falling fly ash transfer device 18' does not have an active conveying device such as a rotary feeder or a screw conveyor, and is simply piping such as ducts and chutes. The fly ash inlet 18A' is connected directly or indirectly via piping to the hopper outlet 17 of the boiler hopper 16. Figure 4 shows an example where the fly ash inlet 18A' is directly connected to the hopper outlet 17. The fly ash outlet 18B' is connected to an opening formed in the outer wall of the main ash chute 13. Therefore, in the fall fly ash transfer device 18', the fall fly ash 21 discharged from the hopper outlet 17 by gravity slides down by gravity and is transferred to the fall fly ash outlet 18B', and is then discharged from the fall fly ash outlet 18B' to the main ash chute 13 with the momentum of its slide. Then, below the bottom ash chute 13, the bottom ash and the fallen fly ash 21 are mixed and transported outside the combustion plant 2. In other words, removal system 1' can automatically mix bottom ash and fly ash and transport them away. Therefore, if bottom ash and fly ash can be mixed and disposed of together, removal system 1' is superior to removal system 1. Furthermore, removal system 1' has the advantage of lower manufacturing costs because its configuration is simpler than that of removal system 1.

[0058] Here, the incinerator 3 and the main ash chute 13 are sealed spaces airtightly connected to the flue 5, and therefore, during the operation of the combustion plant 2, they are under negative pressure, just like the flue 5. However, when comparing the air pressure in the boiler lower hopper 16 (referred to here as "air pressure A") with the air pressure in the incinerator 3 and main ash chute 13 (referred to here as "air pressure B"), the air pressure A in the boiler lower hopper 16 is more negative than the air pressure B in the incinerator 3 and main ash chute 13 because it is closer to the induced draft fan 6. In other words, although air pressure A and air pressure B are both negative pressure, the relationship is atmospheric pressure > air pressure B > air pressure A.

[0059] The control by the control device 29 in removal system 1' is the same as described in "(1) When only the pressure sensor 25 is installed and the temperature sensor 26 is not installed" in removal system 1, so it will be omitted here. In removal system 1', for example, in the control of (1) (1-1), if the air pressure information received by the control device 29 indicates that the air pressure has increased from air pressure A, which is a negative pressure lower than atmospheric pressure, toward atmospheric pressure, and that this increased air pressure B has been maintained for a first predetermined time (for example, about 1 minute), the control device 29 activates the projectile launcher 22 to launch the projectile. In this explanation, the fall fly ash transfer device 18' is described as simply a pipe, but a conveying device such as a conveyor may be installed inside the pipe to facilitate the transfer of the fall fly ash 21 to the main ash chute 13.

[0060] As described above, the boiler lower hopper arching removal system of the present invention makes it possible to safely remove arching that has occurred in the boiler lower hopper 16 without damaging the boiler lower hopper 16 during the operation of the combustion plant 2 equipped with a boiler. The first to fourth predetermined times mentioned above can be set as appropriate according to the design of the combustion plant 2. Furthermore, the control device 29 may appropriately control the starting and driving of equipment provided by the combustion plant 2, such as the stoker 12, feeder 11, induced draft fan 6, ash removal device 15, rotary valve 19, and screw conveyor 20. Furthermore, in the case of a combustion plant in which the aforementioned fourth flue is connected to the third flue 5C, a separate boiler hopper may be formed below the fourth flue, distinct from the boiler hopper 16. In this case, similar to the case of the boiler hopper 16, the control device 29 may control a projectile launcher positioned in accordance with this separate boiler hopper. [Explanation of Symbols]

[0061] 1.1' Boiler lower hopper arching removal system (removal system) 2 Combustion plant 3 Incinerator 4 Chimneys 5 Flue 5A First flue (1 pass) 5B Second flue (2 passes) 5C Third flue (3 passes) 6. Induced draft fan 7 Heat transfer tubes 8. Defrosting tower 9 Bug Filter 10 Hoppers 11 feeders 12 Stalker 13. Main Ash Shot 14 Economizer 15 Ash removal equipment 16. Boiler hopper 16A Front (wall) 16B Rear (wall) 17 Hopper discharge port 18, 18′ Falling fly ash transfer device 18A, 18A′ Falling fly ash inlet 18B, 18B′ Falling fly ash outlet 19 Rotary valve 20 Screw conveyors 21 Fallen fly ash 21A Fine fall ash 21B Clumpy fall ash 22. Arching Removal Projectile Launcher (Projectile Launcher) 23 Aperture 24 Injection tube 24A one end 24B Other end 24C straight pipe section 24D horizontal section 25 Pressure Sensor 26 Temperature Sensor 27 Piping 28 Piping 29 Control device

Claims

1. A boiler-bottom hopper is provided, in which exhaust gas containing fly ash from a combustion plant equipped with a boiler is drawn into an induced draft fan and flows through a flue, the fly ash adheres to heat transfer tubes arranged in the flue, and the fly ash that falls through the flue is discharged as fallen fly ash from the hopper outlet, A projectile launcher that launches projectiles, mainly composed of non-metallic materials, towards an arching formed by the falling fly ash near the hopper discharge port, through an opening formed in the wall of the hopper below the boiler, A fall ash transfer device is provided, wherein a fall ash inlet is connected to the hopper outlet either directly or indirectly by piping, and the fall ash introduced from the fall ash inlet is discharged from the fall ash outlet. A temperature sensor that measures the temperature of the outer or inner surface of the boiler lower hopper below the arching and near the hopper outlet, or the outer or inner surface of the falling fly ash transfer device near the hopper outlet, or the outer or inner surface of the piping, and a pressure sensor that measures the air pressure inside the boiler lower hopper below the arching and near the hopper outlet, or inside the falling fly ash transfer device near the hopper outlet, or inside the piping, either one or both of these, A control device that receives temperature information measured by the temperature sensor or air pressure information measured by the pressure sensor, and based on the temperature information or air pressure information, causes the projectile to be launched from the projectile launcher during the operation of the combustion plant. It has, The path of the projectile from the projectile launching device to the opening is kept airtight. The control device is If the temperature sensor is not installed and the pressure sensor is installed, When the air pressure information indicates that the air pressure increased from a negative pressure lower than atmospheric pressure toward atmospheric pressure, and then maintained the increased air pressure for a first predetermined time, the projectile launcher is instructed to launch the projectile. If the pressure sensor is not installed and the temperature sensor is installed, When the temperature information indicates that the temperature has changed from a high temperature to a low temperature exceeding a predetermined temperature range, and that this low temperature has been maintained for a second predetermined time, the projectile launcher is instructed to launch the projectile. When both the pressure sensor and the temperature sensor are installed, When the air pressure information indicates that the air pressure is increasing from the negative pressure to atmospheric pressure, and the temperature information indicates that the temperature has changed from the high temperature to the low temperature, the projectile launcher is instructed to launch the projectile. Arching removal system for the hopper below the boiler.

2. The system further includes an ejection tube which is the path for the aforementioned projectile, The injection tube includes a straight section positioned at an angle of 30 to 85 degrees from horizontal upwards, inclined from the opening toward the extension direction of the injection tube. The boiler hopper arching removal system according to claim 1.

3. The injection tube is a straight or curved tube that does not protrude into the hopper below the boiler, with one end connected to the opening and the other end connected to the projectile launching device. The arching removal system for a boiler hopper according to claim 2.

4. The wall surface of the hopper below the boiler has an inverted square pyramidal shape, consisting of a front surface on the upstream side, a rear surface on the downstream side, and two side surfaces connected to the front and rear surfaces, respectively, when viewed in relation to the flow of exhaust gas. The opening is installed on the front surface. The boiler hopper arching removal system according to claim 3.

5. The aforementioned projectile has fly ash, clinker, concrete, ice, or dry ice as its main components. The boiler hopper arching removal system according to claim 4.

6. The flue comprises at least a first flue extending vertically upward, a second flue connected to the first flue and extending vertically downward, and a third flue connected to the second flue and extending vertically upward. The third flue is equipped with the heat transfer tube, The boiler hopper is located at the point where the second flue and the third flue are connected. The aforementioned fly ash transfer device includes at least a rotary valve or a screw conveyor. The boiler hopper arching removal system according to any one of claims 1 to 5.

7. The aforementioned combustion plant is a plant equipped with a waste incinerator, The waste incinerator further has a bottom ash chute for discharging bottom ash, The flue comprises at least a first flue extending vertically upward, a second flue connected to the first flue and extending vertically downward, and a third flue connected to the second flue and extending vertically upward. The third flue is equipped with the heat transfer tube, The boiler hopper is located at the point where the second flue and the third flue connect. The falling fly ash transfer device connects the hopper outlet of the boiler lower hopper to the main ash chute, and transfers the falling fly ash from the hopper outlet to the main ash chute. The pressure sensor is installed The boiler hopper arching removal system according to any one of claims 1 to 5.

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