Alkali metal-containing fuel combustion system and alkali metal-containing fuel combustion method

Abstract

To suppress defective fluidization due to agglomeration in a fluid medium forming a fluidized bed in a combustion furnace.SOLUTION: A combustion system using a combustion furnace in which a fluidized layer is formed by a fluidized medium and a fuel is combusted in the fluidized layer includes a fuel supply part for supplying a first fuel containing an alkali metal and a second fuel having a smaller content of the alkali metal than the first fuel to the combustion furnace, a sieve for separating the fluidized medium discharged from the combustion furnace into a fluidized medium having a predetermined particle size value or less and a lump having a particle size value exceeding the predetermined particle size value, a circulation line for returning the fluidized medium having the predetermined particle size value or less to the combustion furnace, a photographing part for photographing the lump and outputting image data of the lump, a determination part for determining a coagulation state of the lump indicated by the image data by using a result of machine learning, a combustion control part for controlling at least one of an amount of the first fuel, a fluidized medium newly supplied to the circulation line, and an amount of the fluidized medium discharged from the circulation line according to a result of the determination part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a combustion system for an alkali metal-containing fuel and a method for burning an alkali metal-containing fuel. [Background technology]

[0002] One method for generating electricity using biomass as fuel is to use a fluidized bed furnace. A fluidized bed furnace uses upward-flowing fluidizing air to create a fluidized bed of high-temperature fluidizing material, and the fuel supplied to the furnace is combusted within the fluidized bed. Low-cost plant-derived biomass, such as palm empty fruit bunches (EFBs), has been attracting attention as a fuel. However, the following problems arise when burning palm empty fruit bunches in a fluidized bed furnace to generate electricity:

[0003] Palm empty fruit bunches contain a large amount of potassium, an alkali metal. Silica sand is used as the fluidizing medium in a fluidized bed furnace. The gaseous potassium released from the palm empty fruit bunches reacts with the silicon oxide in the silica sand particles inside the furnace, producing the SiO2-K2O compound on the surface of the silica sand particles. Because the melting temperature of this SiO2-K2O compound is lower than the temperature inside the fluidized bed furnace, it melts and forms an adhesive layer on the surface of the silica sand particles. When this adhesive layer forms, several silica sand particles fuse together, causing the silica sand to aggregate and agglomerate, preventing the silica sand from flowing and hindering normal operation of the fluidized bed furnace. Patent documents 1 and 2, for example, disclose inventions that address these issues.

[0004] In the invention disclosed in Patent Document 1, the bed material is made of particulate minerals and / or particulate slag, and the quartz content is 14 mass% or less. Because the amount of quartz contained in the bed material is 14 mass% or less, even if the quartz in the bed material reacts with the alkali metal components in the fuel to form an adhesive layer on the particle surface, aggregation or clumping of the bed material does not occur, or if it does occur, it occurs only to a small extent, and the fluidized bed can maintain good fluidity.

[0005] The invention disclosed in Patent Document 2 uses a laser monitoring device to detect the upward flow of the bed material near the outlet of the fluidized-bed furnace while controlling the fluidizing gas velocity inside the furnace to approximately 4 m / s, and feeds back the amount of incineration air corresponding to the upward flow state to the combustion air supply side. By increasing the fluidizing gas velocity inside the fluidized-bed furnace to approximately 4 m / s, it is possible to increase the limit of salt accumulation in the bed material, thereby increasing the amount of waste that can be treated without causing poor fluidization in the fluidized bed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-106244 [Patent Document 2] Patent No. 3294172 Summary of the Invention [Problem to be solved by the invention]

[0007] The invention disclosed in Patent Document 1 lists garnet, ilmenite, olivine, ferronickel slag, and the like as bed materials. However, as shown in Table 2 of Patent Document 1, these are more expensive than inexpensive, general-purpose silica sand, and replacing the bed material is costly. The invention of Patent Document 2 can increase the critical salt accumulation amount in the bed material, but because agglomeration occurs with even a slight change in alkali metal, there is a risk that agglomeration will occur suddenly if the critical salt accumulation amount is exceeded, resulting in poor flow.

[0008] The present invention has been made in view of the above, and has an object to suppress poor fluidity due to agglomeration in a fluidized medium that forms a fluidized bed in a combustion furnace. [Means for solving the problem]

[0009] A combustion system for an alkali metal-containing fuel according to one aspect of the present invention is a combustion system that uses a combustion furnace to form a fluidized bed using a fluidized medium and combust a fuel containing alkali metal in the fluidized bed, and includes: a fuel supply unit that supplies a first fuel containing alkali metal and a second fuel having a lower alkali metal content than the first fuel to the combustion furnace; a sieve that separates the fluidized medium discharged from the combustion furnace into fluidized medium having a particle size below a predetermined value and agglomerates having a particle size above the predetermined value; a circulation line that returns the fluidized medium having a particle size below the predetermined value separated by the sieve to the combustion furnace; a photographing unit that photographs the agglomerates separated by the sieve and outputs image data representing the photographed agglomerates; a determination unit that determines the aggregation state of the agglomerates in the image represented by the image data output by the photographing unit using the results of machine learning using the image data; and a combustion control unit that controls at least the amount of the first fuel supplied by the fuel supply unit, the amount of the fluidized medium newly supplied to the circulation line, and the amount of the fluidized medium discharged from the circulation line, depending on the result of the determination unit.

[0010] Furthermore, the combustion system for an alkali metal-containing fuel according to the present invention may have a temperature sensor that measures the temperature of the top of the combustion furnace, and the combustion control unit may use the measurement results of the temperature sensor in addition to the judgment result of the judgment unit to control the amount of the first fuel supplied by the fuel supply unit, the amount of the bed material newly supplied to the circulation line, and the amount of the bed material discharged from the circulation line.

[0011] Furthermore, the combustion system for an alkali metal-containing fuel according to the present invention may include pressure sensors that measure the pressure at the bottom and top of the combustion furnace, and the combustion control unit may use the difference between the pressure at the bottom and the pressure at the top of the combustion furnace measured by the pressure sensor in addition to the judgment result of the judgment unit and the measurement result of the temperature sensor to control the amount of the first fuel supplied by the fuel supply unit, the amount of the bed material newly supplied to the circulation line, and the amount of the bed material discharged from the circulation line.

[0012] In addition, in the combustion system for alkali metal-containing fuel according to the present invention, the judgment unit may perform machine learning to classify the aggregation state of the agglomerates into multiple classes using the image data, thereby judging the aggregation state.

[0013] A method for burning an alkali metal-containing fuel according to one aspect of the present invention is a combustion method using a combustion furnace in which a fluidized bed is formed with a fluidized medium within the furnace and a fuel containing an alkali metal is burned in the fluidized bed, the method comprising: a fuel supply step of supplying a first fuel containing an alkali metal and a second fuel having a lower alkali metal content than the first fuel to the combustion furnace; a separation step of separating the fluidized medium discharged from the combustion furnace into fluidized medium having a particle size equal to or smaller than a predetermined particle size value and agglomerates having a particle size exceeding the predetermined particle size value; a circulation step of returning the fluidized medium having a particle size equal to or smaller than the predetermined particle size value separated in the separation step to the combustion furnace; and a photographing step of photographing the agglomerates separated in the step (a) and outputting image data showing the photographed agglomerates; a determination step of determining the aggregation state of the agglomerates in the image shown by the image data output in the photographing step using the results of machine learning using the image data; and a combustion control step of controlling, depending on the results of the determination step, at least the amount of the first fuel supplied in the fuel supply step, the amount of the bed material newly supplied to a circulation line that returns the bed material having a particle size equal to or smaller than a predetermined particle size value separated in the separation step to the combustion furnace, or the amount of the bed material discharged from the circulation line. [Effects of the Invention]

[0014] According to the present invention, it is possible to suppress poor flow due to agglomeration in a fluidized medium that forms a fluidized bed in a combustion furnace. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram showing the configuration of a combustion system according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing the configuration of the control device. [Figure 3]FIG. 3 is a functional block diagram of the functions realized by the control unit. [Figure 4A] FIG. 4A is a schematic diagram of an image represented by labeled image data. [Figure 4B] FIG. 4B is a schematic diagram of an image represented by the labeled image data. [Figure 4C] FIG. 4C is a schematic diagram of an image represented by the labeled image data. [Figure 5] FIG. 5 is a flowchart showing the flow of processing executed by the control unit. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments described below. It should be noted that the drawings are schematic and that the dimensional relationships between elements may differ from the actual ones.

[0017] [Embodiment] FIG. 1 is a diagram showing the configuration of a combustion system 1000 according to an embodiment of the present invention. The combustion furnace 1 is a circulating fluidized bed (CFB) furnace. The combustion furnace 1 fluidizes a bed material 81 inside to form a fluidized bed, and combusts fuel 73 supplied into the combustion furnace 1 in the fluidized bed. The combustion furnace 1 is mainly composed of a riser 10 as the furnace body, and a downcomer 20 that collects a portion of the bed material 81 and returns it to the riser 10.

[0018] The riser 10 is provided at its lower part with an air diffuser 11 for blowing primary air supplied from a blower 91 upward. In addition, on the side wall at the lower part of the riser 10, there are provided, in order from bottom to top, a bed material supply port 12 for supplying bed material 81 into the riser 10 above the air diffuser 11, a fuel supply port 13 for supplying fuel 73 into the riser 10, and a secondary air inlet 14 for blowing secondary air supplied from the blower 92 into the riser 10. In addition, a discharge part 15 for discharging the bed material 81 and furnace bottom ash inside the riser 10 is provided at the bottom of the riser 10.

[0019] The riser 10 is also provided with pressure sensors 93a and 93b and a temperature sensor 94. The pressure sensors 93a and 93b are sensors for measuring the differential pressure between the bottom and top of the riser 10, i.e., the differential pressure of the riser 10. The pressure sensor 93a measures the pressure at the bottom of the riser 10, and the pressure sensor 93b measures the pressure at the top of the riser 10. The pressure sensors 93a and 93b output pressure data indicating the measurement results to the control device 100. The temperature sensor 94 is a sensor for measuring the temperature inside the riser 10. The temperature sensor 94 is provided at the top of the riser 10 and measures the temperature at the top of the riser 10. The temperature sensor 94 outputs temperature data indicating the measurement results to the control device 100.

[0020] The fuel supply unit 70 is a device that sends fuel 73 to be burned in the combustion furnace 1 to the fuel supply port 13. The fuel supply unit 70 sends the fuel 73, which is a mixture of a first fuel 71 and a second fuel 72, to the fuel supply port 13. The fuel supply unit 70 changes the mixing ratio of the first fuel 71 and the second fuel 72 under control of the control device 100. The first fuel 71 is a fuel with a high alkali metal content, such as palm empty fruit bunches. The second fuel 72 is a fuel with a lower alkali metal content than the first fuel 71, such as wood chips. The fuel supply unit 70 preferably supplies the fuel 73 so that the calorific value of the fuel 73 input per unit time is constant. Note that the fuel supply unit 70 may supply only the second fuel 72 as the fuel 73 without mixing the first fuel 71 and the second fuel 72 to suppress agglomeration. The step of fuel supply unit 70 supplying fuel 73 is an example of a fuel supply step.

[0021] The downcomer 20 is connected to the upper part of the riser 10 by a pipe 30. The downcomer 20 has a collection section 21 that collects the bed material 81 sent from the riser 10 together with the exhaust gas, a return pipe 22 for returning the bed material 81 collected in the collection section 21 to the lower part of the riser 10, and a seal section 23 that prevents the gas from the riser 10 from ascending inside the collection section 21.

[0022] A circulation line 40 is provided near the combustion furnace 1 to return the bed material 81 discharged from the discharge section 15 to the combustion furnace 1. In the circulation line 40, a cooling device 41, a sieve 42, and a bed material supply section 43 are arranged in this order from the discharge section 15. The step of returning the bed material 81 to the combustion furnace 1 by the circulation line 40 is an example of a circulation step according to the present invention.

[0023] The cooling device 41 is, for example, a screw conveyor that cools and transports the material being transported. The cooling device 41 cools the bed material 81 and furnace bottom ash discharged from the discharge section 15 and transports them to the sieve 42 by the screw.

[0024] The sieve 42 is a sieve through which bed material 81 with a particle size equal to or smaller than a predetermined particle size passes. The particle size of the bed material 81 passing through the sieve 42 is, for example, 1 mm or smaller. The sieve 42 receives the bed material 81 and furnace bottom ash transported from the cooling device 41 and sends the bed material 81 with a particle size equal to or smaller than the predetermined particle size that passes through the sieve 42 to the bed material supply section 43. Agglomerates of the bed material 81 that have become larger than the predetermined particle size due to agglomeration and incombustible materials generated after the combustion of the fuel 73 do not pass through the sieve 42 and are sent to the disposal line 51 for disposal of the bed material 81. The step in which the sieve 42 separates the bed material 81 transported from the cooling device 41 into bed material 81 with a particle size equal to or smaller than the predetermined particle size and bed material 81 with a particle size larger than the predetermined particle size is an example of a separation step according to the present invention. The agglomerates of the bed material 81 sent from the sieve 42 to the disposal line 51 are photographed by the camera 61. The camera 61, which is an example of an imaging unit, outputs image data showing the image of the captured clump of the fluid medium 81 to the control device 100. The step in which the camera 61 captures an image of the fluid medium 81 and outputs the image data is an example of an imaging step according to the present invention.

[0025] The bed material supply unit 43 stores the bed material 81 sent from the sieve 42 and supplies the bed material 81 into the riser 10. In this embodiment, the bed material 81 is, for example, silica sand. A portion of the bed material 81 stored in the bed material supply unit 43 is discarded from the bottom of the bed material supply unit 43. In the bed material supply unit 43, a portion of the stored bed material 81 is discarded, and new bed material 81 is replenished to make up for the discarded portion. The bed material 81 stored in the bed material supply unit 43 is sent to the bed material supply port 12 and supplied from the bed material supply port 12 into the riser 10.

[0026] 2 is a block diagram showing the configuration of the control device 100. The operation unit 102 has a keyboard, a mouse, and various buttons for operating the control device 100, and is operated by an operator of the combustion system 1000. The display unit 103 is, for example, a display device, and displays various information related to the control performed by the control device 100. The interface 104 is controlled by the control unit 101, and outputs a control signal for controlling the controlled object to the controlled object. The interface 104 also acquires image data output by the camera 61, pressure data output by the pressure sensors 93a and 93b, and temperature data output by the temperature sensor 94.

[0027] The control unit 101 includes a calculation unit and a storage unit. The calculation unit is configured, for example, by a CPU (Central Processing Unit). The storage unit is configured, for example, by a portion configured by ROM (Read Only Memory) and a portion configured by RAM (Random Access Memory). The portion configured by ROM stores various programs and data used by the calculation unit to perform calculation processing. The RAM is used as a workspace when the calculation unit performs calculation processing and to store the results of the calculation processing of the calculation unit.

[0028] The control unit 101 controls the discharge unit 15, bed material supply unit 43, fuel supply unit 70, etc. according to image data, pressure data, and temperature data by the CPU executing a program stored in the ROM, thereby realizing the function of suppressing poor flow due to agglomeration in the combustion furnace 1. The functions of the control unit 101 are realized as a functional unit by the CPU reading and executing the program from the ROM. A block diagram of the functions realized by the control unit 101 is shown in Figure 3.

[0029] The acquisition unit 101a acquires image data, pressure data, and temperature data. The determination unit 101b determines the agglomeration state of the fluid medium 81 based on the image data acquired by the acquisition unit 101a. The determination unit 101b performs machine learning image recognition in advance using multiple image data of the agglomerates of the fluid medium 81, and determines the agglomeration state of the agglomerates through multi-class classification. The machine learning performed by the control device 100 uses, for example, AlexNet, VGG-NET, GoogleNet Inception, ResNet, DenseNet, MobileNet, and the like, which use convolutional neural networks. In the machine learning, image data labeled with first, second, and third states for the agglomeration states of the agglomerates is prepared in advance, and data augmentation is performed on the prepared image data, and learning is performed based on the data augmented image data.

[0030] 4A to 4C are schematic diagrams of images represented by labeled image data. FIG. 4A is a schematic diagram of an image in which a first state is labeled as the aggregation state of the agglomerates, FIG. 4B is a schematic diagram of an image in which a second state is labeled as the aggregation state of the agglomerates, and FIG. 4C is a schematic diagram of an image in which a third state is labeled as the aggregation state of the agglomerates. In FIGS. 4A to 4C, black circles represent agglomerates of the bed material 81, with small circles representing agglomerates 81a having a particle size of 10 mm or less, for example, and large circles representing agglomerates 81b having a particle size of 30 mm to 50 mm. In this embodiment, for example, the particle size values ​​of the agglomerates are recognized by image recognition technology, and the recognized aggregation states of the agglomerates are labeled.

[0031] For example, if the frequency of clumps of fluid medium 81 of 30 mm to 50 mm in the image is less than a first threshold, the image data is labeled as a first state as the clump aggregation state; if the frequency of clumps of fluid medium 81 of 30 mm to 50 mm in the image is equal to or greater than the first threshold and less than a second threshold, the image data is labeled as a second state as the clump aggregation state; and if the frequency of clumps of fluid medium 81 of 30 mm to 50 mm in the image is equal to or greater than the second threshold, the image data is labeled as a third state as the clump aggregation state.

[0032] The combustion control unit 101c controls the discharge unit 15, the bed material supply unit 43, and the fuel supply unit 70 based on the determination result of the determination unit 101b, the pressure data, and the temperature data.

[0033] Next, we will explain the operation of the combustion system 1000. In the combustion furnace 1, primary air sent from the blower 91 is blown into the riser 10 through the air diffuser 11, and secondary air sent from the blower 92 is blown into the riser 10 through the secondary air inlet 14, thereby fluidizing the bed material 81 and forming a fluidized bed in the riser 10.

[0034] Furthermore, fuel 73 is supplied into the riser 10 from the fuel supply port 13. From the viewpoint of operating costs, it is preferable that the proportion of the first fuel 71 is large in the fuel 73 supplied from the fuel supply port 13. The fuel 73 supplied into the riser 10 is combusted in the fluidized bed.

[0035] Specifically, the bed material 81 is fluidized by the primary air blown in from the air diffuser 11, forming a dense layer in the lower part of the riser 10. In this dense layer, the high heat capacity and stirring effect promote drying of the fuel 73 and release of volatile matter. In addition, in the upper part of the riser 10, the bed material 81 is blown up by the blowing of primary and secondary air, forming a thin layer in which the bed material 81 is thin. In this thin layer, the fuel 73 is burned by the heat capacity and stirring effect of the bed material 81. In other words, by forming a fluidized layer consisting of a dense layer and a thin layer in the riser 10, the combustion furnace 1 prevents the generation of char, which is unburned carbon, and efficiently combusts the palm empty fruit bunches, which are the fuel 73. The combustion region in the riser 10 is maintained at approximately 850 to 900°C.

[0036] The exhaust gas generated by the combustion of the fuel 73 in the riser 10 is supplied to the collection section 21 of the downcomer 20 via the pipe 30. A portion of the bed material 81 is also sent from the riser 10 to the collection section 21 together with the exhaust gas. In the collection section 21, the bed material 81 and ash with relatively large particle sizes are recovered and returned to the bottom of the riser 10 through the seal section 23 and the return pipe 22. The exhaust gas and ash with relatively small particle sizes are discharged from the top of the downcomer 20 and sent to an exhaust gas treatment facility via a superheater (not shown), where the steam is superheated, and after dust removal in the exhaust gas treatment facility, the steam is released to the outside from a chimney (not shown).

[0037] In this embodiment, the first fuel 71 (palm empty fruit bunches) contained in the fuel 73 combusted in the riser 10 releases gaseous potassium, which is an alkali metal component. This gaseous potassium reacts with silicon oxide in the silica sand particles, which are the bed material 81, to produce SiO2-K2O compounds on the surfaces of the silica sand particles. This SiO2-K2O compound melts and forms an adhesive layer on the surfaces of the silica sand particles. This adhesive layer causes several grains of bed material 81 to fuse together and fall to the bottom of the riser 10. The fused and fallen bed material 81 further fuses to form clumps. A predetermined amount of the bed material 81 including the clumps and incombustible matter remaining after combustion of the fuel 73 is discharged per unit time from the discharge section 15 and sent to the cooling device 41.

[0038] The cooling device 41 cools the bed material 81 and non-combustible material discharged from the discharge section 15, and transports the cooled bed material 81 and non-combustible material to the sieve 42. The sieve 42, to which the bed material 81 and non-combustible material are sent, allows bed material 81 with a particle size below a predetermined size to pass through. The bed material 81 that has passed through the sieve 42 is sent to the bed material supply section 43. In the bed material supply section 43, a portion of the bed material 81 is discarded from the bottom of the bed material supply section 43, and new bed material 81 is replenished from the top. The sieve 42 also sends out the non-combustible material after combustion and lumps of bed material 81 with a particle size exceeding the predetermined particle size to the disposal line 51. The bed material 81 sent from the sieve 42 to the disposal line 51 is photographed by the camera 61.

[0039] 5 is a flowchart showing the flow of processing executed by the control unit 101. The control unit 101 acquires image data output from the camera 61, pressure data output from the pressure sensors 91a and 91b, and temperature data output from the temperature sensor 94 (step S11).

[0040] Next, the control unit 101 determines the aggregation state of the clumps of fluid medium 81 based on the image data sent from the camera 61 (step S12). Step S12 is an example of a determination step according to the present invention. Here, the control unit 101 performs machine learning in advance using multiple image data on the aggregation state of the clumps of fluid medium 81, and determines the aggregation state of the clumps of fluid medium 81 sent to the disposal line 51 as either state 1, state 2, or state 3 using multi-class classification based on the image represented by the image data.

[0041] Next, the control unit 101 controls the discharge unit 15, the bed material supply unit 43, and the fuel supply unit 70 based on the determination result of the agglomeration state of the bed material 81, the temperature indicated by the temperature data, and the pressure indicated by the pressure data (step S13). Step S13 is an example of a combustion control step according to the present invention. Specifically, when the determination result of the agglomeration state of the bed material 81 indicates the first state, the control unit 101 controls the fuel supply unit 70 to increase the proportion of the first fuel 71 and decrease the proportion of the second fuel 72 in the fuel 73. Furthermore, when the determination result of the agglomeration state of the bed material 81 indicates the first state, the control unit 101 controls the bed material supply unit 43 to supply a predetermined amount of new bed material 81 per unit time to the bed material supply unit 43 and to discharge a predetermined amount of bed material 81 per unit time from the bed material supply unit 43. In this way, when the agglomeration state of the bed material 81 indicates the first state, the proportion of the low-cost first fuel 71 is increased, thereby reducing the operating costs of the combustion system 1000.

[0042] Furthermore, when the determination result of the agglomeration state of the agglomerates is the second state and the temperature indicated by the temperature data is higher than the predetermined furnace top temperature, the control unit 101 controls the fuel supply unit 70 to reduce the proportion of the first fuel 71 in the fuel 73. When the determination result of the agglomeration state of the agglomerates is the second state and the temperature indicated by the temperature data is higher than the predetermined furnace top temperature, the control unit 101 controls the bed material supply unit 43 to increase the amount of new bed material 81 fed into the bed material supply unit 43 per unit time and to increase the amount of bed material 81 discharged from the bed material supply unit 43 per unit time, compared to when the agglomeration state of the agglomerates is the first state. In this way, when the agglomeration state of the agglomerates changes, by reducing the proportion of the first fuel 71 and increasing the amount of new bed material 81, poor fluidity of the bed material 81 can be suppressed.

[0043] Furthermore, when the determination result of the agglomeration state of the agglomerates is the third state, the temperature indicated by the temperature data is higher than a predetermined furnace top temperature, and the pressure difference between the pressure indicated by the pressure data from the pressure sensor 91a and the pressure indicated by the pressure data from the pressure sensor 91b is higher than a predetermined pressure difference, the control unit 101 controls the fuel supply unit 70 to not supply the first fuel 71 and to send out only the second fuel 72 as the fuel 73. Furthermore, when the determination result of the agglomeration state of the agglomerates is the third state, the temperature indicated by the temperature data is higher than a predetermined furnace top temperature, and the pressure difference between the pressure indicated by the pressure data from the pressure sensor 91a and the pressure indicated by the pressure data from the pressure sensor 91b is higher than a predetermined pressure difference, the control unit 101 controls the bed material supply unit 43 to increase the amount of new bed material 81 introduced into the bed material supply unit 43 and increase the amount of bed material 81 discharged from the bed material supply unit 43, compared to when the determination result of the agglomeration state of the agglomerates is the second state. In this way, if the aggregation state of the agglomerates changes further, the supply of the first fuel 71 to the riser 10 can be stopped and new bed material 81 can be added, thereby preventing the bed material 81 from becoming poorly fluid.

[0044] [Variations] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be implemented in various other forms. For example, the above-described embodiments may be modified as follows to implement the present invention. The above-described embodiments and the following modifications may be combined with each other. The present invention also includes configurations in which the components of the above-described embodiments and modifications are appropriately combined. Furthermore, further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspects of the present invention are not limited to the above-described embodiments and modifications, and various modifications are possible.

[0045] In the above-described embodiment, the combustion furnace 1 is a circulating fluidized bed furnace, but it may also be a bubbling fluidized bed (BFB) furnace.

[0046] In the present invention, in order to prevent a decrease in the temperature inside the riser 10 due to the supply of new bedrock material 81 into the riser 10, the amount of fuel 73 supplied into the riser 10 may be increased according to the amount of bedrock material 81 supplied. In this case, in order to prevent agglomeration from occurring, the proportion of the second fuel 72 may be increased. In addition, in order to prevent a decrease in the temperature inside the riser 10 due to an increase in the amount of bedrock material 81 supplied, kerosene or heavy oil may be supplied as an auxiliary fuel.

[0047] In the present invention, the fuel 73 may include palm kernel shells (PKS).

[0048] In the present invention, the control unit 101 may control the fuel supply unit 70 and the bed material supply unit 43 based only on the determination result of the agglomeration state of the agglomerates based on the image data, without using the pressure data and the temperature data. Specifically, when the determination result of the agglomeration state of the agglomerates is the second state, the control unit 101 controls the fuel supply unit 70 to increase the proportion of the first fuel 71 and decrease the proportion of the second fuel 72 in the fuel 73, and controls the bed material supply unit 43 to increase the amount of new bed material 81 fed to the bed material supply unit 43 per unit time and to increase the amount of bed material 81 discharged from the bed material supply unit 43 per unit time. In addition, when the determination result of the aggregation state of the agglomerates is the third state, the control unit 101 controls the fuel supply unit 70 not to supply the first fuel 71 and to send out only the second fuel 72 as fuel 73, and controls the bed material supply unit 43 so that the amount of new silica sand fed into the bed material supply unit 43 increases and the amount of silica sand discharged from the bed material supply unit 43 increases compared to when the aggregation state of the agglomerates of the bed material 81 is the second state.

[0049] In the cooling device 41, as the number of agglomerates of the bed material 81 increases, the agglomerates may become caught in the screw, increasing the torque of the motor and increasing the current value of the motor driving the screw. Therefore, in the present invention, the current value of the current flowing through the motor driving the screw in the cooling device 41 may be measured, and the control unit 101 may control the controlled object using the measurement result of the current value. For example, when the determination result of the agglomerate aggregation state is the second state or the third state and the current value of the current flowing through the motor driving the screw is equal to or greater than a predetermined threshold, the control unit 101 controls the fuel supply unit 70 to not supply the first fuel 71 and to send only the second fuel 72 as the fuel 73, and controls the bed material supply unit 43 to increase the amount of new bed material 81 introduced into the bed material supply unit 43 and increase the amount of new bed material 81 discharged from the bed material supply unit 43. Even in this modification, by stopping the supply of the first fuel 71 to the riser 10 and further increasing the amount of new bed material 81, poor fluidity of the bed material 81 can be suppressed.

[0050] In the bed material supply unit 43, as the number of agglomerates of the bed material 81 increases, the amount of bed material 81 sent from the sieve 42 decreases, resulting in a decrease in the amount of bed material 81 stored therein. Therefore, in the present invention, the amount of bed material 81 stored in the bed material supply unit 43 may be measured, and the control unit 101 may use the measurement result to control the controlled object. For example, when the determination result of the agglomeration state of the agglomerates indicates the third state and the amount of bed material 81 stored in the bed material supply unit 43 is equal to or less than a predetermined threshold, the control unit 101 controls the fuel supply unit 70 to not supply the first fuel 71 and to send only the second fuel 72 as the fuel 73, and controls the bed material supply unit 43 to increase the amount of new bed material 81 introduced into the bed material supply unit 43 and increase the amount of bed material 81 discharged from the bed material supply unit 43. Even in this modification, by stopping the supply of the first fuel 71 to the riser 10 and further increasing the amount of new bed material 81, poor fluidity of the bed material 81 can be prevented. [Explanation of symbols]

[0051] 1. Combustion furnace 15 Discharge section 40 Circulation Line 41 Cooling device 42 Sieve 43 Fluid medium supply section 51 Disposal Line 61 Camera 70 Fuel supply section 71 1st fuel 72 2nd fuel 81 Fluid medium 100 control device 101 Control section 101a Acquisition Department 101b Judgment section 101c Combustion control unit 1000 Combustion System

Claims

1. A combustion system using a combustion furnace in which a fluidized bed is formed by a bed material and a fuel containing an alkali metal is burned in the fluidized bed, a fuel supply unit that supplies a first fuel containing an alkali metal and a second fuel having a lower alkali metal content than the first fuel to the combustion furnace; a sieve that separates the bed material discharged from the combustion furnace into bed material having a particle size equal to or smaller than a predetermined particle size value and agglomerates having a particle size greater than a predetermined particle size value; a circulation line for returning the bed material having a particle size equal to or smaller than a predetermined particle size value separated by the sieve to the combustion furnace; an imaging unit that images the agglomerates separated by the sieve and outputs image data representing the imaged agglomerates; a determination unit that determines the aggregation state of the agglomerates in the image represented by the image data output by the imaging unit using a result of machine learning using the image data; a combustion control unit that controls at least one of the amount of the first fuel supplied by the fuel supply unit, the amount of the fluidized medium newly supplied to the circulation line, and the amount of the fluidized medium discharged from the circulation line, depending on the result of the determination unit; A combustion system for an alkali metal-containing fuel comprising:

2. a temperature sensor for measuring the temperature of the top of the combustion furnace; The combustion control unit controls the amount of the first fuel supplied by the fuel supply unit, the amount of the bed material newly supplied to the circulation line, and the amount of the bed material discharged from the circulation line using the measurement result of the temperature sensor in addition to the determination result of the determination unit.

10. The alkali metal-containing fuel combustion system of claim 1.

3. pressure sensors for measuring the pressure at the bottom and top of the combustion furnace; The combustion control unit controls the amount of the first fuel supplied by the fuel supply unit, the amount of the bed material newly supplied to the circulation line, and the amount of the bed material discharged from the circulation line, using the difference between the pressure at the bottom of the combustion furnace and the pressure at the top of the furnace measured by the pressure sensor in addition to the determination result of the determination unit and the measurement result of the temperature sensor.

3. The system for burning an alkali metal-containing fuel according to claim 2.

4. The determination unit performs machine learning to classify the aggregation state of the agglomerates into multiple classes based on the image data, and determines the aggregation state.

10. The alkali metal-containing fuel combustion system of claim 1.

5. A combustion method using a combustion furnace in which a fluidized bed is formed with a fluidizing medium in the furnace and a fuel containing an alkali metal is burned in the fluidized bed, a fuel supply step of supplying a first fuel containing an alkali metal and a second fuel having a lower alkali metal content than the first fuel to the combustion furnace; a separation step of separating the bed material discharged from the combustion furnace into bed material having a particle size equal to or smaller than a predetermined particle size value and agglomerates having a particle size greater than a predetermined particle size value; a circulating step of returning the bed material having a particle size equal to or smaller than a predetermined particle size value separated in the separating step to the combustion furnace; an imaging step of imaging the agglomerates separated in the separation step and outputting image data representing the imaged agglomerates; a determination step of determining the aggregation state of the agglomerates in the image represented by the image data output in the photographing step using a result of machine learning using the image data; a combustion control step of controlling, depending on the result of the determination step, at least any one of the amount of the first fuel supplied in the fuel supply step, the amount of the bed material separated in the separation step and having a particle size equal to or smaller than a predetermined value and newly supplied to a circulation line returning the bed material to the combustion furnace, and the amount of the bed material discharged from the circulation line; A method for burning an alkali metal-containing fuel, comprising:

Images