Fluidized bed boiler, fluidized bed boiler system and method for operating a fluidized bed boiler

Abstract

To provide a fluidized bed boiler, a fluidized bed boiler system, and an operation method of the fluidized bed boiler capable of keeping a temperature in a fluidized bed within a proper range.SOLUTION: A fluidized bed boiler includes a furnace in which a fluidized bed is formed, a fuel supply port disposed in the furnace and configured to supply fuel to the fluidized bed, and a pulverized-fuel supply port disposed in the furnace above the fuel supply port and configured to supply pulverized fuel to a freeboard formed in the furnace above the fluidized bed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a fluidized bed boiler, a fluidized bed boiler system, and a method of operating a fluidized bed boiler. [Background technology]

[0002] A fluidized bed boiler generates steam for power generation by introducing fuel such as biomass into a fluidized bed formed in a furnace using a fluidizing medium such as silica sand (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-230280 Summary of the Invention [Problem to be solved by the invention]

[0004] If the temperature in the fluidized bed becomes too high, the fluidizing medium or combustion ash will melt and solidify, forming agglomerates called agglomerations.

[0005] For example, when biomass is used as fuel, alkaline components such as potassium or sodium contained in the biomass melt in a high-temperature environment and react with silica sand, producing sintered compounds as agglomerations. If these compounds grow further, they can cause poor fluidity in the fluidized bed. Specifically, they can cause uneven flow near the heat transfer tubes in the cooling layer, causing wear on the heat transfer tubes and hindering boiler operation. Furthermore, the lowering of the melting point of ash derived from biomass fuels can accelerate corrosion of the heat transfer tubes, potentially leading to increased maintenance costs for the fluidized bed boiler.

[0006] As described above, in order to suppress the occurrence of agglomeration, the temperature in the fluidized bed must be kept within an appropriate temperature range.

[0007] An object of the present disclosure is to provide a fluidized bed boiler, a fluidized bed boiler system, and a method for operating a fluidized bed boiler that can keep the temperature in the fluidized bed within an appropriate range. [Means for solving the problem]

[0008] A fluidized bed boiler according to at least one embodiment of the present disclosure includes: A fluidized bed boiler having a furnace in which a fluidized bed is formed, a fuel supply port disposed in the furnace and configured to supply fuel to the fluidized bed; a pulverized fuel supply port disposed in the furnace above the fuel supply port and configured to supply pulverized fuel to a freeboard formed in the furnace above the fluidized bed; Equipped with.

[0009] A fluidized bed boiler system according to at least one embodiment of the present disclosure includes: The fluidized bed boiler described above; a controller for controlling the operation of the fluidized bed boiler; Equipped with The controller an intra-bed temperature acquisition unit for acquiring an intra-bed temperature, which is the temperature of the fluidized bed; a fuel control unit for controlling the amount of fuel supplied from the fuel supply port and the amount of pulverized fuel supplied from the pulverized fuel supply port based on the temperature in the bed; Includes:

[0010] A method of operating a fluidized bed boiler according to at least one embodiment of the present disclosure includes: A method for operating the fluidized bed boiler, comprising: an intra-bed temperature acquisition step of acquiring an intra-bed temperature, which is the temperature of the fluidized bed; a fuel control step for controlling the amount of fuel supplied from the fuel supply port and the amount of pulverized fuel supplied from the pulverized fuel supply port based on the temperature in the bed; Equipped with. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to provide a fluidized bed boiler, a fluidized bed boiler system, and a method of operating a fluidized bed boiler that can keep the temperature in the fluidized bed within an appropriate range. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram of a fluidized bed boiler according to a first embodiment. [Figure 2] FIG. 4 is a schematic diagram of a fluidized bed boiler according to a second embodiment. [Figure 3] 1 is a schematic diagram of a fluidized bed boiler system according to one embodiment. [Figure 4] 3 is a flowchart of operation control of a fluidized bed boiler according to one embodiment. [Figure 5] 3 is a flowchart of operation control of a fluidized bed boiler according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, several embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure. For example, expressions expressing relative or absolute arrangement such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" not only express such an arrangement exactly, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions such as "identical," "equal," and "homogeneous" that indicate that something is in an equal state not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. For example, expressions representing shapes such as a square shape or a cylindrical shape not only represent shapes such as a square shape or a cylindrical shape in the strict geometric sense, but also represent shapes including uneven portions, chamfered portions, etc., to the extent that the same effect can be obtained. On the other hand, the expressions "comprise," "include," or "have" one element are not exclusive expressions that exclude the presence of other elements. Note that the same components will be denoted by the same reference numerals and the description thereof will be omitted.

[0014] The fluidized bed boiler 1 of the present disclosure includes a furnace 5 having a fluidized bed 2 and a freeboard 3 formed therein. The fluidized bed 2 is formed by blowing a fluidizing medium such as silica sand upward with primary air. In the fluidized bed 2, fuel introduced into the furnace 5 is combusted within the fluidized bed 2. The freeboard 3 is a combustion space formed above the fluidized bed 2, and combustion of fuel suspended in the freeboard 3 occurs as secondary air or the like is supplied. Below, a fluidized bed boiler 1A(1) according to a first embodiment and a fluidized bed boiler 1B(1) according to a second embodiment will be described in order.

[0015] <Fluidized bed boiler 1A(1) according to the first embodiment> FIG. 1 is a schematic diagram of a fluidized-bed boiler 1A(1) according to a first embodiment. The fluidized-bed boiler 1A is a bubbling fluidized-bed boiler equipped with a fluidized-bed material supply device 13 that supplies a fluidized bed material to a furnace 5, a primary air supply port 11 that supplies primary air upward within the furnace 5, and a fluidized-bed material return line 12 that returns the fluidized bed material discharged from the bottom of the furnace 5 to the furnace 5. The primary air supply port 11 may be either an air nozzle or an air diffuser. The illustrated furnace 5 is provided with a heat transfer tube 15 through which cooling water flows to cool the fluidized bed 2; however, as described below, the heat transfer tube 15 is not an essential component of the present disclosure.

[0016] The fluidized bed boiler 1A further includes a fuel supply port 34 disposed on the furnace wall 6 of the furnace 5. The fuel supply port 34 is configured to supply fuel with relatively large particle sizes, such as biomass fuel such as wood chips, to the fluidized bed 2. The fuel is supplied to the fuel supply port 34 by a fuel supply device 30. The fuel supply device 30 may be a supply device capable of supplying biomass fuel, which is configured with a rotary valve and a fuel chute, or may be a screw feeder or a spreader. Note that, as just one example, the biomass fuel is woody biomass (thinned wood).

[0017] The fluidized bed boiler 1A according to the first embodiment further includes a pulverized fuel supply port 44A disposed on the furnace wall 6 above the fuel supply port 34. The pulverized fuel supply port 44A is configured to supply pulverized fuel having a relatively small particle size, such as pulverized biomass fuel or pulverized coal, to the freeboard 3. The pulverized fuel is guided to the pulverized fuel supply port 44A through a pulverized fuel supply pipe 42A through which a carrier gas, such as air, flows. A pulverized fuel control valve 46 is disposed in the pulverized fuel supply pipe 42A. In this embodiment, the pulverized fuel control valve 46 is an on-off valve, which may be a pneumatic valve. The pulverized fuel is, by way of example only, a high-chlorine-containing fuel such as RPF (Refuse Paper and Plastic Fuel), RDF (Refuse Derived Fuel), or waste plastic.

[0018] As an example, the pulverized fuel supply ports 44A are arranged in multiple stages (more specifically, two stages) vertically on the furnace wall 6. Furthermore, a secondary air supply pipe 22 is connected to each pulverized fuel supply port 44A according to the first embodiment, and the pulverized fuel supply pipe 42A described above is connected to the secondary air supply pipe 22 upstream of the fuel supply port 34. Furthermore, the upstream end of each pulverized fuel supply pipe 42A is connected to a distributor 45, and a fuel storage device (not shown) for storing pulverized fuel is arranged upstream of the distributor 45. A feed device 47 (see FIG. 3) for feeding pulverized fuel is arranged below the fuel storage device, and the amount of fuel fed by the feed device 47 is controllable. In this example, a secondary air supply port 25 is arranged below the fuel supply port 34. The secondary air supply port 25 is configured to solely supply secondary air into the furnace 5.

[0019] The operation of the fluidized bed boiler 1A(1) is outlined as follows. Fuel is supplied into the furnace 5 from the fuel supply port 34 by operation of the fuel supply device 30. The fuel falls to the fluidized bed 2 and undergoes a combustion reaction. At this time, all of the multiple pulverized fuel control valves 46 are closed and the feed device 47 is stopped, and secondary air is supplied to the freeboard 3 from the secondary air supply port 25 and the multiple fuel supply ports 34. The combustion gas generated by the combustion of the fuel in the fluidized bed 2 and the freeboard 3 passes through a heat exchanger (not shown) such as a reheater or superheater located downstream of the furnace 5, and steam (superheated steam) is generated in the heat exchanger.

[0020] During operation of the fluidized bed boiler 1A, the in-bed temperature, which is the temperature of the fluidized bed 2, preferably falls within a predetermined temperature range (for example, 700°C to 900°C). Whether the in-bed temperature falls within the predetermined temperature range is determined based on the measurement results of an in-bed temperature sensor 19 provided on the furnace wall 6.

[0021] For example, if the intra-bed temperature measured by the intra-bed temperature sensor 19 exceeds the allowable upper limit temperature, which is the maximum value of the temperature range, each pulverized fuel control valve 46 switches to an open state, the discharge device 47 operates, and the fuel supply device 30 reduces the amount of fuel supplied. While the amount of fuel supplied from the fuel supply port 34 is reduced, pulverized fuel is supplied to the furnace 5 from the pulverized fuel supply port 44A together with secondary air. Because the pulverized fuel supplied to the freeboard 3 reacts with the secondary air to cause a combustion reaction, the reduction in heat input to the fluidized-bed boiler 1A due to the reduction in the amount of fuel supplied from the fuel supply port 34 is compensated for by the combustion of the pulverized fuel. Therefore, while maintaining the heat input to the fluidized-bed boiler 1A, combustion in the freeboard 3 can be promoted relative to combustion in the fluidized bed 2. Therefore, the intra-bed temperature can be reduced while maintaining the amount of steam generated. The allowable upper limit temperature is, for example, 900°C, but the present disclosure is not limited thereto.

[0022] Thereafter, when the measured temperature in the bed falls below the allowable lower limit temperature, which is the minimum value of the temperature range, each pulverized fuel control valve 46 switches to a closed state, the discharge device 47 stops, and the fuel supply device 30 increases the amount of fuel supplied. Pulverized fuel is no longer supplied from the pulverized fuel supply port 44A, and the amount of fuel supplied from the fuel supply port 34 increases. This makes it possible to increase the temperature in the bed while maintaining the amount of steam generated. Note that the allowable lower limit temperature is 700°C as an example, but the present disclosure is not limited to this.

[0023] The fluidized bed boiler 1A is configured to include the fuel supply port 34 and the pulverized fuel supply port 44A, so that the temperature in the fluidized bed 2 can be kept within an appropriate range. This makes it possible to avoid problems in the fluidized bed 2, such as wear and corrosion of the heat transfer tubes 15. Furthermore, since the pulverized fuel supplied from the pulverized fuel supply port 44A performs the function of cooling the fluidized bed 2, it becomes possible to shorten the length of the heat transfer tubes 15 in the fluidized bed 2, or even to eliminate the heat transfer tubes 15 in the fluidized bed 2. In other words, there is room for simplifying the structure of the furnace 5.

[0024] Furthermore, since the above-mentioned pulverized fuel supply port 44A functions not only as a port for supplying pulverized fuel but also as a port for supplying secondary air, the configuration of the furnace 5 can be simplified compared to when the secondary air supply port and the pulverized fuel supply port 44A are arranged separately.

[0025] The description of the configuration of the fluidized bed boiler 1A will continue with reference to Figure 1. The fluidized bed boiler 1A includes an auxiliary gas supply port 54 configured to supply auxiliary gas to the freeboard 3, an auxiliary gas supply pipe 52 for guiding the auxiliary gas to the auxiliary gas supply port 54, and an auxiliary gas control valve 56 arranged in the auxiliary gas supply pipe 52. The auxiliary gas supply port 54 is arranged in the furnace wall 6 below the pulverized fuel supply port 44A and above the fuel supply port 34.

[0026] The auxiliary gas is a non-flammable gas, such as steam or combustion gas. When steam is used as the auxiliary gas, the auxiliary gas supply pipe 52 is an extraction pipe that extracts the steam generated in the fluidized bed boiler 1A and leads it to the auxiliary gas supply port 54. When combustion gas is used as the auxiliary gas, the auxiliary gas supply pipe 52 is a return pipe that returns a portion of the combustion gas flowing through the furnace 5 to the auxiliary gas supply port 54. The auxiliary gas control valve 56 in this example is an on-off valve, and when the auxiliary gas control valve 56 is opened, auxiliary gas is supplied from the auxiliary gas supply port 54.

[0027] According to the above configuration, the flow of auxiliary gas supplied into the furnace 5 through the auxiliary gas supply port 54 can promote combustion in the freeboard 3 relatively to combustion in the fluidized bed 2. As a more specific example, the auxiliary gas in the furnace 5 assists the floating of the pulverized fuel supplied from the pulverized fuel supply port 44A to the freeboard 3, thereby promoting combustion of the pulverized fuel in the freeboard 3 even when the size of the pulverized fuel varies. This makes it possible to more reliably lower the temperature in the bed when the temperature in the bed exceeds the allowable upper limit temperature. Note that the auxiliary gas control valve 56 may be a flow regulation valve instead of an on-off valve. Even in this case, the above technical advantages can be obtained.

[0028] The fluidized bed boiler 1A further includes a lower pulverized fuel supply port 64 disposed in the furnace 5 below the fuel supply port 34. The lower pulverized fuel supply port 64 is configured to supply pulverized fuel to the fluidized bed 2. The pulverized fuel supplied from the lower pulverized fuel supply port 64 may be different from the pulverized fuel supplied from the pulverized fuel supply port 44A, but the configuration of the fluidized bed boiler 1A can be simplified if the pulverized fuel is the same. Specifically, the pulverized fuel cut out by the cut-out device 47 can be supplied to the lower pulverized fuel supply port 64.

[0029] The fluidized bed boiler 1A further includes a lower pulverized fuel supply pipe 62 for supplying pulverized fuel to the lower pulverized fuel supply port 64, and a lower pulverized fuel control valve 66 disposed in the lower pulverized fuel supply pipe 62. The lower pulverized fuel control valve 66 in this example is an on-off valve, and when the lower pulverized fuel control valve 66 is in an open state, the pulverized fuel is supplied from the lower pulverized fuel supply port 64 to the fluidized bed 2. The lower pulverized fuel control valve 66 may be a pneumatic valve.

[0030] According to the above configuration, the lower pulverized fuel supply port 64 supplies the pulverized fuel into the fluidized bed 2, thereby increasing the temperature inside the bed. Since the target of the supply from the lower pulverized fuel supply port 64 is the pulverized fuel and the supply destination of the pulverized fuel is inside the fluidized bed 2, the time from when the supply of the pulverized fuel starts to when the temperature inside the bed starts to increase is short. Therefore, when the temperature inside the bed falls below the allowable lower limit temperature, the temperature inside the bed can be immediately increased, and the temperature inside the bed can be kept within an appropriate range.

[0031] <Fluidized bed boiler 1B(1) according to the second embodiment> Fig. 2 is a schematic diagram of a fluidized bed boiler 1B(1) according to a second embodiment. In Fig. 2, the same components as those in the first embodiment are denoted by the same reference numerals as those in Fig. 1, and the description thereof may be omitted or simplified below.

[0032] The fluidized bed boiler 1B(1) includes multiple stages of secondary air supply ports 24 arranged above the secondary air supply port 25, and multiple stages of pulverized fuel supply ports 44B arranged above the multiple stages of secondary air supply ports 24. The secondary air supply ports 24 are connected to the secondary air supply pipe 22 and are configured to exclusively supply secondary air to the fluidized bed 2. The pulverized fuel supply port 44B is connected to the pulverized fuel supply pipe 42B and is configured to exclusively supply pulverized fuel entrained in the carrier gas to the fluidized bed 2.

[0033] In this example, the number of secondary air supply ports 24 is two, and therefore the number of pulverized fuel supply ports 44B is also two. The pulverized fuel supplied into the furnace 5 from the pulverized fuel supply port 44B is easily floated by the secondary air supplied from the secondary air supply port 24 located directly below the pulverized fuel supply port 44B. Therefore, even if the size of the pulverized fuel fluctuates, the combustion of the pulverized fuel in the freeboard 3 can be promoted. Therefore, when the temperature in the bed exceeds the allowable upper limit temperature, the pulverized fuel control valve 46 arranged in the pulverized fuel supply pipe 42B is switched to an open state, the feed device 47 is activated, and the pulverized fuel is supplied from the pulverized fuel supply port 44B.

[0034] <Fluidized bed boiler system 10> Fig. 3 is a schematic diagram of a fluidized bed boiler system 10 according to an embodiment of the present disclosure. The fluidized bed boiler system 10 includes the above-described fluidized bed boiler 1 and a controller 90 that controls the operation of the fluidized bed boiler 1. The fluidized bed boiler 1 shown in Fig. 3 may be either the fluidized bed boiler 1A or 1B. In the following description, the pulverized fuel supply ports 44A and 44B may be collectively referred to as "pulverized fuel supply port 44," and the pulverized fuel supply pipes 42A and 42B may be collectively referred to as "pulverized fuel supply pipe 42."

[0035] The functional configuration of the controller 90 will be described (the physical configuration of the controller 90 will be described later). The controller 90 functions as an in-bed temperature acquisition unit 91 and a fuel control unit 92.

[0036] The in-bed temperature acquiring unit 91 acquires the in-bed temperature measured by the in-bed temperature sensor 19. The fuel control unit 92 controls the amount of fuel supplied from the fuel supply port 34 and the amount of pulverized fuel supplied from the pulverized fuel supply port 44 based on the acquired in-bed temperature. The control of the fuel supply amount is executed through the control of the fuel supply device 30, and the control of the pulverized fuel supply amount is executed through the control of the pulverized fuel control valve 46 and the feed device 47 disposed in the pulverized fuel supply pipe 42. According to the above configuration, the fuel supply amount and the pulverized fuel supply amount are controlled based on the in-bed temperature, so that the fluidized bed boiler system 10 is realized which can keep the in-bed temperature within an appropriate range.

[0037] The fuel control unit 92 includes a fluidized bed temperature reduction control unit 93 that lowers the temperature inside the bed, and a first fluidized bed temperature increase control unit 95 that raises the temperature inside the bed, and both control units control the temperature inside the bed through control of the fuel supply device 30, the pulverized fuel control valve 46, and the extrusion device 47.

[0038] Specifically, when the temperature inside the bed exceeds the allowable upper limit temperature, the fluidized bed temperature reducing control unit 93 controls the fuel supply device 30, the pulverized fuel control valve 46, and the feed device 47 to reduce the amount of fuel supplied and increase the amount of pulverized fuel supplied. This makes it possible to promote combustion in the freeboard 3 relative to combustion in the fluidized bed 2 while maintaining the heat input to the fluidized bed boiler 1. Therefore, it is possible to reduce the temperature inside the bed while maintaining the amount of steam generated in the fluidized bed boiler 1A.

[0039] Furthermore, when the temperature inside the bed falls below the allowable lower limit temperature, the first fluidized bed temperature rise control unit 95 controls the fuel supply device 30, the pulverized fuel control valve 46, and the feed device 47 to increase the fuel supply amount and decrease the pulverized fuel supply amount. This allows the combustion inside the fluidized bed 2 to be promoted relatively to the combustion in the freeboard 3 while maintaining the heat input amount of the fluidized bed boiler 1. Therefore, the temperature inside the bed can be increased while maintaining the amount of steam generated in the fluidized bed boiler 1A.

[0040] Furthermore, the controller 90 shown in FIG. 3 functions as an auxiliary gas control unit 96, a lower pulverized fuel control unit 97, and a second fluidized bed temperature rise control unit 98.

[0041] The auxiliary gas control unit 96 is a control unit for lowering the intra-bed temperature by controlling the auxiliary gas control valve 56. Specifically, if the intra-bed temperature remains above the allowable upper limit temperature even after control by the fluidized-bed temperature reducing control unit 93, the auxiliary gas control unit 96 controls the auxiliary gas control valve 56 to increase the amount of auxiliary gas supplied from the auxiliary gas supply port 54. The flow of auxiliary gas supplied into the furnace 5 assists the floating of the pulverized fuel, so that combustion in the freeboard 3 can be promoted relatively to combustion in the fluidized bed 2. As a result, the intra-bed temperature can be lowered to fall within a predetermined range.

[0042] The lower pulverized fuel control unit 97 is a control unit for increasing the temperature in the bed through the control of the lower pulverized fuel control valve 66. Specifically, if the temperature in the bed is below the allowable lower limit temperature even after the control by the first fluidized bed temperature increase control unit 95, the lower pulverized fuel control valve 66 is controlled to increase the amount of lower pulverized fuel supplied from the lower pulverized fuel supply port 64. By adding pulverized fuel to the fluidized bed 2, the temperature in the bed can be immediately increased and can be kept within a predetermined range.

[0043] The second fluidized bed temperature rise control unit 98 is a control unit for increasing the temperature in the bed through the control of the fuel supply device 30 and the lower pulverized fuel control valve 66. Specifically, when the temperature in the bed falls below the allowable lower limit temperature, the second fluidized bed temperature rise control unit 98 controls the fuel supply device 30 and the lower pulverized fuel control valve 66 so as to reduce the amount of fuel supplied from the fuel supply port 34 and increase the amount of lower pulverized fuel supplied from the lower pulverized fuel supply port 64. Since the amount of fuel supplied is reduced and the amount of lower pulverized fuel supplied is increased, the temperature in the bed can be increased while maintaining the amount of steam generated by the fluidized bed boiler 1. Note that this control is executed under the condition that pulverized fuel is not supplied from the lower pulverized fuel supply port 64.

[0044] <Operation control of fluidized bed boiler 1> 4 and 5, the operation control of the fluidized bed boiler 1 will be described. This operation control (operation method) is executed by a processor constituting the controller 90 with the aim of keeping the temperature inside the bed within a predetermined temperature range while the fluidized bed boiler 1 is in operation. In the following description, "step" may be abbreviated as "S."

[0045] First, the processor executes an intra-bed temperature acquisition step (S1) of acquiring an intra-bed temperature based on the measurement result of the intra-bed temperature sensor 19. The processor executing S1 is an example of the intra-bed temperature acquisition unit 91.

[0046] Next, the processor determines whether the temperature inside the bed obtained in S1 exceeds the allowable upper limit temperature (S3). This determination may be a determination of whether the current temperature inside the bed has exceeded the allowable upper limit temperature, or a determination of whether the temperature inside the bed will exceed the allowable upper limit temperature in the future. If it is determined that the temperature inside the bed is equal to or lower than the allowable upper limit temperature (S3: NO), the processor proceeds to S13, which will be described later.

[0047] When it is determined that the temperature in the bed exceeds the allowable upper limit temperature (S3: YES), the processor executes a fluidized bed temperature reduction control step (S5). The processor that executes S5 is an example of the fluidized bed temperature reduction control unit 93. By executing S5, the amount of fuel supplied from the fuel supply port 34 is reduced. At the same time, the pulverized fuel control valve 46 is switched to an open state, the discharge device 47 is activated, and the pulverized fuel is supplied from the pulverized fuel supply port 44. In other words, the amount of pulverized fuel supplied from the pulverized fuel supply port 44 is increased. This reduces the temperature in the bed.

[0048] Thereafter, the processor acquires the temperature inside the bed (S7). S7 is a step similar to S1. The processor determines whether the temperature inside the bed acquired in S7 exceeds the allowable upper limit temperature (S9). S9 is a step similar to S3. If it is determined that the temperature inside the bed is equal to or lower than the allowable upper limit temperature (S9: NO), the processor proceeds to S13, which will be described later.

[0049] On the other hand, if it is determined that the temperature in the bed still exceeds the allowable upper limit temperature (S9: YES), the processor executes an auxiliary gas control step (S11). The processor that executes S11 is an example of the auxiliary gas control unit 96. By executing S11, the auxiliary gas control valve 56 switches to an open state, and auxiliary gas begins to be supplied from the auxiliary gas supply port 54. In other words, the amount of auxiliary gas supplied from the auxiliary gas supply port 54 increases. By executing S11, the temperature in the bed falls within a range below the allowable upper limit temperature.

[0050] Next, the processor acquires the bed temperature (S13). S13 is the same step as S1. The processor determines whether the bed temperature acquired in S13 is below the allowable lower limit temperature (S15). This determination may be a determination of whether the current bed temperature has fallen below the allowable lower limit temperature, or a determination of whether the bed temperature will fall below the allowable lower limit temperature in the future. When S5 and S11 are executed, the bed temperature is basically within the appropriate temperature range and is equal to or higher than the allowable lower limit temperature (S15: NO). In this case, the processor ends the operation control process.

[0051] On the other hand, immediately after this control process is started from S1, the temperature in the bed may fall below the allowable lower limit temperature (S3: NO, S15: YES). In this case, the processor determines whether pulverized fuel is being supplied from the pulverized fuel supply port 44 (S17). If pulverized fuel is being supplied (S17: YES), the processor executes the first fluidized bed temperature increase control step (S19). The processor that executes S19 is an example of the first fluidized bed temperature increase control unit 95. By executing S19, the amount of fuel supplied by the fuel supply device 30 increases. On the other hand, the pulverized fuel control valve 46 switches to the closed state and the feed device 47 stops, thereby ending the supply of pulverized fuel through the pulverized fuel supply port 44. In other words, the amount of pulverized fuel supplied from the pulverized fuel supply port 44 decreases. This causes the temperature in the bed to rise.

[0052] Next, the processor acquires the temperature inside the bed (S21). S21 is a step similar to S1. The processor determines whether the temperature inside the bed acquired in S21 is below the allowable lower limit temperature (S23). S23 is a step similar to S15. If it is determined that the temperature inside the bed is equal to or higher than the allowable lower limit temperature (S23: NO), the processor ends the operation control process.

[0053] On the other hand, when it is determined that the temperature in the bed is still below the allowable lower limit temperature (S23: YES), the processor executes a lower pulverized fuel control step (S25). The processor that executes S25 is an example of the lower pulverized fuel control unit 97. By executing S25, the lower pulverized fuel control valve 66 is switched to an open state, and pulverized fuel is supplied from the lower pulverized fuel supply port 64. That is, the lower pulverized fuel from the lower pulverized fuel supply port 64 increases. By executing S25, the temperature in the bed becomes equal to or higher than the allowable lower limit temperature, and the processor ends the operation control process.

[0054] Furthermore, in S17, if pulverized fuel is not being supplied from the pulverized fuel supply port 44 (S17: NO), the processor executes a second fluidized bed temperature rise control step (S27). The processor that executes S27 is an example of the second fluidized bed temperature rise control unit 98. By executing S27, the amount of fuel supplied by the fuel supply device 30 decreases. On the other hand, the lower pulverized fuel control valve 66 switches to the open state, thereby starting the supply of pulverized fuel from the lower pulverized fuel supply port 64. In other words, the amount of lower pulverized fuel supplied from the lower pulverized fuel supply port 64 increases. By executing S27, the temperature in the bed becomes equal to or higher than the allowable lower limit temperature, and the processor ends the operation control process.

[0055] In S1, the processor may acquire the supply amounts of fuel, primary air, and secondary air instead of acquiring the measurement results of the bed temperature sensor 19. The bed temperature can be acquired (estimated) based on these supply amounts. In addition, S11 does not have to be executed after S5. For example, if it is determined in S3 that the bed temperature exceeds the allowable upper limit temperature (S3: YES), the processor may execute S5 after executing a step corresponding to S11.

[0056] <Other> The controller 90 described above is configured by a computer and includes a processor, a memory (storage medium), and an external communication interface. The processor may be a CPU, a GPU, an MPU, a DSP, or a combination thereof. The processor according to other embodiments may be implemented by an integrated circuit such as a PLD, an ASIC, an FPGA, or an MCU. The memory is configured to temporarily or non-temporarily store various data and may be implemented by at least one of a RAM, a ROM, and a flash memory. The processor executes various control processes according to instructions from a program loaded into the memory. The controller 90 may also be a DCS panel that constitutes one of multiple control panels for a plant.

[0057] <Summary> The contents of the above-described embodiments can be understood, for example, as follows.

[0058] 1) A fluidized bed boiler (1) according to at least one embodiment of the present disclosure includes: A fluidized bed boiler having a furnace (5) in which a fluidized bed (2) is formed, a fuel supply port (34) disposed in the furnace and configured to supply fuel to the fluidized bed; a pulverized fuel supply port (44) disposed in the furnace above the fuel supply port and configured to supply pulverized fuel to a freeboard (3) formed in the furnace above the fluidized bed; Equipped with.

[0059] According to the configuration 1) above, when the bed temperature, which is the temperature in the fluidized bed, exceeds the allowable upper limit temperature, it is possible to reduce the amount of fuel supplied from the fuel supply port and increase the amount of pulverized fuel supplied from the upper supply port. This promotes combustion in the freeboard relatively to combustion in the fluidized bed, thereby lowering the bed temperature. Furthermore, even if the amount of fuel supplied from the fuel supply port decreases, the amount of pulverized fuel supplied from the pulverized fuel supply port increases, so the heat input to the fluidized bed boiler can be maintained. This realizes a fluidized bed boiler that can keep the temperature in the fluidized bed within an appropriate range.

[0060] 2) In some embodiments, the fluidized bed boiler described in 1) above is a secondary air supply pipe (22) connected to the pulverized fuel supply port and configured to introduce secondary air mixed with the pulverized fuel to the pulverized fuel supply port; The pulverized fuel supply port is configured to supply the secondary air mixed with the pulverized fuel to the freeboard.

[0061] According to the above configuration 2), it is not necessary to separately arrange the pulverized fuel supply port and the secondary air supply port, so that the configuration of the furnace can be simplified.

[0062] 3) In some embodiments, the fluidized bed boiler described in 1) above is a pulverized fuel supply pipe (42) connected to the pulverized fuel supply port and configured to guide the pulverized fuel entrained in the carrier gas to the pulverized fuel supply port; The pulverized fuel supply port is configured to supply the pulverized fuel entrained in the carrier gas to the freeboard.

[0063] According to the configuration of 3) above, the pulverized fuel supplied into the furnace from the pulverized fuel supply port is easily lifted by the flow of secondary air supplied into the furnace. Therefore, even if the size of the pulverized fuel fluctuates, the combustion of the pulverized fuel in the freeboard can be promoted, and when the temperature in the bed exceeds the allowable upper limit temperature, the temperature in the bed can be more reliably lowered.

[0064] 4) In some embodiments, the fluidized bed boiler according to any one of 1) to 3) above, The furnace further includes an auxiliary gas supply port (54) disposed in the furnace below the pulverized fuel supply port and configured to supply auxiliary gas to the freeboard.

[0065] According to the configuration of 4) above, the flow of auxiliary gas supplied through the auxiliary gas supply port can promote combustion in the freeboard relatively to combustion in the fluidized bed. As a more specific example, the auxiliary gas in the furnace helps the pulverized fuel to float, and can promote combustion of the pulverized fuel in the freeboard even when the size of the pulverized fuel varies. As a result, when the temperature in the bed exceeds the allowable upper limit temperature, the temperature in the bed can be more reliably lowered.

[0066] 5) In some embodiments, the fluidized bed boiler described in any one of 1) to 4) above is The furnace further includes a lower pulverized fuel supply port (64) disposed below the fuel supply port for supplying pulverized fuel to the fluidized bed.

[0067] According to the configuration of 5) above, the temperature inside the bed rises when the lower pulverized fuel supply port supplies pulverized fuel into the fluidized bed. Since the object supplied by the lower pulverized fuel supply port is pulverized fuel and the supply destination of the pulverized fuel is inside the fluidized bed, the time from when the supply of pulverized fuel starts to when the temperature inside the bed starts to rise is short. Therefore, when the temperature inside the bed falls below the allowable lower limit temperature, it is possible to immediately raise the temperature inside the bed, and to keep the temperature inside the bed within the appropriate range.

[0068] 6) At least one embodiment of the fluidized bed boiler system (10) of the present disclosure includes: The fluidized bed boiler (1) described above in 1), a controller (90) for controlling the operation of the fluidized bed boiler; Equipped with The controller an intra-bed temperature acquisition unit (91) for acquiring an intra-bed temperature, which is the temperature of the fluidized bed; a fuel control unit (92) for controlling the amount of fuel supplied from the fuel supply port and the amount of pulverized fuel supplied from the pulverized fuel supply port based on the temperature in the bed; Includes:

[0069] According to the configuration 6) above, the fuel supply amount and the pulverized fuel supply amount are controlled based on the temperature inside the bed, so that a fluidized bed boiler system is realized that can keep the temperature inside the bed within an appropriate range.

[0070] 7) In some embodiments, the fluidized bed boiler system according to 6) above, The fuel control unit includes a fluidized bed temperature reduction control unit (93) for controlling the amount of fuel supplied from the fuel supply port to be reduced and the amount of pulverized fuel supplied from the pulverized fuel supply port to be increased when the temperature inside the bed exceeds the allowable upper limit temperature.

[0071] According to the configuration of 7) above, when the temperature inside the bed exceeds the allowable upper limit temperature, combustion in the freeboard is promoted relative to combustion inside the fluidized bed. Even if the fuel supply amount decreases, the amount of pulverized fuel supplied from the fuel supply port increases, so the heat input to the fluidized bed boiler can be maintained. Therefore, the temperature inside the bed can be lowered while maintaining the amount of steam generated in the fluidized bed boiler.

[0072] 8) In some embodiments, the fluidized bed boiler system according to 6) or 7) above, the fluidized bed boiler further includes an auxiliary gas supply port (54) disposed in the furnace below the pulverized fuel supply port and configured to supply auxiliary gas to the freeboard; The controller further includes an auxiliary gas control unit (96) that controls the amount of auxiliary gas supplied from the auxiliary gas supply port so as to increase when the temperature in the bed exceeds an allowable upper limit temperature.

[0073] According to the above configuration 8), when the bed temperature exceeds the allowable upper limit temperature, the supply of auxiliary gas can promote combustion in the freeboard relatively to combustion in the fluidized bed, thereby lowering the bed temperature, thereby keeping the bed temperature within an appropriate range.

[0074] 9) In some embodiments, the fluidized bed boiler system according to 7) above, the fluidized bed boiler further includes an auxiliary gas supply port (54) disposed in the furnace below the pulverized fuel supply port and configured to supply auxiliary gas to the freeboard; The controller further includes an auxiliary gas control unit (96) for controlling the amount of auxiliary gas supplied from the auxiliary gas supply port to increase if the temperature in the bed exceeds the allowable upper limit temperature even after control by the fluidized bed temperature reduction control unit.

[0075] According to the configuration of 9) above, if the temperature inside the bed exceeds the allowable upper limit temperature even after control by the fluidized bed temperature reduction control unit, the flow of auxiliary gas supplied from the auxiliary gas supply port assists the floating of the pulverized fuel. This can promote combustion in the freeboard relatively to combustion inside the fluidized bed, and can lower the temperature in the fluidized bed, so that the temperature inside the bed can be kept within an appropriate range.

[0076] 10) In some embodiments, the fluidized bed boiler system according to 6) or 7) above, The fuel control unit includes a first fluidized bed temperature rise control unit (95) for controlling the amount of fuel supplied from the fuel supply port to increase and the amount of pulverized fuel supplied from the pulverized fuel supply port to decrease when the temperature inside the bed falls below the allowable lower limit temperature.

[0077] According to the configuration of 10) above, when the temperature in the bed is below the allowable lower limit temperature, combustion in the fluidized bed is promoted relative to combustion in the freeboard, and the temperature in the bed can be raised. Also, even if the amount of pulverized fuel supplied from the pulverized fuel supply port decreases, the amount of fuel supplied from the fuel supply port increases, so the heat input to the fluidized bed boiler can be maintained. Therefore, the temperature in the bed can be raised while maintaining the amount of steam generated in the fluidized bed boiler.

[0078] 11) In some embodiments, the fluidized bed boiler system according to 10) above, the fluidized bed boiler further includes a lower pulverized fuel supply port (64) disposed in the furnace below the fuel supply port for supplying pulverized fuel to the fluidized bed; The controller further includes a lower pulverized fuel control unit (97) for controlling the amount of lower pulverized fuel supplied from the lower pulverized fuel supply port to increase if the temperature inside the bed remains below the allowable lower limit temperature even after control by the first fluidized bed temperature rise control unit.

[0079] According to the configuration of 11) above, if the intra-bed temperature remains below the allowable lower limit temperature even after control by the first fluidized-bed temperature rise control unit, the amount of lower pulverized fuel supplied from the lower pulverized fuel supply port is increased, thereby raising the intra-bed temperature. Here, since the target supplied from the lower pulverized fuel supply port is the pulverized fuel, and the supply destination of the pulverized fuel is within the fluidized bed, the time from when the supply of pulverized fuel begins to when the intra-bed temperature starts to rise is short. Therefore, if the intra-bed temperature remains below the allowable lower limit temperature even after control by the first fluidized-bed temperature rise control unit, the intra-bed temperature can be raised immediately, and the intra-bed temperature can be kept within an appropriate range.

[0080] 12) In some embodiments, the fluidized bed boiler system according to any one of 6) to 9) above, the fluidized bed boiler further includes a lower pulverized fuel supply port (64) disposed in the furnace below the fuel supply port for supplying pulverized fuel to the fluidized bed; The controller includes a second fluidized bed temperature rise control unit (98) for controlling the amount of fuel supplied from the fuel supply port to decrease and the amount of lower fine fuel supplied from the lower fine fuel supply port to increase when the temperature inside the bed falls below the allowable lower limit temperature.

[0081] According to the above configuration 12), when the temperature in the bed falls below the allowable lower limit temperature, the amount of fuel supplied from the fuel supply port is reduced and the amount of lower pulverized fuel supplied from the lower pulverized fuel supply port is increased, thereby making it possible to increase the temperature in the bed while maintaining the amount of steam generated.

[0082] 13) A method of operating a fluidized bed boiler according to at least one embodiment of the present disclosure, comprising: A method for operating the fluidized bed boiler (1) described above in 1), an in-bed temperature acquisition step (S1, S13) of acquiring an in-bed temperature, which is the temperature of the fluidized bed; a fuel control step (S5, S19) for controlling the amount of fuel supplied from the fuel supply port and the amount of pulverized fuel supplied from the pulverized fuel supply port based on the temperature in the bed; Equipped with.

[0083] The configuration 13) above provides the same technical advantages as the configuration 6) above. [Explanation of symbols]

[0084] 1A, 1B(1): Fluidized bed boiler 2: Fluidized bed 3: Freeboard 5: Furnace 6: Furnace wall 10: Fluidized bed boiler system 11: Primary air supply port 12: Bed medium return line 13: Fluid medium supply device 15: Heat transfer tube 19: Layer temperature sensor 22: Secondary air supply pipe 24,25: Secondary air supply port 30:Fuel supply device 34: Fuel supply port 42A,42B(42):Powdered fuel supply pipe 44A, 44B (44): Pulverized fuel supply port 45: Cutting device 46: Pulverized fuel control valve 52: Auxiliary gas supply pipe 54: Auxiliary gas supply port 56: Auxiliary gas control valve 62: Lower pulverized fuel supply pipe 64: Lower pulverized fuel supply port 66: Lower pulverized fuel control valve 90: Controller 91: In-layer temperature acquisition section 92: Fuel control unit 93: Fluidized bed cooling control unit 95: First fluidized bed temperature rise control section 96: Auxiliary gas control section 97: Lower pulverized fuel control unit 98: Second fluidized bed temperature rise control section

Claims

1. A fluidized bed boiler having a furnace in which a fluidized bed is formed, a fuel supply port disposed in the furnace and configured to supply fuel to the fluidized bed; a pulverized fuel supply port disposed in the furnace above the fuel supply port and configured to supply pulverized fuel to a freeboard formed in the furnace above the fluidized bed; A fluidized bed boiler comprising:

2. a secondary air supply pipe connected to the pulverized fuel supply port and configured to introduce secondary air mixed with the pulverized fuel to the pulverized fuel supply port; The pulverized fuel supply port is configured to supply the secondary air mixed with the pulverized fuel to the freeboard. The fluidized bed boiler according to claim 1.

3. a pulverized fuel supply pipe connected to the pulverized fuel supply port and configured to guide the pulverized fuel entrained in the carrier gas to the pulverized fuel supply port; The pulverized fuel supply port is configured to supply the pulverized fuel entrained in the carrier gas to the freeboard. The fluidized bed boiler according to claim 1.

4. an auxiliary gas supply port disposed in the furnace below the pulverized fuel supply port and configured to supply auxiliary gas to the freeboard; A fluidized bed boiler according to any one of claims 1 to 3.

5. a lower pulverized fuel supply port disposed in the furnace below the fuel supply port for supplying pulverized fuel to the fluidized bed; A fluidized bed boiler according to any one of claims 1 to 3.

6. The fluidized bed boiler according to claim 1; a controller for controlling the operation of the fluidized bed boiler; Equipped with The controller an intra-bed temperature acquisition unit for acquiring an intra-bed temperature, which is the temperature of the fluidized bed; a fuel control unit for controlling the amount of fuel supplied from the fuel supply port and the amount of pulverized fuel supplied from the pulverized fuel supply port based on the temperature in the bed; Contains Fluidized bed boiler system.

7. The fuel control unit includes a fluidized bed temperature reducing control unit for controlling the amount of fuel supplied from the fuel supply port to decrease and the amount of pulverized fuel supplied from the pulverized fuel supply port to increase when the temperature in the bed exceeds an allowable upper limit temperature. The fluidized bed boiler system according to claim 6.

8. The fluidized bed boiler further includes an auxiliary gas supply port disposed in the furnace below the pulverized fuel supply port and configured to supply auxiliary gas to the freeboard; The controller further includes an auxiliary gas control unit that controls the amount of auxiliary gas supplied from the auxiliary gas supply port so as to increase when the temperature in the bed exceeds an allowable upper limit temperature. The fluidized bed boiler system according to claim 6 or 7.

9. The fluidized bed boiler further includes an auxiliary gas supply port disposed in the furnace below the pulverized fuel supply port and configured to supply auxiliary gas to the freeboard; The controller further includes an auxiliary gas control unit for controlling the amount of auxiliary gas supplied from the auxiliary gas supply port to increase if the temperature in the bed exceeds the allowable upper limit temperature even after control by the fluidized bed temperature reducing control unit. The fluidized bed boiler system according to claim 7.

10. The fuel control unit includes a first fluidized bed temperature rise control unit for controlling the amount of fuel supplied from the fuel supply port to increase and the amount of pulverized fuel supplied from the pulverized fuel supply port to decrease when the temperature in the bed falls below an allowable lower limit temperature. The fluidized bed boiler system according to claim 6 or 7.

11. The fluidized bed boiler further includes a lower pulverized fuel supply port disposed in the furnace below the fuel supply port for supplying pulverized fuel to the fluidized bed; The controller further includes a lower pulverized fuel control unit for controlling the amount of lower pulverized fuel supplied from the lower pulverized fuel supply port to increase when the temperature in the bed is still below the allowable lower limit temperature after control by the first fluidized bed temperature rise control unit. The fluidized bed boiler system according to claim 10.

12. The fluidized bed boiler further includes a lower pulverized fuel supply port disposed in the furnace below the fuel supply port for supplying pulverized fuel to the fluidized bed; The controller includes a second fluidized bed temperature rise control unit for controlling the amount of fuel supplied from the fuel supply port to decrease and the amount of lower fine pulverized fuel supplied from the lower fine pulverized fuel supply port to increase when the temperature in the bed falls below an allowable lower limit temperature. The fluidized bed boiler system according to claim 6.

13. 2. A method for operating a fluidized bed boiler according to claim 1, comprising: an intra-bed temperature acquisition step of acquiring an intra-bed temperature, which is the temperature of the fluidized bed; a fuel control step for controlling the amount of fuel supplied from the fuel supply port and the amount of pulverized fuel supplied from the pulverized fuel supply port based on the temperature in the bed; A method for operating a fluidized bed boiler comprising the steps of:

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