Boiler control system and boiler control method

Abstract

To keep a steam header pressure value within a prescribed adjustable pressure range.SOLUTION: A boiler control system 1 comprises a plurality of boiler units A1, B1 to B6, A2, and A3, a steam header 40, a header pressure sensor 60, and a unit-count control device 30. In a first independent operation control, the system determines whether or not a steam pressure value is equal to or lower than a prescribed first threshold and, when equal to or lower than the first threshold, initiates combustion operation of a corresponding boiler 10. In a coordinated operation control, the system determines whether or not the steam pressure value is equal to or lower than a prescribed second threshold that is lower than the first threshold and, when lower than the second threshold, outputs a combustion command on the basis of the combustion amount of the boilers in the second boiler units B1 to B6, and each operation control devices 20 receiving the combustion command initiates combustion operation of each corresponding boiler 10. The first independent operation control and the coordinated operation control are executed in parallel.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] One aspect of the present invention relates to a boiler control system and a boiler control method. [Background technology]

[0002] Patent Document 1 discloses a multi-boiler installation system that includes multiple boilers, an operation control device provided for each boiler, a steam header that collects steam, a pressure sensor for the steam header, and a number control device that controls the number of boilers based on the pressure value detected by the pressure sensor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-101095 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-described number control, various processes may take time. The time required for the processes makes it difficult to appropriately follow steam load fluctuations, and there is a risk that the steam header pressure value may not be kept within a predetermined pressure adjustment range.

[0005] One aspect of the present invention has been made in view of the above circumstances, and relates to a boiler control system and a boiler control method that can keep the pressure value of a steam header within a predetermined pressure adjustment range. [Means for solving the problem]

[0006] A boiler control system according to one aspect of the present invention includes a plurality of boiler units, each having a boiler, a boiler pressure sensor that detects a steam pressure value corresponding to the boiler, and an operation control device that controls the operation of the boiler; a steam header that collects steam from the boilers of each boiler unit; a header pressure sensor that detects a steam pressure value in the steam header; and a number control device that adjusts the number of boilers that are to be fired based on the steam pressure value detected by the header pressure sensor. The plurality of boiler units are divided at least into one or more first boiler units that perform independent operation and a plurality of second boiler units that perform linked operation, and a first independent operation control that is control related to the first boiler unit includes: The operation control device of the boiler unit determines whether the steam pressure value detected by the boiler pressure sensor is below a predetermined first threshold, and if it is below the first threshold, starts combustion operation of the corresponding boiler.In the linked operation control, which is control for the second boiler unit, the number control device determines whether the steam pressure value detected by the header pressure sensor is below a predetermined second threshold which is smaller than the first threshold, and if it is below the second threshold, outputs a combustion command to the operation control device corresponding to the boiler to be burned based on the combustion amount of the boiler of the second boiler unit.The operation control device that receives the combustion command starts combustion operation of the corresponding boiler.The first independent operation control and linked operation control are executed in parallel.

[0007] In one embodiment of the present invention, a boiler control system performs parallel interlocking operation of multiple second boiler units in response to steam pressure values ​​detected by a header pressure sensor, and parallel independent operation of one or more first boiler units in response to steam pressure values ​​detected by a boiler pressure sensor. The first threshold value of the steam pressure value that triggers the start of combustion operation in the independent operation is set to a value greater than the second threshold value of the steam pressure value that triggers the output of a combustion command in the interlocking operation. Therefore, the independent operation is initiated first, and then the interlocking operation is initiated when the steam pressure value further decreases. Interlocking operation requires various processes for increasing or decreasing the number of operating units and transmitting combustion command values ​​from the unit count control device to each boiler's operation control device, which can result in the time required for steam generation and shutdown. In this regard, by first performing independent operation and then performing interlocking operation in parallel when the steam pressure value further decreases, delays in steam generation and shutdown can be suppressed by the independently operating boiler. This improves response to steam load fluctuations and appropriately maintains the steam header pressure value within a predetermined pressure adjustment range.

[0008] The plurality of boiler units may be divided into one or more first boiler units, a plurality of second boiler units, and one or more third boiler units operating independently, and in the second independent operation control for the third boiler unit, the operation control device of the third boiler unit may determine whether the steam pressure value detected by the boiler pressure sensor is equal to or less than a predetermined third threshold value that is smaller than the second threshold value, and if the steam pressure value is equal to or less than the third threshold value, start the combustion operation of the corresponding boiler. In this way, by performing independent operation by the third boiler unit when the steam pressure value drops to equal to or less than the third threshold value that is smaller than the second threshold value, independent operation that can be performed without time delay even when, for example, there is a sudden (large) steam load fluctuation is performed, and a drop in the steam header pressure value even during a large steam load fluctuation can be prevented, and the steam header pressure value can be kept within a predetermined pressure adjustment range.

[0009] The plurality of boiler units may be arranged in rotation as the first boiler unit, the second boiler unit, and the third boiler unit. In this way, by arranging the boiler units in rotation as the first boiler unit which has the most opportunities to perform combustion operation, the second boiler unit which has the next most opportunities, and the third boiler unit which has the least opportunities, it is possible to prevent deterioration and the like due to excessive operation of only some of the boiler units.

[0010] A boiler control method according to one embodiment of the present invention is a boiler control method executed by a boiler control system, and includes determining whether the steam pressure value in one or more first boiler units operating independently is equal to or less than a predetermined first threshold, and if equal to or less than the first threshold, starting combustion operation of the boilers included in the first boiler unit; determining whether the steam pressure value in a steam header that collects steam is equal to or less than a predetermined second threshold that is smaller than the first threshold, and if equal to or less than the second threshold, adjusting the number of combustion boilers in multiple second boiler units operating in tandem, and starting combustion operation of the boilers to be combusted. [Effects of the Invention]

[0011] According to one aspect of the present invention, the pressure value of the steam header can be kept within a predetermined pressure adjustment range. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram schematically showing the configuration of a boiler control system according to this embodiment. [Figure 2] FIG. 2 is a diagram illustrating the operation of each boiler unit. [Figure 3] FIG. 3 is a diagram illustrating the operation of each boiler. [Figure 4] FIG. 4 is a flowchart showing the processing of the boiler control system. [Figure 5] FIG. 5 is a graph illustrating the effects of the boiler control system according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals, and redundant explanations will be omitted.

[0014] 1 is a diagram schematically illustrating the configuration of a boiler control system 1 according to this embodiment. The boiler control system 1 includes a plurality of boiler units A1, B1 to B6, A2, and A3, a unit count control device 30, a steam header 40, steam piping 50, and a header pressure sensor 60. The plurality of boiler units A1, B1 to B6, A2, and A3 have the same configuration, but are divided according to their roles into a first boiler unit A1 that operates independently, a plurality (six) of second boiler units B1 to B6 that operate in conjunction with each other, and a plurality (two) of third boiler units A2 and A3 that operate independently. As described above, since all of the boiler units have the same configuration, they are arranged in rotation in the first boiler unit, the second boiler unit, and the third boiler unit, respectively. For example, the boiler unit designated as the first boiler unit A1 in FIG. 1 may rotate to become the second boiler units B1 to B6, or the third boiler units A2 and A3. Such rotation may be performed daily, or may be performed, for example, once every few weeks or months. While the present embodiment is described assuming that the three types of boiler units described above are provided, it is also possible that only the first boiler unit and the second boiler unit are provided, and no third boiler unit is provided. Furthermore, the number of boiler units that operate independently is not limited to the above, and may be, for example, two first boiler units and one third boiler unit.

[0015] Each boiler 10 of the multiple boiler units A1, B1 to B6, A2, and A3 is connected to a steam header 40 via a steam pipe 50. The steam header 40 collects steam from the boilers 10 of each boiler unit and supplies the steam to a steam usage location (not shown). A header pressure sensor 60 detects the steam pressure value in the steam header 40. A unit count control device 30 adjusts the number of combustion units of each of the multiple boiler units B1 to B6 that operate in conjunction with each other, based on the steam pressure value detected by the header pressure sensor 60 (details will be described later).

[0016] The multiple boiler units A1, B1 to B6, A2, and A3 have the same configuration, and each includes a boiler 10, an operation control device 20, and a boiler pressure sensor 70. The boiler 10 may be, for example, a water tube boiler, or more specifically, a once-through boiler. The boiler pressure sensor 70 detects the steam pressure value in the corresponding boiler 10. The boiler pressure sensor 70 outputs the detected steam pressure value to the operation control device 20.

[0017] The operation control device 20 controls the operation of the corresponding boiler 10. The operation control of the boiler 10 by the operation control device 20 is different for first independent operation control for the first boiler unit A1 performing independent operation, linked operation control for the second boiler units B1 to B6 performing linked operation, and second independent operation control for the third boiler units A2 and A3 performing independent operation. Details of each operation control are explained below. The first independent operation control and second independent operation control are controlled by the operation control device 20, and the linked operation control is controlled by the number-of-units control device 30 and the operation control device 20.

[0018] (First independent operation control) The first independent operation control is executed by the operation control device 20 of the first boiler unit A1. The operation control device 20 of the first boiler unit A1 determines whether the steam pressure value detected by the boiler pressure sensor 70 of the first boiler unit A1 is equal to or less than a predetermined first threshold value. If the steam pressure value is equal to or less than the first threshold value, the operation control device 20 starts the combustion operation of the boiler 10 of the first boiler unit A1. Note that the boiler 10 of the first boiler unit A1 may be in standby mode in a minimum combustion mode using only a pilot flame before starting the combustion operation. The first threshold value is a value greater than a second threshold value related to the linked operation and a third threshold value related to the second independent operation, which will be described later, and may be, for example, approximately 0.990 MPa. Note that the value of the first threshold value is merely an example and may be set appropriately depending on various conditions. As described above, because the first threshold value is greater than the second threshold value and the third threshold value, the first independent operation control is executed prior to other controls when the steam pressure value drops. That is, the boiler 10 of the first boiler unit A1 starts the combustion operation first.

[0019] (Interlocking operation control) The linked operation control is performed by the number of boilers control device 30 and the operation control devices 20 of the second boiler units B1 to B6. The linked operation control is performed simultaneously (in parallel) with the first and second independent operation controls. The number of boilers control device 30 determines whether the steam pressure value detected by the header pressure sensor 60 is equal to or less than a predetermined second threshold value that is smaller than the first threshold value. If the steam pressure value is equal to or less than the second threshold value, the number of boilers control device 30 outputs a combustion command to the operation control device 20 corresponding to the boiler 10 to be combusted, based on the combustion amount of each boiler 10 of the second boiler units B1 to B6. The combustion command value may be a value indicating 0 to 100%, for example, with the maximum combustion amount being 100%. The second threshold value is a value smaller than the first threshold value and greater than a third threshold value (described later), and may be approximately 0.980 MPa, for example. The value of the second threshold value is merely an example and may be set appropriately according to various conditions.

[0020] When the steam pressure value detected by the header pressure sensor 60 is equal to or lower than the second threshold value, the number of units control device 30 first outputs a combustion command to the operation control device 20 corresponding to one of the second boiler units B1. Then, the number of units control device 30 adjusts the number of combustion boilers 10 based on the combustion amount of each boiler 10 in the second boiler units B1 to B6. After outputting the combustion command to the operation control device 20 corresponding to the second boiler unit B1, the number of units control device 30 determines whether the combustion amount of the boiler 10 in linked operation (here, the boiler 10 of the second boiler unit B1) is equal to or higher than a predetermined percentage (for example, 50% or higher) of the maximum value, and if it is equal to or higher than the predetermined percentage, outputs a combustion command to the operation control device 20 corresponding to the second second boiler unit B2.

[0021] More specifically, when the combustion amount of the boiler 10 in linked operation (here, the boiler 10 of the second boiler unit B1) is equal to or greater than a predetermined percentage of the maximum value (for example, 50% or greater), an additional boiler timer count-up process and an operation preparation process are performed, and then a combustion command is output to the operation control device 20 corresponding to the second boiler unit B2. The additional boiler timer count-up process is performed to prevent the number of boilers from being increased too much when the combustion amount has only increased temporarily, and is a process that counts a predetermined number of seconds (for example, 30 seconds) and determines whether the combustion amount is still equal to or greater than a predetermined percentage of the maximum value after the count. The operation preparation process is performed only when it is determined in the additional boiler timer count-up process that the combustion amount is still equal to or greater than the predetermined percentage of the maximum value after the count.

[0022] The operation preparation process is performed in the boiler 10 (here, the boiler 10 of the second boiler unit B2) that starts operation in response to an instruction from the number control device 30. In the operation preparation process, for example, after pre-purging, pilot burner ignition, main burner ignition, and pressure increase at low combustion are performed, it is confirmed that the detection value of the boiler pressure sensor 70 is equal to or greater than a predetermined value (e.g., 0.590 MPa). This operation preparation process takes, for example, about three minutes. After the operation preparation process is performed, a combustion command is output to the operation control device 20 corresponding to the second boiler unit B2.

[0023] Then, after outputting a combustion command to the operation control device 20 corresponding to the second boiler unit B2, the number control device 30 determines whether the combustion amount of the boilers 10 in linked operation (here, the boilers 10 of the second boiler units B1 and B2) is equal to or greater than a predetermined percentage (e.g., 50% or more) of the maximum value, and if it is equal to or greater than the predetermined percentage, outputs a combustion command to the operation control device 20 corresponding to the third second boiler unit B3. More specifically, if the combustion amount of the boilers 10 in linked operation (here, the boilers 10 of the second boiler units B1 and B2) is equal to or greater than a predetermined percentage (e.g., 50% or more) of the maximum value, an additional boiler timer count-up process and an operation preparation process are performed, and then a combustion command is output to the operation control device 20 corresponding to the second boiler unit B3.

[0024] On the other hand, if the total (or average) combustion amount of the two boilers 10 operating in linked operation is, for example, 10% or less of the maximum value, the number control device 30 outputs a first standby command (complete standby command) to the operation control device 20 corresponding to the second second boiler unit B2. More specifically, if the combustion amount of the boilers 10 operating in linked operation is, for example, 10% or less of the maximum value, a can reduction timer count-up process is performed, and then the first standby command is output to the operation control device 20 corresponding to the second second boiler unit B2. The can reduction timer count-up process is performed to prevent the number of boilers from being reduced too much when the combustion amount has only temporarily decreased. The can reduction timer count-up process counts a predetermined number of seconds (for example, 30 seconds) and determines whether the combustion amount is still below a predetermined percentage of the maximum value after the count. Only when it is determined in the can reduction timer count-up process that the combustion amount is still below the predetermined percentage of the maximum value after the count, is the first standby command output to the operation control device 20 corresponding to the second second boiler unit B2.

[0025] Furthermore, the number control device 30 further determines whether the steam pressure value detected by the header pressure sensor 60 is equal to or greater than a second threshold value, and if it is equal to or greater than the second threshold value, outputs a second standby command (minimum standby command) to the operation control device 20 corresponding to the second boiler unit B1.

[0026] After outputting a combustion command to the operation control device 20 corresponding to the second boiler unit B3, the number control device 30 determines whether the total (or average) combustion amount of the three boilers 10 in linked operation (here, the boilers 10 of the second boiler units B1, B2, and B3) is equal to or greater than a predetermined percentage (e.g., 50% or more) of the maximum value, and if it is equal to or greater than the predetermined percentage, outputs a combustion command to the operation control device 20 corresponding to the fourth second boiler unit B4. More specifically, if the combustion amount of the boilers 10 in linked operation (here, the boilers 10 of the second boiler units B1, B2, and B3) is equal to or greater than a predetermined percentage (e.g., 50% or more) of the maximum value, after performing an additional boiler timer count-up process and an operation preparation process, a combustion command is output to the operation control device 20 corresponding to the second boiler unit B4.

[0027] On the other hand, if the total (or average) combustion amount of the three boilers 10 in linked operation is, for example, 10% or less of the maximum value, the number of units control device 30 outputs a first standby command to the operation control device 20 corresponding to the third second boiler unit B3. More specifically, if the combustion amount of the boilers 10 in linked operation is, for example, 10% or less of the maximum value, the can reduction timer count-up process is performed, and then the first standby command is output to the operation control device 20 corresponding to the third second boiler unit B3. In this case, the number of units control device 30 starts again from the process of determining whether the total (or average) combustion amount of the two boilers 10 in linked operation (here, the boilers 10 of the second boiler units B1 and B2) is equal to or greater than a predetermined percentage (for example, equal to or greater than 50%) of the maximum value.

[0028] After outputting a combustion command to the operation control device 20 corresponding to the second boiler unit B4, the number control device 30 determines whether the total (or average) combustion amount of the four boilers 10 (here, the boilers 10 of the second boiler units B1, B2, B3, and B4) in linked operation is equal to or greater than a predetermined percentage (e.g., 50% or more) of the maximum value, and if it is equal to or greater than the predetermined percentage, outputs a combustion command to the operation control device 20 corresponding to the fifth second boiler unit B5. More specifically, if the total (or average) combustion amount of the four boilers 10 (here, the boilers 10 of the second boiler units B1, B2, B3, and B4) in linked operation is equal to or greater than a predetermined percentage (e.g., 50% or more) of the maximum value, an additional boiler timer count-up process and an operation preparation process are performed, and then a combustion command is output to the operation control device 20 corresponding to the second boiler unit B5.

[0029] On the other hand, if the total (or average) combustion amount of the four boilers 10 in linked operation is, for example, 10% or less of the maximum value, the number of units control device 30 outputs a first standby command to the operation control device 20 corresponding to the fourth second boiler unit B4. More specifically, if the total (or average) combustion amount of the four boilers 10 in linked operation is, for example, 10% or less of the maximum value, the can reduction timer count-up process is performed, and then the first standby command is output to the operation control device 20 corresponding to the fourth second boiler unit B4. In this case, the number of units control device 30 starts again from the process of determining whether the total (or average) combustion amount of the three boilers 10 in linked operation (here, the boilers 10 of the second boiler units B1, B2, and B3) is equal to or greater than a predetermined percentage (for example, equal to or greater than 50%) of the maximum value.

[0030] After outputting a combustion command to the operation control device 20 corresponding to the second boiler unit B5, the number control device 30 determines whether the total (or average) combustion amount of the five boilers 10 in linked operation (here, the boilers 10 of the second boiler units B1, B2, B3, B4, and B5) is equal to or greater than a predetermined percentage (e.g., 50% or more) of the maximum value, and if it is equal to or greater than the predetermined percentage, outputs a combustion command to the operation control device 20 corresponding to the sixth second boiler unit B5. More specifically, if the combustion amount of the boilers 10 in linked operation (here, the boilers 10 of the second boiler units B1, B2, B3, B4, and B5) is equal to or greater than a predetermined percentage (e.g., 50% or more) of the maximum value, after performing an additional boiler timer count-up process and an operation preparation process, a combustion command is output to the operation control device 20 corresponding to the second boiler unit B6.

[0031] On the other hand, if the total (or average) combustion amount of the five boilers 10 in linked operation is, for example, 10% or less of the maximum value, the number of units control device 30 outputs a first standby command to the operation control device 20 corresponding to the fifth second boiler unit B5. More specifically, if the combustion amount of the boilers 10 in linked operation is, for example, 10% or less of the maximum value, the can reduction timer count-up process is performed, and then the first standby command is output to the operation control device 20 corresponding to the fifth second boiler unit B5. In this case, the number of units control device 30 starts again from the process of determining whether the combustion amount of the boilers 10 in linked operation (here, the boilers 10 of the second boiler units B1, B2, B3, and B4) is equal to or greater than a predetermined percentage (for example, equal to or greater than 50%) of the maximum value.

[0032] After outputting a combustion command to the operation control device 20 corresponding to the second boiler unit B6, the number control device 30 continues to output combustion commands to the operation control devices 20 of all second boiler units B1 to B6 until the total (or average) combustion amount of the six boilers 10 operating in tandem (here, the boilers 10 of the second boiler units B1, B2, B3, B4, B5, and B6) becomes, for example, 10% or less of the maximum value.

[0033] On the other hand, if the total (or average) combustion amount of the six boilers 10 in linked operation (here, the boilers 10 in the second boiler units B1, B2, B3, B4, B5, and B6) is, for example, 10% or less of the maximum value, the number of units control device 30 outputs a first standby command to the operation control device 20 corresponding to the sixth second boiler unit B6. More specifically, if the combustion amount of the boilers 10 in linked operation is, for example, 10% or less of the maximum value, after the can reduction timer count-up process is performed, the first standby command is output to the operation control device 20 corresponding to the sixth second boiler unit B6. In this case, the number of units control device 30 starts again from the process of determining whether the combustion amount of the boilers 10 in linked operation (here, the boilers 10 in the second boiler units B1, B2, B3, B4, and B5) is equal to or greater than a predetermined percentage (e.g., 50% or more) of the maximum value. In this way, the number of units control device 30 adjusts the number of combustion units of the boilers 10 based on the combustion amounts of the second boiler units B1 to B6. Note that the number of units control device 30 may also determine the number of combustion units to perform combustion operation based on the steam pressure value detected by the header pressure sensor 60.

[0034] The operation control device 20 that receives the combustion command starts the combustion operation of the corresponding boiler 10. Furthermore, the operation control device 20 that receives the standby command stops the combustion operation of the corresponding boiler 10. The operation control device 20 of the second boiler unit B1 (the boiler unit that will operate in interlocking operation first) that receives the second standby command may put the boiler 10 on standby in the minimum combustion mode with only a pilot light. The operation control device 20 of the second boiler units B2 to B6 (boiler units other than the boiler unit that will operate in interlocking operation first) that receives the first standby command may put the boiler 10 on standby in a complete standby state without even a pilot light. The second boiler unit B1 that starts combustion operation first may always be arranged in rotation.

[0035] (Second independent operation control) The second independent operation control is performed by the operation control device 20 of the two third boiler units A2 and A3. The operation control device 20 of the third boiler unit A2 determines whether the steam pressure value detected by the boiler pressure sensor 70 of the third boiler unit A2 is equal to or less than a predetermined third threshold value that is smaller than the second threshold value. If the steam pressure value is equal to or less than the third threshold value, the operation control device 20 starts the combustion operation of the boiler 10 of the third boiler unit A2. Similarly, the operation control device 20 of the third boiler unit A3 determines whether the steam pressure value detected by the boiler pressure sensor 70 of the third boiler unit A3 is equal to or less than a predetermined third threshold value that is smaller than the second threshold value. If the steam pressure value is equal to or less than the third threshold value, the operation control device 20 starts the combustion operation of the boiler 10 of the third boiler unit A3. The third threshold value is smaller than the first threshold value for the first independent operation and the second threshold value for the linked operation, and may be, for example, approximately 0.960 MPa. Note that the value of the third threshold value is merely an example and may be set appropriately depending on various conditions.

[0036] The processes of the two third boiler units A2 and A3 may be performed in series. That is, for example, the operation control device 20 of the third boiler unit A2 may be controlled first, and then the operation control device 20 of the third boiler unit A3 may be controlled. In this case, for example, first, it is determined whether the steam pressure value detected by the boiler pressure sensor 70 of the third boiler unit A2 is equal to or less than the third threshold. If it is equal to or less than the third threshold, the combustion operation of the boiler 10 of the third boiler unit A2 is started. Then, for example, after a predetermined period of time has elapsed, it is determined whether the steam pressure value detected by the boiler pressure sensor 70 of the third boiler unit A3 is equal to or less than the third threshold. If it is equal to or less than the third threshold, the combustion operation of the boiler 10 of the third boiler unit A3 is started. Thereafter, after a predetermined period of time has elapsed, it is determined whether the steam pressure value detected by the boiler pressure sensor 70 of the third boiler unit A3 is equal to or greater than the third threshold. If it is equal to or greater than the third threshold, the boiler 10 of the third boiler unit A3 is stopped. Furthermore, after a predetermined period of time has elapsed, it is determined whether the steam pressure value detected by the boiler pressure sensor 70 of the third boiler unit A2 is equal to or greater than a third threshold, and if it is equal to or greater than the third threshold, the boiler 10 of the third boiler unit A2 is stopped. The operation control device 20 of the third boiler units A2 and A3 may put the boiler 10 on standby in a minimum combustion mode with only a pilot fire.

[0037] FIG. 2 is a diagram illustrating the operation of each of the above-mentioned boiler units (first boiler unit A1, second boiler units B1 to B6, and third boiler units A2 and A3). Assume that the first threshold for first boiler unit A1 is set to 0.990 MPa, the second threshold for second boiler units B1 to B6 is set to 0.980 MPa, and the third threshold for third boiler units A2 and A3 is set to 0.960 MPa. When the steam pressure value drops below the first threshold (0.990 MPa), combustion begins in the boiler 10 of the first boiler unit A1, which is operating independently. Until combustion begins, the boiler 10 of the first boiler unit A1 is in the minimum combustion mode with only a pilot flame. When the steam pressure value further drops below the second threshold (0.980 MPa), combustion begins in the second boiler units B1 to B6, which are operating in linked operation. When the steam pressure value further decreases and falls below the third threshold (0.960 MPa), combustion begins in the third boiler units A2 and A3, which are operating independently. Note that until combustion begins, the boilers 10 of the third boiler units A2 and A3 are in the minimum combustion mode with only a pilot flame.

[0038] 3 is a diagram illustrating the detailed operation of each boiler unit. Regarding the second boiler units B1 to B6 that perform linked operation, for example, only the boiler 10 of the second boiler unit B1, which starts combustion operation first, is set to the minimum combustion mode with only a pilot light, while the boilers 10 of the other second boiler units B2 to B6 are set to a complete standby state (a standby state without a pilot light). When the steam pressure value drops below the second threshold (0.980 MPa), the boiler 10 of the second boiler unit B1 starts combustion operation first, and the boilers 10 of the other second boiler units B2 to B6 start combustion as appropriate based on the combustion volume of the boilers 10 that are currently burning.

[0039] In addition, as shown in the example columns for the second boiler units B2 and B3 in Figure 3, as described above, the can increase timer count-up process and operation preparation process are performed when combustion starts, and the can decrease timer count-up process is performed when standby starts.

[0040] Next, a boiler control method executed by the boiler control system 1 will be described with reference to the flowchart of Fig. 4. Fig. 4 is a flowchart showing the processing of the boiler control system 1. Note that in the description using Fig. 4, the description of the can increase timer count-up processing, operation preparation processing, and can decrease timer count-up processing described above will be omitted.

[0041] First, each boiler 10 is placed in a standby state (step S1). For example, the boilers 10 of the first boiler unit A1, the second boiler unit B1, and the third boiler units A2 and A3 are placed in a standby state in a minimum combustion mode with only a pilot light. The boilers 10 of the second boiler units B2 to B6 are placed in a completely standby state with no pilot light.

[0042] Next, it is determined whether the steam pressure value detected by the boiler pressure sensor 70 of the first boiler unit A1 is equal to or less than the first threshold value TH1 (step S2). While it is determined in step S2 that the steam pressure value is not equal to or less than the first threshold value TH1, the determination in step S2 is repeated periodically at predetermined time intervals.

[0043] On the other hand, if it is determined in step S2 that the steam pressure value is equal to or less than the first threshold value TH1, the combustion operation of the boiler 10 of the first boiler unit A1 is started (step S3). Thereafter, it is determined whether the steam pressure value has returned to equal to or greater than the first threshold value TH1 (step S4), and if it has returned to equal to or greater than the first threshold value TH1, the boiler 10 of the first boiler unit A1 is put into standby state again (step S5).

[0044] If the steam pressure value has not recovered to above the first threshold value TH1 in step S4, it is determined whether the steam pressure value detected by the header pressure sensor 60 is below the second threshold value TH2 (step S6). If it is determined in step S6 that the steam pressure value is not below the second threshold value TH2, the process of step S4 is executed again.

[0045] On the other hand, if it is determined in step S6 that the steam pressure value is equal to or less than the second threshold value TH2, linked operation control is started (step S7). In the linked operation control, combustion operation is started by the boilers 10 of the combustion targets based on the combustion amounts of the boilers 10 of the second boiler units B1 to B6. Thereafter, it is determined whether the steam pressure value detected by the header pressure sensor 60 has returned to equal to or greater than the second threshold value TH2 (step S8). If it has returned to equal to or greater than the second threshold value TH2, the boilers 10 of the second boiler units B1 to B6 are placed in the standby state again (step S9), and the processing of step S4 is executed again.

[0046] In parallel with the processing of step S6, it is determined whether the steam pressure value detected by the boiler pressure sensor 70 of the third boiler unit A2 is equal to or less than a third threshold value TH3 (step S10). If it is determined in step S10 that the steam pressure value is not equal to or less than the third threshold value TH3, the processing of step S4 is executed again.

[0047] On the other hand, if it is determined in step S10 that the steam pressure value is equal to or less than the third threshold value TH3, a second independent operation control is initiated (step S11). In the second independent operation control, for example, first, it is determined whether the steam pressure value detected by the boiler pressure sensor 70 of the third boiler unit A2 is equal to or less than the third threshold value TH3, and if it is equal to or less than the third threshold value TH3, the combustion operation of the boiler 10 of the third boiler unit A2 is initiated. Then, for example, after a predetermined period has elapsed, it is determined whether the steam pressure value detected by the boiler pressure sensor 70 of the third boiler unit A3 is equal to or less than the third threshold value TH3, and if it is equal to or less than the third threshold value TH3, the combustion operation of the boiler 10 of the third boiler unit A3 is initiated. After that, after a predetermined period has elapsed, it is determined whether the steam pressure value detected by the boiler pressure sensor 70 of the third boiler unit A3 is equal to or greater than the third threshold value TH3, and if it is equal to or greater than the third threshold value TH3, the boiler 10 of the third boiler unit A3 is placed in a standby state. Furthermore, after a predetermined period of time has elapsed, it is determined whether or not the steam pressure value detected by the boiler pressure sensor 70 of the third boiler unit A2 is equal to or greater than the third threshold value TH3 (step S12). If the steam pressure value is not equal to or greater than the third threshold value TH3, the process of step S11 is executed again, and if the steam pressure value is equal to or greater than the third threshold value TH3, the boiler 10 of the third boiler unit A2 is placed in a standby state (step S13), and the process of step S4 is executed again.

[0048] Next, the effects of the boiler control system 1 according to this embodiment will be described.

[0049] The boiler control system 1 according to this embodiment includes a plurality of boiler units A1, B1 to B6, A2, and A3, each having a boiler 10, a boiler pressure sensor 70 that detects a steam pressure value corresponding to the boiler 10, and an operation control device 20 that controls the operation of the boiler 10, a steam header 40 that collects steam from the boilers 10 of the boiler units A1, B1 to B6, A2, and A3, a header pressure sensor 60 that detects the steam pressure value in the steam header 40, and a unit count control device 30 that adjusts the number of boilers 10 that are to be fired based on the steam pressure value detected by the header pressure sensor 60. The plurality of boiler units A1, B1 to B6, A2, and A3 are divided at least into a first boiler unit A1 that operates independently and a plurality of second boiler units B1 to B6 that operate in conjunction with each other. In the first independent operation control for the first boiler unit A1, the operation control device 20 of the first boiler unit A1 determines whether the steam pressure value detected by the boiler pressure sensor 70 is equal to or less than a predetermined first threshold, and if so, starts the combustion operation of the corresponding boiler 10. In the linked operation control for the second boiler units B1 to B6, the number control device 30 determines whether the steam pressure value detected by the header pressure sensor 60 is equal to or less than a predetermined second threshold that is smaller than the first threshold, and if so, outputs a combustion command to the operation control device 20 corresponding to the boiler 10 to be combusted based on the combustion amount of the boiler of the second boiler units B1 to B6, and the operation control device 20 that receives the combustion command starts the combustion operation of the corresponding boiler 10. The first independent operation control and the linked operation control are executed in parallel.

[0050] In the boiler control system 1 according to this embodiment, interlocking operation by the second boiler units B1-B6 is performed in parallel in response to the steam pressure detected by the header pressure sensor 60, and independent operation by the first boiler unit A1 is performed in response to the steam pressure detected by the boiler pressure sensor 70. The first threshold value of the steam pressure, which triggers the start of combustion operation in the independent operation, is set to a value greater than the second threshold value of the steam pressure, which triggers the output of a combustion command in the interlocking operation. Therefore, the independent operation is initiated first, and then the interlocking operation is initiated when the steam pressure value further decreases. When increasing or decreasing the number of operating units in the interlocking operation, the aforementioned boiler increase timer count-up process or the boiler decrease timer count-up process may be performed, each of which takes approximately 30 seconds. Furthermore, when starting a new combustion from a standby state without a pilot light, the aforementioned preparation process takes approximately 3 minutes. Thus, in the past, the time required for various processes in interlocking operation made it difficult to appropriately follow steam load fluctuations, resulting in an inability to maintain the steam header pressure value within a predetermined pressure adjustment range. Furthermore, since the combustion command value must be transmitted from the unit count control device 30 to the operation control device 20 of each boiler 10, time delays in the various processes described above can be a problem. In this regard, by configuring the boilers to first perform independent operation and then perform linked operation in parallel if the steam pressure value further decreases, delays in steam generation and shutdown can be suppressed by the independently operating boiler. This improves the ability to follow steam load fluctuations and appropriately keeps the pressure value of the steam header 40 within a predetermined pressure adjustment range.

[0051] Fig. 5 is a graph illustrating the effects of the boiler control system according to this embodiment. In Fig. 5, the horizontal axis represents time and the vertical axis represents pressure. The solid line represents the pressure of the steam header 40 when only the interlocking operation is performed (steam header pressure I), and the two-dot chain line represents the pressure of the steam header 40 when the first independent operation and the interlocking operation are performed in parallel (steam header pressure II). Also, in Fig. 5, the dotted lines represent the upper and lower limits of the pressure adjustment range of the steam header 40. As shown in Fig. 5, when the first independent operation and the interlocking operation are performed in parallel (steam header pressure II), fluctuations in the pressure value of the steam header 40 can be reduced and kept within the pressure adjustment range, compared to when only the interlocking operation is performed (steam header pressure I).

[0052] The plurality of boiler units may be divided into a first boiler unit A1, a plurality of second boiler units B1 to B6, and two third boiler units A2 and A3 that perform independent operation. In the second independent operation control for the third boiler units A2 and A3, the operation control device 20 of the third boiler units A2 and A3 may determine whether the steam pressure value detected by the boiler pressure sensor 70 is equal to or less than a predetermined third threshold value that is smaller than the second threshold value, and may start the combustion operation of the corresponding boiler 10 if the steam pressure value is equal to or less than the third threshold value. In this way, the third boiler units A2 and A3 perform independent operation when the steam pressure value drops to or less than the third threshold value that is smaller than the second threshold value. This allows for independent operation that can be performed without time delay, for example, when there is a sudden (large) steam load fluctuation. This prevents the pressure value of the steam header 40 from decreasing even during a large steam load fluctuation, and allows the pressure value of the steam header 40 to remain within a predetermined pressure adjustment range.

[0053] In Fig. 5, the dashed line indicates the pressure of the steam header 40 (steam header pressure III) when the first isolated operation, the linked operation, and the second isolated operation are performed in parallel. As shown in Fig. 5, when the first isolated operation, the linked operation, and the second isolated operation are performed in parallel (steam header pressure III), the fluctuations in the pressure value of the steam header 40 were further reduced compared to when the above-mentioned first isolated operation and the linked operation are performed in parallel (steam header pressure II).

[0054] The plurality of boiler units may be arranged in rotation among the first boiler unit A1, the second boiler units B1 to B6, and the third boiler units A2 and A3. By arranging the boiler units in rotation among the first boiler unit A1, which has the most opportunities to perform combustion operation, the second boiler unit B1, etc., which has the next most opportunities, and the third boiler units A2 and A3, which have the least opportunities, it is possible to prevent deterioration and the like due to excessive operation of only some of the boiler units. [Explanation of symbols]

[0055] 1...boiler control system, 10...boiler, 20...operation control device, 30...unit number control device, 40...steam header, 60...header pressure sensor, 70...boiler pressure sensor, A1...first boiler unit, B1 to B6...second boiler unit, A2, A3...third boiler unit.

Claims

1. a plurality of boiler units each having a boiler, a boiler pressure sensor for detecting a steam pressure value corresponding to the boiler, and an operation control device for controlling the operation of the boiler; a steam header that collects steam from the boilers of each boiler unit; a header pressure sensor for detecting a steam pressure value in the steam header; a number control device that adjusts the number of boilers that are to be fired based on the steam pressure value detected by the header pressure sensor, The plurality of boiler units are divided at least into one or more first boiler units that perform independent operation and a plurality of second boiler units that perform linked operation, In the first isolated operation control which is the control related to the first boiler unit, the operation control device of the first boiler unit determines whether the steam pressure value detected by the boiler pressure sensor is equal to or less than a predetermined first threshold value, and if the steam pressure value is equal to or less than the first threshold value, starts a combustion operation of the corresponding boiler; In the linked operation control which is the control related to the second boiler unit, the number control device determines whether the steam pressure value detected by the header pressure sensor is equal to or less than a predetermined second threshold value that is smaller than the first threshold value, and if the steam pressure value is equal to or less than the second threshold value, outputs a combustion command to the operation control device corresponding to the boiler to be combusted based on the combustion amount of the boiler of the second boiler unit; The operation control device that has received the combustion command starts the combustion operation of the corresponding boiler, The first independent operation control and the linked operation control are executed in parallel.

2. The plurality of boiler units are divided into the one or more first boiler units, the plurality of second boiler units, and one or more third boiler units that operate independently, In the second independent operation control which is the control related to the third boiler unit, 2. The boiler control system of claim 1, wherein the operation control device of the third boiler unit determines whether the steam pressure value detected by the boiler pressure sensor is equal to or less than a predetermined third threshold value that is smaller than the second threshold value, and if the steam pressure value is equal to or less than the third threshold value, starts combustion operation of the corresponding boiler.

3. The boiler control system according to claim 2 , wherein the plurality of boiler units are arranged in rotation among the first boiler unit, the second boiler unit, and the third boiler unit, respectively.

4. A boiler control method executed by a boiler control system, comprising: determining whether or not a steam pressure value in one or more first boiler units operating independently is equal to or less than a predetermined first threshold value, and if the steam pressure value is equal to or less than the first threshold value, starting a combustion operation of a boiler included in the first boiler unit; a boiler control method including: determining whether a steam pressure value in a steam header that collects steam is equal to or less than a predetermined second threshold value that is smaller than the first threshold value; and, if the steam pressure value is equal to or less than the second threshold value, adjusting the number of combustion boilers in a plurality of second boiler units that perform linked operation, and starting combustion operation of the boiler to be combusted.

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