JP5838885B2 - Boiler system - Google Patents

Description

  The present invention relates to a boiler system including a boiler group having a plurality of boilers capable of burning at a plurality of stepwise combustion positions.

2. Description of the Related Art Conventionally, a boiler system has been proposed that includes a boiler group having a plurality of boilers that can be combusted at a plurality of staged combustion positions, and a control unit that controls the combustion state of the boiler group according to a required load.
For example, Patent Document 1 proposes a boiler system that shifts one of the boilers to a combustion position higher than the high-efficiency combustion position after shifting a plurality of boilers to the high-efficiency combustion position.

JP 2010-48533 A

  By the way, in a boiler capable of burning at a plurality of stepwise combustion positions, the set water level of water (canned water) held in the boiler differs depending on the combustion position. That is, the water level of the can water is set high at a low combustion position where the can water boils gently and evaporates. On the other hand, the water level of the can water is set low at a high combustion position where the can water boils violently and evaporates.

  Here, the boiler includes a can body that generates steam and a separator that separates moisture in the steam generated by the can body. Therefore, for example, when the required load fluctuates and the transition is from a low combustion position to a high combustion position, the amount of evaporation increases while the water level of the can water is high, so that part of the can water is taken out to the separator. Even if it does, the moisture in the steam is separated by the separator, and the dryness of the steam supplied from the boiler can be prevented from decreasing.

  However, when fluctuations in the required load are repeated in a range that accompanies a change in the combustion position, the number of times of shift of the combustion position from the low combustion position to the high combustion position also increases. Then, the amount of can water taken out from the can body to the separator is increased, so that moisture in the steam cannot be sufficiently separated in the separator, and as a result, the dryness of the steam supplied from the boiler is lowered.

  Therefore, the present invention provides a boiler system including a boiler group having a plurality of boilers that can burn at a plurality of stepwise combustion positions, even when the required load repeatedly fluctuates within a predetermined range. An object of the present invention is to provide a boiler system in which the dryness of steam is unlikely to decrease.

  The present invention is capable of combustion at a plurality of stepwise combustion positions including a base combustion position, a high combustion position that is a combustion position higher than the base combustion position, and a low combustion position that is a combustion position lower than the base combustion position. A boiler system comprising a boiler group including a plurality of boilers and a control unit that controls a combustion state of the boiler group according to a required load, wherein the control unit is one of the boiler groups If the combustion position is changed between the base combustion position and the high combustion position a predetermined number of times in a predetermined time, the boiler in which the combustion position is changed is maintained at the high combustion position, and the boiler A boiler system for controlling a combustion state of the boiler group by switching a combustion position of a boiler located at the base combustion position in the group between the base combustion position and the lower combustion position On.

  Further, the control unit is configured such that the required load is located at a combustion amount at the base combustion position of a boiler located at the high combustion position in the boiler group, and at the high combustion position among the boiler groups. It is preferable to shift the combustion position of the boiler maintained at the high combustion position to the base combustion position when the sum of the combustion quantity at the low combustion position of the non-boiler is below the sum.

  Further, the control unit is configured such that the required load is a combustion amount of a boiler located in the higher combustion position in the boiler group and a base of the boiler not located in the higher combustion position in the boiler group. When the sum of the combustion amount at the combustion position is exceeded, it is preferable to shift the combustion position of any one of the boilers located at the base combustion position to the higher combustion position.

  The boiler is configured to be combustible at four positions of a combustion stop position, a low combustion position, an intermediate combustion position, and a high combustion position, the base combustion position corresponds to the intermediate combustion position, and the high combustion position is Preferably, the low combustion position corresponds to the high combustion position, and the low combustion position corresponds to the low combustion position.

  According to the boiler system of the present invention, the dryness of the steam supplied from the boiler is unlikely to decrease even when the required load fluctuates repeatedly within a predetermined range.

It is a figure showing the outline of the boiler system concerning one embodiment of the present invention. It is a figure showing the outline of the boiler group concerning one embodiment of the present invention. It is a figure which shows the relationship between the combustion pattern and priority of each boiler which concerns on one Embodiment of this invention, and the steam pressure zone in a steam pressure control range. It is a figure which shows the combustion pattern of the boiler group after the change changed from the combustion pattern of the boiler group shown in FIG. It is a figure which shows operation | movement of the boiler system which concerns on one Embodiment of this invention, and is a flowchart which shows the flow of a change of the combustion pattern of the boiler group by a control part. It is a figure which shows operation | movement of the boiler system which concerns on one Embodiment of this invention, and is a flowchart which shows operation | movement when a demand load falls after the change of a combustion pattern. It is a figure which shows operation | movement of the boiler system which concerns on one Embodiment of this invention, and is a flowchart which shows operation | movement when a request | requirement load increases after the change of a combustion pattern.

Hereinafter, a preferred embodiment of a boiler system of the present invention will be described with reference to the drawings.
First, the overall configuration of the boiler system 1 of the present invention will be described with reference to FIG.
The boiler system 1 includes a boiler group 2 including a plurality of (three) boilers 20, a steam header 6 that collects steam generated in the plurality of boilers 20, and steam that measures the pressure inside the steam header 6. A pressure sensor 7 and a number control device 3 having a controller 4 that controls the combustion state of the boiler group 2 are provided.

The boiler group 2 produces | generates the vapor | steam supplied to the steam use installation 18 as a load apparatus.
The steam header 6 is connected to a plurality of boilers 20 constituting the boiler group 2 via a steam pipe 11. A downstream side of the steam header 6 is connected to a steam use facility 18 via a steam pipe 12.
The steam header 6 collects and stores the steam generated in the boiler group 2, thereby adjusting the pressure difference and pressure fluctuation of the plurality of boilers 20, and supplying the steam whose pressure is adjusted to the steam using facility 18. Supply.

  The vapor pressure sensor 7 is electrically connected to the number control device 3 via the signal line 13. The steam pressure sensor 7 measures the steam pressure inside the steam header 6 (steam pressure generated in the boiler group 2), and sends a signal (steam pressure signal) related to the measured steam pressure via the signal line 13. It transmits to the control apparatus 3.

  The number control device 3 is electrically connected to the plurality of boilers 20 through the signal line 16. The number control device 3 controls the combustion state of each boiler 20 based on the steam pressure inside the steam header 6 measured by the steam pressure sensor 7. Details of the number control device 3 will be described later.

The above boiler system 1 can supply the steam generated in the boiler group 2 to the steam using equipment 18 via the steam header 6.
The load required in the boiler system 1 (required load) is the amount of steam consumed in the steam using facility 18. The number control device 3 determines the fluctuation of the steam pressure inside the steam header 6 corresponding to the fluctuation of the steam consumption based on the steam pressure (physical quantity) inside the steam header 6 measured by the steam pressure sensor 7. The amount of combustion of each boiler 20 which comprises the boiler group 2 is calculated and controlled.

  Specifically, the demand load (steam consumption) increases due to an increase in demand for the steam use facility 18, and if the supply steam quantity is insufficient, the steam pressure inside the steam header 6 decreases. On the other hand, if the demand load (steam consumption) decreases due to a decrease in the demand of the steam use facility 18, and the supply steam amount becomes excessive, the steam pressure inside the steam header 6 increases. Therefore, the boiler system 1 can monitor the fluctuation of the required load based on the fluctuation of the vapor pressure measured by the vapor pressure sensor 7. Then, the boiler system 1 calculates a target evaporation amount corresponding to the consumed steam amount (required load) of the steam using facility 18 based on the steam pressure of the steam header 6.

Here, the several boiler 20 which comprises the boiler system 1 of this embodiment is demonstrated. FIG. 2 is a diagram showing an outline of the boiler group 2 according to the present embodiment.
The boiler 20 of this embodiment consists of a stage value control boiler having a plurality of staged combustion positions. A step-value control boiler controls the amount of combustion by selectively turning combustion on / off, adjusting the size of the flame, etc., and gradually changes the amount of combustion according to the selected combustion position. It is a boiler that can be increased or decreased.

  The combustion amount at each combustion position of the boiler 20 is set so as to generate an amount of steam corresponding to the pressure difference of the steam pressure in the steam header 6 to be controlled. In the three boilers 20 composed of the step value control boilers, the combustion amount and the combustion capacity at each combustion position may be set to be equal or different from each other.

  As shown in FIG. 2, the boiler 20 in the present embodiment includes a combustion stop position (0%), a low combustion position (20%) as a low combustion position, a medium combustion position (60%) as a base combustion position, and It is constituted by a so-called four-position control boiler 20 that can be combusted at four combustion positions of a high combustion position (100%) as a high combustion position. In this case, for example, when the combustion amount in the fuel state (high combustion state) in the high combustion position of one boiler 20 is 3000 kg / h, the combustion amount in the middle combustion position is 1800 kg / h, and in the low combustion position. The combustion amount is 600 kg / h.

  The N position control represents that the combustion amount of the step value control boiler can be controlled step by step to the N position including the combustion stop position. The number of combustion positions may be 3 positions (combustion stop position, low combustion position, and high combustion position), or 5 positions or more.

In the boiler group 2 described above, a plurality of combustion patterns are set that are combinations of the boilers 20 and their combustion positions. FIG. 3 is a diagram showing the relationship between the combustion pattern and priority of each boiler 20 according to the present embodiment, and the steam pressure zone in the steam pressure control range.
In the present embodiment, as shown in FIG. 3, the combustion pattern is “H” when the boiler is burned at the high combustion position (high combustion state), and is burned at the middle combustion position (medium combustion state). ) Is indicated as “M”, the combustion state at the low combustion position (low combustion state) is indicated as “L”, and the combustion stop state is indicated as “−”.

  As the combustion pattern, a pattern is selected such that the smaller the required load, that is, the higher the vapor pressure detected by the vapor pressure sensor 7, the smaller the combustion amount. Further, a pattern in which the combustion amount increases as the required load increases, that is, as the vapor pressure decreases, is selected. As shown in FIG. 3, in the present embodiment, the vapor pressure control range is divided into ten vapor pressure zones a to j. Then, the boiler system 1 sets a corresponding combustion pattern, that is, a combustion state (combustion position) for each steam pressure zone, and determines the combustion amount depending on which pressure zone the steam pressure corresponds to. Ten combustion patterns are set corresponding to ten vapor pressure zones.

  More specifically, as shown in FIG. 3, in the uppermost steam pressure zone a (when the required load is small), all the boilers 20 are positioned at the combustion stop position (−), and the lowest steam pressure is reached. In the band j (when the required load is large), all the boilers 20 are located at the high combustion position (H).

  A priority order is set for each of the boilers 20. The priority order is used to select a boiler that performs a combustion instruction or a combustion stop instruction. The priority order can be set, for example, using an integer value so that the lower the numerical value, the higher the priority order. As shown in FIGS. 2 and 3, when the priority order of “1” to “3” is assigned to each of the No. 1 to No. 3 units of the boiler 20, the No. 1 priority is the highest and Lowest priority. This priority order is changed at predetermined time intervals (for example, 24 hour intervals) under the control of the control unit 4 described later.

  In this embodiment, as shown in FIG. 3, when the vapor pressure decreases from the highest vapor pressure zone a toward the lowest vapor pressure zone j, the highest priority is given in normal control. After the boiler (No. 1 boiler) is changed from the combustion stop state (-) to the low combustion state (L), the next highest boiler (No. 2 boiler) is changed from the combustion stop state (-) to the low combustion state (-). The combustion state (L) is changed. Then, after all the boilers 20 are changed to the low combustion state (L), the boiler 20 having the highest priority (here, No. 1 boiler) is changed to the middle combustion state (M) in order. Moreover, after all the boilers 20 are changed to the middle combustion position (M), the boilers having the highest priority are changed to the high combustion position (H) in order.

Next, details of control of the combustion state of the plurality of boilers 20 by the boiler system 1 of the present embodiment will be described.
Based on the vapor pressure signal from the vapor pressure sensor 7, the number control device 3 calculates the required combustion amount of the boiler group 2 according to the required load and the combustion position (combustion state) of each boiler 20 corresponding to the required combustion amount. Then, the number control signal is transmitted to each boiler 20 (local control unit 25 described later). As shown in FIG. 1, the number control device 3 includes a storage unit 5 and a control unit 4.

  The storage unit 5 includes information such as the contents of instructions given to each boiler 20 under the control of the number control device 3 (control unit 4), the combustion state (combustion position) received from each boiler 20, and a plurality of boilers. Information on the setting conditions of the 20 combustion patterns, information on setting priority of the plurality of boilers 20, information on setting on changing priority (rotation), and the like are stored.

  The control unit 4 gives various instructions to the boilers 20 through the signal lines 16 and receives various data from the boilers 20 to determine the combustion states (combustion positions) and priority of the three boilers 20. Control the ranking. When each boiler 20 receives a signal for changing the combustion position from the number control device 3, it controls the boiler 20 according to the instruction.

  As shown in FIG. 1, the boiler 20 controls a boiler body 21 in which combustion is performed, a local vapor pressure measurement unit 27 that measures the vapor pressure inside the boiler 20, and a combustion position (combustion state) of the boiler 20. A local control unit 25.

  The local vapor pressure measurement unit 27 includes a vapor pressure sensor, and measures the vapor pressure inside the boiler 20.

The local control unit 25 changes the combustion position (combustion state) of the boiler 20 according to the required load. Specifically, the local control unit 25 determines the steam pressure inside the boiler 20 based on the number control signal transmitted from the number control device 3 via the signal line 16 or measured by the local steam pressure measurement unit 27. Based on the above, the combustion state of the boiler 20 is controlled.
Further, the local control unit 25 transmits a signal used in the number control device 3 to the number control device 3 via the signal line 16. The signals used in the number control device 3 include the steam pressure inside the boiler 20, the actual combustion state of the boiler 20, and other data.

  In the present embodiment, the control unit 4 determines whether the middle combustion position (M) as the base combustion position and the high combustion position (L) as the high combustion position in any of the boilers 20 in the boiler group 2. When the combustion position is changed a predetermined number of times (for example, 5 times) in a predetermined time (for example, 10 minutes), the boiler 20 in which the combustion position has been changed is maintained at the high combustion position (H). In this case, the control unit 4 determines the combustion position of the boiler 20 located at the middle combustion position (M) in the boiler group 2 as the middle combustion position (M) for the subsequent fluctuations in required load, and the like. The combustion state of the boiler group 2 is controlled by switching between the low combustion position (L) as the low combustion position.

  Specifically, for example, in the boiler group 2 shown in FIG. 3, when the required load is stable at around 65%, the No. 2 boiler and the No. 3 boiler burn at the middle combustion position (M). Since the amount of steam generated by the boiler group 2 exceeds the amount of steam used in the steam use equipment 18 by continuing the state in which the No. boiler burns at the high combustion position (H), the steam header 6 is measured. The value of the vapor pressure increases gradually. When the value of the steam pressure measured by the steam header 6 exceeds the upper limit value (lower limit value of g) of the steam pressure zone h, the control unit 4 instructs to burn the No. 1 boiler at the middle combustion position (M). Put out.

  On the other hand, when the required load is stable at around 65%, the No. 1 boiler burns at the middle combustion position (M) (that is, the No. 1 boiler to the No. 3 boiler all burn at the middle combustion position (M)). Since the amount of steam generated by the boiler group 2 is less than the amount of steam used in the steam use facility 18, the value of the steam pressure measured by the steam header 6 gradually decreases. When the value of the steam pressure measured by the steam header 6 falls below the upper limit value (lower limit value of g) of the steam pressure zone h, the control unit 4 instructs to burn the No. 1 boiler at the high combustion position (H). Put out.

  Thus, when the required load is stable within a certain range (here, 65%), the value of the steam pressure measured by the steam header 6 is a predetermined boiler 20 (here, No. 1). The threshold value (here, the upper limit value of the vapor pressure zone h) for changing the combustion position of the boiler between the middle combustion position (M) that is the base combustion position and the high combustion position (H) that is the higher combustion position. Repeatedly go up and down. As a result, the predetermined boiler 20 repeatedly changes the combustion position between the middle combustion position (M) and the high combustion position (H).

Therefore, in this embodiment, when the number of instructions for burning the No. 1 boiler stored in the storage unit 5 at the high combustion position (H) reaches a predetermined number within a predetermined time, the control unit 4 is shown in FIG. Thus, even if the combustion pattern of the boiler group 2 is changed and the value of the steam pressure measured by the steam header 6 exceeds the upper limit value (lower limit value of g) of the steam pressure zone h, No. 1 boiler Controls the combustion state of the boiler group 2 so as to maintain the high combustion position (H).
In this case, the control part 4 is when the value of the steam pressure measured by the steam header 6 exceeds the upper limit value (lower limit value of g) of the steam pressure zone h (including the case where the required load falls below 60%). Next, among the boilers 20 located at the middle combustion position (M), the No. 3 boiler with the lower priority is shifted from the middle combustion position (M) to the low combustion position (L). Moreover, the control part 4 makes the No. 2 boiler a middle combustion position (when the value of the steam pressure measured by the steam header 6 exceeds the upper limit value of the steam pressure zone g (when the required load falls below 47%)). M) is shifted to the low combustion position (L).

  That is, after the change of the combustion pattern, when the value of the steam pressure measured by the steam header 6 repeatedly rises and falls across the upper limit value of the steam pressure zone h, the No. 2 boiler is set to the middle combustion position (M). By changing the position between the high combustion position (H), the combustion state of the boiler group 2 is controlled. This prevents the No. 1 boiler from repeatedly changing the combustion position between the middle combustion position (M) and the high combustion position (H).

  Further, the control unit 4 determines the combustion load at the middle combustion position (M) of the boiler 20 in which the required load is located at the high combustion position (H) in the boiler group 2 and the high combustion position ( The combustion position of the boiler 20 maintained at the high combustion position (H) when the combustion amount at the low combustion position (L) of the boiler 20 not located at H) is below the sum of the combustion amount at the high combustion position (H). To migrate. In this case, the control unit 4 returns the combustion pattern of the boiler group 2 to the combustion pattern before the change (see FIG. 3).

  Specifically, in the boiler group 2 shown in FIG. 3, the required load is the combustion amount (1800 kg / h) at the middle combustion position (M) of the No. 1 boiler located at the high combustion position (H), When the combustion amount (600 kg / h + 600 kg / h) at the low combustion position (L) of the No. 2 and No. 3 boilers is below 3000 kg / h (when the required load is below 33%), The value of the vapor pressure measured by the vapor header 6 exceeds the upper limit value of the vapor pressure zone f. When the value of the steam pressure measured by the steam header 6 exceeds the upper limit value of the steam pressure zone f, the control unit 4 gives an instruction to burn the No. 1 boiler at the middle combustion position (M). Moreover, the control part 4 returns a combustion pattern to the combustion pattern before a change shown in FIG.

  Further, the control unit 4 changes the combustion pattern, and then the required load is the combustion amount of the boiler 20 positioned at the high combustion position (H) in the boiler group 2 and the high combustion position ( The combustion position of any one of the boilers 20 located in the middle combustion position (M) when the sum of the combustion amount in the middle combustion position (M) of the boiler 20 not located in H) is exceeded. Is moved to the high combustion position (H). Also in this case, the control unit 4 returns the combustion pattern of the boiler group 2 to the combustion pattern before the change (see FIG. 3).

  Specifically, in the boiler group 2 shown in FIG. 3, the required load is the combustion amount (3000 kg / h) of the No. 1 boiler located at the high combustion position (H), the No. 2 boiler and the No. 3 boiler. When it exceeds 6600 kg / h which is the sum of the combustion amount (1800 kg / h + 1800 kg / h) at the middle combustion position (M) (when the required load exceeds 73%), it is measured by the steam header 6. The value of the vapor pressure is below the lower limit value of the vapor pressure zone h. And if the value of the steam pressure measured by the steam header 6 falls below the lower limit value of the steam pressure zone h, the control unit 4 is the boiler 20 having the highest priority among the No. 2 boiler and the No. 3 boiler. An instruction to burn the boiler at the high combustion position (H) is issued. Moreover, the control part 4 returns a combustion pattern to the combustion pattern before a change shown in FIG.

Next, the operation of the boiler system 1 of the present embodiment will be described with reference to FIGS. 5 to 7 are flowcharts showing the operation of the boiler system 1.
Here, first, as shown in FIG. 3, when the priority order of “1” to “3” is assigned to each of the first to third units of the boiler 20, The steam pressure of the steam header 6 measured by the steam pressure sensor 7 is the lower limit value of the steam pressure zone g (upper limit of h) in a state where all the boilers 20 are combusting at the middle combustion position (M) as the base combustion position. The operation of the boiler system 1 when it is repeated up and down across (value) will be described. In this state, the vapor pressure of the vapor header 6 measured by the vapor pressure sensor 7 is located in the range of the vapor pressure band g shown in FIG.

  In this case, as shown in FIG. 5, first, in step ST <b> 1, the control unit 4 monitors the vapor pressure of the vapor header 6 measured by the vapor pressure sensor 7. Here, when the vapor pressure of the vapor header 6 measured by the vapor pressure sensor 7 does not fall below the first threshold value which is the lower limit value of the vapor pressure zone g shown in FIG. 3, the process returns to step ST1. When the vapor pressure of the vapor header 6 measured by the vapor pressure sensor 7 falls below the first threshold value, the process proceeds to step ST2.

  In step ST2, the control unit 4 places the No. 1 boiler 20 in the high combustion position (H) in the local control unit 25 of the No. 1 boiler 20 having the highest priority among the boilers 20 burning at the middle combustion position (M). ) (High combustion transition instruction) is issued. The local control unit 25 of the No. 1 boiler 20 burns the No. 1 boiler 20 at the high combustion position (H). Then, the process proceeds to step ST3.

  In step ST <b> 3, the control unit 4 stores the content of the instruction issued to the No. 1 boiler 20 and the time when the instruction is issued in the storage unit 5. Then, the process proceeds to step ST4.

  In step ST4, the control part 4 determines whether the frequency which issued the instruction | indication which transfers No. 1 boiler 20 to a high combustion position (H) is over predetermined frequency. Specifically, based on the information stored in the storage unit 5, the control unit 4 has a time from the high combustion transition instruction n times before (for example, 4 times before) to the current high combustion transition instruction for T1 time. It is determined whether it is less than (for example, 10 minutes). If the control unit 4 determines that the time from the nth previous high combustion transition instruction to the current high combustion transition instruction is less than T1 time, the process proceeds to step ST5. If the control unit 4 does not determine that the time from the nth previous high combustion transition instruction to the current high combustion transition instruction is less than T1 time, the process flow ends.

  In step ST5, the control unit 4 maintains the combustion position of the No. 1 boiler 20 at the high combustion position (H) when the steam pressure of the steam header 6 measured by the steam pressure sensor 7 exceeds the first threshold value. The combustion pattern of the boiler group 2 is changed so that the combustion position of the No. 3 boiler 20 is shifted from the middle combustion position (M) to the low combustion position (L), and the processing of this flow is finished. Specifically, the control unit 4 changes the combustion pattern of the boiler group 2 from the combustion pattern shown in FIG. 3 to the combustion pattern shown in FIG.

  Next, the operation of the boiler system 1 when the required load decreases after the control unit 4 changes the combustion pattern of the boiler group 2 will be described with reference to FIG.

  In this case, first, in step ST11, the control unit 4 determines whether the vapor pressure of the vapor header 6 measured by the vapor pressure sensor 7 exceeds the first threshold value. When it is determined that the vapor pressure of the vapor header 6 measured by the vapor pressure sensor 7 exceeds the first threshold, the process proceeds to step ST12. When it is determined that the vapor pressure of the vapor header 6 measured by the vapor pressure sensor 7 does not exceed the first threshold value, the process returns to step ST11.

  In step ST12, the control unit 4 instructs the local control unit 25 of the No. 3 boiler 20 to shift the No. 3 boiler 20 to the low combustion position (L). The local control unit 25 of the No. 3 boiler 20 burns the No. 3 boiler 20 at the low combustion position (L). Then, the process proceeds to step ST13.

  In step ST13, the control unit 4 determines whether the vapor pressure of the vapor header 6 measured by the vapor pressure sensor 7 exceeds a second threshold value that is the upper limit value of the vapor pressure band g shown in FIG. When it is determined that the vapor pressure of the vapor header 6 measured by the vapor pressure sensor 7 has exceeded the second threshold value, the process proceeds to step ST14. When it is determined that the vapor pressure of the vapor header 6 measured by the vapor pressure sensor 7 has not exceeded the second threshold value, the process returns to step ST13.

  In step ST14, the control unit 4 instructs the local control unit 25 of the No. 2 boiler 20 to shift the No. 2 boiler 20 to the low combustion position (L). The local control unit 25 of the No. 2 boiler 20 burns the No. 2 boiler 20 at the low combustion position (L). Then, the process proceeds to step ST15.

  In step ST15, the control unit 4 determines whether the vapor pressure of the vapor header 6 measured by the vapor pressure sensor 7 exceeds a third threshold value that is the upper limit value of the vapor pressure zone f shown in FIG. When it is determined that the vapor pressure of the vapor header 6 measured by the vapor pressure sensor 7 exceeds the third threshold value, the process proceeds to step ST16. When it is determined that the vapor pressure of the vapor header 6 measured by the vapor pressure sensor 7 has not exceeded the third threshold value, the process returns to step ST15. Here, the third threshold value is the vapor pressure corresponding to the case where the No. 1 boiler 20 is burned at the middle combustion position (M) and the No. 2 boiler 20 and the No. 3 boiler 20 are burned at the low combustion position (L). Corresponds to the value.

  In step ST16, the control unit 4 instructs the local control unit 25 of the No. 1 boiler 20 to shift the No. 1 boiler 20 to the middle combustion position (M). The local control unit 25 of the No. 1 boiler 20 burns the No. 1 boiler 20 at the middle combustion position (M). Then, the process proceeds to step ST17.

  In step ST17, the control part 4 returns the combustion pattern of the boiler group 2 to the combustion pattern before a change, and complete | finishes the process of this flow.

  Next, the operation of the boiler system 1 when the required load further increases after the control unit 4 changes the combustion pattern of the boiler group 2 will be described with reference to FIG.

  In this case, first, in step ST21, the control unit 4 determines whether or not the vapor pressure of the vapor header 6 measured by the vapor pressure sensor 7 is lower than a fourth threshold value that is the lower limit value of the vapor pressure zone h shown in FIG. judge. If it is determined that the vapor pressure of the vapor header 6 measured by the vapor pressure sensor 7 has fallen below the fourth threshold, the process proceeds to step ST22. If it is determined that the vapor pressure of the vapor header 6 measured by the vapor pressure sensor 7 has not fallen below the fourth threshold, the process returns to step ST21. Here, the fourth threshold value is the vapor pressure corresponding to the case where the No. 1 boiler 20 is burned at the high combustion position (H) and the No. 2 boiler 20 and the No. 3 boiler 20 are burned at the medium combustion position (M). Corresponds to the value.

  In step ST22, the control unit 4 instructs the local control unit 25 of the No. 2 boiler 20 to shift the No. 2 boiler 20 to the high combustion position (H). The local control unit 25 of the No. 2 boiler 20 burns the No. 2 boiler 20 at the high combustion position (H). Then, the process proceeds to step ST23.

  In step ST23, the control part 4 returns the combustion pattern of the boiler group 2 to the combustion pattern before a change, and complete | finishes the process of this flow.

  According to the boiler system 1 of this embodiment demonstrated above, there exist the following effects.

  (1) In the boiler system 1, when the change of the combustion position from the low combustion position to the high combustion position is repeated in a short time, the amount of can water taken out from the can body to the separator increases, so that the separator In this case, water in the steam cannot be sufficiently separated. As a result, the dryness of the steam supplied from the boiler 20 decreases. Therefore, the control unit 4 has a medium combustion position (M) as a base combustion position and a high combustion position (H) as a high combustion position in any of the boilers 20 (No. 1 boiler 20 in this embodiment). When the combustion position is changed a predetermined number of times during a predetermined time, the No. 1 boiler 20 is maintained at the high combustion position (H) and the boiler 20 positioned at the middle combustion position (M) (2 in this embodiment). The combustion position of the boiler group 2 was controlled by switching the combustion position of the No. boiler 20 and No. 3 boiler 20) between the middle combustion position (M) and the low combustion position (L) which is the low combustion position. This prevents the combustion position from being repeatedly changed between the middle combustion position (M) and the high combustion position (H), so that the combustion position from the middle combustion position (M) to the high combustion position (H) can be prevented. It can prevent the steam dryness from being changed repeatedly. Therefore, even if the required load fluctuates repeatedly, the dryness of the steam supplied from the boiler 20 can be prevented from decreasing.

  (2) The control unit 4 has the required load at the middle combustion position (M) of the boiler 20 at the high combustion position (H) and the boiler 20 not at the high combustion position (H). The combustion position of the boiler 20 maintained at the high combustion position (H) was shifted to the middle combustion position (M) when the sum of the combustion amount at the low combustion position (L) was below the sum. As a result, when the required load is sufficiently reduced, the boiler 20 located at the high combustion position (H) can be burned at the middle combustion position (M), which is the base combustion position. Can be improved.

  (3) The boiler system 1 is applied to a four-position controlled boiler 20, the base combustion position is set to the middle combustion position (M), the high combustion position is set to the high combustion position (H), and the low combustion position is set to the low combustion position ( L). This prevents frequent change of the combustion position from the middle combustion position (M) to the high combustion position (H) where the can water boils and evaporates vigorously. The effect of reducing the dryness can be further improved.

The preferred embodiment of the boiler system 1 of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and can be modified as appropriate.
For example, in this embodiment, although the boiler system 1 of this invention was applied to the boiler 20 of 4 position control, it is not restricted to this. That is, the boiler system 1 of the present invention may be applied to a three-position control boiler, or may be applied to a five-position control or more boiler having a plurality of medium combustion positions. When the boiler system of the present invention is applied to a three-position control boiler, the base combustion position corresponds to the low combustion position, and the high combustion position corresponds to the high combustion position. The lower combustion position corresponds to a combustion stop position (including a pilot operation state or a purge operation state which is a steam supply preparation state). Further, when the boiler system is applied to a five-position control boiler, the base combustion position is made to correspond to the combustion position with the highest boiler efficiency among the plurality of medium combustion positions.

  Further, in the present embodiment, the control unit 4 controls the boiler group 2 based on the frequency of change of the combustion position from the middle combustion position (M) that is the base combustion position to the high combustion position (H) that is the high combustion position. Although the combustion state was controlled, it is not limited to this. That is, the control unit may control the combustion state of the boiler group based on the frequency of change of the combustion position from the high combustion position to the base combustion position.

  In the present embodiment, the required load is the combustion amount (1800 kg / h) at the middle combustion position (M) of the No. 1 boiler located at the high combustion position (H), the No. 2 boiler and the No. 3 boiler. When the combustion amount (600 kg / h + 600 kg / h) at the low combustion position (L) falls below 3000 kg / h (when the required load falls below 33%), the No. 1 boiler 20 is moved to the high combustion position (H ) To the middle combustion position (M), but is not limited thereto. That is, when the required load is less than 3000 kg / h (when the required load is less than 33%), the No. 1 boiler is not moved to the middle combustion position (M) but is located at the low combustion position (L). The No. 2 boiler or the No. 3 boiler may be moved to the combustion stop position (−).

  Moreover, although this invention was applied to the boiler system provided with the boiler group 2 which consists of the three boilers 20 in this embodiment, it is not restricted to this. That is, the present invention may be applied to a boiler system including a boiler group including four or more boilers, or may be applied to a boiler system including a boiler group including two boilers.

1 Boiler System 2 Boiler Group 4 Controller 20 Boiler L Low Combustion Position (Low Combustion Position)
M Medium combustion position (base combustion position)
H High combustion position (high combustion position)

Claims (4)

A plurality of boilers capable of burning at a plurality of stepwise combustion positions including a base combustion position, a high combustion position that is a combustion position higher than the base combustion position, and a low combustion position that is a combustion position lower than the base combustion position A boiler system comprising: a boiler group comprising: a control unit that controls a combustion state of the boiler group according to a required load;
The controller is
In any one of the boiler groups, when the combustion position is changed a predetermined number of times in a predetermined time between the base combustion position and the high combustion position, the boiler in which the combustion position is changed Is maintained at the high combustion position, and the combustion position of the boiler located at the base combustion position in the boiler group is switched between the base combustion position and the low combustion position to control the combustion state of the boiler group system.   The control unit is configured such that the required load is a combustion amount at the base combustion position of a boiler located at the high combustion position in the boiler group, and a boiler not located at the high combustion position in the boiler group. 2. The boiler system according to claim 1, wherein the combustion position of the boiler maintained at the high combustion position is shifted to the base combustion position when the sum of the combustion amount and the combustion amount at the low combustion position is below.   The control unit includes a combustion amount of a boiler in which the required load is located at the higher combustion position in the boiler group, and a base combustion position of a boiler that is not located in the higher combustion position in the boiler group. 3. The boiler system according to claim 1, wherein, when the sum of the amount of combustion in the boiler exceeds the sum, the combustion position of any one of the boilers located at the base combustion position is shifted to the higher combustion position. The boiler is configured to be combustible at four positions of a combustion stop position, a low combustion position, a middle combustion position, and a high combustion position,
The base combustion position corresponds to the middle combustion position;
The high combustion position corresponds to the high combustion position;
The boiler system according to claim 1, wherein the low combustion position corresponds to the low combustion position.

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