JP2016114335A - Boiler system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a boiler system 1 in which a maximum number of boilers performing combustion is set, and which suppresses significant deterioration of header pressure by activating a spare boiler even in a case where a steam load exceeding the combustion amount of the maximum number of boilers performing combustion occurs.SOLUTION: A control unit 4 of a boiler system 1 in which a maximum number of boilers performing combustion is set, includes a spare boiler combustion number control part 43 that adds one spare boiler to a control object when all control object boilers perform combustion at a preset first combustion ratio or more and it is detected that a state where a header pressure value lowers has been continued for a preset first time.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a boiler system. More specifically, the present invention relates to a boiler system that controls the number of boilers for which the maximum number of combustion units is set.

Conventionally, as a boiler system that burns a plurality of boilers to generate steam, the maximum number of combustion units or the maximum amount of steam used is set in advance as a preset value, and only the boilers included in the maximum number of combustion units (hereinafter also referred to as “controlled boilers”) There has been proposed a boiler system that performs combustion control of a boiler so as not to burn a boiler that is out of the maximum number of combustion (hereinafter also referred to as “preliminary boiler”).
For example, in Patent Document 1, if the boiler system 1 (boiler group 2) includes five boilers 20 and the maximum number of combustion units is set to three, among the five boilers 20, priority order is given. There is described a boiler system 1 in which three boilers having a high priority are set as control target boilers, and two boilers having a low priority are set as spare boilers. And in the control method of the boiler proposed by this patent document 1, the combustion control of the boiler is performed so that only the three control target boilers are burned and the remaining two spare boilers are not burned.

JP 2013-072609 A

  By the way, in the boiler system described in Patent Document 1, if the maximum number of burners or the maximum amount of steam used is set to be small, for example, due to a sudden load fluctuation or a temporary increase in required steam amount, When a steam load exceeding the combustion amount is generated, the spare boiler does not burn endlessly, so that the combustion amount is insufficient and the header pressure is significantly reduced.

  In the boiler system in which the maximum number of combustion units is set, for example, when a steam load exceeding the combustion amount for the maximum number of combustion units occurs due to a rapid load fluctuation or a temporary increase in the required steam amount, the spare boiler is installed. It aims at providing the boiler system which suppresses the big fall of header pressure by starting.

  The present invention includes a boiler group composed of a plurality of boilers, a steam header that collects steam generated in the boiler group, and a steam pressure measuring unit that measures a header pressure value that is a steam pressure inside the steam header; A control unit that controls a combustion state of the boiler group based on the header pressure value, wherein the control unit controls a preset number of boilers in the boiler group. The control target boiler setting unit that is set in the control target boiler that is the control target by the unit, and all the control target boilers are combusted at a preset first combustion rate or more and the header pressure value decreases in advance. When the first state is detected by the first state detection unit that detects the first state that continues for the set first time, and the first state detection unit, the control target boiler setting unit One preliminary boilers which have not been set as the control target boiler comprises a pre-boiler combustion count control unit to be added to the controlled object, and relates to a boiler system.

  The control unit cancels the function of the preliminary boiler combustion number control unit until the header pressure value reaches a preset first pressure value after the operation of the boiler system is started. It is preferable to further include a combustion number control stop unit.

  Further, the control unit further includes a required steam amount calculation unit that calculates a required steam amount based on a header pressure value, and a combustion continuation target boiler excluding one boiler that can be reduced among all the control target boilers. A reduced-can reference steam amount calculation unit that calculates a reduced-can reference steam amount that is the sum of the steam amounts when burned at a preset second combustion rate that is less than or equal to the first combustion rate, and the control target boiler setting In a case where a spare boiler that has not been set as a control target boiler is added to the control target by the unit, a state in which the state where the required steam amount falls below the can-reduction reference steam amount continues for a preset second time A second state detection unit that detects a state, and when the second state detection unit detects the second state, the preliminary boiler combustion number control unit removes the boiler that is to be reduced from the control target. But Kill.

  Further, the control unit controls a combustion state of the control target boiler so that the header pressure value falls within a preset pressure range, and the control unit is further controlled by the control target boiler setting unit. When a spare boiler that has not been set as a boiler is added as a control target, a third state in which a state in which the header pressure value exceeds a preset second pressure value continues for a preset third time is detected. A state detection unit is provided, and when the third state detection unit detects the third state, the spare boiler combustion number control unit can remove one spare boiler from the control target.

  The second pressure value is preferably higher than a lower limit value of the set pressure range and not more than an upper limit value.

  According to the boiler system of the present invention, when a steam load exceeding the combustion amount for the maximum number of combustion units occurs due to, for example, a rapid load fluctuation or a temporary increase in the required steam amount, the header is started by starting the spare boiler. A significant drop in pressure can be suppressed.

It is a figure showing the outline of the boiler system concerning a 1st embodiment of the present invention. It is a figure showing the outline of the boiler group concerning a 1st embodiment of the present invention. It is a figure showing the outline of the boiler group concerning a 1st embodiment of the present invention. It is a functional block diagram which shows the structure of the control part 4 which concerns on 1st Embodiment of this invention. It is a figure showing operation of boiler system 1 concerning a 1st embodiment of the present invention. It is a flowchart which shows operation | movement of the boiler system 1 which concerns on 1st Embodiment. It is a figure showing operation of boiler system 1 concerning a 1st embodiment. It is a figure showing operation of boiler system 1 concerning a 1st embodiment. It is a functional block diagram which shows the structure of 4 A of control parts of 2nd Embodiment. It is a flowchart which shows operation | movement of the boiler system 1 which concerns on 2nd Embodiment.

Hereinafter, preferred embodiments of the boiler system of the present invention will be described with reference to the drawings.
First, the overall configuration of the boiler system 1 according to the first embodiment of the present invention will be described with reference to FIG.

[First Embodiment]
The boiler system 1 includes a boiler group 2 including a plurality of (five) 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, if the required load (steam consumption) increases due to an increase in demand for the steam use facility 18, and the amount of steam supplied to the steam header 6 is insufficient, the steam pressure inside the steam header 6 decreases. It will be. On the other hand, if the demand load (steam consumption) decreases due to a decrease in the demand for the steam use facility 18 and the amount of steam supplied to the steam header 6 becomes excessive, the steam pressure inside the steam header 6 increases. Become. 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 necessary steam amount that is a steam amount required according 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.
The several boiler 20 which comprises the boiler system 1 can be comprised by the step value control boiler which has several stepwise combustion positions, or a continuous control boiler.

  A step-value control boiler controls the amount of combustion by selectively turning combustion on / off or adjusting the size of the flame, etc., and gradually increases or decreases the amount of combustion according to the selected combustion position. It is a possible boiler. As shown in FIG. 2A, the boiler 20 is a four-position (combustion stop position, low combustion position, middle combustion position, and high combustion position) control boiler.

  The step value control boiler is not limited to the 4-position control. The stage value control boiler can be a boiler 20 that can control N position control, that is, the combustion amount of the stage value control boiler in a stepwise manner to the N position including the combustion stop state, where N is an arbitrary integer. For example, the number of combustion positions may be 2 positions (that is, only on / off), 3 positions (combustion stop position, low combustion position, and high combustion position), or 5 positions or more.

  In each of the five boilers 20 composed of the step value control boilers, the combustion amount and the combustion capacity (combustion amount in the high combustion state) at each combustion position may be set equal or differently set. It may be.

  It should be noted that the combustion of the stage value control boiler or its stop can be handled in units of virtual boilers. In the virtual boiler, differences in combustion position (combustion amount) (low combustion position, medium combustion position, high combustion position, etc.) in the boiler are regarded as independent boilers, and the respective evaporation amounts are virtually assumed in the boiler. For example, in the case of an on / off boiler (two-position boiler), there is one virtual boiler, which matches the actual number of physical boilers. Further, even if the three-position boiler is physically one unit, it can be virtually counted as two units of a low combustion amount boiler and a (high combustion amount-low combustion amount) boiler. The four-position boiler can be virtually counted as a low combustion amount boiler, a (medium combustion amount-low combustion amount) boiler, and a (high combustion amount-medium combustion amount) boiler. Therefore, if the three-position boiler is in a low combustion state, it can be handled for control if a combustion instruction is given to the low combustion amount boiler, while the (high combustion amount−low combustion amount) boiler can be handled. On the other hand, if a combustion stop instruction is given, it can be handled in terms of control.

  Moreover, a continuous control boiler is a continuous control boiler which can burn by changing a combustion rate continuously. As shown in FIG. 2B, the combustion amount can be continuously controlled at least in the range from the minimum combustion state S1 (for example, the combustion state at 20% of the maximum combustion rate) to the maximum combustion state S2. It is a boiler. The continuous control boiler adjusts the amount of combustion by, for example, controlling the opening degree (combustion ratio) of a valve that supplies fuel to the burner and a valve that supplies combustion air.

In the continuous control boiler, the change of the combustion state between the combustion stop state S0 and the minimum combustion state S1 of the continuous control boiler is controlled by turning on / off the combustion of the continuous control boiler (burner). In the range from the minimum combustion state S1 to the maximum combustion state S2, the combustion amount can be controlled continuously.
It should be noted that the continuous control of the combustion amount means that calculations and signals in the local control unit described later are digitally handled in stages (for example, the output (combustion amount) of the continuous control boiler is in increments of 1%). Even when the output is controlled).

More specifically, a unit steam amount U which is a unit of variable steam amount is set in the continuous control boiler. Thereby, the continuous control boiler can change the amount of steam in units of unit steam amount U in the range from the minimum combustion state S1 to the maximum combustion state S2.
Here, the unit steam amount U can be appropriately set according to the steam amount (maximum steam amount) in the maximum combustion state S2 of the continuous control boiler, but the viewpoint of improving the followability of the output steam amount to the necessary steam amount in the boiler system. Therefore, it is preferably set to 0.1% to 20% of the maximum steam amount of the continuous control boiler, and more preferably set to 1% to 10%.

  Next, each of the boilers 20 is set with a priority order. The priority order is used to select the boiler 20 that performs a combustion instruction, a combustion stop instruction, or the like. 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 FIG. 2A or FIG. 2B, when the priority order of “1” to “5” is assigned to each of the first to fifth units of the boiler 20, the first unit has the highest priority and Lowest priority. In the normal case, 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 addition, when handling combustion of a step value control boiler or its stop in a virtual boiler unit, a priority can be set in a virtual boiler unit. For example, as shown in FIG. 6 (A), the priority order of the virtual boiler unit is set from the highest to the first low combustion amount boiler, the second low combustion amount boiler, and the first unit (medium combustion amount-low combustion amount). ) Boiler, Unit 2 (medium combustion amount-low combustion amount) boiler, Unit 3 low combustion amount boiler, Unit 3 (medium combustion amount-low combustion amount) boiler, Unit 1 (High combustion amount-low combustion amount) ) Boiler No. 2 (high combustion amount-low combustion amount) boiler, No. 3 (high combustion amount-low combustion amount) boiler can be set.

  Each of the plurality of boilers 20 is electrically connected to the number control device 3 via the signal line 16, and the combustion state (combustion amount) is controlled by the control of the number control device 3.

The boiler 20 demonstrated above is provided with the boiler main body 21 in which combustion is performed, and the local control part 22 which controls the combustion state of the boiler 20, as shown in FIG.
The local control unit 22 changes the combustion state of the boiler 20 according to the steam consumption. Specifically, the local control unit 22 controls the combustion state of the boiler 20 based on a control signal transmitted from the number control device 3 via the signal line 16 or a control signal input by a driver's manual operation. To do. Further, the local control unit 22 transmits a signal used in the number control device 3 to the number control device 3 via the signal line 16. Examples of signals used in the number control device 3 include the actual combustion state of the boiler 20 and other data.

  In the boiler system 1 configured as described above, the steam generated in the boiler group 2 is supplied to the steam using facility 18 via the steam header 6.

Next, details of the number control device 3 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 state of each boiler 20 corresponding to the required combustion amount, The number control signal is transmitted to the boiler 20 (local control unit 22). As shown in FIG. 1, the number control device 3 includes a storage unit 5 and a control unit 4.

  The storage unit 5 preliminarily stores the contents of instructions given to each boiler 20 under the control of the number control device 3 (control unit 4), information such as the combustion state received from each boiler 20, and the boiler system 1 in advance. Information on the maximum number of burners or the maximum amount of steam used, information on the first combustion rate of each boiler 20 to be described later, and information on the second combustion rate that is equal to or lower than the first combustion rate, first time and second time to be described later , A first pressure value to be described later, information on setting priority of the plurality of boilers 20, information on setting related to change (rotation) of priority, and the like are stored.

  The control unit 4 gives various instructions to each boiler 20 via the signal line 16 and receives various data from each boiler 20 to control the combustion state and priority order of the five boilers 20. . When each boiler 20 receives a signal for changing the combustion state from the number control device 3, it controls the boiler 20 according to the instruction.

  As shown in FIG. 3, the control unit 4 includes a control target boiler setting unit 41, a first state detection unit 42, a preliminary boiler combustion number control unit 43, a preliminary boiler combustion number control stop unit 44, and a necessary steam amount A calculation unit 45, a can reduced reference steam amount calculation unit 46, and a second state detection unit 47 are provided.

[Controlled boiler setting unit 41]
The control target boiler setting unit 41 uses, for example, the control unit 4 to determine the minimum number of boilers 20 satisfying the preset maximum number of combustion units or the preset maximum use steam amount from the boiler group 2 based on the priority order. Set as a combustion control target (control target boiler). In addition, the boiler 20 which remove | deviated from the minimum number satisfying the maximum combustion number or the maximum amount of used steam is set as a backup boiler. Hereinafter, the boiler set as a control target by the control target boiler setting unit 41 is also referred to as a “control target boiler on setting”. Further, a boiler that is excluded from the control target by the control target boiler setting unit 41 is also referred to as a “preliminary boiler on setting”.
For example, referring to FIG. 2A or FIG. 2B, when the maximum number of combustion is three, the first to third machines are set as control target boilers, and the remaining fourth and fifth machines are set as spare boilers. The

[First state detection unit 42]
The first state detection unit 42 is a state in which all the control target boilers 20 burn at a preset first combustion rate (for example, the maximum combustion rate) or more and the header pressure value PV decreases in the combustion state. Is in a state that continues for a preset first time (hereinafter also referred to as “first state”).

  When the boiler 20 is a step value control boiler, the first combustion rate can be set by a combustion position (for example, a high combustion position, a middle combustion position, etc.). In this case, the intermediate combustion position can be designated in addition to the high combustion position as the first combustion rate for each stage value control boiler 20.

  For example, when the steam load is suddenly increased and the controlled boiler 20 is shifted from the combustion stop state to the maximum combustion state, the control target boiler 20 stops the combustion with a decrease in the total load, for example. When it is the boiler 20 over a long period, the heat which the said boiler had already emitted may be cooled. When such a cooled boiler (hereinafter also referred to as “cold boiler”) is newly burned, the controller 4 instructs the boiler 20 to burn at the maximum combustion rate. For example, if it does not take about 3 minutes, there is a possibility that the combustion state of the maximum combustion rate is not achieved.

  Therefore, in order to determine whether the control target boiler 20 is in a combustion state equal to or higher than the first combustion rate, the first state detection unit 42 includes information on the control target boiler itself (the combustion state of the boiler and the pressure of the boiler). ) Is collected and it is determined that the combustion state of the boiler 20 is combusting at a first combustion rate or more and the pressure in the boiler 20 is equivalent to the header pressure. It is preferable to determine that the boiler 20 is in a state of burning at the first combustion rate or higher.

[Preliminary boiler combustion number control unit 43]
Each time the preliminary boiler combustion number control unit 43 detects the first state by the first state detection unit 42 (that is, all the control target boilers 20 burn at a preset first combustion rate or more, respectively) In a state where the header pressure value PV decreases in the combustion state in a state in which the header pressure value PV continues for the preset first time), for example, based on the priority order, it is not set as the control target boiler by the control target boiler setting unit 41 One spare boiler is added to the control target from among the spare boilers 20.
Thus, the control target boiler including the backup boiler (on the setting) added to the control target by the preliminary boiler combustion number control unit 43 is referred to as a control target boiler for control. That is, the control target boiler for control is composed of a control target boiler for setting and a spare boiler for setting added to the control target.
When a first state is detected by the first state detection unit 42 after adding one (on the setting) spare boiler to the control target, there is another spare boiler not added to the combustion control target Adds another spare boiler from among the other spare boilers 20 to the control target.
For example, in FIG. 2A or FIG. 2B, when No. 1 to No. 3 are set as boilers to be controlled and the remaining No. 4 and No. 5 are set as spare boilers, No. 1 to No. 3 are respectively set in advance. When the combustion is performed at the first combustion rate or higher and the state in which the header pressure value decreases in the combustion state continues for a preset first time, the fourth machine is added to the control target.
By doing this, for example, when a steam load exceeding the combustion amount for the maximum number of combustion units occurs due to a rapid load fluctuation or a temporary increase in the required steam amount, a header boiler pressure is added by adding a spare boiler to the control target. Can be suppressed.
In addition, since the condition in which the header pressure value decreases continues for a preset first time, in the boiler system 1, when the combustion state temporarily exceeds the first combustion rate, the spare boiler Is not added to the control target, and it is possible to suppress the useless activation of the spare boiler.
The process when the spare boiler combustion number control unit 43 removes the spare boiler added to the control target from the control target under certain conditions will be described later.

[Preliminary boiler combustion unit control stop unit 44]
When the operation of the boiler system 1 is started and the number control of the boiler group 2 is started, the number control is started from a state in which the header pressure is significantly low. Therefore, the control unit 4 is controlled by the control target boiler setting unit 41. It occurs that all the control target boilers 20 set as boilers are burned in a maximum combustion state (a combustion state equal to or higher than the first combustion rate).
Therefore, after the operation of the boiler system 1 is started and the number control of the boiler group 2 is started, the preliminary boiler combustion number control is performed until the header pressure value PV reaches a predetermined pressure value (first pressure value P1). It is preferable to cancel the operation of the function of the unit 43 so that the spare boiler is not added to the control target.

The preliminary boiler combustion unit control stop unit 44 functions as the preliminary boiler combustion unit control unit 43 until the header pressure value PV reaches the preset first pressure value P1 after the operation of the boiler system 1 is started. Cancel.
In this way, immediately after the operation of the boiler system 1, for example, when the controlled boiler 20 is combusted with the maximum combustion of all the units so that the start-up becomes faster, the spare boiler combustion unit control unit 43 It is possible to suppress unnecessary activation of the spare boiler without adding the boiler to the control target.

  Next, a process when one spare boiler is excluded from the control target after one or more set-up spare boilers 20 are added to the control target by the spare boiler combustion unit control unit 43 will be described.

[Required steam amount calculation unit 45]
First, the required steam amount calculation unit 45 will be described. The required steam amount calculation unit 45 calculates the required steam amount MV based on the header pressure value PV.

[For proportional distribution control]
When the plurality of boilers 20 of the boiler system 1 are step value control boilers, the combustion amount of the step value control boiler to be controlled is controlled so that the header pressure value PV falls within a preset pressure range, and the header pressure value A proportional distribution control system in which the required amount of steam is uniquely determined by PV can be adopted.

In this case, the required steam amount calculation unit 45 calculates the required steam amount MV _n based on the pressure deviation P _D1 that is the difference between the header pressure value PV and the upper limit pressure value P _max of the set pressure range for each control cycle. To do. Here, the subscript n indicates the number of repetitive operations performed every control cycle (the nth time: positive integer value of n = 1, 2,..., N).
More specifically, the required steam amount calculation unit 45 sets the pressure deviation P _D1 of the header pressure value PV (difference between the upper limit pressure value P _max of the set pressure range and the header pressure value PV) for each control cycle. based on the ratio P _R1 divided by the control width P ₁ is the difference between the upper limit pressure value P _max and the lower limit pressure value P _min of the pressure range, the amount of steam to be generated in a boiler in accordance with the required load (hereinafter, "requires The amount of vapor MV _n ”) is also calculated by Equation 1.

Necessary steam amount MV _n = maximum steam amount JG × _P R1 ······· (Equation 1)

Here, the maximum steam amount JG is the sum of the steam amounts (maximum steam amount) when the boilers 20 constituting the boilers to be controlled in the control of the boiler system 1 are burned at the preset maximum combustion rate. .

The required steam amount calculation unit 45 is based on the deviation amount between the required steam amount MV calculated by Equation 1 and the output steam amount JT calculated for each control cycle and the fluctuation state of the header pressure value PV for each control cycle. By selecting the combustion position of the stage value control boiler 20, the combustion state can be controlled.
The combustion control by the proportional distribution control method can be applied even when the plurality of boilers 20 of the boiler system 1 are continuous control boilers.

[In the case of PI control or PID control]
When the plurality of boilers 20 of the boiler system 1 are continuous control boilers, the combustion amount of the continuous control boiler to be controlled is controlled so that the header pressure value PV matches the preset target pressure value SV. PI control or PID control in which the required amount of steam is uniquely determined can be employed.

In this case, the necessary steam amount calculating unit 45, so as to maintain the header pressure value PV to the target pressure value SV, calculated by the velocity-type PI algorithm or velocity type PID algorithm necessary steam amount MV _n at the present time.

More specifically, the required steam amount calculation unit 45 has zero deviation between the header pressure value PV (feedback value) measured by the steam pressure sensor 7 and a preset target pressure value SV (set value). As described above, the current required steam amount MV _n is calculated by the speed type PID algorithm shown below. Note that the speed type PI algorithm is obtained by omitting the D control output (change) in the speed type PID algorithm, and a description thereof will be omitted.

Necessary steam amount calculating unit 45, a necessary amount of steam MV _n at the present time to be generated from a plurality of the boiler 20, is calculated by the velocity-type calculation formula (Equation 2).
MV _n = MV _n−1 + ΔMV _n (Equation 2)
In (Expression 2), MV _n : current required steam amount (current required steam amount), MV _n-1 : required steam amount at the previous control cycle (previous required steam amount), ΔMV _n : from the previous time to this time This is the required amount of steam change. Here, the subscript n indicates the number of iterations (the nth: a positive integer value of n = 1, 2,..., N).
The speed type calculation calculates only the necessary steam amount change ΔMV _n from the previous time to the current time every control cycle, and adds the previous required steam amount MV _n−1 to this to calculate the current required steam amount MV _n . Is the method.
On the other hand, the PID control algorithm that directly calculates the required steam amount MV _n this time for each control cycle is referred to as position type calculation.

The required amount of steam change ΔMV _n from the previous time to the current time is calculated by the following (formula 3).
ΔMV _n = ΔP _n + ΔI _n + ΔD _n ... (Formula 3)
In (Equation 3), ΔP _n : P control output (change), ΔI _n : I control output (change), ΔD _n : D control output (change), respectively, It is obtained by equation 6).
_{ΔP n = K P × (e} n -e n-1) ·············· ( Equation 4)
ΔI _n = K _P × (Δt / T _I ) × e _n (Equation 5)
_{ΔD n = K P × (T} D / Δt) × (e n -2e n-1 + e n-2) ··· ( Formula 6)
In (Expression 4) to (Expression 6), Δt: control cycle, K _P : proportional gain, T _I : integration time, T _D : differentiation time, e _n : current deviation amount, e _n-1 : previous control Deviation amount at the cycle time, e _n-2 : Deviation amount at the previous control cycle time.
Deviation e _n at the present time is a target pressure value SV, a difference between the header pressure value PV measured by the vapor pressure sensor 7, is determined by the following equation (7).
e _n = SV-PV (Equation 7)

The necessary steam amount calculation unit 45 adds the outputs (changes) calculated in (Equation 4), (Equation 5), and (Equation 6) according to (Equation 3). Vapor amount change ΔMV _n is calculated.
The necessary steam amount calculating unit 45, as shown in (Equation 2), by adding the required amount of steam variation .DELTA.MV _n the last necessary steam amount MV _n-1, to calculate the time required steam amount MV _n it can.

  The combustion control by the PI control method or the PID control method can be applied even when the plurality of boilers 20 of the boiler system 1 are step value control boilers.

  As described above, the required steam amount calculation unit 45 is based on the header pressure value PV, and the required steam amount (MV) that is a steam amount required according to the consumed steam amount (required load) of the steam using facility 18. Can be calculated. Hereinafter, it is assumed that the required steam volume (MV) is calculated as described above.

[Can reduction standard steam amount calculation unit 46]
Next, the can reduced reference steam amount calculation unit 46 will be described.
The can reduction reference steam amount calculation unit 46 is configured such that all combustion target boilers excluding one boiler that can be reduced from all control target boilers burn at a preset second combustion rate that is equal to or lower than the first combustion rate. The total amount of steam (hereinafter also referred to as “canned reference steam amount”) is calculated.
Reduced boiler target is a target to be removed from the control target under certain conditions when the number of control target boilers exceeds the set control target number of boilers after adding a spare boiler to the control target. Means boiler.

[Second state detection unit 47]
Next, the second state detection unit 47 will be described.
When a spare boiler is added as a control target boiler by the preliminary boiler combustion unit control unit 43 as a control target boiler, the second state detection unit 47 reduces the required steam amount (MV) calculated by the required steam amount calculation unit 45, and decreases A comparison with the reduced can reference steam amount calculated by the can reference steam amount calculation unit 46, and a state where the required steam amount (MV) is lower than the reduced can reference steam amount continues for a preset second time ( (Also referred to as “second state”).

  When the boiler 20 is a step value control boiler, the second combustion rate (set to be equal to or lower than the first combustion rate) can be set by the combustion position (for example, a high combustion position, a middle combustion position, etc.). In this case, an intermediate combustion position can be designated as the second combustion rate for each stage value control boiler 20 in addition to the high combustion position.

[Preliminary boiler combustion number control unit 43]
A process in the case where the spare boiler combustion unit control unit 43 removes the spare boiler added to the control target from the control target under a certain condition will be described.
When the spare boiler is added to the control target as the control target boiler and the second state detection unit 47 detects the second state, the preliminary boiler combustion unit control unit 43 determines that the control boiler control unit 43 The boiler 20 with the lowest priority among the control target boilers 20 can be used as the boiler for reducing the number of boilers.
Note that, after the removal of the can reduction target boiler 20 from the control target boiler 20 in terms of control, the combustion reduction is stopped when the reduction determination is performed in the normal combustion amount increase / decrease determination.
Note that the number of controlled boilers set by the controlled boiler setting unit 41 does not decrease.

  The operation in which the preliminary boiler combustion number control unit 43 excludes the boiler 20 to be reduced from being controlled will be described with reference to FIG.

  As shown in FIG. 4, a boiler group including five boilers 20 is provided, the maximum steam amount (maximum output) of each boiler 20 is 7000 kg / h, and the first combustion rate and the second combustion rate are 100%, respectively. As a model, the boiler system 1 is preset.

  First, as shown to (A), the control object boiler setting part 41 set the 1st-3rd machine as a control object boiler, and set the remaining 4th and 5th machines as a spare boiler.

  Thereafter, as shown in (B), the spare boilers for the No. 4 and No. 5 units were added to the control targets by the spare boiler combustion number control unit 43. At this time, the required steam volume (MV) calculated by the required steam volume calculation unit 45 is 35000 kg / h, and when the boiler 5 having the lowest priority is the boiler to be reduced, the reduced steam reference steam volume is It becomes 28000 kg / h, which is the total amount of steam when all of Units 1 to 4 burn at the second combustion rate (100%).

  Thereafter, the load decreases, the required steam volume (MV) decreases to 28000 kg / h as shown in (C), and the required steam volume (MV) decreases to 27900 kg / h as shown in (D). did. At this time, the reduced steam reference steam amount is 28000 kg / h.

Thereafter, the state where the required steam volume (MV) is lower than the canned reference steam volume (28000 kg / h) continues for the first time (T seconds). As a result, as shown in FIG. As a result, the spare boiler No. 5 having the lowest priority, which is the boiler for which can be reduced, is removed from the control target.
At this point, the required steam volume (MV) is 27,900 kg / h, and if the boiler 4 with the lowest priority is the boiler to be reduced, the reduced standard steam volume is the second combustion for all of Units 1 to 3 It becomes 21000 kg / h, which is the total amount of steam when burning at a rate (100%).

  Thereafter, the load continued to decrease, and in (F), the required steam volume (MV) was 20900 kg / h. At this point, the reduced steam reference steam amount is 21000 kg / h.

  After that, as a result of continuing the state where the required steam amount (MV) is lower than the canned reference steam amount (21000 kg / h) for the first time (T seconds), as shown in FIG. The spare boiler No. 4 having the lowest priority, which is a boiler that can be reduced, is removed from the control target.

  Next, the flow of control of the combustion state of the boiler group 2 by the boiler system 1 of the present embodiment will be described with reference to FIG. FIG. 5 is a flowchart showing the operation of the boiler system 1.

  In step ST <b> 1, for example, when the operation switch is turned on and combustion control by the control unit 4 is started, the control target boiler setting unit 41 sets the control target boiler 20 from the plurality of boilers 20. At this time, the preliminary boiler combustion number control stop unit 44 cancels the function of the preliminary boiler combustion number control unit 43 after the operation of the boiler system 1 is started.

  In step ST2, the control unit 4 controls the combustion state of the controlled boiler 20 based on the header pressure value PV.

  In step ST3, the preliminary boiler combustion number control stop unit 44 determines whether or not the header pressure value PV has reached a preset first pressure value P1. When the header pressure value PV reaches the preset first pressure value (Yes), the process proceeds to step ST4. When the header pressure value PV has not reached the preset first pressure value P1 (No), the process returns to step ST2.

  In step ST <b> 4, the preliminary boiler combustion number control stop unit 44 finishes canceling the function of the preliminary boiler combustion number control unit 43 and validates the function of the preliminary boiler combustion number control unit 43.

  In step ST <b> 5, the control unit 4 controls the combustion state of the controlled boiler 20 based on the header pressure value PV for each control cycle.

  In step ST <b> 6, the preliminary boiler combustion number control unit 43 determines whether or not the first state is detected by the first state detection unit 42. When the 1st state is detected by the 1st state detection part 42 (Yes), it moves to step ST7. When the first state is not detected (No), the process proceeds to step ST11.

  In step ST7, the spare boiler combustion number control unit 43 adds one spare boiler 20 as a control target boiler.

  Thereafter, the process returns to step ST5.

  In step ST11, the spare boiler combustion number control unit 43 adds the preset spare boiler 20 to the control target (when the number of controlled target boilers exceeds the maximum number of combustion), and detects the second state. The unit 47 determines whether the second state is detected. When the second state is detected (Yes), the process proceeds to step ST12. When the second state is not detected (No), the process returns to step ST5.

  In step ST12, for example, the spare boiler combustion number control unit 43 removes one boiler with a lowest priority according to the priority order from the control target.

  Thereafter, the process returns to step ST5.

Next, with reference to FIG. 6 or FIG. 7, an operation when the number control according to the first embodiment is performed will be described. 6 shows a case where the boiler 20 is a step value control boiler, and FIG. 7 shows a case where the boiler 20 is a continuous control boiler.
As shown in FIG. 6 (A) or FIG. 7 (A), the control unit 4 (control target boiler setting unit 41) controls the No. 1 to No. 3 boilers corresponding to the maximum number of combustion units of three. As a result, Units 4 and 5 are used as spare boilers. Then, the control part 4 (1st combustion control part 45) controls the combustion state of No. 1 machine-No. 3 machine based on the header pressure value PV.

Thereafter, as shown in FIG. 6B or FIG. 7B, all the boilers to be controlled (No. 1 to No. 3) burn at the first combustion rate (here, the maximum combustion rate) or more, When the state where the header pressure value PV decreases in the combustion state continues for a preset first time, as shown in FIG. 6C or FIG. 7C, the control unit 4 (preliminary boiler combustion) The number control unit 43) adds the spare boiler No. 4 to the control target. At this time, as shown in FIG. 6C, the priority order of virtual boiler units is changed.
Thereafter, as shown in FIG. 6D or FIG. 7D, a state in which a state in which the required steam amount MV calculated based on the header pressure value PV is lower than the can lowering reference steam amount is set in advance. When it is detected that it is in a state (second state) that continues for a time, as shown in (E) of FIG. 6 or (E) of FIG. . At this time, as shown in FIG. 6E, the priority order of the virtual boiler unit is changed.
The No. 4 machine (bottle reduction target boiler) removed from the control target is then stopped when a decrease determination is made in the normal combustion amount increase / decrease determination.

  The boiler system 1 according to the present embodiment described above has the following effects.

The control unit 4 sets, in the boiler group 2, a preset maximum number of boilers (for example, No. 1 to No. 3) as control target boilers to be controlled by the control unit 4. The setting unit 41 and all control target boilers detect a first state in which a state in which the combustion is performed at a preset first combustion rate or more and the header pressure value PV is lowered continues for a preset first time. When the first state detection unit 42 and the first state detection unit 42 detect the first state, one boiler (for example, No. 4 machine) that is not set as the control target boiler by the control target boiler setting unit 41, A preliminary boiler combustion number control unit 43 to be added to the control target.
Thus, for example, when a steam load exceeding the combustion quantity for the maximum number of combustion units (3 units) is generated due to a rapid load fluctuation or a temporary increase in the required steam amount, the spare boiler (unit 4 and / or unit 5) ) Can suppress a significant drop in header pressure.

In addition, the control unit 4 cancels the function of the preliminary boiler combustion number control unit 43 until the header pressure value PV reaches the preset first pressure value P1 after the operation of the boiler system 1 is started. A boiler combustion unit control stop unit 44 is further provided.
As a result, immediately after the operation of the boiler system 1, for example, when the controlled boiler 20 (for example, three of No. 1 to No. 3) is burned with maximum combustion of all the units, The boiler combustion unit number control unit 43 can prevent the spare boiler from being activated in vain without adding a spare boiler (for example, No. 4 and / or No. 5) to the control target.

When the spare boiler combustion unit control unit 43 adds the spare boiler 20 to the control target, the required steam amount (MV) calculated based on the header pressure value PV by the second state detection unit 47 is the reduced-can base reference steam amount. When it is detected that the state lower than is in a state that continues for the preset second time, the boiler 20 to be reduced is excluded.
By doing so, the control unit 4 normally controls the number of units with the minimum number of boilers 20 (for example, three units) that satisfies the preset maximum number of combustion units or the preset maximum use steam amount, and in the event of an emergency (For example, when the load suddenly increases exceeding the maximum combustion quantity for the maximum number of combustion units), the spare boiler can be operated as a combustion control target (control target boiler), and the header pressure can be significantly reduced. Can be deterred.

[Second Embodiment]
Next, the boiler system 1 which concerns on 2nd Embodiment of this invention is demonstrated, referring FIG.8 and FIG.9.
The plurality of boilers 20 of the boiler system 1 of the second embodiment are step value control boilers, and control the combustion amount of the step value control boiler to be controlled so that the header pressure value PV falls within a preset pressure range. Then, a so-called proportional distribution control method is adopted in which the required steam amount MV is uniquely determined by the header pressure value PV.
The second embodiment is different in processing when the spare boiler combustion number control unit 43 in the first embodiment removes the spare boiler added to the control target from the control target under a certain condition. For this reason, the reserve boiler combustion number control part in 2nd Embodiment is represented as 43A.
In the description of the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

In the second embodiment, the spare boiler combustion number control unit 43A, when the spare boiler 20 is added as a control target, the header pressure value PV is set in advance, and the upper limit value P _{min is} greater than or equal to the lower limit value P _min of the set pressure range. _{When the} state exceeding the second pressure value P2, which is a value equal to or less than _max, continues for a preset third time period, the set-up spare boiler 20 that is set as the control target boiler for control is removed from the control target. Control.

For this reason, in 2nd Embodiment, the memory | storage part 5 is the content of the instruction | indication given with respect to each boiler 20 by control of the number control apparatus 3 (control part 4), the combustion state received from each boiler 20, etc. Information, information on the maximum number of burners or maximum steam used in advance for the boiler system 1, the first combustion rate (maximum combustion rate) of each boiler 20, and the second combustion rate that is a value equal to or less than the first combustion rate. Information, first time, first pressure value, priority setting information for the plurality of boilers 20, and setting information related to priority change (rotation), a third time to be described later and a second to be described later. A pressure value is preset and stored. Here, the second pressure value P2 is a value not less than the lower limit value _{Pmin and not} more than the upper limit value _Pmax of the set pressure range.

  In the second embodiment, as shown in FIG. 8, the control unit 4 </ b> A includes a controlled boiler setting unit 41, a first state detection unit 42, a preliminary boiler combustion number control unit 43 </ b> A, and a preliminary boiler combustion number control. The stop part 44 and the 3rd state detection part 48 are provided.

As in the first embodiment, the spare boiler combustion unit number control unit 43A detects the first state by the first state detection unit 42 (that is, all the boilers 20 to be controlled are respectively set in advance to the first state). If the combustion is performed at a combustion rate (maximum combustion rate) or more and the state in which the header pressure value decreases in the combustion state continues for a preset first time), for example, based on the priority order, One spare boiler is added to the control target from the spare boilers 20 that have not been set as the control target boiler by the boiler setting unit 41.
Unlike the first embodiment, the spare boiler combustion number control unit 43A is preset with a state in which the header pressure value PV exceeds the preset second pressure value P2 when the spare boiler 20 is added as a control target. When the third time is continued, for example, control is performed such that the spare boiler 20 having the lowest priority among the control target boilers 20 is removed from the control target for control.

  For this reason, the header pressure value PV exceeds the preset second pressure value P2 when the spare boiler 20 is added to the control target by the spare boiler combustion number control unit 43A by including the third state detection unit 48. A state in which the state continues for a preset third time can be detected.

  That is, when the spare boiler 20 is added to the control target, the spare boiler combustion unit number control unit 43A detects the third state by the third state detection unit 48, and sets one spare boiler 20 from the control target. Control to remove.

  By doing so, the control unit 4A normally controls the number of units with the minimum number of boilers 20 (for example, three units) satisfying the preset maximum number of combustion units or the maximum amount of steam used, and in an emergency (for example, the maximum number of units). In the case of a sudden load increase exceeding the maximum combustion amount for the number of combustion units), it is possible to operate the spare boiler as a combustion control target (control target boiler), and to suppress a significant drop in header pressure. it can.

  Next, the flow of control of the combustion state of the boiler group 2 by the boiler system 1 of the second embodiment will be described with reference to FIG. FIG. 9 is a flowchart showing the operation of the boiler system 1 of the second embodiment.

  In step ST <b> 1, when the combustion control by the control unit 4 </ b> A is started, the control target boiler setting unit 41 sets the control target boiler 20 from the plurality of boilers 20. At this time, the preliminary boiler combustion number control stop unit 44 cancels the function of the preliminary boiler combustion number control unit 43 after the operation of the boiler system 1 is started.

  In step ST2, the control unit 4A controls the combustion state of the controlled boiler 20 so that the header pressure value PV falls within the set pressure range.

  In step ST3, the preliminary boiler combustion number control stop unit 44 determines whether or not the header pressure value PV has reached a preset first pressure value P1. When the header pressure value PV has reached the preset first pressure value P1 (Yes), the process proceeds to step ST3. When the header pressure value PV has not reached the preset first pressure value P1 (No), the process returns to step ST2.

  In step ST4, the preliminary boiler combustion number control stop unit 44 ends the cancellation of the function of the preliminary boiler combustion number control unit 43A and validates the function of the preliminary boiler combustion number control unit 43A.

  In step ST5, the control unit 4A controls the combustion state of the controlled boiler 20 so that the header pressure value PV falls within the set pressure range for each control cycle.

  In step ST <b> 6, the spare boiler combustion number control unit 43 </ b> A determines whether or not the first state is detected by the first state detection unit 42. When the 1st state is detected by the 1st state detection part 42 (Yes), it moves to step ST7. When the first state is not detected (No), the process proceeds to step ST11.

  In step ST7, the spare boiler combustion number control unit 43A adds one spare boiler 20 as a control target boiler.

  Thereafter, the process returns to step ST5.

  In step ST11, the spare boiler combustion number control unit 43A adds the preset spare boiler 20 to the control target (when the number of controlled target boilers exceeds the maximum number of combustion), and detects the third state. It is determined by the part 48 whether the 3rd state was detected. When the third state is detected (Yes), the process proceeds to step ST12. When the third state is not detected (No), the process returns to step ST5.

  In step ST12, for example, the spare boiler combustion number control unit 43A removes one control target boiler having the lowest priority order from the control target according to the priority order.

  Thereafter, the process returns to step ST5.

  According to the boiler system 1 of 2nd Embodiment demonstrated above, there exists an effect similar to the boiler system 1 of 1st Embodiment.

  The preferred embodiments of the boiler system 1 of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and can be modified as appropriate.

  For example, in each embodiment, although this invention was applied to the boiler system 1 provided with the boiler group 2 which consists of the five boilers 20, and sets the maximum combustion number to three units, it is not restricted to this. That is, you may apply this invention to a boiler system provided with the boiler group which consists of 2 units | sets-4 units | sets or 6 units | sets or more boilers. Further, the maximum number of combustion can be set as appropriate.

  Moreover, in embodiment of this invention, although all the continuous control boilers 20 were made into the same boiler capacity | capacitance, it is not restricted to this. In other words, the present invention can be applied to the case where the combustion capacity as the minimum combustion amount, the unit steam amount, and the maximum combustion amount is different for each continuous control boiler 20.

In the embodiment of the present invention, as the PI (or PID) control algorithm for the boiler group 2, only the necessary steam amount change ΔMV _{n for} each control cycle is calculated, and the previous required steam amount MV _n−1 is added to this. Thus, although the PI or PID control by the speed type PI (or speed type PID) algorithm for calculating the required steam amount MV _n is applied this time, the present invention is not limited to the speed type PI (or speed type PID) algorithm. The required amount of steam MV _n time in each control cycle may be applied to PI or PID control by the position-type PI (or position-type PID) algorithm for direct computation.

  Further, in the embodiment of the present invention, the change of the combustion state between the combustion stop state S0 and the minimum combustion state S1 in the continuous control boiler 20 is controlled by turning on / off the combustion of the boiler 20, and the minimum combustion is performed. In the range from the state S1 to the maximum combustion state S2, the continuous control boiler 20 capable of continuously controlling the combustion amount is configured, but the present invention is not limited thereto. That is, the boiler may be configured by a continuous control boiler that can continuously control the combustion amount in the entire range from the combustion stop state to the maximum combustion state.

  Moreover, in embodiment of this invention, although the step value control boiler was made into 4 position control, it is not limited to 4 position control. The stage value control boiler can be a boiler that can control N position control, that is, the combustion amount of the stage value control boiler in a stepwise manner to the N position including the combustion stop state, where N is an arbitrary integer. For example, the number of combustion positions may be 2 positions (that is, only on / off), 3 positions (combustion stop position, low combustion position, and high combustion position), or 5 positions or more. Further, in each of the step-value controlled boilers constituting the boiler group, the combustion amount and the combustion capacity (combustion amount in the high combustion state) at each combustion position may be set equal or different from each other. May be.

In the embodiment of the present invention, the combustion of the stage value control boiler or its stop can be handled in units of virtual boilers. For example, four-position boilers can be virtually counted as three units: a low combustion amount boiler, a (medium combustion amount-low combustion amount) boiler, and a (high combustion amount-medium combustion amount) boiler.
In this case, the difference in combustion position (combustion amount) in the step value control boiler (low combustion position, medium combustion position, high combustion position, etc.) is regarded as an independent boiler, and the maximum set by the control target boiler setting unit 41. The virtual boiler can be counted as one unit and set as the minimum number that satisfies the amount of steam used.
For example, the control target boiler setting unit 41 sets a low combustion amount boiler, which is a virtual boiler in a 4-position boiler, and a (medium combustion amount−low combustion amount) boiler as a control target boiler, and is a virtual boiler (high combustion amount− Medium combustion amount) The boiler can be a spare boiler. In this case, the preliminary boiler combustion number control unit 43 can add a boiler (high combustion amount−medium combustion amount), which is a virtual boiler that is a preliminary boiler, to the control target based on the priority order of the virtual boilers.

DESCRIPTION OF SYMBOLS 1 Boiler system 2 Boiler group 20 Boiler 3 Number control apparatus 4 Control part 4A Control part 41 Control object boiler setting part 42 First state detection part 43 Preliminary boiler combustion number control part 43A Preliminary boiler combustion number control part 44 Preliminary boiler combustion number control Stop unit 45 Required steam amount calculation unit 46 Canned reference steam amount calculation unit 47 Second state detection unit 48 Third state detection unit 5 Storage unit 6 Steam header 7 Steam pressure sensor

Claims (5)

A boiler group consisting of a plurality of boilers;
A steam header for collecting steam generated in the boiler group;
Vapor pressure measuring means for measuring a header pressure value which is a vapor pressure inside the vapor header;
A control unit for controlling the combustion state of the boiler group based on the header pressure value;
A boiler system comprising:
The controller is
Of the boiler group, a control target boiler setting unit that sets a preset number of boilers in a control target boiler that is a control target by the control unit;
A first state detection unit that detects a first state in which all of the boilers to be controlled are burned at a preset first combustion rate or more and the state where the header pressure value decreases continues for a preset first time. When,
When the first state is detected by the first state detection unit, one spare boiler that is not set as a control target boiler by the control target boiler setting unit, a preliminary boiler combustion number control unit that adds to the control target;
A boiler system. The controller is
After the operation of the boiler system is started, a preliminary boiler combustion number control stop unit that cancels the function of the preliminary boiler combustion number control unit is further provided until the header pressure value reaches a preset first pressure value. The boiler system of Claim 1 provided. The control unit further includes:
A required steam amount calculation unit for calculating a required steam amount based on the header pressure value;
This is the total amount of steam in the case where all of the boilers to be controlled excluding one boiler for reducing cans are burned at a preset second combustion rate equal to or lower than the first combustion rate. A reduced can reference vapor amount calculation unit for calculating a reduced can reference vapor amount;
When a spare boiler that has not been set as a control target boiler by the control target boiler setting unit is added as a control target, a state in which the required steam amount is lower than the can lowering reference steam amount is a preset second A second state detection unit for detecting a second state that continues for a time,
The boiler system according to claim 1 or 2, wherein, when the second state detection unit detects the second state, the preliminary boiler combustion number control unit removes the boiler that is to be reduced from the control target.
The control unit controls the combustion state of the boiler to be controlled so that the header pressure value falls within a preset pressure range,
In the case where the control unit further adds a spare boiler that has not been set as the control target boiler by the control target boiler setting unit to the control target, the state in which the header pressure value exceeds the preset second pressure value is A third state detection unit that detects a third state that continues for a set third time, and the spare boiler combustion number control unit detects one third boiler when the third state detection unit detects the third state; The boiler system according to claim 1, wherein the boiler system is excluded from a control target.   The boiler system according to claim 4, wherein the second pressure value exceeds a lower limit value of the set pressure range and is not more than an upper limit value.

Images