JP2015055367A - Boiler system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a boiler system capable of improving pressure stability in a case of changing a target pressure value or the like.SOLUTION: A boiler system includes a number-of-boilers control device 3 controlling a combustion amount of control target boilers 20 so that a vapor pressure can match a target pressure value on the basis of the vapor pressure measured by a vapor pressure sensor 7. If a set value X of setting conditions including at least the target pressure value is changed, the number-of-boilers control device 3 changes stepwise the set value X to be changed over predetermined time. At the time of changing, the number-of-boilers control device 3 calculates a set-value differential value X3 by subtracting the set value 1 before change from a set value X2 after change, and calculates a unit differential value ΔX by dividing the set-value differential value X3 by a divisor n. For the set value X to be changed, the number-of-boilers control device 3 adds the unit differential value ΔX to the set value X1 before change for every unit time ΔT that is time obtained by dividing transition time by the divisor n to obtain the set value X2 after change after passage of the transition time, thereby changing stepwise the set value X.

Description

  The present invention relates to a boiler system that controls a combustion amount of a boiler to be controlled so that a steam pressure inside a steam collecting portion matches a target pressure value.

  In a boiler system configured by a group of boilers composed of a plurality of boilers, steam generated in the boiler group is collected in a steam collecting part (steam header), and steam is supplied from the steam collecting part to a load device. In such a boiler system, the combustion amount of the boiler to be controlled is controlled so that the steam pressure (steam pressure) in the steam collecting section matches the target pressure value.

  As control of the combustion amount of the boiler, the relationship between the combustion pattern and priority of the boiler and the steam pressure zone of the steam pressure control range is set (see FIG. 3 of Patent Document 1 below), and the steam inside the steam collecting part Conventionally, a control system for controlling the combustion amount of a boiler with a combustion pattern set in a vapor pressure zone corresponding to the pressure has been known.

  By the way, in the boiler system, the setting conditions for combustion control may be changed, and if there is a large difference between the setting conditions before the change and the setting conditions after the change, The internal vapor pressure will increase or decrease rapidly, and the pressure stability may decrease. For example, when the target pressure value as the setting condition is changed to a low value, the steam pressure of the steam collecting portion that was appropriate before the change becomes higher than the target pressure value after the change, and the steam pressure inside the steam collecting portion is changed. There is a possibility that combustion of all boilers stops (all cans stop) when the target pressure value is exceeded.

In response to such a problem, the present applicant, after changing the target combustion amount in the combustion control, when the required combustion amount significantly decreases before and after the setting condition is changed in a boiler system composed of a plurality of boilers. Has proposed a boiler system that makes a gradual (gradual) transition toward the required amount of combustion (see Patent Document 2 below).
According to this boiler system, even if the steam pressure inside the steam collecting section exceeds the upper limit threshold of the set pressure range due to the change of the set condition, the combustion of all the boilers is not stopped, and is reduced by half every predetermined time. The boilers in the combustion state can be reduced one by one, and the control can be smoothly shifted to the set condition after the change.

JP 2013-072609 A JP 2010-223485 A

  However, the technology related to the control described in Patent Document 2 assumes a case where the required steam amount is significantly reduced by changing the setting conditions (for example, when the amount is reduced to less than 50%). Effective when the steam volume has increased significantly, or when the required steam volume after the change has decreased slightly relative to the required combustion volume before the change (for example, when it has decreased to 50% or more and less than 100%) is not. Therefore, in the technology related to the control described in Patent Document 2, in the case of an unexpected change in the setting conditions, a plurality of boilers may be started or stopped simultaneously, thereby causing hunting.

  In recent years, a target pressure value is set, and the combustion amount of the boiler is controlled by performing feedback control by PID (PI) control with respect to the deviation between the target pressure value and the steam pressure inside the steam collecting portion. It is also widely done. In this regard, in the boiler system of Patent Document 2, the combustion amount of the boiler is controlled by setting a combustion pattern corresponding to the vapor pressure zone as in Patent Document 1, and the combustion amount of the boiler is controlled by feedback control. It is not always appropriate to apply to a boiler system that controls

  Therefore, the present invention provides a target pressure value and a pressure control range in a boiler system including a number control means for controlling the combustion amount of a boiler to be controlled so that the steam pressure inside the steam collecting portion matches the target pressure value. An object of the present invention is to provide a boiler system that can improve the stability of pressure when the setting conditions such as the above are changed.

The present invention comprises a plurality of boilers, a boiler group for supplying steam to load equipment, a steam collecting part for collecting steam generated in the boiler group, and a vapor pressure inside the steam collecting part. At least a target pressure value is set as a setting condition related to the vapor pressure measured by the vapor pressure measuring unit in order to generate a vapor having a target vapor amount corresponding to the required load from the vapor pressure measuring unit and the load device. Unit control means for controlling the amount of combustion of the boiler to be controlled so that the steam pressure matches the target pressure value based on the steam pressure measured by the steam pressure measuring means. When any one or more setting values of the setting conditions are changed, the control unit changes the setting value to be changed over a transition time, and at that time, the changed setting value is changed. Before change from value A setting value difference value is calculated by subtracting a setting value, and the setting value difference value is divided by the number of divisions to calculate a unit difference value. For the setting value to be changed, the transition time is calculated by the number of divisions. The present invention relates to a boiler system that adds a unit difference value to a setting value before change for each unit time that is a divided time, and changes the setting value so that the setting value becomes a changed value after a transition time has elapsed.
Moreover, the said number control means can set the upper limit pressure value of the range in which the said vapor pressure is settled as said setting conditions.

  Moreover, it is preferable that the said number control means sets the upper limit pressure value of the range in which the said vapor pressure is settled as said setting conditions.

  Further, it is preferable to calculate the unit time by dividing the transition time by the division number before adding the unit difference value to the set value before the change.

  Further, it is preferable to calculate the number of divisions by dividing the transition time by the unit time before calculating the unit difference value.

  According to the present invention, in a boiler system including a unit control means for controlling the combustion amount of a boiler to be controlled so that the steam pressure inside the steam collecting portion matches the target pressure value, the target pressure value, the upper limit pressure value Thus, it is possible to provide a boiler system that can improve pressure stability when the setting conditions such as the above are changed.

It is a figure showing the outline of the boiler system concerning a 1st embodiment of the present invention. It is a figure which shows the outline of a boiler group. It is a figure which shows the operation example in case a control part changes setting conditions. It is a flowchart which shows operation | movement of the boiler system which concerns on 1st Embodiment. It is a flowchart which shows operation | movement of the boiler system which concerns on 2nd Embodiment.

[First Embodiment]
Hereinafter, with reference to drawings, boiler system 1 concerning a 1st embodiment of the present invention is explained. FIG. 1 is a diagram showing an outline of a boiler system 1 according to the first embodiment of the present invention.
The boiler system 1 according to the first embodiment of the present invention is a plurality of proportional control boilers, that is, a boiler system including a plurality of boilers capable of burning by continuously changing the combustion amount. Not limited. The present invention is also applied to a boiler system composed of a plurality of step value control boilers or a boiler system in which a proportional control boiler and a step value control boiler are mixed.
As shown in FIG. 1, the boiler system 1 of the first embodiment includes a boiler group 2 including a plurality (five) of boilers 20 and a steam header 6 as a steam collecting unit that collects steam generated in the boiler 20. And a vapor pressure sensor 7 as a vapor pressure measuring means and a number control device 3 as a number control means.
The boiler group 2 produces | generates the vapor | steam supplied to the steam use installation 18 as a load apparatus.

  The upstream side of the steam header 6 is connected to the boiler group 2 (each boiler 20) via a steam pipe 11. The downstream side of the steam header 6 is connected to the steam use facility 18 via the steam pipe 12. The steam header 6 collects and stores the steam generated in the boiler group 2 to adjust the pressure difference and pressure fluctuation between the boilers 20, and supplies the steam whose pressure is adjusted to the steam using equipment 18. It is like that.

  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 boiler system 1 of the present embodiment is capable of supplying the steam generated by the boiler group 2 to the steam use facility 18 operated by steam through 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. At the time of controlling the number of units, the fluctuation of the steam pressure inside the steam header 6 corresponding to this steam consumption is calculated based on the steam pressure (physical quantity) inside the steam header 6 measured by the steam pressure sensor 7. The combustion amount of each boiler 20 constituting the boiler group 2 is controlled.

  If the demand load increases due to an increase in demand for the steam use facility 18 and the amount of steam to be supplied is insufficient, the steam pressure inside the steam header 6 decreases. On the other hand, if the required load decreases due to a decrease in demand for the steam use facility 18 and the amount of supplied steam becomes excessive, the steam pressure inside the steam header 6 increases. For this reason, the fluctuation | variation of a request | requirement load can be monitored with the vapor pressure signal from the vapor pressure sensor 7. FIG. The boiler system 1 calculates the target steam amount according to the steam consumption (required load) of the steam using equipment 18 based on this steam pressure.

  The number control device 3 includes a control unit 4 and a storage unit 5. The number control device 3 can change, for example, the setting conditions (target pressure value, pressure control range, boiler priority order, etc.) stored in the storage unit 5 regarding the combustion control of the boiler group 2. Note that setting and changing of the setting conditions may be performed in whole or in part manually, or may be performed in whole or in part automatically.

  The boiler 20 is composed of a proportional control boiler capable of burning by continuously changing the combustion rate. As shown in FIG. 2, the proportional control boiler means that the combustion amount is continuously at least in the range from the minimum combustion state S1 (for example, the combustion state at a combustion amount of 20% of the maximum combustion rate) to the maximum combustion state S2. It is a boiler that can be controlled. The proportional 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.

  Further, the continuous control of the combustion amount means that the calculation or signal in the local control unit 22 described later is a digital method and is handled in stages (for example, the output (combustion amount) of the boiler 20 in increments of 1%). Even when the output is controlled).

The boiler in this embodiment is controlled by turning on / off the combustion of the boiler 20 (burner) for the change of the combustion state between the combustion stop state S0 and the minimum combustion state S1 of the boiler 20. In the range from the minimum combustion state S1 to the maximum combustion state S2, the combustion amount can be controlled continuously.
More specifically, a unit steam amount U, which is a unit of variable steam amount, is set for each of the plurality of boilers 20. Thereby, the boiler 20 can change the amount of steam in unit steam amount U unit in the range from the minimum combustion state S1 to the maximum combustion state S2.

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 boiler 20, but from the viewpoint of improving the followability of the output steam amount to the necessary steam amount in the boiler system 1. It is preferably set to 0.1% to 20% of the maximum steam amount of 20, and more preferably set to 1% to 10%.
The output steam amount indicates the steam amount output by the boiler group 2, and this output steam amount is represented by the total value of the steam amounts output from each of the plurality of boilers 20.

  A priority order is set for each of the boilers 20. The priority order is used to select the boiler 20 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 FIG. 2, when the priorities of “1” to “5” are assigned to the first to fifth units of the boiler 20, the first unit has the highest priority, and the fifth unit has the highest priority. Lowest. 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.

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 required load. Specifically, the local control unit 22 controls the combustion state of the boiler 20 based on the number control signal transmitted from the number control device 3 via the signal line 16.
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 the signal used in the number control device 3 include an actual combustion state of the boiler 20 and other data.

Next, details of the number control device 3 will be described.
The number control device 3 calculates the target steam amount of the boiler group 2 according to the required load based on the steam pressure signal from the steam pressure sensor 7, and the combustion state of each boiler 20 corresponding to the target steam 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, and is electrically connected to each boiler 20 via a signal line 16.

  The storage unit 5 stores information on the contents of instructions given to each boiler 20 under the control of the number control device 3 (control unit 4), the combustion state received from each boiler 20, and unit steam of the plurality of boilers 20. Information relating to the setting of the amount U, information relating to the setting of the priority order of the plurality of boilers 20, information relating to the setting change (rotation) of the priority order, setting conditions described later, 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.

  Further, the control unit 4 controls the combustion state of each boiler 20 by feedback control based on the pressure of steam generated from the boiler group 2 (steam pressure of steam stored in the steam header 6). That is, the control unit 4 is necessary for the header pressure to become the target pressure value by performing feedback control based on a predetermined PI or PID algorithm for the deviation between the steam pressure of the steam header 6 and the target pressure value. The amount of steam is calculated, and the boiler 20 is controlled to generate the calculated amount of steam.

In order to execute such feedback control, the unit control device 3 sets a target pressure value and a pressure control range (upper limit pressure value and lower limit pressure value) as setting conditions related to the steam pressure measured by the steam pressure sensor 7. Set and store in the storage unit 5.
Here, in the boiler system 1 according to the present embodiment, the number control device 3 can control only a part of the five boilers 20. That is, when the required load decreases, the number control device 3 may decrease the number of boilers 20 to be controlled, for example, set four boilers 20 as control targets.

  When the number of boilers 20 to be controlled is changed, the control unit 4 changes the target pressure value and pressure control range (upper limit pressure value and lower limit pressure value) as setting conditions. More specifically, the control unit 4 takes a predetermined transition time when one or more values (set values) of the target pressure value, the upper limit pressure value, and the lower limit pressure value are changed. Change the setting value to be changed step by step. In the following, the target pressure value is represented by a symbol “P”, the upper limit pressure value is represented by a symbol “Pu”, the lower limit pressure value is represented by a symbol “Pd”, and these target pressure value P, upper limit pressure value Pu, and lower limit pressure value Pd are represented by Overall, set value X. Further, a predetermined transition time is defined between time T1 and time T2. In addition, for the signs such as the set value X (target pressure value P, upper limit pressure value Pu, and lower limit pressure value Pd), the suffix “1” is attached to the one before the change, and the suffix is attached to the one after the change. When “2” is added and common explanations are made before and after the change, no suffix is added.

With reference to FIG. 3, an example of changing the set value X by the control unit 4 will be described. FIG. 3 is a diagram illustrating an operation example when the control unit 4 changes the target pressure value P as the setting condition by reducing the number of boilers 20 to be controlled.
In FIG. 3, the procedure for changing the target pressure value P among the set conditions will be described, but the same applies to the case where the set values of other set conditions such as the upper limit pressure value Pu and the lower limit pressure value Pd are changed.

As shown in FIG. 3A, before changing the set value X (target pressure value P), five (No. 1 to No. 5) proportional control boilers 20 are operating. At this time, it is assumed that the number of boilers 20 to be controlled is changed (No. 5 is stopped) due to a decrease in required load and the like, and four (No. 1 to No. 4) proportional control boilers 20 are operating.
With the change in the number of boilers 20 to be controlled, the set value X (target pressure value P) is also changed.

  At this time, as shown in FIG. 3B, if the target pressure value P1 is changed to the target pressure value P2 at the timing of the time T1 when the number of boilers 20 is changed, the range of change of the target pressure value P increases. , Pressure stability will be impaired.

  Therefore, in the present embodiment, the control unit 4 changes the set value X (target pressure value P) to be changed stepwise. That is, the control unit 4 decreases the target pressure value P1 to the target pressure value P1 ′ at the timing of the time T1, and then sets the target pressure value P1 ′ to the target pressure at the timing of the time Ta that is between the time T1 and the time T2. The target pressure value P1 ″ is decreased to the target pressure value P1 ″ at the time Tb between the time Ta and the time T2, and then the target pressure value P1 ″ is decreased to the target P1 ″. The pressure value P1 '' '' is reduced to the target pressure value P2.

That is, the control unit 4 changes the set value X (target pressure value P) in the following procedure.
(1) A setting value difference value X3 that is a difference between the setting value X2 after the change and the setting value X1 before the change is calculated.
(2) The unit time ΔT is calculated by dividing the difference between the time T2 to reach the set value X2 after the change and the time T1 when the setting condition is changed by the predetermined division number n.
(3) The unit difference value ΔX is calculated by dividing the set value difference value X3 by the predetermined division number n.
(4) The unit difference value ΔX is added to the set value X1 before the change every unit time ΔT.
(5) By doing this, the set value X is changed stepwise so that the set value X2 after the transition is reached at the time T2 after the transition time (T2-T1) has elapsed.

  Subsequently, an operation in which the control unit 4 changes the setting value X from the setting value X1 to the setting value X2 will be described with reference to FIG. FIG. 4 is a flowchart showing the operation of the boiler system 1 according to the embodiment.

  As shown in FIG. 4, in step ST1, the number control device 3 (control unit 4) calculates a set value difference value X3 by subtracting the set value X1 before the change from the set value X2 after the change.

  In step ST2, the number control device 3 (control unit 4) calculates the unit time ΔT by dividing the transition time (time T2−time T1) by a predetermined division number n.

  In step ST3, the number controller 3 divides the set value difference value X3 by the division number n to calculate a unit difference value ΔX.

  In step ST4, the unit control device 3 adds the unit difference value ΔX for the set value X to be changed to the set value X1 before the change for each unit time ΔT.

  In step ST5, the set value X becomes the changed set value X2 at time T2 after the transition time has elapsed.

According to the boiler system 1 of the first embodiment, for example, the following effects are produced.
In the boiler system 1 according to the first embodiment, the unit control device 3 changes any one or more set values X of the target pressure value P, the upper limit pressure value Pu of the pressure control range, and the lower limit pressure value Pd. In the case of changing the set value X to be changed in stages over a predetermined transition time, the set value difference is obtained by subtracting the set value X1 before the change from the set value X2 after the change. The value X3 is calculated, the transition time is divided by the predetermined division number n to calculate the unit time ΔT, the set value difference value X3 is divided by the division number n to calculate the unit difference value ΔX, and the setting to be changed For the value X, the unit difference value ΔX is added to the setting value X1 before the change every unit time ΔT, and the setting value X is changed step by step so that the setting value X2 after the transition time has elapsed To do.

  Therefore, according to the first embodiment, when the setting conditions such as the target pressure value and the upper limit pressure value are changed, the amount of change in the required steam amount can be suppressed, so that the pressure stability can be improved. it can.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. The second embodiment will be described mainly with respect to differences from the first embodiment, and detailed description of the same configuration as the first embodiment will be omitted. In the second embodiment, the description of the first embodiment is appropriately applied to points that are not particularly described. Also in the second embodiment, the same effects as in the first embodiment are achieved.

  A second embodiment will be described with reference to FIG. FIG. 5 is a flowchart showing the operation of the boiler system according to the second embodiment. The second embodiment is mainly different from the first embodiment in that the division number n is calculated. Therefore, the second embodiment will be described with a focus on calculating the division number n.

  In the boiler system according to the second embodiment, when any one or more set values X of the target pressure value P, the upper limit pressure value Pu, and the lower limit pressure value Pd are changed, the set value X is set to the set value X1. The operation of changing from to the set value X2 will be described with reference to FIG.

  As shown in FIG. 5, in step ST11, the number control device 3 calculates a setting value difference value X3 by subtracting the setting value X1 before the change from the setting value X2 after the change.

  In step ST12, the number control device 3 calculates the division number n by dividing the transition time (time T2−time T1) by a predetermined unit time ΔT.

  In step ST13, the unit control device 3 divides the set value difference value X3 by the division number n to calculate a unit difference value ΔX.

  In step ST14, the number control device 3 adds the unit difference value ΔX to the setting value X1 before the change for each unit time ΔT for the setting value X to be changed.

  In step ST15, the set value X becomes the changed set value X2 at time T2 after the transition time has elapsed.

As mentioned above, although preferred embodiment was described, this invention is not limited to embodiment mentioned above, It can implement with a various form.
For example, in the embodiment, the changed set value X2 is smaller than the changed set value X1. Therefore, the set value difference value X3 and the unit difference value ΔX are both minus (−). However, the changed set value X2 may be larger than the changed set value X1. In this case, the set value difference value X3 and the unit difference value ΔX are plus (+).

  In the first embodiment, before adding the unit difference value ΔX to the setting value X1 before the change, after calculating the unit time ΔT by dividing the transition time by the predetermined division number n, the setting value difference value The unit difference value ΔX is calculated by dividing X3 by the division number n, but is not limited thereto. Before adding the unit difference value ΔX to the setting value X1 before the change, after dividing the setting value difference value X3 by the division number n to calculate the unit difference value ΔX, the transition time is divided by the division number n. Thus, the unit time ΔT may be calculated.

  Also, all of the target pressure value P, the upper limit pressure value Pu, and the lower limit pressure value Pd may be changed, or any one or more of the set values may be changed.

  The steam collecting unit is not limited to the steam header 6 that stores the collected steam, and may be, for example, a steam collecting pipe that simply collects steam.

1 Boiler system 2 Boiler group 3 Number control device (number control means)
6 Steam header (steam collecting part)
7 Vapor pressure sensor (Vapor pressure measuring means)
18 Steam use facilities (load equipment)
20 boiler

Claims (4)

A group of boilers that supply steam to the load equipment,
A steam collecting part for collecting steam generated in the boiler group;
Vapor pressure measuring means for measuring the vapor pressure inside the vapor collecting section;
In order to generate a steam having a target steam amount corresponding to a required load from a load device, at least a target pressure value is set as a setting condition related to the steam pressure measured by the steam pressure measuring means, and the steam pressure measuring means A unit control means for controlling the combustion amount of the boiler to be controlled so that the steam pressure matches the target pressure value based on the steam pressure measured by
With
The number control means changes the setting value to be changed over a transition time when any one or more setting values of the setting conditions are changed,
At that time, subtract the setting value before the change from the setting value after the change to calculate the setting value difference value,
Divide the set value difference value by the number of divisions to calculate a unit difference value;
For the setting value to be changed, the unit difference value is added to the setting value before the change for each unit time that is the time obtained by dividing the transition time by the number of divisions, and the setting after the change is made after the transition time has elapsed. Change the setting value so that the value becomes
Boiler system. The number control means sets, as the setting condition, an upper limit pressure value in a range where the vapor pressure is contained,
The boiler system according to claim 1. Before adding each unit difference value to the set value before change, the unit time is calculated by dividing the transition time by the number of divisions.
The boiler system according to claim 1 or 2. Before calculating the unit difference value, divide the transition time by the unit time to calculate the number of divisions,
The boiler system according to claim 1 or 2.

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