JP2016109357A - Boiler system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure a prescribed combustion amount or more of a sub-boiler group 2B regardless of an amount of used steam, in a boiler system 1 in which a target steam pressure value P1 of a main boiler group 2A is set high, a target steam pressure value P2 of the sub-boiler group 2B is set low, and the target pressure values are individually controlled.SOLUTION: A combustion state of a main boiler group 2A is PI-controlled or PID-controlled so that a header pressure value PV is agreed with a predetermined first target steam pressure value P1, and a sub-boiler group 2B is controlled on the basis of a fixed combustion control portion 41B for combustion with a fixed combustion rate so that a constant steam amount as a base load is output, and a feedback control portion 42B for controlling a combustion state by PI-control or PID-control so that the header pressure value PV is agreed with a predetermined second target steam pressure value P2.SELECTED DRAWING: Figure 1

Description

  In the present invention, a first boiler group having one or more boilers whose combustion rate is determined so that the steam pressure value becomes a preset target steam pressure value, and the steam pressure value is set in the first boiler group. A plurality of boiler groups comprising a second boiler group having one or more boilers not belonging to the first boiler group, the combustion rate of which is determined to be a target steam pressure value different from the target steam pressure value It relates to a mixed boiler system.

  In a boiler system that collects steam generated in a boiler group consisting of multiple boilers in a steam header and supplies steam to the load equipment from this steam header, the boiler group is roughly divided into two types, and these are controlled in number Boiler systems are known. For example, Patent Document 1 broadly classifies an eco-operation boiler group that burns a boiler group at a combustion rate that increases boiler efficiency, and a load-following boiler group that burns by changing a load factor according to fluctuations in required load. It is described to do.

Further, although not described in Patent Document 1, there are two types of boiler groups, and both boiler groups are individually set so that the pressure values of the steam headers are set to the target steam pressure values set in advance. When target value control is performed, if the target steam pressure values of both boiler groups are made the same, the operation of performing load follow-up is performed on both sides, and therefore there is a high possibility that the control will become unstable.
For this reason, when the two types of boiler groups are individually controlled by the target pressure value, normally, one of the boiler groups is normally burned (hereinafter also referred to as “main boiler group”), and the other boiler group is controlled. A method in which the boiler group burns in a form that compensates for the shortage (hereinafter also referred to as “sub-boiler group”) is common.

For this reason, for example, when the target steam pressure value of the main boiler group is set high and the target steam pressure value of the sub boiler group is set low, the steam header pressure becomes the target pressure of the main boiler group when the overall load is low. It will be stable around the value. In this case, even in the sub-boiler group, the steam header pressure is stabilized near the target pressure value of the main boiler group.
Then, since the steam header pressure of the sub boiler group greatly exceeds the target pressure value set in advance in itself, the combustion amount of the sub boiler group is basically zero.

JP 2014-98529 A

In this case, load imbalance occurs between the boiler systems. As a result, for example, when the total load is low and the main boiler group can cover the entire required amount, the boilers of the sub-boiler group may stop burning and may stand by all units. If it does so, the fear of boiler can body corrosion by low load will arise. Moreover, since the load bias is too large between the boiler groups, there is a problem of non-uniform boiler load.
For this reason, even when the target steam pressure value of the main boiler group is set high and the target steam pressure value of the sub boiler group is set low, it is desirable that the boilers of the sub boiler group are burned to some extent.

  In the present invention, by setting a predetermined steam amount or a fixed number corresponding to the base load in the sub boiler group in advance, for example, the overall load is low (the steam header pressure exceeds the target pressure value of the sub boiler group). ) In the case, the boiler for the base load allocated to the sub-boiler group is fixedly burned at a fixed combustion rate corresponding to a predetermined constant steam amount, and then the overall load increases, and it becomes impossible to cover only with the main boiler group In the case (when the steam header pressure drops to near the target pressure value of the sub-boiler group), a boiler system that can perform load following with all the boilers belonging to the sub-boiler group including the fixed combustion boiler that burns at a fixed combustion rate The purpose is to provide.

  The present invention generates a first boiler group (main boiler group) composed of one or more boilers, a second boiler group (sub-boiler group) composed of one or more boilers, and the boiler group A steam header for collecting the generated steam, a steam pressure measuring means for measuring a header pressure value which is a steam pressure inside the steam header, and the header pressure value so as to coincide with a preset first target pressure value A boiler system comprising: a first control unit that performs PI control or PID control on the combustion state of the first boiler group; and a second control unit that controls the combustion state of the second boiler group. A fixed combustion control unit configured to burn a boiler to be burned in the second boiler group at a preset fixed combustion rate so as to output a constant steam amount serving as a preset base load; The combustion state of the second boiler group is set so that the header pressure value measured by the vapor pressure measuring means matches a preset second target pressure value that is smaller than the first target pressure value. A feedback control unit that performs PI control or PID control, and when the header pressure value exceeds a preset threshold that is greater than or equal to the second target pressure value and less than the first target pressure value, The boiler system which controls the combustion state of the 2nd boiler group by the fixed combustion control part, and controls the combustion state of the 2nd boiler group by the feedback control part, when the header pressure value becomes below the threshold .

  In addition, the fixed combustion rate may be a combustion rate with the highest combustion efficiency of the boiler to be burned (hereinafter also referred to as “eco-operating point”).

  Further, the fixed combustion rate can be a minimum combustion rate of the boiler to be burned.

  According to the boiler system of the present invention, there are two types of boiler groups, the target steam pressure value of one boiler group (main boiler group) is set high, and the target steam pressure value of the other boiler group (sub-boiler group) is set. In the boiler system that burns in a form that compensates for the shortage of the output steam amount of the main boiler group by setting low, the sub-boiler group can be burned by a certain amount even when the overall load is low. While preventing can body corrosion, the load nonuniformity between boiler groups can be improved.

It is a figure showing the outline of boiler system 1 concerning a 1st embodiment of the present invention. It is a figure which shows the outline of a boiler group. It is a functional block diagram which shows the structure of the 2nd control part 4B. It is a flowchart which shows operation | movement of the boiler system 1 which concerns on 1st Embodiment. It is a flowchart which shows operation | movement of the boiler system 1 which concerns on 1st Embodiment. It is a figure which shows transition of the amount of generated steam in a main boiler group and a sub boiler group in the case of implementing the conventional number control. It is a figure which shows transition of the amount of generated steam in a main boiler group and a sub boiler group when the number control which concerns on 1st Embodiment is implemented.

[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.

  The boiler system 1 includes a first boiler group 2A composed of three continuous control boilers 20A (hereinafter also referred to as “main boiler group”) and a second boiler group 2B composed of two continuous control boilers 20B (hereinafter referred to as “sub-boilers”). A group of boilers 2), a steam header 6 for collecting steam generated in the plurality of continuous control boilers 20A and 20B, and a steam pressure sensor 7 for measuring the pressure inside the steam header 6; A number control device 3A having a first control unit 4A for controlling the combustion state of the first boiler group 2A, and a number control device 3B having a second control unit 4B for controlling the combustion state of the second boiler group 2B. Prepare.

  As shown in FIG. 1, the continuous control boilers 20A and 20B respectively include boiler bodies 21A and 21B in which combustion is performed, and local control units 22A and 22B that control the combustion state of the continuous control boilers 20A and 20B. .

The boiler group 2 generates steam to be supplied to the steam use facility 18.
The steam header 6 is connected to a plurality of continuous control boilers 20 </ b> A and 20 </ b> B 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 between the plurality of continuous control boilers 20 </ b> A and 20 </ b> B. Supply to use equipment 18.

  The vapor pressure sensor 7 is electrically connected to the number control devices 3A and 3B through the signal line 13, respectively. The vapor pressure sensor 7 measures the vapor pressure inside the vapor header 6 (the pressure of the vapor generated in the boiler group 2), and sends a signal (vapor pressure signal) related to the measured vapor pressure via the signal line 13. Each is transmitted to the number control devices 3A and 3B.

  The number control devices 3A and 3B are electrically connected to a plurality of continuous control boilers 20A and 20B via signal lines 16A and 16B, respectively. The number control devices 3A and 3B control the combustion state of the continuous control boilers 20A and 20B based on the steam pressure inside the steam header 6 measured by the steam pressure sensor 7, respectively.

  The above boiler system 1 can supply the steam generated in the first boiler group 2 </ b> A and the second boiler group 2 </ b> B to the steam use facility 18 via the steam header 6.

  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 boilers 20A and 20B which comprise the boiler system 1 of 1st Embodiment are demonstrated. FIG. 2 is a diagram schematically illustrating the boiler group 2 according to the first embodiment.
The boilers 20A and 20B of the first embodiment are continuous control boilers that can be combusted by continuously changing the load factor.
The continuous control boiler is a boiler in which 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 amount) to the maximum combustion state S2. It is. 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.

  Further, the continuous control of the combustion amount means that the computations and signals in the local control units 22A and 22B are digitally handled in stages (for example, the output (combustion amount) of the boilers 20A and 20B is 1%). Even when the output can be controlled in a continuous manner.

The change of the combustion state between the combustion stop state S0 and the minimum combustion state S1 in the boilers 20A and 20B in the first embodiment is controlled by turning on / off the combustion of the boilers 20A and 20B (burner), respectively. The 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 in each of the boilers 20A and 20B. Thus, the boilers 20A and 20B can change the steam amount in units of the unit steam amount U 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 boilers 20A and 20B. From the viewpoint of improving the followability of the output steam amount to the necessary steam amount in the boiler system 1. The maximum steam amount of the boiler 20 is preferably set to 0.1% to 20%, more preferably 1% to 10%.
The output steam amount indicates the steam amount output by the first boiler group 2A and the second boiler group 2B, and this output steam amount is a total value of the steam amounts output from the plurality of boilers 20A and 20B. It is represented by

  Moreover, in 1st Embodiment, the eco-operation point which is a load factor with which boiler efficiency becomes the highest is set to the several boilers 20A and 20B.

Moreover, the priority order is set to each of the boilers 20A and 20B. The priority order is used for the number control devices 3A and 3B to select the boilers 20A and 20B that give the combustion instruction and the combustion stop instruction, respectively. 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, for example, when the priority order of “1” to “3” is assigned to each of the No. 1 to No. 3 machines of the boiler 20A of the first boiler group 2A, the No. 1 priority order is the highest. High and Unit 3 has the lowest priority. In the normal case, this priority is changed at predetermined time intervals (for example, 24 hour intervals) under the control of the first control unit 4A described later.
Similarly, when priority of “1” and “2” is assigned to each of No. 4 and No. 5 of the boiler 20B of the second boiler group 2B, No. 4 has the highest priority and No. 5 has priority. The ranking is the lowest. In the normal case, this priority order is changed at predetermined time intervals (for example, 24 hour intervals) under the control of the second control unit 4B described later.

As described above, the continuous control boilers 20A and 20B include boiler bodies 21A and 21B in which combustion is performed, and local control units 22A and 22B that control the combustion state of the boilers 20A and 20B, respectively.
The local control units 22A and 22B change the combustion state of the boilers 20A and 20B according to the steam consumption. Specifically, the local control units 22A and 22B are based on control signals transmitted from the number control devices 3A and 3B via the signal lines 16A and 16B, respectively, or control signals input by a driver's manual operation, respectively. The combustion state of the boilers 20A and 20B is controlled. Further, the local control units 22A and 22B transmit signals used in the number control device 3 to the number control devices 3A and 3B, respectively, via the signal lines 16A and 16B. Examples of signals used in the number control devices 3A and 3B include actual combustion states of the boilers 20A and 20B, other data, and the like.

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

Next, details of the number control devices 3A and 3B will be described.
As described above, the number control devices 3A and 3B, based on the steam pressure signal from the steam pressure sensor 7, respectively, the target steam amount of the first boiler group 2A and the second boiler group 2B corresponding to the required load, and the target The combustion state of each boiler 20A and 20B corresponding to the amount of steam is calculated, and a unit number control signal is transmitted to each boiler 20A and 20B (local control units 22A and 22B). As shown in FIG. 1, the number control devices 3A and 3B include a first storage unit 5A and a second storage unit 5B, a first control unit 4A and a second control unit 4B, respectively, and signal lines 16A and 16B, respectively. Are electrically connected to the boilers 20A and 20B.

The first control unit 4A and the second control unit 4B transmit various instructions to the boilers 20A and 20B via the signal lines 16A and 16B, respectively, and receive various data from the boilers 20A and 20B, respectively. Then, control of the combustion state and the number of operating units of the boilers 20A and 20B is executed. When each boiler 20A and 20B receives a signal for changing the combustion state from the number control devices 3A and 3B, the boilers 20A and 20B control the combustion amount of the corresponding boilers 20A and 20B according to the instruction. The first control unit 4A and the second control unit 4B receive information related to the combustion states of the boilers 20A and 20B via the signal lines 16A and 16B, respectively.
Detailed configurations of the first control unit 4A and the second control unit 4B will be described later.

  The first storage unit 5A and the second storage unit 5B are the contents of instructions given to the boilers 20A and 20B, respectively, under the control of the number control devices 3A and 3B (first control unit 4A and second control unit 4B). Information on the combustion state received from each of the boilers 20A and 20B, information on the setting of the unit steam amount U of each of the boilers 20A and 20B, information on setting of the priority order of the boilers 20A and 20B, change of priority order Information on settings related to (rotation) is stored.

Further, in the first storage unit 5A and the second storage unit 5B, the first target pressure value P1 related to the combustion control of the first boiler group 2A and the setting conditions related to the steam pressure measured by the steam pressure sensor 7 are respectively set. The second target pressure value P2 related to the combustion control of the second boiler group 2B can be set in advance.
Further, in the second storage unit 5B, a predetermined steam amount or a fixed number of boilers corresponding to the base load is set in the second boiler group 2B in advance, and a constant steam amount corresponding to the base load is output. A fixed combustion rate can be preset for each boiler 20B of the two-boiler group 2B. In the second storage unit 5B, a threshold value P that is equal to or higher than the second target pressure value P2 and lower than the first target pressure value P1 can be set in advance.
As will be described later, the second control unit 4B of the second boiler group 2B controls the combustion state of the second boiler group 2B by the fixed combustion control unit 41B described later by comparing the header pressure value PV and the threshold value P. Or the feedback control unit 42B described later determines whether to control the combustion state of the second boiler group 2B.

Next, detailed configurations of the first control unit 4A and the second control unit 4B will be described.
First, the first control unit 4A will be described.

The first control unit 4A sets a control amount such that the pressure of the steam generated from the first boiler group 2A (the steam pressure of the steam stored in the steam header 6) becomes a preset first target pressure value P1. The amount of combustion of the boiler 20A that constitutes the first boiler group 2A is controlled based on this control amount.
That is, the first control unit 4A has a predetermined PI with respect to the deviation between the header pressure value PV of the steam header 6 and the first target pressure value P1 of the first boiler group 2A set in the first storage unit 5A in advance. By performing feedback control based on the algorithm or PID algorithm, the steam amount MV _n necessary for the header pressure value PV to become the first target pressure value P1 is calculated, and the calculated steam amount MV _n is generated. A boiler 20A constituting one boiler group 2A is controlled.

Here, feedback control based on the PID algorithm of the first controller 4A will be briefly described.
The first control unit 4A sets the current pressure so that the deviation between the header pressure value PV (feedback value) measured by the vapor pressure sensor 7 and the first target pressure value P1 (set value) set in advance becomes zero. The 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.

The first control unit 4A is a necessary steam amount 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 1).
MV _n = MV _n-1 + ΔMV _n (Equation 1)
In (Expression 1), MV _n : current required steam volume (current required steam volume), MV _n-1 : required steam volume at the previous control cycle (previous steam volume), 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 2).
ΔMV _n = ΔP _n + ΔI _n + ΔD _n ... (Formula 2)
In (Expression 2), ΔP _n : P control output (change), ΔI _n : I control output (change), and ΔD _n : D control output (change), respectively, It is obtained by equation 5).
_{ΔP n = K P × (e} n -e n-1) ·············· ( Equation 3)
ΔI _n = K _P × (Δt / T _I ) × e _n (Equation 4)
_{ΔD n = K P × (T} D / Δt) × (e n -2e n-1 + e n-2) ··· ( Equation 5)
In (Expression 3) to (Expression 5), Δt: control period, 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, the first target pressure value P1, a difference between the header pressure value PV measured by the vapor pressure sensor 7, is determined by the following equation (6).
e _n = P1-PV (Equation 6)

The first control unit 4A sums the outputs (changes) calculated in (Equation 3), (Equation 4), and (Equation 5) according to (Equation 2), so that the necessary steam from the previous time to this time is obtained. The amount of change ΔMV _n is calculated.
Then, the first control unit 4A can calculate the present required steam amount MV _n by adding the required steam amount change ΔMV _n to the previous required steam amount MV _n−1 as in (Equation 1). .
By doing so, the first control unit 4A calculates the steam amount necessary for the header pressure value PV to become the first target pressure value P1, and sets the first boiler group 2A so as to generate the calculated steam amount. The boiler 20A to be configured is controlled.
The first control unit 4A that controls the first boiler group 2A including the continuous control boiler 20A has been described above.

Next, the second control unit 4B will be described.
As shown in FIG. 3, the second control unit 4B includes a fixed combustion control unit 41B and a feedback control unit 42B.

The fixed combustion control unit 41B burns the boiler 20B to be burned in the second boiler group 2B at a preset fixed combustion rate so as to output a constant steam amount that becomes a preset base load.
By doing so, even if the overall load is low, the second boiler group 2B can be burned by a certain amount, so that the boiler can body corrosion is prevented and the first boiler group 2A and the second boiler group 2B. It is possible to improve the load non-uniformity.

The fixed combustion rate is preferably set to the highest combustion rate of the combustion efficiency of the boiler 20B to be burned in the second boiler group 2B. Further, the fixed combustion rate can be set to the minimum combustion rate of the boiler 20B to be burned in the second boiler group 2B. Further, the fixed combustion rate can be set to the medium combustion rate of the boiler 20B to be burned in the second boiler group 2B.
As described above, the fixed combustion rate is set in advance for each boiler 20B of the second boiler group 2B in the second storage unit 5B so that the second boiler group 2B outputs a constant amount of steam corresponding to the base load. can do.

Feedback controller 42B, compared deviation between the second target pressure value P2 of the second boiler group 2B, which is set in advance the second storage unit 5B and the header pressure value PV of the steam header _{6 (e n = P2-PV} ) Te, by performing feedback control based on a predetermined PI algorithm or PID algorithm calculates the amount of steam MV _n required for header pressure value PV becomes the second target pressure value P2, the calculated amount of steam MV _n The boiler 20B which comprises the 2nd boiler group 2B is controlled so that it may generate | occur | produce.
Note that the calculation method of the required steam amount by the PID algorithm of the feedback control unit 42B is the same as the calculation method of the required steam amount by the PID algorithm of the first control unit 4A described above, and thus the description thereof is omitted.

<Switching control between fixed combustion control unit 41B and feedback control unit 42B>
When the header pressure value PV exceeds the threshold value P preset in the second storage unit 5B, the second control unit 4B controls the combustion state of the second boiler group 2B by the fixed combustion control unit 41B, and the header pressure value When PV becomes the threshold value P or less, the feedback controller 42B controls the combustion state of the second boiler group 2B.
By doing so, for example, when the overall load is low (the steam header pressure is stable in the vicinity of the first target pressure value P1 of the first boiler group 2A and exceeds the second target pressure value P2 set in advance by itself) In the case), the fixed combustion control unit 41B causes the boiler 20B to be burned in the second boiler group 2B to burn at a preset fixed combustion rate so as to output a constant steam amount serving as a preset base load.

  Conversely, when the overall load increases and cannot be covered by only the first boiler group 2A (when the steam header pressure decreases to the vicinity of the second target pressure value P2 of the second boiler group 2B), the feedback control unit 42B. Thus, load follow-up can be performed by performing feedback control based on the PI algorithm or PID algorithm in all the boilers 20B belonging to the second boiler group 2B including the fixed combustion boilers that burn at a fixed combustion rate.

Next, the flow of processing for realizing the operation of the boiler system 1 of the first embodiment will be described with reference to FIGS. 4 and 5. 4 and 5 are flowcharts showing the flow of processing of the first boiler group 2A and the second boiler group 2B, respectively.
First, the flow of processing in the first boiler group 2A will be described with reference to FIG.

  As a preparation for the process, the first target pressure value P1 is set for the first boiler group 2A and stored in a predetermined area of the first storage unit 5A (not shown).

  In step ST1, combustion control of the first boiler group 2A is started by the number control device 4A.

In step ST2, the combustion state of the first boiler group 2A is controlled by the first control unit 4A for each control cycle.
More specifically, the first control unit 4A sets the steam pressure value of the steam header 6 and the first target pressure value P1 of the first boiler group 2A set in the first storage unit 5A in advance for each control cycle. relative deviation, by performing feedback control based on a predetermined PI algorithm or PID algorithm, the amount of steam header pressure value PV calculates the amount of steam MV _n needed to become a first target pressure value P1, was calculated The boiler 20A constituting the first boiler group 2A is controlled so as to generate MV _n .

  The first control unit 4A repeats step ST2 for each control cycle.

Next, the flow of processing in the second boiler group 2B will be described with reference to FIG.
As a pre-process preparation, a second target pressure value P2 is set for the second boiler group 2B and stored in the second storage unit 5B. For each boiler 20B of the second boiler group 2B, a predetermined steam amount or a fixed number of boilers corresponding to the base load is set in advance in the second boiler group 2B, and a constant steam amount corresponding to the base load is output. Then, a fixed combustion rate is set and stored in the second storage unit 5B. Further, the threshold value P is set to a range not less than the second target pressure value P2 and less than the first target pressure value P1, and is stored in the second storage unit 5B (not shown).

  In step ST1, combustion control of the second boiler group 2B is started by the number control device 4B.

  In step ST2, the second control unit 4B determines whether or not the header pressure value PV exceeds the threshold value P. When the header pressure value PV exceeds the threshold value P (Yes), the process proceeds to step ST3. When the header pressure value PV does not exceed the threshold value P (No), the process proceeds to step ST4.

  In step ST3, the 2nd control part 4B performs the combustion control of the 2nd boiler group 2B by the fixed combustion control part 41B. More specifically, the fixed combustion control unit 41B burns the boiler 20B for burning the second boiler group 2B at a preset fixed combustion rate so as to output a constant steam amount that becomes a preset base load. Let

  Thereafter, the process proceeds to step ST2.

In step ST4, the second control unit 4B controls the combustion of the second boiler group 2B by the feedback control unit 42B. More specifically, the feedback control unit 42B deviates between the steam pressure value of the steam header 6 and the second target pressure value P2 of the second boiler group 2B set in the second storage unit 5B in advance for each control cycle. On the other hand, by performing feedback control based on a predetermined PI algorithm or PID algorithm, the steam amount MV _n necessary for the header pressure value PV to become the second target pressure value P2 is calculated, and the calculated steam amount MV _The boiler 20B which comprises the 2nd boiler group 2B is controlled so that _n may be generated.

  Thereafter, the process proceeds to step ST2.

  Next, referring to FIGS. 6 and 7, the target steam pressure value P1 of the main boiler group 2A is set high, and the target steam pressure value P2 of the sub boiler group 2B is set low, and a predetermined PI algorithm or PID algorithm is set. The operation when the number control according to the first embodiment is performed will be described in comparison with the case of performing feedback control based on the above (hereinafter referred to as “conventional number control”).

  Here, FIG. 6 is a diagram showing the transition of the header pressure when the “conventional number control” is performed. On the other hand, FIG. 7 is a figure which shows transition of the header pressure at the time of implementing the unit control which concerns on 1st Embodiment of this invention.

<Conventional unit control>
When the conventional number control is performed, as shown in FIG. 6, when the overall load is low (t0 to t1), the main boiler group 2A has steam necessary for the header pressure value PV to become the first target pressure value P1. Generate quantity. During this time, all the sub-boiler groups 2B are in a standby state.
Thereafter, even if the overall load increases, until the time t2, the main boiler group 2A can cover the steam amount necessary for the header pressure value PV to become the first target pressure value P1 with its output steam amount. it can. During this time, all the sub-boiler groups 2B are in a standby state.
After time t2, when the steam amount necessary for the header pressure value PV to become the first target pressure value P1 exceeds the maximum steam amount X that can be output from the main boiler group 2A, the steam header pressure decreases, but the header pressure Until the value PV becomes equal to or less than the threshold value P (t3), the sub-boiler group 2B is in a standby state for all units.
After t3, since the amount of steam used still exceeds the maximum steam amount X that can be output from the main boiler group 2A, the main boiler group 2A outputs the maximum steam amount X that can be output, and the sub-boiler group 2B The amount of steam necessary for the header pressure value PV to become the second target pressure value P2 is calculated so as to compensate for the shortage of the amount of steam used, and the calculated amount of steam is generated.
As described above, when the conventional number control is performed, the sub-boiler groups 2B are in a stand-by state until the amount of steam used exceeds the maximum steam amount X that can be output from the main boiler group 2A.

<Number control according to the first embodiment>
On the other hand, when the number control according to the first embodiment is performed, as shown in FIG. 7, when the overall load is low (t0 to t1), the sub-boiler group 2B has a constant steam for a preset base load. Output quantity.
Thereafter, even if the overall load increases and the amount of steam used increases, until the time t2, the main boiler group 2A determines the amount of steam necessary for the header pressure value PV to become the first target pressure value P1. Can be covered by the output steam volume.
After t2, when the steam amount necessary for the header pressure value PV to become the first target pressure value P1 exceeds the maximum steam amount X that can be output from the main boiler group 2A, the steam header pressure decreases, but the header pressure value Until the time point PV becomes equal to or less than the threshold value P (t3), the sub-boiler group 2B outputs a predetermined amount of steam for the base load.
After t3, since the amount of steam used still exceeds the maximum steam amount X that can be output from the main boiler group 2A, the main boiler group 2A outputs its own maximum steam amount X that can be output, and the sub-boiler group 2B is used In order to compensate for the shortage of the steam amount, the steam amount necessary for the header pressure value PV to become the second target pressure value P2 is calculated, and the calculated steam amount is generated.
In this way, when the number control according to the first embodiment is performed, the sub-boiler group 2B can be burned by a certain amount or more regardless of the amount of steam used.

According to the boiler system 1 of the first embodiment, for example, the following effects are produced.
In the boiler system 1 of the first embodiment, the combustion state of the main boiler group 2A is PI-controlled or PID-controlled so that the header pressure value PV matches the preset first target pressure value P1. On the other hand, the sub-boiler group 2B is configured to burn the boiler 20B to be burned at a preset fixed combustion rate so as to output a certain amount of steam that becomes a preset base load, or a header pressure value PV. Is controlled by the feedback control unit 42B that performs PI control or PID control of the combustion state of the sub-boiler group 2B so that the value coincides with the second target pressure value P2 that is smaller than the preset first target pressure value P1. . The combustion state of the sub-boiler group 2B is controlled by the fixed combustion control unit 41B when the header pressure value PV exceeds a preset threshold value P (second target pressure value P2 ≦ threshold P <first target pressure value P1). When the header pressure value PV becomes equal to or less than the threshold value P, the feedback control unit 42B controls the header pressure value PV.

  Therefore, according to 1st Embodiment, since it can ensure the combustion amount more than predetermined amount with respect to the sub boiler group 2B irrespective of the amount of steam used, while preventing boiler can body corrosion, between boiler groups Uneven load can be improved.

  Moreover, in the boiler system 1 of 1st Embodiment, the preset fixed combustion rate can be made into the combustion rate (eco-operation point) with the highest combustion efficiency of the boiler 20B burned in the sub boiler group 2B.

  Therefore, according to the first embodiment, when the overall load is low, the sub-boiler group 2B can be burned efficiently.

  Moreover, in the boiler system 1 of 1st Embodiment, the preset fixed combustion rate can be made into the minimum combustion rate of the boiler 20B made to burn in the sub boiler group 2B.

  Therefore, according to the first embodiment, it is possible to provide the boiler system 1 having excellent load followability when the overall load increases and the sub boiler group 2B compensates for the shortage of the output steam amount of the main boiler group 2A. it can.

The preferred embodiment of the boiler system of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and can be modified as appropriate.
For example, in the first embodiment, the present invention is applied to a boiler system 1 including a boiler group 2 including a first boiler group 2A including three boilers 20A and a second boiler group 2B including two boilers 20B. However, it is not limited to this. That is, the present invention may be applied to a boiler system including a first boiler group including four or more boilers 20 and applied to a boiler system including a first boiler group including one or two boilers. May be.
Similarly, the present invention may be applied to a boiler system including a second boiler group composed of three or more boilers 20 or applied to a boiler system including a second boiler group composed of one boiler. Also good.

  In the first embodiment, the continuous control boilers 20A and 20B are all set to the same boiler capacity, but the present invention is not limited to this. In other words, the present invention is also applicable when the continuous combustion boilers 20A and 20B have different combustion capacities as the minimum combustion amount, unit steam amount, and maximum combustion amount.

  In the first embodiment, as a PI (or PID) control algorithm for the first boiler group 2A and the second boiler group 2B, a position type PI (or position type PID) that directly calculates the required steam amount for each control cycle is used. Although the PI or PID control by the algorithm is applied, the present invention is not limited to the position type PI (or position type PID) algorithm. Apply only PI or PID control by the speed type PI (or speed type PID) algorithm that calculates the required amount of steam this time by calculating only the required amount of steam change per control cycle and adding the previous required amount of steam to this. May be.

  In the first embodiment, the change of the combustion state between the combustion stop state S0 and the minimum combustion state S1 in the boilers 20A and 20B is controlled by turning on / off the combustion of the boilers 20A and 20B, respectively. In the range from the minimum combustion state S1 to the maximum combustion state S2, it is configured by the continuous control boilers 20A and 20B capable of continuously controlling the combustion amount, but 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.

  In the first embodiment, the plurality of boilers 20A of the first boiler group 2A and the plurality of boilers 20B of the second boiler group 2B are respectively configured by continuous control boilers, but the first boiler group 2A and / or It is good also as comprising the 1st boiler group 2B by a step value control boiler. The stage value control boiler has a plurality of staged combustion positions, and controls the amount of combustion by selectively turning on / off combustion, adjusting the size of the flame, etc. It is a boiler that can increase or decrease the amount of combustion in stages according to the selected combustion position. As an example, the plurality of boilers 20A and 20B may be configured by a three-position boiler having three positions of a combustion stop position, a low combustion position, and a high combustion position. Of course, the boilers 20A and 20B are not limited to three positions, and may have arbitrary N positions of combustion positions.

  Moreover, when comprised by a stage value control boiler, it is good also as a thing which changes the boiler capacity | capacitance, the stage number N of a combustion position, the combustion rate in each combustion position, etc. for every stage value boiler.

DESCRIPTION OF SYMBOLS 1 Boiler system 2 Boiler group 2A 1st boiler group 2B 2nd boiler group 20 Boiler 20A Continuous control boiler 20B Continuous control boiler 3A Number control apparatus 4A 1st control part 5A 1st memory | storage part 3B Number control apparatus 4B 2nd control part 41B Fixed combustion control unit 42B Feedback control unit 5B Second storage unit 6 Steam header (steam collecting unit)
7 Vapor pressure sensor (Vapor pressure measuring means)
18 Steam use facilities (load equipment)

Claims (3)

A boiler group consisting of a first boiler group consisting of one or more boilers and a second boiler group consisting of one or more 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 first control unit that performs PI control or PID control on a combustion state of the first boiler group so that the header pressure value matches a preset first target pressure value;
A second control unit for controlling the combustion state of the second boiler group;
A boiler system comprising:
The second controller is
A fixed combustion control unit for burning the boilers to be burned in the second boiler group at a preset fixed combustion rate so as to output a constant steam amount serving as a preset base load;
The combustion state of the second boiler group is set so that the header pressure value measured by the vapor pressure measuring means matches a preset second target pressure value that is smaller than the first target pressure value. A feedback control unit that performs PI control or PID control,
When the header pressure value exceeds a preset threshold value that is greater than or equal to the second target pressure value and less than the first target pressure value, the fixed combustion control unit determines the combustion state of the second boiler group. And when the header pressure value is equal to or lower than the threshold value, the feedback control unit controls the combustion state of the second boiler group.
Boiler system.   The boiler system according to claim 1, wherein the fixed combustion rate is a combustion rate with the highest combustion efficiency of the boiler to be burned.   The boiler system according to claim 1, wherein the fixed combustion rate is a minimum combustion rate of the boiler to be burned.

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