JP2022156440A - boiler system - Google Patents

Abstract

To provide a boiler system which suppresses overshoot of a header pressure when controlling the number of boilers.SOLUTION: While a boiler which does not belong to a number control boiler group 2 performs steam supply and a pressure value is transient lower than a target pressure value of the number control boiler group 2, when number control of the number control boiler group 2 is started, in the cases where (i) a header pressure value PV continuously rises for a predetermined time, (ii) a necessary steam amount MVn exceeds a total value of steam amounts generated by boilers 20 supplying steam in the number control boiler group 2 and (iii) the header pressure value PV becomes a value exceeding, equal to or more than a border value that is a value obtained by subtracting a preset pressure value α from a target pressure value PTV, from a value smaller than the border value, in the number control boiler group 2, the required steam amount calculated by PID control is replaced with the total value of the generated steam amounts being outputted from the actually steam supplying boilers.SELECTED DRAWING: Figure 1

Description

The present invention relates to a boiler system in which a number-controlled boiler group having one or more boilers and one or more boilers not included in the number-controlled boiler group coexist.

In a boiler system in which steam generated in a boiler group consisting of a plurality of boilers is collected in a steam header and steam is supplied from this steam header to load equipment, the boiler group is roughly divided into two types and these are controlled. Boiler systems are known. For example, one boiler group (“first boiler group”) is set to a first target in which an internal pressure value (hereinafter also referred to as “internal pressure value”), which is a pressure value in the can body of each boiler, is set in advance. A group of boilers in which the combustion state of each boiler is locally controlled so as to match the pressure value, and the other boiler group ("second boiler group") is set to the steam pressure value inside the steam header (hereinafter referred to as "header pressure value ”) is a preset second target pressure value, a boiler system is known in which the number of boilers is controlled so that the combustion state of the first boiler group is controlled (for example, Patent Document 1). Here, the first target pressure value is set higher than the second target pressure value so that the first boiler group is mainly burned and the second boiler group is burned so as to make up for the shortage.
On the other hand, in a boiler system in which a number-controlled boiler group having one or more boilers and one or more boilers not belonging to the number-controlled boiler group coexist, for example, one or more boilers not belonging to the number-controlled boiler group The boilers are operated at low load, such as at night, and the header pressure value is maintained at a pressure lower than the target pressure value of the number-controlled boiler group. In some cases, the operation is started so that the header pressure value becomes the target pressure value in accordance with the start.

JP 2016-180573 A

In this case, when only one or more boilers that do not belong to the number-controlled boiler group are in operation, the header pressure value changes so as to maintain a pressure lower than the target pressure value of the number-controlled boiler group. . After that, when the number control of the number-controlled boiler group is started, since the header pressure value<the target pressure value, the number-controlled boiler group is controlled so that combustion is prioritized, and in the number-controlled boiler group, the header pressure Based on the value, a steam amount (manipulated variable) MV required according to the steam consumption amount (required load) of the steam using facility is calculated. However, in accordance with the calculated manipulated variable MV, a combustion command is output from the number control device that controls the number control boiler group to the plurality of boilers in the number control boiler group, but for example, the response delay due to the pre-purge and the in-vessel pressure Due to a delay in the response until the boiler rises, there is a state in which steam output is not performed for several minutes after the number control of the number control boiler group is started.
Then, since the state of header pressure value<target pressure value continues, the manipulated variable MV calculated in the number control of the number-controlled boiler group continues to increase. It is possible to reach the total maximum output of all controlled boilers, which is the maximum value of the quantity. After that, the boilers in the number-controlled boiler group start steaming one by one, for example, so that the header pressure value rises, and the manipulated variable MV starts to decrease as the header pressure value rises. However, although the manipulated variable MV decreases, the manipulated variable MV >> the generated steam amount, so the boiler generated steam amount continues to increase.
As a result, the header pressure value rises sharply, and although the amount of decrease in the manipulated variable MV increases, the manipulated variable MV reaches the total maximum output of all controlled boilers. If an overshoot occurs and the header pressure value exceeds the control upper limit pressure value, the number of boilers should be controlled to stop all boilers (hereinafter also referred to as "all boilers stop"). There is

The present invention relates to a boiler system comprising a number-controlled boiler group whose number is controlled so that a header pressure value becomes a preset target pressure value, and one or more boilers not included in the number-controlled boiler group. , when only one or more boilers not included in the number-controlled boiler group are in operation, and the header pressure value transitions so as to maintain a pressure lower than the target pressure value of the number-controlled boiler group; It is an object of the present invention to provide a boiler system capable of suppressing overshoot of header pressure and stably operating when the number control of the number-controlled boiler group is started.

The present invention provides a boiler group consisting of a number-controlled boiler group consisting of one or more boilers and one or more boilers not included in the number-controlled boiler group,
a steam header for collecting steam generated in the boiler group;
steam pressure measuring means for measuring a header pressure value, which is the steam pressure inside the steam header;
A boiler system comprising
The number-controlled boiler group includes a control unit that controls the combustion state of the number-controlled boiler group,
The control unit
A required steam amount calculation unit for calculating a current required steam amount _MVn by a rate-type PI algorithm or a rate-type PID algorithm so that the header pressure value measured by the steam pressure measuring means is maintained at a preset target pressure value. When,
an output control unit that controls the combustion state of the boilers in the number-controlled boiler group so as to generate the current required steam amount _MVn calculated by the required steam amount calculating unit;
In a state where one or more boilers not included in the number-controlled boiler group are in operation and the header pressure value transitions at a value lower than the target pressure value of the number-controlled boiler group, the output control unit When the control of the number-controlled boiler group is started, the header pressure value continues to rise for a predetermined time, and the required steam amount _MVn is the steam generated by all the boilers supplying steam to the number-controlled boiler group. when the total value of the volume is exceeded, the header pressure value is less than a boundary value that is the target pressure value minus a preset pressure value α, exceeds the boundary value, or exceeds the boundary value. and a detection unit that detects whether or not the value of
The required steam amount calculation unit further
When the detecting unit detects that the header pressure value has changed from a value smaller than the boundary value to a value exceeding the boundary value or exceeding the boundary value, in the process of calculating the current required steam amount MV _n , It is detected that the header pressure value has changed from a value smaller than the boundary value to a value exceeding the boundary value as the current required steam amount MV _n or the previous required steam amount MV _n-1 . The present invention relates to a boiler system that sets the total value of the amount of steam generated by all the boilers that are supplying steam to the number-controlled boiler group at a given point in time.

Further, when the number-controlled boiler group is started, one or more boilers not included in the number-controlled boiler group are in operation, and the header pressure value is higher than the value obtained by subtracting the pressure value α from the target pressure value. It is preferable that it stays at a low value.

The one or more boilers not included in the number-controlled boiler group include continuously controlled boilers, and the boiler internal pressure value or header pressure value is maintained at a value lower than the target pressure value. may

According to the present invention, a boiler comprising a number-controlled boiler group whose number is controlled so that the header pressure value becomes a preset target pressure value, and one or more boilers not included in the number-controlled boiler group. In the system, when only one or more boilers not included in the number-controlled boiler group are in operation and the header pressure value is transitioning at a pressure lower than the target pressure value of the number-controlled boiler group, the number of boilers It is possible to provide a boiler system capable of suppressing overshoot of the header pressure and stably operating when the number control of the controlled boiler group is started.

1 is a schematic configuration diagram of a boiler system 1 according to a first embodiment; FIG. Using the boiler system 1 according to the first embodiment as a model, temporal transitions of the header pressure value, the required steam amount (manipulated amount), and the actual generated steam amount when pressure control is performed by a normal rate-type PID algorithm are shown. FIG. 10 shows. 3 is a functional block diagram showing the configuration of a controller 4 of the number-of-units control device 3 according to the first embodiment; FIG. Using the boiler system 1 according to the first embodiment as a model, this is a diagram showing the temporal transition of the header pressure value, the required steam amount (manipulated amount), and the actual generated steam amount when the pressure value is set to 0.10 MPa. be. Using the boiler system 1 according to the first embodiment as a model, this is a diagram showing temporal transitions of the header pressure value, the required steam amount (manipulated amount), and the actual generated steam amount when the pressure value is set to 0.00 MPa. be. Using the boiler system 1 according to the first embodiment as a model, this is a diagram showing temporal transitions of the header pressure value, the required steam amount (manipulated amount), and the actual generated steam amount when the pressure value is set to 0.05 MPa. be. Using the boiler system 1 according to the first embodiment as a model, this is a diagram showing the temporal transition of the header pressure value, the required steam amount (manipulated amount), and the actual generated steam amount when the pressure value is set to 0.15 MPa. be. 4 is a flow chart showing the flow of feedback control in the number-controlled boiler group 2 of the boiler system 1 according to the first embodiment.

[First embodiment]
A boiler system 1 according to an embodiment (hereinafter referred to as "first embodiment") of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an outline of a boiler system 1. FIG. In this embodiment, as boilers that do not belong to the number-controlled boiler group 2, there is one boiler 20A outside the number-controlled boiler (hereinafter also simply referred to as "the boiler outside the number-controlled boiler 20A") and eight boilers 20. A boiler system consisting of a control boiler group 2 is exemplified.
Here, the boilers 20A and 20 are both continuously controlled boilers capable of continuously changing the amount of combustion for combustion. A 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 a combustion amount of 20% of the maximum combustion amount) to the maximum combustion state S2. is. A continuous control boiler adjusts the amount of combustion by, for example, controlling the opening degree (combustion ratio) of a valve that supplies fuel to a burner and a valve that supplies combustion air. More specifically, each of the boilers 20A and 20 is set with a unit steam amount U, which is a variable steam amount unit. As a result, the boilers 20A and 20 can change the steam amount in units of the unit steam amount U within the range from the minimum combustion state S1 to the maximum combustion state S2.
The configurations of the boilers not belonging to the number-controlled boiler group 2 and the number-controlled boiler group 2 illustrated in the present embodiment are examples. In the present invention, when the number control of the number-controlled boiler group is started, (i) boilers that do not belong to the number-controlled boiler group are supplying steam, and (ii) the header pressure value is equal to that of the number-controlled boiler group. Any boiler that satisfies the fact that the pressure is kept lower than the target pressure value set in . For example, boilers 20A that do not belong to the number-controlled boiler group may be set as a plurality of number-controlled boilers 20A.
Specifically, the number-controlled boiler 20A may be a boiler that is locally controlled so that the boiler internal pressure value is maintained at a target pressure value lower than the target pressure value set for the number-controlled boiler group. Boilers that do not belong to the number-controlled boiler group 2 may include boilers whose header pressure values are controlled to maintain a lower target pressure value than the target pressure value set in the number-controlled boiler group 2. In addition, as a boiler that does not belong to the number-controlled boiler group, the maximum set pressure value of the header pressure value is set so as to fall within the control pressure band set at a value lower than the target pressure value set for the number-controlled boiler group 2. A controlled step value control boiler may be included. Also, the boilers that do not belong to the number-controlled boiler group may be composed of a plurality of boiler groups. The number-controlled boiler group 2 may be any number of boilers. Boiler capacities (minimum combustion amount, unit steam amount, maximum combustion amount, etc.) may be different.

As shown in FIG. 1 , the boiler system 1 includes one uncontrolled boiler 20A and a steam header 6 that collects steam generated in eight boilers 20 . The steam header 6 is connected to the uncontrolled boiler 20</b>A and eight boilers 20 via steam pipes 11 . The downstream side of this steam header 6 is connected to a steam using facility 18 via a steam pipe 12 . In this way, the steam header 6 collects and stores the steam generated by the boiler group 2, thereby adjusting the mutual pressure difference and pressure fluctuation between the uncontrolled boilers 20A and the plurality of boilers 20. The conditioned steam is supplied to the steam using facility 18 .

The boiler system 1 includes a steam pressure sensor 7 as steam pressure measuring means for measuring the steam pressure value inside the steam header 6 (hereinafter also referred to as “header pressure value”), and the combustion state of the number-controlled boiler group 2. and a number control device 3 as a control device having a control unit 4 that controls the number of machines. The steam pressure value inside the steam header 6 measured by the steam pressure sensor 7 is hereinafter also referred to as "header pressure value PV". As shown in FIG. 1 , the vapor pressure sensor 7 is electrically connected to the number control device 3 via a signal line 13 . The vapor pressure sensor 7 measures the header pressure and transmits a signal (vapor pressure signal) related to the measured header pressure value PV to the number control device 3 via the signal line 13 . The number control device 3 is also electrically connected to the plurality of boilers 20 via signal lines 16 . By doing so, the number control device 3 controls the combustion state of each boiler 20 based on the header pressure value PV measured by the steam pressure sensor 7, as will be described later.
Next, the number-controlled boiler group 2 and the number-uncontrolled boiler 20A that constitute the boiler system 1 will be described.

<Number of control boiler group 2>
The boilers 20 of the number-controlled boiler group 2 are, for example, multi-tube once-through boilers. The boiler 20 includes a boiler main body 21 in which combustion is performed, and a local control section 22 that controls the combustion state of the continuous control boiler 20 . The boiler 20 is configured, for example, to output steam with an equivalent evaporation amount of 3 t/h when the combustion amount is 100%.

As described above, the number control device 3 as a control device is electrically connected to the plurality of boilers 20 via the signal line 16 . Based on the header pressure value PV measured by the steam pressure sensor 7, the number control device 3 adjusts the combustion state of each boiler 20 so that the header pressure value PV is maintained at a preset target pressure value PTV. Control. That is, the local control section 22 controls the combustion state of the boilers 20 based on the control signal transmitted from the number control device 3 via the signal line 16 . Conversely, the local control unit 22 transmits signals used by the number control device 3 (for example, the actual combustion state of the boilers 20 and the like) to the number control device 3 via the signal line 16 . The number-controlled boiler group 2 has been described above. Next, the number-of-unit-uncontrolled boiler 20A will be described.

<Number of uncontrolled boilers 20A>
The number-uncontrolled boiler 20A is composed of, for example, a once-through boiler and/or a water tube boiler. The boiler 20A includes a boiler main body 21A in which combustion is performed, a boiler pressure detection section 23A as a can internal pressure measuring means for measuring the internal pressure value of the boiler 20A, and a local control section 22A.
The number-uncontrolled boiler 20A is, for example, configured to be able to output steam with an equivalent evaporation amount of 6 t/h when the combustion amount is 100%.

23 A of boiler pressure detection parts measure the can pressure value PVA of the boiler 20A, and transmit the measured can pressure value PVA to 22 A of local control parts.
Based on the can pressure value PVA measured by the boiler pressure detection unit 23A, the local control unit 22A controls the boiler 20A so that the can pressure value PVA maintains a pressure value PLV lower than the target pressure value PTV. Control the combustion state.

More specifically, the local control unit 22A determines that the internal pressure value of the steam generated from the boiler 20A, that is, the internal pressure value PVA measured by the boiler pressure detection unit 23A is lower than the target pressure value PTV. A controlled variable is calculated to achieve the value PLV, and the combustion amount of the boiler 20A is controlled based on this controlled variable.
That is, the local control unit 22A controls the deviation between the in-can pressure value PVA of the boiler 20A and the pressure value PLV of the boiler 20A set in advance in the local storage unit (not shown) at each control cycle by a predetermined value. By performing feedback control based on the PI algorithm or PID algorithm, the steam volume MVAn required for the in-vessel pressure value PVA to become the pressure value PLV is calculated, and the boiler 20A is controlled to generate the calculated steam volume MVAn. do. Here, n is an index (natural number) for identifying the control cycle by, for example, setting the initial value at the start of control to 1 and adding 1 for each next control cycle. The number-of-unit-uncontrolled boiler 20A has been described above.

In the boiler system 1 of the present embodiment, when the number-of-unit-uncontrolled boilers 20A are maintained at a pressure value PLV lower than the target pressure value PTV, the boiler system 1, for example, starts full-scale operation of the factory. , the number control of the number control boiler group 2 is started. The number-controlled boiler group 2 is controlled so that the header pressure value maintains the target pressure value PTV, which is set higher than the pressure value PLV, as described above.

A case where the present invention is not applied to the boiler system 1 of the present embodiment will be described with a specific example. 2, the pressure value PLV is set to 1.30 MPa, the target pressure value PTV is set to 1.50 MPa, and the unit-uncontrolled boiler 20A maintains a pressure value PLV lower than the target pressure value PTV of the unit-controlled boiler group 2. FIG. 10 is a simulation diagram showing fluctuations in the header pressure value PV after the number control of the number-controlled boiler group 2 is started when the number-controlled boiler group 2 changes as shown in FIG. Here, the horizontal axis indicates the elapsed time (seconds), the left vertical axis indicates the header pressure value (MPa), and the right vertical axis indicates the generated steam amount (t/h). In addition, the thick solid line (A) represents the header pressure value PV, the thick dashed line (B) represents the required steam amount (manipulated amount) MV, the solid line (C) represents the required steam amount (steam load), the dashed lines (D) and (E) represents the amount of steam generated by the uncontrolled boilers 20A and the amount of steam generated by the boiler group 2, respectively. It is assumed that the required steam amount (steam load) is constant at 2.2 t/h when the boiler group 2 is started under the number control, and changes to an increasing trend 270 seconds after the start of the number control.

As shown in FIG. 2, when the number control of the boiler group 2 is started, the header pressure value PV (solid line A) (≈ pressure value PLV) < the target pressure value PTV, so the number control boiler group 2 has priority. In the number-controlled boiler group 2, the required amount of steam (operation amount) MV continues to increase.
Specifically, a combustion command is output to the plurality of boilers 20 of the number-controlled boiler group 2 from the number-control device 3 that controls the number-controlled boiler group 2 in accordance with the calculated manipulated variable MV (broken line B). For example, due to a response delay due to pre-purge and a response delay until the boiler internal pressure rises, as shown in FIG. is not performed.
On the other hand, since the state of header pressure value PV (solid line A) (solid line A)<target pressure value PTV (1.50 MPa) continues, the manipulated variable MV (dashed line B) calculated in the unit control of the unit control boiler group 2 continues to increase, for example, the manipulated variable MV (dashed line B) reaches the total maximum output of all controlled boilers (24/t), which is the maximum amount of steam generated by the number-controlled boiler group 2, after about 75 seconds. After that, the boilers 20 of the number-controlled boiler group 2 start steaming, for example, one by one (broken line E), and after about 170 seconds, the header pressure value PV (solid line A) rises from the pressure value PLV. It will be done. Thereafter, as the header pressure value PV (solid line A) rises, the amount of steam generated by the number-of-uncontrolled boilers 20A decreases, and the manipulated variable MV (broken line B) begins to decrease.
However, although the manipulated variable MV (broken line B) decreases greatly, the manipulated variable MV (broken line B) still greatly exceeds the amount of steam generated by the number-controlled boiler group 2 (broken line E), so the amount of steam generated (broken line E) further increases and the header pressure value PV (solid line A) continues to rise.
After about 195 seconds, the manipulated variable MV (broken line B) falls below the amount of steam generated by the number-controlled boiler group 2 (broken line E). Solid line A) rises, overshoots, and reaches 1.812 MPa after about 200 seconds.

In order to solve such a problem, when the number-controlled boiler 20A maintains a pressure value PLV lower than the target pressure value PTV of the number-controlled boiler group 2, the number-controlled boiler group 2 A function of the number control device 3 that prevents overshoot of the header pressure and enables stable operation even when the number control is started will be described in detail.

As described above, the number control device 3 calculates the combustion state of each boiler 20 according to the required load based on the steam pressure signal from the steam pressure sensor 7, Send control signals. As shown in FIG. 1 , the number control device 3 includes a storage section 5 and a control section 4 and is electrically connected to each boiler 20 via a signal line 16 .

The control unit 4 transmits various instructions to the boilers 20 via the signal line 16, receives various data from each boiler 20, and controls the combustion state of the boilers 20 and the number of boilers in operation. When each boiler 20 receives a command to change the combustion state from the number control device 3, it controls the combustion amount of the boiler 20 in accordance with the command. Note that the control unit 4 receives information regarding the combustion state of the boiler 20 via the signal line 16 .
Before describing the detailed configuration of the control unit 4, the storage unit 5 will be described.

The storage unit 5 stores the contents of instructions given to each boiler 20 under the control of the control unit 4, information such as the combustion state received from each boiler 20, information on setting the priority order of the plurality of boilers 20, priority It stores setting information and the like related to the change (rotation) of the order. By doing so, the storage unit 5 can store in the storage unit 5 the total amount of generated steam output from the boiler 20 during steam supply.
It should be noted that the boiler 20 that is being steamed refers to the boiler 20 that is actually in a combustion state and whose boiler can internal pressure value is equivalent to the header pressure value PV. More specifically, for example, when the difference between the header pressure value PV and the boiler can internal pressure value is equal to or less than a preset pressure deviation, it is determined that the boiler 20 is supplying steam. Further, after the difference between the header pressure value PV and the boiler can internal pressure value becomes equal to or less than the pressure deviation, it may be determined that the boiler 20 has become a steaming boiler after a predetermined time (for example, 3 seconds) has elapsed. . Further, when a value obtained by subtracting a predetermined margin (for example, 0.01 MPa to 0.02 MPa) from the difference between the header pressure value PV and the boiler can internal pressure is equal to or less than the pressure deviation, the boiler 20 is supplied with steam. You may judge that it is in the middle.
Further, the storage unit 5 stores a target pressure value PTV related to combustion control of the number-controlled boiler group 2, which is set in advance as a setting condition related to the header pressure value PV measured by the steam pressure sensor 7. good too.

A detailed configuration of the control unit 4 that executes combustion control of the number-controlled boiler group 2 will be described. FIG. 3 is a functional block diagram showing the configuration of the control section 4 of the number control device 3. As shown in FIG.
As shown in FIG. 3 , the control unit 4 includes a detection unit 41 , a necessary steam amount calculation unit 42 and an output control unit 43 . Next, each function part of the control part 4 is demonstrated.

<Detector 41>
As described above, when the number-controlled boiler 20A maintains the pressure value PLV lower than the target pressure value PTV of the number-controlled boiler group 2, the detection unit 41 detects that the number-controlled boiler group 2 is started, it is detected at each control cycle whether or not a predetermined condition is satisfied.
Here, the predetermined conditions are (i) that the header pressure value PV continues to rise for a predetermined period of time after starting the number control of the number-controlled boiler group 2, and (ii) that the required steam amount MV _n It exceeds the total amount of steam generated by the boilers 20 during steam supply of the control boiler group 2 (that is, the total amount of steam generated by each boiler 20 supplying steam), and (iii) the header The three conditions are that the pressure value PV changes from a value smaller than a boundary value, which is a value obtained by subtracting a preset pressure value α from the target pressure value PTV, to a value that exceeds or exceeds the boundary value. It means fulfilling at the same time. The pressure value α is set to a value less than the difference between the target pressure value PTV and the pressure value PLV. In addition, as condition (iii), "the header pressure value PV is a value that exceeds the boundary value or exceeds the boundary value, which is a value obtained by subtracting a preset pressure value α from the target pressure value PTV. In other words, "the header pressure value PV is a value equal to or less than a boundary value obtained by subtracting a preset pressure value α from the target pressure value PTV, and a value exceeding the boundary value. You can also say "what happened".

<Required steam amount calculation unit 42>
The required steam amount calculation unit 42 calculates a predetermined Based on the PI algorithm or PID algorithm, the necessary steam amount MVn required for the header pressure value PV to become the target pressure value PTV is calculated. Here, the subscript n is an index (natural number) for identifying the control cycle by setting the initial value at the start of the control of the number of units to 1, for example, and adding 1 for each control cycle. n-th time: n=1, 2, . . . ).
In the required steam amount calculation unit 42 of the present invention, as a PID control algorithm, only the required steam amount change ΔMVn from the previous time to the current time is calculated for each control cycle, and the previous required steam amount MVn-1 is added to this. , apply the velocity type calculation for calculating the required steam amount MVn this time. In addition to the velocity-type calculation, there is a position-type calculation for directly calculating the current required steam amount MVn for each control cycle, but this is not adopted in the present invention.
More specifically, the required steam amount calculation unit 42 calculates the current required steam amount MVn as follows.

The required steam amount calculation unit 42 calculates the current required steam amount MVn to be generated from the plurality of boilers 20 constituting the number-controlled boiler group 2 using the following speed-type calculation formula (Equation 1).

MVn=MVn−1+ΔMVn (Formula 1)
In (Equation 1), MVn: required steam amount at present (current required steam amount), MVn-1: required steam amount at the time of the previous control cycle (previous required steam amount), ΔMVn: required steam amount from the previous time to this time. It is the amount of change.

The required steam amount change ΔMVn from the previous time to the current time is calculated by the following (Equation 2).
ΔMVn=ΔPn+ΔIn+ΔDn (Formula 2)
In (Equation 2), ΔPn: P control output (variation), ΔIn: I control output (variation), and ΔDn: D control output (variation), which are represented by (Equation 3) to (Equation 5) below. required by
ΔPn=KP×(en−en−1) (Formula 3)
ΔIn=KP×(Δt/TI)×en (Formula 4)
ΔDn=KP×(TD/Δt)×(en−2en−1+en−2) (Formula 5)
In (Formula 3) to (Formula 5), Δt: control cycle, KP: proportional gain, TI: integral time, TD: differential time, en: current deviation amount, en-1: deviation amount at the time of the previous control cycle , en-2: the amount of deviation at the time of the last control cycle.
The current deviation amount en is the difference between the target pressure value PTV and the header pressure value PVn measured by the steam pressure sensor 7, and is obtained by the following (Equation 6).
en=PTV-PVn (Formula 6)

The required steam amount calculation unit 42 sums the respective outputs (changes) calculated by (Equation 3), (Equation 4), and (Equation 5) according to (Equation 2), thereby A steam amount change ΔMVn is calculated.
Then, the required steam amount calculation unit 42 can calculate the current required steam amount MVn by adding the required steam amount change ΔMVn to the previous required steam amount MVn−1 as shown in (Equation 1).

Further, the required steam amount calculation unit 42 determines that the header pressure value PV continues to rise for a predetermined time after the above-described predetermined condition, that is, (i) the number control of the number-controlled boiler group 2 is started by the detection unit 41. (ii) the required steam amount _MVn exceeds the total amount of steam generated by the boilers 20 during steam supply in the number-controlled boiler group 2; and (iii) the header pressure value PV is equal to the target pressure value When it is detected that three conditions are simultaneously satisfied, that is, a value smaller than a boundary value, which is a value obtained by subtracting a preset pressure value α from PTV, and a value exceeding or exceeding the boundary value. , in the process of calculating the current required steam amount MV _n , as the current required steam amount MV _n or as the previous required steam amount MV _n−1 , the header pressure value PV changes from a value smaller than the boundary value to a value exceeding the boundary value At the time when it is detected that the value has reached or exceeded the value, the total value of the generated steam amount of all the boilers 20 supplying steam to the number-controlled boiler group 2 is set.
More specifically, at time t _n when the three conditions described above are satisfied, the required steam amount calculation unit 42 calculates the value of the previous required steam amount MV _n−1 or the current required steam amount MV _n from the actual boiler during steam supply. is replaced by the total value of the amount of generated steam output by , and the amount of steam required this time MV _n is calculated.

<Output control unit 43>
The output control unit 43 controls the combustion state (combustion amount) of the boiler 20 based on the currently required steam amount MV _n calculated by the required steam amount calculating unit 42 . The output control unit 43 controls the combustion state of each boiler 20 so that the boiler group 2 generates a required amount of steam.

The output control unit 43 sets the number of boilers 20 for combustion based on the required steam amount calculated according to the steam consumption amount (steam load) in the required steam amount calculation unit 42 . The output control unit 43 sets the boilers 20 to start or stop combustion according to the priority listed in the storage unit 5, and sends a number control signal (to start or stop operation) to the local control unit 22 of these boilers 20 stop). As a result, the combustion state of each boiler 20 is controlled so that the required amount of steam is generated from the boiler group 2 , thereby supplying the steam header 6 with the amount of generated steam corresponding to the required amount of steam.

In the boiler system 1 according to the present embodiment, the process of replacing the required steam amount with the total value of the generated steam amount actually output by the boiler during steam supply when a predetermined condition is satisfied will be described with a specific example.
4, similarly to FIG. 2, the pressure value PLV is set to 1.30 MPa, the target pressure value PTV is set to 1.50 MPa, and the pressure value α is set to 0.10 MPa. FIG. 11 is a simulation diagram showing the fluctuation of the header pressure value PV after the number control of the number-controlled boiler group 2 is started when the pressure value PLV lower than the target pressure value PTV of the boiler group 2 is maintained. is.

Referring to FIG. 4, the header pressure value PV (solid line A) was preset from the target pressure value of 1.50 MPa about 180 seconds before during the period when the conditions (i) and (ii) are satisfied. It can be seen that the value changes from a value smaller than the boundary value (1.40 MPa), which is the value obtained by subtracting the pressure value α (0.1 MPa), to a value greater than or equal to the boundary value, satisfying condition (iii).
Then, since it is detected that the predetermined condition is satisfied at a point in time (assumed to be control cycle n) about 180 seconds before, the required steam amount calculation unit 42 calculates the previous required steam amount MV _n−1 or the current required steam amount MV n−1. The current required steam amount MV _n (broken line B) is calculated by replacing the value of the amount MV _n with the total value of the generated steam amount actually output by the boiler during steam supply. Then, as shown in FIG. 4, the header pressure value PV (solid line A) becomes 1.50 MPa after about 190 seconds, and after about 220 seconds, it is maintained at 1.50 MPa. . In this way, as shown in FIG. 4, the boiler system 1 prevents the header pressure value PV (solid line A) from overshooting after about 190 seconds, and the actual amount of generated steam is equal to the amount of steam consumed ( demanded load). Then, the header pressure value PV (solid line A) converges near the target pressure value PTV (1.50 MPa).

Next, simulation results when the pressure value α is set to 0.00 MPa, 0.05 MPa, and 0.15 MPa will be described. 5, 6, and 7 show simulations when the pressure value α is set to 0.00 MPa, 0.05 MPa, and 0.15 MPa, respectively.

When the pressure value .alpha. Referring to FIG. 5, it can be seen that the condition (iii) is satisfied at approximately 185 seconds (assumed to be control cycle n) during the period when the conditions (i) and (ii) are satisfied. Then, at this time, the required steam amount calculation unit 42 calculates the value of the previous required steam amount MV _n−1 or the current required steam amount MV _n based on the total amount of generated steam actually output by the boiler during steam supply. Instead, the required steam amount MV _n (broken line B) is calculated this time. Then, as shown in FIG. 5, the header pressure value PV (solid line A) becomes 1.627 MPa after about 195 seconds, and after about 250 seconds, it is maintained at 1.50 MPa. .

Next, when the pressure value .alpha. Referring to FIG. 6, in the period in which the conditions (i) and (ii) are satisfied, the condition (iii) is satisfied after approximately 180 seconds to a few seconds (assumed to be control cycle n). I understand. Then, at this time, the required steam amount calculation unit 42 calculates the value of the previous required steam amount MV _n−1 or the current required steam amount MV _n based on the total amount of generated steam actually output by the boiler during steam supply. Instead, the required steam amount MV _n (broken line B) is calculated this time. Then, as shown in FIG. 6, the header pressure value PV (solid line A) becomes 1.584 Pa after about 190 seconds, and then maintains 1.50 MPa from about 240 seconds. I understand.

Next, when the pressure value .alpha. Referring to FIG. 7, in the period in which the conditions (i) and (ii) are satisfied, the condition (iii) is satisfied about 5 seconds before about 180 seconds (control cycle n). I understand. Then, at this time, the required steam amount calculation unit 42 calculates the value of the previous required steam amount MV _n−1 or the current required steam amount MV _n based on the total amount of generated steam actually output by the boiler during steam supply. Instead, the required steam amount MV _n (broken line B) is calculated this time. Referring to FIG. 7, in the period in which the conditions (i) and (ii) are satisfied, the condition (iii) is satisfied after about 180 seconds to a few seconds (assumed to be control cycle n). I understand. Then, as shown in FIG. 7, it can be seen that the header pressure value PV (solid line A) does not overshoot and maintains 1.50 MPa from around 240 seconds.

As described above, by setting the pressure value α to an appropriate value, the boiler system 1 prevents the header pressure value PV (solid line A) from overshooting, as shown in FIGS. The amount of generated steam quickly follows fluctuations in the amount of steam consumed (required load). Then, the header pressure value PV (solid line A) converges near the target pressure value PTV. 4 and 7, the header pressure value PV (solid line A) reaches the target pressure value PTV earlier in the simulation shown in FIG. From this, it can be said that 0.1 MPa, for example, is an appropriate value for the pressure value α.

Next, operation of the boiler system 1 of the first embodiment will be described with reference to FIG. In the boiler system 1, FIG. 4 is a flow chart showing the control of the control unit 4 after starting the number control of the control boiler group 2. FIG.

As described above, the control unit 4 obtains from each boiler 20 from the local control unit 22 of each boiler 20 included in the number-controlled boiler group 2 via the signal line 16, and the boiler 20 during feeding actually performs The storage unit 5 is configured to store the total value of the amount of generated steam that is output.

The flow of feedback control in the number-controlled boiler group 2 is as follows.
In step ST1, the required steam amount calculator 42 acquires the header pressure value PV _n based on the steam pressure signal transmitted from the steam pressure sensor 7 every control cycle n.

In step ST2, the required steam amount calculation section 42 calculates the required steam amount change (ΔMV _n ) in the control period n based on Equations (1) to (6).

In step ST<b>3 , the required steam amount calculation unit 42 acquires the generated steam amounts output from all boilers 20 during steam supply stored in the storage unit 5 .

In step ST4, the detection unit 41 satisfies the above three conditions (i) that the header pressure value PV continues to rise for a predetermined time after starting the number control of the number-controlled boiler group 2, and (ii) the required steam. and (iii) the header pressure value PV is a pressure value preset from the target pressure value _PTV . It is determined whether or not the condition that a value smaller than a boundary value obtained by subtracting α from a value exceeding the boundary value or a value exceeding the boundary value is satisfied. If the three conditions (predetermined conditions) are satisfied (Yes), the process proceeds to step ST5. If not satisfied (No), go to step ST6.

In step ST5, the required steam amount calculation unit 42 determines that the current required steam amount MV _n is a value smaller than the boundary value, which is the target pressure value PTV minus a preset pressure value α. , set the total amount of steam generated by all steaming boilers that are burning at the time when the value exceeds or exceeds the boundary value.
After that, the process moves to step ST7.

In step ST6, the required steam amount calculator 42 calculates the required steam amount MV _n in the control cycle n.

In step ST<b>7 , the required steam amount calculation unit 42 outputs the current required steam amount MV _n to the output control unit 43 .

In step ST<b>8 , the output control unit 43 controls the combustion state (combustion amount) of the boiler 20 based on the currently required steam amount MV _n calculated by the required steam amount calculating unit 42 . The output control unit 43 controls the combustion state of each boiler 20 so that the boiler group 2 generates a required amount of steam.
After that, the process returns to step ST1.

In step ST5 of the flowchart showing the control of the control unit 4 after starting the number control of the number-controlled boiler group 2 shown in FIG. _n , when the header pressure value PV exceeds or exceeds the boundary value, which is a value obtained by subtracting a preset pressure value α from the target pressure value PTV, combustion occurs. Although the total value of the amount of steam generated by all the boilers during steaming is set, it is not limited to this. For example, in step ST5, the required steam amount calculation unit 42 calculates the boundary where the header pressure value PV is a value obtained by subtracting a preset pressure value α from the target pressure value PTV as the previous required steam amount MV _n−1 . Required steam volume for each control cycle The current required steam amount MV _n may be calculated by adding the amount of change ΔMV _n .

As described above, in the boiler system 1 according to the first embodiment, the number-controlled boiler 20A maintains the in-vessel pressure value PVA at a pressure value PLV that is lower than the target pressure value PTV of the number-controlled boiler group 2. When the number-controlled boiler group is started so that the number-controlled boiler group is controlled so that the header pressure value maintains the target pressure value, the overshoot of the header pressure can be suppressed and stable operation can be achieved.

The boiler system 1 of the first embodiment described above has the following effects.

In the boiler system 1 according to the first embodiment described above, the internal pressure value, which is the pressure value inside the boiler during operation of the number-controlled boiler 20A, is a pressure value lower than the target pressure value PTV of the number-controlled boiler group 2. When the number control of the number-controlled boiler group 2 is started while the PLV is maintained, (i) the header pressure value continues to rise for a predetermined time, and (ii) the required steam amount MV _n reaches the number-controlled boiler group. (iii) the header pressure value is subtracted from the target pressure value PTV by the preset pressure value α It is detected whether the header pressure value has changed from a value smaller than the boundary value to a value exceeding the boundary value or a value exceeding the boundary value, and the header pressure value changes from a value smaller than the boundary value to a value exceeding the boundary value , the required steam amount calculation unit 42 calculates the current required steam amount MV _n or the previous required steam amount MV _n-1 in the process of calculating the current required steam amount MV _n . , when it is detected that the header pressure value has changed from a value smaller than the boundary value to a value exceeding or exceeding the boundary value, all the boilers 20 that are supplying steam to the number-controlled boiler group 2 Set the total amount of generated steam.
As a result, when the number control of the number-controlled boiler group 2 is started while the pressure value PLV lower than the target pressure value PTV of the number-controlled boiler group 2 is maintained in the number-controlled boiler 2A. In addition, overshooting of the header pressure can be suppressed and stable operation can be achieved. As a result, the pressure stability of the boiler system 1 can be improved.

Although a preferred embodiment of the boiler system according to the present invention has been described above, the present invention is not limited to the above-described embodiment and can be modified as appropriate.

In the first embodiment described above, the boiler system 1 including one unit of the number-controlled boiler 20A and the number-controlled boiler group 2 consisting of eight boilers 20 was illustrated, but the present invention is not limited to this. As described above, when the number control of the number-controlled boiler group is started, (i) the boiler not belonging to the number-controlled boiler group is supplying steam, and (ii) the header pressure value is equal to the number-controlled boiler group. Any boiler that satisfies the fact that the pressure is kept lower than the target pressure value set in .
As described above, for example, the unit-uncontrolled boiler 20A is a continuously controlled boiler, and the header pressure value is independently controlled so as to maintain a target pressure value lower than the target pressure value set in the unit-controlled boiler group 2. A group of boilers whose number is controlled may be included. Moreover, the boiler outside the number-controlled boiler 20A may be a boiler that is locally controlled so that the boiler can internal pressure value is maintained at a target pressure value lower than the target pressure value set for the number-controlled boiler group. Also, for boilers that do not belong to the number-controlled boiler group, control is performed so that the maximum set pressure value of the header pressure value falls within a control pressure band that is set at a value lower than the target pressure value set for the number-controlled boiler group 2. It may also include a step value control boiler that is Also, the boilers that do not belong to the number-controlled boiler group may be composed of a plurality of boiler groups. The number-controlled boiler group 2 may be any number of boilers. Boiler capacities (minimum combustion amount, unit steam amount, maximum combustion amount, etc.) may be different.

In the first embodiment described above, the detection unit 41 sets the target pressure value PTV to a value higher than the pressure value PLV, and the number-controlled boiler 20A sets the pressure value PLV lower than the target pressure value PTV of the number-controlled boiler group 2. Condition ( iii), "The header pressure value PV has changed from a value smaller than a boundary value, which is a value obtained by subtracting a preset pressure value α from the target pressure value PTV, to a value exceeding or exceeding the boundary value. ”, but instead, ``the header pressure value PV has changed from a value below the boundary value, which is a value obtained by subtracting a preset pressure value α from the target pressure value PTV, to a value exceeding the boundary value.'' may be Note that when α is a value equal to or greater than a preset second pressure value β and the header pressure value PV < boundary value (PTV-α) while the number-controlled boiler group 2 is stopped. , (i) after starting the number control of the number-controlled _boiler group 2, the header pressure value PV continues to rise for a predetermined time; The above-described correction may be performed at the time when the total amount of steam generated by the inner boilers 20 is exceeded.

In the above-described first embodiment, when controlling the amount of steam in the control unit 4, the PID control is mainly described as the control algorithm, and the details of the PI control are omitted. The steam amount control to be executed is not limited to PID control, and may be PI control.

1 Boiler System 11 Steam Pipe 12 Steam Pipe 13 Signal Line 20A Boiler Outside Control Number 21A Boiler Body 22A Local Control Part 23A Boiler Pressure Detection Part 2 Boiler Control Unit Group 20 Boiler 21 Boiler Body 22 Local Control Part 3 Number Control Device 4 Control Part 41 detection unit 42 required steam amount calculation unit 43 output control unit 5 storage unit 6 steam header 7 steam pressure sensor 16 signal line 18 steam using facility

Claims (3)

a boiler group consisting of a number-controlled boiler group consisting of one or more boilers and one or more boilers not included in the number-controlled boiler group;
a steam header for collecting steam generated in the boiler group;
steam pressure measuring means for measuring a header pressure value, which is the steam pressure inside the steam header;
A boiler system comprising
The number-controlled boiler group includes a control unit that controls the combustion state of the number-controlled boiler group,
The control unit
A required steam amount calculation unit for calculating a current required steam amount _MVn by a rate-type PI algorithm or a rate-type PID algorithm so that the header pressure value measured by the steam pressure measuring means is maintained at a preset target pressure value. When,
an output control unit that controls the combustion state of the boilers in the number-controlled boiler group so as to generate the current required steam amount _MVn calculated by the required steam amount calculating unit;
In a state where one or more boilers not included in the number-controlled boiler group are in operation and the header pressure value transitions at a value lower than the target pressure value of the number-controlled boiler group, the output control unit When the control of the number-controlled boiler group is started, the header pressure value continues to rise for a predetermined time, and the required steam amount _MVn is the steam generated by all the boilers supplying steam to the number-controlled boiler group. when the total value of the volume is exceeded, the header pressure value is less than a boundary value that is the target pressure value minus a preset pressure value α, exceeds the boundary value, or exceeds the boundary value. and a detection unit that detects whether or not the value of
The required steam amount calculation unit further
When the detecting unit detects that the header pressure value has changed from a value smaller than the boundary value to a value exceeding the boundary value or exceeding the boundary value, in the process of calculating the current required steam amount MV _n , It is detected that the header pressure value has changed from a value smaller than the boundary value to a value exceeding the boundary value as the current required steam amount MV _n or the previous required steam amount MV _n-1 . A boiler system for setting the total amount of steam generated by all the boilers supplying steam in the number-controlled boiler group at a time point. When the number-controlled boiler group is started, one or more boilers not included in the number-controlled boiler group are in operation, and the header pressure value is a value lower than the value obtained by subtracting the pressure value α from the target pressure value. 2. The boiler system of claim 1, wherein the transition is . 2. The one or more boilers not included in the number-controlled boiler group include continuously controlled boilers, and the boiler internal pressure value or the header pressure value changes at a value lower than the target pressure value. The boiler system according to claim 2.

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