JP6119253B2 - Boiler system - Google Patents

Description

  The present invention relates to a boiler system that performs unit control.

  Conventionally, a boiler system that generates steam by burning a plurality of boilers is provided with a steam header that collects and stores the steam generated by the plurality of boilers so that the steam pressure in the steam header falls within a certain range. In addition, the control unit controls the number of boilers to be burned and the combustion state of each boiler.

Here, since the stability is lost when the steam pressure in the steam header is significantly reduced, in such a boiler system, a safety device is provided when the steam pressure is lowered. Specifically, when the steam pressure falls below the set value, the boiler control (number control) based on the steam pressure is stopped, all the boilers are burned in a high combustion state, and the steam pressure is quickly raised. .
In this regard, Patent Document 1 is provided with a pressure switch, and when the steam pressure is lower than a set value on the low pressure side and the pressure switch is turned on, all of the plurality of boilers are burned in a high combustion state and the steam pressure is increased. The system is described.

JP 2007-192435 A (paragraphs 0017 and 0022)

By the way, immediately after the boiler is started, the steam is not accumulated in the steam header, and the steam pressure in the steam header is lower than the set value of the pressure switch. However, in the boiler system of Patent Document 1, the boiler is started. Even immediately after, all the boilers are burned in a high combustion state, that is, the number control by the control unit is stopped.
In this regard, when the number control is stopped and all the boilers are burned, the steam pressure in the steam header does not fall within a certain range (control target pressure range) as shown in FIG. 3 as the steam pressure rises. There is a possibility (overshoot). And if the overshoot occurs every time the boiler is started, the equipment is damaged by a water hammer or the like accompanying the subsequent hunting phenomenon.
In addition, if the number control is stopped and all the boilers are burned in a high combustion state, an originally unnecessary boiler is temporarily burned and activated at the time of activation.

  It is an object of the present invention to prevent the number control by the control unit from always stopping in a state where the steam pressure is low in a boiler system including a plurality of boilers. In particular, an object of the present invention is to provide a boiler system that prevents the number control by the control unit from stopping immediately after the boiler is activated, thereby preventing overshooting at the time of boiler activation and unnecessary activation of the boiler.

  The present invention is a boiler system including a boiler group including a plurality of boilers, and a control unit that controls a combustion state of the boiler group according to a required load, wherein the control unit satisfies a predetermined condition. The predetermined condition is satisfied by the condition determining unit that determines whether the output steam pressure output from the boiler group is lower than a first threshold, and the condition determining unit. A control stop unit that stops the control of the combustion state of the boiler group when it is determined that the output steam pressure is lower than the first threshold value by the pressure determination unit. It relates to boiler systems.

  Further, it is preferable that the predetermined condition is satisfied when the output steam pressure exceeds a second threshold value which is a value equal to or higher than the first threshold value.

  Moreover, it is preferable that the said 2nd threshold value is more than the said 1st threshold value, and is below the lower limit of the control object pressure range.

  In addition, the control unit further includes a stop instructing unit for instructing the boiler group to stop, and the established condition is canceled when the stop instructing unit issues a stop instruction to the boiler group. It is preferred that

  According to the present invention, control by the control unit does not stop unless a predetermined condition is satisfied, and therefore control by the control unit does not always stop in a state where the steam pressure is low. In particular, it is possible to prevent the number control by the control unit from being stopped immediately after the boiler is activated, and as a result, it is possible to prevent overshoot at the time of boiler activation and unnecessary activation of the boiler.

It is a figure showing the outline of the boiler system concerning the embodiment of the present invention. It is a graph which shows the relationship between the change of the steam pressure inside a steam header, and the operation state of a boiler group. It is a graph which shows the change of the steam pressure inside the steam header in the past.

  Hereinafter, with reference to FIG. 1, the boiler system 1 which concerns on embodiment of this invention is demonstrated. FIG. 1 is a diagram showing an outline of a boiler system 1 according to an embodiment of the present invention.

  As shown in FIG. 1, the boiler system 1 of the present embodiment includes a boiler group 2 including a plurality of (three) boilers 20, a steam header 6 that collects steam generated in the boiler 20, and steam headers 6. A pressure sensor 7 that measures the internal pressure, a pressure switch 8 that switches ON / OFF according to the internal pressure of the steam header 6, and a unit control device 4 that controls the combustion state of the boiler group 2 are provided.

The boiler group 2 includes a plurality of (three) boilers 20 and generates steam to be supplied to the steam use facility 18 as a load device.
The boiler 20 is composed of a proportional control boiler capable of burning by changing the load factor continuously, or a multi-position control boiler capable of burning by changing the load factor in stages. The proportional control boiler is a boiler in which the combustion amount can be continuously controlled at least from the minimum combustion state (for example, the combustion state at a combustion amount of 20% of the maximum combustion amount) to the maximum combustion state. . A multi-position control boiler has a plurality of combustion positions (combustion stop position, low combustion position, middle combustion position, high combustion position, etc.), and the combustion amount can be controlled in stages by switching the combustion positions. It is a boiler that has been.

As shown in FIG. 1, such a boiler 20 includes a boiler body 21 in which combustion is performed, and a local control unit 22 that controls the combustion state of the boiler 20.
The local control unit 22 changes the combustion state of the boiler 20 according to the required load. Specifically, the local control unit 22 controls the combustion state of the boiler 20 based on a control signal transmitted from the number control device 4 via the signal line 16. Further, the local control unit 22 transmits a signal used in the number control device 4 to the number control device 4 via the signal line 15. Examples of the signal used in the number control device 4 include the actual combustion state of the boiler 20 and other data.

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

  The pressure sensor 7 is electrically connected to the number control device 4 via the signal line 13. The pressure sensor 7 measures the steam pressure inside the steam header 6 (steam pressure generated in the boiler group 2), and controls the number of signals (steam pressure signal) related to the measured steam pressure via the signal line 13. Transmit to device 4.

  The pressure switch 8 is electrically connected to the number control device 4 via the signal line 14. The pressure switch 8 switches the presence or absence of signal output when the steam pressure inside the steam header 6 deviates from the switch operating pressure range K2w (see FIG. 2) having a predetermined upper limit threshold K2u and lower limit threshold K2d. Specifically, the pressure switch 8 changes from the OFF state to the ON state when the steam pressure inside the steam header 6 falls below the lower limit threshold value K2d (first threshold value), and outputs an ON signal to the unit control device 4. On the other hand, the pressure switch 8 changes from the ON state to the OFF state when the steam pressure inside the steam header 6 exceeds the upper limit threshold value K2u, and outputs an OFF signal to the unit control device 4.

  The number control device 4 is electrically connected to a plurality of boilers 20 via signal lines 15 and 16. The number control device 4 controls the combustion state of each boiler 20 based on the steam pressure inside the steam header 6 measured by the pressure sensor 7. Details of the number control device 4 will be described later.

The above boiler system 1 can supply the steam generated in the boiler group 2 to the steam using equipment 18 via the steam header 6.
The load required in the boiler system 1 (required load) is the amount of steam consumed in the steam using facility 18. The number control device 4 calculates the fluctuation of the steam pressure inside the steam header 6 corresponding to the fluctuation of the steam consumption based on the steam pressure (physical quantity) inside the steam header 6 measured by the pressure sensor 7. And the combustion amount of each boiler 20 which comprises the boiler group 2 is controlled.

Specifically, if the required load (steam consumption) increases due to an increase in demand for the steam use facility 18 and the steam amount (output steam amount) supplied to the steam header 6 is insufficient, the inside of the steam header 6 Steam pressure will decrease. On the other hand, if the demand load (steam consumption) decreases due to a decrease in 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 steam pressure measured by the pressure sensor 7. And the boiler system 1 calculates the required steam quantity which is the steam quantity required according to the consumed steam quantity (required load) of the steam use equipment 18 based on the steam pressure inside the steam header 6, The combustion amount of each boiler 20 is controlled so that the amount of steam corresponding to the required amount of steam is supplied.
Note that controlling the boiler 20 by the number control device 4 is sometimes referred to as “number control”, and stopping the control by the number control device 4 and burning the boiler 20 is hereinafter referred to as “manual operation”. Sometimes. In manual operation, all the plurality of boilers 20 are burned in a high combustion state, and the steam pressure is quickly increased.

  Next, details of the number control device 4 will be described. The number control device 4 includes a storage unit 4B and a control unit 4A.

  The storage unit 4 </ b> B is set in the boiler system 1, the contents of instructions given to each boiler 20 under the control of the number control device 4 (control unit 4 </ b> A), information on the combustion state received from each boiler 20, and the like. Information on various thresholds and flags is stored. Various threshold values and flags set in the boiler system 1 will be described later with reference to FIG.

The control unit 4A gives various instructions to the boilers 20 through the signal lines 16 and receives various data from the boilers 20 through the signal lines 15 to determine the combustion states of the plurality of boilers 20. Control. When each boiler 20 receives a combustion state change instruction signal from the unit control device 4, it controls the boiler 20 according to the instruction.
As shown in FIG. 1, the control unit 4 </ b> A includes a condition determination unit 41, a pressure determination unit 42, a control stop unit 43, and a stop instruction unit 44.

Here, as shown in FIG. 2, the following threshold values and flags are set in the boiler system 1 of the present embodiment. FIG. 2 is a graph showing changes in the steam pressure inside the steam header 6.
The thresholds and flags described below are set by the administrator, stored in the storage unit 4B of the number control device 4, and referred to by the control unit 4A.

(1) As shown in FIG. 2, in the boiler system 1, a control target pressure range K1w is set. The control target pressure range K <b> 1 w is a range in which the number control device 4 attempts to contain the steam pressure inside the steam header 6 based on the steam pressure measured by the pressure sensor 7. The upper limit threshold value K1u is a threshold value indicating the upper limit of the control target pressure range K1w. The lower limit threshold value K1d is a threshold value that indicates the lower limit of the control target pressure range K1w.

(2) Moreover, in the boiler system 1, the upper limit threshold value K2u and the lower limit threshold value K2d of the switch operating pressure range K2w for switching between the ON state and the OFF state of the pressure switch 8 are set. The upper limit threshold value K2u is a threshold value at which the pressure switch 8 changes from the ON state to the OFF state (the ON signal is not output from the state where the ON signal is output). The lower limit threshold value K2d is a threshold value at which the pressure switch 8 changes from the OFF state to the ON state (the ON signal is output from the state where the ON signal is not output). The lower limit threshold K2d is lower than the upper limit threshold K2u by a differential value (the same size as the switch operating pressure range K2w).

  In the boiler system 1, a manual operation valid flag is set. The manual operation valid flag is a flag for determining whether or not to enable manual operation. When the manual operation valid flag is established, the manual operation is valid, and when the manual operation valid flag is not established. Manual operation is disabled.

(3) The manual operation valid flag is established when the steam pressure exceeds a flag update threshold (second threshold) set as a value equal to or higher than the lower limit threshold K2d of the switch operating pressure range K2w, and is updated from the unestablished state to the established state. (The lower limit threshold K2d or more is synonymous with the steam pressure or more at which the pressure switch 8 is turned on from the OFF state). As described above, in the boiler system 1, since the steam pressure inside the steam header 6 is stored in the range of the control target pressure range K1w, the upper limit value of the flag update threshold is set as the lower limit threshold of the control target pressure range K1w. More preferably, it is set to K1d.
Here, since the boiler system 1 according to the present invention is configured to prevent manual operation immediately after start-up, that is, to prevent all the boilers 20 from being burned in a high combustion state immediately after start-up, the flag update threshold is set to the pressure switch 8. May be equal to or higher than the lower limit threshold K2d of the switch operating pressure range K2w in which is turned on, and can be set to an arbitrary value. In this regard, in this embodiment, the lower limit threshold value K1d of the control target pressure range K1w is adopted as the flag update threshold value, and the manual operation valid flag is updated based on the steam pressure measured by the pressure sensor 7. Of course, a value different from the lower limit threshold K1d of the control target pressure range K1w can be adopted as the flag update threshold. As an example, when the upper limit threshold K2u of the switch operating pressure range K2w is adopted, the manual operation valid flag may be updated based on not only the signal from the pressure sensor 7 but also the ON / OFF signal of the pressure switch 8. it can.
With such a setting, manual operation immediately after the startup of the boiler group 2 can be invalidated, while the steam pressure inside the steam header 6 significantly decreases after the transient state after startup becomes stable and steady. In this case, the unit pressure control can be stopped and the steam pressure can be quickly increased by manual operation.

(4) Further, the establishment of the manual operation valid flag is canceled when a stop instruction is given to the boiler group 2, and is updated from the established state to the unestablished state. Accordingly, the manual operation valid flag is not established when the boiler group 2 is stopped, and it is possible to prevent manual operation from being performed when the boiler group 2 is started thereafter. The stop instruction is an instruction to stop the boiler group 2, and the output mode is not particularly limited. As an example, in the boiler system 1, a stop instruction is output by an operation of a stop switch by an operator, an alarm stop, a stop by a program function based on an operation schedule, or the like.

Returning to FIG. 1, the condition determination unit 41 refers to the storage unit 4 </ b> B to determine whether or not the manual operation valid flag (predetermined condition) is established.
Moreover, the pressure determination part 42 determines whether the output steam pressure (steam pressure inside the steam header 6) output from the boiler group 2 is lower than the lower limit threshold K2d (first threshold). Specifically, the pressure determination unit 42 determines whether or not the signal output from the pressure switch 8 has been switched from the OFF signal to the ON signal, thereby determining whether or not the lower limit threshold K2d has been reached. Of course, the pressure determination unit 42 may determine whether or not the steam pressure inside the steam header 6 is lower than the lower limit threshold K2d based on a signal output from the pressure sensor 7.

The control stop unit 43 determines that the manual operation valid flag is established by the condition determination unit 41 and the pressure determination unit 42 determines that the steam pressure inside the steam header 6 has fallen below the lower limit threshold K2d. Then, control of the combustion state of the boiler group 2 by the number control device 4 (number control) is stopped. Thereby, the control of the boiler group 2 is switched from the unit control to the manual operation, all of the plurality of boilers 20 are burned in a high combustion state, and the steam pressure is quickly increased. Therefore, stopping the number control by the control stop unit 43 is synonymous with burning all of the plurality of boilers 20 in a high combustion state.
Further, the stop instruction unit 44 instructs the boiler group 2 to stop.

  Next, with reference to FIG. 2, operation | movement of the boiler system 1 of this embodiment is demonstrated.

(1) Time t0 is a timing at which the stopped boiler group 2 starts activation. At this time t0, since it is immediately after startup, steam is not accumulated in the steam header 6, and an ON signal is output from the pressure switch 8, but since the boiler group 2 has stopped, the manual operation valid flag is not established. It is in a state. That is, although the steam pressure is low, the manual operation is set to be invalid. Therefore, the boiler group 2 is controlled by the control unit 4A of the number control device 4 so that all the plurality of boilers 20 are not burned in a high combustion state, for example, the required number of boilers 20 are warmed up with low combustion. .

(2) Time t1 is a timing at which the steam pressure inside the steam header 6 reaches the lower limit threshold K1d of the control target pressure range K1w after the start. At time t1, although the manual operation valid flag is updated from the unestablished state to the established state, the pressure switch 8 has already switched from the ON state to the OFF state, and the OFF signal is output from the pressure switch 8. Therefore, the boiler group 2 is controlled by the control unit 4A of the number control device 4, and the combustion state of the boiler 20 is controlled so that, for example, the steam pressure inside the steam header 6 falls within the control target pressure range K1w.

(3) At time t2, when the steady state is reached, the steam pressure inside the steam header 6 falls to the lower threshold K2d of the switch operating pressure range K2w, in other words, some abnormality occurs after the steady state is reached. Equally, the steam pressure inside the steam header 6 deviates significantly from the control target pressure range K1w. At time t2, the pressure switch 8 is switched from the OFF state to the ON state, and the ON signal is output from the pressure switch 8. Moreover, since it is not immediately after starting of the boiler group 2, a manual driving effective flag is also established. Therefore, the control by the control unit 4A of the number control device 4 is stopped, and the boiler group 2 is in a manual operation state. That is, all of the plurality of boilers 20 are burned in a high combustion state, and the steam pressure is increased.

(4) Time t3 is a timing at which the steam pressure inside the steam header 6 rises to the upper limit threshold K2u of the switch operating pressure range K2w with manual operation. At time t3, although the manual operation valid flag is established, the pressure switch 8 is switched from the ON state to the OFF state, and the OFF signal is output from the pressure switch 8. Therefore, the manual operation is finished, and the boiler group 2 is controlled by the control unit 4A of the number control device 4, and the combustion state of the boiler 20 is set so that, for example, the steam pressure inside the steam header 6 falls within the control target pressure range K1w. Be controlled.

(5) Time t4 is a timing at which a stop instruction is given to the boiler group 2. At time t4, the establishment of the manual operation valid flag is canceled based on the stop instruction, and the state is updated to an unestablished state. In the boiler group 2, the combustion of all the boilers 20 is stopped in accordance with the stop instruction, and the steam pressure inside the steam header 6 is reduced.

(6) Time t5 is a timing at which the steam pressure inside the steam header 6 drops to the lower limit threshold K2d of the switch operating pressure range K2w after the combustion of all the boilers 20 is stopped. At time t5, the pressure switch 8 is switched from the OFF state to the ON state, and an ON signal is output from the pressure switch 8. In addition, since the manual operator effective flag is not established, the steam pressure inside the steam header 6 is lowered while the combustion is stopped in the boiler group 2 without performing manual operation.

  The boiler system 1 of the present embodiment has been described above. According to such a boiler system 1, for example, the following effects are exhibited.

In the boiler system 1, the control stop unit 43 determines that the manual operation valid flag is established by the condition determination unit 41, and the pressure determination unit 42 determines that the steam pressure inside the steam header 6 is within the switch operating pressure range K2w. When it is determined that the value is below the lower limit threshold K2d (time t2 in FIG. 2), the number control by the number control device 4 is stopped and the boiler group 2 is manually operated.
Thereby, even if the steam pressure inside the steam header 6 is low, the number control by the number control device 4 stops in a state where the manual operation valid flag is not established (time t0 to t1 in FIG. 2). Therefore, the originally unnecessary boiler 20 is not burned.

Moreover, in the boiler system 1, the flag update threshold value in which the steam pressure inside the steam header 6 is a value equal to or higher than the lower limit threshold K2d of the switch operating pressure range K2w (more preferably, the lower limit threshold K1d of the control target pressure range K1w) is set. If exceeded, the manual operation valid flag was established.
As a result, the number control by the number control device 4 does not stop immediately after the boiler startup when the steam pressure inside the steam header 6 is below the lower threshold K2d regardless of the abnormality, Unnecessary boiler activation can be prevented. On the other hand, when the steam pressure inside the steam header 6 drops due to some abnormality after the steady state is reached, the number control is stopped and manual operation is performed, so safety when the steam pressure drops can be ensured. .

In the boiler system 1, the steam pressure inside the steam header 6 uses the lower limit threshold value K1d of the control target pressure range K1w as the flag update threshold value.
Thereby, the manual operation valid flag can be updated after the steam pressure inside the steam header 6 is stabilized.

In the boiler system 1, the stop instruction unit 44 that instructs the boiler group 2 to stop is provided, and the establishment of the manual operation valid flag is canceled in accordance with the stop instruction by the stop instruction unit 44.
Thus, since the manual operation valid flag is not established at the next start-up, it is possible to prevent overshoot at the time of boiler start-up and unnecessary start-up of the boiler.

As mentioned above, although demonstrated about preferable embodiment of the boiler system 1 of this invention, this invention is not restrict | limited to the above-mentioned embodiment, It can change suitably.
For example, in the above embodiment, when the steam pressure inside the steam header 6 exceeds the upper limit threshold K2u of the switch operating pressure range K2w, the pressure switch 8 changes from the ON state to the OFF state, and the steam pressure is the lower limit threshold of the switch operating pressure range K2w. When the pressure switch 8 falls below K2d, the pressure switch 8 changes from the OFF state to the ON state, and when the predetermined condition is satisfied with the pressure switch 8 in the ON state, the operation is switched to manual operation. In this regard, considering the backup at the time of disconnection of the signal line 14 connecting the pressure switch 8 and the unit control device 4 (switching to the manual operation), the condition for switching between the ON state and the OFF state, and the condition for switching to the manual operation May be reversed. That is, when the steam pressure inside the steam header 6 exceeds the upper limit threshold K2u of the switch operating pressure range K2w, the pressure switch 8 changes from the OFF state to the ON state, and when the steam pressure falls below the lower limit threshold K2d of the switch operating pressure range K2w The switch 8 may be switched to the manual operation when a predetermined condition is satisfied in a state where the switch 8 is turned off and the pressure switch 8 is turned off.

  For example, in the said embodiment, although this invention was applied to the boiler system 1 provided with the boiler group 2 which consists of the three boilers 20, it is not restricted to this. That is, the present invention may be applied to a boiler system including a boiler group including four or more boilers, or may be applied to a boiler system including a boiler group including two boilers.

DESCRIPTION OF SYMBOLS 1 Boiler system 2 Boiler group 20 Boiler 4 Number control apparatus 4A Control part 41 Condition determination part 42 Pressure determination part 43 Control stop part 44 Stop instruction | indication part K2d Lower limit threshold value (1st threshold value)
K2u upper limit threshold, flag update threshold (second threshold)

Claims (3)

A boiler system including a boiler group including a plurality of boilers, and a number control unit that controls a combustion state of the boiler group according to a required load,
The number controller is
A condition determination unit for determining whether or not a predetermined condition is satisfied;
A pressure determination unit that determines whether or not an output steam pressure output from the boiler group has fallen below a first threshold after it is determined that the predetermined condition is satisfied by the condition determination unit;
After the predetermined condition is determined to be satisfied by the condition judging section, wherein when the said output vapor pressure by the pressure determination unit is determined lower than the first threshold value, the number of the combustion state of the boiler group A control stop unit for stopping control,
When the unit control is stopped by the control stop unit, all the boilers in the boiler group are burned by manual operation,
The boiler system characterized in that the predetermined condition is that the output steam pressure exceeds a second threshold value that is a value equal to or greater than the first threshold value .   The boiler system according to claim 1, wherein the second threshold value is equal to or lower than a lower limit value of a control target pressure range. The number control unit further includes a stop instruction unit that gives a stop instruction to the boiler group,
3. The boiler system according to claim 1, wherein the predetermined condition that is satisfied is canceled when the stop instruction unit issues a stop instruction to the boiler group. 4.

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