JP3818459B2 - Boiler control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a boiler control device for a boiler plant in which a once-through boiler and a different type of boiler different from the once-through boiler are integrated to supply steam to a common load from a common steam supply unit.
[0002]
[Prior art]
Some boiler plants that supply steam based on demand in factories or the like integrate and supply steam generated by many boilers. Among them, there is a boiler plant in which a once-through boiler and a boiler of a different type from a once-through boiler such as a water tube boiler and a flue tube boiler are arranged in parallel. In addition, there is a boiler plant in which a water tube boiler, a furnace flue tube boiler, and the like are already installed, and an once-through boiler that is easy to operate is added or partially replaced. In such a boiler plant, conventionally, different types of boiler groups have been independently operated and controlled. Usually, the once-through boiler is operated by three-position control, and a different type boiler such as a water tube boiler is operated by proportional control or proportional-integral control.
[0003]
However, in such control, each boiler performs self-control, so the once-through boiler frequently turns on / off or repeats low combustion / high combustion, and stable operation is not performed. There is a problem in that the load followability is deteriorated because the once-through boiler is operated after the remaining capacity of the different types of boilers is lost. Also, when the different types of boilers are controlled by proportional integral control, the amount of evaporation of the different types of boilers becomes the maximum or minimum and can no longer follow the load fluctuation, and the once-through boiler is turned on / off after the steam pressure drops or rises. There was a problem that it would be turned off or switched to high combustion / low combustion, and that time would be further delayed.
[0004]
[Problems to be solved by the invention]
The present invention solves the above-described problems in the prior art, and provides a boiler control apparatus that can follow a load variation and can operate a boiler efficiently in a boiler plant that uses both a once-through boiler and another type of boiler. This is the issue.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides a steam supply system for supplying a steam to a common load from a common steam supply unit by integrating a once-through boiler and a different type of boiler different from the once-through boiler. In the boiler control device of the boiler plant
A once-through boiler individual control unit for controlling the operation of the once-through boiler;
A pressure detection unit for detecting a vapor pressure of the common steam supply unit;
A heterogeneous boiler control unit that controls the amount of fuel of the heterogeneous boiler corresponding to the detected pressure of the pressure detection unit;
A fuel amount corresponding signal transmitting unit for transmitting a fuel amount corresponding signal which is an amount corresponding to the fuel amount;
An evaporation amount increase / decrease determination unit for determining a lower value and an upper value of the fuel amount corresponding signal;
The determined value of the evaporation amount increase / decrease determination unit and the transmission value of the fuel amount corresponding signal transmission unit are input and compared, and when the transmission value becomes larger than the upper value, the evaporation amount of the once-through boiler is increased, and A once-through boiler operation command unit that sends a signal to the once-through boiler individual control unit so as to reduce the evaporation amount of the once-through boiler when the transmitted value is smaller than the lower value;
It is characterized by having.
[0006]
In addition to the above, the invention of claim 2 is provided with a plurality of the once-through boilers, and has an operation order determining unit that determines an operation order of the plurality of once-through boilers, and the once-through boiler operation command unit includes: The evaporation amount of the once-through boiler is increased or decreased according to the order determined by the operation order determining unit.
[0007]
The invention of claim 3 is characterized in that, in addition to the above, the operation order can be automatically changed.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an example of a boiler plant including a boiler control device to which the present invention is applied.
The boiler plant integrates the first to third once-through boilers 1, 2, and 3 as the once-through boiler and the flue tube boiler 4 as the different type boiler different from the once-through boiler, and is a common steam supply unit. Steam is supplied from the steam header 5 to the common load. The boiler control device includes each of the once-through boiler control devices 11, 21, and 31 as the once-through boiler individual control unit, the pressure detector 6 as the pressure detection unit, the furnace boiler control device 41 as the different boiler control unit, A proportional control unit 41a, an evaporation amount increase / decrease determination unit 7, an operation number control device 8 as a once-through boiler operation command unit, an operation order determination unit 9 and the like are provided.
[0009]
The once-through boilers 1, 2, and 3 have the same configuration in this example. Therefore, the first once-through boiler 1 will be described. The first once-through boiler 1 is a three-position controlled boiler that is controlled to one of three states of stop, low combustion, and high combustion, and includes a low combustion fuel valve 12, a high combustion fuel valve 13, The damper 14 etc. which are set to the opening degree corresponding to each of three positions are provided. The once-through boiler control device 11 opens the fuel valve 12 and closes the fuel valve 13 to set the damper 14 at the low combustion position when performing low combustion, and opens the fuel valves 12 and 13 to raise the damper 14 when performing high combustion. Set to combustion position. The operation is performed in the order of stop-low combustion-high combustion, and pre-purge and post-purge are performed between the stop-low combustion.
[0010]
The furnace tube smoke tube boiler 4 includes the furnace tube boiler control device 41, a proportional controller 41a therein, a fuel valve 42, an air damper 43, a servo motor 44, and the like. The pressure detector 6 detects the pressure of the steam header 5, and the furnace boiler control device 41 controls the fuel amount corresponding to the pressure detected by the pressure detector 6, but in this example, it is proportional by the proportional control unit 41 a. Control. Thus, for example, as shown in FIG. 2, between 7 kgf / cm ² and 8 kgf / cm ² as a vapor pressure, and outputs a maximum signal of 100% at 7 kgf / cm ^2, 10% as the minimum signal at 8 kgf / cm ² In this period, the signal Fpv is output linearly, and this signal is given to the servo motor 44, and the servo motor 44 rotates linearly in the range of 0 ° to 90 °, for example. This rotation is transmitted to the fuel valve 42 and the air damper 43 by a link mechanism or the like, and eventually the fuel amount is controlled in inverse proportion to the steam pressure, and the necessary air amount is supplied thereto.
[0011]
In this example, a proportional control unit 41 a in the furnace boiler control device 41 is used as a fuel amount corresponding signal transmitting unit that transmits a fuel amount corresponding signal that is an amount corresponding to the fuel amount. That is, the signal Fpv transmitted from the proportional control unit 41a controls the amount of fuel via the rotation angle of the servo motor 44, so that the signal is a signal corresponding to the amount of fuel. However, the fuel amount corresponding signal transmitting unit is not limited to the proportional control unit 41a, and may be an appropriate detector such as a detector that detects and transmits the rotation angle of the servo motor, the actual fuel flow rate, the converted value of the steam pressure, and the like. It may be anything.
[0012]
As shown in FIG. 2, the evaporation amount increase / decrease signal determination unit 7 determines, for example, 40% as the lower value Fsv ₁ and 80% as the upper value Fsv ₂ of the fuel amount corresponding signal Fpv in the range of 10% to 100%. This determination is usually made by setting an adjustable setter by a person, but it may be set to a constant value from the beginning, or automatically determined from the value of the proportional control band. It may be like this.
[0013]
The operation order determining unit 9 determines the operation order of a plurality of boilers, and this determination is also usually provided with an adjustable setter, and in this example, for example, the once-through boilers 1, 2, 3 Although it is performed by a person setting to drive sequentially, a certain order may be determined from the beginning. However, in order to equalize the operation time of each once-through boiler, it is desirable to automatically rotate the operation order every week by, for example, a calendar timer.
[0014]
The number-of-operations control device 8 is formed by, for example, a microcomputer or the like, and the determined values Fsv ₁ (40% in the previous example) and Fsv ₂ (80% in the previous example) of the evaporation amount increase / decrease determination unit 7 and the proportional control unit of the furnace boiler control device The transmission value Fpv (from 10% to 100% in the previous example) is input and compared. When the transmission value exceeds the upper value Fsv ₂ , the evaporation amount of the once-through boiler increases, and the transmission value is the lower value. When it becomes smaller than Fsv ₁ , a signal is transmitted to the once-through boiler control devices 11, 21, and 31 according to the determination of the operation order determination unit 9 so as to reduce the evaporation amount of the _once- through boiler. In this case, in the once-through boiler controlled at three positions as in this example, the increase or decrease in the evaporation amount is stepwise in three states: stop-low combustion (hereinafter referred to as “L”) — high combustion (hereinafter referred to as “H”). To be done. 1 shows an example in which the operation number control device 8 includes the evaporation amount increase / decrease determination unit 7 and the operation order determination unit 9, but the operation number control device 8 is installed on the boiler side and determined. The units 7 and 9 may be installed in the operation monitoring room of the boiler plant so that they can be set remotely.
[0015]
FIG. 3 shows the operation state of the boiler plant by the above control.
For example, in a certain operation state A, the operation order of the once-through boilers 1, 2, and 3 is determined in this order, and the furnace boiler 4 and the once-through boiler 1 are operated at the low combustion L and are detected by the pressure detector 6. The steam pressure is 7.5 kgf / cm ² , and the furnace boiler 4 is stably controlled in proportion to the fuel amount of 60%. The operation state at this time is indicated by “A: R + 1L”.
[0016]
Next, assuming that the steam consumption on the steam demand side in factories and the like increases rapidly, the steam pressure drops to about 7.2 kgf / cm ² or less, which corresponds to an 80% fuel amount, and the fuel amount of the furnace boiler 4 is reduced. The flow-through boiler 1, which is controlled at three positions so as to increase the amount of evaporation, becomes 80% or more and changes from L to high combustion H, and tries to respond to steam demand.
According to this control, rapid evaporation increase by proportional control of the furnace boiler, replenishment of evaporation due to evaporation of the retained water in the furnace boiler with a large amount of water and a large time constant, and instantaneous evaporation of the once-through boiler With the increase, both boilers will respond very effectively to the sudden increase in load. The operating state at this time is indicated by “B: R + 1H”.
[0017]
If the degree of rapid increase in load is large and the steam pressure further decreases or does not recover to a pressure of 7.2 kgf / cm ² corresponding to 80% of the fuel amount, the once-through boiler will increase the evaporation amount according to priority. 2 is driven. In this case, in order to reflect the effect of increasing the evaporation amount due to the switching of the once-through boiler 1 from L to H, etc., a certain time of about 20 seconds, for example, is set with a timer or the like, and after this time has passed, It is desirable to increase the evaporation amount of the boiler 2.
[0018]
The once-through boiler 2 is started from the stop and becomes L. At this time, for example, a pre-purge time of about 30 seconds is required. In the steam plant of this example, there is a furnace boiler with a large time constant, so even if there is such a pre-purge time, the steam pressure may not decrease much. However, in order to prevent a time delay for pre-purging, when the once-through boiler 1 becomes H, control may be performed so that pre-purge of the once-through boiler 2 is started immediately. The state at this time is indicated by “C: R + 1H + 2L”. Although the control is somewhat complicated, when the state of B, that is, the once-through boiler 1 becomes H, the once-through boiler 2 is activated and set to L so that the evaporation amount of the next once-through boiler can be immediately increased. It is also possible to use a control method in which the once-through boiler 1 is changed from H to L, the L boiler is always secured, and the evaporation amount can be increased without the need for pre-purge.
[0019]
Thus, even when the degree of sudden increase in the load is large, according to the control of this example, before the fuel amount of the furnace boiler reaches 100%, that is, while the furnace boiler has sufficient capacity to increase the evaporation amount. Further, the rapid activation of the once-through boiler and the large time constant of the furnace tube boiler can suppress the decrease in steam pressure very effectively.
[0020]
If the steam pressure rises and recovers to, for example, 7.5 kgf / cm ² and stabilizes at the point F after “E: R + 1H + 2H + 3L” by such control, this operation state is maintained. When the boiler load decreases, the same process as described above is followed, and the once-through boiler sequentially decreases the evaporation amount. This state is indicated by G, H, I, J, and K in FIG. Even in this case, the excessive increase in the steam pressure is effectively prevented by the once-through boiler capable of quickly reducing the load. Further, according to the control as described above, a state in which the furnace boiler is operated at a low load for a long time while operating the once-through boiler is avoided, so that the boiler plant can be efficiently operated as a whole.
[0021]
In the above description, the example in which the furnace flue tube boiler is proportionally controlled has been described. However, the present invention can also be applied to a case where proportional integral control is performed. In this case, the fuel amount control signal PID is transmitted and controlled so that the vapor pressure detected by the pressure detector 6 becomes constant. Therefore, as in the case of proportional control, the evaporation amount of the once-through boiler can be increased or decreased using the upper and lower values of the PID signal.
[0022]
Note that when the furnace tube boiler 4 is not in operation, the fuel supply amount signal is not transmitted by the furnace tube boiler control device 41, so that only the once-through boilers with the once-through boilers 1, 2, and 3 are in an operating state. In this case, the normal once-through boiler group is controlled by, for example, a method using the priority order as described above. For this purpose, as shown in FIG. 1, the pressure of the pressure detector 6 is introduced into the operation number control device 8, and control using this pressure is performed. In order to prevent the control from being confused even when a sudden stop such as a trip of the furnace tube boiler 4 is performed, when the operation signal of the furnace tube boiler 4 is introduced into the operation number control device 8 and the operation is stopped, only the once-through boiler group is immediately It is desirable to switch to operation.
[0023]
In the above, an example in which three once-through boilers are provided has been described. However, the present invention is naturally not limited to such a number, and can be applied to a case in which only one once-through boiler is provided. In this case, the operating number control device 8 is an evaporation amount switching control device. This device may be integrated with the once-through boiler control device 11.
[0024]
Furthermore, although the case where the dissimilar boiler is one furnace tube boiler has been described above, the present invention can be similarly applied even when there are a plurality of furnace tube boilers. In this case, a fuel corresponding amount signal is sent from the control device for any one of the operated furnace boilers to the operating number control device 8. Further, the different type boiler may be another type of boiler such as a water tube boiler. In this case, the different types of boilers may be of a plurality of different types. In any case, the effects as described above are exhibited by the application of the present invention.
[0025]
【The invention's effect】
As described above, according to the present invention, in a boiler plant including a once-through boiler and a heterogeneous boiler, a fuel amount corresponding signal transmission unit and an evaporation amount increase / decrease signal determination unit are provided, and a once-through boiler operation is performed. The command unit compares both signals, and controls to increase / decrease the evaporation amount of the once-through boiler when the former exceeds the upper / lower value of the latter. Along with the increase / decrease capability, the rapid evaporation amount increase / decrease capability of the once-through boiler can be effectively utilized to perform control with extremely good followability to load fluctuations. Further, since the furnace tube boiler is not operated at a low load for a long time while operating the once-through boiler, the boiler plant can be operated efficiently.
[0026]
In the invention of claim 2, when a plurality of once-through boilers are provided, an operation order determining unit for determining the operation order of these boilers is provided, and the evaporation amount of the once-through boiler is increased or decreased according to the determination. The once-through boiler of the table is smoothly controlled, and the above effect can be obtained.
[0027]
In the invention of claim 3, since the operation order is automatically changed, the operation time of a plurality of once-through boilers can be averaged.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a boiler plant to which a boiler control device of the present invention is applied.
FIG. 2 is an explanatory diagram showing a relationship between a fuel amount correspondence signal and its upper and lower values in the control device.
FIG. 3 shows an operation state of a boiler plant using the control device, where (a) shows a case where the boiler load increases and (b) shows a case where the boiler load decreases.
[Explanation of symbols]
1, 2, 3 1st to 3rd once-through boiler (through-flow boiler)
4 Furnace fire tube boiler (different type boiler)
5 Steam header (common steam supply part)
11, 21, 31 Cross-flow boiler control device (through-flow boiler individual control unit)
6 Pressure detector (pressure detector)
7 Evaporation amount increase / decrease signal determination unit 8 Number of units control device (through-flow boiler operation command unit)
9 Operation order determination unit 41 Furnace boiler control device (heterogeneous boiler control unit)
41a Proportional control unit (fuel quantity compatible signal transmitter)

Claims (3)

In a boiler control device for a boiler plant in which a once-through boiler and a different type of boiler different from the once-through boiler are integrated to supply steam to a common load from a common steam supply unit,
A once-through boiler individual control unit for controlling the operation of the once-through boiler;
A pressure detection unit for detecting a vapor pressure of the common steam supply unit;
A heterogeneous boiler control unit that controls the amount of fuel of the heterogeneous boiler corresponding to the detected pressure of the pressure detection unit;
A fuel amount corresponding signal transmitting unit for transmitting a fuel amount corresponding signal which is an amount corresponding to the fuel amount;
An evaporation amount increase / decrease determination unit for determining a lower value and an upper value of the fuel amount corresponding signal;
The determined value of the evaporation amount increase / decrease determination unit and the transmission value of the fuel amount corresponding signal transmission unit are input and compared, and when the transmission value becomes larger than the upper value, the evaporation amount of the once-through boiler is increased, and A once-through boiler operation command unit that sends a signal to the once-through boiler individual control unit so as to reduce the evaporation amount of the once-through boiler when the transmitted value is smaller than the lower value;
A boiler control device comprising: A plurality of the once-through boilers are provided, and an operation order determining unit that determines an operation order of the plurality of once-through boilers is provided, and the once-through boiler operation command unit is arranged according to the order determined by the operation order determining unit. The boiler control device according to claim 1, wherein the amount of evaporation of the boiler is increased or decreased. The boiler control device according to claim 2, wherein the operation order can be automatically changed.

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