JP6337697B2 - Boiler system - Google Patents

Description

  The present invention relates to a boiler system that controls a combustion amount of a boiler according to steam consumption by a PI or PID algorithm.

  DESCRIPTION OF RELATED ART Conventionally, the boiler system provided with the boiler and the control part which controls the combustion amount of a boiler according to the steam consumption (required load) of a steam using facility is known. In such a boiler system, the steam pressure of the steam header (hereinafter also referred to as “header pressure”) is adjusted according to the fluctuation of the steam consumption so that the target steam pressure value is constant regardless of the fluctuation of the steam consumption. The amount of combustion of the boiler is controlled. Conventionally, in order to keep the steam pressure value of the steam header at the target steam pressure value against fluctuations in steam consumption, a method of controlling the steam amount (hereinafter also referred to as “indicated steam amount”) to be generated in the boiler by a PID algorithm Has been proposed (see, for example, Patent Documents 1 and 2).

JP 2002-73105 A Japanese Patent No. 3805611

In PID control, the total value of the operation amount calculated in each of the P control, I control, and D control is final. In PI control, the total value of the operation amount calculated in each of the P control and I control is final. Operating amount (also referred to as “indicated steam amount”). When boiler number control is performed by PID control (or PI control), if the header pressure is less than the target pressure, the I-control operation amount will continue to increase, and conversely, the header pressure may be in the state where the target pressure exceeds the target pressure. In this case, the amount of operation for I control continues to decrease.
If the header pressure exceeds the target pressure due to a decrease in load, the amount of I control operation up to that point can remain, so that the combustion boiler can be secured, but if the header pressure exceeds the target pressure, the I will gradually increase. The control operation amount continues to decrease, and eventually the final operation amount becomes 0 or less, so that all boilers may stop (hereinafter also referred to as “all can stop”).
When all the cans are stopped, the header pressure greatly decreases due to the start delay after the combustion stops, and the header pressure becomes unstable.
Further, in this case, an excessive amount of I-control operation calculated by PID calculation (or PI calculation) is secured. Thereafter, the boiler starts burning and the amount of generated steam increases, so that the header pressure value changes from decreasing to increasing. The operation amount (indicated steam amount) continues to decrease from the time when the header pressure value starts to increase, but at that time, an excessive amount of operation for I control is ensured. And since the generated steam volume has not caught up with the manipulated volume (indicated steam volume), the generated steam volume continues to increase, and the header pressure value continues to increase. If the upper limit of pressure is exceeded, all cans are stopped, and the header pressure value may drop rapidly.
When this repetition occurs, a so-called hunting phenomenon in which the header pressure value fluctuates up and down without converging to the target steam pressure value may occur and may continue.
Thus, from the viewpoint of ensuring pressure stability at low loads, although the header pressure exceeds the target pressure, if the header pressure is in a downward trend, it is desirable to continue combustion instead of stopping all cans. I can say that.

  The present invention provides an operation amount by PID calculation (or PI calculation) when the header pressure exceeds the target pressure due to overshoot when the load is suddenly reduced and then the pressure starts to drop while the header pressure exceeds the target pressure. It is an object of the present invention to provide a boiler system that avoids stopping all cans even when is 0 or less and quickly converges a header pressure value to a target vapor pressure value.

  The present invention is composed of one or more boilers that can be combusted by changing a combustion rate, a boiler group that supplies steam to a load device, a steam header in which steam generated in the boiler group gathers, and a load device A control unit that controls a combustion state of the one or more boilers in accordance with a required load of the steam, and the control unit sets a steam pressure value inside the steam header to a target steam with respect to fluctuations in steam consumption. An operation amount calculation unit that calculates an operation amount by a PI algorithm or a PID algorithm so as to maintain a pressure value, and a combustion state of the one or more boilers is controlled based on the operation amount calculated by the operation amount calculation unit An output control unit that performs, a first detection unit that detects that a steam pressure value inside the steam header exceeds a target pressure value, and whether or not the steam pressure value inside the steam header tends to increase Detect A second detector, and when the operation amount calculated by the operation amount calculator is less than or equal to zero, the output controller determines a steam pressure value inside the steam header by the first detector. When it is detected that the target pressure value is exceeded, and the second detection unit detects that the steam pressure value inside the steam header tends to increase, all the one or more boilers are in a combustion stopped state. The present invention relates to a boiler system.

  When the operation amount calculated by the operation amount calculation unit is less than or equal to zero, the output control unit is configured such that the steam pressure value inside the steam header does not exceed a target pressure value by the first detection unit. If one of the one or more boilers is detected, or if the second detection unit detects that the steam pressure value inside the steam header is not in an upward trend, the boiler is brought into a minimum combustion state. be able to.

  The minimum combustion state is preferably a combustion state with a combustion rate of 20%.

  The control unit presets a control pressure upper limit value as a threshold value for bringing all of the one or more boilers into a combustion stop state, and the output control unit determines that the steam pressure value inside the steam header is equal to the control pressure upper limit value. If the value is exceeded, all of the one or more boilers can be put into a combustion stopped state.

  According to the present invention, when the header pressure exceeds the target pressure due to overshoot when the load is suddenly reduced, and then the header pressure changes to a pressure drop with the target pressure exceeding the target pressure, the PID calculation (or PI calculation) is performed. Even if the operation amount is 0 or less, it is possible to provide a boiler system that avoids stopping all cans and quickly converges the header pressure value to the target vapor pressure value.

It is a schematic structure figure of boiler system 1 concerning one embodiment of the present invention. It is a figure which shows the outline of a boiler group. It is a functional block diagram which shows the structure of a control part. It is a graph which shows the steam pressure and the amount of steams when pressure control is implemented only by the usual PID algorithm, using a boiler system consisting of a single boiler as a model. The figure which shows the time transition of the header pressure value at the time of implementing the pressure control by the PID algorithm which concerns on one Embodiment of this invention in addition to the pressure control by a normal PID algorithm, using the boiler system which consists of a single boiler as a model. It is. It is a graph which shows the steam pressure and the amount of steams when pressure control is implemented only by the usual PID algorithm, using a boiler system consisting of a single boiler as a model. The figure which shows the time transition of the header pressure value at the time of implementing the pressure control by the PID algorithm which concerns on one Embodiment of this invention in addition to the pressure control by a normal PID algorithm, using the boiler system which consists of a single boiler as a model. It is.

  Hereinafter, a preferred embodiment of a boiler system according to the present invention will be described with reference to the drawings.

  First, an embodiment of a boiler system according to the present invention will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram of a boiler system 1 according to an embodiment.

  As shown in FIG. 1, the boiler system 1 according to the present embodiment includes a boiler group 2 including five boilers 20, a steam header 6 that collects steam generated in the boiler 20, and an interior of the steam header 6. A vapor pressure sensor 7 for measuring pressure and a number control device 3 for controlling the combustion state of the boiler group 2 are provided.

  The boiler group 2 includes five boilers 20 and generates steam to be supplied to the steam use facility 18 as load equipment. Each boiler 20 generates steam (heat energy) according to the amount of combustion of fuel. That is, the boiler 20 of this embodiment is a steam boiler.

  As shown in FIG. 1, the 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 steam consumption. Specifically, the local control unit 22 controls the combustion state of the boiler 20 based on the number control signal transmitted from the number control device 3 via the signal line 16. The number control signal will be described later. Further, the local control unit 22 transmits a signal used in the number control device 3 to the number control device 3 via the signal line 16. Examples of signals used in the number control device 3 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. The downstream side of the steam header 6 is connected to the steam use facility 18 via the steam pipe 12.

  The steam header 6 collects and stores the steam generated in the boiler group 2. The steam header 6 adjusts the pressure difference and pressure fluctuation of one or more boilers 20 to be combusted, and supplies steam whose steam pressure value is adjusted to be constant (target steam pressure value) to the steam using facility 18.

  The vapor pressure sensor 7 is electrically connected to the number control device 3 via the signal line 13. The vapor pressure sensor 7 measures the vapor pressure value of the vapor header 6 (hereinafter also referred to as “header pressure value”), and sends a vapor pressure signal corresponding to the vapor pressure value via the signal line 13 to the unit control device 3. Send to.

  The number control device 3 is electrically connected to the plurality of boilers 20 through the signal line 16. The number control device 3 controls the combustion state (combustion amount) of each boiler 20 based on the steam pressure value of the steam header 6 measured by the steam pressure sensor 7. The number control device 3 will be described later.

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

  In the boiler system 1, the header pressure value varies according to the steam consumption (required load) in the steam using facility 18. The number control device 3 (control unit 4) calculates an operation amount (indicated steam amount) by a PID algorithm based on the header pressure value (physical amount). In other words, the instruction steam amount is a steam amount necessary for setting the header pressure value to the target steam pressure value. The number control device 3 controls the combustion amount of each boiler 20 constituting the boiler group 2 based on the calculated instruction steam amount. As a result, the amount of steam supplied from each boiler 20 to the steam header 6 (hereinafter also referred to as “generated steam amount”) is adjusted, so that the header pressure value can be brought close to the target steam pressure value. That is, the header pressure value can be kept at a constant target steam pressure value according to the fluctuation of the steam consumption.

  Specifically, the steam consumption increases due to an increase in demand for the steam use facility 18, and if the amount of generated steam supplied to the steam header 6 is insufficient, the header pressure value decreases. On the other hand, if the steam consumption decreases due to a decrease in the demand of the steam use facility 18 and the generated steam amount supplied to the steam header 6 becomes excessive, the header pressure value increases. The number control device 3 monitors the fluctuation of the steam consumption based on the fluctuation of the header pressure value. Then, the number control device 3 calculates an instruction steam amount corresponding to the steam consumption amount of the steam using facility 18 based on the header pressure value, and the steam generation amount corresponding to the instruction steam amount is supplied to the steam header 6. The combustion amount of each boiler 20 is controlled as described.

  The boiler 20 of the present embodiment is a continuous control boiler configured to be able to increase or decrease the combustion amount continuously.

  The continuous control boiler can increase or decrease the combustion amount continuously at least in the range from the minimum combustion state (for example, the combustion state at 20% of the maximum combustion amount) to the maximum combustion state. The continuous control boiler can adjust the amount of combustion by controlling the opening degree (combustion ratio) of a valve that supplies fuel to the burner and a valve that supplies combustion air, for example.

  Next, the configuration of the number control device 3 will be described in detail. As shown in FIG. 3, the number control device 3 includes a control unit 4 as a control unit and a storage unit 5.

  The control unit 4 transmits various instructions to each boiler 20 via the signal line 16 and receives various data from each boiler 20 to control the combustion state and the number of operating units of the five boilers 20. Execute. When each boiler 20 receives a signal for changing the combustion state from the number control device 3, it controls the combustion amount of the corresponding boiler 20 in accordance with the instruction. The detailed configuration of the control unit 4 will be described later.

  The storage unit 5 stores information related to the instructions transmitted to each boiler 20, information related to the combustion state received from each boiler 20, information related to the priority order of each boiler 20, data necessary for calculating an instruction steam amount, which will be described later, and the like. To do.

  Next, the configuration of the control unit 4 will be described in more detail. As shown in FIG. 4, the control unit 4 includes an operation amount calculation unit 41, a first detection unit 42, a second detection unit 43, and an output control unit 44.

  The operation amount calculation unit 41 calculates an operation amount (indicated steam amount) based on a preset target steam pressure value, a header pressure value measured by the steam pressure sensor 7, and the like. Specifically, the operation amount calculation unit 41 sets the operation amount (indicated steam amount) to a PID described later so that the header pressure value measured by the steam pressure sensor 7 becomes a preset target steam pressure value. Calculated by algorithm.

The operation amount calculation unit 41 calculates an operation amount (indicated steam amount) based on the following equation (1).
Operating amount (indicated steam amount) = Deviation proportional output (P control) + Deviation integral output (I control) + Deviation derivative output (D control)
... (1)

Moreover, each component which comprises the operation amount (indication vapor | steam amount) is calculated by following formula (2)-(4).
Deviation proportional output (PID_E) = PID_K × (target steam pressure value−current steam pressure value)
... (2)
Here, PID_K (proportional gain) is the boiler output (steam amount) per unit pressure deviation (1 MPa).

The relationship between the proportional band Pb and the proportional gain Kp will be briefly described.
For example, the relationship between the proportional band Pb and the proportional gain Kp can be expressed by the following equation.
Proportional gain PID_K = Maximum steam volume / (Proportional band Pb x Full scale pressure)
... (3)
Note that the value of the proportional gain is not a fixed value and can be adjusted based on the combustion rate of the boiler 20, for example, so that the proportional gain becomes smaller as the combustion rate of the boiler 20 is lower.
As is clear from the equations (2) and (3), when the proportional band Pb is set large, the proportional gain becomes small, and a small manipulated variable (indicated steam volume) with respect to the deviation between the target steam pressure value and the header pressure value. ) Is calculated and the proportional band is set small, the proportional gain increases, and a large manipulated variable (indicated steam amount) is calculated with respect to the deviation between the target steam pressure value and the header pressure value.

Deviation integral output (PID_EI) = PID_EI + PID_E / integration time (seconds)
... (4)
As is clear from equation (4), if the integration time is set long, a small manipulated variable (indicated steam amount) is calculated with respect to the deviation between the target steam pressure value and the header pressure value, and if the integration time is set short. A large manipulated variable (indicated steam amount) is calculated with respect to the deviation between the target steam pressure value and the header pressure value.

Deviation differential output (PID_ED) =
PID_K × (steam pressure value of previous control cycle−current steam pressure value) × differentiation time (seconds)
... (5)

  The operation amount calculation unit 41 of the present embodiment calculates the operation amount (indicated steam amount) by summing up the outputs calculated by the above formulas (2), (4), and (5).

  In the operation amount calculation unit 41, when the state where the header pressure exceeds the target pressure continues, the operation amount of the I control gradually decreases, and finally the final operation amount (that is, the indicated steam amount) is 0 or less. It becomes.

  The first detection unit 42 detects whether or not the header pressure value measured by the vapor pressure sensor 7 exceeds a preset target vapor pressure value. For example, the first detection unit 42 determines whether or not the header pressure value exceeds the target steam pressure value by determining whether or not the deviation proportional output (PID_E) calculated by the operation amount calculation unit 41 is a negative value. Or can be detected.

The second detection unit 43 detects whether or not the header pressure value measured by the vapor pressure sensor 7 tends to increase.
For example, the second detection unit 43 determines whether or not the header pressure value tends to increase by determining whether or not the deviation differential output (PID_ED) calculated by the operation amount calculation unit 41 is a negative value. can do.
In addition, for example, the second detection unit 43 has the deviation differential output (PID_ED) calculated by the operation amount calculation unit 41 a predetermined number of times including the current time (for example, a total of 3 times, this time, the previous time, and the previous time). By determining whether or not the negative value has continued, it may be detected whether or not the header pressure value tends to increase. The predetermined number of times can be set as appropriate.
Further, for example, in addition to the above determination, the second detection unit 43 determines whether or not the header pressure value tends to increase by determining whether or not the pressure gradient of the header pressure value is greater than or equal to a predetermined value. You may make it do.
When the manipulated variable calculation unit 41 is based on the PI algorithm, the second detection unit 43 calculates the value of (steam pressure value of the previous control cycle−current steam pressure value) in the same manner as described above. It is possible to detect whether or not the header pressure value tends to increase.

  The output control unit 44 performs so-called number control in which a required number of boilers 20 are combusted according to the operation amount (indicated steam amount). Specifically, when the steam consumption increases and the number of boilers 20 to be burned is increased, the output control unit 42 starts burning in order from the boilers 20 having a preset priority. In addition, when the steam consumption is reduced and the number of boilers 20 to be burned is reduced, the output control unit 42 stops the combustion in order from the boiler 20 having a low priority set in advance.

  The output control unit 44 sets the number of boilers 20 to be burned based on the operation amount (indicated steam amount) calculated according to the steam consumption amount in the operation amount calculation unit 41. The output control unit 42 sets the boilers 20 that start or stop combustion in accordance with the priority order described in the storage unit 5, and sends a unit control signal (operation start or operation) to the local control unit 22 of the boilers 20. Stop) is output. Thereby, the steam amount (generated steam amount) corresponding to the operation amount (indicated steam amount) is supplied to the steam header 6 from the boiler 20 to be combusted.

  When the operation amount (instructed steam amount) calculated by the operation amount calculation unit 41 is less than or equal to zero, the output control unit 44 causes the first detection unit 42 to set the steam pressure value inside the steam header 7 to the target pressure value. When it is detected that the steam pressure value inside the steam header 7 tends to increase by the second detector 43, the boilers in the boiler group 2 are all in a combustion stopped state (hereinafter, It is also called “all can stop”).

  Even when the operation amount (indicated steam amount) calculated by the operation amount calculation unit 41 is less than or equal to zero, the output control unit 44 causes the first detection unit 42 to change the steam pressure value inside the steam header 7. When it is detected that the target pressure value is not exceeded or the second detection unit 43 detects that the steam pressure value inside the steam header 7 is not increasing, the boiler group 2 is not stopped at all cans. One of the boilers is brought into a minimum combustion state. The minimum combustion state can be, for example, a combustion state with a combustion rate of 20%. Note that it is possible to appropriately set the combustion state at which the combustion rate is the minimum combustion state.

  The output control unit 44 presets a control pressure upper limit value as a threshold value for setting all the boilers of the boiler group 2 in a combustion stopped state, and the output control unit 44 determines that the steam pressure value inside the steam header 7 is the control pressure. When the upper limit is exceeded, the boiler group 2 is stopped at all cans regardless of the above.

  Next, in the operation amount calculation unit 41 of the control unit 4, the result of the simulation calculation when the comparative example when the pressure control is performed only by the normal PID algorithm and the PID algorithm according to one embodiment of the present invention is executed. Will be described with reference to FIGS.

  4 and 6 are graphs showing the results of simulation calculation of steam pressure and steam amount when pressure control is executed only with a normal PID algorithm using a boiler system composed of a single boiler as a model. FIGS. 5 and 7 are graphs showing simulation calculation results of steam pressure and steam volume when pressure control is executed by a PID algorithm according to an embodiment of the present invention using a boiler system composed of a single boiler as a model. is there.

The simulation conditions for the simulation calculation of the steam pressure and the steam amount in FIGS. 4 to 7 were a target steam pressure value of 1.2 MPa, a proportional band of 5%, and a differential time of 2 seconds.
The integration time was set to 20 seconds in the simulation of the steam pressure and the steam amount in FIGS. 4 and 5, and set to 10 seconds in the simulation of the steam pressure and the steam amount in FIGS. 6 and 7.
Therefore, the conditions for the simulation calculation of the steam pressure and the steam amount in FIGS. 4 and 5 are different from the conditions for the simulation calculation of the steam pressure and the steam amount in FIGS. .

  As a pattern of the required steam amount for the simulation calculation of the steam pressure and the steam amount in FIGS. 4 to 7, as shown in FIGS. 4 to 7, the required steam amount during an elapsed time of 300 seconds to 360 seconds. The required steam volume drops from 2400 kg / h to 1400 kg / h during the period from 1400 kg / h to 2400 kg / h and from 660 seconds to 720 seconds, and the elapsed time reaches from 1020 seconds to 1080 seconds During this period, the required steam volume increases from 1400 kg / h to 3400 kg / h, and the required steam volume decreases from 3400 kg / h to 1400 kg / h during the period from 1380 seconds to 1440 seconds, and the elapsed time of 1740 seconds. The required steam volume increases from 1400 kg / h to 4400 kg / h during the period up to 1800 seconds, and reaches 2100 seconds to 2160 seconds. The required steam amount rises from 1400 kg / h to 5400 kg / h during the period from 2400 seconds to 2520 seconds, and the pattern in which the required steam amount drops from 4400 kg / h to 1400 kg / h. The required steam volume drops from 5400 kg / h to 1400 kg / h during the period from 1 second to 2880 seconds, and the required steam volume ranges from 1400 kg / h to 6000 kg / h during the elapsed time from 3180 seconds to 3240 seconds. A pattern including a pattern in which the required steam amount decreases from 6000 kg / h to 1400 kg / h during a period from 3540 seconds to 3600 seconds was set, and simulation calculation was performed.

  4 to 7, the horizontal axis indicates the elapsed time (seconds), the right vertical axis indicates the steam volume (t / h), and the left vertical axis indicates the steam pressure value (MPa). 4 to 7, the thick solid line represents the pressure value of the steam header 6, the broken line represents the required steam amount, and the thin solid line represents the generated steam amount supplied to the steam header 6.

  Next, a case where the simulation is executed with the integration time set to 20 seconds will be described with reference to FIGS.

  First, a case where pressure control is performed only with a normal PID algorithm will be described with reference to FIG. As shown in FIG. 4, the generated steam amount supplied from the boiler 2 to the steam header 6 follows the fluctuation of the required steam amount from the elapsed time 0 to the elapsed time 2100 seconds.

  On the other hand, when the required steam volume suddenly decreases from 4400 kg / h to 1400 kg / h over an elapsed time of 2100 seconds to 2160 seconds, the header pressure exceeds the target pressure due to overshoot, and then the pressure starts after 2160 seconds. It has turned down. However, since the target pressure was still exceeded, the manipulated variable of I control continued to decrease, and eventually the manipulated variable became 0 or less, and it was considered that the combustion stopped around 2200 seconds. Thereafter, there is a start delay after the combustion is stopped for about 20 seconds, and it is considered that the generated steam amount corresponding to the operation amount (indicated steam amount) is output after 2220 seconds. Thereafter, after 2340 seconds, the generated steam amount converges to the required steam amount, and the steam pressure value of the steam header 6 also converges near the target steam pressure value.

  And the required steam volume increased from 1400 kg / h to 5400 kg / h from 2460 seconds to 2520 seconds, but the required steam volume was 5400 kg / h from 2520 seconds to 2820 seconds. Therefore, the generated steam amount converges to the required steam amount, and the steam pressure value of the steam header 6 also converges near the target steam pressure value.

  Next, when the required steam volume suddenly decreases from 5400 kg / h to 1400 kg / h over an elapsed time of 2820 seconds to 2880 seconds, the header pressure exceeds the target pressure due to overshoot, and then after 2880 seconds The pressure has started to drop. However, since the target pressure was still exceeded, the manipulated variable for I control continued to decrease, and eventually, the manipulated variable became 0 or less, and it was considered that the combustion stopped around 2910 seconds. After that, there is a start delay after the combustion is stopped for about 20 seconds, and it is considered that the generated steam amount corresponding to the operation amount (indicated steam amount) is output after around 2930 seconds. Thereafter, in 3060 seconds, the generated steam amount converges to the required steam amount, and the steam pressure value of the steam header 6 also converges near the target steam pressure value.

  As described above, when the integration time is set to 20 seconds and the pressure control is executed only by the normal PID algorithm using a boiler system consisting of a single boiler as a model, the steam header 6 is stopped by the combustion stop during the pressure drop. The steam pressure value suddenly dropped and the pressure temporarily became unstable, but no hunting phenomenon occurred.

On the other hand, when a PID algorithm according to an embodiment of the present invention is executed under a simulation condition in which an integration time is set to 20 seconds using a boiler system consisting of a single boiler as a model, an elapsed time as shown in FIG. When the required steam volume suddenly decreases from 4400 kg / h to 1400 kg / h from 2100 seconds to 2160 seconds, the header pressure exceeds the target pressure due to overshoot, and then the pressure starts to decrease after 2160 seconds. Yes. At this time, since the target pressure was exceeded, it is considered that the manipulated variable for I control continued to decrease and eventually the manipulated variable became 0 or less. However, in this case, since the steam pressure value of the steam header 6 tends to decrease, the combustion is not stopped and the continuous combustion is performed in the minimum combustion state.
Therefore, as compared with FIG. 4, it is recognized that the steam pressure value of the steam header 6 is only moderately decreased and is stable near the target steam pressure value.

Similarly, when the required steam volume suddenly decreases from 5400 kg / h to 1400 kg / h from 2820 seconds to 2880 seconds, the header pressure exceeds the target pressure due to overshoot, and then the pressure decreases after 2880 seconds. It has turned to. At this time, since the target pressure was exceeded, the operation amount of the I control continued to decrease, and it is considered that the operation amount eventually became 0 or less, but the steam pressure value of the steam header 6 tends to decrease. Therefore, the combustion is performed in the minimum combustion state without stopping the combustion.
Therefore, as compared with FIG. 4, it is recognized that the steam pressure value of the steam header 6 is only moderately decreased and is stable near the target steam pressure value.

  As described above, when the integration time is set to 20 seconds and the PID algorithm according to the embodiment of the present invention is executed, the overshoot occurs when the load is drastically reduced as compared with the case of only the pressure control by the normal PID algorithm. After the header pressure exceeds the target pressure due to the above, when the header pressure exceeds the target pressure and the pressure starts to drop, even if the operation amount by the PID calculation is 0 or less, all the cans are not stopped. By continuing the combustion, it is recognized that the hunting phenomenon does not occur and the steam pressure value of the steam header 6 can be stabilized.

  Next, a case where the simulation is executed with the integration time set to 10 seconds will be described with reference to FIGS. Since the integration time is set to 10 seconds, the integration time is set to 20 seconds, and the case where the simulation is executed is compared with FIGS. 4 and 5, and the target steam pressure value and the header pressure value are compared. It is recognized that a large operation amount is calculated with respect to the deviation.

First, a case where pressure control is performed only with a normal PID algorithm will be described with reference to FIG. As shown in FIG. 6, when the required steam amount suddenly decreases from 5400 kg / h to 1400 kg / h over an elapsed time of 2820 seconds to 2880 seconds, the header pressure exceeds the target pressure due to overshoot, and then The pressure starts to decrease after 2880 seconds. However, since the target pressure was still exceeded, the manipulated variable for I control continued to decrease, and eventually, the manipulated variable became 0 or less, and it was considered that the combustion stopped around 2910 seconds. After that, there is a start delay after the combustion is stopped for about 20 seconds, and it is considered that the generated steam amount corresponding to the operation amount (indicated steam amount) is output after around 2930 seconds. However, because the combustion is stopped and the header pressure value suddenly drops, the operation amount (indicated steam amount) calculated by the PID calculation is secured excessively, so the boiler starts combustion and the generated steam amount increases. As a result, the header pressure value changes from a decrease to an increase, and the operation amount (indicated steam amount) continues to decrease. However, since the operation amount (indicated steam amount) is excessively secured at that time, it is around 2940 seconds. The amount of generated steam continues to increase until the header pressure value continues to increase rapidly until around 2960 seconds.
As a result, the increase in the header pressure value cannot be suppressed, the header pressure again exceeds the target pressure due to overshoot, then the pressure starts to decrease, the combustion stops again, and the header pressure value drops rapidly. As a result, it is recognized that the hunting phenomenon occurred from 2940 seconds to 3180 seconds.

  As described above, when the integration time is set to 10 seconds and the pressure control is executed only with the normal PID algorithm using a boiler system consisting of a single boiler as a model, the steam header 6 is stopped by the combustion stop during the pressure drop. As a result of the sudden drop in the steam pressure value, the operation amount (indicated steam amount) is secured excessively, the generated steam amount continues to increase, and the increase in the header pressure value cannot be suppressed. It is recognized that a hunting phenomenon has occurred in which the header pressure has exceeded the target pressure, and then has started to decrease in pressure, and then combustion has stopped again, causing the header pressure value to rapidly decrease.

On the other hand, when a PID algorithm according to an embodiment of the present invention is executed using a boiler system consisting of a single boiler as a model, the required steam amount is 5400 kg / h over an elapsed time of 2820 seconds to 2880 seconds as shown in FIG. When a sudden decrease occurs from 1400 kg / h to 1400 kg / h, the header pressure exceeds the target pressure due to overshoot, and then the pressure starts to decrease after 2880 seconds. At this time, since the target pressure was exceeded, the operation amount of the I control continued to decrease, and it is considered that the operation amount eventually became 0 or less, but the steam pressure value of the steam header 6 tends to decrease. Therefore, the combustion is performed in the minimum combustion state without stopping the combustion.
For this reason, compared with FIG. 6, it is recognized that the steam pressure value of the steam header 6 is only moderately decreased and is stable near the target steam pressure value.

  Thus, when the PID algorithm according to an embodiment of the present invention is executed, even when a relatively small value of 10 seconds is set as the integration time, compared to the case of only pressure control by a normal PID algorithm, When the header pressure exceeds the target pressure due to overshoot when the load is suddenly reduced, and when the header pressure exceeds the target pressure and the pressure starts to drop, even if the manipulated variable by PID calculation is 0 or less, all By continuously burning without stopping the can, the hunting phenomenon does not occur and the steam pressure value of the steam header 6 can be stabilized.

  As described above, when the PID algorithm according to an embodiment of the present invention is executed, after the header pressure exceeds the target pressure due to overshoot when the load is suddenly decreased, the pressure decreases in a state where the header pressure exceeds the target pressure. , Even if the amount of operation by PID calculation (or PI calculation) is 0 or less, it is possible to avoid the stoppage of all cans and quickly converge the header pressure value to the target vapor pressure value. it can.

  The preferred embodiment of the boiler system 1 of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and can be modified as appropriate.

In the said embodiment, although this invention was applied to the boiler system provided with the boiler group 2 which consists of the five boilers 20, it is not restricted to this. In other words, the present invention may be applied to a boiler system including a boiler group including six or more boilers 20 or four or less boilers 20 and combustion of a single boiler as in the simulation described above. You may apply to control.
Moreover, in the said embodiment, although it is supposed that all the five boilers 20 are comprised with the same boiler, it is not restricted to this, It is good also as a capacity | capacitance varying for every boiler 20. FIG.
Moreover, although the boiler 20 of the said embodiment consisted of the continuous control boiler comprised so that combustion amount could be increased / decreased continuously, it is not restricted to this. The present invention can also be applied to a case where the boiler 20 is composed of a stage value control boiler capable of burning at a plurality of staged combustion positions.

  Moreover, in the said embodiment, the operation calculation part 41 demonstrated the example which calculates operation amount (indication vapor | steam amount) with a PID (proportional + integral + differentiation) algorithm based on the steam pressure value (physical quantity) of the steam header 6. . The present invention is not limited to this, and the present invention can also be applied to control for calculating an operation amount (indicated steam amount) by a PI (proportional + integral) algorithm.

DESCRIPTION OF SYMBOLS 1 Boiler system 2 Boiler group 3 Number control device 4 Control part 5 Memory | storage part 6 Steam header 7 Steam pressure sensor 18 Steam use equipment 20 Boiler 41 Operation amount calculation part 42 1st detection part 43 2nd detection part 44 Output control part

Claims (4)

A set of one or more boilers capable of burning at different combustion rates and supplying steam to the load equipment;
A steam header in which steam generated in the boiler group gathers;
A control unit that controls a combustion state of the one or more boilers according to a required load from a load device,
The controller is
An operation amount calculation unit for calculating an operation amount by a PI algorithm or a PID algorithm so as to keep a steam pressure value inside the steam header at a target steam pressure value with respect to fluctuations in steam consumption;
An output control unit that controls a combustion state of the one or more boilers based on the operation amount calculated by the operation amount calculation unit;
A first detector for detecting that a steam pressure value inside the steam header exceeds a target pressure value;
A second detection unit that detects whether or not the steam pressure value inside the steam header tends to increase,
When the operation amount calculated by the operation amount calculation unit is less than or equal to zero, the output control unit is configured such that a steam pressure value inside the steam header exceeds a target pressure value by the first detection unit. When it is detected and the second detection unit detects that the steam pressure value inside the steam header tends to increase, all the one or more boilers are put into a combustion stop state. .   When the operation amount calculated by the operation amount calculation unit is less than or equal to zero, the output control unit is configured such that the steam pressure value inside the steam header does not exceed a target pressure value by the first detection unit. If one of the one or more boilers is detected, or if the second detection unit detects that the steam pressure value inside the steam header is not in an upward trend, the boiler is brought into a minimum combustion state. The boiler system according to claim 1.   The boiler system according to claim 2, wherein the minimum combustion state is a combustion state with a combustion rate of 20%. The control unit presets a control pressure upper limit value as a threshold value for bringing all of the one or more boilers into a combustion stop state,
The output controller is configured to put all the one or more boilers in a combustion stopped state when a steam pressure value inside the steam header exceeds the control pressure upper limit value. 4. The boiler system according to any one of items 3.

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