JP2015140975A - boiler system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a boiler system capable of feedback controlling which enhances the pressure stability.SOLUTION: A boiler system 1 comprises: a boiler group 2 including a plurality of boilers 20 capable of burning by changing its burning rate; and a control part 4 that controls the combustion state of the boiler group 2 by the feedback control of the steam output outputted from the boiler group 2, in which the control part 4 includes: a burning rate calculation part 41 that calculates the burning rate of the boiler group 2; a proportional gain adjustment part 42 that regulates the proportional gain to lower as the burning rate of the boiler group 2 is lower and regulates the proportional gain to higher as the burning rate of the boiler group 2 is higher; and a feedback control part 43 that controls the combustion state of the boiler group 2 on the basis of the regulated proportional gain.

Description

  The present invention relates to a boiler system including a boiler group having a plurality of boilers that can burn by changing a combustion rate.

Conventionally, a boiler system including a plurality of boilers and a control unit that controls the combustion rate of the boiler according to the steam consumption (required load) of the steam-using facility is known. In such a boiler system, the combustion rate of the boiler is controlled by performing feedback control of the steam pressure so that the steam pressure of the steam header becomes a constant target pressure regardless of the fluctuation of the steam consumption.
That is, a value obtained by multiplying the deviation between the target pressure and the steam pressure of the steam header by a proportional gain is calculated as an operation amount (indicated steam amount), and steam corresponding to the indicated steam amount is generated from a plurality of boilers according to this operation amount. To control the combustion rate of the boiler.

  In such feedback control, it is necessary to appropriately set a proportional gain in order to improve pressure stability. In this regard, Patent Document 1 discloses a number control method for boilers that adjusts a pressure control proportional band in accordance with the number of boilers that burn. According to this number control method, the pressure control proportional band is changed in accordance with the number of boilers. As a result, the proportional gain is also changed depending on the number of combustion.

Japanese Patent No. 3808303

  By the way, in the number control method of patent document 1, since the pressure control proportional band (PBa) is calculated by PBa = PB (1+ (Nc−1) K), the pressure control proportional band (PBa increases as the number of combustion (Nc) increases. ) Becomes wider and the number of combustion (Nc) becomes smaller, the pressure control proportional band (PBa) becomes narrower. As a result, in the number control method of Patent Document 1, the proportional gain decreases as the number of combustion (Nc) increases (when the load is high), and the proportional gain increases as the number of combustion (Nc) decreases (when the load is low).

  In this regard, when the proportional gain is set high, a large operation amount is calculated with respect to the deviation, and when the proportional gain is set low, a small operation amount is calculated with respect to the deviation. Therefore, if the proportional gain is set low at high load when the steam-using facility uses a lot of steam as in the number control method of Patent Document 1, the manipulated variable is excessively calculated at high load, and load follow-up is delayed. Pressure stability at high load will decrease. Similarly, when the proportional gain is set high at low load when the steam-using equipment does not use much steam, the manipulated variable is excessively calculated at low load, and pressure stability at low load decreases due to occurrence of hunting, etc. .

  This invention is made | formed in view of such a problem, and it aims at providing the boiler system in which the feedback control which can improve pressure stability is possible.

  The present invention includes a boiler group including a plurality of boilers capable of burning at different combustion rates, and a control unit that controls the combustion state of the boiler group by feedback control of steam output output from the boiler group. In the boiler system, the control unit calculates a combustion rate of the boiler group, a proportional gain adjustment unit that adjusts a proportional gain used for the feedback control based on the calculated combustion rate, A feedback control unit that controls the combustion state of the boiler group by the feedback control based on the adjusted proportional gain, and the proportional gain adjustment unit decreases the proportional gain as the combustion rate of the boiler group decreases. The present invention relates to a boiler system that adjusts and adjusts the proportional gain higher as the combustion rate of the boiler group is higher.

  Moreover, it is preferable that the said combustion rate calculation part calculates the combustion rate of the said boiler group by dividing the output steam amount output from the said boiler group by the maximum steam amount which the said boiler group can output.

  In the present invention, it is preferable that the combustion rate calculation unit calculates a combustion rate of the boiler group based on the number of boilers in a combustion state.

  According to the present invention, since the proportional gain is appropriately adjusted according to the combustion rate of the boiler group, it is possible to provide a boiler system capable of feedback control capable of enhancing pressure stability.

It is a figure showing the outline of the boiler system concerning the 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 explanatory drawing which shows the control flow of a control part. It is explanatory drawing which shows the calculation method of a proportional gain (KP).

Hereinafter, preferred embodiments of the boiler system of the present invention will be described with reference to the drawings.
First, the overall configuration of the boiler system 1 of the present invention will be described with reference to FIG. The boiler system 1 includes a boiler group 2 including a plurality of (five) boilers 20, a steam header 6 that collects steam generated in the plurality of boilers 20, and steam that measures the pressure inside the steam header 6. A pressure sensor 7 and a number control device 3 having a controller 4 that controls the combustion state of the boiler group 2 are provided.

The boiler group 2 generates steam to be supplied to the steam use facility 18.
The steam header 6 is connected to a plurality of 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 vapor pressure sensor 7 is electrically connected to the number control device 3 via the signal line 13. The steam pressure sensor 7 measures the steam pressure inside the steam header 6 (steam pressure generated in the boiler group 2), and sends a signal (steam pressure signal) related to the measured steam pressure via the signal line 13. It transmits to the control apparatus 3.

  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 of each boiler 20 based on the steam pressure inside the steam header 6 measured by the steam pressure sensor 7. Details of the number control device 3 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 3 determines 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 steam pressure sensor 7. It calculates and controls the combustion state of each boiler 20 which comprises the boiler group 2. FIG.

  Specifically, if the required load (steam consumption) increases due to an increase in demand for the steam use facility 18 and the amount of steam supplied to the steam header 6 (output steam amount described later) is insufficient, the steam header 6 The internal vapor pressure will decrease. On the other hand, if the demand load (steam consumption) decreases due to a decrease in the demand for the steam use facility 18 and the amount of steam supplied to the steam header 6 becomes excessive, the steam pressure inside the steam header 6 increases. Become. Therefore, the boiler system 1 can monitor the fluctuation of the required load based on the fluctuation of the vapor pressure measured by the vapor pressure sensor 7. Then, the boiler system 1 calculates a necessary steam amount that is a steam amount required according to the consumed steam amount (required load) of the steam using facility 18 based on the steam pressure of the steam header 6.

Here, the several boiler 20 which comprises the boiler system 1 of this embodiment is demonstrated. FIG. 2 is a diagram showing an outline of the boiler group 2 according to the present embodiment.
The boiler 20 of the present embodiment is composed of a proportional control boiler capable of burning by continuously changing the combustion rate.
The proportional control boiler is a boiler whose combustion rate can be continuously controlled at least in the range from the minimum combustion state S1 (for example, the combustion state of 20% of the combustion rate) to the maximum combustion state S2. The proportional control boiler adjusts the combustion rate, for example, by controlling the opening degree (combustion ratio) of a valve that supplies fuel to the burner and a valve that supplies combustion air.

  Also, the continuous control of the combustion rate means that the calculation or signal in the local control unit 22 described later is a digital method and is handled in stages (for example, the output (combustion rate) of the boiler 20 is in increments of 1%). Even when the output is controlled).

In this embodiment, the change of the combustion state between the combustion stop state S0 and the minimum combustion state S1 of the boiler 20 is controlled by turning on / off the combustion of the boiler 20 (burner). In the range from the minimum combustion state S1 to the maximum combustion state S2, the combustion rate can be continuously controlled.
More specifically, a unit steam amount U, which is a unit of variable steam amount, is set for each of the plurality of boilers 20. Thus, the boiler 20 can change the steam amount in units of the unit steam amount U in the range from the minimum combustion state S1 to the maximum combustion state S2.

The unit steam amount U can be appropriately set according to the steam amount (maximum steam amount) in the maximum combustion state S2 of the boiler 20, but from the viewpoint of improving the followability of the output steam amount to the necessary steam amount in the boiler system 1. It is preferably set to 0.1% to 20% of the maximum steam amount of 20, and more preferably set to 1% to 10%.
In addition, the maximum steam amount of the boiler 20 of this embodiment is 7000 kg / h (that is, the boiler 20 is a 7 t boiler). Further, the output steam amount indicates the steam amount output by the boiler group 2, and this output steam amount is represented by the total value of the steam amounts output from each of the plurality of boilers 20.

  Moreover, the priority order is set to each of the plurality of boilers 20. The priority order is used to select the boiler 20 that performs a combustion instruction or a combustion stop instruction. The priority order can be set, for example, using an integer value so that the lower the numerical value, the higher the priority order. As shown in FIG. 2, when the priorities of “1” to “5” are assigned to the first to fifth units of the boiler 20, the first unit has the highest priority, and the fifth unit has the highest priority. Lowest. In the normal case, this priority order is changed at predetermined time intervals (for example, 24 hour intervals) under the control of the control unit 4 described later.

Next, details of control of the combustion state of the plurality of boilers 20 by the boiler system 1 of the present embodiment will be described.
Based on the vapor pressure signal from the vapor pressure sensor 7, the number control device 3 calculates the required combustion amount of the boiler group 2 according to the required load and the combustion state of each boiler 20 corresponding to the required combustion amount, The number control signal is transmitted to the boiler 20 (a local control unit 22 described later). More specifically, the unit control device 3 provides feedback based on a predetermined PID algorithm with respect to the deviation between the target pressure set in advance according to the steam use facility 18 and the steam pressure (header pressure) in the steam header 6. By performing the control, the total steam amount (operation amount) necessary for the header pressure to become the target pressure is calculated, and combustion of the boiler 20 is performed so that steam for the calculated total steam amount is output from the boiler group 2. Control the state.
As shown in FIG. 1, the number control device 3 includes a storage unit 5 and a control unit 4.

  The storage unit 5 includes information on instructions given to each boiler 20 under the control of the number control device 3 (control unit 4), information such as the combustion state received from each boiler 20, and combustion patterns of a plurality of boilers 20. Information on setting conditions, information on setting priorities of a plurality of boilers 20, information on settings on changing priority (rotation), and the like. The storage unit 5 also stores information (such as a maximum proportional gain described later) necessary for calculating the proportional gain.

  The control unit 4 gives 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 priority order of the five boilers 20. . When each boiler 20 receives a signal for changing the combustion state from the number control device 3, it controls the boiler 20 according to the instruction.

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 required load. 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.
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 the signal used in the number control device 3 include an actual combustion state of the boiler 20 and other data.

  FIG. 3 is a functional block diagram showing the configuration of the control unit 4 of the number control device 3. The control unit 4 includes a combustion rate calculation unit 41, a proportional gain adjustment unit 42, and a feedback control unit 43.

The combustion rate calculation unit 41 calculates the combustion rate of the boiler group 2. Here, the combustion rate calculated by the combustion rate calculation unit 41 is the combustion rate of the boiler group 2. For example, in a state where all of the five boilers 20 are burned at a combustion rate of 100%, the combustion rate of the boiler group 2 is 100%, and three of the five boilers 20 are 100%. In the state in which the other boilers 20 are not combusted, the combustion rate of the boiler group 2 is 60%.
The combustion rate may be calculated by an arbitrary method. For example, the combustion rate calculation unit 41 divides the output steam amount output from the boiler group 2 by the maximum steam amount that the boiler group 2 can output. Thus, the combustion rate of the boiler group 2 may be calculated. In this embodiment, since the five boilers 20 are 7t boilers, the maximum amount of steam that can be output by the boiler group 2 is 35000 kg / h. Therefore, for example, when the output steam amount output from the boiler group 2 is 21000 kg / h, the combustion rate calculation unit 41 calculates the combustion rate of the boiler group 2 as 60%.
Moreover, the combustion rate calculation part 41 is good also as calculating the combustion rate of a boiler group based on the number of the boilers 20 in a combustion state. Specifically, a combustion rate per unit is set in advance for the boiler 20, and the set combustion rate is added by the number of boilers 20 in the combustion state, whereby the combustion rate of the boiler group 2 is increased. May be calculated. In this embodiment, since the boiler group 2 is comprised by the five boilers 20, it is preferable that the combustion rate per 1 unit | set is 20% or less. As an example, when 15% per unit is set, when the number of boilers 20 in the combustion state is two, the combustion rate of the boiler group 2 is 30%, and the number of boilers 20 in the combustion state When there are three, the combustion rate of the boiler group 2 is 45%.

  The proportional gain adjustment unit 42 adjusts a proportional gain used for feedback control for controlling the combustion state of the boiler 20 based on the calculated combustion rate of the boiler group 2. As will be described later in detail, the proportional gain adjustment unit 42 adjusts the proportional gain lower as the combustion rate of the boiler group 2 is lower, and adjusts the proportional gain higher as the combustion rate of the boiler group 2 is higher.

  The feedback control unit 43 controls the combustion state of the boiler group 2 by feedback control based on the adjusted proportional gain. That is, the feedback control unit 43 performs a predetermined calculation based on a proportional gain with respect to the deviation between the target pressure and the header pressure (P control), so that the total steam amount necessary for the header pressure to become the target pressure. (Operation amount) is calculated, and the combustion state of the boiler 20 is controlled based on the operation amount.

  Next, the operation of the control unit 4 will be described with reference to FIG. FIG. 4 is an explanatory diagram showing a control flow of the control unit 4.

  First, when the combustion rate calculation unit 41 calculates the combustion rate of the boiler group 2, the calculated combustion rate is supplied to the proportional gain adjustment unit 42, and the proportional gain is calculated. In the calculation of the proportional gain, the proportional gain adjustment unit 42 reads the proportional gain maximum value and the proportional gain minimum value from the storage unit 5.

The proportional gain maximum value (KPmax) is a proportional gain when the combustion rate of the boiler group 2 is 100%. The maximum proportional gain value (KPmax) is calculated by dividing the maximum steam volume (35000 kg / h) of the boiler group 2 by the control width calculated from the proportional band and the full scale pressure. I shall keep it.
Proportional gain maximum value (KPmax) = Maximum steam volume / (Proportional band x Full-scale pressure)
Proportional band x full scale pressure = control width

Further, the minimum proportional gain (KPmin) is a proportional gain when the combustion rate of the boiler group 2 is 0%, that is, when all of the boilers 20 stop combustion. The minimum proportional gain value (KPmin) is calculated by multiplying the maximum proportional gain value (KPmax) by the correction coefficient (A). The correction coefficient (A) is an arbitrary value between 0.1 and 1.0 and is set in advance.
Proportional gain minimum value (KPmin) = Proportional gain maximum value (KPmax) × Correction coefficient (A)

  When the proportional gain maximum value (KPmax) and the proportional gain minimum value (KPmin) are read from the storage unit 5, the proportional gain adjustment unit 42 determines the combustion rate (F), the proportional gain maximum value (KPmax), and the proportionality of the boiler group 2. Based on the current combustion rate (F), the proportional gain (KP) is calculated (adjusted) based on the minimum gain value (KPmin).

ここで、燃焼率（Ｆ）は、「出力蒸気量／最大蒸気量」により算出されるため、上記式は、以下のように表される。

Here, a method of calculating the proportional gain (KP) will be specifically described with reference to FIG. FIG. 5 is an explanatory diagram showing a method of calculating the proportional gain (KP) by the proportional gain adjusting unit 42.
Referring to FIG. 5 (1), the proportional gain (KP) corresponding to the current combustion rate (F) uses a straight line passing through two points of the proportional gain maximum value (KPmax) and the proportional gain minimum value (KPmin). To calculate. That is, the proportional gain (KP) corresponding to the current combustion rate (F) is calculated by the following equation.

Here, since the combustion rate (F) is calculated by “output steam amount / maximum steam amount”, the above equation is expressed as follows.

  In FIG. 5 (1), the proportional gain (KP) corresponding to the current combustion rate (F) using a “straight line” passing through two points of the proportional gain maximum value (KPmax) and the proportional gain minimum value (KPmin). However, the present invention is not limited to this, and may be calculated using arbitrary curves L1 and L2 passing through two points as shown in FIG.

  As a result, the proportional gain adjusting unit 42 adjusts the proportional gain (KP) lower as the combustion rate (F) of the boiler group 2 is lower, and increases the proportional gain (KP) as the combustion rate (F) of the boiler group 2 is higher. Can be adjusted higher.

  Returning to FIG. 4, when the proportional gain (KP) is adjusted according to the combustion rate (F) of the boiler group 2, the feedback control unit 43 operates from the deviation between the target pressure and the header pressure and the proportional gain (KP). (Amount of steam to be output) is calculated, and the combustion state of each boiler 20 is controlled based on this manipulated variable. Thereby, the combustion state of the boiler 20 can be controlled so that the steam pressure in the steam header 6 substantially matches the target pressure.

  According to the boiler system 1 of this embodiment demonstrated above, there exist the following effects.

(1) In the boiler system 1 of the present embodiment, the combustion state of the boiler group 2 is controlled by feedback control based on the deviation between the target pressure and the header pressure, and the proportional gain (KP) used for feedback control is used for the boiler group 2. It adjusts according to the combustion rate (F). Specifically, the control unit 4 of the number control device 3 adjusts the proportional gain (KP) lower as the combustion rate (F) of the boiler group 2 is lower, and is proportional as the combustion rate (F) of the boiler group 2 is higher. Adjust the gain (KP) high.
As a result, when the load is high, a large operation amount is calculated with respect to the deviation between the target pressure and the header pressure, so that rapid load following can be realized and pressure stability is improved. In addition, when the load is low, a small manipulated variable is calculated with respect to the deviation between the target pressure and the header pressure. This improves the control stability and prevents the occurrence of hunting and the like, and improves the pressure stability. .

  (2) The control unit 4 calculates the combustion rate (F) of the boiler group 2 by dividing the output steam amount output from the boiler group 2 by the maximum steam amount that the boiler group 2 can output. According to such a configuration, since the combustion rate (F) of the boiler group 2 can be accurately calculated, the proportional gain (KP) can be adjusted more appropriately.

  (3) The control unit 4 calculates the combustion rate (F) of the boiler group 2 based on the number of boilers 20 in the combustion state. According to such a configuration, even when the combustion rate (F) of the boiler group 2 cannot be directly calculated, the combustion rate (F) of the boiler group 2 is indirectly calculated from the number of boilers 20 in the combustion state. This is preferable.

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.
For example, in the above embodiment, only P control is described for feedback control, and details of other controls (I control and D control) are omitted. In this regard, the feedback control executed by the feedback control unit 43 is not limited to P control, and may be PI control, PID control, or the like.

  Moreover, in the said embodiment, although it is supposed that the some boiler 20 is comprised with a proportional control boiler, the boiler 20 is good also as not only a proportional control boiler but with a step value control boiler. The step value control boiler has a plurality of stepwise combustion positions, and controls the amount of combustion by selectively turning on / off combustion, adjusting the size of the flame, etc. It is a boiler that can increase or decrease the amount of combustion in stages according to the selected combustion position. As an example, the plurality of boilers 20 may be configured by a three-position boiler having three positions, a combustion stop position, a low combustion position, and a high combustion position. Of course, the boiler 20 is not limited to three positions, and may have arbitrary N positions of combustion positions.

  For example, in this 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. That is, the present invention may be applied to a boiler system including a boiler group including six 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 3 Number control apparatus 4 Control part 41 Combustion rate calculation part 42 Proportional gain adjustment part 43 Feedback control part

Claims (3)

A boiler system comprising: a boiler group including a plurality of boilers capable of burning at different combustion rates; and a control unit that controls a combustion state of the boiler group by feedback control of steam output output from the boiler group. And
The controller is
A combustion rate calculation unit for calculating the combustion rate of the boiler group;
A proportional gain adjustment unit that adjusts a proportional gain used for the feedback control based on the calculated combustion rate;
A feedback control unit for controlling a combustion state of the boiler group by the feedback control based on the adjusted proportional gain;
With
The proportional gain adjustment unit adjusts the proportional gain lower as the combustion rate of the boiler group is lower, and adjusts the proportional gain higher as the combustion rate of the boiler group is higher.   2. The boiler according to claim 1, wherein the combustion rate calculation unit calculates the combustion rate of the boiler group by dividing an output steam amount output from the boiler group by a maximum steam amount that can be output by the boiler group. system. The boiler system according to claim 1, wherein the combustion rate calculation unit calculates a combustion rate of the boiler group based on the number of boilers in a combustion state.

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