JP2014219118A - Boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a boiler capable of performing feedback control which can enhance pressure stability.SOLUTION: A boiler 1 which can combust by changing a combustion rate includes a control device 70 for controlling a combustion state of the boiler 1 by feedback control of steam output outputted from the boiler 1. The control device 70 includes: a combustion rate calculation unit 71 for calculating the combustion rate of the boiler 1; a proportional gain adjustment unit 72 for adjusting a proportional gain in such a manner that the lower the combustion rate of the boiler 1, the lower the proportional gain, and the higher the combustion rate of the boiler 1, the higher the proportional gain; and a feedback control unit 73 for controlling the combustion state of the boiler 1 by feedback control based on the adjusted proportional gain.

Description

  The present invention relates to a boiler capable of burning at a different combustion rate.

  In a steam boiler that generates steam, it is common to control the combustion rate of the boiler by performing feedback control of the steam pressure so that the steam pressure in the header becomes a constant target pressure regardless of fluctuations in the steam consumption. Has been done. In this feedback control, a value obtained by multiplying the deviation between the target pressure and the steam pressure in the header by a proportional gain is calculated as the manipulated variable (indicated steam quantity), and steam corresponding to the indicated steam quantity is generated from the boiler according to this manipulated variable. The combustion state of the boiler is controlled as follows.

  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 in which the feedback control which can improve pressure stability is possible.

  The present invention is a boiler capable of burning at a different combustion rate, and includes a control unit that controls a combustion state of the boiler by feedback control of steam output output from the boiler, and the control unit includes the boiler A combustion rate calculation unit that calculates a combustion rate of the engine, a proportional gain calculation unit that adjusts a proportional gain used for the feedback control based on the calculated combustion rate, and the boiler that performs the feedback control based on the adjusted proportional gain. And a proportional gain adjustment unit that adjusts the proportional gain lower as the combustion rate of the boiler is lower and adjusts the proportional gain higher as the combustion rate of the boiler is higher. Related to boilers.

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

It is a figure showing an outline of a boiler concerning an embodiment of the present invention. It is a functional block diagram which shows the structure of a control apparatus. It is explanatory drawing which shows the control flow of a control apparatus. It is explanatory drawing which shows the calculation method of a proportional gain (KP).

Hereinafter, a preferred embodiment of the boiler of the present invention will be described with reference to the drawings.
The boiler 1 of the present embodiment is a steam boiler that generates steam by heating water. As shown in FIG. 1, the boiler 1 includes a can body 10, a blower 20 that sends combustion air to the can body 10, and an air supply duct 30 that connects the can body 10 and the blower 20 and through which combustion air flows. A damper 40 disposed in the air supply duct 30, a fuel supply device 50 that supplies fuel gas to the air supply duct 30, an exhaust pipe 60 through which the combustion gas discharged from the can body 10 circulates, and the can body 10 A water supply channel (not shown) for supplying water to the boiler 1 and a control device 70 for controlling the combustion state of the boiler 1 are provided.

As shown in FIG. 1, the can 10 includes a boiler housing 11, a plurality of water pipes 12, a lower header 13, an upper header 14, and a burner 15.
The boiler housing | casing 11 comprises the external shape of the can 10, and is formed in the rectangular parallelepiped shape of planar view. An air supply port 16 is formed in the first side surface 11a located on one end side in the longitudinal direction of the boiler casing 11, and a second side surface 11b located on the other end side in the longitudinal direction of the boiler casing 11 is An exhaust port 17 is formed.

The plurality of water pipes 12 are disposed so as to extend in the vertical direction inside the boiler housing 11 and are disposed at predetermined intervals in the longitudinal direction and the width direction of the boiler housing 11.
The lower header 13 is disposed at the lower part of the boiler casing 11. The lower header 13 is connected to the lower ends of the plurality of water pipes 12.

The upper header 14 is disposed on the upper portion of the boiler casing 11. The upper header 14 is connected to the upper ends of the plurality of water pipes 12. The upper header 14 is provided with a vapor pressure sensor 18.
The vapor pressure sensor 18 is electrically connected to the control device 70 via a signal line. The vapor pressure sensor 18 measures the vapor pressure inside the upper header 14 (the pressure of the vapor generated in the boiler 1), and transmits a signal (vapor pressure signal) related to the measured vapor pressure to the control device 70.

The burner 15 is disposed in the air supply port 16.
The blower 20 includes a blower body 21 having a fan and a motor that rotates the fan, and an inverter 22 that increases or decreases the number of rotations of the fan (motor). The blower 20 feeds combustion air into the can body 10 when the fan rotates at a predetermined rotation speed in accordance with the frequency input to the inverter 22.

The air supply duct 30 has an upstream end connected to the blower 20 and a downstream end connected to the air supply port 16. The air supply duct 30 supplies the combustion air sent from the blower 20 to the can body 10.
The damper 40 is in a closed state in which the combustion air flow path inside the air supply duct 30 is closed and rotated 90 degrees from this closed state to open the combustion air flow path in the air supply duct 30. It is arranged to be rotatable between states.

The fuel supply device 50 includes a gas supply line 51, and an adjustment valve 52 and a nozzle 53 provided in the gas supply line.
The gas supply line 51 is connected to the downstream side of the air supply duct 30 from the position where the damper 40 is disposed, and supplies the fuel gas to the air supply duct 30.
The adjustment valve 52 adjusts the flow rate of the fuel gas supplied to the air supply duct 30.
The nozzle 53 is disposed at the tip of the gas supply line 51 and ejects fuel gas into the air supply duct 30.

The exhaust tube 60 is connected to the exhaust port 17. The exhaust cylinder 60 discharges the combustion gas generated by the combustion of the fuel gas inside the can 10.
The control device 70 includes a control unit and a storage unit, and controls the combustion state (combustion rate) of the boiler 1 by controlling the supply amount of combustion air and the supply amount of combustion gas to the can 10. The amount of steam generated by the boiler 1 is adjusted.

  According to the boiler 1 described above, the combustion air fed into the air supply duct 30 by the blower 20 is mixed with the fuel gas supplied from the gas supply line 51, and the mixed gas of the fuel gas and the combustion air is burned. 15 is injected into the inside of the can 10 and burned. And the water supplied with the combustion of the mixed gas by the burner 15 heats the water supplied from the lower header 13 to the inside of the plurality of water pipes 12, and generates steam. The steam generated in the plurality of water pipes 12 is collected in the upper header 14 and then led to the outside through a steam outlet pipe (not shown). Further, the combustion gas generated by the combustion of the mixed gas is discharged from the exhaust cylinder 60 to the outside.

Next, details of control of the combustion state of the boiler 1 by the control device 70 will be described.
The control device 70 changes the combustion rate of the boiler 1 and adjusts the amount of steam generated according to the amount of steam consumed by the load equipment to which the boiler 1 supplies steam. Here, the demand load (steam consumption) increases due to an increase in demand for load equipment, and the amount of steam supplied to the upper header 14 (that is, the amount of steam generated from the boiler 1 (hereinafter referred to as “output steam amount”). If there is a shortage), the steam pressure inside the upper header 14 will decrease. On the other hand, if the demand load (steam consumption) decreases due to a decrease in demand for load equipment and the amount of steam supplied to the upper header 14 becomes excessive, the steam pressure inside the upper header 14 increases. Therefore, the boiler 1 can monitor the fluctuation of the required load based on the fluctuation of the steam pressure measured by the steam pressure sensor 18. And the control apparatus 70 can detect the excess or deficiency of steam amount by comparing the preset target pressure with the steam pressure (header pressure) of the upper header 14.
Therefore, in the control device 70, the header pressure becomes the target pressure by performing feedback control based on a predetermined PID algorithm with respect to the deviation between the target pressure set in advance according to the load device and the header pressure. A necessary steam amount (operation amount) is calculated, and the combustion state of the boiler 1 is controlled so that steam corresponding to the calculated steam amount is output from the boiler 1.

Here, in this embodiment, the boiler 1 is comprised by the proportional control boiler which can change a combustion rate continuously. The proportional control boiler is a boiler in which the combustion rate can be continuously controlled at least in the range from the minimum combustion state (for example, the combustion state at a combustion rate of 20% of the maximum combustion amount) to the maximum combustion state. .
It should be noted that continuously changing the combustion rate is included in changing the combustion rate virtually continuously even when the combustion rate is controlled in increments of 0.1% to 2%, preferably in increments of 1%. .

In this embodiment, the change of the combustion rate between the combustion stop state of the boiler 1 and the minimum combustion state is controlled by turning on / off the combustion of the boiler 1 (burner). In the range from the minimum combustion state to the maximum combustion state, the combustion rate can be controlled continuously.
In the following, control of the combustion state in the boiler 1 in which the combustion rate can be continuously changed in the range of 20% to 100% will be described.

  FIG. 2 is a functional block diagram illustrating the configuration of the control unit of the control device 70. The control unit of the control device 70 includes a combustion rate calculation unit 71, a proportional gain adjustment unit 72, and a feedback control unit 73.

  The combustion rate calculation unit 71 calculates the combustion rate of the boiler 1. Here, the calculation of the combustion rate may be performed by an arbitrary method, and the combustion rate calculation unit 71 calculates the combustion rate of the boiler 1 based on, for example, an operation amount that controls the combustion state of the boiler 1.

  The proportional gain adjustment unit 72 adjusts a proportional gain used for feedback control for controlling the combustion state of the boiler 1 based on the calculated combustion rate of the boiler 1. Although details will be described later, the proportional gain adjustment unit 72 adjusts the proportional gain lower as the combustion rate of the boiler 1 is lower, and adjusts the proportional gain higher as the combustion rate of the boiler 1 is higher.

  The feedback control unit 73 controls the combustion state of the boiler 1 by feedback control based on the adjusted proportional gain. That is, the feedback control unit 73 performs a predetermined calculation based on a proportional gain with respect to the deviation between the target pressure and the header pressure (P control), and the amount of steam necessary for the header pressure to become the target pressure (P (Operation amount) is calculated, and the combustion state of the boiler 1 is controlled based on the operation amount.

  Next, the operation of the control unit of the control device 70 will be described with reference to FIG. FIG. 3 is an explanatory diagram showing a control flow of the control device 70.

  First, when the combustion rate calculation unit 71 calculates the combustion rate of the boiler 1, the calculated combustion rate is supplied to the proportional gain adjustment unit 72, and the proportional gain is calculated. In the calculation of the proportional gain, the proportional gain adjustment unit 72 reads the proportional gain maximum value and the proportional gain minimum value from the storage unit.

The proportional gain maximum value (KPmax) is a proportional gain when the combustion rate of the boiler 1 is 100%. The proportional gain maximum value (KPmax) is calculated by dividing the maximum steam amount of the boiler 1 by the control width calculated from the proportional band and the full scale pressure, and is set in advance in this embodiment.
Proportional gain maximum value (KPmax) = Maximum steam volume / (Proportional band x Full-scale pressure)
Proportional band x full scale pressure = control width

The minimum proportional gain (KPmin) is a proportional gain when the combustion rate of the boiler 1 is 20%, that is, when the boiler 1 is burning in the minimum combustion state. 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, the proportional gain adjustment unit 72 reads the combustion rate (F), the proportional gain maximum value (KPmax), and the proportional gain minimum of the boiler 1. Based on the value (KPmin), a proportional gain (KP) is calculated (adjusted) based on the current combustion rate (F).

なお、αは、２点を結ぶ直線のＹ切片である。
ここで、ボイラ１から出力する出力蒸気量と燃焼率（Ｆ）とは一対一の関係にあるため、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. 4 is an explanatory diagram showing a method for calculating the proportional gain (KP) by the proportional gain adjusting unit 72.
Referring to FIG. 4A, 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.

Α is a Y intercept of a straight line connecting two points.
Here, since the output steam amount output from the boiler 1 and the combustion rate (F) are in a one-to-one relationship, the above equation is expressed as follows.

  In FIG. 4 (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.

  Accordingly, the proportional gain adjustment unit 72 adjusts the proportional gain (KP) lower as the combustion rate (F) of the boiler 1 is lower, and adjusts the proportional gain (KP) higher as the combustion rate (F) of the boiler 1 is higher. can do.

  Returning to FIG. 3, when the proportional gain (KP) is adjusted in accordance with the combustion rate (F) of the boiler 1, the feedback control unit 73 determines the operation amount (KP) from the deviation between the target pressure and the header pressure and the proportional gain (KP). The amount of steam to be output) is calculated, and the combustion state of the boiler 1 is controlled based on this manipulated variable. Thereby, the combustion state of the boiler 1 can be controlled so that the steam pressure in the upper header 14 substantially matches the target pressure.

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

In the boiler 1 of this embodiment, when the combustion state of the boiler 1 is controlled by feedback control based on the deviation between the target pressure and the header pressure, the proportional gain (KP) used for the feedback control is set to the combustion rate (F) of the boiler 1. Adjust according to. Specifically, the control unit of the control device 70 adjusts the proportional gain (KP) to be lower as the combustion rate (F) of the boiler 1 is lower, and the proportional gain (KP) is higher as the combustion rate (F) of the boiler 1 is higher. Adjust higher.
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. .

The preferred embodiment of the boiler 1 of the present invention has been described above, but 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 73 is not limited to P control, and may be PI control, PID control, or the like.

  Moreover, in the said embodiment, although the boiler 1 shall be comprised with a proportional control boiler, the boiler 1 is good also as not only a proportional control boiler but with a step value control boiler. The stage value control boiler has a plurality of staged 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 boiler 1 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 1 is not limited to three positions, and may have arbitrary N positions of combustion positions.

1 Boiler 70 Controller 71 Combustion Rate Calculation Unit 72 Proportional Gain Adjustment Unit 73 Feedback Control Unit

Claims (1)

A boiler capable of burning at a different combustion rate,
A controller that controls the combustion state of the boiler by feedback control of steam output output from the boiler;
The controller is
A combustion rate calculation unit for calculating the combustion rate of the boiler;
A proportional gain calculation 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 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 is lower, and adjusts the proportional gain higher as the combustion rate of the boiler is higher.

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