JP6102350B2 - boiler - Google Patents

Description

  The present invention relates to a boiler. More specifically, the present invention relates to a boiler that can supply a suitable amount of combustion air in accordance with changes in the combustion state.

  Conventionally, in a boiler that includes a burner that burns fuel, a fuel supply device that supplies fuel to the burner, and a blower that supplies combustion air to the burner and is burned in a plurality of combustion states (combustion rates) The amount of air required for combustion differs depending on the combustion rate. Therefore, the blower includes a fan, a motor that rotates the fan, and an inverter that varies the drive (rotation speed) of the motor, and increases or decreases the rotation speed of the motor (fan) according to the combustion rate. Thus, a technique for supplying an appropriate amount of combustion air to the burner is used.

  Thus, when adjusting the supply amount of combustion air by increasing / decreasing the rotational speed of the fan, the supply amount of combustion air is reduced by decreasing the rotational speed of the fan in a low combustion rate state. However, when the rotation speed of the fan is decreased to reduce the supply amount of combustion air, the supply pressure of the combustion air supplied to the burner becomes weak and the combustion state may be difficult to stabilize.

  Therefore, a technique has been proposed in which a damper is disposed on the downstream side of the blower and the supply amount of combustion air is adjusted by opening and closing the damper (see, for example, Patent Document 1). According to the technique proposed in Patent Document 1, in a low combustion position with a low combustion rate, the damper is closed with a small opening while controlling the rotational speed of the fan to maintain a predetermined supply pressure. While maintaining the supply pressure of the combustion air supplied to the burner, an appropriate amount of combustion air is supplied to the burner. Further, at a high combustion position where the combustion rate is high, the damper is opened with a large opening and the rotational speed of the fan is increased to supply an appropriate amount of combustion air to the burner.

JP 2006-138561 A

Patent Document 1 proposes a technique for controlling the supply amount of combustion air in a stage value control boiler that is burned at multi-stage combustion positions including a low combustion position and a high combustion position.
On the other hand, in recent years, there has been a demand for a boiler capable of controlling the combustion state more finely than a conventional step value control boiler. When the combustion state of the boiler is finely controlled, the amount of combustion air supplied to the burner is also required to be finely controlled according to the change in the combustion state.

  Therefore, an object of the present invention is to provide a boiler capable of supplying a suitable amount of combustion air according to changes in the combustion state.

  The present invention is a boiler capable of burning at a different combustion rate, having a burner that burns fuel, a fan, a blower that rotates the fan and supplies combustion air to the burner, and the burner And a damper that is disposed between the blower and that can be opened and closed within a predetermined range of opening, and a controller that controls the opening of the damper and the rotational speed of the fan in accordance with a change in the combustion rate. The control unit controls the supply amount of the combustion air according to the opening degree of the damper while fixing the rotation speed of the fan at a combustion rate in the first range, and in the first range. The present invention relates to a boiler that changes the opening / closing speed of the damper so that the change rate of the combustion rate is constant.

  Moreover, it is preferable that the said control part makes the opening / closing speed of the said damper in the range with the said large opening degree faster than the opening / closing speed of the said damper in the range with the said small opening degree.

  The control unit opens and closes the damper at a first speed when the opening is less than or equal to the first opening, and opens and closes the damper when the opening exceeds the first opening. Is preferably gradually accelerated from the first speed.

  In addition, the control unit controls the supply amount of the combustion air according to the rotational speed of the fan while fixing the opening of the damper at a combustion rate in the second range larger than the combustion rate in the first range. It is preferable to do.

  Moreover, it is preferable that a boiler is comprised by the proportional control boiler which can change a combustion rate continuously.

  According to the boiler of the present invention, a suitable amount of combustion air can be supplied in accordance with changes in the combustion state.

It is a figure showing typically one embodiment of the boiler of the present invention. It is a figure which shows the relationship between the opening degree of a damper when the rotational speed of a fan is made constant, and the flow volume of the combustion air which distribute | circulates an air supply duct. It is a figure which shows the relationship between a combustion rate and the opening degree of a damper in the case of changing a combustion rate to 20%-40%. It is a figure which shows the relationship between the opening degree of a damper, and the speed which opens and closes a damper. It is a figure which shows the relationship between the change of a combustion rate, and the transition time concerning the change of a combustion rate.

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 and a control unit 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 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 18. 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 controller 70 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 body 10 and adjusts the amount of steam generated by the boiler 1. To do.

  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 the control of the combustion state of the boiler 1 by the control unit 70 will be described.
The control unit 70 changes the combustion rate of the boiler 1 according to the amount of steam consumed by the load equipment to which the boiler 1 supplies steam, and adjusts the amount of steam generated.

  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. .

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.

  The controller 70 increases or decreases the rotational speed of the fan of the blower 20 by increasing or decreasing the frequency input to the inverter 22, and controls the amount of combustion air fed into the air supply duct 30. Further, the control unit 70 controls the amount of combustion air flowing through the air supply duct 30 toward the burner 15 by controlling the opening degree of the damper 40.

  Here, in a state where the combustion rate is low, if the rotation speed of the fan is decreased to reduce the supply amount of the combustion air, the supply pressure of the combustion air supplied to the burner 15 becomes weak and the combustion state is difficult to stabilize. . Therefore, in this embodiment, the control unit 70 fixes the rotational speed of the fan and adjusts the opening degree of the damper 40 in the first range (20% to 40%) where the combustion rate is low. Control air supply. And in the 2nd range (40%-100%) with a high combustion rate, the control part 70 fixes the opening degree of the damper 40 (for example, fully open), adjusts the rotational speed of a fan, and is for combustion Control air supply.

  Here, as shown in FIG. 2, when the rotational speed of the fan is fixed at a constant speed and the flow rate of the combustion air is adjusted by the opening degree of the damper 40, the damper 40 has a small opening, that is, the damper. In the range where 40 is close to the closed state (for example, the opening degree is 35 degrees or less), the change in the flow rate of the combustion air with respect to the change in the opening degree of the damper 40 becomes large.

On the other hand, in the range where the opening degree of the damper 40 is large, that is, in the range where the damper 40 is close to the open state (for example, the opening degree is 35 degrees or more), the change in the flow rate of combustion air with respect to the change in the opening degree of the damper 40 is Get smaller.
That is, when the opening degree of the damper 40 is small, there is a large change in the flow rate of combustion air with a slight change in the opening degree, whereas when the opening degree of the damper 40 is large, the change in the opening degree is large. Otherwise, the flow rate of combustion air cannot be changed greatly.
Therefore, the relationship between the combustion rate and the opening degree of the damper 40 when the combustion rate is changed from 20% to 40% is as shown in FIG. That is, when changing the combustion rate from 35% to 40%, it is necessary to change the opening degree of the damper 40 largely compared to changing the combustion rate from 20% to 35%.

  Therefore, the control unit 70 changes the opening / closing speed of the damper 40 so that the change rate of the combustion rate in the first range (20% to 40%) is constant. Specifically, the control unit 70 includes a range in which the opening degree of the damper 40 is larger than the opening / closing speed in a range in which the opening degree of the damper 40 is small (for example, 20 degrees to 35 degrees). , 35 to 70 degrees) is increased.

  More specifically, as shown in FIG. 4, the controller 70 moves the damper 40 to the first speed (for example, 10 deg / s) in the range where the opening degree of the damper 40 is not more than the first opening (for example, 35 degrees). In the range where the opening degree of the damper 40 exceeds the first opening degree (for example, a range of 35 degrees to 70 degrees), the opening / closing speed of the damper 40 is gradually accelerated from the first speed. That is, in the range exceeding the first opening, the rate of change of the combustion rate in this range is the first opening in which the amount of change in the degree of opening of the damper 40 is approximately proportional to the amount of change in the combustion air flowing. The opening / closing speed of the damper 40 is accelerated so as to be equal to the change rate of the combustion rate up to the degree.

  Thereby, according to this embodiment, as shown to the continuous line part of FIG. 5, in the 1st range (20%-40%), the speed which changes a combustion rate can be made constant, and a combustion rate is changed. The transition time in the case can be shortened. 5 indicates the relationship between the change in the combustion rate and the transition time when the opening / closing speed of the damper 40 is fixed to the first speed at all opening degrees.

According to the boiler 1 of this embodiment demonstrated above, there exist the following effects.
(1) In a state where the combustion rate is low, if the rotation speed of the fan is decreased to reduce the supply amount of combustion air, the supply pressure of the combustion air supplied to the burner 15 becomes weak and the combustion state is difficult to stabilize. . On the other hand, when the amount of combustion air supplied to the burner 15 is adjusted by the opening degree of the damper 40, while the opening degree of the damper 40 is small, there is a large change in flow rate with a slight change in opening degree. In the state where the opening degree of the damper 40 is large, the flow rate cannot be changed greatly unless the change in the opening degree is increased. Therefore, the control unit 70 changes the opening / closing speed of the damper so that the change rate of the combustion rate becomes constant in the first range where the combustion rate is low. Specifically, the controller 70 is caused to make the opening / closing speed of the damper 40 in the large opening range faster than the opening / closing speed of the damper 40 in the small opening degree range. Thereby, even when the combustion state of the boiler 1 is finely controlled in the first range where the combustion rate is low, the amount of combustion air supplied to the burner 15 can be appropriately adjusted according to the change in the combustion state. Moreover, the transition time when changing the combustion rate can be shortened.

  (2) As shown in FIG. 3, in the range where the opening degree of the damper 40 is not more than the first opening degree (about 35 degrees), the amount of change in the combustion rate (the amount of change in the combustion air) and the required damper 40 The amount of change in the opening is generally proportional. On the other hand, in the range where the opening degree of the damper 40 exceeds the first opening degree, the change amount of the opening degree of the damper 40 required for the change amount of the combustion rate increases exponentially. Therefore, the control unit 70 opens and closes the damper 40 at the first speed when the opening degree of the damper 40 is less than or equal to the first opening degree, and when the opening degree of the damper 40 exceeds the first opening degree, the damper 40 is opened. Was gradually accelerated from the first speed. Thereby, in the 1st range, the speed which changes a combustion rate can be made constant easily.

  (3) The controller 70 controls the supply amount of the combustion air by the rotation speed of the fan with the opening degree of the damper 40 fixed at the combustion rate in the second range larger than the combustion rate in the first range. . Thus, in the first range where the combustion rate is low, the combustion air can be supplied to the burner 15 without lowering the supply pressure by adjusting the opening of the damper 40, and in the second range where the combustion rate is high, the fan An appropriate amount of combustion air can be supplied to the burner 15 by adjusting the rotation speed. Therefore, combustion air can be more suitably supplied in accordance with changes in the combustion state.

As mentioned above, although one preferable embodiment of the boiler of this invention was described, this invention is not restrict | limited to embodiment mentioned above, It can change suitably.
For example, in the present embodiment, the present invention is applied to a proportional control boiler, but is not limited thereto. That is, the present invention may be applied to a stage value control boiler capable of burning by changing the combustion rate in stages.

  Further, in the present embodiment, the control unit 70 opens and closes the damper 40 at the first speed when the opening degree of the damper 40 is equal to or less than the first opening degree, and the opening degree of the damper 40 exceeds the first opening degree. In the range, the opening / closing speed of the damper 40 is gradually accelerated from the first speed, but the present invention is not limited to this. That is, based on the correlation between the combustion rate and the opening degree of the damper, a function for making the speed for changing the combustion rate constant may be obtained, and the opening / closing speed of the damper may be changed based on this function.

1 Boiler 15 Burner 20 Blower 40 Damper 70 Control Unit

Claims (5)

A boiler capable of burning at a different combustion rate,
A burner that burns fuel;
A blower having a fan and rotating the fan to supply combustion air to the burner;
A damper that is disposed between the burner and the blower, and that can be opened and closed at a predetermined range of opening;
A control unit that controls the opening degree of the damper and the rotational speed of the fan according to the change in the combustion rate,
The controller is
With the combustion rate in the first range, the rotational speed of the fan is fixed, the amount of combustion air supplied is controlled by the opening of the damper, and the rate of change of the combustion rate in the first range is A boiler that changes the opening and closing speed of the damper so as to be constant.   The boiler according to claim 1, wherein the control unit increases the opening / closing speed of the damper in a range where the opening degree is larger than the opening / closing speed of the damper in a range where the opening degree is small. The controller is
In the range where the opening is not more than the first opening, the damper is opened and closed at a first speed,
The boiler according to claim 1 or 2, wherein the opening / closing speed of the damper is gradually accelerated from the first speed in a range where the opening degree exceeds the first opening degree.   The control unit controls the supply amount of the combustion air according to a rotation speed of the fan while fixing the opening degree of the damper at a combustion rate in a second range larger than the combustion rate in the first range. Item 4. The boiler according to any one of Items 1 to 3.   The boiler in any one of Claims 1-4 comprised by the proportional control boiler which can change a combustion rate continuously.

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