JP2024046838A - Boiler control device - Google Patents

Abstract

[Problem] To provide a boiler control device that can stably ignite after purging. [Solution] A boiler control device for controlling a boiler equipped with a blower that sends air to a combustion chamber and an exhaust damper that controls the amount of exhaust gas discharged from the combustion chamber, and after purging is performed by controlling the blower and the exhaust damper when combustion is started in the boiler, control is started to set the opening degree of the exhaust damper to a predetermined opening degree corresponding to the start of combustion at a predetermined timing that is not related to the amount of air sent by the blower. [Selected Figure] Figure 2

Description

The present invention relates to a boiler control device for controlling a boiler that burns fuel to generate steam, hot water, etc.

Conventionally, in the ventilation line of a multi-boiler system in which the combustion exhaust gas from each of the boilers is combined and exhausted in a collective exhaust stack, a flow control device is provided to adjust the flow rate of the combined combustion exhaust gas, and by controlling the flow control device, the pressure in the collective exhaust stack is kept constant and the backflow of the combustion exhaust gas is prevented (for example, see Patent Document 1).

Patent No. 2962541

However, in conventional boiler control devices, the flow rate control device is controlled according to the pressure in the collective exhaust stack even when the boiler is ignited. For this reason, for example, when purging before boiler ignition, the flow rate control device is controlled to the open side in response to the increase in pressure, and when ignition is subsequently performed, the flow rate control device is controlled to the closed side in response to the decrease in pressure, but the operation of the flow rate control device may not be completed in time, and ignition may proceed under an excessive negative pressure condition, making ignition impossible. On the other hand, if ignition is not allowed to proceed until the negative pressure condition is resolved, unnecessary time may be wasted, which may reduce efficiency.

The present invention was conceived in light of this situation, and its purpose is to provide a boiler control device that can ignite stably and efficiently after purging.

To achieve the above object, a boiler control device according to one aspect of the present invention is a boiler control device for controlling a boiler having a blower that sends air to a combustion chamber and an exhaust damper that controls the amount of exhaust gas discharged from the combustion chamber, and when combustion is started in the boiler, the control device controls the blower and the exhaust damper to purge, and then starts control to set the opening of the exhaust damper to a predetermined opening corresponding to the start of combustion at a predetermined timing that is independent of the amount of air sent by the blower.

According to the above configuration, control is started at a predetermined timing to set the exhaust damper opening to a predetermined opening corresponding to the start of combustion, so that ignition can be performed stably and efficiently after purging.

Preferably, when starting combustion, the boiler starts ignition in the combustion chamber at an ignition transition timing, and the predetermined timing is the same as the ignition transition timing.

According to the above configuration, control is started at the timing of the ignition transition to set the exhaust damper opening to a predetermined opening corresponding to the start of combustion, so ignition can be performed stably and efficiently after purging.

Preferably, when starting combustion, the boiler starts ignition after the flow rate of air sent by the blower reaches a flow rate corresponding to the start of combustion, and the predetermined timing is set to the timing until the flow rate of air sent by the blower reaches a flow rate corresponding to the start of combustion.

With the above configuration, control is started to set the exhaust damper opening to a predetermined opening corresponding to the start of combustion before ignition begins, allowing for stable and efficient ignition after purging.

Preferably, the boiler control device is capable of controlling multiple boilers, the exhaust damper is provided in a collective exhaust passage that joins and discharges exhaust gas from each of the multiple boilers, and the predetermined opening corresponding to the start of combustion is set according to the total combustion amount of each of the multiple boilers at the start of combustion.

The above configuration allows stable and efficient ignition after purging, even when combustion is occurring in two or more boilers.

Preferably, the predetermined opening corresponding to the start of combustion is smaller than the opening when the purging is performed.

The above configuration can prevent ignition transition from occurring under excessive negative pressure.

FIG. 2 is a diagram illustrating a schematic configuration of a boiler control device. 4 is a flowchart illustrating an example of an ignition control process.

<Overview of the Configuration>
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, a schematic configuration of a boiler system according to this embodiment will be described with reference to Fig. 1. As shown in Fig. 1, the boiler system includes a plurality of boilers 1 (for example, two boilers), an exhaust passage 2 for discharging exhaust gas from each of the plurality of boilers 1, a collective exhaust passage 3 for merging and discharging exhaust gas from each of the plurality of boilers 1, a pressure detection unit 5 for measuring a pressure (back pressure) in the collective exhaust passage 3, an exhaust damper 6 provided in the collective exhaust passage 3, and a number control device 7 for controlling the combustion state of each of the plurality of boilers 1. The plurality of boiler bodies 1a are not limited to those having the same performance, and may include boilers having different performances (for example, maximum combustion amount, etc.).

The boiler 1 includes a boiler body 1a that burns fuel to generate steam, hot water, etc., a blower 1b that sends air into the boiler body 1a through an air supply passage 1c, an exhaust passage 2 that draws out exhaust gas from the boiler body 1a, and a fuel supply line (not shown) that supplies fuel to the boiler body 1a. In the burner 1d (including a pilot burner and a main burner), fuel supplied from the fuel supply line is injected and mixed with air blown from the blower 1b through the air supply passage 1c for combustion. The pilot burner is used at the time of ignition, when the main burner is ignited to start combustion in the boiler 1. The main burner starts combustion of the combustion air supplied from the blower 1b and the fuel supplied from the fuel supply line. Note that the fuel is not limited to a liquid such as oil, but may be a gas such as gas.

The exhaust damper 6 is provided in the collective exhaust passage 3, and controls the amount of exhaust gas discharged from the combustion chamber of the boiler body 1a by adjusting the flow rate of the collective exhaust passage 3. When the exhaust damper 6 is fully closed, the flow of the collective exhaust passage 3 is essentially blocked. When the exhaust damper 6 is opened, exhaust is possible.

The opening degree of the exhaust damper 6 is controlled by the number control device 7 via signal line 9. The pressure detection unit 5 detects the pressure (back pressure) in the collective exhaust passage 3, and transmits a pressure value signal for identifying the detected pressure value to the number control device 7 via signal line 8. The analog signal output from the pressure detection unit 9 is converted to a digital signal and input to the number control device 7. The number control device 7 identifies the pressure (back pressure) in the collective exhaust passage 3 based on the pressure value signal, and performs control (hereinafter also referred to as constant control) to adjust the opening degree of the exhaust damper 6 so that the opening degree corresponds to the pressure and the total combustion amount in the multiple boilers.

The number control device 7 includes a memory unit 7a, an input unit 7b, and a control unit 7c. The memory unit 7a stores programs for controlling each of the multiple boilers 1 (including a program for performing the ignition control process shown in FIG. 2), identification information, and the like. The identification information includes information for identifying the pressure value detected by the pressure detection unit 5, information for controlling the open/close state of the exhaust damper 6, and information for identifying the opening degree of the exhaust damper 6 that is set according to the pressure and total combustion amount. Furthermore, the identification information is input from the input unit 7b in response to an operation by an operator.

The number control device 7 can transmit a control signal for controlling each of the multiple boilers 1 via the signal line 10. When starting combustion in any of the multiple boilers 1, the number control device 7 controls the exhaust damper 6 to be in a fully open state, and transmits a control signal for driving the blower 1b of the boiler 1 (hereinafter also referred to as the controlled boiler) to the controlled boiler to start combustion, thereby starting a purge to ventilate the inside of the boiler body (boiler body 1a). After completing the purge, the number control device 7 transmits an ignition transition signal to the controlled boiler, and transitions to a main try to ignite the burner 1d (main burner) through pre-ignition, which generates a spark to form a flame in the burner 1d (pilot burner), ignition try, which ignites the pilot burner, and pilot only, which extinguishes the spark and burns only the pilot burner. Hereinafter, pre-ignition, ignition try, pilot only, and main try may be collectively referred to as "ignition". In the boiler to be controlled, upon receiving the ignition transition signal, a process is started to adjust the amount of air sent by the blower to the amount of air corresponding to the start of combustion, and after the amount of air corresponding to the start of combustion is reached, a process is started to supply fuel from the fuel supply line to the burner 1d (pilot burner), and a process is performed to ignite the burner 1d (pilot burner) by the ignition device.

On the other hand, if a fixed control is applied at the stage of ignition after purging, for example, adjusting the opening of the exhaust damper 6 according to the pressure detected by the pressure detection unit 9, the opening of the exhaust damper 6 is adjusted retroactively according to the amount of air actually sent by the blower, resulting in a transition to the main try under an excessively negative pressure state, which could result in failure to ignite.

Therefore, in this embodiment, at the stage of ignition after purging, a fixed control is not applied to the control of the exhaust damper 6, and control is started to set the opening of the exhaust damper 6 to a predetermined opening corresponding to the start of combustion at a predetermined timing regardless of the amount of air sent by the blower 1b.

The predetermined timing is set to an ignition transition timing before the start of combustion, which is the same as the ignition transition timing at which an ignition transition signal for transitioning to pre-ignition is sent in the boiler to be controlled, but is not limited to this and may be set to any timing before the main try transition timing, for example, the timing of ignition try or the timing of pilot only. The predetermined opening corresponding to the start of combustion is smaller than the opening when purging is performed (for example, fully open), and is an opening that provides an appropriate pressure that does not become an excessive negative pressure in the collective exhaust passage 3. The predetermined opening corresponding to the start of combustion is set in advance according to the performance of the boiler, the total combustion amount of each of the multiple boilers at the start of combustion, etc.

As a result, control is started early at the ignition transition timing to set the exhaust damper 6 to a predetermined opening corresponding to the start of combustion, so that the exhaust damper 6 opening is already at or close to the predetermined opening when the ignition device ignites the burner 1d (pilot burner and main burner) in the controlled boiler. As a result, ignition can be performed stably and efficiently after purging in the controlled boiler. Note that in the combustion state after ignition, a fixed control is applied to control the exhaust damper 6.

<Ignition control process>
2 is a flowchart for explaining an example of an ignition control process performed by the unit count control device 7. The control unit 7c of the unit count control device 7 executes the ignition control process when starting combustion in any one of the plurality of boilers 1.

In step S01, the exhaust damper 6 is controlled to be fully open, and the blower 1b of the boiler to be controlled is driven to start exhausting (purging) the exhaust gas. Specifically, a control signal for driving the blower 1b of the boiler to be controlled is sent to the boiler to be controlled.

In step S02, it is determined whether or not the purge is complete. For example, the completion of the purge may be determined in step S02 when a predetermined time has elapsed since the blower 1b was driven to start the purge. If it is determined that the purge is complete, the process proceeds to step S03, and if it is determined that the purge is not complete, the process returns to step S02.

In step S03, an ignition transition signal is sent to the boiler to be controlled. This causes the boiler to transition to ignition processing. In the ignition processing, the blower 1b starts processing to blow the amount of air corresponding to the start of combustion, and after the amount of air blown reaches the amount of air corresponding to the start of combustion, the pre-ignition, ignition try, pilot only, and main try described above are performed.

At the timing when the number control device 7 transmits the ignition transition signal, in step S04, control is started to set the opening degree of the exhaust damper 6 to a predetermined opening degree corresponding to the start of combustion. The predetermined opening degree is a predetermined opening degree at which the pressure in the collective exhaust passage 3 is appropriate corresponding to the amount of combustion at the start of combustion, and when two or more boilers are controlled to a combustion state, it is a predetermined opening degree at which the pressure in the collective exhaust passage 3 is appropriate corresponding to the total amount of combustion of each of the two or more boilers. Information for specifying the predetermined opening degree is stored in the memory unit 7a. In step S04, a control signal for adjusting the opening degree of the exhaust damper 6 to a predetermined opening degree is transmitted to the exhaust damper 6. As a result, control is started early at the ignition transition timing to set the opening degree of the exhaust damper 6 to a predetermined opening degree corresponding to the start of combustion, so that ignition can be performed stably and efficiently after purging in the controlled boiler. Note that this is executed following the transmission of the ignition transition signal in step S03. Therefore, step S04 is started and executed at a timing before the transition to the main try occurs in the ignition process that is started in the controlled boiler upon receiving the ignition transition signal.

Even if two or more boilers are controlled to be in a combustion state, the opening is controlled according to the total combustion amount of each of the two or more boilers, so that stable and efficient ignition can be performed after purging in the controlled boiler. Note that the opening according to the total combustion amount may be a different opening determined for each total combustion amount, or an opening may be determined for each of a number of predetermined ranges, and an opening corresponding to the range to which the total combustion amount belongs may be set.

In addition, since the specified opening is smaller than the opening (full open) when purging, the pressure in the collective exhaust passage 3 is kept at an appropriate pressure without becoming excessively negative, and ignition transition can be prevented under excessively negative pressure conditions.

The present invention is not limited to the above-described embodiment, and various modifications and applications are possible. Modifications of the above-described embodiment that can be applied to the present invention will be described below.

In the above embodiment, an example of a number control device that controls multiple boilers and controls an exhaust damper provided in a collective exhaust passage that joins and discharges exhaust gas from each of the multiple boilers has been described. However, the present invention is not limited to this, and the exhaust damper provided in the exhaust passage of each of the multiple boilers may be controlled. In this case, it is preferable to provide a pressure sensor in each exhaust passage. Also, a control device that controls one boiler may control an exhaust damper provided in the exhaust passage that discharges exhaust gas from the boiler. In this case, the boiler control device starts control to set the opening of the exhaust damper to a predetermined opening corresponding to the start of combustion at the ignition transition timing when transitioning to pre-ignition after purging, thereby enabling stable and efficient ignition after purging.

In the above embodiment, the ignition transition timing for transitioning to pre-ignition is exemplified as the predetermined timing for starting control to set the exhaust damper opening to a predetermined opening corresponding to the start of combustion. However, the predetermined timing is not limited to this as long as it is a timing until actual ignition occurs, and may be, for example, a timing until the flow rate of air sent by the blower reaches a flow rate corresponding to the start of combustion (for example, a timing when a time shorter than the average time required for the flow rate of air sent by the blower to reach a flow rate corresponding to the start of combustion has elapsed after transitioning to pre-ignition), or a timing prior to the ignition transition timing (for example, a timing when purging is completed, a predetermined time has elapsed since the completion of purging, etc.).

In the above embodiment, an example was described in which control is started to set the opening of the exhaust damper 6 to a predetermined opening corresponding to the start of combustion at a predetermined timing, regardless of the amount of air sent by the blower 1b, during the ignition stage after purging. However, depending on the situation, it may be the case that the opening of the exhaust damper 6 is already (by chance) the predetermined opening corresponding to the start of combustion during the ignition stage after purging, in which case the opening is maintained.

In the above embodiment, an example was described in which the main try is performed in the order of pre-ignition, ignition try, and pilot only. However, in the case of a boiler that does not have a pilot burner and only has a main burner, such as an oil-fired boiler, pre-ignition is performed, and then the main try is performed to ignite the main burner. Even in this case, control may be started to set the opening of the exhaust damper 6 to a predetermined opening corresponding to the start of combustion at a timing prior to the timing of transition to the main try.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope of the claims.

1 Boiler 1a Boiler body 1b Blower 1c Air supply passage 1d Burner (pilot burner and main burner)
2 Exhaust passage 3 Collective exhaust passage 5 Pressure detection unit 6 Exhaust damper 7 Number control device 7a Memory unit 7b Input unit 7c Control unit 8 Signal line 9 Signal line 10 Signal line

Claims (5)

A boiler control device for controlling a boiler having a blower for blowing air into a combustion chamber and an exhaust damper for controlling exhaust gas discharged from the combustion chamber,
A boiler control device that controls the blower and the exhaust damper to purge when combustion is started in the boiler, and then begins control of the exhaust damper to a predetermined opening corresponding to the start of combustion at a predetermined timing regardless of the amount of air being sent by the blower. When starting combustion, the boiler starts ignition in the combustion chamber at an ignition transition timing,
The boiler control device according to claim 1 , wherein the predetermined timing is the same timing as the ignition transition timing. When starting combustion, the boiler starts ignition after the flow rate of air sent by the blower reaches a flow rate corresponding to the start of combustion,
The boiler control device according to claim 1 , wherein the predetermined timing is set to a timing at which a flow rate of the air sent by the blower reaches a flow rate corresponding to a time when the combustion starts. The boiler control device is capable of controlling a plurality of boilers,
The exhaust damper is provided in a collective exhaust passage that joins and discharges exhaust gases from the respective boilers,
4. The boiler control device according to claim 1, wherein the predetermined opening corresponding to the start of combustion is set according to a total combustion amount of each of the plurality of boilers at the start of combustion. 4. The boiler control device according to claim 1, wherein the predetermined opening corresponding to the start of combustion is smaller than the opening when the purging is performed.

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