JPH11108347A - Method of monitoring air-fuel ratio control in boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To monitor whether the output signal of an inverter is fit for a fuel command value or not, in stages. SOLUTION: In a boiler which controls a proportional control valve 16 and an inverter 28 by inputting the load of a boiler as an input signal into the proportional control valve 16 and the inverter (revolution controller), and controls the quantity of supplied fuel by the proportional control valve 16, and also controls the quantity of air for combustion from a blower 20 by the output signal of the inverter, this method monitors, by comparison, that the output signal of the inverter is within the range of adaptation where the conditions are set to the set load zone, in place of monitoring that the output signal of the inverter is fit for the set load (fuel command value).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiler for controlling the amount of combustion air from a blower by inverter control.
The present invention relates to a method of monitoring whether or not a combustion air amount matches a fuel load (fuel supply amount) to a boiler, and more particularly, to a method of comparing inverter output condition values for a load zone and monitoring stepwise.

[0002]

2. Description of the Related Art In a continuous control (proportional control) boiler,
When controlling the amount of combustion air from the blower by inverter control, the proportional control valve is controlled by the fuel load command to the boiler to adjust the fuel supply amount, and the load is input from the inverter (rotation speed control device). By outputting the rotation speed (frequency) of the blower and controlling the motor of the blower, the amount of combustion air to the boiler is controlled. In this case, if the amount of combustion air is insufficient with respect to the amount of fuel supplied to the boiler, incomplete combustion may occur and black smoke may be generated, and the amount of combustion air may be reduced relative to the amount of fuel supplied to the boiler. Is excessive, not only wasteful consumption of blowing power but also burnout of the burner may occur. Therefore, in a boiler in which the amount of combustion air from a blower is controlled by inverter control, monitoring of the amount of combustion air, that is, whether the output signal of the inverter matches the fuel load (fuel command value) to the boiler is performed. is necessary.

Japanese Patent Application Laid-Open No. 8-178271 discloses that in a three-position control boiler, when shifting from low combustion to high combustion,
First, increase the rotation speed of the blower, detect the amount of air from the blower from the discharge pressure or rotation speed of the blower, and when the amount of air is appropriate for high combustion, open the high combustion oil solenoid valve and burn the high combustion fuel to the burner. It is described that when the combustion shifts from high combustion to low combustion, the rotation speed of the blower is lowered, and the amount of air from the blower is detected from the discharge pressure or rotation speed of the blower to be suitable for low combustion. It is described that, when the air volume becomes sufficient, the high combustion oil solenoid valve is closed to supply low burn fuel to the burner. Further, it is described that instead of detecting the amount of air from the blower and increasing or decreasing the combustion amount, the fuel is increased or decreased after a lapse of a predetermined time from an instruction to increase or decrease the rotation speed of the blower.

[0004]

In order to monitor whether the output signal of the inverter conforms to the fuel command value, the fuel command value (fuel load on the boiler) and the output signal of the inverter are one-to-one. As long as it can be monitored continuously,
Since there is a time difference between the input of the signal to the inverter and the output of the signal from the inverter, it is difficult to constantly monitor the fuel command value and the output signal of the inverter on a one-to-one basis over the entire area. That is, in response to the boiler load command, the opening and closing of the fuel proportional control valve is performed relatively quickly,
While the amount of fuel supplied quickly becomes the fuel command value, the range of change in the command value and the fan Depending on the inertia, a considerable amount of time (eg, 5-20
(Approximately 2 seconds), and this time difference makes it difficult to constantly monitor the fuel command value and the output signal of the inverter on a one-to-one basis over the entire area.

In the method described in Japanese Patent Application Laid-Open No. 8-178271, when the combustion shifts from low combustion to high combustion, the number of rotations of the blower (including the case of detecting by wind pressure or time) increases to a predetermined value. Since the oil solenoid valve is opened from the beginning, incomplete combustion due to a shortage of air is unlikely to occur, and smoke can be prevented. However, when transitioning from high combustion to low combustion, the oil solenoid valve is closed after the blower speed has been reduced, so the amount of air decreases when the appropriate amount of fuel is supplied for high combustion. As a result, incomplete combustion occurs due to insufficient air volume, and smoke is generated. Also, JP-A-8-1
The three-position control boiler described in Japanese Patent No. 78271 controls the amount of combustion air from a blower by inverter control, and an output signal of an inverter (rotation speed control device) is applied to a fuel load (fuel command value) to the boiler. Compliance needs to be monitored.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a boiler in which the amount of combustion air from a blower is controlled by inverter control, wherein a fuel load on the boiler and an output signal of the inverter are paired. Provided is a method of stepwise monitoring whether or not the amount of combustion air is compatible with a fuel load on a boiler by comparing and monitoring an inverter output condition value with respect to a load zone without monitoring in step 1. It is in.

[0007]

In order to achieve the above-mentioned object, a method of monitoring air-fuel ratio control in a boiler according to the present invention comprises the steps of setting a load of a boiler as an input signal to a fuel control valve and an inverter (rotation speed control device). A load (fuel command value) set in a boiler that inputs and controls a fuel control valve and an inverter, controls a fuel supply amount by a fuel control valve, and controls a combustion air amount from a blower by an output signal of the inverter. Instead of monitoring that the output signal of the inverter conforms to the above, it is characterized in that the output signal of the inverter is compared with the set load zone and is monitored within the conformity range set by the condition. (See FIG. 1).

For example, the inverter output value (frequency [Hz]) when the load is 30% is N3, the inverter output value when the load is 50% is N5, and the inverter output value when the load is 70% is N7. If the inverter output value is N10 when the load is 100%, these can be set on a one-to-one basis. Therefore, when the load is 30% or more and the inverter output value is N3 or more after the continuation of the T time operation, and when the load is 50% or more, the inverter output value is N5 or more after the continuation of the T time operation and the load is 50% or more.
%, The inverter output value is less than N5 after the continuation of the T-hour operation, and the load is 70% or more, and the inverter output value is N7 or more after the continuation of the T-time operation. A condition is set such that the load is 100% and the inverter output value is N10 after continuation of the operation for T hours, and the matching between the fuel command value and the inverter output value is monitored. The time T is determined in consideration of a time difference between the input of the signal to the inverter and the output of the signal from the inverter. Normally, the time T is about 5 to 20 seconds, depending on the range of change of the command value and the inertia of the blower.

[0009]

FIG. 1 schematically shows an apparatus for implementing a method for monitoring air-fuel ratio control in a boiler according to an embodiment of the present invention. In the present embodiment, in a continuous control (proportional control) boiler, the amount of combustion air from a blower is controlled by inverter control (no link mechanism). As the boiler, for example, a multi-tube once-through boiler is used, but other boilers can of course be used. In FIG. 1, reference numeral 10 denotes a boiler main body, and a burner 14 is provided above a combustion chamber 12 of the boiler main body 10. The burner 14 has a proportional control valve (fuel flow control valve)
Fuel is supplied from a fuel supply pipe 18 having 16. Oil, gas or the like is used as the fuel. On the other hand, the combustion air is supplied from the blower 20 to the wind box 24 through the air supply pipe 22, and is supplied to the burner 14 for combustion. In the present embodiment, since the boiler is a continuous control (proportional control) boiler, a proportional control valve is used as a fuel control valve, but another control valve may be used. When a master signal for instructing the load of the boiler is sent to the control panel 26, the fuel supply amount is controlled by the proportional control valve 16 connected to the control panel 26, and the inverter (rotation speed control) connected to the control panel 26 The output value (frequency) from the device 28 is sent to the motor 30 of the blower 20 to control the air supply amount. Reference numeral 32 denotes an exhaust gas duct that accommodates the economizer, and reference numeral 34 denotes a steam separator.

Here, in order to monitor whether or not the output value of the inverter conforms to the fuel command value, the output value from the inverter (rotation speed control device) 28 is controlled by the control panel 26.
To the control panel 2 as a master signal.
6 is compared with the boiler load (fuel command value) sent thereto, and as described above, the fuel command value and the output value of the inverter are constantly monitored on a one-to-one basis over the entire area. Is difficult, so in the control panel 26,
It is monitored that the output value of the inverter for the set load zone is within the conforming range set by the condition.

For example, the inverter output value (frequency [Hz]) when the load is 30% is N3, the inverter output value when the load is 50% is N5, the inverter output value when the load is 70% is N7, If the inverter output value is N10 when the load is 100%, these can be set on a one-to-one basis. Therefore, when the load is 30% or more and the inverter output value is N3 or more after the continuation of the T time operation, and when the load is 50% or more, the inverter output value is N5 or more after the continuation of the T time operation and the load is 50% or more.
%, The inverter output value is less than N5 after the continuation of the T-hour operation, and the load is 70% or more, and the inverter output value is N7 or more after the continuation of the T-time operation. A condition that the load is 100% and the inverter output value is N10 after the continuation of the operation for T hours is input to the control panel 26, and the matching between the fuel command value and the inverter output value is compared and monitored. The time T is determined in consideration of a time difference between the input of the signal to the inverter and the output of the signal from the inverter.

[0012]

As described above, the present invention has the following effects. (1) It is only necessary to monitor that the output signal of the inverter is within the conforming range set in the condition with respect to the set load zone.
There is no need to constantly monitor the entire area on a one-to-one basis. (2) Since it is possible to monitor the amount of air for combustion so that it matches the fuel command value, the amount of air is insufficient, incomplete combustion occurs and black smoke is generated, or the amount of air becomes excessive and The power is not wasted and the burner does not blow out.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an apparatus for implementing a method for monitoring air-fuel ratio control in a boiler according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Boiler main body 12 Combustion chamber 14 Burner 16 Proportional control valve 18 Fuel supply pipe 20 Blower 22 Air supply pipe 24 Wind box 26 Control panel 28 Inverter (rotation speed control device) 30 Motor 32 Exhaust gas duct 34 Gas-water separator

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Fumitoshi Masai 1000 Aochi-cho, Kusatsu-shi, Shiga Prefecture

Claims (1)

[Claims] 1. A boiler load is input to a fuel control valve and an inverter as an input signal to control the fuel control valve and the inverter, and a fuel supply amount is controlled by the fuel control valve. In a boiler that controls the amount of combustion air, instead of monitoring that the output signal of the inverter conforms to the set load, the output signal of the inverter falls within the conforming range that is set for the set load zone. A method for monitoring air-fuel ratio control in a boiler, characterized in that: