JPH11108348A - Method of monitoring control of air-fuel ratio in boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To monitor whether the volume of air for combustion is fit for the load (fuel command value) of a boiler or not, by setting the conditions with the physical quantity such as the wind pressure of a wind box, the pressure within a furnace, the temperature of exhaust gas, etc., and monitoring these condition values, in place of monitoring the output value of an inverter, to the load of the boiler. SOLUTION: In a boiler which controls a proportional control valve 16 and an inverter 28 by inputting the load of the 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 to the set load zone is within the range of adaptation by monitoring that the physical quantity (wind pressure Pw of a wind box, the pressure Pf within a furnace, and the temperature T of discharge gas) relevant to the combustion state of the boiler is within the range where 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.
A method of monitoring whether the amount of combustion air is compatible with the fuel load (fuel supply amount) to the boiler. Specifically, instead of monitoring the output of the inverter, The present invention relates to a method of setting a condition by a physical quantity, and comparing and monitoring the condition value.

[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 Although it depends on the inertia, it takes a considerable amount of time (for example, about 20 seconds). 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. is there.

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 has as its object to monitor an output signal of an inverter with respect to a fuel load on a boiler in a boiler that controls the amount of combustion air from a blower by inverter control. Instead, by setting conditions for the load zone with physical quantities (pressure, temperature, etc.) related to the combustion state of the boiler, and comparing and monitoring these condition values, the combustion air is added to the fuel load on the boiler. It is to provide a way to monitor whether the quantities are compatible.

[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 is compatible with the set load zone, the set load zone was monitored by monitoring that the physical quantity related to the combustion state of the boiler was within the condition set range. It is characterized by comparing and monitoring that the output signal of the inverter for the load zone is within the applicable range (see FIG. 1).

In the above-mentioned method of the present invention, wind box wind pressure, furnace pressure, and exhaust gas temperature are used as physical quantities related to the combustion state of the boiler (see FIG. 1). The condition for the load zone is set with the two or more physical quantities, and the condition value is monitored instead of monitoring the inverter output. The physical quantity relating to the combustion state of the boiler is merely an example, and instead of monitoring the inverter output, it is possible to monitor that the combustion air amount matches the fuel load on the boiler. If so, it is of course possible to set and monitor conditions with other physical quantities.

For example, the following describes an example of a case where conditions are set and monitored based on wind box wind pressure as physical quantities related to the combustion state of a boiler. Assuming that the wind box wind pressure when the load is 50% is P5 [mmAq], it is monitored that the wind box wind pressure is P5 or more after operation is continued for T hours at a load of 50% or more. In this case, a sensor such as a wind pressure switch is attached to the wind box, the ON / OFF of the sensor is set to P5, and it is monitored that the sensor is ON at P5 after the operation is continued for T hours when the load is 50% or more. When it is less than 50%, the above is reversed, and it is monitored that the sensor is OFF at P5. 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, depending on the range of change of the command value and the inertia of the blower,
The time T is about 5 to 20 seconds. The same applies to the case where conditions are set and monitored by physical quantities such as furnace pressure and exhaust gas temperature.

[0010]

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, an inverter (rotation speed control device) 2
In order to monitor whether or not the output value from the fuel cell 8 conforms to the fuel command value to the proportional control valve 16, as described above, the fuel command value and the output value of the inverter have a one-to-one correspondence.
Since it is difficult to constantly monitor the entire area, the output value from the inverter (rotational speed control device) 28 is
6 and monitor the conformity with the boiler load (fuel command value) sent to the control panel 26 as a master signal, the control panel 26 controls the wind box wind pressure Pw and the furnace pressure for the set load zone. It is monitored that Pf or the exhaust gas temperature T is within the range in which the condition is set, and that the output value of the inverter for the set load zone is within the applicable range. It is also possible to adopt a configuration in which two or more of the wind box wind pressure Pw, the furnace pressure Pf, and the exhaust gas temperature T are simultaneously set as monitored physical quantities. In FIG. 1, the wind box wind pressure Pw, the furnace pressure Pf, and the exhaust gas temperature T are shown as physical quantities related to the combustion state of the boiler. As long as it is possible to monitor that the amount of air for use is appropriate, it is of course possible to set and monitor the conditions with other physical quantities.

Referring to FIG. 1, a case where conditions are set and monitored by wind box wind pressure Pw as physical quantities relating to the combustion state of the boiler will be described as follows. Assuming that the wind box wind pressure when the load is 50% is P5 [mmAq], it is monitored that the wind box wind pressure is P5 or more after the operation is continued for T hours when the load is 50% or more. That is, the ON / OFF of the pressure sensor 36 such as a wind pressure switch attached to the wind box 24 is set to P5, and the control panel 26 connected to the pressure sensor 36
The pressure sensor 36 after the operation continues for T hours when the load is 50% or more.
Is turned on at P5, and when the load is less than 50%, conversely, it is monitored that the pressure sensor 36 is turned off at P5. This embodiment is a case where ON-OFF control is performed using a sensor such as a wind pressure switch.
It is also possible to adopt a configuration in which control is performed stepwise according to the set load zone. 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. Also, in FIG. 1, when conditions are set and monitored with the furnace pressure Pf, the boiler body 10
When the conditions are set using the pressure sensor 38 attached to the combustion chamber 12 and the conditions are set and monitored with the exhaust gas temperature T, the conditions are set using the temperature sensor 40 attached to the exhaust gas duct 32. . The method of setting and monitoring the conditions based on the furnace pressure Pf and the exhaust gas temperature T is the same as in the case of the wind box wind pressure Pw described above.

[0013]

As described above, the present invention has the following effects. (1) The set load zone is monitored by monitoring that the physical quantities (wind box pressure, furnace pressure, exhaust gas temperature, etc.) related to the combustion state of the boiler are within the set conditions for the set load zone. , The output signal of the inverter can be monitored to be within the applicable range, so that it is not necessary to constantly monitor the load of the boiler and the output signal of the inverter on a one-to-one basis over the entire area. (2) Without monitoring the output value of the inverter for the boiler load, conditions are set by physical quantities such as wind box wind pressure, furnace pressure, exhaust gas temperature, etc., and these condition values are compared and monitored. In addition, it is possible to easily monitor whether the amount of combustion air matches the load (fuel command value) of the boiler. (3) Since it is possible to monitor the amount of air for combustion so as to match 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 36 Pressure sensor 38 Pressure sensor 40 Temperature sensor

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FIF23N 5/18 F23N 5/18 L (72) Inventor Fumitoshi Masai 1000 Aochi-cho, Kusatsu-shi, Shiga Prefecture in the factory

Claims (2)

[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 matches the set load, the physical quantity related to the combustion state of the boiler is set for the set load zone. A method for monitoring air-fuel ratio control in a boiler, characterized by monitoring that the output signal is within a specified range, and comparing and monitoring that the output signal of the inverter for the set load zone is within the applicable range. 2. The physical quantity relating to the combustion state of the boiler is:
2. The method for monitoring air-fuel ratio control in a boiler according to claim 1, wherein the air-fuel ratio is at least one of wind box wind pressure, furnace pressure, and exhaust gas temperature.