JP2000088241A - Controller and control method of air supply to boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power consumption of a fan by detecting flow rate of fuel being supplied to a boiler and setting the r.p.m. of the fan for the boiler such that the oxygen concentration of exhaust gas from the boiler is optimized for the detected flow rate of fuel. SOLUTION: Flow rate of fuel being supplied to a boiler 5 is detected using a load oscillator comprising a fuel flow rate regulating valve 1 and an angle sensor for detecting the rotational angle of a rotary shaft 11, i.e., a link mechanism, linked with the opening regulator for an air damper 10. In order to optimize the oxygen concentration of exhaust gas from the boiler 5 for the detected flow rate of fuel, operating state of the boiler 5 is assumed while being divided by about ten points from light load to heavy load and the r.p.m. of a fan 7 is determined by performing test run of the boiler 5 at each point thus reduce power consumption of the fan 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a boiler - relates blowing amount control method and control apparatus for, more specifically, (sometimes hereinafter referred to as O ₂₎ oxygen sensor is not required, and maintenance is simple The present invention relates to a method and a device for controlling the amount of air blown to a boiler having an extremely fast response time.

[0002]

2. Description of the Related Art Due to the recent increase in global environmental problems, there is a demand for an energy-saving operation method for operating a boiler. In general, an appropriate amount of air is required in a combustion state of not only a boiler but also various devices. That is, if the amount of air is insufficient, incomplete combustion occurs, and not only harmful unburned gas is discharged into the atmosphere as exhaust gas, but also a dangerous combustion state in which an explosion or the like may occur. Conversely, if the amount of air is excessive, the amount of exhaust gas increases. In general, it is known that the amount of heat carried by exhaust gas increases in proportion to the amount of air. If the amount of air is excessive, fuel is consumed unnecessarily, and it cannot be said that the combustion state is efficient. Therefore, in the operation of a boiler, as an energy-saving operation method, an operation method has been conventionally proposed in which the amount of air is reduced as much as possible while maintaining a combustion state in which incomplete combustion is not caused by an insufficient amount of air, that is, the oxygen concentration in exhaust gas is reduced as much as possible. ing.

In general, a boiler controls the output (steam amount) by adjusting the amount of fuel and the amount of air.
I have. That is, the amount of fuel is usually adjusted by adjusting the opening of the automatic control valve, and the amount of air is adjusted by adjusting the opening of the air damper. However, in the conventional air damper opening adjustment, the air damper has a simple structure, so that the delicate adjustment of the air amount is structurally impossible, and the opening is adjusted to prevent a danger of explosion. Since the operation is often performed in a slightly open state, the operation is performed while the oxygen concentration in the exhaust gas is high, and there is a problem that the operation for energy saving cannot be sufficiently performed.

As a method for solving this problem, a method of detecting the oxygen concentration in the exhaust gas and adjusting the air volume (a rotation speed control method by O ₂ feedback) has been proposed. In a boiler actually called a package boiler, a method has been proposed. Are operated by this method. A typical example of this operation method will be described with reference to FIG. That is, according to this method, the oxygen concentration detected by the exhaust gas oxygen concentration detector (6) is fed back and converted into a rotation speed command by the controller (8), and the output is used as the rotation speed control device of the blower (7). The rotation speed of the blower (7) is adjusted.

On the other hand, the steam pressure of the boiler (drum pressure)
Is fed back to a master controller (12), and an output from the master controller (12) is mechanically transmitted via a link mechanism (11), and one is an AC valve (also referred to as an automatic control valve or a fuel flow control valve) (1). Controls the amount of fuel, and the other controls the amount of air using an air damper (10). In this case, usually, the air damper (10) is used for auxiliary use (slightly opening) or in a fully opened state.

However, in this method, the fuel amount and the air amount are configured as separate systems, and the exhaust gas oxygen concentration detector (6) is required, so that the system becomes complicated and expensive. In addition, trouble is likely to occur due to failure of the sensor of the exhaust gas oxygen concentration detector or dirt or clogging by the exhaust gas, and delay in controllability (from detecting the actual value to shifting to control, that is, the controlled combustion gas After reaching the exit, pass through the tube until it reaches the sensor.
(It takes about 0 seconds to 1 minute)), and the boiler combustion cannot be operated stably and the energy saving operation cannot be sufficiently performed.

[0007]

[SUMMARY OF THE INVENTION The present invention has been made from the viewpoint, O ₂ sensor is not required, maintain simple and the response time is extremely fast, blower power consumption can be boiler reduce - to An object of the present invention is to provide a method and a device for controlling the amount of air blow.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have conducted a test run of a boiler in advance to feed the gas so that the amount of oxygen in the exhaust gas becomes optimal. By measuring the relationship between the amount of fuel and the amount of combustion air, and adjusting the amount of air blown to the boiler based on the relationship, the optimal oxygen is constantly maintained over a wide range from low load operation to high load operation. The inventors have found that an operation for increasing the concentration is possible, and have completed the present invention.

That is, the present invention provides a method and apparatus for controlling the amount of air blown to a boiler as described below. 1. A method of controlling the amount of air blown to a boiler, which detects the flow rate of fuel supplied to the boiler, and controls the blower to the boiler so that the oxygen concentration in the boiler exhaust gas is optimal for the detected fuel flow rate. A method for controlling the amount of air blown to a boiler, comprising setting a rotation speed. 2. A method for controlling the amount of air blown to a boiler, comprising detecting a flow rate of fuel supplied to the boiler and an opening degree of a damper in an air passage to the boiler, and detecting boiler exhaust gas with respect to the detected fuel flow rate and the opening degree of the damper. A method for controlling the amount of air blown to a boiler, wherein the number of rotations of the blower to the boiler is set so that the oxygen concentration in the air becomes optimal. 3. The relationship between the flow rate of fuel supplied to the boiler and the amount of air blown to the boiler is measured in advance so that the amount of oxygen in the boiler exhaust gas is optimized, and the number of rotations of the blower to the boiler is determined based on the relationship. 3. The method for controlling the amount of air blown to the boiler according to the above item 1 or 2, wherein 4. A controller for controlling the amount of air blown to a boiler, comprising: means for detecting the flow rate of fuel supplied to the boiler; and using the fuel flow rate obtained by the detecting means as an input value so that the oxygen concentration in the boiler exhaust gas is optimized. A control device, comprising: a calculating means for calculating the rotation speed of the blower to the fan; and a means for transmitting the calculation result to a rotation speed controller of the blower. 5. A controller for controlling the amount of air blown to a boiler, comprising: means for detecting a flow rate of fuel supplied to the boiler; means for detecting an opening degree of a damper in an air passage to the boiler; and a fuel flow rate and a damper opening obtained by the detecting means. Means for calculating the number of rotations of the blower to the boiler so that the oxygen concentration in the boiler exhaust gas is optimized with the degree as an input value, and means for transmitting the calculation result to the number of rotations controller of the blower. Control device. 6. In the calculating means for calculating the number of rotations of the blower to the boiler, the amount of oxygen in the boiler exhaust gas is optimized based on the relationship between the flow rate of fuel supplied to the boiler and the amount of air blown to the boiler measured in advance. 6. The control device according to the above item 4 or 5, wherein the number of rotations of the blower to the boiler is set in the control unit. 7. The fuel flow rate detection means and the damper opening degree detection means are:
7. The control device according to any one of the above 4 to 6, wherein the control device is provided for a rotary shaft connected to the fuel flow control valve and the damper opening adjuster. 8. The fuel flow rate detection means and the damper opening degree detection means are:
4 to 7 which are angle sensors for detecting a rotation angle of a rotation shaft connected to a fuel flow rate control valve and a damper opening degree adjuster.
The control device as described.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to FIG. 2 showing one embodiment of the present invention. 1. The method for controlling the amount of air blown to the boiler of the present invention, the method for controlling the amount of air blown to the boiler of the present invention detects the flow rate of the fuel supplied to the boiler, and compares the detected fuel flow rate in the boiler exhaust gas. The rotation speed of the blower to the boiler is set so that the oxygen concentration is optimal. (1) Fuel In the present invention, the fuel supplied to the boiler includes:
There is no particular limitation, heavy oil, kerosene, and liquefied natural gas (LNG)
And liquefied petroleum gas (LPG). (2) Means for detecting the flow rate of fuel supplied to the boiler The means for detecting the flow rate of fuel supplied to the boiler in the present invention has a function of detecting a signal corresponding to the fuel amount and converting the signal into an electric signal. There is no particular limitation as long as it is one. This detection means may be configured independently, or may be configured to be combined with another device. For example, an opening adjuster of the automatic control valve (1) for adjusting the fuel flow rate may be used. Preferably, an angle sensor for detecting the rotation angle of the rotating shaft connected to the fuel flow control valve (1) is used.

In the embodiment of the present invention, the rotation angle of a rotary shaft (also referred to as a link mechanism (11)) connected to the fuel flow control valve (1) and the air damper (10) opening adjuster is detected. Load transmitter (1)
Using 3), the flow rate of fuel supplied to the boiler was detected. The load transmitter (13) is a boiler load,
That is, it has a function of detecting and transmitting a signal proportional to the fuel amount.

The position of the device for detecting the flow rate of the fuel is, as shown in FIG. 2 showing one embodiment of the present invention, an example of the position from the output shaft of the master controller (12) to the air damper (10). What is necessary is just to be in the range (11) of the link mechanism. Within this range, any of the following locations may be used. (A) Output shaft of master controller (12) and rotating part of link mechanism (a) Opening and closing part of air damper (10) part (c) Vertical movement part of rod connected to link mechanism (d) Arm of link mechanism Preferably, as shown in FIG. 2, an angle sensor is installed on an output shaft of the master controller (12) or a link mechanism portion of a rotating portion of the link mechanism. In this case, since the output shaft of the master controller (12) drives the link mechanism, it is preferable that the rotation angle be changed according to the boiler load. If it is installed at a position outside this range, detection may be difficult.

As the angle sensor, a position sensor or the like can be used. Further, the angle sensor merely changes its output according to a change in angle, and does not need to have an adjusting function or a correcting function. Therefore, the system is simple and economical.
Further, maintenance is easy. (3) A state in which the oxygen concentration in the exhaust gas is optimal In general, ideal combustion is when the oxygen concentration in the exhaust gas is 0%. In the case of boilers, it is more efficient if the oxygen concentration in the exhaust gas is as close to 0% as possible because the amount of heat carried away by the exhaust gas is small, but if it is too low, unburned components are generated due to incomplete combustion and smoke and dust are generated. Some excess air is needed to achieve this. Therefore, the optimum oxygen concentration in the exhaust gas is a value specific to the boiler, and means an oxygen concentration at which the oxygen concentration in the exhaust gas can be operated to be the lowest in a combustion state in which smoke or dust is not generated. (4) Method of setting the rotation speed of the blower (7) to the boiler The method of setting the rotation speed of the blower (7) to the boiler is not particularly limited as long as the object of the present invention can be achieved. Preferably, the relationship between the flow rate of fuel supplied to the boiler and the amount of air blown to the boiler is measured in advance so that the amount of oxygen in the boiler exhaust gas is optimized, and the blower to the boiler is determined based on the relationship. This is a method of setting the number of rotations of (7). More specifically, the above relationship is recorded in a device having an arithmetic function, and based on the above relationship in which the arithmetic function is recorded, a boiler is used by using a device that easily outputs the above relationship as an arithmetic result. This is a method for setting the number of rotations of the blower (7). If such a method is specifically shown, the following examples can be given.

That is, assuming that the range from low load to high load operation of the boiler is divided into about 10 points, a test run of the boiler is performed at each point, and the blower (7) in which the oxygen concentration in the exhaust gas is optimum is obtained. ) Determine the number of rotations. The obtained data is stored in a device having an arithmetic function, here a controller (8), as a relationship between the load (= fuel amount) of the boiler and the rotation speed. The measurement of the oxygen concentration in the exhaust gas uses a commercially available oxygen concentration meter for exhaust gas. In this way, the rotation speed of the blower (7) to the boiler in the actual operation is set based on the data stored in the controller (8). That is, a signal related to the flow rate of the fuel from the load transmitter (13) is sent to the regulator (8), and the blower (7) from the regulator (8) to the boiler is adjusted to match the already recorded rotation speed. Is set. In this case, the signal emitted from the load transmitter (13) does not necessarily need to be exactly proportional to the angle or the fuel, and is not particularly limited as long as it is related to a change in the fuel amount. Specifically, a current signal (4 to 20 mA) of a continuous general analog signal and a voltage signal (0 to 20 mA) are used.
To 5 V or 0 to 10 V). Preferably, 4 to 20 mA or 0 to 5 V is used.
The control (electrical) mounting position of the regulator (8) is located between the load transmitter (13) and the rotation speed controller (9). The physical installation position of the controller (8) is not particularly limited, but it is most economical and preferable to install it in the inverter panel. However, the purpose can also be achieved by mounting it in another control panel for the convenience of the site. (5) Air Damper (10) The air damper (10) is not necessarily used in the present invention. When used, it is preferable that the setting is slightly changed to slightly open compared to the opening during normal operation without implementing the present invention (in a state where it is directly connected to the link mechanism (11) as it is at present). . By setting in this way, there are the following merits (a) to (d). However, it is not impossible to use it in the fully opened state. (A) In the case of an inverter failure or the like, it is easy to deal with a case where the blower (7) is switched to a normal operation in which the present invention is not performed. (A) In the case of a low load, a certain amount of wind speed (for the effect of mixing and diffusing fuel and air) near the nozzle of the burner (3) is required, and this can be easily achieved by squeezing with the air damper (10). (C) If the link mechanism (11) is removed from the link mechanism (11) and fully opened, a facility for automatically closing the air damper (10) when stopping is required, which is economically disadvantageous. (D) The connection to the link mechanism (11) hardly impairs the energy saving effect (because the pressure loss is almost eliminated by slightly opening it). (6) Method of controlling the amount of air blown to boiler (5) Fuel is supplied to burner (3) when the operation of boiler (5) is started. At the same time, link mechanism (11) moves, and the load transmitter (13) operates. ) And the controller (8) are controlled such that an optimum rotation speed (= air volume) is obtained from the relationship between the load and the air volume stored in the adjuster (8) in advance. In order to change the signal from the regulator (8) to the rotation speed of the blower (7), a normal variable speed control device can be used.
For example, examples of the variable speed control device include a variable speed control device (inverter) and a fluid coupling. 2. Control device of air volume to boiler (5) The control device of air volume to the boiler (5) according to the present invention is a device for detecting the flow rate of fuel supplied to the boiler (5),
A calculation means for obtaining the rotation speed of the blower (7) to the boiler so that the oxygen concentration in the boiler exhaust gas is optimized by using the fuel flow rate obtained by the detection means as an input value, and a calculation result of the rotation of the blower (7) It is characterized by comprising means for transmitting to the number control device (9).

The present invention can be implemented by modifying an existing boiler so that the object of the present invention can be achieved.

[0016]

Next, the present invention will be specifically described by way of examples.
The present invention is not limited to the following examples. The oxygen concentration was measured according to the following method. (1) Oxygen concentration (%) An oxygen sensor was installed in the chimney and measured. [Embodiment] An example in which a steam boiler having a water pipe type of 20 t / h and a blower capacity of 55 kW is used as a boiler and the air volume control system shown in FIG. 2 is applied.

(1) Setting of the regulator (8) In the above-mentioned boiler, the boiler load is gradually increased so that the smoke of the chimney is not visible for several fuel amounts and the O ₂ meter of the oxygen sensor is used. The output (rotational speed) of the blower (7) so that the instruction was minimized was obtained. The obtained data was stored as a relationship between an input (fuel amount) and an output (rotational speed) in a controller (8) capable of approximating a broken line (linearization). Note that a linearizer was used as the controller (8). (2) Operation A load transmitter (13) having a link mechanism (11) for controlling an air damper (10) with an angle sensor is used as the load transmitter (13), and the above-mentioned adjuster (8) is used as an adjuster (8). The fuel was operated using heavy fuel oil A. Air damper (1
0) was performed slightly open. The rotation speed control device (9)
, An inverter was used. FIG. 3 shows the result of measuring the oxygen concentration in the exhaust gas while changing the load factor. COMPARATIVE EXAMPLE FIG. 3 shows the results in the case where a conventional air flow control system as shown in FIG. 1 is used in place of the air flow control system of the present invention in the embodiment.

It can be seen that the use of the combustion control system of the present invention clearly has an effect of reducing O ₂ .

[0019]

According to the present invention, the use of a method for controlling the amount of air blown to a boiler and an apparatus for controlling the amount of air blown to a boiler, which does not require an O ₂ sensor, is easy to maintain, and has an extremely fast response time, reduce equipment costs, and Stable operation (high reliability)
And the power consumption of the blower can be reduced, contributing to energy saving. The boiler to which the present invention can be applied is not particularly limited, and is basically applicable to any boiler as long as the boiler has a proportional control type in which the amounts of fuel and air are constituted by a mechanical link mechanism or the like. It is possible. If a specific example is given, as a package boiler, a water tube boiler, a furnace tube boiler, etc. can be illustrated.

[Brief description of the drawings]

FIG. 1 is a diagram showing a conventional system for controlling the amount of air sent to a boiler.

FIG. 2 is a diagram showing a system for controlling the amount of air blown to a boiler according to the present invention.

FIG. 3 is a diagram showing a relationship between a boiler load factor and an oxygen concentration in exhaust gas in Examples and Comparative Examples.

[Explanation of symbols]

 1: AC valve 2: Solenoid valve 3: Burner 4: Wind box 5: Boiler 6: Exhaust gas oxygen concentration detector 7: Blower 8: Regulator 9: Rotation speed control device 10: Air damper 11: Link mechanism 12: Master controller 13: Load transmitter

Claims (8)

[Claims] 1. A method for controlling the amount of air blown to a boiler,
To the boiler, which detects the flow rate of the fuel supplied to the boiler and sets the rotation speed of the blower to the boiler so that the oxygen concentration in the boiler exhaust gas is optimal for the detected fuel flow rate. How to control the air flow. 2. A method for controlling the amount of air blown to a boiler,
The flow rate of the fuel supplied to the boiler and the opening degree of the damper in the air passage to the boiler are detected, and the boiler is adjusted so that the oxygen concentration in the boiler exhaust gas becomes optimal with respect to the detected fuel flow rate and the opening degree of the damper. A method for controlling the amount of air blown to a boiler, comprising setting the number of rotations of a blower to be blown. 3. The flow rate of fuel previously supplied to the boiler and the boiler so that the amount of oxygen in the boiler exhaust gas is optimized.
The method according to claim 1 or 2, wherein the relationship between the amount of air blown to the boiler is measured, and the number of rotations of the blower to the boiler is set based on the relationship. 4. A control device for controlling the amount of air blown to a boiler,
Detecting means for detecting the flow rate of the fuel supplied to the boiler, calculating means for determining the number of rotations of the blower to the boiler so that the oxygen concentration in the boiler exhaust gas is optimized with the fuel flow rate obtained by the detecting means as an input value, and A control device comprising means for transmitting a calculation result to a rotation speed controller of a blower. 5. A control device for controlling the amount of air blown to a boiler,
Detecting means of the flow rate of the fuel supplied to the boiler, detecting means of the opening degree of the damper in the air passage to the boiler, and using the fuel flow rate and the damper opening degree obtained by the detecting means as input values, the oxygen concentration in the boiler exhaust gas is reduced. A control device, comprising: a calculation unit for obtaining a rotation speed of a blower to a boiler so as to be optimal; and a unit for transmitting a calculation result to a rotation speed controller of the blower. 6. An arithmetic unit for determining the number of rotations of a blower to a boiler, wherein the amount of oxygen in the boiler exhaust gas is determined based on the relationship between the flow rate of fuel supplied to the boiler and the amount of air blown to the boiler measured in advance. The control device according to claim 4 or 5, wherein the number of rotations of the blower to the boiler is set so that is optimized. 7. The control according to claim 4, wherein the fuel flow rate detecting means and the damper opening degree detecting means are provided for a rotary shaft connected to the fuel flow rate adjusting valve and the damper opening degree adjuster. apparatus. 8. An angle sensor, wherein the fuel flow detecting means and the damper opening detecting means are angle sensors for detecting a rotation angle of a rotary shaft connected to the fuel flow regulating valve and the damper opening adjuster. A control device for the amount of air blown to the boiler as described.