JPH0375402A - Combustion control for fluidized bed furnace - Google Patents

Abstract

PURPOSE:To eliminate a delay in time and make it possible to reflect exactly the combustion quantity by providing a brightness detection sensor which detects the brightness in a furnace and correcting the outputs of said sensor by the output of an oxygen concentration meter and changing the volume of the air flow by obtaining more exact signal of state of combustion and in accordance to said signal. CONSTITUTION:In the upper section of the free board 12 of a furnace 10 with a fluidized bed a brightness detector 24 is provided which detects the brightness in the furnace, and in an exhaust gas route downstream of a gas cooling chamber 15 an exhaust gas oxygen concentration meter 23 is provided which detects the oxygen concentration in the exhaust gas. An output S1 of the exhaust gas oxygen concentration meter 23 and an output S2 of the brightness detector 24 are inputted to a calculator 25. The brightness detector 24 can detect relative changes in the state of combustion without delay, and the oxygen concentration in the exhaust gas that is detected by the exhaust gas oxygen concentration meter 23 can detect exactly the state of combustion in the furnace even though there is a delay. With this arrangement a calculator 25 corrects the output S2 of the brightness detector 24 by the output S1 of the exhaust gas oxygen concentration meter 23 and can output a signal of state of combustion which reflects more exact state of combustion as an output S3 to calculators 26, 27, and 28 respectively.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a combustion control method in a fluidized bed furnace, and in particular, it is possible to accurately detect the combustion state (combustion amount) in the furnace without time delay, and to The present invention relates to a combustion control method that controls combustion conditions and maintains a substantially constant combustion state.

[Prior art]

Fluidized bed furnaces have very excellent combustion characteristics and are often used as incinerators or boilers for municipal garbage and industrial waste. However, fluidized bed furnaces have excellent combustion characteristics, so when burning homogeneous combustible materials as a boiler, it is not as difficult to maintain a nearly constant combustion state as with combustion furnaces, but municipal waste When a combustible material that cannot be continuously supplied in a constant quantity due to its nature is put into this fluidized bed furnace, the combustible material burns quickly and in a short time, so variations in the amount of combustible material input directly cause fluctuations in the combustion gas. This also leads to variations in the oxygen concentration in the combustion gas, which also causes various problems in exhaust gas countermeasures and the air system and exhaust gas system of furnace equipment.

Therefore, when there is a fluctuation in the amount of combustibles fed into the fluidized bed furnace as mentioned above, as a measure to prevent a large amount of combustibles from burning instantaneously, the present applicant has previously applied PCT/
There is a combustion control method in a fluidized bed furnace disclosed in JP88100437. This combustion control method reduces the amount of so-called fluidized air sent from the bottom of the fluidized bed when combustion in the furnace is active, suppressing the gasification of the combustion products, and increases the amount of fluidized air when combustion is inactive. This is designed to activate the gasification of combustion materials. This makes it possible to maintain a substantially constant combustion state within the furnace regardless of fluctuations in the combustible materials introduced into the furnace.

[Problem to be solved by the invention]

In the above-mentioned combustion control method that changes the amount of flowing air depending on the combustion state in the furnace, whether the function of maintaining the combustion state in the furnace at a constant level works well or not depends on the detection accuracy of the combustion amount or the amount of combustible material supplied. It's on.

As a method for detecting the combustion state in the furnace, that is, the amount of combustion, there is a method of measuring the oxygen concentration in the exhaust gas with an oxygen concentration meter. This is usually detected at the location where the exhaust gas exits the fluidized bed furnace and is cooled, so local differences in the flow path cross section are small;
Although the measurement value is highly accurate, it takes time for the exhaust gas to reach the measurement point and there is a time delay, so it cannot be used as an effective control signal for the above combustion control method.

In addition, unlike the method of measuring the oxygen concentration in the exhaust gas mentioned above, the method of detecting the combustion state in the furnace by the brightness inside the furnace is a combustion signal in the furnace with no time delay, but the brightness and the amount of combustion Although there is a relative proportional relationship, when the combustible material is municipal garbage, etc., due to its nature, the so-called 1 doka fall due to sticking causes rapid combustion, a large amount of smoke, etc. is generated, and combustion becomes active. Despite this, there are cases where the inside of the furnace becomes dark and a false signal indicating that combustion is inactive is output, making it impossible to accurately control combustion based on brightness alone.

Similarly, although the signal from the oxygen concentration meter installed inside the furnace has little time delay, it is local and may not be representative of the oxygen concentration in the entire furnace depending on the installation location. In addition, although the amount of combustion can be detected in advance by using signals obtained by observing the falling condition of combustible materials such as urban garbage using an industrial television camera and processing the image, as well as by using the weight of the combustible materials that have fallen, the accuracy of these signals alone is insufficient. The problem was that it was not possible to achieve good combustion control.

The present invention has been made in view of the above points, and includes a combustion control method that controls the combustion amount to a constant level by changing the amount of flowing air depending on the combustion state in the furnace. In order to maintain the maintenance function to the highest level, the fluidized bed obtains a control signal that accurately reflects the combustion amount without any time delay, and uses this control signal to control the amount of fluidized air to accurately control the combustion state. The purpose of this invention is to provide a combustion control method in a furnace.

[Means to solve the problem]

In order to solve the above problems, the present invention provides a combustion control method in a fluidized bed furnace as follows.

The fluidized medium is made to flow by air sent from the lower part of the fluidized bed, the combustion state is detected, and the amount of air sent from the lower part of the fluidized bed is changed according to the combustion state, regardless of fluctuations in the combustible material introduced into the furnace. In a combustion control method in a fluidized bed furnace that maintains the combustion amount at a substantially constant level, an oxygen concentration meter is installed to measure the oxygen concentration in the exhaust gas, and a brightness meter is installed to detect the brightness inside the furnace as a means of detecting the combustion state inside the furnace. The present invention is characterized in that a combustion state detection sensor is provided, the output of the detection sensor is corrected by the output of the oxygen concentration meter, a more accurate combustion state signal is obtained, and the amount of flowing air is changed in accordance with the combustion state signal.

Further, as a means for detecting the combustion state in the furnace, an oxygen concentration detection sensor is provided in the furnace, and an industrial television camera is provided to observe the combustion material put into the oxygen enriched furnace. It is characterized by using image processing signals.

Further, as the means for detecting the combustion state in the furnace, a weight measuring means for measuring the weight of the combustible material put into the furnace is provided, and the output of the weight measuring means is used.

Further, as a means for detecting the combustion state in the furnace, an exhaust gas flow rate detection sensor for detecting the flow rate of exhaust gas from the furnace is provided,
The present invention is characterized in that the output of the exhaust gas flow rate detection sensor is used.

Further, as the means for detecting the in-furnace combustion state, an in-furnace pressure detection sensor for detecting the in-furnace pressure is provided, and the output of the in-furnace pressure detection sensor is used.

Further, as means for detecting the combustion state in the furnace, the output of the furnace brightness detection sensor, the output of the furnace oxygen concentration detection sensor, and image processing of an industrial television camera that observes the combustion material put into the furnace. It is characterized in that two or more of the following are used in combination: a signal, an output of a weight measuring means for measuring the weight of the combustion material, an output of an exhaust gas flow rate detection sensor, and an output of an in-furnace pressure detection sensor.

[Effect]

In the combustion control method in a fluidized bed furnace as described above, the output of the in-furnace brightness detection sensor, the output of the in-furnace oxygen concentration detection sensor, the image processing signal of an industrial television camera that observes the combustion material introduced into the furnace, The output of the weight measuring means that measures the weight of the combustion material, the output of the exhaust gas flow rate detection sensor, and the output of the furnace pressure detection sensor can detect relative changes in the combustion state without time delay, and the oxygen concentration in the exhaust gas can be detected over time. Although there is a delay, the combustion state inside the furnace can be accurately detected.

Therefore, by combining a signal that detects relative changes in the combustion state without any time delay and a signal that accurately detects the combustion state in the furnace, albeit with a time delay, and correcting the former with the latter, it is possible to Since a signal reflecting the accurate combustion state is obtained and the amount of flowing air is changed based on this signal, combustion in the furnace can be precisely controlled.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a diagram showing a schematic configuration of an incineration facility using a fluidized bed incinerator to which the control method according to the present invention is applied. In the same figure, 10 is a fluidized bed furnace, and the fluidized bed furnace 10 is equipped with a fluidized bed 11 and a freeboard 12, and a forced air blower 14.
The fluidized medium is made to flow by forcing fluidized air sent from the lower part of the fluidized bed 11. When combustible materials such as municipal waste are fed into the fluidized bed furnace 10 from the combustible material supply hopper 13, the combustible materials are gasified in the fluidized bed 11 and combusted in the freeboard 12. Then, the exhaust gas passes through the gas cooling chamber 15, passes through the air preheater 16, preheats the air sent from the forced air blower 14, and enters the electrostatic precipitator 17. The exhaust gas from which particulate matter has been removed by the electrostatic precipitator 17 is drawn by an induced draft fan 18 and discharged into the atmosphere from a chimney 19.

A brightness detector 24 that detects the brightness inside the furnace is provided above the freeboard 12 of the fluidized bed furnace 10 and includes a phototransistor, etc. An exhaust gas oxygen concentration meter 23 is provided to detect the oxygen concentration in the exhaust gas. Note that the installation position of the exhaust gas oxygen concentration meter 23 is not limited to the downstream side of the gas cooling chamber 15. The output SI of the exhaust gas oxygen concentration meter 23 and the output SI of the brightness detector 24 are input to a calculator 25 . As will be detailed later, the brightness detector 24 can detect relative changes in the combustion state without any time delay, and the oxygen concentration in the exhaust gas detected by the exhaust gas oxygen concentration meter 23 can be detected with a time delay, but the oxygen concentration in the furnace Since the combustion state can be detected accurately, the computing unit 25
is the output S2 of the brightness detector 24 and the exhaust gas oxygen concentration meter 23.
A combustion state signal reflecting a more accurate combustion state is output as an output S8 to the computing units 26 and 27, respectively.

The computing unit 26 generates a control signal S for controlling the motor 29 that drives the combustion material supply hopper 13 from the output SI of the computing unit 25.
4 is calculated and output to the motor 29. As a result, the amount of combustible material fed into the fluidized bed furnace 10 from the combustible material supply hopper 13 is increased or decreased depending on the combustion amount in the furnace, and the amount of combustible material supplied is controlled so that the combustion state in the furnace is appropriate. .

Further, the computing unit 27 outputs a control signal SI for controlling the secondary air control valve 21 from the output SI of the computing unit 25 to the secondary air control valve 21.
Output to 1. Thereby, the secondary air sent from the secondary air blower is increased or decreased according to the amount of combustion in the furnace, and the oxygen concentration in the exhaust gas is controlled to an appropriate value.

Further, the computing unit 28 outputs a control signal S for controlling the bypass control valve 20 from the output SI of the computing unit 25 to the bypass control valve 2
Output to 0. Thereby, the bypass control valve 20 is controlled according to the combustion amount, and the amount of fluidized air forced into the fluidized bed 11 is increased or decreased. That is, when the combustion amount is large, the output SI of the computing unit 25 that accurately reflects the combustion amount is used to reduce the amount of flowing air and make the flow of the fluid medium inactive, slowing down the gasification of the incinerated material, and reducing the amount of combustion. When the amount of gas is low, the amount of fluidized air is returned to its original value or increased to make the flow of the fluidized medium more active, thereby speeding up the gasification of the incinerated material.

Figure 2 shows that the brightness inside the furnace is 2 without changing the amount of flowing air.
[%] and the measured value of the oxygen concentration O3 [%] in the exhaust gas. FIG. 3 is an enlarged view of the period from 300 seconds to 800 seconds in FIG. 2. As is clear from the figure, the brightness l inside the furnace varies depending on the amount of combustion. That is, the output S1 of the brightness detector 24 detects a relative change in the amount of combustion without any time delay. On the other hand, the oxygen concentration in the exhaust gas
There is a time delay until the gas reaches the discharge end of the gas cooling chamber 15, and as is clear from Fig. 3, the time delay is 30 minutes.
It is about seconds. Also, the oxygen concentration in this exhaust gas is 0. Since it leaves the fluidized bed furnace 10 and is detected in the wake of the gas cooling chamber 15, there are few local differences in the cross section of the flow path, and the accuracy of the measured value is high.Although there is a time delay, the amount of combustion in the furnace is detected. accurately reflects.

Therefore, in this embodiment, the computing unit 25 uses the brightness inside the furnace, which represents the relative change in the amount of combustion without any time delay, that is, the output S1 of the brightness detector 24, as the oxygen in the exhaust gas, which accurately represents the amount of combustion. By correcting the concentration O2, that is, the output SI of the exhaust gas oxygen concentration meter 23, a control signal that enables accurate combustion control is obtained as the output SI of the calculator 25.

FIG. 4 is a diagram showing the configuration of the arithmetic unit 25, in which the output SI (exhaust gas oxygen concentration O2) of the exhaust gas oxygen concentration meter 23 passes through a first-order lag function 31, and is determined by the exhaust gas oxygen concentration controller 32 as the oxygen concentration setting value. It is compared and outputted so as to maintain the oxygen concentration in the exhaust gas at the set value, and is inputted to the multiplication unit 34 along with the output signal SI (brightness J2) of the brightness detector 24 through the line interval number 33, and the primary The signal passes through a delay function 35, passes through a polygonal line interval 36, and is output as a control signal SI.

Although it only indicates a situation, the signal is about 30 seconds earlier than the output of the exhaust gas oxygen concentration meter 23. Therefore, combustion control cannot be performed using only the output of the exhaust gas oxygen concentration meter 23, but combustion control is performed using the output S of the brightness detector 24, and the output of the exhaust gas oxygen concentration controller 32 is converted into a polygonal line function 33. By correcting S as a coefficient, the disadvantages of controlling combustion using only the output S of the brightness detector 24 can be compensated for.

FIG. 5 is a diagram showing another configuration of the calculator 25, in which the output S of the exhaust gas oxygen concentration meter 23 (exhaust gas oxygen concentration) and the output S2 (brightness l) of the brightness detector 24 are each delayed by a first order. After passing through functions 41 and 42, the division unit 43 calculates 51'/S! ' is determined, and the S.

/S,' and the output S are input to the multiplier 44, passed through the oxygen concentration controller 45, and output as the control signal S.

Incidentally, in the above embodiment, an example is shown in which the brightness detector 24 is used as a means for detecting relative changes in the combustion state without time delay, but as a means for detecting relative changes in the combustion state without time delay. There are other methods as follows.

■The oxygen concentration inside the furnace depends on the amount of combustion (combustion state).When the amount of combustion is large, the oxygen concentration inside the furnace is low, and when the amount of combustion is small, the oxygen concentration inside the furnace is high, so the oxygen concentration inside the furnace is detected. A method of installing an in-furnace oxygen concentration detection sensor and using this output.

Since this reflects the amount of combustion, this method involves installing an industrial television camera to observe the combustion material being put into the furnace, and using the image processing signal from the industrial television camera.

■In addition, in a fluidized bed furnace, the weight of the combustible material introduced also reflects the amount of combustion, so a method is to provide a weight measuring means for measuring the weight of the combustible material and use the output of the weight measuring means. .

(2) Since the flow rate of exhaust gas discharged from the combustion furnace also reflects the amount of combustion, a method of providing an exhaust gas flow rate detection sensor for detecting the exhaust gas flow rate and utilizing the output of the exhaust gas flow rate detection sensor.

■In addition, when the amount of combustion is large, the amount of combustion gas increases, so the pressure inside the furnace is high, and when the amount of combustion is small, the pressure inside the furnace is low, so the furnace pressure detection sensor detects the inside pressure. A method in which the output of the in-furnace pressure detection sensor is used.

Therefore, it goes without saying that the combustion control may be performed using the above-mentioned signals 1 to 2 as control signals, and the results may be fed back as the output of the exhaust gas oxygen concentration meter 23.

Furthermore, combustion control may be performed using a combination of two or more of the above-mentioned items (1) to (2) as control signals, and the result may be fed back as the output of the exhaust gas oxygen concentration meter 23.

〔Effect of the invention〕

As described above, according to the present invention, the output of the furnace brightness detection sensor, the output of the furnace oxygen concentration detection sensor, the furnace The image processing signal of an industrial television camera that observes the combustion material thrown into the furnace, the output of the weight measuring means that measures the weight of the combustion material, the output of the exhaust gas flow rate detection sensor, the output of the furnace pressure detection sensor, or these signals. By using a combination of two or more, the detected oxygen concentration in the exhaust gas is used as a signal that can accurately detect the combustion result, although there is a time delay. Combustion control is performed by combining these, so the combustion in the furnace can be controlled accurately. An excellent effect of controllability can be obtained.

[Brief explanation of drawings]

Figure 1 is a diagram showing the schematic configuration of an incinerator using a fluidized bed furnace to which the control method according to the present invention is applied, and Figure 2 shows the brightness inside the furnace of 2% and the exhaust gas without changing the amount of fluidized air. Oxygen concentration inside is 0! Figure 3 shows the results of actual measurement of [%].
2 is an enlarged view of the time period 300s to 8008, FIG. 4 is a diagram showing the configuration of the arithmetic unit, and FIG. 5 is a diagram showing another configuration of the arithmetic unit. In the figure, 10...Fluidized bed furnace, 11...Fluidized bed, 1
2... hood, 13... combustible material supply hopper, 14... forced blower, 15... gas cooling chamber, 16... air preheater, 17...・Electric dust collector, 18...Induced fan, 19...Chimney, 20...
... Bypass control valve, 21 ... Secondary air control valve,
22... Secondary air blower, 23... Exhaust gas oxygen concentration meter, 24... Brightness detector, 25.26, 27
．． 28... Arithmetic unit.

Claims (7)

[Claims] (1) The fluidized medium is made to flow by the air sent from the lower part of the fluidized bed, the combustion state of the combustion material is detected, and the amount of air sent from the lower part of the fluidized bed is changed according to the combustion state, and the air is introduced into the furnace. In a combustion control method in a fluidized bed furnace that maintains the combustion amount approximately constant regardless of fluctuations in the combustion materials, an oxygen concentration meter is installed to measure the oxygen concentration in the exhaust gas,
A brightness detection sensor that detects the brightness inside the furnace is provided as a means for detecting the combustion state in the furnace, and the output of the detection sensor is corrected by the output of this oxygen concentration meter to obtain a more accurate combustion state signal. A combustion control method in a fluidized bed furnace characterized by changing the amount of fluidized air according to a combustion state signal. (2) Combustion in a fluidized bed furnace according to claim (1), wherein an oxygen concentration detection sensor is provided in the furnace and the output of the oxygen concentration detection sensor is used as the means for detecting the combustion state in the furnace. Control method. (3) As a means for detecting the combustion state in the furnace, an industrial television camera for observing the combustion material put into the furnace is provided, and an image processing signal of the industrial television camera is used. (1) Combustion control method in the fluidized bed furnace described. (4) As the means for detecting the combustion state in the furnace, a weight measuring means for measuring the weight of the combustion material put into the furnace is provided, and the output of the weight measuring means is used. ) Combustion control method in the fluidized bed furnace described. (5) As a means for detecting the combustion state in the furnace, an exhaust gas flow rate detection sensor for detecting the flow rate of exhaust gas from the furnace is provided,
The combustion control method in a fluidized bed furnace according to claim 1, characterized in that the output of the exhaust gas flow rate detection sensor is used. (6) Claim (1) characterized in that the means for detecting the in-furnace combustion state is provided with an in-furnace pressure detection sensor for detecting in-furnace pressure, and the output of the in-furnace pressure detection sensor is used.
Combustion control method in the described fluidized bed furnace. (7) As a means for detecting the combustion state in the furnace, the output of the furnace brightness detection sensor, the output of the furnace oxygen concentration detection sensor, and the image of an industrial television camera that observes the combustion material put into the furnace Claim (1) characterized in that any two or more of the processing signal, the output of the weight measuring means for measuring the weight of the combustion material, the output of the exhaust gas flow rate detection sensor, and the output of the furnace pressure detection sensor are used in combination. combustion control method in a fluidized bed furnace.