JPH10111187A - Fluidized bed combustor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To deal with variation in the mass/quality of fuel quickly by calculating the temperature distribution in a furnace based on the sound wave propagation time of an acoustic sensor and feeding a quantity of air determined based on the temperature distribution in a furnace into a fluidized bed. SOLUTION: An acoustic gas temperature measuring controller 9 calculates a sound wave propagation time of an acoustic sensor 8 gas temperature, and temperature distribution. A primary air quantity controller 10 controls the primary air quantity based on a gas temperature distribution thus measured to vary the quantity of air being thrown into a furnace. The temperature measuring controller 9 measures temperature distribution on a measurinq plane and determines high and low temperature parts and a mean temperature. The quality of dust fuel currently thrown into the furnace can be estimated from the mean temperature and an optimal quantity of primary air to be thrown in is determined based the quality of dust. When a region higher than a predetermined temperature is present in the temperature distribution, concentration of low quality flame retardant dust fuel at that region is predicted and air supply to the lower temperature region is decreased by decreasing air supply to a high temperature region correspondingly. Consequently, variation in the mass/ quality of fuel can be dealt with quickly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluidized bed combustion apparatus, and more particularly to a fluidized bed combustion furnace which maintains a constant gas temperature in a fluidized bed combustion furnace.
The present invention relates to a fluidized bed combustion apparatus suitable for suppressing local generation of O and NOx.

[0002]

2. Description of the Related Art FIG. 15 shows a schematic configuration of a basic fluidized bed combustion apparatus with a boiler. The apparatus includes a fluidized bed furnace 1, a boiler 2 installed above the furnace, a dust feeder 3, a primary air blowing port 4, a secondary air blowing port 5, and the like. Waste fuel such as municipal waste and sludge is put into a hopper by a crane, sent to a dust feeder 3 via a crusher and a conveyor, and then put into the fluidized bed furnace 1 from the dust feeder 3.

[0003] The injected refuse fuel forms a fluidized bed 6 together with a fluidized medium by primary air blown from a primary air blowing port 4 in a furnace and performs primary combustion. Then, secondary combustion is performed by the secondary air blown from the secondary air blowing port 5 at the upper part, and the combustion is completed. The combustion exhaust gas generated in the fluidized-bed furnace 1 heats water in a boiler 2 at the top of the furnace to generate high-temperature steam.

[0004]

The fluidized bed type combustion apparatus using the waste fuel has a peculiarity that the quality and quantity of the waste fuel supplied into the combustion furnace are constantly changed. This is because the fuel is garbage, and very fast burning materials such as paper and slow burning materials such as garbage are mixed. Therefore, it is necessary to appropriately adjust the primary air amount and the secondary air amount according to the quality and amount of the supplied refuse fuel.

[0005] For example, when the dust fuel poor quality is turned on, if not decrease the total amount of air supplied to the furnace becomes excess air combustion, the amount of the NO _X with the boiler efficiency is lowered tends to increase. Conversely, when the quality of the refuse fuel is good, if the total air amount is not increased, there will be a shortage of air and a large amount of CO will be generated.

Conventionally, a thermometer 7 is installed at the outlet of the furnace to measure the gas temperature at the outlet of the furnace, thereby estimating the current quality and quantity of the fuel, and determining the primary air quantity and the secondary air quantity. It controls the amount or amount of refuse fuel input. However, this method has the following problems.

First, in the conventional method, a thermocouple is used as the thermometer. This is because the furnace contains S content, and the contacts of the thermocouple corrode. For this purpose, the surface must be covered with a porcelain or SUS tube. For this reason, the change in the measured temperature is later than the change in the actual gas temperature, and it is not possible to perform control that quickly responds to the change in the quality / quantity of fuel.

Second, since the thermocouple only measures the temperature at one point, a temperature distribution occurs in the furnace, and it is not possible to cope with a change in the quality and quantity of fuel in a specific area. have. .

SUMMARY OF THE INVENTION An object of the present invention is to overcome such disadvantages of the prior art, to respond quickly to changes in fuel quality / quantity, and to achieve high efficiency, low CO and low NOx operation in a fluidized bed combustion apparatus. Is to provide.

[0010]

In order to achieve the above object, the present invention provides an acoustic sensor installed above a fluidized bed so as to traverse the inside of a furnace, and a method for measuring the propagation time of a sound wave path measured by the acoustic sensor. Calculating means for calculating the temperature distribution in the air, air amount control means for determining the amount of air to be injected into a local region in the fluidized bed based on the temperature distribution, and in the fluidized bed based on the determined air amount. Air supply means for supplying air.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The speed of sound propagating in gas can be expressed by the following equation.

Sound velocity c = α · ΔT (1) In the equation, α is a constant determined by a gas composition, and T is a gas temperature (K). That is, when the distance between the acoustic sensors is known, the gas temperature between the sensors can be calculated by measuring the propagation time of the sound wave between the sensors.

The method of measuring the propagation time of a sound wave between acoustic sensors and converting the measured time to gas temperature can directly determine the temperature of the combustion gas at that time, and thus is caused by the heat capacity of a measuring device such as a thermocouple. There is no time delay. Therefore, control with good responsiveness can be performed.

In the method using an acoustic sensor, the gas temperature between the transmitter and the receiver is measured. Therefore, a specific point is not measured as in a thermocouple, but the influence of the entire furnace is measured. It will be the received temperature. Furthermore, if the propagation time of many paths is measured, the temperature distribution can be determined by the following method.
The inside of the furnace is divided into several regions, and individual control is possible.

Hereinafter, a method of calculating the temperature distribution will be briefly described. First, the measuring unit is divided into several grids i, and it is assumed that the gas temperature Ti in each grid is constant. Considering a case where a propagation path j between a certain sensor passes through a grid i, a time t _{i, j at} which this path passes through a grid i can be expressed by the following equation.

[0016]

(Equation 2)
… (2)

L _{i, j} in the equation is the distance that the path j passes through the grid i. That is, since the total propagation time of the path j is the sum of the propagation times passing through each lattice, it can be expressed by the following equation.

[0018]

(Equation 3)
… (3)

Since this equation (3) can be created by the number of paths, the temperature T _{i of} each lattice can be obtained by solving them simultaneously.

FIG. 1 is a schematic configuration diagram of a fluidized bed type combustion apparatus according to a first embodiment of the present invention. The basic structure is the same as the conventional one, but an acoustic sensor 8 is installed below the secondary air inlet 5 in the furnace wall.

FIG. 2 shows a cross section of a fluidized bed furnace. First, the lower side of the fluidized bed (area A in the figure) is an area where the fluid medium and the refuse as fuel are mixed and violently flow by the primary air introduced from below. Middle of the fluidized bed (B in the figure)
Region) is a region in which a light flowing medium having a small particle diameter (about 1 mm or less) and a fuel as the refuse are flowing, so that the upper portion is a very fine flowing medium (50 μm).
m) and the area where the ash after combustion is floating. The regions A and B are regions in which the combustion reaction is progressing violently, and are not suitable for gas temperature measurement because the concentration of the fluid medium is high. Then, the acoustic sensor 8 was installed at the position of the area C. This position is an area that reflects the combustion state of the flowing part, and is an area where gas temperature can be measured. Since the combustion state changes due to the inflow of the secondary air, the secondary air blowing port 5 is required to grasp the combustion state of the fluidized bed.
It is necessary to install the acoustic sensor 8 at a lower position and measure the gas temperature.

As shown in FIG. 1, an acoustic gas temperature measurement controller 9 for transmitting and receiving a sound wave from the acoustic sensor 8, calculating a propagation time, and calculating a gas temperature and a temperature distribution is provided. Further, a primary air amount control device 10 for controlling the primary air amount based on the measured gas temperature distribution, and a primary air introduction device 11 capable of changing an air introduction amount to a local part in the furnace are provided. I have.

Next, a detailed configuration of each section will be described.
FIG. 3 is a view of the cross section indicated by line a in FIG. 1 as viewed from above. A total of eight acoustic sensors 8 are installed on each furnace wall 12, and the propagation times of 24 paths indicated by solid lines in the figure are measured. Further, the measurement area was divided into 16 areas in a plane as indicated by a broken line in the figure, and the temperature distribution was calculated. This division of the temperature distribution was set in accordance with the shape of the primary air ejection portion. In the present embodiment, the time required for measuring the propagation time of 24 paths and calculating the temperature distribution was about several seconds.

In this embodiment, the primary air is divided into 16 nozzles and supplied as shown in FIG. Thus, the gas was divided into 16 parts so that the gas temperature in the vicinity of each nozzle was known. If the primary air ejection structure is different,
A different temperature distribution calculation method is used. For example, FIG. 5 shows an example in which primary air is ejected from four nozzles. In this case, FIG.
The inside of the furnace is divided into four parts as shown by broken lines in accordance with the position of the nozzle of the primary air as shown in FIG.

FIG. 7 is a diagram showing a detailed structure of the acoustic sensor 8. As shown in the figure, a waveguide 13 is installed in an opening of a furnace wall 12, and an electromagnetic speaker 14 and an electromagnetic microphone 15 are installed behind the waveguide 13. The waveguide 13 is provided to protect the electromagnetic speaker 14 and the electromagnetic microphone 15 from heat or corrosive gas in the furnace, and an air outlet is provided on the way to cool the inside and prevent ash from adhering. 16 are provided.

In some cases, such as when the input amount of primary air is locally changed, the flowing medium may scatter above the normal flowing portion. At this time, there is a concern that the flowing medium may enter the acoustic sensor 8. The particle size of the fluid medium is about 1 mm, and it is difficult to blow it off with ash removing air. Therefore, a metal mesh having a mesh size equal to or smaller than the particle diameter of the fluid medium (0.5 mm in the present embodiment) is provided at the opening of the waveguide 13 of the acoustic sensor 8 so as to prevent the fluid medium from being mixed.
If the ratio of the metal net to the entire surface on which the metal net is installed increases, the sound is interrupted and measurement becomes impossible. In this embodiment, a wire mesh is installed such that the ratio of the wire mesh to the entire surface does not become 0.5 or more. In this embodiment, a wire mesh is provided. However, a similar effect can be obtained with a ceramic grid or the like.

The frequency of the sound wave transmitted from the electromagnetic speaker 14 was selected as follows. If there are particles in the space where the sound wave propagates, the sound is attenuated by the scattering phenomenon. The magnitude of the attenuation varies depending on the particle concentration, the particle diameter, the frequency of the sound wave, and the like. FIG. 8 shows the attenuation characteristics when the particle diameter is assumed to be 1 mm and the propagation distance is assumed to be 10 m. It can be seen that the attenuation increases when the frequency of the sound exceeds 5000 Hz. In addition, since the main component of the furnace noise is less than 500 Hz, if a sound of less than 500 Hz is transmitted from the electromagnetic speaker 14, it cannot be distinguished from the furnace noise. Therefore, in the present embodiment, a sound wave selected from the frequency range of 500 Hz to 5 kHz is transmitted. The optimum frequency is selected depending on the noise characteristics in the furnace to be measured, the media particles, the size of the furnace, and the like.

FIG. 9 is a block diagram showing a schematic configuration of the acoustic gas thermometer controller 9. As shown in FIG. As shown in the figure, an acoustic gas thermometer controller 9 includes a controller 17 for controlling the operation of each device and a waveform transmitter 1 for transmitting a preset waveform.
8, a transmitting amplifier 19 for amplifying a waveform signal, a relay 20 for switching a transmitting speaker to an amplifier, a receiving amplifier 21 for amplifying a signal from a receiver, and an A / A for digitizing the amplified received signal. D converter 22 and signal processor 23 for detecting the arrival time of a sound wave from a digital signal
And a temperature calculator 24 for converting the temperature from the arrival time of the detected sound wave, and a temperature distribution calculator 25 for calculating the temperature distribution on the measurement surface from the temperature of each path.

Next, an example of the combustion control of the fluidized bed type combustion apparatus according to the embodiment of the present invention will be described. First, the temperature distribution on the measurement surface is measured by an acoustic gas thermometer. FIG. 10 shows a measurement example. From these results, the low temperature portion, the high temperature portion, and the average temperature can be found. From the average temperature (and its trend)
It is possible to estimate the quality of refuse fuel currently in the furnace.
Then, the optimum primary air input amount is determined based on the estimated waste quality.

Next, the temperature distribution is observed again. If there is an area at or above the predetermined temperature, it is expected that poor-quality flame-retardant refuse fuel is concentrated in that area. Reduce the air volume in the area. By performing such an operation, the flame-retardant refuse fuel concentrated in the low-temperature region can be dispersed in the furnace, so that unbalanced combustion can be prevented.

For example, in the measurement example shown in FIG. 10, the temperature is about 920 ° C. as a whole,
There is an area as low as 0 ° C., and an area as high as 980 ° C. at the lower right. Based on this result, in order to disperse the low-temperature region at the upper left, the opening degree of the valves B and D of the primary air split supply device shown in FIG. Then, an operation of lowering the opening degrees of the valves N and P by the increased amount to reduce the amount of supplied air is automatically performed.

As described above, by controlling the total air amount at the average temperature, the overall combustion state and gas temperature can be controlled with good responsiveness. Further, by controlling the gas temperature of the local, it is possible to reduce the amount of CO and NO _X generated locally.

FIG. 11 shows a second embodiment of the present invention, in which only one pair of acoustic sensors 8 is installed. Even in this case, the gas temperature over the entire width of the furnace can be instantaneously measured, which is sufficiently effective for combustion control in the furnace.

FIG. 12 is a view showing a third embodiment of the present invention, and is a view showing an installation example of an acoustic sensor 8 corresponding to a furnace whose primary air amount can be controlled only in the furnace width direction. In this case, even if the temperature distribution in the depth direction of the furnace cannot be controlled, the primary air amount is controlled by measuring only in the width direction.

FIG. 13 is a view showing a fourth embodiment of the present invention, in which another set of acoustic sensors 8 is installed above the secondary air blowing port 5. In general, in order to lower NO _X operation, set the air amount of the primary combustion zone below the theoretical air amount shortfall (or more) a method of introducing more secondary air is employed. Further, in order to suppress the generation of dioxin, it is necessary to control to keep the temperature of the secondary combustion zone at a certain value or more. It is known that both are caused by local fuel distribution imbalance or air charging imbalance. Therefore, the temperature distribution in the primary combustion zone and the temperature distribution in the secondary combustion zone are measured, and the primary air volume is measured. By controlling the local distribution of the secondary air amount, the local distribution of the secondary air amount, and the distribution of the primary air amount and the secondary air amount, lower NO _x and lower dioxin operation can be achieved.

FIG. 14 is a view showing a fifth embodiment of the present invention, in which a fuel amount controller 27 is provided, and fuel is supplied in accordance with a gas temperature distribution in a combustion region calculated based on the acoustic sensor 8. This is an example in which the fuel amount is obtained by the fuel amount controller 27 and the fuel supply device 26 is thereby controlled. 1 based on the gas temperature in the combustion zone
Simultaneously controlling the following air quantity by controlling the supply amount of the fuel, more stable combustion, low CO, it is possible to control the low NO _X.

In each embodiment of the present invention, an example in which the present invention is applied to waste incineration has been described. However, the present invention is not limited to this. For example, a fluidized bed type combustion apparatus having another configuration such as a coal-fired fluidized bed may be used. Is also applicable.

[0038]

As described above, the present invention calculates the temperature distribution in the furnace from the acoustic sensor installed above the fluidized bed so as to cross the furnace and the propagation time of the sound wave path measured by the acoustic sensor. Calculation means, air amount control means for determining the amount of air to be injected into a local region in the fluidized bed based on the temperature distribution, and air supply for supplying air into the fluidized bed based on the determined air amount And means are provided. By adopting such a configuration, fuel quality /
The amount of possible to quickly respond to changes, high efficiency, low CO, low NO _X
Driving becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a fluidized bed type combustion apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory sectional view showing a relationship between a state in a fluidized bed and a mounting position of an acoustic sensor.

FIG. 3 is a schematic plan view showing an arrangement example of acoustic sensors in the fluidized-bed combustion device according to the first embodiment.

FIG. 4 is an explanatory diagram showing a primary air split supply device in the fluidized bed combustion device according to the first embodiment.

FIG. 5 is an explanatory diagram showing another arrangement example of the primary air split supply device.

FIG. 6 is a schematic plan view showing another arrangement example of the acoustic sensors corresponding to the primary air split supply device shown in FIG.

FIG. 7 is a schematic configuration diagram of an acoustic thermometer.

FIG. 8 is a diagram showing characteristics of sound attenuation in a fluidized bed furnace.

FIG. 9 is a schematic configuration diagram of an acoustic gas thermometer controller according to an embodiment of the present invention.

FIG. 10 is an explanatory diagram showing an example of measurement by an acoustic thermometer in the fluidized bed combustion apparatus according to the first embodiment.

FIG. 11 is a schematic configuration diagram of a fluidized bed combustion apparatus according to a second embodiment of the present invention.

FIG. 12 is a schematic configuration diagram of a fluidized bed combustion device according to a third embodiment of the present invention.

FIG. 13 is a schematic configuration diagram of a fluidized bed combustion apparatus according to a fourth embodiment of the present invention.

FIG. 14 is a schematic configuration diagram of a fluidized bed combustion device according to a fifth embodiment of the present invention.

FIG. 15 is a schematic configuration diagram of a conventional fluidized bed combustion device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fluid bed furnace 2 Boiler 4 Primary air blow-in port 5 Secondary air blow-in port 6 Fluidized bed 8 Acoustic sensor 9 Acoustic gas thermometer controller 10 Primary air amount control device 11 Primary air input device 12 Furnace wall 13 Introduction Wave tube 14 Electromagnetic speaker 15 Electromagnetic microphone 16 Air outlet 17 Controller 18 Waveform generator 19 Transmitting amplifier 20 Relay 21 Receiving amplifier 22 A / D converter 23 Signal processor 24 Temperature calculator 25 Temperature distribution calculator

Claims (8)

[Claims] An acoustic sensor installed so as to cross the inside of a furnace above a fluidized bed, calculating means for calculating a temperature distribution in the furnace from a propagation time of a sound wave path measured by the acoustic sensor, Air amount control means for determining the amount of air to be originally injected into the local area in the fluidized bed, and air amount supply means for supplying air to the fluidized bed based on the determined air amount are provided. Fluid bed type combustion device. 2. A fluidized bed combustion apparatus according to claim 1, wherein a plurality of said acoustic sensors are provided. 3. The fluidized bed combustion apparatus according to claim 1, wherein the frequency of the sound wave output from the acoustic sensor is selected from a range of 500 Hz to 5 kHz. 4. The fluidized bed combustion apparatus according to claim 1, wherein the acoustic sensor is disposed between the fluidized bed and a secondary air blowing port. 5. The apparatus according to claim 2, wherein the area measured by the plurality of acoustic sensors is divided into a plurality of areas, and the air amount control means determines an air amount for the divided area. A fluidized bed combustion device characterized by being performed. 6. The fluidized bed combustion apparatus according to claim 1, wherein the fuel supplied to the fluidized bed is refuse. 7. The fluidized bed combustion apparatus according to claim 1, wherein the acoustic sensor is installed in a waveguide opened in a furnace wall. 8. The fluidized bed combustion apparatus according to claim 7, wherein a filter is provided at an opening of the waveguide.