JPH0915065A - Acoustic thermometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the temperature of gas while reflecting the state of furnace more sensitively by making a large number of ejection holes of a medium for preventing adhesion of ash around the opening of a horn on the sound transmitter side and sound receiver side. SOLUTION: An acoustic sensor comprises a horn 20 coupled with a speaker 3, a large number of ejection holes of a medium for preventing adhesion of ash made in the inner and outer circumferences of a ring 36 fitted at the opening of horn, and an air ejection hole 23. A waveguide tube 21 coupled, at one end thereof, with a microphone 4 is inserted into the horn 20. Since noise is generated at the time of jetting air to disturb the measurement, the air pipe is provided with a solenoid valve 33 for preventing jetting of air when a sound wave is generated from the speaker 3 and the opening/closing of the solenoid valve 33 is controlled by a controller. The controller detects the propagation time of sound wave through the furnace based on a signal generated from the microphone 4 upon receiving the sound wave transmitted from the speaker 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas fluid thermometer, and more particularly to an acoustic system for determining the temperature of a high temperature gas by measuring the sound velocity of the high temperature gas in which molten ash is suspended, such as in a coal fired boiler. Regarding thermometer.

[0002]

2. Description of the Related Art As one of the methods for measuring the temperature of a fluid flowing in a duct, the speed of sound in the fluid is the temperature T (K) of the fluid.
There is a way to take advantage of changing by. The sound velocity c (m / s) in the fluid is expressed by the following equation. In the formula, α is a constant determined by the composition of the gas, and T is the gas temperature.

C = α√ (T) (1) FIG. 6 shows a specific device configuration using this method. Generally, when measuring the temperature of a fluid, as shown in the figure, an acoustic transmitter 3 and an acoustic receiver 4 are installed with a fluid to be measured interposed therebetween,
The propagation time t during that time is measured. At this time, the propagation time t can be expressed by the following equation.

T = L / [α√ (T)] (2) where L is the distance between the acoustic transmitter 3 and the acoustic receiver 4 and needs to be measured in advance. The gas temperature T can be calculated from this propagation time t.

When this method is applied to the temperature measurement of high temperature gas, the device configuration is as shown in FIG. Generally, the heat resistant temperature of the acoustic sensor is about 60 ° C. Therefore, in order to measure the temperature of the high temperature gas of 100 ° C. or more, the acoustic transmitter (speaker) 3 and the acoustic receiver ( Microphone) 4 is installed. Further, in order to emit a loud sound into the duct 19, the horn 20 may be used on the side of the acoustic transmitter 3.

Further, the temperature measurement using this sound wave is shown in FIG.
As shown in FIG. 5, a plurality of acoustic sensors 18 (sensors having both the acoustic transmitter 3 and the acoustic receiver 4) are arranged around the duct 19 to measure the temperature distribution.

Incidentally, as a conventional related art, Japanese Patent Laid-Open No. 63-63
There are proposals described in JP-A-231682, JP-A-1-304334, JP-A-1-68627 and the like.

FIG. 9 is a diagram showing an example in which an acoustic sensor 18 is installed on the furnace wall of the boiler superheater on the furnace side and the gas temperature is measured.

If the gas temperature on the furnace side of the superheater 26 can be measured, it becomes possible to accurately know the combustion state in the furnace, the endothermic state in the furnace wall, etc., which is effective in controlling the coal-fired boiler. . The signal from the acoustic sensor 18 installed on the furnace side of the superheater 26 is sent to the acoustic thermometer 27, and the boiler controller 28 controls the fuel regulator 30 based on the signal to adjust the fuel to the burner.

[0010]

However, when the above system is applied to a coal-fired boiler, the following problems occur.

In a coal fired boiler, ash remains after combustion of coal, which is a fuel. The melting temperature of this ash is generally 1
300 to 1500 ° C. Since the temperature inside the furnace is about 1200 to 1300 ° C. at the furnace outlet, the molten ash adheres to the furnace wall and the heat transfer tubes.

In the coal-fired boiler, in order to prevent this ash from adhering to the superheater 26, as shown in FIG.
An ash removing heat transfer tube 29 is installed on the upstream side of 6. By installing this ash removal heat transfer tube 29, the ash in the furnace is cooled and solidified by the ash removal heat transfer tube 29, and most of it adheres to the ash removal heat transfer tube 29 and is then peeled off by a soot blower (not shown). Ashes are removed from the bottom of the furnace. Most of the ash that has passed through the ash removal heat transfer tube 29 without being collected is in a solidified state, and a small amount of ash adheres to the superheater 26.

However, since the ash-removing heat transfer tube 29 is located on the upstream side, the ash removing heat transfer tube 29 is located at the position indicated by A in FIG.
When the acoustic sensor 18 is installed, the gas temperature measured by the acoustic sensor 18 is the gas temperature cooled by the ash removal heat transfer tube 29, and is therefore not the gas temperature sensitively reflecting the state of the furnace.

In order to measure the gas temperature which more sensitively reflects the state of the furnace, the acoustic sensor 18 is used as the heat transfer tube 2 for removing ash.
A method of installing on the upstream side of 9 (position B in FIG. 10) can be considered. However, the gas temperature on the upstream side of the ash removal heat transfer tube 29 is 1300 ° C. or higher, and the ash is in a molten state. Therefore, when the acoustic sensor 18 is installed on the side wall on the upstream side of the ash-removing heat transfer tube 29, there is a problem that ash adheres to the acoustic sensor 18 and the holes for transmitting and receiving sound waves are blocked.

FIGS. 11A and 11B are views showing the state of ash adhesion when the acoustic sensor 18 is installed upstream of the ash removing heat transfer tube 29 of the coal-fired furnace. FIG. 11A is a front view of the horn, and FIG. Is a side view. Ash 31 is attached to the tip of the horn 20 to close the hole 35. Therefore, the sound wave emitted from the speaker 3 cannot be sent into the furnace and the gas temperature cannot be measured. Reference numeral 21 is a microphone waveguide, and 23 is an air ejection hole opened in the speaker waveguide 2.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide an acoustic thermometer capable of measuring the gas temperature which more sensitively reflects the state of the furnace.

[0017]

In order to achieve the above object, the present invention provides an acoustic transmitter installed on one side wall and an acoustic receiver installed on the other side wall between the acoustic transmitter and the acoustic receiver. In an acoustic thermometer that measures the propagation time of sound waves and converts it to the temperature of the gas flowing between the side walls, a spout hole that spouts an ash adhesion prevention medium around the opening of the horn on the acoustic transmitter side and the acoustic receiver side. It is characterized in that a large number of are formed.

More specifically, a large number of the ejection holes are formed on each of the inner peripheral surface and the outer peripheral surface of the ring provided in the opening of the horn.

[0019]

In the present invention, the ash floating in the furnace is prevented from adhering to the opening of the horn by ejecting the gas from around the tip of the horn, so that the gas temperature more sensitively reflecting the state of the furnace can be obtained. Can be measured.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an acoustic sensor according to an embodiment.

This apparatus is an acoustic sensor portion of an acoustic thermometer manufactured to measure the furnace outlet gas temperature of a coal-fired boiler. This acoustic sensor, as shown in FIG.
It is installed on the upstream side (position B) of the ash removal heat transfer tube 29 of the coal-fired boiler, and catches the fluctuation of the gas temperature at the furnace outlet to reflect it in the boiler control.

The acoustic sensor according to the present invention has a horn 20 having an inner diameter of 200 mm to which the speaker 3 is connected, and a large number of ash deposits provided at predetermined intervals on the inner and outer circumferences of the ring 36 installed in the horn opening (hole 35). Preventing medium ejection hole 34
And an air ejection hole 23 provided in the narrowed portion of the horn 20 for blowing off the ash that has entered the horn 20. The horn 20 has a water cooling structure using the water wall 1 in order to prevent ash from adhering to the horn 20 and to prevent the horn 20 from being heated by radiant heat from the furnace.

A microphone waveguide 21 having a microphone 4 attached to one end is inserted into the horn 20.

Noise is generated when air is ejected, which hinders measurement. Therefore, when transmitting a sound wave from the speaker 3, an electromagnetic valve 33 is provided in the air pipe so as not to eject air, and the opening / closing of the electromagnetic valve 33 is controlled by the control device.

The control device for transmitting the sound wave from the sound wave transmitter 3, detecting the time during which the sound wave propagates in the furnace from the signal transmitted through the furnace and received by the other sound wave receiver 4 and converting it into temperature is shown in FIG. As shown in FIG. 5, a controller 5, a waveform generator (composed of a power supply 7, a capacitor 8, and a switch circuit 9) 6, a relay 10, a receiving amplifier 12, a bandpass filter 13, A
The D / D converter 14, the propagation time detector 15, the propagation time corrector 25, the temperature converter 16 and the display 17 are provided.

The procedure for measuring the temperature using this apparatus will be described below. First, the controller 5 sends a relay control signal to the relay 10, and switches the relay 10 to connect the speaker 3 that emits a sound wave and the waveform generator 6. It is now assumed that the speaker 3-1 is set to transmit sound waves.

Next, the controller 5 sends a signal for closing the solenoid valve 33 to the solenoid valve 33, closes the solenoid valve 33, and stops air from being blown out from each air jet hole 23.

After that, the controller 5 sends a measurement start signal to the waveform generator 6, and in response to this signal, the waveform generator 6 sends a pulse to the speaker 3-1. The waveform generator 6 generates a pulse by discharging the electric charge stored in the capacitor 8 by the switch circuit 9 for a certain period of time. Speaker 3-
The sound wave emitted from No. 1 is sent to the inside of the furnace via the waveguide 2-1 and the horn 20-1, propagates in the gas in the furnace, and propagates through the microphone waveguide 21-2 on the opposite side to the microphone. Reach 4-2. The signal received by the microphone 4-2 is once amplified by the microphone amplifier 11 of the acoustic sensor unit and transmitted to the control panel.

In the control panel, this signal is again amplified by the receiving amplifier 12 and then passed through the band pass filter 13,
It is digitized by the A / D converter 14. Propagation time detector 1
At 5, the sound wave propagation time t12 between the speaker 3-1 and the microphone 4-2 is detected from this digital signal.

On the other hand, when the sound wave is sent from the horn 20-1 into the furnace, a part of the sound wave reaches the microphone 4-1 through the microphone waveguide 21-1. The time tm1 is obtained from the signal received by the microphone 4-1. Similarly, the speaker 3-
If the sound wave is transmitted from 2, the speaker 3-2 to the microphone 4
The time t21 at which the sound wave propagates to −1 and the time tm2 at which the sound wave propagates from the speaker 3-2 through the microphone waveguide 21-2 to the microphone 4-2 are obtained. Then, the propagation time corrector 25 calculates the propagation time t transmitted in the furnace based on the following equation.

T = [(t12 + t21)-(tm1 + tm2)] / 2 (3) In the temperature converter 16, the propagation time t is converted into the gas temperature in the furnace based on the equation (2), and the indicator 17 is used. Display the measured temperature.

After that, the controller 5 sends a signal for opening the solenoid valve 33 to the solenoid valve 33, the solenoid valve 33 is opened, and air is ejected from each air ejection hole 23 to prevent ash from adhering.

As described above, the time taken to close the electromagnetic valve 33, measure the temperature, and reopen the electromagnetic valve 33 is about 2 seconds. The interval for measuring the temperature is determined by the controller 5. Normally, the interval is 30 seconds when the boiler is operated at a constant load, and 2 seconds when the temperature in the furnace changes suddenly due to load changes. The intervals are set.

FIGS. 3A and 3B are schematic views showing how the ash adhesion preventing medium is ejected from the ejection holes in the opening of the horn according to the first embodiment. FIG. 3A is a front view and FIG. It is a figure.

A ring 36 is provided in the opening (hole 35) of the horn 20, and ejection holes 34 are formed on the inner and outer circumferences thereof.

Since it is possible that the ash 31 enters from between the jetted air, the positions of the jet holes 34 were determined so that the jetted air overlaps the air jetted from the adjacent holes 35.
When the diameter of the ash adhesion preventing medium ejection hole 34 is set to 3 mm, the ejection hole 34 has a diameter of 25 mm in consideration of the spread of ejected air.
It is necessary to install at an interval of mm or less.

In this embodiment, the ring 3 is provided at 18 mm intervals.
32 spout holes 34 are formed around 6 and 10 to 30 Nm
³ / h of air was ejected. In this way, the horn 20
It can be seen that the ash 31 can be prevented from adhering when air is ejected from around the tip of the. Next, the water cooling structure of the horn will be described.

When the acoustic sensor 3 is installed closer to the furnace than the water wall 1, the amount of heat received from the inside of the furnace (mainly radiant heat) increases. For example, the gas temperature of the wake of the conventional water wall 1 is set to 1100.
Assuming that the temperature of the gas in the upstream of the water wall 1 is 1300 ° C., the amount of heat received is doubled. Therefore, the acoustic sensor 3
It is necessary that the horn 20 has a water cooling structure.

Further, when measuring the temperature, the electromagnetic valve 33 is closed to stop the ejection of air. Although it is a short time, the ash 31 may enter the horn 20 at this time. Therefore, it is necessary to consider the case where the ash 31 enters the horn 20. When the molten ash 31 adheres, the adhesion strength differs depending on whether it adheres to a high temperature wall or a low temperature (water cooling) wall. In the case of a low temperature wall, the ash 31 solidifies when it adheres to the wall, but the ash 31 contracts because it is rapidly cooled by the low temperature wall. Therefore, it is easy to peel from the wall. Therefore, the ash 31 can be easily blown off by the air blown out from the air ejection holes 23 provided in the narrowed portion of the horn 20.

4A and 4B are schematic views showing a state in which the ash adhesion preventing medium is ejected from the ejection hole of the opening portion of the horn according to the second embodiment. FIG. 4A is a front view and FIG. It is a figure.

In this embodiment, the ash adhesion preventing medium ejection holes 34 are installed so as to form a swirling flow at an angle to the circumferential direction. By ejecting the air while swirling, it is possible to prevent the ash 31 from entering between the jet flows, so that the number of the jet holes 34 can be reduced.

In the example of FIG. 4, the acoustic microphone 4 is attached so as to form an angle of 20 degrees with respect to the tangent to the edge of the waveguide 21, but within the range of 10 to 40 degrees, it is almost the same. effective.

FIGS. 5A and 5B are schematic views showing how the ash adhesion preventing medium is ejected from the ejection holes in the opening of the horn according to the third embodiment. FIG. 5A is a front view and FIG. It is a figure.

In this embodiment, the ash adhesion preventing medium ejection hole 3 is used.
This is an example in which 4 is formed in a slit shape and arranged so as to overlap in two rows. Even in such a structure, there is an effect of preventing adhesion of ash similar to the above.

Although the above has described the example in which air is used as the ejection medium for preventing the adhesion of ash, the medium for preventing ash adhesion may be other than air, for example, low temperature exhaust gas or steam. Well, almost the same effect as air can be obtained.

[0046]

According to the present invention, by blowing gas from around the tip of the horn, the ash floating in the furnace does not adhere to the opening of the horn, so the molten ash floats. The gas temperature can always be measured even in the furnace. Therefore, the temperature that is hardly affected by the water system can be measured, and the coal-fired boiler can be controlled with higher accuracy.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an acoustic sensor according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of an acoustic thermometer according to an embodiment of the present invention.

FIG. 3 is a schematic diagram showing how the ash adhesion preventing medium is jetted from the jet holes in the opening of the horn according to the first embodiment of the present invention.

FIG. 4 is a schematic diagram showing how an ash adhesion preventing medium is ejected from ejection holes in an opening of a horn according to a second embodiment of the present invention.

FIG. 5 is a schematic diagram showing how an ash adhesion preventing medium is ejected from ejection holes in an opening of a horn according to a third embodiment of the present invention.

FIG. 6 is a basic conceptual diagram of an acoustic thermometer.

FIG. 7 is a schematic diagram when an acoustic thermometer is applied to high temperature gas temperature measurement.

FIG. 8 is a schematic diagram showing an example of measuring a temperature distribution by applying an acoustic thermometer.

FIG. 9 is a schematic diagram showing an example in which an acoustic thermometer is used for controlling a boiler.

FIG. 10 is a schematic diagram showing another example in which an acoustic thermometer is used for controlling a boiler.

FIG. 11 is a schematic view showing a state in which ash is attached to the tip of the horn.

[Explanation of symbols]

 3 Sound wave transmitter 4 Sound wave receiver 20 Horn 34 Spout hole 36 Ring

Claims (2)

[Claims] 1. A gas flowing between sidewalls by installing an acoustic transmitter on one side wall and an acoustic receiver on the other side wall, measuring a propagation time of a sound wave between the acoustic transmitter and the acoustic receiver. In the acoustic thermometer for converting to the temperature of the above, an acoustic thermometer characterized by forming ejection holes for ejecting the ash adhesion preventing medium around the opening of the horn on the acoustic transmitter side and the acoustic receiver side. . 2. The acoustic thermometer according to claim 1, wherein a large number of ejection holes are formed on each of an inner peripheral surface and an outer peripheral surface of a ring provided in the opening of the horn.