JP4836630B2 - Apparatus and method for monitoring the amount of deposits in liquid - Google Patents

Description

The present invention relates to an apparatus and method for monitoring the amount of liquid in the deposit monitoring the amount of deposits such as the cooling water bath of thermal power plants by utilizing the ultrasonic waves.

  In a thermal power plant that burns heavy oil, a cooling water tank is installed in the lower part of the chimney, and water vapor evaporated from the cooling water tank is supplied to the upper part of the chimney to prevent heating of the inner wall of the chimney. Chemical substances such as naphtha contained in the flue gas fall into the cooling water tank installed below the flue and accumulate on the bottom. Since this naphtha is hot inside the chimney, when it falls into the cooling water, it raises the temperature of the cooling water. In order to keep the temperature of the cooling water in the cooling water tank uniform, stirring of the cooling water is performed.

  The typical dimensions of a cooling water tank are 10 meters x 2 meters and a depth of 1.5 meters. Since the water level in the cooling water tank is kept constant, if the amount of naphtha accumulated increases and the amount of cooling water in the tank decreases, the water temperature in the tank will be affected by the amount of heat carried by the naphtha falling from the flue. It starts to soar. When the inner wall surface of the chimney is overheated due to the sudden rise in water temperature, a serious situation is reached in which the entire thermal power generation system is shut down in order to avoid thermal damage to the chimney.

  Conventionally, in order to prevent a serious situation that the entire thermal power generation system is stopped, an operator monitors a naphtha accumulation layer in a cooling water tank and scrapes it with a rake when it becomes thick. The amount of naphtha contained in the smoke depends on the type of fuel oil used as fuel, while the type of fuel oil burned is frequently changed. As a result, the speed of naphtha accumulation in the cooling water tank fluctuates, and if scraping is periodically performed, it may not be possible to cope with unexpected situations. That is, continuous monitoring of the thickness of the deposited layer is required, and automation thereof is desired.

Conventionally, systems that automatically measure the distribution of the amount of sludge deposited on the bottom of a sedimentation basin such as a sewage treatment system or a water purification system using an ultrasonic sensor are known (Patent Documents 1, 2, and 3). . In these measurement systems, the thickness of the sedimentary layer is automatically measured by subtracting the depth from the known depth of the bottom of the tank, conduit, or sedimentation basin to the surface of the sedimentary layer that was actually measured. The
Japanese Patent Laid-Open No. 9-192411 Japanese Patent Laid-Open No. 9-192212 JP 2001-141438 A

  If the technology related to the measurement of sediment layer thickness such as the sewage treatment system described above is applied to the measurement of the thickness of the deposition layer of chemical substances such as naphtha formed in the cooling water tank of the above-mentioned thermal power plant, The following problems arise. First, naphtha is roughly acicular and irregular in shape, so its scattering component increases, and its reflectance is extremely small compared to sediment that accumulates in sedimentation basins of sewage treatment systems. For this reason, in order to ensure SN, it is necessary to transmit a high power ultrasonic wave.

  Moreover, since the reflectance of naphtha is small, a considerable part of the emitted ultrasonic wave penetrates the inside through the surface of the deposited layer, and the reflected wave generated inside is received. For this reason, the position of the surface of the deposition layer determined by the elapsed time from the emission of the ultrasonic wave to the reception of the reflected wave is blurred, and it becomes difficult to accurately detect the thickness of the deposition layer.

  Further, since the cooling water is agitated in order to make the water temperature in the cooling water tank uniform, the deposited naphtha rises and floats in the cooling water, and the position of the surface of the deposited layer changes. As a result, there is a problem that the position of the surface of the deposited layer becomes more blurred. In addition, there is a problem that the level of ultrasonic waves reaching the deposition layer is lowered by the reflected wave from the floating naphtha, and it is necessary to further increase the output.

  Furthermore, in order to improve the measurement accuracy of the thickness distribution, it is necessary to radiate ultrasonic waves vertically downward. However, since a high-temperature naphtha falls from the top in the central part of the cooling water tank, it is necessary to add a mechanism for thermally protecting the holding mechanism of the ultrasonic sensor and the cable, which increases the cost. is there.

Accordingly, one object of the present invention is to provide a device for monitoring the amount of liquid in the deposit which does not require a large output of the ultrasound. Another object of the present invention is the depth of the surface of the deposition chamber to provide an apparatus for monitoring the amount of unnecessary liquid in the deposit to be measured with high accuracy. Still another object of the present invention is to provide a device for monitoring the amount of improvement and submerged sediment suitable for automation of the efficiency of monitoring operations. Still another object of the present invention is to provide a device for monitoring the amount of unnecessary liquid in the deposit of installing an ultrasonic sensor in the center of the cooling water bath.

An apparatus for monitoring the amount of deposits in liquid according to the present invention that solves the above-described problems of the prior art is to ultrasonically measure the amount of deposits contained in the liquid, such as naphtha deposited in a cooling water tank of a thermal power plant. Use to monitor. The apparatus for monitoring the amount of the liquid in the deposit transmits ultrasound into the liquid, a transmitting and receiving means including an ultrasonic sensor for receiving the reflected waves generated in the liquid, this receiving means receives reflected An adding means for adding an amplitude greater than or equal to a predetermined value included in the wave over a predetermined range on the time axis; and a determining means for determining the amount of deposit based on the magnitude of the added value obtained by the adding means. .

According to the apparatus for monitoring the amount of sediment in the liquid according to the present invention, the total amount of reflected waves from the liquid is detected as an index indicating the progress of deposition, instead of measuring the thickness of the sediment layer such as earth and sand. Therefore, the progress of the deposition can be monitored without making the output level of the ultrasonic wave excessive and without worrying about the detection accuracy of the surface of the deposition layer.

  According to one preferred embodiment of the present invention, it is possible to further increase the efficiency of the monitoring work by further including a display unit that displays the determination result of the determination unit.

  According to another preferred embodiment of the present invention, it is possible to automate the monitoring work by further including an alarm generation means for generating an alarm when the determination result of the determination means exceeds a predetermined value.

  According to another preferred embodiment of the present invention, an ultrasonic sensor is installed in the peripheral part of the liquid tank, and ultrasonic waves are transmitted and received obliquely toward the central part of the liquid tank, so that the high temperature naphtha can be used. A thermal protection mechanism for protecting the ultrasonic sensor can be simplified and reduced in cost.

  Since the ultrasonic sensor has a directivity angle that allows almost the entire liquid tank to be viewed, it is possible to reduce the number of installations and to reduce the cost by omitting the scanning mechanism.

Figure 2 is a functional block diagram showing the configuration of an apparatus for monitoring the amount of water deposit according to an embodiment of the present invention. Apparatus for monitoring the amount of water deposit transducer 1, the transmission unit 2, the receiving section 3, the control unit 4, A / D conversion unit 5, memory 6, comparing and adding and determination unit 7, setting unit 8, the display part 9 and the alarm generation part 10 are provided.

FIG. 1 is a conceptual diagram showing a cooling water tank and a transducer 1 to be monitored by the monitoring apparatus of FIG. The cooling water tank P is installed below the chimney of the thermal power plant, and its dimensions are 10 meters × 2 meters and the depth is 1.5 meters. A compound mainly composed of high-temperature naphtha falls from the flue existing above the cooling water tank P, and a deposited layer Q of deposits is formed at the bottom of the cooling water tank P. The water level in the cooling water tank is kept constant by a liquid level gauge or a water supply device (not shown). A stirring device (not shown) is attached to the cooling water tank P, and stirring in the tank is performed in order to make the water temperature of the cooling water uniform.

  An ultrasonic transmitter / receiver 1 is attached to a peripheral portion on the short side of the cooling water tank P toward the lower side of the central portion. This ultrasonic transducer 1 has a wide directivity angle that can cover almost the entire short side of the cooling water tank P in the illustrated mounting state. Only one transducer 1 is attached to the central portion of the long side of the cooling water tank P.

  Referring to the functional block diagram of FIG. 2, the control unit 4 causes the transmission unit 2 to start a transmission operation by supplying a trigger pulse to the transmission unit 2. This trigger pulse is also supplied to the comparison / addition / determination unit 7 to start its operation. A transmission pulse of an electric signal is supplied from the transmitter 2 that has started operation to the transducer 1, and an ultrasonic pulse is emitted from the transducer 1 into the cooling water. The reflected wave generated in the cooling water is received by the receiving unit 3.

FIG. 3 is a waveform diagram showing a typical example of the reflected wave received by the receiving unit 3. Immediately after transmission, a large amplitude received signal T appears due to the wraparound of the transmission pulse. Subsequently, the reflected waves q ₁ and q ₂ generated by the sediments Q ₁ and Q ₂ floating in the water and the reflected wave q generated by the deposited layer Q appeared, and finally occurred at the bottom surface of the cooling water tank P. A reflected wave R having a relatively large amplitude appears.

The received reflected wave is converted into a digital signal by the A / D converter 5 and supplied to the comparison / addition / determination unit 7. The comparison / addition / determination unit 7 compares the amplitude of the digital received reflected wave supplied from the A / D conversion unit 5 with the threshold value Lth stored in the memory unit 6 and continues addition for amplitudes greater than Lth. To do. This addition is performed from time t ₁ to time t ₂ shown in the waveform diagram of FIG. The addition start time t ₁ is a time immediately after the reception of the large amplitude reception signal T due to the wraparound of the transmission pulse, and the addition completion time t ₂ is a relatively large amplitude reflected wave generated on the bottom surface of the cooling water tank P. This is the time immediately before R appears. The addition start and end times t ₁ and t ₂ are stored in the memory unit 6.

When the comparison / addition from the time point t ₁ to t ₂ is completed, the comparison / addition / determination unit 7 updates the addition value being displayed on the display unit 9 with the new addition value. Further, the comparison / addition / determination unit 7 compares the new addition value with the determination threshold value Dth stored in the memory 6 and ends the processing if it is less than the determination threshold value. If the new addition value is equal to or greater than the determination threshold value Dth, the comparison / addition / determination unit 7 determines that scraping of the deposited layer 3 is necessary, and activates the alarm generation unit 10. The activated alarm generation unit 10 sounds a built-in buzzer or notifies a remote worker via a communication path (not shown). Each parameter Lth, Dth, t ₁ , t ₂ for the determination is written from the setting unit 8 to the memory unit 6.

As illustrated in q ₁ and q ₂ in the waveform diagram of FIG. 3, the amount of naphtha floating in the cooling water by stirring is also transferred to the addition value of the criterion. In the conventional method for detecting the water depth on the surface of the deposited layer, q ₁ and q ₂ in the waveform diagram are discarded as unnecessary components. Therefore, in order to compensate for the discarded loss, a higher output of ultrasonic waves is obtained. Needs to be made. Moreover, since the discarded unnecessary component acts as noise, it is necessary to further increase the output of the ultrasonic wave in order to increase the SN of a necessary signal.

  Further, unlike the conventional apparatus that measures the spatial distribution of the thickness of the deposited layer, it is not necessary to emit ultrasonic waves from directly above the deposited layer, and the installation mechanism is simplified. This is a cooling water layer with a size of about 10 meters, unlike large water channels and sedimentation layers, and the liquid is not contaminated. The operator can know this visually.

  As described above, the configuration in which the alarm is generated when the one-time addition value exceeds the determination threshold value Dth has been exemplified. However, a configuration may be adopted in which an alarm is generated when a state in which the added value exceeds the determination threshold value Dth occurs continuously a predetermined number of times.

  Moreover, the case where the ultrasonic sensor is used for both transmission and reception is illustrated. However, it is also possible to use ultrasonic sensors dedicated to transmission and reception. In this case, it is also possible to install both of them separated from each other across the cooling water tank.

  Moreover, the structure which installed only one ultrasonic transducer 1 in the intermediate part of the long side of the cooling water tank P was illustrated. However, a plurality of these can be installed on the long side along the periphery, or scanned in the long side direction to perform the above comparison, addition, and judgment on each received reflected wave, and the received reflected wave of each sensor can be synthesized. A common comparison / addition / determination unit can perform comparison / addition / determination with respect to the above.

  Furthermore, the case where the deposit was naphtha was illustrated. However, the present invention can also be applied to a deposit having a low density and a low reflectance such as sludge. Moreover, the case of water was illustrated as a liquid. However, the present invention can also be applied to deposits in an appropriate liquid other than water, such as fuel and chemicals.

It is a conceptual diagram which shows the condition (amount) of the deposit in the cooling water tank to which this invention is applied. It is a functional block diagram which shows the structure of the apparatus which monitors the quantity of the deposit in a liquid concerning one Example of this invention. It is a wave form diagram which shows the example of the reflected wave which arises from the deposit in the cooling water tank shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmitter / receiver 2 Transmitter 3 Receiving unit 4 Control unit 5 A / D conversion unit 6 Memory unit 7 Comparison / addition / determination unit 8 Setting unit 9 Display unit
10 Alarm generator P Cooling water tank Q Deposit layer Q ₁ and Q ₂

Claims (9)

An apparatus for monitoring the amount of deposits contained in a liquid using ultrasonic waves,
Transmitting and receiving means including an ultrasonic sensor that transmits ultrasonic waves in the liquid and receives reflected waves generated in the liquid;
Adding means for adding an amplitude greater than or equal to a predetermined value included in the reflected wave received by the transmitting and receiving means over a predetermined range on the time axis;
Equipment characterized in that the addition means and a determination means for determining the amount of deposits on the basis of the magnitude of the added value obtained. In claim 1,
Further equipment you characterized by comprising display means for displaying the determination result of said determining means. In claim 1 or 2,
Further equipment you comprising the alarm generating means determination result of said determining means for generating an alarm when it exceeds a predetermined value. In any one of Claims 1 thru | or 3,
The ultrasonic sensor equipment you characterized in that it is installed on the periphery of the liquid tank accommodating the liquid. In claim 4,
The ultrasonic sensor equipment you characterized by transmitting and receiving ultrasonic waves obliquely towards the central portion of the liquid tank. In either of claims 4 or 5,
The ultrasonic sensor equipment you characterized as having a directivity angle looking into substantially the whole of the liquid bath. In any one of Claims 4 thru | or 6.
The ultrasonic sensor equipment you characterized in that it is installed across the central portion of the liquid tank. In any one of Claims 1 thru | or 7,
The liquid tank is a cooling water tank installed below a chimney of a thermal power plant, and the deposit is a compound mainly composed of naphtha that falls into the cooling water tank from above the chimney. that equipment. A method for monitoring the amount of deposits contained in the liquid using ultrasonic waves, including transmitting and receiving ultrasonic waves into the liquid and including an ultrasonic sensor that receives reflected waves generated in the liquid; ,
A process of adding an amplitude greater than or equal to a predetermined value included in a reflected wave received by the process of transmitting and receiving over a predetermined range on the time axis;
And a process of determining the amount of deposit based on the magnitude of the added value obtained by the adding process.

Images