JPS6315548B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a concentration measuring device for measuring the concentration of a suspension such as sewage or industrial wastewater, and in particular, a device for measuring the concentration of a suspension containing air bubbles by reducing the influence of air bubbles. The present invention relates to a concentration measuring device for measuring concentration.

Suspension liquids such as sewage and industrial wastewater often contain air bubbles. For this reason, conventionally, a concentration detector with a defoaming device is used to cyclically defoam the suspension and measure the concentration of the suspension after defoaming. This densitometer with defoaming device consists of a densitometer main body, a defoaming control section that outputs a valve closing command signal and a defoaming command signal at a predetermined timing, and a valve closing command signal output from the defoaming control section. and a valve body that closes the upstream and downstream flow paths of the concentration meter main body in response to the defoaming command signal output from the defoaming control unit after the valve is closed, sends a predetermined pressurized air to defoam. It consists of a defoaming device with a pressure source such as an air compressor.

In this case, the series of timings for the defoaming operation consisting of defoaming time, concentration measurement time, and sample discharging/refilling time are determined in advance based on human intuition, taking into consideration the properties of the suspension and the like. In particular, among the series of timings of the defoaming operation, the defoaming time is very uncertain to human perception, and naturally measurement values with errors will be obtained.

Hereinafter, the relationship between the series of timings of the defoaming operation and the defoaming rate of bubbles contained in the suspension will be explained with reference to FIG. As is clear from the figure, for example, in the case of a sample containing fine bubbles, the bubbles are easily dissolved, so that the sample exhibits a defoaming rate characteristic such as ◯I-1. Therefore, in such a sample, there is ample time for defoaming, and the waiting time until concentration measurement is long, resulting in a large amount of wasted time. In the case of the defoaming rate characteristic shown in A-2, the bubble dissolution time and the defoaming time exactly match, so that the above-mentioned wasted time is eliminated. In the case of the defoaming rate characteristic of A-3, the defoaming time is insufficient and the concentration is measured while bubbles remain, resulting in measured values with errors. In the case of ○E-4, this tendency becomes even more pronounced than in ○E-3, and a significant error occurs.

Therefore, as is clear from the defoaming rate characteristics shown in FIG. 1, the defoaming rate of bubbles differs significantly depending on the bubble-containing state of the suspension. In this case, as mentioned above, the defoaming rate of bubbles can be determined based on the properties of the suspension, but the bubble content does not depend only on the properties of the suspension; It is changing, and the degree of change is very large. Therefore, in order to ensure uniformity of defoaming time, very high pressurizing pressure is applied to the suspension, or defoaming is performed by allowing a sufficient margin for defoaming time.

However, even if the pressurizing force is increased as in the former case, there is a limit, and even then, unless the bubble content is uniform, the defoaming rate will vary, causing errors in measurement values, and shortening the life of the defoaming device. There is a problem with making it shorter. Further, in the latter case, a large amount of wasted time occurs for concentration measurement, and since the series of defoaming operations are performed cyclically, the wasted time of each defoaming time increases cumulatively. For this reason, particularly in batch-type concentration measuring devices, most of the series of defoaming operations are performed during defoaming time unrelated to concentration measurement, which is disadvantageous in that proper concentration measurement cannot be carried out promptly.

The present invention has been made in view of the above-mentioned circumstances, and has a bubble detection function, and operates the defoaming device only when bubbles have a large effect on the concentration measurement value, thereby eliminating wasted defoaming time. Moreover, it is an object of the present invention to provide a concentration measuring device that measures concentration while reducing the influence of air bubbles.

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 2, reference numeral 11 denotes an ultrasonic densitometer with an antifoaming device, which is connected to a pipe 12 through which the suspension flows and transmits ultrasonic waves to the suspension and obtains a concentration signal from the received signal.

This ultrasonic densitometer with defoaming device 11 is composed of a densitometer main body, a defoaming control section, a valve body, a pressurizing pressure source, and other defoaming devices, similar to the conventional configuration. The densitometer 11 outputs a valve closing command signal and a defoaming command signal at a predetermined timing only when a defoaming command signal is received from the outside, thereby defoaming the suspension.

Reference numeral 13 denotes a transducer that intermittently transmits ultrasonic waves in response to a signal from the transmitter 14 and receives reflected waves reflected by air bubbles contained in the suspension. The reflection of ultrasonic waves by these bubbles is significantly different from the reflection by suspended matter other than bubbles, and if it exceeds the appropriate range value determined by preliminary analysis, it is determined that defoaming is necessary. Reference numeral 15 denotes a receiver that receives the ultrasonic waves transmitted by the transducer 13. 16 and 17 are signal amplifiers operated by the switching signal of the switching circuit 18, and the amplifier 16 is connected to the transducer 13 side,
The amplifiers 17 are each connected to the receiver 15 side. 19 and 20 are hold circuits that hold the concentration signals output from the transducer 13 and the receiver 15, respectively, and the signals held here are sent to the judgment circuit 21. This judgment circuit 21 compares the output signals of the hold circuits 19 and 20 to evaluate the influence of bubbles, and if the influence is large, sends a defoaming command signal to the ultrasonic densitometer 11 with a defoaming device. 22 is a correction circuit that complements the hold value of the sample and hold circuit 20 with a received signal of the reflected wave by the transducer 13; 23 is a correction circuit 2;
This is a signal converter that appropriately converts the density signal corrected in step 2.

That is, by pre-analyzing the suspension that is the medium to be measured, the possible range of received waves and reflected waves depending on the content of bubbles is analyzed, and the appropriate range value is determined by this analysis. If this value is exceeded, it is determined that there is an abnormal condition that requires defoaming. The correction circuit 22 performs correction by adding the attenuation due to bubbles to the output of the hold circuit 20.

Next, the operation of the apparatus configured as above will be explained. Generally, if the suspension contains bubbles, the ultrasonic waves transmitted from the transducer 13 are received at the timing shown in FIG. 3. That is, A is a signal transmitted from the transducer 13, B is a signal reflected by a bubble and received by the transducer 13, and C is a signal transmitted from the transducer 15.
This is the signal received by.

In the figure, t ₁ is the time it takes for an ultrasonic wave to be transmitted from the transducer 13 and reflected by a bubble to reach the transducer 13, and t ₂ is the time for the ultrasonic wave to be received from the transducer 13. This is the time it takes to reach the wave device 15. Therefore, t ₁ is a shorter time than t ₂ , e.g.
If the distance from 3 to receiver 15 is 300 mm, t ₁
is set to 0.1ms, and _t2 is set to about 0.2ms.

Therefore, the switching circuit 18 operated by the output signal of the ultrasonic transmitter 14 switches the signal amplifier 1 at the above timing.
6, 17 and the correction circuit 22 are selectively operated.

First, a signal is output from the transmitter 14 and supplied to the transducer 13. At this time, the switching circuit 18 sets the signal amplifier 16 and the correction circuit 22 in an open state so that the signal from the oscillator 14 does not directly enter. The transducer 13 that receives the signal from the transmitter 14 transmits ultrasonic waves, but in this case, the more bubbles the suspension contains, the more the ultrasonic waves are reflected by the bubbles near the transducer 13. The reflected signal is received by the transducer 13 at a high reflected signal level, while at the receiver 15 it is received at a low signal level.

Since the pipe diameter of the conduit 12 is constant, the wave reception by the wave receiver 15 is performed at a certain time after the wave is transmitted by the wave transmitter/receiver 13. Since the transducer 13 also receives reflections from bubbles near the receiver 15, it generates the next ultrasonic wave at a sufficient interval.

Therefore, when the switching circuit 18 closes the signal amplifier 16 and the correction circuit 22 after transmitting ultrasonic waves from the transducer 13, the signal reflected by the bubble and received by the transducer 13 is transmitted to the signal amplifier 16 and the correction circuit 22. circuit 2
2, the output signal of the signal amplifier 16 is held in the subsequent sample and hold circuit 19. Further, the correction circuit 22 similarly holds the received signal from the transducer 13.

On the other hand, the signal received by the receiver 15 also enters the signal amplifier 17 through the switching circuit 18.
The signal amplified and output here is similarly held in the subsequent sample and hold circuit 20. and,
The signals held in each of the hold circuits 19 and 20 enter the subsequent judgment circuit 21, where the influence of bubbles is judged from the deviation value of both signals, and if it is judged that there is an effect, a defoaming command signal is issued. The defoaming device performs defoaming operation.

In other words, when determining the influence of bubbles from the deviation value, for example, {(output voltage of the hold circuit 20) -
(Output voltage of the hold circuit 19)}<A, when
It is judged that there is an influence of air bubbles. Note that the value of A is a criterion value that is determined experimentally in advance.

The wave is received by the receiver 15 and sent to the sample hold circuit 2.
The concentration signal held at 0 enters the correction circuit 22, where the concentration signal is corrected according to the signal level received by the transducer 13 and sent to the subsequent signal converter 23 as an appropriate concentration signal. .

Therefore, in the above-mentioned apparatus, the defoaming operation is not performed if the amount of bubbles does not affect the measured value. This has the advantage that the defoaming time can be significantly reduced, unlike the conventional defoaming which always occurs at a fixed timing.

Next, FIG. 4 is a diagram showing another embodiment of the device of the present invention, in which the transducer 13 is connected to the transmitter 13a.
and the receiver 13b are installed separately, and the transmitter 13
It is configured to continuously transmit ultrasonic waves from a. Therefore, in this case as well, the signal received by the receiver 13b enters the signal amplifier 16 and the correction circuit 22, and is held by the subsequent circuit 19 and the same circuit 22, as in FIG. On the other hand, the signal received by the receiver 15 is held by the sample and hold circuit 20.

Then, the signals from both circuits 20 are used in a determining circuit 21 to determine the influence of bubbles and determine whether or not the defoaming device performs the defoaming operation. Further, the hold signal of the sample hold circuit 20, that is, the density signal, is input to the correction circuit 22, corrected, and outputted as a proper density signal.

Fig. 5 uses a burst wave as in Fig. 2, but while using this burst wave, one transducer 13 receives the signal reflected by the bubble and the signal reflected by the opposite wall, respectively. The signal amplifiers 16 and 17 are adjusted to match the timing.
The correction circuit 22 is selectively controlled in a time-division manner. Note that 24 is a gate that is opened and closed at the same time as the signal amplifier 16.

Generally, when using this type of device, the properties of the medium to be measured must be analyzed in advance by manual analysis or by comparing the measured values after defoaming with the measurements taken without defoaming. is being carried out. This preliminary analysis estimates the properties of the medium to be measured, that is, the amount of suspension.

The reliability of this device is ensured based on this estimation result and the fact that the presence of bubbles in the medium (liquid) to be measured significantly attenuates the ultrasonic waves, and the amount of reflected ultrasonic waves becomes larger than the amount of transmitted ultrasonic waves.

As detailed above, according to the present invention, it is determined whether or not the bubbles contained in the suspension affect the measured value, and the defoaming operation is performed only when it is determined that the bubbles have an effect. When there are few bubbles contained in the turbid liquid, there is almost no need to perform a defoaming operation. Therefore, the defoaming time, which was conventionally performed cyclically, can be completely eliminated as wasted time. Moreover, since the concentration signal is appropriately corrected for the effect of this slight bubble by the correction circuit, an accurate concentration signal can be measured.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining a series of timings of a conventional defoaming operation, Fig. 2 is a configuration diagram showing an embodiment of the device of the present invention, and Fig. 3 is an explanation of the reception time of transmitted ultrasonic waves. 2, FIG. 4, and FIG. 5 are configuration diagrams showing other embodiments of the present device, respectively. 11... Ultrasonic concentration meter with defoaming device, 13... Wave transducer, 13a... Wave transmitter, 13b... Wave receiver,
14... Transmitter, 15... Receiver, 19, 20...
...Sample hold circuit, 21...Judgment circuit, 2
2... Correction circuit, 23... Signal converter.

Claims (1)

[Scope of Claims] 1. A device for measuring the concentration of a suspension, which includes: an ultrasonic densitometer with an anti-foam device that transmits ultrasonic waves into a suspension containing air bubbles and has an anti-foam device; A first signal reflected by the bubbles of the ultrasonic wave and a second signal passed through the suspension are respectively received, and these first and second received signals are compared to 1. A concentration measuring device comprising: a determination circuit for determining the influence of bubbles; and when the determination circuit determines that there is an influence of bubbles, a defoaming command signal is given to the defoaming device. 2. The concentration measuring device according to claim 1, wherein a single transducer transmits the ultrasonic waves and receives the first and second signals. 3. The concentration measuring device according to claim 1, wherein the first signal is used as a correction signal for the second signal.