JPH02112757A - Instrument for measuring concentration of particulate matter in piping - Google Patents

Abstract

PURPOSE:To make prompt measurement by providing >=1 pairs of ultrasonic oscillators and receivers to the circumference of a piping, measuring the attenuation quantity of the ultrasonic waves in the ultrasonic propagation routes formed therebetween and detecting the concn. of particulate matter in accordance with the attenuation quantity. CONSTITUTION:Three pairs of the oscillators 3 and receivers 4 are mounted to the outer side of a circular piping 1 in which pulverized coal and the air for transporting this coal flow in the form of solid-gas two-phase flow 2. The instrument is constituted in such a manner and the signal from a computer 7 is amplified by an amplifier 6 to drive the transmitters 3. The ultrasonic waves received by the receivers 4 are converted to electric signals by the receivers. The electric signals are amplified by an amplifier 6A and are returned to the computer 7. The attenuation quantity of the respective propagation lines connecting the oscillators 2 and the receivers 4 from the reception level is determined at this time and the concn. of the powder is detected from the calibration chart of the previously measured ultrasonic transmittance and the concn. of the pulverized coal. The detected concns. are respectively displayed on a distribution display device 8 and an average value display device 9. The pressure drop in the piping is eliminated in this way and the errors by the moisture in the fluid are eliminated as well.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a measuring device for powder and granular materials in piping, and particularly to a non-contact measuring device for powder and granular materials in a solid-gas two-phase flow in piping. The present invention relates to a powder/granular material concentration measuring device suitable for.

[Conventional technology]

In recent years, cheap coal has been used as fuel in large commercial boilers instead of oil.

However, in the case of coal, because it is transported as a solid, there are many technical issues related to transportation, unlike in the case of oil, which is a liquid. In particular, measuring the flow rate of pulverized coal when it is sent from a mill to a burner is necessary to ensure smooth combustion in multiple burners and improve combustion efficiency. The technology to do so has not yet been established.

As a method for measuring the powder concentration in a solid-gas two-phase flow within a pipe, a venturi type as shown in FIG. 8 is generally used. This takes advantage of the fact that pressure loss changes depending on the presence of powder. In FIG. 8, 1 is a circular pipe for transporting a mixed fluid of air and pulverized coal, 2 is a solid gas two-phase flow, 41 is a constricted part, 42 is a straight pipe part, and 43 is an enlarged part.

Moreover, FIG. 8A is a diagram showing the relationship between the flow direction position and the static pressure distribution in FIG. 8. Since the velocity of the powder is higher than that of air in the enlarged portion 43, the pressure loss 44 of A over a suitable length is almost the same as in the case (B) without powder. Therefore, the amount of air can be determined from this pressure loss. On the other hand, the pressure loss in the four constricted parts is larger when there is powder than when there is no powder, so the amount of powder is calculated from this difference. Furthermore, the powder concentration is calculated from these air amounts and powder amounts. Note that some devices use an orifice instead of a venturi shape, but the principle is the same.

[Problem to be solved by the invention]

However, in the method shown in Figure 8, a pressure loss of about 100 dragons of water occurs due to the provision of a constriction part in the piping, which increases the power cost required for transportation, and when used in horizontal piping, the powder concentration is biased downward. , the average concentration is less than <<, so it has the disadvantage that it can only be used in vertical piping.

In addition, there is a method of measuring the flow rate of solid-gas two-phase flow in a pipe that uses the amount of charge on powder, but the above-mentioned drawbacks have not been overcome and this method has not been put to practical use.

There is also a method of measuring powder concentration by inserting a sampling probe directly into the pipe as a temporary measurement method.
Do not pass through the needle side at all times.

As described above, all conventional measurement methods are affected by the flow conditions and physical properties of powder, and cannot accurately measure the flow rate of a solid-gas two-phase flow.

An object of the present invention is to provide an apparatus that can accurately measure powder concentration in a solid-gas two-phase flow.

[Means to solve the problem]

The object of the present invention described above is to provide a device for measuring the concentration of powder and granular material in a pipe through which a mixed fluid of powder and granular material and a gas for transporting the powder and granular material is provided. An ultrasonic transmitter and a receiver, a device for measuring the amount of ultrasonic attenuation in an ultrasonic propagation path formed between the transmitter and the receiver, and a device for calculating the concentration of powder or granular material based on the amount of attenuation. This is achieved by a device for measuring the concentration of powder or granule in a pipe, which is characterized by comprising:

〔Example〕

An embodiment of the present invention is shown in FIG. In FIG. 1, pulverized coal and air for transporting it flow as a solid-gas two-phase flow 2 inside a circular pipe 1. Three pairs of ultrasonic transmitters 3 and receivers 4 are attached to the outside of the circular pipe.

A signal output from the computer 7 is amplified by an amplifier 6 and drives the oscillator 3. The received ultrasonic waves are converted into electrical signals by the receiver 4, amplified by the amplifier 6A, and returned to the computer 7. The attenuation of each propagation path connecting the transmitter 3 and receiver 4 is calculated from the reception level at this time, and the attenuation of each propagation path connecting the transmitter 3 and receiver 4 is determined from the calibration diagram of ultrasonic transmittance and pulverized coal concentration shown in Figure 2, which was measured in advance. The powder concentration is calculated and displayed on the distribution display 8 and the average value display 9.

The average flow velocity of the air used in this example was 15 m/s, the air flow rate was 70 kg/min, and the diameter of the circular tube was 300 + n. The average particle size of the pulverized coal to be transported is 70 microns, and the flow rate is 70 kg/min.

FIG. 3 shows a sectional view of a portion of the mounting of the transmitter 3.

The transmitter 3 and receiver 4 are mounted so as to face each other.

The transmitter 3 and the receiver 4 are separated from the circular tube 1 by a soundproof material 11. A filter 10 is placed inside the tube to prevent fine pulverized coal from entering and colliding with the transmitter and receiver.

A 300 kilohertz electrical pulse is sent to the transmitter 4. The reason why a pulse signal is used is to avoid resonance within the tube. When resonance occurs, the attenuation of ultrasound waves cannot be measured correctly. The frequencies used were selected varying from 20 kilohertz to 1 megahertz. For materials that are finer than pulverized coal, such as cement powder, a frequency of around 500 kilohertz has a high S/N (noise to received signal ratio) ratio and is suitable.

Furthermore, in the present invention, since the level detection of the received ultrasonic wave affects the accuracy, the electric signal is passed through a band-pass filter to reduce noise, and further pulses are emitted 20 times and the average thereof is taken.

The embodiment shown in FIG. 4 is similar to the X-ray CT method, and eight ultrasonic transmitter/receivers 15 are installed.
As shown in the cross-sectional view of the figure, the attenuation amount is measured along as many propagation paths 20 as possible. From a plurality of attenuation amounts, the powder concentration for the multiple elements 21 shown as divided by dotted lines in FIG. 6 is determined, and the powder concentration in the pipe is displayed as shown in FIG. 7.

This method can also be applied when a concentration distribution of pulverized coal occurs in horizontal piping.

In addition, if you use an orifice or venturi to measure the flow rate, you can also find out the absolute amount of flow rate.

Further, if the moisture content of the powder does not change, the same measurement can be performed using electromagnetic waves instead of the ultrasonic waves in this example.

〔Effect of the invention〕

According to the device of the present invention, it is possible to immediately measure the concentration of powder or granular material in the piping at all times without causing pressure loss in the piping and without errors due to moisture in the fluid to be measured. It does not disturb the flow of fluid.

[Brief explanation of drawings]

Fig. 1 shows an example of the present invention, Fig. 2 shows the relationship between pulverized coal concentration and ultrasonic transmittance in a mixed fluid of pulverized coal and air, and Fig. 3 shows how the ultrasonic transmitter is attached to piping. 4 is a diagram of another embodiment of the present invention, FIG. 5 is a sectional view showing the propagation path of ultrasonic waves, FIG. 6 is a side view of the element division within the cross section to be measured, and FIG. FIG. 8 is an explanatory diagram of the prior art. FIG. 8A is a diagram showing the relationship between the position in the flow direction and the static pressure distribution in FIG. 8. 1... Circular pipe, 2... Mixed flow of pulverized coal and air, 3...
- Transmitter, 4... Receiver, 5... Cable, 6.6
A... Amplifier, 7... Computer, 8... Concentration distribution display, 9... Average value display, 10... Filter, 11... Soundproofing material. Applicant Babcock Hitachi Co., Ltd. Agent Patent Attorney Takeshi Kawakita

Claims (1)

[Claims] (1) In a device that measures the concentration of a powder or granule in a pipe through which a mixed fluid of a powder or a gas for transporting the powder or granule flows, one or more pairs of ultrasonic transmitters and receivers are arranged around the pipe. A device for measuring the amount of ultrasonic attenuation in the ultrasonic propagation path formed between the transmitter and the receiver, and a device for calculating the concentration of the powder based on the amount of attenuation. A device for measuring the concentration of powder and granules in piping.