JPS63138214A - Method and device for measuring powder flow rate by attenuation of sound wave - Google Patents

Abstract

PURPOSE:To execute an exact measurement which is excellent in its responsiveness, by calculating a powder flow rate from the product of a powder concentration calculated by measuring an attenuation of a sound wave by powder, and a powder speed calculated by measuring a delay time between measuring points. CONSTITUTION:Powder 70 is carried by passing through the inside of a carrying pipe 80. A sound wave generator 11 generates a sound wave between 1kHz and 1kHz, and this sound wave is emitted to the inside of the carrying pipe 80 by a sound wave element 12. The emitted sound wave is attenuated due to existence of the powder 70 and reaches a sound wave element 22. The sound wave transmitted to the element 22 is detected by a sound wave detector 21, and converted to a powder concentration by a concentration detector 31. The same measurement is executed between the elements 11, 12 and sound wave elements 14, 24 separated in the flow direction of the powder 70, as well. Results of detection of detectors 31, 32 are sent to a powder average flow rate calculator 60 through an average concentration calculator 40 and a speed computing element 50. In such a way, the measurement of a powder flow rate, which is excellent in its responsiveness can be executed.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a device for pneumatically conveying powder used in quartz-fired boilers, coal gasification, etc., and particularly relates to a powder flow rate measurement device with high accuracy and quick response. METHODS AND APPARATUS.

[Conventional technology]

Coal is a useful energy source with abundant reserves, but its solid state makes it difficult to handle.

However, if coal is pulverized, it can be used for a variety of purposes by being transported by air current. This has greatly expanded the range of applications, and its use is particularly promising in the field of power generation. In the field of power generation, load fluctuations are especially essential, and accurate and quick-response measurement of the pulverized coal fuel supply amount, that is, the powder flow rate, is required.

The flow rate of powder is generally expressed as the product of powder velocity and powder concentration. Methods for measuring the flow rate include directly determining the amount of powder supplied, and measuring the powder velocity and concentration separately. There is an indirect method of calculating by calculating the product. ” The method to directly determine the amount of powder supplied is the 1 weight reduction method.
The weight reduction method is a method in which a device such as a hopper that supplies powder is equipped with a device that measures the weight of the powder in the hopper, and the flow rate of the powder is calculated from the rate of decrease in the weight of the powder. The absolute value of powder flow rate has the highest reliability.

When powder is transported by air flow, the powder concentration in the transport gas is not constant, and the speed of the transport gas and the powder speed are also different. Therefore, in order to indirectly measure the powder flow rate, it is necessary to determine the powder concentration and the powder velocity separately from the measurement of the carrier gas amount and the carrier gas velocity.

Methods for determining powder concentration include differential pressure method, capacitance method, Coriolis method, light transmission gravity, and the like.

Differential pressure method: Find the differential pressure, which is the sum of the kinetic energy of both the powder and the carrier gas, subtract the kinetic energy of the carrier gas from this, find the apparent density of the powder from the velocity of the powder, and find the powder concentration. .

Capacitance method: Find the capacitance of powder in a certain area and convert it to powder concentration.

Coriolis method: Determine the Coriolis force, which indicates the inertial force of the powder, and determine the apparent density of the powder from the velocity of the powder to determine the powder concentration. JP-A-60-198414 describes a method of detecting the particle concentration using this method and determining the powder flow rate assuming that the powder velocity and the carrier gas velocity are equal.

Light transmission method: Determine the light transmittance and convert it to the concentration of the powder.

Methods for determining the velocity of powder include a laser method, an ultrasonic method, a correlation method, and the like.

Laser @ = L D V (Laser Dapple
r Veloci+meter) to determine the particle velocity at a specific point and the particle velocity over the entire cross section.

Ultrasonic method: Measures particle velocity using the Doppler effect that occurs when ultrasonic waves are projected onto moving powder.

Correlation method: Measures changes over time in physical quantities related to the powder on the upstream side of the flow in the pipe that conveys the powder, and changes over time in the physical quantities on the downstream side, and measures the velocity of the powder from the correlation with the delay time. . JP-A No. 61-54457 describes a method for determining powder velocity using powder friction sound as this physical quantity.

[Problem that the invention seeks to solve]

In the above conventional techniques, there is a problem that the response is slow in the direct method, and even in the indirect method, there is no appropriate method to calculate the powder concentration, and the correlation method, which is the best for measuring powder velocity, Physical quantities did not exist.

The direct method has a problem in that it takes time to smooth the supply amount when calculating the rate of decrease, resulting in a slow response. Even if it is indirect, there is no suitable method as described below.

Differential pressure method: Information on the powder is obtained using carrier gas as a medium, so
Sensitive to carrier gas pressure.

Capacitance method: Capacitance is sensitive to moisture, so the measured value changes depending on the moisture content of the powder.

Coriolis method: To generate Coriolis force in powder,
Since the conveyance piping must be bent in a complicated manner, stable conveyance is hindered.

Light transmission method: When the powder concentration is high, no light is transmitted and the speed cannot be measured.

Laser method: Similar to the light transmission method, when the powder concentration is high, the laser light does not pass through and the speed cannot be measured.

Ultrasonic method: When the powder concentration is high, the signal due to the Doppler effect cannot be identified.

Correlation method: JP-A No. 61-54457 describes a method for determining powder velocity using powder friction sound as a physical quantity for which correlation is to be determined. , which can be a physical quantity indicating that the powder has passed, is difficult to find a correlation with.

An object of the present invention is to develop a measuring method that accurately indicates powder concentration using an indirect method with excellent responsiveness, and to provide a method and apparatus for accurately and quickly measuring flow rate.

[Means for solving problems]

The above problem was solved by transmitting sound waves through the powder passing through the transport pipe at multiple locations separated by a certain distance within the transport pipe, and continuously measuring the attenuation of the sound waves by the powder. % P(t)...Sound pressure PO reduced by powder...Powder concentration is calculated from the sound pressure when there is no powder, and the powder concentration is calculated from the correlation of the measured values at the multiple locations. In addition to the method of calculating the velocity and calculating the flow rate by multiplying the concentration and velocity of the powder, the method further includes a plurality of oscillators that emit sound waves, a plurality of detectors that measure attenuation of the emitted sound waves, and a method using the detectors. There is a concentration calculator that calculates the powder concentration from the attenuation of measured sound waves, a speed calculator that calculates the powder velocity from the correlation of measurement data from multiple locations, and a This is achieved by providing a powder flow rate measuring device using acoustic attenuation, which has a powder flow rate calculator for calculating the powder flow rate.

[Effect]

The attenuation of the sound waves when they are transmitted through the powder passing through the conveyor tube varies greatly depending on the frequency of the sound waves, and is
There is less attenuation at frequencies below.

It was discovered that the attenuation is severe at frequencies above I MHz. And the frequency of the sound wave is from IKHz to I MH2+
When the powder concentration inside the conveying tube is between.

The attenuation of sound pressure has a relationship shown by the linear equation, and the influence of the carrier gas on this attenuation is due to the influence of the powder concentration p(t)・
・Sound pressure Pa attenuated by powder ・Undamped sound pressure when there is no powder C(t) ・Powder concentration K ・Proportional constant This equation can be further applied to powder measurement Expressed in general form, C(t)
=ao+azD+azD''+aaD'P.

aol al+ az, aa... Convey pipe shape coefficient.

Furthermore, the attenuation signals obtained at the detection points installed a distance apart in the flow direction are Fl(t) and F2(t), respectively.

When , the correlation between these signals is expressed as follows. τ at which this φ(τ) is maximum indicates the time required for the powder to pass the distance. Therefore, the velocity V of the powder is expressed as V=-τ.

The powder concentration C(t) is calculated by the concentration calculator from the attenuation amount P(shi) of the sound wave measured by the detector, and the attenuation signal F1 (t
) * Fz (t) is added to the velocity calculator to calculate the powder velocity V. 0 Then the powder concentration C(t) and the powder velocity V are added to the powder flow rate calculator to calculate the powder flow rate. is calculated.

〔Example〕

Embodiment 1 of the present invention will be described below with reference to FIG.

The present embodiment is composed of a detector provided in the transport pipe 80 and a calculator connected to the detector.

The sonic element 12 and the sonic element 22 are provided facing each other in the conveying tube 80, and the line connecting the sonic element 12 and the sonic element 22 is arranged at a position perpendicular to the flow direction of the powder in the conveying tube. The acoustic wave element 12 is connected to the acoustic wave generator 11 . The sonic element 22 is connected to a sonic detector 21, and the sonic detector 21 is connected to a concentration calculator 31.

A sonic element 14 and a sonic element 24 are provided facing each other along the conveyance pipe 80 at a distance from the sonic element 12,
A line connecting the sonic elements 14 and 24 is arranged at a position perpendicular to the flow direction of the powder in the conveying pipe. The acoustic wave element 14 is connected to the acoustic wave generator 13 . Sonic element 2
4 is connected to a sonic detector 23, and the sonic detector 23 is connected to a concentration calculator 32.

A sound wave generator 11, a sound wave element 12, a sound wave element 22,
The sonic wave detector 21 is collectively referred to as a detector 1, and the sonic wave generator 13, the sonic element 14, the sonic element 24, and the sonic wave detector 23 are collectively referred to as a detector 2.

An average concentration calculator 40 is connected to the concentration calculator 31.32, and a speed calculator 50 likewise connects to the concentration calculator 31.3.
Connected to 2. Further, a powder average flow rate calculator 60 is connected to the average concentration calculator 40 and the speed calculator 5o.

Next, the operation of this embodiment will be explained. The powder 70 is transported through the transport pipe 80 . Since the powder 70 is transported by air current, the powder concentration within the tube changes over time. The sound wave generator 11 generates sound waves between IKHz and IMHz.

This sound wave is emitted into the transport pipe 80 by the sound wave element 12. The emitted sound wave is transmitted through the airflow inside the transport pipe, but
It reaches the acoustic wave element 22 after being attenuated by the presence of the powder 7o. The degree of this attenuation varies depending on the powder concentration. The sound wave (attenuated signal) transmitted to the sound wave element 22 is converted into an electrical signal by the sound wave detector 21. This electric signal is converted by the concentration calculator 31 connected to the sonic wave detector 21 into a signal representing the powder concentration according to the following equation.

Ct (t) = a zo + a tzD + a 1
xD"+ a llID'IO Here, C1(t) is the powder concentration, Pt(t) is the sound pressure after being attenuated by the powder, and pto is the unattenuated sound pressure when there is no powder. , 1"lo are measured in advance without powder. Also a io, a 11+
a tz* a 18 is a constant determined by the size and shape of the conveying pipe, the particle size distribution of the powder, etc., and detects the powder concentration between the sonic elements 12 and 22 by operation of 0 or more. A similar operation is performed between the sonic element 14 and the sonic element 24, and the resulting attenuated sound pressure is set as Pg(t), and the powder concentration is set as C2,(t).

The speed calculator 50 connected to the concentration calculator 31, 32 is
The powder velocity V is calculated from this concentration C1c t ) * CxCt ). The correlation between C5(t) and Ct(t) is expressed by the following equation.

τ at which φ(τ) is maximum is the time taken for the powder to pass between two points separated by the distance at time t (
1), therefore, the velocity of the powder is expressed by the following equation.

Average concentration calculator 40 connected to concentration calculators 31 and 32
calculates the average powder concentration Ca(t) expressed by the following formula from Ct(tL CxCt).

The powder average flow rate calculator 6o connected to the average concentration calculator 40 and the speed calculator 5o calculates the average powder flow rate F from the powder speed V(t) and the average powder concentration Ca(t) using the following formula.
(t) is calculated.

F(t)=V'(t) ·Ca(t) In this embodiment, since the concentrations measured at two points are averaged, the accuracy of flow rate calculation is high.

FIG. 2 shows a second embodiment of the present invention. The configuration of the device is similar to that of the first embodiment, but the speed calculator is replaced by the concentration calculator 3.
1.32 instead of the sonic detector 21.23
The difference is that it is connected to

To calculate the speed, the attenuation signal converted from the sound wave to an electric signal by the sound wave detectors 21, 23 is directly used to obtain a correlation, and the speed is calculated from this, so signal processing is fast and responsiveness is improved.

FIG. 3 shows a third embodiment. Sonic elements 15 and 16 are elements that combine sound wave emitting and receiving elements, and the sound waves generated by the sound wave generator 11.13 are transmitted through the sound wave elements 15.16.
The powder is ejected into the powder 70 in the conveying pipe 80 by the following. The sound waves attenuated by the powder 70 are reflected by the opposing tube wall surface, and after being attenuated again by the powder 70, the sound waves are transmitted to the sound wave element 15.
．． It is received at 16. The subsequent signal processing is similar to that of the second embodiment. According to this embodiment, the number of elements installed in the conveying pipe can be halved.

In the embodiments described so far, acoustic waves and electric signals are used as the signal transmission medium, but acoustic waves and optical signals or a signal medium that is a combination of them may also be used.

〔Effect of the invention〕

According to the present invention, by measuring the flow rate of powder being transported in a pipe by the attenuation of sound waves due to the powder being transported, It becomes possible to measure accurately and quickly, and has the effect of being able to respond accurately and quickly to fluctuations in the load on equipment.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing a first embodiment of the present invention, FIG. 2 is a system diagram showing a second embodiment, and FIG. 3 is a system diagram showing a third embodiment. 11.12, 21.22...Detector, 13, 14°2
5.24...Detector, 31.32...Concentration calculator,
50... Speed calculator, 60... Powder flow rate calculator, 7
0...Powder, 80...Transport pipe.

Claims (1)

[Claims] 1. In a method of measuring the flow rate of powder conveyed by air current, on the one hand, a sound wave is emitted to the powder passing through a conveyance pipe, and the attenuation of the sound wave by the powder is measured; On the other hand, the powder velocity is calculated by measuring the delay time between measurement points using the attenuated signal obtained by carrying out the above measurements at multiple points separated in the flow direction, and then calculating the powder velocity. A method for measuring a powder flow rate using acoustic attenuation, characterized in that the powder flow rate is calculated from the product of the powder concentration and the powder velocity. 2. Measurement of powder flow rate by sonic attenuation according to claim 1, wherein the frequency of the sound wave emitted to the powder passing through the conveying pipe is between 1 KHz and 1 MHz. Method. 3. When calculating the powder concentration, C(t)=a_0+a_1D+a_2D^2+a_3D
^3 However, D=l_n[P(t)]/P_0, C(t)
...Powder concentration, a_0, a_1, a_2, a_3...
- Convey pipe shape factor P_0...Sound pressure when there is no powder P(t)...Sound pressure attenuated by powder is calculated using the formula. Claim 1 Method for measuring powder flow rate using acoustic attenuation as described in Section 1. 4. The method for measuring a powder flow rate by acoustic attenuation according to any one of claims 1 to 2, wherein the attenuation signal used to measure the delay time is a powder concentration. 5. Claims 1 to 2, characterized in that the attenuated signal used to measure the delay time is a signal obtained by converting attenuated sound pressure into an electrical signal, and is not subjected to arithmetic processing. A method for measuring powder flow rate using acoustic attenuation as described in any of the above. 6. A detector that is attached to a conveying pipe that conveys powder by airflow and measures the attenuation of sound waves caused by the conveyed powder, and a detector that is connected to the detector and determines the powder concentration from the attenuation of the sound waves measured by the detector. A concentration calculator that calculates the powder velocity, a speed calculator that receives attenuation signals from multiple locations in the flow direction and calculates the powder velocity by measuring the delay time between measurement points based on the correlation, and a concentration calculator and a speed calculator. A powder flow rate measuring device using acoustic attenuation, which has a powder flow rate calculator connected to the powder flow rate calculator that calculates the powder flow rate by the product of powder concentration and powder velocity. 7. When calculating the powder concentration from the attenuation of the sound wave, C(t
)=a_0+a_1D+a_2D^2+a_3D^3 However, D=l_n[P(t)]/P_0 C(t)...Powder concentration a_0, a_1, a_2, a_3...Conveying tube shape factor P(t)... Measurement of powder flow rate by sound wave attenuation according to claim 6, characterized in that the measurement is performed using the formula: sound pressure P_0 attenuated by powder: sound pressure when there is no powder. Device. 8. Any one of claims 6 to 7, characterized in that the speed calculator is connected to the concentration calculator, and the output data of the concentration calculator is the input data of the speed calculator. A measuring device for powder flow rate using acoustic wave attenuation described in . 9. According to any one of claims 6 to 7, the speed calculator is connected to a detector, and the output data of the detector is the input data of the speed calculator. A device for measuring powder flow rate using acoustic wave attenuation. 10. An average concentration calculator connected to a plurality of concentration calculators to calculate the powder average concentration; and an average concentration calculator connected to the average concentration calculator and the speed calculator to calculate the powder by the product of the powder average concentration and the powder speed. 10. A powder flow rate measurement device using acoustic attenuation according to any one of claims 6 to 9, further comprising a powder average flow rate calculator for calculating a powder flow rate. 11. Claims 6 to 10 characterized in that the detector has a separate element that emits sound waves to the powder in the conveyance tube and an element that receives the sound waves attenuated by the powder. A powder flow rate measuring device using acoustic attenuation according to any one of the items. 12. Claim 6, characterized in that it has a detector that combines and integrates an element that emits sound waves to the powder in the conveyance pipe and an element that receives the sound waves attenuated by the powder.
A powder flow rate measurement device using acoustic attenuation according to any one of items 1 to 10. 13. The frequency of the sound wave emitted to the powder in the conveying tube is 1K.
13. A powder flow rate measuring device using acoustic attenuation as claimed in any one of claims 6 to 12, characterized by having a detector having a frequency between Hz and 1 MHz.