JP2861664B2 - Flow measurement method for high concentration powder conveyed in pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a flow rate of a high-concentration powder conveyed by a conveying medium in a pipe.

[0002]

2. Description of the Related Art Conventionally, as a method for measuring the flow rate of powder, a method using a light transmission type powder densitometer is known. FIG.
To show an example. As shown in FIG. 7, the powder transfer pipe two opposite viewing window 2 to 1 it was placed, and the incident parallel light beam 4 emitted from one of the observation window 2 from light source 3, the powder transfer pipe 1
Incident inside. The incident light attenuated by the powder 7, taken out the rest of the transmitted light from the other observation window 2, the light amount detection end 5
To detect the amount of transmitted light. Here, when the incident light intensity Io passes through the particle group of the powder 7 and attenuates to the transmitted light intensity I, the transmittance I / Io is expressed by the Lambert-Beer rule of Formula 1 . Reference numeral 6 denotes an O-ring for sealing.

[0003]

(Equation 1)

By measuring the transmittance (I / Io), the particle concentration (φ _m ) of the powder is determined, and further assuming that the moving speed of the powder particles is equal to the flow speed of the carrier medium (gas), It calculates the powder flow rate value from the product of the powder density value and the transport medium average flow velocity value.

[0005]

However, in the measurement using the powder densitometer based on the light transmission method described above, the maximum measurable powder concentration is restricted. Transfer medium (gas) from powder transfer tube
Or it sucked constant speed, or by or provided a branch pipe, it is necessary to measure by sampling a portion of the particles. Even with such an improved system, the maximum powder concentration of a practically used dust concentration meter is about 200 g / m ³ ,
Light is decays for more concentration particles
Because, by applying the light transmission type powder concentration meter measuring the high density powder flow rate is difficult.

[0006] The present invention has been made to solve the above problems, a high powder density measurement of the density region to allow, Hisage how that can measure the powder flow rate in line <br />.

[0007]

[Means for Solving the Problems In order to achieve the above Symbol purpose
Flow rate measurement of a high density powder conveyed through the tube according to the invention
The method consists of two light transmission measurements facing each other at a fixed tip distance.
Project the pipe into the pipe where the powder is transported by the transport medium
Installed, and maintain two tips for light transmission while keeping the tip spacing constant.
The constant tube is moved within the tube, and the light transmission measurement is performed.
Light is transmitted through the tube into the tube, and the light is transmitted to each position in the tube.
Takes the transmittance of light is measured, that calculates the powder average <br/> concentration from the measured transmittance, and calculates the powder flow amount from the powder average density and the flow rate value of the transport medium Features
You .

[0008] In this case, the powder transfer pipe in the measuring section is vertical.
With a continuous section concentric with the adjacent pipe,
And shall have a length of at least six times its diameter.
Then, 70 mm in the length direction from the powder entry side end of the powder transfer tube.
An opening is provided at a position of ~ 80% and a measuring tube for light transmission is installed.
To maintain uniformity of powder flow in the measuring section.
preferable.

[0009]

[Action] In the present invention, at a constant tip interval in the powder transfer tube,
Through a light transmission measurement tube protruding so as to face
Then, light is transmitted through the powder.
Is equal to the diameter of the powder transfer tube)
And the attenuation of light transmission can be suppressed,
It becomes possible to measure the concentration of the powder. Also, in the present invention,
In order to make it possible to easily realize a large parallel light beam,
Using a continuous light source such as laser light as the light source
I do.

That is, the present inventors have found that powders having a high concentration
In this case, the intensity of the transmitted light is reduced in accordance with the above equation (1).
Measurement accuracy deteriorates, but to prevent this, light
Consideration focused on reducing transmission length (optical path length)
Then, the powder average concentration and transmittance (I / I
o) and the above invention has been achieved.

FIG . 3 shows silica sand No. 5 (harmonic mean diameter (dp3
2) is 0.34 mm, and the true specific gravity (ρ) of the particle is 2.58)
Transmission obtained by a test using powdered air as a carrier medium
FIG. 4 is a diagram showing the relationship between the ratio (I / Io) and the average powder concentration.
You.

Here, the inside diameter of the powder transfer tube is D,
The distance between the tips of the light transmission measurement tubes inserted into the transfer tube,
Let L be the transmission length (optical path length) of L in the range of D> L.
And the transmittance (I / Io)
It is the one that got the relationship. Tip spacing of light transmission measurement tube
The transmitted light intensity I increases as L decreases. here
Show that measurement up to about 3 kg / m ³ is possible
I have. For comparison, a powder densitometer as shown in FIG. 7 was used.
Was case, up to about 0.2 kg / m ³ as indicated by the dotted line
Could not be measured.

With the laser light source used in this experiment,
It is necessary to set the transmittance to 0.15 or more to measure the powder density.
It was necessary to improve the constant accuracy. But the amount of light
By improving the accuracy of the detection end, the transmittance can be further increased.
Can be smaller.

In actual powder flow measurement, the particle size of the powder
In a so-called mixed particle state with different diameters and different types of powder
Therefore, in the present invention, as shown in FIG.
Using the relational expression between transmittance and measurement conditions, the output of the light
The average powder concentration is determined based on the force signal.

FIG . 5 shows the powder flow rate measurement of FIGS. 1 and 2 described later.
Between the transmittance (I / Io) when using the apparatus and the measurement conditions
This diagram shows the relationship, using two types of silica sand and iron ore as powder.
It was obtained by a test. It is clear from FIG.
Thus, even if the powder particle size is different, the true specific gravity of the powder particles (ρ)
Is considered, the transmittance (I / Io) becomes one
The measurement could be made in agreement with the calibration straight line. this thing
Therefore, in the present invention, even if powder particle size and powder type are mixed,
I found that it was possible.

That is, a light transmission measuring tube as a measuring device is used.
The tip distance L is specified, and the true specific gravity (ρ) and
And harmonic mean diameter (dp32)
Measurement, the transmittance (I / Io) is measured.
From the relational expression of FIG. 5, the powder average concentration value (kg
/ M ³ ) can be determined uniquely.

On the other hand, flow velocity detection for measuring the flow velocity of the transport medium
Calculates the average flow velocity value of the transport medium based on the output signal at the end.
You. That is, the detection signal of the pressure by the existing pitot tube, or
The temperature detection signal from the hot-wire type
By using a general relational expression with the uniform flow velocity,
Can be calculated. Furthermore, the above powder average concentration
Is multiplied by the average flow velocity value of the transport medium.
The body flow can be calculated.

Further, in the present invention, two opposing two
With the distance L between the tips of the measuring tubes for light transmission kept constant,
Traverse two light transmission measuring tubes in the powder transfer tube
So that the average powder concentration in the radial direction of the powder
Measure the distribution.

FIG . 4 shows the powder distribution in the diameter direction in the powder transfer tube.
FIG. 4 is an explanatory diagram for estimating. Tip of measuring tube for light transmission
Keep the interval L at a constant interval and reduce the
Both, from the pipe center toward one pipe wall,
Moves continuously along the radius of the pipe in steps as a unit
By doing so, the transmitted light amount corresponding to the moving position in the tube
From the attenuation distribution, measure the distribution of the average powder concentration in the diameter direction in the pipe.
At the same time, using the following weighted average formula of Equation 2
Find the average concentration of powder inside.

[0020]

(Equation 2)

[0021]

【Example】 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
You. 1 and 2 are views showing an embodiment of the present invention.
1 is from the light transmittance detector, the flow detector, and the arithmetic unit
Shows a state in which the powder flow measurement device
FIG. 2 is a main part of the light transmittance detector shown in FIG.
FIG. In these figures, 10 is the light transmittance
Detector, 11a and 11b are measuring tubes for light transmission, 12 is tip
An interval adjusting device, 13 is a flow velocity detecting end, and 7 is a powder.

The powder flow measuring device used in the present invention is a powder flow measuring device.
7 is provided in a piping system 9 transported by the transport medium,
Vertical powder transfer pipe with the same cross-sectional area as the adjacent upper and lower pipes
Opposed openings located on a line E orthogonal to the axis C of one
Inserted into the portions 8a and 8b and opposed at a constant tip interval L
Measuring tubes 11a, 11 arranged so as to protrude
b and the tip attached to the light transmission measurement tubes 11a and 11b.
Separation adjusting device 12 and rear end of one light transmission measuring tube 11a
Light source body 3 for parallel light beam incidence arranged in
Light amount detection end 5 disposed at the rear end of overuse measurement tube 11b
And the flow rate of the transport medium are measured.
Flow rate detecting end 13, light quantity detecting end 5 and flow rate detecting end 13
From the output signal of
Calculate and multiply these to calculate the powder flow rate.
And the arithmetic unit 14.

The arithmetic unit 14 includes a light amount detecting end 5 and a flow rate detecting end.
Receives a transmission signal obtained by converting the measured value into a signal from the output terminal 13.
The calculation unit 15 calculates the flow rate of the powder 7 on the display unit 16.
Is displayed. 17 is a storage unit. The flow rate of the powder 7 is
The flow rate adjusting mechanism for the transport medium (not shown)
It can be adjusted by instructing the body supply mechanism etc.
I can do it. In the above description, the length of the powder transfer tube 1 is six times its diameter.
And an opening 8 at a position 75% from the powder entry end.
a and 8b, and light transmission measuring tubes 11a and 11b.
Was placed.

Here, the light source body 3 and the light amount detection end 5 are
A light converging lens 20 is provided to enlarge and reduce the light flux
ing. Measuring tube for light transmission to detect light flux accurately
11a and the light transmission measurement tube 11b have the same diameter.
It is necessary to install them so that they are coaxial.
In addition, in order to accurately detect the light beam, the observation window 2 (transparent glass)
S), an airtight mechanism such as an O-ring 6 is used. Further
In order to prevent disturbance, the light source body 3 and the light amount detection end 5
A cover 19 is provided.

Next, using the powder flow rate measuring device described above,
The case where the present invention is performed will be described. Convey powder 7
The powder 7 is transported into a powder transfer pipe 1 provided in a piping system 9.
Let through. Here, the powder transfer pipe 1 is connected to a pipe system 9.
Uniform cross-sectional area with pipes inside, uniform flow in the measuring section
The powder 7 passing therethrough
The degree is the same as the concentration of the powder 7 in the piping system 9.

The light transmission measurement tubes 11a and 11b are
It is located on the line E perpendicular to the axis C of the pipe 1
Since it is inserted and arranged in the openings 8a and 8b, light transmission
Measuring tubes 11a and 11b have the same diameter,
Match. Thereby, the end of the light transmission measurement tube 11a
The light beam incident from the connected light beam source 3 is flat.
The light beam 4 traverses the powder transfer tube 1 at a right angle as a
Passing through the light transmission measuring tube 11b,
Will be issued.

From the light transmission measurement tube 11a to the light transmission measurement tube
11b, and attenuates the amount of transmitted light to reflect the original light.
Average concentration of powder in powder transfer tube 1 obtained by comparing with light intensity
Is calculated. In this case, the optical path length L of the measuring unit is
1 is smaller than the diameter of the powder of FIG.
From the relationship between the average density and the transmittance, select the tip interval L as appropriate.
Thus, the attenuation of the light transmission amount can be suppressed. The result
As a result, the average concentration of the high concentration particles of the powder 7 is accurately measured.
I can do it.

In the present invention, in actual powder flow rate measurement,
So-called mixed particles in which the powder 7 has different particle diameters and different types of particles
In the state shown in FIG. 5, based on FIG.
The relational expression between the transmittance and the measurement condition is stored in the storage unit 1 of the arithmetic unit 14.
7 is stored in advance, and the output of the measured light amount detection end 5 is output.
The calculation unit 15 calculates the average powder concentration based on the force signal.
You.

On the other hand, calculation is performed from the output signal of the flow velocity detecting end 13.
The transport medium average flow velocity value is calculated by the unit 15. here
Pressure detection signal by pitot tube
By using the general relational expression, the average flow velocity
Calculate the value. Furthermore, the average powder concentration and the average
By multiplying the flow velocity value by the calculation unit 15, the powder
Calculate the body flow value.

In the present invention, the inside of the powder transfer tube 1 is
And the opposing measurement tubes for light transmission 11a, 11b are
Keeping the tip interval L at a predetermined interval, the inside of the powder transfer pipe 1
Continuous from one tube wall to the other within the diameter range
At a speed along the diameter of the powder transfer tube 1.
And the amount of transmitted light corresponding to the moving position in the powder transfer tube 1 is reduced.
From the decay distribution, the powder concentration distribution in the diameter direction in the powder transfer tube 1 and
An average density value is calculated. These values are displayed on the display unit 16.
Is displayed.

In the present invention, the diameter of the powder transfer tube 1 and the light transmission
As the optimum relationship range with the diameter of the measuring tubes 11a and 11b
Can be determined by the following equation (3). This is
It is for a reason. If the diameter of the light transmission measurement tubes 11a and 11b is large,
Disturbance of the flow in the pipe 1 causes doubts in the measurement. The relationship between the diameter of the light transmission measurement tubes 11a and 11b and the powder particle size.
The staff detects that the diameter of the light transmission measurement tubes 11a and 11b is large.
Outgoing price stabilizes.

[0032]

(Equation 3)

In the present invention, the light transmission measuring tubes 11a and 11b are used.
The optimum range of the tip interval L of the
Can be. Tip spacing L is too narrow for lower limit
And the flow velocity distribution in the measurement section is disturbed.
The minimum interval that can not be received. Generally, light transmission measurement tube
It is about three times the diameter dt of 11a and 11b. To the upper limit
When the distance L between the tips is large, the attenuation of light transmission increases.
Therefore, the interval is set so that the light transmission amount attenuation can be tolerated.

According to the present invention, the condition that the pipe length is 2.0
m, a powder transfer pipe 1 having a pipe diameter of 0.2 m is arranged in a piping system 9,
Opening 8 provided at a position 75% from the entrance side of powder transfer tube 1
Insert the light transmission measurement tubes 11a and 11b into the
And set it so that the tip distance L is 0.1 m.
And, as the powder 7, silica sand No. 5 (dp32 = 0.34mm,
ρ = 2.58) using air as a carrier medium and a flow velocity of 20 m / sec.
In the case of transport by
Came. Fig. 6 shows the powder flow rate (ton / hour) and the elapsed measurement time.
FIG.

Here, the sampling interval of the powder concentration is
0.6 second, multiplying the average powder concentration by the air velocity value
Are calculated and plotted. the above
As is clear from the results, the powder concentration measurement in the high concentration region
Therefore, the powder flow rate can be measured online.
You.

[0036]

【The invention's effect】 According to the present invention, the following effects can be obtained.
You. Powder concentration 3kg / m ^Three Measurement of high concentrations up to
You. It is possible to measure a large amount of transported high-concentration powder. The distribution of the powder concentration in the radial direction of the powder transfer tube can be measured.

[Brief description of the drawings]

FIG. 1 is a view showing a state where a powder flow rate measuring device used in the present invention is installed.

FIG. 2 is a diagram showing a main part of a light transmittance detection unit used in the present invention.

3 is a diagram showing the relationship between the powder average density and transmittance in the case of changing the tip gap by the present invention.

FIG. 4 is an explanatory diagram for measuring a powder concentration distribution in a diameter direction in a tube according to the present invention .

FIG. 5 shows transmittance and measurement conditions determined from one embodiment of the present invention.
Is a diagram showing the relationship between.

6 is a diagram showing the relationship between the measured elapsed time powder flow amount according to an embodiment of the present invention.

FIG. 7 is a diagram showing an example of a conventional light transmission type powder densitometer.

[Description of Signs ] 1 powder transfer tube 2 observation window 3 light source 4 parallel light beam 5 light quantity detection end 6 O-ring 7 powder 8a, 8b opening 9 piping system 10 light transmittance detector 11a, 11b light transmission measurement tube 12 distal spacing adjustment device 13 flow rate detecting end 14 arithmetic device 15 calculating unit 16 display unit 17 storage unit 18 instruction unit

Claims (1)

(57) [Claims] 1. Two light transmissions facing each other at a fixed tip interval.
Projecting pipe into the pipe where the powder is transported by the transport medium.
Out and set it up, and keep the tip
The overused measuring tube is moved within said tube and the light transmission
The light is transmitted through the measuring tube through
The light transmittance was measured in the location, the powder average density calculated from the measured transmittance, and calculates the powder flow rate from the powder average density and the flow rate value of the transport medium tube
Method for measuring the flow rate of high-concentration powder conveyed inside .