JP2797856B2 - Method and apparatus for measuring flow rate of high-concentration powder conveyed by a conveyance medium in a 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 and apparatus for measuring the flow rate of a high-concentration powder conveyed in a tube by a conveying medium.

[0002]

2. Description of the Related Art Conventionally, as a method and apparatus for measuring the flow rate of powder, a method using a light transmission type powder densitometer is known. FIG. 7 shows an example. In FIG. 7, two observation windows 2 facing the powder transport tube 1 are provided. A parallel light flux 4 emitted from the light source 3 is incident on one observation window 2 and is incident on the powder transfer tube 1. The incident light is attenuated by the powder 7 and the remaining transmitted light is taken out from the other observation window 2 and introduced into the photodetector 5 to detect the amount of transmitted light. Here, when the incident light intensity Io passes through the particle group and attenuates to the transmitted light intensity I, the transmittance I / Io is expressed by the Lambert-Beer's rule of Formula 1.

[0003]

(Equation 1)

By measuring the transmittance (I / Io), the particle concentration (φ _m ) is determined. Further, assuming that the moving speed of the particles is equal to the flow speed of the carrier medium (gas), the particle concentration value and the carrier medium are determined. The powder flow rate value is calculated from the product of the average flow rate values.

[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
It is necessary to sample a part of the particles by suction at a constant velocity or to provide a branch pipe for measurement.
Even with such an improved method, the maximum powder concentration of a practically used dust concentration meter is about 200 gr / m ³ ,
Since the light is attenuated for the high-concentration particles more than that, it has been difficult to measure the flow rate of the high-concentration powder by applying the light transmission method.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and provides a method and apparatus capable of measuring powder concentration in a high-concentration region and measuring powder flow rate on-line. The purpose is to do.

[0007]

In order to achieve the above object, the present invention provides an inner tube having a fixed length and an axis parallel to the tube in a tube in which powder is conveyed by a conveying medium. The light is transmitted through a light transmission measurement tube that is fixed to the opening of the inner tube wall facing the line perpendicular to the axis of the inner tube, and is disposed so as to face the inner tube. Measuring, calculating a powder average concentration value therefrom, and calculating a powder flow value from a multiplied value of the calculated value and the flow velocity value of the conveyance medium, wherein the high concentration conveyed by the conveyance medium in the pipe is characterized by: This is a powder flow measurement method.

[0008] As a measuring apparatus suitable for the method of the present invention,
A pipe having an opening positioned on a line perpendicular to the axis and opposed to the pipe, an inner pipe provided in the pipe so that the axis is parallel to the pipe with a fixed length, and A light transmission measurement tube that is inserted and fixed to and opposed to the opening of the inner tube wall facing a line orthogonal to the axis of the inner tube,
A tip spacing adjustment device attached to the light transmission measurement tube, a light beam incident light source disposed at the rear end of one measurement tube, and a light amount detection end disposed at the rear end of the other measurement tube. The light transmittance detection unit provided, the detection end for measuring the flow velocity of the transport medium, and the powder average concentration value and the medium average flow velocity value are respectively calculated from the output signals thereof, and these are multiplied to obtain the powder flow rate value. Is a flow rate measuring device for high-concentration powder conveyed by a conveyance medium in a pipe formed by combining the devices for calculating the flow rate.

In this case, a vertical tube is used as a tube in the measuring section, and has a concentric continuous coaxial section having a length of at least 6 times its diameter, and a length from the powder entry side end of the tube. 70 in the vertical direction
An opening is provided at a position of about 80%, and the inner pipe size is determined from the relationship between the inner pipe diameter and the length shown in FIG. It is preferable to maintain uniformity.

[0010]

According to the present invention, an inner pipe is provided in a pipe having the above-described structure.
Light is transmitted through the powder through an opposing measurement tube for light transmission fixed to the opening of the inner tube wall located on a line perpendicular to the axis of the inner tube. The measuring tube is inserted opposite to make the optical path length of the measuring section smaller than the actual diameter of the powder transfer tube to suppress the attenuation of the light transmission amount.
In addition, as the light source of the present invention, a continuous light source such as a laser beam can be used so that a parallel light beam having a large light intensity can be easily realized.

In other words, the present inventors have made a study focusing on reducing the transmission length (optical path length) in the case of a high powder concentration, since the transmitted light intensity is reduced from the above-described formula (1). , The average powder concentration value and the transmittance (I / I
o) The above-mentioned invention has been attained by obtaining the relationship of o).

In FIG. 3, silica sand No. 5 (having a harmonic mean diameter (dp32) of 0.
FIG. 7 is a diagram of an example showing a relationship between light transmittance and powder average density value obtained by a calibration test using powder having a true specific gravity (ρ) of 2.58) of 34 mm as a carrier medium.

Here, the inside diameter of the vertical tube is D, the distance between the tips of the light transmission measurement tube fixed to the inner tube, ie, the transmission length (measurement section optical path length) is L, and L is variously set in the range of D> L. And averaged powder value and transmittance (I / Io)
The relationship was obtained. As L is smaller, the transmitted light intensity (I) increases. Here, it is shown that measurement up to about 3 kg / m ³ is possible. As a comparison, when a measuring device as shown in FIG. 7 was used, it was possible to measure only up to about 0.2 kg / m ³ as shown by the dotted line.

In this case, the inner tube to which the light transmission measurement tube is attached is provided in order to prevent the powder flow in the tube from being disturbed by the light transmission measurement tube inserted into the transport tube. . By the above action, the flow velocity and the powder concentration of the medium inside the inner pipe can accurately represent the flow velocity and the powder concentration of the medium in the entire cross-sectional area of the transport pipe. In addition, the powder concentration in the entire cross section of the transfer pipe can be accurately grasped.

Further, the flow rate value of the conveyed powder can be obtained by multiplying the powder concentration value of the inner pipe by the average flow velocity value of the medium in the conveyer pipe. In the laser light source used in this experiment, it was necessary for the transmittance to be 0.15 or more to improve the measurement accuracy of the powder density. However, the transmittance can be further reduced by improving the performance of the light amount detection end.

In the present invention, in actual powder flow rate measurement,
Since the powders have different particle diameters and different types of particles in a so-called mixed particle state, based on FIG. 3, the relation between the transmittance and the measurement conditions as shown in FIG. The arithmetic unit of the present invention calculates the average powder concentration value from the output signal.

FIG. 5 is a graph showing the relationship between the transmittance (I / Io) and the measurement conditions when the measuring apparatus of FIGS. 1 and 2 is used, and a calibration test using two types of silica sand and iron ore as powder. It was obtained by As is apparent from FIG. 5, even when the powder particle diameters are different, the transmittance (I / Io) can be measured in accordance with one calibration line by taking the true specific gravity (ρ) into consideration. done. From this, it has been found that measurement is possible in the present invention even if the powder particle size and powder type are mixed.

That is, L as a measuring device is specified, and since the true specific gravity (ρ) and the harmonic mean diameter (dp32) of the powder of the object to be measured are obvious as eigenvalues of the handling process, the transmittance (I / Io) is measured, and the average powder concentration value (kg / m ³ ) is uniquely determined from the straight line in FIG. On the other hand, a medium average flow velocity value is calculated by the arithmetic unit of the present invention from the detection end for measuring the flow velocity of the transport medium and its output signal.

That is, the above-described medium average flow velocity value is calculated by using a pressure detection signal from an existing pitot tube or a temperature detection signal from a hot wire flow velocity detection end and a general relational expression between the medium average flow velocity. . Furthermore, the powder flow rate value can be calculated by multiplying the powder average concentration value and the medium average flow velocity value by the arithmetic unit of the present invention.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are views showing an embodiment of the present invention, FIG. 1 is a view showing a state in which the apparatus of the present invention is installed, and FIG. 2 is a main part of a light transmittance detecting section of the apparatus of the present invention. FIG.
In the figure, reference numeral 10 denotes a light transmittance detector of the powder flow meter,
Reference numerals a and 11b denote measurement tubes for light transmission, reference numeral 12 denotes a tip interval adjusting device, reference numeral 13 denotes a flow velocity detecting end, and reference numeral 21 denotes an inner tube. Reference numeral 7 denotes powder particles.

The powder flow rate measuring apparatus of the present invention has pipe wall openings 8a and 8b provided in a pipe system 9 in which powder is conveyed by a conveying medium and opposed on a line perpendicular to the axis. A vertical pipe 1 and an inner pipe 2 having openings 8c and 8d of inner pipe walls opposed to each other on a line perpendicular to an axis provided in the vertical pipe 1
And light transmission measurement tubes 11a, 11 inserted into the openings 8a, 8b and fixed to the openings 8c, 8d of the inner tube 21.
b, a tip spacing adjusting device 12 attached to the light transmission measurement tubes 11a, 11b, a light beam incident light source 3 disposed at a rear end of one measurement tube 11a, and a rear end of the other measurement tube 11b A light transmittance detecting section detecting section 10 comprising a light quantity detecting end 5 disposed in the section, and a flow rate detecting end 1 for measuring the flow rate of the transport medium.
3, and a device for calculating a powder average concentration value and a medium average flow velocity value from output signals from their detection terminals, multiplying them, and calculating a powder flow rate value.

In the arithmetic unit, the light amount detecting end 5 and the flow velocity detecting end 1
Each of the measured values is converted into a signal from 3 and transmitted to the arithmetic unit 14, the arithmetic unit 15 calculates the signal, and the display unit 16 displays the flow rate of the powder 7. 17 is a storage unit. The flow rate of the powder can be adjusted by giving an instruction from the command unit 18 to a not-shown transport medium flow rate adjusting mechanism, a powder supply mechanism, and the like. In the above description, the length of the vertical pipe was six times the pipe diameter, an opening was provided at a position 75% from the powder entry end, and the light transmission measurement pipe was installed.

The length l and the inner diameter d of the inner tube were determined based on L, and the value of l determined from FIG. 4 was taken as the length of the inner tube. Here, a lens 20 is provided between the light source body 3 and the light amount detection end 5 in order to enlarge or reduce the light flux. It is necessary to use the light transmission measurement tubes 11a and 11b having the same diameter and to install them so that they have the same axis.
This is for accurately detecting the light flux. An airtight mechanism such as an observation window (transparent glass) 2 and an O-ring 6 is used to accurately detect the light flux. Further, the light source body 3 and the light amount detection end 5 are provided with a cover 19 for preventing disturbance.

The case where the method of the present invention is performed using the apparatus of the present invention will be described. The powder is passed by a transport medium through a vertical pipe 1 provided in a piping system 9 for transporting the powder. Here, since the vertical pipe 1 has the same cross-sectional area as the pipe in the pipe system 9, the uniformity of the flow in the measuring section is maintained. 7 is the same as the powder concentration.

The light transmission measuring tubes 11a and 11b are vertical tubes 1
The openings 8a and 8b are located on a line E orthogonal to the axis C of the inner tube 21 and are opposed to the openings 8c and 8d are located on the same line and are orthogonal to the inner tube 21 and are disposed. Therefore, the light transmission measurement tubes 11a and 11b have the same diameter,
The axes match. Accordingly, the light beam incident from the light source 3 for light beam incidence connected to the end of the measuring tube 11a crosses the powder in the vertical tube 1 at a right angle as a parallel light beam 4, passes through the measuring tube 11b, and emits light. It is detected at the detection end 5.

Light is transmitted from one of the opposed measuring tubes provided with a constant tip distance (L) to the other by the apparatus of the present invention, and the attenuation of the transmitted light amount is compared with the intensity of the original light. Then, the average powder concentration value in the inner tube is calculated. In this case, since the optical path length (L) of the measuring section is smaller than the actual powder conveying pipe diameter, the tip distance is selected from the average powder concentration and the transmittance in FIG. Can be suppressed. As a result, the powder average concentration value of the high-concentration particles of the powder can be accurately measured.

In the present invention, in actual powder flow rate measurement,
Since the powder is in a so-called mixed particle state having different particle diameters and different types of particles, the relational expression between the transmittance and the measurement conditions as shown in FIG. 5 is stored in the storage unit 17 of the arithmetic unit based on FIG. The average density value of the powder is stored in advance and calculated from the output signal of the light amount detection end 5 measured by the calculation unit 15.

On the other hand, from the output signal of the flow velocity detecting end 13, the arithmetic section 15 calculates an average flow velocity value of the medium. Here, the medium average flow velocity value is calculated by using a general relational expression between the detection signal of the pressure by the pitot tube and the medium average flow velocity value. Further, the arithmetic unit 15 multiplies the average powder concentration value and the average medium flow velocity value to calculate a powder flow value. These values are displayed by the display unit 16.

In the present invention, the inner pipe is used. The optimum relationship between the diameter of the vertical pipe and the diameter of the measuring pipe is expressed by the following equation (2).
Can be determined by This is for the following reason. If the diameter of the measuring tube is large, the flow in the vertical tube is disturbed, and the measurement is questionable. Regarding the relationship between the diameter of the measuring tube and the particle diameter of the powder, the detected value is stable when the diameter of the measuring tube is large.

[0030]

(Equation 2)

In the present invention, the optimum range of the interval between the tips of the light transmission measurement tubes, ie, the inner diameter of the inner tube, can be determined for the following reasons. As for the lower limit, if the interval is too narrow, the flow velocity distribution in the measurement section between the intervals is hindered. Generally, the transfer pipe is about 1/10. The upper limit is set to an allowable interval for the attenuation of the light transmission amount since the light transmission amount attenuation increases when the interval is wide.

The length of the inner tube according to the present invention is determined from the viewpoint of preventing disturbance of the powder flow by the light transmission measuring tube and accurately estimating the powder flow rate. It may be similar to the shape, or may be a circular tube.

By fixing these light transmission measurement tubes to the inner tube as opposed to each other as in the present invention, the optical path of the two light transmission measurement tubes due to misalignment due to vibration, thermal expansion, etc. of the pipes is reduced. There is also an advantage that a situation such as interruption can be avoided.

According to the method of the present invention, a pipe length of 2.0
m, a vertical pipe having a diameter of 0.2 m is arranged in the piping system, and a light transmission measuring pipe is inserted and protruded from an opening provided at a position 75% from the entrance side of the vertical pipe to have an inner diameter of 0.1 m and a length of 0.1 m. It is fixed to the inner pipe of 0.5m, and silica sand No.5 (dp32 = 0.34mm, ρ = 2.58) as powder
Is transported at a flow rate of 20 m / sec using air as a medium.
The result as shown in was able to be obtained. FIG. 6 is a diagram showing the relationship between the powder flow rate (ton / hour) and the elapsed measurement time.

Here, the sampling interval of the powder concentration is set to 0.
6 seconds, from the multiplication of the average powder concentration value and the gas flow rate value,
The powder flow rate is calculated and plotted. As is clear from the above results, the powder flow rate can be measured online by measuring the powder concentration in the high concentration region.

[0036]

According to the present invention, the following effects can be obtained. The inner tube provided with the light transmission measurement tube prevents disturbance of the flow of the powder in the transport tube, and improves the detection of the powder concentration and the measurement accuracy of the powder flow value. High concentration measurement up to 3 kg / m ³ powder concentration is possible. It is possible to measure a large amount of transported high-concentration powder. By fixing these light transmission measurement tubes to the inner tube so as to face each other, it is possible to avoid a situation such as interruption of the optical path due to misalignment of the two light transmission measurement tubes due to vibration of the piping, thermal expansion and the like.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state where the device of the present invention is installed in a piping system.

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

FIG. 3 is a diagram showing the relationship between the average powder concentration and the transmittance when the tip interval is changed according to the present invention.

FIG. 4 is a diagram showing the relationship between the length of an inner tube and measurement conditions according to the present invention.

FIG. 5 is a diagram showing a relationship between transmittance and measurement conditions according to one embodiment of the present invention.

FIG. 6 is a diagram showing a relationship between a powder flow rate and a measurement elapsed time according to an embodiment of the present invention.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Light transmittance detection part of powder flow meter 11a, 11b Light transmission measurement tube 12 Tip spacing adjustment device 13 Flow velocity detection end 14 Calculation device of powder flow meter 21 Inner tube

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01F 1/74

Claims (2)

(57) [Claims] 1. An inner pipe having a fixed length and an axis parallel to the pipe is provided in a pipe in which the powder is transported by a transport medium, and is fixed to the inner pipe so as to face the inner pipe. Through a light transmission measuring tube, light is transmitted, its transmittance is measured, the powder average concentration is calculated from the light transmission tube, and the powder flow rate is calculated from the calculated value and the flow velocity value of the transport medium. A method for measuring a flow rate of a high-concentration powder conveyed by a conveyance medium in a pipe. 2. A tube having an opening in a tube wall facing and located on a line orthogonal to the axis, and a shaft having a fixed length provided in the tube so as to be parallel to the tube. An inner tube, a light transmission measurement tube inserted into the opening and fixed to and opposed to the opening of the inner tube wall facing a line perpendicular to the axis of the inner tube; Equipped with a tip spacing adjusting device attached to the transmission measuring tube, a light source for light beam incidence arranged at the rear end of one measuring tube, and a light amount detection end arranged at the rear end of the other measuring tube. The light transmittance detection unit and the detection end for measuring the flow velocity of the transport medium, the average powder concentration and the average flow velocity of the medium are respectively calculated from the output signals thereof, and these are multiplied.
An apparatus for measuring the flow rate of a high-concentration powder conveyed by a conveyance medium in a pipe formed by combining a device for calculating a powder flow rate.