JPH0915136A - Laser diffraction/scattering type particle size distribution measuring apparatus - Google Patents

Abstract

PURPOSE: To obtain a laser diffraction/scattering type particle size distribution measuring apparatus in which the particle size distribution can be measured accurately without requiring a large dispersion tank even when it is specified to measure the particle size distribution using a large quantity of sample. CONSTITUTION: Specified quantity of sample is not entirely diluted to an optimal concentration before being circulated through a flow cell 1 but a high concentration suspension is prepared in a first dispersion tank 11 using all samples. It is then dispensed to a second dispersion tank 12 and diluted with a liquid medium to a concentration within an optimal range before being circulated through the flow cell 1. After measuring the intensity distribution of diffracted/scattering light, the sample is discarded. The operation is repeated and when the measurement is ended for all samples, accumulated measurements of the intensity distribution of diffracted/scattering light is expressed in terms of particle size distribution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser diffraction / scattering type particle size distribution measuring apparatus, and more particularly to a laser diffraction / scattering type particle size measuring device suitable for measuring the particle size distribution of earth and sand used in the field of civil engineering and construction. The present invention relates to a distribution measuring device.

[0002]

2. Description of the Related Art In a laser diffraction / scattering type particle size distribution measuring apparatus, generally, a sample suspension in which a group of particles to be measured is dispersed in a liquid medium is made to flow into a flow cell made of a translucent material, Diffracted / scattered light obtained by irradiating the sample suspension with laser light through the light is received by an optical sensor array such as a ring detector and the spatial intensity distribution thereof is measured, and the measurement result is analyzed by Mie's scattering theory or It is converted to the particle size distribution of the measured particle group using the Fraunhofer diffraction theory.

In this type of measuring apparatus, a dispersion tank equipped with a stirrer, an ultrasonic vibrator, etc. is usually provided, and the particle group to be measured and the liquid medium are put into the dispersion tank to make the optimum measurement. The particles to be measured are uniformly dispersed in the medium so that the concentration falls within the concentration range, and while the sample suspension is circulated between the dispersion tank and the flow cell in that state, the flow cell is irradiated with laser light. And measure the diffracted / scattered light.

[0004]

By the way, in measuring the particle size distribution of earth and sand, etc. used in the field of civil engineering and construction, conventionally, the measurement using a sieve has been mainly adopted. There is a movement to replace the laser diffraction / scattering method, which has a short measurement time and is easy to operate, in order to save power and save labor.

[0005] In measuring the particle size distribution of earth and sand in the field of civil engineering and construction, the sample amount is defined in the standards such as JIS, and the sample amount is assumed to be measured using a sieve. Therefore, it is quite large.

Using the above-mentioned conventional laser diffraction / scattering type particle size distribution measuring device, a large amount of such a sample is stored in a dispersion tank, and this is stored in a concentration range optimum for measurement by a medium liquid, and a flow cell To cycle between
It is necessary to make the dispersion tank very large, and there is a problem that the device becomes extremely large.

The present invention has been made in view of such circumstances, and even if it is necessary to measure the particle size distribution using a large amount of sample, without using a particularly large dispersion tank,
An object of the present invention is to provide a laser diffraction / scattering type particle size distribution measuring device capable of measuring an accurate particle size distribution.

[0008]

A structure for achieving the above object will be described with reference to FIG. 1 which is an embodiment drawing, and a laser diffraction / scattering type particle size distribution measuring apparatus of the present invention will be described. Diffracted / scattered light obtained by irradiating the flow cell 1 in which a sample suspension in which a group of particles is dispersed in a liquid medium is flowed with laser light is used as a plurality of optical sensors 3b and 3c.
And the like to measure the spatial intensity distribution of the diffracted / scattered light, guide the measurement result to the calculation means (particle size distribution conversion unit) 62, and convert it to the particle size distribution of the measured particle group. First dispersion tank 11 for containing sample suspension
And the suspension in the first dispersion tank 11 becomes
And a second dispersion tank provided with a liquid medium via a liquid medium supply valve 22 and a liquid outlet provided in the second dispersion tank 12. It is set to either a state in which the sample suspension in 12 is circulated between the second dispersion tank 12 and the flow cell 1 or a state in which the suspension in the second dispersion tank 12 is discarded. The switching valve 23 is provided. In addition, at the beginning of the measurement, the fractionation valve 21 and the medium liquid supply valve 22 are driven so that the high-concentration suspension liquid and the suspension liquid obtained by introducing the medium liquid into the second dispersion tank 12 are Storage means (concentration adjustment memory) 64 for storing information relating to the amount of high-concentration suspension and the amount of medium liquid required to fall within the set optimum concentration range, and the suspension whose concentration was adjusted at the beginning of measurement. After measuring and storing the diffraction / scattered light intensity distribution of the second dispersion tank 12 by driving the switching valve 23 to discard the suspension and driving the valves 21, 22 and 23 described above. Storage means 64 in
After measuring and storing the diffraction / scattered light intensity distribution while circulating the suspension prepared by fractionating the high-concentration suspension and supplying the medium solution in an amount based on the content of The calculation means 62 has a control means (measurement operation control section) 65 for executing the operation of discarding the suspension,
Characterized by being configured to convert the integrated value of the scattered light intensity distribution measurement result into a particle size distribution.

Here, in the present invention, the second dispersion tank 1
The information regarding the high-concentration suspension amount and the medium liquid amount required for the suspension in 2 to fall within the preset optimum concentration range is, for example, a suspension within the optimum concentration range. The total opening time of each of the preparative valve 21 and the medium liquid supply valve 22 required for the above, or each of these valves 2
1 and 22 are configured to be opened for a predetermined time each by one drive, and these valves 21 and 22 required to form a suspension in an optimum concentration range are formed.
Say the number of times of opening. Further, the suspension in the optimum concentration range may be prepared by artificially operating the preparative valve 21 and the medium liquid supply valve 22 to form a suspension in the optimum concentration range.
Alternatively, the suspension in the second dispersion tank 12 is added to the flow cell 1
A means for automatically driving and controlling the preparative valve 21 and the medium liquid supply valve 22 may be provided so that the output of the light sensor 3b and the like is monitored while monitoring the output of the optical sensor 3b.

[0010]

The present invention does not dilute all the specified amount of sample into the optimum concentration range and circulate and supply the sample to the flow cell, but performs the operations of preparative sample-dilution-diffraction / scattered light intensity distribution measurement / storage-discarding. It is intended to obtain the particle size distribution of the entire sample by continuously repeating the measurement and storage of all the samples and then integrating the diffraction / scattered light intensity distribution measurement results and converting the result into a particle size distribution. .

That is, a high-concentration suspension consisting of a prescribed sample amount of particles to be measured and a liquid medium is stored in the first dispersion tank 11, and the preparative valve 21 is set at the beginning of the measurement.
And the liquid medium supply valve 22 is driven to drive the second dispersion tank 1
An appropriate amount of a high-concentration suspension and a liquid medium are supplied to the inside of 2 to prepare a suspension having a concentration range optimum for measurement. When adjusting the concentration,
Information regarding the amounts of the high-concentration suspension and the liquid medium that have been collected or supplied is stored in the storage unit 64.

The suspension in the second dispersion tank 12 which is initially adjusted as described above is discarded by the switching valve 23 after the measurement and storage of the diffraction / scattered light intensity distribution.
Then, thereafter, the high-concentration suspension liquid and the medium liquid in the first dispersion tank 11 are supplied into the second dispersion tank 12 in an amount according to the stored contents of the storage means 64 to form a suspension liquid. The operation of being circulated and supplied to the flow cell 1 and used for measuring / storing the diffracted / scattered light and then discarded is repeated. The integrated value of the diffraction / scattered light intensity distribution measurement results thus obtained and stored is converted into a particle size distribution by the computing means 62.

[0013]

FIG. 1 is a schematic diagram showing the overall construction of an embodiment of the present invention. The main body of the particle size distribution measuring apparatus comprises a flow cell 1 in which a sample suspension is flown, a laser light source 2a for irradiating the flow cell 1 with parallel laser light, and a collimator lens 2.
b and the irradiation optical system 2, the measurement optical system 3 for measuring the diffracted / scattered light by the particle group to be measured in the flow cell 1, and the diffracted / scattered light information measured by the measuring optical system 3 are input. The data processing unit 6 for performing data processing is mainly used.

The measurement optical system 3 is placed at the focal point of the condenser lens 3a for converging the diffracted / scattered light forward by the particle group to be measured, and the focal point of the condensing lens 3a. The ring detector 3b is connected to the light receiving surface, and the side scattered light sensor 3c and the back scattered light sensor 3d respectively receive the side scattered light and the back scattered light. The ring detector 3b is an optical sensor array in which a plurality of optical sensors having circular or semi-circular light receiving surfaces having different radii are concentrically arranged.

The outputs of the sensors in the ring detector 3b, the side scattered light sensor 3c, and the back scattered light sensor 3d are individually amplified by the amplifier 4 and then A
The data processing unit 6 is digitized by the -D converter 5.
It is taken in.

The sample suspension flowed in the flow cell 1 is 2
It is made by a sampler, which is composed of two dispersion tanks 11 and 12 and a liquid medium supplier 10 and the like, which will be described in detail below. A specified amount of particles to be measured is put into the first dispersion tank 11 prior to the measurement, and an appropriate amount of the liquid medium is supplied from the liquid medium supply device 10 via the valve 24 so that a predetermined amount of the medium liquid is supplied. The measurement particle group is accommodated in the first dispersion tank 11 in a high-concentration suspension state. A preparative valve 21 is attached to the liquid outlet provided on the bottom surface of the first dispersion tank 11.

The high-concentration suspension in the first dispersion tank 11 is collected in the second dispersion tank 12 via the preparative valve 21 based on an operation command from the data processing unit 6 which will be described later. At the same time, the medium liquid is supplied from the medium liquid supply device via the medium liquid supply valve 22, and the suspension having the preset concentration range most suitable for the measurement is adjusted in the second dispersion tank 12. A pump 25 is provided at the liquid outlet provided on the bottom surface of the second dispersion tank 12, and a switching valve 23 is provided at the discharge port of the pump 25. The switching valve 23 circulates the suspension in the second dispersion tank 12 sucked by the pump 25 between the second dispersion tank 12 and the flow cell 1 through the circulation path 26,
It is set to any one of a state in which it is discarded to the outside of the apparatus via the discard path 27.

First and second dispersion tanks 11 and 12
Are the agitators 11a and 12a and the ultrasonic transducer 1 respectively.
1b and 12b are provided, and the group of particles to be measured in the suspension inside can always be uniformly dispersed in the medium liquid. Further, regarding the liquid medium supplier 10, FIG.
Although a tank-like structure is shown in Fig. 1, the medium liquid may be tap water when measuring the particle size distribution of earth and sand in the field of civil engineering, and therefore the medium liquid supply device 10 is kept at a constant flow rate, for example. It can be configured by a water tap itself or a tank equipped with a pump in which tap water from the water tap is temporarily stored and set to a constant discharge amount.

The sorting valve 21 and the medium liquid supply valve 22 described above are actually electromagnetically-operated opening / closing valves, and the switching valve 24 is also an electromagnetically-driven directional control valve. Along with the pump 25, drive control is performed by a control signal from a driver 7 that operates based on a command supplied from the data processing unit 6.

Now, the data processing unit 6 includes the AD converter 5
The data output from each sensor, that is, the data memory 61 for storing the diffraction / scattered light intensity distribution data, and the diffraction / scattered light intensity distribution data stored in the data memory 61 are calculated by the calculation described later to determine the particle size of the particle group to be measured. In addition to the particle size distribution conversion unit 62 that converts to a distribution, the second
To make a suspension in the optimum concentration range in the dispersion tank 12 of
An optimum concentration adjusting unit 63 that gives a drive command to the preparative valve 21 and the medium liquid supply valve 22 while taking in a specific sensor output in the ring detector 3b via the -D converter 5.
And a concentration adjustment memory 6 for storing information relating to the supply amounts of the high-concentration suspension and the medium liquid during the optimum concentration adjustment operation.
4 and a measurement operation control unit 65 for controlling the entire measurement operation of the apparatus. The measurement operation control unit 65 and the optimum concentration adjustment unit 63 supply a command to the driver 7 to operate each valve and pump. Drive controlled. Although the data processing unit 6 is shown in the block diagram of each function in FIG. 1, it is actually composed of a computer and its peripheral devices.

FIG. 2 is a flow chart showing the operation of the data processing section 6. The operation of the embodiment of the present invention will be described below with reference to this figure. Prior to the measurement, a specified amount of particles to be measured was put into the first dispersion tank 11, and the valve 24 was used.
Is opened and a proper amount of the medium liquid is injected to form a high-concentration suspension in the first dispersion tank 11. In this embodiment, the start command is given in this state.

When a start command is given, first, the first
An appropriate amount of the high-concentration suspension and the medium solution in the dispersion tank 11 is injected into the second dispersion tank 12 to prepare a suspension having an optimum concentration range for measurement. An example of this specific operation will be described. The preparative valve 21 and the medium liquid supply valve 22 are appropriately opened to dilute the high-concentration suspension with the medium liquid in the second dispersion tank 12, and the pump 25 is used. Also, the switching valve 23 is driven to circulate and supply the diluted suspension to the flow cell 1, and the ring detector 3b is also supplied via the AD converter 5.
Each sensor output is monitored, and the preparative valve 21 and the medium liquid supply valve 22 are intermittently opened so that the magnitude of each output falls within a preset size range. In this concentration adjustment operation, the second dispersion tank 1
If the concentration in the second dispersion tank 12 is too high even though the amount in the second suspension reaches the specified amount, the switching valve 23 is driven to change the concentration of the suspension in the second dispersion tank 12. It is necessary to discard a part and inject the liquid medium. In this case, a part of the specified amount of particles to be measured is lost, which is not preferable.
Therefore, in this concentration adjustment operation, for example, after supplying an appropriate amount of the medium liquid into the second dispersion tank 12, the high concentration suspension is repeatedly dispensed in small portions to obtain a suspension in the optimum concentration range. It is preferable to take a procedure for making a liquid. It should be noted that whether or not the suspension is within the optimum concentration range is determined as a whole when the output of each sensor of the ring detector 3b is too small when the suspension concentration is too thin, and conversely when it is too thick. The output of the sensor at the center of the ring detector 3b is used to determine the intensity of the light transmitted through the suspension, as described above, by utilizing the fact that the output of each sensor becomes saturated. In other words, since it correlates with the suspension concentration, the concentration may be determined based on the transmitted light intensity.

Now, as described above, the second dispersion tank 12
At the time when it is determined that a suspension having an optimum concentration range has been prepared in the inside, information relating to the amount of high-concentration suspension and the amount of medium liquid required for the concentration adjustment, for example, the preparative valve 21 and The total opening time, the number of times, etc. of each of the liquid medium supply valves 22 are stored in the concentration adjustment memory 64. In addition, the second dispersion tank 1 after the concentration is within the optimum concentration range
The suspension in 2 is subsequently circulated to the flow cell 1,
In that state, the ring detector 3b and the side scattered light sensor 3c
The respective output data of the backscattered light sensor 3d and the output data of the backscattered light sensor 3d are used as the first diffraction / scattered light intensity distribution data in the data memory 61.
Is stored in

Next, the switching valve 23 is switched, the suspension liquid in the second dispersion tank 12 is discarded, and the medium liquid supply valve 22 is opened to open the second dispersion tank 12.
A liquid medium is injected into the inside of the second dispersion tank 12 to clean it.

After that, the switching valve 23 is returned to the circulating state, and the preparative valve 21 and the medium liquid supply valve 22 are opened by an amount corresponding to the content of the concentration adjusting memory 64 to raise the pressure in the second dispersion tank 12. The concentrated suspension and the liquid medium are supplied to make a suspension having an optimum concentration. Then, after the diffracted / scattered light intensity distribution data of the suspension is collected and stored in the data memory 61 as the second diffracted / scattered light intensity distribution data, the switching valve 23 is switched to the second dispersion. The suspension in the tank 12 is discarded.

Next, in the same manner as above, based on the contents stored in the cleaning-concentration adjusting memory 64 in the second dispersion tank 12, the high-concentration suspension is dispensed into the second dispersion tank 12 and the medium liquid is collected. The operations from the preparation of the optimum concentration suspension by the supply to the collection of the diffraction / scattered light intensity distribution data are repeated until the high concentration suspension in the first dispersion tank 11 is exhausted.

In the above operation, assuming that the diffraction / scattered light intensity distribution is measured, for example, L times in total, the data memory 61 has L diffraction / scattered light intensity distribution data. The particle size distribution conversion unit 62 uses the L pieces of diffracted / scattered light intensity distribution data to be detected by each sensor of the ring detector 3b, the side scattered light sensor 3c, and each back scattered light sensor 3d in each measurement. The measured light intensity is integrated for each sensor to obtain the diffraction / scattered light intensity distribution data (vector) s for all the measured particle groups, and the data (vector) s is used to measure the particle size distribution of the measured particle size distribution group. Convert to.

Diffraction / scattered light intensity distribution data s after integration
(Vector) is

[0029]

(Equation 1)

And each element s _i is

[0031]

(Equation 2)

Is as follows. That is, the sensors of the ring detector 3b, the side scattered light sensor 3c, and the back scattered light sensor 3d are numbered in order from the one having the smallest diffraction / scattering angle, and i (i = 1, 2, ... ... m)
, And the light intensity detected by the i-th sensor at the time of the kth data collection is s _i, k (k = 1, 2, ... L). Then, the integrated value of the light intensity detection values of the i-th sensor over L times is set as s _i .

The diffracted / scattered light intensity distribution data (vector) s after such integration, in other words, the diffracted / scattered light intensity distribution data (vector) regarding all the measured particle groups of a specified amount.
Using s, the particle size distribution is calculated by the following equation (3).

[0034]

(Equation 3)

Here, q is a particle size distribution (frequency distribution%) vector. The particle size distribution range is finite, and within this range n
It is divided into the maximum value d ₁ and the minimum value d _{n + 1} . Each of the divided sections [d _j , d _{j + 1} ] is represented by one particle diameter x _j . Elements q _j of the vector q (j = 1, 2, ...
··· N) is the amount of particles corresponding to the particle diameter x _j . Normally,

[0036]

(Equation 4)

Normalization is performed by A is a coefficient matrix for converting the particle size distribution (vector) q into the light intensity distribution (vector) s. Element a of A
The physical meaning of _{i, j} (i = 1,2, ... m, j = 1,2, ... n) is that the particles are diffracted / scattered by a group of particles with a unit particle amount of particle diameter x _j. It is the amount of incident light on the i-th sensor.

The numerical value of a _{i, j} can be theoretically calculated. For this, the Fraunhofer diffraction theory is used when the particle diameter is sufficiently larger than the wavelength of the laser light from the light source. However, in the submicron region where the particle system is at the same level as or smaller than the wavelength of laser light,
It is necessary to use Mie scattering theory. The Fraunhofer diffraction theory can be considered to be an excellent approximation of the Mie scattering theory, which is effective in the case of forward small angle scattering when the particle system is sufficiently larger than the laser wavelength. In order to calculate the elements of the coefficient matrix (vector) A using the Mie scattering theory, it is necessary to set the refractive index of the particles to be measured and the medium liquid in which the particles are dispersed.

The particle size distribution (vector) q obtained by the above calculation is obtained by diffracting a plurality of times by sequentially collecting all of the specified amount of particles to be measured put in the first dispersion tank 11. / Because it is based on the data obtained by integrating the scattered light intensity distribution measurement results, the particle size distribution can be in accordance with JIS and other regulations. Further, in the case of a high-concentration suspension initially prepared in the first dispersion tank 11 using a specified amount of particles to be measured, if the concentration is high, segregation of particles is unavoidable to some extent. In the present invention, even if the high-concentration suspension sampled in each measurement is affected by the segregation, all the high-concentration suspensions in the first dispersion tank 11 are subjected to the measurement and their diffraction / Since the particle size distribution is calculated using the integrated value of the scattered light intensity distribution data, the effect of segregation does not occur on the obtained particle size distribution measurement result.

In the above embodiment, at the beginning of the measurement, the high-concentration suspension and the medium liquid in the first dispersion tank 11
Although the apparatus having the optimum concentration adjusting function for automatically producing the suspension in the optimum concentration range has been described, the present invention is not limited to this, and the suspension in the optimum concentration range at the beginning of the measurement is adjusted. May be performed manually. In this case, for example, the ring detector 3b is used to determine whether the concentration is optimum.
Each sensor output is monitored by a CRT or the like, and a switch for opening the preparative valve 21 and the liquid medium supply valve 22 respectively for a predetermined time is provided so that the suspension within the optimum concentration range is It is only necessary to store the number of times of operation of each switch operated until it is made in the density adjustment memory 64.

[0041]

As described above, according to the present invention,
A high concentration suspension containing a specified amount of particles to be measured is stored in the first dispersion tank, and the high concentration suspension is fractionated in the second dispersion tank and diluted with a medium liquid. Repeat the operation of making a suspension in the optimum concentration range with and discarding the suspension after measuring the diffraction / scattered light intensity distribution.
Since the particle size distribution of the measured particle group is obtained using the integrated value of the diffraction / scattered light intensity distribution measurement results of each time, even if the specified amount of the measured particle group to be used for the particle size distribution is extremely large, it is particularly large. Therefore, it became possible to obtain an accurate particle size distribution using all particle groups without using the dispersion tank of 1.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the overall configuration of an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the data processing unit 6.

[Explanation of symbols]

 1 Flow Cell 2 Irradiation Optical System 3 Measurement Optical System 3b Ring Detector 3c Side Scattered Light Sensor 3d Backscattered Light Sensor 6 Data Processing Unit 61 Data Memory 62 Particle Size Distribution Conversion Unit 63 Optimal Concentration Adjustment Unit 64 Concentration Adjustment Memory 65 Measurement Operation Control Unit 21 preparative valve 22 medium liquid supply valve 23 switching valve 25 pump

Claims (1)

[Claims] 1. A plurality of photosensors receive diffracted / scattered light obtained by irradiating a flow cell in which a sample suspension in which a group of particles to be measured is dispersed in a liquid medium is irradiated with laser light. An apparatus for measuring a spatial intensity distribution of the diffracted / scattered light and guiding the measurement result to a calculation means to be converted into a particle size distribution of a particle group to be measured, which is a first dispersion tank containing a high-concentration sample suspension. And a second dispersion tank in which the suspension liquid in the first dispersion tank is supplied through a preparative valve and a liquid medium is supplied through a liquid medium supply valve, and the second dispersion tank A state where the sample suspension in the second dispersion tank is circulated between the second dispersion tank and the flow cell provided at the liquid outlet in the tank, and the suspension in the second dispersion tank is discarded. The switching valve that is set to either the Also, it was necessary to drive the medium liquid supply valve and introduce the high-concentration suspension liquid and the medium liquid into the second dispersion tank so that the suspension liquid obtained fell within the preset optimum concentration range. A storage means for storing information on the amount of high-concentration suspension and the amount of medium, and after measuring and storing the diffraction / scattered light intensity distribution of the suspension whose concentration was adjusted at the beginning of measurement, drive the switching valve. The suspension is discarded, and the valves are driven to dispense a high-concentration suspension and supply the medium liquid in the second dispersion tank in an amount based on the contents of the storage means. And a control means for performing an operation of discarding the suspension after measuring and storing the diffraction / scattered light intensity distribution while circulating the suspension thus prepared with the flow cell. Converts the integrated value of multiple diffraction / scattered light intensity distribution measurement results into a particle size distribution. A laser diffraction / scattering particle size distribution measuring apparatus characterized by being configured.