JP2002340779A - Instrument for measuring particle size distribution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser diffraction/scattering particle size distribution measuring instrument in which the time required for measuring cycle can be shortened greatly. SOLUTION: The apparatus for measuring particle size distribution comprises a medium liquid supply/discharge system 2 in which a medium liquid is supplied to a flow cell 3 and then discharged to the outside and a particle group being measured can be thrown in at any time on the upstream side of the flow cell 3, an optical system 5 for measuring the spatial intensity distribution of a light diffracted/scattered by the particle group, and an operating means 7 for calculating a stored particle distribution using the output from the measuring optical system 5 as effective data when it has reached a preset level. The particle group being measured flows into the flow cell 3 only for a moment following throw-in thereof and discharged immediately to the outside of the system so that a state where the inside of the system is cleaned by clean medium liquid is brought about thus eliminating the conventional process for cleaning the inside of the system.

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 an apparatus which needs to sample particles to be measured at short intervals and measure the particle size distribution one after another. The present invention relates to a particle size distribution measuring device suitable for a device.

[0002]

2. Description of the Related Art A so-called laser diffraction / scattering type particle size distribution measuring apparatus based on a laser diffraction / scattering method is known as an apparatus for accurately measuring the particle size distribution of particles in a relatively short time. This laser diffraction / scattering type particle size distribution measuring device measures the spatial intensity distribution of the diffracted / scattered light generated by irradiating the measured particle group in the dispersed and flying state with laser light, and the light intensity distribution is measured by Mie scattering. Utilizing the theory or the Fraunhofer diffraction theory, the particle size distribution of the particles to be measured is calculated from the measurement results of the spatial intensity distribution of the diffracted / scattered light by calculation based on the Mie scattering theory or the Fraunhofer diffraction theory.

[0003] In this type of conventional particle size distribution measuring apparatus, an apparatus configuration as illustrated in FIG. 2 is employed.
That is, the particle group P to be measured is put into the dispersion tank 210 provided with the stirrer 212 and the ultrasonic vibrator 213 together with the medium liquid L supplied from the medium liquid supply pump 211, and the medium P A suspension S in which the particle groups P are dispersed is generated. The dispersion tank 210 communicates with the flow cell 230 via a circulation pipe 221 and a circulation / discharge pump 2.
By driving the suspension 22, the suspension S circulates between the dispersion tank 210 and the flow cell 230.

In a state where the suspension S is circulating, that is, in a state where the suspension S is flowing in the flow cell 230, the laser light from the laser light source 241 is transmitted through the condenser lens 242, the spatial filter 243 and the collimator 244. Flow cell 2
By irradiating the laser beam 30, the laser beam is diffracted and scattered by the measured particle group P in the flow cell 230. Of the diffracted / scattered light, the forward diffracted / scattered light is condensed on the light receiving surface of the forward scattered light sensor 252 via the condenser lens 251 and measured. The backscattered light is measured by the light sensor 253 and the backscattered light sensor 254.

The forward scattered light sensor 252 has a plurality of light sensors PS having light receiving surfaces forming a part of rings having different radii concentrically arranged as shown in the front view of FIG. 3A. The forward scattered light sensor 252
3 can measure the spatial intensity distribution of the diffracted / scattered light in a predetermined angle range in the forward direction, and together with the measurement by the side scattered light sensor 253 and the back scattered light sensor 254, FIG.
As shown in the bar graph showing the measurement results in FIG.
The spatial intensity distribution of the scattered light can be measured in a wide angle range.

The light intensity distribution measured as described above is transmitted to a computer via a data sampling circuit 260 comprising an amplifier for amplifying the output of each optical sensor and an AD converter for digitizing the amplified signal. 270. The computer 270 uses the measured data of the spatial intensity distribution of the diffracted / scattered light and the refractive indices of the particle group P to be measured and the medium L to obtain a known calculation based on Mie's scattering theory or Fraunhofer's diffraction theory. Thereby, the particle size distribution of the measured particle group P can be calculated.

Here, in FIG. 2, reference numeral 223 denotes a circulation / discharge valve. By operating the circulation / discharge valve 223, the suspension S is supplied to the flow cell 2 as described above.
30 or the suspension S in the dispersion tank 210 and the flow cell 230 can be discharged to the outside. After the measurement of one sample, the suspension S is discharged to the outside. Dispersion tank 210 and circulation pipe 22
1 and by washing the inside of the flow cell 230,
The influence of the first sample can be prevented from affecting the measurement result of the second sample.

In the above-mentioned laser diffraction / scattering type particle size distribution measuring apparatus, the time required for measuring the diffraction / scattered light is short, and therefore, compared to the particle size distribution measuring apparatus using other measurement methods, There is a great merit that the time required for the process is short.

[0009]

By the way, in a high-speed pulverizer that has become widespread in recent years, in order to monitor the pulverization process, the particle size distribution of the powder is repeatedly measured in a short time, for example, about every 20 seconds. There is a demand to continue / stop the operation of the crusher based on the result.

In the above-mentioned conventional laser diffraction / scattering type particle size distribution measuring apparatus, the time required for measuring the spatial intensity distribution of the diffracted / scattered light is short, but
The time required for one cycle of the measurement including the sampling of the particle group to be measured cannot meet the above-mentioned requirements very much.

That is, in the conventional laser diffraction / scattering type particle size distribution measuring apparatus, “supply of a medium solution into a dispersion tank → input sample into the dispersion tank as well → dispersion → circulation of suspension → diffraction / scattered light One cycle of measurement is “measurement → discharge of suspension → cleaning of circulation system”, and the washing process itself requires a process of “supply of the liquid medium into the dispersion tank → circulation for a certain time → discharge”. Therefore, it is substantially impossible to make one cycle as a whole measurement several tens of seconds.

The present invention has been made in view of such circumstances, and one cycle of measurement can be greatly shortened as compared with a conventional laser diffraction / scattering type particle size distribution measuring apparatus. It is an object of the present invention to provide a particle size distribution measuring device which can sufficiently satisfy the above-mentioned requirements in a pulverizer.

[0013]

In order to achieve the above object, a particle size distribution measuring apparatus according to the present invention comprises a space for diffracted and scattered light obtained by irradiating a group of particles to be measured in a dispersed and flying state with a laser beam. A particle size distribution measuring device that measures an intensity distribution and calculates a particle size distribution of a group of particles to be measured using the measurement result, and supplies a medium to the flow cell and the flow cell, and flows out of the flow cell. A medium supply / discharge system configured to discharge the medium fluid that has been discharged and to be able to input a particle group to be measured upstream of the flow cell, an irradiation optical system that irradiates the flow cell with laser light, and the laser light. Measurement optical system that measures the spatial intensity distribution of the diffracted and scattered light generated by the irradiation of light, and when the light intensity measured by the measurement optical system exceeds a predetermined level, Characterized by that it comprises a calculating means for calculating a particle size distribution by using the measurement result by Manabu system.

The present invention does not circulate a suspension in which particles to be measured are dispersed in a liquid medium between a flow cell and a dispersion tank as in a conventional laser diffraction / scattering type particle size distribution analyzer. A medium liquid supply / discharge system that constantly supplies and discharges a clean medium liquid to the flow cell is provided, and when measuring the particle size distribution, the particles to be measured are put into the system so that the flow cell becomes a suspension. It is intended to achieve its intended purpose by discharging it through the outside.

That is, in the present invention, a clean medium liquid is supplied to the flow cell, the medium liquid exiting the flow cell is discharged to the outside, and the particles to be measured are located upstream of the flow cell of the medium liquid supply / discharge system. A portion into which the group can be put is provided, and the flow cell is constantly irradiated with laser light from the irradiation optical system. Therefore, by introducing the particle group to be measured into the medium liquid supply / discharge system, the medium liquid is suspended, flows through the flow cell, and is then discharged to the outside. Only while the suspension is flowing in the flow cell, the spatial intensity distribution of the diffracted / scattered light by the measured particle group is measured by the measuring optical system.
At this time, since the level of the measured value of the spatial intensity distribution of the diffracted / scattered light by the measuring optical system increases, when the level exceeds a preset level, the arithmetic unit uses the measurement result to cover the level. Calculate the particle size distribution of the measured particle group.

By using such a sampling system, the charged particles to be measured are discharged to the outside immediately after flowing through the flow cell, and a clean medium is supplied before the next particles to be measured are charged. Since the liquid always flows in the system and the sampling system is substantially washed, even if the interval between the input of the particles to be measured, and thus the interval of the measurement, is shortened, it is not affected by the previously input particles. And accurate measurement of the particle size distribution becomes possible.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an embodiment of the present invention, and is a diagram showing both a schematic diagram showing a configuration of an optical system and a block diagram showing an electrical configuration.

The dispersion tank 1 has a stirrer 11 and an ultrasonic vibrator 12 as in the above-described conventional measuring apparatus. Liquid is supplied. The lower end of the dispersion tank 1 communicates with the suction port of the liquid feed pump 21, and the discharge port of the liquid feed pump 21 communicates with the lower end opening of the flow cell 3 via the liquid supply pipe 22. The upper end opening of the flow cell 3 communicates with the liquid discharge pipe 23. The liquid supply pump 21, the liquid supply pipe 22, and the liquid discharge pipe 23 constitute a medium liquid supply / discharge system 2, and the medium is discharged to the outside after flowing through the flow cell 3. ing. Further, the dispersion tank 1 is opened upward, so that a group of particles to be measured can be introduced at any time from the opening.

The flow cell 3 is irradiated with laser light from an irradiation optical system 4. The irradiation optical system 4 includes a laser light source 41, a condenser lens 42, a spatial filter 43, and a collimator 44 as in the related art, and can irradiate a parallel laser beam to the flow cell 3.

A condensing lens 51 and a forward scattered light sensor 52 placed at the focal point thereof are disposed on the opposite side of the irradiation optical system 4 with the flow cell 3 interposed therebetween. A side scattered light sensor 53 and a back scattered light sensor 54 are arranged further behind the flow cell 3, that is, on the side of the irradiation optical system 4, and these constitute a measurement optical system 5 similar to the conventional one. The output of each optical sensor is captured by a computer 7 via a data sampling circuit 6 comprising an amplifier and an A / D converter.

In using the above embodiment of the present invention, the medium liquid supply pump 13 and the liquid supply pump 21, the stirrer 11 and the ultrasonic oscillator 12 are always driven, and the flow cell 3 is cleaned. The medium is constantly flowed, and the medium flowing in the flow cell 3 is sequentially discharged to the outside. The flow cell 3 is constantly irradiated with a laser beam from the irradiation optical system 4, and the output of each sensor of the measurement optical system 5 is digitized by the data sampling circuit 6 every predetermined minute time and is taken into the computer 7 every moment. It is. When measuring the particle size distribution, an appropriate amount of the particles to be measured is dispersed in the dispersion tank 1.
Put in. As a result, the particle group is dispersed in the medium, becomes a suspension, is guided into the flow cell 3, is then discharged out of the system, and only the medium flows in the flow cell 3 again. The laser beam applied to the flow cell 3 is
Only when the particle group passes through the flow cell 3 is diffraction /
Receive scattering.

The computer 7 monitors the magnitude of the output of each optical sensor of the measurement optical system 5, and outputs the output of each optical sensor to valid data only while the output value reaches a preset level. Accumulates every moment. More specifically, for example, the output of one optical sensor located at a specific scattering angle in the forward scattered light sensor 52 is monitored, and the output value is compared with a preset level to determine the output value. Only when the level is reached, the outputs of all the optical sensors of the measuring optical system 5 are sequentially accumulated for each sensor. When the output value of the monitored optical sensor falls below the above level, the output of each sensor accumulated up to that point is used as spatial intensity distribution data of the diffracted / scattered light, and the particle size distribution is calculated by a known calculation. And displayed on the attached display 7a.

According to the above embodiment of the present invention, the medium in the medium supply / discharge system 2 including the flow cell 3 is used only for a short time after the particles to be measured have been put into the dispersion tank 1. The output of the measurement optical system 5 in that state is automatically accumulated as effective data and used for calculation of the particle size distribution, but the suspension is immediately out of the system after passing through the flow cell 3. After being discharged and only the clean medium flows through the system, after a lapse of a short time after the introduction of the particle group to be measured, the inside of the medium supply and discharge system 2 including the flow cell 3 is substantially After being washed, the apparatus is in a standby state for measuring the next group of particles to be measured. Therefore, one cycle of the measurement is significantly shorter than that of the conventional laser diffraction / scattering type particle size distribution measuring apparatus illustrated in FIG.

In the above embodiment, after the particles to be measured are put into the dispersion tank 1, the forward scattered light sensor 5
2 shows an example in which the output of each optical sensor is accumulated as valid data and used for calculation of the particle size distribution only while the output of one specific optical sensor in 2 exceeds the set level. For example, the outputs of a plurality of optical sensors may be monitored, and the output of each optical sensor may be used as valid data only while the average value exceeds a set level. When the output of one specific optical sensor or the average value of the outputs of specific multiple optical sensors exceeds the higher level, the accumulation of the output of each optical sensor is started. The accumulation may be terminated when the level becomes lower than the level on the smaller side. In other words, it is determined that the particle group to be measured exists in the flow cell 3 at a predetermined concentration or higher. Output of any suitable optical sensor If the accumulation of the output of each optical sensor can be automatically terminated when the concentration of the particle group to be measured in the flow cell 3 becomes so low that valid data cannot be collected, it is optional. Method can be adopted.

In the above embodiment, the method of charging the particle group to be measured into the dispersion tank 1 is not particularly described. However, for example, a container for charging is prepared, and the particle group to be measured is placed in the container. In addition, a charging mechanism is provided for automatically filling the same container with the particles to be measured and charging the same into the dispersion tank 1, and driving the charging mechanism by a switch operation to collect the particles to be measured. Into the dispersion tank 1,
Alternatively, it is also possible to adopt a configuration in which the charging mechanism is driven at regular intervals to automatically charge the particle group to be measured into the dispersion tank 1.

[0026]

As described above, according to the present invention, a medium supply / discharge system for supplying a medium into a flow cell irradiated with laser light and then discharging the medium outside the system is provided. After introducing the particles to be measured through the discharge system at any time, suspending the particles, introducing the particles into the flow cell, and then immediately discharging the suspension to the outside of the system, and introducing the particles to be measured. Is automatically detected from the output of the measurement optical system, and is provided to calculate the particle size distribution as effective data. The inside of the medium supply / discharge system including the flow cell is automatically washed by the flow of the clean medium, eliminating the need for a separate washing step as in the past, greatly shortening the measurement cycle. can do. As a result, it became possible to control these devices and plants by applying the results of the particle size distribution measurement to a high-speed pulverizer or a granulation plant.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, showing a schematic diagram illustrating a configuration of an optical system and a block diagram illustrating an electrical configuration.

FIG. 2 is a diagram showing a configuration example of a conventional laser diffraction / scattering type particle size distribution measuring apparatus, and is a diagram showing both a schematic diagram showing a configuration of an optical system and a block diagram showing an electrical configuration.

3A and 3B are explanatory diagrams of a forward scattered light sensor frequently used in a laser diffraction / scattering type particle size distribution measuring device, wherein FIG. 3A is a front view showing a configuration example thereof, and FIG.
6 is a graph showing a measurement example of the spatial intensity distribution of the diffracted / scattered light by the output of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dispersion tank 11 Stirrer 12 Ultrasonic oscillator 13 Medium supply pump 2 Medium supply / discharge system 21 Liquid supply pump 22 Liquid supply pipe 23 Liquid discharge pipe 3 Flow cell 4 Irradiation optical system 41 Laser light source 42 Condensing lens 43 Spatial filter 44 Collimator 5 Measurement optical system 51 Condenser lens 52 Forward scattered light sensor 53 Side scattered light sensor 54 Back scattered light sensor 6 Data sampling circuit 7 Computer 7a Display

Continued on the front page (72) Inventor Sanshiro Higuchi 1 Nishinokyo Kuwaharacho, Nakagyo-ku, Kyoto City Shimadzu Corporation

Claims (1)

[Claims] 1. A method for measuring a spatial intensity distribution of diffracted / scattered light obtained by irradiating a laser beam onto a group of particles to be measured in a dispersed and flying state, and calculating a particle size distribution of the group of particles to be measured using the measurement result. A particle size distribution measuring device, comprising: supplying a flow cell and a medium to the flow cell;
And a medium liquid supply / discharge system configured to discharge the medium liquid flowing out of the flow cell and to be capable of introducing a group of particles to be measured upstream of the flow cell, and an irradiation optical system for irradiating the flow cell with laser light. System, a measurement optical system that measures the spatial intensity distribution of the diffraction and scattered light generated by the irradiation of the laser light, and the diffraction and the diffraction measured by the measurement optical system.
When the scattered light intensity becomes equal to or higher than a predetermined level, the particle size distribution measuring device is provided with a calculating means for calculating a particle size distribution using a measurement result by the measuring optical system.