JP3783574B2 - Particle size distribution measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
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 particle size distribution measuring apparatus suitable for use in a field where it is necessary to sample a group of particles to be measured at short intervals and measure the particle size distribution one after another. About.
[0002]
[Prior art]
A so-called laser diffraction / scattering 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 a granule in a relatively short time. In this laser diffraction / scattering type particle size distribution measuring device, the spatial intensity distribution of diffracted / scattered light generated by irradiating laser light to a group of particles in a dispersed flight state is measured, and the light intensity distribution is scattered by Mie. Based on the theory or the diffraction theory of Fraunhofer, the particle size distribution of the particle group to be measured is calculated from the measurement result of the spatial intensity distribution of the diffracted / scattered light by calculation based on Mie's scattering theory or 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 including the stirrer 212 and the ultrasonic vibrator 213 together with the liquid medium L supplied from the liquid medium supply pump 211, where the measured liquid group P is measured in the liquid medium L. A suspension S in which the particle group P is dispersed is generated. The dispersion tank 210 communicates with the flow cell 230 via a circulation pipe 221, and the suspension S circulates between the dispersion tank 210 and the flow cell 230 by driving the circulation / discharge pump 222.
[0004]
In a circulating state of the suspension S, 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 passed to the flow cell 230 via the condenser lens 242, the spatial filter 243, and the collimator 244. By irradiating, 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 collected and measured on the light receiving surface of the forward scattered light sensor 252 via the condenser lens 251, and the side scattered light is side-scattered. Scattered light from the optical sensor 253 and backward is measured by a backscattered light sensor 254.
[0005]
As illustrated in the front view of FIG. 3A, the forward scattered light sensor 252 is a concentric arrangement of a plurality of light sensors PS having light receiving surfaces that are part of rings having different radii. The spatial intensity distribution of diffracted / scattered light in a predetermined forward angle range can be measured by the forward scattered light sensor 252. FIG. 3 (B) is combined with the measurement by the side scattered light sensor 253 and the back scattered light sensor 254. ), The spatial intensity distribution of diffracted / scattered light can be measured over a wide angular range, as shown in the bar graph showing the measurement results.
[0006]
The light intensity distribution measured as described above is taken into the computer 270 via the data sampling circuit 260 including an amplifier that amplifies the output of each optical sensor and an A / D converter that digitizes the amplified signal. It is. The computer 270 uses the measurement data of the spatial intensity distribution of the diffracted / scattered light and the refractive index of the particle group P to be measured and the liquid medium L to calculate a known calculation based on Mie's scattering theory or Fraunhofer's diffraction theory. Thus, the particle size distribution of the particle group P to be measured can be calculated.
[0007]
Here, in FIG. 2, reference numeral 223 denotes a circulation / discharge valve. By operating this circulation / discharge valve 223, the suspension S is circulated with the flow cell 230 or dispersed as described above. The suspension S in the tank 210 and the flow cell 230 can be discharged to the outside. After measurement of one sample, the suspension S is discharged to the outside and the dispersion tank 210, the circulation pipe 221 and the flow cell 230 are discharged. By cleaning the inside, it is possible to prevent the influence of the previous sample from affecting the measurement result of the subsequent sample.
[0008]
In the laser diffraction / scattering type particle size distribution measuring apparatus as described above, the time required for measuring the diffraction / scattered light is short, and therefore the time required for the measurement compared to the particle size distribution measuring apparatus using other measurement methods. Has the great advantage of being short.
[0009]
[Problems to be solved by the invention]
By the way, in high-speed pulverizers that have become widespread in recent years, in order to monitor the pulverization process, the measurement of the particle size distribution of the powder is repeated for a short time, for example, about every 20 seconds. There is a request to continue / stop operation.
[0010]
Here, in the conventional laser diffraction / scattering particle size distribution measuring apparatus described above, the time required for measuring the spatial intensity distribution of the diffracted / scattered light is short, but sampling of the group of particles to be measured is included. The time required for one cycle of measurement cannot meet the above requirements.
[0011]
In other words, the conventional laser diffraction / scattering type particle size distribution measuring device is described as follows: “Supplying the liquid medium into the dispersion tank → Put the sample into the dispersion tank → Dispersion → Suspension circulation → Diffraction / scattered light measurement → Suspension “Discharging of turbid liquid → cleaning of circulation system” is one cycle of measurement, and the cleaning process itself requires a process of “supply of liquid medium into dispersion tank → circulation of certain time → discharge”. It is practically impossible to make one cycle as a whole measurement to be several tens of seconds.
[0012]
The present invention has been made in view of such circumstances, and can greatly shorten one cycle of measurement as compared with a conventional laser diffraction / scattering type particle size distribution measuring apparatus, and thus in a high-speed crusher. An object of the present invention is to provide a particle size distribution measuring apparatus that can sufficiently satisfy the above-described requirements.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the particle size distribution measuring apparatus of the present invention measures the spatial intensity distribution of diffracted / scattered light obtained by irradiating laser light to a group of particles in a dispersed flight state, and the measurement result Is a particle size distribution measuring device for calculating the particle size distribution of the particle group to be measured using a flow cell, a dispersion tank for dispersing the charged particle group to be measured in a liquid medium, and the dispersion tank A liquid supply pump for continuously supplying the liquid medium, a liquid feed pump and liquid supply pipe for continuously feeding the liquid in the dispersion tank into the flow cell, and discharging the liquid flowing in the flow cell to the outside. A liquid discharge pipe , an irradiation optical system for irradiating the flow cell with laser light, a measurement optical system for measuring the spatial intensity distribution of diffraction / scattered light generated by the laser light irradiation, and the measurement optical system Output Computation means is provided for detecting the presence of a group of particles to be measured based on whether or not a preset level has been reached, and calculating the particle size distribution of the group of particles to be measured using the output in the presence detection state as valid data. It is characterized by having.
[0014]
The present invention does not circulate a suspension obtained by dispersing a group of particles to be measured in a liquid medium between a flow cell and a dispersion tank as in a conventional laser diffraction / scattering type particle size distribution measuring apparatus. A liquid supply / discharge system that constantly supplies and discharges clean medium liquid is provided, and when measuring particle size distribution, a group of particles to be measured is introduced into the system as a suspension, which is passed through the flow cell to the outside. By trying to discharge, we are going to achieve the intended purpose.
[0015]
That is, in the present invention, a clean medium was continuously supplied to the flow cell, medium liquid exiting the flow cell as well as discharged to the outside, can be put the particles to be measured on the upstream side of that flow cell In order to configure the liquid tank, the liquid supply pump for continuously supplying the liquid medium to the dispersion tank is provided, and the liquid in the dispersion tank is continuously fed to the flow cell by the liquid feed pump to flow through the flow cell. A pipe for discharging the liquid to the outside is provided, and the flow cell is always irradiated with laser light from the irradiation optical system. Therefore, by introducing the particles to be measured into the dispersion tank as needed while the medium is continuously flowing to the flow cell, the medium is suspended and flows through the flow cell, and then externally. Discharged. Only while this suspension is flowing in the flow cell, the spatial intensity distribution of the diffracted / scattered light by the group of particles to be measured is measured by the measurement optical system. At this time, since the level of the measured value of the spatial intensity distribution of the diffracted / scattered light by the measurement optical system increases, the calculation means uses the measurement result to cover the level when the level exceeds a preset level. The particle distribution of the measurement particle group is calculated.
[0016]
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 always supplied until the next particles to be measured are charged. Since the sampling system is substantially washed by flowing through the system, even if the input interval of the particle group to be measured, and hence the measurement interval, is shortened, it is not affected by the particle group that has been input first, and is accurate. The particle size distribution can be measured.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of an embodiment of the present invention, and is a diagram illustrating a schematic diagram showing a configuration of an optical system and a block diagram showing an electrical configuration.
[0018]
The dispersion tank 1 includes a stirrer 11 and an ultrasonic vibrator 12 as in the above-described conventional measuring apparatus of this type, and a clean medium liquid is supplied to the dispersion tank 1 from a medium supply pump 13. Is done. 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 feed pump 21, the liquid supply pipe 22 and the liquid discharge pipe 23 constitute a medium supply / discharge system 2, and the medium is discharged to the outside after flowing through the flow cell 3. ing. Moreover, the dispersion tank 1 is opened upward, and a group of particles to be measured can be introduced at any time from this opening.
[0019]
The flow cell 3 is irradiated with laser light from the 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 conventional case, and can irradiate the flow cell 3 with parallel laser light.
[0020]
A condensing lens 51 and a forward scattered light sensor 52 placed at the focal position thereof are arranged on the opposite side of the irradiation optical system 4 with the flow cell 3 interposed therebetween, and side scattering is provided on the side of the flow cell 3. The optical sensor 53 is further provided with a backscattered light sensor 54 behind the flow cell 3, that is, on the irradiation optical system 4 side, and these constitute the measurement optical system 5 similar to the conventional one. The output of each optical sensor is taken into the computer 7 through the data sampling circuit 6 comprising an amplifier and an A / D converter.
[0021]
In using the above-described embodiment of the present invention, the medium supply pump 13 and the liquid feed pump 21, and the stirrer 11 and the ultrasonic vibrator 12 are always driven, and the flow cell 2 has a clean medium. Is constantly flowing, and the liquid medium that has flowed through the flow cell 3 is sequentially discharged to the outside. In other words, the liquid medium is continuously flowed through the flow cell 3, and the liquid medium is continuously discharged through the flow cell 3. The flow cell 3 is always irradiated with laser light 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 taken into the computer 7 every moment. It is. When measuring the particle size distribution, an appropriate amount of particles to be measured is put into the dispersion tank 1. As a result, the particle group is dispersed in the liquid medium to be a suspension, guided into the flow cell 3 and then discharged out of the system, so that only the liquid medium flows through the flow cell 3 again. The laser light applied to the flow cell 3 is diffracted and scattered only while the particle group passes through the flow cell 3.
[0022]
The computer 7 monitors the output level of each optical sensor of the measurement optical system 5 and only outputs the output of each optical sensor as effective data every time the output value reaches a preset level. accumulate. 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. Only while the level is reached, the output of the all-optical sensor of the measurement optical system 5 is sequentially accumulated for each sensor. When the output value of the optical sensor being monitored falls below the above level, the output of each sensor accumulated so far is used as the spatial intensity distribution data of diffracted / scattered light, and the particle size distribution is obtained by a known calculation. And is displayed on the attached display 7a.
[0023]
According to the above-described embodiment of the present invention, the liquid medium in the liquid supply / discharge system 2 including the flow cell 3 is suspended by the particle group only for a short time after the particle group to be measured is introduced into the dispersion tank 1. Although 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, the suspension is immediately discharged out of the system after passing through the flow cell 3, After that, since only the clean fluid flows through the system, after a short time after the introduction of the particles to be measured, the fluid supply / discharge system 2 including the flow cell 3 is substantially cleaned. Therefore, the next measurement target particle group is in a standby state, and therefore, one measurement cycle is significantly shorter than that of the conventional laser diffraction / scattering particle size distribution measuring apparatus illustrated in FIG.
[0024]
In the embodiment described above, each time only after the output of one specific photosensor in the forward scattered light sensor 52 exceeds the set level after the particles to be measured are put into the dispersion tank 1, Although the example in which the output of the optical sensor is accumulated as effective data and used for calculation of the particle size distribution has been shown, the present invention is not limited to this, for example, the output of a plurality of optical sensors is monitored, and the average value is The output of each photosensor may be used as valid data only while the set level is exceeded, and two levels of different sizes are set, and the output of one specific photosensor or a specific plurality of It may be configured to start accumulation of the output of each photosensor when the average value of the output of the photosensor exceeds the level on the large side, and to terminate the accumulation when it becomes less than the level on the small side. Well, in short, the particles to be measured are The presence of a concentration higher than a predetermined concentration in the cell 3 is automatically detected based on the output of any suitable optical sensor in the measurement optical system 5, and the concentration of the measured particle group in the flow cell 3 is effective. Any method can be adopted as long as the accumulation of the output of each optical sensor can be automatically terminated when the data becomes low enough to collect no data.
[0025]
In the above embodiment, no particular mention was made of a method for charging the particle group to be measured into the dispersion tank 1, but for example, a container for charging is prepared, and the container to be measured is filled with the particle group to be measured. In addition to being charged manually, a similar mechanism is used to automatically fill the measured particle group into the dispersion tank 1 and to throw it into the dispersion tank 1, and by driving the switch mechanism to move the measured particle group to the dispersion tank 1 Alternatively, it may be configured such that the particle group to be measured is automatically charged into the dispersion tank 1 by driving the charging mechanism at regular intervals.
[0026]
【The invention's effect】
As described above, according to the present invention, the liquid medium supply pump that continuously supplies the liquid medium to the dispersion tank is provided, and the liquid in the dispersion tank is continuously supplied to the flow cell by the liquid feed pump. By providing piping that discharges to the outside after sending the liquid, the flow medium always flows a clean liquid medium, and the liquid medium suspends only when the particles to be measured are introduced into the dispersion tank at any time , The suspension is configured to be discharged out of the system immediately after flowing through the flow cell, and automatically detects from the output of the measurement optical system that the measured particle group has been introduced, and is effective. Since it is configured to produce the particle size distribution as data, the medium supply / discharge system including the flow cell is automatically turned on by the flow of clean liquid after a short period of time after the particles to be measured are introduced. Will be washed automatically. It is not necessary to separately provide a washing step as described above, one cycle of measurement can be significantly shortened. As a result, it has become possible to control these devices and plants by feeding them back to the particle size distribution measurement results when applied to high-speed crushers and granulation plants.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an embodiment of the present invention, and is a diagram illustrating a schematic diagram showing a configuration of an optical system and a block diagram showing an electrical configuration.
FIG. 2 is a diagram illustrating a configuration example of a conventional laser diffraction / scattering particle size distribution measuring apparatus, which is a diagram illustrating a schematic diagram illustrating a configuration of an optical system and a block diagram illustrating an electrical configuration.
FIGS. 3A and 3B are explanatory diagrams of a forward scattered light sensor frequently used in a laser diffraction / scattering type particle size distribution measuring apparatus. FIG. 3A is a front view showing a configuration example thereof, and FIG. It is a graph which shows the example of a measurement of the spatial intensity distribution of the diffracted / scattered light by the output of.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Dispersion tank 11 Stirrer 12 Ultrasonic vibrator 13 Medium liquid supply pump 2 Medium liquid supply / discharge system 21 Liquid feed 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 Measuring optical system 51 Condensing lens 52 Forward scattered light sensor 53 Side scattered light sensor 54 Back scattered light sensor 6 Data sampling circuit 7 Computer 7a Display

Claims (1)

A particle size distribution measuring device that measures the spatial intensity distribution of diffracted / scattered light obtained by irradiating laser particles to a group of particles in a dispersed flight state, and calculates the particle size distribution of the group of particles to be measured using the measurement results Because
A flow cell, a dispersion tank for dispersing the charged particles to be measured in the liquid medium, a medium liquid supply pump for continuously supplying the liquid medium to the dispersion tank, and the liquid in the dispersion tank A liquid feed pump and a liquid supply pipe continuously fed into the flow cell; a liquid discharge pipe for discharging the liquid flowing in the flow cell to the outside; and an irradiation optical system for irradiating the flow cell with laser light; The measurement optical system that measures the spatial intensity distribution of the diffracted / scattered light generated by the laser light irradiation, and the presence of the group of particles to be measured depending on whether or not the output of the measurement optical system has reached a preset level. A particle size distribution measuring device comprising: a calculating means for detecting and calculating a particle size distribution of a group of particles to be measured using the output in the presence detection state as effective data.

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