JP4101217B2 - Particle size distribution measuring device - Google Patents

Description

  The present invention relates to a particle size distribution measuring apparatus for measuring the particle size distribution of particles such as a granular sample.

  Particle measurement technology is indispensable for determining and evaluating the performance of powders in a wide range of fields such as medicine, food, ceramics, cosmetics, paints, and pigments, and its importance is increasing day by day. Yes. One of the methods for measuring the particle size distribution of such a granular material is a laser diffraction / scattering particle size distribution measuring apparatus. For example, in Patent Document 1, a granular material as a sample is distributed and diffused in a dispersion medium to form a suspension, and this suspension is supplied to the flow cell. In this state, the flow cell is irradiated with laser light. Then, the laser light scattered by the particles in the suspension is detected by a detector, and the resulting diffraction and / or the intensity of the scattered light is processed based on the Franhofer diffraction or Mie scattering theory, The particle diameter is determined.

In order to supply the suspension to such a flow cell, a circulation channel for circulating the suspension is formed, and in this circulation channel, there is a circulation bath in which a sample is dispersed in a dispersion medium. A circulation pump is interposed, and the dispersion medium sucked up from the dispersion medium tank is injected into the circulation bus through the dispersion medium supply system.
JP 2000-155088 A

  By the way, in such a conventional dispersion medium supply system, the injection end is set at an upper position of the circulation bus, and the dispersion medium is discharged from the injection bus and injected into the circulation bus. For this reason, a part of the air existing in the circulation path is pushed further into the circulation path at the time of initial injection, and air is mixed in by dropping at the time of replenishment. There is a bug. In order to cope with this, there is a problem that the preparation time becomes long if the air venting process is sufficiently performed after injection, and there is a high possibility that the foam remains in the circulation path by the air venting process. This is a factor that reduces the S / N ratio by generating light.

  The present invention has been made paying attention to such problems, and can supply the dispersion medium to the circulation path without mixing air, thereby suitably eliminating the above-mentioned problems associated with residual air. An object of the present invention is to provide a particle size distribution measuring apparatus.

  In order to achieve the above object, the present invention takes the following measures.

  That is, the present invention comprises a general configuration as this kind of particle size distribution measuring apparatus, and the dispersion medium supply system is connected to the vicinity of the drain outlet of the circulation flow path constituting the suspension circulation system, The dispersion medium is pumped from the dispersion medium supply system to the circulation channel.

  In such a case, since the drain outlet is usually provided at a low position of the circulation flow path, the introduction of the dispersion medium into this portion serves to expel air. Moreover, since new contamination of ambient air can be avoided, the present invention can basically eliminate the need for air venting.

  As a specific embodiment, there may be mentioned one in which the drain outlet is provided in a pipe located at the lowest position of the circulation flow path, and the dispersion medium supply system is connected to the upstream of the drain outlet of the pipe. .

  In order to prevent the circulating powder particles from entering the injection pipe without degrading the measurement accuracy, the dispersion medium supply system can be selectively communicated with the suspension circulation system through the opening / closing operation of the valve body. It is preferable that the inner end of the valve body at the closed position is substantially flush with the inner surface of the circulation passage.

  In order to further reduce the possibility of residual air, and at the same time simplify the structure and reduce costs, the suspension drainage system, suspension supply system, and circulation channel assembly can be combined with a single housing component. It is desirable to unitize.

  Since the present invention is configured as described above, it is possible to basically eliminate the need for air venting after the dispersion medium has been injected and to shorten the time required to start the measurement. In particular, when the injection speed of the dispersion medium is increased under such a structure, not only air mixing does not increase, but conversely, the remaining air is effectively purged, and the time required for injection itself can be shortened. . As a result, it is possible to eliminate residual air and the generation of unnecessary scattered light by the air becoming bubbles, and the S / N ratio of the measured scattered light can be accurately improved.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram schematically showing a configuration of a light scattering particle size distribution measuring apparatus according to an embodiment of the present invention. This particle size distribution measuring apparatus connects the circulation bath 11 and the flow cell 12 via the circulation channel 13 so as to circulate the suspension 1a in which the particles of the particulate sample x are dispersed in the dispersion medium 3a. The suspension circulation system 1 and the suspension 1a flowing in the flow cell 12 are irradiated with laser light 2a as inspection light, and the granular material in the suspension 1a based on the diffraction and / or scattered light. An optical measurement system 2 for measuring the particle size distribution of the sample x, a dispersion medium supply system 3 for supplying the dispersion medium 3a to the suspension circulation system 1, and a drain port provided in a part of the circulation channel 1 14 and a suspension drainage system 4 for draining the suspension 1a.

  In the suspension circulation system 1, the circulation bath 11 mixes a granular material sample x (or slurry) to be added and a dispersion medium 3 a (for example, pure water or alcohol) that disperses the powder sample x (or slurry). 1a, a stirring blade 15 that can be driven by a stirring motor 15a is immersed in an intermediate liquid tank part 11c between an upper liquid tank part 11a and a lower liquid tank part 11b, and also serves as a drain pump A circulation pump 16 of a mold is attached to the bottom of the circulation bus 11 in a liquid-tight manner and can be driven by a circulation motor 16a. In the circulation bath 11, there is provided a float type water level sensor 10 (see FIG. 2) for detecting the water level of the suspension 1a. Then, the outlet of the circulation pump 16 attached to the circulation bus 11 is connected to the flow cell 12 via an outgoing pipe 13a that forms a part of the circulation channel 13, and the outlet of the flow cell 12 is connected to a part of the circulation channel 13. The circulation bus 11 is connected via a return pipe 13b.

  The flow cell 12 is arranged in the sample chamber A, and allows the suspension 1a introduced from the outside to flow out in a liquid-tight manner between a pair of translucent transparent plates. The plate is irradiated with laser light 2a.

  The forward piping 13 a has an ultrasonic transducer 18 that generates ultrasonic waves in the middle, and prevents aggregation of powder particles in the suspension 1 a toward the flow cell 12.

  The return pipe 13 b is connected to the intermediate liquid tank section 11 c in the circulation bus 11 so that the circulated suspension 1 a is refluxed to the circulation bus 11.

  On the other hand, as shown in FIG. 1, the optical system measurement system 2 includes a laser light source 21, a light projection lens 22, a narrow-angle scattered light detector 23, and a wide-angle scattered light so as to surround a sample chamber A containing a flow cell 12. The detector 24 is arranged, and the signal processing unit 25 and the arithmetic processing unit 26 that process signals output from the narrow-angle scattered light detector 23 and the wide-angle scattered light detector 24 are configured.

  The laser light source 21 is provided at the facing position of the flow cell 12, and emits parallel laser light 2a. The light projection lens 22 is provided between the laser light source 21 and the flow cell 12, and appropriately collects the laser light 2 a emitted from the laser light source 21 to irradiate the suspension 1 a in the flow cell 12.

  The narrow-angle scattered light detector 23 is disposed at a position that does not directly face the flow cell 12, that is, a position where the laser light 2a that passes through the flow cell 12 and is bent by the movable mirror 23a is condensed and focused. The narrow-angle scattered light detector 23 is formed by concentrically arranging a plurality of photosensors having ring-shaped or semi-ring-shaped light receiving surfaces having different radii around the optical axis of the condenser lens 22. Of the condensed laser light 2x diffracted or scattered by the inner particles, light scattered / diffracted at a relatively small angle is received at each scattering angle, and the light intensity thereof is measured. That is, the photosensor disposed relatively on the outer peripheral side receives light having a larger scattering angle, and the photosensor disposed on the inner peripheral side receives light having a smaller scattering angle. In general, the smaller the particle size, the greater the scattering, so the light intensity detected by the outer photosensor reflects the amount of particles with a smaller particle size, and the light intensity detected by the inner photosensor This reflects the amount of sample particles with a larger diameter.

  The wide-angle scattered light detector 24 is configured around the flow cell 12, and the light scattered / diffracted at a relatively large angle out of the condensed laser light 2 x diffracted or scattered by particles having a smaller particle diameter in the flow cell 12, Detect individually for each scattering angle. Specifically, the wide-angle scattered light detector 24 has a plurality of photosensors 24a provided at positions where the laser light 2x scattered at a different angle from the condensed laser light 2x incident on the narrow-angle scattered light detector 23 can be received. It consists of ˜24h, and the scattered light by the particles in the flow cell 12 is detected for each scattering angle in accordance with each arrangement angle. Photosensors 24a to 24e detect forward scattered light, and photosensors 24f to 24h detect backscattered light.

  The signal processing unit 25 sequentially takes in signals output from the narrow-angle scattered light detector 23 and the photosensors 24a to 24h, performs AD conversion, and inputs the signals to the arithmetic processing unit 26.

  In this embodiment, the arithmetic processing unit 26 uses a general-purpose computer function. As shown in FIG. 3, the arithmetic processing unit 26 includes a CPU 26a, a memory 26b, an input / output interface 26c, and a user interface 26d. The output of the narrow-angle scattered light detector 23 and the photosensors 24a to 24h converted into digital signals (digital data regarding the light intensity) is processed based on the Fraunhofer diffraction theory or the Mie scattering theory, and the particle size distribution in the particle group And a program for density check described below based on the transmitted light amount and the irradiated light amount. The CPU 26a reads out these programs as appropriate, performs predetermined calculations and processing, stores the calculation results in the memory 26b, or displays them on a display or the like constituting a part of the user interface 26d. In this embodiment, by detecting diffracted light and scattered light in a wide range as described above, the particle size distribution in the particle group is obtained all at once from a relatively large particle size to a very small particle size. Make it possible.

  In order to secure a wider measurement range from large particles to fine particles, not only the laser beam 2a but also LED beams 2z having different wavelengths as shown in FIG. 1 can be used in combination. For this purpose, the apparatus is provided with an LED light source 21z, a light projection lens 22z, and a light receiver 23z corresponding to the laser light source 21, the light projection lens 22, and the narrow-angle scattered light detector 23. The photosensors 24d and 24e are also used to receive the scattered light of the LED light 2z.

  On the other hand, the dispersion medium supply system 3 includes a dispersion medium storage tank 31, a dispersion medium supply pipe 32 having one end immersed in the dispersion medium storage tank 31 and the other end connected to the suspension circulation system 1, and the dispersion medium. An injection pump 33 interposed in the medium supply pipe 32 is provided. By driving the injection pump 33, the dispersion medium 3 a is sucked up from the dispersion medium storage tank 31 and supplied to the suspension circulation system 1. I have to.

  The suspension drainage system 4 is connected to a circulation flow path 13 constituting the suspension circulation system 1 via an electromagnetic switching valve 17 and circulates through the suspension drainage system 4 at a closed position. Disconnected from the channel 13, one end of the suspension drainage system 4 is connected to the circulation channel 13 at the open position, and the suspension 1 a in the circulation channel 13 is discharged to the drain located on the other end side. The switching valve 17 is switched and driven by a solenoid.

  Next, the operation of this particle size distribution measuring apparatus will be described. First, a large amount of the powder sample x is put into the circulation bath 11. Next, the injection pump 33 of the dispersion medium supply system 3 is operated to start supplying (injecting) the dispersion medium 3 a into the circulation bus 11. At this time, the switching valve 17 is set to the circulation mode.

  When a predetermined amount of the dispersion medium 3a is supplied over the circulation bus 11 and the circulation flow path 13, the supply pump 33 of the dispersion medium supply system 3 is stopped based on the output signal of the water level sensor 10, and the supply of the dispersion medium 3a is stopped. Stop.

  Thereafter, by the operation for starting the operation of the dispersion processing, the circulation motor 16a is activated, the circulation pump 16 is activated, and the ultrasonic transducer 18 is activated. As a result, the suspension 1a mixed with the particulate sample x is repeatedly circulated such that it flows through the circulation channel 13 from the circulation bath 11, passes through the flow cell 12 and returns to the circulation bus 11 again.

  The concentration of the obtained suspension 1a is checked by irradiating the flow cell 12 with laser light 2a from the laser light source 21 of the measurement system 2 in a state of circulating in the circulation channel 7. Is performed based on the ratio between the light amount of the light source and the transmitted light amount detected by the narrow-angle scattered light detector 23. The program for checking the density is stored in the memory 26b as described above, and the CPU 26a reads and executes the program as the distributed processing starts. When the concentration of the suspension 1a is not an appropriate concentration, the suspension 1a flowing through the flow cell 12 is subjected to a concentration check again after being diluted by supplying the dispersion medium 3a and being concentrated by adding the powder sample x. When the concentration is suitable for measurement, particle size distribution measurement is performed. If the suspension 1a is already full or may become full by supply, the suspension 1a is drained through the suspension drainage system 4 in advance.

  In the above configuration, the present embodiment particularly connects the dispersion medium supply system 3 to the vicinity of the drain port 14 of the circulation flow path 13 constituting the suspension circulation system 1, and the circulation flow from the dispersion medium supply system 3. The dispersion medium 3 a is pumped to the path 13.

  Specifically, in the present embodiment, as shown in FIG. 2, the drainage port 14 is opened to a pipeline located at the lowest position of the circulation channel 13, that is, a pipeline in the middle of the forward piping 13a. A dispersion medium supply pipe 32 constituting the dispersion medium supply system 3 is connected to a drain outlet upstream portion 13x of the pipe line. In FIG. 1, it seems that the dispersion medium supply pipe 32 is connected directly above the drain port 14, but this figure is an overall schematic system diagram, and in fact, as shown in FIG. 2, the forward pipe 13 a. The drain outlet upstream portion 13x located at substantially the same height as the drain outlet 14 that opens to a pipe line extending substantially horizontally at the lowest position. Of course, the effects of the present invention can be sufficiently achieved without strictly setting the lowest position, and the connection of the dispersion medium supply pipe 32 may be performed from the vertically lower side or from the horizontal direction.

  FIG. 4 shows a check valve 34 provided at a position where the dispersion medium supply pipe 32 intersects the circulation flow path 13. The check valve 34 selectively connects the dispersion medium supply pipe 32 to the forward pipe 13a of the circulation flow path 13 through the opening / closing operation of the valve body 34a. The valve body 34a can advance and retreat in the valve housing 34b. Thus, the opening / closing operation is performed by attaching / detaching the tapered portion 34d provided on the valve body 34a to / from the tapered seat 34c provided on one end portion of the valve housing 34b. A spring 34e provided between the valve housing 34b and the valve body 34a elastically biases the valve body 34a in the direction of seating on the seat 34c. The check valve 34 is opened by opening the valve element 34a when the injection pump 33 is operated, and is closed by the biasing force of the spring 34e and the static pressure in the circulation flow path 13 when the injection pump 33 is stopped. To do.

  The inner end, that is, the upper surface 34 a 1 of the valve body 34 a in the closed position is set to be substantially flush with the pipe inner surface 13 y of the circulation channel 13.

  As described above, in the present embodiment, the dispersion medium supply system 3 is connected to the vicinity of the drain port 13x located at the lower position of the circulation flow path 13 constituting the suspension circulation system 1, and the dispersion medium supply system 3 Since the dispersion medium 3a is pumped to the circulation flow path 13, the air existing in the circulation flow path 13 is expelled and new air is prevented from being mixed. it can. For this reason, it is possible to effectively shorten the time required to start the measurement. In particular, when the injection speed of the dispersion medium 3a is increased under such a structure, not only the air mixing does not increase, but also the action of expelling residual air is increased, so that the time required for the injection itself can be shortened, Further reduction in the residual air rate can be achieved. Along with this, the generation factor of unnecessary scattered light is removed, and the S / N ratio of the measured scattered light can be effectively improved.

  More specifically, the drain port 14 is provided in the pipeline of the forward piping 13a located at the lowest position of the circulation channel 13, and the dispersion medium supply piping 32 is connected to the drain port upstream portion 13x of this pipeline. Therefore, you can expect almost the maximum air expelling effect.

  In particular, since the dispersion medium supply pipe 32 can be selectively communicated with the circulation flow path 13 of the suspension circulation system 1 through the opening and closing operation of the valve body 34, the circulating powder particles are dispersed in the dispersion medium. Mixing into the supply pipe 32 can be effectively prevented, and contamination of the dispersion medium 3a, occurrence of dilution errors, and the like can be effectively avoided. At that time, since the inner end 34a1 of the valve body 34 in the closed position is set to be a substantially surface with respect to the inner surface of the outgoing pipe 13a constituting the circulation flow path 13, the powder and air It is not necessary to create inadvertent irregularities that remain, and it is possible to suitably avoid a decrease in measurement accuracy.

  The specific configuration of each part is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  For example, when the dispersion medium 3a is preloaded, it is possible to effectively use tap water or the like as the dispersion medium by arranging an on-off valve 134 instead of the check valve as shown in FIG. become. Even in this case, the same effect as described above can be obtained by placing the dispersion medium supply path 3 at the lowest position of the suspension circulation system 1.

  Further, since the suspension drainage 4 and the dispersion medium injection system 3 are gathered at a position close to the suspension circulation system 1, they are collected by a collective pipe 100 as a single casing component as shown in FIG. Unitization is also effective.

  By doing this, the connection part is smooth and free of unevenness and steps, reducing the residual air as much as possible, reducing dead volume, and reducing the number of parts, simplifying the structure and reducing costs Can also be obtained. A drain actuator 100a controls the drainage of the suspension. Even in this case, the same effect as described above can be obtained by placing the dispersion medium supply path 3 in the lowest position of the suspension circulation system 1 in the collecting pipe 100.

The system diagram which shows the outline | summary of the particle diameter distribution measuring apparatus which concerns on one Embodiment of this invention. The figure which specifies the connection location of the dispersion medium supply system in the embodiment. Functional explanatory drawing of the arithmetic processing unit used in the embodiment. FIG. 3 is a schematic cross-sectional view of a check valve used in the same embodiment. The figure which shows other embodiment of this invention. The figure which shows other embodiment of this invention.

Explanation of symbols

x ... granular material 1 ... suspension circulation system 1a ... suspension 2 ... optical side fixed system 3 ... dispersion medium supply system 3a ... dispersion medium 4 ... suspension drainage system 11 ... circulation bath 12 ... flow cell 13 ... Circulating flow path 13x ... Drain outlet upstream portion 13y ... Pipe inner surface 14 ... Drain outlet 34a ... Valve element 34a1 ... Inward end (upper surface)
100: Housing parts (collective piping)

Claims (4)

A suspension circulation system in which a circulation bath and a flow cell are connected via a circulation channel to circulate a suspension in which particles are dispersed in a dispersion medium, and an inspection light is supplied to the suspension flowing in the flow cell. An optical measurement system that measures the particle size distribution of the sample in the suspension based on diffraction and / or scattered light, a dispersion medium supply system that supplies a dispersion medium to the suspension circulation system, In what comprises a suspension drainage system that drains suspension from a drain outlet provided in the circulation channel,
The dispersion medium supply system is connected to the vicinity of a drain outlet of a circulation flow path constituting the suspension circulation system, and the dispersion medium is pumped from the dispersion medium supply system to the circulation flow path. Particle size distribution measuring device. 2. The particle size distribution measuring apparatus according to claim 1, wherein the drain outlet is provided in a pipe located at the lowest position of the circulation flow path, and the dispersion medium supply system is connected to the upstream of the drain outlet of the pipe. The dispersion medium supply system can be selectively communicated with the suspension circulation system through the opening and closing operation of the valve body, and the inner end of the valve body in the closed position is connected to the inner surface of the circulation passage. The particle size distribution measuring device according to claim 1 or 2, wherein the particle size distribution measuring device is set so as to be substantially flush with each other. The particle size distribution measuring apparatus according to claim 1 , 2 or 3, wherein the suspension drainage system, the suspension supply system, and the assembly portion of the circulation flow path are unitized by a single casing part.