JP3136745B2 - Particle size distribution analyzer - Google Patents

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.

[0002]

2. Description of the Related Art In a laser diffraction / scattering type particle size distribution measuring apparatus, generally, a laser beam is irradiated to a group of particles to be measured in a dispersed and flying state, and the spatial distribution of the intensity of diffraction / scattered light by the group of particles to be measured is measured. The particle size distribution of the group of particles to be measured is measured by calculation based on the Fraunhofer diffraction theory or the Mie scattering theory.

In the wet measurement using such a laser diffraction / scattering type particle size distribution measuring apparatus, usually, a suspension formed by dispersing a group of particles to be measured in a medium or an emulsion is transmitted. While flowing into a flow cell made of a conductive material, laser light is irradiated from outside the cell.

[0004]

By the way, in the wet measurement in the conventional particle size distribution measuring device, the sample suspension or the emulsion flows in the flow cell, so that the particles to be measured easily adhere to the inner surface of the cell. . If particles adhere to the inner surface of the cell, it may cause diffraction / scattered light to include measurement errors.

[0005] The concentration of the sample suspension or emulsion must be reduced to such a level that the laser beam does not cause multiple diffraction (scattering). The upper limit of the concentration at which multiple diffraction (scattering) occurs is limited. It is affected by the optical path length of the laser beam in the suspension or the emulsion, and the measurement of a sample with a higher concentration can be performed by shortening the optical path length. In order to shorten the optical path length, it is necessary to reduce the inner width of the flow cell (the distance between the inner surfaces of the cell in the optical axis direction of the irradiation laser beam). There is also a problem that the work becomes difficult.

The present invention has been made in view of the above points, and it is difficult for particles to be measured to adhere to the inner surface of a flow cell during wet measurement, and the inner surface of the cell is easily cleaned even if the optical path length is shortened. Accordingly, it is an object of the present invention to provide a particle size distribution measuring apparatus capable of measuring a sample having a substantially higher concentration.

[0007]

In order to achieve the above object, a particle size distribution measuring apparatus according to the present invention is characterized in that a suspension or emulsion in which particles to be measured are dispersed in a medium is flowed into a cell. ,
A particle size for measuring the intensity distribution of diffraction / scattered light obtained by irradiating the suspension or emulsion with laser light from outside the cell, and calculating the particle size distribution of the particle group to be measured from the measurement result In the distribution measuring device, the cell is provided such that a nozzle having a slit-shaped discharge port therein is disposed so that the longitudinal direction of the discharge port is along a direction orthogonal to the optical path of the irradiation laser light, and Separately, it has an inlet, the medium is flowed into the cell through this inlet, and the suspension or the emulsion keeps the width of the outlet from the outlet of the nozzle. It is characterized by being configured to be flowed to a substantially central portion along the flow of the medium.

[0008]

The sample suspension or emulsion coming out of the outlet of the nozzle flows in the cell while being surrounded by the medium, and the particles to be measured do not contact the inner surface of the cell.

Further, since the optical path length of the laser beam is determined by the same width of the discharge port of the nozzle irrespective of the inner width of the cell in the laser optical axis direction, the inner width of the cell is increased to facilitate the cleaning of the inner surface. Can be measured with a short optical path length,
It becomes possible to measure a sample having a substantially higher concentration than before.

[0010]

1 is a structural view of an embodiment of the present invention, FIG. 2 is a perspective view showing the structure of a cell 3, and FIG. 3 is a longitudinal sectional view of the cell 3 cut along a plane including a laser optical axis L. is there.

A sample suspension or emulsion (hereinafter, simply referred to as a suspension) S in which particles to be measured are dispersed in a medium.
Is stored in a suspension reservoir 1 provided with a stirring device 1a, and introduced into a cell 3 by opening a stop valve 2 as described later.

The cell 3 has a rectangular shape having glass plates 31 and 32 parallel to each other, and has a medium liquid inlet 33 formed in a lower portion of a side wall thereof and a discharge port 34 formed in an upper portion thereof. Apart from these, a nozzle 35 is inserted in a watertight manner from the bottom portion into the inside. The nozzle 35 has a slit-shaped discharge port 35a formed at the tip thereof, and the longitudinal direction of the discharge port 35a is the optical axis L of the laser light described later.
, That is, the glass plates 31 and 32
Are fixed to the cell 3 at the central portion between the glass plates 31 and 32 in a state of being parallel to.

The stop valve 2 communicates with the nozzle 35 via the pipe 4. When the stop valve 2 is opened, the suspension S is introduced into the cell 3 from the discharge port 35a of the nozzle 35.

On the other hand, the inlet 33 of the cell 3 communicates with the medium reservoir 7 containing the same type of medium M as the medium used for the suspension S via the pressure regulating valve 5. . Cell 3
Is connected to the suction port of the pump 6. Therefore, by driving the pump 6, the medium M is supplied into the cell 3 through the inlet 33 by the constant pressure set by the pressure regulating valve 5. It flows under pressure (flow velocity).

A laser light source 8 is disposed on one outer side of the cell 3, and a condenser lens 9 and a condensing lens 9 are disposed on the optical axis L of the laser light on the opposite side of the cell 3. A detector 10 on the focal plane is provided, and the diffracted / scattered light by the group of particles to be measured in the cell 3 is combined by the condenser lens 9 on the light receiving surface of the detector 10. The detector 10 is, for example, a plurality of photosensors having semi-ring-shaped light receiving surfaces having different radii and arranged concentrically around the laser optical axis L. The intensity of the diffracted / scattered light is determined from the output of each sensor. (Light intensity for each diffraction / scattering angle) can be obtained. The output of the detector 10 is taken into a computer 12 via an amplifier and an A / D converter 11, and a baseline measurement result or the like based on a blank measurement value (output of the detector 10 in a state where only the medium is flown) is obtained. In addition, it is converted into the particle size distribution of the particle group to be measured by a known calculation.

Next, the operation of the above embodiment of the present invention will be described together with the method of using the same. First, the pump 6 is driven with the stop valve 2 closed, and the medium liquid M is caused to flow into the cell 3 under a constant pressure (flow rate) to perform a blank measurement. When the stop valve 2 is opened in that state, the suspension S is sucked and the discharge port 3
5a flows into the flow of the medium M, and these flow out of the cell 3 from the outlet 34. FIG. 4 is a sectional view of the cell 3 showing this state. In the optical path space of the laser light,
The suspension S has a width w in the direction of the optical axis L of the discharge port 35a in the medium M.
Therefore, the optical path length is substantially equal to the width w of the discharge port 35a, and the inner surface of the glass plates 31 and 32 of the cell 3 has the suspension S at least in the vicinity of the laser beam irradiation portion. Are not in contact with each other, the particles to be measured do not adhere thereto, and the glass plate 31,
Even if the distance between the inner surfaces of the 32 is increased to facilitate the cleaning, the measurement can be performed under a short optical path length.

FIG. 5 is a sectional view of a main part of a cell 30 according to another embodiment of the present invention. The difference between the cell 30 in this example and the cell 3 in the previous example is that a glass plate 301 for irradiating the cell 30 with a laser beam and a glass plate 302 opposed thereto are provided.
Are squeezed inward on the upstream side of the flow of the suspension S and the medium M from the laser beam irradiation part, and the opposing surfaces of the two on the optical axis L of the laser light due to the presence of the throttle part 300 The difference is that the distance between them is smaller than that on the upstream side, and the other configurations are the same as those in the previous example.

In this example, when the stop valve 2 is opened as in the previous example with the medium M flowing, the suspension S similarly flows out of the discharge port 35a of the nozzle 35 into the medium M. However, since the entire flow is throttled in the direction along the optical axis L of the laser beam in the throttle unit 300, the thickness of the flow of the suspension S in the direction of the optical axis L is equal to the optical axis L of the discharge port 35a of the nozzle 35. The width becomes smaller than the width w in the direction, and the optical path length can be made smaller than in the previous embodiment.

Therefore, in this embodiment, the nozzle 35
By setting the width dimension w of the discharge port 35a in the direction of the optical axis L to such an extent that the largest expected particle can pass through, the optical path length is further shortened, and the upper limit of the measurable suspension concentration Can be greatly increased as compared with the related art.

That is, in the laser diffraction / scattering method, the concentration of the sample suspension or emulsion must be usually 0.1% or less. The reason for this is that when the concentration is high, multiple diffraction (scattering) occurs in which light diffracted / scattered by one particle hits another particle and is diffracted / scattered again. In order to reduce this phenomenon, there is a method of shortening the optical path length other than reducing the concentration. In the conventional apparatus, the optical path length was shortened by reducing the thickness of the cell in the optical axis direction. However, this measure not only causes large particles to be caught in the cell but also makes cleaning extremely difficult.
Using the cell 30 of the embodiment shown in FIG.
By making the width w of the discharge port 35a slightly larger than the diameter of the largest particle as described above, the thickness of the flow of the suspension S in the L direction on the optical axis L, that is, the optical path length becomes Since the particle diameter can be shorter than the maximum particle diameter, the upper limit of the concentration at which multiple diffraction (scattering) does not occur is greatly relaxed, and a high-concentration sample can be measured.

[0021]

As described above, according to the present invention,
In a cell for flowing a sample suspension or an emulsion, a nozzle having a slit-shaped outlet is arranged so that the longitudinal direction of the outlet is orthogonal to the optical axis of the irradiation laser light, and A separate introduction port is provided to allow the medium to flow into the cell, and the sample suspension or emulsion flows from the nozzle outlet along the flow of the medium in a state surrounded by the medium. Therefore, the thickness of the flow of the sample suspension or emulsion in the direction of the laser optical axis is almost the same as the width of the discharge port of the nozzle in the same direction. Measurement error of diffraction / scattered light does not occur by adhering to the surface, and even if the inner surface width of the cell in the laser optical axis direction is widened to facilitate the inner surface cleaning work, measurement with a short optical path length becomes possible. Substantially higher concentrations of the sample can be measured.

[Brief description of the drawings]

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

FIG. 2 is a perspective view showing the structure of the cell 3;

FIG. 3 is a longitudinal sectional view showing the structure of the cell 3;

FIG. 4 is an operation explanatory view of an embodiment of the present invention shown in a sectional view of a main part of a cell 3.

FIG. 5 is a longitudinal sectional view of a main part of a cell according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Suspension reservoir 2 Stop valve 3 Cell 31, 32 Glass plate 33 Inlet 34 Outlet 35 Nozzle 35a Discharge port 6 Pump 7 Medium reservoir 8 Laser light source 9 Condensing lens 10 Detector 12 Computer S Suspension M Medium L laser beam axis

Claims (1)

(57) [Claims] 1. A suspension or emulsion in which particles to be measured are dispersed in a medium is flowed into a cell, and the suspension or emulsion is irradiated with laser light from outside the cell. In the apparatus for measuring the intensity distribution of the diffracted / scattered light obtained as described above and calculating the particle size distribution of the particle group to be measured from the measurement result, the cell has a nozzle having a slit-shaped discharge port inside. While the longitudinal direction of the outlet is arranged along the direction orthogonal to the optical path of the irradiation laser light, the outlet has an inlet separately from the nozzle, and the medium flows through the inlet into the cell. Characterized in that the suspension or the emulsion is configured to flow from a discharge port of the nozzle to a substantially central portion thereof along the flow of the medium while maintaining the width of the discharge port. Particle size distribution measuring device.