JP3697564B2 - Particle size distribution measuring device - Google Patents

Description

となる。ただし、
【数２】

【数３】

ｓは光強度分布ベクトルである。その要素ｓ_i （ｉ＝１，２，・・・ｍ）は、リングディテクタの各素子及び側方散乱光センサによって検出される入射光量である。
ｑは粒度分布（頻度分布％）ベクトルである。粒度分布範囲を有限とし、この範囲内をｎ分割して、最大値をｄ₁ 、最小値をｄ_n+1 とする。それぞれの分割区間〔ｄ_j ，ｄ_j+1 〕を一つの粒子径ｘ_j （ｊ＝１，２，・・ｎ）で代表させる。ｑの要素ｑ_j （ｊ＝１，２，・・ｎ）は、粒子径ｘ_j に対応する粒子量である。 通常は、
【数４】

となるように正規化（ノルマライズ）を行っている。
Ａは、粒度分布（ベクトル）ｑを、光強度分布（ベクトル）ｓに、返還する係数行列である。Ａの要素ａ_i,j （ｉ＝１，２，・・・ｍ，ｊ＝１，２，・・・ｎ）の物理的意味は、粒子径ｘ_j の単位粒子量の粒子群によって回折／散乱した光のｉ番目の素子に対する入射光量である。 ａ_i,j の数値は、理論的に計算することができる。これには、粒子径が光源となるレ−ザ光の波長に比べて十分に大きい場合には、Fraunhofer回折理論を用いる。しかし、粒子径がレ−ザ光の波長と同程度か、それより小さいサブミクロン野領域ではMie 散乱理論を用いる必要がある。Fraunhofer回折理論は、前方微小角散乱において、粒子径が波長に比べて充分大きな場合に有効なMie 散乱理論の優れた近似であると考えることができる。
【００１０】
Mie 散乱理論を用いて、係数行列Ａの要素を計算するためには、粒子及びそれを分散させる媒液の屈折率を設定する必要がある。
さて、数１の式に基づいて粒度分布（ベクトル）ｑの最小自乗解を求める式を導出すると、
【数５】

が得られる。ただし、Ａ^T はＡの転置行列であり、（ ）^- は逆行列を表す。 数４の右辺において、光強度分布（ベクトル）ｓの各要素は、リングディテクタおよび側方散乱光センサで検出される数値である。また、係数行列Ａは、Fraunhofer回折理論或いはMie 散乱理論を用いて予め計算しておくことができる。 従って、それらの既知のデ−タを用いて数５の計算を実行すれば、粒度分布（ベクトル）ｑが求まることは明らかである。
【００１１】
以上が、レ−ザ回折／散乱法の基本的な測定原理であるが、ここで示したのは、粒度分布の計算方法の一例であり、この他にも様々なバリエ−ションが存在する。また、センサ、ディテクタの種類、配置にかかわらずサブミクロン粒子の粒度分布を測定するためには、測定対象となる粒子及びそれを分散させる媒液の屈折率を設定する必要がある。
【００１２】
以上のレ−ザ回折／散乱法の原理に基づくこの発明の具体的実施の形態について図面を参照しながら説明する。
図１は、この発明の粒度分布測定装置の要部の斜視図である。この粒度分布測定装置では、下方向から上方向にかけて、レ−ザ光源１，コリメ−タレンズ２，セル取付台３，回折レンズ（集光レンズ）４，検出器となる前方回折／散乱光センサのリング状フォトダイオ−ドアレイ５（下側は検出面），等がこの順に配置されている。
【００１３】
前記セル取付台３には、ゼロ点設定用の媒液を入れたセル６と、試料懸濁液を入れたセル７とを並べて設置することができるようにしてある。該セル取付台３に配置するゼロ点設定用の媒液を入れたセル６及び試料懸濁液を入れたセル７の下側は透明カバ−或いはレ−ザ光透過穴が設けられている。更に、該セル取付台３は端部には側面にラック８を形成したバ−９が接続してある。そして該ラック８にはモ−タ１０で駆動するピニオン１１が噛合させてある。また、該ラック８を設けたバ−９の下側にはシャッタ１２，１３，１４が取り付けてあり、これらのシャッタがフォトセンサ１５の位置に来て光を遮蔽するとこのセル取付台３を停止させるようになっている。
【００１４】
上記構成とした粒度分布測定装置は、レ−ザ光源１から照射されたレ−ザ光をコリメ−タレンズ２で平行光線としてセル取付台３に設置されたゼロ点設定用の媒液を入れたセル６及び試料懸濁液を入れたセル７を透過させ、回折レンズ（集光レンズ）４を透過させてリング状フォトダイオ−ドアレイ５にリング状の回折／散乱像を結ぶ。この回折／散乱像を検出器（図示省略）で検出し、上記したレ−ザ回折／散乱法の原理により粒度分布を測定する。
【００１５】
次に、この粒度分布測定装置による具体的測定方法について説明する。
上記するように、前記セル取付台３は同じ形のバッチセルとしたゼロ点設定用の媒液を入れたセル６及び試料懸濁液を入れたセル７を２個セットできるようにしてラック８とピニオン１１により光軸と垂直な面で往復運動できるように構成されている。このバッチ式セルの停止位置は、ゼロ点設定用のセル６が光軸にセットされる点（図１の（１）のシャッタ１２がフォトセンサ１５を遮蔽する位置）、実測用の懸濁液を入れたセル７がスキャンされる開始点（図１の（２）のシャッタ１３がフォトセンサ１５を遮蔽する位置）、同スキャン終了点（図１の（３）のシャッタ１４がフォトセンサ１５を遮蔽する位置）、である。
【００１６】
実測時には、ゼロ点設定用セル６に媒液のみ満たし、実測用セル７には測定試料懸濁液を満たす。
この状態で、先ず、停止位置の図１の（１）でゼロ点測定を行う。続いて、実測に移ると、ラック８とピニオン１１が測定試料懸濁液を入れたセル７を図１の（２）の位置まで移動させ、回折／散乱光のデ−タ収集を開始する。次に、ラック８とピニオン１１が図１の（２）から（３）までセル７を移動させる。図２及び図３はこのときのセル７の測定箇所の移動状態を示す図である。このように、セル７を移動させつつ数カ所の粒度分布を測定する。そしてこの間の回折／散乱光デ−タは積算され平均化される。
【００１７】
この発明の粒度分布測定装置の構成は以上のようであるが、上記実施例において、セル取付台３の移動機構はラック８とピニオン１１の代わりに他の移動機構、例えばエアシリンダ或いはベルトやチェ−ン駆動機構等によってもよい。また、停止位置の制御はシャッタとフォトインタラプタによる制御としたが、パルスモ−タによる制御でもよい。なお、セル取付台３は直線運動する場合で説明したが、回転運動による場合でも同様に実施することができる。
更に、前記セル取付台３には、実施の形態ではゼロ点設定用の媒液を入れたセル６と試料懸濁液を入れたセル７とを並べて設置する実施例で説明したが、該セル取付台３には多数の測定用セルを設置するように改造することも可能であり、従ってこの場合マルチサンプラ測定も実施することができる。
【００１８】
【発明の効果】
以上詳述したように、この発明の粒度分布測定装置によれば、縦型で生じやすいサンプリング誤差を軽減することができるため測定精度を向上させることができる。また、同時に媒液によるゼロ点も測定するためその設定が簡単となる。更に、バッチセルタイプのマルチサンプラ（多数サンプル連続自動測定）へ拡張することも容易である。
【図面の簡単な説明】
【図１】 この発明の粒度分布測定装置の要部の斜視図である。
【図２】 この発明の粒度分布測定装置のセル取付台に載せたゼロ点設定用の媒液を入れたバッチセルと試料懸濁液を入れたバッチセルの一部正面図である。
【図３】 この発明の粒度分布測定装置のセル取付台を移動させつつ粒度分布を測定するときの試料懸濁液を入れたバッチセルの底面図である。
【図４】 レ−ザ回折／散乱法による粒度分布測定装置の基本的な構成を示す斜視図である。
【図５】 従来の粒度分布測定装置で使用される横型のバッチセルで粒度分布を測定する状態を示す図である。
【図６】 従来の粒度分布測定装置で使用される縦型のバッチセルで粒度分布を測定する状態を示す図である。
【図７】 従来の粒度分布測定装置で使用される縦型のバッチセルで粒度分布を測定する状態を示すバッチセルの底面図である。
【符号の説明】
１ レ−ザ光源
２ コリメ−タレンズ
３ セル取付台
４ 回折レンズ
５ フォトダイオ−ドアレイ
６ ゼロ点設定用セル
７ 試料用セル
８ ラック
９ バ−
１０ モ−タ
１１ ピニオン
１２，１３，１４ シャッタ
１５ フォトセンサ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a particle size distribution measuring device for various types of granular materials, and more particularly to a particle size distribution measuring device configured to be vertically movable as an optical system and to move a batch-type cell so as to reduce a measurement error.
[0002]
[Prior art]
Of the particle size distribution measurement methods, the wet measurement method detects the light diffracted and scattered by the particles by thoroughly stirring the sample suspension in the measurement vessel and irradiating it with laser light, and measures the particle size distribution. To do. Such a particle size distribution measuring apparatus using a laser diffraction / scattering method is roughly classified into a horizontal type and a vertical type as arrangement of optical systems. In addition, the particle size distribution measuring device has a reflux type that mixes powder samples and measures a well-stirred suspension while refluxing it with a pump, and a batch cell type that sets and measures a container with a predetermined capacity at the measurement position. There is.
[0003]
In the case of a particle size distribution measuring apparatus using a batch cell method, as shown in FIG. 5, the horizontal type is prepared by putting the suspension in a sample container 20 having a deep water depth in the vertical direction and stirring well with the stirrer 21 and then starting from the horizontal direction. -Irradiate the light and measure the diffracted / scattered light.
Similarly, in the vertical batch cell type particle size distribution measuring apparatus, as shown in FIG. 6, the suspension is put in a sample container 23 which is long in the horizontal direction and shallow in water depth, and laser light is irradiated from the vertical direction. The diffraction / scattered light is measured. Accordingly, stirring of the suspension is indispensable in the horizontal type because the influence of the sedimentation rate of the particles is large, whereas in the vertical type, it is not always necessary to stir because it is hardly affected by the sedimentation rate of the particles.
[0004]
[Problems to be solved by the invention]
Of the batch cell type particle size distribution measuring apparatus described above, the vertical type is usually not stirred by a stirrer, so that there is a large amount of unevenness of particles, i.e., when the particle size distribution is not uniform and the particle size is large. When the laser beam is irradiated to a position where the particle size distribution is relatively large, the sampling error increases. For example, in FIG. 7, if the laser beam is incidentally gathered with large diameter particles such as particles 30a, 30b, 30c,..., The measurement error increases. Some batch cell types automatically perform continuous measurement, but in such a case, many samples with large sampling errors may occur. In particular, in a vertical batch cell type particle size distribution measuring apparatus having no stirring function, a sampling error cannot be ignored for a sample having a large particle size.
[0005]
The present invention has been made paying attention to the above-described problems, and is a batch cell type particle size distribution measuring apparatus using a small amount of suspension, and even if there is a certain amount of deviation in the particle size of the distributed sample, a sampling error is caused. It is an object of the present invention to provide a particle size distribution measuring apparatus that can reduce the number and can perform continuous measurement with high accuracy even with a large number of batch cells.
[0006]
[Means for Solving the Problems]
That is, in order to solve the problems this invention to the aforementioned, the invention according to claim 1, the cell for loading a laser light source for irradiating a laser beam to the sample, the sample cell containing the sample In the particle size distribution measuring apparatus equipped with a mounting base and a detector for detecting scattered light from the sample,
The cell mounting base can be moved by a driving mechanism, and when the scattered light is measured by the detector while irradiating the sample cell with a laser beam, the measurement point in the sample cell is moved by the driving mechanism. The diffracted / scattered light data during this period is integrated and averaged .
[0007]
The invention according to claim 2 is characterized in that a zero point setting cell and a single or a plurality of sample cells are placed side by side into which the liquid for zero point setting is placed in the cell mounting base, and the driving mechanism The zero point setting cell and the sample cell can be moved to the irradiation position of the laser beam, respectively.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
First, the principle of the laser diffraction / scattering method will be described.
FIG. 4 is a diagram showing a basic configuration of a particle size distribution measuring apparatus using a laser diffraction / scattering method. As shown in this figure, Les - is irradiated with laser light, the light intensity distribution pattern of spatially diffracted / scattered light - - Les the particles 30 to be measured from the laser light source 1 down occurs. Among these, the light intensity distribution pattern of the forward scattered light is collected by the diffraction lens 4 and forms a ring-shaped diffraction / scattered image on the detection surface at the focal length. This is detected by the ring-shaped photodiode array 5. Further, the side scattered light and the back scattered light are detected by the side scattered sensor 31 and the back scattered sensor 32.
[0009]
This light intensity distribution pattern varies depending on the size of the particles. Since particles of different sizes are mixed in an actual sample, the light intensity distribution pattern generated from the particle group is an overlap of diffracted / scattered light from each particle.
If this is expressed in a matrix,
[Expression 1]

It becomes. However,
[Expression 2]

[Equation 3]

s is a light intensity distribution vector. The element s _i (i = 1, 2,... M) is the amount of incident light detected by each element of the ring detector and the side scattered light sensor.
q is a particle size distribution (frequency distribution%) vector. The particle size distribution range is finite, and the range is divided into n, and the maximum value is d ₁ and the minimum value is d _{n + 1} . Each divided section [d _j , d _{j + 1} ] is represented by one particle diameter x _j (j = 1, 2,... N). The element q _j (j = 1, 2,... n) of q is the amount of particles corresponding to the particle diameter x _j . Normally,
[Expression 4]

Normalization is performed so that
A is a coefficient matrix that returns the particle size distribution (vector) q to the light intensity distribution (vector) s. Element a _i of A, j (i = 1,2, ··· m, j = 1,2, ··· n) The physical meaning of the diffracted by the particles of unit particles of particle size x _j / This is the amount of light incident on the i-th element of scattered light. The numerical value of a _{i, j} can be calculated theoretically. For this, the Fraunhofer diffraction theory is used when the particle diameter is sufficiently larger than the wavelength of the laser beam as the light source. However, it is necessary to use the Mie scattering theory in the sub-micron field region where the particle diameter is the same as or smaller than the wavelength of the laser beam. The Fraunhofer diffraction theory can be considered as an excellent approximation of the Mie scattering theory, which is effective when the particle diameter is sufficiently larger than the wavelength in forward small angle scattering.
[0010]
In order to calculate the elements of the coefficient matrix A using the Mie scattering theory, it is necessary to set the refractive index of the particles and the liquid medium in which the particles are dispersed.
Now, when deriving an equation for obtaining the least squares solution of the particle size distribution (vector) q based on the equation of Equation 1,
[Equation 5]

Is obtained. Here, ^AT is a transposed matrix of A, and () ⁻ represents an inverse matrix. On the right side of Equation 4, each element of the light intensity distribution (vector) s is a numerical value detected by the ring detector and the side scattered light sensor. The coefficient matrix A can be calculated in advance using Fraunhofer diffraction theory or Mie scattering theory. Therefore, it is obvious that the particle size distribution (vector) q can be obtained by performing the calculation of Formula 5 using these known data.
[0011]
The above is the basic measurement principle of the laser diffraction / scattering method. What has been shown here is an example of a method for calculating the particle size distribution, and there are various other variations. The sensor, the type of detector, in order to measure the particle size distribution of submicron particles regardless arrangement, it is necessary to set the refractive index of the particles and medium liquid dispersing it be measured.
[0012]
A specific embodiment of the present invention based on the principle of the above laser diffraction / scattering method will be described with reference to the drawings.
FIG. 1 is a perspective view of the main part of the particle size distribution measuring apparatus of the present invention. In this particle size distribution measuring apparatus, a laser light source 1, a collimator lens 2, a cell mounting base 3, a diffractive lens (condensing lens) 4, a forward diffracted / scattered light sensor serving as a detector from the lower direction to the upper direction. A ring-shaped photodiode array 5 (lower side is a detection surface), etc. are arranged in this order.
[0013]
On the cell mount 3, a cell 6 containing a medium for setting a zero point and a cell 7 containing a sample suspension can be installed side by side. A transparent cover or a laser light transmitting hole is provided on the lower side of the cell 6 containing the medium for zero point setting and the cell 7 containing the sample suspension arranged on the cell mounting base 3. Further, a bar 9 having a rack 8 formed on a side surface is connected to the end of the cell mounting base 3. The rack 8 is engaged with a pinion 11 driven by a motor 10. Further, shutters 12, 13, and 14 are attached to the lower side of the bar 9 provided with the rack 8. When these shutters come to the position of the photosensor 15 and shield the light, the cell mounting base 3 is stopped. It is supposed to let you.
[0014]
Particle size distribution measuring apparatus with the above configuration is - a laser light collimator - - Le emitted from laser light source 1 placed transfer fluid for zero-setting installed in the cell mount 3 as parallel rays in data lens 2 The cell 6 and the cell 7 containing the sample suspension are transmitted, and the diffraction lens (condensing lens) 4 is transmitted to form a ring-shaped diffraction / scattering image on the ring-shaped photodiode array 5. This diffraction / scattering image is detected by a detector (not shown), and the particle size distribution is measured by the principle of the laser diffraction / scattering method described above.
[0015]
Next, a specific measuring method using this particle size distribution measuring apparatus will be described.
As described above, the cell mounting base 3 has the same shape as a batch cell, the cell 6 containing the zero point setting liquid and the cell 7 containing the sample suspension so that two racks 8 can be set. The pinion 11 is configured to reciprocate on a plane perpendicular to the optical axis. The stop position of this batch type cell is the point where the cell 6 for setting the zero point is set on the optical axis (the position where the shutter 12 in FIG. 1 (1) shields the photosensor 15), the suspension for measurement. 1 is scanned (the position where the shutter 13 in FIG. 1 (2) shields the photosensor 15), and the scanning end point (the shutter 14 in (3) of FIG. Shielding position).
[0016]
At the time of actual measurement, the zero point setting cell 6 is filled with only the liquid medium, and the actual measurement cell 7 is filled with the measurement sample suspension.
In this state, first, zero point measurement is performed at (1) in FIG. Subsequently, in actual measurement, the rack 8 and the pinion 11 move the cell 7 containing the measurement sample suspension to the position (2) in FIG. 1, and start collecting data of diffracted / scattered light. Next, the rack 8 and the pinion 11 move the cell 7 from ( 2) to (3) in FIG. 2 and 3 are diagrams showing the movement state of the measurement location of the cell 7 at this time. In this way, particle size distributions at several locations are measured while moving the cell 7. The diffracted / scattered light data during this period is integrated and averaged.
[0017]
The configuration of the particle size distribution measuring apparatus of the present invention is as described above. In the above embodiment, the moving mechanism of the cell mount 3 is replaced with another moving mechanism such as an air cylinder, a belt or a chain instead of the rack 8 and the pinion 11. It may also be a negative drive mechanism or the like. The stop position is controlled by the shutter and the photo interrupter, but may be controlled by a pulse motor. In addition, although the cell mounting base 3 demonstrated in the case of a linear motion, it can implement similarly also in the case of a rotational motion.
Further, in the embodiment, the cell mounting base 3 has been described in the embodiment in which the cell 6 containing the medium for setting the zero point and the cell 7 containing the sample suspension are installed side by side. It is possible to modify the mounting base 3 so that a large number of measurement cells are installed. Therefore, in this case, multi-sampler measurement can also be performed.
[0018]
【The invention's effect】
As described above in detail, according to the particle size distribution measuring apparatus of the present invention, it is possible to reduce the sampling error that is likely to occur in the vertical type, so that the measurement accuracy can be improved. At the same time, since the zero point due to the liquid medium is also measured, the setting becomes simple. Furthermore, it is easy to expand to a batch cell type multisampler (multiple sample continuous automatic measurement).
[Brief description of the drawings]
FIG. 1 is a perspective view of a main part of a particle size distribution measuring apparatus according to the present invention.
FIG. 2 is a partial front view of a batch cell containing a zero point setting medium liquid and a batch cell containing a sample suspension placed on a cell mount of the particle size distribution measuring apparatus of the present invention.
FIG. 3 is a bottom view of a batch cell containing a sample suspension when a particle size distribution is measured while moving a cell mount of the particle size distribution measuring device of the present invention.
FIG. 4 is a perspective view showing a basic configuration of a particle size distribution measuring apparatus using a laser diffraction / scattering method.
FIG. 5 is a diagram showing a state in which a particle size distribution is measured by a horizontal batch cell used in a conventional particle size distribution measuring apparatus.
FIG. 6 is a diagram showing a state in which a particle size distribution is measured by a vertical batch cell used in a conventional particle size distribution measuring apparatus.
FIG. 7 is a bottom view of a batch cell showing a state in which a particle size distribution is measured by a vertical batch cell used in a conventional particle size distribution measuring apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Laser light source 2 Collimator lens 3 Cell mounting base 4 Diffraction lens 5 Photodiode array 6 Zero point setting cell 7 Sample cell 8 Rack 9 Bar
10 motor 11 pinion 12, 13, 14 shutter 15 photo sensor

Claims (2)

In a particle size distribution measuring apparatus comprising a laser light source for irradiating a sample with laser light, a cell mounting base for mounting a sample cell containing the sample, and a detector for detecting scattered light from the sample,
The cell mounting base can be moved by a driving mechanism, and when the scattered light is measured by the detector while irradiating the sample cell with a laser beam, the measurement point in the sample cell is moved by the driving mechanism. The particle size distribution measuring apparatus characterized by integrating and averaging the diffraction / scattered light data between them. A zero-point setting cell and a single or a plurality of sample cells for placing a medium for zero-point setting on the cell mount are installed side by side, and the driving mechanism sets the zero-point setting cell and the sample cell The particle size distribution measuring device according to claim 1, wherein the particle size distribution measuring device can be moved to an irradiation position of the laser beam.

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