JPH0441296B2 - - Google Patents

Description

Detailed Description of the Invention The present invention involves raising test particles uniformly dispersed in a medium solution under centrifugal force, detecting the particle concentration at a certain lifting distance, and utilizing the difference in rising speed with respect to particle size. This invention relates to an apparatus for determining the particle size distribution of sample particles.

Generally, when particles with a lower density than the medium solution are uniformly dispersed in a medium solution and a centrifugal force is applied to the particles, the particles rise in the opposite direction to the direction of the centrifugal force, and the rising speed v is from the center of rotation to the point where the particles exist. If the distance to R is R, the rotational angular velocity is ω, the particle density is ρp, the medium solution density is ρl, the particle diameter is Dp, and the medium solution viscosity is η, then v=Rω ² (ρl−ρp) Dp ² /18η… ...(1) As is clear from this formula, the particle size
The larger Dp is, the faster the particles rise. A test sample consisting of various particles is uniformly dispersed in a medium solution and raised in a centrifugal force field. Each particle rises at a speed according to the particle size according to equation (1), and reaches a certain floating distance. Now, the concentration in this medium solution is measured in time series, and the time t on the time axis corresponding to each measurement point, that is, the time t from the start of applying centrifugal force to the time of each measurement, ( t={1.05η/N ² (ρl−ρp)} ・log(R ₁ /R ₂ )・1/Dp ² ……(2) where N ; Number of revolutions per unit time (1 second) R ₂ ; Distance between the center of rotation and the bottom of the medium solution container R ₂ ; Calculate the time t on the time axis corresponding to each measurement point by the distance between the center of rotation and the measurement position. By converting to the particle size Dp, each particle size that is considered to have finished rising from the concentration measurement position and the corresponding concentration of the medium solution are determined, and the particle size distribution can be calculated from these. can.

Particle size distribution measurement by the above-described method is applied to the measurement of particles whose density is smaller than that of a medium solution, which could not be measured using a conventional sedimentation type particle size distribution measuring device. In a centrifugal force field, as mentioned above, particles rise in the opposite direction to the direction in which centrifugal force acts, so as the particles approach the center of rotation, as shown in Fig. The distance is reduced,
An increasing number of particles or concentration per unit volume of medium solution is detected.

In order to explain the above more clearly,
Considering a test sample consisting of only one type of particles, in the gravitational field, as shown in Figure 2, the particles in the medium solution are initially stirred to a uniform state, so they are not present at the concentration measurement position. Even if the particles present at the bottom of the medium solution container rise, particles are simultaneously replenished from the bottom to the concentration measurement position, and the concentration at that position does not change. Concentration changes are detected only after passing over the measurement position. In the centrifugal force field, as shown in FIG. 3, the concentration gradually increases due to the aforementioned reduction in the distance between particles, and then decreases before being detected. The above is also true for samples made of particles of many different sizes; in a centrifugal force field, changes in concentration can be attributed to particles with a certain size finishing rising and passing through the concentration measurement position. Therefore, calculating the particle size distribution using this method includes errors due to concentration.

The present invention has been made in view of the above, and an object of the present invention is to provide a particle size distribution measuring device that can automatically correct errors caused by particle concentration in a centrifugal force field to determine a more accurate particle size distribution.

Embodiments of the present invention will be described below based on the drawings.

FIG. 4 is a block diagram showing the configuration of an embodiment of the present invention.

The apparatus consists of a container 1 that seals a sample that has been uniformly stirred into a suspension in a medium solution, a rotating disk 2 to which the container is attached, a centrifuge motor 3 that rotationally drives the rotating disk 2, and a rotation center. The light source 4 is located at a certain distance from the rotating suspension and detects the concentration of the rotating suspension by a light transmission method, the light receiving element 5 receives the light through the slit 6, and the rotating container 1 is connected to the light source 4.
measurement position detection device 7 that extracts the output of the light receiving element 5 only when it comes to a predetermined position with respect to the light receiving element 5;
an amplifier 8 that amplifies the output of the light-receiving element 5; an A-D converter 9 that converts the analog value into a digital value; and an A-D converter 9 that measures the time after centrifugal force is applied to the sample. Timer 10, a program that stores the measurement program, the above-mentioned functional equation (2) related to the time t after applying centrifugal force and the particle diameter Dp, and the correction equation for correcting errors due to particle diffusion in the centrifugal force field, which will be described later. A storage device 11, an arithmetic and control device 12 that executes the measurement program and calculates the above-mentioned function formula and the above-mentioned correction formula, and input/output ports 13 and 14 attached thereto, the measurement conditions entered in advance and the above-mentioned function formula (2) and A data storage device 15 that sequentially stores values calculated by the correction formula, a keyboard 16 for inputting measurement conditions, measurement start commands, etc. to the arithmetic and control device 12, and a concentration after correction calculated by the arithmetic and control device 12. It consists of a display 17 that displays the particle size distribution based on the data, a printer 18, and the like.

The operation of the embodiment of the present invention configured as described above will be explained below.A sample whose particle size distribution is to be measured is stirred in a medium solution and placed in a container.
and mounted on the rotating disk 2. keyboard 1
When a measurement start command is inputted to the arithmetic and control unit 12 by 6, a signal is outputted to rotate the centrifuge motor 3 via the input/output port 14 according to the measurement program stored in the program storage device 11 in advance. The centrifuge motor 3 rotates and the particles in the container 1 begin to rise inside the rotation. The rising speed v of the particle rises faster as the particle becomes larger, according to the above equation (1).
When the concentration is measured by the light transmission method using the light source 4 and the light receiving element 5 at a certain distance from the center of rotation as shown in FIG. 4, the rising process curve represented by the time-concentration correlation is shown in FIG. The result will be as shown below. In other words, at the beginning of the ascent, particles are concentrated, and large particles with the next highest velocity are ray B in Figure 4.
As the particles move higher toward the center of rotation, they no longer exist at the position of the light beam B, and as time passes, smaller particles also float to the inside of the light beam B. In this way, the detected concentration once becomes larger than the initial state and then decreases due to the aforementioned reduction in the interparticle distance.
The above function equation (2) is stored in advance in the program storage device 11, and measurement conditions η, N, ρp, ρl, R ₁ ,
R ₂ is stored in the data storage device 15. The output signal from the light receiving element 5 that receives the light beam B from the light source 4 passing through the rotating container 1 is sent to the amplifier 8, A- at regular intervals according to a measurement program stored in advance in the program storage device 1. Arithmetic and control device 12 via D converter 9 and input/output port 13
This is sequentially stored in the data storage device 15, and at the same time, the time t after the start of applying the centrifugal force corresponding to the signal reception, which is measured by the timer 10, is calculated by the function equation (2) stored in the program storage device 11.
When the arithmetic and control unit 12 converts the particle size Dp into a particle size Dp and stores it in the data storage device 15, the data storage device 15 stores the particle size that is considered to have passed the concentration detection position and the corresponding sample size. Since the concentration signal is stored, the relationship between the particle diameter and the particle amount, that is, the particle size distribution, can be calculated by the arithmetic and control unit 12 after the measurement is completed according to the measurement program. However, as mentioned above, in a centrifugal force field, there is an error in the concentration signal of the sample due to particle concentration due to a reduction in the distance between particles in the upward direction of the particles, so this can be corrected as shown below. do. In the program storage device 11,
The following formula for correcting the above error is memorized. Co is the oversize concentration at the infinitely small particle size of the sample particle, that is, when Dp = 0,
C ₁ , C ₂ ... C ₂ n is the oversize concentration after correcting the concentration in the centrifugal field, r ₁ , r ₂ ... r ₂ n is the absorbance given by the detection device before correcting the concentration. value, the subscript 1...2n is a number representing the particle section, that is, the smaller the number, the smaller the particle diameter, and k is the distance from the center of rotation to the bottom of the suspension container and the distance from the center of rotation to the concentration detection position. C ₁ = Co + 2k/(1-2k)e ^2K-1・r ₁ As described above, the particle diameter and the corresponding concentration signal are taken and stored in the data storage device 15 at certain time intervals until the measurement is completed, and the concentration signal at this time is obtained by the light transmission method using the light source 4 and the light receiving element 5. r ₁ of the above correction formula, which is converted into a predetermined electrical signal by the amplifier 8 and the A-D converter.
…corresponds to r ₂ n. The end of the measurement is determined by the arithmetic and control unit 12 when the concentration signal becomes less than a certain value set in advance in the measurement program, and the interval at which the concentration signal is taken in is set at an extremely short time interval also set in the measurement program. shall be. The way the arithmetic and control unit 12 corrects the concentration detection error caused by particle concentration using the above correction equation is to set the oversize concentration at the end of the measurement, that is, Co in the above correction equation, to Co=1. because,
This is because all the particles in the sample are considered to be larger than the point where the particle diameter is infinitely small, that is, Dp=0.
Then, the time measured by the timer 10 from the start of centrifugal force application at each concentration signal intake interval is converted into a particle diameter using the above _- mentioned function formula ( ₂ ), and the concentration is detected at the corresponding time. Concentration signals r ₁ ... r ₂ n stored in the data storage device 15 from the device are sequentially substituted into the above correction formula according to the measurement program, calculated by the arithmetic and control device 12, and sequentially stored in the data storage device 15. . This Ci is the concentration of particles larger than Dpi, which corrects the concentration of particles in the centrifugal force field, that is, the oversize concentration. When _the C ₁ .

The concentration intake interval in the embodiment of the present invention described above may be determined as described above, or if the storage capacity is small, the particle diameter for performing the above correction formula may be determined in advance, and the concentration intake interval may be determined using the function equation (2). It is also possible to calculate the sedimentation time corresponding to the particle size and to store only the concentration signal when the sedimentation time reaches the sedimentation time.

Further, although light was used to detect the concentration in the above embodiments, other electromagnetic waves may be used, and the absorbance may be the transmittance. Moreover, instead of non-contact detection, for example, a method of direct sampling and weighing may be used.

As explained above, according to the present invention, since the particle size distribution is calculated by correcting the error caused by particle concentration in the centrifugal force field, a more accurate particle size distribution can be obtained. A graph showing the particle size distribution measurement results by the device and the particle size distribution measurement results by the examples of the present invention in terms of oversize concentration (%) is shown as an example, but the sample particles have a particle size range from 15 μm to around 0 μm. It can be clearly seen that although there are apparently no particles of 9 μm or more in the conventional apparatus, according to the present invention, particles of up to 15 μm are distributed according to the particle size distribution of the sample.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the effect of particle rise in a centrifugal force field, Figs. 2 and 3 are characteristic diagrams of suspension concentration in a gravimetric field and a centrifugal force field, and Fig. 4 is an illustration of an example of the present invention. FIG. 5 is a block diagram showing the configuration, FIG. 5 is a characteristic curve diagram of the rising process, and FIG. 6 is a graph showing a comparison between a conventional particle size distribution measurement apparatus and an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Container, 2... Rotating disk, 3... Centrifuge motor, 4... Light source, 5... Light receiving element, 8... Amplifier, 9... A-D converter, 10... Timer, 11
...Program storage device, 12... Arithmetic control device, 15... Data storage device, 16... Keyboard.

Claims (1)

[Claims] 1 A container for enclosing supply particles uniformly dispersed in a medium solution; A centrifuge for attaching the container to apply centrifugal force to the sample particles; Detecting the particle concentration in the rising process of the sample particles a converter that converts the detected value into a predetermined electric signal; a timer that measures the time from the start of applying centrifugal force; a functional formula that converts the rising speed related to the particle diameter into the rising time; , a correction formula for correcting the detection error of the above-mentioned detection device due to particle concentration due to a reduction in the distance between particles in the rotation tangential direction and radial direction related to the particle floating distance of each particle upward trajectory in a centrifugal force field, and a measurement program are stored. a program storage device that executes the measurement program, calculates each particle diameter using the function formula from each elapsed time by the time measurement means, and performs the detection by the detection device using the correction formula after all the particles float. an arithmetic and control device that performs error correction; measurement conditions entered in advance, particle diameters for each elapsed time calculated using the above functional formula, and detected values for each elapsed time by the detection device; a data storage device that sequentially stores the correction results calculated using the above correction formula; A particle size distribution measurement device that corrects errors caused by particle concentration in a force field to obtain a more accurate particle size distribution.