JP2001056282A - Particle size distribution measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a particle size distribution measuring device capable of executing continuous measurement of particle sizes of salt crystals in a salt manufacturing process or the like by an in-line system. SOLUTION: A fixed quantity of crystals 2 is thrown into a sedimentation leg 5. A particle size distribution is obtained from a time range in which the crystals 2 sediment in liquid 4 and passes through a sensor 6 and from a measurement output of the sensor 6. The weight of the crystals 2 is measured by the sensor 6. Time ranges in which the crystals 2 classified in each particle size range pass through the sensor 6 are memorized. A correction formula obtained from a proportional relation between an integrated value of an output of the sensor 6 in the time range and an integrated value in the time range corresponding to a particle size range different therefrom is memorized. A calibration curve obtained from the relation between the integrated value of the measurement output in the time range and the crystal weight is memorized. The measurement output is integrated in the time range, and the integrated value is corrected by the correction formula, and a weight distribution in each particle size range is calculated by using the calibration curve from the integrated and corrected value. The weight distribution is corrected corresponding to the density of the liquid 4 detected by a differetial pressure gage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a particle size distribution measuring device for measuring a particle size distribution of a powder by a sedimentation method.

[0002]

2. Description of the Related Art Conventionally, a particle size distribution measuring method that has been used includes a method of measuring after sampling a powder as in "Testing method for screening of chemical products" (JIS-K-0069),
As described in "Method for Measuring Particle Size Distribution of Fine Ceramics Raw Material by Laser Diffraction / Scattering Method" (JIS-R-1629), there are some which can directly measure the slurry concentration of the suspension of the powder, although there are restrictions.

[0003] The sedimentation method is described in "General rules for measuring particle size distribution of powder by liquid phase sedimentation method" (JIS-Z-8820) and "Method of measuring particle size distribution of powder by sedimentation mass method" (JIS- Z-8822),
As in "Method for measuring particle size distribution of fine ceramics powder by liquid sedimentation light transmission method" (JIS-R-1619), it is necessary to measure spherical particles with Reynolds number in the Stokes region of sampled powder. Used. In these official methods, the sedimentation leg is filled with a liquid having a constant composition and a known density at the temperature to be measured.

[0004]

However, in the measurement such as the "screening method for chemical products", the measurement must be performed after sampling the powder, which is troublesome. However, there is a drawback that the measurement cannot be performed if the slurry concentration of the powder suspension is high, for example, in the method of "Method for Measuring Particle Size Distribution by Particles". Furthermore, there is no case that can be applied in-line in the measurement by the sedimentation method.

Further, in the official method using the sedimentation method, it is impossible to measure the particle size distribution of particles other than spherical particles having a small particle size such that the sampled particle has a Reynolds number in the Stokes region. For example, there is a drawback in that it is not possible to measure a crystal having a non-spherical particle shape or an allene region having a particle size of about 2000 μm, such as a crystal formed by crystallization such as a sodium chloride crystal. In addition, there is a drawback that if the properties of the liquid change due to impurities contained in the liquid filling the sedimentation legs or fluctuations in the temperature of the liquid due to the influence of the outside air temperature, the measurement error increases.

As an example of measuring the particle size distribution of the powder in the step of producing the powder, there is a method implemented in a salt factory that industrially produces sodium chloride. In the salt production process, raw seawater is produced by using an ion-exchange membrane electrodialysis tank to produce brine, which is concentrated brine, and the brine is further concentrated by an evaporation method using a vacuum evaporator to produce sodium chloride crystals. Measuring the particle size distribution of sodium chloride crystals produced in an evaporator and the standard deviation of this distribution is important for quality control and operation control. At present, salt testing methods (Salt Business Center, April 1, 9
138-141). However, in this method, not only are sampling, sample pretreatment, and measurement operations complicated, but also the time required for these operations is enormous. For this reason, the particle size distribution measurement at a salt factory is performed only several times a day in one evaporator, and these data are used only for quality evaluation, and are fed back to the process and used for operation management. At present, it is not applicable to the purpose, and there is a demand for an apparatus and a method capable of continuous measurement in-line. SUMMARY OF THE INVENTION It is an object of the present invention to provide a particle size distribution measuring apparatus capable of performing in-line continuous measurement. In the sedimentation method, reducing the effect of density change due to the composition or temperature of the liquid that causes the particles to settle is particularly useful when applied in-line, and it is also an issue to provide such a particle size distribution measuring device. And

[0007]

According to a first aspect of the present invention, there is provided a particle size distribution measuring apparatus for sampling a fixed amount of powder from a main pipe through which a suspension of the powder flows, and A settling leg for settling a certain amount of powder,
A sensor for measuring the weight or volume of the powder settling on the settling leg, wherein the powder is measured based on a time range required for the powder settling on the settling leg to pass through the sensor and a measurement output of the sensor. It is characterized in that the particle size distribution of the body is obtained.

A particle size distribution measuring apparatus according to a second aspect of the present invention is provided with the configuration according to the first aspect, wherein in the particle size distribution measuring apparatus using a sedimentation method, the powder classified into each particle size range is used. Using a calibration curve and a correction formula previously determined from the time range required for the sedimentation leg to settle and pass through the sensor, the measurement output of the sensor, and the powder weight, the powder for measuring the particle size distribution is settled. After the measured output when sedimenting and passing through the sensor is corrected by the correction formula, the weight distribution of each particle size range is calculated by the calibration curve to obtain the particle size distribution.

Further, the particle size distribution measuring device according to claim 3 of the present invention comprises a sedimentation leg for sedimenting a certain amount of powder, a sensor for measuring the weight or volume of the powder sedimenting the sedimentation leg, Density detecting means for detecting the density of the liquid filled in the settling legs, a time range required for the powder that settles in the settling legs to pass through the sensor, a measurement output of the sensor, and the density detection. The particle size distribution of the powder is obtained from the density detected by the means.

The particle size distribution measuring device according to a fourth aspect of the present invention is provided with the configuration according to the third aspect, wherein the sedimentation leg in which the powder classified into each particle size range is filled with the liquid adjusted to the reference density. Using a calibration curve and a correction formula previously determined from the time range required to settle and pass through the sensor and the measurement output of the sensor and the powder weight, the powder for which the particle size distribution is to be settled down the settling legs. After the measurement output when passing through the sensor is corrected by the correction formula, the weight distribution of each particle size range is calculated by the calibration curve to determine the particle size distribution, and the particle size distribution is adjusted for the powder. Using the density correction formula obtained in advance by measuring the particle size distribution at the reference density and other densities, correcting the obtained particle size distribution based on the density detected by the density detecting means and the density correction formula. To obtain the particle size distribution.

According to a fifth aspect of the present invention, there is provided a particle size distribution measuring apparatus according to the third or fourth aspect, wherein the density detecting means comprises two points having different heights for the liquid filled in the settling legs. The density of the liquid is detected by a differential pressure gauge that measures a pressure difference between the liquids.

Therefore, the particle size distribution measuring device according to the first aspect of the present invention automatically measures the particle size distribution by sampling automatically and in-line measures the particle size distribution of the suspension of the powder having a high slurry concentration. It becomes possible to measure.

The particle size distribution measuring device according to the second aspect of the present invention has the same effect as that of the first aspect, and also has a large particle size regardless of the shape of the particles, even if the crystals formed by crystallization are large. The particle size distribution of the powder can be measured.

In the particle size distribution measuring apparatus according to the third aspect of the present invention, it is not necessary to prepare a liquid adjusted to a reference density as a liquid to be filled in the sedimentation leg when performing in-line measurement. The particle size distribution can be measured irrespective of the property change due to the influence of, which is suitable for in-line measurement.

Further, the particle size distribution measuring apparatus according to claim 4 of the present invention has the same effect as that of claim 3, and uses a density correction formula, so that the calibration curve is only one for the reference density. Well, the configuration is simple.

According to the particle size distribution measuring device of the present invention, the same effect as that of the third or fourth aspect can be obtained, and the liquid filled in the sedimentation leg has different heights. Since the density is detected from the pressure difference between the two, it is possible to measure the average density of the liquid filled in the sedimentation leg, and to express the property change due to the influence of impurities and temperature of the liquid at the time of measurement with the density measurement value And the measurement error of the particle size distribution can be reduced.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a particle size distribution measuring device according to claim 1 of the present invention. In the figure, 1 is a crystallizer, 2 is a salt crystal as a powder precipitated as crystals from the crystallizer 1, 3 is a suspension in which the crystals 2 are uniformly distributed, and 4 is a specific gravity smaller than the crystals 2. And crystal 2
5, a sedimentation leg filled with the liquid 4 and having a certain height, 6 a sensor provided below the sedimentation leg 5 for measuring the weight or volume of the crystal 2 sedimented in the liquid 4,
7 is a discharge valve provided below the sensor 6 to discharge the crystal 2 and the liquid 4, 8 is a liquid supply device for supplying the liquid 4 to the sedimentation leg 5 and the sensor 6, and 9 is a cleaning liquid for supplying the sedimentation leg 5 and the sensor 6. The cleaning liquid supply device 10 is a main pipe through which the suspension 3 flows, 11 is a bypass branched from the main pipe 10 and the suspension 3 flows, and 12 is a flow of the suspension 3 through the main pipe 10 and the bypass 11. Three-way valve for changing the flow path that can be changed,
A sampling three-way valve 13 is provided in the main pipe 10 downstream of the three-way valve 12 for changing the flow path and serves as a sampling means for automatically feeding a certain amount of crystals 2 to the sedimentation leg 5.
A is a measurement control unit composed of a personal computer.

In the present apparatus, the crystals 2 precipitated as crystals in the crystallizer 1 flow through the main pipe 10 as a suspension 3. At the time of measurement, the measurement control unit A controls switching of the three-way valve 12 for changing the flow path and the three-way valve 13 for sampling,
At the same time, the flow path of the suspension 3 is changed to the bypass 11 by the three-way valve 12 for changing the flow path, and at the same time, a certain amount of the crystal 2 is put into the sedimentation leg 5 by the three-way valve 13 for sampling. Thereby, the flow of the suspension 3 is returned to the main pipe 10. Thereby, the charged crystal 2 is gravity-sedimented in the liquid 4 and classified, and then passes through the sensor 6. On this occasion,
The measurement control unit A obtains a particle size distribution from the time range required for the crystal 2 to pass through the sensor 6 and the measurement output of the sensor 6. When the measurement is completed, the crystal 2 and the liquid 4 are discharged from the discharge valve 7 and the cleaning liquid is supplied from the cleaning liquid supply device 9 to clean the settling leg 5 and the sensor 6, and then the liquid 4 is supplied and settled by the liquid supply device. Fill legs 5

(Measurement Method Using This Apparatus) FIG. 2 is a diagram mainly showing details of the measurement control unit A corresponding to the particle size distribution measurement apparatus according to the second aspect of the present invention. The measurement control unit A is constituted by a personal computer or the like, and it is well known that various arithmetic functions can be realized by executing a program in a personal computer by a CPU. Since it can be realized by a known storage device, FIG. 2 shows the details of the measurement control unit A in a functional block diagram.

In the figure, reference numerals 2 to 13 are the same as those in FIG. 1, and a signal 14 indicates a measured output obtained by measuring the weight or volume of the crystal 2 by the sensor 6. Reference numeral 15 denotes time range data obtained by previously measuring a time range required for the crystals classified into respective particle size ranges to pass through the sensor 6 by a sieve or the like, and 16 denotes a time required for the classified crystals to pass the sensor 6. A correction equation previously determined from a proportional relationship between the integral value of the measured output in the range and the integral value in the time range corresponding to the particle size range different from the above, 17 represents the correction value in the time range required for the classified crystal to pass through the sensor 6. A calibration curve previously obtained from the relationship between the integrated value of the measured output and the crystal weight, 18 is an integral calculating section for integrating the measured output 14 in the time range data 15, data 19 is an integrated value output from the integral calculating section 18, and 20 is an integral value. The integral value 19 is obtained by the correction formula 16
, A data 21 is an integral correction value output from the corrector 20, and 22 is a calculation unit that calculates the weight distribution of each particle size range from the integral correction value 21 using the calibration curve 17 and obtains the particle size distribution. It is.

In the present apparatus, first, the measurement output of the sensor 6 was obtained using crystals classified into each particle size range. From this result, the time range required for the crystals classified into the respective particle size ranges to pass through the sensor 6 is obtained as time range data 15, and the integration in the time range required for the classified crystals to pass through the sensor 6 is obtained. Calibration curve 1
7 was sought.

(Measurement Example Using This Apparatus) Here, as a measurement example in which the shape of the particles is not spherical, from 850 μm to 200 μm
The results obtained by measuring sodium chloride crystal particles classified into 6 stages using a 0 μm sieve as sample crystal 2 are shown.

In this embodiment, the inner diameter is 50 mm and the height is 3000 mm.
, And an absorbance meter was used as the sensor 6.
A saturated aqueous solution of sodium chloride was introduced and circulated into the sedimentation leg 5 to fill the liquid, and was allowed to stand for a while. Then, the sampling three-way valve 13 was opened to allow the sample crystal to settle in the sedimentation leg 5. In the measurement, the sampling three-way valve 13 was opened, the output voltage of the absorbance meter was converted by the AD converter, and the data was acquired for 600 seconds at an interval of 0.02 seconds by the notebook computer as the measurement control unit A. The AD converter is NR-11 manufactured by Keyence Corporation.
0, the absorbance meter used was JT-6100 manufactured by Tokyo Koden Co., Ltd., and the notebook computer used was PC-9821nf manufactured by NEC Corporation. All experiments were performed at room temperature.

FIG. 3 shows the measured output (voltage) of the absorptiometer (sensor 6) when the classified sample crystals are individually put into the sedimentation leg 5 and settled. In this result, although the magnitude relationship of the particle size is seen at the rise of each measurement output, the end time overlaps with the rise of the measurement output on the smaller particle size side. Due to the overlap of the measured outputs, the integrated values of the measured outputs in the time range required to pass through the sensor 6 when the classified sample crystals are mixed and settled have an influence on each other for each particle size range, This effect was obtained as a correction equation 16 as follows.

FIG. 4 is a diagram showing an example of a method for obtaining a correction equation. FIG. 4A shows the individual measurement outputs of the two kinds of sample crystals having a single particle size classified on one coordinate by adjusting the measurement time. FIG. 4 (B) is a plot of the measurement output in the case where the same two types of sample crystals are mixed, with respect to the measurement time.

In this example, the integrated value S1 in the time range R1 required for the crystal classified in FIG. 4A to pass through the sensor 6 (the area between the curve L1 and the time axis).
And the corrected integrated value S1 'in the different time range R2 (the area of the hatched portion between the right half of the curve L1 and the time axis)
Is proportional (S1 ′ = A1 × S1: A1 is a constant). Therefore, as shown in FIG. 4B, when measuring the particle size distribution of a sample in which crystal particles of various particle sizes are mixed, the time range R1 Value I1 of this sample (sample in which crystal grains of various particle sizes are mixed)
From the area of the portion between the curve L and the time axis in the time range R1 in FIG. 4B, the corrected integrated value S1 '(S1 in FIG. 4A)
(The area of the hatched portion of FIG. 4) was obtained, and it was assumed that this was substantially equal to S1 ′ (the hatched portion) of FIG. 4 (B). Similarly, the corrected integrated value S3 ″ (the area of the hatched portion in S3 in FIG. 4A) obtained from the integrated value S3 (the portion between the curve L3 and the time range R3 in FIG. 4A). ) Is also substantially equal to S3 ″ in FIG. 4 (B), and the integrated value I2 of this sample in the time range (curve L in the time range R2) is obtained.
From the area between the time axis and the time axis)
And the corrected integral value S3 '' are subtracted to obtain an integral value S2 solely on the small particle size side.

As described above, when the measurement output of a crystal particle of one kind of particle size range (particle size serving as a classification standard) changes with time, the integral value of the time range in which the crystal particle of the particle size range passes is obtained. From the above, the integrated value of the measurement output through which the crystal particles having a different particle size range pass in the same time range is predicted, and the predicted integrated value is calculated from the integrated value obtained when the crystal particles having different particle sizes are mixed. By subtracting,
Since we are trying to find the integral value of the particle size alone,
In each particle size range, the relationship can be determined by organizing these relationships and solving simultaneous equations.

For example, the case of three types of particle sizes as shown in FIG. 4B will be described.
S2 and S3 are the integrated value I1 of the sample in the time range R1, the integrated value I2 of the sample in the time range R2, the integrated value I3 of the sample in the time range R3, and a coefficient that is previously known for each particle size. It can be obtained by solving the following simultaneous equations based on A1, B1, B2, and C1.

[0029]

(Equation 1)

Note that the coefficient A1 is the predicted value of S1 (S1 ') of the overlapping portion of the time intervals R1 and R2 and the proportional coefficient of S1 as a whole, and the coefficient B1 is the predicted value of S2 of the overlapping portion of the time intervals R1 and R2 and S2 The overall proportional coefficient, coefficient B2, is the predicted value of S2 at the overlap of time intervals R2 and R3 and the proportional coefficient of S2, and coefficient C1 is the predicted value of S3 at the overlap of time intervals R2 and R3, and the proportional coefficient of S3. It is.

Next, using the results obtained from the classified sample crystals, the particle size distribution of the sample crystals in which the crystal particles having various particle sizes are mixed is measured. First, the crystal 2 charged into the sedimentation leg 5 filled with the liquid 4 passes through the sensor 6 after being classified by gravity sedimentation in the sedimentation leg 5. At this time, the measurement output 14 from the sensor 6 is integrated by the integration calculator 18 in the time range of the time range data 15 to obtain an integrated value 19. However, the integrated value 19 obtained here includes an error due to the overlap of the measurement outputs of the crystals classified into the respective particle size ranges. Therefore, the correction unit 20 calculates the integral value 19 from the correction expression 16.
And an integral correction value 21 is obtained. That is, as described above, the integral correction value 21 is obtained by sequentially correcting the integral value of each particle size alone. Next, the arithmetic unit 22 calculates the weight distribution of each particle size range from the integral correction value 21 using the calibration curve 17 and obtains the particle size distribution from the weight distribution.

Here, as an example of the measurement by the present apparatus, the results obtained by comparing the average particle diameter and the standard deviation of sodium chloride crystals between the measurement according to the second embodiment of the present invention and the measurement using a sieve are shown in FIGS. Shown in From these results, the measurement results of the two were in good agreement with each other, and the average error was 19 μm in average particle diameter and 15 μm in standard deviation.

FIG. 7 is a view showing a main part of a particle size distribution measuring apparatus according to another embodiment of the present invention. In FIG.
Elements denoted by 22 are the same as those in FIG. 1 or FIG. 2, and the detailed description is omitted. In FIG. 7, reference numeral 31a denotes a pressure gauge attached to the sedimentation leg 5 near the sampling three-way valve 13, and reference numeral 31b denotes a pressure gauge attached to the sedimentation leg 5 near the upper portion of the sensor 6. This pressure gauge 31
Each of a and 31b detects the pressure of the liquid 4 in the settling leg 5, and the differential pressure of the detected pressure is converted into an average density by the density output unit 31c.

As described above, the pressure gauges 31a and 31b and the density output section 31c constitute a differential pressure gauge 31 as a density detecting means. The average density of the liquid 4 is determined by the differential pressure detected by the pressure gauges 31a and 31b and the pressure gauges 31a and 31b.
Needless to say, it can be obtained from the distance between 31b.

In this embodiment, the crystal 2
Flows through the main pipe 10 as the suspension 3. At the time of measurement,
A certain amount of crystal 2 is introduced into the settling leg 5 by the sampling three-way valve 13. The charged crystal 2 passes through the sensor 6 after being classified by gravity settling in the liquid 4. On this occasion,
The particle size distribution is determined from the time range required for the crystal 2 to pass through the sensor 6 and the average density of the liquid 4 measured from the measurement output of the sensor 6 and the measurement output of the differential pressure gauge 31. In addition,
When the measurement is completed, the crystal 2 and the liquid 4 are discharged from the discharge valve 7 and the cleaning liquid is supplied from the cleaning liquid supply device 9 to clean the settling leg 5 and the sensor 6, and then the liquid 4 is supplied and settled by the liquid supply device. Fill legs 5

In FIG. 7, reference numeral 23 denotes the data of the particle size distribution output from the arithmetic unit 22, and reference numeral 24 denotes a value obtained in advance by measuring the particle size distribution of the crystal whose particle size distribution has been adjusted at the reference density and other densities. Density correction formula, 25 is differential pressure gauge 3
Average density data measured from the measurement output of No. 1, 26
Denotes a density correction unit for performing density correction on the particle size distribution 23 based on the density correction formula 24 and the density data 25.

In the present apparatus, first, the measured output of the sensor 6 at the reference density was obtained using the crystals classified into the respective particle size ranges. From this result, similarly to the above embodiment, the time range required for the crystals classified into the respective particle size ranges to pass through the sensor 6 is measured as time range data 15, and the classified crystals pass through the sensor 6. The calibration curve 17 was determined from the relationship between the integral value and the crystal weight in the time range required for the measurement.

At this time, in the example in which the sodium chloride crystal particles were measured, the time range data 15 overlapped, and the integrated value in the time range required for the classified crystals to pass through the sensor 6 was calculated for each particle size range. Therefore, as in the above-described embodiment, this influence was obtained as a correction equation 16.

Subsequently, the measured output 1 of the sensor 6 was measured at the reference density and other densities using the powder whose particle size distribution was adjusted.
4 was obtained. From this result, the particle size distribution was calculated using the calibration curve 17 and the correction formula 16, and the density correction formula 24 was obtained from the relationship between the particle size distribution measured at the reference density and the particle size distribution measured at other densities. .

Here, the average particle size is 800 μm, and the standard deviation is 2
For the prepared crystals of 50 μm, the liquid density 1.2
At 0, 1.25 and 1.30 g / cm ³ , the sensor 6
When the output was measured, a result almost as shown in FIG. 12 was obtained. As shown in the figure, the rising time and peak time of the output (absorbance) tend to be slower as the density increases. However, there was no large difference in the integrated value of the absorbance output (the area surrounded by the curve) even when the density was changed, and no correlation was found between the integrated value and the density. Thus, it is considered that the influence of the density of the liquid is greater on the settling time than on the integrated value of the absorbance, and that the output becomes a time delayed waveform as the density increases.

Therefore, a calibration curve obtained at a density of 1.20 g / cm ³ in the same manner as in the above-described embodiment was obtained.
The measurement was performed by applying to estimation of the particle size distribution at 1.30 g / cm ³ . As an example of this measurement, sodium chloride crystal particles are used as crystals, and the average particle size is 300 μm to 1300 μm.
Liquids 1.20, 1.25, 1.3 for crystals prepared in three types with different μm and standard deviation of 50 μm each.
In 0 g / cm ^3, and calculating the average particle diameter and the standard deviation by the correction equation calibration curve measured at the reference density 1.20 g / cm ^3. Then, the results were stapled against the measured values by the sieving method, as shown in FIGS. 10 and 11. Thus, it is understood that the relationship between the two is favorably correlated with the straight line passing through the origin at each density. Therefore, a density correction equation was obtained from this relationship.

Here, the correlation equation in FIG.
(3).

[0043]

(Equation 2)

In addition, the correlation equation in FIG.
(6).

[0045]

(Equation 3)

In these approximations, the slope tends to decrease as the density increases. Based on the above approximation, for example, from the estimated value Le of the particle size as shown in the following expression for the case of density ρ = 1.25: It was found that when the correction value Lc of the particle diameter was obtained, the error of the correction value and the error of the standard deviation were also reduced.

[0047]

(Equation 4)

Therefore, the following equations (7) and (8) were prepared from the previous equations (1) to (6).

[0049]

(Equation 5)

Then, as described above, the sodium chloride crystal particles are used as crystals, and the average particle size is from 300 μm to 130 μm.
Crystals prepared in three types having a difference of 0 μm and a standard deviation of 50, respectively, were subjected to liquid densities of 1.20, 1.25, and 1.30 g / c.
At m ³ , the average particle diameter and the standard deviation were calculated from the calibration curve and the correction formula for the reference density of 1.20 g / cm ³ , and were corrected by the density correction formulas (7) and (8). FIG. 8 and FIG. 9 show the results obtained by dot stitching on the measured values obtained by the sieving method. Thus, it can be seen that the measured results of the two agree very well.

The differential pressure gauge 31 according to the embodiment detects the average density of the liquid 4 from the position at which sedimentation starts to just before passing through the sensor 6 in the sedimentation leg 5 to improve the measurement accuracy. ing. In other words, the speed of the crystal 2 which settles in the liquid 4 is affected by all the densities in the sedimentation process. Since the average density is detected in almost all the sedimentation processes, the influence of the density is sufficiently corrected. it can.

[0052]

According to the particle size distribution measuring device according to the first aspect of the present invention, the particle size distribution is measured by automatically sampling, and the particle size distribution of the suspension having a high slurry concentration is measured in-line. can do.

Further, according to the particle size distribution measuring apparatus according to the second aspect of the present invention, it is possible to measure the particle size distribution of a crystal having a large particle size, regardless of the shape of the crystal formed by crystallization. .

According to the particle size distribution measuring apparatus of the third aspect of the present invention, when measuring in-line, it is not necessary to prepare a liquid adjusted to a reference density as a liquid to be filled in the settling legs. The particle size distribution can be measured irrespective of the property change due to the influence of temperature or temperature, which is suitable for in-line measurement.

According to the particle size distribution measuring apparatus of the present invention, the same effect as that of the third aspect is obtained, and the calibration curve is only one for the reference density because the density correction formula is used. And the configuration becomes simple.

Further, according to the particle size distribution measuring apparatus of the present invention, the same effect as that of the third or fourth aspect can be obtained, and the height of the liquid filled in the settling legs is different between two points. Since the density is detected from the pressure difference, the average density of the liquid filled in the sedimentation leg can be measured,
Changes in properties due to the influence of impurities and temperature of the liquid at the time of measurement can be represented by density measurement values, and furthermore, measurement errors in the particle size distribution can be reduced.

[Brief description of the drawings]

FIG. 1 is a view for explaining an embodiment of a particle size distribution measuring device according to claim 1 of the present invention.

FIG. 2 is a view for explaining an embodiment of a particle size distribution measuring device according to claim 2 of the present invention.

FIG. 3 is a diagram showing the results of measuring the classified sodium chloride crystal particles as crystals.

FIG. 4 is a diagram showing an example of a method for obtaining a correction equation in the embodiment of the present invention.

FIG. 5 is a view showing a result of comparing the average particle diameter of sodium chloride crystals between the measurement according to the embodiment of the present invention and the measurement using a sieve.

FIG. 6 is a diagram showing a result of comparing the standard deviation of sodium chloride crystals between the measurement by the embodiment of the present invention and the measurement by the sieve.

FIG. 7 is a view showing a main part of a particle size distribution measuring apparatus according to claims 3 to 5 of the present invention.

FIG. 8 is a view showing the results of comparing the average particle diameter of sodium chloride crystals between the measurement according to the examples of claims 3 to 5 of the present invention and the measurement using a sieve.

FIG. 9 is a diagram showing the results of comparison between the measurement according to the examples of claims 3 to 5 of the present invention and the measurement using a sieve with respect to the standard deviation of sodium chloride crystals.

FIG. 10 is a diagram showing a result of comparing the average particle diameter calculated based on the reference density of sodium chloride crystals with the measurement by the examples according to claims 3 to 5 of the present invention and the measurement by a sieve.

FIG. 11 is a graph showing the results of comparison between the measurement according to the examples of claims 3 to 5 of the present invention and the measurement using a sieve with respect to the standard deviation calculated based on the reference density of sodium chloride crystals.

FIG. 12 is a graph showing measurement results showing changes in sedimentation velocity with respect to changes in density of sodium chloride crystals.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Crystallizer, 2 ... Crystal (powder), 3 ... Suspension, 4 ... Liquid, 5 ... Sedimentation leg, 6 ... Sensor, 7 ... Discharge valve, 8 ... Liquid supply device, 9 ... Cleaning liquid supply device, 10 ... Main piping, 11
... bypass, 12 ... three-way valve for changing flow path, 13 ... three-way valve for sampling, 14 ... measurement output, 15 ... time range data, 16 ... correction formula, 17 ... calibration curve, 18 ... integral calculation unit,
19: integral value, 20: correction unit, 21: integral correction value, 22
... Calculation unit, 24 ... Density correction formula, 26 ... Density correction unit, 31
… Differential pressure gauge

Claims (5)

[Claims] 1. A sampling means for sampling a fixed amount of powder from a main pipe through which a suspension of powder flows, a settling leg for sinking the sampled fixed amount of powder, and a sinker for setting the settling leg. A sensor for measuring the weight or volume of the powder, the particle size distribution of the powder from the time range required for the powder to settle on the settling leg to pass through the sensor and the measurement output of the sensor. A particle size distribution measuring device characterized by being obtained. 2. In a particle size distribution measuring apparatus using a sedimentation method, a time range required for powder classified into each particle size range to settle on the sedimentation leg and pass through the sensor, and measurement of the sensor Using a calibration curve and a correction formula obtained in advance from the output and the powder weight, after correcting the measurement output when the powder whose particle size is measured settles down the sedimentation leg and passes through the sensor, using the correction formula 2. The particle size distribution measuring apparatus according to claim 1, wherein a weight distribution in each particle size range is calculated by the calibration curve to obtain a particle size distribution. 3. A sedimentation leg that sediments a certain amount of powder, a sensor that measures the weight or volume of the powder that sediments the sedimentation leg, and a density detector that detects the density of a liquid filled in the sedimentation leg. Means, and the particle size distribution of the powder from the time range required for the powder settling on the settling leg to pass through the sensor, the measurement output of the sensor, and the density detected by the density detection means. A particle size distribution measuring device characterized by being obtained. 4. The time range required for the powder classified into each particle size range to settle on the settling leg filled with the liquid prepared to the reference density and pass through the sensor, the measurement output of the sensor and the powder output. Using a calibration curve and a correction formula obtained in advance from the body weight, the measurement output when the powder whose particle size distribution is settled down the sedimentation leg and passed through the sensor was corrected by the correction formula, and then the calibration was performed. Calculate the weight distribution of each particle size range by the line to obtain the particle size distribution, and the density correction formula previously obtained by measuring the particle size distribution at the above-mentioned reference density and other densities for the powder having the prepared particle size distribution. 4. The particle size distribution measuring device according to claim 3, wherein the particle size distribution is obtained by correcting the obtained particle size distribution based on the density detected by the density detecting means and the density correction formula. . 5. The apparatus according to claim 1, wherein said density detecting means detects the density of the liquid filled in the settling leg by a differential pressure gauge which measures a pressure difference between two points having different heights. 5. The particle size distribution measuring device according to 3 or 4.