JPS5950926B2 - Powder specific surface area diameter measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention allows gas, for example, air to pass through a sample powder-filled layer, and depending on the permeability, the specific surface area diameter of the sample powder can be determined.
That is, the present invention relates to an improvement of a powder specific surface area diameter measuring device for measuring an average particle diameter.

When the sample powder is considered to be composed of spherical uniform particles, the specific surface area of the powder is 5w, and the flow rate of a fluid, such as air, passing through the powder-filled layer during a certain period of time is Q.
At that time, the following Ko2eny-Carman (Ko2eny-Carman) is present between the pressure difference △P between both ends of the packed layer.
lan) generally holds true.

,',00,. ......) However, η・L−
Q K−・・・・・・・・・(O), △P−A−ε=1−−・・・・・・・・・f→ ρ・A−L Here ε: Sample filling layer , ρ: density of sample powder, η: viscosity coefficient of air, L: thickness of sample layer, A: cross-sectional view of sample layer, W: weight of sample.

Therefore, to determine the specific surface area Sw of the sample powder based on formula (a), a sample powder with a weight W weighed in advance is put into a sample cell, and is appropriately compressed and filled with a filling piston. Air at a constant pressure higher than atmospheric pressure is sent into this packed layer, and the air is allowed to permeate, and the pressure drop caused by the resistance during permeation, that is, the differential pressure △P between both ends of the sample layer, is calculated for a certain period of time, for example, 1 second. The amount of permeated air Q is measured.

Assuming that the sample powder consists of a single sample with clear components, the density ρ is known, the cross-sectional area A of the sample layer is known as the characteristic value of the sample-filled cell, and the thickness L of the sample layer is Since the value of , is known from the stroke position of the filling piston at the end of filling, the porosity ε of the sample filling layer is calculated by equation (c). Regarding the K value, the viscosity coefficient η of air is known, L and A are known as described above, and Q/t, for example, the amount of permeated air per second,
The differential pressure ΔP between both ends of the sample layer can be obtained as a measured value or calculated using the equation. Therefore, ρ,K
, ε are determined as known values or calculated values, the specific surface area Sw of the sample powder is determined by performing calculations according to equation (A). Further, if the specific surface area diameter of the sample powder, that is, the average particle diameter is Dm, then if the specific surface area Sw is determined, the density ρ of the sample powder is known, so the particle diameter Dm of the sample powder can be easily calculated. .

Therefore, when measuring the specific surface area Sw and specific surface area diameter, that is, the average particle diameter Dm, of a sample powder using a powder specific surface area diameter measuring device based on the air permeation method, it is especially important to use the above-mentioned ΔP and It is desirable that both values of Q/t can be measured accurately and quickly. Figures 1 and 2 are △
A graph showing how Q/t changes in response to the average particle diameter Dm of the sample powder by changing the porosity ε when P = 5g/Cnl2, 2OOg/CIn. It is.

From these figures, when the average particle diameter Dm is 1μ or less, the resistance when air permeates through the powder-filled layer is large, so the pressure difference △P between both ends of the packed layer is increased to allow air to pass through, and the average particle diameter Dm When is considerably larger than 1μ, it is preferable to keep the pressure difference ΔP small, and when the degree of filling is rough, that is, when the porosity ε is large, the amount of permeated air Q/t per second becomes large. It can be seen that the measurement of Q/t must be carried out over a wide range without compromising accuracy. If the sample powder is a fine particle with a particle size of about 1 μm, the differential pressure between both ends of the sample packed layer will be quite large, so it is preferable to make the measurement with a small Q/t. If the body is coarse particles, the differential pressure will be small, so it is preferable to send a large amount of Q/t to measure in order to obtain the differential pressure necessary for measurement.
In order to measure Q/t accurately over a wide range, the measurement range has traditionally been set according to the size of Q/t, for example from O to
0.05cc/S, O~1.0cc/S, O~20.0
Switching is performed in three stages of cc/s. Further, depending on the particle size of the sample powder, a large difference occurs in the differential pressure generated between both ends of the sample-filled layer. Therefore, in order to accurately and quickly measure both the above-mentioned values of Q/T and ΔP, the following measures are taken in the conventional apparatus. That is, the output electrical signal of the differential pressure gauge that measures the pressure difference ΔP is input to the differential pressure setting servo amplifier, and the air pump is driven by a servo motor operated by the output signal of the servo amplifier. An automatic control circuit is provided to change the pressure of permeated air and control the pressure difference ΔP, and the servo amplifier can be set to one of three set differential pressures, for example, 5.50 and 200 g/Cm2. Connect the differential pressure setting circuit as described above, and set the switching setting of the differential pressure setting circuit described above while watching the indicated value of the flowmeter so that Q/t is measured close to the full scale of each range described above. A means of manual operation is provided. By taking such measures, it has become possible to measure the flow rate with high precision and in a fairly short time. However, conventional devices equipped with such means, such as Japanese Patent Publication No. 50-1695,
Particle size measuring device according to Publication No. 7-1 - This servo amplifier 1
The reference voltage 21 inputted to 9 is used to manually set one of the three types of set differential pressures described above in a stepwise manner. However, the automation of measurement is still at the first step, and the current situation is that it is not sufficient to shorten the measurement time. In view of the above-mentioned current situation, the present invention has been developed by providing a differential pressure calculation setting circuit that continuously calculates and sets a pressure difference appropriate for flow rate measurement with respect to the measured porosity. As mentioned above. The object of the present invention is to provide a powder specific surface area diameter measuring device that automates measurement by omitting manual stepwise differential pressure setting switching operation and enables a significant reduction in measurement time.

The powder specific surface area diameter measuring device according to the present invention consists of a sample cell 1 in which a sample powder 4 is accommodated, a piston 5 and a piston rod 7 for compressing and filling the sample powder 4 accommodated in the sample cell 1. The pressurizing means 6 and this pressurizing means 6
means 9 for supplying air from the bottom of the sample cell 1 to the sample-filled layer compressed and filled by the sample-filling layer; a flowmeter 12 for measuring the flow rate of air that has passed through the sample-filled layer; Pressure difference generated between both ends of the packed layer △
It is equipped with a differential pressure gauge 13 that measures P, and a thickness measuring device 8 that moves in synchronization with the piston 5 and measures the thickness L of the sample filling layer from the amount of displacement thereof, Powder specific surface area to determine the specific surface area diameter of the sample powder 4 from the measured values of the permeation air flow rate Q/T of the packed layer, the differential pressure △P of air pressure before and after passing through the sample packed layer, and the thickness L of the sample packed layer. In the diameter measuring device, the porosity ε is determined from the thickness value L of the sample-filled layer, ε=1−''! - When calculated based on the formula, ρ・AL, porosity ε and appropriate differential pressure △P are obtained.

The relationship between the two is inputted in advance, and the appropriate differential pressure ΔP is determined from the calculated porosity ε. A differential pressure calculation setting circuit 21 calculates and sets the differential pressure value △P measured by the differential pressure gauge 13 to the set differential pressure value △.
P. and a means for automatically controlling the air pressure supplied from the air supply means 9 to the sample cell 1 so as to match the flow rate Q/T with respect to the measured porosity ε.
By continuously calculating and setting a suitable differential pressure for measurement, manual stepwise differential pressure setting switching operation can be made automatic and continuous. EMBODIMENT OF THE INVENTION Hereinafter, the powder specific surface area diameter measuring device according to the present invention will be explained with reference to the drawings.

FIG. 3 is a schematic explanatory diagram showing the configuration of the embodiment device.

In the figure, 1 is a sample filling cell made of stainless steel, for example, which can be detachably attached to a cell holder 2, and 3 and 3' are sieve plates with a thickness of 2.
It is a metal plate with a number of pores of about 3 mm in diameter.
The upper surface and the lower surface 3' are in contact with the sample powder 4 through filter paper, respectively. 5 is a piston of a compression and filling press 6, and 7 is a piston rod.

Reference numeral 8 denotes a thickness measuring device that automatically measures the thickness L of the packed layer of the powder sample 4 by the amount of vertical movement of the detection end connected to the piston rod 7, and converts the measured value electrically. It is designed to be output as a signal, and when the piston 5 descends and the sieve plates 3 and 3' are pressed through the two plates of filter paper when there is no powder sample 4, the measured value becomes 0. Adjustments are made in advance so that

Reference numeral 9 denotes an air pump, which is connected to an introduction hole made at the bottom of the sample cell 1 through a pipe 10 and a pocket of the cell holder 2, and which pumps air sucked in through a valve (not shown) to atmospheric pressure. The purpose is to compress it to the above pressure and send it to the sample cell 1.

11 is a flow meter 1 that measures the air that has passed through the packed layer of powder sample 4.
2, a part of the piston rod 7 and the piston 5
are flexibly connected to conductive paths provided through the central portions of each.

The flow meter 12 measures the amount of permeated air Q/t per second depending on the amount, for example, 0.05cc/S, O to 1.0cc/S.
, O to 20.0 cc/s, the range is automatically switched in three steps, and the measured value is output as an electrical signal. 13 is a differential pressure gauge that measures the pressure difference ΔP between the upper and lower ends of the packed layer of the powder sample 4, and is connected to branch pipes 14 and 15 of the pipe 10 and pipe 11, respectively, and the measured value is It is designed to be output as an electrical signal.

16 is a servo amplifier, and 17 is a servo motor controlled by its output signal.

The output shaft of the servo motor 17 is connected via a gear train to a threaded rod 18 which is rotatably supported at a fixed position.
The threaded rod 18 is threadedly engaged with a piston rod 19 of the air pump 9. 19' is a rotation stopper for the piston rod 19.

Therefore, if the threaded rod 18 has a right-hand thread, for example, and the output shaft of the servo motor 17 is rotated counterclockwise in direct opposition to it, the piston rod 19 is moved to the left, and the piston 20 is pushed in. , the pressure of the air discharged to the pipe 10 is increased. 21
1 is a differential pressure calculation setting circuit, which is connected to the thickness measuring device 8 so that an electric signal indicating the measured value of the thickness L of the packed layer of the sample powder 4 is input thereto.

If the step area A of the sample layer 4, the weight W and the density ρ of the powder sample 4 are input into the calculation circuit in advance, then
When a signal indicating the thickness L of the filled layer from the thickness measuring device 8 is input, the porosity of the sample filled layer 4 is calculated by a pre-installed program to perform calculations according to formula (c). ε is calculated. In addition, in order to set an appropriate pressure difference value △PO for the calculated porosity ε when measuring the flow rate, for example, a program is created to set the appropriate pressure difference △PO from the porosity ε shown in Fig. 4. It is incorporated in the differential pressure calculation setting circuit 21 in advance. When a signal indicating the thickness L of the filling layer is input from the thickness measuring device 8 to this circuit 21, the porosity ε of the sample filling layer is calculated, and the calculated porosity ε is calculated in advance. An appropriate pressure difference ΔPO value for flow rate measurement is set by the built-in program, and a signal corresponding to the set value is input to the servo amplifier 16.
The graph for determining the appropriate value △PO for measuring the flow rate of differential pressure for the value of porosity ε shown in Figure 4 is based on the graph shown in both Figures 1 and 2 at 5 to 200 g/CIll2. For example, prepare for the differential pressure △P of 10 g/CIn2 increments between
For each value of 0.8, the amount of permeated air per second Q/t (
Cc/s) may be created by selecting the value of ΔP so as to indicate a value close to the full scale in each range of flowmeter 2.

In addition, in order to simplify the calculation process for calculating the porosity ε from the thickness L of the filled layer, it is necessary to match the weight of the powder sample 4 to be filled with the value of its density ρ, for example, the sample powder 4 of pure iron.
For this purpose, it is convenient to weigh 7.86 g, which is equal to the density ρ of the sample, into sample cell 1, and to design the area of the filled part of sample cell 1 to be, for example, 2cIn2. . This is because if you do it this way.

The servo amplifier 16 also receives the differential pressure △P from the differential pressure gauge 13.
An electrical signal indicating O is inputted.

22 is a computing unit that includes an electrical signal from the thickness measuring device 8 indicating the thickness L of the sample layer, an electrical signal indicating the amount of permeated air Q/t per second passing through the sample layer from the flow meter 12, and a differential pressure gauge. 1
The electrical signal indicating the pressure difference △P between the upper and lower ends of the sample layer from 3. These measuring instruments are connected to each other so as to be inputted, and in addition to these inputted electric signals, air viscosity η, which is inputted separately,
The cross-sectional area A of the sample layer, the density ρ of the powder sample 4 input each time, and its weight (amount W) does not need to be input.

), respectively, are electrical signals corresponding to (a), (mouth),
(c) Calculations are performed according to a pre-installed program that performs calculations according to each formula, and the sample powder 4
The specific surface area SW is calculated, and although not shown, it is displayed or recorded on a display or a recorder, respectively. Also, regarding the specific surface area diameter, that is, the average particle diameter Dm, a program is installed in advance to perform calculation processing according to equation (d), and the calculation is performed by this program, and the average particle diameter Dm is displayed or recorded.
Next, the operation of this device will be explained.

A powder sample 4 is weighed into the sample cell 1 in an amount equal to the number of points of its density ρ, and is compressed and filled by a press 6. Generally, this filling is performed so that the pressing force of the piston 5 is constant. When the filling operation is completed, the thickness L of the filling layer is automatically measured by the thickness measuring device 8, and an electric signal indicating the measured value is input to the differential pressure calculation setting circuit 21 and the calculator 22. Ru. The electrical signal input to the differential pressure calculation setting circuit 21 is processed by a pre-loaded program as described above, and the porosity ε of the sample powder 4 is calculated. Furthermore, as described above, the appropriate pressure difference △PO is converted and set by a program that sets an appropriate value for flow rate measurement of the differential pressure △P with respect to the porosity ε, which is pre-installed in this circuit 21. , this signal is input to the servo amplifier 16. Further, an output signal from the servo amplifier 16 based on this signal causes the servo motor 17 to rotate. Then, the torque is increased through the reduction gear train, and the threaded rod 18 rotatably supported at a fixed position is driven to rotate, and the piston rod 19, that is, the piston 20, is driven in the horizontal direction. piston 2
The air compressed by
0, and is fed into the sample cell 1 through the introduction hole at its bottom. The air at a pressure higher than atmospheric pressure sent into the sample cell 1 passes through the sieve plate 3 and filter paper, permeates the sample layer 4, passes through the filter paper and sieve plate 3' again, and reaches the piston of the press 6. 5 and the piston rod 7, and further passes through the pipe line IL branch pipe 15 to reach the differential pressure gauge 13. On the other hand, the air that branches from the pipe 10 and flows into the branch pipe 14 also flows into the differential pressure gauge 13. reach. Therefore, by the differential pressure gauge 13,
Differential pressure △P corresponding to the pressure drop between the upper and lower ends of the packed layer
is measured, and an electrical signal indicating the measured value is fed back to the servo amplifier 16. This feedback signal is the appropriate differential pressure ΔP that was previously input from the differential pressure calculation setting circuit 21 to the servo amplifier 16. The air pump 9 is driven by the servo motor 17 to feed air into the sample cell 1 until the two become the same, and the differential pressure △P between the upper and lower ends of the sample layer 4 is Set appropriate differential pressure △P. This differential pressure △P. The value is input from the differential pressure gauge 19 to the calculator 22 as an electrical signal. At the same time, this differential pressure △P is detected from the flow meter 12. The amount of permeated air Q/t per second is also input to the calculator 22 as an electrical signal.
In this case, the range of Q/t measured by the flowmeter 12 is automatically switched depending on the amount, and the optimum differential pressure ΔP is set so as to show a value close to the full scale. is set, the measurement at the flow meter 12 is accurate,
and is done in a short period of time. As described above, the calculator 22 includes the thickness L of the sample layer measured from the thickness measuring device 8, the flow meter 12, and the differential pressure gauge 13, the amount of permeated air per second Q/t, and the upper and lower sides of the sample layer 4. Pressure difference between both ends △P (△P
0) are input as electrical signals, and these electrical signals and electrical signals corresponding to the air viscosity η and the cross-sectional area A of the sample layer, which are input separately, are input into a pre-installed program. Yotsute (a), (
), (-1) Calculations are performed according to each formula, and sample powder 4
The specific surface area SW is calculated, and the value is displayed or recorded on a display or recorder, respectively. In addition, the specific surface area diameter, that is, the average particle Dm, is calculated according to Wataru's formula by a program installed in advance, and the value is displayed on the display or recorder in this embodiment device.
Although the thickness measuring device 8 measures its displacement via a rod that moves integrally with the piston rod 7, the measuring rod may be attached directly to the piston 5. As is clear from the above description, in the powder specific surface area diameter measuring device according to the present invention, as in the conventional device, the set differential pressure is changed in steps, for example, while checking the indicated value of the flowmeter during measurement. The time-consuming manual operation of setting an appropriate differential pressure for flow rate measurement has been changed to a continuous calculation and setting of an appropriate differential pressure for grain size measurement based on the measured porosity ε. Since it can be completely omitted by providing a differential pressure calculation setting circuit, it is possible to significantly shorten the measurement time while maintaining good flow measurement accuracy. As a result, the specific surface area diameter, that is, the average particle diameter, of a powder sample can now be measured automatically, accurately, and in a shorter time.

[Brief explanation of drawings]

Figures 1 and 2 show the pressure difference △P as 5g/Cm2,2O.
Air gap' when set to Og/Cm2
FIG. 3 is a graph showing how the amount of permeated air per second Q/t changes in accordance with the size of the average particle diameter Dm of the sample powder as the rate ε is changed. A schematic explanatory diagram showing the configuration of an example device, FIG. 4 shows differential pressure ΔP optimal for flow rate measurement. This is a graph in which the porosity is set from the porosity ε. 1...
... Sample cell, 4... Powder sample (sample filling layer), 6... Press, 8... Thickness measuring device, 9... Air Pump, 12...Flowmeter, 13...Differential pressure gauge, 21...Differential pressure calculation setting circuit, 22...Calculator, ε... ...
・Porosity, A... Cross-sectional area of sample layer, L...
...Thickness of sample layer, W... Weight of sample, ρ...
...Density of sample powder.

Claims (1)

[Claims] 1. A sample cell in which sample powder is accommodated, a pressurizing means consisting of a piston and a piston rod for compressing and filling the sample powder accommodated in this sample cell, and A means for supplying air from the bottom of the sample cell to the compressed sample-filled layer, a flow meter for measuring the flow rate of air passing through the sample-filled layer, and a pressure generated between both ends of the sample-filled layer of the permeated air. A differential pressure gauge that measures the difference;
a thickness measuring device that is configured to move in synchronization with the piston and measures the thickness of the sample-filled layer from its displacement position;
In a powder specific surface area diameter measuring device that calculates the specific surface area diameter of the sample powder from the measured values of the air pressure difference before and after passing through the sample packed layer and the thickness of the sample packed layer, the pore size is calculated from the thickness value of the sample packed layer. Let the rate ε be ε=1−W/ρ・A
Calculation is performed based on the formula of L, and the relationship between the porosity and the appropriate differential pressure is input in advance, and the calculated porosity ε
a differential pressure calculation setting circuit that calculates and sets an appropriate differential pressure from the differential pressure; and a differential pressure calculation setting circuit that automatically adjusts the air pressure supplied from the air supply means to the sample cell so that the differential pressure value measured by the differential pressure gauge matches the set differential pressure value. 1. A powder specific surface area diameter measuring device, characterized in that it is provided with a controlling means. W... Weight of sample, ρ... Density of sample powder, A...
- Cross-sectional area of the sample filling layer, L...thickness of the sample filling layer.