JPH0686975B2 - Adsorption amount measuring device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an apparatus for measuring the physical adsorption amount of a sample by the volumetric method, and also to an apparatus that can be used for a specific surface area measuring apparatus and a pore distribution measuring apparatus by the adsorption method. .

<Prior art> In the measurement of the adsorption amount by the volume method, in general, a sample is put into a sample cell, a gas phase adsorbate is filled in the cell, and the volume, temperature, and pressure change of the space in the cell are changed. From quantity,
Measure the amount of sample adsorbed. When making this measurement,
In order to make physical adsorption dominant, the sample cell is immersed in a coolant such as liquid nitrogen. And in this case,
It is extremely important to keep the immersion depth of the sample cell in the refrigerant, that is, the inner volume of the cell immersed in the refrigerant constant, in order to improve the measurement accuracy.

Therefore, conventionally, in order to keep the liquid surface of the refrigerant in the Dewar containing the refrigerant constant, a tank for storing the refrigerant is separately provided, and the liquid in the storage tank is automatically detected by the liquid level detection signal in the Dewar. In general, it is made to flow into the Dewar bottle.

Conventionally, there are several types of methods for supplying the refrigerant into the Dewar bottle, and for example, FIG. 4 shows an example of the configuration. This example is called a natural pressurization type, in which the tank internal pressure due to the vaporization of the refrigerant in the storage tank 41 is maintained at a predetermined pressure by a relief valve 42, and a transport pipe between the Dewar bottle 43 and the storage tank 41.
In the middle of 44, an electromagnetic on-off valve 45 is provided, and when the liquid level sensor 46 provided in the Dewar bottle 43 detects a decrease in the refrigerant liquid level, by opening the electromagnetic on-off valve 45 by a command from the controller 47, The refrigerant is introduced into the Dewar bottle 43.

Further, FIG. 5 shows a main part of a conventional device called a cryo-type. In this method, the internal pressure of the storage tank 51 is set to atmospheric pressure, and the inner pipe 52a and the outer pipe 52b are internally provided.
The siphon tube 52 consisting of is inserted, the valves 52c and 52d are attached to the lower ends of the inner tube 52a and the outer tube 52b, respectively, and the drive signal of the motor 58 is generated from the controller 57 based on the output of the liquid level sensor, By expanding and contracting the bellows 59, the refrigerant is guided into the Dewar via the transport pipe 54.

<Problems to be solved by the invention> By the way, the rate of weight reduction due to vaporization of a refrigerant such as liquid nitrogen (hereinafter referred to as LN ₂ ) in a Dewar bottle is The amount of heat from the sample inflows, the heat of adsorption is generated when the adsorbed gas is introduced, or the measurement takes a long time, so it is not constant due to changes in room temperature and atmospheric pressure. Therefore, the supply interval of LN ₂ is not constant, and when the supply of LN ₂ is not necessary for a long time, the supply is repeated many times or once. Since the amount was insufficient, the temperature of the transport pipe and the like is remarkably different from that when the gas is supplied again.

When LN ₂ is not supplied for a long period of time, the temperature of the LN ₂ transport path such as the transport pipe is high and LN ₂ may boil violently during transportation and may flow into the Dewar bottle as a jet. , As a result, it disturbs the liquid level in the Dewar bottle,
Alternatively, there is a problem that the LN ₂ in the Dewar bottle is agitated to cause a temperature change, which deteriorates the measurement accuracy of the adsorption amount.

In particular, although the natural pressurizing type and the like are cheaper than the cryotor type, the above-mentioned phenomenon is remarkable because the electromagnetic on-off valve 45 has a large heat capacity. In addition, in each type, a simple type of Teflon (trade name) tube covered with foam insulation was used instead of an expensive vacuum double tube. Even in this case, the ejection into the Dewar bottle becomes severe. The same applies when the transport pipe is made longer.

The object of the present invention is to supply a liquid-phase refrigerant such as LN ₂ from the storage tank into the Dewar bottle as a jet flow into the Dewar bottle even if it has not been supplied for a long time. Therefore, it is an object of the present invention to provide an adsorption amount measuring device capable of highly accurate adsorption amount measurement by improving the refrigerant liquid level accuracy in the Dewar bottle and stabilizing the refrigerant temperature in the Dewar bottle. .

<Means for Solving Problems> The configuration of the present invention will be described based on the basic conceptual diagram shown in FIG. 1. The adsorption amount measuring apparatus of the present invention comprises a sample cell 1 containing a sample W to be measured. , A refrigerant supply device a which is immersed in the liquid phase refrigerant in the Dewar bottle 2 and operates based on the output from the sensor 3 in the Dewar bottle 2 in order to keep the liquid level of the refrigerant in the Dewar bottle 2 constant. By supplying the refrigerant in the refrigerant storage tank 4 into the Dewar bottle 2 via the transport pipe 5 by this refrigerant supply device a, a certain range of the sample cell 1 is cooled, and in that state, the sample cell 1 In a device for measuring the physical adsorption amount of a sample W to be measured by filling the inside thereof with a gas phase adsorbate, a gas-liquid separator b is arranged in the middle of the transport pipe 5, and a refrigerant supply device a The means c for instructing the temporary supply is provided, and It is characterized in that a small amount of the refrigerant in the refrigerant storage tank 4 is temporarily supplied prior to the operation of supplying the refrigerant.

<Operation> If a predetermined small amount of refrigerant is temporarily supplied before actually supplying the refrigerant into the Dewar bottle 2, even if a long time has elapsed since the previous supply of the refrigerant, the transport pipe 5, the gas-liquid separator When the refrigerant passage such as b is cooled and the refrigerant is actually supplied in that state, the refrigerant may flow into the Dewar bottle 2 as a jet in combination with the action of the gas-liquid separator b. Absent. Further, at the time of provisional supply, the provisional supply of the refrigerant does not disturb the liquid level in the Dewar bottle 2 by providing a small amount of the supply of the refrigerant and further providing the gas-liquid separator b. .

<Example> An example of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram of an embodiment of the present invention.

The sample cell 1 in which the sample W to be measured is enclosed is hermetically connected to a gas reservoir (not shown) via the cell connecting portion 1a. A pressure gauge for measuring the pressure in the system, a vacuum gauge, a vacuum pump, a helium source as a non-adsorbate, a nitrogen source as an adsorbed gas, and the like are connected to the gas reservoir, and the adsorption amount of the sample is measured by a known capacitance method. To be measured.

The sample cell 1 is immersed in LN ₂ as a refrigerant contained in the Dewar bottle 2. A liquid level sensor 3 is provided in the Dewar bottle 2 and is configured to output a detection signal when the liquid level of LN ₂ drops below a specified position.

Storage tank 4, when the LN ₂ amount in the dewar 2 is reduced, a tank for storing LN ₂ for performing the replenishment, and LN ₂ inlet 4a which may be sealed, the interior of the LN ₂ A relief valve 4b for releasing an excessive increase in internal pressure due to vaporization and maintaining the internal pressure at a predetermined value is provided. In this storage tank 4,
One end of the suction pipe 6 is inserted, and the other end of the suction pipe 6 communicates with one end of the first transport pipe 5a via an electromagnetic opening / closing valve 7. When the solenoid valve 7 is opened, LN ₂ in the storage tank 4
Is the first transport pipe 5a via the suction pipe 6 due to the tank internal pressure.
Will be led to.

The other end of the first transport pipe 5a is open inside the LN ₂ trap 8. The LN ₂ trap 8 is for separating the inflowing LN ₂ and its vaporized gas (hereinafter referred to as GN ₂ ), and has a gas outlet 8a at the top and a liquid outlet 8b at the bottom. This LN ₂
The liquid outlet 8b of the trap 8 is passed through a second transport pipe 5b formed by covering the outer wall of the Teflon (trade name) tube with a heat insulating material,
It communicates with the Dewar bottle 2.

The electromagnetic opening / closing valve 7 is opened / closed by an operation signal from the controller 9. The controller 9 inputs the detection signal from the liquid level sensor and controls the opening / closing of the electromagnetic opening / closing valve 7 based on the logic as described below.

FIG. 3 is a flowchart showing the logic of the controller 9. Based on the output signal of the liquid level sensor 3, after waiting for 10 seconds when the LN ₂ in Dewar 2 to determine whether they meet or are missing, they meet and repeats the determination. If there is a shortage, first, a timer (referred to as an experience timer) that measures the elapsed time from the previous supply time is immediately determined by determining whether or not it is a predetermined fixed time, for example, 60 seconds or more. It is determined whether to actually supply LN ₂ (hereinafter, referred to as main supply) or to supply a predetermined trace amount of LN ₂ (hereinafter, referred to as temporary supply) before the main supply.

When the experience timer is over 60 seconds, the previous LN
₂ Long time has passed from the time of supply, and the first and second transportation pipes 5
a and 5b, the LN ₂ supply path such as the LN ₂ trap 8 and the solenoid on-off valve 7 is warm, so if this supply is executed immediately, the presence of the LN ₂ trap 8 will still cause LN ₂ , G
There is a risk that N ₂ will flow in as a jet flow, so in this case, provisional supply before the main supply is performed. The temporary supply is performed by opening the electromagnetic opening / closing valve 7 for a predetermined minute time, for example, 1 second. Initially, by the time LN ₂ reaches the second transport pipe 5b, it becomes GN ₂ and is discharged from the gas outlet 8a of the LN ₂ trap 8. Such provisional supply, for example,
By repeating 10 times, all the supply paths up to the second transport pipe 5b are cooled. Then, after this operation, the main supply is executed. The main supply is performed by opening the electromagnetic opening / closing valve 7 for only 6 seconds, for example. As a result, at the time of main supply
LN ₂ does not flow into the Dewar ₂ as a jet.

If the experience timer is less than 60 seconds, the LN ₂ supply path is not so warm, and in this case, the main supply is executed immediately.

In the above embodiment, when the LN ₂ in Dewar 2 is insufficient, although it is determined whether to execute the temporary supply by time measurement result by experience timer, without this determination, of the supply The provisional supply may be performed before the execution.

Further, although the example in which the present invention is applied to the naturally pressurized LN ₂ supply device has been described above, it goes without saying that the present invention can also be applied to a cryotor type as shown in FIG.

<Effect> As described above, according to the present invention, the gas-liquid separator is provided in the refrigerant supply path between the Dewar bottle and the storage tank, and the vaporized portion of the refrigerant is disposed in front of the Dewar bottle. In addition, since the supply passage is cooled by flowing a small amount of the refrigerant prior to the actual supply of the refrigerant, the supply passage is always kept at a predetermined temperature or less at the time of the actual supply of the refrigerant. The refrigerant can flow into the Dewar as a jet and disturb the liquid level, or the temperature is not changed by stirring, and highly accurate adsorption amount measurement is possible. Further, conventionally, even in the case of a naturally pressurized type supply device in which the ejection phenomenon of the refrigerant is remarkable due to the presence of the electromagnetic on-off valve, which is inexpensive, the ejection phenomenon is suppressed by the present invention,
It has become fully usable. Further, for the same reason, it becomes possible to use a tube covered with a heat insulating material without using an expensive vacuum double tube for the transportation tube. It is needless to say that the present invention can further improve the liquid level accuracy and stabilize the temperature by using a cryostat-type supply device and a vacuum double pipe transport pipe.

[Brief description of drawings]

FIG. 1 is a basic conceptual diagram showing the configuration of the present invention, FIG. 2 is a configuration diagram of an embodiment of the present invention, FIG. 3 is a flow chart showing the supply logic of the opening / closing operation signal of the electromagnetic on-off valve 7 by the controller 9, FIG. 4 and FIG. 5 are diagrams showing a conventional device configuration. 1 ... Sample cell, 2 ... Dewar bottle 3 ... Liquid level sensor, 4 ... Storage tank 4b ... Relief valve, 5a ... First supply pipe 5b ... Second transport pipe, 6 ... Suction Tube 7: electromagnetic on-off valve, 8: LN ₂ trap 9: controller

Claims (1)

[Claims] 1. A sample cell in which a sample to be measured is enclosed is immersed in a liquid phase refrigerant in a Dewar bottle, and in order to keep the liquid level of the refrigerant in the Dewar bottle constant, Provided with a refrigerant supply device that operates based on the output, by supplying the refrigerant in the refrigerant storage tank by the refrigerant supply device into the Dewar via the transport pipe, to cool a certain range of the sample cell, In the state of filling the gas phase adsorbate in the sample cell, in the device for measuring the physical adsorption amount of the sample to be measured, with the gas-liquid separator in the middle of the transport pipe, in the refrigerant supply device On the other hand, an adsorption amount measuring device comprising means for instructing the temporary supply of the refrigerant, and temporarily supplying a small amount of the refrigerant in the refrigerant storage tank prior to the operation of supplying the refrigerant by the refrigerant supply device.