JP2022137370A - Stirring method and apparatus for low-temperature liquefied gas mixture sample - Google Patents

Abstract

To provide a stirring method and apparatus for low-temperature liquefied gas mixture samples eliminating any necessity of separately adding a stirring device for a liquefaction container and the periphery thereof and capable of stirring a low-temperature liquefied gas mixture sample by using an existing combustion/exploration test apparatus.SOLUTION: A stirring apparatus for stirring a low-temperature liquefied gas mixture sample 3 in a combustion/exploration test for igniting by supplying a fusing current for fusing a fusing line 45, to the fusing line 45 immersed in the low-temperature liquefied gas mixture sample 3 formed by mixing a combustion-supporting low-temperature liquefied gas and a combustible material in a container 5, the stirring apparatus supplies a heating current, the current lower than the fusing current, to the fusing line 45 via a pair of conductors 41 to heat the low-temperature liquefied gas mixture sample 3, and stirs the low-temperature liquefied gas mixture sample 3 by convection generated by heating.SELECTED DRAWING: Figure 4

Description

The present invention is a combustion and explosion test of a mixture of a combustion-supporting low-temperature liquefied gas (liquid oxygen, liquid nitrogen, etc.) and a combustible substance (hereinafter referred to as a "low-temperature liquefied gas mixed sample"), especially an ignition method by a fusion cutting method. It relates to a stirring method and a stirring device for a low-temperature liquefied gas mixed sample in the one using
In addition to combustible liquefied gases such as liquid methane and liquid propane, combustible substances in the present invention include flame-retardant gases such as freon, oils and fats such as machine oil and grease, and flame-retardant materials such as metal powder and resin powder. Including flammable substances.

In order to safely handle mixtures of combustible cryogenic liquefied gases and combustible substances, it is necessary to measure the conditions that cause combustion and explosion, such as the explosion range, the minimum ignition energy, and the power of explosion.
As examples of test equipment used for such measurements, those targeting combustible gases include, for example, the "explosive limit region measuring apparatus" disclosed in Patent Document 1 and the " There is a simple facility such as a combustible gas/vapor explosion test device.
Examples of test equipment for powder include the "dust explosion test apparatus" disclosed in Patent Document 3 and the "dust explosion test apparatus and dust explosion test method" disclosed in Patent Document 4.

On the other hand, there are Patent Documents 5 and 6 as prior art relating to explosion tests of low-temperature liquefied gas. Patent Literatures 5 and 6 include a liquefaction container that cools and liquefies the introduced low-temperature liquefied gas in a gaseous state, and the low-temperature liquefied gas in the liquefaction container is maintained at a predetermined temperature. Thus, it is essential to keep the temperature and pressure in the liquefied container constant in order to stably perform the explosion test of low-temperature liquefied gas.

In addition, in order to obtain accurate test results in the explosion test of the low-temperature liquefied gas mixture sample, it is necessary to ignite the low-temperature liquefied gas mixture sample in a uniform concentration state. If the combustible substance is a substance with low solubility such as organic solvent, machine oil, grease, metal powder, resin powder, etc., or a substance that does not dissolve in the first place, sufficiently stir before ignition to reduce the concentration of the low-temperature liquefied gas mixture sample. uniformity must be ensured.

The uniformity of concentration is affected not only by the solubility of the low-temperature liquefied gas and the combustible substance, but also by the specific gravity and melting point. A case where liquid oxygen (hereinafter referred to as “LO ₂ ”) is used as the combustion-supporting low-temperature liquefied gas will be described below as an example.
If the combustible substance to be mixed with LO ₂ is, for example, liquid methane (hereinafter referred to as “LCH ₄ ”), which has a high solubility in LO ₂ , the liquid density and solid density are about 0.4 g/cc (LO ₂ is 1.14 g/cc), and the melting point is higher than the boiling point of LO _2. Therefore, simply introducing CH ₄ into LO ₂ does not result in a homogeneous layer, nor does it establish a vapor-liquid equilibrium state.
Moreover, if the combustible substance is low in solubility, such as propane or acetylene, it is difficult to achieve a uniform concentration simply by liquefying and mixing.
Therefore, even if the combustible substance is a low-temperature liquefied gas, a stirring operation is required to ensure uniform concentration.

General methods for stirring gases and liquids include those using rotary blades illustrated in FIG. and so on. However, these methods are difficult to apply to thin-walled, small-capacity liquefied containers that ensure airtightness at low temperatures, such as those used in explosion tests for low-temperature liquefied gases. In addition, a test in which a combustible substance other than the test object coexists in the system, or a test in which there is a risk of ignition due to friction of the oscillating part, etc., is also unsuitable for the test for judging the explosiveness of the test object.

Therefore, there is a method disclosed in Patent Document 7 as a stirring method applicable to the explosion test of low-temperature liquefied gas.
In Patent Document 7, the low-temperature liquefied gas in the gas state is introduced into the low-temperature liquefied gas in the liquid state in the liquefaction vessel, and the low-temperature liquefied gas is stirred by bubbling. Cryogenic liquefied gas can be stirred without

Also, as ignition methods used in the combustion/explosion test as described above, a discharge method, a heating method, and a fusion cutting method are known.
The discharge method is a method of igniting by causing discharge between a pair of spaced apart electrodes, as disclosed in Patent Documents 8 to 10, for example. The discharge method is generally widely used because it is easy to quantify emitted energy, has good reproducibility, and allows repeated use of electrodes.

In the heating method, for example, as disclosed in Patent Documents 11 to 13, Non-Patent Document 1, etc., a nichrome wire (hereinafter referred to as "Ni-Cr wire") is heated by passing an electric current through it, and the gas is heated by the heat. It is a method of igniting when the gas exceeds the self-ignition temperature. The heating method requires low voltage and low current, and the heat input can be easily estimated.

As disclosed in Non-Patent Documents 2 and 3, the fusing method is a platinum wire (hereinafter referred to as "Pt wire") or Ni-Cr wire with a current (hereinafter referred to as "fusing current") that causes the wire to break. This is a method in which a spark is used as an ignition source. The fusing method can use both alternating current and direct current and requires low voltage, so the cost of power supply equipment and power supply is low, and several J to several tens of J of emitted energy can be obtained.

JP-A-8-145921 JP-A-2010-8135 JP-A-2000-310583 JP 2011-220813 A Japanese Patent No. 6178645 Japanese Patent No. 6322103 Japanese Patent No. 6568780 JP 2013-152196 A JP-A-11-201925 Japanese Patent No. 6596264 JP-A-2006-29629 JP-A-2001-113156 Japanese Patent No. 4764728

Experimental Evaluation of Explosion Limit of Lubricating Oil, 50th Safety Engineering Research Conference Proceedings (2017), p. 79 Fiscal 2016 Commissioned by Ministry of Economy, Trade and Industry High Pressure Gas Safety Measures Project (2) High Pressure Gas Safety Regulations and Examination of Legal and Technological Issues Concerning Various Products Using High Pressure Gas Report (2017), High Pressure Gas Safety Institute, p. 11-p. 12 line 6 Research on Explosion Hazard of Hydrogen, Ministry of Labor, Industrial Safety Research Institute, Research Report RR-18-1 (1969)

The low-temperature liquefied gas stirring device of Patent Document 7 has a buffer tank that accumulates the gaseous low-temperature liquefied gas. The gaseous low-temperature liquefied gas is introduced into the liquid-state low-temperature liquefied gas inside, and the low-temperature liquefied gas is stirred by bubbling.
Therefore, in addition to the buffer tank, it is necessary to provide a heating means for heating the buffer tank, a circulation path for returning the gaseous low-temperature liquefied gas in the liquefaction container to the buffer tank, and the like around the liquefaction container.

However, in the explosion test, if an explosion occurs and the liquefaction vessel ruptures, the surroundings of the liquefaction vessel are also affected.

The present invention has been made to solve the above problems, and there is no need to add a separate device for stirring to the liquefaction vessel and its surroundings, and low-temperature liquefied gas can be obtained using existing combustion and explosion test equipment. It is an object of the present invention to provide a stirring method and a stirring apparatus for a low-temperature liquefied gas mixed sample that can stir the mixed sample.

In order to solve the above problems, the inventors have made extensive studies.
Since the configuration of the explosion test apparatus differs depending on the ignition method described above, we first examined the optimal ignition method for the combustion and explosion test of the low-temperature liquefied gas mixture sample.
Important points regarding the above considerations are as follows.

(1) Direct ignition in the liquid phase Most flame-retardant combustible substances, such as machine oil, grease, metal powder, and resin powder, have low vapor pressures, especially in LO ₂ , where oxygen gas and oxygen gas enter the gas phase in the explosion range ( concentration). Even if the liquid phase is within the explosive range, if the concentration of the combustible substance in the gas phase is not within the explosive range, even if the gas phase is ignited, it will not ignite, and flame propagation cannot be expected.
Therefore, for combustible substances with remarkably low vapor pressures at low temperatures, it is necessary to use an ignition method capable of directly igniting the liquid phase.

(2) Supply of sufficient ignition energy It is necessary to supply sufficient ignition energy to confirm the explosion range and low-temperature explosiveness of flame-retardant liquefied gases such as freon. The ISO10156 "Gases and gas mixtures-Determination of fire potential and oxidizing ability for the selection of cylinder valve outlets" standard specifies that 10J of discharge energy should be secured as the ignition energy used to determine whether a mixed gas is combustible. Therefore, in order to determine whether or not a substance is flammable or explosive, an ignition method with a corresponding release energy is desired.

From the above point of view, the ignition method suitable for the combustion/explosion test of the low-temperature liquefied gas mixed sample was examined among the three ignition methods of the discharge method, the heating method, and the fusion method.
First, in the discharge method, a voltage several hundred times higher than that in the gas phase is required for discharge ignition in the liquid phase. requires a large amount of expense.
Next, in the case of the heating method, the energy density varies depending on the surface area of the wire to be heated and the temperature difference, resulting in poor reproducibility.

On the other hand, the fusing method can use both alternating current and direct current, and can obtain a large amount of energy released compared to the discharge method and heating method. be.
From the above, the fusing method is suitable as an ignition method for combustion and explosion tests of low-temperature liquefied gas mixture samples.

In addition, the knowledge that if a combustion/explosion test device that uses the fusion cutting method as an ignition method is used, a low-temperature liquefied gas mixture sample can be stirred without adding a separate device for stirring to the existing liquefaction container and its surroundings. got
The present invention is based on such findings, and specifically includes the following configurations.

(1) The method of stirring a low-temperature liquefied gas mixed sample according to the present invention is to melt-cut the fusing line immersed in the low-temperature liquefied gas mixed sample in which the combustion-supporting low-temperature liquefied gas and the combustible substance are mixed. A method of stirring the low-temperature liquefied gas mixture sample in a combustion/explosion test in which ignition is performed by supplying a fusing current to the low-temperature liquefaction by supplying a heating current that is lower than the fusing current to the fusing line. It is characterized by heating a gas mixture sample and stirring the low-temperature liquefied gas mixture sample by convection caused by the heating.

(2) In addition, in the above-mentioned (1), the low-temperature liquefied gas is vaporized by the heating, and bubbles of the vaporized low-temperature liquefied gas are generated in the low-temperature liquefied gas in a liquid state. It is characterized by stirring a cryogenic liquefied gas mixture sample.

(3) In the above (1) or (2), the heating current is supplied so that the internal pressure of the airtight container in which the low-temperature liquefied gas mixed sample is stored does not exceed a predetermined pressure. It is characterized by

(4) Further, a low-temperature liquefied gas mixed sample stirring apparatus according to the present invention is for realizing the low-temperature liquefied gas mixed sample stirring method described in (3) above, wherein the low-temperature liquefied gas mixed sample is a cooling device for cooling the low-temperature liquefied gas mixed sample in the airtight container; an internal pressure of the airtight container is constantly detected; and a current supply device for supplying a constant heating current to the fusing wire immersed in the low-temperature liquefied gas mixed sample, wherein the current supply The device stops the supply of the heating current when a Hi signal is input from the first pressure detection device, and controls to start the supply of the heating current when a Low signal is input. It is characterized by having control means.

(5) Further, a low-temperature liquefied gas mixed sample stirring apparatus according to the present invention is for realizing the low-temperature liquefied gas mixed sample stirring method described in (3) above, wherein the low-temperature liquefied gas mixed sample is an airtight container for storing, a cooling device for cooling the low-temperature liquefied gas mixture sample in the airtight container, a second pressure detection device for constantly detecting the internal pressure of the airtight container and transmitting the detected pressure, the low temperature a current supply device for supplying a heating current to the fusing wire immersed in the liquefied gas mixed sample, wherein the current supply device PID-controls the current value of the heating current based on the input from the second pressure detection device. It is characterized by having a second control means for controlling.

In the present invention, the low-temperature liquefied gas mixed sample is heated by supplying a heating current that is lower than the fusing current to the fusing line, and the low-temperature liquefied gas mixed sample is stirred by the convection caused by the heating, whereby the liquefied container and its There is no need to add a separate device for stirring in the vicinity, and the low-temperature liquefied gas mixture sample can be stirred using the existing combustion/explosion test device.

FIG. 2 is a flow chart for explaining a method of stirring a low-temperature liquefied gas mixture sample according to Embodiment 1 of the present invention; BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing the overall structure of a combustion/explosion test apparatus to which a method for stirring a low-temperature liquefied gas mixture sample according to Embodiment 1 of the present invention is applied, and is a partial vertical cross-sectional view of the combustion/explosion test apparatus; FIG. 3 is a diagram showing an installation state of a liquefaction container installed inside a pressure-resistant and constant-temperature container in the combustion/explosion test apparatus shown in FIG. 2; FIG. 4 is a diagram showing positions for measuring temperature when controlling the temperature of a low-temperature liquefied gas mixed sample. FIG. 5 is a view showing the internal structure of the airtight container shown in FIGS. 3 and 4, and is a vertical cross-sectional view of the airtight container. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an ignition method and an apparatus configuration for ignition according to Embodiment 1 of the present invention; 4 is a graph showing values of fusing current for fusing each wire when Pt wire or Ni-Cr wire is immersed in LN _2. FIG. FIG. 6 is an explanatory diagram for explaining a cryogenic liquefied gas mixed sample stirring device according to Embodiment 2 of the present invention. FIG. 10 is an explanatory diagram for explaining a cryogenic liquefied gas mixed sample stirring device according to Embodiment 3 of the present invention. 4 is a graph showing the relationship between the supply of heating current, the concentration of methane in the gas phase, and the internal pressure of the airtight container in the example of the present invention.

[Embodiment 1]
A method of stirring a low-temperature liquefied gas mixture sample according to Embodiment 1 of the present invention stirs a low-temperature liquefied gas mixture sample before ignition in a combustion/explosion test in which ignition is performed using a fusion cutting method.
Prior to explaining the method of stirring the low-temperature liquefied gas mixture sample in the present embodiment, first, an example of a test apparatus used for the combustion/explosion test will be explained with reference to FIGS. 2 to 6. FIG.

FIG. 2 shows the overall structure of a combustion/explosion test apparatus 1 for a low-temperature liquefied gas mixture sample that is ignited using the fusion cutting method.
Since the combustion/explosion test apparatus 1 of FIG. 2 uses the same configuration as the "combustion/explosion test apparatus" described in Patent Document 5, detailed description thereof will be omitted, and main portions will be outlined below. It should be noted that the names of the members used in the explanation are not necessarily the same as those of the "combustion/explosion test apparatus" of Patent Document 5.
Also, the "combustion/explosion test apparatus" of Patent Document 5 uses discharge ignition, and the components related to ignition are different. This point will be described in detail later.

As shown in FIGS. 2 and 3, the combustion/explosion test apparatus 1 includes an airtight container 5 for storing the low-temperature liquefied gas mixture sample 3, and a pressure-resistant constant temperature container 7 for holding the low-temperature liquefied gas mixture sample 3 at a predetermined temperature. , and a refrigerator 9 for generating cold heat to be transferred to the pressure-resistant and constant-temperature container 7 .
The pressure-resistant constant temperature container 7 and the refrigerator 9 correspond to the cooling device in the present invention.

The pressure-resistant constant-temperature container 7 accommodates the airtight container 5 and has a container body 11 having pressure resistance performance assuming an explosion, a first cold heat transfer mechanism 13 for transferring cold heat into the container body 11, and heat penetrating into the container body 11. and a container holding mechanism 17 for holding the airtight container 5 .

The first cold heat transfer mechanism 13 includes a cold base 19 covering the bottom of the container body 11 (see FIG. 3), one end connected to the cold base 19, and the other end passing through the container body 11 to the outside of the container body 11. It has a cold rod 21 (see FIG. 3) arranged thereon. Cold rod 21 is connected to refrigerator 9 via cold heat transfer member 23 .

The second cold heat transfer mechanism 15 includes a solid heat conductive member 25 that contacts the outer peripheral surface of the container body 11 and transfers cold heat to the outer peripheral surface, and the solid heat conductive member 25 is connected to the refrigerator 9. .

Also, the first cold heat transfer mechanism 13 and the second cold heat transfer mechanism 15 are provided with a temperature adjustment device (not shown) that adjusts the temperatures of the cold rod 21 and the solid heat transfer member 25 . The temperature control of the cold rod 21 and the solid heat conducting member 25 is performed by a temperature sensor 31 (see FIG. 4) provided on the holding member 29, which will be described later, and a heater (not shown) equipped on the cold rod 21 and the solid heat conducting member 25. By controlling the heater so that the temperature of the temperature sensor 31 reaches a predetermined temperature, the low-temperature liquefied gas mixture sample 3 in the airtight container 5 can be maintained at a predetermined temperature.

The container holding mechanism 17, as shown in FIGS. An airtight container 5 is attached to the holding member 29 . A temperature sensor 31 is provided near the portion of the holding member 29 to which the airtight container 5 is fixed.

The combustion/explosion test apparatus 1 according to the present embodiment includes the pressure-resistant constant-temperature container 7 configured as described above. 23, cold rod 21, cold base 19, base plate 27, holding member 29, airtight container 5, and airtight container 5 is cooled.
Cold heat generated by the refrigerator 9 is transmitted to the container body 11 via the solid heat conducting member 25 of the second cold heat transfer mechanism 15 to cool the container body 11 .
Further, as described above, the first cold heat transfer mechanism 13 and the second cold heat transfer mechanism 15 adjust the temperature of the cold heat transfer member 23 and the solid heat transfer member 25 based on the temperature of the holding member 29, and the temperature inside the airtight container 5 is held in equilibrium.

The airtight container 5 seals the low-temperature liquefied gas mixed sample 3 which is the test object, is fixed to the holding member 29 as described above, and is arranged in the central portion of the container body 11 of the pressure- and constant-temperature container 7 .
As shown in FIG. 5 , the airtight container 5 includes a cooling block 33 fixed to the holding member 29 and a bottomed tubular liquid reservoir 35 .
The cooling block 33 has a gas introduction port 37 for introducing gas.
If the combustible substance is liquid or solid at room temperature, the combustible substance may be introduced into the liquid reservoir 35 in advance.

An introduction joint 39 protrudes from the upper part of the cooling block 33 , and a pair of conducting wires 41 are inserted into the airtight container 5 through the introduction joint 39 . A part of the conducting wire 41 is covered with an insulating material 43 in order to prevent contact short circuit with the inner wall of the airtight container 5 or the like. It is desirable to use a non-combustible material (such as an insulator if necessary) for the insulating material 43 . Combustible materials are undesirable because they cause combustion of objects other than the object.

FIG. 5 shows an example in which a hermetic seal (an insulating joint consisting of a screw joint, a pipe and an insulator) is used as the introduction joint 39. As shown in FIG. In addition to a hermetic seal, a sealing gland or the like may be used for the introduction joint 39 as long as insulation and airtightness can be secured at a low temperature.
Further, the internal pressure of the airtight container 5 can be constantly monitored by a pressure detector (not shown).

A fusing wire 45 is attached to the ends of the pair of conducting wires 41 inserted into the airtight container 5 , and the fusing wire 45 is arranged in the liquid reservoir 35 . When adjusting the liquefaction of the low-temperature liquefied gas, the fusing wire 45 is adjusted to be immersed in the liquid. It is recommended to use a Pt wire for the fusing wire 45, but if the system requires a long time for liquid preparation or if the catalytic effect of the Pt surface affects the preparation, Ni-Cr wire, tungsten wire, or other wire may be used. materials can be used. A silver solder is preferable for the connection between the fusing wire 45 and the lead wire 41, and solder, which may cause a reaction when ignited, is not preferable.

The ends of the pair of conductors 41 outside the airtight container 5 are connected to a current supply device 47 for supplying current to the fusing wire 45 as shown in FIG. The current supply device 47 can supply a current (fusing current) capable of fusing the fusing wire 45, and can set and change the current value. Also, by turning ON/OFF the switch 49 manually or by a signal from the outside, the supply of current can be started and stopped.
The conducting wire 41 connecting the current supply device 47 and the fusing wire 45 has sufficient material and wire diameter corresponding to the current supplied from the current supply device 47, and is designed to be used stably. It is connected to the current supply device 47 and the fusing wire 45 .

Next, in the combustion/explosion test performed using the combustion/explosion test apparatus 1 of the present embodiment configured as described above, FIG. Description will be made with reference to FIGS. 6 and 7. FIG.
In the method of stirring a low-temperature liquefied gas mixture sample according to the present embodiment, a heating current lower than the fusing current is supplied to the fusing wire 45 to heat the low-temperature liquefied gas mixture sample 3, and the convection caused by the heating causes the low temperature. It is characterized by stirring the liquefied gas mixture sample 3 .

First, the value of the fusing current for fusing the fusing wire 45 near the operating temperature is measured in advance. As an example, FIG. 7 shows a graph showing the fusing current of a Pt wire and a Ni--Cr wire when used while immersed in liquid nitrogen (hereinafter referred to as "LN ₂ "). FIG. 7 shows that, for example, when a Pt wire with a diameter of φ0.3 is immersed in LN ₂ , the Pt wire melts when a current of about 30 A or more is supplied to the Pt wire.
_The fusing current is determined by the electrical resistance specific to the fusing wire type, the melting temperature, the wire diameter, the temperature difference between the melting temperature and the _liquefied gas, and the heat transfer coefficient. No big difference.

Next, a combustion-supporting low-temperature liquefied gas and a combustible substance are introduced into the airtight container 5 , and the low-temperature liquefied gas mixture sample 3 to be tested is stored in the airtight container 5 . Specifically, by introducing a combustion-supporting gas and a combustible gas from the gas inlet 37 (see FIG. 5) and liquefying it in the airtight container 5, the low-temperature liquefied gas mixture sample 3 is a liquid reservoir. Store at 35.

After storing the low-temperature liquefied gas mixture sample 3 so that the fusing line 45 is sufficiently immersed, the low-temperature liquefied gas mixture sample 3 is stirred. An example of a specific stirring method is shown in FIG.
First, a current value lower than the fusing current measured in advance is set in the current supply device 47, and the switch 49 is turned on to start supplying current (hereinafter, this current is referred to as "heating current") ( step S1). The fusing wire 45 supplied with the heating current is heated without fusing, and the low-temperature liquefied gas mixture sample 3 is heated by the heated fusing wire 45 . When the low-temperature liquefied gas mixture sample 3 is heated, convection occurs in the liquid phase, and this convection promotes stirring of the low-temperature liquefied gas mixture sample 3 .

Further, the value of the heating current may be adjusted to increase the amount of heating to partially evaporate the low-temperature liquefied gas mixture sample 3 . By generating bubbles of vaporized low-temperature liquefied gas in liquid-state low-temperature liquefied gas, the generated bubbles rise in the liquid phase and can be stirred more efficiently.
However, when the low-temperature liquefied gas is vaporized as described above, the internal pressure of the airtight container 5 increases due to the increase in gas phase. Therefore, in order to prevent damage to the airtight container 5, the heating current must be supplied so that the internal pressure of the airtight container 5 does not exceed a predetermined pressure.

In this regard, in the present embodiment, the upper limit of the internal pressure of the airtight container 5 (hereinafter referred to as "upper limit pressure") is set in advance, and the heating current is supplied when the internal pressure of the airtight container 5 becomes equal to or higher than the upper limit pressure. Stop. Specifically, after starting the supply of the heating current (step S1), the internal pressure of the airtight container 5 is monitored using a pressure detector (not shown) provided in the airtight container 5 or the gas introduction path (step S3), It is determined whether or not the internal pressure is equal to or higher than the upper limit pressure (step S5). When the internal pressure has not reached the upper limit pressure, the supply of heating current and the monitoring of the internal pressure are continued. When the internal pressure reaches the upper limit pressure, the switch 49 is turned off to stop the supply of the heating current (step S7).

At this time, it is determined whether the stirring is sufficiently performed and the concentration of the low-temperature liquefied gas mixture sample 3 is uniform (step S9), and if it is determined that the stirring is sufficient, the stirring is terminated. . As a method for judging the uniformity of the concentration of the low-temperature liquefied gas mixed sample 3, a method corresponding to the composition of the low-temperature liquefied gas mixed sample 3 may be appropriately used. A specific example of a method for determining uniformity will be described later in Examples.

If it is determined in step S9 that the stirring is not sufficient, the low temperature liquefied gas mixture sample 3 is allowed to stand while the supply of the heating current is stopped (step 11). As described above, since the airtight container 5 is controlled to maintain a predetermined temperature, the low-temperature liquefied gas mixed sample 3 heated by the supply of the heating current is allowed to stand still, so that the first cold heat transfer mechanism 13, It is cooled to a predetermined temperature by the second cold heat transfer mechanism 15 .

By cooling, the vaporized low-temperature liquefied gas mixture sample 3 is condensed again, so the internal pressure of the airtight container 5 is lowered. In the present embodiment, a lower limit value (hereinafter referred to as "lower limit pressure") of the internal pressure of the airtight container 5 is set in advance as a guideline for resuming the supply of the heating current. The lower limit pressure is, for example, the internal pressure before the heating current is supplied, that is, the internal pressure when the pressure and constant temperature container 7 is held at a predetermined temperature.

The internal pressure that decreases due to cooling is monitored (step S13), and it is determined whether or not the internal pressure is equal to or lower than the lower limit pressure (step S15). If the internal pressure has not decreased to the lower limit pressure, continue to stand still and monitor the internal pressure. When the internal pressure of the airtight container 5 drops to the lower limit pressure, the supply of heating current is restarted (step S1).
Thereafter, steps 1 to 15 are repeated until step 9 determines that the stirring is sufficient (the concentration of the low-temperature liquefied gas mixed sample 3 is uniform).

When the stirring is completed, the set value of the current supply device 47 is changed to a current value at which the fusing wire fuses, and the switch 49 is turned ON to supply the fusing current, thereby fusing the fusing wire 45 and igniting the object. be able to.

As described above, according to the method of stirring a low-temperature liquefied gas mixture sample of the present embodiment, the low-temperature liquefied gas mixture sample 3 is can be stirred, there is no need to add a separate device for stirring to the liquefaction container (airtight container 5) and its surroundings. It can also be used for small volume explosion tests.

In the example shown in FIG. 1, since the internal pressure of the airtight container 5 is increased, the heating current is supplied intermittently to repeat heating and cooling of the object, but the present invention is limited to this. can't For example, the value of the heating current may be adjusted according to the internal pressure of the airtight container 5. In that case, the heating can be performed while the internal pressure of the airtight container 5 is kept constant. Heating current can be supplied continuously. In this case, air bubbles are less likely to occur, but convection occurs in the subject even if the heating does not involve the generation of air bubbles.

[Embodiment 2]
Embodiment 1 was an example of manually starting and stopping the supply of the heating current. Describe the device.

As shown in FIG. 8, a low-temperature liquefied gas mixed sample stirring device 51 (hereinafter simply referred to as "stirring device 51") according to the present embodiment includes an airtight container 5 for storing the low-temperature liquefied gas mixed sample 3 and an airtight A cooling device (not shown) that cools the low-temperature liquefied gas mixture sample 3 in the container 5, and a first pressure that constantly detects the internal pressure of the airtight container 5 and transmits a Hi signal or a Low signal based on the detected pressure. A detection device 53 and a current supply device 47 for supplying a constant heating current to the fusing wire 45 immersed in the low-temperature liquefied gas mixed sample 3 are provided. It has a first control means 55 for controlling the start and stop of the supply of the heating current.
The same parts as those of the combustion/explosion test apparatus 1 described in Embodiment 1 are denoted by the same reference numerals, and the description thereof is omitted. The control means 55 will be specifically described below. It should be noted that dashed arrows in FIG. 8 indicate electrical connections.

<First pressure detector>
The first pressure detection device 53 is composed of, for example, a pressure gauge with a contact, and transmits a Hi signal or a Low signal to the first control means 55 based on the detected pressure. The first pressure detection device 53 is provided, for example, in a gas introduction pipe 57 for introducing gas into the airtight container 5 , and always detects the pressure of the gas introduction pipe 57 as equivalent to the internal pressure of the airtight container 5 . Two thresholds (upper limit value H and lower limit value L) are set in advance in the first pressure detection device 53, and when the detected pressure is equal to or higher than the set upper limit value H, a Hi signal is set, and the set lower limit value L or less is output. When , a Low signal is transmitted to the first control means 55 .

<First Control Means>
The first control means 55 is composed of, for example, a sequencer or the like, and outputs a signal for controlling ON/OFF of the switch 49 (see FIG. 6) of the current supply device 47 based on the input from the first pressure detection device 53. It transmits to the current supply device 47 and controls the start and stop of the supply of the heating current. The first control means 55 transmits an OFF signal to the current supply device 47 when a Hi signal is input from the first pressure detection device 53 and an ON signal when a Low signal is input.
When the OFF signal is input from the first control means 55, the current supply device 47 turns off the switch 49 to stop supplying the heating current. When the ON signal is input, the switch 49 is turned ON to start supplying the heating current.

The operation of the stirring device 51 configured as described above will be described below with reference to FIG.
First, a combustion-supporting gas is introduced into the cooling block 33 of the airtight container 5 through the gas introduction pipe 57 by the gas control device 59 . The introduced combustion-supporting gas is cooled and liquefied by the cooling block 33 and stored in the liquid reservoir 35 . Similarly, combustible gas is introduced into the airtight container 5 and liquefied, and is stored in the liquid reservoir 35 . A predetermined amount of the low-temperature liquefied mixed gas mixture sample 3 in which the combustion-supporting low-temperature liquefied gas and the combustible low-temperature liquefied gas are mixed is stored in the airtight container 5, and the fusion wire 45 arranged in the liquid reservoir 35 is immersed. Let

A lower limit value L is set to a value corresponding to the internal pressure of the airtight container 5 at this time. Also, the upper limit value H is set based on the pressure resistance performance of the airtight container 5 .
The fusing current of the fusing wire 45 is measured in advance, and a current value lower than the fusing current is set in the current supply device 47 .

The switch 49 of the current supply device 47 is turned on to start supplying the heating current. A heating current is supplied to the fusing wire 45 through the lead wire 41 to heat the fusing wire 45 . By heating the fusing wire 45, the low-temperature liquefied gas mixture sample 3 is heated, and a part of the mixed sample 3 is vaporized to generate bubbles. The low-temperature liquefied gas mixed sample 3 is stirred by generating the low-temperature liquefied gas in the gas state in the low-temperature liquefied gas in the liquid state.

As the vapor phase of the low-temperature liquefied gas mixed sample 3 increases, the internal pressure of the airtight container 5 rises. As the internal pressure of the airtight container 5 rises, the internal pressure of the gas introduction pipe 37 also rises and reaches the pressure set to the upper limit value H. When the first pressure detection device 53 detects a pressure equal to or higher than the upper limit value H, it sends a Hi signal to the first control means 55 .
The first control means 55 transmits an OFF signal to the current supply device 47 when the Hi signal is input from the first pressure detection device 53 .
When the OFF signal is input from the first control means 53, the current supply device 47 turns off the switch 49 to stop supplying the heating current.

When the supply of the heating current is stopped, the low-temperature liquefied gas mixed sample 3 in the airtight container 5 is cooled by a cooling device (corresponding to the pressure-resistant constant-temperature container 7 and the refrigerator 9 in Embodiment 1) not shown, and vaporized at a low temperature. The liquefied gas is condensed and the internal pressure of the airtight container 5 is lowered. As the internal pressure of the airtight container 5 decreases, the internal pressure of the gas introduction pipe 57 also decreases to the pressure set to the lower limit value H.
When the first pressure detection device 53 detects a pressure equal to or lower than the lower limit value L, it sends a Low signal to the first control means 55 .
The first control means 55 transmits an ON signal to the current supply device 47 when the Low signal is input from the first pressure detection device 53 .
When the ON signal is input from the first control means 55, the current supply device 47 turns on the switch 49 to restart the supply of the heating current.
The above operation is repeated until the concentration of the low-temperature liquefied gas mixed sample 3 becomes uniform.

As described above, in the present embodiment, by providing the first pressure detection device 53 and the first control means 55, the start and stop of the heating current supply are automatically controlled based on the internal pressure of the airtight container 5. can be done with As a result, the low-temperature liquefied gas mixed sample 3 can be automatically stirred as described in FIG.

[Embodiment 3]
In Embodiments 1 and 2, a constant heating current is supplied to the fusing wire 45, and the supply of the heating current is stopped when the internal pressure of the airtight container 5 rises above a predetermined pressure. In this embodiment, an example using PID control will be described as another aspect of the stirring device that automatically controls the supply of heating current so that the internal pressure of the airtight container 5 does not exceed a predetermined pressure.

As shown in FIG. 9, a low-temperature liquefied gas mixed sample stirring device 61 (hereinafter simply referred to as "stirring device 61") according to the present embodiment includes an airtight container 5 for storing the low-temperature liquefied gas mixed sample 3 and an airtight A cooling device (not shown) for cooling the low-temperature liquefied gas mixture sample 3 in the container 5, a second pressure detection device 63 for constantly detecting the internal pressure of the airtight container 5 and transmitting the detected pressure, and low-temperature liquefied gas. A current supply device 47 that supplies a heating current to the fusing wire 45 immersed in the mixed sample 3, and the current supply device 47 PID-controls the current value of the heating current based on the input from the second pressure detection device 63. It has a second control means 65 for controlling.
As in FIG. 8, the same parts as those of the combustion/explosion test apparatus 1 described in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. 63 and the second control means 65 will be specifically described below. It should be noted that dashed arrows in FIG. 9 indicate electrical connections as in FIG.

<Second pressure detection device>
The second pressure detection device 63 is composed of, for example, a pressure transmitter, and transmits the detected pressure to the second control means 65 . The second pressure detection device 63 is provided, for example, in the gas introduction pipe 57 or the like, detects the pressure of the gas introduction pipe 57 as equivalent to the internal pressure of the airtight container 5, and always uses the detected pressure value for the second control. send to means 65;

<Second Control Means>
The second control means 65 is composed of, for example, a PID controller or the like, and performs PID control of the output current value of the current supply device 47 based on the input from the second pressure detection device 63 .
A set value of the internal pressure of the airtight container 5 is input in advance to the second control means 65, and the amount of operation (the amount of change in the current value) necessary for the internal pressure of the airtight container 5 to reach this set value is set to the current value. Send to supply device 47 . Specifically, if the pressure value input from the second pressure detection device 63 is higher than the set value, a signal to decrease the current value is sent to the current supply device 47, and if it is lower than the set value, the current value is increased. A signal is sent to the current supply device 47 .

The operation of the stirring device 61 configured as described above will be described below with reference to FIG.
First, a predetermined amount of the low-temperature liquefied gas mixture sample 3 is stored in the airtight container 5 in the same manner as in the second embodiment, and the fusing wire 45 arranged in the liquid reservoir 35 is immersed.

Next, the set value of the internal pressure of the airtight container 5 is input to the second control means 65 .
Also, the fusing current of the fusing wire 45 is measured in advance, and a current value lower than the fusing current is set in the current supply device 47 .

The switch 49 of the current supply device 47 is turned on to start supplying the heating current. A heating current is supplied to the fusing wire 45 through the lead wire 41 to heat the fusing wire 45 . The low-temperature liquefied gas mixed sample 3 is heated by heating the fusing wire 45 , and the low-temperature liquefied gas mixed sample 3 is agitated by convection caused by the heating.

At this time, if the second pressure detection device 63 detects a pressure higher than the set value, the second control means 65 controls the current supply device 47 so as to lower the current value of the heating current. As the current value of the heating current decreases, the amount of cooling by the cooling device (not shown) exceeds the amount of heating by the heating current, and the internal pressure of the airtight container 5 decreases.
Also, when the second pressure detector 63 detects a pressure lower than the set value, the second control means 65 controls the current supply device 47 so as to increase the current value of the heating current.
The above operation is continued until the concentration of the low-temperature liquefied gas mixed sample 3 becomes uniform.

As described above, in this embodiment, by PID-controlling the current value of the heating current, the heating current can be continuously supplied while the internal pressure of the airtight container 5 is kept constant. The density of the sample 3 can be made uniform.
By selecting the PID parameter so that the PID control speed of the heating current is faster than the response speed of the cold heat transfer system from the cold head of the cooling device to the airtight container 5, interference with the temperature control of the airtight container 5 and Thermal equilibrium can be minimized and the stirring effect can be enhanced.

A specific experiment was conducted to confirm the effects of the stirring method and the stirring apparatus for a low-temperature liquefied gas mixture sample according to the present invention, and the results will be described below.

In this example, using a stirring device 51 shown in FIG. 8, a stirring experiment was conducted on a low-temperature liquefied gas mixture sample ₃ obtained by mixing a combustion-supporting liquefied gas LO2 and a combustible substance _LCH4 .
PSW-360L30 manufactured by Texio Technology Co., Ltd. was used as the current supply device 47 .
A Pt wire with a wire diameter of φ0.3 was used for the fusing wire 45 .
For the first pressure detection device 53, the upper limit value H was set to 0.2 MPaG and the lower limit value L was set to 0.02 MPaG using a pressure gauge with a contact.
The first control means 55 used a sequencer.
As described above, a cooling device (not shown) is connected to the airtight container 5 in the stirring device 51 of FIG.

First, a mixture of oxygen gas (O ₂ ) and methane gas (CH ₄ ) was introduced into the airtight container 5, and the cooled and liquefied mixture (LO ₂ +LCH ₄ mixture) was stored.
After storing a predetermined amount of the LO ₂ + LCH ₄ mixture (low-temperature liquefied gas mixture sample) in the airtight container 5, the current value of the current supply device 47 is set to 13 A, which is smaller than the fusing current in this case, and the heating current is applied. did. After that, the ON/OFF of the switch 49 of the current supply device 47 was performed by automatic control.

Furthermore, in this example, in the process of stirring, part of the O ₂ +CH ₄ mixture was sampled from the gas phase in the airtight container 5, and the sampled gas was introduced into a mass spectrometer (not shown) to measure the CH ₄ concentration. It was measured.
The above sampling was performed at a frequency that does not affect the gas composition of the mixture.

FIG. 10 shows the results of this example.
The lower graph in FIG. 10 shows the start and stop times of the heating current supply.
The solid line in the upper graph of FIG. 10 indicates the internal pressure of the airtight container ₅ , and the broken line indicates the _CH4 concentration of the sampled _O2 +CH4 mixture.

As shown in FIG. 10, after the heating current was applied, the internal pressure of the airtight container 5 rose to the upper limit value H of 0.2 MPaG set in the first pressure detection device 53. When the pressure reached 0.2 MPaG, the current was automatically supplied. stopped. After that, the internal pressure of the container decreased due to cooling by the cooling device, and after about 5 minutes, it decreased to the lower limit L of 0.02 MPaG set in the first pressure detection device 53 . When the internal pressure of the vessel reached 0.02 MPaG, the supply of heating current was automatically restarted, and the heating current was applied intermittently by automatic control in the same way thereafter.
The heating current was applied 3 times, each application time was 20 to 30 seconds, and the application interval was about 5 to 7 minutes.

The time for the internal pressure of the container to drop from the upper limit value H to the lower limit value L is short, about 5 to 7 minutes. This is because the heat capacity of the cold heat transfer system up to 5 overwhelmingly exceeds the heat capacity of the low-temperature liquefied gas mixture sample 3 in the airtight container 5 .

Due to the lower specific gravity of _LCH4 compared to LO2 at the beginning, the _CH4 concentration in the gas phase inside the airtight container ₅ is higher than the _CH4 concentration in the _O2 + _CH4 mixture before liquefaction. . However, when a heating current is applied to the fusing wire 45, the LO ₂ +LCH ₄ mixture in the airtight container 5 is agitated, and the CH ₄ concentration in the gas phase decreases accordingly.
Furthermore, by intermittently applying pressure so that the internal pressure of the airtight container 5 does not exceed a predetermined pressure (0.2 MPaG, which is the upper limit value H in this embodiment), the rate of decrease in CH ₄ concentration slows down with the number of times of application. It was assumed that the composition in the liquid phase became uniform because the CH ₄ concentration almost did not change before and after the application of the heating current.

As described above, according to the stirring method and the stirring device for the low-temperature liquefied gas mixture sample according to the present invention, the low-temperature liquefied gas mixture sample is heated by introducing a heating current smaller than the fusing current to the fusing wire immersed in the low-temperature liquefied gas mixture sample. By doing so, it was demonstrated that the low temperature liquefied gas mixed sample can be stirred and the composition of the low temperature liquefied gas mixed sample can be made uniform.

1 Combustion/explosion test device 3 Low-temperature liquefied gas mixture sample 5 Airtight container 7 Pressure-resistant constant-temperature container 9 Refrigerator 11 Container body 13 First cold heat transfer mechanism 15 Second cold heat transfer mechanism 17 Container holding mechanism 19 Cold base 21 Cold rod 23 Cold heat transfer Member 25 Solid thermally conductive member 27 Base plate 29 Holding member 31 Temperature sensor 33 Cooling block 35 Liquid reservoir 37 Gas introduction port 39 Introduction joint 41 Lead wire 43 Insulating material 45 Fusing wire 47 Current supply device 49 Switch 51 Stirrer (Embodiment 2)
53 First pressure detection device 55 First control means 57 Gas introduction pipe 59 Gas control device 61 Stirrer (third embodiment)
63 second pressure detection device 65 second control means

Claims (5)

In a combustion/explosion test in which a fusing wire immersed in a low-temperature liquefied gas mixture sample obtained by mixing a combustion-supporting low-temperature liquefied gas and a combustible substance is ignited by supplying a fusing current for fusing the fusing wire, the low-temperature A low-temperature liquefied gas mixed sample stirring method for stirring a liquefied gas mixed sample,
A low-temperature liquefaction characterized by supplying a heating current lower than the fusing current to the fusing wire to heat the low-temperature liquefied gas mixed sample, and stirring the low-temperature liquefied gas mixed sample by convection generated by the heating. A method of stirring a gas mixture sample. 3. The low-temperature liquefied gas mixed sample is stirred by vaporizing the low-temperature liquefied gas by the heating and generating bubbles of the vaporized low-temperature liquefied gas in the liquid state of the low-temperature liquefied gas. 2. The method for stirring the cryogenic liquefied gas mixed sample according to 1. 3. Agitation of a low temperature liquefied gas mixture sample according to claim 1 or 2, wherein the heating current is supplied so that the internal pressure of the airtight container in which the low temperature liquefied gas mixture sample is stored does not exceed a predetermined pressure. Method. A low-temperature liquefied gas mixed sample stirring device for realizing the low-temperature liquefied gas mixed sample stirring method according to claim 3,
an airtight container for storing the cryogenic liquefied gas mixed sample;
a cooling device for cooling the low-temperature liquefied gas mixture sample in the airtight container;
a first pressure detection device that constantly detects the internal pressure of the airtight container and transmits a Hi signal when the detected pressure is equal to or higher than a predetermined upper limit, and a Low signal when the detected pressure is equal to or lower than a predetermined lower limit;
A current supply device that supplies a constant heating current to the fusion wire immersed in the low-temperature liquefied gas mixture sample,
The current supply device stops supplying the heating current when a Hi signal is input from the first pressure detection device, and controls to start supplying the heating current when a Low signal is input. A low-temperature liquefied gas mixed sample stirring apparatus comprising a first control means. A low-temperature liquefied gas mixed sample stirring device for realizing the low-temperature liquefied gas mixed sample stirring method according to claim 3,
an airtight container for storing the cryogenic liquefied gas mixed sample;
a cooling device for cooling the low-temperature liquefied gas mixture sample in the airtight container;
a second pressure detection device that constantly detects the internal pressure of the airtight container and transmits the detected pressure;
a current supply device that supplies a heating current to the fusing wire immersed in the low-temperature liquefied gas mixture sample,
The low-temperature liquefied gas agitator, wherein the current supply device has second control means for PID-controlling the current value of the heating current based on the input from the second pressure detection device.

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