JP2017167015A - Method for collecting oil constituent in low temperature liquid gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for collecting an oil constituent in a low-temperature liquid gas capable of securely collecting the oil constituent in the low-temperature liquid gas and precisely performing analysis thereafter.SOLUTION: An amount of a low-temperature liquid gas made to circulate through a filter is obtained by making the low-temperature liquid gas circulate with a filter 11 having a plurality of pores being cooled at a temperature of the low-temperature liquid gas, making the filter capture and collect an oil constituent contained in the low-temperature liquid gas in a solid state, and making the low-temperature liquid gas passing through the filter segmented by the pores to be gasified at a downstream side of the filter to measure a flow quantity of the gasified gas.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for recovering an oil component in a low-temperature liquefied gas, and more particularly to a method for recovering an oil component contained in various liquefied gases such as liquefied oxygen, liquefied nitrogen, and liquefied argon that are liquid at normal temperature and pressure. .

  In the field of organic industrial chemistry and semiconductor manufacturing, quality control of various industrial gases such as oxygen gas, nitrogen gas, and argon gas, which are gases at room temperature and normal pressure, for example, 25 ° C. and 1 atm, Analysis is being carried out. Similarly, it is necessary to carry out quality control of various liquefied gases such as liquefied oxygen, liquefied nitrogen, and liquefied argon that are liquid at normal temperature and pressure. The impurities contained in the liquefied gas include hydrocarbons having 5 or more carbon atoms (hereinafter referred to as “oil component”). Therefore, analysis of oil components is also required for quality control and security control.

  Conventionally, a method for recovering low-temperature liquefied gas directly to a stainless steel pail can and analyzing the oil component remaining on the bottom of the can as a residue after vaporization is generally known. There was a difficulty of being easy to receive. On the other hand, as a method for measuring the oil component that is an impurity in the gas, for example, an adsorption cylinder filled with an adsorbent such as an inorganic adsorbent such as activated alumina, diatomaceous earth, molecular sieve, activated carbon, or a polymer adsorbent is used. After the gas containing the component is circulated and the oil component is adsorbed by the adsorbent, the adsorbing cylinder is heated while the inert gas such as nitrogen gas, helium gas, and argon gas is circulated, and is adsorbed by the adsorbent. It is known to desorb an oil component and analyze the oil component entrained in an inert gas (see, for example, Patent Document 1).

JP 2014-62815 A

  Analysis of the oil component in the gas can be performed by the method described in Patent Document 1, but when analyzing the oil component in the liquefied gas, it is necessary to vaporize the liquefied gas before analysis, There is a possibility that an oil component to be analyzed remains in an apparatus for vaporizing the liquefied gas, for example, an evaporator. For this reason, it was difficult to accurately and accurately analyze the oil component concentration in the liquefied gas.

  Accordingly, an object of the present invention is to provide a method for recovering an oil component in a low-temperature liquefied gas that can reliably recover the oil component in the low-temperature liquefied gas and that can be accurately analyzed thereafter.

  In order to achieve the above object, an oil component recovery method in a low-temperature liquefied gas according to the present invention includes a plurality of pores in the oil component recovery method in a low-temperature liquefied gas for separating and recovering an oil component in a low-temperature liquefied gas. In a state where the filter is cooled to the temperature of the low-temperature liquefied gas, the low-temperature liquefied gas is circulated through the filter, and the oil component contained in the solid state in the low-temperature liquefied gas is captured and collected by the filter. The low-temperature liquefied gas passing through the filter is vaporized on the downstream side of the filter by subdividing the pores, and the amount of the low-temperature liquefied gas circulated through the filter is determined by measuring the flow rate of the vaporized gas. It is a feature.

Furthermore, in the method for recovering an oil component in the low-temperature liquefied gas of the present invention, the filter has 100 to 1 million pores per 1 mm ² , the filter is a sintered metal filter, The filter is formed in a tip dome cylindrical shape having a tip formed in a dome shape.

  According to the oil component recovery method in the low-temperature liquefied gas of the present invention, since the low-temperature liquefied gas is circulated through the filter cooled to the low-temperature liquefied gas temperature, the solid oil component contained in the low-temperature liquefied gas is left as it is. Can be reliably captured and collected by the filter.

It is explanatory drawing which shows one example of an apparatus structure which can implement the oil component recovery method in the low-temperature liquefied gas of this invention. It is explanatory drawing which shows the example of 1 shape of a metal filter.

  FIG. 1 and FIG. 2 are explanatory diagrams showing an example of an apparatus configuration capable of implementing the oil component recovery method in the low-temperature liquefied gas of the present invention. The oil component recovery apparatus shown in this embodiment includes a filter having a plurality of pores, for example, an oil component recovery pipe 12 having a metal filter 11 mounted therein, and a low-temperature liquefied gas connected to the inlet side of the oil component recovery pipe 12 An inlet path 13, a vaporized gas outlet path 14 connected to the outlet side of the oil component recovery pipe 12, a recovery inlet valve 15 provided in the low temperature liquefied gas inlet path 13, and an upstream side of the recovery inlet valve 15. A precooling path 16, a discharge path 17 branched from the precooling path 16, a discharge valve 18 provided in the discharge path 17, a recovery outlet valve 19 and a flow meter 20 provided in the vaporized gas outlet path 14. I have. A low temperature liquefied gas container 23 is connected to the precooling path 16 via a low temperature liquefied gas outlet path 22 having a low temperature liquefied gas container outlet valve 21 whose opening degree can be adjusted.

The metal filter 11 is for capturing and recovering a solid oil component in the low-temperature liquefied gas passing through the oil component recovery pipe 12, for example, a micrometer level of 0.01 to 100 μm in diameter. A metal filter having about 100 to 1 million pores per mm ² and a sintered metal filter can be used as a specific example. The shape of the metal filter 11 is arbitrary. For example, as shown in FIG. 2, a tip dome cylindrical metal filter 11a having a dome-shaped tip that protrudes into the oil component recovery pipe 12 is provided. What was supported in the airtight state by the support member 11b can be used. By forming in such a cylindrical shape, the area of the metal filter 11 can be expanded, and the amount of low-temperature liquefied gas treated can be increased.

  The low-temperature liquefied gas container 23 is a container in which a low-temperature liquefied gas to be analyzed is stored, and any structure can be used as long as it can store various low-temperature liquefied gases. An evaporator can be used. The flow meter 20 is for measuring the flow rate of gas vaporized when passing through the metal filter 11 and being led out from the oil component recovery pipe 12 to the vaporized gas lead-out path 14, as long as the gas flow rate can be measured. A general gas flow meter can be used. Moreover, the said each path | route and valve should just use the general piping material for low temperature, for example, the thing made from stainless steel.

  Next, a method for collecting and recovering the oil component contained in the solid state in the low-temperature liquefied gas by the metal filter 11 using the oil component recovery apparatus thus formed will be described.

  First, in order to prevent contamination from the outside, a sufficiently cleaned metal filter 11 is attached to the oil component recovery pipe 12, and then the recovery inlet valve 15 and the recovery outlet valve 19 are closed in the oil component recovery pipe 12. The liquefied gas introduction path 13 and the vaporized gas outlet path 14 are connected. Further, the low-temperature liquefied gas outlet path 22 in a state where the low-temperature liquefied gas container outlet valve 21 is closed is connected to the low-temperature liquefied gas introduction path 13 via the pre-cooling path 16 to store the low-temperature liquefied gas to be the oil component recovery target. An oil component recovery device is connected to the low temperature liquefied gas container 23.

  Next, after opening the discharge valve 18, the low-temperature liquefied gas container outlet valve 21 is opened, and the low-temperature liquefied gas flowing out from the low-temperature liquefied gas container 23 expels the air present in the low-temperature liquefied gas outlet path 22 and the precooling path 16. Both channels 22 and 16 are cooled to the low temperature liquefied gas temperature. By confirming that the low-temperature liquefied gas flows out from the discharge path 17, the cooling of both the paths 22 and 16 is completed.

  Then, the recovery outlet valve 19 is opened, the recovery inlet valve 15 is opened, the discharge valve 18 is closed, and the low temperature liquefied gas is introduced from the precooling path 16 through the low temperature liquefied gas introduction path 13 into the oil component recovery pipe 12. As a result, the oil component in the low-temperature liquefied gas is captured by the metal filter 11 while maintaining a solid state, and the low-temperature liquefied gas is fragmented into mist by passing through the pores of the metal filter 11. The gas flows out into the vaporized gas lead-out path 14 in the state, vaporizes in the vaporized gas lead-out path 14 at atmospheric pressure in the outside air temperature state (from minus 20 ° C. to 50 ° C.), and the flow rate is measured through the flow meter 20 in the gas state. . At this time, by adjusting the opening degree of the low-temperature liquefied gas container outlet valve 21 so that the gas flow rate measured by the flow meter 20 is constant, the gas amount is calculated based on the flow rate and time measured by the flow meter 20. be able to.

  In general, the pressure of the low-temperature liquefied gas flowing out from the low-temperature liquefied gas container 23 has a pressure corresponding to the pressure (head pressure) of the gas phase portion of the low-temperature liquefied gas container 23 and the amount of stored liquefied gas. The low temperature liquefied gas can be introduced into the oil component recovery pipe 12 at an appropriate flow rate by adjusting the opening degree of the low temperature liquefied gas container outlet valve 21. When the pressure of the low-temperature liquefied gas is low, a liquefied gas pump can be used.

  When a predetermined amount of the low-temperature liquefied gas is introduced into the oil component recovery pipe 12, the low-temperature liquefied gas container outlet valve 21, the recovery inlet valve 15, and the recovery outlet valve 19 are closed in this order. As a result, the oil component in the low-temperature liquefied gas is captured by the metal filter 11. The oil component captured by the metal filter 11 can be analyzed using a known analyzer by extracting the oil component from the metal filter 11 with an appropriate solvent. Furthermore, since the amount of low-temperature liquefied gas (mass kg or volume L) can be calculated based on the flow rate measured by the flow meter 20, the introduction time of the low-temperature liquefied gas, the outside air temperature, and the outside pressure, the oil component in the low-temperature liquefied gas can be calculated. The type and concentration can be determined accurately.

  In this way, since the low-temperature liquefied gas is directly introduced into the metal filter 11 that has been washed in advance and cooled to the temperature of the low-temperature liquefied gas, the oil is solidified in the low-temperature liquefied gas without causing external contamination. The component can be reliably captured by the metal filter 11. In addition, since the mist-like low-temperature liquefied gas that has passed through the metal filter 11 is vaporized and the flow rate is measured in a gas state, the amount of the low-temperature liquefied gas can also be accurately calculated.

  In particular, since the metal filter 11 is provided in the oil component recovery pipe 12, contamination and condensation from the outside can be prevented. In addition, when collecting a small amount of oil component in the low-temperature liquefied gas, it is only necessary to increase the amount of liquefied gas flowing to the metal filter 11, so that a large collection container is not required. Further, since the oil component is captured while adsorbed on the metal filter 11, the oil component is hardly desorbed from the metal filter 11 due to the flow of the low temperature liquefied gas, and the oil component is extracted from the metal filter 11. The oil component can be extracted with a small amount of solvent capable of dissolving the oil component.

  In addition, a filter having a plurality of pores only needs to be able to withstand a low-temperature liquefied gas temperature. Therefore, in addition to a filter formed of a metal such as stainless steel or aluminum, a synthetic resin such as a fluororesin, a metal oxide, or carbon A filter formed of an inorganic material such as can also be used. Furthermore, the shape and structure of the filter can be appropriately set according to conditions such as the diameter of the oil component recovery pipe 12.

An oil component recovery experiment was performed using the oil component recovery apparatus having the configuration shown in FIG. The low temperature liquefied gas to be analyzed was liquefied nitrogen (minus 196 ° C.) containing 10 mg / L of n-hexadecane as an oil component. As the oil component recovery pipe 12, a 1/4 inch stainless steel pipe having a length of 150 mm was used. As the metal filter 11, a sintered metal filter having about 10,000 micrometer-level pores 15a with an average diameter of 1 μm per 1 mm ² is formed in a cylindrical shape at the tip dome having an outer diameter of 4 mm, an inner diameter of 2 mm, and a length of 30 mm. And what was supported by the supporting member of outer diameter 11.8mm and thickness 1mm was used.

  Liquefied nitrogen was introduced into the oil component recovery pipe 12 equipped with the sufficiently cleaned metal filter 11 by the above-described procedure. The liquefied nitrogen was introduced for 50 minutes by adjusting the opening of the low-temperature liquefied gas container outlet valve 21 so that the flow rate measured by the flow meter 20 at 35 ° C. was 20 L / min. The amount of liquefied nitrogen at this time is 1.4L.

  After the introduction of liquefied nitrogen, the metal filter 11 was taken out from the oil component recovery tube 12, and the oil component captured by the metal filter 11 was extracted with 25 mL of a chlorofluorocarbon solvent, and analyzed with an infrared spectrometer. As a result, 13.8 mg of oil component was detected. Since the theoretical amount of oil component in 1.4 L of liquefied nitrogen containing n-hexadecane at 10 mg / L is 14 mg, by recovering the oil component in liquefied nitrogen in the above procedure using the oil component recovery device. It can be seen that the oil component was recovered at a high recovery rate of 98% or more.

  As a conventional method, as described above, liquefied nitrogen containing 10 mg / L of n-hexadecane is put into a 2 L stainless steel pail can to vaporize the liquefied nitrogen in an atmospheric environment, and then all inside the stainless steel pail can. The adhering oil component was extracted with 50 ml of chlorofluorocarbon solvent and similarly analyzed with an infrared spectrometer. As a result, 17 mg of oil component was detected. This seems to be because many oil components were detected due to the influence of external contamination. Further, it took about 6 hours to completely vaporize the liquefied nitrogen in the stainless steel pail.

  A metal filter 11 previously coated with 15 mg of n-hexadecane is attached to the oil component recovery tube 12, and liquefied nitrogen containing no oil component (oil component concentration of less than 0.1 mg / L) is applied at a rate of 20 L / min. Introduced for 50 minutes. After introducing the liquefied nitrogen, the metal filter 11 was taken out, and the oil component captured by the metal filter 11 was extracted with 25 mL of a chlorofluorocarbon solvent and analyzed with an infrared spectrometer. As a result, 14.9 mg of the oil component was detected. Therefore, it was confirmed that 99% or more of the oil component applied to the metal filter was retained. On the other hand, the same amount of n-hexadecane was applied to the inner surface of the stainless steel pail, 1.4 L of liquefied nitrogen was added, and the oil component extracted with 50 ml of chlorofluorocarbon solvent after liquefied nitrogen vaporization was analyzed in the same manner as above. Only the oil component could be detected. This is probably because part of the oil component evaporated together with the vaporization of liquefied nitrogen.

  DESCRIPTION OF SYMBOLS 11 ... Metal filter, 11a ... Tip dome cylindrical metal filter, 11b ... Support member, 12 ... Oil component recovery pipe, 13 ... Low temperature liquefied gas introduction path, 14 ... Vaporized gas outlet path, 15 ... Recovery inlet valve, 16 ... Pre-cooling Path, 17 ... discharge path, 18 ... discharge valve, 19 ... recovery outlet valve, 20 ... flow meter, 21 ... low temperature liquefied gas container outlet valve, 22 ... low temperature liquefied gas outlet path, 23 ... low temperature liquefied gas container

Claims (4)

  In the oil component recovery method in the low temperature liquefied gas for separating and recovering the oil component in the low temperature liquefied gas, the filter having a plurality of pores is cooled to the temperature of the low temperature liquefied gas, and the low temperature liquefaction is applied to the filter. The gas is circulated, and the oil component contained in the low-temperature liquefied gas in a solid state is captured and collected by the filter, and the low-temperature liquefied gas passing through the filter is subdivided by the pores to downstream the filter. A method for recovering an oil component in a low-temperature liquefied gas, characterized in that the amount of the low-temperature liquefied gas circulated through the filter is determined by measuring the flow rate of the vaporized gas. ^2. The oil component recovery method in low-temperature liquefied gas according to claim 1, wherein the filter has 100 to 1 million pores per 1 mm ² .   3. The oil component recovery method in low-temperature liquefied gas according to claim 1, wherein the filter is a sintered metal filter.   4. The method for recovering an oil component in low-temperature liquefied gas according to claim 1, wherein the filter is formed in a tip dome cylindrical shape having a tip formed in a dome shape.

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