JPS61272577A - Method of refining he - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for purifying He by condensing or solidifying impurities in impure He.

In detail, He can be purified stably over a long period of time, and impure He (hereinafter sometimes referred to as raw material He) can be purified.
H exhibits stable purification function even when there are fluctuations in purity.
This relates to e-purification methods.

[Prior Art] Methods for obtaining purified He by removing impurities such as water, carbon dioxide, and air from impure He can be roughly divided into adsorption methods and coagulation methods. Among these, the coagulation method has advantages such as compact equipment and good operability, and is therefore more widely put into practical use than the adsorption method. He by this type of coagulation method
A representative example of a purification method is, for example, Japanese Patent Publication No. 52-4517.
I can list the numbers.

That is, the He purification method uses a purification heat exchanger configured to exchange heat between a first He flow path and a second He flow path.
While impure He flows through the flow path, purified low-temperature He (for example, He extracted from a low-pressure He pipe of a He liquefaction/refrigeration device) is introduced into the second He flow path to cool and solidify the impurities. It is deposited and attached to the wall surface of the first He channel. The high-purity He obtained in this way is supplied to a demand section (for example, the high-pressure side He conduit in the aforementioned He liquefaction/refrigeration system). When the impurity coagulation accumulation aIk in the first He flow path increases due to the purification operation, the flow resistance to impure He increases, so this is detected by the pressure change in the first He flow path and the purification process is stopped. After that, the process moves on to the discharge process of solidified impurities, but at this time, He is pumped into the first and second He channels.
The supply is interrupted, and especially for the second He channel, the introduction of high-temperature He is switched to raise the temperature in the first He channel, and the solidified impurities in the channel are heated and melted, and then discharged to the outside of the system.

However, conventional general-purpose coagulation methods, including the method disclosed above, are based on the concept of coagulating and removing all impurities that can be removed, so it is necessary to apply a considerable amount of cooling to complete coagulation. Also, all impurities are impurity H
Since solidification is performed in the a flow path (first He flow path), if there are many impurities, the flow path will be blocked by the solidified impurities in a short period of time. Purification of the first He channel, i.e., melting of solidified impurities.
Since it is necessary to switch to the discharge process, the He purification efficiency is forced to decline. Moreover, in this step, in order to remove solidified impurities, it is necessary to raise the temperature until they liquefy or vaporize, which requires a considerable amount of heat and time. Not only does the cost of refrigeration used for the above-mentioned total FFI solidification increase, but also the cooling and heating are repeated each time the purification-regeneration cycle is repeated, resulting in an extremely large loss from a thermoeconomic perspective.

[Problems to be Solved by the Invention] As a result of various studies aimed at resolving these situations, the present inventors have discovered that the cause of low He purification efficiency and waste of heating energy is that all impurities are in a solidified state. It was noticed that the helium was separated from the raw material He.

That is, the impurities to be removed exist in the gaseous state in the raw material He, but when this is cooled in the first He flow path,
Some substances (such as 002) solidify in -air, while others (such as H20 and air) once condense into a liquid state and then are further cooled and solidify. Therefore, if only the separation from gaseous He is considered, the latter H2O and air, especially H2O, are already in a state where they can be separated from gaseous He at the time of condensation, but with conventional means, they are still in liquid form from the first He flow path. There was no thought to take it out, and the original idea was to capture all impurities including air, which could only be captured at extremely low temperatures, so these liquid components were further cooled to extremely low temperatures. It is thought that it had solidified.

The present inventors conducted research focusing on the condensation and solidification behavior of impurities in the first He flow path, and found that for impurities that can be extracted in liquid form, additional cooling is applied more than necessary. He learned that if He was extracted after cooling to the condensing temperature, the waste of cold energy would be reduced and He purification efficiency would be improved. Based on this knowledge, he filed a patent application (Japanese Patent Application No. 511 -2111
No. 2573).

FIG. 2 is a schematic flow diagram for explaining the prior invention in detail, and the heat exchange section A is composed of four heat exchangers 1a to 1d, and is a refrigerant supply source for the heat exchange section A. He liquefaction/refrigeration equipment that also serves as a demand unit for purified He! A He purifier S is configured by combining the IB with this. The illustrated He liquefaction/refrigeration system! B itself is not unique and operates according to a general procedure. That is, during refrigeration operation, the high pressure H obtained by pressurizing with the compressor 20
e is sequentially passed into the heat exchangers 21a to 21f (high pressure side line), and the low temperature and low pressure He passes through the heat exchangers 21f to 21a.
(low pressure side line), heat exchange takes place between the two. Furthermore, a part of the high pressure He is sent to the expander 2.
The cold obtained by adiabatic expansion in 2a and 22b is also subjected to heat exchange, and the high-pressure He cooled through these is further cooled and liquefied by a Joule-Thomson (J' T ) valve 23. The He containing the liquid He thus obtained is a cryogenic ring.
It is supplied to the boundary section 24. On the other hand, the cryogenic environment section 24
As mentioned above, the low-pressure He that has cooled and vaporized itself exchanges heat with the high-pressure He while sequentially passing through the heat exchangers 21f to 21a (low-pressure side line) to raise the temperature and is returned to the suction side of the compressor @ 20. .

When purifying He using the He purifier S, the valves 14, 16, and 18 are opened and the valve 10 is opened.
is closed, and valve 19 is left open), low-temperature, low-pressure He extracted from the low-pressure side line of He liquefaction refrigeration system B is sequentially introduced into the medium flow paths 3d to 3a, and further passed through valve 16 to the compressor. On the other hand, impure He6 is returned to the suction side of 20, and after being pressurized by compressor 4, it is sequentially passed through valves 19 and 18 to heat exchangers 1a to 1d, where impurities are condensed, solidified, and removed. By the way, the low-temperature refrigerant supplied from the He liquefaction/refrigeration system 1B exchanges heat with impure He in the heat exchangers 1d to 1a to cool it down, and the temperature rises, so the impure He in the heat exchanger The temperature is the lowest in the heat exchanger 1d, where the refrigerant temperature is low, and increases toward the heat exchanger 1a.

In this example, the impure He temperature in heat exchanger 1a is designed to be approximately 0°C, and the impure He temperatures in heat exchangers 1b, lc, and Ld to be approximately -100°C, approximately -205°C, and approximately -240°C, respectively. do. As a result, in the heat exchanger 1a, moisture is condensed and stored in the trap 5a, in the heat exchanger i1b, the remaining moisture and carbon dioxide are solidified and deposited inside the heat exchanger lb, and in the heat exchanger 1c, the remaining moisture and carbon dioxide are solidified and deposited in the heat exchanger lb. , nitrogen, etc. are condensed and stored in the trap 5b, and further, in the heat exchanger 1d, the remaining impure gas is solidified and deposited in the heat exchanger Ld. The liquid stored in the traps 5a and 5b is drawn out as appropriate, and the purified He obtained by removing impurity gas in this way is introduced into the high-pressure side line of the He liquefaction/refrigeration equipment via the valve 14. be done. Reference numeral 25 indicates a temperature control device, and when the temperature of the purified He introduction line 26 becomes higher than the set value during refining operation, the electromagnetic pulp 19 at the outlet of the compressor 4
is closed, the inside of the heat exchange section A is exclusively cooled by the refrigerant, and when the temperature falls below the set value, the electromagnetic valve 19 is opened to resume He purification. The purified He cooled to a predetermined temperature (30″K) or lower is introduced into the He liquefaction/refrigeration device B.

Next, the impure He in the heat exchange section A, especially the heat exchanger 1b or Ld,
If solidified impurities accumulate in the flow path and the flow path resistance becomes significantly lower,
Close valves 18, 14.18 and close valve 10.10.
a is opened, and the vacuum pump 15 is operated. By doing this, the normal temperature and high pressure H pressurized by the compressor 20
A portion of e (heat medium) reaches the heat exchange section A via the valve 17, passes through the medium channels 3a to 3d in sequence, and is introduced into the low-pressure He line of the He liquefaction refrigeration system B. On the other hand, heat exchange part A
The impure He flow path inside is in a considerably low pressure state as it is sucked by the vacuum pump 15, and the solidified impurities adhering to the impure He flow path are vaporized (sublimated) at once due to the heating and pressure reduction by the heating medium, and the vacuum pump 15 is discharged from the system through the

In this prior invention, as described above, the impurities are condensed or solidified at the appropriate temperature, and the condensed impurities are extracted in liquid form, so that the amount of solidified impurities adhering to the impurity He flow path is small. Therefore, He purification can be performed stably for a long period of time. In addition, when removing solidified impurities and purifying the heat exchange section A, the solidified impurities are heated under reduced pressure conditions, so vaporization (sublimation) progresses rapidly and the purification is completed in a short time. be able to.

However, in this method, since the heat exchanger is heated, even temporarily, to remove the coagulated material, it cannot be denied that some cooling loss occurs on the heat exchange section A side.

The present invention has been made in view of these circumstances, and its purpose is to provide a He purification method that maintains the features of the prior invention and also minimizes cold loss during purification of the heat exchange section. It is intended to provide a method.

[Means for Solving the Problems] The configuration of the He purification method according to the present invention that has achieved the above-mentioned objects is that when removing impurities solidified and remaining in the impure He flow path, the impure He flow is The gist is that the inside of the passage is once sealed, and then a reduced pressure is applied from the upstream or downstream side to discharge solidified residual impurities out of the heat exchanger and remove them by liquefying or vaporizing them.

[Function] A comparison of the condensation point, freezing point, and sublimation point of representative components of impurities contained in impure He under 1 atm is as shown in Table 1 below.

Table 1 ("O)" In other words, most of the water can be condensed at temperatures down to 0°C, and oxygen and nitrogen can be condensed at temperatures up to -209.88°C. If you want to extract it in the liquid stage, 1. For example, connect a moisture extraction line to the cooling temperature down to 0°C in the heat exchanger configured as described above, and connect a gas-liquid separation mechanism such as a trap to the line. -209 in the heat exchanger
．． If a liquid extraction line is connected to the cooling temperature area up to 88° C. and a gas-liquid separation mechanism is attached to the line, liquid nitrogen and liquid oxygen can be extracted all at once. As a result, the amount of impurities remaining in He is significantly reduced, so even if impure He is solidified and deposited in the flow path in the heat exchanger as before, the He purification line will not be blocked in a short time. will disappear. Moreover, in the present invention, as will be described in detail later, no heat is applied to the He purification line in the step of removing solidified impurities, and the line on which the impurity solidified substances are adhered is once sealed and then a reduced pressure is applied to this area. Solidified impurities are discharged outside the heat exchanger and removed by liquefaction or vaporization, and cooling loss in the purification process can also be minimized.

[Embodiment] FIG. 1 is a schematic flow diagram showing an embodiment of the present invention, and the essential configuration is the same as that of the prior invention shown in FIG. The ffi double explanation is omitted.

In the example of FIG. 1, the vacuum pump 15 connected to the traps 5a and 5b in FIG. In place of these, a gas bag 31 is connected via a valve 30 to the most upstream side of the heat exchange section (that is, immediately downstream of the valve 18). The shape and structure of the gas bag 31 are not limited at all.

Purification of He using this device is performed using the valve 19, similar to the example shown in FIG. Open xa, is and 14, valves 10, 10a
and 31 are closed, and while the impure He pressurized by the compressor 4 is sequentially flowing to the heat exchangers 1a-1d, a part of the low-temperature He extracted from the He liquefaction/refrigeration device B is transferred to the heat exchanger 1d-1.
By sequentially flowing in the direction a and cooling the impure He, impurities therein are removed. Specifically, the impure He temperature in the heat exchanger 1a is about θ°C, and the temperature in the heat exchanger 1b.

The operating conditions are set so that the impure He temperatures in lc and ld are about -100°C, about -205°C and about -240°C, respectively, and moisture is condensed in the heat exchanger 1a and stored in the trap 5a. In the heat exchanger 1b section, the remaining moisture and carbon dioxide are solidified and attached to the inner wall of the pipe inside the heat exchanger 1b, and in the heat exchanger IC section, oxygen, nitrogen, etc. are condensed and stored in the trap 5b, Furthermore, in the heat exchanger 1d section, the remaining impure gas is solidified and attached to the inner wall of the pipe, and the purified He is sequentially sent to the liquefaction/refrigeration wave RB.The liquid material stored in the traps 5a and 5b is appropriately discharged from the system. Pull it out.

Next is the heat exchange section A, especially the heat exchanger? Impure He in ntb or ld
When solidified impurities accumulate in the flow path and flow path resistance increases,
valve! 4, 16, 18 is closed to seal the heat exchange part A, and then the pulp 30 is opened. Then, the inside of the impurity (Ie) flow path instantly becomes depressurized, and the gas in the flow path flows into the gas bag 31. I'll come. At this time, the heat exchanger 1b.

The impure solidified material adhering to the wall surface of the LD is crushed by the expansion of the He gas mixed inside the solidified material itself under a pressurized atmosphere, and is carried along the flow path in the direction of the gas bag 31. is transported to the high temperature side (that is, the upstream side in the He purification process). Then, it is heated and liquefied in the high-temperature section, or as described later, is heated and liquefied by the impure He gas introduced into the flow path after the purification treatment, and is then liquefied into the traps 5a and 5b as a liquid. be captured. in this case,
It is preferable to provide a filter at the impure He gas inlet of the traps 5a and 5b, since the impure coagulates transported in the purification process are filtered out by the filter and reliably captured in the traps 5a and 5b. In this way, the trap 5a,
The impurities captured in the pulp 5b can be appropriately extracted from the pulp 10, 10a. After the impurity He channel has been purified in this way, the pulp 30 is closed and the pulps 14, 18° 18 are opened to remove the impurities again. During the initial stage of purification of He, the impure solidified matter transported to the upstream side of the channel and remaining in an unliquefied state is heated by impure He gas and liquefied, and is collected in the traps 5a and 5b. After the valve 10, 10a
It is extracted from the system as appropriate. In addition, the gas bag 31 is compressed at the initial stage of restarting refining, and the He collected in the purification process is
It is preferable to return the gas from the pulp 30 to the purification line because it eliminates the loss of impure He gas. By repeating the above purification and purification steps at appropriate intervals, He can be purified. Able to perform smoothly for long periods of time.

In particular, in the present invention, impurity coagulation in the flow path can be removed during the purification process without heating the purification line from the outside at all, so there is no cooling loss, and the purification process is instantaneous as described above. Since this can be carried out by reduced pressure treatment, the time required for purification is extremely short, and the time ratio of the purification process can be maximized.

The present invention is configured as shown below, for example, but the drawings are representative examples and are not intended to limit the present invention, and various changes may be made within the scope of the spirit of the preceding and following descriptions. For example, FIG. 1 shows an example in which four heat exchangers are arranged in series, but the number of combinations of heat exchangers can be changed as desired. Furthermore, the mounting position of the gas bag is not limited to the position shown in the figure; for example, it can be connected directly upstream or downstream of the flow path where impurity coagulum has accumulated, or it can also be connected directly to the trap. . Furthermore, it is also possible to use a simple decompression line instead of a gas bag, and the point is that the impurities solidified in the impure He flow path inside the heat exchanger are discharged outside the heat exchanger and then liquefied or vaporized. Anything that can be removed is included within the technical scope of the present invention.

Example 1 Using the equipment shown in FIG.
When 0% impure He was purified, the purity was 99.999%.
The above purified He could be obtained with a recovery rate of 88.5%, and the rate of decrease in the amount of liquefaction at this time was only 30%.

[Effects of the Invention] The present invention is configured as described above, and its effects can be summarized as follows.

(1) A method for removing impurities in impure He using both coagulation and condensation methods is adopted, and the condensate can be sequentially extracted during the purification process, so that the coagulation impurities in the impure He flow path can be removed. The accumulation rate is slow and He purification can be continued for a long time.

(2) The solidified impurities accumulated in the impure He channel can be liquefied or vaporized and discharged by being discharged outside the heat exchanger through instantaneous pressure reduction treatment, and the purification of the channel can be completed promptly. I can do it.

(3) There is no need to heat the channel from the outside during the purification process, so there is no cooling loss.

(Since it is an individual discharge method by condensation and coagulation, even if the purity of impure He used as a raw material fluctuates, it has little effect on He purification efficiency, and the range of application of raw material gas is widened. Also, high-purity He can be produced in high yields. It can be recovered at a certain rate.

[Brief explanation of drawings]

Figure f51 is a schematic flow diagram showing an example of the present invention, and Figure 2 is a schematic flow diagram illustrating the purification method of the prior invention, which is the basis of the present invention. 1.1a-1d...Heat exchanger 3,3a-3d...
Heat medium flow path 4...pressure wI machine 5a, 5b...
Trap 10.10a, 14, 16, 18.30--
Valve 3! ...gas bag

Claims (1)

[Claims] When refining He using a heat exchanger that includes a medium flow path and an impure He flow path, impurities in the impure He are cooled by introducing a refrigerant into the medium flow path. A portion is condensed and discharged outside the system as a liquid, and the remaining portion is solidified in the impure He flow path of the heat exchanger and becomes He.
In this method, in order to remove the solidified residual impurities in the impure He flow path, the inside of the impure He flow path is once sealed, and then reduced pressure is applied from the upstream or downstream side to remove the solidified residual impurities. A method for purifying He, characterized by discharging He to the outside of a heat exchanger and removing it by liquefying or vaporizing.