JPS61127609A - Purification device for helium - Google Patents

Abstract

PURPOSE:To obtain helium having purity with high rate of recovery and inexpensive cost without using a cryogenic solvent by purifying crude He using a gas separating membrane device and a pressure swing adsorption device in combination. CONSTITUTION:Crude gas 1 contg. He is compressed by a compressor 8a, introduced into a pretreating adsorption tower 10a where the moisture and CO2, etc. contained in the crude gas 1 are removed. Then, the pretreated cruded gas is introduced into a purifying zone (b) provided with a gas separation membrane and separated into permeable He and impermeable impurities 7; the impurities 7 are discharged out of the system. The crude gas having permeated the separating membrane 11 is compressed by a compressor 8b, and introduced into an adsorption tower 12a for purifying He in a pressure swing adsorption zone (c). Impurities remaining in the crude gas is adsorbed to active carbon, etc.; purified He is stored in a tank 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a He purification device that can be operated at around room temperature and that can obtain high purity He at a high recovery rate.

[Conventional technology]

Low-temperature adsorption type H that is widely used as one of the He purification devices
The e-purification device brings raw He into contact with an adsorbent (activated carbon, etc.) cooled with liquid nitrogen, etc. to remove impurities (air, etc.) in the raw He.
While adsorbing impurities to obtain high-purity He, the adsorbent that has adsorbed impurities is heated and vacuumed to desorb the impurities and regenerate the adsorbent. Because of its excellent performance, it has an overwhelming track record of use in this field.

However, the above-mentioned low-temperature adsorption type He purification equipment requires cryogenic refrigerants such as liquid nitrogen, which not only increases the cost of He purification, but also increases the risk of accidents such as frostbite and oxygen deficiency when handling these. There remains a risk that this will occur. Furthermore, in the case of the above-mentioned He purification apparatus, it often takes several hours to complete the preparatory operation of cooling the adsorbent by supplying liquid nitrogen, which, combined with the complexity of the operation, also poses a problem in terms of processing efficiency.

In view of these circumstances, studies are underway on technologies that can replace low-temperature adsorption devices, and pressure swing adsorption devices and gas separation membrane devices that can be operated at room temperature have been proposed.

The former is a He purification device that takes advantage of the characteristic that the adsorption rate of gas on an adsorbent changes significantly depending on the pressure.
When the raw material He gas is brought into contact with an adsorbent under pressure, impurities are preferentially adsorbed and a high purity gas is obtained. On the other hand, if the adsorbent saturated with impurities is released from the pressurized state or reduced in pressure, the impurities are desorbed and the adsorbent is regenerated.

On the other hand, a gas separation membrane device is a device that purifies He using a special gas separation membrane developed by Monsanto and others. Gas purification is made possible by allowing only the gas to pass through and trapping large molecular impurities on the non-permeable side.

[Problem that the invention seeks to solve]

Among alternative devices to low-temperature adsorption devices, pressure swing adsorption devices have the problem of low recovery rates, and it is said that the maximum recovery rate in He purification is about 70%. In order to develop industrial applications, it is strongly desired to improve the recovery rate. On the other hand, gas separation membrane devices for He purification are still in the development stage and cannot be said to be fully developed, and although some have been proposed that have slightly better recovery rates, the purity of purified He is said to be low. However, although further improvement research is underway, it is considered difficult to achieve a purity (99,999% or more) comparable to the other two methods mentioned above.

Concerned about the above-mentioned situation, the present inventors have developed various methods to provide a He purification device that can be operated at room temperature and that can obtain high-purity He at a high recovery rate, which is suitable for low-temperature adsorption devices. After much consideration.

As a result, the present inventors focused on the fact that pressure swing type adsorption devices and gas separation membrane devices have a relationship that can compensate for each other's shortcomings, and by combining the two, the present inventors realized that a low-temperature adsorption device can be operated at room temperature. We came up with the idea that it might be possible to provide a device that can perform a purification function equivalent to or better than that of the previous method.

[Means for solving problems]

The present invention was completed as a result of research based on the above idea, and its gist is that the raw material He introduction section, the gas separation membrane purification section, the pressure swing adsorption section, and the purge gas discharge section of the pressure swing adsorption section are They are connected by a circuit that rotates in any direction, and an impurity discharge line is attached to the gas separation membrane purification section, and a He extraction line is attached to the pressure swing adsorption section.

[Effect]

The combination arrangement system of the gas separation membrane purification section and the pressure swing adsorption section in the present invention can be roughly divided into two systems.

First, the first combination is to first supply He as a raw material to the gas separation membrane purification section to increase He purity to a certain level.
The main procedure is to supply this to a pressure swing adsorption section to further increase He purity. In this method, the purge gas from the pressure swing adsorption section is directly connected to the source gas introduction section. According to this type of He purification device, most of the impurities in the raw material gas cannot pass through the gas separation membrane purification section and are captured, so the raw material He with increased He purity is supplied to the pressure swing adsorption section. It turns out. As a result, the load for removing impurities in the pressure swing adsorption section is reduced, so that high purity He (product) can be obtained at a considerably high recovery rate. In addition, impurities captured by the adsorbent in the pressure swing adsorption section are discharged from the pressure swing adsorption section after being supplied with purge He gas (for example, a part of the high-purity product He mentioned above) after the pressure is released, and the raw material gas is fed. It is returned to the supply path and returned to the gas separation membrane purification section together with the raw material gas, where it is captured and discharged out of the system. Therefore, impurities do not accumulate in the circuit, and even if the He purification operation is continued, there is no problem such as a decrease in He purity. On the other hand, for purging, the He used and the He mixed in the impurities in an unrecovered state are purified together with the raw material gas in the gas separation membrane purification section and the pressure swing adsorption section, and are recovered again. Therefore, He loss is also greatly suppressed and the He recovery rate is extremely high.

Next, the second combination method will be explained. First, the raw material He
He is pressurized and supplied to a pressure swing adsorption section for purification and recovery of high purity He. However, here, we do not aim to increase the recovery rate, and for the adsorbent that has adsorbed a considerable amount of He along with impurities, we supply He for purging (for example, the high-purity product He mentioned above) after the pressure has been resolved. However, it is the opposite of that during purification. direction), impurities and unrecovered He are desorbed. Then, the purge gas containing the impurities and desorbed He is supplied to the gas separation membrane purification section, and impurities that cannot pass through the membrane are captured by the gas separation membrane and discharged to the outside of the system. On the other hand, the He that has passed through the gas separation membrane (however, the purity is not very high) is returned to the raw material gas supply path and supplied to the pressure swing adsorption section together with the raw material gas, where it is highly purified and recovered as a high-purity He product. As described above, high purity He can be obtained at a high recovery rate in the second combination method as well as in the first combination method. In the second combination method, when the He purity in the raw material gas fluctuates significantly, the fluctuation immediately appears as a load change in the pressure swing adsorption unit, so it is not possible to follow the operation of the pressure swing adsorption unit. It may become difficult. In addition, since the purge gas from the pressure swing adsorption section is processed in the gas separation membrane purification section, the flow rate fluctuates greatly between when purging is in progress and when it is not being purged (steady operation), resulting in a decrease in separation accuracy in the gas purification section of 8M. That is, there is a greater risk that a portion of He will be discharged to the outside of the system together with impurities. On the other hand, in the first combination method, since the raw material gas is constantly supplied to the gas separation membrane purification section, the fluctuation in the flow rate depending on whether or not purging is in progress can be reduced. In addition, load fluctuations due to fluctuations in He purity of the raw material gas are easily absorbed in the gas separation membrane purification section, and high-purity He gas is always supplied to the pressure swing adsorption section, so load fluctuations in the pressure swing adsorption section are small and high purity H is absorbed.
It is possible to efficiently collect e.

In addition, as an application example of the He purification device according to the present invention, liquid He
Although a manufacturing device can be mentioned, it goes without saying that the application of the device of the present invention is not limited thereto. That is, the liquid He production device installs the He purification device according to the present invention on the upstream side of the He liquefaction device, and produces liquid He by supplying the high-purity He gas obtained here to the He liquefaction device. It is something to do.

〔Example〕

FIG. 1 is a flow explanatory diagram showing a preferred embodiment of the He purification apparatus according to the present invention, and shows the above-mentioned first combination method. The device S manufactured by Hel has a pre-processing section a.

It consists of a gas separation membrane purification section and a pressure swing adsorption section C. When performing 1FTe refining, for the three-way valves 14, 17, and 20, the flow passages on the left side in the drawing are opened, and for the three-way valve 15°, 18, and 19, the flow passage on the right side in the drawing is opened. After the source gas 1 is left open and pressurized by the compressor 8a, it is introduced into the pretreatment adsorption tower 10a via the three-way valve 14 to remove moisture and carbon dioxide contained in the source gas. In addition, by appropriately switching the three-way valves 14 to 16, the pretreatment adsorption towers 10a and 10b
can be used alternately. Further, the pretreatment adsorbent is regenerated using a suction pump 9. Next, the pretreated raw material gas is introduced into the gas separation membrane purification section via the three-way valve 16, and is separated into permeable He and non-permeable impurities (mainly air) by the gas separation membrane 11. 7 is appropriately discharged from the system. On the other hand, the raw material gas that has passed through the separation membrane 11 (he purity has increased considerably) is pressurized by the compressor 8b and sent to the He adsorption tower 12a via the three-way valve 17 of the pressure swing adsorption section C. The impurities remaining in the raw material gas are adsorbed by the adsorbent in the column.

The purified He is transferred to the He tank 13 via the 3-way valve 20.
Once the helium is stored in the helium, it can be taken out as a product if necessary. (When the He purification operation is performed and the impurity adsorption capacity on the He adsorption tower 12a side reaches saturation, the opening direction of the three-way valves 17 to 20 is changed to Then, while He purification is continued by the He adsorption tower 12b, the He adsorption tower 12b
The pressure inside the adsorption tower 12a is reduced and the He tank 13 is connected to the three-way valve 19.
(into the He adsorption tower 12a) (-) to desorb impurities from the adsorbent and, in parallel, some amount of adsorbed He (including desorbed impurities and desorbed He) ( - Digas is discharged from the pressure swing adsorption section C via the three-way valve 18, is returned to the raw material gas supply pipe 2, is merged with the raw material gas 1, and circulates through the purification channel together with the raw material gas 1.

In the above He purification, the raw material gas with increased He purity in the gas separation membrane purification section is transferred to the pressure spink adsorption section C.
In the pressure swing adsorption section C, He
Purification proceeds efficiently and highly pure He can be obtained at a high recovery rate. In addition, impurities and unrecovered adsorbed He are removed by purge H.
Since the He gas is combined with the raw material gas together with the He gas and circulates within the He purification device, the loss of He is extremely small, and an extremely high recovery rate can be obtained as a whole.

FIG. 2 is a flow explanatory diagram showing another embodiment of the present invention, and shows the above-mentioned second combination method. The He purifier S' includes a pretreatment section a in the gas flow direction.

The pressure swing adsorption section C2 is configured by arranging the gas separation membrane purification section in this order. When refining He, of the three-way valves 14, 16, and 17°20, the left flow passages in the drawing are opened, and the three-way valves 15, 18, and 19 are opened in the right flow passage in the drawing. Keep all roads open. Then, the raw material gas that has been pressurized and pretreated in the same manner as above is introduced into the pressure swing adsorption section C, where impurities are adsorbed and removed.
High purity He is stored in the He tank 3. On the other hand, the purge gas discharged from the pressure swing adsorption section C in the same manner as above is pressurized by the compressor 8d and then introduced into the gas separation membrane purification section, and impurities in the purge gas are removed from the gas separation M
11 in a somewhat non-transparent manner and discharged out of the system. The He that has passed through the gas separation membrane 11 is introduced into the source gas supply line 2 and circulates through the flow path together with the source gas.

In this system, He that has not been recovered in the pressure swing adsorption section C is supplied to the gas separation membrane purification section together with purge gas, and after being separated from impurities, it joins with the raw material gas and circulates within the He purification device S. There is almost no loss He
Recovery rate can be improved. On the other hand, impurities are captured in the gas separation membrane purification section and discharged outside the system, so He
Impurities do not accumulate in the purification device, and He purity does not decrease due to impurity accumulation. Furthermore, since He is also prevented from being discharged at the same time as the impurities are discharged, a decrease in the He recovery rate due to this can also be prevented.

Example 1 He:8 was added to the Helr1m device with the flow shown in FIG.
0 volume i-%, air = 20 volume chi (however, H, O and CO3
After supplying the raw material gas (which has already been removed) and boosting the pressure to 912 kg/c♂G by the compressor 8a, the permeate gas pressure at this time is 580 kg/c♂G.
torr) sFurthermore, compressor 8b 15kg/c-
After increasing the pressure to G, the He was supplied to a pressure swing adsorption section C using activated carbon as an adsorbent to highly purify He. He
The desorption pressure in the purification adsorption tower 12a j12b is 7
The pressure was 30 torr, and the switching period of the tower was 2 minutes per cycle. Raw material gas supply pipe 2. Sample gases were collected from the gas separation membrane outlet 3 and purified gas take-off pipe 4, and 1) He purity (calculated from oxygen and nitrogen concentrations) was measured using a gas chromatograph. was installed, and the He purity and recovery rate were determined. Thirty minutes after the start of operation, the purity of the product He was almost constant, and the purification results for the next one hour were as follows.

He purity (average) at the gas separation membrane outlet: 97. Solubility: Purified He purity (average): 99.9993 Volume: Recovery rate (integrated): 98.3 Example 2 In Example 1, the raw material gas composition was changed to He: 60 volumes, air: 40 volumes. When the change was made in a stepwise manner, only the He purity at the gas separation membrane outlet (permeated gas) changed from 97.3 to 97.1 by volume, but no change was observed in the purified gas composition.

Gas content 1aM He purity (average) at the outlet: 97.1 volumes He purity (average): 99.9993 volumes Recovery rate (integrated): 98.3 [Effects of the Invention] The present invention is as described above. With this configuration, you can obtain the following effects.

(1) Without using cryogenic refrigerants such as liquid nitrogen,
Since it can be operated under normal temperature conditions, the He purification cost is low, and since the above-mentioned cryogenic refrigerant is not directly handled, safety is also high. Furthermore, since there is no need to cool the adsorbent at the start of operation unlike in low-temperature adsorption systems, preparation time (start-up time) is shortened and excellent processing efficiency can be obtained.

(2) Since it is constructed by combining a gas separation membrane purification section and a pressure swing adsorption section, it eliminates both the disadvantages of pressure swing adsorption type devices such as low He recovery rate and the disadvantages of gas separation membrane type devices such as low He purity. As a result, highly pure He can be obtained with a high recovery rate.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are flow explanatory diagrams showing a He purification apparatus according to the present invention. 1... Raw material gas 2... Raw material gas supply pipe 7.
...Impurities 8a to 8d...Compressor 11...
・Gas separation membranes 12a, 12b...He purification adsorption tower 13...He
Tank 14-20... Three-way valve a... Pretreatment section b... Gas separation membrane purification section C... Pressure swing adsorption section

Claims (1)

[Claims] The raw He introduction section, the gas separation membrane purification section, the pressure swing adsorption section, and the purge gas discharge section of the pressure swing adsorption section are connected by a circuit that rotates in any direction, and an impurity discharge line is connected to the gas separation section and to the pressure swing adsorption section. A He purification device is characterized in that it is equipped with He extraction lines.