JPS61243273A - Air liquefying separating method - 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 [Field of Industrial Application] The present invention relates to an air liquefaction separation method, particularly an air liquefaction separation method suitable for simultaneously collecting argon.

[Prior art] - Generally, argon production involves extracting oxygen with a high argon content from the upper column of a double rectification column as a raw material gas, sending it to a crude argon column, and rectifying it in the crude argon column to produce a crude product. This is done by using argon, removing oxygen from the crude argon, and then rectifying it in a high-purity argon column to obtain high-purity argon.

As an air liquefaction separation method involving argon production, for example, as shown in FIG. It is introduced into the container 2, where it is cooled to remove water and carbon dioxide from the raw air.
The air reaches the saturation temperature of +/ and passes through the pipe 3 to the upper column 4a.
, a condenser 4b, and a lower column 4C of the double rectification column 4.

In the lower column 4G, preliminary rectification of air is performed.
Impure liquefied nitrogen is extracted from the top of C and guided to the top of the upper column 4a via pipe 5, and liquefied air is extracted from the bottom of the lower column 4C via pipe 6 and introduced into the intermediate stage of the upper column 4a. The reflux liquid flows down in the upper column 4a as a reflux liquid, and the reflux liquid in the upper column 4a is vaporized in the condenser 4b, and the reflux liquid in the lower column 4C is
Liquefaction of the rising gas of
.

Rectification progresses in the lower column 4G.

Then, impure nitrogen gas flows from the top of the upper column 4a to the pipe 7.
Further, oxygen gas is extracted from the lower part of the upper column 4a into the tubes 8 and sent to the reversing heat exchanger 2, where it is humidified by heat exchange with the raw material air and extracted as a gas at room temperature.

Further, an argon raw material gas consisting of 5 to 15% argon, 1% or less nitrogen, and the balance oxygen is introduced from an intermediate stage of the upper column 4a through a pipe 11 to a crude argon column 10 provided with a crude argon condenser 9. Ru.

A part of the liquefied air discharged from the bottom of the lower column 4c is branched from the pipe 6 and introduced into the crude argon condenser 9 through the pipe 12, where the rising gas from the crude argon column 10 is condensed. The reflux liquid flows down through the crude argon column 10 and is subjected to rectification.

As a result, from the top of the crude argon column 10, argon 9
Crude argon containing approximately 5 to 98% oxygen, 1 to 3% oxygen, and 1 to 3% nitrogen is led out to a pipe 13, and is sent to a known argon purification process (not shown) to collect high purity argon. The liquefied air introduced into the crude argon condenser 9 is vaporized into the pipe 1.
4 to the intermediate stage of the upper column 4a.

In order to supplement the cold necessary for operating the device, a part of the compressed air is branched from the pipe 3 to the pipe 15, reheated in the reversing heat exchanger 2, and further adiabatically expanded in the expansion turbine 16. It is sent from the pipe 17 to the intermediate stage of the upper column 4a.

(Problems to be Solved by the Invention) As described above, in the air liquefaction separation method involving argon extraction, the low-temperature low-pressure air adiabatically expanded in the expansion turbine 16 and the low-temperature low-pressure air vaporized in the crude argon condenser 9 are Since it is blown into the upper column 4a in gaseous form, it has the advantage of being able to produce oxygen gas at low cost as a separation method mainly aimed at oxygen, but it is a relatively expensive method that requires strict conditions close to complete separation. In the case of rectification aimed at the co-production of argon, blowing gas into the upper column 4a is a highly undesirable operation.

Therefore, in the conventional apparatus, the rectification conditions of the upper column 4a are changed by introducing the low-temperature, low-pressure air that has been adiabatically expanded in the expansion turbine 16 through the pipe 18 shown in FIG. There are many examples of efforts being made to improve argon production and increase argon production.

In this case, there was a problem in that oxygen and argon contained in the low-pressure air passing through the pipe 18 were not involved in the rectification and were simply dissipated.

Therefore, there is a method shown in Japanese Patent Publication No. 57-42832 as a method for reducing the gas feed to the upper column, but this method requires delicate operation and a circulation compressor is used in the crude argon column condenser. This causes pressure fluctuations, making stable operation switching difficult.

Furthermore, since the liquid air is completely vaporized in the crude argon column condenser, acetylene and hydrocarbons will precipitate even in a closed loop, which is dangerous.

The present invention was made in view of the above points, and an object of the present invention is to provide an air liquefaction separation method that involves argon extraction, which makes it possible to increase the production of argon and improve the yield or purity of oxygen.

[Means for solving problems]

In order to achieve the above object, in the first invention, raw air is pressurized to 5 to 10 ko/cdG, cooled, purified by removing CO2 and H2O, and introduced into a double rectification column. In the air liquefaction separation method, in which liquefaction rectification is performed to collect oxygen and nitrogen, argon raw material gas is extracted from the intermediate stage of the upper column, sent to the crude argon column, and rectified and separated to collect argon. The low-temperature, low-pressure gas is heated by exchanging heat with the gas discharged from the compressor (described later), then recompressed by the compressor, cooled by exchanging heat with the discharge gas of the expansion turbine, and then transferred to the lower column of the double rectification column. In the second invention, the low-temperature, low-pressure gas adiabatically expanded by the expansion turbine is heated by exchanging heat with discharged gas from the compressor, which will be described later, and then recompressed by the compressor, The gas is cooled by exchanging heat with the discharge gas of the expansion turbine, and then liquefied by exchanging heat with liquid oxygen in the main condenser, and after being expanded by an expansion valve, it is introduced into the upper column of the vision rectification column.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

Note that the same members as in FIG. 5 are designated by the same reference numerals and their explanations will be omitted.

FIG. 1 shows a first embodiment of the present invention, in which low-temperature, low-pressure air is reheated in a reversing heat exchanger 2 through a pipe 15 branched from a pipe 3, and further expanded in an expansion turbine 16. It is introduced into the heat exchanger 20 through the pipe 19, and when it reaches room temperature, it is sucked into the compression l1lJ22 through the pipe 21, where it is compressed to a slightly higher pressure than the lower column, and is introduced into the heat exchanger 20 again through the pipe 23. The air is cooled by exchanging heat with the low-temperature, low-pressure air expanded in the expansion turbine 16 to become low-temperature compressed air, and then introduced into the bottom of the lower column 4C.

FIG. 2 shows the lower tower 4C as the processing gas for the expansion turbine 16.
This example shows an example in which a gas derived from a gas, for example, nitrogen gas, is used. The nitrogen gas extracted from the lower column 4C through the pipe 25 is reheated in the reversing heat exchanger 2, and then heated in the expansion turbine 16. Adiabatically expanded, tube 19. heat exchanger 20
．． It is sucked into a compressor 22 through a pipe 21, compressed to a pressure slightly higher than the lower column pressure, and then passed through a pipe 23. It is introduced into the upper part of the lower column 4C via the heat exchanger 20.

FIG. 3 shows a third embodiment, in which pipe 1 is branched from pipe 3.
The low-temperature, low-pressure air that has been adiabatically expanded in the expansion turbine 16 via the tube 19. Heat exchanger 20. Compressor 22 via pipe 21
about 4.2 kO, which is lower than the lower column pressure.
/cdG, tube 23, heat exchanger 20. The air is exchanged with liquid oxygen from the condenser 4b of the double rectification column 4 through the pipe 24 in the heat exchanger 26 to vaporize the oxygen and liquefy the air. will be introduced to

FIG. 4 shows an embodiment in which a gas, for example, nitrogen gas, led out from the lower column 4C is used as the processing gas for the expansion turbine 16 in the third embodiment. As in the second embodiment, the nitrogen gas extracted from the lower column 4C through the pipe 25 is adiabatically expanded in the expansion turbine 16, and then passed through the pipe 19. Heat exchanger 20. Approximately 5 kg is sucked into the compressor 22 through the pipe 21.
/cnQ, tube 23. Heat exchanger 20. Through the pipe 24, the heat exchanger 26 exchanges heat with the liquid oxygen from the condenser 4b of the double rectification column 4, vaporizing the oxygen and liquefying the nitrogen. be introduced.

By doing the above, the gas that was blown into the upper column 4a to compensate for the refrigeration necessary for operating the device can be turned into low-temperature compressed gas to the lower column or liquefied gas to the upper column. , the rectification effect is improved, and the production of oxygen and argon can be increased.

When introducing the liquefied gas into the upper column, the compressor 22
The discharge pressure may be lower than the raw material air pressure, and it is more economical than increasing the production of oxygen and argon by simply increasing the amount of raw material air. In addition, when it is introduced into the lower column as a low-temperature gas, it is not necessary to remove CO2 and H2O or to increase the capacity of the purging heat exchanger, which is suitable for remodeling existing equipment. Also, when the compressor 22 starts and stops, the valve 17a
Alternatively, by keeping the valve 18a open, the influence on the rectifying section can be reduced, allowing smooth operation changes. moreover,
If a bypass valve is provided to return the compressed R22 from the discharge to the suction, and the pressure is adjusted based on the discharge pressure, operation changes can be made even easier, and only need to mainly operate the valve 24a. Further, even if the compressor 22 is stopped due to a failure or the like, the process can be carried out, and therefore a reduced-volume operation is also possible. Furthermore, the existing equipment can be easily modified by adding a heat exchanger and a compressor, thereby easily increasing the capacity of the existing equipment.

In each of the above embodiments, the heat exchanger 2 is C02°H2O.
Although the description has been made using a reparsing heat exchanger that also serves to remove heat, other types of heat exchangers may be used, and air may be extracted from the middle of the heat exchanger 2 instead of reheating.

〔Effect of the invention〕

As described above, in order to generate the refrigeration necessary for the conventional equipment, low-temperature air is expanded with an expansion turbine and then blown into the upper column of the double rectification column. The low-pressure air is heated in a heat exchanger, then boosted in pressure by a compressor, cooled again by a heat exchanger, and introduced into the lower tower as low-temperature compressed air.In the second invention, the low-temperature compressed air cooled by the heat exchanger is It exchanges heat with the liquid oxygen accumulated in the condenser of the double rectification column, liquefies it, expands it with an expansion valve, and introduces it into the upper column, improving the rectification conditions in the upper column and increasing the production of argon and oxygen. I can do it. Moreover, when nitrogen gas from the lower column is used instead of the above-mentioned air, the rectification effect of the upper column is further improved, and the production of oxygen and argon can be further increased. In addition, operation operations such as changing operating conditions are easy, and there is no worry about accumulation of hydrocarbons such as acetylene, making it highly safe.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing the first embodiment of the method of the present invention, Fig. 2 is a system diagram showing the second embodiment, Fig. 3 is a system diagram showing the third embodiment, and Fig. 4 is a system diagram showing the fourth embodiment. A system diagram showing an example, FIG. 5 is a system diagram of a conventional air liquefaction separation method. 4...Double rectification column 4a...Upper column 4b...
Condenser 4C... Lower column 9... Crude argon condenser 10... Crude argon column 16... Expansion turbine 20... Heat exchanger 22... Compressor 26.
··Heat exchanger

Claims (1)

[Claims] 1. Pressurize raw air to 5 to 10 kg/cm^2G, cool it, remove CO_2 and H_2O, purify it, and introduce it into a double rectification column to perform liquefaction rectification, In the air liquefaction separation method, in which oxygen and nitrogen are extracted, argon raw material gas is simultaneously extracted from the intermediate stage of the upper column, sent to the crude argon column, and then subjected to rectification separation to extract argon. It is characterized by being heated by exchanging heat with the gas discharged from the compressor to be described later to raise the temperature, then being recompressed by the compressor, cooling the gas by exchanging heat with the discharge gas of the expansion turbine, and then introduced into the double rectification column. Air liquefaction separation method. 2. The gas adiabatically expanded by the expansion turbine is a branched part of the purified feed air, and is recompressed by a compressor and cooled by heat exchange, and then introduced into the lower column of the double rectification column. An air liquefaction separation method according to claim 1. 3. The gas that is adiabatically expanded by the expansion turbine is a gas derived from the lower column of the double rectification column, and is recompressed by a compressor and cooled by heat exchange, and then introduced into the lower column of the double rectification column. An air liquefaction separation method according to claim 1. 4. The air liquefaction separation method according to claim 3, wherein the gas adiabatically expanded by the expansion turbine is nitrogen derived from the lower column of the replica rectification column. 5. The raw air is pressurized to 5 to 10 kg/cm^2G, cooled, and purified by removing CO_2 and H_2O, and then introduced into a double rectification column to perform liquefaction rectification. Oxygen and nitrogen are collected, and at the same time the upper In an air liquefaction separation method in which argon raw material gas is extracted from an intermediate stage of the tower, sent to a crude argon tower, and subjected to rectification separation to collect argon, the low-temperature, low-pressure gas that has been adiabatically expanded by an expansion turbine is discharged from a compressor as described below. After heating up by exchanging heat with the gas, it is recompressed by the compressor, cooled by exchanging heat with the discharge gas of the expansion turbine, and then liquefied by exchanging heat with liquid oxygen in the main condenser, expanded by the expansion valve, and then connected. An air liquefaction separation method characterized by introducing air into an upper column of a rectification column. 6. The air liquefaction separation method according to claim 5, wherein the gas adiabatically expanded by the expansion turbine is a branched part of the purified raw material air. 7. The air liquefaction separation method according to claim 5, wherein the gas adiabatically expanded by the expansion turbine is gas derived from a lower column of a double rectification column. 8. The air liquefaction separation method according to claim 7, wherein the gas adiabatically expanded by the expansion turbine is nitrogen derived from a lower column of a double rectification column.