JPS58190680A - Method of liquefying and separating air - 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 The present invention relates to an air liquefaction separation method, and particularly to an air liquefaction separation method suitable for simultaneously collecting argon.

Generally, argon production involves extracting oxygen with a high argon content as a raw material gas from the upper column of a double rectification column in an air liquefaction separation device, sending it to a crude argon column, and rectifying it in the crude argon column to produce crude argon. After removing oxygen from the crude argon, it is rectified in a high-purity argon column to obtain high-purity argon. As an air liquefaction separation method involving the production of argon, a method using, for example, a production apparatus as shown in FIG. 1 is known.

The raw air compressed to about 3 Kf/ml by a compressor (not shown) is introduced from the pipe 1 to the reparsing heat exchanger 2, where it is cooled and water and carbon dioxide in the raw air are removed. The air reaches a saturation temperature of 3 V4/cj and is sent through pipe 3 to the lower part of lower column 4C of double rectification column 4, which consists of upper column 4a, condenser 4h, and lower column 4C. Preliminary rectification of air is performed in the lower column 4C, and liquefied nitrogen is extracted from the top of the lower column 4C and guided to the top of the upper column 4a via a pipe 5. Impure liquefied nitrogen is extracted from the middle of the lower column 4C. Liquefied air is extracted from the bottom of the lower column 4c through a tube 7 and guided to the intermediate stage of the upper column 4a through a pipe 6, and the liquefied air is taken out from the bottom of the lower column 4c and introduced to the intermediate stage of the upper column 4a. The gas flows down in the column 4a, and the reflux liquid in the upper column 4a is vaporized in the condenser 4b, and the rising gas in the lower column 4c is liquefied, thereby proceeding with rectification in the upper column 4a and the lower column 4c. Then, nitrogen gas is extracted from the top of the upper column 4a into the pipe 8, impure nitrogen gas is extracted from the middle stage tube 9 of the upper column 4a, and oxygen gas is extracted from the lower column 10GC of the upper column 4a, and the reversing heat exchange is performed. Sent to vessel 2. Here, it is heated by exchanging heat with the raw material air and taken out as a gas at room temperature.

The crude argon column 12 equipped with the argon condenser 11 receives argon j~/j% from the intermediate stage of the upper column 4a.
, nitrogen/X or less, and the remainder oxygen ↓, an argon source gas is introduced through the pipe 13.

A part of the liquefied air extracted from the bottom of the lower column 4c of the rectification column 4 is branched from the pipe 7 to the argon condenser 11.
The argon raw material gas is introduced through a pipe 14, where it is condensed, and flows down the crude argon column 12 as a reflux liquid, where it is rectified. This liquid 5-23%, acid #c/~3%,
Nitrogen/crude argon having a concentration of 3% is led out to a pipe 15 and sent to a known argon purification process (not shown below) to collect high purity argon. The liquefied air introduced into the argon condenser 11 is vaporized and passed through the pipe 16 for rectification #! It is sent to the intermediate stage of the upper column 4a of r4.

In order to compensate for the cold required to operate these devices, 1
A part of the compressed low-temperature air is branched from the pipe 3 to the pipe 17, reheated in the reversing heat exchanger 2, further adiabatically expanded in the expansion turbine 18, and then sent from the pipe 19 to the upper column 4a of the rectification column 4. is sent to the intermediate stage.

By the way, in the air liquefaction separation method that involves argon extraction as described above, the low-temperature, low-pressure air adiabatically expanded in the expansion turbine 18 is a gas with almost the same composition as the air that has not undergone preliminary rectification in the lower column 4c. , and in gaseous form in the upper column 4
Since it is blown into the barrel, the rectifying effect of the upper column 4a is deteriorated. Further, the gas vaporized in the argon condenser 11 similarly has almost the same composition as air, and is blown into the upper column 4a in gaseous form, which similarly deteriorates the rectification conditions in the upper column 4a. For this reason, this type of air liquefaction separation method has poor oxygen separation efficiency, and especially when strict conditions are required for rectification such as argon extraction, it is extremely difficult to blow gas into the upper column. This is an undesirable operation.

This invention was made in view of the above circumstances, and it significantly improves the rectification effect in the upper column, making it possible to increase the production of argon, and also improve the yield or purity of oxygen. In order to provide a liquefaction separation method, the liquefied nitrogen extracted from the lower column of the rectification column is used as a cooling source for the argon condenser of the crude argon column, and the nitrogen gas vaporized here is sent to the heat exchanger. This method is characterized by heating the nitrogen gas in the air, then adiabatically expanding it in an expansion turbine, and further heating it in a heat exchanger to collect nitrogen gas at room temperature.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 142 shows an apparatus used in an example of the air liquefaction separation method of the present invention, and the same components as those shown in FIG.

The liquefied nitrogen extracted from the upper part of the lower column 4c of the rectification column 4 is sent via a pipe 20 to the argon condenser 11 of the crude argon column 12 as a cooling edge. Here, the liquefied nitrogen exchanges heat with the argon source gas and is vaporized to become nitrogen gas. At this time, assuming that the temperature difference between the argon source gas and liquefied nitrogen in the argon condenser 11 is the same as the temperature difference between the conventional argon source gas and liquefied air, the pressure of the vaporized nitrogen gas is:
Approximately /S~/-. This /S odor/- nitrogen gas is sent from the argon condenser 11 through the pipe 21 to the reheating system of the reversing heat exchanger 2 where it is reheated, and then adiabatically expanded in the expansion turbine 18 to approximately The pressure becomes Kf/-, and it is sent to the IJ purging heat exchanger 2 via the pipe 22 again.
It exchanges heat with the raw air to compensate for the coldness required for operation, and is emitted from the air at room temperature.

According to such an air liquefaction separation method, all the raw material air is introduced into the lower column 4 cK, preliminary rectification is performed, and the expansion turbine 1
8, air is not used for the operation, and the liquefied nitrogen extracted from the upper part of the lower column 4c is used as the cooling source for the argon condenser 11 of the crude argon column 12, and the medium-pressure nitrogen gas vaporized in the argon condenser 11 is transferred to the expansion turbine. By using the 180°C operation for cold replenishment and not blowing gas into the upper column 4a, the rectification conditions in the upper column 4a are not deteriorated and the rectification efficiency is increased. The yield of argon increases accordingly.

In the above embodiment, since the pressure of the nitrogen gas from the argon condenser 11 supplied to the expansion turbine 18 is low, the amount of cold generated is less than in the conventional method, and there may be a shortage. In this case, part of the medium pressure nitrogen may be extracted from the upper part of the lower column 4C and combined with the medium pressure nitrogen from the argon condenser 11.

Furthermore, when extracting crude argon in liquid form or increasing production of crude argon, more refrigeration is required for operation, making it necessary to extract a large amount of medium-pressure nitrogen from the upper part of the lower column 4C. This will inhibit the increase in argon production, so in such cases, a cold source such as liquefied oxygen or liquefied nitrogen is supplied from outside the system. Furthermore, in order to maintain the heat balance of the equipment, the medium-pressure nitrogen extracted from the upper part of the F column 4C is sent to the reversing heat exchanger 2 in a separate system from the medium-pressure nitrogen generated in the argon condenser 11, where it is reheated and It can also be introduced into an expansion turbine and expanded under the pressure of the lower column 4c.

As explained above, the air liquefaction separation method of this invention is
As a cooling source for the crude argon column condenser, liquefied nitrogen extracted from the lower column of the rectification column is used, and the vaporized nitrogen gas is heated in a heat exchanger, then adiabatically expanded in an expansion turbine, and heat exchanged again. Since this method is sent to a vessel and heated, it is extracted as room-temperature nitrogen gas, so compared to the conventional air liquefaction separation method that involves extraction of argon, there is no need to blow gas into the upper column. Deterioration of conditions is prevented,
The yield of argon improves, making it possible to increase argon production. In addition, since the rectification conditions in the upper column are improved, the yield of oxygen is also improved, and the power consumption of product oxygen is reduced or the purity of oxygen is improved.

Furthermore, since liquefied air is not used as a cooling source for the argon condenser of the crude argon column, there is no condensation of hydrocarbons such as acetylene in the argon condenser, which is advantageous in terms of operational safety.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an apparatus used in a conventional air liquefaction separation method involving argon extraction, and FIG. 2 is a schematic configuration diagram showing an apparatus used in an example of the air liquefaction separation method of the present invention. DESCRIPTION OF SYMBOLS 1...Pipe, 2...Repanning heat exchanger, 3...Pipe, 4...Rectification column, 4a.
...Lower tower, 4b...Condenser, 4c...
... Lower m tower, 11 ... Argon condenser, 1
2...crude argon column, 18...expansion turbine, 20.21.22...tube. Applicant Nippon Sanso Co., Ltd.

Claims (1)

[Claims] Air liquefaction: Oxygen and nitrogen are separated in the rectification column of the air liquefaction separation device, and the raw material gas for argon extracted from the middle stage of the upper column of the rectification column is sent to the crude argon column, where it is rectified and separated to collect argon. In the separation method, the crude argon column condenser is cooled by the liquefied nitrogen extracted from the lower column of the rectification column, and the vaporized nitrogen gas is heated in a heat exchanger and adiabatically expanded in an expansion turbine. An air liquefaction separation method characterized by sending the air to an exchanger and releasing it as nitrogen gas at room temperature.