JPH0219398B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to air separation in which oxygen is collected from feed air using rectification separation in a rectification column, and in particular, the present invention relates to air separation in which oxygen is collected from feed air using rectification separation in a rectification column, and in particular, the present invention relates to The present invention relates to an improved air separation method and device that does not contain boiling point impurities.

[Background of the invention]

Generally, an air separation method for obtaining product oxygen by separating oxygen from feed air using a rectification column is as follows. That is, air is pressurized, moisture and carbon dioxide in the air after pressurization are removed by an adsorption tower, and the raw material air after moisture and carbon dioxide removal is cooled to a cryogenic temperature in a heat exchanger, and the raw material after this cooling is Air is blown into the lower column of the double rectification column, and oxygen-rich liquid air is obtained at the bottom of the lower column by rectification separation in the lower column, and this liquid air is blown into the upper column of the double rectification column.
Oxygen is obtained at the bottom of the upper column by rectification separation in the upper column. Such an air separation method for collecting oxygen is disclosed in Japanese Patent Application Laid-Open No. 56-97772 and Japanese Patent Application Laid-open No. 56-97772.
It is disclosed in JP-A No. 80581, Japanese Unexamined Patent Publication No. 152374-1974, and the like.

By the way, the oxygen gas produced by this type of air separation method contains impurities having a higher boiling point than oxygen (high boiling point impurities). In other words, since rectification separation takes advantage of the difference in boiling points, impurities with a lower boiling point than oxygen such as nitrogen and hydrogen can be separated by rectification from oxygen and high-boiling impurities in the upper column. Separation with boiling point impurities is not possible; they together accumulate in the bottom of the upper column. Therefore, the product oxygen extracted from the bottom of the upper column contains high-boiling point impurities in addition to oxygen. In this case, high boiling point impurities include hydrocarbons such as methane and ethane. The concentration of impurities contained in oxygen used in semiconductor processes and the like is strictly limited, and it is undesirable for high boiling point impurities to be mixed into the oxygen.

When particularly high-purity oxygen is required, oxygen containing high-boiling point impurities that has been rectified in an air separation device is supplied as raw oxygen to the oxygen purification equipment, and the high-boiling impurities are removed by the oxygen purification equipment. , thereby obtaining high purity oxygen. The oxygen purification equipment is, for example, as shown in FIG. That is, when the raw material oxygen gas is heated, the heater 31 and the catalyst tank 3 react with high boiling point impurities in the raw material oxygen gas heated by the heater to water and carbon dioxide.
2, a cooler 33, and an adsorption tower 34 that adsorbs and removes water and carbon dioxide generated in the catalyst tank and outputs highly purified oxygen gas. With such a configuration, high-boiling point impurities (especially hydrocarbons) in the raw material oxygen gas can be removed to obtain product oxygen with high purity. However, when using this type of oxygen purification equipment, not only does the equipment configuration become complicated, but the operation also requires power consumption due to the use of the heater, use of cooling water in the cooler, and use of regenerated gas in the adsorption tower. This is not desirable as it will cost a lot of money.

[Purpose of the invention]

An object of the present invention is to provide an air separation method and apparatus capable of collecting high purity oxygen free of high boiling point impurities.

[Summary of the invention]

The present invention provides air separation for extracting oxygen.
The oxygen gas stored in the bottom of the upper column of the double rectification column is extracted and supplied to the purified oxygen column having a condensation section at the top, and the reflux liquid rectified in the lower column is passed through the condensation section in the purified oxygen column. The oxygen is then supplied to the upper tower, where oxygen and high-boiling point impurities are separated by rectification in the purified oxygen tower.
It is characterized in that the liquid oxygen after the rectification and separation is returned from the lower part of the purified oxygen column to the bottom of the upper column, and high-purity oxygen from which high-boiling point impurities have been removed is collected from the upper part of the purified oxygen column.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail using specific examples.

FIG. 1 is a flow sheet showing one embodiment of the present invention. In FIG. 1, 1 is a double rectification column, which has a lower column 2, an upper column 3, and a main condenser 4. Reference numeral 5 denotes a purified oxygen tower, which has a condensing section 6 at the top. 7 and 8 are pressure regulating valves.
11 to 20 indicate conduits.

First, the raw air is compressed and cooled, and then
Moisture and carbon dioxide are removed by a pretreatment device (such as an adsorption tower) that removes moisture and carbon dioxide.
In the heat exchanger, heat is exchanged with cold return gas such as product gas and exhaust gas, and the product gas is cooled to a cryogenic temperature. The feed air, which has been cooled to deep cooling temperature and partially liquefied, is transferred to conduit 1.
1 and is blown into the intermediate stage of the lower column 2. In the lower column 2, rectification is performed, nitrogen is separated in the upper part of the lower column 2, and liquid oxygen containing a large amount of oxygen is stored in the bottom of the lower column 2. Nitrogen is blown into the upper part of the upper column 3 via conduit 14 and valve 8. In addition, the oxygen-rich liquid oxygen is extracted through the conduit 12, passes through the valve 7, and is supplied to the condensing section 6 of the purified oxygen tower 5.
The gas rising in the column is condensed, and the gas itself is vaporized and blown into the intermediate stage of the upper column 3 through the conduit 13. In the upper column 3, nitrogen is separated at the top of the upper column 3 and oxygen at the bottom of the upper column 3 by rectification separation. The temperature of the nitrogen is recovered through a heat exchanger (not shown) from the conduit 15, and the nitrogen is sent to the nitrogen demand destination. The temperature of the exhaust gas is recovered through a heat exchanger (not shown) through the conduit 16, and then the exhaust gas is discharged into the atmosphere. The oxygen obtained at the bottom of the upper column 3 is removed as a gas or liquid via a conduit 17 and sent to the consumer. The oxygen in this case contains high-boiling point impurities as described above, and its purity is not high. Therefore, in order to obtain high-purity oxygen, the oxygen gas stored at the bottom of the upper tower 3 is transferred to the conduit 18.
This is then supplied to the lower part of the purified oxygen tower 5. The oxygen gas supplied to the purified oxygen tower 5 is
It rises in the column, is condensed in the condensing section 6, becomes liquid oxygen containing many high-boiling point impurities, descends in the column, and is returned to the bottom of the upper column 3 through a conduit 19. Through this rectification operation, high-purity oxygen gas from which high-boiling point impurities have been removed is obtained in the upper part of the purified oxygen tower 5, and this is transported to the demand destination or storage via the conduit 20. sent to the container. In other words, oxygen containing high-boiling point impurities separated at the upper bottom of the double rectification column 1 is supplied to the purified oxygen tower 5, where oxygen and high-boiling point impurities are separated by rectification separation. High purity product oxygen is obtained by extracting the product gas from the upper part of the purified oxygen tower 5 from which high purity oxygen gas containing no impurities is separated.

According to this embodiment, oxygen containing high-boiling point impurities is supplied to the purified oxygen tower, and product oxygen is extracted from a portion free of high-boiling point impurities, so that highly pure oxygen can be obtained. In addition, the only additional equipment needed to obtain high-purity oxygen is a purified oxygen tower and a few conduits, eliminating the need for large-scale purification equipment. In addition, there is almost no operating cost to obtain high-purity oxygen.

〔Effect of the invention〕

According to the present invention, in air separation for collecting oxygen, oxygen gas stored at the bottom of the upper column of a double rectification column is extracted and supplied to the lower part of the purified oxygen column having a condensation section at the top, and is purified in the lower column. The distilled reflux liquid is supplied to the upper column through the condensation section in the purified oxygen column, and oxygen and high-boiling point impurities are separated by rectification in the purified oxygen column. Pure oxygen can be easily collected.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing an example of oxygen purification equipment. 1...Double rectification column, 2...Lower column, 3...Upper column,
4... Main condenser, 5... Purified oxygen tower, 6... Condensing section, 7, 8... Valve, 10-20... Conduit.

Claims (1)

[Claims] 1. Feed air is blown into the lower column of the double rectification column, and oxygen-rich liquid air is obtained at the bottom of the lower column by rectification separation in the lower column, and the liquid air is In an air separation method in which oxygen is blown into the upper column of a double rectification column and oxygen from which low-boiling impurities have been removed is obtained at the bottom of the upper column by rectification separation in the upper column, The oxygen gas stored at the bottom of the upper tower is extracted and supplied to the lower part of the purified oxygen tower, which has a condensation section at the top, and the reflux liquid rectified in the lower tower is passed through the condensation section in the purified oxygen tower to the upper tower. The purified oxygen tower is supplied with oxygen and high-boiling point impurities are separated by rectification in the purified oxygen tower, and the liquid oxygen after the rectification separation is returned from the lower part of the purified oxygen tower to the bottom of the upper tower. An air separation method characterized by collecting high purity oxygen from which higher boiling point impurities have been removed. 2. Feed air is blown into the lower column of the double rectification column, and oxygen-rich liquid air is obtained at the bottom of the lower column by rectification separation in the lower column, and the liquid air is transferred to the top of the double rectification column. In an air separation device configured to blow into a column and obtain oxygen from which low-boiling impurities have been removed at the bottom of the upper column by rectification separation in the upper column, the upper column bottom of the double rectification column; A passage that communicates with the lower part of the purified oxygen tower having a condensation section at the top and extracts oxygen gas stored at the bottom of the upper tower, and a passage that returns liquid air after rectification and separation in the purified oxygen tower to the bottom of the upper tower. In addition, a passageway was provided to guide the reflux liquid rectified in the lower column of the double rectification column to the upper column via the condensation section in the purified oxygen column, so that high-boiling point impurities were removed from the upper column of the purified oxygen column. An air separation device characterized in that it is configured to collect high-purity oxygen.