JP3282040B2 - Ultra high purity oxygen sampling method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for collecting ultrapure oxygen, and more particularly, to a method for removing exhaust gas discharged from a generally used nitrogen production apparatus, that is, oxygen contained in oxygen-enriched air. The present invention relates to a method and an apparatus for collecting high-purity oxygen.

[0002]

2. Description of the Related Art Hitherto, high-purity nitrogen has been produced by a nitrogen production apparatus having the structure shown in FIG. As is well known, this nitrogen production apparatus comprises a rectification column 1 and a condenser 2
The raw material air compressed, purified and cooled by a raw material air compressor, a raw material air refining facility, a heat exchanger and the like (not shown) is introduced into the rectification column 1 through a pipe 3. It is rectified and separated into high-purity nitrogen gas at the top of the tower and oxygen-enriched liquefied air at the bottom of the tower.

[0003] The high-purity nitrogen gas at the top of the tower is led out to a pipe 4, a part of which is collected as high-purity nitrogen gas of the product by a pipe 5, and the remainder is introduced into the condenser 2 for liquefaction. A part thereof is collected as liquefied nitrogen by a pipe 6, and the remainder is introduced as a reflux liquid of the rectification column 1 to the top of the rectification column.

[0004] The oxygen-enriched liquefied air at the bottom of the tower is led out to a pipe 7, expanded by an expansion valve 8, becomes a cold source for liquefying the nitrogen gas in the condenser 2, and is itself vaporized to a pipe 9.
Is derived. The oxygen-enriched air in the pipe 9 is discharged as exhaust gas after cooling by an expansion turbine (not shown). That is, the oxygen-enriched liquefied air at the bottom of the column is used as a cold source for generating a reflux liquid (liquefied nitrogen) of the rectification column 1 and a cold source for cooling the raw material air, and then discharged out of the system. Have been.

As an apparatus for producing oxygen, a double rectification column comprising a high-pressure column (lower column) and a low-pressure column (upper column) is used to liquefy and separate air to produce nitrogen and argon together with oxygen. This method is known, and is widely used in fields such as iron making that consume a large amount of oxygen. Further, a number of proposals have conventionally been made as a method for obtaining ultra-high-purity oxygen, but most of them are methods for removing impurity components using oxygen gas or liquefied oxygen obtained by the oxygen production apparatus as a raw material. there were.

[0006]

On the other hand, in the field of the semiconductor industry in recent years, demand for high-purity industrial gas has been increasing in accordance with higher performance and higher quality of semiconductors. It is used and the demand for high purity oxygen is negligible compared to nitrogen.

When the demand for high-purity oxygen is extremely small as compared with the demand for high-purity nitrogen as in the semiconductor industry described above, a high-purity nitrogen production apparatus as shown in FIG. The installation of the (air liquefaction / separation apparatus) is sufficiently cost-effective, but in order to obtain a small amount of high-purity oxygen, an oxygen production apparatus or an oxygen purification apparatus using the double rectification column is required. Installation is not worth the cost.

Accordingly, the present invention provides an oxygen collection method and apparatus capable of collecting a small amount of ultra-high-purity oxygen using oxygen-enriched air discharged as exhaust gas from a conventional high-purity nitrogen production apparatus as a raw material. It is an object.

[0009]

In order to achieve the above object, an ultrapure oxygen sampling method according to the present invention is directed to a nitrogen production apparatus for producing a nitrogen gas by separating raw air by a cryogenic liquefaction rectification separation method. A method for separating and collecting oxygen using a portion of the oxygen-enriched air discharged from the raw material as a raw material, wherein a portion or the liquefied air of the oxygen-enriched liquefied air derived from the bottom of the rectification column of the nitrogen production device is A part of the vaporized oxygen-enriched air is introduced into the first sub-rectification column to increase the gas- liquid ratio L / V in the column from 0.1 to 0.1.
The high-boiling components are concentrated and discharged at the bottom of the first sub-rectification column, and the gas separated at the top of the first sub-rectification column is liquefied and then liquefied to the second sub-rectification column. The fraction is introduced into the top of the distillation column to adjust the gas- liquid ratio L / V in the column to approximately 1, and rectified. The low-boiling component is concentrated and discharged to the top of the second sub-rectification column, and the second sub-rectification column is discharged. The method is characterized in that oxygen separated at the bottom of the sub-rectification column is collected as gas and liquid .

Further, the ultrapure oxygen sampling apparatus of the present invention
An apparatus for separating and collecting oxygen by attaching a raw material air to a nitrogen production apparatus for producing nitrogen gas by separating it by a cryogenic liquefaction rectification separation method, which is derived from the bottom of a rectification column of the nitrogen production apparatus. If a part of the oxygen-enriched liquefied air or a part of the oxygen-enriched air obtained by vaporizing the liquefied air has a gas-liquid ratio L / V of 0.1 in the tower,
A first sub-rectification column for rectifying under the conditions of 0.3 to 0.3, a path for discharging high boiling components concentrated at the bottom of the first sub-rectification column, and a separation at the top of the first sub-rectification column. A condenser for liquefying gas,
The gas liquefied by the condenser is introduced into the top part, and the gas-liquid ratio L
A second sub-rectification column that rectifies under the condition that V / V is approximately 1;
A route for discharging low-boiling components concentrated at the top of the sub-rectification column,
A process of collecting oxygen separated at the bottom of the second sub-rectification column with a gas
It is characterized by having a path and a path for sampling with a liquid .

[0011]

[Operation] According to the above configuration, high-purity oxygen gas can be collected from a part of the oxygen-enriched liquefied air derived from the bottom of the rectification column of the nitrogen production apparatus. That is, high-boiling components contained in oxygen-enriched liquefied air or oxygen-enriched air obtained by evaporating the liquefied air, such as various hydrocarbons, nitrogen oxides, and fluorocarbons, are deposited at the bottom of the first sub-rectification column. Concentrated and separated,
On the other hand, low boiling components such as nitrogen are concentrated and separated at the top of the second sub-rectification column, and ultra-high purity oxygen gas and liquefied oxygen are separated at the bottom of the second sub-rectification column.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail based on one embodiment shown in FIG. The same elements as those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The apparatus of this embodiment is introduced into a nitrogen production apparatus comprising the rectification column 1 and the condenser 2, which is led out from the bottom of the rectification column 1 to a pipe 7, depressurized by an expansion valve 8, and vaporized by the condenser 2. A first sub-rectification column 11 for introducing a part of the oxygen-enriched air as an ascending gas, a sub-condenser 12 for liquefying a gas derived from the top of the first sub-rectification column 11, Secondary rectification column 1 that introduces a part of the liquefied gas liquefied in reactor 12 as a reflux liquid
3 and a reboiler 14 installed at the bottom of the second sub-rectification column 13 as main components.

Hereinafter, a procedure for collecting ultrahigh-purity oxygen in accordance with the flow of gas and liquid will be described. In addition, all compositions are volume%.

First, oxygen-enriched air (for example, 66.34% of nitrogen, 32.23% of oxygen, 32.23% of oxygen, and 1.0% of argon) introduced from the pipe 9 to the pipe 15 and introduced into the first sub-rectification column 11 as rising gas. 43% and a small amount of impurity components are rectified in the first sub-rectification column 11, so that high-boiling components (various hydrocarbons, nitrogen oxides, chlorofluorocarbons, etc.) having a boiling point higher than oxygen at the bottom of the column. Are concentrated, and a gas (for example, a gas of 71.56% of nitrogen, 27.06% of oxygen, and 1.38% of argon) that does not contain these high-boiling components is separated at the top of the column.

The rectification conditions of the first sub-rectification column 11 vary depending on various conditions such as the condition of the raw material air, the operating conditions of the nitrogen production apparatus, and the composition of the ultra-high purity oxygen to be collected. Since the high boiling point components to be used are very small, the rectification stage is also one.
A stage or several stages, for example, about seven stages, is sufficient, the amount of reflux liquid may be small, and the gas-liquid ratio L / V in the column may be in the range of 0.1 to 0.3.

The liquefied gas containing the high-boiling components at the bottom of the first sub-rectification column 11 is supplied to a pipe 16 as a path for discharging the high-boiling components.
After being expanded by the expansion valve 17 and becoming a cold source of the sub-condenser 12 and vaporized, it is discharged from the pipe 18.

The gas containing no high-boiling components at the top of the first sub-rectification column 11 is led to a pipe 19 and liquefied in the sub-condenser 12 to become a liquefied gas. In this sub-condenser 12,
As a cold source for liquefying the gas not containing the high boiling point component, in addition to the liquefied gas containing the high boiling point component, a part of the oxygen-enriched liquefied air led out from the rectification column 1 to the pipe 7 is used. Is used by being branched into a pipe 20 and expanded by an expansion valve 21.

The liquefied gas liquefied in the sub-condenser 12 is
Part (the amount corresponding to L / V = 0.1 to 0.3)
Is introduced into the top of the first sub-rectification column 11 through a pipe 22 to form a reflux liquid, and the remainder is introduced into the top of the second sub-rectification column 13 through a pipe 23 and an expansion valve 24.

The second sub-rectification column 13 is operated at a low pressure of 0.5 to 1.0 kg / cm ² G in order to improve the efficiency of separation of oxygen from low boiling components such as nitrogen and argon. The rectification is performed with a reflux liquid composed of a liquefied gas containing no high-boiling components and an ascending gas composed of oxygen gas vaporized in the reboiler 14 installed at the bottom of the column. The components are concentrated, and liquefied oxygen of ultra-high purity (for example, 99.9999% or more) is separated at the bottom of the column.

The rectification conditions of the second sub-rectification column 13 vary depending on the composition of the ultrahigh-purity oxygen to be collected and the like. However, usually, a large amount of low-boiling components such as nitrogen gas to be separated is present. It is desirable to increase the number of rectification stages, for example, it is preferable to provide about 50 stages, and it is also preferable to set the column gas-liquid ratio L / V to a value close to 1.

Ultra-high-purity liquefied oxygen at the bottom of the second sub-rectification column is collected from a tube 25, and ultra-high-purity oxygen gas is collected from a tube 26. The ultra-high-purity oxygen may be collected either by gas or liquid depending on demand, or by both.
On the other hand, the low-boiling component concentrated at the top of the second sub-rectification column is led out to a pipe 27 which is a path for discharging the low-boiling component, and is cooled together with the gas in which the high-boiling component is concentrated in the pipe 18 as a cooling source for the raw air. It is discharged after being used as.

As the heat source introduced into the reboiler 14, a part of the high-purity nitrogen gas led out from the top of the rectification column 4 to the pipe 4 is branched into a pipe 28 and used. The liquefied nitrogen liquefied by vaporizing the ultrahigh-purity liquefied oxygen in 14 is combined with the liquefied nitrogen liquefied in the condenser 2 by a pipe 29.

As described above, a part of the oxygen-enriched air which has been discharged in the past is rectified by the first rectification column 11 and the second sub-rectification column 13 as described above, so that an extremely high-purity oxygen is obtained. Can be collected. The amount of the high-purity oxygen that can be collected can be set to an appropriate amount according to the demand and the purity.
1% or less is suitable for the amount of raw material air, and can sufficiently cope with high-purity nitrogen and ultra-high-purity oxygen required by the semiconductor industry.

In addition, the system including the first and second sub-rectification towers and the sub-condenser can be significantly reduced in size as compared with the production of oxygen using a double rectification column. Because extremely high-purity oxygen can be obtained compared to a normal double rectification column,
It is no longer necessary to provide an oxygen purification facility conventionally provided in a double rectification column, and ultra-high-purity oxygen that meets demand can be collected at a small facility cost. In addition, since the amount of ultrapure oxygen to be collected is small relative to the total amount, there is almost no increase in operating costs.

In the above embodiment, the first oxygen-enriched liquefied air discharged from the rectification column of the nitrogen production apparatus is
Although the liquefied air is introduced as a rising gas into the sub-rectification column, the liquefied air may be directly introduced into the first sub-rectification column. However, in this case, it is necessary to install a reboiler or the like for evaporating the oxygen-enriched liquefied air into a rising gas at the bottom of the first sub-rectification column.

As the heat source to be introduced into the reboiler of the second sub-rectification column, for example, a part of the raw air may be used in addition to the above-mentioned nitrogen gas. , Liquefied gas can be used.

[0028]

As described above, according to the present invention,
Ultra-high-purity oxygen can be collected using part of the oxygen-enriched air that has been discharged from conventional nitrogen production equipment. For the semiconductor industry, which uses a small amount of ultra-high-purity oxygen together with a large amount of high-purity nitrogen It is most suitable as an air liquefaction separation device.

In addition, a nitrogen production apparatus using a normal single rectification column can be used as a main apparatus as it is, and ultra-high purity oxygen can be collected without reducing nitrogen production. Can be obtained.

[Brief description of the drawings]

FIG. 1 is a system diagram showing one embodiment of the present invention.

FIG. 2 is a system diagram showing an example of a conventional nitrogen production apparatus.

[Explanation of symbols]

1: rectification tower 2: condenser 8, 17, 21, 24 ...
Expansion valve 11: first sub-rectification column 12: sub-condenser 13: second sub-rectification column 14: reboiler

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-61-190277 (JP, A) JP-A-64-75883 (JP, A) JP-A-2-282683 (JP, A) JP-A-3- 17488 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) F25J 1/00-5/00

Claims (2)

(57) [Claims] 1. A method for separating and collecting oxygen from a part of oxygen-enriched air discharged from a nitrogen production apparatus for producing a nitrogen gas by separating a raw air by a cryogenic liquefaction rectification separation method, Introducing a part of the oxygen-enriched liquefied air or a part of the oxygen-enriched air vaporized from the liquefied air into the first sub-rectification column ,
The rectification is performed by adjusting the gas-liquid ratio L / V from 0.1 to 0.3, and the high-boiling components are concentrated and discharged to the bottom of the first sub-rectification column. After the liquefied gas is introduced into the top of the second sub-rectification column, the gas- liquid ratio L / V in the column is substantially reduced.
Rectifying to 1 and concentrating and discharging low boiling components at the top of the second sub-rectification column , and collecting oxygen separated by gas and liquid at the bottom of the second sub-rectification column. Characterized ultra-high purity oxygen sampling method. 2. An apparatus for separating and collecting oxygen by attaching a raw material air to a nitrogen production apparatus for producing nitrogen gas by separating the raw air by a cryogenic liquefaction rectification separation method. A part of the oxygen-enriched liquefied air derived from the bottom or a part of the oxygen-enriched air obtained by vaporizing the liquefied air is converted into a gas-liquid ratio L in the column.
/ V rectification under the condition of 0.1 to 0.3, a first sub-rectification column, a path for discharging a high boiling point component concentrated at the bottom of the first sub-rectification column, A condenser for liquefying the gas separated at the top of the distillation column, and introducing the gas liquefied by the condenser to the top.
A second sub-rectification column for rectifying under the condition that the gas-liquid ratio L / V in the column is approximately 1, a path for discharging a low-boiling component concentrated at the top of the second sub-rectification column, gas oxygen separated in the fractionator bottoms
An ultra-high-purity oxygen collecting apparatus, comprising: a path for sampling with a liquid; and a path for sampling with a liquid .