JPH0410545Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to an apparatus for producing high purity nitrogen gas that does not contain low boiling point gases such as neon Ne, hydrogen H ₂ and helium He.

Conventional technology As a device for producing nitrogen gas by liquefaction rectification of air, compressed air from which moisture, carbon dioxide, etc. have been removed is cooled by heat exchange with low-temperature gas such as product nitrogen gas, and is partially liquefied. Introduced into the bottom of the rectification column,
Equipment is commonly used to extract the product gas from the top of the tower. Although the nitrogen gas produced by this type of equipment is highly pure, it contains low-boiling point gases such as neon, hydrogen, and helium without being removed, making it unsuitable for applications such as the semiconductor industry. It was hot.

An example of an apparatus for eliminating this drawback and producing high-purity nitrogen gas free of low-boiling components is the one described in Japanese Patent Application Laid-Open No. 58-64478.

The high-purity nitrogen production apparatus described in the above publication is equipped with a heat exchanger with a vaporization section at the top and a liquefaction section at the bottom via a condensation section, and the product gas (high-purity nitrogen gas) collected from the top of the single rectification column is ) is introduced into the liquefaction section of this heat exchanger and liquefied by cooling with reduced pressure liquid nitrogen in the vaporization section, and the low-boiling components contained therein are discharged as uncondensed gas from the condensation section, and the liquefied nitrogen is transferred to the liquefaction section. The nitrogen gas is introduced into the vaporization section via a pressure reducing valve, where it is vaporized and collected as a high-purity nitrogen gas product that does not contain low-boiling components.

However, in this device, the liquid nitrogen that is vaporized and becomes a product is taken out from the top of the single rectification column and condensed in the condensation section of the heat exchanger, and the gas containing low-boiling components is purged from the condensation. Since it is in equilibrium with the above, it can be said that it still contains low-boiling components that are impurities.

Therefore, in order to further remove low-boiling point components, the inventors of the present invention decided to use a rectification plate that is liquefied in an aluminum brazing type nitrogen condenser and returns high-purity liquid nitrogen from which low-boiling point components have been removed. has filed a utility model registration application for a high-purity nitrogen production device that extracts product gas from a rectifier plate several stages below. (Jitsugan Showa 62
-136828) (hereinafter referred to as the "earlier invention" in the present specification) The present invention relates to an improvement of the earlier invention.

Problems to be Solved by the Invention The present invention provides a high-purity nitrogen production device that is more compact and energy-saving than the device devised in the earlier application.

Means for Solving the Problems The inventors of the present invention have successfully developed the device of the present invention as a result of various studies and experiments, and the technical structure of the present invention is specified in each claim of the above-mentioned utility model registration. However, a detailed explanation will be given based on the attached drawings showing a specific example of the device of the present invention.

Example 1 (Figure 1) Raw air of 5000Nm ³ /hr is compressed to 8.0Kg/cm ² , and after removing moisture, carbon dioxide, etc., the temperature is 20℃.
The product nitrogen gas enters the heat exchanger 2 from pipe 1,
It is cooled to −167° C. with waste gas, etc., taken out through a pipe 3, and introduced into the lower part of a single rectification column 4. 3500 Nm ³ /hr of nitrogen gas is taken out from the top of the rectification column 4 through a pipe 5, introduced into an aluminum brazing type nitrogen condenser 6, where it is cooled and liquefied,
Uncondensed gas containing impurities such as neon and helium
1 Nm ³ /hr is purged from line 7. The liquid nitrogen liquefied in the nitrogen condenser 6 was 3499Nm ³ /hr.
It is returned to the rectification plate A at the top of the rectification column 4 through a pipe 8. 3199 Nm ³ /hr of oxygen-enriched liquid air (-172°C) is taken out from the bottom of the rectification column 4 through a pipe 9, and after being reduced in pressure to 3.8 Kg/cm ² by an expansion valve 10, it is replaced with nitrogen. It is introduced into the condenser 6 and becomes a cold source. The liquid air vaporized here is taken out from the pipe 11 as cold air (oxygen rich) at -173°C, and is taken out from the heat exchanger 2.
After the feed air is cooled, the temperature is raised to -150°C, and the air is taken out through a pipe 12. The air is then expanded to 0.5Kg/cm ² in the expansion turbine 13 to a temperature of -180°C, taken into the heat exchanger 2 again through the pipe 14, used to cool the raw air, heated to room temperature, and discharged into the pipe as waste gas. It is discharged from channel 15.

High purity liquid nitrogen containing no low boiling point components
1800Nm ³ /hr is taken out from rectifying plate B of rectifying column 4 (several stages below rectifying plate A) through conduit 16, and is taken out through expansion valve 17.
After being expanded to 7.5 kg/cm ² , the raw air is introduced into the sub-condenser 18 and supplied through a pipe 19 branched from the pipe 3, at a rate of 3000 Nm ³ /hr, which is cooled and at least a part of it is liquefied. , pipe 20 in a gas-liquid mixed state at -167℃
It joins the pipe 3 and is supplied to the lower part of the rectification column 4. Vaporized high-purity nitrogen gas is passed through pipe 21
The feed air is then taken out from the heat exchanger 2, cooled, and heated to room temperature.
2 is extracted as a product gas. When producing or co-producing high-purity nitrogen gas for applications that do not pose a problem even if it contains low-boiling components, all or part of the nitrogen gas in the pipe 5 is sent to the pipe 23, and the nitrogen gas is transferred to the heat exchanger 2. It can be heated to room temperature and taken out as a product from the pipe line 24.

Embodiment (FIG. 2) This embodiment is the same as the embodiment of FIG. 1 except that the purge line for uncondensed gas containing low-boiling components is different.

The liquid nitrogen taken out from the pipe 5 and cooled and liquefied in the aluminum brazing type nitrogen condenser 6 is transferred to the pipe 25.
It is taken out and guided to the gas-liquid separator 26, where it is separated into gas and liquid. Most of the low boiling point components condensed in the gas phase enter the gas during gas-liquid separation,
The nitrogen gas is extracted as general-purpose high-purity nitrogen gas through the pipe 33, heat exchanger 2, and pipe 24. The liquid nitrogen at the bottom of the gas-liquid separator 26 is returned to the rectification plate A of the rectification column 4 through the pipe 8.

When producing or co-producing general purpose high-purity nitrogen gas, it becomes possible by increasing the flow rate of the pipe line 23.

Effects of the invention The device of the present invention, like the device devised in the earlier application, can of course produce high-purity nitrogen gas with a very low content of low-boiling components.
In addition, a sub-condenser 18 is provided to condense air-nitrogen.
When evaporation is performed, the following effects can be obtained because the liquefaction temperature of air is higher than that of nitrogen. That is, the total heat transfer area of the nitrogen condenser 6 and the sub-condenser 18 can be made smaller than the heat transfer area of the nitrogen condenser of the device devised by the earlier application, and the supply pressure of raw air can be lowered, resulting in cost and energy savings. It becomes possible to measure.

Furthermore, since a portion of the feed air is liquefied in the sub-condenser 18, at least a portion of the feed air supplied to the rectification column 4 is in liquid form, and the amount of gas rising inside the rectification column 4 is reduced. Therefore, there is an advantage that the volume of the rectifying column 4 can be reduced accordingly.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing an example of the device of the present invention, and FIG. 2 is a flow sheet showing a modification of the device shown in FIG. 1 with a gas-liquid separator.
1... Raw material air, 2... Heat exchanger, 4... Nitrogen rectification column, 6... Nitrogen condenser, 10, 17... Expansion valve, 13... Expansion turbine, 15... Waste gas, 1
8...Sub-condenser, 22...High purity nitrogen gas, 24
... Nitrogen gas, 26 ... Gas-liquid separator, A,
B... Rectifier plate, other symbols indicate pipes.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) The raw air that has been cooled by the heat exchanger 2 after removing moisture, carbon dioxide, etc. is introduced into the lower part of the nitrogen rectification column 4, and is liquefied and rectified to produce nitrogen at the top of the column. In the high-purity nitrogen production apparatus, the liquid air is separated in the lower part, a part of the separated nitrogen is collected as a product gas, and the remaining part is liquefied by heat exchange with the liquid air to become a reflux liquid. Nitrogen rectification column 4 Nitrogen gas from the top of the column is liquefied by heat exchange with expanded liquid air from the bottom of the column, and cooled by a nitrogen condenser 6 and a heat exchanger 2 for returning the liquefied gas to the top of the column. At least a part of the raw material air is liquefied by heat exchange with the expanded high-purity liquid nitrogen from below the liquid nitrogen return section of the nitrogen rectification column 4, and the nitrogen is liquefied. A high-purity nitrogen production apparatus characterized by being provided with a sub-condenser 18 for supplying to the lower part of the rectification column 4. (2) The high-purity nitrogen production apparatus according to claim 1, wherein the nitrogen condenser 6 includes a purge line 7. (3) The high-purity nitrogen production apparatus according to claim 1, wherein a gas-liquid separator 26 is attached to the nitrogen condenser 6.