JPS61225568A - Air separator - 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 Application of the Invention] The present invention relates to an air separation device for separating a product gas such as nitrogen from air.

[Background of the invention]

In general, air separation equipment uses a compressor to compress and pressurize feed air, cools the feed air, which has become high in temperature due to the heat of compression, in an aftercooler, and then cools the feed air with moisture (H
2O) and carbon dioxide (CO,) are adsorbed and removed by an adsorption tower, and the raw air after H2O and CO2 removal is co-fed to a rectification medium via a heat exchanger to separate product gas (nitrogen or oxygen) by rectification. are doing. Such air separation devices are disclosed in, for example, JP-A-56-97772 and JP-A-55-49.
No. 681, JP-A-55-38423, JP-A-54-1
No. 52667 and Japanese Patent Application Laid-Open No. 54-84888.

Incidentally, large amounts of nitrogen are used in semiconductor manufacturing processes and the like, and the nitrogen used here is required to be of extremely high purity. In particular, the inclusion of carbon monoxide and hydrogen in nitrogen is undesirable as it causes performance deterioration and quality defects of semiconductors. Nitrogen gas produced by cryogenic separation contains a substance having a boiling point similar to or lower than that of nitrogen. Such substances include helium, neon, hydrogen, argon, and carbon oxide. On the other hand, hydrocarbons and chlorine.

Carbon dioxide, water, etc. have higher boiling points than nitrogen.

Nitrogen contains almost no hydrogen, so when nitrogen used in semiconductor manufacturing processes is produced by air fractionation using cryogenic separation, the problem is how to remove hydrogen and carbon monoxide. Under such a background, purification equipment for removing hydrogen and carbon oxide contained in nitrogen gas has conventionally been used. The configuration of a conventional purification device will be briefly described below. Figure ff14 shows a system diagram of a conventional hydrogen and carbon monoxide removal device.

Oxygen gas for combustion is added through a conduit 42 to nitrogen gas containing hydrogen and carbon oxide supplied from a conduit 41 . How much oxygen gas to add?

The amount of hydrogen and carbon monoxide should be a little smaller than the amount required to burn it, so that no unburned hydrogen or carbon oxide remains.

Next, this mixed gas is heated by an electric heater 51 to
After being heated to about 120° C., it is supplied to a catalyst tank 52 filled with a combustion catalyst. This is because although hydrogen reacts and burns with oxygen even at room temperature, it is necessary to raise the temperature to the above-mentioned temperature in order to start burning carbon oxide. In the catalyst tank 52,
Hydrogen reacts with oxygen to form water, and carbon oxide reacts with oxygen to form carbon dioxide. The unreacted excess oxygen is reacted and absorbed by a catalyst tank filled with an oxygen absorption catalyst (for example, Cu) provided in the primary stage, and is removed from the nitrogen gas. Then, the cooler is humiliated through the conduit,
Here, it is cooled in a chamber. The cooled nitrogen gas is supplied to the adsorption column group via conduit 47, and water and carbon dioxide are removed by the adsorbent packed therein. usually,
Two oxygen absorption catalysts 1f152 and two adsorption tower groups are installed, and are used alternately. That is, while one is in the absorption or adsorption operation, the other regenerates its function, and by switching between the two, the absorption or adsorption operation is performed continuously.

By adding such a purification device, it is possible to purify the nitrogen produced by the left-hand separation device and remove carbon monoxide and hydrogen from the nitrogen.

However, in this case, the entire 'AM becomes complicated, and the operating cost increases due to the consumption of energy due to the use of high-purity oxygen.

[Purpose of the invention]

An object of the present invention is to provide an air separation IIN that does not contain carbon monoxide or hydrogen in the separated gas. A catalyst tank that reacts combustible components in the air (carbon oxide, hydrogen, etc.) with oxygen, an adsorption tower that adsorbs and removes moisture and carbon dioxide from the raw air after the reaction in this catalyst tank, and this adsorption tower. It is characterized by having an apparatus for rectifying and separating a product gas from the raw material air that has passed through the air.

[Embodiments of the invention]

below,! 5@Ming will be explained using examples. FIG. 1 is a flow sheet diagram showing one embodiment of the present invention.

In FIG. 1, a filter 1 removes dust and the like from the air, which is a raw material. The air compressor 2 compresses (increases the pressure) the raw air that has passed through the filter 1. The catalyst tank 3 is filled with a catalyst such as platinum or palladium, and combustible components in the air are burned here.

The cooler 4 cools the raw air. The adsorption tower 5 is filled with an adsorbent that adsorbs moisture and carbon dioxide, and adsorbs and removes moisture and carbon dioxide from the raw air. Reference numeral 100 denotes a cryogenic separation section, which is composed of 6.7, etc.

The heat exchanger 6 cools the return gas from the rectification column, which is raw material air, to lower it to a deep cooling temperature. The rectifying column 7 is supplied with the raw material air that has been cooled by the heat exchanger 6, and rectifies and separates the product gas (in this example, only nitrogen). The waste gas and product gas here become the return gas of the heat exchanger 6. 8 is a condenser at the top of the rectification column, 11 to 23 are conduits, 31
is an expansion valve, and 32 to 39 are switching valves of the adsorption tower 5.

A catalyst tank 3 filled with a combustion catalyst for burning hydrogen, carbon oxide, etc. is provided between the outlet of the air compressor 2 and the cooler 4. This means that the temperature of the air increases to 90℃ due to the heat of compression.
Taking advantage of the fact that the temperature has risen to ~120'C, the catalyst tank 3
This is to cause a reaction in. hydrogen in the air,
- Carbon oxide reacts with oxygen, which is present in large excess in the air, under a combustion catalyst. The reaction products are moisture and carbon dioxide.

With respect to 21% oxygen, the concentration of hydrogen and carbon oxide is at most several tens of ppm 8 degrees, and it is very unlikely that unreacted hydrogen and carbon oxide remain. The heat generated by the reaction is only T, and the temperature rise is at most several layers C, so there is no need to take measures to prevent heating. The air from which hydrogen, carbon oxide, etc. have been burned off is led to a cooler 4 through a conduit 3. After being cooled down to room temperature by water in a cooler, the conductor Irf! 14
This leads to the adsorption tower 5. Usually, two or more adsorption towers are provided, and one of them is regenerated and used by switching alternately. Since the adsorption tower 5 is filled with an adsorbent that adsorbs and removes moisture and carbon dioxide, the air at the outlet of the adsorption tower contains almost no moisture or carbon dioxide. The air coming out of the adsorption tower 5 is guided to a cryogenic separation section 100 consisting of a heat exchanger 6, a rectification tower 7, etc., and the feed air is introduced into the heat exchanger 6 through a conduit. Ru. Here, the raw air is cooled by exchanging heat with nitrogen gas and waste gas. Furthermore, this air is fed to the bottom of the rectification column 7 through a conduit 16. Here, the raw air comes into gas-liquid contact with the liquid on a large number of rectification plates provided in the column, and is separated by rectification. As a result, liquid air with a high oxygen concentration accumulates at the bottom of the rectification column 7.

On the other hand, nitrogen gas is extracted from the rectification column through the conduit 17 at the top of the rectification column, and its temperature is recovered inside the air heat exchanger 6.
The product nitrogen gas is delivered through conduit 18. In this case, CO and H2 are removed by a rectification operation, and carbon monoxide and hydrogen are not included in the product nitrogen gas. Although a rectification column is used, this may be a double rectification column that simultaneously extracts oxygen gas.On the other hand, liquid air is extracted from the rectification column through a conduit 19, and is depressurized by an expansion valve 31 on the way. , due to the so-called Joule-Thomson effect, the rate of heat decreases, and then it is supplied to the condenser as a cold heat source for the condenser 8, where it evaporates, and then returns to normal temperature through the conduit 21. It is used as regeneration gas in the adsorption tower 5 and is discharged into the atmosphere through conduit n.

In the embodiment described above, since the heat of compression is utilized, a heater for raising the temperature of hydrogen and carbon oxide to the combustion temperature is unnecessary. Furthermore, since it is combined with a deep-cooling type air separation device Σ, it is possible to simultaneously obtain effects such as being able to remove hydrocarbons having a boiling point lower than that of nitrogen gas.

FIG. 2 shows another embodiment of the present invention when the heat of compression of air is insufficient. A heater 9 is provided between the compressor 2 and the catalyst tank 3, and the temperature is raised by the heater to a temperature suitable for combustion of hydrogen and carbon monoxide.

Examples of the heat source for the heater include electricity, steam, and combustion gas. The system after removing hydrogen, carbon oxide, etc. is the same as that shown in FIG. 1, and the details are omitted.

IE3 diagram shows compressed air after it passes through cooler 4.

This is another embodiment of the present invention in which hydrogen and carbon oxides are removed. Examples of this are common when compressed air is used for purposes other than air separation, and where the compressed air source is separate.

The compressed air cooled to room temperature by the cooler 4 exchanges heat in the heat exchanger 10 with the high-temperature compressed air from which hydrogen and carbon oxides have been removed, thereby increasing its temperature. After the temperature is further raised by a heater, hydrogen and carbon oxides are burned off in the catalyst tank 3, and then cooled to room temperature in the heat exchanger 10. On the large side, when the amount of air to be processed is large, heat is recovered by a heat exchanger, which is advantageous because the capacity of the heater can be reduced.

For small-sized devices, the order of installation for compressed air in the equipment shown in Figure 3 is 4. Heater9. The device will be simpler if the catalyst tank 3 is provided and the cooler 4 is further provided after the catalyst tank 3. In the third example, the system after hydrogen and carbon oxide removal is
Since it is the same as the example, the explanation will be omitted.

〔Effect of the invention〕

As explained above, it is possible to provide an air separation device that does not contain hydrogen and carbon monoxide in the separated gas.

[Brief explanation of the drawing]

1 to 3 are system diagrams showing uninvented embodiments, and FIG. 2 is a system diagram showing an example of a conventional nitrogen purification apparatus. 1...Filter, 2...Air compressor, 3...Catalyst tank, 4...1.・・Cooler, 5・
...adsorption tower, 6 ... heat exchanger, 7 ...
Rectification column, 8...Condenser, 11-23...
・Conduit, 31...Expansion valve 1 Figure 2 Figure 4 Procedural amendment (method) Indication of the case Showa 60 patent application No. 63534 Name of the air separation device Amended person's hand Relationship with gender Patent applicant name □510) Hitachi Co., Ltd. Manufacturer H1! Contents of curvature correction for a simple explanation of the concave surface of MJ@.

Claims (1)

[Claims] 1. A compressor that compresses raw material air, a catalyst tank that reacts combustible components in the compressed raw material air with oxygen, and a catalyst tank that adsorbs and removes moisture and carbon dioxide in the raw material air after the reaction. An air separation apparatus comprising an adsorption tower and an apparatus main body for rectifying and separating a product gas from the raw air that has passed through the adsorption tower.