JPS5816175A - Method and device for 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 aerodynamic M# method and apparatus using a cryogenic separation method. In particular, the present invention provides a process suitable for extracting a large amount of nitrogen [Mt] and a small amount of oxygen. The present invention relates to an air separation method and apparatus having the following features.

“Air separation method using conventional cryogenic separation method”? and equipment first.
This will be explained with the help of a diagram. Figure 1 is a process system diagram showing the basic configuration of an air separation device that collects a large amount of nitrogen at a pressure lower than the pressure of the raw air, about 14/cr/IG, and a small amount of oxygen. be. In Figure 1, the pressure is approximately 6
The feed air of 1 hour/cl O is supplied to the main heat exchanger 2 through the conduit 1, and after being cooled down to approximately -170°C in the main heat exchanger 2, it is sent to the conduit 3 and sent to the rectification filling lower column (hereinafter referred to as the lower column). omitted) 4. The lower column 4 has a large number of trays 5, from the upper part of which the product nitrogen is supplied, and from the lower part of which the oxygen supply 3.
0-degree liquid air is extracted. In this case, the amount of product nitrogen that can be extracted from the upper part of the lower column 4 includes the operating pressure of the lower column 4,
5 number of shelves, product nitrogen purity and oxygen.

A theoretical upper limit exists depending on the thermodynamic properties of air components such as nitrogen and argon. For example, in order to obtain high purity nitrogen with an operating pressure of approximately 6 KSI/(iG of 99.94 or higher), feed air in an amount approximately 2.5 to 3 times the amount of product nitrogen must be pumped into the lower column 4. need to be supplied to

The liquid air extracted from the lower part of the lower column 4 as a raw material for obtaining product oxygen from the lower part of the upper column (hereinafter referred to as the upper column) 6 passes through the conduit 7 to the expansion valve 8 ↓ to the upper column. After being expanded to an operating pressure of about 0.6 to 9/cdG, it is fed to the upper part of the upper column 6 via conduit 9. In addition to this, raw air is diverted to the upper part of the upper tower 6 at the middle of the main heat exchanger 2, and a conduit 10. Valve 11. The air that has passed through the conduit 12 is separated from the raw material air in the middle of the conduit 3, and the air is separated from the raw material air in the conduit 13. The air that has passed through the valve 14 joins and is supplied via a conduit 15 to an expansion turbine 16, which is a device for compensating the cooling loss of the air separation device, and the air expanded by the expansion turbine 16 is also supplied through a conduit 17. . The liquid air supplied to a part of the upper tower 6 is internally connected to the upper tower 6, and the liquid air is
The oxygen flows down the top of the upper tower 6], evaporates in the main condenser 19, and is rectified while coming into contact with the vapor rising in the upper tower 6, producing high purity oxygen of over 99%. Two units are obtained at the bottom of 6. In this case, the minimum required amount of liquid air to produce oxygen is 1-1.
number, liquid air oxygen concentration, product oxygen purity and oxygen,
The thermodynamic properties of air components such as nitrogen and argon can contribute to this theory. For example, the operating pressure of upper tower 6 is 0.4?
/,ffl In order to obtain high purity oxygen with a purity of 99 or higher using G, the oxygen concentration of liquid air is about 30 g, so an amount of liquid air that is about 4 to 5 times the amount of oxygen must be sent to the upper tower 6. need to be supplied.

In addition, nitrogen is extracted from the upper part of the lower column 4, passed through a conduit, and after temperature recovery in the main heat exchanger 2, is collected as product nitrogen through the conduit 21. Oxygen is extracted from the lower part of the upper column 6. Extracted,
After the temperature is recovered in the main heat exchanger 2 through the conduit n, it is collected as product oxygen from the conduit row.

The residual waste gas from which oxygen has been separated is extracted from the upper part of the upper tower 6, passes through a line of conduits, recovers its temperature in the main heat exchanger 2, and then enters the conduit 5.
It is extracted as impure nitrogen.

In a conventional air separation device having the configuration and process as described in 7 above, the amount of liquid air is determined regardless of the amount of oxygen, so the entire amount of liquid air remaining after nitrogen is separated in the lower column 5 is sent to the upper column 6. If only a small amount of oxygen is required, the pressure of liquid air will not be utilized and the pressure will be reduced to 0.41'l/iGt, resulting in a waste of energy. The disadvantage was that it was not fully usable. Further, due to the oxygen concentration of the liquid air, there was a problem in that the diameter of the upper column 6 could not be made any smaller and the number of plates could not be reduced any further.

The object of the present invention is to eliminate the above-mentioned drawbacks and to solve the above-mentioned problems by installing a reboiler condenser for evaporating liquid air of pressure 61'f/cdG under a selected operating pressure. The air evaporated from the liquid air in the reboiler condenser drives an expansion turbine to generate refrigeration, thereby compensating for the refrigeration loss of the air separation device. One embodiment will be explained with reference to FIG. Second
In the figure, the same equipment as in FIG. 1 is denoted by the same reference numerals and the explanation thereof will be omitted. The section is a first reboiler condenser installed at the upper part of the lower column 4, and the first reboiler condenser boosting section is connected to the lower part of the lower column 4 by a conduit 7.27 having an expansion valve 8 at the joint. In addition, conduits from the upper part of the first reboiler condenser and others pass through the main heat exchanger 2 and are connected to the inlet side of the expansion turbine 6, and conduits from the outlet side of the expansion turbine 16 are connected to the upper part of the upper tower 6. It is connected to a bank of conduits entering the main heat exchanger 2 from the main heat exchanger 2 . Further, the lower part of the first reboiler fundenser 26 and the upper part of the upper tower 6 are conduits with an expansion valve 31 installed at the joint.

As the saying goes, it is connected. 33 is a second reboiler condenser installed at the bottom of the upper tower 6.

According to such a configuration, the pressure is approximately 6 Ky/dG
The feed air is supplied to the main heat exchanger 2 through the conduit 1, where it is cooled to about -170°C, and then supplied to the lower column 4 through the conduit 3. Thereafter, the product nitrogen is withdrawn from the upper part of the lower column 4, subject to the same quantitative limitations as in the prior art. On the other hand, from the lower part of the lower column 4, liquid air containing approximately 30 liters of oxygen is extracted, and the conduit 7. It is supplied to the first reboiler condenser via an expansion valve 8 and a conduit n. In this case, the operating pressure of the first reboiler condenser is a pressure (approximately 1 to 3 KP/d G
) was selected. The air evaporated from the liquid air in the first reboiler condenser is returned to the main heat exchanger through a series of conduits.
It exchanges heat with the raw material air, recovers its temperature to around -160°C, and is supplied to the expansion turbine 16 via a conduit. Adiabatic expansion to approximately 0.46'/cIIG in the expansion turbine 16 generates refrigeration, lowers the temperature of the air, and compensates for the refrigeration losses of the air separation device. In this case, there is no need to separately supply raw material air to the expansion turbine 16, and only the raw material air for nitrogen and oxygen extraction is required, so that the air leaving the reduced amount of raw material air 16 passes through the conduit 4 from the column 6. It joins with the waste gas of , passes through a line of conduits, recovers its temperature in the main heat exchanger 2, and is then taken out through a conduit 6 as cine-pure nitrogen.

In this case, all of the liquid air extracted from the lower tower 4
It does not evaporate in the reboiler condenser, but a part of it is extracted from the lower part of the reboiler condenser as liquid air with an even higher oxygen concentration (approximately 50 to 60 g of oxygen) and is extracted from the lower part of the reboiler condenser. Valve 31. It is supplied to the upper part of the upper column 6 through the conduit 32 and used as a raw material for separating oxygen.In this case, liquid air with a high oxygen concentration is used for oxygen separation, so the amount of liquid air used is the same as before. Therefore, the diameter of the upper column 6 can be made smaller and the number of plates can be reduced.The oxygen separated in the upper column 6 is transferred from the second reboiler condenser to the Extracted,
After the temperature is recovered in the main heat exchanger 2 through the conduit n, it is collected as product oxygen through the conduit 6. On the other hand, the residual waste gas from which oxygen has been separated is extracted from the upper Q: a-J: section, joins with the air from the expansion turbine 16 in the conduit row, and after temperature recovery in the main heat exchanger 2, the conduit 5 It is extracted as cine-pure nitrogen.

As explained above, the present invention installs a first reboiler condenser at the upper part of the lower column of the rectification column of an air separation device, a second reboiler condenser at the bottom of the upper column of the rectification column, and Under the selected operating pressure, the air evaporated from the oxygen-rich liquid air extracted from the lower column of the 'nI distillation column can be used to compensate for the cooling loss of the air separation equipment, reducing the amount of feed air. This method has the effect of achieving energy savings, and since the liquid air, which has been evaporated in the first reboiler condenser and has an even higher oxygen concentration, is used as the raw material for separating oxygen, the column diameter of the upper column of the rectification column can be reduced, and See the effect of reducing the number of shelves.

[Brief explanation of the drawing]

Figure 1 explains an air separation method and equipment using a conventional cryogenic separation method.
It is a process system diagram showing the basic configuration of an air separation device that collects nitrogen at a pressure as low as IG and a small amount of oxygen. The tAz diagram is a process system diagram showing the basic configuration of an air separation apparatus according to the present invention that extracts a large amount of nitrogen and extracts a small amount of oxygen. 2...Main heat exchanger, 4...Upper column of rectification column, 6...Upper column of rectification column, 16...Expansion turbine, ...vg1 reboiler capacitor, 3
3...Second revoice capacitor

Claims (1)

[Claims] 1. In an air separation method using a cryogenic separation method, in which a large amount of nitrogen is collected and a small amount of oxygen is collected,
The liquid air at the bottom of the rectification column of the air separation device according to the air separation method is evaporated under a predetermined pressure, and the evaporated air is introduced into an expansion turbine to compensate for the cooling loss of the air separation device, and to compensate for the evaporation. An air separation method characterized by introducing liquid air with a high oxygen concentration into the upper column of a rectification column as a reflux liquid. 2. Air separation equipment using the cryogenic separation method, consisting of a rectification column lower column, a rectification column upper column, an expansion turbine, a main heat exchanger, etc., which extracts a large amount of nitrogen and a small amount of oxygen. In the separation device, a first reboiler condenser is installed in the upper part of the lower column of the rectification column, and a conduit with an expansion valve in the middle connects the upper part of the first reboiler condenser and the lower part of the lower column of the rectification column to the lower part of the 1A boiler condenser and the lower column of the rectification column. The upper part of the column is connected to the first reboiler condenser section and the expansion turbine inlet 11 side by a conduit that passes through the main heat exchanger on its way through a conduit with an expansion valve in the middle, and an expansion turbine outlet conduit is connected to the upper part of the column. is connected to the waste gas extraction conduit from the sheath filling upper tower at the front part of the main heat exchange type I, and a second reboiler condenser is installed at the bottom of the upper rectification tower. .