JPH0131117B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method of liquefying and separating air,
In particular, the present invention relates to a method for economically producing high-purity oxygen by separating air using a completely low-pressure system.

[Prior art] By liquefying air and rectifying it, N ₂ , O ₂ ,
Air liquefaction separation equipment that separates Ar, etc. is in operation in various fields. In this type of air liquefaction separation equipment, it is necessary to pressurize and depressurize the feed air and product oxygen according to the operating conditions, so the compressor,
It is essential to install equipment such as an expander. Of the power required for such equipment, the power for compression in particular occupies a large proportion, and the reality is that the power cost for the compressor accounts for most of the power cost for the air liquefaction separation device. In particular, many air liquefaction separation devices have a large capacity and the power cost is high, so there is a strong demand for a reduction in the power cost as part of efforts to reduce the manufacturing cost of product oxygen. This situation is exactly the same in so-called total low-pressure air separation devices, but few effective measures have been taken.

Conventional all-low pressure air separation methods are generally carried out according to a system diagram as shown in FIG. That is, raw air is supplied from an air filter 1, compressed and pressurized to about 4.6 ata by an air compressor 2, and then cooled by an aftercooler 3. Next, it enters a reversible heat exchanger 4, where it exchanges heat with product oxygen and impure nitrogen, and is cooled to approximately the boiling point. Furthermore, it is introduced into the first condenser 6 at the bottom of the rectification column low pressure column (hereinafter simply referred to as "upper column") 5, and in the condenser 6 it is supercooled to below the boiling point by heat exchange with the reflux liquid from the upper column 5. be done. Therefore, some of it liquefies. Next, gas-liquid separator 7
The liquid air is separated into gaseous air and liquid air within the tank, and the liquid air is led to a rectification column medium-pressure column (hereinafter simply referred to as the "lower column") 8. The liquid air introduced into the lower column 8 vaporizes and becomes a rising gas, and is brought into contact with the reflux liquid (nitrogen-rich liquid) obtained by condensation at the top of the lower column 8 for crude rectification. Nitrogen-rich gas is obtained at the top of the column 8, and the reflux liquid becomes liquid air with an oxygen content of about 40% at the bottom of the lower column 8. The gaseous air extracted from the middle part of the lower tower 8 enters the expansion turbine 9 through pipes 31 and 32, where it is cooled and then guided to the upper tower 5 through the pipe 33.

The liquid air crudely rectified as described above in the lower column 8 is
After being introduced into the liquid air subcooler 10 through a pipe 34 and cooled, it is led from a pipe 35 to a second condenser 12 disposed at the top of the crude argon column 11,
After the liquid air is gasified by heat exchange with the argon-rich gas in the crude argon column 11 in the condenser 12,
It is led to the upper tower 5 from the pipe 36. On the other hand, the nitrogen-rich liquid stored at the top of the lower tower 8 is introduced into the liquid air subcooler 10 through a pipe 37 and cooled, and then guided to the upper part of the upper tower 5 through a pipe 38. The gaseous air separated by the gas-liquid separator 7 is sent from the pipe 27 to the liquefier 1.
After the entire amount is liquefied while passing through the pipe 29,
The liquid air is guided to the upper part of the upper tower 5 via the liquid air subcooler 10 and the pipe line 30. Furthermore, the high-purity oxygen-rich liquid that is rectified and separated in the upper column 5 and stored at the bottom is extracted from the lowermost end of the bottom of the upper column 5 and guided to the lower part of the crude argon column 11 through a pipe 51. It is further rectified. Thereafter, high-purity oxygen-rich gas is extracted from the bottom of the crude argon column 11 through a pipe 45 and then guided to the liquefier 13 through a pipe 46. The high-purity oxygen-rich gas whose temperature has been slightly recovered in the liquefier 13 is further introduced into the reversible heat exchanger 4 through the pipe 47.
The temperature recovers significantly inside. The oxygen is then introduced into the oxygen compressor 14 through the pipe 48 and pressurized, and then recovered to the outside as product oxygen.

[Problems to be Solved by the Invention] However, in order to smoothly recover high-purity oxygen using the total low-pressure air separation method as described above, the pressure inside the crude argon column must be reduced to about 0.8 ata to 1.0 ata. While maintaining the pressure of product oxygen during recovery at approximately 1.0ata
Need to adjust to ~1.2ata. Therefore, in the conventional total low-pressure air separation method, an oxygen compressor 14 is disposed in the middle of a pipe 48 for extracting the product oxygen that has passed through the reversible heat exchanger 4, and the crude argon column 1
The above conditions are satisfied by suctioning and depressurizing the crude argon column 11, and approximately
After being extracted at 0.8 ata to 1.0 ata, the pressure drop decreases to about 0.7 ata when passing through the reversible heat exchanger 4. By compressing the product oxygen, the pressure is adjusted to about 1.2 ata to satisfy the above conditions. It's forcing me. In this way, a large-scale oxygen compressor is used to reduce or increase pressure in a relatively small range, which still leads to a rise in power costs, which is a limiting factor in improving the economic efficiency of the air separation equipment as a whole. It is becoming. Therefore, in the all-low-pressure air separation method, it has been desired to develop a technology that satisfies the above operating conditions while reducing the power cost required for the means to satisfy these conditions as much as possible.

The present invention has been made in view of these circumstances, and its purpose is to discontinue the use of the above-mentioned oxygen compressor in a total low-pressure air separation system and to organically combine a separate new technical means. As a result, while satisfying the above operating conditions, the power cost required for the conventional oxygen compressor can be reduced, and the economical efficiency of the entire low-pressure air separation apparatus can be improved.

[Means for Solving the Problems] The air separation method of the present invention that achieves the above objects satisfies the above operating conditions by extracting argon-rich gas from the top of the crude argon column with a blower, The gist of this method is that liquid oxygen is extracted from the bottom of the crude argon column below the liquid level, and the above operating conditions are satisfied by self-pressurizing the liquid oxygen by the action of gravity.

[Operations and Examples] The structure and operation and effects of the present invention will be explained below based on the drawings of the embodiments. However, the following embodiments are merely representative examples, and changes may be made as appropriate in accordance with the spirit of the preceding and following. Needless to say, it can be implemented by

Fig. 1 shows a system diagram of the all-low-pressure air separation method of the present invention, and Fig. 3 shows a conventional example and the basic process is the same, so parts of the same configuration are given the same reference numerals and will be explained repeatedly. is omitted. This embodiment is most different from the conventional example, and is characterized by the top and bottom of the crude argon column 11' and the pipe 4.
8', and this structure will be mainly explained below, and the explanation of the same structure as the conventional example will be omitted. That is, argon-rich gas is stored at the top of the crude argon column 11', and the argon-rich gas is extracted from the blower 15 through the pipe 52. In this case, the blower 15 is operated so that the inside of the crude argon column 11' is maintained at about 0.8 ata to 1.0 ata. On the other hand, a high-purity oxygen-rich liquid is stored at the bottom of the crude argon column 11', and the high-purity oxygen-rich liquid is drawn out from below the liquid level through the descending pipe 45'.
In this case, since the bottom of the crude argon column 11' is located relatively higher than the pipe 46, approximately
The oxygen-rich liquid extracted at 0.8ata to 1.0ata is transferred to pipe 4.
While descending within 5', it self-pressurizes to about 1.2 ata due to gravity. As a result, the pipe line 46, the liquefier 1
3. Even if there is a slight pressure loss while passing through the pipe 47 and the reversible heat exchanger 4, the pressure of the oxygen recovered to the outside from the pipe 48' can be adjusted and maintained at about 1.0 ata.

As described above, in this embodiment, the pressure inside the crude argon column 11' is adjusted by the argon-rich extraction blower 15, and the pressure adjustment during recovery of product oxygen is performed by the self-pressurizing effect due to the head difference. Therefore, in comparison with the configuration of the conventional example shown in FIG.
4 is removed, but instead a blower 15 for extracting argon-rich gas is attached. However, the gas throughput of the blower 15 (argon-rich gas flow rate)
is the gas processing amount of the oxygen compressor 14 (product oxygen flow rate)
The scale is small because it is only about 1/20 of
The power cost of the entire low-pressure air separation device can be greatly reduced due to the large savings in power cost associated with the elimination of However, Tomi Argon extraction blower 15
Since it must satisfy the specifications for a so-called low-temperature blower, some consideration is required from a structural standpoint. On the other hand, as shown in FIG. 2, the argon-rich gas extracted from the crude argon column 11' is once passed through the supercooler 10' and the reversible heat exchanger 4, and then passed through the argon-rich extraction blower 15'. If configured to release the cold air contained in the argon-rich gas, the cold contained in the argon-rich gas can be effectively recovered.
Since a so-called normal temperature blower can be used as 5', it is economical, and the above-mentioned power cost reduction effect can be further enhanced.

[Effects of the Invention] Since the air separation method of the present invention is roughly configured as described above, it has become possible to produce high purity product oxygen more economically. Furthermore, by reducing the power required to operate the air separation device, it is possible to achieve so-called energy saving, so it plays a large role in the industrial world today, when there is a strong demand for energy saving.

[Brief explanation of drawings]

1 and 2 are system diagrams illustrating the all-low-pressure air separation method of the present invention, and FIG. 3 is a system diagram showing a conventional all-low-pressure air separation method. 2...Air compressor, 4...Reversible heat exchanger, 5
...Low pressure column, 6 ... First condenser, 7 ... Gas-liquid separator, 8 ... Medium pressure column, 9 ... Expansion turbine, 1
0,10'...Liquid air supercooler, 11...Crude argon column, 12...Second condenser, 13...Liquifier, 14...Oxygen compressor, 15,15'...Blower.

Claims (1)

[Claims] 1. Feed air compressed by a compressor and further cooled by a heat exchanger is led to the first condenser at the bottom of the low pressure column, where it exchanges heat with liquid oxygen in the low pressure column, evaporates the liquid oxygen, and cools the low pressure column. At the same time as the rising gas, the feed air is supercooled to a temperature below the boiling point to partially liquefy the rising gas, and the rising gas is brought into contact with the reflux liquid from the top of the low-pressure column to be rectified, thereby being stored at the bottom of the low-pressure column. The reflux liquid produced is made into an oxygen-enriched liquid, while the liquefied air is introduced into the medium pressure column and vaporized to become the rising gas of the medium pressure column.The liquefied air is then condensed at the top of the medium pressure column and brought into contact with the resulting reflux liquid for rectification. Nitrogen-rich gas is obtained at the top of the medium-pressure column, and the reflux liquid is converted into liquid air at the bottom of the medium-pressure column.The liquid air is further cooled and then led to a second condenser at the top of the crude argon column, where it is converted into crude argon gas. In an air separation method in which liquid air is gasified by heat exchange with rich argon gas in an argon column and then guided to a low-pressure column, liquid oxygen is extracted from the bottom of the crude argon column and self-pressurized by gravity, and then reversible. An air separation method characterized by gasifying product oxygen using a heat exchanger and maintaining the interior of the crude argon column in a reduced pressure state by extracting argon-rich gas at the top of the crude argon column using a blower.