JPH0514152Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an air separation device that uses air as a raw material and uses self-cooling heat to produce oxygen gas and nitrogen gas by compressing, cooling, liquefying, and rectifying the air.

Conventional technology In an air separation device, when raw air is separated in a cold box (non-vacuum type perlite insulated cold storage tank) to produce oxygen gas, nitrogen gas, etc., the amount of refrigeration equivalent to the following thermal energy is It becomes necessary.

Thermal energy entering the cold box from outside air Thermal energy difference due to the temperature difference at the high temperature end of the heat exchanger In general air separation equipment, the necessary cold energy mentioned above is generated by adiabatic expansion using an expander. and cold water from a liquefied nitrogen storage tank installed outside the cold box.
In some cases, liquefied nitrogen is supplied to the high-pressure rectification column inside the box.

Problems that the invention aims to solve When using an expander in the conventional method, there are obstacles such as increased equipment costs, difficulty in operation, and complexity of maintenance. When supplying liquefied nitrogen from the storage tank to the high-pressure rectification column in the cold box, the liquefied nitrogen in the liquefied nitrogen storage tank must be introduced while overcoming the internal pressure of the high-pressure rectification column. Therefore, it was necessary to heat and pressurize the liquefied nitrogen in the liquefied nitrogen storage tank. Conventionally, this means that a portion of the cooling power contained in liquefied nitrogen is wasted.

Means for Solving the Problems Therefore, the device of the present invention is a cold-cold device that uses compressed air as a raw material to produce oxygen gas and nitrogen gas using a double rectification column equipped with a high-pressure rectification column and a low-pressure rectification column. In an air separation device enclosed in a box, a liquefaction unit and conduit that liquefies a portion of the nitrogen gas taken out from the top of the high-pressure rectification column and returns it to the vicinity of the top of the high-pressure rectification column, as well as a conduit for returning it to the high-pressure rectification column. It has a conduit for taking out the liquefied nitrogen from the same level as the return conduit to the rectification column and feeding it to an adiabatic liquefied nitrogen storage tank installed outside the cold box, It communicates with the top of the low-pressure rectification column via a pipe, and the insulated pipe is characterized by having an expansion valve in the cold box.

Hereinafter, the present invention will be described in more detail with reference to the attached flow sheet showing an embodiment of the air separation device according to the present invention.

Embodiment As shown in the figure, raw air is compressed in a raw air compressor 1 to the pressure required for separation, and then cooled and washed in a water washing tower 2.

The raw air that has been cooled and cleaned to room temperature is introduced into the low-temperature separation equipment, where it is passed through a switching air heat exchanger (3, 4...
The water and carbon dioxide gas are cooled by counter-current waste gas and product gas in a high temperature heat exchanger 3 and a low temperature heat exchanger 4), and water and carbon dioxide are condensed and solidified in these heat exchangers.

Air and waste gas are connected to switching valves 24a and 24.
b, 24c, 24d (when 24a and 24b are closed, 24c and 24d are open) and Clapette box 25
a and 25b are periodically switched, and the condensed and solidified impurities in the air are sublimed and removed by the waste gas. On the other hand, the product oxygen gas and the product nitrogen gas flow through a constant flow path of the switched air heat exchanger.

The purified feed air undergoes countercurrent heat exchange with the product gas and waste gas in the switching air heat exchangers 3 and 4, and is cooled to near the liquefaction temperature.
Sent to the bottom. The feed air is separated into pure nitrogen gas at the top of the column and oxygen-rich liquid air at the bottom of the column in a high-pressure rectification column.

The nitrogen gas at the top of the high-pressure rectification column 5 exchanges heat with the evaporated liquefied oxygen in the main evaporator 6 installed near the top of the high-pressure rectification column 5, liquefies it, and is supplied to the high-pressure rectification column 5 again. Ru.

The liquefied nitrogen at the top of the column is used as a reflux liquid in the high-pressure rectification column 5. A part of the liquefied nitrogen in the middle of the column is used as a reflux liquid in the high-pressure rectification column 5, and the remainder is sent to the nitrogen supercooler 9, where it is supercooled by waste gas, expanded by the expansion valve 15a, and sent to the liquefied nitrogen storage tank. After merging with liquefied nitrogen which is a cold source of this apparatus from 12, it is introduced into the low pressure rectification column 10.
Used as top reflux liquid.

The liquefied air at the bottom of the high-pressure rectification column 5 passes through a two-column switching type adsorption column 7, after which hydrocarbons are adsorbed and removed.
After being supercooled by the liquefied air supercooler 8, the expansion valve 1
6 and introduced into the upper part of the low-pressure rectification column 10, where it is used as a reflux liquid in the upper part of the low-pressure rectification column 10.

The final separation of air is carried out in a low-pressure rectification column 10, producing waste gas at the top of the column, argon-rich gas at the middle of the column, and liquefied oxygen at the bottom of the column.

Liquefied oxygen is taken out from the bottom of the low-pressure rectification column 10, pressurized by the liquefied oxygen pump 13, passed through the two-column switching type adsorption column 14, and after adsorption and removal of hydrocarbons, it is transferred to the main evaporator 6 as described above. The oxygen gas exchanges heat with nitrogen gas, becomes oxygen gas, and is again supplied to the bottom of the low-pressure rectification column 10.

A portion of the oxygen gas at the bottom of the low-pressure rectification column 10 is heated in a switching air heat exchanger and then becomes product oxygen gas (oxygen gas line in the figure).

The cold heat source required for the device of the present invention is connected to the cold box (C/B) by a double shell vacuum insulated conduit 18 from a double shell vacuum insulated liquefied nitrogen storage tank 12 arranged outside the cold box (C/B). ), the liquid nitrogen passes through an expansion valve 18a located in The nitrogen gas taken out at 38 is branched through a conduit 49 and liquefied in a liquefaction unit 50 (of a known mechanism), which is produced by the apparatus of the present invention. In the figure, this liquefaction unit 5
The liquefied nitrogen liquefied at 0 is returned to near the top of the high-pressure rectification column 5 in a conduit 51 and is sent to the storage tank 12 by a conduit 48 from the same rectification plate. By once returning the liquefied nitrogen to the high-pressure rectification column 5, the flash gas at that time is recovered within the high-pressure rectification column 5, contributing to efficient rectification. Liquefaction unit 50
It is also possible to send the flash gas directly from the storage tank 12 to the storage tank 12, but in that case a conduit for returning the flash gas in the storage tank 12 to the high pressure rectification column 5 is required.

As described above, in the device of the present invention, a part of the product nitrogen taken out from the conduit 38 during liquid operation is liquefied in the liquefaction unit 50 and stored in the storage tank 12, and during gas operation, the liquefied nitrogen in the storage tank 12, that is, the self-cooling heat is used. It is taken out through a conduit 18 and supplied from the top of the low-pressure rectification column 10 as a source of cold heat necessary for the apparatus of the present invention.

The argon-rich gas formed in the middle of the low-pressure rectification column is blown into the bottom of the argon rectification column 11 and rectified. At the top of the argon rectification column 11,
A condenser 20 is installed, and the crude argon gas is liquefied by exchanging heat with the expanded liquefied air through the conduit 21 and the expansion valve 17. The liquefied crude argon is used as the reflux liquid of the argon rectification column.

A portion of the crude argon gas at the top of the argon rectification column 11 is heated through a heat exchanger (not shown in the attached drawing) and becomes crude argon gas (crude argon line in the drawing).

The argon-rich liquid at the bottom of the argon rectification column 11 is again introduced into the middle of the low-pressure rectification column 10 and used as the reflux liquid at the bottom of the low-pressure rectification column 10.

The waste gas at the top of the low-pressure rectification column 10 passes through a liquefied nitrogen supercooler 9 and a liquefied air supercooler 8, and then is heated to room temperature in the switching air heat exchangers 4 and 3 and released into the atmosphere (Fig. middle waste gas line).

A portion of the nitrogen gas at the top of the high-pressure rectification column 5 is heated by the switching air heat exchangers 4 and 3 and becomes a product nitrogen gas (nitrogen gas line in the figure).

The switching heat exchangers 3 and 4 are systems that physically remove impurities in the raw air (solidification←→sublimation), and to remove impurities, the temperature difference within these heat exchangers is adjusted (i.e., sublimation). Temperature ΔT required to
This adjustment is carried out by opening and closing the regulating valve 23 of the pipe 22 branched from the middle part of the heat exchangers 3 and 4 to extract a part of the nitrogen gas to adjust the flow rate. The discharged nitrogen gas is combined in the waste gas line before the liquefied nitrogen supercooler 9 and becomes waste gas.

As mentioned above, the present invention is an air separation device that can produce a large amount of liquefied oxygen or nitrogen, and can operate on gas (manufacture gas products) when there is a difference in supply and demand or when the liquefaction unit is stopped. It provides:

Effects of the device As mentioned above, the liquefied nitrogen produced by this device is stored in an insulated storage tank installed outside the cold box of the air separation device, and is further transported to the upper part of the low-pressure rectification column of the air separation device using an insulated pipe. By supplying the liquefied nitrogen's self-cooling heat, it is possible to simultaneously satisfy the cooling and reflux liquid requirements for this device.

This eliminates the need for an expander, and eliminates the increased equipment costs, operational difficulties, and complexity of maintenance associated with installing this equipment.

In addition, in the device of the present invention, as mentioned earlier, the nitrogen gas taken out from the top of the high-pressure rectification column 5 is liquefied in the liquefaction unit 50 and returned to the vicinity of the top of the high-pressure rectification column 5. Liquefied nitrogen is poured into the storage tank 12 from the distillation column. By once returning the liquefied nitrogen to the high-pressure rectification column 5 and then flowing it into the storage tank 12, the flash gas at the time of return to the high-pressure rectification column is recovered into the high-pressure rectification column and made to contribute to rectification. I can do it. Furthermore, the supply of liquefied nitrogen from the storage tank 12 to the low-pressure rectification column 10 also utilizes only the pressure difference.
If the high pressure rectification column 5 is to be supplied from the storage tank 12, a liquid pump is required. Otherwise, the pressure in the storage tank 12 is increased when supplying to the high pressure rectification column 5, and when storing liquefied nitrogen, the pressure inside the storage tank 12 is increased. The operation of lowering the pressure must be repeated. Repetition of such pressurization and depressurization causes vaporized gas to be released, resulting in increased cooling loss.

The device of the present invention does not require a liquid pump as described above, and there is no cooling loss, so the cold self-cooling heat of liquefied nitrogen can be effectively utilized, and the device has the advantage of being able to smoothly change its operating mode.

[Brief explanation of drawings]

Fig. 1 is a flow sheet showing a specific example of the device of the present invention. high-temperature heat exchanger, 4 is a low-temperature heat exchanger), 5... high-pressure rectification column,
6...Main evaporator, 7...Adsorber (two-column switching type...
liquefied air supercooler), 8... liquefied air supercooler, 9
...Liquid nitrogen supercooler, 10...Low pressure rectification column, 1
1...Argon rectification column, 12...Double shell vacuum insulated liquefied nitrogen storage tank, 13...Liquid oxygen pump, 14...
...Adsorber (two-column switching type...liquefied oxygen absorber), 1
8...Double shell vacuum insulated conduit, 20...Condenser, 2
4a, 24b, 24c, 24d... switching valve,
25a, 25b...Frappet Box, 50
...Liquification unit, C/B... Cold box, 26-49, 51... Conduit.

Claims (1)

[Scope of utility model registration request] A cold box CB that uses compressed air as a raw material to produce oxygen gas and nitrogen gas using a double rectifier that includes a high-pressure rectifier 5 and a low-pressure rectifier 10.
In the air separation device sealed in the high pressure rectification column 5, a liquefaction unit 5 liquefies a part of the nitrogen gas taken out from the top of the high pressure rectification column 5 and returns it to the vicinity of the top of the high pressure rectification column 5.
0, conduits 49, 51, and the high-pressure rectification column 5 are taken out from the same level as the return conduit 51 to the rectification column and transferred to an adiabatic liquefied nitrogen storage tank 12 installed outside the cold box CB. The adiabatic liquefied nitrogen storage tank 1 has a conduit 48 for feeding
2 is connected to the top of a low-pressure rectification column 10 via an insulated pipe 18, and the insulated pipe 18 is equipped with an expansion valve 18a in a cold box CB.