KR101890531B1 - Cryogenic air separation system having recycling device - Google Patents

Abstract

The present invention relates to an air separation system including a liquefied air recycling device. The air separation system includes: a rectifying part including an air separator comprising a lower tower of a rectification tank for storing liquefied air in the lower part and an upper tower of the rectification tank for receiving the liquefied air from the lower tower of the rectification tank and separating liquefied oxygen and liquefied nitrogen through heat exchange with the liquefied oxygen stored in the lower part, and a liquefied air tank for supplying the liquefied air to the lower tower of the rectification tank; a heat exchanging part including a heat exchanger obtaining low temperature liquefied air supplied from the lower tower of the rectification tank of the air separator through a heat exchange between room-temperature compressed air supplied from an air compressor and the liquefied oxygen, the liquefied nitrogen, and impure nitrogen discharged from the air separator; and a recycling part rectifying and then storing the liquefied oxygen and liquefied nitrogen including impurities received from the air separator and liquefied argon including impurities.

Description

Technical Field [0001] The present invention relates to an air separation system having a liquid air recycling apparatus,

The present invention relates to an air separation system equipped with a liquid air recycling apparatus, and more particularly, to an air separation system having a liquid air recycling apparatus, in which liquid oxygen, liquid nitrogen and liquid argon, which are discarded in an air separation system, are passed through an apparatus capable of removing impurities, To an air separation system equipped with a liquid air recycling apparatus which allows the gases to be discarded into the atmosphere and recycled when necessary.

In general, an air separation unit is a facility for sucking and compressing air in the atmosphere to produce oxygen and nitrogen of high purity using oxygen (-183 deg. C, nitrogen: -196 deg. C, argon: -186 deg. Such an air separation apparatus is widely used as a manufacturing apparatus capable of supplying oxygen or nitrogen in industrial fields such as iron, chemical, and electronics.

FIG. 1 shows a conventional air separation apparatus, which includes a rectification tower 12 having a liquid air storage unit at a lower portion thereof and a liquid oxygen storage unit at a lower portion thereof, (10) having a rectifying tower (11) for separating liquid nitrogen and liquid oxygen from air through heat exchange between liquid air and liquid oxygen, and an air separator (10) having an air separator A heat exchanger 20 for obtaining low-temperature liquid air supplied to the rectifying tower 12 of the air separator 10 through heat exchange between liquid nitrogen of low temperature discharged from the air separator 10 and liquid nitrogen and impure nitrogen, A liquid air storage tank for storing the low temperature liquid air discharged from the heat exchanger 20 and storing the liquid air supplied to the rectifying tower 11 in the rectifier tank 12 of the air separator 10, (30) And an evaporation tank 40 for allowing the impurities contained in the inside to be dissipated into the atmosphere together with steam when the valves 41, 42 and 43 connected to the air separator 10 are opened.

When the conventional air separation unit constructed as above is operated for a long time, impurities such as moisture, carbon dioxide, and hydrocarbons are accumulated in the air separator 10. Such moisture and carbon dioxide cause a problem of closing the heat exchanger 20, and the hydrocarbon causes a problem that the air separator 10 may explode. Accordingly, the conventional air separation apparatus stops operation when a predetermined time elapses, opens a large amount of liquid oxygen, liquid nitrogen, and liquid argon stored in the air separator 10 into the manual valve 41, 42, And then performs the export operation. The liquid air discharged to the outside flows into the evaporation tank 40. Steam is generated by a vaporizer installed in the evaporation tank 40 so that the liquid air introduced into the evaporation tank 40 exchanges heat with steam, So that it can be dissipated into the atmosphere. Finally, after the above-described operation, the inside of the air separator 10 is heated with dry nitrogen or dry air not containing moisture, carbon dioxide, or hydrocarbons.

However, in the conventional air separation apparatus, when performing an operation for removing impurities in the air separator 10 as described above, there is a problem that liquid oxygen, liquid nitrogen, and liquid argon are discarded to the atmosphere through the evaporation tank 40 In order to vaporize the liquid oxygen, the liquid nitrogen, and the liquid argon, which are drained to the evaporation tank 40, an enormous amount of steam is required, which results in a problem of high energy consumption.

A related prior art is Korean Patent No. 10-0674451 (registered on Jan. 19, 2007).

The object of the present invention is to solve the above-described problems, and it is an object of the present invention to provide a dehumidifying layer for removing moisture to remove impurities, a method for removing carbon dioxide and hydrocarbons There is provided an air separation system provided with a liquid air recycling device for purifying and recycling liquid air without throwing it into the air by using an impurity removing device composed of an adsorption layer of a molecular sieve to be removed .

The air separation system having the liquid air recycling apparatus according to an embodiment of the present invention includes a rectifying tower for storing liquid air at a lower portion thereof, and a heat exchanger for receiving liquid air from the rectifying tower, A rectifying section including an air separator composed of a rectifying column top for separating liquid nitrogen and liquid oxygen and a liquid air tank for supplying liquid air to the rectifying column top; A heat exchanger including a heat exchanger for obtaining low-temperature liquid air supplied from the rectifying tower of the air separator through heat exchange between the discharged liquid oxygen and liquid nitrogen and impure nitrogen, and a heat exchanger including a liquid oxygen And liquid nitrogen and impurities in liquid argon. And the like.

Specifically, the recycling section includes: an impurity removing device for purifying the liquid oxygen, the liquid nitrogen, and the liquid argon containing the impurities; and a primary oxygen storage device for storing the liquid oxygen, the liquid nitrogen and the liquid argon purified by the impurity removing device And a secondary liquid storage tank for storing the liquid oxygen, the liquid nitrogen and the liquid argon from the liquid storage tank and the primary liquid storage tank and storing the liquid oxygen, the liquid nitrogen and the liquid argon.

Specifically, the impurity removing device may include a dehumidifying layer for removing moisture and an adsorption layer for removing carbon dioxide and hydrocarbons.

Specifically, the dehumidifying layer is made of alumina gel, and the adsorption layer is made of a molecular sieve.

Specifically, the impurity removing apparatus includes a first drain valve provided on a flow path connected to the air separator to open the second valve, to receive liquid oxygen containing impurities, and a second drain valve to open the liquid nitrogen containing the impurities And the third drain valve is opened to supply liquid argon containing impurities.

Specifically, the recycling unit is configured to recycle liquid oxygen, liquid nitrogen, and liquid argon stored in the primary liquid storage tank using a primary transfer pump provided on a flow path between the primary liquid storage tank and the secondary liquid storage tank And then transferred to the secondary liquid storage tank.

Specifically, the recycling unit may be configured to recycle liquid oxygen, liquid nitrogen, liquids, and the like stored in the secondary liquid storage tank using a secondary transfer pump provided on a flow path connected between the secondary liquid storage tank and the rectifying air- Argon is supplied to the interior of the rectifying tower of the air separator to accelerate the cooling time, thereby shortening the startup time.

Specifically, when the oxygen and nitrogen gas produced in the air separator becomes insufficient, the recycle unit supplies the ultra-low temperature liquid stored in the secondary liquid storage tank to the air separator inside the air separator, thereby supplying oxygen and nitrogen gas So that it is possible to carry out the evaporation.

As described above, according to the present invention, the evaporation tank used in the conventional air separation apparatus is replaced with a dehumidifying layer for removing moisture, and an adsorption layer for a molecular sieve for removing carbon dioxide and hydrocarbons, It is possible to store liquefied oxygen, liquid nitrogen and liquid argon, which are discarded when impurities are removed, to be recycled.

Further, since the impurity removing device includes a dehumidifying layer for removing water and an adsorbing layer for a molecular sieve for removing carbon dioxide and hydrocarbons, a huge amount of steam for removing impurities is not needed, It is effective.

Further, since the purified liquid air having passed through the impurity removing device is stored in the liquid storage tank and then the ultra-low temperature cold air is supplied to the inside of the rectifying tower, which is an air separator, by using the pump, It is possible to shorten the operation time for the evaporation.

1 is a system diagram of a conventional air separation apparatus.
2 is a flow diagram of an air separation system equipped with a liquid air recycling apparatus according to an embodiment of the present invention.
FIG. 3 is a schematic diagram showing the recycling unit shown in FIG. 2 in detail.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventive concept. Other embodiments falling within the scope of the inventive concept may readily be suggested, but are also considered to be within the scope of the present invention.

The same reference numerals are used to designate the same components in the same reference numerals in the drawings of the embodiments.

FIG. 2 is a system diagram of an air separation system equipped with a liquid air recycling apparatus according to an embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a recycling unit shown in FIG. The air separation system may include a rectification unit 100, a heat exchange unit 200, and a recycling unit 300.

The rectification unit 100 may include an air separator 110 and a liquid air tank 120.

The air separator 110 may include a rectification top tower 111 and a rectification top tower 112. The rectification top tower 111 receives liquid air from the top of the rectification top tank 112, And the rectifying and collecting tower 112 performs a function of storing the liquid air in the lower part.

The liquid air tank 120 is positioned between the air separator 110 and the heat exchanger 210 as a storage tank for supplying liquid air to the air separator 110 and the rectifying tower 112.

The heat exchange unit 200 may include a heat exchanger 210 and a liquid oxygen supply pump 220.

The heat exchanger 210 exchanges heat between the compressed air at room temperature supplied from the air compressor 1 and liquid oxygen discharged from the air separator 110 through liquid nitrogen and impure nitrogen, 112 to obtain low-temperature liquid air.

The liquid oxygen supply pump 220 is provided on the flow path connected to the lower portion of the heat exchanger 210 and functions to supply liquid oxygen to the heat exchanger 210.

Specifically, the liquid oxygen supply pump 220 is provided on a liquid oxygen storage unit provided below the rectifying tower 110 of the air separator 110 and on an oxygen supply line which is a flow path connected to a lower portion of the heat exchanger 210 The liquid oxygen discharged from the liquid oxygen storage part by the operation of the liquid oxygen supply pump 220 is supplied to the lower part of the heat exchanger 210 through the oxygen supply line through the liquid oxygen supply pump 220, So that it can be supplied to the use place after heat exchange. In addition, an oxygen level detector may be installed in the liquid oxygen storage portion provided under the rectifying tower 110 of the air separator 110.

The recycle section 300 may include an impurity removing device 310, a primary liquid storage tank 320 and a secondary liquid storage tank 330. The recycle section 300 may include an impurity- And liquid argon containing liquid nitrogen and impurities.

The impurity removing device 310 includes an inlet valve 311, a dehumidifying layer 312, an adsorption layer 313, a first drain valve 314, a second drain valve 315 and a third drain valve 316 To purify liquid oxygen, liquid nitrogen and liquid argon containing impurities.

The dehumidifying layer 312 is embedded in the upper end of the container of the impurity removing device 310, and functions to remove moisture present on the incoming liquid air.

In an embodiment of the present invention, the dehumidifying layer 312 may be made of alumina gel. The alumina gel is an aqueous solution containing aluminum ions, which is made neutral by ammonia, It is a gel of alumina hydrate which is washed and dried (washed with water) and dehydrated to about 500 ° C or less. The gel of alumina hydrate is easy to dissolve in acid and alkali and used for antacid, etc. Alumina gel is used for adsorbent and dehydration catalyst.

In the embodiment of the present invention, as an example of the dehumidifying layer 312, an alumina gel is illustrated as an example of the moisture removing material used in the impurity removing apparatus 310. However, It should be understood that the materials of < RTI ID = 0.0 >

The adsorption layer 313 functions to remove carbon dioxide and hydrocarbons present on the incoming liquid air by being embedded in the lower end of the container of the impurity removing device 310.

The adsorption layer 313 may be a molecular sieve as a material in an embodiment of the present invention. The molecular sieve is also referred to as a molecular sieve and refers to a synthetic zeolite, and has a large number of uniform size It is a kind of adsorbent that has a cavity and allows only molecules passing through the cavity to be adsorbed in the cavity.

The first drain valve 314 is provided on the flow path connected to the air separator and performs a function of supplying liquid oxygen containing impurities when the first valve 314 is open.

The second drain valve 315 is provided on the flow path connected to the air separator to perform a function of supplying liquid nitrogen containing impurities when opened.

And the third drain valve 316 functions to receive liquid argon containing impurities at the time of opening.

The primary liquid storage tank 320 includes the primary liquid level sensor 321, the primary transfer pump 322 and the primary tank internal pressure regulating valve 323, Nitrogen and liquid argon.

A primary transfer pump 322 is provided on the flow path between the primary liquid storage tank 320 and the secondary liquid storage tank 330 and connected to the flow path. By the operation of the primary transfer pump 322, The liquid oxygen, the liquid nitrogen, and the liquid argon stored in the primary liquid storage tank 320 are transferred to the secondary liquid storage tank 330.

The secondary liquid storage tank 330 includes a secondary level meter 331, a secondary transfer pump 332, a secondary tank internal pressure regulating valve 333 and a secondary manual outlet valve 334, Liquid nitrogen, and liquid argon from the tank and stores the liquid oxygen, the liquid nitrogen, and the liquid argon.

A secondary transfer pump 332 is provided on the flow path between the secondary liquid storage tank 330 and the rectification air upstream tower 111 of the air separator 110 so that the operation of the secondary transfer pump 332 The liquid oxygen, the liquid nitrogen, and the liquid argon stored in the secondary liquid storage tank 330 are supplied to the interior of the rectifying tower 110 of the air separator 110.

As described above, the liquid air stored in the secondary liquid storage tank 330 flows into the inside of the rectifying tower 110 so as to accelerate the cooling time of the air separator 110, thereby shortening the startup time of the air separation system .

2 and 3, the valves used in the air separation system equipped with the liquid air recycling apparatus according to an embodiment of the present invention are shown to be used in various places other than the above- And may be operated according to the control signal of the control unit. That is, the valves may be used together with a level meter or temperature detectors, and a solenoid valve, which can be automatically opened and closed by electricity, may be used so that the controller can automatically adjust the valve according to the detected data.

Hereinafter, the operation of the air separation system having the liquid air recycling apparatus according to one embodiment of the present invention will be described.

First, in a manufacturing plant using blast furnace, oxygen steel, etc., the air separation system is restarted after equipment is checked and repaired after stopping the equipment for maintenance of the equipment.

The re-operation is performed by removing air from the adsorber 3 through the water-washing tower 2 by air having a room temperature of about 25 ° C compressed at 5.2 kg / cm ² in the air compressor 1, passing through the booster 4 and the turbine 5 And is made to be low temperature liquid air of? 173 ° C by passing through the heat exchanger 210. Then, the low temperature liquid air is fed into the air separator 110.

At this time, the heat exchanger 210 separates the liquid at room temperature supplied to the air separator 110, nitrogen gas at 173 ° C produced at the lower end of the air separator 110, 173 ° C by exchanging heat between the liquid oxygen produced in the lower portion of the rectifying tower 110 of the air separator 110 and the impure nitrogen produced in the upper portion of the rectifying tower 110 of the air separator 110. The nitrogen gas produced in the rectifying tower 112 and the liquid oxygen and impure nitrogen produced in the rectifying tower 110 pass through the heat exchanger 210 at a room temperature of 25 ° C.

The air which is a flow path connected between the adsorber 3 and the heat exchanger 210 is subjected to heat exchange with the liquid oxygen of the rectifying tower 110 via the heat exchanger 210, Due to the rectifying action, it is separated into nitrogen and liquid air in the rectifying tower 112, and then the liquid air is transferred to the rectifying tower 110.

In the rectifying column top tower 111, the oxygen gas vaporized by the heat exchange is heat-exchanged with the liquid air supplied from the rectifying tower 112 to be separated into liquid oxygen, impurity argon and impurity nitrogen.

At this time, the heat exchange action with air suddenly occurs due to insufficient rectification action at the beginning of re-starting of the equipment, so that the vaporization amount of liquid oxygen is increased and the liquid air There is a possibility that the oxygen gas which is vaporized due to the shortage of oxygen can not be sufficiently liquefied.

Accordingly, when the liquid oxygen level detector of the rectifying tower 110 of the air separator 110 and the liquid air level detector of the rectifying tower 112 detect an oxygen level and an air level as electrical signals, The solenoid valve installed in the outlet line of the liquid air tank 120 is operated.

The supply flow rate of the liquid air supplied to the rectifying tower 112 is increased through the outlet valve of the liquid air tank 120. Since the liquid air can be continuously supplied to the rectifying tower 110, It is possible to prevent a drop in the level of the signal.

Hereinafter, the basic operation of the air separation system after re-operation is explained. Hereinafter, before the restart of the facility, that is, when the air separation system equipped with the liquid air recycling apparatus is stopped, the air separator 110 is operated for a long time A process for discharging liquid oxygen, liquid nitrogen, and liquid argon containing impurities and purifying them will be described.

First, the first to third drain valves are opened to send liquid oxygen, liquid nitrogen, and liquid argon, in which impurities are accumulated, to the impurity removing apparatus 310 of the recycling unit 300.

Next, the inlet valve 311 of the impurity removing device 310 is opened to remove the alumina gel, carbon dioxide (CO 2), and hydrocarbons of the dehumidifying layer 312, So that the molecular sieve of the adsorption layer 313 is penetrated.

The cryogenic liquid of liquid oxygen, liquid nitrogen, and liquid argon, through which the impurities have been purified through the impurity removing device 310, is transferred through the flow path and stored in the primary liquid storage tank 320.

At this time, the pressure inside the primary liquid storage tank 320 due to the vaporization gas is maintained at a constant pressure by the primary tank internal pressure regulating valve 323 provided at the upper part, and the pressure of the primary liquid storage tank 320 When the indication of the primary level meter 321 rises by 30% or more, the primary transfer pump 322 provided on the flow path connected between the primary liquid storage tank 320 and the secondary liquid storage tank 330 is operated, And stores the liquid air stored in the liquid storage tank 320 in the secondary liquid storage tank 330.

The internal pressure of the secondary liquid storage tank 330 is maintained at a constant pressure by the secondary tank internal pressure regulating valve 333 provided at the upper portion as in the primary liquid storage tank 320. [

The above is the operation of the air separation system equipped with the liquid air recycling apparatus according to the embodiment of the present invention when the air separation system is stopped for maintenance, So that the liquid air stored in the storage tank 330 can flow into the rectifying unit 100.

That is, when the air separation system is started, the secondary passive outlet valve 334 provided in the secondary liquid storage tank 330 is opened and the flow passage connected between the secondary liquid storage tank 330 and the air separator 110 The second liquid transfer pump 332 provided in the second liquid storage tank 330 is operated to supply the liquid air of ?? 180 ° C stored in the secondary liquid storage tank 330 to the interior of the rectifying tower 110 of the air separator 110.

Accordingly, according to the above-described operation of the recycling unit 300, the cooling time of the air separator 110 apparatus is promoted and the startup time can be shortened.

When the oxygen and nitrogen gas produced in the process of the blast furnace or the like produced by the air separator 110 is insufficient, the recycled part 300 may be installed in the air separator 110, The superheated liquid stored in the secondary liquid storage tank 330 is supplied to the inside of the upper tower 111, so that oxygen and nitrogen gas can be directly vaporized.

As described above, according to the present invention, the evaporation tank used in the conventional air separation apparatus is replaced with an impurity removing apparatus including a dehumidifying layer for removing moisture and a adsorption layer for a molecular sieve for removing carbon dioxide and hydrocarbons, Can be stored in a liquid storage tank and reused. Therefore, liquefied oxygen, liquid nitrogen, and liquid argon, which are discarded when impurities are removed, can be purified and recycled.

Further, since the impurity removing device includes a dehumidifying layer for removing water and an adsorbing layer for a molecular sieve for removing carbon dioxide and hydrocarbons, a huge amount of steam for removing impurities is not needed, It is effective.

Further, since the purified liquid air having passed through the impurity removing device is stored in the liquid storage tank and then the ultra-low temperature cold air is supplied to the inside of the rectifying tower, which is an air separator, by using the pump, It is possible to shorten the operation time for the evaporation.

The air separation system equipped with the liquid air recycling apparatus of the present invention is not limited to the configuration and operation of the embodiments described above. The embodiments may be configured so that all or some of the embodiments may be selectively combined so that various modifications may be made.

1: air compressor 2: wash tower
3: adsorber 4: booster
5: Turbine
10: air separator 11: rectification tower
12: rectification tower 20: heat exchanger
40: evaporation tank 41: first drain valve
42: second drain valve 43: third drain valve
100: rectification part 110: air separator
111: rectification tower 110: rectification tower
120: Liquid air tank 200: Heat exchanger
210: heat exchanger 220: liquid oxygen supply pump
300: Recycler 310: Impurity removing device
311: inlet valve 312: dehumidifying layer
313: adsorption layer 314: first drain valve
315: second drain valve 316: third drain valve
320: primary liquid storage tank 321: primary level meter
322: Primary transfer pump 323: Primary tank pressure regulating valve
330: Secondary liquid storage tank 331: Secondary level meter
332: Secondary transfer pump 333: Secondary tank pressure regulating valve
334: Secondary manual outlet valve
P: Pump V: Valve

Claims (8)

A rectifying tower for storing liquid air at a lower portion thereof and an air separator for receiving liquid air from the rectifying tower and separating liquid nitrogen and liquid oxygen through heat exchange with the liquid oxygen stored in the lower portion; A liquid rectification section including a liquid air tank for supplying liquid air to the lower tower; and a heat exchanger for exchanging the compressed air at room temperature supplied from the air compressor and the liquid oxygen discharged from the air separator through heat exchange between liquid nitrogen and impure nitrogen, A heat exchanger including a heat exchanger for obtaining low-temperature liquid air supplied from the rectifying tower of the air separator; And a recycling unit for purifying and storing liquid oxygen and liquid nitrogen containing impurities introduced from the air separator and liquid argon containing impurities,
Wherein the recycle section comprises: an impurity removal device for purifying liquid oxygen, liquid nitrogen and liquid argon containing the impurities; and a primary liquid storage tank for storing the liquid oxygen, liquid nitrogen and liquid argon purified in the impurity removing device ; And a secondary liquid storage tank for receiving and storing the liquid oxygen, liquid nitrogen and liquid argon from the primary liquid storage tank,
The impurity removing apparatus includes a dehumidifying layer for removing moisture and an adsorption layer for removing carbon dioxide and hydrocarbons,
Wherein the first drain valve is opened on the flow path connected to the air separator to receive liquid oxygen containing impurities, the second drain valve is opened to supply the liquid nitrogen containing the impurities, 3 drain valve is opened and liquid argon containing impurities is supplied and then passes through the dehumidifying layer and the adsorption layer and is stored in the primary liquid storage tank and the pressure of the primary liquid storage tank is increased by 30% The recycling section recycles liquid oxygen, liquid nitrogen, and liquid argon stored in the primary liquid storage tank to the secondary liquid by using a primary transfer pump provided on the flow path connected between the primary liquid storage tank and the secondary liquid storage tank Liquid nitrogen, and liquid argon, which are accumulated in the air separator for a long period of time to accumulate impurities, An air separation system with a liquid air recycling apparatus as.
delete delete The method according to claim 1,
Wherein the dehumidifying layer is made of alumina gel, and the adsorption layer is made of a molecular sieve.
delete delete The method according to claim 1,
The recycling unit,
Liquid nitrogen, and liquid argon stored in the secondary liquid storage tank by means of a secondary transfer pump provided on the flow path between the secondary liquid storage tank and the rectification top plate of the air separator, So that the cooling time can be promoted to shorten the startup time by supplying the air to the inside of the tower.
The method according to claim 1,
The recycling unit,
When oxygen and nitrogen gas produced in the air separator become insufficient, oxygen and nitrogen gas can be vaporized by supplying the cryogenic liquid stored in the secondary liquid storage tank to the air separator inside the air separator And an air recycling device for recycling the air.

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