JPH0914830A - Oxygen and nitrogen liquefying device - Google Patents

Abstract

PURPOSE: To enable an oxygen compressor to be eliminated by a method wherein there are provided a nitrogen liquefying cycle line for liquefying gaseous nitrogen obtained from an air separator and an oxygen liquefying device for liquefying gaseous oxygen obtained from the air separator and the gaseous oxygen is liquefied by an evaporating latent heat of liquefied nitrogen fed out of the nitrogen liquefying cycle line. CONSTITUTION: An oxygen and nitrogen liquefying device 1 is comprised of a nitrogen liquefying cycle line L for liquefying a gaseous nitrogen GN and an oxygen supplying line L3 for liquefying gaseous oxygen GO. A liquefied nitrogen tank 6 is connected to a downstream end of the liquefied nitrogen line L4 and a oxygen liquefying device 7 is connected to a downstream end of the oxygen supplying line L3. With such an arrangement as above, inconveniences in the prior art in which gaseous oxygen was not liquefied under a heat exchanging operation with liquefied nitrogen unless a pressure of the gaseous oxygen was increased up to a substantial same pressure as that of the gaseous nitrogen increased in its pressure by the nitrogen compressor can be eliminated and the gaseous oxygen can be liquefied without arranging any compressor for the gaseous oxygen. Accordingly, it becomes possible to eliminate the compressor for the gaseous oxygen, to reduce facility cost and also to reduce an operation cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen-nitrogen liquefaction device for liquefying oxygen and nitrogen separated by an air separation device in the same device.

[0002]

2. Description of the Related Art Conventionally, an oxygen-nitrogen liquefier as shown in FIG. 4 has been known. This oxygen-nitrogen liquefaction device 10 is an air separation device S that separates air A into 5-10 kgf / cm ² G of gaseous oxygen GO and gaseous nitrogen GN by a cryogenic separation method.
It has a nitrogen liquefaction circulation line L10 for liquefying the gas nitrogen GN and an oxygen liquefaction circulation line L20 for liquefying the gas oxygen GO.

The nitrogen liquefaction circulation line L10 is composed of a nitrogen forward line L110 and a nitrogen return line L120. The nitrogen compressor 20 is provided on the upstream side of the nitrogen forward line L110, and the downstream end of the nitrogen return line L120 is connected to the nitrogen forward line L110 on the upstream side of the nitrogen compressor 20. And 30-60k by the nitrogen compressor 20
The gaseous nitrogen GN pressurized to gf / cm ² G is cooled through the first heat exchanger 31, the refrigerator heat exchanger 41, and the second heat exchanger 32 which the nitrogen outgoing line L110 penetrates. Part of the cooled gaseous nitrogen GN is the third heat exchanger 33.
Liquefaction tank 2 liquefied by passing through to become liquid nitrogen LN
01, and the remainder is the expansion turbine 50.
And is subjected to adiabatic expansion work to become the cold GN1 for cooling, and is returned to the nitrogen compressor 20 through the nitrogen return line L120.

The nitrogen return line L120 passes through the third heat exchanger 33, the second heat exchanger 32, and the first heat exchanger 31, and the cold GN1 in the nitrogen return line L120 in these heat exchangers. Supplies cold heat to the gaseous nitrogen GN in the nitrogen outgoing line L110 in a counterflow to cool it, and
The temperature of the cold GN1 itself is sequentially increased, and the temperature of the cold GN1 is returned to the nitrogen compressor 20 after reaching the normal temperature.

On the other hand, the oxygen liquefaction circulation line L20 is
The oxygen outward line L210 and the oxygen return line L220 are provided, the oxygen compressor 30 is provided on the upstream side of the oxygen outward line L210, and the liquid acid tank 202 is provided at the downstream end.
Is provided. An oxygen recovery line L220 is extended from the upper part of the liquid acid tank 202, and its downstream end is connected to the oxygen outward line L210 on the upstream side of the oxygen compressor 30. The oxygen outgoing line L210 is sequentially penetrated from the upstream side to the first heat exchanger 31, the refrigerator heat exchanger 41, the second heat exchanger 32, and the third heat exchanger 33,
The oxygen return line L220 is sequentially penetrated through the heat exchangers in the reverse order.

Then, by the oxygen compressor 30, 25 to 5
The gaseous oxygen GO pressurized to 5 kgf / cm ² G is supplied to the nitrogen return line L1 in each of the heat exchangers 31, 32 and 33.
Heat exchange with nitrogen in 20 and heat exchanger 41 for refrigerator
In the third heat exchanger 33, the cold heat from the cold GN1 is liquefied and liquefied to be liquid oxygen LO, which is introduced into the liquid acid tank 202. Has become.

The oxygen vapor GO1 generated by vaporization in the liquid acid tank 202 passes through the oxygen return line L220,
In each of the heat exchangers 33, 32, 41, 31 the cold heat is given to the gaseous oxygen GO in the oxygen outgoing line L210, the temperature becomes normal at the outlet of the first heat exchanger 31, and is returned to the oxygen compressor 30. ing.

The liquid nitrogen LN and the liquid oxygen LO obtained by the operation of the nitrogen compressor 20 and the oxygen compressor 30 are stored in the liquid nitrogen tank 201 and the liquid acid tank 2, respectively.
No. 02 is temporarily stored, and is appropriately taken out of the system.

[0009]

By the way, in the oxygen nitrogen liquefaction apparatus 10, the gaseous oxygen GO is replaced by the oxygen compressor 3.
The pressure is increased to 25 to 55 kgf / cm ² G by 0. This is for the following reason. That is, gaseous nitrogen G
The heat balance is designed so that N is liquefied in a state of being pressurized to 30 to 60 kgf / cm ² G, and the pressure of the gaseous oxygen GO matches the pressure of the pressurized gaseous nitrogen GN. This is because the gas nitrogen GN is not liquefied by heat exchange with the liquid nitrogen LN in terms of heat balance unless the pressure is increased to the pressure.

The gas nitrogen GN is 30-60 kgf /
Whereas is boosted to cm ² G, the gaseous oxygen GO is boosted slightly below that of 25~55kgf / cm ² G, the boiling point of nitrogen at atmospheric pressure whereas it is -193 ° C. , The boiling point of oxygen is slightly higher than -183 ℃
This is because oxygen is easier to liquefy than nitrogen, and therefore it is not necessary to make it as high as nitrogen.

Therefore, conventionally, it is considered that the oxygen compressor 30 is indispensable for liquefying the gaseous nitrogen GN and the gaseous oxygen GO obtained from the air separation device S, and the presence of the oxygen compressor 30. Therefore, there is a problem that the equipment cost and the operating cost of the oxygen-nitrogen liquefaction device 10 increase.

The present invention has been made in order to solve the above-mentioned problems, and in simultaneously liquefying gaseous oxygen and gaseous nitrogen, an oxygen compressor can be omitted. It is an object of the present invention to provide an oxygen-nitrogen liquefaction device that can contribute to a reduction in operating cost.

[0013]

The oxygen-nitrogen liquefaction apparatus according to claim 1 of the present invention is an oxygen-nitrogen liquefaction apparatus that liquefies gaseous oxygen and gaseous nitrogen separated by an air separation apparatus into liquid oxygen and liquid nitrogen. A nitrogen liquefaction cycle line for liquefying gaseous nitrogen from the air separation device and an oxygen liquefaction device for liquefying gaseous oxygen from the air separation device are provided, and the oxygen liquefaction device is provided from the nitrogen liquefaction cycle line. It is characterized in that it is configured to liquefy gaseous oxygen by the derived latent heat of vaporization of liquid nitrogen.

According to a second aspect of the present invention, there is provided an oxygen-nitrogen liquefaction apparatus according to the first aspect, wherein the nitrogen-liquefaction cycle line has a compressor for compressing gaseous nitrogen into compressed gaseous nitrogen. A refrigerator for cooling the compressed gaseous nitrogen, an expansion turbine for producing cold for nitrogen liquefaction by adiabatic expansion work of a part of the compressed gaseous nitrogen cooled by the refrigerator, the cold and the compression A heat exchanger for converting the remaining gaseous nitrogen to liquid nitrogen by performing heat exchange with the remaining gaseous nitrogen on the downstream side of the machine is provided, and the cold used for the heat exchange is returned to the upstream side of the compressor. A gas oxygen line is provided for performing heat exchange between the gas oxygen and the cold in the heat exchanger, and the oxygen liquefier has an oxygen liquefaction chamber and a vaporization means arranged in the oxygen liquefaction chamber. The above-mentioned gaseous oxygen The downstream end of the emission is connected to the oxygen liquefaction chamber, the vaporizing means is characterized in that it is configured so as to evaporate the liquid nitrogen derived from the nitrogen liquefaction cycle line.

The oxygen-nitrogen liquefaction apparatus according to claim 3 of the present invention is the oxygen-nitrogen liquefaction apparatus according to claim 2, in which the pressure of the liquid nitrogen derived from the nitrogen liquefaction cycle line is reduced on the upstream side of the oxygen liquefier. It is characterized in that a valve is provided.

The oxygen-nitrogen liquefier according to claim 4 of the present invention is the oxygen-nitrogen liquefaction device according to claim 2 or 3, wherein a line is provided for returning refrigeration drawn from the vaporizing means of the oxygen liquefier to the compressor. It is characterized by being.

[0017]

According to the oxygen-nitrogen liquefaction apparatus of the first aspect, the gaseous nitrogen supplied from the air separation apparatus to the nitrogen liquefaction cycle line is cooled in the circulation process to become liquid nitrogen. On the other hand, the gaseous oxygen from the air separation device supplied to the oxygen liquefier is cooled and liquefied by heat exchange with the cold heat obtained by the evaporation of liquid nitrogen led out from the nitrogen liquefaction cycle line.

As described above, the gaseous oxygen is derived from the nitrogen liquefaction cycle line and is liquefied by the adiabatic expansion of the liquid nitrogen in a state independent of the pressure of the gaseous nitrogen in the cycle line. Oxygen is liquefied without increasing the pressure of oxygen until it becomes substantially equal to the pressure of gaseous nitrogen before liquefaction.

According to the oxygen-nitrogen liquefaction apparatus of the second aspect, the gaseous nitrogen introduced from the air separation apparatus to the nitrogen liquefaction cycle line is compressed by the compressor and cooled by the refrigerator, and a part thereof is expanded. By being supplied to the turbine and performing adiabatic expansion work, it is further cooled and becomes refrigerated, and this refrigeration is used for heat exchange with the rest of the compressed gaseous nitrogen in a heat exchanger, and the rest of the gas is exchanged by this heat exchange. Nitrogen is liquefied.

On the other hand, the gaseous oxygen supplied from the air separation device to the oxygen supply line is precooled to a predetermined temperature by heat exchange with the cold in the heat exchanger and introduced into the oxygen liquefier. On the other hand, the liquid nitrogen derived from the nitrogen liquefaction cycle line is introduced into the vaporization means of the oxygen liquefaction device, where it is adiabatically expanded to lower the temperature and become cold, so the pre-cooling introduced into the oxygen liquefaction device is performed. The already-exhausted gaseous oxygen is cooled and liquefied by heat exchange with the cold.

As described above, since the gaseous oxygen is cooled by the adiabatic expansion of liquid nitrogen in the oxygen liquefier provided separately from the heat exchanger, the pressure of nitrogen in the vaporizing means is liquefied with nitrogen. It is possible to match the pressure of gaseous oxygen, which is independent of the pressure of nitrogen in the cycle line, so that it is possible to compress gas oxygen to the pressure of gaseous nitrogen in the conventional manner. Oxygen is liquefied without a machine.

According to the oxygen-nitrogen liquefaction apparatus of the third aspect, since the pressure reducing valve for reducing the pressure of the liquid nitrogen derived from the nitrogen liquefaction cycle line is provided on the upstream side of the oxygen liquefier, the pressure reducing valve By adjusting the opening degree, the amount of nitrogen supplied to the vaporizing means can be adjusted, and the liquid nitrogen is adiabatically expanded by the pressure reduction by the pressure reducing valve to lower the temperature.

According to the oxygen-nitrogen liquefaction apparatus of the above-mentioned claim 4, since a line for returning the cold drawn out from the vaporizing means of the oxygen liquefier to the compressor is provided, the cold passes through this line to the system. It circulates inside, and the nitrogen used as cold is recovered.

[0024]

1 is an explanatory view showing a first embodiment of an oxygen-nitrogen liquefaction apparatus according to the present invention. As shown in this figure, the oxygen-nitrogen liquefaction device 1 is connected to the downstream side of an air separation device S that separates the air A by the cryogenic separation method. In this air separation device S, the air A is deeply cooled to become liquid air, and this liquid air is separated into nitrogen and oxygen by a rectification process using a boiling point difference, and these are separated into gaseous nitrogen GN.
And gaseous oxygen GO is discharged from the air separation device S. And the oxygen nitrogen liquefaction device 1
Is for liquefying the derived gas nitrogen GN and gas oxygen GO into liquid nitrogen LN and liquid oxygen LO.

The above-mentioned oxygen-nitrogen liquefying apparatus 1 is composed of gaseous nitrogen GN.
A nitrogen liquefaction cycle line L for liquefying oxygen and an oxygen supply line L3 for liquefying the gaseous oxygen GO are provided. A nitrogen compressor 2, a refrigerator 4, and an expansion turbine 5 are connected to the nitrogen liquefaction cycle line L. In addition, the heat exchanger 3 through which each of the lines L and L3 penetrates
Is provided. A liquid nitrogen line L4 is branched from the nitrogen liquefaction cycle line L, and this liquid nitrogen line L4
The liquid nitrogen tank 6 is connected to the downstream end of the. An oxygen liquefier 7 is connected to the downstream end of the oxygen supply line L3.

The heat exchanger 3 is composed of a first heat exchanger 31, a second heat exchanger 32, and a third heat exchanger 33, which are sequentially arranged in series from the air separating device S side.
The nitrogen liquefaction cycle line L is composed of a nitrogen forward line L1 and a nitrogen return line L2.
Is provided at the upstream end of the nitrogen forward line L1. The nitrogen forward line L1 is located downstream of the nitrogen compressor 2 and has the first heat exchanger 3
The first and second heat exchangers 32 are penetrated, and a branch line L5 connecting the upstream side and the downstream side of the first heat exchanger 31 is provided, and the refrigerator 4 is provided in the branch line L5. There is.

Therefore, the gaseous nitrogen GN delivered by the nitrogen compressor 2 is partly branched to the nitrogen forward line L1 and the balance is branched to the branch line L5 on the upstream side of the first heat exchanger 31,
Part of the heat is exchanged in the first heat exchanger 31, and the rest is cooled by the refrigerator 4 so as to be joined on the downstream side of the first heat exchanger 31.

Further, the nitrogen forward line L1 is branched from the liquid nitrogen line L4 on the downstream side of the second heat exchanger 32. The liquid nitrogen line L4 penetrates the third heat exchanger 33, and its downstream end is It is connected to the liquid nitrogen tank 6.

The downstream nitrogen line L1 of the second heat exchanger 32 is connected to the inlet side of the expansion turbine 5, and the upstream side of the nitrogen return line L2 is connected to the outlet side thereof. The nitrogen return line L2 is sequentially passed through the third heat exchanger 33, the second heat exchanger 32, and the first heat exchanger 31, and its downstream end is connected to the upstream side of the nitrogen compressor 2.

The gaseous nitrogen GN supplied to the expansion turbine 5 performs adiabatic expansion work here to lower the temperature, and the cold GN1.
Is supplied to the nitrogen recovery line L2. Then, the cold GN1 is used for heat exchange with the gas nitrogen GN in the liquid nitrogen line L4 in the third heat exchanger 33, and the gas nitrogen GN is cooled to be converted into the liquid nitrogen LN, and at the same time, the second heat exchanger 32 is used. And, in the first heat exchanger 31, the heat is exchanged with the gaseous nitrogen GN in the nitrogen outward line L1 in a counterflow, and the temperature of the outlet of the first heat exchanger 31 becomes normal temperature and the nitrogen compressor 2 is supplied with the room temperature. There is.

An oxygen cooling nitrogen line L6 is provided between the bottom of the liquid nitrogen tank 6 and the nitrogen return line L2 on the downstream side of the expansion turbine 5. The oxygen cooling nitrogen line L6 is arranged so as to pass through the oxygen liquefier 7. A liquid nitrogen derivation line L7 is branched from the oxygen cooling nitrogen line L6, and a part of the liquid nitrogen LN derived from the liquid nitrogen tank 6 is part of the oxygen cooling nitrogen line L6.
Is discharged to the outside of the system through the oxygen cooling nitrogen line L6 and the rest is cooled GN in the nitrogen return line L2.
It is designed to be merged into 1.

A vaporized nitrogen line L9 is provided between the top of the liquid nitrogen tank 6 and the nitrogen return line L2 on the downstream side of the expansion turbine 5, and the gas vaporized in the liquid nitrogen tank 6 is provided. The nitrogen GN is returned to the nitrogen return line L2 through the vaporized nitrogen line L9.

A decompression valve 8 is provided in the oxygen cooling nitrogen line L6 downstream of the branch point to the liquid nitrogen derivation line L7, and an opening of the decompression valve 8 directs the oxygen liquefier 7. The flow rate and pressure of the delivered liquid nitrogen LN are adjusted.

The oxygen liquefier 7 is a kind of adiabatic expander, and the liquid nitrogen LN supplied therein is adiabatically expanded in the meandering heat exchanger (vaporizer) 71 and cooled under reduced pressure. By this, cold GN2 that liquefies gaseous oxygen GO is generated.

On the other hand, the oxygen supply line L3 penetrates through the first heat exchanger 31, the second heat exchanger 32, and the third heat exchanger 33, and its downstream end is connected to the oxygen liquefier 7.
Then, the gaseous oxygen GO introduced into the oxygen liquefier 7 is
It is cooled by heat exchange with the cold GN2 in the heat exchanger 71 to become liquid oxygen LO. A liquid oxygen lead-out line L8 is connected to the bottom of the oxygen liquefier 7, and the liquid oxygen LO in the oxygen liquefier 7 is appropriately led out of the system through the liquid oxygen lead-out line L8. .

In this embodiment, the pressures of the gaseous nitrogen GN and the gaseous oxygen GO discharged from the air separation unit S are set to 10 kgf / cm ² G, and the gaseous nitrogen GN at this pressure is set to the nitrogen compressor 2. By 60kgf
The pressure is increased to / cm ² G. Also, gaseous nitrogen GN of 60 kgf / cm ² G by the expansion turbine 5 is to be stepped down to the 10kgf / cm ² G. Furthermore, the liquid nitrogen L in the oxygen cooling nitrogen line L6
N is made to fall to 10 kgf / cm ² G in the heat exchanger 71.

The operation of the present invention will be described below. The 10 kgf / cm ² G of gaseous nitrogen GN derived from the air separation device S is compressed by the nitrogen compressor 2 in the nitrogen outward line L1 of the nitrogen liquefaction cycle line L to 60 kgf /
The pressure is increased to cm ² G. Then, a part of the gas nitrogen GN pressurized on the downstream side of the nitrogen compressor 2 is branched off from the branch line L5.
The divided nitrogen gas GN is cooled to a predetermined temperature in the refrigerator 4. On the other hand, gaseous nitrogen G
The rest of N flows down the nitrogen outgoing line L1 as it is, is cooled by heat exchange with the cold GN1 and GN2 in the first heat exchanger 31, and is cooled from the refrigerator 4 on the downstream side of the first heat exchanger 31. It joins the gaseous nitrogen GN cooled to the temperature. The temperature of the combined gaseous nitrogen GN is approximately -40 ° C.

Next, the combined gaseous nitrogen GN is exchanged with the cold GN1 and L2 in the second heat exchanger 32, so that it is substantially negative.
It is cooled to 100 ° C. The gaseous nitrogen GN cooled to approximately −100 ° C. is partly branched to the liquid nitrogen line L4 on the downstream side of the second heat exchanger 32, and the rest is introduced into the expansion turbine 5. And the expansion turbine 5
The gaseous nitrogen GN introduced into the above performs adiabatic expansion work here and is decompressed to 10 kgf / cm ² G, and
It is cooled to 165 ° C., becomes cold GN1, and is led to the nitrogen return line L2.

Then, the above 10 kgf / cm ² G, -1
The cold GN1 at 65 ° C. passes through the nitrogen return line L2 to the third
It is introduced into the heat exchanger 33, where cold heat is given to the gaseous nitrogen GN in the liquid nitrogen line L4, whereby the gaseous nitrogen G
N is cooled to −150 ° C. and becomes liquid nitrogen LN.
The nitrogen having a boiling point of −196 ° C. at normal pressure is liquefied at −150 ° C. because the gaseous nitrogen GN is pressurized to 60 kgf / cm ² G.

Cold GN that has passed through the third heat exchanger 33
1 merges with the cold GN2 from the oxygen liquefier 7 and sequentially passes through the second heat exchanger 32 and the first heat exchanger 31. At this time, the cold nitrogen heats the gaseous nitrogen GN in the nitrogen forward line L1 and cools itself. Is heated to normal temperature, is discharged from the first heat exchanger 31, and is returned to the nitrogen compressor 2.

The liquid nitrogen LN discharged from the third heat exchanger 33 flows down the liquid nitrogen line L4 and is supplied to the liquid nitrogen tank 6, where it is temporarily stored and then part of the liquid nitrogen discharge line. While being discharged to the outside of the system through L7, the rest is supplied to the heat exchanger 71 of the oxygen liquefier 7 through the oxygen cooling nitrogen line L6, where it is adiabatically expanded to 1
While the pressure is reduced to 0 kgf / cm ² G, -15
It becomes cold GN2 having a temperature lower than 0 ° C., and merges with the nitrogen return line L2.

On the other hand, the gaseous oxygen GO discharged from the air separation device S to the oxygen supply line L3 is the first heat exchanger 31,
While passing through the second heat exchanger 32 and the third heat exchanger 33, they are sequentially cooled by heat exchange with the cold GN1 and GN2 in the nitrogen return line L2, and are cooled to −150 ° C. and introduced into the oxygen liquefier 7. .

By the way, even if the gaseous oxygen GO is cooled to -150 ° C. by the heat exchange, its pressure is 10
Since it is kgf / cm ² G, the above 60 kgf / cm ² G
It does not liquefy like the gaseous nitrogen GN. Therefore, -15
The gaseous oxygen GO at 0 ° C. is introduced into the oxygen liquefier 7 in a state where it is not liquefied, but inside the oxygen liquefier 7 is −150 due to the adiabatic expansion of the liquid nitrogen LN in the heat exchanger 71.
Since the temperature is lowered to below 0 ° C., the gaseous oxygen GO obtains this cold heat and is liquefied to become liquid oxygen LO, which is temporarily stored in the oxygen liquefier 7. The liquid oxygen LO is appropriately led out of the system via the liquid oxygen lead line L8.

According to the oxygen-nitrogen liquefier 1 of this embodiment,
Since the oxygen liquefier 7 that generates a cold heat source by adiabatically expanding the liquid nitrogen LN is provided in the system, the pressure of the gaseous oxygen GO is conventionally 60 by the nitrogen compressor 2.
If the pressure is not increased to almost the same pressure as the gas nitrogen GN that has been increased to kgf / cm ² G, the inconvenience of not being liquefied by heat exchange with the liquid nitrogen LN is solved, and a compressor for gas oxygen GO is used. Without providing, the oxygen gas GO is 10 kgf
/ Cm ² G is liquefied as it is. Therefore, the conventionally provided compressor for gaseous oxygen can be omitted, which is effective in reducing the facility cost and the operating cost.

FIG. 2 is an explanatory view showing a second embodiment of the oxygen-nitrogen liquefaction apparatus according to the present invention. In this embodiment, the oxygen cooling nitrogen line L6a is branched from the liquid nitrogen line L4 on the upstream side of the liquid nitrogen tank 6, and the oxygen liquefier 7 and the heat exchanger 3 (third heat exchanger 33, second heat exchanger 33, The heat is passed through the heat exchanger 32 and the first heat exchanger 31) and returned to the intermediate stage of the nitrogen compressor 2. Others are the same as those in the first embodiment.

The reason for doing so is that when the downstream end of the oxygen cooling nitrogen line L6a is connected to the nitrogen return line L2 on the downstream side of the expansion turbine 5 as in the first embodiment (FIG. 1), the nitrogen return line L2 is connected. Pressure of cold GN1 in L2 (10kg
f / cm ² G) is affected by oxygen cooling nitrogen line L6
This is because the cold GN2 in a has its pressure reduced to 10 kgf / cm ² G. To prevent this, the pressure of the cold GN2 in the oxygen cooling nitrogen line L6 is set to 15 kgf / cm.
^In order to achieve ² G, in this embodiment, the downstream end of the oxygen cooling nitrogen line L6a is not connected to the nitrogen return line L2 but is returned directly to the intermediate stage of the nitrogen compressor 2.

The pressure in the oxygen cooling nitrogen line L6a is set to 15 kgf / cm ² G because the boiling point of oxygen is higher than that of nitrogen, and therefore 10 kgf / cm ² G
Cooled to -150 ° C or lower for gaseous oxygen GO of 1
This is because gaseous oxygen GO is sufficiently liquefied with 5 kgf / cm ² G of nitrogen.

In this way, the pressure of the cold GN2 returned to the nitrogen compressor 2 is 5 kgf / cm ² G higher than 10 kgf / cm ² G, so the power of the nitrogen compressor 2 is correspondingly increased. Reduced and oxygen nitrogen liquefaction device 1
It is possible to reduce the operating cost of

FIG. 3 is an explanatory view showing a third embodiment of the oxygen-nitrogen liquefying apparatus according to the present invention. This embodiment corresponds to the case where the pressure of the gaseous oxygen GO discharged from the air separation device S is slightly higher than the normal pressure (for example, 1 kgf / cm ² G). Therefore, the pressure of the cold GN2 in the oxygen cooling nitrogen line L6b is 4 kgf / cm ^2.
The pressure is set to G. Also, this 4kg
A small-sized nitrogen recovery compressor 9 for boosting the f / cm ² G cold GN2 is provided at the downstream end of the oxygen cooling nitrogen line L6b, whereby the cold GN2 consisting of gaseous nitrogen in the oxygen cooling nitrogen line L6b is provided. Pressure is 10 kgf / cm ²
The pressure is increased to G. This boosted cold G
N2 is returned to the nitrogen compressor 2. Others are the same as those in the second embodiment.

By doing so, even if the pressure of the gaseous oxygen GO discharged from the air separation device S is slightly higher than the normal pressure, the pressure of the cold GN2 is 4 kg, which is commensurate with the pressure.
Since it is f / cm ² G, the gaseous oxygen GO is surely liquefied. Further, the nitrogen reduced in pressure to 4 kgf / cm ² G by driving the nitrogen recovery compressor 9 is 10 kgf.
Since the pressure is increased to / cm ² G and is returned to the nitrogen liquefaction cycle line L, the loss of nitrogen is reliably prevented.

[0051]

According to the oxygen-nitrogen liquefaction device of the first aspect of the present invention, the gaseous nitrogen from the air separation device supplied to the nitrogen liquefaction cycle line is cooled in the circulation process,
Since a part of the heat is used for heat exchange for cooling the gaseous nitrogen, the remaining gas nitrogen becomes liquid nitrogen by this heat exchange. On the other hand, the gaseous oxygen from the air separation device supplied to the oxygen liquefaction device is used as a cold heat source by evaporating the liquid nitrogen derived from the nitrogen liquefaction cycle line. It is possible to reduce the pressure by adiabatic expansion to almost the same pressure as the pressure of the gaseous oxygen to be liquefied regardless of the pressure of the gaseous nitrogen in the nitrogen gas. Gaseous oxygen is liquefied without increasing the pressure to almost the same pressure, so there is no need to provide a compressor for increasing the pressure of gaseous oxygen as in the conventional case, which is convenient for reducing equipment costs and operating costs. is there.

According to the oxygen-nitrogen liquefier of the second aspect of the present invention, the gaseous nitrogen introduced from the air separator to the nitrogen liquefaction cycle line is compressed by the compressor and cooled by the refrigerator, and a part thereof Is supplied to the expansion turbine to perform further adiabatic expansion work, whereby it is further cooled to be chilled, and this chill is subjected to heat exchange with the rest of the compressed gaseous nitrogen in a heat exchanger, and the rest is due to this heat exchange. The gaseous nitrogen is liquefied.

On the other hand, the gaseous oxygen supplied from the air separation device to the oxygen supply line is precooled to a predetermined temperature by heat exchange with the cold in the heat exchanger and introduced into the oxygen liquefier. On the other hand, the liquid nitrogen derived from the nitrogen liquefaction cycle line is introduced into the vaporization means of the oxygen liquefaction device, where it is adiabatically expanded to lower the temperature and become cold, so the preliminary cooling introduced into the oxygen liquefaction device. The already-exhausted gaseous oxygen is cooled and liquefied by heat exchange with the cold.

As described above, since the gaseous oxygen is cooled by the adiabatic expansion of liquid nitrogen in the oxygen liquefier provided separately from the heat exchanger, the pressure of nitrogen in the vaporizing means is liquefied with nitrogen. It is possible to match the pressure of gaseous oxygen, which is independent of the pressure of nitrogen in the cycle line, so that it is possible to compress gas oxygen to the pressure of gaseous nitrogen in the conventional manner. This is effective in realizing the liquefaction of oxygen without installing a machine and reducing the equipment cost and operating cost.

According to the oxygen-nitrogen liquefaction apparatus of the third aspect of the present invention, since the decompression valve for decompressing the liquid nitrogen derived from the nitrogen liquefaction cycle line is provided upstream of the oxygen liquefier, this decompression is performed. By adjusting the opening of the valve, the amount of nitrogen supplied to the vaporizing means can be adjusted, and the liquid nitrogen is adiabatically expanded by the decompression of the decompression valve to lower the temperature.

According to the oxygen-nitrogen liquefying apparatus of the fourth aspect of the present invention, since a line for returning the cold drawn out from the oxygen liquefier to the compressor is provided, the cold is passed through this line to the inside of the system. The nitrogen used as cold is recovered.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a first embodiment of an oxygen-nitrogen liquefaction device according to the present invention.

FIG. 2 is an explanatory view showing a second embodiment of the oxygen-nitrogen liquefaction device according to the present invention.

FIG. 3 is an explanatory view showing a third embodiment of the oxygen-nitrogen liquefier according to the present invention.

FIG. 4 is an explanatory diagram showing an example of a conventional oxygen-nitrogen liquefaction device.

[Explanation of symbols]

 1 Oxygen-nitrogen liquefier 2 Nitrogen compressor 3 Heat exchanger 31 1st heat exchanger 32 2nd heat exchanger 33 3rd heat exchanger 4 Refrigerator 5 Expansion turbine 6 Liquid nitrogen tank 7 Oxygen liquefier 71 Heat exchanger 8 Pressure reducing valve 9 Nitrogen recovery compressor S Air separator A Air GN Gaseous nitrogen GO Oxygen oxygen LN Liquid nitrogen GN1, GN2 Cold LO liquid oxygen L Nitrogen liquefaction cycle line L1 Nitrogen forward line L2 Nitrogen return line L3 Oxygen supply line L4 Liquid nitrogen Line L5 Branch line L6, L6a, L6b Oxygen cooling nitrogen line L7 Liquid nitrogen derivation line L8 Liquid oxygen derivation line

Claims (4)

[Claims] 1. An oxygen-nitrogen liquefaction device for liquefying gaseous oxygen and gaseous nitrogen separated by an air separation device into liquid oxygen and liquid nitrogen, and a nitrogen liquefaction cycle line for liquefying gaseous nitrogen from the air separation device. And an oxygen liquefaction device for liquefying gaseous oxygen from the air separation device, and the oxygen liquefaction device is configured to liquefy gaseous oxygen by the latent heat of vaporization of liquid nitrogen derived from the nitrogen liquefaction cycle line. An oxygen-nitrogen liquefaction device characterized in that 2. The nitrogen liquefaction cycle line comprises a compressor for compressing gaseous nitrogen into compressed gaseous nitrogen, a refrigerator for cooling the compressed gaseous nitrogen, and a compressed gaseous nitrogen cooled by the refrigerator. An expansion turbine that produces cold for nitrogen liquefaction by performing adiabatic expansion work on a part, and heat exchange between the cold and the residual gaseous nitrogen on the downstream side of the compressor causes the residual gaseous nitrogen to become liquid. A heat exchanger for making nitrogen is provided, and the cold used for the heat exchange is returned to the upstream side of the compressor, and a gas oxygen line for performing heat exchange between the gas oxygen and the cold in the heat exchanger is provided. Provided, the oxygen liquefier has an oxygen liquefaction chamber and a vaporization means arranged in the oxygen liquefaction chamber, the downstream end of the gas oxygen line is connected to the oxygen liquefaction chamber, the vaporization means, the From nitrogen liquefaction cycle line The oxygen-nitrogen liquefaction apparatus according to claim 1, which is configured to evaporate the liquid nitrogen that is drawn out. 3. The oxygen-nitrogen liquefaction apparatus according to claim 2, further comprising a decompression valve for decompressing the liquid nitrogen derived from the nitrogen liquefaction cycle line on the upstream side of the oxygen liquefier. 4. The oxygen-nitrogen liquefaction apparatus according to claim 2 or 3, further comprising a line for returning the cold drawn out from the vaporizing means of the oxygen liquefier to the compressor.