JP3355009B2 - Oxygen and nitrogen gas production equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen / nitrogen gas producing apparatus capable of obtaining oxygen gas and nitrogen gas in a pressurized state.

[0002]

2. Description of the Related Art Conventionally, oxygen gas and nitrogen gas have been
It is manufactured by using an air separator to separate the two using the difference in the boiling points of nitrogen and oxygen. As shown in FIG. 3, a typical air separation device of this type sucks raw air from a raw air suction pipe 1, compresses the raw air with an air compressor 2, and passes through a pipe 3 a first and a second air. It cools via heat exchangers 4 and 5 and further via pipe 7 and rectification column 8
Into the lower tower 8 'in a state of being cooled to near the liquefaction point. In the lower tower 8 ',
The air is rectified, oxygen-rich liquid air accumulates at the bottom of the lower column 8 ', and nitrogen moves upwards in gaseous form and is drawn off by a pipe 10 from the top of the lower column 8'. The derived nitrogen gas exchanges heat in the second and first heat exchangers 5 and 4, becomes a product nitrogen gas near normal temperature, and is derived from the pipe 33. A part of the nitrogen gas derived from the top of the lower tower 8 'is introduced into the condenser 16 of the upper tower 8 "through a pipe 17, where it is liquefied and becomes liquid nitrogen, and is passed through a pipe 18 to the lower tower. The upper column 8 "is fed with oxygen-rich liquid air from the bottom of the lower column 8 'via a pipe 12 with an expansion valve 12'. In the upper tower 8 ″, liquid air is rectified, liquid oxygen 9 accumulates at the bottom, and nitrogen-rich exhaust gas is led out from the top of the tower by a pipe 21. The discharged exhaust gas is subjected to the second heat exchange. Via the heat exchanger 5, via the pipe 24 and the valve 25, into the expansion turbine 26, where it undergoes adiabatic expansion to produce the required refrigeration of the device, and then via the pipe 29 the second and first heat exchangers 5, 4, where cold is imparted to the feed air, which is itself discharged into the atmosphere from pipe 31. A valve 32 provided in pipe 29
Due to the liquid level in the upper tower 8 ″, the system 2 of the expansion turbine 26
1 to control the amount of exhaust gas supplied. Liquid oxygen is led out from the bottom of the upper tower 8 "by a pipe 10 'and vaporized through the second and first heat exchangers 5 and 4 to become oxygen gas, which is then pressurized by a pressurizing pump P, It becomes product oxygen gas in a pressurized state and is provided for demand.

[0003]

In this type of air separation apparatus, when it is necessary to obtain product gas in a pressurized state,
The gas extracted as a product must be pressurized by a pressurizing pump in a gaseous state. However, in order to pressurize the gas in a gaseous state, considerable energy is required, and there is a problem that the cost is increased. Further, in the above-described apparatus, since the cold balance during operation is normally controlled to be appropriately maintained, even if the supply amount of the raw material air per unit time is increased in order to respond to an unplanned increase in demand, expansion is not performed. Since a time delay occurs in increasing the amount of cold generated by the turbine, there is also a problem that the purity of the product oxygen gas is reduced.

The present invention has been made in view of such circumstances, and can efficiently produce oxygen gas and nitrogen gas in a pressurized state at low cost, and can sufficiently cope with an unexpected increase in demand. Excellent oxygen that can respond
It is an object of the present invention to provide a nitrogen gas producing apparatus.

[0005]

In order to achieve the above object, an oxygen / nitrogen gas producing apparatus according to the present invention comprises an air compressing means for compressing raw air, and a heat exchanging means for cooling the compressed air to an extremely low temperature. The lower rectification tower which introduces compressed air cooled to the ultra-low temperature to liquefy oxygen by liquefaction and separates and keeps nitrogen in a gaseous state, and the liquid air taken out from the bottom of the lower rectification tower into the tower. An upper rectification tower for introducing and liquefying oxygen by liquefaction and separation and storing the liquefied oxygen at the bottom, a liquid oxygen extraction path for extracting liquid oxygen from the bottom side of the upper rectification tower, and a heat exchange means extending from the tip of the liquid oxygen extraction path And a product oxygen gas take-out path for evaporating the liquid oxygen and taking it out as a product via the above, and a part of the gas nitrogen provided in the upper rectification column and introduced into the lower rectification column to condense and liquefy. Means and this condensing means A liquid nitrogen recirculation path for recirculating the liquid nitrogen taken out from the lower rectification column, a liquid nitrogen extraction path for extracting a part of the liquid nitrogen via the liquid nitrogen recirculation path, and a liquid nitrogen extraction path from the tip of the liquid nitrogen extraction path. A nitrogen gas take-out path extending and evaporating the liquid nitrogen through the heat exchange means to take out the liquid nitrogen as product nitrogen gas. The liquid oxygen take-out path is provided with a first pressurizing means for pressurizing liquid oxygen. At the same time, a flow path downstream of the pressurizing means is formed to have a structure for providing cold through the heat exchanging means, then to the first cold heat generating expander, and again to the heat exchanging means. A second pressurizing means for pressurizing liquid nitrogen is provided in the liquid nitrogen take-out path, and a flow path downstream of the pressurizing means passes through the heat exchanger and a second pressurizing means. Via the cold heat inflator A configuration that is formed in the structure to impart cold through the heat exchange means.

[0006]

That is, in the apparatus of the present invention, the rectification tower is
The liquid oxygen generated in the upper rectification column (hereinafter abbreviated as "upper column") is taken out, pressurized in a liquid state, sent to a heat exchanger, and then introduced into an expander for generating cold heat. Then, adiabatic expansion is performed to generate cold, and the generated cold is sent to a heat exchanger to serve as a cold source of the apparatus. As described above, when oxygen is pressurized in a liquid state, the pressurization cost can be significantly reduced as compared with the case where oxygen is pressurized in a gaseous state (for example, 1 mol of oxygen is 2 mol if gas is gaseous).
In liquids, oxygen is only 16 grams compared to 2.4 liters). Moreover, in the present invention, since oxygen is pressurized in a liquid state as described above, it is vaporized in a heat exchanger, and this pressure is used to drive an expander for generating cold heat such as an expansion turbine to obtain cold. The energy used for the oxygen pressurization can be used for cold generation,
As a result, a reduction in product cost can be realized. This is the most important feature of the present invention. Besides,
In the present invention, a part of the reflux liquid nitrogen introduced into the lower rectification column (hereinafter, abbreviated as “lower column”) is taken out to obtain product nitrogen gas, which is also pressurized in a liquid state,
Then, it is vaporized by a heat exchanger, introduced into a cold heat generating expander, adiabatically expanded to generate cold, and the generated cold is sent again to the heat exchanger to be used as a cold source of the apparatus. Therefore, also for the product nitrogen gas, the pressurizing energy can be used for the driving energy of the expander for generating cold energy, so that the cost of the product nitrogen gas can be significantly reduced.

Next, the present invention will be described in detail based on embodiments.

FIG. 1 shows an embodiment of the present invention.
In the figure, 51 is an air compressor for compressing raw material air, 5
2 is a drain separator, 53 is a CFC cooler, and 54 is a set of two adsorption towers. The adsorption tower 54 is filled with a molecular sieve, and adsorbs and removes impurities such as H ₂ O, CO ₂ and CO in the air compressed by the air compressor 51. Reference numeral 55 denotes a compressed air supply pipe for sending compressed air from which impurities are removed by adsorption. Reference numeral 56 denotes a first heat exchanger to which compressed air from which impurities have been removed by the adsorption tower 54 is sent. Reference numeral 57 denotes a second heat exchanger to which the compressed air having passed through the first heat exchanger 56 is sent. Reference numeral 58 denotes a rectification column including an upper column 59 and a lower column 60.

The lower tower 60 is cooled to an extremely low temperature by the first and second heat exchangers 56 and 57, further cools the compressed air sent through the pipe 55, liquefies part of the compressed air, and forms a liquid air 61. At the bottom, and nitrogen at the top in a gaseous state. A condenser 62 is built in the bottom side of the upper tower 59, and a part of the nitrogen gas accumulated in the upper part of the lower tower 60 is sent in through a first reflux pipe 63. The upper tower 59, than the lower tower within 60 have become reduced pressure, the stored liquid air in the bottom of the lower column _{(N 2 50~70%, O 2} 30~50%) 61 is piped expansion valve 65 The liquid is sent at 66 and is vaporized to cool the internal temperature of the upper tower 59 to a temperature lower than the boiling point of liquid nitrogen. By this cooling, the nitrogen gas sent into the condenser 62 is liquefied. This liquid nitrogen is introduced as a reflux liquid into the upper part of the lower tower 60 through the second reflux pipe 64, and flows downward in the lower tower 60 via the liquid nitrogen reservoir 67, from the bottom of the lower tower 60. It comes into contact with the rising compressed air in a countercurrent manner, cools and partially liquefies. In this process, the high-boiling component oxygen gas in the compressed air is liquefied and accumulates at the bottom of the lower column 60, and the low-boiling component nitrogen gas accumulates at the upper portion of the lower column 60. 64a is a gas-liquid separator. 90 is the second
A part of the liquid nitrogen that returns is taken out by a liquid nitrogen extraction pipe branched from the reflux pipe 64.

On the other hand, the liquid air collected at the bottom of the lower tower 60 is sent to the upper part of the upper tower 59 via a pipe 66, and is subjected to a rectification action in the upper tower 59. As a result, oxygen of the high boiling point component in the liquid air is liquefied and accumulates as liquid oxygen 71 at the bottom of the upper tower 59. Reference numeral 80 denotes a pipe that supplies liquid oxygen into the upper tower 59 when the oxygen gas producing apparatus is started and when the amount of liquid oxygen in the upper tower 59 decreases. The pipe 80 extends from a liquid oxygen storage tank (not shown). This tank stores liquid oxygen produced by the apparatus or liquid oxygen produced by another apparatus and transported by a tank truck or the like. Reference numeral 81 denotes a liquid oxygen supply control valve, which is opened when the cold balance during operation becomes inadequate due to the liquid level of the liquid level gauge 82 to supply cold liquid oxygen, and the liquid level of liquid oxygen is constantly maintained. It is controlled at a constant level to balance the rectification. The gas of the low boiling point component including the nitrogen gas is led out from the top of the upper tower 59 as exhaust gas by the pipe 70, and is discharged to the second and first heat exchangers 57 and 56.
And is released into the atmosphere via The liquid oxygen 71 collected at the bottom of the upper tower 59 is led out by a liquid oxygen outlet pipe 72, is pressurized by a first pressurizing pump 73, and is pressurized in the second heat exchanger 57. And is vaporized and converted into product oxygen gas and taken out from a product oxygen gas extraction pipe 74.

It should be noted that this oxygen gas extraction pipe 7
4 is provided with a first expansion turbine 75, which generates cold by using the pressurized pressure of the product oxygen gas as a drive source. That is, the product oxygen gas is 35 kg / c before entering the first expansion turbine.
pressure of about m ² , but 10 kg / cm
² and by performing thermodynamic external work, the temperature becomes extremely low and cold occurs. In this state, the heat enters the second heat exchanger 57 again, further enters the first heat exchanger 56, and The generated cold is imparted to the raw material air by heat exchange with the air, and the temperature of the raw material air itself becomes normal, and the product air is taken out from the end of the product oxygen gas extraction pipe 74 as a product. Since the first expansion turbine 75 uses a pressurized product oxygen gas as a driving source, a material that does not easily react with oxygen, for example, (copper alloy, for example, brass, nickel alloy (Ni—Cr—Fe)) , Stainless steel (SUS316
L) and an aluminum alloy (Al-Zn)) to prevent a disaster such as an explosion from occurring.

On the other hand, a part of the reflux liquid nitrogen taken out from the liquid nitrogen take-out pipe 90 is
1 and is introduced into the second heat exchanger 57 in a pressurized state to be vaporized, turned into nitrogen gas, and introduced into the product nitrogen gas extraction pipe 92. The product nitrogen gas extraction pipe 92 is provided with a second expansion turbine 93, which uses the pressurized pressure of the nitrogen gas as a drive source to generate cold as in the case of the expansion turbine 75. Then, the nitrogen gas again enters the second heat exchanger 57, further enters the first heat exchanger 56, exchanges heat with the raw material air, and applies generated cold to the raw material air,
The temperature of the product itself becomes room temperature, and the product nitrogen gas is taken out from the tip of the pipe 92.

A fin-type heat exchanger 100 is provided at the end of the product oxygen gas extraction pipe 74 and at the end of the product nitrogen gas extraction pipe 92, respectively. This is to prevent ultra-low temperature liquid oxygen or liquid nitrogen from being taken out as it is in the event that the cold balance in the heat exchangers 56 and 57 is lost.

Using this apparatus, product oxygen gas and product oxygen gas can be produced, for example, as follows. That is, first, the raw air is compressed by the air compressor 51, and the raw air is separated into the drain separator 52, the CFC cooler 53, the adsorption tower 54 for removing impurities, the first and second air.
Through the heat exchangers 56 and 57, and cooled to an ultra-low temperature state and sent into the lower column 60 of the rectification column 58.

In the lower tower 60, the compressed air is cooled by bringing it into countercurrent contact with the liquid nitrogen overflowing from the liquid nitrogen reservoir 67, and is partially liquefied to form a liquid at the bottom of the lower tower. Store as air 61. In this process, the difference between the boiling points of nitrogen and oxygen (boiling point of oxygen -183 ° C, boiling point of nitrogen -196
C), oxygen which is a high-boiling component in the compressed air is liquefied, and nitrogen remains as a gas. A part of the nitrogen gas collected on the ceiling of the lower tower 60 is removed from the first reflux pipe 6.
3, is introduced into the condenser 62 provided in the upper tower 59, where it is cooled and liquefied by the liquid oxygen accumulated at the bottom of the upper tower 59, and passes through the second reflux pipe 64. It is led out to the reflux liquid reservoir 67 of the lower tower 60.

The liquid air stored at the bottom of the lower tower 60 is fed into the upper tower 59 in an adiabatic expansion state via a pipe 66 and an expansion valve 65, and is subjected to a rectification operation. Then, oxygen, which is a high-boiling component, is liquefied and accumulates at the bottom, and low-boiling component gas containing nitrogen gas is sent out as exhaust gas from the top of the upper tower 59 via the pipe 70. The discharged exhaust gas passes through the second and first heat exchangers 57 and 56, is heated to near normal temperature, and is released into the atmosphere. Upper tower 5
The liquid oxygen 71 accumulated at the bottom of the pipe 9 is pressurized in a liquid state by a first pressurizing pump 73 via a pipe 72, and then introduced into a second heat exchanger 57, where heat exchange is performed. And is introduced into a product oxygen gas extraction pipe 74. Then, the introduced oxygen gas is adiabatically expanded by the first expansion turbine 75 provided in the product oxygen gas extraction pipe 74 to generate a necessary amount of cooling for the entire apparatus, and again the second expansion turbine 75 is used.
The heat exchanger 57 enters the first heat exchanger 56 and exchanges heat with the raw material air in the two heat exchangers 57 and 56. The heat exchanger itself becomes oxygen gas at normal temperature, and the product oxygen gas extraction pipe 74 Taken out from the tip of A part of the recirculated liquid nitrogen taken out by the liquid nitrogen take-out pipe 90 is pressurized by a second pressurizing pump 91 in a liquid state, and then introduced into a second heat exchanger 57. It is gasified by heat exchange and introduced into the product nitrogen gas extraction pipe 92. Then, the introduced nitrogen gas is adiabatically expanded by the second expansion turbine 93 provided in the product nitrogen gas extraction pipe 92 to generate cold, and again the second heat exchanger 5
7, further enters the first heat exchanger 56, exchanges heat with the raw material air in both heat exchangers 57, 56, and turns itself into nitrogen gas at normal temperature, and a product nitrogen gas extraction pipe 74.
Taken out from the tip of

Therefore, according to this apparatus, since the liquid oxygen is pressurized in a liquid state, a pressurized product oxygen gas can be obtained at low cost. Moreover, since the pressurized liquid oxygen is vaporized and then introduced into the first expansion turbine 75, the gas pressure before entering the expansion turbine 75 increases,
Thereby, the efficiency of adiabatic expansion can be greatly improved. In this case, since the pressurizing pressure of the pressurizing pump 73 for pressurizing the product oxygen gas can be used, effective utilization of energy can be realized, and the cost of the product pressurized gas can be considerably reduced. On the other hand, the line for taking out the product nitrogen gas also has the same configuration as described above, so that the cost of the product nitrogen gas can be considerably reduced.

In the apparatus of the above embodiment, the liquid level meter 82
Is provided to control the liquid oxygen supply control valve 81. Therefore, when the demand amount of the product oxygen gas or the product nitrogen gas sharply increases and the supply amount of the raw material air is correspondingly increased, depending on the two expansion turbines 75 and 93, it is possible to rapidly increase the generated cooling. However, at this time, the control valve 81 is actuated by the output signal from the liquid level gauge 82 to quickly supply the liquid oxygen to the upper tower 59 to eliminate the cold shortage.

In the above embodiment, the liquid level gauge 82 is used to read the liquid oxygen level in the upper tower 59. However, the liquid level gauge 82 is provided on the lower tower 60 side and the lower tower 60 is provided. There is no problem if the liquid surface level of the liquid air accumulated inside is read.

Further, in the above embodiment, a part of the liquid nitrogen is taken out from the second reflux pipe 64, but it may be taken out from the liquid nitrogen reservoir 67.

FIG. 2 shows an apparatus according to another embodiment of the present invention. In this device, a first pressurizing pump 73 is housed in a sealed casing 73c, and liquid oxygen is introduced into the casing 73c, pressurized, and led out to a pipe 72. The return pipe 2 returns oxygen gas generated by vaporization from the upper part of the casing 73c to the upper tower 59.
3b is provided. Further, the second pressure pump 91 is housed in a sealed casing 91c, and the casing 91c
Liquid nitrogen is introduced therein, pressurized and led out to the pipe 90. A return pipe 91b is provided to return the nitrogen gas generated by vaporization from the upper part of the casing 91c to the lower tower 60. The other parts are the same as those of the apparatus shown in FIG. With this configuration, it is possible to prevent a situation in which the gas bubbles are sucked and the pressure pumps 91 of the first pressure pumps 73 and 2 run idle (gas biting phenomenon).

[0022]

As described above, in the oxygen / nitrogen gas producing apparatus of the present invention, the rectification column is divided into upper and lower columns, and the liquid oxygen produced in the upper column is taken out and pressurized in a liquid state. Then, it is sent to a heat exchanger, further introduced into a cold-heat generating expander, adiabatically expanded to generate cold, and the generated cold is sent to a heat exchanger to serve as a cold source of the apparatus. As described above, when oxygen is pressurized in a liquid state, the pressurization cost can be significantly reduced as compared with the case where oxygen is pressurized in a gaseous state. Moreover, in the present invention, since oxygen is pressurized in a liquid state as described above, it is vaporized in a heat exchanger, and this pressure is used to drive an expander for generating cold heat such as an expansion turbine to obtain cold. The energy used for oxygen pressurization can be used for cold generation, and as a result,
Product costs can be reduced. This is the most important feature of the present invention. In addition, in the present invention, a part of the reflux liquid nitrogen introduced into the lower tower is taken out to obtain product nitrogen gas, which is also pressurized in a liquid state, then vaporized by a heat exchanger, and cooled and cooled. It is introduced into a generator inflator and adiabatically expanded to generate cold,
The generated cold is sent again to the heat exchanger and used as a cold source for the entire apparatus. Therefore, for product nitrogen gas,
Since the pressurized energy can be used for driving energy of the cold heat generating expander, the cost of the product nitrogen gas can be significantly reduced. Due to these advantages, the device of the present invention can be effectively used in a wide range of fields such as the steel manufacturing field, the chemical industry field, and the thermal power generation field.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of another embodiment of the present invention.

FIG. 3 is a configuration diagram of a conventional example.

[Explanation of symbols]

 51 air compressor 56,57 heat exchanger 58 rectification tower 59 upper tower 60 lower tower 61 liquid air 71 liquid oxygen 72 liquid oxygen extraction pipe 73 first pressurizing pump 74 product oxygen gas extraction pipe 75 first expansion turbine 90 Liquid Nitrogen Extraction Pipe 91 Second Pressurizing Pump 92 Product Nitrogen Gas Extraction Pipe 93 Second Expansion Turbine

Claims (3)

(57) [Claims] 1. An air compression means for compressing raw air, a heat exchange means for cooling said compressed air to an ultra-low temperature, and introducing said compressed air cooled to an ultra-low temperature to liquefy and separate oxygen to convert nitrogen into gas. A lower rectification tower that holds the liquid in a state, an upper rectification tower that introduces liquid air taken out from the bottom of the lower rectification tower into the tower, liquefies oxygen by liquefaction and stores the oxygen at the bottom, and an upper rectification tower A liquid oxygen take-out path for taking out liquid oxygen from the bottom side of the tower, a product oxygen gas take-out path extending from the end of the liquid oxygen take-out path and evaporating the liquid oxygen through a heat exchange means and taking out the product as a product; Condensing means provided in the distillation tower to introduce and condense and liquefy a part of the gaseous nitrogen in the lower distillation tower; and liquid nitrogen for refluxing the liquid nitrogen taken out from the condensation means to the lower distillation tower Reflux path and the liquid A liquid nitrogen take-out path for taking out a part of the liquid nitrogen via the nitrogen recirculation path, and a nitrogen gas extending from the tip of the liquid nitrogen take-out path and evaporating the liquid nitrogen through the heat exchange means and taking out as the product nitrogen gas An extraction path, and a first liquid oxygen pressurizing means is provided in the liquid oxygen extraction path.
And a flow path downstream of the pressurizing means passes through the heat exchanging means, passes through the first cold-heat generating expander, and again passes through the heat exchanging means. A second pressurizing means for pressurizing the liquid nitrogen is provided in the liquid nitrogen take-out path, and a flow path downstream of the pressurizing means is provided with the heat exchange passage. An oxygen / nitrogen gas producing apparatus, wherein the apparatus is configured to apply cold through the heat exchange means again through the second cooler generating expander after passing through the heat exchanger. 2. A liquid oxygen storage means for supplying liquid oxygen to said upper rectification tower, and a liquid oxygen supply from said liquid oxygen storage means such that the liquid level of said upper rectification tower or lower rectification tower is constant. 2. The oxygen / nitrogen gas producing apparatus according to claim 1, further comprising control means for controlling the amount. 3. The oxygen / nitrogen gas producing apparatus according to claim 1, wherein said first cold-heat generating expander is an expansion turbine made of a material having low reactivity to oxygen.