JPH09318244A - Air liquefying and separating device and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To intermittently manufacture oxygen gas by providing a nitrogen circulating system for circulating the nitrogen whose amount is corresponding substantially to the half of the amount of liquefied nitrogen extracted from a device at the time of using oxygen. SOLUTION: Liquefied nitrogen is obtained through heat exchange between liquefied oxygen, running out into a condensing evaporator 15 at the bottom of a low-pressure tower, and nitrogen gas in the top part of a high-pressure tower 14 while the liquefied oxygen itself is evaporated to obtain oxygen gas and a part of the oxygen gas is extracted to obtain product oxygen gas through the cold heat exchanging unit 10b of a main heat exchanger 10 and the hot heat exchanging unit 10a of the same to increase the temperature of the same through heat exchange between material air at substantially a normal temperature. The nitrogen gas, led out into a flow passage 35 from the top of the low-pressure tower, is heated to the normal temperature through the cold heat exchanging unit 10b and the hot heat exchanging unit 10a, then, is conducted to the outside of the system through a flow passage 36. A part of the nitrogen gas, branched from the flow passage 36 into a flow passage 39, is introduced into a nitrogen compressor 40 to compress and pressurize it, then, is introduced from a flow passage 41 into the hot heat exchanging unit 10 and the cold heat exchanging unit 10b again to introduce it into the top of the high-pressure tower 14 after effecting heat exchange between feedback gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for producing oxygen mainly from air as a raw material. More specifically, the product oxygen gas is increased / decreased in response to fluctuations in demand for oxygen gas, and is stably supplied. Apparatus and method for obtaining the same.

[0002] The present invention relates to an apparatus and method suitable for supplying oxygen gas, which is particularly used in industries such as electric furnace operation where oxygen gas is intermittently used only in a specific time zone. Further, the present invention relates to an apparatus and method suitable for supplying oxygen to an oxygen combustion / metal melting system that intermittently uses a larger amount of oxygen gas than an electric furnace.

[0003]

2. Description of the Related Art Conventionally, in the field of using oxygen such as metal refining as described above, a liquefied oxygen storage tank has been installed in the vicinity of a refining furnace using oxygen, and when oxygen is used, it is vaporized and used. .
Similarly, a PSA device is installed near the place where oxygen is used, and this is used intermittently.

Further, the conventional demand fluctuation type air liquefaction separation apparatus takes out and stores it as liquefied oxygen when the demand for oxygen decreases, and when the demand for oxygen increases,
The stored liquefied oxygen is reversely sent to be vaporized and taken out as gaseous oxygen, and the cooling of the liquefied oxygen is generally performed by liquefying and taking out nitrogen to transfer it to prevent a cold loss.

[0005]

Although the liquefied oxygen vaporization supply system is convenient for intermittent use of oxygen gas, it is expensive because of the cost required for liquefaction and transportation.

In the case of the PSA device, since it is used intermittently, not only the operating rate is low, but also there is inconvenience such as wasting in starting and stopping, and if oxygen gas is compressed and stored to increase the operating rate, a large capacity is required. Requires a high pressure gas holder.

Furthermore, since the conventional air liquefaction separation apparatus employs a tray (sieve tray) type rectification column as the rectification column, there is a limit to the demand fluctuation. That is, the weight reduction limit of the sieve tray rectification column is about 60 to 75%, while the weight reduction limit of the air compressor is about 75% when one unit is used. Regarding the weight reduction limit of the apparatus, even if the raw material air reduced to about 75% was introduced and the product oxygen was stored as liquefied oxygen, the reduction limit of the product oxygen gas was 65 to 70%.

The increase limit depends on the margin inherent in the apparatus, but the maximum amount (100%) of the feed air is introduced into the air compressor, and at the same time, the stored liquefied oxygen is introduced into the rectification column. However, the limit was 130% of the oxygen amount during the standard operation.

Therefore, in the field of refining metals that use oxygen gas intermittently as described above, there has been no example of on-site supply by an air liquefaction separation device.

Furthermore, the cold transfer method, which is a general method of the conventional air liquefaction separation apparatus for demand fluctuation, changes the operating condition in response to the fluctuation of oxygen demand, and in most cases, the rectification column is accompanied by it. Since the internal state changes and the composition distribution in the column changes, the product purity is affected, and in order to suppress this, the fluctuation range is limited, and the oxygen yield is lowered. In particular, in an apparatus equipped with an argon sampling facility, composition fluctuations inside the low-pressure column are a major obstacle to the sampling of argon, so measures have been considered.

Therefore, the present invention provides an air liquefaction / separation device as a device that responds to large fluctuations in demand of oxygen gas with a relatively simple device configuration, or as a device that responds to applications in which oxygen gas is intermittently used, Further, an object of the present invention is to provide an air separation method capable of maintaining a substantially constant composition distribution in the rectification column even when performing a transfer operation of liquefied oxygen and liquefied nitrogen using the apparatus, and capable of operating in a wide range of fluctuation. And

[0012]

The apparatus configuration of the present invention for achieving the above-mentioned object is an air compressor for compressing raw material air, a pretreatment device for purifying compressed air, and a heat exchange for cooling compressed purified air. It has a double rectification column consisting of a high-pressure column and a low-pressure column that introduces a refining unit and compressed and purified cooling air to rectify and separate it. In the apparatus, a flow path for introducing nitrogen gas from the upper part of the low-pressure column and raising the temperature by exchanging heat with the raw air in the heat exchanger, and introducing at least a part of the heated nitrogen gas discharged from the heat exchanger. A nitrogen compressor for boosting pressure, a flow path for introducing pressurized nitrogen gas discharged from the nitrogen compressor into the heat exchanger again after cooling and introducing it into the high pressure column, and nitrogen gas discharged from the upper part of the high pressure column as the heat The temperature is raised in the exchanger and it is derived at the intermediate temperature. Expansion turbine for expansion, flow path for introducing low temperature nitrogen gas derived from the expansion turbine into the heat exchanger to recover refrigeration, liquefied oxygen storage tank for deriving and storing liquefied oxygen at the bottom of the low pressure column, the liquefied oxygen storage tank Liquefied oxygen pump and flow path to derive liquefied oxygen from the liquefied nitrogen to the lower part of the low pressure column, liquefied nitrogen storage tank to derive and store liquefied nitrogen from the top of the high-pressure tower, liquefied nitrogen from the liquefied nitrogen storage tank to lower the low pressure It is characterized by having a flow path to be introduced to the top of the tower.

The air compressor for compressing the raw material air is a plurality of compressors or a compressor capable of reducing the amount to 50% or less.

Further, the air liquefaction / separation apparatus using the double rectification column is characterized by being equipped with an argon column.

Further, at least one of the high pressure column and the low pressure column is a packed column.

Furthermore, the nitrogen discharged from the high-pressure column is passed through the heat exchanger, the flow path for raising the temperature to an intermediate temperature and discharged, and the nitrogen discharged from the nitrogen compressor are passed through the heat exchanger,
The flow paths introduced into the high-pressure column are the same flow path.

Furthermore, a flow path for introducing the low temperature nitrogen gas discharged from the expansion turbine into the heat exchanger to recover refrigeration draws nitrogen gas from the upper part of the low pressure column and exchanges heat with the raw material air. It is characterized in that it is a flow passage that joins a flow passage connected to a heat exchanger that heats up.

Further, the constitution of the method of the present invention for achieving the above object is to compress, purify and cool the raw material air and introduce it into the rectification column to collect oxygen, nitrogen and the like by liquefaction rectification separation, In the air liquefaction separation method involving the operation change, at the time of oxygen gas sampling, at least a part of the nitrogen gas discharged from the heat exchanger is pressurized and introduced again into the heat exchanger, and after cooling, is introduced into the high-pressure column, The expansion turbine is stopped, liquefied oxygen is introduced from the liquefied oxygen storage tank to the lower part of the low pressure column, and liquefied nitrogen corresponding to the amount of liquefied oxygen introduced is discharged from the top part of the high pressure column,
Oxygen gas is discharged from the lower part of the low-pressure column and collected as a product by raising the temperature in the heat exchanger.When not collecting oxygen gas, the amount of raw air introduced is reduced in accordance with the amount of liquefied oxygen to be described later,
Depressurized nitrogen gas from the upper part of the high-pressure column, heated to an intermediate temperature, introduced into an expansion turbine for expansion and cooling, recovering and releasing generated cold, and discharging the liquefied nitrogen from the liquefied nitrogen storage tank to the low pressure. It is characterized in that it is introduced at the top of the column and the liquefied oxygen generated at the bottom of the low pressure column is discharged and stored in the liquefied oxygen storage tank.

Further, the rectification column is a packed column, and the ratio of the maximum introduction amount and the minimum introduction amount of the raw material air is 1: 0.
It is characterized by being about 35.

The oxygen gas sampling operation is mainly performed in the daytime, and the oxygen gas non-sampling operation is mainly performed in the nighttime.

Further, the amount of introduced raw material air is reduced according to the amount of oxygen collected, introduced from the upper part of the low pressure column and introduced into a heat exchanger to exchange heat with the raw material air, and nitrogen gas discharged from the heat exchanger is removed. After cooling at least a part of the pressurized nitrogen gas introduced into the heat exchanger again, at least a part of the pressurized nitrogen gas is branched out from the intermediate part of the heat exchanger and introduced into an expansion turbine to expand and cool the temperature. The generated cold is collected and released, and liquefied nitrogen from the liquefied nitrogen storage tank is introduced to the top of the low-pressure column, and the liquefied oxygen generated at the bottom of the low-pressure column is led out and stored in the liquefied oxygen storage tank. The method is characterized in that product oxygen gas is discharged from the lower part of the tower. Further, the remainder of the pressurized nitrogen gas that is branched out from the intermediate part of the heat exchanger and introduced into the expansion turbine enters the heat exchanger cold heat exchange part, is cooled to around the boiling point, and is introduced into the high pressure column top part. This is a characteristic method.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is carried out by adopting the above-mentioned structure. The feature of this structure is that the air liquefaction / separation device intermittently increases or decreases the oxygen gas in response to demand fluctuations. For the purpose of manufacturing, the introduction of liquefied oxygen at the time of sampling oxygen gas, and the introduction of liquefied nitrogen for transfer, a nitrogen circulation system that circulates the amount of nitrogen gas equivalent to about half of that is provided, thereby increasing or decreasing oxygen gas sampling. This is because the quantity range has been expanded significantly compared to conventional equipment.

Further, in the case of a packed column, the rectification column load at the time of collecting oxygen gas is focused on that the reduction operation can be performed up to about 30%. By carrying out the above operation, it is possible to intermittently produce oxygen gas. That is, when the lower limit of the oxygen gas collection is zero, the rectification column load can be reduced to about 30% of the maximum load capacity and the operation can be performed for a predetermined time. The lower limit of this reduction is 60 to 75% in the tray column using the usual sieve tray. Therefore, it is possible to increase or decrease by combining the process including the above nitrogen circulation and the packed column with the allowable lower limit of the load fluctuation of about 30%. The quantity range has expanded dramatically compared to conventional equipment.

The time ratio between the maximum sampling of oxygen gas and the minimum sampling (non sampling) and the selection of the time zone are arbitrary, but the power required per hour during the maximum oxygen gas sampling operation is Approximately 1/2 of that, so, for example, by performing non-oxygen sampling operation at night to store liquefied oxygen and performing maximum oxygen sampling operation in the daytime, nighttime electricity that effectively uses nighttime electricity with a low electricity rate It can be used as a usage-type device, which can greatly reduce the production cost.

In the oxygen gas sampling operation, liquefied oxygen is introduced,
The operation is to take out liquefied nitrogen, but the amount of reflux nitrogen supplied from the high-pressure column to the low-pressure column becomes small, so the expansion turbine is stopped and the amount of reflux nitrogen that is still insufficient is compensated for by circulation. At this time, the cold for maintaining the operation is supplied due to the difference in heat quantity between the liquefied oxygen and the liquefied nitrogen that are introduced and discharged.

In the oxygen gas non-collecting operation, liquefied oxygen is withdrawn and liquefied nitrogen is introduced, which is the reverse of the above.
Therefore, nitrogen gas is extracted from the high-pressure column and cold is generated by the expansion turbine.

When the oxygen gas sampling operation and the oxygen gas non-sampling operation are alternately performed, it is necessary to generate the total amount of cold required for 24 hours / day operation at 10 hours / day. Requires a large capacity expansion turbine. In order to secure this turbine flow rate, a circulating nitrogen system is formed and cold is supplied by circulating nitrogen gas.

When the air separation device has a small capacity, that is,
When the required amount of cold is less than a certain amount, it is not necessary to operate the circulating nitrogen system because the nitrogen extracted from the lower tower can cover the required amount.

The present invention will be described below in more detail with reference to the drawings. First, the device configuration and process will be described according to the flow path from the introduction of raw material air to the product oxygen collection.

The raw material air from the flow path 1 is branched by the branch flow path 2 and introduced into the air compressor A, and a predetermined pressure, for example, 6 kg.
It is pressurized and compressed to / cm ² and led to the flow path 4. The other branched source air is introduced into the other air compressor B, compressed to the same pressure as the air compressor A, and led out to the flow path 6. The compressed air in the flow channels 4 and 6 merges and flows from the flow channel 7,
The water is introduced into a pretreatment device 8 for removing contained water and carbon dioxide. The pretreatment device 8 is mainly composed of a plurality of adsorption towers which are filled with molecular sieves and switched and used. One tower introduces raw material air to adsorb and remove carbon dioxide gas and water in the raw material air. However, during that time, the other adsorption towers are in the regeneration process, and the carbon dioxide gas and the moisture adsorbed in the previous step are carried out along with the regeneration gas.

The compressed and purified air discharged from the pretreatment device 8 is cooled from the flow passage 9 to near the liquefaction temperature at the pressure through the hot heat exchange portion 10a and the cold heat exchange portion 10b of the main heat exchanger 10, and the flow passage 12 is obtained. Is introduced into the lower part of the high pressure column 14 located in the lower part of the double rectification column 13.

The compressed and purified cooling air introduced into the high-pressure column 14 rises while making gas-liquid contact in the column to become a nitrogen-enriched gas, and is liquefied in the top condenser evaporator 15 to become a reflux liquid,
It descends while making gas-liquid contact in the tower.

The oxygen-enriched liquefied air distilled at the bottom of the high-pressure column 14 is discharged from the flow path 16, supercooled by the supercooler 17 and discharged to the flow path 18, expanded and reduced in pressure by the valve 19, and partly expanded. It is vaporized and introduced into the middle part of the low pressure column 20. The oxygen-enriched liquefied air introduced into the low-pressure column 20 descends while making gas-liquid contact with the rising gas in the column, gradually enriches in oxygen, reaches the bottom of the column, and distills out as liquefied oxygen. The liquefied oxygen at the bottom of the low-pressure column 20 exchanges heat with the nitrogen gas at the top of the high-pressure column 14 in the condenser / evaporator 15 at the bottom of the column to make it liquefied nitrogen, which itself is vaporized to become a rising gas, and In the oxygen gas sampling operation, a part thereof is taken out from the flow path 21 as a product gas.

A part of the liquefied nitrogen condensed in the condenser evaporator 15 is returned to the top of the high pressure column 14 as a reflux liquid, but a part thereof is led out from the flow path 22 and supercooled in the supercooler 17. It is expanded by the valve 23 and introduced as a reflux liquid to the top of the low pressure column 20.

The liquefied nitrogen in the flow path 22 is partially led out of the system depending on operating conditions. That is, during the oxygen gas sampling operation, the liquefied nitrogen storage tank 25 is partially branched and passed through the flow path 24.
It is introduced and stored in. The stored liquefied nitrogen is expanded and reduced in pressure from the flow path 26 through the valve 27 during the oxygen gas non-collecting operation, and then introduced into the top of the low pressure column 20 to become a reflux liquid.

The liquefied oxygen distilled into the condensation evaporator 15 at the bottom of the low-pressure column 20 exchanges heat with the nitrogen gas at the top of the high-pressure column 14 to condense it into liquefied nitrogen, which itself is vaporized to oxygen. The gas becomes a gas, and a part of the gas is discharged from the flow path 21 and passes through the cold heat exchange section 10b and the hot heat exchange section 10a of the main heat exchanger 10 to exchange heat with the raw material air to heat up to a temperature near room temperature. It is derived as oxygen gas.

When a large amount of product oxygen gas is sampled, liquefied oxygen is discharged from the liquefied oxygen storage tank 29, pressurized by the liquefied oxygen pump 30, and introduced into the condenser / evaporator 15 via the flow path 31. Is vaporized by exchanging heat with the nitrogen gas, and is discharged from the flow path 21 as product oxygen gas.

During the oxygen gas non-collecting operation, liquefied oxygen is extracted from the condenser / evaporator 15 through the flow path 28 and stored in the liquefied oxygen storage tank 29.

Product nitrogen gas and exhaust nitrogen gas are taken out from the top of the low-pressure column 20. In this embodiment, the case where the product nitrogen gas and the exhaust nitrogen gas are not separated but taken out from the same flow path will be exemplified. That is, the nitrogen gas led out to the flow path 35 is heated to near room temperature through the cold heat exchange section 10b and the hot heat exchange section 10a, and is taken out of the system from the flow path 36.

A part of the nitrogen gas branched from the flow path 36 to the flow path 39 is introduced into the nitrogen compressor 40, and about 6 k
The compressed nitrogen gas is pressurized and compressed to g / cm ^2, and the pressurized nitrogen gas is supplied from the flow path 41 again to the hot heat exchange section 10a and the cold heat exchange section 10b.
Is introduced into the upper part of the high pressure column 14 and becomes a low temperature by exchanging heat with the return gas.

Since nitrogen as a heat source at the top of the high-pressure column 14 is not required when oxygen gas is not collected, the nitrogen compressor 4 is used.
The gas supply by 0 becomes unnecessary, the valve 38 is closed, the nitrogen from the flow path 39 becomes zero, and the nitrogen compressor 40 is stopped.

At this time, the produced oxygen is taken out of the system in the state of liquefied oxygen. Therefore, in order to replenish the cold required for this, nitrogen gas is discharged from the top of the high pressure column 14 through the flow path 41, and After the temperature is raised to an intermediate temperature in the cold heat exchange section 10b, the flow is branched to the flow path 45, the pressure is reduced to approximately atmospheric pressure by the expansion turbine 47 via the valve 46 in the open state, and the low temperature nitrogen gas is supplied from the flow path 48 to the flow path 36. Through the cold heat exchange section 10
b, the cold is recovered in the heat exchange section 10a, and the flow path 36
From outside the system. That is, when collecting liquefied oxygen,
A nitrogen circulation system including the expansion turbine 47 is formed to generate and supplement cold.

Further, in the case of collecting an intermediate amount of oxygen gas, the nitrogen gas in the flow path 36 is branched by a predetermined amount and the valve 38,
The pressure is increased by the nitrogen compressor 40 through the flow path 39, the temperature is lowered through the flow path 41 through the heat exchanging section 10a to the intermediate temperature, at least a part of which is branched to the flow path 45, the valve 46, and the expansion turbine. After expanding through 47, it expands to the flow path 48, merges into the flow path 36, collects cold in the cold heat exchange section 10b and the hot heat exchanger section 10a, and is discharged to the outside of the system.

Depending on the conditions, the main heat exchanger 1 may also be used.
From the middle part of 0 to the flow path 45 and branch out to the expansion turbine 47.
The rest of the nitrogen gas introduced into the main heat exchanger 10 enters the cold heat exchange section 10b of the main heat exchanger 10, is cooled to near the boiling point, and is adjusted in pressure by the valve 42, and then introduced into the top of the high pressure column 14.

[0045]

[Examples] Next, the operating states in the examples when the oxygen gas increase sampling is performed, when the oxygen gas is not collected, and when the intermediate amount is collected will be described.
First, a case where a product oxygen gas of 10,000 Nm ³ / h is sampled will be described as an example at the time of collecting the oxygen gas increase amount.

The compressor for the raw air is one of the air compressors A
Only the operating condition, atmospheric air 17,500 Nm ³ /
h is compressed to about 6 kg / cm ² and introduced into the system. The compressed air is removed of carbon dioxide gas and water in the pretreatment device 8 and introduced into the main heat exchanger 10, cooled to a temperature just before liquefaction, and introduced into the lower part of the high pressure column 14 of the double rectification column 13 and the column. Rise inside. The reflux liquid that has descended from the top of the column becomes oxygen-enriched liquefied air at the bottom of the column and distills to the bottom of the column. This oxygen-enriched liquefied air 9,300 Nm ³ / h is led out to the flow path 16 from the bottom of the tower, is expanded by the valve 19 through the supercooler 17 and the flow path 18, and is introduced into the low pressure tower 20. It is rectified and separated inside.

The high-purity nitrogen separated at the top of the high-pressure column 14 is liquefied in the condenser evaporator 15 to become liquefied nitrogen, which again becomes a reflux liquid in the high-pressure column and descends. 900 Nm ³ / h is derived from the flow path 22,
It is further branched and part of it is liquefied nitrogen 4,900 Nm ³ / h
Goes through the supercooler 17 and expands and is reduced in pressure by the valve 23 to reduce pressure in the low-pressure tower 2
It is expanded and introduced into 0, becomes a reflux liquid, and descends in the tower. Another part of the branched liquefied nitrogen of 7,000 Nm ³ / h is introduced from the flow path 24 into the liquefied nitrogen storage tank 25 and stored therein.

The oxygen gas 10,000 Nm ³ / h separated into the lower part of the low pressure column 20 by rectification is introduced into the flow path 21 and heat-exchanged with the compressed purified air in the main heat exchanger 10 to raise the temperature. , As product oxygen gas.

At this time, the oxygen gas deficient as the product is pumped out from the liquefied oxygen storage tank 29 by the liquefied oxygen pump 30, passes through the flow path 31, and the condensation evaporator 15 at the bottom of the low pressure column 20.
And is heat-exchanged with nitrogen gas at the top of the high-pressure column 14 to be vaporized into oxygen gas, which is the product oxygen gas.

Nitrogen gas 10 separated at the top of the low-pressure column 20,
800 Nm ³ / h is led out from the flow path 35 provided at the top of the tower, introduced into the main heat exchanger 10 through the supercooler 17, heated up to about room temperature and led out, and after 2 minutes, On the other hand, 7,000 Nm ³ / h of nitrogen gas is released outside the system. The other branched nitrogen gas of 3,800 Nm ³ / h was measured by the valve 38,
Approximately 6 kg / cm enters the nitrogen compressor 40 through the flow path 39.
^It is pressurized and compressed to ² and cooled in the main heat exchanger 10 and the valve 4
2. It is introduced into the top of the high-pressure column 14 via the flow path 41 and serves as a heating source for the condensation evaporator 15.

Next, as an example when oxygen gas is not collected,
The case where only product liquefied oxygen of 9,100 Nm ³ / h is collected as a product will be described. Only the part different from the case of the above oxygen gas collection will be described, and the part having the same operating condition will be omitted.

The raw material air 45,500 Nm ³ / h is pressurized and fed by both air compressors A and B and introduced. The oxygen-enriched liquefied air discharged from the bottom of the high-pressure column 14 to the low-pressure column 20 via the flow path 16 is 24,200 Nm ³ / h,
The amount of liquefied nitrogen discharged from the top of the high-pressure column 14 and introduced into the top of the low-pressure column 20 is 3,300 Nm ³ / h. But,
Since the amount of liquefied nitrogen is insufficient for the reflux liquid of the low-pressure column 20, the liquefied nitrogen storage tank 25 will produce 9,800 Nm of liquefied nitrogen.
³ / h is sent under its own pressure and introduced into the top of the high-pressure column 14.

Nitrogen gas 2 discharged from the top of the low pressure column 20
8,200 Nm ³ / h is led out of the system via the flow path 35 and the main heat exchanger 10. Also, from the top of the high pressure tower 14,
Nitrogen gas of 18,000 Nm ³ / h is used for the flow path 41, the valve 42,
After passing through the cold heat exchange section 10b, the temperature is raised to an intermediate temperature and the flow path 45
Through the valve 46 to the expansion turbine 47 to be expanded, reduced and reduced in temperature, and combined with the nitrogen gas 28, 200 Nm ³ / h discharged from the flow passage 48 from the top of the low pressure column 20 of the flow passage 36, and then the heat exchange portion 10b again. 10a enters to transfer the generated cold to the raw material air.

In the above-mentioned embodiment, oxygen gas is not collected as a product, but only as liquefied oxygen is collected and stored. Therefore, if the operation is carried out by combining the two embodiments with the above-mentioned embodiment, for example, refining work can be performed. In the case of carrying out only during the daytime, it can be used as an air liquefaction separation device capable of supplying intermittently only during the daytime and producing and storing only liquefied oxygen at night, which can be intermittently supplied.

Next, as an example of collecting the intermediate amount of oxygen gas, the case of collecting 4,500 Nm ³ / h of product oxygen gas will be described. Both of the air compressors A and B operate at about 70%. That is, 12,200 by the air compressor A
Nm ³ / h, the air compressor B 19,600Nm ³ /
The raw material air, which is pressurized and compressed to about 6 kg / cm ² of h, 31,800 Nm ³ / h in total, is introduced from the flow passage 7 into the high pressure column 14 through the flow passages 9 and 12.

High-pressure tower 14 From the bottom of the tower 22,300 Nm ³ /
The oxygen enriched liquefied air of h is sent to the middle part of the low pressure column 20. As for the liquefied nitrogen for reflux to the top of the low-pressure column 20, 9,500 Nm ³ / h is introduced from the top of the high-pressure column 14 and 2,300 Nm ³ / h from the liquefied nitrogen storage tank 25.

From the top of the low-pressure column 20, 25,000 Nm ³ / h of the product nitrogen gas and the exhaust nitrogen gas was discharged,
After passing through the flow path 35 and the main heat exchanger 10, after warming to room temperature 1,
000 Nm ³ / h flows from the flow path 36 through the valve 38 to the flow path 39
And is pressurized and compressed to about 6 kg / cm ² by the nitrogen compressor 40 and led out to the flow path 41. Then, it enters into the heat exchanging section 10a of the main heat exchanger 10, is cooled to an intermediate temperature, is led out, is introduced into the expansion turbine 47, is expanded and reduced in temperature, is led down to the flow path 48, and is discharged into the nitrogen gas in the flow path 35. 25,0
Refrigeration is recovered in 26,000Nm ³ / h next main heat exchanger 10 merges with 00Nm ³ / h, the 1000N
The remaining 25000Nm ³ / h branched circulated m ³ / h is discharged as described above.

Oxygen gas from the bottom of the low pressure column 20 is 4,
500 Nm ³ / h is derived and taken out as a product through the flow path 21.

Further, liquefied oxygen of 2,100 Nm ³ / h distilled at the bottom of the low-pressure column 20 is discharged and stored in the liquefied oxygen storage tank 29 through the flow path 28.

Table 1 shows a comparison of the gas flow rates of the above three embodiments.

[0061]

[Table 1]

As is clear from the flow rates of the respective parts described above, the ratio (L / L) between the amount of rising gas and the amount of falling liquid in the low-pressure column 20 in any of the three operating patterns.
V) is approximately the same value. That is, in any case, the upper half of the column has 0.45 to 0.47 and the lower half has 1.32 to 1.36. This indicates that even if various operation patterns are selected, the rectification state inside the low-pressure column 20 is substantially the same, so that even if the amount of product gas collected changes significantly, It shows that products of the same quality can be obtained even if intermittent operation is performed.

This is a very important requirement especially in an air liquefaction separation apparatus equipped with an argon sampling system.
That is, in order to extract the argon feed gas from the middle part of the low-pressure column 20 and supply it to the crude argon column (not shown) to collect the crude argon, it is a requirement that this argon feed gas can be always delivered in a constant state. Become. In the present invention, a nitrogen circulation system including the nitrogen compressor 40 and the expansion turbine 47 is provided, and further a liquefied oxygen storage tank 29 and a liquefied nitrogen storage tank 25 are provided, and these are used to set the optimum operating conditions according to demand. As a result, it is possible to perform the operation corresponding to various demand fluctuation patterns including the oxygen gas intermittent sampling operation and further the argon sampling operation.

[0064]

As described above, according to the method / apparatus of the present invention, a conventional liquefied oxygen-liquefied nitrogen transfer type demand fluctuation compliant air liquefaction separation apparatus can be used to control the amount of liquefied nitrogen extracted from the apparatus when oxygen is used. By providing a nitrogen circulation system that circulates nitrogen in an amount corresponding to about half, it has become possible to intermittently produce oxygen gas.

By using a rectification column as a packed column,
The fractionator load when collecting oxygen gas is 60 ~
75%, the lower limit of weight reduction of packed column type rectification column is about 30
By paying attention to the fact that the operation can be performed at about%, the intermittent production of oxygen gas is also possible by performing the operation under this condition.

Therefore, according to the method / apparatus of the present invention, it is possible to perform the intermittent production of oxygen gas as well as the operation satisfying the conditions of the normal demand fluctuation type air liquefaction separation apparatus.
Furthermore, by using this, by performing oxygen gas sampling operation (liquefied oxygen injection, liquefied nitrogen storage) in the daytime and oxygen gas non-collection operation (liquefied oxygen storage, liquefied nitrogen injection) at night, low cost of electricity use at night Production is now possible.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of an air liquefaction separation device of the present invention.

[Explanation of symbols]

A, B ... Air compressor, 8 ... Pretreatment device, 10 ... Main heat exchanger, 10a ... Warm heat exchange section, 10b ... Cold heat exchange section, 17 ...
Supercooler, 13 ... Double rectification column, 14 ... High pressure column, 15 ... Condensing evaporator, 20 ... Low pressure column, 19, 23, 27, 38, 4
2, 46 ... Valve, 25 ... Liquefied nitrogen storage tank, 29 ... Liquefied oxygen storage tank, 30 ... Liquefied oxygen pump, 40 ... Nitrogen compressor, 47 ...
Expansion turbine

Claims (8)

[Claims] 1. An air compressor for compressing raw material air, a pretreatment device for purifying compressed air, a heat exchanger for cooling compressed purified air, a high pressure column for introducing compressed purified cooling air and rectifying and separating it. Having a double rectification column consisting of a low-pressure column, oxygen, nitrogen, etc. are collected by rectification separation, and in an air liquefaction separation device accompanied by a change in operation, the nitrogen gas is derived from the upper part of the low-pressure column and the heat exchanger is used. A flow path that heats up by exchanging heat with the raw material air, a nitrogen compressor that introduces at least a part of the heated nitrogen gas that has led out the heat exchanger to raise the pressure, and a pressurized nitrogen gas that has led out the nitrogen compressor. A flow path that is introduced into the heat exchanger again and then cooled and then introduced into the high-pressure column, nitrogen gas derived from the upper part of the high-pressure column is heated at the heat exchanger and derived at an intermediate temperature, and expansion is performed to expand the nitrogen gas. Turbine, low temperature nitrogen derived from the expansion turbine A flow path for introducing gas into the heat exchanger to recover refrigeration, a liquefied oxygen storage tank for deriving and storing liquefied oxygen at the bottom of the low-pressure column, liquefied oxygen from the liquefied oxygen storage tank for introduction into the lower part of the low-pressure column A liquefied oxygen pump and a flow path, a liquefied nitrogen storage tank for discharging and storing liquefied nitrogen from the top of the high-pressure column, and a flow path for discharging liquefied nitrogen from the liquefied nitrogen storage tank and introducing it to the top of the low-pressure column. Air liquefaction separator. 2. An air compressor for compressing the raw material air,
The air liquefaction separation device according to claim 1, wherein the air liquefaction separation device is a plurality of compressors or a compressor capable of reducing the amount to 50% or less. 3. The air liquefaction separation device according to claim 1, wherein the air liquefaction separation device using the double rectification column is further provided with an argon column. 4. The high pressure column, the low pressure column and at least one of the argon columns are packed columns.
The air liquefaction separation device described. 5. The raw material air is compressed, purified, cooled, introduced into a rectification column, and oxygen, nitrogen, etc. are collected by liquefaction rectification separation,
In the air liquefaction separation method with operation change, when collecting oxygen gas, pressurize at least part of the nitrogen gas discharged from the heat exchanger, introduce it again into the heat exchanger, and after cooling, introduce it into the high pressure column. The expansion turbine that expands the liquid is stopped, liquefied oxygen is introduced from the liquefied oxygen storage tank to the lower part of the low-pressure column, liquefied nitrogen corresponding to the amount of liquefied oxygen introduced is discharged from the top of the high-pressure column, and oxygen gas is discharged from the lower part of the low-pressure column. The temperature is raised in the heat exchanger and collected as a product.When not collecting oxygen gas, the amount of raw air introduced is reduced in accordance with the amount of liquefied oxygen collected to be described later, and nitrogen gas is discharged from the upper part of the high pressure column, After raising the temperature, it is introduced into an expansion turbine to expand and lower the temperature, and the generated cold is recovered and released, and liquefied nitrogen from a liquefied nitrogen storage tank is introduced into the low pressure column top section and liquefied oxygen generated in the low pressure column bottom section. Derive Cryogenic air separation method characterized by storing the serial liquid oxygen storage tank. 6. The rectification column is a packed column, and the ratio of the maximum introduction amount and the minimum introduction amount of the raw material air is 1: 0.
It is about 35, The air liquefaction separation method of Claim 5 characterized by the above-mentioned. 7. The air liquefaction separation method according to claim 5, wherein the oxygen gas sampling operation is performed mainly in the daytime, and the oxygen gas non-sampling or oxygen gas reduction sampling operation is performed mainly at night. 8. The raw material air is compressed, purified, cooled, introduced into a rectification column, and oxygen, nitrogen, etc. are collected by liquefaction rectification separation,
In the air liquefaction separation method that involves a change in operation, the amount of feed air introduced is reduced according to the amount of oxygen collected, and it is led from the upper part of the low-pressure column and introduced into the heat exchanger to exchange heat with the feed air, and from the heat exchanger. At least a part of the nitrogen gas is pressurized, introduced again into the heat exchanger and cooled, and then at least a part of the pressurized nitrogen gas is led out from the intermediate part of the heat exchanger and introduced into the expansion turbine to expand. The temperature is lowered, the generated cold is recovered and released, and the liquefied nitrogen from the liquefied nitrogen storage tank is introduced into the top of the low-pressure column, and the liquefied oxygen generated in the bottom of the low-pressure column is discharged and stored in the liquefied oxygen storage tank. An air liquefaction separation method, characterized in that product oxygen gas is discharged from the lower part of the low pressure column.