JPH07190613A - Air-liquefaction-separation apparatus - Google Patents

Abstract

PURPOSE:To provide an apparatus for the liquefaction-separation of air in which even during quantitative decrease in operation the pressure in the lower column can be maintained at a specified point and, even when the quantitative decrease is by a considerable rate, the operation can be stabilized. CONSTITUTION:A condenser 2 provided in a composite rectifying column 1 is equipped with an intermediate tank 4 having, for example, a liquid level gauge 3 as a means of detecting the level of liquid nitrogen in the condenser 2. Furthermore, there is provided a regulating valve 6 for controlling the discharge rate of liquid nitrogen drawn from the condenser 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is an air liquefaction / separation device for introducing compressed, purified and cooled raw material air into a double rectification column for liquefaction rectification separation and collecting nitrogen, oxygen, argon and the like as products. Regarding

[0002]

2. Description of the Related Art Conventionally, an air liquefaction separation apparatus using a double rectification column has been widely known as an apparatus for separating air components such as nitrogen and oxygen from air as a raw material. The air liquefaction separation apparatus using this double rectification column introduces the compressed, purified and cooled raw material air into the lower column of the double rectification column to perform liquefaction rectification separation,
Nitrogen gas is separated at the top of the lower column, oxygen-enriched liquefied air is separated at the bottom, and then liquefied rectification separation is performed at the upper part of the double rectification column to obtain nitrogen gas at the upper part of the upper column and liquid oxygen at the bottom. To separate.

Further, the double rectification column is provided with a condenser (main condensing evaporator) between the lower column and the upper column, in which nitrogen gas at the upper part of the lower column and the bottom part of the upper column are provided. The liquefied oxygen is heat-exchanged with the liquefied oxygen to evaporate the liquefied oxygen to obtain an ascending gas in the upper tower and to liquefy the nitrogen gas. The liquefied nitrogen liquefied in the condenser is collected as a product in addition to being used as the reflux liquid of the lower tower or the reflux liquid of the upper tower.

In addition to the liquefied nitrogen from the condenser, the products include medium pressure nitrogen gas in the upper part of the lower tower, liquefied oxygen in the lower part of the upper tower, oxygen gas in the lower part of the upper tower, low pressure nitrogen gas in the upper part of the upper tower, etc. Is collected, and when a crude argon column is attached to the upper column, crude argon is derived from the crude argon column.

[0005]

In such an air liquefaction / separation apparatus, the product output amount is increased or decreased according to the increase or decrease of the product demand. Generally, the product output amount is changed according to the product output amount. The amount of raw material air introduced is increased or decreased.

However, the amount of raw air introduced is reduced,
The so-called reduction operation reduces the throughput of the condenser,
Since the load of the condenser is reduced and the condensing capacity for condensing the nitrogen gas has a margin, the relative liquefaction amount of the nitrogen gas increases, which causes a phenomenon that the pressure in the lower column decreases.

When the pressure in the lower column is lowered, the pressure of the medium pressure nitrogen gas discharged from the lower column is also lowered. Therefore, it may be necessary to provide a nitrogen compressor to raise the pressure of the product medium pressure nitrogen gas in some cases. There is also. Further, when an expansion turbine using this medium-pressure nitrogen gas as a processing fluid and a nitrogen cycle for generating cold are provided, the amount of cold generated in the expansion turbine and the nitrogen cycle will be affected.

Therefore, in order to operate the device in a stable state, it is necessary to suppress the width of the reduction operation to a certain extent, but when the product demand is small, a part of the product gas must be released. And the product yield decreases,
It also becomes a problem in terms of cost.

Therefore, according to the present invention, the pressure in the lower column can be maintained at a predetermined pressure even when the volume reduction operation is performed, and the stable operation can be performed even when the volume reduction operation is significantly performed. The purpose is to provide a separating device.

[0010]

In order to achieve the above object, the air liquefaction separation apparatus of the present invention introduces compressed, purified and cooled raw material air into a double rectification column equipped with a condenser for liquefaction. In an air liquefaction separation device for rectifying and separating, the condenser is provided with means for detecting the liquid level height of liquefied nitrogen in the condenser, and the amount of liquefied nitrogen discharged from the condenser is controlled. It is characterized by the provision of a control valve.

Further, the present invention is an air liquefaction / separation apparatus for introducing liquefied rectification separation by introducing compressed, purified, and cooled raw material air into a double rectification column equipped with a condenser. Nitrogen derived from the tower is introduced into a cold generation path provided with a compressor, an expansion turbine, and a heat exchanger to provide a nitrogen cycle for generating cold, and the condenser is provided with a liquid nitrogen liquid in the condenser. It is characterized in that a means for detecting the surface height and a control valve for controlling the amount of liquefied nitrogen discharged from the condenser are provided.

[0012]

[Operation] According to the above configuration, the effective heat transfer area of the condenser is changed by controlling the amount of liquefied nitrogen discharged from the condenser by the control valve to adjust the liquid level height in the condenser. It is possible to make the liquefied amount of nitrogen gas an appropriate amount by this,
The pressure in the lower tower can be maintained at the required pressure. Therefore, the medium pressure nitrogen gas discharged from the lower tower is also maintained at a predetermined pressure, and the amount of cold generation in the expansion turbine and the nitrogen cycle for cold generation can be kept constant, so that the device can be operated in a stable state. .

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below with reference to the embodiments shown in the drawings. First, FIG. 1 shows the first embodiment of the present invention.
An example is shown, and the condenser 2 provided in the double rectification column 1
In the part of, as a means to detect the liquid level height of liquefied nitrogen,
An intermediate tank 4 provided with a liquid level gauge 3 is provided, and a control valve 6 for controlling the amount of liquefied nitrogen discharged from the condenser 2 is provided in a path 5 for introducing liquefied nitrogen from the intermediate tank 4 to the lower tower top.
Is provided.

In the apparatus of this embodiment, the raw material air compressed by a compressor (not shown) and purified by the adsorber is cooled to near the liquefaction point in the main heat exchanger 11, and then the tube 12 is passed through the double rectification column 1 Is introduced into the lower tower 13 of.

The raw material air introduced into the lower tower 13 is separated into nitrogen gas at the top and oxygen-enriched liquefied air at the bottom (hereinafter referred to as liquefied air) by a rectification operation in the lower tower 13. The liquefied air is led from the bottom of the lower tower 13 to the pipe 14, and introduced into the middle stage of the upper tower 17 via the supercooler 15 and the pressure reducing valve 16.

On the other hand, the nitrogen gas at the top of the lower column is led to a pipe 18, and then partly branched to a pipe 19 to become product intermediate-pressure nitrogen gas, which is collected through the main heat exchanger 11. The remaining nitrogen gas is introduced into the condenser 2 from the pipe 18 through the pipe 20, and is condensed and liquefied into liquefied nitrogen.
Flows in. In the intermediate tank 4, the pressure in the condenser 2, that is, the pressure of the medium-pressure nitrogen gas introduced into the condenser 2 from the pipe 20 and the inside of the intermediate tank 4 are the same, and the liquid level in the intermediate tank 4 is In order to make the height equal to the height of the liquid surface in the condenser 2, a balance pipe 7 that connects the inside of the intermediate tank 4 and the inside of the pipe 20 is provided.

Part of the liquefied nitrogen discharged from the bottom of the intermediate tank 4 into the pipe 22 is branched into the pipe 23 and introduced into the top of the upper tower 17 as a reflux liquid through the subcooler 15 and the pressure reducing valve 24. The remaining liquefied nitrogen is introduced as a reflux liquid into the top of the lower column 13 through the pipe 5 and the control valve 6.

The liquefied air introduced into the upper tower 17 via the pressure reducing valve 16 and the liquefied nitrogen introduced into the upper tower 17 via the pressure reducing valve 24 are rectified in the upper tower 17 and rectified in the top. Separate into nitrogen gas and liquefied oxygen at the bottom. The liquefied oxygen is heated by the nitrogen gas in the condenser 2 to evaporate and become the rising gas in the upper tower 17.

Nitrogen gas at the top of the upper tower 17 is led to a pipe 25 and collected through the subcooler 15 and the main heat exchanger 11. Further, from the lower part of the upper tower 17, a part of the oxygen gas evaporated in the condenser 2 is led out to the pipe 26, and the main heat exchanger 1
Collected through 1. Further, impure nitrogen gas is extracted as exhaust gas from the upper part of the upper tower 17 into the pipe 27,
It is led out through the subcooler 15 and the main heat exchanger 11, and is used as a regenerated gas of the adsorber.

Further, a part of the medium pressure nitrogen gas introduced into the main heat exchanger 11 from the pipe 19 is branched from the intermediate portion of the main heat exchanger 11 into a pipe 28 and expanded in an expansion turbine 29 to be cooled. Is generated, merges with the pipe 25 through which the nitrogen gas derived from the top of the upper tower 17 flows, and is again introduced into the main heat exchanger 11. In addition, as the processing fluid of the expansion turbine 29, it is possible to use a part of the raw material air instead of the medium pressure nitrogen. In this case, as shown by the broken line in FIG. 1, a part of the raw material air is branched and extracted from the intermediate portion of the raw material air path of the main heat exchanger 11 to the pipe 28a and expanded by the expansion turbine 29 to generate cold. The above gas may be allowed to join from the pipe 30a to the pipe 27 that is the path of the exhaust gas.

In the air liquefaction / separation apparatus having such a structure, when the demand for product gas is reduced and the apparatus is operated in a reduced amount, the amount of raw material air introduced is reduced to an amount commensurate with the amount of product generated and the above adjustment is performed. The valve 6 is throttled to reduce the amount of liquefied nitrogen discharged from the condenser 2. For adjusting the opening of the control valve 6 at this time, for example, the condenser liquid level with respect to the pressure in the lower tower 13 is set in advance, and the liquid surface in the intermediate tank 4 is changed according to the change in the pressure in the lower tower 13. This can be done by opening and closing the control valve 6 so that the height is at a predetermined position. This control may be performed by manually operating the control valve 6 while observing the states of the pressure gauge and the liquid level gauge 3 installed in the lower tower 13, or by providing a controller or automatically by a computer or the like. You may do it.

That is, when the amount of raw material air introduced decreases, the liquid level in the intermediate tank 4 is raised to raise the liquid level in the condenser, so that the nitrogen gas in the condenser and the liquefaction outside the condenser are liquefied. The heat transfer heat transfer area with oxygen can be reduced,
The relative liquefaction amount of nitrogen gas can be maintained at an appropriate amount. As a result, the pressure in the lower tower 13 can be maintained at a predetermined pressure, and the pressure drop of the product intermediate-pressure nitrogen discharged from the lower tower 13 can be prevented. at the same time,
Since the pressure of the system for introducing the raw material air into the lower tower 13 is also maintained at a predetermined pressure, stable operation of pretreatment equipment such as an adsorber can be achieved. Further, since the inlet pressure of the expansion turbine 29 using the medium pressure nitrogen gas or a part of the raw material air as the processing fluid can also be kept at a predetermined pressure, a predetermined amount of cold can be obtained in a stable state.

The pressure in the lower column 13 can be changed by adjusting the liquid level of the condenser even during the above-described reduction operation, so that the pressure of the medium pressure nitrogen gas discharged from the lower column 13 and The amount of cold generated by the expansion turbine 29 can also be adjusted.

FIG. 2 shows a second embodiment of the present invention and shows an example of an apparatus equipped with a crude argon column for collecting crude argon and a nitrogen cycle for generating cold. The same elements as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

First, the crude argon column 31 is provided with a pipe 32 into which an argon source gas is introduced from the middle part of the upper column and a pipe 33 for returning liquefied oxygen separated at the bottom part of the column to the middle part of the upper column. The apparatus is provided with an argon condenser 34 at the top and a pipe 35 for leading the separated crude argon to the top. The crude argon led to the pipe 35 is collected via the main heat exchanger 11.

In the argon condenser 34, a part of the liquefied air led to the pipe 14 from the bottom of the lower tower is pipe 36.
And is introduced via a pressure reducing valve 36a. From the argon condenser 34, a part of the liquefied air is fed through a pipe 37, and a vaporized gas is fed through a pipe 38.
It is introduced in the middle section.

After condensing and liquefying in the condenser 2,
Part of the liquefied nitrogen branched to the pipe 23 is collected as product liquefied nitrogen from the pipe 41, and part of the liquefied oxygen at the bottom of the upper column 17 is collected as product liquefied oxygen via the pipe 42 and the supercooler 15. ing.

On the other hand, the nitrogen cycle 50 comprises a nitrogen compressor 52 for compressing room temperature medium pressure nitrogen discharged from the upper part of the lower tower through the pipes 18, 19 and the main heat exchanger 11 into the pipe 51.
A first booster 53 and a second booster 54 for further compressing the nitrogen gas boosted by the nitrogen compressor 52, and the first booster 53
And a second expansion turbine 56 connected to the second booster 54, a first heat exchanger 57 on the room temperature side and a second heat exchanger 58 on the low temperature side. , Is provided to obtain the cold required to collect the pre-liquid product.

The nitrogen gas pressurized by the nitrogen compressor 52 is cooled by the aftercooler 52a, and then the pipe 61 and the pipe 62 are provided.
And the first booster 53 and the second booster 5 respectively.
Introduced in 4. The nitrogen gas introduced into the first booster 53 and further boosted in pressure is introduced into the first heat exchanger 57 via the aftercooler 53a and the pipe 62, cooled to an intermediate temperature, and then subjected to the first expansion via the valve 55a. It is introduced into the turbine 55 and expanded to generate cold, and the generated power is transmitted to the first booster 53 and led out to the pipe 63.
Through the heat exchanger 58, the pipe 64, the first heat exchanger 57, and the pipe 65, the temperature is raised to room temperature, and the pipe 51 is joined with the medium-pressure nitrogen gas and circulated.

The nitrogen gas introduced into one of the second boosters 54 and further boosted in pressure is introduced into the first heat exchanger 57 via the aftercooler 54a and the pipe 66. A part of this nitrogen gas branches from the middle of the first heat exchanger 57 into a pipe 67, is introduced into the second expansion turbine 56 via the valve 56a, expands to generate cold, and is generated by the generated power. The second
After driving the booster 54, it is led out to the pipe 68 and
4 merges with the nitrogen gas and circulates through the first heat exchanger 57 and the pipe 65. In addition, the remaining part of the nitrogen gas is discharged from the first heat exchanger 57 to the pipe 69, and then the second heat exchanger 5
It returns to the upper part of the lower tower 13 through 8, the pipe 70, and the valve 70a.

The pipe 1 is drawn out from the lower tower 13
Part of the medium pressure nitrogen gas flowing through 9 is the main heat exchanger 11
Of the pipe 6 via the valve 71a.
It joins the nitrogen gas of No. 3, and a part of the medium pressure nitrogen gas is
It branches into a pipe 72 in the middle of the main heat exchanger 11, and joins the nitrogen gas in the pipe 64 through a valve 72a. Further, the flow rate of nitrogen gas in each part is determined by valves 55a, 56a, 70a, 71a, 72 provided at predetermined positions according to conditions such as set temperature.
regulated by a.

In the air liquefaction separation apparatus equipped with the nitrogen cycle 50 as described above, the intermediate tank 4 equipped with the liquid level gauge 3 for detecting the liquid level of the liquid in the condenser 2 or nitrogen as described above.
And a control valve 6 for controlling the amount of liquefied nitrogen discharged from the intermediate tank 4, so that the amount of liquefied nitrogen discharged from the condenser 2 should be set appropriately by adjusting the control valve 6. Thereby, the pressure in the lower tower 13 can be set to a desired pressure. As a result, it is possible to maintain the pressure of the medium pressure nitrogen gas, which is discharged from the lower tower 13 and is introduced into the nitrogen cycle 50, at a predetermined pressure, and to prevent the amount of cold generated due to the decrease in suction pressure of the nitrogen compressor 52 from being insufficient. It is possible to obtain a predetermined amount of generated cold.

Therefore, in the apparatus for collecting the liquid product as described above, a necessary and sufficient amount of cold can be obtained even when the apparatus is operated in a reduced amount, so that the liquid product can be stably collected. Further, by controlling the condensation amount of nitrogen gas in the condenser 2, the evaporation amount of liquefied oxygen in the upper tower 17 is also automatically controlled, so the upper tower 17 and the lower tower 13
It is possible to operate while keeping the balance of the gas amount of the above substantially constant, and it is possible to collect the product in a stable state.

[0034]

As described above, the air liquefaction separation apparatus of the present invention can maintain the pressure in the lower column at a predetermined pressure even during the reduction operation, so that the medium pressure nitrogen gas discharged from the lower column is discharged. The pressure of can be kept constant. As a result, the delivery pressure when delivering the intermediate pressure nitrogen gas as a product can be kept constant, and stable operation of the expansion turbine and the nitrogen cycle using the intermediate pressure nitrogen can be achieved. The pressure of can also be kept constant.

Therefore, since the balance of each part can be kept substantially constant even during the weight reduction operation, the weight reduction operation range can be expanded, and the product yield can be improved by performing the operation according to the product demand. Can be achieved.

[Brief description of drawings]

FIG. 1 is a system diagram showing a first embodiment of the present invention.

FIG. 2 is a system diagram showing a second embodiment of the present invention.

[Explanation of Codes] 1 ... Double rectification column, 2 ... Condenser, 3 ... Liquid level gauge, 4 ... Intermediate tank,
6 ... Control valve, 11 ... Main heat exchanger, 13 ... Lower tower, 17 ...
Upper tower, 29 ... Expansion turbine, 31 ... Crude argon tower, 5
0 ... Nitrogen cycle, 52 ... Nitrogen compressor, 53 ... First booster, 54 ... Second booster, 55 ... First expansion turbine, 56
... second expansion turbine, 57 ... first heat exchanger, 58 ... second
Heat exchanger

Claims (2)

[Claims] 1. An air liquefaction separation apparatus which introduces compressed, purified, and cooled raw material air into a double rectification column equipped with a condenser to perform liquefaction rectification separation. An air liquefaction / separation device, characterized in that it is provided with a means for detecting the liquid level of liquefied nitrogen and a control valve for controlling the amount of liquefied nitrogen discharged from the condenser. 2. An air liquefaction separation apparatus for introducing compressed, purified, and cooled raw material air into a double rectification column equipped with a condenser to perform liquefaction rectification separation, which is derived from the lower column of the double rectification column. Nitrogen is introduced into a cold generation path provided with a compressor, an expansion turbine, and a heat exchanger to provide a nitrogen cycle for generating cold, and the condenser is provided with a liquid level height of liquefied nitrogen in the condenser. An air liquefaction separation device, characterized in that it is provided with a detection means and a control valve for controlling the amount of liquefied nitrogen discharged from the condenser.