JP3026091B2 - Air liquefaction separation device and start-up method thereof - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air liquefaction / separation apparatus and a method for starting the same, and more particularly, to an air liquefaction / separation apparatus in which raw air is purified by an adsorption facility, and the starting time of the apparatus is reduced. The present invention relates to an apparatus configuration that can be shortened and a method of starting the apparatus.

[Conventional technology]

2. Description of the Related Art Conventionally, air liquefaction / separation apparatuses which compress, purify, cool, introduce raw material air into a rectification column, and liquefy and separate to separate nitrogen and oxygen columns have been widely used. In such an air liquefaction / separation apparatus, it is specified that the apparatus is periodically stopped and heated to remove impurities which may be concentrated in the apparatus.

FIGS. 4 to 6 are system diagrams showing the configuration of a conventional air liquefaction / separation apparatus provided with the above-mentioned adsorption equipment, showing examples in which the expansion turbines are used in different ways.

First, in the air liquefaction / separation apparatus 1 shown in FIG. 4, the raw material air A compressed and pressurized by the compressor 2 is introduced into an adsorption equipment 4 composed of a pair of adsorbers 3, 3 used for switching. The carbon dioxide and water in it are removed by adsorption and purified. Next, the purified raw air A is introduced into the main heat exchanger 6 from the pipe 5 and exchanges heat with a return gas such as an exhaust gas or a product gas described later, and is cooled. Most raw air
After the GA is cooled to near the liquefaction point, it is introduced into the lower tower 9 of the double rectification column 8 through the pipe 7 and liquefied and rectified as is well known, and the nitrogen gas GN at the top of the lower tower and the oxygen rich Liquefied air (hereinafter, liquefied air) is separated into LA. A part of the raw air GB is led out of the intermediate portion of the main heat exchanger 6 to the pipeline 10, the flow rate of which is adjusted by the control valve 11, introduced into the expansion turbine 12, and expanded to generate cold. Is valve 13, line 1
After passing through 4, it is introduced into the middle stage of the upper tower 15, and the remainder merges with the exhaust gas W in the pipe line 17 via the valve 16 and is discharged after being used as a cooling source of the raw air A in the main heat exchanger 6.

The liquefied air LA at the bottom of the lower tower 9 is led out to a pipe 18 and is introduced into a middle stage of the upper tower via a supercooler 19 and a pressure reducing valve 20.
On the other hand, the nitrogen gas GN is liquefied in the main condensing evaporator 21 at the bottom of the upper column to become liquefied nitrogen LN, most of which is returned to the top of the lower column via the valve 22 as the reflux liquid of the lower column 8, and the remainder is excess Cooler
19, through a pressure reducing valve 23, a reflux liquid of the upper tower 15 is introduced from a pipe 24 to the top of the upper tower.

The raw material air GB, liquefied air LA, and liquefied nitrogen LN introduced into the upper column 15 are rectified in the column and separated into liquefied oxygen LO at the bottom of the column and high-purity nitrogen gas HN at the top of the column. The liquefied oxygen LO at the bottom of the upper column is vaporized in the main condensing evaporator 21 to become oxygen gas GO, led out to the pipe 25, and collected from the valve 26 via the main heat exchanger 6. The nitrogen gas NH at the top of the upper tower is
From the valve 28 through the subcooler 19 and the main heat exchanger 6. Further, from the upper middle part of the upper tower 15, exhaust gas W is led out through the pipe 17, and is discharged through the subcooler 19 and the main heat exchanger 6.

The air liquefaction / separation device 30 shown in FIG. 5 increases the compression pressure of the raw material air A from the compression pressure of the raw material air in the air liquefaction / separation device 1 and converts the raw material air GA led out from the main heat exchanger 6 to the pipeline 7. The pressure in the lower tower 9 is reduced by the pressure reducing valve 31 to the operating pressure of the lower tower 9 of the double rectification tower, and the pressure of the raw material air GB after expansion in the expansion turbine 12 is also set to the operating pressure of the lower tower 9.
And is introduced into the lower tower 9. In addition, the air liquefaction / separation device 40 shown in FIG.
Gas that has been heated to a predetermined temperature in the main heat exchanger 6
GX. After generating the cold which expanded in the expansion turbine 12, this gas merges with the exhaust gas W in the pipeline 17, and is discharged through the main heat exchanger 6.

Normally, this type of air liquefaction / separation apparatus is started by the compressor 2
To start the supply of the raw material air A, and transmit the cold generated in the expansion turbine 12 to the raw material air A by heat exchange in the main heat exchanger 6, and the cooled raw material air GA is mainly kept in a gaseous state. The rectification is performed by cooling the rectification section such as the double rectification tower 8 to a predetermined temperature by supplying it to the tower 9 and the upper tower 15.

Here, in the air liquefaction / separation apparatus in which a reversible heat exchanger is provided as a means for purifying and cooling the raw air, at the cold end of the reversible heat exchanger, from the raw air path to the purge gas (return exhaust gas) path. At startup, the startup valve is opened to return a part of the raw air to increase the load on the reversible heat exchanger to prevent drift and prevent carbon dioxide precipitated in the passage. Although gas and water are purged, as described above, in the case where the adsorption equipment is employed as a means for purifying the raw material air, temporary drift in the main heat exchanger is allowed. No start-up valve, such as an exchanger, was provided.

[Problems to be solved by the invention]

However, the liquefied gas (liquefied air, liquefied nitrogen) is supplied from the lower tower 9 in the air liquefaction / separation apparatus having the various configurations described above.
The pressure reducing valves 20 and 23 provided in the respective pipelines 18 and 24 for introducing the liquid to the upper tower 15 control the flow rate of the liquid (liquefied gas) in the normal operation. It is not possible to distribute a gas having substantially the same volume as the liquid. That is, since a sufficient amount of gas (raw air) cannot be led out from the lower tower 9, the amount of raw air that can be introduced into the lower tower 9 decreases, and the amount of heat exchange in the main heat exchanger 6 also decreases. As a result, the amount of heat exchange in the main heat exchanger 6 at the time of startup was not sufficient, and sufficient cooling could not be introduced into each rectification section including the lower tower 9. Therefore, the cold generated by the expansion turbine 12, which is generated about twice as much as the rated value at the time of startup, cannot be sufficiently carried into the double rectification column 8, and a long startup time is required.

As shown in FIG. 6, when the gas GX derived from the lower tower 9 is used as the working fluid of the expansion turbine 12, a larger amount of gas is used than in the other FIGS. 4 and 5. Can be extracted from the lower tower 9, but the expansion turbine 12
Since the throughput of the raw material is about 10 to 30% of the raw material air volume,
It is still not enough to transfer the cold.

As described above, since the cold transfer to the rectifying section cannot be performed sufficiently, only the main heat exchanger 6 is cooled, and the temperature of the gas introduced into the expansion turbine 12 on the turbine inlet side gradually decreases. When the temperature of the gas at the outlet of the expansion turbine approaches the liquefaction point, it is necessary to reduce the amount of processing fluid in the expansion turbine 12, which is a cold generation source, even though the rectification section is not yet sufficiently cooled. Will happen. For this reason, in the conventional apparatus, the start-up time required 60 to 70 hours.

Therefore, an object of the present invention is to provide an air liquefaction / separation device capable of shortening the start-up time of the upper air / air liquefaction / separation device and a method of starting the same.

[Means for solving the problem]

In order to achieve the above object, the air liquefaction / separation apparatus of the present invention comprises at least an adsorption facility for purifying pressurized raw air and a main heat exchanger for cooling the purified raw air by heat exchange with a return gas. And a double rectification column equipped with a lower tower upper tower and main condensing evaporator for rectifying and separating the cooled raw material air, and expanding a part of the raw material air before introducing the lower tower or the separated gas after leaving the lower tower. An air liquefaction / separation apparatus having an expansion turbine that generates cold by causing the gas in the lower tower to be introduced into a gas system derived from the upper tower and returned to the main heat exchanger. A circuit for starting the apparatus is provided, which comprises at least one of a pipe with a valve, and (b) a pipe with an on-off valve for introducing the gas in the lower tower into the upper tower.

Further, the (b) pipeline with an on-off valve is connected to an independent pipeline with an on-off valve connecting the lower tower and the upper tower, and a pipeline for introducing gas into the upper tower during normal operation, A pipe with an on-off valve for introducing the gas in the lower tower to the pipe, a liquefied gas in the lower tower or a liquefied gas liquefied in the main condensing evaporator during normal operation, the pressure of which is reduced by a pressure reducing valve to the upper tower. Or a pipe with an on-off valve that bypasses the pressure reducing valve of the system introduced into the system.

Further, the starting method of the air liquefaction / separation device according to the present invention, when starting the air liquefaction / separation device, introduces about half or more of the raw material air into the lower tower during the steady operation, and from the lower tower, The gas introduced through a circuit for starting the apparatus is introduced into the main heat exchanger directly or via the upper tower.

(Operation)

By configuring as above, a large amount of gas can be extracted from the lower tower or the lower tower and the upper tower,
A large amount of raw material air cooled by the main heat exchanger can be introduced into the lower tower, and the rectifying section can be quickly cooled.

〔Example〕

Hereinafter, the present invention will be described in more detail based on embodiments shown in the drawings. In the following description, the same elements as those of the conventional example are denoted by the same reference numerals, and detailed description will be omitted.

First, the air liquefaction / separation device 50 shown in FIG.
The apparatus includes substantially the same equipment as the air liquefaction / separation apparatus 1 shown in the figure, and comprises a compressor 2, an adsorption facility 4, a main heat exchanger 6, a lower tower 9, and an upper tower 15. It is composed of a rectification column 8, a main condensing evaporator 21, a subcooler 19, various valves 11, 13, 16, 20, 22, 23, 26, 28, and the like. It is configured to collect nitrogen gas HN.

The air liquefaction / separation apparatus 50 includes a lower part of the lower tower 9 and a pipe 14 for introducing a part of the raw material air expanded by the expansion turbine 12 into the upper tower 15 as a circuit used at the time of starting the apparatus. A starting circuit 51 composed of a connecting pipe 51a and an on-off valve 51b provided in the connecting pipe 51a, a pipe 52a connecting a middle stage of the lower tower 9 and a pipe 17 for extracting exhaust gas W from the upper tower 15. A starting circuit 52 comprising an on-off valve 52b provided in the pipe 52a, a pipe 53a connecting the top of the lower tower 9 and the pipe 27 for leading high-purity nitrogen gas HN from the upper tower 15; A start-up circuit comprising an on-off valve 53b provided in a pipe 53a
53 are provided respectively.

When starting the air liquefaction / separation apparatus 50 thus configured, the compressor 2 is started at normal temperature of the apparatus and the double rectification column 8 is started.
Of the raw air A to the expansion turbine 12 is also supplied. At this time, the amount of gas extracted from the lower tower 9 to the pipes 18 and 24 and introduced into the upper tower 15 is, as described above, approximately 1% from the capacity of the pressure reducing valves 20 and 23.
0% (the ratio to the amount of raw material air during normal operation, the same applies hereinafter).
The amount of raw air introduced into the furnace is about 30%. Therefore,
The amount of raw air that can be introduced into the lower tower 9 via the main heat exchanger 6 is about 10% of the amount of gas discharged from the lower tower 9.
In this state, at the cold end 6a of the main heat exchanger 6,
About 10% of the raw material air is exchanged with about 40% of each return gas returning from the pipes 17, 25 and 27. That is, since the amount of the return gas, which is a cold fluid, is larger than the amount of the feed air, which is a hot fluid to be supplied, the temperature difference in the central portion of the main heat exchanger 6 increases, and as described above, the expansion turbine 12
Inconvenience occurs because the temperature of the fluid (part of the raw material air GB) to be introduced into the furnace decreases.

Therefore, the opening / closing valves 51b, 52b, 53b of part or all of the upper starting circuits 51, 52, 53 are opened, and the gas in the lower tower 9 is transferred to the upper tower 15 or the pipes via the pipes 51a, 52a, 53a. By extracting to the gas system returning to the main heat exchanger 6, the lower tower 9
The amount of raw material air introduced into the tank can be greatly increased.

For example, by extracting 60% of the gas in the lower tower 9 using the starting circuits 51, 52, 53, the supply amount of the raw air A is reduced to 10%.
For 0%, the amount of gas supplied from the lower tower 9 to the upper tower 15 via the liquid lines 18 and 24 and the pressure reducing valves 20 and 23 is 10%.
%, The amount of gas supplied to the upper tower 15 via the expansion turbine 12 is 30%, and the amount of gas extracted from the starting circuits 51, 52, 53 is 60%. Within
70% can be introduced into the lower tower 9. This allows
At the cold end 6a of the main heat exchanger 6, 70% of the raw air A and 100% of the return gas exchange heat, and sufficient heat exchange is possible. The temperature difference is also reduced, and there is no need to reduce the throughput of the expansion turbine 12.

In this way, a sufficient amount of cold can be generated in the expansion turbine 12 and the cold can be moved to the rectification unit by a large amount of the raw material air A, so that the rectification unit can be cooled quickly. The startup time of the air liquefaction / separation device 50 can be greatly reduced.

Each of the gases extracted through the above-mentioned starting circuits 51, 52, 53 is supplied to a subcooler before being introduced into the main heat exchanger 6.
Since it passes through 19, the supercooler 19 can be sufficiently cooled.

The effect of the shortening of the start-up time is as follows.
As shown in FIG. 2, not only 1, 52 and 53, but also from the pipe 54a and the on-off valve 54b connecting the middle stage of the lower tower 9 and the pipe 17 for drawing the exhaust gas W after the supercooler 19 is drawn out. Starting circuit 54,
The top of the lower tower 9 and a conduit for leading the high-purity nitrogen gas HN
Pipeline 55a and open / close valve 55b connecting the 27 subcooler 19
The same applies to a starting circuit 55 composed of a starting circuit 55, or a starting circuit 56 including a pipe 56a connecting the top of the lower tower 9 and the pipe 25 for leading the oxygen gas GO and an on-off valve 56b. it can.

Further, as shown in FIG. 3, the liquefied air L
A, It is also possible to provide bypass lines 57a, 58a so as to bypass the pressure reducing valves 20, 23 for controlling the flow rate and pressure of the liquefied nitrogen LN, and to provide on-off valves 57b, 58b in the bypass lines 57a, 58a, respectively. Starting circuits 57 and 58 can be formed.
That is, by opening the on-off valves 57b and 58b of the bypass pipes 57a and 58a at the time of startup, a large amount of gas can be introduced from the lower tower 9 to the upper tower 15 through the pipes 57a and 58a. A large amount of raw air A can be introduced into the lower tower 9.

These starting circuits take into account the product purity during normal operation, and the composition of the gas extracted from the lower tower 9 at the time of starting,
It is preferable to connect them so that the gas composition in each pipe during normal operation is similar. Accordingly, when the starting circuit 56 is connected from the top of the lower tower 9 in FIG. 2 to the line 25 for oxygen gas collection, the line 56a of the starting circuit 56 is connected as shown in FIG. The opening and closing valves 56b and 56c are provided in two places, and a blow line 56e having an opening and closing valve 56d is provided between the two opening and closing valves 56b and 56c. At the time of startup, the opening and closing valves 56b and 56c are opened and the opening and closing valve 56d is closed. As a result, the gas in the lower tower 9 is extracted to the oxygen gas pipe 25, and during normal operation, the on-off valves 56c and 56d are closed and the on-off valve 56d is opened, whereby the gas in the pipes 25 and 56a is opened. Even if the gas leaks from the open / close valve 56c or the open / close valve 56b, it is preferable that the gas escapes from the open / close valve 56d and the gas in the conduits 25 and 56a is not mixed.

The starting circuit of the present invention includes (a) a pipe with an on-off valve for introducing the gas in the lower tower 9 into a gas system which is led out of the upper tower 15 and returns to the main heat exchanger 6; A) a pipe with an on-off valve for introducing gas in the lower tower 9 to the upper tower 15,
The pipe with an on-off valve (a) is an on-off valve that connects the middle stage of the lower tower 9 and the pipe 17 that leads the exhaust gas W from the upper tower 15.
A pipe 52a with 52b, a pipe 53a with an on-off valve 53b connecting the top of the lower tower 9 and a pipe 27 for leading high-purity nitrogen gas HN from the upper tower 15, exhaust gas from the middle and upper tower 15 of the lower tower 9 A pipe 54a with an on-off valve 54b connecting the pipe 17 for leading W to the supercooler 19 after the cooling, a subcooling of a pipe 27 for leading high-purity nitrogen gas HN from the top of the lower tower 9 and the upper tower 15 A pipe 55a with an on-off valve 55b connecting the outlet of the vessel 19 and an on-off valve 56b connecting the top of the lower tower 9 and the pipe 25 for leading out the oxygen gas GO from the upper tower 15.
The conduit 56a with (or on-off valves 56b, 56c) is disclosed in the above embodiment, and the conduit with on-off valve (b) is
A pipe with an on-off valve connected to a pipe for introducing gas into the upper tower 15 during normal operation and introducing gas in the lower tower 9 to the pipe, and a liquefied gas (main condensate) in the lower tower 9 during normal operation. A liquefied gas liquefied by the evaporator 21 is reduced by a pressure reducing valve and introduced into the upper tower 15 by a pressure reducing valve of a system that bypasses a pressure reducing valve. Part of the raw air expanded by the lower part of the tower 9 and the expansion turbine 12
A line 51a with an on-off valve connecting the line 14 for introducing the GB into the upper tower 15 is disclosed in the above embodiment, and the line controls the flow rate and pressure of the liquefied air LA during normal operation. Bypass line 57a with on-off valve 57b that bypasses pressure reducing valve 20
The bypass line 58a with the on-off valve 58b that bypasses the pressure reducing valve 23 that controls the flow rate and pressure of the liquefied nitrogen LN during the passage operation is disclosed in the above-described embodiment.
Including the respective circuits exemplified in the above embodiment, for example,
The lower tower 9 and upper tower 15
And a line with an on-off valve (not shown) for connecting the valve, the capacity of the line to be connected and the valve provided in the line, and the balance of gas derived from the lower tower. In consideration of the above, a plurality of portions can be provided as appropriate, a sufficient effect can be exerted even at only one portion, and it is also possible to appropriately join or branch.

Further, the present invention is not limited to the air liquefaction / separation apparatus shown in the above-described embodiment, but may be applied to air liquefaction / separation apparatuses of various configurations including the air liquefaction / separation apparatus shown in FIGS. To obtain the same function and effect.

The same operation and effect can be obtained by applying the present invention to a gas-liquid separation apparatus in the same manner.

〔The invention's effect〕

As described above, according to the present invention, when the air liquefaction / separation apparatus is started, a start-up circuit capable of extracting gas in the lower tower and returning the gas to the main heat exchanger is provided. Can be introduced into the rectification section including the double rectification column, and the ability of the expansion turbine can be sufficiently exhibited, so that the rectification section can be quickly cooled. Therefore, the start-up time of the device can be greatly reduced, and the power cost required for the start-up can be reduced and the operation efficiency of the device can be improved.

[Brief description of the drawings]

1 to 3 are system diagrams of an air liquefaction / separation device showing an embodiment of the present invention, and FIGS. 4 to 6 are system diagrams of a conventional air liquefaction / separation device. 2 ... Compressor, 4 ... Adsorption equipment, 6 ... Main heat exchanger, 8
... double rectification tower, 9 ... lower tower, 12 ... expansion turbine, 15
…… Top tower, 50 …… Air liquefaction separation equipment, 51,52,53,54,5
5,56,57,58 …… Startup circuit

Claims (3)

(57) [Claims] 1. At least an adsorption facility for purifying pressurized raw air, a main heat exchanger for cooling the purified raw air by heat exchange with a return gas, and a lower part for rectifying and separating the cooled raw air. A double rectification column equipped with a tower, an upper tower and a main condensing evaporator, and an expansion turbine that generates a cold by expanding a part of the raw material air before the introduction of the lower tower or the separated gas after derivation from the lower tower. In the air liquefaction / separation apparatus, (a) a pipe with an on-off valve for introducing gas in the lower tower into a gas system which is led out of the upper tower and returns to the main heat exchanger; An air liquefaction / separation apparatus, comprising a circuit for starting the apparatus, the circuit including at least one of a pipe with an on-off valve for introducing the gas into the upper tower. 2. The pipeline with an on-off valve of (b) is connected to an independent pipeline with an on-off valve connecting the lower tower and the upper tower, and a pipeline for introducing gas into the upper tower during normal operation. A pipe with an on-off valve for introducing gas in the lower tower into the pipe, a liquefied gas in the lower tower or a liquefied gas liquefied in the main condensing evaporator during normal operation is depressurized by a pressure reducing valve. The air liquefaction / separation apparatus according to claim 1, wherein the pipe is a line with an on-off valve that bypasses the pressure reducing valve of the system introduced into the upper tower. 3. The method for starting an air liquefaction / separation apparatus according to claim 1, wherein at the time of start of the air liquefaction / separation apparatus, approximately half or more of the raw material air during steady operation is introduced into the lower tower,
A method for starting an air liquefaction / separation apparatus, wherein gas derived from the lower tower through the circuit for starting the apparatus is introduced into the main heat exchanger directly or via the upper tower.