JPH0789008B2 - Condensing evaporator - Google Patents

Description

TECHNICAL FIELD The present invention relates to a condensing evaporator, and more particularly to a condensing evaporator suitable for use in a double rectification column of a large air liquefaction separation device.

[Conventional technology]

In the double rectification column of the air liquefaction separation device that liquefies air to collect nitrogen, oxygen, etc., the liquefied oxygen in the upper column and the nitrogen gas in the lower column are heat-exchanged to evaporate and liquefy the liquefied oxygen to produce oxygen gas. A condensing evaporator for condensing and liquefying nitrogen gas into liquefied nitrogen is provided. This condensing evaporator is usually composed of a heat exchanger provided with an open oxygen chamber and a closed nitrogen chamber, is used by being immersed in liquefied oxygen accumulated in the bottom of the upper tower, and is used in the nitrogen chamber. Nitrogen gas in the lower tower is introduced for heat exchange.

Also, as the size of the equipment increases, so does the size of the condensation evaporator.
If it is left as it is, it will be difficult in terms of equipment to install it at the upper bottom of the double rectification column due to its performance. Therefore, a condensation evaporator may be installed separately from the double rectification column to form a two-column type, or a condensation evaporator may be installed. It was set up in multiple stages up and down.

For example, in a condenser / evaporator for a rectification column disclosed in Japanese Patent Publication No. 49-37627, a plurality of heat exchanger groups constituting a condenser / evaporator are arranged in parallel at each stage by partitioning the bottom of the upper column into a plurality of bottom plates. In addition to the above, an overflow pipe for flowing liquefied oxygen from each stage to the lower stage was provided in each stage, and a predetermined amount of liquefied oxygen was retained in each stage.

[Problems to be solved by the invention]

However, in all of the above-mentioned ones, the heat exchanger constituting the condensation evaporator is used by immersing it in liquefied oxygen, so a large amount of liquefied oxygen is required to immerse the heat exchanger when starting the apparatus. Therefore, a long start-up operation was required. Further, when the apparatus was stopped, it was necessary to release this large amount of liquefied oxygen.

Furthermore, if a condensing evaporator is provided separately from the rectification column to form a two-column type, a large amount of liquefied oxygen is required because the liquefied oxygen pools are located at the bottom of the upper tower and at two places in the condensing evaporator. In addition, the piping connecting the rectification column and the condenser-evaporator becomes complicated, and the liquefied oxygen pump for sending liquefied oxygen to the condenser-evaporator is required, so power costs are also required, and valves and instrumentation are required for the piping. It had to be installed, which was a factor of cost increase. Further, since the liquid pool has a large capacity, it is necessary to give sufficient consideration to the concentration of impurities.

Therefore, the present invention is easy to install in a large double rectification column,
Moreover, it is an object of the present invention to provide a condensing evaporator which can be operated without accumulating a large amount of liquefied oxygen.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention is a condensing evaporator used for a double rectification column of an air liquefaction separation device, and a plurality of heat exchangers constituting the condensing evaporator are arranged in upper and lower stages, The heat exchanger is divided into a plurality of closed oxygen chambers and a nitrogen chamber, and a liquefied oxygen inlet header for introducing liquefied oxygen into the oxygen chamber is provided at the bottom of the oxygen chamber, and vaporized oxygen gas and oxygen are provided at the top. Oxygen outlet headers for discharging liquefied oxygen overflowing from the chamber are respectively provided, and the liquefied oxygen inlet header of the upper heat exchanger and the liquefied oxygen inlet header of the lower heat exchanger are connected by an overflow pipe, The overflow portion of the overflow pipe is provided at substantially the same height as the oxygen outlet header of the upper heat exchanger.

[Work]

Therefore, since the operation of the condensation evaporator can be started by introducing liquefied oxygen from the liquefied oxygen inlet header into the oxygen chamber of the heat exchanger, it is not necessary to store it in the condensation evaporator, the start-up time can be shortened, and the heat exchanger can be shortened. Since they are arranged in multiple stages vertically, they can be easily installed in the rectification column. In addition, the piping can be simplified and a liquefied oxygen pump or the like can be eliminated as compared with a condenser / evaporator provided separately from the double rectification column.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of a condenser evaporator in which heat exchangers are arranged in three rows and three stages, and FIG. 1 is a schematic front view showing a state in which the condenser evaporator is incorporated in a double rectification column, 2 is the same schematic side view, FIG. 3 is the same schematic plan view, FIG. 4 is a schematic front view showing the flow of liquefied oxygen and oxygen gas in the oxygen chamber, and FIG. 5 is nitrogen gas and liquefied nitrogen in the nitrogen chamber. 6 is a schematic side view showing the flow of oxygen and nitrogen in the heat exchanger, and FIG. 7 is an enlarged front view near the outlet of the oxygen outlet header of the oxygen chamber.

The condensing evaporator 1 is incorporated between the upper tower 3 and the lower tower 4 of the double rectification tower 2, and the outer cylinder 5 of the condensing evaporator 1 doubles as a mount for the upper tower 3 and serves as the upper tower 3 and the lower tower. 4 and the diameter thereof are substantially the same.

The heat exchangers 6 and 6a constituting the condenser evaporator 1 are internally divided into an oxygen chamber 7 and a nitrogen chamber 8 (FIG. 6),
A liquefied oxygen inlet header 9 is provided in the lower part of the oxygen chamber 7, and an oxygen outlet header 10 is provided in the upper part.

A liquefied oxygen inlet pipe 11 is connected to the liquefied oxygen inlet header 9, and an oxygen gas outlet pipe 12 is connected to the oxygen outlet header 10.
And the liquefied oxygen return pipe 13 are connected to each other. The liquefied oxygen introducing pipe 11 is connected to the oxygen outlet header 10 of the heat exchangers 6 and 6a arranged above and the lower portions of the overflow pipes 14 and 14a where the overflow portion at the upper end is provided at substantially the same height position. The liquefied oxygen return pipe 13 is also connected to the overflow pipes 14 and 14a. That is, the liquefied oxygen inlet header 9 of the uppermost heat exchanger 6a, the liquefied oxygen inlet header 9 of the middle heat exchanger 6, and the liquefied oxygen inlet header 9 of the middle heat exchanger 6 and the lowermost heat exchanger 6 Liquefied oxygen inlet header 9 and overflow pipes 14, 14 respectively
And the overflow portions of the overflow pipes 14 and 14 are provided at substantially the same height positions as the oxygen outlet header 10 of the upper heat exchangers 6a and 6, respectively.

On the other hand, the oxygen gas outlet pipe 12 is connected to an oxygen gas outlet main pipe 15 provided as a double pipe on the inner peripheral side of the overflow pipes 14 and 14a. Further, at the end of the oxygen outlet header 10, there is provided a demister 16 which is formed of a wire mesh or the like and separates and collects the liquid mist contained in the evaporated gas (Fig. 7).

The overflow pipe 14a connected to the uppermost heat exchanger 6a is connected to the distribution plate 17 above the condenser-evaporator 1 in a state of penetrating the distribution plate 17 and slightly projecting the oxygen gas. The upper end of the main pipe 15 extends through the distribution plate 17 to the vicinity of the rectification plate 18 of the upper tower 3. Further, the distribution plate 17 has a condenser evaporator 1
A balance tube 19 is provided to balance the atmospheric pressure inside.
An oxygen gas sampling pipe 20 is connected to the outer cylinder 5 above the distribution plate 17. Further, between the distribution plate 17 and the rectification plate 18, a liquefied oxygen guide tube for guiding liquefied oxygen flowing from the upper tower 3 is introduced.
21 are provided.

On the other hand, in the nitrogen chamber 8 of the heat exchanger 6, 6a, the nitrogen gas inlet header 22 is on the upper side and the liquefied nitrogen outlet header is on the lower side.
23 is provided, a nitrogen gas inlet pipe 24 is connected to the nitrogen gas inlet header 22, the liquefied nitrogen outlet header 23
A liquefied nitrogen derivation pipe 25 is connected to (Fig. 5).

The gas-liquid flow of the condensation evaporator 1 formed as follows will be described.

First, the nitrogen gas GN is supplied from the top of the lower tower 4 through the nitrogen gas outlet pipe.
Ascending 24, nitrogen gas inlet header 22 of each heat exchanger 6, 6a
Is introduced into the nitrogen chamber 8. The nitrogen gas GN exchanges heat with the liquefied oxygen LO in the nitrogen chamber 8 to be liquefied and become liquefied nitrogen LN, which flows down and is returned from the liquefied nitrogen outlet header 23 to the lower tower 4 through the liquefied nitrogen outlet pipe 25. This flow of nitrogen is in a system similar to that of a conventional condenser evaporator.

Next, the liquefied oxygen LO is guided from the rectification plate 18 at the lowermost stage of the upper tower 3 to the distribution plate 17 by being guided by the liquefied oxygen guide pipe 21, and each heat exchanger provided in three rows from each overflow pipe 14a. It is distributed evenly to groups 6 and 6a and flows down. Liquefied oxygen L flowing down the overflow pipe 14a
O flows into the liquefied oxygen inlet header 9 from the liquefied oxygen introduction pipe 11 and rises in the oxygen chamber 7. Where the nitrogen gas GN
Part of the gas is vaporized into oxygen gas GO, which is discharged from the oxygen outlet header 10.

The liquid mist of the liquefied oxygen LO, which has risen to the oxygen outlet header 10 together with the oxygen gas GO, is separated by the demister 16 and returned from the liquefied oxygen return pipe 13 to the overflow pipes 14 and 14a.
Is introduced above the distribution plate 17 through the oxygen gas outlet pipe 12 and the oxygen gas outlet main pipe 15, and a part of the product is an oxygen gas sampling pipe.
It is collected from 20 and the rest becomes the rising gas of the upper tower 3. At this time, the flow velocity of the oxygen gas GO released from the oxygen gas lead-out main pipe 15 rapidly decreases at the opening of the oxygen gas lead-out main pipe 15, so that the liquefied oxygen slightly contained in the oxygen gas GO.
The LO mist is separated by spontaneous fall and falls on the distribution plate 17.

Further, a part of the liquefied oxygen LO flowing from the liquefied oxygen introduction pipe 11 into the liquefied oxygen inlet header 9 does not flow into the oxygen chamber 7 and rises in the overflow pipe 14 portion connected to the lower heat exchanger 6, It is introduced from the overflow pipe 14 into the oxygen chamber 7 through the liquefied oxygen introduction pipe 11 and the liquefied oxygen inlet header 9 of the heat exchanger 6 below, and heat exchange is similarly performed with the nitrogen gas GN.

As described above, since the heat exchangers partitioned and formed in the oxygen chamber and the nitrogen chamber, which are respectively sealed, are stacked in a multi-tiered manner to form the condenser evaporator, the size, arrangement, and the number of layers of each heat exchanger are appropriately set. By selecting it, it can be easily incorporated into a double rectification column of various sizes, and even in a large double rectification column, the upper and lower columns can be integrally formed. As a result, the equipment cost and the power cost during operation can be significantly reduced as compared with the case where the condenser evaporator is provided separately from the double rectification column. Furthermore, since it is sufficient to introduce liquefied oxygen into the oxygen chamber of the heat exchanger that constitutes the condenser / evaporator, it is possible to operate the condenser / evaporator with a smaller amount of liquefied oxygen than before, and it is possible to significantly shorten the startup time. While you can
The amount of oxygen released when the device is shut down is also reduced.

Further, an overflow pipe having an overflow portion is provided at substantially the same height as the oxygen outlet header above the heat exchanger, and liquefied oxygen is made to flow down to the heat exchanger below by the overflow pipe. Since the liquefied oxygen in the chamber rises to the height of the overflow portion of the overflow pipe, that is, to the oxygen outlet header portion, the liquefied oxygen amount (liquid level height) can be made substantially constant. As a result, it is possible to avoid temperature changes due to the addition of liquid liquefied oxygen, use the heat transfer area of each heat exchanger without waste, and keep the amount of heat exchange with nitrogen gas constant. Further, by causing the liquefied oxygen to flow downward in sequence, the liquefied oxygen is not partially retained in the condenser evaporator, and local concentration of impurities can be avoided.

Furthermore, by providing a demister at the end of the oxygen outlet header, liquid mist rising with oxygen gas can be recovered and returned to the overflow pipe, so waste of the flow of liquefied oxygen is eliminated and heat exchange efficiency is improved. You can look down.

Further, by forming the overflow pipe and the oxygen gas outlet main pipe by double pipes as in the above embodiment, the piping space can be reduced and the condenser-evaporator can be made compact.

〔The invention's effect〕

As described above, according to the present invention, the heat exchangers partitioned and formed in the oxygen chamber and the nitrogen chamber are arranged in the upper and lower stages, and the liquefied oxygen is caused to flow down to the lower heat exchanger by the overflow pipe. By appropriately selecting the size, arrangement, and number of stacks, it is possible to easily incorporate into a double rectification column of various sizes, and even in a large double rectification column, the upper and lower columns can be integrally formed.

In addition, since the condensation evaporator can be operated by introducing liquefied oxygen into the oxygen chamber of the heat exchanger that constitutes the condensation evaporator, the air liquefaction separation device can be operated with a smaller amount of liquefied oxygen than the conventional immersion type. In addition, the start-up time can be greatly shortened, and the amount of oxygen released when the device is stopped is also reduced.

[Brief description of drawings]

FIG. 1 is a schematic front view showing a state in which a condensation evaporator is incorporated in a double rectification column, FIG. 2 is a schematic side view of the same, FIG. 3 is a schematic plan view of the same, and FIG. 4 is liquefied oxygen in an oxygen chamber. And a schematic front view showing the flow of oxygen gas, FIG. 5 is a schematic front view showing the flow of nitrogen gas and liquefied nitrogen in the nitrogen chamber, and FIG. 6 is a schematic side view showing the flow of oxygen and nitrogen in the heat exchanger. ,
FIG. 7 is an enlarged front view of the vicinity of the outlet of the oxygen outlet header of the oxygen chamber. 1 ... Condensation evaporator, 2 ... Double rectification tower, 3 ... Upper tower, 4
...... Lower tower, 6,6a ...... Heat exchanger, 7 ...... Oxygen chamber, 8 ......
Nitrogen chamber, 9 ... Liquefied oxygen inlet header, 10 ... Oxygen outlet header, 11 ... Liquefied oxygen introduction pipe, 12 ... Oxygen gas outlet pipe, 13 ... Liquefied oxygen return pipe, 14, 14a ... Overflow pipe , 15 ……
Oxygen gas outlet main pipe, 16 ... Demister, 17 ... Distribution plate,
22 …… Nitrogen gas inlet header, 23 …… Liquefied nitrogen outlet header, 24 …… Nitrogen gas inlet pipe, 25 …… Lower liquefied nitrogen outlet pipe, GN …… Nitrogen gas, GO …… Oxygen gas, LN …… Liquefied nitrogen , LO …… liquefied oxygen

Claims (1)

[Claims] 1. A condensing evaporator used in a double rectification column of an air liquefaction separation apparatus, wherein a plurality of heat exchangers constituting the condensing evaporator are arranged in upper and lower stages, and the heat exchangers are each sealed. A plurality of oxygen chambers and a nitrogen chamber, and a liquefied oxygen inlet header for introducing liquefied oxygen into the oxygen chamber is provided at the bottom of the oxygen chamber, and vaporized oxygen gas at the top and liquefied oxygen overflowing from the oxygen chamber. Oxygen outlet headers for each of the above are provided, and the liquefied oxygen inlet header of the upper heat exchanger and the liquefied oxygen inlet header of the lower heat exchanger are connected by an overflow pipe, and the overflow portion of the overflow pipe is connected. Is provided at substantially the same height as the oxygen outlet header of the upper heat exchanger.