JPH05157447A - Method and apparatus for low-temperature separation of carbon monoxide - Google Patents

Abstract

PURPOSE:To obtain carbon monoxide gas as a highly purified product in a refining system in which the purity of the reflux to the tower top in a rectifying column is increased efficiently. CONSTITUTION:Material gas is fed through a material gas feed pipe 32 and to the bottom of a reboiler 20, where the material gas refined in its passageway by heat exchange with liquid from the bottom of the rectifying column. The highly purified gas resulting from this refining is supplied as reflux to the tower top of the rectifying column 18 through refined gas conveyor lines 38, 40, 42, 46.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for cryogenic separation of carbon monoxide from a mixed gas containing at least carbon monoxide and hydrocarbons.

[0002]

2. Description of the Related Art In general, gases obtained by reforming hydrocarbons such as propane and butane are carbon monoxide and hydrogen,
Hydrocarbons such as methane are contained in a proportion of several percent or less,
When the product carbon monoxide gas is to be obtained from such a mixed gas, not only the separation of hydrogen but also the separation of the above hydrocarbons is required.

Conventionally, a cryogenic separation method using a rectification column has been often used for the separation of such hydrocarbons (see, for example, Nippon Oxygen Technical Report No. 1 (1982) "Cryochemistry in C ₁ chemistry". Separation "
reference). In such a cryogenic separation method, carbon monoxide gas, which is a product gas, is generally taken out from the top of the rectification column. Therefore, in order to increase the purity of the product gas, the reflux gas supplied to the top of the column is used. It is extremely effective to increase the purity of the liquid.

As an apparatus for increasing the purity of such a reflux liquid, there is known one as shown in FIGS. 8 and 9. In the apparatus shown in FIG. 8, the rectification tower 90 is composed of a lower tower 91 and an upper tower 92.
And a condenser 93 of the lower tower 91 which also functions as a reboiler of the upper tower 92 is provided between both towers 91 and 92, and the raw material gas is first purified in the lower tower 91, and the purified gas is It is extracted from the top of the lower tower 91 and supplied as a reflux liquid to the top of the upper tower 92. Also, FIG.
In the apparatus shown in (1), a part of the product gas extracted from the top of the rectification column 90 is passed through a condenser 94, and this is returned to the top of the column as a reflux liquid.

[0005]

In the device shown in FIG. 8,
Since the double rectification column in which the lower column 91 and the upper column 92 are connected must be used, the structure of the rectification column becomes complicated and expensive. Further, since the tower length is large, the size of the entire cold-insulating box for accommodating the tower is also increased, which hinders downsizing of the device.

On the other hand, in the apparatus shown in FIG. 9, part of the product gas once purified is returned to the rectification column 90 as a reflux liquid, so that the amount of processing in the rectification column 90 increases by the amount of this return. Becomes inefficient.

In view of such circumstances, the present invention efficiently purifies the high-purity reflux liquid supplied to the top of the rectification column, whereby a high-purity product carbon monoxide gas can be obtained. An object of the present invention is to provide a cryogenic separation method and apparatus for carbon oxide.

[0008]

The present invention is a method for separating carbon monoxide from a mixed gas containing at least carbon monoxide and hydrocarbons in a rectification column, the mixed gas being a reboiler of the rectification column. Flow upward from the bottom of the column, and in this reboiler, heat is exchanged between the bottom liquid of the rectification column and the mixed gas to evaporate the bottom liquid and rectify the mixed gas. The rectified gas is introduced from the upper part of the reboiler to the top of the rectification column as a reflux liquid (Claim 1). The present invention is also an apparatus for carrying out the above method, which comprises at least carbon monoxide and A rectification column that separates carbon monoxide from a mixed gas containing hydrocarbons and a reboiler that evaporates the bottom liquid of this rectification column are provided, and the reboiler has a bottom liquid evaporation passage and a mixed gas passage. And both passages A reboiler so that heat is exchanged between the flowing fluids, and further, a raw material gas introduction passage for introducing a raw material gas into the mixed gas passage from its lower portion, and a mixed gas passage from the upper portion of the mixed gas passage. And a rectification gas transfer passage for introducing the rectification gas rectified in (3) as a reflux liquid to the top of the rectification tower (claim 2).

[0009]

According to the above construction, the raw material gas is passed through the reboiler from its lower part, and heat exchange is performed between the raw material gas and the bottom liquid, whereby the bottom liquid is evaporated and
Part of the raw material gas condenses and descends, and the raw material gas can be rectified by contacting the descending condensate with the rising raw material gas. Therefore, purified gas with high carbon monoxide purity can be extracted from the upper part of this reboiler, and by supplying this as reflux liquid to the upper part of the rectification column, high-purity product carbon monoxide gas can be purified. You can

Specifically, according to the apparatus of claim 2,
Supplying the mixed gas to the lower part of the mixed gas passage in the reboiler through the raw material gas introduction passage, and causing heat exchange between the mixed gas rising in the raw material gas introduction passage and the bottom liquid in the bottom liquid evaporation passage. With the evaporation of the bottom liquid,
The raw material gas can be rectified. Therefore, by introducing the rectified gas in the upper part of the mixed gas passage into the top of the rectification column as a high-purity reflux liquid through the rectification gas transfer passage, the high-purity carbon monoxide gas in the rectification column is introduced. Can be purified.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the overall configuration of a deep-chill separation system equipped with the device of the present invention. Note that this system uses a reformed gas such as propane or butane as a raw material and separates carbon monoxide gas from this gas. The method and apparatus of the present invention contain at least carbon monoxide and hydrocarbons. It is widely applicable when separating carbon monoxide from a mixed gas.

The system shown in FIG. 1 comprises a refrigerator 10, a gas-liquid separator 11, an MS (molecular sieve) adsorption device 12,
And a cold storage box 14, and in the cold storage box 14, a main heat exchanger 16, a rectification column 18, a reboiler 20, condensers 22 and 2 are provided.
8, a first gas-liquid separator 24, a second gas-liquid separator 25, a third gas-liquid separator 26, a heat exchanger 27, a nitrogen gas-liquid separator 30 and the like.

The MS adsorption device 12 comprises a main heat exchanger 16
It is connected to the bottom of the reboiler 20 via a source gas introduction pipe 32 passing through. The bottom of the reboiler 20 is connected to the middle abdomen of the first gas-liquid separator 24 via a transfer pipe 34, and the heat exchanger 27,
A condenser 28 and an expansion valve 36 are provided. The bottom part of the first gas-liquid separator 24 is connected to the middle part of the rectification column 18 via a condenser 22.

The top of the reboiler 20 is connected to the middle part of the second gas-liquid separator 25 via the purified gas transfer pipes 38 and 40, and the condenser 22 is provided in the middle of the purified gas transfer pipes 38 and 40. , 28 are connected. The bottom portion of the second gas-liquid separator 25 is the purified gas transfer pipe 4
2 is connected to the middle abdomen of the third gas-liquid separator 26, and the bottom of the third gas-liquid separator 26 is connected to the top of the rectification column 18 via the purified gas transfer pipe 46. An expansion valve 44 is provided in the middle of the purified gas transfer pipe 42. Further, the reboiler 20 is connected to the bottom of the rectification column 18 via a column bottom liquid outlet pipe 48 and a gas reflux pipe 49.

Next, the structure of the reboiler 20 will be described with reference to FIGS.

As shown in FIG. 2, the reboiler 20 has a heat exchange section 50. A column bottom liquid inlet port 51 is attached to the lower portion of the side surface of the heat exchange unit 50, and a reflux gas outlet port 52 is similarly provided to the upper portion of the side surface of the heat exchange unit 50.
A raw material gas inlet port 53 is mounted on the lower end surface, and a purified gas outlet port 54 is mounted on the upper end surface. Then, the tower bottom liquid outlet port 48 is connected to the tower bottom liquid inlet port 51.
Similarly, the gas reflux pipe 49 is connected to the reflux gas outlet port 52, and the purified gas transfer pipe 38 is connected to the purified gas outlet port 54. Further, a gas-liquid separation pipe 56 having a bottom is connected to the raw material gas inlet port 53, the transfer pipe 34 is connected to the bottom of the gas-liquid separation pipe 56, and the transfer pipe 34 is located above the transfer pipe 34. A source gas introduction pipe 32 is connected.

As shown in FIGS. 3 to 7, the heat exchange section 5 is used.
No. 0 is equipped with a large number of partition plates 58 made of aluminum or the like, which are arranged in parallel to each other. Between these partition plates 58, the bottom liquid evaporating passage 59a and the raw material gas passage (mixed gas passage) are provided. And 59b are formed alternately.

As shown in FIG. 4, the bottom liquid evaporation passage 59a.
A pair of L-shaped side bars 60 around the step forming the
a is provided. As shown in FIG. 6, these side bars 60a are arranged between both partition plates 58 so as to be in close contact with them. These sidebars 60a
The upper and lower ends and part of the side ends of the tower bottom liquid evaporation passage 59a are blocked, and an opening 62a is formed in the lower part of one side end.
Is formed, and the opening 63a is formed in the upper part of the other side end. Then, the tower bottom liquid inlet port 51 is installed at a position closing the opening 62a, and the reflux gas outlet port 52 is installed at a position closing the opening 63a.

A corrugated plate-shaped fin 64a extending in the vertical direction is provided in the middle part of the raw material gas passage. A fin 65 extending obliquely upward from the opening 62a to the fin 64a is provided below the fin 64a, and a fin 66 extending obliquely upward from the fin 64a to the opening 63a is provided above the fin 64a. There is. These fins 64a, 65, 66 are made of aluminum or the like, and are joined to the surface of the partition plate 58 by welding or the like as shown in FIG.

On the other hand, as shown in FIG. 5, a side bar 60b is provided at the side end of the step forming the raw material gas passage 59b to close the side end over the entire area in the vertical direction. These side bars 60b are also the side bars 60 described above.
Similar to a, it is arranged between both partition plates 58 so as to be in close contact with them. As a result, openings 62b and 63b are formed at the lower end and the upper end of this step, respectively, and the source gas inlet port 5 is provided at the position where the opening 62b is closed.
3 is mounted, and the purified gas outlet port 54 is mounted at a position that closes the opening 63b. Also, both sidebars 6
The corrugated plate-shaped fins 64b extending in the vertical direction are provided between 0b, and the fins 64b are also joined to the surfaces of the joining plates 58 by welding or the like.

Therefore, the heat exchange section 50 shown here includes the partition plate 58, the fins 64a, 65, 66, the partition plate 58,
The fins 64b, the partition plate 58, ... Are laminated in this order.

Next, a deep-chill separation method for carbon monoxide carried out in this apparatus will be described.

First, the raw material gas (mixed gas) is the refrigerator 10.
The water that has been cooled in the above manner and condensed here is separated by the gas-liquid separator 11. The remaining gas is sent to the MS adsorption device 12, where moisture and carbon dioxide are removed, and then introduced into the cold insulation box 14 through the raw material gas introduction pipe 32.

This gas exchanges heat with the return gas in the main heat exchanger 16 and is cooled, and then introduced into the raw material gas inlet port 53 of the reboiler 20 through the gas-liquid separation pipe 56 shown in FIG. Since only the opening 62b shown in FIGS. 3 (b) and 5 faces the raw material gas inlet port 53, the gas is fed from the opening 62b into the raw material gas evaporation passage 59b in the heat exchanging section 50, that is, both of them. It flows upward into the passage surrounded by the side bar 60b (arrow B).

On the other hand, the bottom liquid of the rectification column 18 is introduced into the bottom liquid inlet port 51 of the reboiler 20 through the bottom liquid introducing pipe 48. Since only the opening 62a shown in FIGS. 3 (b) and 4 faces the tower bottom liquid inlet port 51, the tower bottom liquid is discharged from the opening 62a through the heat exchange section 5.
0 in the bottom liquid evaporation passage 59a, that is, both side bars 6
It flows into the passage surrounded by 0a (arrow A).

With the introduction of these, as shown in FIG.
Column bottom liquid evaporation passage 59a and raw material gas passage 5 adjacent to each other
The vaporized gas (arrow A) and the raw material gas (arrow B) of the column bottom liquid respectively flow in 9b, and heat exchange is performed between them.
By this heat exchange, the column bottom liquid in the column bottom liquid evaporation passage 59a is heated and evaporated, and this evaporated gas is returned to the bottom of the rectification column 18 through the reflux gas outlet port 52 and the reflux gas passage 49 (arrow AG). ). At the same time, the raw material gas in the raw material gas passage 59b cooled by the heat exchange is partially condensed and descends, and the descending condensate and the rising raw material gas are contacted to rectify the raw material gas. Purified gas having a high carbon monoxide concentration is generated at the top of the raw material gas passage 59b.

Here, the condensate collects from the raw material gas inlet port 53 at the bottom of the gas-liquid separation pipe 56 and passes from the bottom to the heat exchanger 27 along the transfer pipe 34 (arrow BL).
It is introduced into the capacitor 28. Liquid nitrogen, which is a cold source, is supplied from the nitrogen gas-liquid separator 30 to the condenser 28, and the raw material gas is cooled by heat exchange with this and the first vapor-liquid separation through the expansion valve 36. Sent to the container 24. The liquid at the bottom of the first gas-liquid separator 24 is
It is introduced into an appropriate portion of the rectification column 18 through a condenser 22.

On the other hand, the purified gas that has risen to the top of the reboiler 20 enters the purified gas transfer pipe 38 from the purified gas outlet port 54, is cooled by the condensers 22 and 28, and then enters the second gas-liquid separator 25. be introduced. Then, it is introduced into the third gas-liquid separator 26 from the bottom of the second gas-liquid separator 25 through the purified gas transfer pipe 42 and the expansion valve 44, and the purified gas transfer pipe is introduced from the bottom of the second gas-liquid separator 26. It is supplied as a reflux liquid to the top of the rectification column 18 through 46.

As described above, the high-purity gas purified from the raw material gas in the reboiler 20 is introduced into the top of the rectification column 18 as a reflux liquid, so that the rectification column 18 has an extremely high-purity carbon monoxide. The gas will be purified, and this gas will be taken out as the product carbon monoxide gas to the outside of the cool box 14 through the product gas outlet passage 47.

As described above, in this method and apparatus, the raw material gas introduced into the cool box 14 is first introduced into the bottom portion of the reboiler 20, and the reboiler 20 performs heat exchange between the raw material gas and the bottom liquid. As a result, the raw material gas is rectified in the raw material gas passage 59b, and the high-purity purified gas obtained thereby is supplied to the top of the rectification column 18 as a reflux liquid. Efficiently generate high-purity reflux liquid by using the existing reboiler 20 also as gas rectification means without using a double rectification column as described above or refluxing a part of the product gas. This makes it possible to obtain high-purity product CO gas at low cost.

The reboiler in the present invention may be any one as long as it has a mixed gas passage (raw material gas passage) and a column bottom liquid evaporation passage and can exchange heat between both passages. Therefore,
This reboiler is not limited to the reboiler 20 shown in the above-mentioned embodiment, but conventionally known heat exchangers such as shell-and-tube heat exchangers and fin-tube heat exchangers can be applied. Is. In either case, the column bottom liquid may be evaporated in one passage, and the raw material gas may be caused to flow from the bottom into the other passage for rectification.

[0032]

As described above, according to the present invention, the mixed gas is first introduced into the bottom of the reboiler of the rectification column, and heat is exchanged between the mixed gas and the bottom liquid in the reboiler, whereby the mixed gas passage The mixed gas is rectified by the above, and the high-purity purified gas obtained by this is supplied to the top of the rectification column as a reflux liquid. Or, by using the existing reboiler also as gas rectification means without refluxing part of the product gas, it is possible to efficiently generate a high-purity reflux liquid, which results in low cost and high cost. There is an effect that a product CO gas having a purity can be obtained.

[Brief description of drawings]

FIG. 1 is a flow sheet showing the overall configuration of a carbon monoxide cryogenic separation system in one embodiment of the present invention.

FIG. 2 is an external front view of a reboiler in the cryogenic separation system.

FIG. 3A is a perspective view showing a state in which the reboiler is laid down, and FIG. 3B is a perspective view showing a state in which each port is removed from the reboiler.

FIG. 4 is a sectional view taken along the line CC of FIG.

5 is a cross-sectional view taken along line DD of FIG. 3 (b).

FIG. 6 is a cross-sectional view taken along the line EE of FIG.

7 is a cross-sectional view taken along the line FF of FIG.

FIG. 8 is a flow sheet showing an example of a conventional carbon monoxide cryogenic separation device.

FIG. 9 is a flow sheet showing an example of a conventional carbon monoxide cryogenic separation device.

[Explanation of symbols]

 18 Fractionation tower 20 Reboiler 32 Raw material gas introduction pipe 38, 40, 42, 46 Purified gas transfer pipe 59a Tower bottom liquid evaporation passage 59b Raw material gas passage (mixed gas passage)

Claims (2)

[Claims] 1. A method for separating carbon monoxide from a mixed gas containing at least carbon monoxide and hydrocarbons in a rectification column, wherein the mixed gas is caused to flow upward from a lower part of a reboiler of the rectification column. In the reboiler, the bottom liquid of the rectification tower and the mixed gas are rectified while evaporating the bottom liquid by performing heat exchange between the mixed gas,
A refrigerating separation method of carbon monoxide, characterized in that the rectified gas is introduced from the upper part of the reboiler to the top of the rectification column as a reflux liquid. 2. Deep cooling of carbon monoxide, comprising a rectification column for separating carbon monoxide from a mixed gas containing at least carbon monoxide and hydrocarbons, and a reboiler for evaporating a bottom liquid of the rectification column. In the separation device, the reboiler is provided with a column bottom liquid evaporation passage and a mixed gas passage, and the reboiler is configured so that heat exchange is performed between the fluids flowing through both passages. A raw material gas introduction passage for introducing a raw material gas, and a rectification gas transfer passage for introducing a rectification gas rectified in the mixed gas passage from the upper portion of the mixed gas passage to the top of the rectification column as a reflux liquid. A cryogenic separation device for carbon monoxide, which is characterized by being provided.