JP3990202B2 - Internal heat exchange distillation column - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an internal heat exchange distillation column that includes a low-pressure column and a high-pressure column and performs heat exchange between the high-pressure column (concentration unit) side and the low-pressure column (recovery unit) side.
[0002]
[Prior art and problems to be solved by the invention]
As an distillation column that excels in energy conservation, a low-pressure column and a high-pressure column are configured to exchange heat between them, and an internal heat exchange type distillation column that does not require heat exchange with others is known. It has been. From the standpoint of promoting energy saving in distillation operation, this internal heat exchange distillation column is of course the principle that is most faithful to energy saving, and it is recognized from the academic viewpoint. By the way.
[0003]
In addition, as an internal heat exchange type distillation column, a plurality of tubes are connected to the main body cylinder by both end tube plates so that the inside and outside of each pipe are separated from each other inside the main body cylinder. Each is provided with a gas-liquid inlet / outlet, and the operating temperature is varied by making a difference in the operating pressure between the inside and outside of the pipe, and the pipe wall of each pipe is used as a heat transfer surface to transfer heat from the high pressure side to the low pressure side Thus, there has been proposed a structure in which one distillation column is configured with the high-pressure side as the concentrating section and the low-pressure side as the recovery section (Japanese Patent Laid-Open No. 8-66601 (Japanese Patent No. 2694425)).
[0004]
As shown in FIG. 5, this internal heat exchange distillation column includes a main body cylinder 1 and a plurality of tubes 25 inserted into the main body cylinder 1, with both end tube sheets (upper tube sheet (top-side tube sheet) 3 a and It is formed by connecting with the main body cylinder 1 by a lower tube sheet (a tower bottom tube sheet) 3b). The inner pipe 4 and the outer pipe 5 of each pipe 25 are separated from each other. The inner pipe 4 serves as a high pressure side concentrating part, and the outer pipe 5 serves as a low pressure side collecting part. Yes.
[0005]
In addition, a recovery unit liquid inlet 6 for supplying a liquid to the outside of the tube (collection unit) 5 and a recovery unit steam outlet 7 for extracting steam from the outside of the tube (collection unit) 5 are disposed at the top of the main body barrel 1. A concentrating section liquid inlet 8 for supplying a liquid to the inside of the pipe (concentrating section) 4 is disposed in the end chamber 14a that communicates with the inside of the pipe (concentrating section) 4 above the upper tube plate 3a. Further, a concentrating part steam outlet 9 for extracting steam from the inside of the pipe (concentrating part) 4 is provided.
[0006]
On the other hand, a recovery unit steam inlet 10 for supplying steam to the outside of the tube (collection unit) 5 and a recovery unit liquid outlet 11 for extracting the liquid from the outside of the tube (collection unit) 5 are disposed at the lower part of the main body barrel 1. The concentrating section steam inlet 12 for supplying steam to the inside of the pipe (concentrating section) 4 is disposed in the end chamber 14b communicating with the inside of the pipe (concentrating section) 4 below the lower tube plate 3b. In addition, a concentration unit liquid outlet 13 for extracting the liquid from the pipe (concentration unit) 4 is provided.
[0007]
By the way, in such an internal heat exchange type distillation column, since the state of gas-liquid contact in the distillation part inside and outside the pipe constituting the concentrating part or the recovery part greatly affects the distillation action, for example, As in the case of the internal heat exchange distillation column in FIG. 5, in the case where the collection unit (packed column) is filled with a packing outside the tube, and the gas-liquid flow is uneven, the target is The distillation effect cannot be obtained.
That is, the liquid sprayed evenly per surface area on the top of the packed bed at the top of the packed tower flows down the packed surface by attractive force, and the steam supplied to the bottom of the tower creates a pressure difference between the top and bottom of the tower. Distillation is carried out by raising the gap between the packings as a driving force and bringing the liquid and steam into contact with each other in the packed tower. Since there is a tendency to flow to a small place and the descending liquid flows to a place where the amount of the rising steam is small, a slight drift causes a large drift in an accelerated manner. Therefore, the positional deviation of the ratio between the descending liquid amount and the ascending steam amount increases from the tower top to the tower bottom, and as a result, the designed gas-liquid contact effect, that is, the distillation performance cannot be obtained.
[0008]
Therefore, in the conventional packed tower, the packed bed is divided at every predetermined packed bed height (generally depending on the tower diameter, but generally every 2 to 5 m). A liquid tool, a liquid dispersing tool, etc. are arranged so that the gas-liquid contact effect as designed can be obtained. However, in such a configuration, not only the equipment structure is complicated, but also the space in which the packed bed receiver, the liquid collecting tool, the liquid dispersing tool and the like are disposed does not function as a distillation unit that performs a distillation action. For this reason, there is a problem in that the height of the distillation column is increased by that amount, resulting in an increase in equipment size and cost.
[0009]
In addition, when a packed column is packed outside the tube, the horizontal cross-sectional shape outside the tube is complicated, and the gas-liquid contact state is likely to be biased. The problem due to (1) becomes more prominent, and it tends to be more difficult to make the gas-liquid contact state per unit area on the horizontal section uniform.
[0010]
The present invention solves the above-mentioned problems, and there is little bias in the gas-liquid contact state in the distillation section without incurring an increase in cost, and an internal heat exchange type capable of exhibiting the target distillation performance An object is to provide a distillation column.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the internal heat exchange distillation column of the present invention (Claim 1) comprises:
By connecting a plurality of tubes to the main body cylinder with both end tube plates, the inside of the main body is separated from the inside and outside of the pipe, and each of the inside and outside of the pipe has a gas-liquid inlet / outlet. ,
At least around each tube with a filling,
By making the operating temperature different by making a difference in the operating pressure between the inside and outside of the pipe, the pipe wall of each pipe is used as the heat transfer surface, and heat is transferred from the high pressure side to the low pressure side, so that the high pressure side is the concentrating section and the low pressure side is An internal heat exchange distillation column configured to function as a recovery unit,
(a) dividing the space outside the tube in which the filler is disposed for each tube periphery by a partition wall;
(b) Each region (partition region) divided by the partition wall has the same horizontal cross-sectional shape.
[0012]
When the space outside the pipe is divided for each pipe by the partition wall, and the horizontal sectional shape of each region (partition region) divided by the partition wall is the same shape, the descending liquid and the rising steam The horizontal flow of the liquid is blocked by the partition wall, and the range of the liquid flowing down the tube is limited to each partition area, and the rising vapor resists the uniform amount of descending liquid flowing down each partition area. Therefore, a uniform amount of steam is generated for each tube from the lower part outside the tube filled with the filling material, that is, for each tube. It will be supplied around the tube.
[0013]
Therefore, the amount of gas-liquid passing through each compartment is the same (constant), and the desired liquid distillation performance can be achieved by making the gas-liquid contact as planned in the outside of the tube (each compartment) filled with packing. Can be demonstrated.
In addition, since the horizontal cross-sectional area of each section area can be made sufficiently small, it is not necessary to collect and redistribute in the middle between the top and bottom of the tower, thereby avoiding complicating the equipment. can do.
In the internal heat exchange distillation column of the present invention, the preferred packing disposed outside the tube has a layered structure, and regular packing in which each layered member is disposed substantially vertically. Although various things etc. are illustrated, it is possible to use other various filling materials. Further, the internal heat exchange distillation column of the present invention can have a structure in which the packing is filled in the tube, and can also have a structure in which the packing is not filled. In addition, as a suitable filling when filling a tube with a filling material, there is exemplified a regular filling material having a layered structure and arranged so that each layered member is substantially vertically oriented. It is also possible to use other fillers.
[0014]
Further, in the internal heat exchange distillation column according to claim 2, the horizontal sectional shape of each region (compartment region) divided by the partition wall is any one of a regular hexagon, a dodecagon, and a circle. It is said.
[0015]
By forming the horizontal cross-sectional shape of each partition area divided by the partition wall as one of a regular hexagon, a dodecagon, and a circle, an extra-tube region having a planar shape that is less likely to be biased in the gas-liquid contact state is formed. It becomes possible to make effective use of the space outside the tube, and the present invention can be effectively realized.
[0016]
The internal heat exchange distillation column according to claim 3 is a distillation of a space formed between an inner wall of the main body cylinder and a partition wall partitioning the periphery of a tube located on the outermost side of the plurality of tubes. It is characterized by not being part.
[0017]
Planar shape that makes it difficult for the gas-liquid contact state to be biased by avoiding the space formed between the inner wall of the main body cylinder and the partition wall that partitions the outer tube space around the outermost tube as a distillation section It is possible to easily form the outside region of the tube having the above, and the present invention can be further improved.
In this case, the space formed between the inner wall of the main body cylinder and the partition wall that partitions the periphery of the outermost pipe does not serve as a distillation section. The horizontal cross-sectional area of the space formed between the outer wall and the partition wall that divides the periphery of the pipe is smaller than the horizontal cross-sectional area of the main body trunk, and does not lead to an increase in the size of the facility that is problematic in practice. .
[0018]
The internal heat exchange distillation column according to claim 4 has three tubes adjacent to each other when the horizontal sectional shape of each region (compartment region) divided by the partition wall is a dodecagon or a circle. The space that is formed by the partition walls and does not surround the pipe is not a distillation section.
[0019]
In the case where the horizontal sectional shape of the partition region is a dodecagon or a circle, the space formed by the partition walls of three tubes adjacent to each other and not surrounding the tube is not used as a distillation part. It is possible to form a partition region having a dodecagonal shape or a circular shape in cross-section so that the gas-liquid contact state is less likely to be biased.
Note that the space that does not surround the pipes formed by the partition walls around the three adjacent pipes does not become a distillation section, so the equipment will be somewhat larger, but the horizontal cross-sectional area of the space that does not surround the pipes Is smaller than the horizontal cross-sectional area of the main body, and does not lead to an increase in the size of the facility that causes practical problems.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be shown and features thereof will be described in detail.
[0021]
[Embodiment 1]
FIG. 1 is a front sectional view schematically showing the configuration of the main part of an internal heat exchange distillation column according to an embodiment of the present invention, and FIG. 2 is a plan sectional view.
This internal heat exchange distillation column is formed by connecting the main body cylinder 1 and a plurality of tubes 25 inserted into the main body cylinder 1 to the main body cylinder 1 by the upper tube plate 3a and the lower tube plate 3b. . The inner pipe 4 and the outer pipe 5 of each pipe 25 are separated from each other. The inner pipe 4 serves as a high pressure side concentrating part, and the outer pipe 5 serves as a low pressure side collecting part. Yes.
[0022]
In addition, a recovery unit liquid inlet 6 for supplying a liquid to the outside of the tube (collection unit) 5 and a recovery unit steam outlet 7 for extracting steam from the outside of the tube (collection unit) 5 are disposed at the top of the main body barrel 1. A concentrating section liquid inlet 8 for supplying a liquid to the inside of the pipe (concentrating section) 4 is disposed in the end chamber 14a that communicates with the inside of the pipe (concentrating section) 4 above the upper tube plate 3a. Further, a concentrating part steam outlet 9 for extracting steam from the inside of the pipe (concentrating part) 4 is provided.
[0023]
On the other hand, a recovery unit steam inlet 10 for supplying steam to the outside of the tube (recovery unit) 5 and a recovery unit liquid outlet 11 for extracting the liquid from the outside of the tube (collection unit) 5 are disposed at the lower part of the main body barrel 1. The concentrating section steam inlet 12 for supplying steam to the inside of the pipe (concentrating section) 4 is disposed in the end chamber 14b communicating with the inside of the pipe (concentrating section) 4 below the lower tube plate 3b. In addition, a concentration unit liquid outlet 13 for extracting the liquid from the pipe (concentration unit) 4 is provided.
[0024]
In the internal heat exchange distillation column of this embodiment, as shown in FIG. 2, the outside of the pipe (space outside the pipe) 5, which is the space around the pipe 25, is separated by the partition wall 15. Divided by perimeter. And each horizontal area | region (division area | region) 16 divided | segmented by the division wall 15 is comprised so that it may become the same shape of a regular hexagon, respectively. Here, the shape of the partition region 16 refers to the shape of the region including the outer tube 5, the tube 25, and the inner tube 4 surrounded by the partition wall 15.
Further, in this internal heat exchange type distillation column, the inside 4 and the partition region 16 (outside 5) are filled with packings (regular packing) 4a and 5a.
[0025]
Further, gas / liquid is not supplied to the space (outer peripheral region) 17 formed between the inner wall of the main body barrel 1 and the partition wall 15 (15a) disposed around the outermost tube 25 ( That is, it is configured so as not to function as a distillation section.
[0026]
In the internal heat exchange distillation column configured as described above, a partition wall 15 that divides the outside of the tube (space outside the tube) 5 for each circumference of each tube 25 is provided, and each of the partitions divided by the partition wall 15 is provided. Since the horizontal cross-sectional shape of the region (compartment region) 16 is a regular hexagon and the same shape, the horizontal flow of the descending liquid and the rising steam is blocked by the partition wall, and the packing is provided. The range of the liquid flowing down the outside of the pipe 5 is limited to each partition region 16, and the rising liquid flows down each partition region 16 with a uniform amount of descending liquid as resistance to each partition region 16. In order to rise, a uniform amount of steam is supplied to the partition region 16 around each tube 25 from the lower part of the outside of the tube 5 (that is, each partition region 16). Become.
[0027]
Therefore, the amount of gas and liquid that passes through each partition region 16 that is a packed tower is constant between the partition regions 16, and the target gas-liquid contact can be performed outside the tube 5 (compartment region 16). And the desired distillation performance can be obtained.
In addition, since the horizontal cross-sectional area of each partition region 16 is sufficiently small, it becomes unnecessary to collect and redistribute in the middle between the tower top and the tower bottom, thereby avoiding complication of the apparatus. it can.
[0028]
[Embodiment 2]
FIG. 3 is a plan sectional view showing the internal structure of an internal heat exchange distillation column according to another embodiment (Embodiment 2) of the present invention. In FIG. 3, the parts denoted by the same reference numerals as those in FIG. 2 indicate the same or corresponding parts.
In the internal heat exchange distillation column of the second embodiment, the outside of the tube (space outside the tube) 5 that is the space around the tube 25 is divided by the partition wall 15 for each periphery of each tube 25. The horizontal sectional shape of each region (partition region) 16 divided by the partition wall 15 is configured to be the same circular shape. Also in this internal heat exchange distillation column, the inside 4 and the partition area 16 (outside 5) are filled with packing (regular packing) 4a and 5a.
[0029]
Further, gas / liquid is not supplied to the space (outer peripheral region) 17 formed between the inner wall of the main body barrel 1 and the partition wall 15 (15a) disposed around the outermost tube 25 ( That is, it is configured so as not to function as a distillation section.
Furthermore, in the internal heat exchange distillation column of the second embodiment, gas and liquid are not supplied to the space 18 that does not surround the pipe 25 and is formed by the partition wall 15 around the three pipes 25 adjacent to each other. (That is, it does not function as a distillation section).
[0030]
In the internal heat exchange distillation column of the second embodiment configured as described above, a partition wall 15 that divides the outside of the tube (space outside the tube) 5 for each circumference of each tube 25 is provided. Since the horizontal sectional shapes of the divided regions (partition regions) 17 are all circular and have the same shape, the horizontal flow of descending liquid and rising steam is the same as in the first embodiment. Is blocked by the partition wall 15, and the range of flow of the liquid flowing down the outside of the tube 5 is limited to each partition region 16, and the descending liquid with a uniform liquid amount in which the rising steam flows down each partition region 16 is used as resistance. Therefore, a uniform amount of steam is generated for each tube 25 from the lower part of the outside of the tube 5 (that is, each partition region 16), and the partition region around each tube 25. 16 will be supplied.
[0031]
Therefore, the amount of gas and liquid that passes through each partition region 16 is constant in each partition region 16, and the desired gas-liquid contact is performed outside the tube 5 (compartment region 16) as designed to achieve the desired distillation performance. Obtainable.
Further, in the internal heat exchange distillation column of the second embodiment, since each partition region 16 is circular, it is possible to further reliably suppress the deviation of the gas-liquid contact state outside the tube.
[0032]
Also in the case of the second embodiment, since the horizontal sectional area of each partition region 16 is sufficiently small, it becomes unnecessary to collect and redistribute the liquid between the tower top and the tower bottom, and the apparatus becomes complicated. Can be avoided.
However, in the case of the second embodiment, a space 18 that does not surround the pipe 25 is formed by the partition wall 15 around the three adjacent pipes 25. It is smaller than the horizontal cross-sectional area of 1 and does not cause an increase in the size of the facility that causes a practical problem.
[0033]
[Embodiment 3]
FIG. 4 is a horizontal sectional view showing the internal structure of an internal heat exchange distillation column according to still another embodiment (Embodiment 3) of the present invention. In FIG. 4, the parts denoted by the same reference numerals as those in FIGS. 2 and 3 indicate the same or corresponding parts.
In the internal heat exchange distillation column of the third embodiment, the outside of the tube (space outside the tube) 5 that is the space around the tube 25 is divided by the partition wall 15 for each periphery of each tube 25. The horizontal sectional shape of each region (partition region) 16 divided by the partition wall 15 is configured to be the same shape of a dodecagon.
[0034]
In addition, gas and liquid are not supplied to the space (outer peripheral region) 17 formed between the inner wall of the main body body 1 and the partition wall 15 (15a) that partitions the tube outer space 5 around the outermost tube 25. (That is, it does not function as a distillation section).
Furthermore, in the internal heat exchange distillation column of the third embodiment, gas and liquid are also supplied to a triangular space 18 that does not surround the pipe 25 and is formed by the partition wall 15 around the three pipes 25 adjacent to each other. (That is, it does not function as a distillation section).
[0035]
Also in the internal heat exchange distillation column configured as described above, it is possible to obtain the same effect as that of the internal heat exchange distillation column in the first and second embodiments, and the target can be obtained in the outside 5 (compartment region 16). It becomes possible to make the gas-liquid contact as designed, and to obtain a desired distillation performance.
In the internal heat exchange distillation column of the third embodiment, each partition region 16 has a dodecagonal shape close to a circle, so that the deviation of the gas-liquid contact state outside the tube 5 (the partition region 16) can be efficiently performed. It becomes possible to suppress.
Further, in the case of the third embodiment, a triangular space 18 that does not surround the pipe 25 is formed by the partition wall 15 around the three adjacent pipes 25. It is smaller than the horizontal cross-sectional area of the main body barrel 1 and does not cause an increase in the size of the facility that causes a practical problem.
[0036]
In the first to third embodiments, the case where the shape of the partition area is a regular hexagon, a circle, and a dodecagon has been described as an example. However, the shape of the partition area is not limited to this, and the arrangement of the tubes is not limited thereto. Depending on the configuration, etc., various shapes such as a quadrangle, an octagon, and the like are possible.
[0037]
In the above embodiment, the case where the outside of the tube is the recovery unit has been described as an example, but the present invention can also be applied to an internal heat exchange distillation column configured so that the inside of the tube becomes the recovery unit. Even in this case, it is possible to obtain the same effect as in the above embodiment.
[0038]
The present invention is not limited to the above embodiment in other points, and various applications and modifications can be made within the scope of the invention.
[0039]
【The invention's effect】
As described above, the internal heat exchange distillation column of the present invention (Claim 1) divides the space outside the pipes by the partition walls for each circumference of each pipe, and each region (sections) divided by the partition walls. Since the horizontal cross-sectional shape of the region is the same shape, the horizontal flow of descending liquid and rising vapor is blocked by the partition wall, and the range of the liquid flowing down the tube is limited to each partition region In addition, since the rising steam rises for each partition region using the descending liquid of a uniform liquid amount flowing down each partition region as a resistance, each tube is discharged from the lower part outside the tube filled with the packing. It is possible to supply a uniform amount of steam per tube around each compartment, i.e. around each tube. Therefore, it is possible to achieve the desired distillation performance by making the gas-liquid amount passing through each partition region the same (constant) and making the gas-liquid contact as the target design in each partition region.
In addition, since the horizontal cross-sectional area of each section area can be made sufficiently small, it is not necessary to collect and redistribute in the middle between the top and bottom of the tower, thereby avoiding complicating the equipment. can do.
[0040]
Further, as in the internal heat exchange distillation column according to claim 2, when the horizontal sectional shape of each partition region divided by the partition wall is a regular hexagonal shape, a dodecagonal shape, or a circular shape, It is possible to form a region outside the tube having a planar shape that is less likely to be biased in the contact state, and it is possible to effectively use the space outside the tube, and to effectively present the present invention. .
[0041]
Further, as in the internal heat exchange distillation column of claim 3, the space formed between the inner wall of the main body and the partition wall partitioning the outer tube space around the outermost tube is not used as a distillation part. By doing so, it becomes possible to easily form a region outside the tube having a planar shape in which the gas-liquid contact state is less likely to be biased, and the present invention can be further effectively realized.
Note that the space formed between the inner wall of the main body cylinder and the partition wall that partitions the periphery of the outermost tube does not become a distillation section, so the equipment will be somewhat larger, but it is located on the outermost side. The horizontal cross-sectional area of the space formed between the partition walls that divide the periphery of the pipe is smaller than the horizontal cross-sectional area of the main body cylinder, and the size of the equipment that is practically problematic is not increased.
[0042]
Further, as in the internal heat exchange distillation column according to claim 4, when the horizontal sectional shape of the partition region is a dodecagon or a circle, the tube is formed by partition walls of three tubes adjacent to each other By avoiding the space that does not surround the distillation portion as a distillation part, it is possible to form a partition region having a dodecagonal shape or a circular shape in the horizontal cross section, and to make it difficult for the gas-liquid contact state to be biased.
Note that the space that does not surround the pipes formed by the partition walls around the three adjacent pipes does not become a distillation section, so the equipment will be somewhat larger, but the horizontal cross-sectional area of the space that does not surround the pipes Is smaller than the horizontal cross-sectional area of the main body, and does not lead to an increase in the size of the facility that causes practical problems.
[Brief description of the drawings]
FIG. 1 is a front sectional view showing a main part of an internal heat exchange distillation column according to an embodiment of the present invention.
FIG. 2 is a plan sectional view showing the internal structure of the internal heat exchange distillation column according to one embodiment (Embodiment 1) of the present invention.
FIG. 3 is a plan sectional view showing the internal structure of an internal heat exchange distillation column according to another embodiment (Embodiment 2) of the present invention.
FIG. 4 is a plan sectional view showing the internal structure of an internal heat exchange distillation column according to still another embodiment (Embodiment 3) of the present invention.
FIG. 5 is a diagram showing the configuration of a conventional internal heat exchange distillation column to which the present invention relates.
[Explanation of symbols]
1 Body trunk 3a Upper tube plate 3b Lower tube plate 4 Inside the tube (concentration part)
4a Filler disposed in the pipe (regular filler)
5 Outside the tube (collection unit)
5a Packing outside the pipe (regular packing)
6 Recovery part liquid inlet 7 Recovery part steam outlet 8 Concentration part liquid inlet 9 Concentration part steam outlet 10 Recovery part steam inlet 11 Recovery part liquid outlet 12 Concentration part steam inlet 13 Concentration part liquid outlets 14a and 14b End chamber 15 Partition wall 15a A partition wall 16 that partitions a tube outer space around an outer tube, a partition region 17, an outer peripheral region 18, and a space 25 that does not surround the tube.

Claims (4)

By connecting a plurality of tubes to the main body cylinder with both end tube plates, the inside of the main body is separated from the inside and outside of the pipe, and each of the inside and outside of the pipe has a gas-liquid inlet / outlet. ,
At least around each tube with a filling,
By differentiating the operating pressure between the inside and outside of the pipe, the operating temperature is varied, and the pipe wall of each pipe is used as a heat transfer surface to transfer heat from the high-pressure side to the low-pressure side. An internal heat exchange distillation column configured to function as a recovery unit,
(a) dividing the space outside the tube in which the filler is disposed for each tube periphery by a partition wall;
(b) An internal heat exchange distillation column characterized in that the horizontal sectional shape of each region (compartment region) divided by the partition wall is the same. 2. The internal heat exchange distillation column according to claim 1, wherein a horizontal sectional shape of each region (compartment region) divided by the partition wall is any one of a regular hexagon, a dodecagon, and a circle. The space formed between the inner wall of the main body cylinder and a partition wall that partitions the periphery of the pipe located on the outermost side of the plurality of pipes is not a distillation section. Internal heat exchange distillation column. When the horizontal sectional shape of each region (partition region) divided by the partition wall is a dodecagon or a circle, a space that does not surround the tube is formed by the partition walls of three adjacent tubes. The internal heat exchange distillation column according to any one of claims 1 to 3, wherein the internal heat exchange distillation column is not a distillation section.

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