JP4943605B2 - Manhole structure of distillation tower - Google Patents

Description

【００３３】
実施例１について
長期連続運転の結果、３ヶ月経過時点で、蒸留塔内の圧力が上昇し始めた。また、目視観察の結果、僅かに重合物が生成していたものの、蓋部５は容易に開けることができた。
実施例２について
長期連続運転の結果、４ヶ月経過時点でも蒸留塔内の圧力上昇は見られなかった。また、目視観察の結果、重合物の生成は見られず、蓋部５は容易に開けることができた。
比較例について
長期連続運転の結果、２ヶ月経過時点で蒸留塔内の圧力が上昇し始めた。また、マンホールへ重合物が蓄積したことにより、マンホールの蓋部５は治具なしでは開けることができない状態になっていた。
【００３４】
以上のように、蒸留塔のマンホールを塔内温度以上に加熱することによって、重合物の生成が抑制されることがわかった。
【００３５】
【発明の効果】
本発明によれば、マンホール胴板および／または蓋部にトレース配管、加熱ジャケット等の加熱手段を設けることでマンホール胴板および／または蓋部を塔内温度以上の温度に維持できるため、易重合性物質を含む蒸気が前記部位において凝縮するのを防止することができる。マンホール部では重合禁止剤を含む還流液と接触しにくいため易重合性物質を含む蒸気が凝縮すると非常に不安定で重合しやすくなるが、本発明では前記の通り、易重合性物質を含む蒸気が凝縮するのを防止することができるため、マンホールでの重合物の生成が低減され、蒸留塔の連続運転が可能になるという効果がある。
【図面の簡単な説明】
【図１】本発明の一実施形態であるマンホール構造を示す分解断面図である。
【図２】本発明の他の実施形態であるマンホール構造の概略を示す分解断面図である。
【図３】本発明のさらに他の実施形態であるマンホール構造の概略を示す分解断面図である。
【図４】通常の蒸留塔を示す概略図である。
【図５】従来のマンホール構造を示す分解断面図である。
【符号の説明】
１ 塔壁
２ 開口部
３ マンホール胴板
４ フランジ
５ 蓋部
６ ガスケット
７ ボルト
８ ナット
９ 取っ手
１０ トレース配管（加熱手段）
１０ａ 供給口
１０ｂ 排出口
１１ 塔壁
１２ 開口部
１３ マンホール胴板
１４ フランジ
１５ 加熱ジャケット（加熱手段）
１５ａ 供給口
１５ｂ 排出口[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a manhole structure of the distillation column used for distillation of the easily polymerizable substance represented by the vinyl compound having a double bond in the molecule.
[0002]
Since an easily polymerizable substance has a property of being easily polymerized by light, heat, or the like, it is extremely easily polymerized at a high temperature such as in a distillation process. If polymerization occurs in the distillation column, it not only leads to a loss, but also hinders continuous operation and decreases productivity. Accordingly, prevention of polymerization is a very important technique in the purification of easily polymerizable substances by distillation, and many methods for preventing polymerization have been proposed in relation to the type, amount, and combination of polymerization inhibitors.
[0003]
FIG. 4 shows a distillation column commonly used for distillation of readily polymerizable substances. This distillation column is provided with packed layers 30 and 31 filled with a packing. The raw material is supplied into the tower from the raw material supply port 33. On the other hand, steam is introduced from the lower steam inlet 34, rises in countercurrent contact with the raw material, and is discharged from the upper steam outlet 35. Reference numeral 36 denotes a reflux liquid inlet, and 37 denotes a liquid outlet.
[0004]
In such a distillation column, a plurality of manholes 38, 39,... 44 are provided for extracting a packing material. FIG. 5 shows the structure of such a manhole. A manhole body plate 46 attached to the wall surface 45 of the tower and protruding from the wall surface 45; a flange 47 attached to the outer periphery of the end of the manhole body plate 46; It comprises a lid portion 48 that closes the front end opening of the body plate 46, and a gasket 49 that is interposed between the lid portion 48 and the flange 47. Then, a bolt 50 is passed through a bolt insertion hole provided in the lid portion 48 and the flange 47 and screwed into the nut 51, and the tip opening of the manhole body plate 46 is closed by the lid portion 48. A handle 52 is attached to the surface of the lid portion 48.
[0005]
When the easily polymerizable substance is distilled using the distillation apparatus, a polymer may be generated at the manhole site. When a polymer is generated in the distillation step, it gradually becomes a nucleus and grows and accumulates to increase the pressure in the tower, and eventually the inside of the tower is blocked. This is not only an increase in product loss, but it is a major factor that hinders continuous operation of the distillation column and reduces productivity. Moreover, it is very difficult to remove the produced polymer, and the removal cost is high.
[0006]
[Problems to be solved by the invention]
The purpose of the present invention to provide when performing distillation of easily polymerizable substance represented by vinyl compound, to reduce the formation of polymer, the manhole structure evaporation column that allows continuous operation of the distillation column It is.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have a portion where the easily polymerizable substance is easily polymerized in the distillation column. It has been found that it is a site where a liquid pool is likely to be formed in the absence. And, by heating the manhole installed in the distillation tower, the vapor containing the easily polymerizable substance is prevented from condensing at a site that is difficult to come into contact with a liquid containing a polymerization inhibitor such as a manhole site. It has been found that formation of a site where an easily polymerizable substance is easily polymerized in the tower can be prevented, and the present invention has been completed.
[0008]
That is, the method for distilling an easily polymerizable substance of the present invention is characterized in that the manhole of the distillation tower is heated when the easily polymerizable substance is distilled.
[0009]
The polymerization inhibitor is usually supplied from the top of the distillation column mixed with the reflux liquid. Since the polymerization inhibitor is substantially non-volatile, the polymerization inhibitor is not contained in the condensate produced by the condensation of the vapor in the distillation column. Therefore, the condensate is very unstable and easily polymerized. This condensate is stabilized by contacting and mixing with a liquid containing a polymerization inhibitor flowing down from the upper part of the distillation column, thereby preventing polymerization. Therefore, as described above, the portion where the vapor is condensed in the distillation column and a liquid pool is easily formed in the absence of the polymerization inhibitor is the portion where the easily polymerizable substance is easily polymerized.
[0010]
As a result of further intensive studies on the cause of polymerization in the distillation column, the present inventors have shown that the manhole portion of the distillation column protrudes in a convex shape from the space in the column as shown in FIG. In this case, since it is cooled by the influence of outside air, the vapor containing easily polymerizable substances is easy to condense, and the manhole part is difficult to contact with the reflux liquid containing the polymerization inhibitor, so the condensate in the manhole part is very It was found that the polymer is unstable and easily formed. In the present invention, as described above, the steam containing the easily polymerizable substance is prevented from being cooled by heating the manhole of the distillation tower and giving the steam a heat quantity equal to or greater than the heat radiation amount. As a result, it is difficult to come into contact with a reflux liquid containing a polymerization inhibitor such as a manhole part of a distillation column, and it is possible to prevent condensation of an easily polymerizable substance at a site that is very easily polymerized. Can be prevented.
[0011]
In the distillation method of the present invention, the temperature of the manhole part is preferably heated to a temperature not lower than the temperature in the tower, more preferably higher than the temperature in the tower, and to a temperature range not exceeding 100 ° C. from the temperature in the tower. Good. Thereby, it can prevent that an easily polymerizable substance condenses and superposes | polymerizes in a manhole part.
[0012]
The manhole structure of the distillation tower of the present invention is a manhole structure provided in a distillation tower that performs distillation of an easily polymerizable substance, the manhole body plate attached to the wall surface of the distillation tower and protruding from the wall surface, and the manhole body plate And a heating means for heating the manhole body plate and / or the cover provided in the manhole.
[0013]
As the heating means, a heating jacket is provided on the outer surface of the manhole plate and / or the lid portion of the manhole, and / or the outer surface of the manhole body plate and / or the lid portion with a trace pipe passing the heat medium. Are preferred.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
One embodiment of the present invention is shown in FIG. FIG. 1 is an exploded sectional view showing a manhole structure according to this embodiment.
[0015]
The manhole shown in FIG. 1 is provided in the distillation tower which performs distillation of the easily polymerizable substance described above. A cylindrical manhole body plate 3 is integrally attached to the outer peripheral edge of the opening 2 provided in the tower wall 1 of the distillation tower by welding or the like. A flange 4 is attached to the outer periphery of the end of the manhole body plate 3 by welding or the like. A gasket 6 is interposed between the flange 4 and the lid 5, a bolt 7 is passed through a bolt insertion hole provided in the flange 4 and the lid 5, and is screwed with a nut 8. Is closed with a lid 5. A handle 9 is attached to the surface of the lid 5.
[0016]
A trace pipe 10 through which a heat medium passes is spirally wound around the manhole body plate 3. If necessary, trace piping may also be installed on the manhole cover. The heat medium is supplied from the supply port 10a and discharged from the discharge port 10b. If necessary, the supply port and the discharge port may be reversed. Due to the heat transferred from the heat medium in the trace pipe 10 to the manhole body plate 3, the manhole body plate 3 is maintained at least at a temperature substantially equal to or higher than the tower temperature, preferably higher than the tower temperature. More preferably, the temperature is higher than the temperature in the tower and does not exceed 100 ° C. from the temperature in the tower, more preferably the temperature is higher than the temperature in the tower and does not exceed 20 ° C. from the temperature in the tower. Is done. Thereby, it can prevent that an easily polymerizable substance condenses in a manhole part. When continuous operation is performed for a long time in a temperature range where the temperature of the manhole body plate 3 is excessively higher than the temperature in the tower, it is disadvantageous in terms of energy, and there may be a problem that the polymerization inhibitor and the attached polymer are burnt. Therefore, it is not preferable.
[0017]
As the heat medium passed through the trace pipe 10, hot water, steam, oil, or the like can be used.
[0018]
FIG. 2 is an exploded sectional view schematically showing a manhole structure according to another embodiment of the present invention. A cylindrical manhole body plate 13 is integrally attached to the outer peripheral edge of the opening 12 provided in the tower wall 11 of the distillation tower shown in FIG. 2 by welding or the like. A heating jacket 15 for passing a heat medium (warm water, steam, oil, etc.) is attached outside the manhole body plate 13. If necessary, a heating jacket may also be installed on the manhole cover. A heating medium supply port 15 a and a discharge port 15 b are respectively provided on the surface of the heating jacket 15. If necessary, the supply port and the discharge port may be reversed. Due to the heat transferred from the heat medium in the heating jacket 15 to the manhole body plate 13, the manhole body plate 13 is maintained at least at a temperature substantially equal to or higher than the temperature in the tower, preferably higher than the temperature in the tower. More preferably, the temperature is higher than the temperature in the tower and does not exceed 100 ° C. from the temperature in the tower, more preferably the temperature is higher than the temperature in the tower and does not exceed 20 ° C. from the temperature in the tower. Is done.
[0019]
A flange 14 is attached to the outer periphery of the front end of the heating jacket 15 by welding or the like. A gasket 6 is interposed between the flange 14 and the lid 5, and a bolt 7 is passed through a bolt insertion hole provided in the flange 14 and the lid 5, and is screwed with a nut 8. Is closed with a lid 5. A handle 9 is attached to the surface of the lid 5.
[0020]
FIG. 3 is an exploded cross-sectional view showing a manhole structure according to still another embodiment of the present invention.
[0021]
The manhole shown in FIG. 3 is provided in a distillation column for performing distillation of the above-described easily polymerizable substance. That is, a cylindrical flange portion 21 is integrally attached to the outer peripheral edge of the opening 2 provided in the column wall 1 of the distillation column by welding or the like. On the surface of the flange portion 21, a plurality of standing bolts 22 are erected at appropriate intervals along the circumferential direction.
[0022]
The inner peripheral surface of the lid portion 23 is in contact with the surface of the flange portion 21 via a gasket 27 to block the opening 2 of the distillation column. The lid portion 23 is a circular plate-like body. A heating jacket 24 for passing a heat medium (hot water or the like) is attached to the upper surface of the lid portion 23. A heating medium supply port 24 a and a discharge port 24 b are respectively provided on the surface of the heating jacket 24. By the heating jacket 24, the lid 23 is maintained at least at a temperature substantially equal to or higher than the tower temperature, preferably at a temperature higher than the tower temperature, more preferably at a temperature higher than the tower temperature, and the tower temperature. It is maintained in a temperature range not exceeding 100 ° C. from the internal temperature, more preferably higher than the temperature in the column, and not exceeding 20 ° C. from the temperature in the column. When the temperature of the lid part 23 is lower than the temperature in the tower, the condensed liquid adheres to the lid part 23 and the polymerized product and the condensate easily accumulate.
[0023]
Further, a bolt insertion hole 25 corresponding to the standing bolt 22 is provided on the periphery of the lid portion 23. Then, a nut 26 is screwed into the upright bolt 22 of the flange portion 21 that protrudes through the bolt insertion hole 25. Thereby, the cover part 23 can be press-fixed to the surface of the flange part 21. In addition, it is preferable that lining is given to the inner surface of the cover part 23 and / or the surface of a flange part.
[0024]
As described above, in the present invention, by providing the trace pipe 10 and the heating jacket 15, the manhole body plate and / or the lid part is maintained at a temperature higher than the temperature in the tower. Thereby, since the vapor | steam of an easily polymerizable substance does not condense in a manhole part and a liquid pool is made, it can prevent producing | generating a polymer.
[0025]
The manhole structure of the present invention is applied to a normal distillation tower as shown in FIG. 4, and is particularly suitable for use in a manhole for extracting a packed material with high polymerization. In the distillation operation, a polymerization inhibitor may be added to the reflux liquid or the supply liquid. Examples of the polymerization inhibitor include one or more of dibutyldithiocarbamate metal salts (copper, manganese, etc.), phenothiazine, methoquinone, hydroquinone and the like.
[0026]
Examples of the readily polymerizable substances include acrylic acid, conjugated acids such as methacrylic acid or esters thereof, amides, derivatives such as nitrile (methyl acrylate, methyl methacrylate, acrylamide, acrylonitrile, etc.), conjugated aldehydes and ketones (acrolein). , Methacrolein, methyl vinyl ketone, etc.), vinyl halides (vinyl chloride, etc.), vinyl group-substituted aromatic compounds (styrene, etc.), vinyl carboxylates (vinyl acetate, etc.), vinyl ethers (methyl vinyl ether, etc.), 1,3- Examples include diolefins (butadiene, isoprene, etc.), ethylene and alkyl-substituted ethylene (propylene, etc.).
[0027]
In addition, as a heating means of the manhole body plate 3, other heating means such as an electric heater may be employed instead of the trace pipe 10 described above.
[0028]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited only to a following example.
[0029]
Example 1
In the distillation tower as shown in FIG. 4 for distilling acrylic acid, the manhole for extracting the packing was changed to the structure as shown in FIG. 1, and a long-term continuous operation was performed. This distillation apparatus was a packed column corresponding to 6 theoretical plates, and was operated under the conditions of a tower top pressure of 55 torr, a distillation rate of 80%, and a reflux ratio of 0.8.
At this time, a small amount of phenothiazine and methoquinone as a polymerization inhibitor was added to the reflux liquid, and a fixed amount of air was supplied to the can part liquid layer part to operate.
Warm water was passed through the trace pipe 10, and the manhole shell plate 3 was maintained at 74 to 77 ° C, which is 2 to 5 ° C higher than the temperature in the tower.
During the continuous operation, the tendency of pressure increase in the distillation column and the state of polymer adhesion to the manhole were periodically examined.
[0030]
Example 2
Long-term continuous operation was performed in the same manner as in Example 1 except that warm water was passed through the trace pipe 10 and the manhole body plate 3 was maintained at 92 ° C., which is 20 ° C. higher than the temperature inside the tower.
During the continuous operation, the tendency of pressure increase in the distillation column and the state of polymer adhesion to the manhole were periodically examined.
[0031]
Comparative Example A long-term continuous operation was performed in the same manner as in Example 1 except that a distillation column as shown in FIG. 4 equipped with the manhole shown in FIG. 4 was used.
During the continuous operation, the tendency of pressure increase in the distillation column and the state of polymer adhesion to the manhole were periodically examined.
[0032]
Table 1 shows long-term continuous operation results of Example 1, Example 2, and Comparative Example.
[Table 1]

[0033]
As a result of long-term continuous operation for Example 1, the pressure in the distillation column began to rise after 3 months. Moreover, as a result of visual observation, although the polymer was slightly formed, the lid 5 could be easily opened.
As a result of long-term continuous operation for Example 2, no pressure increase in the distillation column was observed even after 4 months. Further, as a result of visual observation, the formation of a polymer was not seen, and the lid 5 could be easily opened.
As a result of long-term continuous operation for the comparative example, the pressure in the distillation column began to rise after 2 months. Further, since the polymer was accumulated in the manhole, the manhole cover 5 could not be opened without a jig.
[0034]
As described above, it was found that by heating the manhole of the distillation column to a temperature equal to or higher than the temperature inside the column, the formation of a polymer is suppressed.
[0035]
【Effect of the invention】
According to the present invention, since the manhole body plate and / or the lid part can be maintained at a temperature higher than the temperature in the tower by providing heating means such as a trace pipe and a heating jacket on the manhole body plate and / or the cover part, It is possible to prevent the vapor containing the active substance from condensing at the site. In the manhole part, it is difficult to come into contact with the reflux liquid containing the polymerization inhibitor, and when the vapor containing the easily polymerizable substance condenses, it becomes very unstable and easily polymerized. Can be prevented from condensing, so that the production of the polymer in the manhole is reduced, and the continuous operation of the distillation column is enabled.
[Brief description of the drawings]
FIG. 1 is an exploded sectional view showing a manhole structure according to an embodiment of the present invention.
FIG. 2 is an exploded sectional view schematically showing a manhole structure according to another embodiment of the present invention.
FIG. 3 is an exploded cross-sectional view showing an outline of a manhole structure which is still another embodiment of the present invention.
FIG. 4 is a schematic view showing a normal distillation column.
FIG. 5 is an exploded cross-sectional view showing a conventional manhole structure.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Tower wall 2 Opening part 3 Manhole body plate 4 Flange 5 Lid part 6 Gasket 7 Bolt 8 Nut 9 Handle 10 Trace piping (heating means)
10a Supply port 10b Discharge port 11 Tower wall 12 Opening portion 13 Manhole body plate 14 Flange 15 Heating jacket (heating means)
15a supply port 15b discharge port

Claims (3)

  A manhole structure provided in a distillation column that performs distillation of an easily polymerizable substance, the manhole body plate that is attached to the wall surface of the distillation column and protrudes from the wall surface, the lid portion that closes the front end opening of the manhole body plate, Heating means for heating at least the lid portion of the manhole body plate and lid portion provided in the manhole to a temperature range higher than the tower temperature and not exceeding 100 ° C. from the tower temperature is provided. A manhole structure of a distillation tower characterized by 2. The manhole structure according to claim 1 , wherein the heating unit is configured to contact a trace pipe through which a heat medium passes through at least an outer surface of the manhole body plate and the lid. 2. The manhole structure according to claim 1 , wherein the heating means includes a heating jacket for passing a heat medium on at least an outer surface of the lid portion of the manhole body plate and the lid portion.

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