JP4185429B2 - Internal reflux multipurpose distillation column and batch distillation using the same - Google Patents

Description

  The present invention relates to a multi-purpose distillation column of internal reflux type, and in particular, in the presence of an azeotropic agent at the initial stage, a multi-component mixed solution of two or more components that are difficult to separate by a normal distillation method due to a slight difference in boiling point. The present invention relates to an internal reflux type multipurpose distillation column suitable for purifying and separating added-value components by azeotropic distillation, and a batch distillation method using the same.

  Conventionally, there is an azeotropic distillation method as a method of separating a mixed solution of two or more components that has a very small difference in boiling point and is difficult to separate by a normal distillation method. Hereinafter, description will be made based on FIG. In this case, an azeotropic agent α that forms a minimum azeotrope with at least one component of the mixed solution F of two or more components and can be liquid-liquid separated is mixed and supplied to the distillation column A. The vapor component of the lowest azeotrope is discharged from the refrigerant and condensed and liquefied by a cooling condenser (condenser part) B provided outside. This condensed liquefied component is left and separated by a decanter C installed at the bottom of the condenser, and the azeotropic agent α ′ containing a part of the light main component D is refluxed to the top of the column, and at the same time, the light main component D is a fractionated component The light main component D is distilled as necessary in the subsequent second distillation column to remove the remaining azeotropic agent α and separated as a purified component. On the other hand, at least the intermediate component S and heavy component W separated from the light components are extracted from the side stream portion or the bottom of the column, and these are further processed in the third distillation column as necessary to obtain two or more components. Each can be purified and separated.

For example, a raw material liquid composed of a mixture of acetic acid and water is azeotropically distilled in the presence of a first azeotropic agent capable of forming a minimum azeotrope with water at a boiling point of 100 ° C. or higher and capable of liquid-liquid separation from water. The vapor component of the lowest azeotrope is condensed and separated from the top of the column, the first azeotropic agent is refluxed with additional azeotropic agent, and water is fractionated and extracted. Hydrous acetic acid from the bottom of the column is further azeotropically distilled in the second distillation column in the presence of a second azeotropic agent capable of forming a minimum azeotrope with water and having a boiling point of less than 100 ° C. and capable of liquid-liquid separation from water. Then, a continuous azeotropic distillation method (for example, see Patent Document 1) is known in which the remaining water is separated from the top of the column and dehydrated purified acetic acid is recovered from the bottom of the column. In addition, as a method for continuous azeotropic distillation purification of a pyridine compound from a mixture obtained when hydrocarboxymethylating an olefin, a distillation separation method in which water is azeotropically distilled using an azeotropic agent and the azeotropic mixture is extracted from the side stream portion. (For example, see Patent Document 2) is also known. Furthermore, an example (for example, refer patent document 3) of a batch distillation method and an apparatus is also known.
Japanese Patent No. 3202150 JP-A-6-166675 Japanese Patent Publication No. 7-4485

  As described above, in the conventional continuous azeotropic distillation method or batch distillation method, the lowest azeotrope extracted from the top or the side stream of the distillation column is supercooled in the condenser part B installed outside the distillation column. Furthermore, liquid-liquid separation into an azeotropic agent component and a light component is carried out with a decanter C, and the light component D is extracted as a fractionation component at the same time as the azeotropic agent main component α ′ is refluxed to the top of the column. The above condenser B and decanter C and piping to them require a large equipment cost and installation location, but have been conventionally used for industrial large-scale equipment for distillation of a large amount of raw material solution. Has been.

  However, when it is desired to separate a small amount of high value-added components from a wide variety of raw material solutions by (azeotropic) distillation, the external condenser B, decanter C, and piping are used as raw material solutions even if the entire equipment is downsized. Therefore, it is necessary to perform a cleaning process every time of switching, and it is impossible to respond quickly to such a raw material change. In particular, tar-based fractions contain a large amount of high-value-added components that have not yet been commercialized. For example, compounds having heterocycles such as pyridine, quinoline, and indole in tar bases have attracted attention as raw materials for pharmaceuticals and agrochemicals. The development of a multipurpose distillation column as a purification and separation method is strongly desired.

  From such a current situation, the problem of the present invention is that it is easy to switch the processing of a large variety of raw material solutions and is effective for separating a small amount of high value-added components by batch or continuous (azeotropic) distillation. It is to provide a method for efficiently distilling a mixed solution of two or more components having close boiling points in the presence of an azeotropic agent at an initial stage.

As a result of intensive investigations to achieve the above-mentioned problems, the present inventors have found that the problems can be solved by an internal dry distillation multi-purpose distillation column having a condenser (condenser) inside the top of the column. completed.
That is, the multi-purpose distillation column of the internal reflux type of the present invention is
(1) In a distillation column equipped with a plurality of gas-liquid contact layers inside and a distillation kettle equipped with a reboiler at the bottom, a condenser part (condenser) of the rising vapor component is built in the top of the tower, and immediately below the condenser part A collector laminar layer having a groove-like flow function is installed in the space portion of the collector laminar layer, leaving a gap for passage of ascending steam and displacing only the descending condensate in the direction of the inner wall of the tower. The entire wall in the tower is provided with a U-shaped cross-section condensate storage section (hereinafter referred to as a collector box) that uses the peripheral wall with the upper part open, and the collector box is a concentric partition weir. It is divided into two chambers, the inner part and the outer part of which communicate with each other by a plate. One of the compartments is provided with a descending pipe for reflux liquid in the column, and the other of the compartments is provided with a distillate extraction pipe for the outside. That features It is intended to.

In addition, the batch distillation method of the present invention,
(2) An azeotrope capable of forming an azeotrope with a mixed solution of two or more components and at least one component in the mixed solution in the distillation tank equipped with a reboiler of the multipurpose distillation column described in (1) above, and performing liquid-liquid separation From the stage where the generated vapor components are condensed and liquefied in the internal condenser at the top of the tower, and after the total reflux to the tower without extraction of the distillate, The condensed liquefied liquid descending is liquid-liquid separated by the specific gravity difference between the liquid phase mainly composed of the azeotropic agent and the liquid phase which is the azeotropic component in the collector box, and the liquid phase mainly composed of the azeotropic agent is The liquid phase as an azeotropic component is withdrawn to the outside as a light boiling component from the other compartment at the same time as refluxing from one compartment.
(3) After the extraction of the light-boiling components is substantially completed, the batch-type distillation method according to (2), wherein the batch-type distillation treatment is continued by a conventional method, and the middle-boiling fraction is fractionated and extracted to the outside. It is.
(4) two or more components of the mixed solution is a pyridine residue oil after pyridine fractionation of tar in the base, at least 2,6-lutidine and β- picoline, it includes γ- picolyl down, the water as azeotropic agent Azeotropic distillation was started, and the vapor component, which is an azeotropic mixture of 2,6 lutidine and water, was condensed and liquefied at the top of the column from the stage when it reached a steady state, and liquid-liquid separation was performed by the specific gravity difference in the collector box. After refluxing in the column with water as the main component from the chamber and extracting 2,6 lutidine as the main component from the outer compartment, β- and γ-picoline were extracted as a high-boiling picoline fraction in a mixed state. The batch distillation method according to (2) or (3), in which the kettle residue of a high boiling point component is extracted from the bottom.

  According to the present invention, since the condenser part (condenser) and the liquid-liquid separator are built in the top of the column, it is not necessary to install a condenser, a decanter, a pipe, or the like outside the distillation column. When switching a variety of small quantities of raw material solutions, only the liquid-liquid replacement by washing treatment inside the distillation tower is sufficient, and the switching work is simplified. In the batch distillation method, the azeotropic mixture in the column is liquid-liquid separated in the vicinity of the condensation temperature in the initial stage, and only the heavy liquid phase mainly composed of the azeotropic agent is refluxed in the column. Efficient azeotropic distillation in the initial stage is achieved. On the other hand, the column top fraction component with less entraining of the azeotropic agent exhibits the effect of reducing the load in the subsequent purification distillation column.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic overall structural view of a multipurpose distillation column showing an example of the present invention, FIG. 2 is an enlarged cross-sectional view schematically showing a part of the top of FIG. 1, and FIG. 3 is a condensate in a collector laminar layer. It is a top view of the AA 'arrow of FIG. In FIG. 1, a multipurpose distillation column 1 of the present invention has a gas-liquid contact layer 3 composed of a plurality of shelves or a plurality of packed layers, which is comprised of any one of a bubble tray, a perforated plate tray, a valve tray and the like. Equipped with a reboiler-equipped distillation kettle 4 with a heating source such as steam. In addition, when using as a batch distillation method, the nozzle corresponding to the supply line of the raw material 2 is provided in the distillation pot 4, and the part for 1 batch processing amount shall be supplied. When used as a continuous distillation method, a raw material supply nozzle communicating with the supply line of the raw material 2 'is provided in the middle of the column and continuously supplied at a constant flow rate.

  A condenser part (condenser) 6 of an ascending steam component cooled by a cooling medium 5 such as water is built in the top of the distillation tower 1, and a space immediately below the condenser part 6 has a second part. As shown in FIG. 2, a collector laminator layer 8 having a groove-like flow function is provided, in which a gap 7 for passing ascending steam is interposed, and only the descending condensate is displaced toward the inner peripheral wall of the tower to incline and flow down. . Further, a condensate storage section (hereinafter referred to as a collector box) 9 having a U-shaped cross-section utilizing the peripheral wall is provided on the entire peripheral wall in the tower below the collector laminar layer 8 and the peripheral wall is used. Further, the collector box 9 is divided into two chambers, the inner part and the outer part, which communicate with each other by a partition weir plate 10 installed concentrically. Here, the inner compartment is provided with a descending pipe 11 for the reflux liquid in the tower to the lower gas-liquid contact layer 3, and the outer compartment is provided with a distillate extraction pipe 12 to the outside. And

  Here, when the specific gravity is larger than the distillate from which the azeotropic agent can be separated into liquid and liquid, the grooved flow tip of the collector laminar layer 8 is inclined and brought close to the inner wall of the tower, and the descending condensate is separated from the outer compartment. The light distillate having a small specific gravity in the outer compartment is separated into the outer compartment, and the main component of the azeotropic agent having a large specific gravity is separated into the inner compartment by the partition weir plate 10. When the specific gravity of the azeotropic agent is smaller than that of the distillate, the descending condensate is allowed to flow into the inner compartment without allowing the groove-like tip of the collector laminar layer 8 to reach the inner wall of the tower. The light distillate having a large specific gravity is liquid-liquid separated by the partition weir plate 10 with the main component of the azeotropic agent having a small specific gravity in the inner compartment.

  Here, when the lower gas-liquid contact layer is a shelf, the reflux liquid in the tower from the downcomer 11 is sequentially refluxed from the outlet wear to the lower shelf via the downcomer section. When the lower gas-liquid contact layer is a packed bed, the downcomer pipe 11 for the reflux liquid in the tower is connected to the header 13 and further uniformly dispersed to the lower gas-liquid contact layer 3 through the distributor and refluxed. It is like that. Furthermore, the light distillate extraction pipe 12 to the outside of the outer compartment is provided higher than the lowest position of the collector box 9 so that the light component D separated from the liquid by the partition weir plate 10 can be extracted. For this purpose, the second distillate extraction pipe 14 is provided at the lowest position as necessary, and is normally shut off by an on-off valve.

  Next, an example of the batch distillation method using the above-mentioned multipurpose distillation column of the present invention will be described. A mixed solution 2 of two or more components whose boiling points are close to the reboiler 4 and an azeotropic mixture with at least one component in the mixed solution are formed, and an azeotropic agent α capable of liquid-liquid separation is supplied and circulated and mixed by a pump And heat. The generated vapor component is gradually raised to the gas-liquid contact layer inside the distillation tower, and the lower boiling point component is gradually concentrated as it approaches the top of the tower by repeating the descending reflux liquid and gas-liquid contact. The high boiling point component is concentrated as it decreases toward the bottom of the column. The vapor component of the azeotropic mixture rising from the top gas-liquid contact portion passes through the gap 7 of the collector laminar layer 8 and is condensed and liquefied by the internal condenser 6 at the top of the tower.

  At first, after refluxing all the way into the column without removing the distillate, the initial fraction of low-boiling components is withdrawn if necessary, and the condensate liquefaction that descends as an azeotrope is collected from the steady state. In box 9, the liquid phase containing the azeotropic agent as the main component and the liquid phase as the azeotropic component are separated from each other by the specific gravity, and the liquid phase containing the azeotropic agent as the main component is dropped from one of the compartments. At the same time, the liquid phase as an azeotropic component is withdrawn to the outside as a light boiling point component D through the extraction pipe 12 from the other compartment. After the extraction of the light-boiling component D is substantially completed, the intermediate product containing the azeotropic agent, a part of the light-boiling component D and a part of the intermediate-boiling fraction S, etc. is extracted by a conventional method. The intermediate boiling component S and the like can be fractionally distilled by continuing the distillation process, and the heavy component and the like can be withdrawn to the outside as the residue component W from the bottom of the column.

  In addition, when liquid-liquid separation is performed by the partition weir plate 10 in the collector box, the lower the mutual solubility between the azeotropic agent and the light distillate, the higher the solution concentration in the upper and lower layers where the liquid-liquid separation is performed. Desirable for external extraction with reflux or high solution concentration. Therefore, it is desirable to obtain the relationship between the mixing temperature in the collector box and the mutual solubility in advance and maintain the optimum temperature. As a result, since the azeotropic agent in a high concentration state is refluxed in the column, the efficiency of the azeotropic distillation in the initial stage can be increased. On the other hand, the high-concentration column top fraction component with less entraining of the azeotropic agent exhibits the effect of reducing the load in the subsequent purification distillation column.

  The above-described multi-purpose distillation column of the present invention is not only suitable for batch-wise or continuous azeotropic distillation depending on the type of raw material solution, but also a normal distillation that does not use an azeotropic agent. It can also be used for processing. In the case of using an azeotropic agent that does not separate liquid and liquid, or in the case of normal distillation treatment, naturally, liquid / liquid separation does not occur in the collector box, and part of it is refluxed in the column and the rest is the fraction obtained from the top of the column. As withdrawing. The raw material solution that can be treated in the internal dry distillation multipurpose distillation column of the present invention is not particularly limited, but each petroleum-based or tar-based fraction contains a large amount of high-value-added components that have not yet been commercialized. Therefore, these high value-added components are preferably used for separation by distillation.

  Hereinafter, the present invention will be described in more detail with reference to an example in which a mixed solution of two or more components is treated with pyridine residual oil after fractionating pyridine from a tar base separated from coal tar or coal liquefied oil. This invention is not limited at all by this Example.

Example 1
A tar base oil separated by coal tar distillation / acid extraction, etc., and pyridine residual oil (CPB) comprising the composition shown in Table 1 below after separation of pyridine by distillation treatment is a component having an approximate boiling point It cannot be separated as a high concentration component by a normal distillation method. Therefore, this pyridine residue (CPB) was subjected to batch distillation according to the block flow shown in FIG.

  Of the block flow shown in FIG. 5, distillation (1) and distillation (2) employ the batch distillation method using the multipurpose distillation column of the present invention described in FIGS. A batch distillation method using a distillation tower is employed. In particular, in the distillation (2), water is mixed as an azeotropic agent in the initial stage and azeotropically distilled. The mutual solubility curve of 2,6-lutidine / water in the upper layer and the lower layer, which are separated from each other under the temperature conditions in the collector box, is as shown in FIG. FIG. 6 shows that when the azeotropic temperature of both is 96 ° C., the concentration of 2,6-lutidine in the upper layer is the maximum, and the concentration of water in the lower layer is the maximum. Therefore, in this example, the distillation was performed while maintaining the temperature in the collector box at 96 ° C. in the azeotropic distillation step of distillation (2). The distillation conditions in distillation (1), distillation (2), and distillation (3) at this time are as shown in Table 2 below.

  Table 3 shows the properties of product 2,6-lutidine obtained by processing under the distillation conditions shown in Table 2 according to the block flow shown in FIG. 5, and Table 4 shows the properties of high-boiling picoline. In both cases, products exceeding the standard quality target were obtained.

1 is an overall schematic diagram of a multipurpose distillation column showing an example of the present invention. It is an expanded sectional view which shows a part of tower top part of FIG. 1 typically. It is an A-A 'arrow top view of FIG. 2 which shows the flow of the condensate in a collector laminar layer. It is a schematic block diagram of the conventional azeotropic distillation tower. It is a block flow which shows the distillation process of a pyridine residual oil (CPB). It is a mutual solubility curve of 2,6-lutidine / water in the upper layer and the lower layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Multi-purpose distillation column 2 Raw material supply line 3 Gas-liquid contact layer 4 Distiller with reboiler 5 Cooling medium 6 Condenser part 7 Gap for passage of rising steam 8 Collector laminar layer 9 Collector box 10 Partition weir plate 11 Lowering for reflux liquid in the tower Pipe 12 Distillate extraction pipe 13 Header 14 Second distillate extraction pipe

Claims (6)

  In a distillation column equipped with a plurality of gas-liquid contact layers inside and equipped with a distillation tank with a reboiler at the bottom, a condenser part (condenser) for the rising vapor component is built in the top of the tower, and a space directly under the condenser part Is provided with a collector laminar layer having a grooved flow function that displaces and flows only the descending condensate in the direction of the inner wall of the tower while leaving a gap for passage of the rising steam, and in the tower below the collector laminar layer The entire peripheral wall is provided with a U-shaped cross-section condensate storage part (hereinafter referred to as a collector box) that uses the peripheral wall with the upper part open, and the collector box is further bottomed by a concentric partition weir plate. Is divided into two chambers that communicate with each other, one of the compartments is provided with a descending pipe for the reflux liquid in the column, and the other of the compartments is provided with a pipe for extracting the distillate to the outside. To Part reflux type of multi-purpose distillation column. 2. A mixed solution of two or more components and an azeotropic agent capable of forming an azeotrope with at least one component in the mixed solution and separating the liquid into a liquid are supplied to the multi-purpose distillation column equipped with a reboiler. The vapor component generated is condensed and liquefied by the internal condenser at the top of the tower, and after the total reflux to the tower without extraction of the distillate, the condensate liquefaction descends from the steady state. In a collector box, the liquid phase is separated into a liquid phase mainly composed of an azeotropic agent and a liquid phase that is an azeotropic component by a specific gravity difference, and the liquid phase mainly composed of the azeotropic agent is in one compartment. A batch distillation method characterized in that the liquid phase as an azeotropic component is withdrawn to the outside as a light boiling component from the other compartment at the same time as refluxing from the column. After the removal of the light-boiling components is substantially complete, batch distillation process according to claim 2 withdrawn to the outside by fractionating the intermediate boiling fraction followed by a conventional method batch distillation process. Two or more components of the mixed solution is a pyridine residue oil after pyridine fractionation of tar in the base, at least 2,6-lutidine and β- picoline, include γ- picolyl down, azeotropic distillation with water as an azeotropic agent The vapor component, which is an azeotropic mixture of 2,6 lutidine and water, is condensed and liquefied at the top of the tower from the stage where it reaches a steady state, and liquid-liquid separation is performed by the specific gravity difference in the collector box, and water is separated from the inner compartment. And 2,6 lutidine as the main component are extracted from the outer compartment, and β- and γ-picoline are extracted as a high-boiling picoline fraction in a mixed state. The batch distillation method according to claim 2 or 3, wherein the residue of the high boiling point component is withdrawn. Batch distillation process according to claim 4 for liquid-liquid separation by condensation liquefied material is specific gravity difference between the 2,6-lutidine and water in the collector box.   6. The batchwise distillation according to claim 4 or 5, wherein 2,6 lutidine extracted from the top fraction is distilled in a distillation column in a separate step to obtain at least water to obtain purified 2,6 lutidine. Law.

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