JP2006069959A - Crystal purification method and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple method for the purification of crystals by using a purification column and provide a purification apparatus having a simple structure free from a driving part in the column. <P>SOLUTION: The crystal purifying apparatus has a crystal filling part B formed in a vertical cylindrical column body of a purification column, a feeding part 23 to feed stock crystals to the crystal filling part and an extraction part 28A to extract a liquid heating medium containing impurities and the purified crystals from the crystal filling part B in liquid state. The feeding part 23 is positioned at or near the top of the column body 11 and the extraction part 28A is positioned at the bottom part of the column body 11. A filtering apparatus 21 for passing the liquid heating medium containing impurities and the purified crystals in liquid state is placed above the extraction part 28A, and the stock crystals are heated and melted with a heating means at the upper part of the column body 11. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a crystal purification method and an apparatus therefor, which purify a raw material crystal containing impurities by utilizing the sweating action of the crystal.

  2. Description of the Related Art Conventionally, there are various types of crystal purification methods, and a method and apparatus for continuously purifying a crystalline substance containing impurities using a purified melt of the crystal component or other solvent. For example, what was disclosed by patent document 1 is known.

  This known method is carried out using a crystal purification apparatus as shown in FIGS. 2, 3 and 4 of the accompanying drawings. As shown in FIG. 4, the apparatus is a vertical cylinder having a cross section as shown in FIG. 4 and is provided with a stirrer 3 and 3 ′ at the center of each of the circles on both sides. . Specifically, as shown in FIGS. 2 and 3, the heating / melting device 4 or the solvent flow-down device and the purified product outlet 5 are provided at the top of the tower, the filtration device 6 and the impurity outlet 7 are provided at the bottom, and crystals are provided in the tower. 2 stirrers 3 and 3 'having both the function of pushing up and transporting and the function of unraveling the crystals. As shown in FIG. 2, the stirrer of this apparatus is arranged so that the blades of the combined stirrer are located between the blades of the other stirrers adjacent to each other. Are engaged with each other. By rotating the stirrer in the opposite direction or the same direction, the crystals in the tower are transported up.

In order to purify a crude crystal containing impurities by using a melt of the target crystal component by the crystal purification apparatus having such a configuration, the raw material crude crystal is supplied into the tower from the charging port at the bottom of the purification tower, It is lifted toward the top of the tower by a stirrer provided inside. At that time, the stirrer unraveles the crystals and transports and raises the inside of the purification tower while preventing the crystals from rising as a lump or adhering to the stirring blades. Thus, the crystals that have reached the top of the tower are melted in the required amount to become a refluxing melt, descended in the purification tower by gravity, and the crystals that have reached the top of the tower while being washed with this melting liquid have the desired purity. Taken from. The impurities contained in the raw crystal are lowered in the purification tower, separated by a filtration device, and removed from the impurity outlet.
JP-B 47-40621

  However, the refining device disclosed in Patent Document 1 requires a stirrer because the raw material crystals are transferred upward from the lower part of the purifying tower by the stirrer, which complicates the device. As a result, equipment costs increase and maintenance is troublesome.

  It is an object of the present invention to provide a crystal refining method and an apparatus therefor, in which a drive unit such as a stirrer is unnecessary, the structure is simple, and high-purity crystals can be easily obtained.

  The present invention relates to a method for purifying a raw material crystal in a purification tower and an apparatus therefor. In the method of the present invention, a raw material crystal particle to be purified is packed into a purification tower having a filtration device at the bottom, and a liquid heating medium is used. The raw material crystals are purified by flowing down through the packed bed of crystal particles in the purification tower, and then the purified crystals in the purification tower are extracted out of the purification tower.

  In the present invention, when the liquid heating medium flows down through the packed bed of raw material crystal particles, the impurities in the raw material crystal particles are transferred to the liquid heating medium by perspiration, and the raw material crystal particles are purified.

  On the other hand, the liquid heating medium that contains impurities from the raw material crystal particles flows down in the packed bed of crystal particles, reaches the filtration device at the bottom of the purification tower, and is separated from the purified crystal particles by the filtration action here. The impurities are extracted out of the purification tower, for example, into an extraction tank. That is, since the purified crystal is a particle, it remains on the filtration device without passing through the filtration device, and the liquid heating medium passes through the filtration device with impurities.

  When the flow of the liquid heating medium is finished, that is, when the purification operation is finished, the purified crystal particles remain in the upper part of the filtration device in the purification tower, and the liquid heating medium containing impurities accumulates in the extraction tank.

  In the present invention, if at least one of pressurizing and pressing the liquid heating medium from the upper part of the purification tower and sucking under reduced pressure from the lower part of the purification tower is performed, the liquid heating medium in the packed bed of raw material crystals Promote the flow down.

  In the present invention, the liquid heating medium may be a melt obtained by melting a part of the crystal particles in the purification tower, a mother liquor at the time of manufacturing the raw material crystal, or a poor solvent for the raw material crystal. It can also be.

  In the present invention, the purified crystal in the purification tower can be melted and drawn out as a purified melt through the filtration device to the outside of the purification tower, or the purified crystal can be dissolved in a solvent and taken out of the purification tower through the filtration device. .

  In the present invention, if purification and crystallization are repeated, the purified crystal purity can be increased.

  With respect to the apparatus for carrying out the above-described purification method, the present invention includes a crystal packing part formed in the columnar column main body of the purification tower, and a supply part for supplying raw crystal to the crystal packing part And a crystal heating apparatus having a liquid heating medium containing impurities and an extraction part for extracting purified crystals in liquid form from the crystal packing part, wherein the supply part is at or near the top of the tower body, and the extraction part is a tower. In addition to being provided at the bottom of the main body, a liquid heating medium containing impurities and a filtration device that permeates purified crystals in liquid form are provided above the extraction part, and the raw material crystals are heated at the top of the tower main body. It has a heating means for melting.

  In the present invention, the heating means has a heating chamber formed in a part of the upper space of the tower body, and can be formed so as to supply a heating medium from the outside to the heating chamber. The heating chamber can be divided into a plurality of sub chambers in the vertical direction, and supply of the heat medium to each sub chamber can be controlled.

  In the present invention, in order to promote the flow of the liquid heating medium in the packed bed of raw material crystal particles, a pressure pump for pressurizing the space at the top of the tower is connected during supply, or An extraction tank can be provided below, and a suction pump for decompressing the upper space in the extraction tank can be connected to the extraction tank.

  In the present invention, as the raw material crystal for purification, a particulate crystal crystallized by suspension crystallization, for example, cooling crystallization in a jacketed tank is suitable.

  In the present invention, as a form of packing the raw crystal into the purification tower, the mother liquor may be removed in advance to fill only the crystal particles. However, the crystal and mother liquor are packed in the purification tower by filling as a slurry consisting of crystals and mother liquor. It is preferable to separate. The reason for this is that the slurry has good fluidity so that it can be easily filled, and that the slurry can be easily connected to the preceding crystal purification apparatus.

  In the present invention, the melt obtained by melting a part of the crystal particles as the liquid heating medium is preferably one in which crystals having a purity higher than the purity of the crystals in the purification tower are dissolved. But you can. Further, the solvent for dissolving the purified crystal for extracting the purified crystal may or may not contain the crystal to be purified as a solute, but the temperature is substantially the same as the temperature of the crystal packed bed in the purification tower. A solvent containing a crystal component at a substantially saturated concentration is preferable. The smaller the impurities other than the crystal component, the more advantageous the solvent is to obtain a high-purity crystal, but a mother liquor at the time of producing the crystal to be purified can also be used.

  In the present invention, examples of the filtering device include a perforated plate, a nonwoven fabric, and a wire mesh.

  In the present invention, the purified crystal can be extracted by melting the crystal and extracting it in a liquid state because the apparatus is simple and easy to operate. Good. In the case of extracting the purified crystal in liquid form, after the liquid heating medium containing impurities accumulated in the take-out tank is transported and emptied by crystal purification operation (flowing in the packed bed of crystal particles of the liquid heating medium), the purified crystal Can be extracted in a liquid form as a melt or solution into an extraction tank. When the purified crystal is extracted as a final product, it is preferable to extract by melting or solid. In the case of multistage implementation in which the crystal to be purified is produced by crystallization from a solution and the crystallization and purification are repeatedly applied to improve the purity, the crystal may be dissolved in a solvent and extracted.

  In the present invention, as described above, since the raw material crystal particles are packed in the purification tower, the liquid heating medium is allowed to flow down in the packed bed, and the raw material crystal is purified by the sweating action, the purification is easily performed. In addition, a mechanical drive unit is not required in the apparatus, which simplifies the apparatus and reduces equipment costs, and facilitates subsequent maintenance. Furthermore, it is difficult to increase the size of the stirrer used in the conventional apparatus, and the apparatus of the present invention that does not have such a stirrer can easily cope with a large apparatus.

  Hereinafter, an embodiment of the present invention will be described based on FIGS. 1A and 1B of the accompanying drawings.

  In FIG. 1A, the purification tower 10 has a vertically long cylindrical tower body 11, and the tower body 11 is sealed by a top plate portion 12 and a base plate portion 13.

  The internal space of the tower body 11 is divided into an upper crystal melting part A and a lower crystal packing part B.

  In the crystal melting part A, a plurality of tubular bodies 14 extending in parallel with the longitudinal axis of the tower body 11 are arranged in a state of being spaced apart from each other (see also FIG. 1B). These tubular bodies 14 are opened at the upper and lower ends.

  In the crystal melting part A, the space between the plurality of tube bodies 14 and the tower body 11 forms a heating chamber 16 as a heating means, and the heating chamber 16 is located at a plurality of positions in the vertical direction and the horizontal partition wall 15. Are divided into a plurality of sub chambers 16A to 16E. In other words, the plurality of tubular bodies 14 opening up and down pass through the plurality of sub chambers 16A to 16E formed by the plurality of horizontal partition walls 15A.

  A heating medium supply pipe 18 that supplies a liquid or gaseous heating medium from a supply source (not shown) is connected to each of the sub chambers 16A to 16E via a valve 17. A heat medium discharge pipe 20 for discharging the heat medium is connected to each of the sub chambers 16A to 16E through a common valve 19.

  The crystal packing part B forms a simple cylindrical space in the tower body 11 and communicates with the tube body 14. For example, a perforated plate 21 is provided at the lowest position of the crystal filling portion B as a filtration device. The pore diameter of the perforated plate 21 is such that purified crystal particles do not permeate.

  The tower body 11 is provided with a heat insulating material 22 on the outer peripheral surface in almost the entire height region extending over the crystal melting part A and the crystal packing part B.

  A raw material supply pipe 23 for supplying a raw material crystal to be purified is connected to the top plate portion 12 of the tower body 11 via a valve 24. The raw material supply pipe 23 is connected to a pressurizing pump 25 for pressurizing the space immediately below the top plate 12. Further, a sub supply pipe 26 is connected to the top plate 12 as necessary. In the present embodiment, the raw material crystal supplied from the raw material supply pipe 23 fills the space in the crystal filling part B and the space in the tube 14 of the crystal melting part A, and then from the heat medium in the sub chambers 16A to 16E. The raw material crystals in the tube body 14 are melted by the heat and flow down to the crystal packed bed B in the crystal packed portion B. That is, the raw material crystal in the crystal melting part A melts and becomes a melt, and acts as a liquid heating medium on the raw material crystal in the crystal filling part B. However, the liquid heating medium can be other media. When using another liquid heating medium, the liquid heating medium is supplied from the sub supply pipe 26.

  A take-out tank 27 is installed below the tower main body 11, and is connected to the bottom of the tower main body 11 via a valve 28 through an extraction pipe 28 </ b> A serving as an extraction part. The take-out tank 27 is connected to a suction pump 29 that depressurizes the upper space in the tank. An extraction pipe 30 is connected to the extraction tank 27 at the bottom.

  In such an apparatus of the present embodiment, the raw crystal is purified in the following manner.

  (1) First, the valve 24 is opened with the valve 28 closed, and the raw material crystal to be purified is supplied from the raw material supply pipe 23. The raw material crystal fills the tube 14 after filling the space of the crystal filling part B through the plurality of tubes 14. At this time, the supply of the raw material crystals is stopped and the valve 24 is closed.

  (2) Next, each valve 17 of the sub chambers 16 </ b> A to 16 </ b> E is appropriately opened, and a high-temperature heat medium is supplied from the heat medium supply pipe 18. This heat medium may be liquid or gas. When the temperature drop due to heat exchange of the heat medium in the sub chambers 16A to 16E is large, the valve 19 is appropriately opened, the heat medium is circulated, and the high temperature heat medium is taken in sequentially. When the heat of the heat medium is sufficient, only some of the valves 16A to 16E are opened to control the supply heat amount of the heat medium.

  (3) The heat of the heat medium heats the raw material crystal in the tube body 14 through the tube wall of the tube body 14, and the raw material crystal is heated and melted to become a liquid state.

  (4) The liquid raw material in the crystal melting part A flows down into the raw material crystal layer in the crystal filling part B as a liquid heating medium, and the raw material crystal in the crystal filling part B is heated and the impurities are liquid heating medium due to sweating action. As a result, purification is performed. The liquid heating medium containing impurities passes through the perforated plate 21 as a filtration device, passes through the opened valve 28, and is stored in the take-out tank 27. On the other hand, since the purified crystal is a particle, it remains on the porous plate 21. In order to promote the flow of the liquid heating medium in the crystal packing part B, the upper space of the tower body 11 is pressurized by the pressure pump 25 with the valve 24 closed, or the valve 28 is opened. In this state, the space below the perforated plate 21 may be decompressed by the suction pump 29. Of course, pressurization by the pressurization pump 25 and decompression by the suction pump 29 may be performed simultaneously.

  (5) Thus, when the purification is completed, the purified crystal is extracted out of the tower. The purified crystal can be extracted in a solid state from an open / close door (not shown) provided in the crystal filling part B. However, the purified crystal is heated to melt or dissolved in a solvent to form a liquid, and After that, it can also flow down to the take-out tank 27 and be extracted in liquid form. As an example of heating and melting the purified crystal and extracting it in liquid form, the liquid heating medium containing impurities in the extraction tank 27 is transferred to another storage tank or the like via the extraction pipe 30 to completely empty the extraction tank 27. After that, a heated crystal (not shown) provided in the crystal packing part B of the purification tower is used to heat the purified crystals existing in the crystal packing part B to melt a part thereof into a liquid and take out through the perforated plate 21. Extract to 27. The refined crystal melt in the take-out tank 27 is taken out to the crystal filling part B through the take-out pipe 30, the sub supply pipe 26 at the top of the purification tower, and the crystal melting part A of the purification tower. The purified crystal melt supplied to the crystal filling part B is heated while passing through the crystal melting part A to become a high-temperature melt, and heat is applied to the purified crystal in the crystal filling part B to melt it to obtain a melt. . When there are no more solid purified crystals in the crystal packing part B, the supply of the purified crystal melt from the take-out tank 27 is stopped, and the extraction of the purified crystals is completed.

  When the purified crystals in the crystal packing part B of the purification tower are dissolved in a solvent and extracted in a liquid state, for example, the solvent for dissolving the purified crystals is supplied to the crystal packing part B through the crystal melting part A from the auxiliary supply pipe 26 at the top. Then, the purified crystal can be dissolved in the solvent and extracted into the extraction tank 27 through the perforated plate 21. The solvent supplied at this time can also be heated in the crystal melting part A.

  (6) As described above, the raw material crystals in the tube 14 in the crystal melting part A are melted to form a liquid heating medium. However, the liquid heating medium may be another type of medium. In this case, the medium is supplied from the sub supply pipe 26.

  (7) In the present embodiment, the purity of the crystals can be increased by providing a plurality of purification towers 10 and repurifying the purified crystals in the next purification tower.

  Analysis of crystals and filtrate in this example was performed using gas chromatography. In the other examples described later and the reference examples to be compared, analysis was similarly performed using gas chromatography.

  Crystal refinement is performed as follows using a cylindrical refining tower as shown in FIG. 1 having a metal mesh with a mesh opening of 0.5 mm as a filtration device at the bottom and a crystal packing portion having an inner diameter of 100 mm and a height of 1500 mm. went.

  A slurry composed of 60.0% by mass of paradichlorobenzene and 40.0% by mass of orthodichlorobenzene is cooled to 5 ° C., and a crystallization slurry is supplied to the purification tower from the upper part of the purification tower and gravity filtered to obtain crystals and liquid. And the crude crystals were filled up to almost the top of the purification tower (this step is referred to as the crude crystal filling step).

  Next, steam at 100 ° C. is poured as a heating medium into the jacket of the crystal melting part of the purification tower (corresponding to the sub chamber 16 in FIG. 1) to heat and melt the crude crystals in the upper part of the purification tower, and the crystal packed bed as liquid The inside flowed down. The liquid was recovered as a filtrate containing impurities (orthodichlorobenzene) through a wire mesh as a filter at the bottom of the purification tower (this process is referred to as a crystal purification process).

  The purified crystals in the purification tower are extracted from the purification tower in a liquid state by flowing steam at 100 ° C. through a jacket provided on the outer periphery of the crystal packing section of the purification tower (this process is called a purification crystal extraction process). ).

  As a result, 10.7 kg of purified crystals and 9.8 kg of filtrate were obtained.

  The purified crystals obtained had a paradichlorobenzene content of 99.99% and the filtrate had a paradichlorobenzene content of 82.60%.

  The time required for one cycle of the purification operation was 130 minutes in total, 30 minutes for the crude crystal filling step, 80 minutes for the crystal purification step, and 20 minutes for the purified crystal extraction step.

  Accordingly, the production capacity of the purified crystals in this example can be calculated as 4.9 kg / h since 10.7 kg of purified crystals were produced in 130 minutes.

  Using the same crude crystals as in Example 1, crystal purification was carried out in the same manner as in Example 1 except that the filtrate was collected while sucking at 20 kPa from the bottom of the purification tower in the crystal purification step.

  As a result, 10.4 kg of purified crystals and 10.1 kg of filtrate were obtained.

  The purified crystals obtained had a paradichlorobenzene content of 99.98% and the filtrate had a paradichlorobenzene content of 82.60%.

  The time required for one cycle of the refining operation was 30 minutes for the crystal filling step, 20 minutes for the crystal purification step, and 20 minutes for the purified crystal extraction step, for a total of 70 minutes.

  Therefore, the production capacity of the purified crystals in this example can be calculated as 8.9 kg / h since 10.4 kg of purified crystals were produced in 70 minutes.

  The power required for suction from the bottom of the purification tower is 0.5 kW, which is calculated to be 0.016 kWh when converted to energy per kg of purified crystals.

  The slurry used in Example 1 was packed in a purification tower in the same manner as in Example 1.

  Next, 8 kg of hot water of 98 ° C. was supplied to the crystal packed bed as a liquid heating medium from the upper part of the purification tower, and the filtrate was recovered from the lower part of the purification tower.

  The purified crystals remaining in the purification tower were heated and melted in the same manner as in Example 1 and extracted in liquid form. The extracted purified crystal was 11.2 kg.

  The purified crystal had a paradichlorobenzene content of 99.99%.

  The time required for one cycle of the purification operation is 30 minutes for the crystal filling step, 80 minutes for the crystal purification step, and 20 minutes for the purified crystal removal step, which is 130 minutes in total. The calculated production capacity of the purified crystals of this example was 5.2 kg / h.

  The hot water which is a liquid heating medium in this embodiment hardly dissolves paradichlorobenzene, orthodichlorobenzene and a mixture thereof, and is a poor solvent for these substances. Even if such a poor solvent is used as a liquid heating medium, the crystals can be purified by perspiration. As described above, the liquid heating medium used in the present invention is not limited as long as it can flow through the raw material crystal particle packed bed and heat the raw material crystal to cause a sweating action. It doesn't matter.

[Reference example]
A conventional heat-melting apparatus shown in FIGS. 2 to 4 and two sets rotating in opposite directions to a 1500 mm-long metal cylinder having a saddle-shaped cross section in which a circle having a diameter of 80 mm is connected at a center distance of 60 mm The crude crystals obtained by filtering the slurry used in Example 1 were fed at 17.6 kg / h from the lower part of the purification tower, and 9.2 kg of the purified crystals were supplied from the upper part of the purification tower. / H.

  The purified crystal had a paradichlorobenzene content of 99.99%.

  The production capacity of the purified crystals in this reference example is 9.2 kg / h.

  In addition, the operation of the crystal purification apparatus of the reference example requires 0.2 kW for continuous supply of crude crystals and 0.2 kW for the stirrer in the purification tower, which is 0.043 kWh when converted to energy per 1 kg of purified crystals. Calculated.

  As is clear from the Examples and Reference Examples, although purified crystals having almost the same purity as the conventional method are obtained, the purifier used in the practice of the present invention compared to the conventional method includes a stirrer and the like. Since there is no drive unit, the structure is simple and suitable for increasing the size of the device.

  In addition, energy consumption is less than when using a conventional apparatus having the same production capacity.

  The present invention is not limited to the illustrated apparatus, and various modifications can be made. For example, the crystal melting part uses a plurality of tubes to uniformly flow the liquid heating medium to the crystal packing part, but without using the tubes, a porous plate, a nonwoven fabric, a wire mesh, etc. By providing, the liquid heating medium can be made to flow uniformly. Furthermore, it is also possible to spray a liquid heating medium with a spray device.

1 shows an apparatus according to an embodiment of the present invention, in which (A) is a longitudinal sectional view, and (B) is a BB transverse sectional view in (A). It is a longitudinal cross-sectional view which shows a conventional apparatus. It is an AA longitudinal cross-sectional view in FIG. FIG. 3 is a BB cross-sectional view in FIG. 2.

Explanation of symbols

10 Purification tower 11 Tower body 16 Heating chamber (heating means)
16A-E Sub chamber 21 Filtration device 23 Supply section (raw material supply section)
25 Pressure pump 27 Extraction tank 28A Extraction part (extraction pipe)
29 Suction pump A Crystal melting part B Crystal filling part

Claims (11)

  In the method of purifying the raw material crystal in the purification tower, the raw material crystal particles to be purified are packed into a purification tower having a filtration device at the bottom, and the liquid heating medium is caused to flow down in the packed bed of crystal particles in the purification tower. And then purifying the raw material crystals, and then extracting the purified crystals in the purification tower out of the purification tower.   2. The crystal purification method according to claim 1, wherein at least one of pressurizing and pressurizing the liquid heating medium from the upper part of the purification tower and sucking under reduced pressure from the lower part of the purification tower is performed.   The crystal purification method according to claim 1 or 2, wherein the liquid heating medium is a melt obtained by melting a part of crystal particles in the purification tower.   The crystal purification method according to claim 1 or 2, wherein the liquid heating medium is a mother liquor at the time of producing the raw material crystal.   The crystal purification method according to claim 1 or 2, wherein the liquid heating medium is a poor solvent for the raw material crystals.   The crystal purification method according to any one of claims 1 to 5, wherein the purified crystal in the purification tower is melted and extracted out of the purification tower as a purified melt.   The crystal purification method according to any one of claims 1 to 5, wherein the purified crystals in the purification tower are dissolved in a solvent and extracted out of the purification tower.   The crystal purification method according to any one of claims 1 to 7, wherein purification and crystallization are repeated to increase purified crystal purity.   A crystal packing part formed in a vertical cylindrical column body of a purification tower, a supply part for supplying raw crystal to the crystal packing part, a liquid heating medium containing impurities from the crystal packing part, and a purified crystal In a crystal refining apparatus having an extraction part for extraction in liquid form, a supply part is provided at or near the top of the tower body, and an extraction part is provided at the bottom part of the tower body, and above the extraction part A crystal having a heating device for heating and melting the raw material crystal at the upper part of the tower body, provided with a liquid heating medium containing impurities at the position and a filtration device that allows the purified crystal to pass through in a liquid state Purification equipment.   The crystal purification according to claim 9, wherein the heating means has a heating chamber formed in a part of the upper space of the tower body, and is configured to supply a heating medium from the outside to the heating chamber. apparatus.   The crystal purification apparatus according to claim 10, wherein the heating chamber is divided into a plurality of sub chambers in the vertical direction, and supply of a heat medium to each sub chamber is controllable.

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