JPH08196802A - Column type crystallization apparatus having inclined refining section - Google Patents

Abstract

PURPOSE: To accelerate the settlement of crystal particle groups, to attain good contact between solid and liquid and to enable efficient refining by inclining the entire part of a crystallization column or the refining section thereof with a perpendicular line. CONSTITUTION: The crystal particle groups of a low settling speed hardly form the dense layers of the crystal particle groups. the crystallization apparatus is, thereupon, arranged by inclining a housing 1 by θ to the perpendicular line. The θ is max. 60 deg.. Approximately the lower half part 2 of the housing 1 is constituted as the refining section and approximately the upper half part 3 thereof constitutes a crystallization section. The liquid 4 to be treated is supplied from the intermediate part of the refining section 2 and the crystallization section 3 and the resulted crystal 5 is removed from the bottom of the housing 1. The discharged liquid 6 overflows from the top end edge of the housing 1. On the other hand, the inclined column increases the settling rate but the counter-current contacting effect between the solid and the liquid lowers. The simultaneous execution of the scraping action of the inside wall by a rotary scraper is possible as well in order to maintain the good contact by gently stirring the slurry in the column.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel crystallizer, and more particularly to a tower-type crystallizer having a gradient refining section which can be used in a field requiring a high degree of separation / purification. .

[0002]

2. Description of the Related Art In recent years, the demand for advanced separation / purification has increased, and therefore purification by crystallization operation has been demanded on an industrial scale. Various crystallization towers (column type crystallization apparatus having a distribution of concentration and temperature in the axial direction within the apparatus) for purification are known. In most of these crystallization towers, the gravity-precipitating crystal particles are brought into countercurrent contact with the reflux liquid to enhance the purification efficiency. Therefore, it has been considered difficult to separate and purify in a system where the difference in density between solid and liquid is small. Crystallizers have been developed for the purpose of purifying organic substances, but in the case of organic substance solutions, the use of crystallizers is limited because the density difference between solid and liquid is generally small, and good crystal particles are also available. It is difficult to obtain (spherical and large-sized particles).

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a tower-type crystallizer suitable for advanced refining based on a principle completely different from the conventional crystallizer.

[0004]

The present invention provides a crystallizer having at least a refining section and a crystallization section, characterized in that at least the refining section is inclined with respect to a vertical line. provide.

The refining section is preferably tilted up to 60 degrees from the vertical line. If this inclination angle exceeds 60 degrees, an increase in the settling speed of crystal particles cannot be expected, which is not preferable. In the present invention, the inclination angle θ from the vertical line should not be zero. The inclination angle θ is preferably selected from 20 to 60 degrees depending on the type of liquid to be treated and the size of the apparatus.

In one embodiment of the present invention, the refining section comprises a hollow housing having a crystal recovery section at the bottom. It is preferable that the hollow housing has a circular inner cross-sectional shape,
It may be a polygon such as a quadrangle.

It is preferable to provide a means for scraping the crystals attached to the inner wall of the hollow housing. In the case of a hollow housing having a circular cross section, a rotating scraper can be used as the scraping means. The rotating scraper must be rotated at a low speed that does not adversely affect the crystallization operation. As the scraping means, any known mechanism other than the rotary scraper can be used.

In a preferred embodiment of the present invention, the purifying section and the crystallization section are constituted by a single continuous hollow housing,
A supply unit for the liquid to be treated is provided between the purification unit and the crystallization unit. In another embodiment of the invention, the crystallization part is provided separately and the slurry coming from the crystallization part is fed to the top of the refining part.

[0009]

[Function] It is difficult to form a dense layer of crystal particles in a group of crystal particles having a low sedimentation speed (low density difference, small particle size, non-granular). This is made more difficult by the presence of rising reflux. The present inventor utilizes the principle of an inclined plate settling tank by inclining the wall of the crystallizer with respect to the vertical line, and distinguishes the settling particle group and the rising exclusion liquid flow from the above. I thought about solving the drawbacks.

On the other hand, the inclined column increases the sedimentation velocity, but the countercurrent contact action between solid and liquid is reduced. Therefore, in the present invention, it is preferable to gently stir the slurry in the tower to maintain good contact. The stirring for this can be performed simultaneously by a rotary scraper that scrapes the inner wall.

In the crystallizer of the present invention, the entire crystallizing tower or the refining section thereof is inclined to promote the settling of the crystal particle group, and the liquid and the crystal group are gently mixed so that the solid-liquid interval is improved. Contacted. As a result, efficient purification is performed.

The present invention will be described below with reference to the accompanying drawings. FIG. 1 is a principle view of the present invention. In this crystallizer, a housing 1 is arranged with an inclination of θ with respect to a vertical line. This θ is at most 60 degrees. The lower half 2 of the housing 1 serves as a refining section, and the upper half 3 thereof constitutes a crystallization section. The liquid to be treated 4 is supplied from an intermediate portion between the purification unit 2 and the crystallization unit 3, the obtained crystals 5 are extracted from the bottom of the housing 1, and the exclusion liquid 6 overflows from the upper edge of the housing 1.

FIG. 2 is a conceptual sectional view of a crystallizer used in a preliminary experiment conducted to confirm the effect of the present invention. In this preliminary experiment, the transparent glass tube 1 was used to observe the crystal growth from the outside by total reflux operation (without supply / discharge). The bottom of the glass tube 1 was covered with a plug 26, and this plug was closed. A heater 25 is wound around the protrusion formed at the center of the inside of 26. A cooling jacket 3a is wound around the upper part of the glass tube 1, and the rotary scraper 7 is rotatably supported inside the glass tube 1.

FIG. 3 is a conceptual cross-sectional view of one embodiment of the crystallizer of the present invention. In this crystallizer, a temperature control jacket 3a is provided on the upper portion of the housing 1 constituting the crystallization part.
And a heater 2a for melting is attached to the lower end of the housing 1 which constitutes the refining section 2. A rotary scraper 7 for scraping off the crystals adhering to the inner wall of the housing 1 is rotatably supported in the housing 1 by an appropriate means (not shown). Liquid supply / drainage (4, 5, 6) is performed according to the principle diagram of the present invention shown in FIG. The rotary scraper 7 does not collide with the supply pipe 4. In the illustrated rotary scraper 7, rods extending in a radial direction from the rotary shaft are alternately attached along the axial direction of the rotary shaft, and a spatula for scraping the entire inner wall of the housing 1 is attached to the tip of each rod.

The shape of the rotary scraper 7 is not limited to this, and can be variously selected depending on the type of the liquid to be treated, the size of the crystallizer, and the like. For example, a spiral scraper in which a spiral ribbon or a spiral wire is sequentially supported by the tips of the rods can be used. In any case,
It is important that the rotating scraper 7 does not adversely affect the settling of the crystal particles in the housing 1 and the rise of the reflux liquid.

FIG. 4 is a modification of FIG. 3, in which the crystallization part of FIG. 3 is replaced by a crystallization tank 8. In this case, the liquid to be treated 4 "is supplied to any crystallization tank 8 equipped with a simple stirrer, and the solution 10 containing the crystal particle group generated (grown) in the crystallization tank 8 is supplied to the supply pipe 4". Is supplied to the upper part of the housing 1 via the '. The drainage liquid 6 is provided above the position of the supply pipe 4'.

FIG. 5 shows another modification of FIG. 3, in which the liquid 23 to be treated is supplied through an internal supply pipe coaxial with the rotary shaft 21 and sent into the housing 11 through a supply port 22. .
In the figure, 24 is a blade attached to the rotary shaft 21 constituting the rotary scraper, 40 is a crystal recovery port, and 50 is an exclusion liquid overflow port. FIG. 6 is a conceptual diagram when the unit units of FIG. 5 are arranged in parallel.

[0018]

EXAMPLES Example 1 An experiment for recovering ε-caprolactam crystals from an ε-caprolactam-water system was carried out by using a preliminary experimental apparatus shown in FIG. A glass cylinder having a diameter of 5 cm and a height of 100 cm was used as a crystallization tower. A jacket for temperature control was attached to the upper half of the glass cylinder, and water was supplied from a constant temperature bath to maintain a constant temperature (becomes a crystallization part). A heater for melting was inserted in the lower end of the glass cylinder. The lower half of the glass cylinder is the refining section. A rotary scraper having wings for scraping off the crystals adhering to the inner wall thereof was placed in the glass cylinder and rotated at a low speed at a predetermined speed. The glass cylinder was installed at an angle of 27 ° with respect to the vertical line.

An ε-caprolactam-water mixture having a concentration of ε-caprolactam of 96% by weight was charged into a substantially middle portion of a glass cylinder, and a total reflux operation was performed under the following conditions to observe: Water temperature for temperature control 45 ° C. heater Part liquid temperature 65 ℃ Rotating shaft rotation speed 0.05 rpm

When observed from the outside of the glass cylinder, the settling of crystal particles was observed, and the reflux liquid was observed to rise from the lower end along the upper surface of the glass cylinder. When the crystals obtained after total reflux for about 10 hours were extracted from the lower end of the glass cylinder and observed with a microscope, they were spherical and good crystal particles with a large diameter.

COMPARATIVE EXAMPLE 1 The example was repeated, but the glass cylinder was 0 with respect to the vertical line.
To ° (ie, not tilt). In this case, the crystal grains generated (grown) at the upper end are fine and hardly settle. In addition, it was observed that the reflux liquid went up together with the crystal particles, and good separation was not performed. Example 1
The crystals obtained after continuous operation for the same time as are fine and small in amount.

[0022]

EFFECT OF THE INVENTION In the crystallizer of the present invention, the entire crystallizing tower or the refining section thereof is inclined to promote the settling of the crystal particle group, and the liquid and the crystal group are gently mixed so that the solid-liquid interval is kept. Good contact. As a result, efficient purification is performed.

[Brief description of drawings]

FIG. 1 is a diagram showing the principle of the present invention.

FIG. 2 is a conceptual sectional view of a crystallizer used in a preliminary experiment.

FIG. 3 is a conceptual cross-sectional view of one embodiment of the crystallizer of the present invention.

FIG. 4 is a conceptual cross-sectional view showing a modified example of FIG.

5 is a conceptual perspective view of another modification of FIG.

6 is a conceptual perspective view of a modified example in which the units of FIG. 5 are arranged.

[Explanation of symbols]

 1 Housing of Crystallizer 2 Purification Section 3 Crystallization Section 4 Liquid to be Treated 5 Crystal 6 Exclusion Liquid 7 Rotating Shaft 8 Crystallization Tank

Claims (6)

[Claims] 1. A crystallizer having a refining section and a crystallization section, wherein at least the refining section is inclined with respect to a vertical line. 2. The apparatus according to claim 1, wherein the refining section is inclined from the vertical line by an angle of at most 60 degrees. 3. The refining section is composed of a hollow housing, and a crystal recovery section is provided at the bottom of the hollow housing.
Or the apparatus according to 2. 4. The hollow housing has means for scraping off the crystals adhering to the inner wall of the hollow housing.
An apparatus according to any one of the preceding claims. 5. The method according to claim 3, wherein the purification section and the crystallization section are formed of a single continuous hollow housing, and the liquid to be treated is supplied between the purification section and the crystallization section. apparatus. 6. The apparatus according to claim 3, wherein the slurry coming from a separate crystallization section is supplied to the upper part of the refining section.