GB2064976A - Crystal refining apparatus - Google Patents

Crystal refining apparatus Download PDF

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Publication number
GB2064976A
GB2064976A GB8037373A GB8037373A GB2064976A GB 2064976 A GB2064976 A GB 2064976A GB 8037373 A GB8037373 A GB 8037373A GB 8037373 A GB8037373 A GB 8037373A GB 2064976 A GB2064976 A GB 2064976A
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United Kingdom
Prior art keywords
unit
tower
feedstock
refining
crystal
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Withdrawn
Application number
GB8037373A
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Kureha Corp
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Kureha Corp
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Publication date
Priority to JP16232679U priority Critical patent/JPS5680202U/ja
Application filed by Kureha Corp filed Critical Kureha Corp
Publication of GB2064976A publication Critical patent/GB2064976A/en
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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D9/00Crystallisation
    • B01D9/004Fractional crystallisation; Fractionating or rectifying columns

Abstract

A crystal refining apparatus of a single erect tower construction for refining crystalline feedstock comprises, in a serial relationship one upon another in the vertical direction, three or more unit cylinder subassemblies having a specific transversal cross- sectional shape of two or more circles with their centers offset away from each other so that the circles may overlap partly with each other, the unit cylinder subassemblies each incorporating therein an agitating and conveying element held at its lower and/or upper end to the end of each of the unit cylinder subassemblies, wherein a unit cylinder subassembly disposed at the top of the apparatus is provided with a heating element to melt crystalline feedstock disposed at the upper part thereof and a discharging outlet to discharge refined crystal at the upper side thereof, a unit cylinder subassembly disposed at the bottom of the apparatus is provided with a supply opening to supply crystalline feedstock to be refined disposed at the lower side thereof and a separating element to separate solid and liquid at the bottom end thereof, whereby it is possible to adjust the total height of the apparatus as desired.

Description

SPECIFICATION Crystal refining apparatus The present invention relates to an apparatus for continuously refining a crystalline feedstock containing impurities therein by applying molten crystal component refined from the crystalline feedstock.

As a typical example of an apparatus of such construction that a crystalline feedstock is refined continuously by using molten crystal component refined from that crystalline feedstock per se, there is generally known the invention published for public inspection on October 1972 in Japan under the Japanese Patent Publication No.4062111972.

The apparatus according to the above mentioned invention is of such construction that there is provided an elongated single tower assembly erected to be upright which comprises an elongated hollow cylinder element having such a specific transversal cross-sectional shape as defined by two or more circles with their centers offset away from each other so that these circles may overlap partly with each other; two or more agitating and conveying means mounted rotatably within the elongated hollow cylinder element and each having a series of stub vanes or blades of a generally rectangular shape and disposed in a single spiral or helical path extending around the central axis of each of the circles offset from each other, having a central axis of rotation coincident with each of the centers of the offset circles, and arranged in such a relationship that the agitating and conveying means may rotate operatively within the elongated hollow cylinder element with their stub blades disposed on the adjacent axes of rotation thereof interleaving staggeredly with each other, thus effecting dual functions to dissolve a mass or cluster of crystalline feedstock to be fed into the hollow cylinder element to a desired grain and propel the crystalline feedstock to be conveyed into the tower assembly; a supplying element mounted at the lower position of the tower assembly and adapted to supply the crystalline feedstock thereto; a heating element mounted at the upper position of the tower assembly and adapted to melt with heat the crystal refined from the crystalline feedstock and feed this-melted refined crystal back to the tower assembly so as to have this-returned molten crystal contacted with the crystalline feedstock to be fed into the tower assembly, thus effecting the refinement of the feedstock; and outlet element adapted to discharge this-refined crystal product.

However, since the prior art crystal refining apparatus stated above is constructed to be a single erect tower type, it is inevitable that there may very possibly occur "mechanical vibrations" from the rotating motion of the agitating and conveying means incorporated therein, and this undesired tendency of vibration would grow to be further significant as the height of the erect tower assembly becomes greater. In this respect, it is not feasible in practice to have the tower height beyond the practical limits in the prior art. Of course, such "mechanical vibrations" may be decreased to a certain extent by the use of an agitator shaft having a substantially large diameter. With a too large diameter of the agitator shaft, however, the effective space of treatment of the crystalline feedstock to be refined through the apparatus would naturally be sacrificed.Moreover, there is another practical limit in the design height of the refining tower assembly, i.e., it is 10 meters or so.

On the other hand, in consideration of the requirements such as the type of impurities contained in the crystalline feedstock to be treated, the desired purity level of a product crystal, etc., it would often be required in practice to design the height of a refining tower to be 20 meters or even higher. However, with the use of the conventional refining apparatus of a single tower construction, it was not practicable to have the crystalline feedstock refined to a desired purity level.

In general, in order to attain a due level of refinement of the crystalline feedstock by way of an apparatus that is designed to repeatedly effect washing and recrystallization operations on the crystalline feedstock by using the molten crystal component refined from that feedstock, it is essential to apply a number of washing and recrystallization operations. Particularly, in the case of a feedstock which can only be refined with difficulties, a great number of such washing and recrystallization cycles would naturally become necessary.As a consequence, for conducting such high frequency of washing and recrystallization operations with the conventional refining apparatus with a relatively short tower height, it would be an inevitable choice to have a relatively small quantity of crystalline feedstock to be fed through the process in the refining apparatus instead of an industrial scale of feed, or otherwise, it would be essential to use a refining tower of a long height enough to cover a feed quantity or capacity on the industrial scale. As stated hereinbefore, however, there has been a certain practical limit in the mechanical design of the refining tower unit having such a desired height according to the conventional refining apparatus of a single tower construction.

The present invention is essentially directed to the provision of an improved crystal refining apparatus design that may reduce the above stated drawbacks particular to the conventional refining apparatus of a single erect tower construction.

According to the present invention there is provided a crystal refining apparatus including an upright tower for refining crystalline feedstock, the tower having three or more aligned cylindrical units, each said unit having a transverse cross-sectional shape defined by two or more partly overlapping circles with offset centers, each said unit including rotatable agitating and conveying means, and the units being connected releasably one upon another.

More particularly the invention provides a crystal refining apparatus including an upright tower having a transverse cross-sectional shape defined by two or more partly overlapping circles with offset centers, agitating and conveying means mounted within the tower and including elements with axes of rotation coincident with each of the centers of said offset circles for agitating and conveying crystalline feedstock, charging means mounted at the lower part of the tower for charging the crystalline feedstock, thereinto, refeeding means mounted at the upper part of the tower for feeding a molten crystal refined from the crystalline feedstock back to the tower so as to contact the crystalline feedstock, and the outlet means mounted at the upper part of the tower to discharge the refined crystal therefrom, the tower comprising a first cylindrical unit, one or more second cylindrical units and a third cylindricl unit releasable connected to, and upon, one another, the cylindrical units having like cross sectional shapes in register with each other and containing like parts of said agitating and conveying means and support means therefor at one or both of the top and bottom thereof, the first cylindrical unit being at the top of the tower, having heating means mounted at its upper part to melt the crystalline feedstock passing therethrough and the outlet means mounted at its upper part to discharge refined crystal therefrom; the or each second cylindrical unit being immediately or immediately and successively below said first cylinsdrical unit, and the third cylindrical unit being mounted immediately below the, or the lower or the lowest second cylindrical unit and having a supply opening mounted at its lower end to supply the crystalline feedstock thereinto from the charging means, and a separator mounted at its bottom to separate solid and liquid formed from the refining process, the support means allowing passage of feedstock to pass from unit to unit.

In practice the agitating and conveying elements extending along the various cylindrical units are operatively connected, with the opposed ends of their rotating shafts joined together by using common joint members so that these rotating shafts are aligned to allow a proper rotating motion within each of the units.

Also, support means mounted at the lower and/or upper ends of the units of the tower assembly for the agitating and conveying means will be specifically designed to allow smooth passage of the crystalline feedstock and thus promote the effect of agitation by the agitating elements, and will have a proper opening area and configuration offering a minimum obstruction to the feedstock. However, openings in the supporting means are not required for the uppermost and lowermost supports in the tower.

Preferably, and essential where there is more than one conveyor means, the transversal cross-sectional shape of each of the cylindrical units, and thus of the tower, is designed so that the eccentric offset between the circles is greater than the radius of each circle.

Preferred aspects of the invention allow the number of second cylindrical units to be selected as desired, while each of the elements for agitating and conveying the crystalline feedstock is supported adequately by the support means at relatively short intervals. This allows a smooth and stable operation with substantially reduced mechanical vibrations, however many of such second units there are.

It is also possible to control the properties and purity of the crystal products by varying the rotational speed of the agitating elements within the upper cylindrical unit cylinder relative to those in other units. As a consequence, it is feasible in practice to change the number of second units according to a property or purity desired of the refined crystal product, so that an efficient refining operation may be obtained.

In order that the invention may be more clearly understood, the following description is given by way of example only with reference to the accompanying drawings in which like parts are designated with like reference numerals and in which: Figure 1 shows a transversal cross-sectional view of a crystal refining apparatus in accordance with this invention; Figure 2 is a longitudinal cross-sectional view of a second unit cylinder subassembly in accordance with the invention; Figure 3 is a similar cross-sectional view to Figure 2 of a third unit cylinder subassembly; Figure 4 is a similar cross-sectional view to Figure 3 of a first unit cylinder subassembly; Figure 5 is also longitudinal cross-sectional view of the general construction of the crystal refining apparatus of the invention erected with the unit cylinder subassemblies assembled together;; Figure 6 is a top plan view of a bearing or support section in accordance with the invention; and Figure 7 is a fragmentary view in longitudinal cross-section of the main part of a connection between the unit cylinder subassemblies.

The present invention will now be described in detail by way of a preferred embodiment thereof in conjunction with the accompanying drawings.

Now, the crystal refining apparatus of this invention is typically of such a single tower construction which comprises the second unit cylinder subassembly as shown in Figure 2 incorporating a cylinder element 2 which has a specific transversal crosssectional shape defined by two circles with their centers offset away from each other so as to define the circles partly overlapping with each other as shown in Figure 1,an agitating element 3 mounted rotatably within the second unit cylinder subassembly and having a series of vanes or blades each having a generally rectangular shape and each disposed in a single spiral or helical path extending around the center of each of the circles offset away from each other as shown in Figure 1, the agitating element 3 being supported rotatably by a support and bearing 4 disposed at the lower and/or upper end of the second unit cylinder 1; a third unit cylinder subassembly as shown in Figure 3 incorporating a cylinder element 5 having the same crosssectional shape as that of the second unit cylinder subassembly and including a like agitating element as in the second unit cylinder subassembly, a supply opening 6 provided at the lower side of the cylinder element 5 for charging the crystalline feedstock to be refined, and a separating element 7 comprising a wire gauze or perforated plate mounted at the bottom end of the element 5 for separating solid and liquid; and a first unit cylinder subassembly as typically shown in Figure 4 incorporating a cylinder element 8 having the same cross-sectional shape and a like agitating element as in the second unit cylinder subassembly, a heating element 9 mounted at the upper part of the cylinder element 8 for melting with heat the crystalline feedstock, and a discharging outlet 10 for discharging refined crystal therefrom, the crystal refining apparatus being constructed in such a manner as generally shown in Figure 5 that there are mounted the third unit cylinder subassembly at the bottom stage of the tower construction, the first unit cylinder subassembly at the top stage thereof, and the second unit cylinder subassembly or subassemblies of a desired number operatively connected between the first and third unit cylinder subassemblies.

Each of the unit cylinder subassemblies is connected to be aligned one upon another by using a flanged part 11 formed at the lower and/or upper end of each of the cylinder elements to be opposed in connection. Also, there are provided a support and bearing means 4 as shown in Figure 6 and a coupling element 12 shown in Figure 7 in the connection of two adjacent agitator shafts of the two opposed cylinder subassemblies to be connected so that one agitator may be connected rigidly to the opposed other by slide-fitting the coupling element at the end of the shaft of one agitating element into the opposed shaft of the other.

The agitating element 3 disposed in a opposed pair within each of the unit cylinder subassemblies as typically shown in Figure 1 each has a series of stub vane or blades 2 disposed spirally on and around a shaft in such a manner that those opposed pair of agitating elements 3 are located in a close or proximal relationship with each other such that the blades 2 on one agitating element may staggeredly interleave with those of the opposed one. When coupling the unit cylinder subassemblies together stage by stage, an agitating element at each stage may be connected operatively with those at the adjacent stages with its shaft extending through a bearing 4 at each stage so that all the agitating elements incorporated at each stage may be operated with a single electric motor 13 through a speed changer 14, as schematically shown in Figure 5.In the figure, there is provided another electric motor designated at 15 for driving the feedstock supply unit.

It has been found convenient in handling or in an assembly work to have a unit cylinder element 60 to 150 cm high, more preferably 70 to 120 cm high.

More specifically, since the agitating element at every stage is held by the bearing provided at a relatively short interval, it is advantageous that there is substantialy no mechanical vibration during operation, however many stages of such agitating elements may be connected as desired, thus enabling quite a stable operation of the apparatus accordingly.

Example There is shown the results of a series of experiments operated to obtain naphthalene crystal of 97% purity by using the refining apparatus shown in Figure 5 which comprises in combination the unit cylinder subassemblies having an 8 cm diameter of the circle in the transversal cross-section each as shown in Figures 2 through 4.

At the first step of the experiment, there was provided the refining apparatus comprising the only first and third unit cylinder subassemblies to have the overall height of 150 cm, to which crude naphthalene crystal was fed at the rate of 4 kg/h, and heated at the temperature of 80.7 C at the top of the tower assembly. Refined napthalene crystal of 98.8% purity was obtained at the rate of 3.6 kg/h.

Next, when applying the refining apparatus added with two stages of the second unit cylinder subassemblies resulting to be the total tower height of 300 cm, the apparatus was operated under the same operating conditions to obtain refined napthalene crystal of 99.5% purity. Further, the refining apparatus was prepared with twenty-two second unit cylinder subassemblies incorporated therein resulting to be the total tower height of 1700 cm. With this apparatus specification, there was obtained the 99.9% purity napthalene crystal under the same operating conditions as in the first mentioned experiment.

With such experiments, it was ascertained that all the supporting means mounted between each stage of unit cylinder subassemblies had turned out to be free from any appreciable damages from the passage of the feedstock to be fed upwardly from the lower part of the apparatus and of the molten refined crystal at a high temperature fed back downwardly from the top of the apparatus.

It was also ascertained that the supporting members are adapted to have the openings which serue as the passages of the feedstock and the improvement of the purity of the refined crystal products may be obtained by making the dimensions of the openings to be adapted to the rates of conveyance and agitation of the crystalline feedstock.

From the results of these experiments, it is to be noted that the crystal refining apparatus of multiple unit cylinder construction according to this invention has now been verified to be so advantageous in which the apparatus may be designed to a desired height without any of such disadvantages as increasing the diameter of the agitator shaft as required in the conventional construction, and which means immediately the possibility that a desired high purity of refined crystal product can be attained in practice through the refining operation on the industrial scale of production.

Claims (8)

1. A crystal refining apparatus including an upright tower for refining crystalline feedstock, the tower having three or more aligned cylindrical units, each said unit having a transverse cross-sectional shape defined by two or more partly overlapping circles with offset centers, each said unit including rotatable agitating and conveying means, and the units being connected releasably one upon another.
2. Apparatus according to claim 1, wherein the rotatable means in each unit are supported at one or both of the lower and upper ends of that unit.
3. Apparatus according to claim 1, wherein said agitating and conveying means in each said unit includes elements with axes of rotation coincident with each of the centers of said offset circles and adapted to agitate and convey the crystalline feedstock along the unit, the elements being supported by supporting means at one or both of the lower and upper ends of the unit which allow the crystalline feedstock to pass therethrough.
4. Apparatus according to claim 1,2 or 3, wherein the uppermost cylindrical unit is provided with heating means mounted at the upper part thereof to melt the crystalline feedstock passing therethrough, and outlet means mounted at said upper part and adapted to discharge refined crystal therefrom.
5. Apparatus according to claim 1,2,3 or 4, wherein the lowermost cylindrical unit is provided with a supply opening mounted at the lower part thereof to supply the crystalline feedstock thereinto, and separating means mounted at the bottom to separate solid and liquid created in the refining process.
6. A crystal refining apparatus including an upright tower having a transverse cross-sectional shape defined by two or more partly overlapping circles with offset centers, agitating and conveying means mounted within the tower and including elements with axes of rotation coincident with each of the centers of said offset circles for agitating and conveying crystalline feedstock, charging means mounted at the lower part of the tower for charging the crystalline feedstock thereinto, refeeding means mounted at the upper part of the tower for feeding a molten crystal refined from the crystalline feedstock back to the tower so as to contact the crystalline feedstock, and outlet means mounted at the upper part of the tower to discharge the refined crystal therefrom, the tower comprising a first cylindrical unit, one or more second cylindrical units and a third cylindrical unit releasable connected to, and upon, one another, the cylindrical units having like cross sectional shapes in registerwith each other and containing like parts of said agitating and conveying means and support means therefor at one or both of the top and bottom thereof, the first cylindrical unit being at the top of the tower, having heating means mounted at its upper part to melt the crystalline feedstock passing therethrough and the outlet means mounted at its upper part to discharge refined crystal therefrom; the or each second cylindrical unit being immediately or immediately and successively below said first cylindrical unit, and the third cylindrical unit being mounted immediately below the, or the lower or the lowest second cylindrical unit and having a supply opening mounted at its lower end to supply the crystalline feedstock thereinto from the charging means, and a separator mounted at its bottom to separate solid and liquid formed from the refining process, the support means allowing passage of feedstock to pass from unit to unit.
7. Apparatus according to claim 6, wherein the support means mounted between the adjacent units have openings of dimensions corresponding to the rates of conveyance and agitation of the crystalline feedstock.
8. Crystal refining apparatus constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.
GB8037373A 1979-11-22 1980-11-21 Crystal refining apparatus Withdrawn GB2064976A (en)

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Application Number Priority Date Filing Date Title
JP16232679U JPS5680202U (en) 1979-11-22 1979-11-22

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GB2064976A true GB2064976A (en) 1981-06-24

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GB8037373A Withdrawn GB2064976A (en) 1979-11-22 1980-11-21 Crystal refining apparatus

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JP (1) JPS5680202U (en)
DE (1) DE3043823A1 (en)
FR (1) FR2469947A1 (en)
GB (1) GB2064976A (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4453959A (en) * 1982-02-25 1984-06-12 Bishkin D Bruce Crystal washing and purification method
US4588562A (en) * 1983-07-21 1986-05-13 Kureha Kagaku Kogyo Kabushiki Kaisha Apparatus for purifying crystals
US4806318A (en) * 1986-04-15 1989-02-21 Kureha Kagaku Kogyo Kabushiki Kaisha Apparatus for purifying crystals
EP1273579A1 (en) * 2000-03-31 2003-01-08 Kureha Kagaku Kogyo Kabushiki Kaisha Method for purification of cyclic ester

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2857891B2 (en) * 1989-10-04 1999-02-17 繁 齋藤 Crystal refining equipment
EP2923748A1 (en) * 2014-03-28 2015-09-30 Sulzer Chemtech AG A modular sub-unit for a suspension crystallization system and a suspension crystallization process using said modular sub-unit

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2800411A (en) * 1954-03-31 1957-07-23 Phillips Petroleum Co Crystal purification apparatus and process
US2922701A (en) * 1956-09-20 1960-01-26 Phillips Petroleum Co Fractional crystallization apparatus
DE1917089B2 (en) * 1968-04-02 1976-05-06 stubstanzen apparatus for the purification of crystalline
CH535058A (en) * 1971-08-30 1973-03-31 Inventa Ag Continuous separator column - for mixed materials of different melting points

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4453959A (en) * 1982-02-25 1984-06-12 Bishkin D Bruce Crystal washing and purification method
US4588562A (en) * 1983-07-21 1986-05-13 Kureha Kagaku Kogyo Kabushiki Kaisha Apparatus for purifying crystals
US4806318A (en) * 1986-04-15 1989-02-21 Kureha Kagaku Kogyo Kabushiki Kaisha Apparatus for purifying crystals
EP1273579A1 (en) * 2000-03-31 2003-01-08 Kureha Kagaku Kogyo Kabushiki Kaisha Method for purification of cyclic ester
EP1273579A4 (en) * 2000-03-31 2003-06-25 Kureha Chemical Ind Co Ltd Method for purification of cyclic ester
US6693204B2 (en) 2000-03-31 2004-02-17 Kureha Kagaku Kogyo K.K. Method for purification of cyclic ester

Also Published As

Publication number Publication date
FR2469947A1 (en) 1981-05-29
DE3043823A1 (en) 1981-06-11
JPS5680202U (en) 1981-06-29

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