JOURNAL OF CHEMICAL ENGINEERING OF JAPAN

Crystal Growth and Nucleation Kinetics

Secondary Growth Phenomena in Industrial Crystallization and Their Effects on Crystal Quality

Masakuni Matsuoka

Article type: Journal Reviews
Subject area: Crystal Growth and Nucleation Kinetics
2002 Volume 35 Issue 11 Pages 1025-1037
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1025

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Growth phenomena and growth rates of crystalline particles in suspension systems are reviewed with an emphasis on the factors that distort the product crystal size distribution of products derived for the ideal mixed suspension mixed product removal (MSMPR) crystallizer. The growth of crystals in suspension systems is defined as secondary growth to distinguish from the growth of single crystals from clear mother liquor. This is in analogy of the classification of nucleation where secondary nucleation mechanisms are highly much complicated and different from the primary one. Roles of growth rate dispersion (GRD), size dependent growth (SDG), growth rate enhancement by micro-crystals (GRE), agglomeration and attrition in distortion of the CSDs are described individually.

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Temperature Dependence of the Crystal Growth Rate of Potassium Sulfate at Low Temperature

Yoji Taguchi, Mika Yoshida, Hiroyuki Kobayashi

Article type: Research Papers
Subject area: Crystal Growth and Nucleation Kinetics
2002 Volume 35 Issue 11 Pages 1038-1044
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1038

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The crystal growth rates of potassium sulfate were measured in a relatively low temperature range from 0 to 35°C. The temperature dependence of the growth rate was examined because of the lack of rate data at low temperatures. A minimum growth rate was found at nearly 20°C. The reason why the growth rate increased at a low temperature of less than 20°C is that ‘fine crystals’ might already exist in a supersaturated solution of potassium sulfate before crystallization and that deposition of these fine crystals on the seed crystal surface may enhance the crystal growth rate. The existence of the fine crystals in supersaturated solution was confirmed by measuring the density and electric conductivity of the mother liquor of potassium sulfate.

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Effects of Suspension Density on Crystal Growth Rate in Multiparticle Agitated Crystallizers

Hiroshi Takiyama, Toshinori Eto, Masakuni Matsuoka

Article type: Research Papers
Subject area: Crystal Growth and Nucleation Kinetics
2002 Volume 35 Issue 11 Pages 1045-1049
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1045

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The single crystal growth rates (primary growth rate G_prim) and the average growth rates of crystalline multiparticles (secondary growth rate G_sec) determined by using a continuous MSMPR crystallizer were measured for a few inorganic systems. The influence of the suspension density M_T on the average growth rate of the multiparticles was evaluated using the ratio of G_sec to G_prim. Relationships between the suspension density M_T and the ratio of two growth rates were compared for the systems investigated.
As a result, the influences of M_T on the ratio of G_sec to G_prim were different depending on the systems. In the case of potassium sulfate crystals, which were readily agglomerated under the low suspension conditions, the ratio of G_prim to G_sec was dependent on M_T. In the potash alum crystals, the more M_T became high, the more the degree of agglomeration of product crystals increased and the ratio of G_prim to G_sec became large. The ammonium sulfate crystals were scarcely agglomerated and M_T did not influence the ratio of two growth rates. It was suggested that the influence of M_T on the growth rate was related to the difference in the degree of attrition and agglomeration.

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Crystal Growth Rate of a Fixed K-Alum Crystal in Suspended Solution of MSMPR Crystallizer

Eiichi Suzuki, Kaoru Ogawa, Luis Americo Guzman, Kenji Shimizu

Article type: Short Communications
Subject area: Crystal Growth and Nucleation Kinetics
2002 Volume 35 Issue 11 Pages 1050-1054
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1050

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The surface structure of the grown crystals and crystal growth rate in suspended supersaturation solution were investigated by using a differential interference microscope with a VTR system and an AFM system. It was found that the surface of the growing crystal had many fine crystals and new growth steps generated from the place of adhered fine crystals. Most of the fine crystals were in the range of 10 μm to 40 μm in size, and their orientations were random. Also the heights of the new growth steps were in the range of a few nm to about 70 nm. The crystal growth rate Gs in suspended solution was faster than the rate Gn in non-suspended solution at the same supersaturation. These rates can be given by

Gs = 1.1 × 10^–1ΔC^0.47 (suspended)

Gn = 4.8 × 10^–2ΔC^0.60 (non-suspended)

where ΔC (=Cs – C) is supersaturation, Cs and C were the saturated and fixed concentration, respectively. The growth rate Gs increased with decrease of the average crystal size Lav of the suspended crystal in an MSMPR crystallizer. An adequate linear correlation between Gs and Lav was obtained.

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A Comparison of Searching Methods for Crystallization Kinetics in an MSMPR Crystallizer

Clifford Y. Tai, Wen-Chen Chien

Article type: Research Papers
Subject area: Crystal Growth and Nucleation Kinetics
2002 Volume 35 Issue 11 Pages 1055-1062
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1055

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Population density data of several systems with and without additives were collected in our laboratory using an MSMPR crystallizer. Two methods for searching crystallization kinetics were used to analyze these data. Crystal growth rate and nucleation rate of zero-size nuclei and effective growth rate and nucleation rate obtained by the two methods are compared. The agreement between the results is generally good for effective rates with the specified crystal size larger than 50 μm, but is violated for smaller crystal size, especially for zero-size nuclei. Thus 50 μm is a good choice for the effective size. The kinetic parameter of the rate equations are also compared. Again, parameters of effective rate equations are more consistent than those of nuclei rate equations. For impure systems the consistency between the two methods is generally poor.

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Batch Crystallization

Seeding Effect on Product Crystal Size in Batch Crystallization

Noriaki Kubota, Norihito Doki, Masaaki Yokota, Donepudi Jagadesh

Article type: Journal Reviews
Subject area: Batch Crystallization
2002 Volume 35 Issue 11 Pages 1063-1071
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1063

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This paper reviews research work concerning the size distribution of product crystals in batch crystallization of well-soluble materials. The discussion was made with particular emphasis on seeding effect on product crystal size distribution and crystallizer performance. First, it is shown by a brief survey of the history of batch crystallization research that the importance of seeding in the performance of a batch crystallizer has been ignored while the importance of cooling profile (or supersaturation profile) had been overestimated. Then, the extensive research work carried out by the group of the present authors on seeding effect is reviewed, where the effectiveness of seeding in controlling product crystal size is clearly shown with experimental evidence. Specifically, it is shown that seed crystals added at the beginning of a batch can be grown with no generation of fine crystals if seed crystals are added enough over a critical seed loading ratio. Finally, recent research work in literature on batch crystallization is briefly surveyed.

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Effects of Undersaturation on Crystal Size Distribution in Cooling Type Batch Crystallization

Hiroshi Takiyama, Kayo Shindo, Masakuni Matsuoka

Article type: Research Papers
Subject area: Batch Crystallization
2002 Volume 35 Issue 11 Pages 1072-1077
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1072

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In the cooling type batch crystallization, the influence of undersaturation operation on crystal size distribution was investigated, and the effectiveness of this operation was discussed. In batch crystallization with seeding, it was clear that undersaturation operations in the early stages of the cooling operation was effective in dissolving the micro-crystals which were generated by the initial bleeding, whereas undersaturation operations halfway through cooling was effective in dissolving the micro-crystals which were generated by attrition.
From the results of applying this cooling temperature program to non-seeded batch crystallization, the design strategy of the temperature program for non-seeded operation was able to be determined. And it became clear that the crystal size distribution was improved by using undersaturation operations also in the case of non-seeded operation. This strategy of undersaturation operations was confirmed from measurement of crystal size distribution using an in-line sensor.

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Seeded Batch Multi-Stage Natural Cooling Crystallization of Potassium Alum

Noriaki Kubota, Norihito Doki, Manabu Ito, Shigeko Sasaki, Masaaki Yok ...

Article type: Research Papers
Subject area: Batch Crystallization
2002 Volume 35 Issue 11 Pages 1078-1082
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1078

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Seed crystals of potassium alum were grown in batches with no secondary nucleation by a multi-stage natural cooling technique, where the temperature of the solution saturated at 40°C was lowered in steps from over the saturation temperature to 20°C. Seed crystals of 42 μm, which were introduced just at the saturation temperature of 40°C, were grown successfully to final sizes of 318, 563, 732, and 1070 μm, with 1-, 3-, 5-, 6-, 7-, and 9-stage coolings. The number of cooling stages and the required temperature decrease in each stage were determined a priori, using a mass balance equation, an experimental correlation of the critical seed loading ratio (over which seed loading it is guaranteed there will be no secondary nucleation) versus seed size, and solubility data. This multi-stage cooling method is a promising technique to grow seed crystals to a desired size in batch cooling crystallization.

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Drowning-out Crystallization of L-Ornithine-Aspartate in Turbulent Agitated Reactor

Dong-Myung Shin, Woo-Sik Kim

Article type: Research Papers
Subject area: Batch Crystallization
2002 Volume 35 Issue 11 Pages 1083-1090
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1083

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When L-ornithin-aspartate was crystallized by drowning-out method in a turbulent agitated semi-batch reactor, the effects of the crystallization conditions, such as the feed concentration, alcohol flow rate, and agitation speed, on the agglomeration and breakage of the L-ornithine-aspartate particles were investigated. The mean particle size of the L-ornithine aspartate in the product suspension was reduced when the agitation speed and holding time were increased. However, a higher feed concentration enhanced the particle agglomeration and nucleation, resulting in larger mean particles. The dependency of the mean particle size on the crystallization conditions was depicted using a power law model of a Camp number, which matched with the experimental data.
Prior to the drowning-out crystallization, the solubility of L-ornithine aspartate in water-alcohol mixtures was examined and correlated as a function of the alcohol composition. Due to the inhibitory effect of alcohol on the intramolecular interaction between the solvent and the solute, the solubility was dramatically reduced when increasing the amount of alcohol in the mixture.

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Scale-up Study on Unseeded Batch Cooling Crystallization Using Co-solvent

Kwang-Joo Kim, Choul-Ho Lee

Article type: Research Papers
Subject area: Batch Crystallization
2002 Volume 35 Issue 11 Pages 1091-1098
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1091

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Crystallization using a co-solvent for producing spherical 3-nitro-1, 2, 4-triazol-5-one (NTO) crystals was carried out in two laboratory-scale and bench-scale crystallizers. The effect of scaling-up the crystallizers on the mean size of crystals of NTO during a batch cooling crystallization was explored. A simplified model based on the crystallization kinetics was established for the estimation of mean crystal size during the scaling-up of the crystallizer. Comparison of the crystals obtained from the laboratory-scale and from the bench-scale operations showed that the model can be successfully correlated with the mean crystal size. Eventually, the mean crystal size was estimated if the co-solvent composition was set optimally and the crystallizer scale-up was reasonable.

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Production of Sodium Chloride Crystals of Uni-Modal Size Distribution by Batch Dilution Crystallization

Norihito Doki, Noriaki Kubota, Masaaki Yokota, Souichiro Kimura, Shige ...

Article type: Research Papers
Subject area: Batch Crystallization
2002 Volume 35 Issue 11 Pages 1099-1104
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1099

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The strategy of producing crystals of uni-modal size distribution was investigated for dilution (or anti-solvent) crystallization. Sodium chloride was crystallized as a model compound from aqueous solution by adding pure ethanol (99 vol.% ethanol) or an ethanol-water (75 vol.% ethanol) mixture as diluent. The effects of external seeding on the product CSD were clearly observed. At high external-seed loadings, uni-modal product crystals of grown seeds were obtained with virtually no nucleation. However, at low external-seed loadings, primary as well as secondary nucleation occurred, so that product crystals with bi-modal size distribution were obtained. This primary nucleation was considered to be due to high local concentration of ethanol (or high local supersaturation) created near the nozzle, through which the diluent was injected. By the addition of the pure ethanol into the non-seeded saturated aqueous solution, fine crystals with an identical uni-modal narrow size distribution were obtained, irrespective of the amount of the diluent added. These fine crystals were grown successfully as internal seeds to product crystals with uni-modal size distribution. This internal seeding is expected to be a promising “seeding” technique in the pharmaceutical industry, where external seeding is not favored.

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Batch Cooling Crystallization of an Organic Photochemical with a Low-Speed Intermittent Stirring Technique

Kazuaki Iwamoto, Masaru Seki, Yoshiyuki Koiwa

Article type: Short Communications
Subject area: Batch Crystallization
2002 Volume 35 Issue 11 Pages 1105-1107
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1105

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An organic photochemical was crystallized in batches-wise both in laboratory and industrial crystallizers. In the laboratory, crystals were produced at different stirring speeds using a 1 L crystallizer, and the centrifugal filtration tests were conducted for the slurries that were obtained slurries. The average specific resistance was reduced much more than expected from the Kozeny-Carmann equation. This suggested that the a change occurred in the channel structure occurred in the cake composed of the crystalline particles that were obtained. Based on the above laboratory tests, batch crystallization with a low-speed intermittent stirring technique was applied for an actual crystallizer. The filtration time was reduced in the actual plant to about 1/10 of that of the previous conventional stirring crystallization.

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Control of Crystal Size Distributions in a Seeded Batch Crystallizer

Toshio Nomura, Kenji Shimizu, Koji Takahashi

Article type: Research Papers
Subject area: Batch Crystallization
2002 Volume 35 Issue 11 Pages 1108-1112
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1108

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The in-situ measurement method of the turbidity of different heights in a vessel was proposed by using a multi sensor, consisting of infrared light emitting diodes and phototransistors. The experimental results showed that the turbidity was able to represent the crystal concentration under the experimental conditions covered in this work. By changing the impeller speed adequately according to the measurement results of the turbidity, an attempt was made to control the crystal size and its distribution and a satisfying result was obtained.

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Molecular and Crystal Structures, Polymorph and Magnetic Effect

Structure Change of p, p′-Biphenol/Dimethyl Sulfoxide (DMSO)-Clathrate Crystal with Releasing Solvated DMSO Molecules by Heating

Masaaki Yokota, Norihito Doki, Shigeko Sasaki, Noriaki Kubota

Article type: Short Communications
Subject area: Molecular and Crystal Structures, Polymorph and Magnetic Effect
2002 Volume 35 Issue 11 Pages 1113-1115
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1113

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Molecules of p, p′-biphenol (PBP) formed a 1:1 inclusion compound with dimethyl sulfoxide (DMSO) in which DMSO guest molecules were trapped in the tunnel formed by PBP host framework. A simultaneous X-ray powder diffractometric and differential scanning calorimetric method revealed that release of the guest molecules through the tunnel took place in several steps with the intermediate formation of other different clathrates.

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Dependence of Polymorphic Transformation on Anti-Solvent Composition and Crystallization Behavior of Thiazole-Derivative Pharmaceutical

Mitsutaka Kitamura, Keiichiro Nakamura

Article type: Research Papers
Subject area: Molecular and Crystal Structures, Polymorph and Magnetic Effect
2002 Volume 35 Issue 11 Pages 1116-1122
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1116

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The transformation and crystallization behaviors of the polymorphs (A and C) and solvated crystals (BH (BPT·0.5H₂O) and D (BPT·MeOH)) of the thiazole-derivative pharmaceutical (BPT) were investigated. The solubility of metastable form was measured with the vigorous stirring using a magnetic stirrer. It was found that at 323 K with the volume fraction of methanol (V_MeOH) of 0.5, A and D forms dose not transform to the stable C form directly, but transform in two steps via the metastable BH form. The stability of A tended to decrease and the stability of D form increased with the decreased of temperature from 323 to 303 K. The A and D forms also transformed to the metastable BH form at 303 K and 313 K. This is because of the selective nucleation and growth of BH crystals due to the specific solute-solvent interaction in comparison with C crystals. The small free energy difference between BH and C forms also stabilizes BH form.
It appeared that the C form is the stable form and A is the metastable form with the methanol composition (V_MeOH) ranges of 0.5–0.8 at 323 K. At the methanol composition of 0.7 A, BH and D forms transformed to the stable form, C. With increase of methanol composition the stability of D form is increased and that of BH form decreased. Such tendency may be due to the dissociation of the solvated crystals.
In the crystallization at 323 K by adding water as an anti-solvent to BPT solution of methanol and water mixture, it cleared that only the metastable forms of BH and D crystallize and the crystallization ratio of these polymorphs depends on the addition rate of water. Further more, it was found that BH transforms to A by solution-mediated mechanism after the crystallization.

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Magnetic Orientation of Amino Acid Crystals

Kaoru Ogawa, Fumiko Yagi, Eiichi Suzuki, Luis Americo Guzman, Kenji Sh ...

Article type: Research Papers
Subject area: Molecular and Crystal Structures, Polymorph and Magnetic Effect
2002 Volume 35 Issue 11 Pages 1123-1132
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1123

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The effect of a magnetic field on the orientation of diamagnetic, non-aromatic amino acids crystals was studied. Amino acids, such as L-alanine or glycine, were crystallized from supersaturated solutions (pure and containing other amino acids as additives) under a vertical or horizontal high magnetic field. We prepared an optical microscope system for in situ observation, which could be used under a high magnetic field. According to the observed results of crystallization with the microscope, the c-axes of small nucleated L-alanine crystals moving in the solution were parallel to the direction of the magnetic field. In the case of glycine, the crystals grew so that the ac-planes were parallel and c-axes were at angles of 55° to the direction of magnetic field. This behavior in orientation is explained based on small magnetic anisotropies of diamagnetic crystals.
Even if the direction of the magnetic field to the gravitational axis was changed, the directions of crystal axes to the magnetic field remain unchanged. Magnetic orientation of DAST (4-N, N-dimethylamino-4′-N′-methyl-stilbazoliumtosylate) crystal, one of the nonlinear optical materials, was also studied for comparison. As similar to the above case, DAST crystals obtained in 1T were oriented so that their a-axes were parallel to the magnetic field. The orientation ratios of the growing crystals were determined at several intensities of magnetic field.

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Aggregation of p-Acetanisidide Molecules in the Under- and Super-saturated Solution and Its Effect on Crystallization

Akira Saito, Koichi Igarashi, Masayuki Azuma, Hiroshi Ooshima

Article type: Research Papers
Subject area: Molecular and Crystal Structures, Polymorph and Magnetic Effect
2002 Volume 35 Issue 11 Pages 1133-1139
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1133

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The aggregation behavior of solute molecules in under- and supersaturated solutions was investigated using an organic compound p-acetanisidide (PAC) as a model compound and NMR method. The aggregation behavior was discussed by comparing the structure of aggregates with that of a single crystal determined by X-ray crystallographic analysis. And also, the relationship between the aggregation and the nucleation was discussed. PAC molecules were found in aggregates before nucleation, not only in the super-saturated solution but also in the under-saturated solution. The growth of aggregates in the under-saturated solution was slower than that in the super-saturated solution. The local structures observed in the aggregates were intermolecular hydrogen bonding between N-H hydrogen and C=O oxygen, and the intra- and intermolecular access of methoxy group hydrogen to (orto-) hydrogen on a benzene ring within a distance of 4 Å. These interactions were also observed between adjacent PAC molecules in crystal. The whole structure of aggregates, however, was not the same as that of the crystal. The formation of aggregates before nucleation in the under-saturation condition suppressed the nucleation, and the formation of aggregates in the super-saturation condition accelerated the nucleation.

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Impurity Effect and Inclusion Formation

The Effect of Immiscible Additives on the Batch Reactive Crystallization of a Benzoic Acid Derivative

Guangyu Yang, Marjatta Louhi-Kultanen, Pekka Oinas, Zuoliang Sha, Juha ...

Article type: Research Papers
Subject area: Impurity Effect and Inclusion Formation
2002 Volume 35 Issue 11 Pages 1140-1145
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1140

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In the present study, the effect of different immiscible additives on the reactive crystallization of a benzoic acid derivative from aqueous solution was investigated using the batch operation mode. Monochlorobenzene was used as the main additive, the effects of which on the crystal size distribution, shape and filterability of the crystal end-product were studied. The other immiscible additives studied here were toluene and hexane. The comparison between the studied additives was based on the obtained crystal size distribution. The experimental results of the crystal size distribution showed that monochlorobenzene and toluene were the compounds that resulted in a larger mean particle size. A microscopic study showed that the mean size increased due to the agglomeration of benzoic acid derivative crystals. Furthermore, the influence of the operating conditions, such as the flow rate of the reactant, mixing intensity and initial concentration, on the crystal size distribution was studied. In the presence of monochlorobenzene, the operating conditions affected the crystal size distribution, whereas without the additive, their influence could be ignored. The mechanism of the additive effect is discussed here.

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Inclusion of Mother Liquor inside KCl Crystals in a Continuous MSMPR Crystallizer

Hideo Miki, Kenta Fukumoto, Kouji Maeda, Keisuke Fukui

Article type: Research Papers
Subject area: Impurity Effect and Inclusion Formation
2002 Volume 35 Issue 11 Pages 1146-1150
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1146

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The crystal size distribution (CSD) and crystal purity of potassium chloride (KCl) have been measured in an MSMPR crystallizer by using two different impellers. A small amount of sodium chloride (NaCl) was added as an impurity tracer in order to measure the inclusion ratio of mother liquor inside KCl crystals. The effects of mixing, residence time, growth rate and crystal size of KCl on the inclusion of mother liquor were investigated. The crystal growth rate and nucleation rate were determined from the population density balance theory. The attrition of crystals changed round shape of the crystal and affected significantly the inclusion of mother liquor in the crystals. The roundness of KCl crystals was proposed as a new factor to take the attrition effects into consideration. An empirical relationship between the inclusion of mother liquor and the operating variables was obtained.

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Behavior of Impurities during the Formation of an Ice Sphere

Jun Guo, Togo Yamaguchi, Yoji Taguchi, Akira Ohkawa

Article type: Research Papers
Subject area: Impurity Effect and Inclusion Formation
2002 Volume 35 Issue 11 Pages 1151-1156
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1151

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The distribution of impurities in an ice sphere was examined by melting an ice sphere formed from a solution containing phosphate and ammonium ions as impurities. To interpret this biased distribution, the adsorption phenomena of phosphate and ammonium ions on the surface of ice crystals were also experimentally examined. The adsorption experiments were performed by forming ice into spherical shapes and immersing the spheres in a solution containing phosphate and ammonium ions under a limited range of solution temperatures from 0 to 0.4°C. The results showed that the phosphate and ammonium ions were adsorbed on the ice surface immediately after the immersion. The amounts adsorbed after the establishment of a quasi-equilibrium state obeyed a Langmuir adsorption isotherm. Based on the adsorption isotherm, we proposed a quantitative explanation for the distributed ions in the ice sphere.

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Miscellaneous Crystallization Techniques

Comparison of a Drum Flaker and CDC (Cooling Disc Crystallizer) for Crystal Purification with a KCP (Kureha Crystal Purifer)

Kentaro Otawara, Takeshi Matsuoka, Yuji Mori, Taketo Kitamura

Article type: Short Communications
Subject area: Miscellaneous Crystallization Techniques
2002 Volume 35 Issue 11 Pages 1157-1160
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1157

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Industry has recently been keenly interested in obtaining highly pure crystal. A KCP (Kureha Crystal Purifer) is one type of equipments for obtaining that kind of crystal. This KCP purifies only crude feed crystal; therefore, it requires a crystallizer. Recently, we have found that the crystal from a CDC (Cooling Disc Crystallizer, manufactured by GMF-Gouda, the Netherlands) is superior to the crystal from a drum flaker and can be best suited for producing the feed crystal for the KCP. Thus, the combination of the KCP and CDC can be one of the most effective types of continuous fractional column crystallization.

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Crystallization of Pastilles from Molten Paraffin—A New Design Method Based on Temperature Effects

Kaoru Onoe, Akie Hoshi, Yumi Kudoh, Takaji Akiya, Kenichi Nishimine, K ...

Article type: Research Papers
Subject area: Miscellaneous Crystallization Techniques
2002 Volume 35 Issue 11 Pages 1161-1168
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1161

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Crystallization of pastilles from molten paraffin was investigated by measuring (1) the layer thickness growth rate, (2) the secondary crystallization rate, and (3) the shape change during the transformation from a paraffin droplet to a pastille. The molten paraffin was dropped from a heated nozzle onto the smooth horizontal plane of the crystallizer, which was cooled by coolant circulated through the inside of the crystallizer, and the progress of the crystallization of molten drops into pastilles was monitored. Changes of shape and size of the droplets during solidification were analyzed, and a relationship between coolant temperature and reasonable operation time has been obtained to better design the melt crystallizer. Furthermore, the effects of cooling and storage temperature on secondary crystallization rate were examined. The secondary crystallization rate, which was determined from the slope of the relationship between the storage time and the change of X-ray peak intensity of products, had a maximum in a specified range of storage temperatures, around 293 K, independent of coolant temperature.
Judging from droplet height and layer thickness changes, the transformation from a paraffin droplet to a pastille could be divided into (I) cooling of droplet, (II) formation of a pastille, and (III) heat withdrawing of a pastille. The formation time was approximately four times as long as the cooling time. Based on these temperature effects, a new design method for a steel-belt crystallizer is proposed to obtain a reasonable operation time.

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Study on Preparation of a Low Density Polyethylene Particle by Emulsion Crystallization

Jae-Kyeong Kim, Kwang-Joo Kim, In-Ho Kim

Article type: Research Papers
Subject area: Miscellaneous Crystallization Techniques
2002 Volume 35 Issue 11 Pages 1169-1177
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1169

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In this work, an emulsion crystallization was made to investigate the possibility of the preparation of fine particles. The method selected was intended to prepare a micron-sized low density polyethylene particle. Dodecanol as a theta solvent and diethylene glycol as a non-solvent were selected. Operating conditions, such as composition of solution, concentration of polyethylene, stirring speed, and temperature of the polymer solution were investigated. The polymer particles obtained by emulsion crystallization were spherical, with mean size ranging from 0.5 μm to 5 μm. As a result, we observed the instability of the emulsion for crystallization conditions. This instability has an effect on the mean diameter and particle size distribution of the prepared particles.

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Modeling and Simulation of Suspension Crystallization

CFD Study of Local Crystal Growth Rate in a Continuous Suspension Crystallizer

Yuko Mori, Zuoliang Sha, Marjatta Louhi-Kultanen, Juha Kallas

Article type: Research Papers
Subject area: Modeling and Simulation of Suspension Crystallization
2002 Volume 35 Issue 11 Pages 1178-1187
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1178

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The objective of the present work is to determine the local crystal growth rate in an imperfectly mixed suspension crystallizer. Experiments were carried out in pure potassium sulphate-water solution. The steady-state Crystal Size Distributions (CSDs) were measured at four different heights of the crystallizer using an in-situ particle image analyzer. Experimentally obtained CSD was used to determine the overall growth rate. Then, Computational Fluid Dynamics (CFD) was used to calculate the Particle Size Distributions (PSDs) of the same kind of suspension which was used in the experiments. The computational study was focused to simulate the mass transfer coefficient between particles and solution, and supersaturation. These quantities were determined from hydrodynamics of suspension in a crystallizer. The multi-fluid model was applied to describe suspension flow in the crystallizer. One continuous phase (water) and six dispersed phases, which were taken to be particles in six size classes, were used to approximate PSD. The crystal growth rate model was based on the diffusion process and was implemented into a CFD environment. The local growth rates were calculated from the slip velocity or from energy dissipation rate at the local temperature and supersaturation.

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Modeling and Simulation of Crystal Size Distribution in Imperfectly Mixed Suspension Crystallization

Zuoliang Sha, Seppo Palosaari

Article type: Research Papers
Subject area: Modeling and Simulation of Suspension Crystallization
2002 Volume 35 Issue 11 Pages 1188-1195
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1188

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A model for simulating crystallization in imperfectly mixed suspensions was developed based on a population balance equation that takes into account the solid suspension density distributions of different sizes of particles in the crystallizer. A simulation method was developed based on mass balance and population balance. With this method, the particle size distributions in the product and in the crystallizer were predicted. The simulated particle size distributions in the product were verified with experimental data.

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Reaction Crystallization

Reaction Crystallization of CaCO₃ in a Gas-Liquid Multistage Column Crystallizer

Hideki Tsuge, Takahiro Okawa, Junji Ishibashi

Article type: Research Papers
Subject area: Reaction Crystallization
2002 Volume 35 Issue 11 Pages 1196-1202
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1196

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A multistage column crystallizer is a column crystallizer partitioned with perforated plates. From the viewpoint of economy, multistage column crystallizers have been developed to overcome the redundancy of equipment due to the duplication of mixers and other hardware in a cascade of mixed-suspension, mixed-product-removal crystallizers. The aims of this study are to clarify the characteristics of the multistage column crystallizers and to control the calcium carbonate particle size. The staging effects of the column crystallizer on the particle size were experimentally investigated by the gas-liquid reaction crystallization of calcium carbonate in the three-stage column crystallizer. The particle size of calcium carbonate obtained by the multistage column crystallizer becomes larger than that obtained by the standard column crystallizer. The dominant particle size increases with a decreasing opening ratio of the perforated plate, whereas it decreases with increasing CO₂ content in the gas, because the particles produced re-dissolve by the dissolution of CO₂.

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Changes in Crystalline Properties of Nanosized Hydroxyapatite Powders Prepared by Low-Temperature Reactive Crystallization

Woon-Soo Kim, Woo-Sik Kim, Izumi Hirasawa

Article type: Research Papers
Subject area: Reaction Crystallization
2002 Volume 35 Issue 11 Pages 1203-1210
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1203

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In the reactive crystallization of hydroxyapatite (HAP) done with CaCl₂, KH₂PO₄ and NaOH solutions at the reaction temperature of 60°C in a semi-batch reactor, the relationship of the crystalline properties of nanosized HAP powders with the operational conditions was experimentally investigated. The crystallinity of needle-like HAP powders was enhanced with decreasing OH^– ion composition and reactants concentration, which corresponded well with the increase in the crystal size, but had nothing to do with the aging of the product suspension. Even though the supersaturation level was predicted not to be influenced by the OH^– ion composition, the crystal growth of the HAP powders was striking at low OH^– ion composition, thereby resulting in larger HAP with high crystallinity. Comparing the growth orientation of the HAP powders before and after sintering, the crystal growth was preferentially promoted on the face of (002) in the direction of the crystallographic c-axis, especially at low OH^– ion composition and reactants concentration during the crystallization, and it was transferred on the (300) face along the a-axis after sintering at 1000°C for 3 h, which seem to be caused by the unbalanced grain coalescing according to the crystallographic axes of HAP.

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Conglomeration and Nucleation

Ultrasonic Study on Conglomeration of Cerium Oxalate Particles Produced by Reaction Crystallization in Series Reactor Including T-mixer and Stirred Tank

Jung-Kyu Hyun , Joon-Soo Kim, Sung-Don Kim, Ho-Sung Yoon, Jin-Young Le ...

Article type: Research Papers
Subject area: Conglomeration and Nucleation
2002 Volume 35 Issue 11 Pages 1211-1218
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1211

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The conglomeration of cerium oxalate crystals was investigated using ultrasound in a T-mixer and mixing tank reactor system. The mean particle size was enlarged when increasing the feeding time, yet insensitive to the length of the T-mixer. The use of ultrasound on the conglomerates revealed that they consisted of both aggregated and agglomerated particles. The aggregated particles were dispersed into individual particles with an ultrasonic intensity above 6 watts. However, the agglomerated particles resisted the vibrational force of the ultrasound up to 30 watts. Also, about 20 min of ultrasonic treatment was found to be sufficient to disperse the aggregated particles. The aggregation fraction in the conglomerates was estimated based on comparing the mean particle sizes obtained from the product suspensions with and without ultrasound treatment. By modifying the holding time in the stirred reactor and the conversion conditions in the T-mixer, the aggregation fraction was also found to depend on both the feeding time and the length of the T-mixer.

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Effect of Supersaturation on Crystal Size and Number of Crystals Produced in Antisolvent Crystallization

Shogo Kaneko, Yasuhiro Yamagami, Heisuke Tochihara, Izumi Hirasawa

Article type: Research Papers
Subject area: Conglomeration and Nucleation
2002 Volume 35 Issue 11 Pages 1219-1223
Published: 2002
Released on J-STAGE: January 13, 2003

DOIhttps://doi.org/10.1252/jcej.35.1219

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The antisolvent crystallization of sodium chloride was carried out in batches to observe crystallization phenomena using ethanol as an antisolvent. To decrease high local supersaturation generated by the addition of antisolvent, the authors have proposed a new idea by choosing high ethanol concentration operational conditions. Obtained crystals seemed to be unagglomerated and monodispersed in the optimum range of ethanol concentration. From the observation of nucleation phenomena, it was considered that nucleation induced by the antisolvent addition occurred due to the local supersaturation generated at the boundary of the starting and feed solutions. On the other hand, crystal growth is considered to proceed by the supersaturation generated by sufficient mixing between the starting and feed solutions. Average crystal size increased with the increase of σ_g. The number of produced crystals increased with the increase of the starting solution concentration C. The induction period for nucleation tended to decrease with increase of C and σ_g. Since the number of produced crystals depended on C, nucleation was considered to be influenced by local mixing between the starting and feed solutions.

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