Systematic design of supersaturation controlled crystallization processes for shaping the crystal size distribution using an analytical estimator

• Published in: Chemical engineering science Vol. 84; pp. 656 - 670
• Main Authors: Nagy, Z.K., Aamir, E.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 24-12-2012; Elsevier
• Subjects: alum; Applied sciences; Chemical engineering; Crystallisation control; Crystallization; Crystallization, leaching, miscellaneous separations; Crystals; Design engineering; Dynamic seeding; Dynamics; Exact sciences and technology; Mathematical analysis; Mathematical models; Population balance modelling; Seed recipe design; Seeds; Size distribution control; Supersaturation; Supersaturation control; temperature; Population balance modelling; Size distribution control; Dynamic seeding; Supersaturation control; Seed recipe design; Crystallisation control; Temperature distribution; Crystals; Crystallization; Supersaturation; Seeding; Modeling; Population balance; Optimization; Design; Particle size distribution; Batchwise; Morphology; Analytical method; Kinetics; Sieve
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2012.08.048

A novel methodology is presented for the systematic design of setpoint operating curves and seed recipes for supersaturation controlled crystallization processes. A design parameter for supersaturation controlled processes is introduced as a function of supersaturation, time and growth kinetics. Based on this parameter and a simplified analytical model, the supersaturation and batch time can be determined for any supersaturation controller crystallisation process, using an optimization approach to obtain a target distribution with desired shape. The approach also gives the temperature profile versus time corresponding to a particular constant supersaturation, providing a direct design approach for practical applications. Additionally, two methods are proposed that use the seed in conjunction with the supersaturation design for CSD control. One designs the seed recipe as a mixture of crystals resulting from sieve analysis, whereas the second evaluates a dynamic seed addition profile, which is able to achieve complex target CSDs. The proposed methods are exemplified for the model system of potash alum in water.
▸ An analytical CSD estimator is derived for crystallisation at constant supersaturation. ▸ A supersaturation controlled crystallisation design parameter is introduced. ▸ Design parameter is determined via optimisation for target CSD shape. ▸ Combined supersaturation and seed recipe optimisation is proposed for CSD shaping. ▸ Analytical estimator is used to evaluate and design dynamic seeding procedures.