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Herman J. M. Kramer - One of the best experts on this subject based on the ideXlab platform.

  • crystallization kinetics in an airlift and a stirred draft tube Crystallizer secondary nucleation models revisited
    Chemical Engineering Research & Design, 2018
    Co-Authors: Fatemeh Anisi, Herman J. M. Kramer
    Abstract:

    Abstract In this research, a process model has been developed for an airlift and compared with that of a draft tube stirred Crystallizer to clarify the crystallization kinetics in this novel type of Crystallizer. Recently it has been shown that although secondary nucleation is strongly suppressed in this Crystallizer, it is not completely absent and further development and scale up requires a more quantitative prediction of the kinetics in this type of Crystallizer. A number of growth and nucleation models were examined in a parameter estimation study in which a dataset of a number of seeded batch experiments has been used to estimate the kinetics in both an airlift and a draft tube stirred Crystallizer. It is shown that a kinetic model, consisting of a two-step growth model and two additive nucleation mechanisms, i.e. an attrition based and a surface nucleation mechanism, gives an excellent and statistically acceptable description of all studied experiments with one parameter set each for both type of Crystallizers. The main difference in the two types of Crystallizers being that the attrition terms by crystal-impeller and crystal–crystal collisions in the airlift Crystallizer can be completely neglected.

  • Minimization of Attrition and Breakage in an Airlift Crystallizer
    2016
    Co-Authors: Anamaria Soare, Richard Lakerveld, Jurjen Van Royen, Giorgia Zocchi, Andrzej I. Stankiewicz, Herman J. M. Kramer
    Abstract:

    Minimization of secondary nucleation by attrition in industrial Crystallizers is a major challenge. In this work, a novel airlift Crystallizer has been designed, constructed, and experimentally tested aiming at the reduction of attrition by using air for mixing instead of a stirrer or a circulation pump. It is experimentally demonstrated that in this Crystallizer ideal growth, i.e., growth of crystals without any nucleation, can be approached up to a seeding load of 0.5% and crystal size of up to 600 μm. Attrition is considerably decreased in an airlift Crystallizer compared to conventional impeller-mixed Crystallizers. This air-mixed Crystallizer enables the production of crystals of high quality and offers a large flexibility of the final crystal size by manipulating the air flow rate and the sparger design. Comparison of different designs showed a large effect of a gas disengagement zone on the performance of the Crystallizer, especially when large crystals were desired. The disengagement zone allows high circulation velocities and thus good mixing without entrainment of the gas bubbles in the downcomer, approaching a uniform suspension of the crystals

  • Nonlinear Model-Based Control of a Semi-Industrial Batch Crystallizer Using a Population Balance Modeling Framework
    IEEE Transactions on Control Systems Technology, 2012
    Co-Authors: Abdelhak Mesbah, Adrie E. M. Huesman, Herman J. M. Kramer
    Abstract:

    This paper presents an output feedback nonlinear model-based control approach for optimal operation of industrial batch Crystallizers. A full population balance model is utilized as the cornerstone of the control approach. The modeling framework allows us to describe the dynamics of a wide range of industrial batch Crystallizers. In addition, it facilitates the use of performance objectives expressed in terms of crystal size distribution. The core component of the control approach is an optimal control problem, which is solved by the direct multiple shooting strategy. To ensure the effectiveness of the optimal operating policies in the presence of model imperfections and process uncertainties, the model predictions are adapted on the basis of online measurements using a moving horizon state estimator. The nonlinear model-based control approach is applied to a semi-industrial Crystallizer. The simulation results suggest that the feasibility of real-time control of the Crystallizer is largely dependent on the discretization coarseness of the population balance model. The control performance can be greatly deteriorated due to inadequate discretization of the population balance equation. This results from structural model imperfection, which is effectively compensated for by using the online measurements to confer an integrating action to the dynamic optimizer. The real-time feasibility of the output feedback control approach is experimentally corroborated for fed-batch evaporative crystallization of ammonium sulphate. It is observed that the use of the control approach leads to a substantial increase, i.e., up to 15%, in the batch crystal content as the product quality is sustained.

Mo Jiang - One of the best experts on this subject based on the ideXlab platform.

  • designs of continuous flow pharmaceutical Crystallizers developments and practice
    CrystEngComm, 2019
    Co-Authors: Mo Jiang
    Abstract:

    Crystallization is an effective, low-cost purification & formulation process widely applied to pharmaceuticals and fine chemicals. This review describes recent advances in research on lab-scale solution-based continuous crystallization, including (1) a 5-step general design procedure; (2) key design/operational parameters; (3) process intensification strategies; and (4) a case study. The continuous Crystallizers reviewed include mixed-suspension mixed-product removal, fluidized beds, oscillatory baffled flow, and tubular laminar/segmented/slug-flow Crystallizers. Their corresponding design and operational considerations are summarized in terms of general parameters (e.g., residence time), and Crystallizer-specific parameters and strategies (e.g., mixing strategies). In-line nucleation and crystal modification methods are categorized, including use of micromixers, wet milling, ultrasonication, temperature cycling, and recycling selection (filtration, sedimentation). Throughout the article, links are drawn with extensive existing knowledge of batch Crystallizers, to facilitate the understanding and design of continuous Crystallizers.

Allan S Myerson - One of the best experts on this subject based on the ideXlab platform.

  • Phase Transformation of Sulfamerazine Using a Taylor Vortex
    2016
    Co-Authors: Sun Lee, Woo-sik Kim, Areum Choi, Allan S Myerson
    Abstract:

    A Couette–Taylor (CT) Crystallizer was used to demonstrate the unique fluid dynamic properties of a Taylor vortex for the phase transformation of sulfamerazine (SMZ). With a conventional Rushton mixing tank (MT) Crystallizer, the phase transformation from a metastable crystalline phase to the stable crystalline phase took more than 60 h with acetonitrile (ACN) as the solvent and an agitation rate of 3000 rpm. Using a CT Crystallizer, this phase transformation occurred within 3–7 h with rotation speeds in the CT Crystallizer of 300–1000 rpm. Increasing the rotation speed of the CT Crystallizer also significantly enhanced the phase transformation, whereas adding water to the solvent increased the solubility difference between the two polymorphs and accelerated the phase transformation in both Crystallizers. The phase transformation in the CT Crystallizer was always many times faster than that in the MT Crystallizer. Nucleation and mass-transfer models were used to describe the nucleation induction time of the stable crystal form and the transformation of metastable crystals into stable crystals. The influence of the fluid motions of the periodic Taylor vortex and random eddy in the CT and MT Crystallizer, respectively, on the induction time was correlated by the nucleation enhancement factor, which was expressed as function of energy dissipation. The resulting induction and transformation times correlated well with the experimental data in terms of the energy dissipation and solubility difference across the whole range of phase transformation conditions, including rotation speeds, water fractions, and temperatures

  • Phase Transformation of Sulfamerazine Using a Taylor Vortex
    Crystal Growth & Design, 2011
    Co-Authors: Sun Lee, Areum Choi, Allan S Myerson
    Abstract:

    A Couette–Taylor (CT) Crystallizer was used to demonstrate the unique fluid dynamic properties of a Taylor vortex for the phase transformation of sulfamerazine (SMZ). With a conventional Rushton mixing tank (MT) Crystallizer, the phase transformation from a metastable crystalline phase to the stable crystalline phase took more than 60 h with acetonitrile (ACN) as the solvent and an agitation rate of 3000 rpm. Using a CT Crystallizer, this phase transformation occurred within 3–7 h with rotation speeds in the CT Crystallizer of 300–1000 rpm. Increasing the rotation speed of the CT Crystallizer also significantly enhanced the phase transformation, whereas adding water to the solvent increased the solubility difference between the two polymorphs and accelerated the phase transformation in both Crystallizers. The phase transformation in the CT Crystallizer was always many times faster than that in the MT Crystallizer. Nucleation and mass-transfer models were used to describe the nucleation induction time of t...

Claudio De Rosa - One of the best experts on this subject based on the ideXlab platform.

  • Oriented Microstructures of Crystalline–Crystalline Block Copolymers Induced by Epitaxy and Competitive and Confined Crystallization
    2016
    Co-Authors: Claudio De Rosa, Finizia Auriemma, Giovanni Talarico, Rocco Di Girolamo, Maria D’avino, Claudia Cioce, Miriam Scoti, Geoffrey W. Coates, Bernard Lotz
    Abstract:

    Polyethylene-block-syndiotactic polypropylene (PE-block-sPP) crystalline–crystalline block copolymers with different block lengths have been synthesized with a stereospecific living organometallic catalyst. Samples of PE-block-sPP have been epitaxially crystallized onto crystals of p-terphenyl (3Ph) to achieve a control over the crystallization of both blocks and study the dependence of the thin film morphology on the sequential crystallization of the two blocks by cooling from the melt. The epitaxial crystallization generates oriented overgrowth of both crystals of sPP and PE, with a highly ordered single orientation of sPP lamellae and a double orientation of PE lamellae onto the (001) face of 3Ph. The final morphology depends on which polymer block crystallizes first, a sequence that depends on the block copolymer composition and block lengths. Ordered nanostructures with alternating lamellar domains are obtained and oriented by the lamellae that crystallize first

  • comparison between polymorphic behaviors of ziegler natta and metallocene made isotactic polypropylene the role of the distribution of defects in the polymer chains
    Macromolecules, 2004
    Co-Authors: Claudio De Rosa, Finizia Auriemma, Clementina Spera, Giovanni Talarico, Oreste Tarallo
    Abstract:

    A comparative analysis of the polymorphic behavior of samples of isotactic polypropylene (iPP) prepared with heterogeneous Ziegler−Natta catalysts and with a single-center homogeneous metallocene catalyst is presented. Different samples of Ziegler−Natta iPP, prepared with MgCl2-supported catalysts modified by adding different Lewis bases, have been fractionated by extraction with boiling solvents. The irregular fraction, insoluble in diethyl ether and soluble in hexane, crystallizes from the melt almost totally in the γ form. The more stereoregular fractions crystallize instead basically in the α form. This confirms that, even in the case of Ziegler−Natta iPP samples, the γ form may develop by melt-crystallization at atmospheric pressure in fractions containing a high concentration of defects. The relative amount of γ form crystallized from the melt is, however, much lower that that observed in samples of metallocene-made iPP containing comparable amount of defects. Since the γ form crystallizes in chains...

Andreas Seidelmorgenstern - One of the best experts on this subject based on the ideXlab platform.

  • numerical approximations of a population balance model for coupled batch preferential Crystallizers
    Applied Numerical Mathematics, 2009
    Co-Authors: Shamsul Qamar, Ilia Angelov, M P Elsner, Adnan Ashfaq, Andreas Seidelmorgenstern, Gerald Warnecke
    Abstract:

    This article is concerned with the numerical approximations of population balance equations for modeling coupled batch preferential crystallization processes. The current setup consists of two batch Crystallizers interconnected with two fines dissolution pipes. The crystallization of both enantiomers is assumed to take place in separate Crystallizers after seeding with their corresponding crystals. The withdrawn fines are assumed to be dissolved in the dissolution unit after heating. Crystallizer, the Crystallizer temperature before entering to the opposite Crystallizer. Two types of numerical methods are proposed for the simulation of this process. The first method uses high resolution finite volume schemes, while the second method is the so-called method of characteristics. On the one hand, the finite volume schemes which were derived for general system in divergence form, are computationally efficient, give desired accuracy on coarse grids, and are robust. On the other hand, the method of characteristics is in general a powerful tool for solving growth processes, has capability to overcome numerical diffusion and dispersion, gives highly resolved solutions, as well as being computationally efficient. A numerical test problem with both isothermal and non-isothermal conditions is considered here. The numerical results show clear advantages of the proposed schemes.

  • efficient separation of enantiomers by preferential crystallization in two coupled vessels
    Aiche Journal, 2009
    Co-Authors: M P Elsner, Andreas Seidelmorgenstern, G Ziomek
    Abstract:

    The focus of this work is to study the enantioseparation of conglomerate forming systems using an innovative configuration for preferential crystallization. Two batch Crystallizers are coupled by an exchange of their liquid phases. In each vessel one of the two enantiomers is seeded initially and crystallizes subsequently. Compared with conventional single batch crystallization the exchange of the crystal free liquid phases between two Crystallizers leads to an increase of the concentrations of the preferred enantiomers and therefore to an increase of the driving forces for the crystallization. This enhances the productivity of the process compared with the conventional operation. © 2009 American Institute of Chemical Engineers AIChE J, 2009