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Herman J. M. Kramer - One of the best experts on this subject based on the ideXlab platform.
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crystallization kinetics in an airlift and a stirred draft tube crystallizer secondary nucleation models revisited
Chemical Engineering Research & Design, 2018Co-Authors: Fatemeh Anisi, Herman J. M. KramerAbstract: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.
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an air lift crystallizer can suppress secondary nucleation at a higher supersaturation compared to a stirred crystallizer
Crystal Growth & Design, 2014Co-Authors: Richard Lakerveld, Jeroen Van Krochten, Herman J. M. KramerAbstract:Secondary nucleation is suppressed in an air-lift crystallizer at levels of supersaturation where in a stirred crystallizer a clear contribution of secondary nucleation is visible. A comparison of batch crystallization of l-ascorbic acid in an air-lift crystallizer and in a stirred crystallizer is presented. The results demonstrate that at low supersaturation, secondary nucleation can be suppressed in both the air-lift crystallizer and the stirred crystallizer. At higher supersaturation, nucleation starts to dominate in the air-lift crystallizer. At an intermediate level of supersaturation, a clear contribution of secondary nucleation in the final product obtained from the stirred crystallizer is visible. However, experiments with similar conditions in the air-lift crystallizer show a significantly smaller contribution of secondary nucleation. The observed enlargement of the operating window in terms of supersaturation where secondary nucleation is suppressed in an air-lift crystallizer may have important...
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Growth behaviour of crystals formed by primary nucleation on different Crystalliser scales
Journal of Crystal Growth, 2002Co-Authors: G.m. Westhoff, Herman J. M. Kramer, B.k. Butler, Peter J. JansensAbstract:The growth behaviour of small ammonium sulphate crystals obtained from primary nucleation in different Crystallisers were studied. The results revealed a broadening of the distribution upon growth of the crystals that is attributed to growth rate dispersion. This phenomenon was somewhat more pronounced in experiments with the fines imported from a 1100 l draft tube baffled Crystalliser compared to those generated in a 2 l cooling Crystalliser. This small difference in the growth behaviour between the crystals originating from the two Crystallisers, however, does not allow one to reject the hypothesis that the outgrowth of the crystals originating from either primary and secondary nucleation is identical for a small and for a large-scale Crystalliser. The growth behaviour of these crystals was simulated using a size-dependent growth model. The simulation results revealed that the growth model (Chem. Eng. Sci. 54 (1999) 1273,1283) is capable of simulating trends in the supersaturation and the median crystal size but was not able to describe the observed broadening of the crystal size distribution.
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towards on scale Crystalliser design using compartmental models
Computers & Chemical Engineering, 1998Co-Authors: Sean K Bermingham, Herman J. M. Kramer, Gerda M Van RosmalenAbstract:Abstract In this paper the importance of on-scale Crystalliser design is outlined. An on-scale approach is specifically required for the analysis and optimisation tasks in design. The need for this approach is a direct consequence of the nonlinear dependency of most physical processes in crystallisation on the degree of saturation, the energy dissipation, the crystal size, and its distribution. The hydrodynamics in a Crystalliser vessel are typically such, that these process variables are distributed non-uniformly throughout the vessel. The conventional, geometrically lumped description of the physical process inside a Crystalliser vessel, i.e nucleation, growth, dissolution, attrition, breakage agglomeration and particle segregation, has therefore never proven to be reliable for scale-up purposes. Furthermore, as the interactions between these processes lead to an intricate dynamic behaviour, models describing the effect of changes in time of process variables on the product quality are essential. Compartmental modelling, a well known technique in reactor engineering and applied within crystallisation since a number of years, facilitates on-scale design since it allows a natural separation of kinetic and hydrodynamic mechanisms. The resulting dynamic models (order of 10 4 equations) can be easily tackled with standard DAE solvers. Here we will focus upon the need for a proper physical description of the aforementioned crystallisation mechanisms. First of all, a brief description of the dependencies of these mechanisms upon local supersaturation or undersaturation, local energy dissipation and crystal size is given. Depending on the type of crystallisation process, suspension crystallisation or precipitation, the dependencies necessary to be included in the compartmental model, in order to describe their overall effect are discussed. The next step is deriving the geometric structure of a compartmental model for a certain scale Crystalliser and material, for which two methodologies will be presented. Finally, the approach will be illustrated for evaporative crystallisation of ammonium sulphate from water in 0.15 and 18.5 m 3 FC (Forced Circulation) and 0.022 and 1.1 m 3 DTB (Draft Tube Baffle) Crystallisers, using size dependent nucleation, growth, dissolution, attrition and segregation models.
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effect of scale of operation on csd dynamics in evaporative crystallizers
Aiche Journal, 1991Co-Authors: Johan Jager, Herman J. M. Kramer, Esso J De Jong, Brian Scarlett, Sjoerd De WolfAbstract:Experimental measurements of the crystal-size distribution (CSD) clearly indicate a pronounced difference in the dynamic behavior of a 20- and 970-L continuous crystallizer that produces ammonium sulfate. The difference in their circulation time offers a probable explanation for this phenomenon. It causes different supersaturation profiles in the two crystallizers, which leads to internal fines dissolution in the large crystallizer. This contributes to the observed oscillations in the 970-L crystallizer as opposed to the first-order responses in the 20-L crystallizer. To numerically study the effect of the supersaturation profile a dynamic model, from which the MSMPR (mixed suspension mixed product removal) assumption is omitted, is developed. Calculated supersaturation profiles differ considerably for the 20-L, the 970-L and an imaginary 50,000-L continuous evaporative crystallizer. Coincident with changes in the supersaturation profiles, the numerical solution of the model indicates the tendency of large crystallizers to oscillate and supports this suggested explanation.
Chris D Rielly - One of the best experts on this subject based on the ideXlab platform.
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solid liquid axial dispersion performance of a mesoscale continuous oscillatory flow Crystalliser with smooth periodic constrictions using a non invasive dual backlit imaging technique
Chemical Engineering Journal, 2020Co-Authors: Iyke I Onyemelukwe, Zoltan K Nagy, Chris D RiellyAbstract:Abstract A dual backlit imaging technique has been developed for liquid and solid phase residence time distribution (RTD) measurements in a mesoscale (millilitre) continuous oscillatory flow Crystalliser with smooth periodic constrictions (herein known as the SPC mesoscale Crystalliser). The pixel-based technique enables reliable determination and direct comparison of experimentally determined hydrodynamic parameters for the liquid and solid phase without concern for errors that may be introduced by utilising different measurement techniques for each phase. Additionally, the non-invasive technique offers benefits over traditional intrusive methods as demonstrated herein. Results of solid-liquid RTD experiments reveal that for a set of oscillatory flow conditions, particles do not experience the same degree of axial dispersion and mean residence time as the continuous liquid phase. The SPC mesoscale Crystalliser, however, provides solid-liquid plug flow at low net flow rates. Findings in this work emphasise the importance of characterising solid phase axial dispersion for active pharmaceutical ingredient (API) systems during continuous crystallisation development to identify minimum dispersion operating conditions essential for solid-liquid plug flow crystallisation.
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state feedback linearization and adaptive model predictive control applied to a simulated msmpr Crystalliser abstract
British Association For Crystal Growth Annual Conference 2017 (BACG 2017), 2017Co-Authors: R Parekh, Brahim Benyahia, Chris D RiellyAbstract:State feedback linearization and adaptive model predictive control applied to a simulated MSMPR Crystalliser [Abstract]
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input output state feedback linearization and model predictive control of an msmpr Crystalliser abstract
20th International Symposium on Industrial Crystallization (ISIC 20), 2017Co-Authors: R Parekh, Brahim Benyahia, Chris D RiellyAbstract:Input-output state feedback linearization and model predictive control of an MSMPR Crystalliser [Abstract]
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pharmaceutical crystallisation processes from batch to continuous operation using msmpr stages modelling design and control
Chemical Engineering and Processing, 2015Co-Authors: Zoltan K Nagy, Chris D RiellyAbstract:In pharmaceuticals manufacturing, the conversion of conventional batch crystallisations to continuous mode has the potential for intensified, compact operation and more consistent production via quality-by-design. A pragmatic conversion approach is to utilise existing stirred tank batch Crystallisers as continuous mixed-suspension mixed-product removal (MSMPR) stages. In this study, a rigorous and general mathematical model is developed for a pharmaceutical crystallisation process under continuous MSMPR operation. In the proposed changeover from batch to continuous operation, concentration control (C-control), which has been well accepted in batch crystallisation operation, is further extended to facilitate the convenient design of the steady-state operating point of a continuous MSMPR Crystalliser; an objective is to ensure that the start-up procedures and on-line control conditions fall within the design-space of the original batch operation. Both single-stage and cascaded two-stage MSMPR Crystallisers were investigated and compared to the conventional batch operation. It was observed that despite the production of a smaller number-based mean crystal size, the proposed continuous MSMPR operation achieved higher production capacity with shorter mean residence time and comparable product yield to the batch operation. Lastly, the robustness of C-control strategy against uncertainties in crystallisation kinetics was also demonstrated for the proposed continuous MSMPR operation.
Zoltan K Nagy - One of the best experts on this subject based on the ideXlab platform.
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solid liquid axial dispersion performance of a mesoscale continuous oscillatory flow Crystalliser with smooth periodic constrictions using a non invasive dual backlit imaging technique
Chemical Engineering Journal, 2020Co-Authors: Iyke I Onyemelukwe, Zoltan K Nagy, Chris D RiellyAbstract:Abstract A dual backlit imaging technique has been developed for liquid and solid phase residence time distribution (RTD) measurements in a mesoscale (millilitre) continuous oscillatory flow Crystalliser with smooth periodic constrictions (herein known as the SPC mesoscale Crystalliser). The pixel-based technique enables reliable determination and direct comparison of experimentally determined hydrodynamic parameters for the liquid and solid phase without concern for errors that may be introduced by utilising different measurement techniques for each phase. Additionally, the non-invasive technique offers benefits over traditional intrusive methods as demonstrated herein. Results of solid-liquid RTD experiments reveal that for a set of oscillatory flow conditions, particles do not experience the same degree of axial dispersion and mean residence time as the continuous liquid phase. The SPC mesoscale Crystalliser, however, provides solid-liquid plug flow at low net flow rates. Findings in this work emphasise the importance of characterising solid phase axial dispersion for active pharmaceutical ingredient (API) systems during continuous crystallisation development to identify minimum dispersion operating conditions essential for solid-liquid plug flow crystallisation.
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chapter 2 fundamentals of population balance based crystallization process modeling
2020Co-Authors: Botond Szilagyi, Aniruddha Majumder, Zoltan K NagyAbstract:Crystallization is ubiquitous in pharmaceutical manufacturing as a means of separation and purification. The pharmaceutical industry is currently going through a paradigm shift from batch to continuous manufacturing due to its various benefits such as improved product consistency, improved productivity, ease of scale up, efficient use of physical space and reduction in energy consumption. Crystallization is a key unit operation in a continuous manufacturing process since in addition to being a critical purification step it also defines the critical properties of the particulate products. In silico evaluation and design of crystallization systems can significantly reduce process development time and allow the understanding and defining of the optimal operating space. While significant progress has been made to date, this chapter is primarily focused on presenting the basic concepts of modeling and simulation of the two continuous crystallizer platforms – mixed suspension mixed product removal (MSMPR) crystallizer and plug flow crystallizer (PFC). Starting from the fundamental concepts of the crystallization process, modeling of the various sub processes such as nucleation, growth, aggregation and breakage are discussed. Then, the population balance model for the continuous crystallizer platforms are discussed along with the numerical techniques that can be used to solve the model equations. Finally, a few case studies are presented including cooling and antisolvent crystallizations, as well as crystallization of polymorphic and enantiomeric systems.
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population balance modeling and optimization of an integrated batch crystallizer wet mill system for crystal size distribution control
Crystal Growth & Design, 2018Co-Authors: Zoltan K Nagy, Botond SzilagyiAbstract:In this work, the modeling, simulation, and optimization of an integrated batch crystallizer, wet mill system are presented. It is shown that by coupling the external wet mill to the crystallizer it is possible to increase the overall system flexibility, increase the attainable crystal size distribution (CSD), and provide a significantly better distribution shaping control than the crystallizer alone. The population balance modeling approach with appropriate mechanisms is applied for the description of crystal population in both the crystallizer and wet mill. This description generates a system of partial differential-integral equations, which are solved with a high resolution finite volume method, involving calculations on parallel graphical processing unit for improved solution time. In the batch crystallizer, it is assumed that primary nucleation and crystal growth are the key mechanisms, whereas in the wet mill, attrition and fragmentation of crystals occurs. The nucleation and growth rate kinetics ar...
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pharmaceutical crystallisation processes from batch to continuous operation using msmpr stages modelling design and control
Chemical Engineering and Processing, 2015Co-Authors: Zoltan K Nagy, Chris D RiellyAbstract:In pharmaceuticals manufacturing, the conversion of conventional batch crystallisations to continuous mode has the potential for intensified, compact operation and more consistent production via quality-by-design. A pragmatic conversion approach is to utilise existing stirred tank batch Crystallisers as continuous mixed-suspension mixed-product removal (MSMPR) stages. In this study, a rigorous and general mathematical model is developed for a pharmaceutical crystallisation process under continuous MSMPR operation. In the proposed changeover from batch to continuous operation, concentration control (C-control), which has been well accepted in batch crystallisation operation, is further extended to facilitate the convenient design of the steady-state operating point of a continuous MSMPR Crystalliser; an objective is to ensure that the start-up procedures and on-line control conditions fall within the design-space of the original batch operation. Both single-stage and cascaded two-stage MSMPR Crystallisers were investigated and compared to the conventional batch operation. It was observed that despite the production of a smaller number-based mean crystal size, the proposed continuous MSMPR operation achieved higher production capacity with shorter mean residence time and comparable product yield to the batch operation. Lastly, the robustness of C-control strategy against uncertainties in crystallisation kinetics was also demonstrated for the proposed continuous MSMPR operation.
Matthias Kind - One of the best experts on this subject based on the ideXlab platform.
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Fluidisation of whey powders above the glass-transition temperature
Powder Technology, 2008Co-Authors: J. J. Nijdam, Alexander Ibach, Matthias KindAbstract:The fluidisation of partially-crystallised whey powder above the glass-transition temperature of lactose has been investigated, with the intent of crystallising the amorphous-lactose fraction in order to reduce the propensity of the powder to cake during storage. Partially-crystallised whey powder can be fluidised in a vibrated fluidised bed at temperatures of 25 to 40 °C above the glass-transition point of lactose, depending on the relative humidity of the air, before the powder becomes too sticky to fluidise. This temperature difference can be increased up to 80 °C by fluidising the powder with fine, relatively non-sticky, fully-crystallised whey powder in order to coat and protect the sticky partially-crystallised whey particulates during fluidisation. Despite this temperature-difference increase, the time required to crystallise the amorphous-lactose fraction in partially-crystallised whey powder is not reduced sufficiently for this process to be viable in industry. An amorphous whey powder crystallisation process is likely to be more feasible, because the reduced salt and protein concentrations in this powder would ensure that lactose crystallisation is faster. Finally, this work has highlighted the potential of using the phenomenon of lactose plasticization above the glass-transition temperature and fines coating to improve the instant properties of milk-based powders.
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determination of the attrition behaviour of ammonium sulphate and of pentaerythritol crystals using a forced circulation Crystalliser
Powder Technology, 2004Co-Authors: Alexander Lieb, Matthias KindAbstract:For many technically relevant systems to be crystallised, attrition of crystals due to their impact onto stirrer blades, pumps, etc., is the main source of nucleation. In this study, a new experimental set-up for continuous crystallisation is applied to quantitatively determine attrition model parameters. These parameters are to be used for simulation calculations of technical Crystallisers. The apparatus provides the possibility to obtain high supersaturation and large crystals under well-mixed conditions. For this purpose on the one hand, a particular pump is used, which obviates attrition. On the other hand, an impingement device is included in the circulation loop of the FC Crystalliser, in order to mechanically stress the crystals in a well-defined manner. Experimental results and simulations are presented for pentaerythritol-water and for ammonium sulphate-water. The simulations well describe the influence of mechanical stress on the crystal size distribution, whereas the influence of residence time is not well described.
Michela Venturelli - One of the best experts on this subject based on the ideXlab platform.
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trace element fractionation through halite crystallisation geochemical mechanisms and environmental implications
Science of The Total Environment, 2020Co-Authors: P Censi, Ido Sirota, Pierpaolo Zuddas, N Lensky, Filippo Saiano, F Sposito, Daniela Piazzese, Manuela Merli, Michela VenturelliAbstract:Abstract Halite is an important mineral for industry, agriculture and food production. It crystallises during water evaporation, and the progressive increase of dissolved metal ions in the brine occurs simultaneously. Thus, halite exploitation may deliver metal ions into the environment and the mechanism of this trace element accumulation has to be studied. In this work, we investigate the distribution of lanthanides and Y (hereafter called rare earth elements, REE), Zr and Hf between crystallising halite and brines in the Dead Sea as geochemical tools for recognising the mechanism of metal ion removal from brines and accumulation in halite. Halite forms cubic crystals where octahedral planes sometimes occur under particular thermal gradient conditions. Our findings indicate that crystal morphology influences the mechanism of metal ion removal from brines because octahedral surfaces are polar unlike those that are cubic. Accordingly, octahedra preferentially fractionate aqueous charged species such as [Hf(OH)5]−, compared to neutral species such as [Zr(OH)4]0. Cubic surfaces do not fractionate aqueous species. In crystal cores, positive Eu anomalies occur suggesting Eu substitution for Na in the lattice. This substitution is energetically justified by ab initio calculations. Hf enrichment relative to Zr also occurs in primary halite-rich evaporites. It is not found in cubic halite from saltworks. The results of this study suggest that primary halite kinetically crystallised from brines can concentrate dissolved metal ions onto crystal surfaces where dissolved charged species are adsorbed. Accordingly, the dissolution of halite due to human activity can release these metal ions to the environment.