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Crystals
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Recent Progress in Industrial Crystallization
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Recent Progress in Industrial Crystallization

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Industrial Crystallization".

Deadline for manuscript submissions: closed (30 June 2022) | Viewed by 32235

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Prof. Dr. Heike Lorenz

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Guest Editor
Max Planck Institute for Dynamics of Complex Technical Systems, 39106 Magdeburg, Germany
Interests: phase equilibria; crystallization kinetics; process monitoring & design; separation of fine chemicals, large scale industrial products and renewable resources; innovative crystallization-based separation concepts; enantiomers; natural products; multi-component mixtures
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Alison Emslie Lewis

E-Mail Website
Guest Editor
Department of Chemical Engineering, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
Interests: industrial crystallization; freeze crystallization; water treatment
Dr. Erik Temmel

E-Mail Website
Guest Editor
Sulzer Chemtech Ltd., Basel, Switzerland
Interests: melt crystallization; crystallizer design; fractional crystallization; phase equilibria; crystallization kinetics; continuous crystallization; process monitoring; process design; applied population balance and process modelling; process intensification and combination; process optimization; novel measurement techniques

Special Issue Information

Crystallization is an important industrial process, a purification technique, a separation process and a branch of particle technology. It also encompasses several key areas of chemical and process engineering. Industrial crystalline products include bulk chemicals, such as sodium chloride and sucrose, fertilizer chemicals such as potassium chloride and urea and, high-price products such as pharmaceuticals, platinum group metal salts, high-grade materials for battery production and organic fine chemicals such as food additives. Industrial crystallization further plays a role in the new and rapidly expanding field of engineered nanoparticles and the production of crystals for the electronics industry and biotechnology. Other prominent industrial application domains comprise the use of crystallization in water and effluent treatment, reflecting the waste-to-resource movement that is becoming increasingly important and relevant in the field.

The overall theme of this Special Issue is how theoretical concepts are adapted in industrial crystallization, and how practical understanding in the field is enhanced through applied research. The latter covers a wide range of subjects, such as crystallization fundamentals, analytical tools for process analysis and monitoring, crystallization process and product design, as well as the integration of crystallization in industrial process chains for, for example, solving environmental and sustainability issues. These topics are also the focus of the 21st International Symposium on Industrial Crystallization (ISIC 21) held from 31 August to 2 September this year (https://dechema.de/en/ISIC_2021), seen as the most important international conference in the field.

This Special Issue is dedicated to Professor Gerda van Rosmalen (27 May 1936–18 January 2021), who was a pioneer in this field. She developed the field of industrial crystallization research through her original courses developed over many decades and given to industrial partners and postgraduate students. Professor van Rosmalen spent 20 years as the Professor of Industrial Crystallization and Clean Technology at the Laboratory for Process Equipment at TU Delft in the Netherlands, and her distinguished positions include being a Board Member of the Working Party on the Industrial Crystallization of the European Federation of Chemical Engineers. She was regarded globally as a pre-eminent figure in industrial crystallization.

The keywords given below encompass examples addressed in the Special Issue, but papers concerning other innovative and novel subjects in industrial crystallization are also welcome.

Prof. Dr. Heike Lorenz
Prof. Dr. Alison Emslie Lewis
Dr. Erik Temmel
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Nucleation
  • Crystal growth
  • Polymorphism, solvates, co-crystals and solid solutions
  • Crystallization
  • Precipitation
  • Monitoring of crystallization
  • Crystallization hybrid processes
  • Application in large-scale, fine chemical, specialty and life science industries
  • Sustainability: circular economy, resource recovery

Related Special Issue

Published Papers (13 papers)

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Research

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9 pages, 872 KiB  
Article
Structural Properties of Bacterial Cellulose Film Obtained on a Substrate Containing Sweet Potato Waste
by Izabela Betlej, Katarzyna Rybak, Małgorzata Nowacka, Andrzej Antczak, Sławomir Borysiak, Barbara Krochmal-Marczak, Karolina Lipska and Piotr Boruszewski
Crystals 2022, 12(9), 1191; https://doi.org/10.3390/cryst12091191 - 25 Aug 2022
Cited by 9 | Viewed by 1794
Abstract
The paper presents the results of research on the microstructure of bacterial cellulose (BC-SP) obtained on a medium containing sweet potato peel, which was compared to cellulose obtained on a synthetic medium containing sucrose and peptone (BC-N). The properties of cellulose were analyzed [...] Read more.
The paper presents the results of research on the microstructure of bacterial cellulose (BC-SP) obtained on a medium containing sweet potato peel, which was compared to cellulose obtained on a synthetic medium containing sucrose and peptone (BC-N). The properties of cellulose were analyzed using the methods: size exclusion chromatography (SEC), X-ray diffraction (XRD), scanning electron microscope (SEM), and computer microtomograph (X-ray micro-CT). BC-SP was characterized by a higher degree of polymerization (5680) and a lower porosity (1.45%) than BC-N (4879, 3.27%). These properties give great opportunities to cellulose for various applications, e.g., the production of paper or pulp. At the same time, for BC-SP, a low value of relative crystallinity was found, which is an important feature from the point of view of the mechanical properties of the polymer. Nevertheless, these studies are important and constitute an important source of knowledge on the possibility of using cheap waste plant materials as potential microbiological substrates for the cultivation of cellulose-synthesizing micro-organisms with specific properties. Full article
(This article belongs to the Special Issue Recent Progress in Industrial Crystallization)
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15 pages, 1960 KiB  
Article
Phase Diagram Determination and Process Development for Continuous Antisolvent Crystallizations
by Corin Mack, Johannes Hoffmann, Jan Sefcik and Joop H. ter Horst
Crystals 2022, 12(8), 1102; https://doi.org/10.3390/cryst12081102 - 06 Aug 2022
Cited by 2 | Viewed by 2240
Abstract
The development of an antisolvent crystallization process requires the construction of an accurate phase diagram for this ternary system of compound, solvent and antisolvent, preferably as a function of temperature. This study gives an efficient methodology to systematically determine such antisolvent phase diagrams, [...] Read more.
The development of an antisolvent crystallization process requires the construction of an accurate phase diagram for this ternary system of compound, solvent and antisolvent, preferably as a function of temperature. This study gives an efficient methodology to systematically determine such antisolvent phase diagrams, exemplified with four model compounds: Sodium bromate, DL-Asparagine Monohydrate, Mefenamic acid and Lovastatin. Using clear point temperature measurements, single solvent and mixed solvent-antisolvent solubilities are obtained, showing strongly non-linear solubility dependencies as well as more complex solubility behaviour as a function of antisolvent fraction. A semi-empirical model equation is used to describe the phase diagram of the antisolvent crystallization system as a function of both temperature and antisolvent fraction. The phase diagram model then allows for the identification of condition ranges for optimal productivity, yield, and suspension density in continuous antisolvent crystallization processes. Full article
(This article belongs to the Special Issue Recent Progress in Industrial Crystallization)
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16 pages, 5875 KiB  
Article
Gypsum Seeding to Prevent Scaling
by Taona Malvin Chagwedera, Jemitias Chivavava and Alison Emslie Lewis
Crystals 2022, 12(3), 342; https://doi.org/10.3390/cryst12030342 - 02 Mar 2022
Viewed by 2321
Abstract
Eutectic freeze crystallization (EFC) is a novel separation technique that can be applied to treat brine solutions such as reverse osmosis retentates. These are often a mixture of different inorganic solutes. The treatment of calcium sulphate-rich brines using EFC often results in gypsum [...] Read more.
Eutectic freeze crystallization (EFC) is a novel separation technique that can be applied to treat brine solutions such as reverse osmosis retentates. These are often a mixture of different inorganic solutes. The treatment of calcium sulphate-rich brines using EFC often results in gypsum crystallization before any other species. This results in gypsum scaling on the cooled surfaces of the crystallizer, which is undesirable as it retards heat transfer rates and hence reduces the yield of other products. The aim of this study was to investigate and understand gypsum crystallization and gypsum scaling in the presence of gypsum seeds. Synthetic brine solutions were used in this research because they allowed an in-depth understanding of the gypsum bulk crystallization process and scaling tendency without the complexity of industrial brines. A cooled, U-shaped stainless-steel tube suspended in the saturated solution was employed as the scaling surface. This was because a tube-shaped surface enabled the introduction of a constant temperature cold surface in the saturated solution and most industrial EFC crystallizers are constructed from stainless steel. Gypsum seeding was effective in decreasing the mass of scale formed on the heat transfer surface. The most effective seed loading was 0.25 g/L, which reduced scale growth rate by 43%. Importantly, this seed loading is six times the theoretical critical seed loading. The seeding strategy also increased the gypsum crystallization kinetics in the bulk solution, which resulted in an increase in the mass of gypsum product. These findings are relevant for the operability and control of EFC processes, which suffer from scaling problems. By using an appropriate seeding strategy, two problems can be alleviated. Firstly, scaling on the heat transfer surface is minimised and, secondly, seeding increases the crystallization kinetics in the bulk solution, which is advantageous for product yield and recovery. It was also recommended that the use of silica as a seed material to prevent gypsum scaling should be investigated in future studies. Full article
(This article belongs to the Special Issue Recent Progress in Industrial Crystallization)
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19 pages, 4280 KiB  
Article
Continuous Isolation of Particles with Varying Aspect Ratios up to Thin Needles Achieving Free-Flowing Products
by Claas Steenweg, Jonas Habicht and Kerstin Wohlgemuth
Crystals 2022, 12(2), 137; https://doi.org/10.3390/cryst12020137 - 19 Jan 2022
Cited by 5 | Viewed by 1775
Abstract
The continuous vacuum screw filter (CVSF) for small-scale continuous product isolation of suspensions was operated for the first time with cuboid-shaped and needle-shaped particles. These high aspect ratio particles are very common in pharmaceutical manufacturing processes and provide challenges in filtration, washing, and [...] Read more.
The continuous vacuum screw filter (CVSF) for small-scale continuous product isolation of suspensions was operated for the first time with cuboid-shaped and needle-shaped particles. These high aspect ratio particles are very common in pharmaceutical manufacturing processes and provide challenges in filtration, washing, and drying processes. Moreover, the flowability decreases and undesired secondary processes of attrition, breakage, and agglomeration may occur intensively. Nevertheless, in this study, it is shown that even cuboid and needle-shaped particles (l-alanine) can be processed within the CVSF preserving the product quality in terms of particle size distribution (PSD) and preventing breakage or attrition effects. A dynamic image analysis-based approach combining axis length distributions (ALDs) with a kernel-density estimator was used for evaluation. This approach was extended with a quantification of the center of mass of the density-weighted ALDs, providing a measure to analyze the preservation of the inlet PSD statistically. Moreover, a targeted residual moisture below 1% could be achieved by adding a drying module (Tdry = 60 °C) to the modular setup of the CVSF. Full article
(This article belongs to the Special Issue Recent Progress in Industrial Crystallization)
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24 pages, 3117 KiB  
Article
Reactive Crystallization Kinetics of K2SO4 from Picromerite-Based MgSO4 and KCl
by Abad Albis, Yecid P. Jiménez, Teófilo A. Graber and Heike Lorenz
Crystals 2021, 11(12), 1558; https://doi.org/10.3390/cryst11121558 - 14 Dec 2021
Cited by 4 | Viewed by 2779
Abstract
In this work, the kinetic parameters, the degrees of initial supersaturation (S0) and the profiles of supersaturation (S) were determined for the reactive crystallization of K2SO4 from picromerite (K2SO4.MgSO4.6H2 [...] Read more.
In this work, the kinetic parameters, the degrees of initial supersaturation (S0) and the profiles of supersaturation (S) were determined for the reactive crystallization of K2SO4 from picromerite (K2SO4.MgSO4.6H2O) and KCl. Different reaction temperatures between 5 and 45 °C were considered, and several process analytical techniques were applied. Along with the solution temperature, the crystal chord length distribution (CLD) was continuously followed by an FBRM probe, images of nucleation and growth events as well as the crystal morphology were captured, and the absorbance of the solution was measured via ATR-FTIR spectroscopy. In addition, the ion concentrations were analyzed. It was found that S0 is inversely proportional to the reactive crystallization temperature in the K+, Mg2+/Cl−, SO42−//H2O system at 25 °C, where S0 promotes nucleation and crystal growth of K2SO4 leading to a bimodal CLD. The CLD was converted to square-weighted chord lengths for each S0 to determine the secondary nucleation rate (B), crystal growth rate (G), and suspension density (MT). By correlation, from primary nucleation rate (Bb) and G with S0, the empirical parameters b = 3.61 and g = 4.61 were obtained as the order of primary nucleation and growth, respectively. B versus G and MT were correlated to the reaction temperature providing the rate constants of B and respective activation energy, E = 69.83 kJ∙mol−1. Finally, a general Equation was derived that describes B with parameters KR = 13,810.8, i = 0.75 and j = 0.71. The K2SO4 crystals produced were of high purity, containing maximal 0.51 wt% Mg impurity, and were received with ~73% yield at 5 °C. Full article
(This article belongs to the Special Issue Recent Progress in Industrial Crystallization)
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11 pages, 2164 KiB  
Article
Solubility and Crystallization of Piroxicam from Different Solvents in Evaporative and Cooling Crystallization
by Iben Ostergaard and Haiyan Qu
Crystals 2021, 11(12), 1552; https://doi.org/10.3390/cryst11121552 - 11 Dec 2021
Cited by 3 | Viewed by 3447
Abstract
In this work, the solubility of a non-steroidal anti-inflammatory drug (NSAID), piroxicam, is investigated. The polymorphic form II, which is the most stable form at room temperature, was investigated in seven different solvents with various polarities. It has been found that the solubility [...] Read more.
In this work, the solubility of a non-steroidal anti-inflammatory drug (NSAID), piroxicam, is investigated. The polymorphic form II, which is the most stable form at room temperature, was investigated in seven different solvents with various polarities. It has been found that the solubility of piroxicam in the solvents is in the following order: chloroform > dichloromethane > acetone > ethyl acetate > acetonitrile > acetic acid > methanol > hexane. Crystallization of piroxicam from different solvents has been performed with evaporative crystallization and cooling crystallization; the effects of solvent evaporation rate and solute concentration have also been studied. Both form I and form II could be produced in cooling and evaporative crystallization, and no simple link can be identified between the operating parameters and the polymorphic outcome. Results obtained in the present work showed the stochastic nature of the nucleation of different polymorphs as well as the complexity of the crystallization of a polymorphic system. Full article
(This article belongs to the Special Issue Recent Progress in Industrial Crystallization)
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15 pages, 3141 KiB  
Article
The Effect of Reaction Conditions and Presence of Magnesium on the Crystallization of Nickel Sulfate
by Ina Beate Jenssen, Oluf Bøckman, Jens-Petter Andreassen and Seniz Ucar
Crystals 2021, 11(12), 1485; https://doi.org/10.3390/cryst11121485 - 30 Nov 2021
Cited by 2 | Viewed by 3856
Abstract
Recycling of valuable metals such as nickel is instrumental to meet the need from the dramatic increase in electric vehicle battery production and to improve its sustainability. Nickel required in the battery manufacture can be recovered from the hydrometallurgical industrial process streams by [...] Read more.
Recycling of valuable metals such as nickel is instrumental to meet the need from the dramatic increase in electric vehicle battery production and to improve its sustainability. Nickel required in the battery manufacture can be recovered from the hydrometallurgical industrial process streams by crystallization of nickel sulfate. Here, crystallization of nickel sulfate is studied from an industrial point of view, investigating the effects of temperature, seeding and presence of magnesium on the formation of various solid phases for the evaluation of their potential influence on the process design. Results showed that the precipitating phase was dictated both by seed amount and reaction temperature. Transformation of metastable phases both in suspension and in a dry state was observed over time. Presence of magnesium was shown to promote formation of NiSO4·7H2O in solution and increased its stability in a dry form. In their dry state, nickel sulfate that was formed in the absence of magnesium transformed towards α-NiSO4·6H2O, whereas those precipitated in the presence of high magnesium concentrations transformed towards β-NiSO4·6H2O, indicating that magnesium inhibited the phase transformation towards α-NiSO4·6H2O. Knowledge about various solid phases of varying crystal morphology and stability can be used as input to decisions for the best suited solid product type and how this relates to the initial conditions of the sidestreams. Full article
(This article belongs to the Special Issue Recent Progress in Industrial Crystallization)
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22 pages, 9507 KiB  
Article
Contact-Mediated Nucleation of Subcooled Droplets in Melt Emulsions: A Microfluidic Approach
by Gina Kaysan, Alexander Rica, Gisela Guthausen and Matthias Kind
Crystals 2021, 11(12), 1471; https://doi.org/10.3390/cryst11121471 - 26 Nov 2021
Cited by 3 | Viewed by 1863
Abstract
The production of melt emulsions is mainly influenced by the crystallization step, as every single droplet needs to crystallize to obtain a stable product with a long shelf life. However, the crystallization of dispersed droplets requires high subcooling, resulting in a time, energy [...] Read more.
The production of melt emulsions is mainly influenced by the crystallization step, as every single droplet needs to crystallize to obtain a stable product with a long shelf life. However, the crystallization of dispersed droplets requires high subcooling, resulting in a time, energy and cost intensive production processes. Contact-mediated nucleation (CMN) may be used to intensify the nucleation process, enabling crystallization at higher temperatures. It describes the successful inoculation of a subcooled liquid droplet by a crystalline particle. Surfactants are added to emulsions/suspensions for their stabilization against coalescence or aggregation. They cover the interface, lower the specific interfacial energy and form micelles in the continuous phase. It may be assumed that micelles and high concentrations of surfactant monomers in the continuous phase delay or even hinder CMN as the two reaction partners cannot get in touch. Experiments were carried out in a microfluidic chip, allowing for the controlled contact between a single subcooled liquid droplet and a single crystallized droplet. We were able to demonstrate the impact of the surfactant concentration on the CMN. Following an increase in the aqueous micelle concentrations, the time needed to inoculate the liquid droplet increased or CMN was prevented entirely. Full article
(This article belongs to the Special Issue Recent Progress in Industrial Crystallization)
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22 pages, 4398 KiB  
Article
Flow Map for Hydrodynamics and Suspension Behavior in a Continuous Archimedes Tube Crystallizer
by Jana Sonnenschein, Pascal Friedrich, Moloud Aghayarzadeh, Otto Mierka, Stefan Turek and Kerstin Wohlgemuth
Crystals 2021, 11(12), 1466; https://doi.org/10.3390/cryst11121466 - 26 Nov 2021
Cited by 3 | Viewed by 1690
Abstract
The Archimedes Tube Crystallizer (ATC) is a small-scale coiled tubular crystallizer operated with air-segmented flow. As individual liquid segments are moved through the apparatus by rotation, the ATC operates as a pump. Thus, the ATC overcomes pressure drop limitations of other continuous crystallizers, [...] Read more.
The Archimedes Tube Crystallizer (ATC) is a small-scale coiled tubular crystallizer operated with air-segmented flow. As individual liquid segments are moved through the apparatus by rotation, the ATC operates as a pump. Thus, the ATC overcomes pressure drop limitations of other continuous crystallizers, allowing for longer residence times and crystal growth phases. Understanding continuous crystallizer phenomena is the basis for a well-designed crystallization process, especially for small-scale applications in the pharmaceutical and fine chemical industry. Hydrodynamics and suspension behavior, for example, affect agglomeration, breakage, attrition, and ultimately crystallizer blockage. In practice, however, it is time-consuming to investigate these phenomena experimentally for each new material system. In this contribution, a flow map is developed in five steps through a combination of experiments, CFD simulations, and dimensionless numbers. Accordingly, operating parameters can be specified depending on ATC design and material system used, where suspension behavior is suitable for high-quality crystalline products. Full article
(This article belongs to the Special Issue Recent Progress in Industrial Crystallization)
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12 pages, 3397 KiB  
Article
Comparison of the Nucleation Parameters of Aqueous l-glycine Solutions in the Presence of l-arginine from Induction Time and Metastable-Zone-Width Data
by Lie-Ding Shiau
Crystals 2021, 11(10), 1226; https://doi.org/10.3390/cryst11101226 - 12 Oct 2021
Cited by 3 | Viewed by 1287
Abstract
Induction time and metastable-zone-width (MSZW) data for aqueous l-glycine solutions in the presence of l-arginine impurity were experimentally measured using a turbidity probe in this study. The nucleation parameters, including the interfacial free energy and pre-exponential nucleation factor, obtained from induction [...] Read more.
Induction time and metastable-zone-width (MSZW) data for aqueous l-glycine solutions in the presence of l-arginine impurity were experimentally measured using a turbidity probe in this study. The nucleation parameters, including the interfacial free energy and pre-exponential nucleation factor, obtained from induction time data, were compared with those obtained from MSZW data. The influences of lag time on the nucleation parameters were examined for the induction time data. The effects of l-arginine impurity concentration on the nucleation parameters based on both the induction time and MSZW data were investigated in detail. Full article
(This article belongs to the Special Issue Recent Progress in Industrial Crystallization)
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15 pages, 8295 KiB  
Article
Thermal Deformations of Crystal Structures in the L-Aspartic Acid/L-Glutamic Acid System and DL-Aspartic Acid
by Roman Sadovnichii, Elena Kotelnikova and Heike Lorenz
Crystals 2021, 11(9), 1102; https://doi.org/10.3390/cryst11091102 - 10 Sep 2021
Cited by 2 | Viewed by 2135
Abstract
The method of temperature-resolved powder X-ray diffraction (TRPXRD) was used to determine the elevated temperature behavior of L-aspartic acid (L-asp), DL-aspartic acid (DL-asp), L-glutamic acid (L-glu), and an L-asp0.25,L-glu0.75 solid solution. These amino acids were not found to undergo any [...] Read more.
The method of temperature-resolved powder X-ray diffraction (TRPXRD) was used to determine the elevated temperature behavior of L-aspartic acid (L-asp), DL-aspartic acid (DL-asp), L-glutamic acid (L-glu), and an L-asp0.25,L-glu0.75 solid solution. These amino acids were not found to undergo any solid-phase (polymorph) transformations. When heated, they all experienced only thermal deformations. The corresponding parameters of the monoclinic cells of L-asp and DL-asp, and the orthorhombic cells of L-glu and L-asp0.25,L-glu0.75, were calculated for the entire range of studied temperatures (up to 220 °C). The data obtained were used to calculate the parameters of the thermal deformation tensors, and to plot the figures of their thermal expansion coefficients. A correlation between the maximum and minimum values of thermal expansion coefficients and the length, type, direction, and number of hydrogen bonds in the crystal structures of the investigated amino acids was established. The observed negative thermal expansion (contraction) of crystal structures of L-asp and DL-asp along the ac plane can be explained as a result of shear deformations occurring in monoclinic crystals with a non-fixed angle β. The studies were related to the presence of amino acids in various natural and technological processes occurring at different temperatures. Full article
(This article belongs to the Special Issue Recent Progress in Industrial Crystallization)
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Review

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31 pages, 4599 KiB  
Review
Crystallization in Fluidized Bed Reactors: From Fundamental Knowledge to Full-Scale Applications
by Marcelo Martins Seckler
Crystals 2022, 12(11), 1541; https://doi.org/10.3390/cryst12111541 - 28 Oct 2022
Cited by 4 | Viewed by 3011
Abstract
A review is presented on fifty years of research on crystallization in fluidized bed reactors (FBRs). FBRs are suitable for recovery of slightly soluble compounds from aqueous solutions, as it yields large, millimeter sized particles, which are suitable for reuse and permits low [...] Read more.
A review is presented on fifty years of research on crystallization in fluidized bed reactors (FBRs). FBRs are suitable for recovery of slightly soluble compounds from aqueous solutions, as it yields large, millimeter sized particles, which are suitable for reuse and permits low liquid residence times in the timescale of minutes. Full-scale applications for water softening have been applied since the 1980s, and since then, new applications have been developed or are in development for recovery of phosphorus, magnesium, fluoride, metals, sulfate, and boron. Process integration with membrane, adsorption, and biological processes have led to improved processes and environmental indicators. Recently, novel FBR concepts have been proposed, such as the aerated FBR for chemical-free precipitation of calcium carbonate, the seedless FBR to yield pure particulate products, a circulating FBR for economic recovery and extended use of seeds, as well as coupled FBRs for separation of chiral compounds and FBRs in precipitation with supercritical fluids. Advances are reported in the understanding of elementary phenomena in FBRs and on mathematical models for fluid dynamics, precipitation kinetics, and FBR systems. Their role is highlighted for process understanding, optimization and control at bench to full-scale. Future challenges are discussed. Full article
(This article belongs to the Special Issue Recent Progress in Industrial Crystallization)
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Other

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2 pages, 1681 KiB  
Obituary
In Memoriam—Gerda van Rosmalen
by Slobodan Jančić
Crystals 2022, 12(2), 177; https://doi.org/10.3390/cryst12020177 - 26 Jan 2022
Viewed by 1800
Abstract
This Special Issue is in memory and in honor of Professor Gerda van Rosmalen, who saddened the crystallization community with her departure and left us with the wide and deep heritage of her work and most pleasant personal memories[...] Full article
(This article belongs to the Special Issue Recent Progress in Industrial Crystallization)
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