The Experts below are selected from a list of 174495 Experts worldwide ranked by ideXlab platform
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, 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.
-
Modeling of industrial crystallizers for control and design purposes
Powder Technology, 2000Co-Authors: Herman J. M. Kramer, J.w. Dijkstra, Peter J.t. Verheijen, Gerda M. Van RosmalenAbstract:Abstract The design of forced circulation (FC) crystallizers, which are widely used for the bulk crystallization of inorganic salts, is hindered by the lack of rules for scale-up, caused by the lack of reliable process models. The absence of a stirrer in the crystallizer and the relatively high temperature increase in the circulation line result, as expected, in a strong deviation from the well-mixed vessel approach often used in modeling. To improve process models, a compartmental approach is presented here to describe the crystallization process of evaporative and cooling suspension crystallizers. The model has been implemented in the dynamic flowsheeting program, speedup , and applied to simulate a 200-l evaporative FC crystallizer, with five compartments. Preliminary simulation results indicate that large supersaturation profiles are present in the crystallizer and that only a part of the crystallizer volume is effectively used for the growth of crystals.
-
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.
Sridhar Komarneni - One of the best experts on this subject based on the ideXlab platform.
-
Epitaxial Crystallization of Seeded Albite Glass
Journal of the American Ceramic Society, 1991Co-Authors: Ulagaraj Selvaraj, Sridhar KomarneniAbstract:Glasses that are extremely difficult to crystallize are generally avoided in making glass-ceramics. It is now possible to crystallize such glasses epitaxially using isostructural seeds. The role of solid-state epitaxy in the crystallization of such albite (NaAlSi3O8) glass to glass-ceramic was investigated. The glass was seeded with extremely fine ZrO2 (nonisostructural) and albite (isostructural) seed crystals. X-ray diffraction results indicated that the albite-seeded glass, heat-treated at 1000°C for 100 h, epitaxially crystallized to albite, while the ZrO2 and unseeded glasses did not crystallize in identical heat-treatment conditions. In addition, the albite-seeded glass, heat-treated at 905°C for 10 d, crystallized mostly to albite, whereas the ZrO2 and unseeded glasses at the same conditions contained only a small amount (
-
epitaxial crystallization of seeded albite glass
Journal of the American Ceramic Society, 1991Co-Authors: Ulagaraj Selvaraj, Sridhar KomarneniAbstract:Glasses that are extremely difficult to crystallize are generally avoided in making glass-ceramics. It is now possible to crystallize such glasses epitaxially using isostructural seeds. The role of solid-state epitaxy in the crystallization of such albite (NaAlSi3O8) glass to glass-ceramic was investigated. The glass was seeded with extremely fine ZrO2 (nonisostructural) and albite (isostructural) seed crystals. X-ray diffraction results indicated that the albite-seeded glass, heat-treated at 1000°C for 100 h, epitaxially crystallized to albite, while the ZrO2 and unseeded glasses did not crystallize in identical heat-treatment conditions. In addition, the albite-seeded glass, heat-treated at 905°C for 10 d, crystallized mostly to albite, whereas the ZrO2 and unseeded glasses at the same conditions contained only a small amount (<5 wt%) of nepheline (NaAlSiO4). The microstructure of the epitaxially grown glass-ceramics showed that extremely fine crystals (∼0.2 μm thickness) were formed around the seed.
Steven Sheriff - One of the best experts on this subject based on the ideXlab platform.
-
Crystallization and Preliminary X-ray Analysis of an Anti-Staphylococcal Nuclease-Staphylococcal Nuclease Complex and of a Second Anti-Staphylococcal Nuclease Antibody
Journal of Molecular Biology, 1994Co-Authors: Chiehying Y. Chang, Patricia Bossart Whitaker, Lydia Tabernero, Howard Einspahr, Lisa J. Workman, David C. Benjamin, Steven SheriffAbstract:Abstract The Fab fragments of several monoclonal antibodies that bind Staphylococcal nuclease have been screened for crystallization conditions. Two of these, N10 and N25, have been crystallized in forms suitable for X-ray structural analysis. The anti-Staphylococcal nuclease antibody complex N10 Fab-nuclease Crystallizes with symmetry consistent with space group C2 and cell parameters of a = 234·7 A; b = 43·5 A; c = 74·4 A; β = 106·4°. A second anti-Staphylococcal nuclease antibody, N25, although crystallized starting with the Fab-nuclease complex, apparently Crystallizes as uncomplexed N25 Fab with symmetry consistent with space group P3121 (or its enantiomorph P3221) and cell parameters of a = b = 80·9 A; c = 138·4 A.
Ulagaraj Selvaraj - One of the best experts on this subject based on the ideXlab platform.
-
Epitaxial Crystallization of Seeded Albite Glass
Journal of the American Ceramic Society, 1991Co-Authors: Ulagaraj Selvaraj, Sridhar KomarneniAbstract:Glasses that are extremely difficult to crystallize are generally avoided in making glass-ceramics. It is now possible to crystallize such glasses epitaxially using isostructural seeds. The role of solid-state epitaxy in the crystallization of such albite (NaAlSi3O8) glass to glass-ceramic was investigated. The glass was seeded with extremely fine ZrO2 (nonisostructural) and albite (isostructural) seed crystals. X-ray diffraction results indicated that the albite-seeded glass, heat-treated at 1000°C for 100 h, epitaxially crystallized to albite, while the ZrO2 and unseeded glasses did not crystallize in identical heat-treatment conditions. In addition, the albite-seeded glass, heat-treated at 905°C for 10 d, crystallized mostly to albite, whereas the ZrO2 and unseeded glasses at the same conditions contained only a small amount (
-
epitaxial crystallization of seeded albite glass
Journal of the American Ceramic Society, 1991Co-Authors: Ulagaraj Selvaraj, Sridhar KomarneniAbstract:Glasses that are extremely difficult to crystallize are generally avoided in making glass-ceramics. It is now possible to crystallize such glasses epitaxially using isostructural seeds. The role of solid-state epitaxy in the crystallization of such albite (NaAlSi3O8) glass to glass-ceramic was investigated. The glass was seeded with extremely fine ZrO2 (nonisostructural) and albite (isostructural) seed crystals. X-ray diffraction results indicated that the albite-seeded glass, heat-treated at 1000°C for 100 h, epitaxially crystallized to albite, while the ZrO2 and unseeded glasses did not crystallize in identical heat-treatment conditions. In addition, the albite-seeded glass, heat-treated at 905°C for 10 d, crystallized mostly to albite, whereas the ZrO2 and unseeded glasses at the same conditions contained only a small amount (<5 wt%) of nepheline (NaAlSiO4). The microstructure of the epitaxially grown glass-ceramics showed that extremely fine crystals (∼0.2 μm thickness) were formed around the seed.
Chiehying Y. Chang - One of the best experts on this subject based on the ideXlab platform.
-
Crystallization and Preliminary X-ray Analysis of an Anti-Staphylococcal Nuclease-Staphylococcal Nuclease Complex and of a Second Anti-Staphylococcal Nuclease Antibody
Journal of Molecular Biology, 1994Co-Authors: Chiehying Y. Chang, Patricia Bossart Whitaker, Lydia Tabernero, Howard Einspahr, Lisa J. Workman, David C. Benjamin, Steven SheriffAbstract:Abstract The Fab fragments of several monoclonal antibodies that bind Staphylococcal nuclease have been screened for crystallization conditions. Two of these, N10 and N25, have been crystallized in forms suitable for X-ray structural analysis. The anti-Staphylococcal nuclease antibody complex N10 Fab-nuclease Crystallizes with symmetry consistent with space group C2 and cell parameters of a = 234·7 A; b = 43·5 A; c = 74·4 A; β = 106·4°. A second anti-Staphylococcal nuclease antibody, N25, although crystallized starting with the Fab-nuclease complex, apparently Crystallizes as uncomplexed N25 Fab with symmetry consistent with space group P3121 (or its enantiomorph P3221) and cell parameters of a = b = 80·9 A; c = 138·4 A.
