Secondary nucleation-mediated effects of stirrer speed and growth rate on induction time for unseeded solution

CrystEngComm ◽  
2012 ◽  
Vol 14 (16) ◽  
pp. 5255 ◽  
Author(s):  
M. Kobari ◽  
N. Kubota ◽  
I. Hirasawa
Keyword(s):  
Growth Rate ◽  
Induction Time ◽  
Stirrer Speed ◽  
Secondary Nucleation ◽  
Mediated Effects

scholarly journals Secondary Nucleation Kinetics of AIBN Crystallisation in Methanol: Online Imaging-Based Measurement and Modelling

Crystals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 506
Author(s):  
Yang Li ◽  
Yang Zhang ◽  
Xue Zhong Wang
Keyword(s):  
Nucleation Rate ◽  
Induction Time ◽  
Nucleation Process ◽  
Stirrer Speed ◽  
Seed Number ◽  
Nucleation Kinetics ◽  
Secondary Nucleation ◽  
On Line ◽  
Small Change ◽  
Crystal Seed

The secondary nucleation process of 2,2-azobisisobutyronitrile (AIBN) seeded crystallisation in methanol in a stirred tank reactor was studied at varying initial supersaturation levels, temperatures, crystal seed numbers, and stirrer speeds. The average secondary nucleation rate, induction time, and agglomeration ratio were measured using on-line microscopic imaging. The initial supersaturation level, temperature, and stirrer speed were found to be positively correlated with the secondary nucleation rate. A small change in the crystal seed number, i.e., 1-20, did not substantially affect the secondary nucleation rate throughout the secondary nucleation process. An increase in the initial supersaturation level and crystal seed number decreased the induction time, and an increase in the strength of agitation promoted the initiation of secondary nucleation at a stirring rate greater than 250 revolutions per minute (rpm). Temperature exerted a complex effect on the induction time. Regarding the agglomeration ratio, the initial supersaturation level positively correlated with the agglomeration ratio, while the stirrer speed negatively correlated with this parameter. Finally, based on the measured data, the average secondary nucleation rate, induction time, and final crystal suspension density were correlated. This study provides guidance for the control of supersaturation, induction time, stirring, and other factors in the crystal seed addition process in AIBN crystallisation.

Continuous Precipitation of Lead Iodide

1994 ◽  
Vol 59 (7) ◽  
pp. 1503-1510
Author(s):  
Stanislav Žáček ◽  
Jaroslav Nývlt
Keyword(s):  
Growth Rate ◽  
Particle Size ◽  
Crystal Size ◽  
Crystal Growth Rate ◽  
Laboratory Model ◽  
Lead Iodide ◽  
Secondary Nucleation ◽  
Equimolar Ratio ◽  
Continuous Precipitation ◽  
The Mean

Lead iodide was precipitated from aqueous solutions of 0.015 - 0.1 M Pb(NO3)2 and 0.03 - 0.2 M KI in the equimolar ratio using a laboratory model of a stirred continuous crystallizer at 22 °C. After reaching the steady state, the PbI2 crystal size distribution was measured sedimentometrically and the crystallization kinetics was evaluated based on the mean particle size. Both the linear crystal growth rate and the nucleation rate depend on the specific output of the crystallizer. The system crystallization constant either points to a significant effect of secondary nucleation by the mechanism of contact of the crystals with the stirrer blade, or depends on the concentrations of the components added due to the micromixing mechanism.

Research Progress on the Driving Force of Gas Hydrate Formation

2012 ◽  
Vol 616-618 ◽  
pp. 902-906 ◽  
Author(s):  
Chun Long Wang ◽  
Xue Min Zhang ◽  
Jin Ping Li ◽  
Lin Jun Wang ◽  
Liang Jiao
Keyword(s):  
Growth Rate ◽  
Gas Hydrate ◽  
Induction Time ◽  
Driving Force ◽  
Hydrate Formation ◽  
Research Direction ◽  
Research Progress ◽  
Force Model ◽  
Hydration Reaction ◽  
Gas Hydrate Formation

Predicting the driving force accurately is the key process to hydrate nucleating and growing of hydration reaction. The nucleating and growing process of hydrate is relevant to temperature, pressure and component of reactant, and the property of reaction tank and intermiscibility of reactant have notable effect on the formation process of hydrate with its nucleating position, the induction time, growth rate and hydration rate. However, the present driving force model of hydrate cannot predict nucleating area, induction time, growth rate and the reaction limit, and also can't explain the influence of some factors such as cooling rate, temperature disturbance and inlet way on the hydration reaction, it is uncertain of the process to gas hydrate nucleation. We introduced some driving force models, analyzed their merits and demerits, and looked into the distance of research direction to driving force in the future.

scholarly journals Non-Isothermal Crystallization Kinetics of Poly(4-Hydroxybutyrate) Biopolymer

Molecules ◽  
2019 ◽  
Vol 24 (15) ◽  
pp. 2840 ◽  
Author(s):  
Ina Keridou ◽  
Luis J. del Valle ◽  
Lutz Funk ◽  
Pau Turon ◽  
Lourdes Franco ◽  
...  
Keyword(s):  
Growth Rate ◽  
Cooling Rate ◽  
Crystallization Temperature ◽  
Isothermal Crystallization ◽  
Secondary Nucleation ◽  
Scanning Calorimetry ◽  
Limited Region ◽  
First Case ◽  
Biodegradable Poly ◽  
Insertion Mechanism

The non-isothermal crystallization of the biodegradable poly(4-hydroxybutyrate) (P4HB) has been studied by means of differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). In the first case, Avrami, Ozawa, Mo, Cazé, and Friedman methodologies were applied. The isoconversional approach developed by Vyazovkin allowed also the determination of a secondary nucleation parameter of 2.10 × 105 K2 and estimating a temperature close to 10 °C for the maximum crystal growth rate. Similar values (i.e., 2.22 × 105 K2 and 9 °C) were evaluated from non-isothermal Avrami parameters. All experimental data corresponded to a limited region where the polymer crystallized according to a single regime. Negative and ringed spherulites were always obtained from the non-isothermal crystallization of P4HB from the melt. The texture of spherulites was dependent on the crystallization temperature, and specifically, the interring spacing decreased with the decrease of the crystallization temperature (Tc). Synchrotron data indicated that the thickness of the constitutive lamellae varied with the cooling rate, being deduced as a lamellar insertion mechanism that became more relevant when the cooling rate increased. POM non-isothermal measurements were also consistent with a single crystallization regime and provided direct measurements of the crystallization growth rate (G). Analysis of the POM data gave a secondary nucleation constant and a bell-shaped G-Tc dependence that was in relative agreement with DSC analysis. All non-isothermal data were finally compared with information derived from previous isothermal analyses.

Studies on nucleation and crystal growth kinetics of plutonium(IV) oxalatex

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Chuanbo Li ◽  
Bo Wang ◽  
Xiang Li ◽  
Taihong Yan ◽  
Weifang Zheng
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Nucleation Rate ◽  
Crystal Growth Rate ◽  
Acid Solutions ◽  
Dilution Ratio ◽  
Secondary Nucleation ◽  
Supersaturation Ratio ◽  
Crystal Growth Kinetics ◽  
Kinetics Of

Abstract A new method is developed to calculate the dilution ratio N of the two reactant solutions during nucleation rate determination. When the initial apparent supersaturation ratio S N  = f(N) in the dilution tank is controlled between 1.66 and 1.67, the counted nuclei is the most, both nuclei dissolving and secondary nucleation avoided satisfactorily. Based on this methoed, Plutonium(IV) oxalate is precipitated by mixing equal volumes of tetravalent plutonium nitrate and oxalic acid solutions. Experiments are carried out by varying the supersaturation ratio from 8.37 to 22.47 and temperature from 25 to 50 °C. The experimental results show that the nucleation rate of plutonium(IV) oxalate in the supersaturation range cited above can be expressed by the equation R N  = A N exp(−E a /RT)exp[−B/(ln S)2], where A N  = 4.8 × 1023 m−3 s−1 , and E a  = 36.2 kJ mol−1, and B = 20.2. The crystal growth rate of plutonium(IV) oxalate is determined by adding seed crystals into a batch crystallizer. The crystal growth rate can be expressed by equation G(t) = k g exp(−E’ a /RT) (c − c eq) g , where k g  = 7.3 × 10−7 (mol/L)−1.1(m/s), E’ a  = 25.7 kJ mol−1, and g = 1.1.

scholarly journals Frazil-ice growth rate and dynamics in mixed layers and sub-ice-shelf plumes

2018 ◽  
Vol 12 (1) ◽  
pp. 25-38 ◽  
Author(s):  
David W. Rees Jones ◽  
Andrew J. Wells
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Large Scale ◽  
Freezing Temperature ◽  
Ice Shelf ◽  
Secondary Nucleation ◽  
Ice Dynamics ◽  
Ice Shelves ◽  
Frazil Ice ◽  
Microphysical Processes

Abstract. The growth of frazil or granular ice is an important mode of ice formation in the cryosphere. Recent advances have improved our understanding of the microphysical processes that control the rate of ice-crystal growth when water is cooled beneath its freezing temperature. These advances suggest that crystals grow much faster than previously thought. In this paper, we consider models of a population of ice crystals with different sizes to provide insight into the treatment of frazil ice in large-scale models. We consider the role of crystal growth alongside the other physical processes that determine the dynamics of frazil ice. We apply our model to a simple mixed layer (such as at the surface of the ocean) and to a buoyant plume under a floating ice shelf. We provide numerical calculations and scaling arguments to predict the occurrence of frazil-ice explosions, which we show are controlled by crystal growth, nucleation, and gravitational removal. Faster crystal growth, higher secondary nucleation, and slower gravitational removal make frazil-ice explosions more likely. We identify steady-state crystal size distributions, which are largely insensitive to crystal growth rate but are affected by the relative importance of secondary nucleation to gravitational removal. Finally, we show that the fate of plumes underneath ice shelves is dramatically affected by frazil-ice dynamics. Differences in the parameterization of crystal growth and nucleation give rise to radically different predictions of basal accretion and plume dynamics, and can even impact whether a plume reaches the end of the ice shelf or intrudes at depth.

scholarly journals Influence of asphaltene polarity on hydrate behaviors in water-in-oil emulsions

2020 ◽  
Author(s):  
Dongxu Zhang ◽  
Qiyu Huang ◽  
Wei Wang ◽  
Rongbin Li ◽  
Huiyuan Li ◽  
...  
Keyword(s):  
Growth Rate ◽  
Nucleation Rate ◽  
Induction Time ◽  
Hydrate Formation ◽  
Polar Fraction ◽  
Side Chain ◽  
Alkyl Side Chain ◽  
Asphaltene Fraction ◽  
Oil Emulsions ◽  
Self Aggregation

Asphaltene was fractionated into four subfractions with different polarities, and used to conduct the hydrate formation and dissociation experiments. It was observed that the more polar fraction could result in a higher tendency of self-aggregation and fewer asphaltenes adsorbing at the water-oil interface mainly due to the larger C/H ratio, higher aromaticity, and shorter length of the alkyl side chain. The nucleation rate decreased with the presence of asphaltenes, and the induction time increased with a reduction in asphaltene polarity in water-in-oil emulsions. The results showed that the formed amount of hydrates were reduced by the addition of asphaltenes. For the asphaltene containing emulsions, less hydrate was formed with the presence of a more polar asphaltene fraction. The presence of asphaltenes was also found to affect the growth rate of hydrate, which varies with the polarity. Meanwhile, all four asphaltene fractions were found to promote the dissociation of hydrate.

scholarly journals Frazil-ice growth rate and dynamics in mixed layers and sub-ice-shelf plumes

2017 ◽  
Author(s):  
David W. Rees Jones ◽  
Andrew J. Wells
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Large Scale ◽  
Freezing Temperature ◽  
Ice Shelf ◽  
Secondary Nucleation ◽  
Ice Dynamics ◽  
Ice Shelves ◽  
Frazil Ice ◽  
Microphysical Processes

Abstract. The growth of frazil or granular ice is an important mode of ice formation in the cryosphere. Recent advances have improved our understanding of the microphysical processes that control the rate of ice-crystal growth when water is cooled beneath its freezing temperature. These advances suggest that crystals grow much faster than previously thought. In this paper, we consider models of a population of ice crystals with different sizes to provide insight into the treatment of frazil ice in large-scale models. We consider the role of crystal growth alongside the other physical processes that determine the dynamics of frazil ice. We apply our model to a simple mixed layer (such as at the surface of the ocean) and to a buoyant plume under a floating ice shelf. We provide numerical calculations and scaling arguments to predict the occurrence of frazil-ice explosions, which we show are controlled by crystal growth, nucleation and, gravitational removal. Faster crystal growth, higher secondary nucleation and slower gravitational removal make frazil-ice explosions more likely. We identify steady-state crystal size distributions, which are largely insensitive to crystal growth rate but are affected by the relative importance of secondary nucleation to gravitational removal. Finally, we show that the fate of plumes underneath ice shelves is dramatically affected by frazil-ice dynamics. Differences in the parameterization of crystal growth and nucleation give rise to radically different predictions of basal accretion and plume dynamics; and can even impact whether a plume reaches the end of the ice shelf or intrudes at depth.

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