Determination of Mass Transfer Coefficients for Crystal Growth of Nitrate Salts
TL;DR: In this article, the crystal growth of sodium nitrate and potassium nitrate from aqueous solutions, in a perfectly stirred batch crystallizer, has been studied considering the effect of temperature, supersaturation degree, and the size of seed crystal growth rate.
Abstract: In this paper, the crystal growth of sodium nitrate and potassium nitrate from aqueous solutions, in a perfectly stirred batch crystallizer, has been studied considering the effect of temperature, supersaturation degree, and the size of seed crystal growth rate. The mass transfer coefficients obtained correlated with Re, Sc and NL dimensionaless numbers. Supersaturation curve determination using a 0.5 mW He-Ne laser, connected to an automated data acquisition system, was the first stage of the study. The supersaturation and saturation curves were closely parallel with average DT value of 4.1 and 6.8 °C for KNO3 and NaNO3 respectively. For the growth kinetics order, unit values were found for both salts, with diffusion as a controlling stage.
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TL;DR: In this article, a semi-empirical approach based on the classical theory of three-dimensional nucleation combined with the formation of n-sized embryos from monomers according to the law of mass action is proposed.
Abstract: Experimental data on the maximum supercooling ΔTmax, a measure of metastable zone width, for solutions saturated at a temperature T0, as a function of cooling rate R are analyzed, for some solute−solvent systems chosen as examples, using Nývlt’s semiempirical approach and a new approach based on the classical theory of three-dimensional nucleation combined with the formation of n-sized embryos from monomers according to the law of mass action. Instead of a linear relation between ln(ΔTmax) and lnR of the Nývlt’s approach, the new approach predicts a linear dependence of (T0/ΔTmax)2 on lnR with slope F1 and intercept F. The quantity F1/F is independent of saturation temperature T0, characteristic of a solute−solvent and is associated with the growth of the stable three-dimensional nuclei to visible entities. The value of F1 is determined by thermodynamic and solvation processes, while that of F is governed by thermodynamic and kinetic parameters as well as processes associated with solvation of solute ions...
111 citations
TL;DR: In this paper, a study of the nucleation kinetics for a cooling crystallisation of paracetamol-ethanol solutions in a batch reactor is described, and two theoretical approaches are employed to estimate the nucleations kinetics, the classical mass based approach of Nývlt, and a more recent approach by Kubota, which also considers number density.
101 citations
TL;DR: In this article, a study of the nucleation kinetics for cooling crystallisation of paracetamol-ethanol solutions in a batch reactor is described, where induction time experiments were conducted in order to estimate the nucleations of the system.
64 citations
TL;DR: In this article, a modified model based on the Sangwal's theory in which the nucleation parameters are not dependent on saturation temperature T 0 and nucleation temperature T 1 was proposed.
41 citations
TL;DR: In this paper, the process of particle formation from evaporating droplets containing more than one solute was studied and two-component microparticles were produced using a piezoceramic dispenser with an inner diameter of 30µm.
Abstract: The process of particle formation from evaporating droplets containing more than one solute was studied. Two-component microparticles were produced using a piezoceramic dispenser with an inner diameter of 30 µm. Initial droplets had a diameter in the range of 70–85 µm and contained sodium nitrate and potassium nitrate in different molar ratios of 30:70, 50:50, and 70:30, corresponding to weight ratios of 26.5:73.5, 45.7:54.3, and 66.2:33.8, in the form of aqueous solutions with initial concentrations of 1 or 10 mg/ml. The monodisperse droplets were dried in a dry laminar gas flow with temperatures of 50°C or 100°C. Different initial conditions affected the particle formation process and the particle morphology. The diameter of the final dried microparticles ranged from 4 to 10 µm. Their density varied from 1250 to 1950 mg/ml. The formulation and process conditions determined the distribution of chemical components in the dried microparticles, especially their surface composition as determined by e...
31 citations
Cites background from "Determination of Mass Transfer Coef..."
...For the same wet bulb temperatures, KNO3 starts to crystallize at a supersaturation of 8.2 and 9.1 molar percentages or 47 (155 mg/ml) and 60 (345 mg/ml) weight percentages, respectively (Graber et al. 1999)....
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...1 molar percentages or 47 (155 mg/ml) and 60 (345 mg/ml) weight percentages, respectively (Graber et al. 1999)....
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...Previous studies have determined the required supersaturation level in aqueous solutions at which crystals start to grow (Tang and Munkelwitz 1994; Graber et al. 1999)....
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01 Jan 1926
848 citations
TL;DR: In this paper, the effects of temperature on the kinetics of crystallization of potassium nitrate were investigated in a continuous mixed-suspension, mixed-product-removal (MPM) crystallizer.
Abstract: A laboratory continuous mixed-suspension, mixed-product-removal crystallizer was used to study the effects of temperature on the kinetics of crystallization of potassium nitrate. A differential refractometer was used to continuously monitor the supersaturation permitting the measurement of supersaturation levels of order 10−3Kg solute/Kg water. The nucleation rate exhibited an inverse relationship with temperature.
59 citations