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Journal ArticleDOI

Application of Ultrasonics in the On-line Determination of Supersaturation

01 Mar 1999-Crystal Research and Technology (WILEY‐VCH Verlag)-Vol. 34, Iss: 3, pp 379-389
TL;DR: In this paper, an ultrasonic technique is used to develop a method based on the measurement of both ultrasonic velocity and temperature of the supersaturated media for the on-line determination of supersaturation.
Abstract: An ultrasonic technique is used to develop a method based on the measurement of both ultrasonic velocity and temperature of the supersaturated media for the on-line determination of the supersaturation. It is demonstrated by the example of aqueous K 2 SO 4 solution in a seeded batch crystallizer. The feasibility of this technique was investigated using a commercial available sensor. The experimental measurements for the desupersaturation versus time trajectory proved that this technique can be successfully employed to measure supersaturation with sufficient accuracy and precision. Such sensor is preferred in the on-line application due to its fast response and the availability to be applied directly in the slurries without any need to the solid-liquid separation.
Citations
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Journal ArticleDOI
TL;DR: In this paper, a multiauthor review article aims to bring readers up to date with some of the current trends in the field of process analytical technology (PAT) by summarizing each aspect of the subject (sensor development, PAT based process monitoring and control methods) and presenting applications both in industrial laboratories and in manufacture.

318 citations

Journal ArticleDOI
TL;DR: In this paper, it is shown that the optimal crystallization process can only be achieved if the metastable zone width and the actual operation point of the crystallizer within this zone is known and controlled during the entire process.

101 citations

Journal ArticleDOI
TL;DR: In this paper, the metastable zone width of borax decahydrate in pure and impure aqueous solutions was determined according to polythermal method by using the ultrasonic technique.

73 citations

Journal ArticleDOI
TL;DR: In this paper, the density and ultrasonic velocity of trichloroethylene solutions of fluoranthene were measured with the help of two microprocessor instruments, and the same instruments and an apparatus for measuring transparency and turbidity were used to investigate the metastable zone width, as well as the solubility of this solvent.

54 citations

Journal ArticleDOI
TL;DR: In this article, the change of ultrasonic velocity and temperature in solutions during a cooling and heating cycle was controlled by using a protected sensor, and the results were compared with those of the unprotected sensor taken from the literature for the chosen substances.
Abstract: The width of metastable zone of unseeded potassium nitrate, potassium sulphate and ammonium sulphate solutions, saturated at 30 °C, was determined by means of an ultrasonic measuring technique at three different cooling rates. The change of ultrasonic velocity and temperature in solutions during a cooling and heating cycle was controlled by using a protected sensor. The results were compared with those of the unprotected sensor taken from the literature for the chosen substances. The change of ultrasonic velocity of supersaturated ammonium sulphate solutions in the presence of crystals was measured at constant temperature by means of a protected sensor. It was found that the protected sensor was reliable and sensitive enough to determine the change of ultrasonic velocity and temperature in both solution and slurry.

42 citations

References
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Journal ArticleDOI
TL;DR: In this article, the size distribution from a batch cooling crystallizer is predicted by the numerical solution of a mathematical model which uses empirical kinetics of nucleation and crystal growth, and the predictions clearly point out the potential advantages of controlled cooling at a constant nucleation rate for improving the product crystal size over that obtained by either natural or linear cooling.

173 citations

Journal ArticleDOI
TL;DR: In this paper, the feasibility of the Attenuated Total Reflection (ATR) Fourier transform infrared (FTIR) spectroscopy for the in situ measurement of supersaturation in crystallization processes is established.

135 citations

Journal ArticleDOI
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

Journal ArticleDOI
TL;DR: In this paper, the growth and dissolution of succinic acid crystals were studied in an isothermal stirred tank crystallizer and an implicit equation was given to accurately represent the crystal growth rate as a function of the supersaturation.
Abstract: Growth and dissolution of succinic acid crystals have been studied in an isothermal stirred tank crystallizer. Seeded desupersaturation and deundersaturation experiments have been performed. Parameters of a desired growth rate equation are estimated by fitting the supersaturation balance equation directly to the supersaturation measurements. The procedure is based on nonlinear optimization techniques. Thus, uncertainties in the traditional approximation of the concentration vs. time curve are circumvented. The growth process for succinic acid crystals in an aqueous solution is found to be controlled by a significant resistance in both the volume diffusion step and in the surface integration step. An implicit equation is given to accurately represent the crystal growth rate as a function of the supersaturation. When extrapolating outside the range of experiments, this equation is shown to predict growth rates that are significantly different from those predicted by a corresponding power law expression. The dissolution rate exhibits a nonlinear dependence on undersaturation which is interpreted as changes in the crystal shape. Initial dissolution rate coefficients are in good agreement with volume diffusion coefficients obtained from growth experiments.

42 citations

Journal ArticleDOI
TL;DR: A technique to evaluate crystal growth kinetics from batch experiments performed in the integral mode is described in this paper, which only requires calculation of the first two derivatives of the desupersaturation curve evaluated at time zero.

41 citations