Raluca Isopescu | University Politehnica of Bucharest (original) (raw)

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Papers by Raluca Isopescu

$Research paper thumbnail of Genetic algorithm optimization of fractional crystallization processes$

Computer Aided Chemical Engineering, 2007

This paper advances the optimization of fractional crystallization separation flowcharts applying... more This paper advances the optimization of fractional crystallization separation flowcharts applying genetic algorithms (GA), using as example the potassium nitrate separation. All feasible separation sequences are described using the thermodynamic state network model The optimization criterion is the minimization of the sum of flows over the entire network. The results obtained are compared with the solution found by solving the non-linear optimization problem implemented in GAMS.

UPB Scientific Bulletin, Series B: Chemistry and Materials Science

This study measures the distribution levels of inorganic anion in tea infusions, either for monit... more This study measures the distribution levels of inorganic anion in tea infusions, either for monitoring consumers’ health issues or for optimization of manufacturing processes. A simple, rapid, and accurate method was used for the quantitative determination of fluoride, chloride, nitrate, phosphate, and sulphate ions in green, black, and white tea infusions, by ion chromatography with conductometric detection. The separation was performed using an anion-exchange column at 30°C by isocratic elution with an aqueous 1.7 mM Na2CO3 + 1.8 mM NaHCO3 eluent. Without special sample processing, the method was successfully applied for 24 tea types available in Romanian shops. The ionic content was subjected to multivariate analysis in order to reduce dimensionality and detect the factors responsible for the registered variability.

Advanced Powder Technology, 2014

ABSTRACT Precipitated calcium carbonate was obtained by CO2 bubbling in CaCl2 solution. Ammonia a... more ABSTRACT Precipitated calcium carbonate was obtained by CO2 bubbling in CaCl2 solution. Ammonia and alkylamines were used to enhance CO2 absorption and control the polymorphic phases. Vaterite and calcite mixtures were obtained, mainly vaterite in ammonia and mono-methylamine and mostly calcite in trimethylamine environment. The thermal decomposition of precipitated calcium carbonate leads to high purity CaO. During the thermal decomposition the vaterite to calcite transformation was noticed but the final spherical shape of vaterite was maintained. As the use of CaO as catalyst in biodiesel synthesis may recommend a spherical shape and high contact surface, a precipitated calcium carbonate, rich in vaterite phase, may be a good precursor for CaO catalyst preparation.

Chemical Engineering Research and Design, 2010

The effects of an organic additive, polyoxyethylene sorbitan trioleate (Tween 85), on the inducti... more The effects of an organic additive, polyoxyethylene sorbitan trioleate (Tween 85), on the induction time for the precipitation of calcium carbonate are experimentally and theoretically investigated. Calcium carbonate was precipitated from aqueous solutions of K 2 CO 3 and Ca(NO) 3 at moderate supersaturations ranging between 5 and 16 with and without the organic additive. Experimentally it has been noticed that the induction period for CaCO 3 precipitation increases at low supersaturation and is also influenced by temperature. An increase of the induction time was noticed when Tween 85 was added in the system. The "cluster coagulation model" proposed by Qian and Botsaris (1997), which combines nucleation models and coagulation theory, was used to explain the effects of operating parameters on the induction time in terms of interfacial energy and cluster sizes.

Chemical engineering & …, 1994

This paper presents a new procedure for optimization of continuous mixed suspension-mixed product... more This paper presents a new procedure for optimization of continuous mixed suspension-mixed product removal (MSMPR) crystallizing systems. Owing to the difficulties of theoretical modelling, simulation of the MSMPR crystallization process is based on the use of ...

Aragonite with sub-micron size particles was synthesized in a liquid-liquid reaction by the contr... more Aragonite with sub-micron size particles was synthesized in a liquid-liquid reaction by the controlled double jet precipitation method. The reaction medium was an ethanol-water solution. The precipitation process depends on supersaturation, pH, temperature, reaction time, agitation specific energy, feeding order of the reacting solutions, the nature, and the presence/absence of the additives. This parameters influence the final solid phase morphology and also the particle sizes. All samples were characterized by FT-IR spectroscopy, XRD, optical and electron microscopy, particle size distribution by laser granulometer and microscopic measurements methods. The results proved that a very small amount of the precipitated particles were agglomerated. The population balance equation describing the precipitation process was integrated using the method of classes (Marshal P. et al, 1988). The kinetic parameters were estimated using a random search optimization method. The results obtained w...

For many applications, the size range of the particles is very important. For example, heat trans... more For many applications, the size range of the particles is very important. For example, heat transfer rates to polymer particles during extrusion and mass transfer rates of plasticizers both depend on particle size. From a phenomenological point of view, the size of drops in suspension ...

CHEMICAL …, 2011

CHEMICAL ENGINEERING TRANSACTIONS Volume 25, 2011 465 Editors Jifi Jaromir Klemes, Petar Sabev Va... more CHEMICAL ENGINEERING TRANSACTIONS Volume 25, 2011 465 Editors Jifi Jaromir Klemes, Petar Sabev Varbanov, Hon Loong Lam Copyright ©2011, AIDIC Servizi Srl, ISBN 978-88-95608-16-7 ISSN 1974-9791 DOI: 10 3303ÍCET1125078 e -Teaching Today Ana ...

CHEMICAL ENGINEERING, Jan 1, 2009

Journal of Crystal Growth, 1996

Precipitation of CaCO 3 in a continuous crystallizer is analyzed on the basis of size-dependent g... more Precipitation of CaCO 3 in a continuous crystallizer is analyzed on the basis of size-dependent growth rate models. The usefulness of such models is demonstrated by fitting them to several sets of experimental data consisting of the crystal size distribution measured under different operating conditions. The kinetic parameters, growth and nucleation rate thus estimated were correlated by empirical expressions in terms of observables. The growth rate of zero particle size has been found to increase with the augmentation of the desupersaturation rate and to decrease at higher suspension densities.

Crystal Research and …, 2000

Cryst. Res. Technol.