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Size-dependent growth kinetics of vitamin C crystals in water solutions of L(+)-ascorbic acid with the addition of methanol and ethanol

100%
Wierzbowska B., Piotrowski K., Koralewska J., Matynia A.
Polish Journal of Chemical Technology
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2008
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vol. 10
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issue 1
60-65
EN
Growth kinetics of vitamin C crystals during the batch mass crystallization process in L(+)-ascorbic acid - methanol - ethanol - water system was determined. The linear growth rate values were estimated on the basis of the product crystal size distributions. The kinetic model of the continuous process in a MSMPR crystallizer was adopted for the batch mode description according to Nyvlt's conception, taking the sizedependent growth (SDG) rate effects into consideration. The kinetic parameter values were determined with a Rojkowski hyperbolic SDG model. A good compatibility between the experimental product crystal population density distributions and the SDG model predictions was observed. The interpretation of the kinetic data was presented and discussed.
2
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Kinetics of the continuous reaction crystallization of barium sulphate in BaCl2- (NH4)2SO4- NaCl - H2O system - neural network model

100%
Piotrowski K., Koralewska J., Wierzbowska B., Matynia A.
Polish Journal of Chemical Technology
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2009
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vol. 11
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issue 4
13-19
EN
One of the main toxic components of post quenching salts formed in large quantities during steel hardening processes is BaCl2. This dangerous ingredient can be chemically neutralized after dissolution in water by means of reaction crystallization with solid ammonium sulphate (NH4)2 SO4. The resulting size distribution of the ecologically harmless crystalline product - BaSO4 - is an important criteria deciding about its further applicability. Presence of a second component of binary quenching salt mixture (BaCl2-NaCl) in water solution, NaCl, influences the reaction-crystallization process kinetics affecting the resulting product properties. The experimental 39 input-output data vectors containing the information about the continuous reaction crystallization in BaCl2 - (NH4)2 SO4 - NaCl - H2 O system ([BaCl2]RM = 10-24 mass %, [NaCl]RM = 0-12 mass %, T = 305-348 K and τ = 900-9000 s) created the database for the neural network training and validation. The applicability of diversified network configurations, neuron types and training strategies were verified. An optimal network structure was used for the process modeling.
3
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Reaction crystallization of struvite in a continuous DTM type crystallizer with a compressed air driven jet pump

76%
Matynia A., Mazieńczuk A., Piotrowski K., Wierzbowska B., Hutnik N., Kozik A.
Polish Journal of Chemical Technology
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2011
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vol. 13
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issue 2
46-53
EN
Experimental tests covering the production of struvite MgNH4PO4·6H2O from water solutions containing 1.0 mass % of phosphate(V) ions using magnesium and ammonium ions in stoichiometric proportions were carried out in a crystallizer of 1.2 dm3 working volume. The process temperature was 298 K. Struvite crystals of mean size Lm from ca. 14 to ca. 38 μm were produced depending on the process environment's pH (9-11) and the mean residence time of suspension in a crystallizer, τ (900-3600 s). In such defined process conditions the linear growth rate of struvite crystals changed from 1.45·10-8 m/s (pH 9, τ 900 s) to 2.06·10-9 m/s (pH 11, τ 3600 s) while the nucleation rate from 5.1·107 to 3.2·109 1/(sm3). Crystal product of the most advantageous granular characteristics was produced at pH 9 and the mean residence time 3600 s. Within this product population the largest sizes reached above 200 μm while the number of crystals smaller than 3 mm was kept below 6%.
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