Krzysztof Alejski

Dynamic simulation of the multicomponent reactive distillation

Abstract A dynamic mathematical model of reactive distillation in case of kinetically controlled chemical reaction is formulated using four basic assumptions: negligible vapour holdup compared to the molar liquid holdup, perfect mixing of phases, corrections of equilibrium values by plate efficiency, corrections of conversion for mixing effects by ‘conversion efficiency’. The accuracy of the dynamic simulation results of reactive distillation obtained under different assumptions is verified by comparing with results of actual experiments on a pilot-scale distillation column. Both the unsteady-state period during start-up and the disturbances of continuous operation are considered. Esterification of ethanol with acetic acid with sulphuric acid as homogeneous catalyst is chosen for experiments. Accuracy of simulation is very good in case of model containing hydraulic description of plates with regard to temperatures inside column and in the reboiler. Responses of component concentrations are less accurate, but imposed disturbances were very large. Observed differences result from simplifications of mathematical model, inaccuracy of the kinetic and vapour-liquid equilibrium description for highly nonideal, multicomponent system and from precision of experimental measurements in case of transient state. Differences between experimental and simulation results in case of different models are the most significant for large holdup on plates in comparison with reboiler. As a general rule, in case of reactive distillation simulation for dynamics, description models taking into consideration plate hydraulics should be used.

A Contributive Study on the Stripping of Zinc(II) from Loaded TBP Using an Ammonia/Ammonium Chloride Solution

Abstract The stripping of zinc(II) from undiluted and 80 v/v% TBP in low aromatic kerosene by means of ammonia/ammonium chloride solution has been studied. It was found that the equilibrium in the system was reached within 2–3 min of vigorous shaking of aqueous and organic phases. The stripping isotherms for zinc, when using undiluted or 80% TBP and 10% or 1.8% hydrochloric acid in the extraction feed, have been obtained. The pregnant strip solutions contained nearly 53 and 63 g/L zinc for both concentrations of the extractant and for 10% or 1.8% HCl levels in the extraction feed, respectively. The strip solution can be further processed for recovery of the metal by electrowinning from NH3/NH4Cl media. The experimental results were modeled. Values of conditioned equilibrium stripping constants in an NH3/NH4Cl solution for the HZnCl3 and ZnCl2 species as high as K S1 = 2.0 × 107 M−5 and K S2 = 2.0–2.3 × 103 M−3, respectively, have been evaluated. The simulation revealed the shares of various zinc ammine and chloride complexes: in the final strip, the metal is present mainly as Zn(NH3)4 2+ and Zn(NH3)3 2+ complexes, the share of all chloride complexes being not higher than 7% of all zinc species. Results for ammonia and water co‐extraction by TBP are also presented and some aspects of the observed phenomenon are discussed.

Kinetics of photo-isomerization and photo-degradation of 2-hydroxy-5-methylbenzophenone (E)- and (Z)-oximes

The kinetics of photo-isomerization and photo-degradation of 2-hydroxy-5-methylbenzophenone (E)- and (Z)-oximes in ethanol, octane, toluene and a mixture of octane and toluene under exposure to UV light was studied. The products of the photo-isomerization/photo-degradation of both oximes are similar but the conversion rate and amount of photo-degradation products of 2-hydroxy-5-methylbenzophenone (Z)-oxime are much higher. Also the photo-degradation of the (Z)-isomer is quicker than its photo-isomerization to the (E)-isomer. The photo-isomerization and photo-degradation kinetic models were developed for both oximes. The formulated kinetic model contains 12 reaction rate constants which have been estimated from experimental data. Good agreement was found between experimental and predicted data.

Separation of 1,3-Propanediol from Aqueous Solutions by Ion Exchange Chromatography

Abstract 1,3-propanediol is a promising monomer with many applications and can be produced by bioconversion of renewable resources. The separation of this product from fermentation broth is a difficult task. In this work, the application of cation exchange resin for the separation of 1,3-propanediol from model aqueous solution was examined. The best effect of separation of 1,3-propanediol from glycerol using sorption method was obtained for H+ resin form, although the observed partition coefficient of 1,3-propanediol was low. On the basis of the results of the sorption of 1,3-propanediol, the ionic forms of the resin were selected and used in the next experiments (H+, Ca2+, Ag+, Na+, Pb2+, Zn2+). The best results in ion exchange chromatography were obtained for cation exchange resin in H+ and Ca2+ form. The use of smaller particle size of resin and a longer length of the column allows to obtain better separation of mixtures.

Interfacial activity and kinetics and mechanism of copper extraction with 2-ethylhexanal oxime

Abstract The interfacial activity, hydrophile—lipophile balance and solubility in the aqueous phase of 2-ethylhexanal oxime were considered and used to discuss the mechanism of copper extraction from chloride solutions. It was demonstrated that complexation can occur both in the bulk of the aqueous phase and at the interface. The volume aqueous mechanism is probably dominant.

ACTIVITIES OF METAL EXTRACTANTS AS DETERMINED FROM INTERFACIAL TENSION ISOTHERM

ABSTRACT Activity/correction coefficients of hydroxyoxime extractants and triisooctylamine in extraction systems containing non-solvating diluents were computed from the interfacial tension isotherms. The deviations from the Gibbs isotherm were considered. in which concentration instead of activities were used. The interfacial tension isotherms were matched by the spline function and the polynomial Computed activity/correction coefficients can be used to model the equilibrium of copper and palladium (II) extraction.

CFD Modelling of Liquid-Liquid Multiphase Slug Flow with Reaction

Microstructured reactors (MSR) receive great attention for obtaining higher surface-to-volume ratios, higher mass and heat transfer rates, higher safety and other advantages over traditional reactors. Extremely good performance of MSR can be obtained due to generation of slug/segmented flow in liquid-liquid systems or Taylor flow in gas-liquid systems. High number of geometrical and process parameters creates great challenge for optimization of such a system. Numerical studies on this problem can improve overall knowledge about process and give opportunity to fast and precise designing of MSR.