Methodology for modelling of pervaporation: step from binary to ternary mixtures

In this work, our methodology proposed earlier for the modelling of pervaporation is applied. The modified Rautenbach model is selected again, as an integral part of our methodology. The applicability of the methodology is investigated in the case of ternary mixtures: the connections between the model parameters of the binary and ternary mixtures are studied. For the possibility of comparison the widely investigated water Á ethanol as binary and water Á ethanol Á 2-propanol as ternary mixture, involved a PERVAP 2210 PVA/PAN composite membrane are chosen. The parameters of the model are capable to describe the system simultaneously the function of temperature and in the range of feed mixture 0.5(10 wt.% water. For the parameter estimation, the mathematical / software GAMS# (GAMS Development Corporation, 2005) is used. The defined number of the model parameters and feed mixtures are applied in our user added subroutine of the ChemCAD# (5.1.3 Professional, 2001) chemical process simulation software. The comparison of measured, modelled and simulated data shows that the parameters of the most permeating component (water) can be taken from either the binary or the ternary measurements. This new result can help to reduce experimental work and improve modelling work. The simulations show high accuracy of the modelling of pervaporation based on the parameters obtained from experimental data.

In this work, the Rautenbach model is improved and tested from the viewpoint of the influence of the model parameters on the modelling. The role of permeability coefficient (Q0) and the possibility to transfer the values determined from binary measurement into ternary systems and vice versa are tested to apply in modelling. The calculations prove that the permeability coefficient has negligible effect on modelling results and it can be eliminated. The expectation that the PAN support has significant relevance of resistance compared to PVA selective layer is not true in this case. It is found that the exchange of respective binary and ternary optimized parameters for the most permeating component (water) is feasible with a 9 1% flexibility. The optimized parameters are used in our user added pervaporation module of the ChemCAD# flowsheeting program. Since in Fig. 1 good agreement can be seen between the measured and simulated data it can be also concluded that the simulation is suitable for extension in size and connection e.g. simulating of hybrid processes. /