September 11-16, 2016
Assuming a concentration-independent flux with an Arrhenius dependence on temperature, and using temperature- and composition-averaged physical properties, an exact analytical expression is derived for the average flux in an adiabatic, single-pass pervaporation module. The envelope of industrially feasible operating conditions for alcohol dehydration systems is completed. The range of feasible activation energies of permeation is established for IPA-water and ethanol–water systems. Within this range a simple approximation to the exact analytical expression is derived. A parameter Jr/Jreheat is proposed where Jreheat is the flux at the retentate composition and feed temperature. It can be used to determine the optimum membrane area within an adiabatic module for systems with concentration-dependent flux and concentration-independent flux. Results indicate that permeate-to-feed ratios above the current industry norm of 5% are economically feasible in some cases. The impact of a recycle on the average flux, retentate composition, retentate temperature and permeate-to-feed ratio is explored. Equations are developed relating flowrates and compositions to the recycle ratio. A module is modelled for concentration-independent flux, concentration-dependent flux and desalination. The results indicate that increases in average flux can be achieved through use of a recycle for some industrial applications including desalination.
Ó Súilleabháin, C., Foley, G., Engineering of pervaporation systems: Exact and approximate expressions for the average flux during alcohol dehydration by single-pass pervaporation, Sep. Purif. Technol. 152 (2015) 160–163.
Santoso, A., Cheng-Ching, Y., Ward, J.D., Analysis of local recycle for membrane pervaporation systems, Ind. Eng. Chem. Res., 2012, 51, 9790-9802.
Cilian O’Súilleabháin and Greg Foley, "Engineering of pervaporation systems: Modelling of dehydration modules, including recycles" in "Advanced Membrane Technology VII", Isabel C. Escobar, Professor, University of Kentucky, USA Jamie Hestekin, Associate Professor, University of Arkansas, USA Eds, ECI Symposium Series, (2016). http://dc.engconfintl.org/membrane_technology_vii/7