Modeling and simulations of plate and frame pervaporative module for the production of low sulfur containing FCC gasoline

Abstract

Pervaporation is now reorganized as one of the most suitable processes for removing aromatic sulfur-containing compounds (thiophenes) from FCC gasoline, which are otherwise difficult to remove by other traditional processes. Industrial-scale membrane-based separation operations require membrane modules to treat large volumes of feed. Most of the pervaporative membranes used for desulfurization are crosslinked flat sheet membranes, for which plate and frame modules are most suitable. The design of industrial-scale desulfurization units requires the development of mathematical models to predict the module's performance.In this study, a mathematical model is developed to predict plate and frame pervaporative module performance for desulfurization by performing microscopic material and thermal energy balance at the feed side and material and mechanical energy balance at permeate side. A binary mixture of n-heptane/thiophene is taken as the model gasoline. For more realistic simulations, transport properties of membrane were taken from the experimental results reported from literature. Simulations showed that feed temperature and the permeate pressure have profound effects on the module performance and thus may be considered the main operating parameters. Lower permeate pressure and higher feed temperature were found suitable operating parameters to increase the fluxes.On the other hand, lower permeate pressure and lower feed temperature improved the enrichment factor of thiophene. The performance of the plate and frame module were different from the performance of the membrane test cell in all simulations. Moreover, enrichment factors with varying permeate pressure for plate and frame module and test cell were inversed. These results confirm the importance of the developed model over available local mass transport models.