Indirect Series of Falling Film Distillation Column to Process Synthetic Naphtha

Abstract

The separation of multicomponent mixture by distillation is commonly accomplished by means of a sequence of columns and/or lateral withdrawals on a column. Desirable specifications for the product stream imply high energy consumption and operational costs due to the low thermodynamic efficiency associated with conventional distillation columns. For these reasons, unconventional technologies are proposed to promote separation, coupled with lower energy consumption. Within the context, the falling film distillation unit assisted by a biphasic thermosyphon provides such improvements. The objective of this study was to evaluate the separation of a multicomponent mixture (synthetic naphtha) in an indirect series of falling films columns. Tests were carried out at atmospheric condition considering the influence of feed flow, feed temperature and vapor chamber temperature. Experimental conditions were previously established from simulations in the Hysys® software, where the mixture was separated into a conventional steady state distillation unit. Results demonstrated that for the first, second and third columns of the series, enriched fractions of hexane obtained in the top stream were of 0.58, 0.72 and 0.82, on a mass basis, respectively. However, heavier compounds were identified in the top stream of the second column, nevertheless, these compounds correspond to less than 0.05 of the mass fraction. Even with a no complete separation, the energetic analysis of the global process shown there was a 12 % reduction in energy consumption of the falling film column compared to the simulated conventional column under the same conditions.