Abstract
ABSTRACT The robustness of the simulation of bioethanol concentration from sugarcane faces two major challenges: the presence of several minor components and the nonlinear behavior of vapor-liquid equilibrium (VLE) calculations. This work assesses the effect of simplifications to overcome these difficulties. From a set of seventeen substances, methanol, n-propanol, isobutanol, 2-methyl-1-butanol and 3-methyl-1-butanol were selected through the examination of the influence of each minor component on vapor-liquid equilibrium calculations of ethanol-water-third component systems. The selection procedure was based on Txy diagrams built using the modified Raoult's law. The influence of the ratio between the vapor phase fugacity coefficients and of the Poynting correction factor were verified. The accuracy of four correlations for vapor pressure was evaluated, and two functional-group activity coefficient models were scrutinized: the recent Functional-Segment Activity Coefficient (F-SAC) and the UNIFAC-Do model.
Highlights
In ethanol production from sugarcane, the concentration process usually comprehends two sets of distillation columns, which are responsible for most of the energy demand
Five substances were selected as most important to be considered in vapor-liquid equilibrium (VLE) calculations, from a set of seventeen minor components present in the ethanol from the sugarcane concentration process
The used criterion was the influence of each component in the vapor-liquid equilibrium of ethanol-water-third compound system, when compared to the ethanol-water binary system
Summary
In ethanol production from sugarcane, the concentration process usually comprehends two sets of distillation columns, which are responsible for most of the energy demand. Reboilers consume about 35% of the total heating energy of an autonomous first generation distillery (Dias et al, 2011) to concentrate an ethanolic mixture from around 0.5% to a requested specification of 92.6-93.8% in mass fraction of ethanol (Marquini et al, 2007; Dias et al, 2011; Furlan, et al, 2012).The feed stream is sugarcane wine, a multicomponent complex mixture having ethanol and water as major components. The use of a large number of compounds in process simulations brings several difficulties. The more compounds in the simulation the larger becomes the size of the plant model, once again penalizing the robustness of the numeric methods
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