In this chapter, main technologies for concentration of dilute aqueous solutions of ethanol obtained during the fermentation step are discussed. The main ethanol dehydration technologies, including the most promising, are disclosed as well. The main advantages and drawbacks of the discussed dehydration schemes are included as well. The utilization of process simulation tools is illustrated through the analysis of different technological schemes for ethanol separation and dehy­dration. The role of thermodynamic-topological analysis during the concep­tual design of separation and dehydration technological configurations is also highlighted.

The recovery of ethanol produced by different technological configurations and from diverse types of feedstocks is accomplished in a very similar way. The ethanol content in the culture broth resulting from fermentation processes oscil­lates between 2.5 and 10% (by weight). The utilization of fuel ethanol as a gaso­line oxygenate requires a high-purity ethanol, so it is necessary to concentrate the ethyl alcohol up to 99% to obtain the anhydrous ethanol, which is the suit­able form used for ethanol-gasoline blends. Because the presence of water in fuel ethanol can lead to failures in the engine during the combustion of such blends (Sanchez and Cardona, 2005). The first step of the ethanol recovery scheme is the concentration of ethanol contained in culture broths. This process is carried out in distillation columns achieving ethanol content of about 50%. The next step is the rectification of this concentrated stream to obtain a product with a composi­tion near to the azeotropic mixture of ethanol and water. In the following section, these two steps are discussed.