(492d) Fuel Alcohol Production by Extractive Distillation with Glycerol Using a Pilot Extractive Column

Bioethanol is currently used as substitute of fossil fuels in order to diminish the pollution caused by them. The main technologies used in the alcohol dehydration step are adsorption using molecular sieves, azeotropic distillation and extractive distillation, being the last one the most promising due to the low energy consumptions and operating costs that it offers. Extractive distillation uses a third component called entrainer to modify the Vapor – Liquid Equilibrium (VLE) and eliminate the azeotropic problems found in conventional distillation.

With the purpose of having an efficient separation process, the entrainer must have the following characteristics: high boiling temperature, do not form additional azeotropes with the components of the original mixture and it must be cheap. The solvents that have been studied are glycols, salts, hydrophobic phenols and amines, being the glycols those that report better performance.

In this work, the use of glycerol as entrainer is studied in the ethanol dehydration process using a pilot extractive distillation column. The distillation column has 11m height and 0.23 m of diameter and it is packed with Nutter Rings. Besides, it is equipped with temperature and pressure sensors that allow having temperature data along the column. Likewise, operating conditions such as entrainer temperature and entrainer/feed molar ratio were studied in order to establish its effect on the separation and on the energy consumption. All the experiments were carried out at 74.66 kPa, atmospheric pressure in Bogotá.

Finally, anhydrous ethanol at 99.2% v/v was obtained using low entrainer/feed molar ratio and feeding the entrainer at 70ºC approximately. These two aspects combined give low operational costs because the steam consumption as well as the entrainer make-up are reduced. Furthermore, the temperature and composition profiles obtained constitute basic information to deep into the study of glycerol as entrainer in this process, in addition to evaluate different control structures of the pilot plant.