Study of Wet Ethanol Energy Balance: From Production to Fuel

摘要

Various studies previously conducted have estimated the net energy value for ethanol, but the variations of data and assumptions used caused the results to lack in precision. However, studies are unanimous in pointing out that the greatest fraction of the energy necessary for making ethanol is spent in water removal (distillation and dehydration), growing exponentially the smaller the amount of water in the final product. By using wet ethanol to avoid the energy cost of dehydration, the purposes of this work were to numerically evaluate the energy spent in the distillation process and compare the results with the efficiency in using wet ethanol as fuel. The simulation was modelled through Matlab software environment, using as base a distillation column for batch process with a variable number of plates to obtain as a final product ethanol with different degrees of hydration. The energy production costs were, then, compared to the results generated by the simulation of an SI engine using each one of the fuel blends, in order to conclude if the production of a more hydrated fuel in fact contributes to a better result regarding the net energy value. A two-zone model was used for calculations of engine combustion cycle and indicated efficiency parameters were used to evaluate each fuel blend. The results show that, as expected, a small increase in water quantity in the distillate can contribute decisively to the process net energy gain, making the use of wet ethanol more attractive.