INTRODUCTION
The rapid growth of global energy demand is met primarily by fossil fuel nonrenewable. This makes it necessary to find clean energy sources to effectively replace fossil fuels and to mitigate the negative effects caused by them. Biodiesel obtained from vegetable and animal fats appears as a good alternative to petroleum fuel (Demirbas, 2009). Biodiesel may be produced from the transesterification reaction of fatty acids of vegetable origin with short chain alcohols catalyzed by bases such as NaOH or sodium methylate.
The transesterification reaction is a reversible reaction of an oil composed of triglycerides with an alcohol to form fatty acid alkyl esters and glycerol. Reaction stoichiometrically requires a 3:1 molar ratio of alcohol to oil with an excess of alcohol (West et al. 2008).
The alcohols used should be of low molecular weight being one of the most used ethanol for its low cost (Zapata et al. 2007; Demirbas, 2009). However, greater conversions into biodiesel can be reached using methanol.
Although the transesterification reaction can be catalyzed by acids or bases, alkaline catalysis is the technique most frequently used for the production of biodiesel. This path has lower reaction times and catalyst cost than those posed by acid catalysis. However, alkaline catalysis has the disadvantage of its high sensitivity to both water and a fatty acid (FFA) present in the oils.
In this paper, the liquid-phase biodiesel production in a pilot continuous reactor at the Pilot Plant of Reaction, Chemical Engineering Dept. (UNCPBA) was studied in order to develop a numerical full model of momentum-mass-heat transfer to predict conversions at the outlet reactor, based on the finite elements method (FEM), a technique especially useful for solve coupled engineering problems where the analytical solution is not possible due its high complex.
The objectives of the present work were: a) to develop a program based on FEM to simulate the transfer of momentum and heat in a pilot tubular reactor, b) to couple the kinetic reaction of catalytic transesterification of a non-conventional oil with an alcohol into the general program, with the aim to optimize the process, c) to use the computational tool Aspen-HYSYS to simulate the process of biodiesel production and estimate useful data for the FEM model, d) to validate the numerical model with experimental data.