Mathematical Modeling of Waste Fat Pre-Treatment for Biodiesel Production

Waste fat produced by tanneries during the processes in which raw hide is transformed into leather represents a very important raw material for biodiesel production. However, the acid number of this feedstock usually exceeds 2 mg KOH/g, which makes it unsuitable for direct processing into biodiesel via alkali-catalyzed transesterification. An effective and economically viable pre-treatment method is needed to overcome this disadvantage and at the same time to maintain the advantage of low price of the feedstock. In this paper, we present a mathematical model of the zonal refining melting process which we have developed within our complex technology of biodiesel production of low quality fats and oils. If the free fatty acid content is still high after pre-treatment, we use esterification in alkali conditions of tetramethylammonium hydroxide. The use of the organic alkali burdens the products (biodiesel and glycerin) with no ballast inorganic salts. Finally, the waste tannery fat potential in biodiesel production is briefly evaluated from the economic and raw material base point of view. Key-Words: Biodiesel, mathematical modeling, refining melting, waste tannery fats