| abstract |
The invention relates to a method for revamping a conventional refinery of mineral oils into a biorefinery, characterized by a production scheme which allows the treatment of raw materials of a biological origin (vegetable oils, animal fats, exhausted cooking oils) for the production of biofuels, prevalently high-quality biodiesel. This method allows the re-use of existing plants, allowing, in particular, the revamping of a refinery containing a system comprising two hydrodesulfurization units, U1 and U2, into a biorefinery containing a production unit of hydrocarbon fractions from mixtures of a biological origin containing fatty acid esters by means of their hydrodeoxygenation and isomerization, wherein each of the hydrodesulfurization units U1 and U2 comprises: a hydrodesulfurization reactor, (Al) for the unit U1 and (A2) for the unit U2, wherein said reactor contains a hydrodesulfurization catalyst; one or more heat exchangers between the feedstock and effluent of the reactor; a heating system of the feedstock upstream of the reactor; an acid gas treatment unit downstream of the reactor, containing an absorbent (B) for H2S, said unit being called Tl in the unit U1 and T2 in the unit U2, and wherein said method comprises: installing a line L between the units U1and U2 which connects them in series; installing a recycling line of the product for the unit U1 and possibly for the unit U2, substituting the hydrodesulfurization catalyst in the reactor Al with a hydrodeoxygenation catalyst; substituting the hydrodesulfurization catalyst in the reactor A2 with an isomerization catalyst; installing a y-pass line X of the acid gas treatment unit T2 of the unit U2; substituting the absorbent (B) in the acid gas treatment unit Tl with a specific absorbent for C02 and H2S. The operative configuration obtained with the method, object of the present invention, also leads to a substantial reduction in emissions of pollutants into the atmosphere, with respect to the original operative mode. The invention also relates to the transformation unit of mixtures of a biological origin obtained with said conversion method and particularly hydrodeoxygenation and isomerization processes. |