Process for the pre-treatment of feeds for the production of biofuels by hydrolysis of fats at high temperature and pressure

A pre-treatment process for removal of impurities from a feed directed to subsequent hydrotreating and isomerization steps in a biofuel production plant wherein said pre-treatment process comprises the following steps:

• a hydrolysis step (B);
• a water and glycerol treatment (F);
• a glycerol concentration (J);
• a glycerol distillation (L);
• an acid esterification (G);
• wherein said feed comprises both:
• a raw stream (1) consisting of an organic feed comprising secondary materials, category 1 animal fats, residual oils or by-products consisting of monoglycerides, diglycerides, triglycerides and free fatty acids, and
• a recycling stream (25) consisting of a mixture of mono-, di- and triglycerides free of said impurities and exiting an esterification unit,
• wherein said impurities consist of phosphorous, chlorides, calcium, magnesium and heavy metals present in ionic form, and
• wherein said feed (1, 25) is routed to said hydrolysis step (B), said hydrolysis taking place with excess water, under controlled pressure and temperature conditions, thus obtaining a partial or total conversion of the incoming feed into glycerol and fatty acids, the excess water introduced into the hydrolysis step acting as a solvent for said impurities present in ionic form, thus removing most of the heavy metals, as well as of the chlorides contained in said incoming feed to obtain a first outcoming stream (3) consisting of fatty acid, wherein the concentration of phosphorus is lower than 3 ppm and the concentrations of calcium and magnesium are lower than 3 ppm, an amount of said first outcoming stream (3) being routed to the esterification step (G) and the remaining part of said outcoming stream (3) routed to the subsequent hydrotreating and isomerization steps, and a second outcoming stream (9) consisting of water and glycerol containing all the removed ions, said second outcoming stream (9) being routed to subsequent purification steps of the water and glycerol treatment (F), the glycerol concentration (J), and the glycerol distillation (L), in order to obtain a pure glycerol stream (15) to be routed to the esterification step (G) to produce the recycle stream (25) to be joined with the raw stream (1).