US Patent 7857964 Method of refining heavy oil and refining apparatus

The present invention relates to a method in which grades of oil are refined according to their object from a feed oil. This method has a solvent extraction process that obtains an extracted oil, and a hydrogenation process that subjects the obtained extracted oil to hydrogenation process in the presence of hydrogen and a catalyst to obtain a hydrorefined oil. The solvent extraction conditions are selected by using the poly-aromatic concentration as an index for calculating the concentration of heptane insoluble components in the residue of the extracted oil obtained by the solvent extraction process that cannot be fractionally distilled.