FIELD: chemistry.
SUBSTANCE: present invention relates to a hydrocracking method combined using vacuum distillation and solvent deasphalting. Hydrocracking method involves the following steps: (a) performing hydrocracking of heavy stock in a hydrocracking reactor to obtain a hydrocracking product which is separated into at least two product streams, including said heavy oil recirculation stream having a concentration of said polycyclic aromatic hydrocarbons; (b) passing a first portion of said recirculation heavy oil stream as a recirculation fed material into said hydrocracking reactor; (c) passing a second portion of said recycle heavy oil stream to a vacuum distillation unit in which said second portion is separated into at least a light vacuum gas oil stream, stream of heavier vacuum gas oil, stream of off-grade oil product/paraffin flow and vacuum residue flow, wherein said stream of light vacuum gas oil has a concentration of polycyclic aromatic hydrocarbons greater than that of polycyclic aromatic hydrocarbons in said stream of heavier vacuum gas oil; (d) passing said stream of heavier vacuum gas oil as feed material to said hydrocracking reactor; (e) using said light vacuum gas oil stream having said higher concentration of polycyclic aromatic compounds as a release stream or product stream which does not return to said hydrocracking process; (f) passing the off-grade oil product/paraffin flow and the vacuum residue stream to the solvent deasphalting plant, wherein the asphaltenes and heavy polycyclic aromatic hydrocarbons are separated from said streams to obtain deasphalted paraffin oil depleted of polycyclic aromatic hydrocarbons; and (g) passing said deasphalted paraffin oil depleted of polycyclic aromatic hydrocarbons as feed material into said hydrocracking reactor.
EFFECT: technical result is reduction of accumulation of polycyclic aromatic (PCA) hydrocarbons in recirculation flow of heavy oil of hydrocracking process.
11 cl, 1 dwg, 1 tbl, 1 ex
