Separating Asphaltenes from Lube Oil Through Supercritical Deasphalting Considering Experimental and Virtual Plants and Thermodynamic Analysis

摘要

Studies of petroleum asphaltenes have gained considerable attention in the past decades due to the increasing production of heavy crude oils. The reduction of light crude oil reservoirs and the increasing of light oil demand, forced the petroleum industry to develop upgrading processes for raw materials and residues. Due to the limited global oil reserves, more and more heavy crudes are being processed. These crudes contain large amounts of asphaltenes and resins. Petroleum must be processed in order to have the major quantity of higher aggregated compounds. All types of petroleum are colloidal systems. In a dispersion medium consisting mainly of hydrocarbons, which can be classified into alkanes, naphthenes and aromatics, there are two groups of dispersed colloidal particles in solution: asphaltenes and petroleum resins. Reduction of asphaltenes and metal content can be achieved by disturbing the solvatation equilibrium via addition of suitable solvents, e.g., propane. The Residuum Oil Supercritical Extraction (ROSE~(TM)) process is the premier deasphalting technology available in industry today. This state-of-the-art process extracts high-quality deasphalted oil (DAO) and asphaltenes from atmospheric or vacuum residues and other heavier feedstocks. The ROSE process operates near to the critical point of the solvent and applies thermodynamic fundamentals and high-pressure phase equilibrium principles in order to provide an energy-efficient process. Depending on the solvent selection, the DAO can be an excellent feedstock for catalytic cracking, hydrocracking, or lube oil blending. The energy consumption in supercritical extraction is considerably lower than in conventional extraction, which requires a higher ratio of solvent to crude. The use of supercritical fluid has some advantages such as higher yield and improved quality of the valuable DAO and asphaltenes product, and recovery of the supercritical solvent, reducing significantly operating costs compared to other solvent deasphalting processes. This work presents a new method for petroleum deasphalting. The proposal involves the extraction of the residue fractions from molecular distillations using supercritical propane or pentane as solvent. The thermodynamic calculation and representation of the ternary system is shown. The calculation is very complex since the asphaltenes have to be represented as a set of molecules whose properties have to be predicted using special methodology and the UNIFAC method. Our research group at State University of Campinas (TJNTCAMP) has developed a real supercritical extraction pilot plant and a virtual one which are optimized and validated. This work is carried out in association with Petrobras (Brazilian Oil Company).