Nam Sun Nho

Solvent recovery in solvent deasphalting process for economical vacuum residue upgrading

The solvent deasphalting (SDA) process is a heavy oil upgrading process and used to separate asphaltene, the heaviest and most polar fraction of vacuum residue (VR) of heavy oil, by using density differences, to obtain deasphalted oil (DAO). The SDA process consists of two main stages: asphaltene separation and solvent recovery. Solvent recovery is a key procedure for determining the operating cost of the SDA process, because it uses a considerable amount of costly solvent, the recovery of which consumes huge amounts of energy. In this study, the SDA process was numerically simulated by using three different solvents, propane, n-butane, and isobutane, to examine their effect on the DAO extraction and the effect of the operating temperature and pressure on solvent recovery. The process was designed to contain one extractor, two flash drums, and two steam strippers. The VR was characterized by identifying 15 pseudo-components based on the boiling point distribution, obtained by performing a SIMDIS analysis, and the API gravity of the components. When n-butane was used, the yield of DAO was higher than in the other cases, whereas isobutane showed a similar extraction performance as propane. Solvent recovery was found to increase with temperature and decrease with pressure for all the solvents that were tested and the best results were obtained for propane.

Kinetic analysis using thermogravimetric analysis for nonisothermal pyrolysis of vacuum residue

Pyrolysis is a relatively simple upgrading process that can produce light oil from unconventional oil and heavy residue. For effective utilization of pyrolysis processes, it is important to understand its kinetic parameters. In this study, the nonisothermal pyrolysis of vacuum residue (VR) was analyzed using a thermogravimetric analyzer and the activation energy of the VR pyrolysis reaction was estimated by several theoretical methods. It was found that isoconversional methods were more suitable than nonisoconversional methods for analyzing complex pyrolysis reaction of VR. The Friedman method, a differential isoconversional method, is thought to be the most appropriate among the various methods tested because it can describe the complexity of the pyrolysis reaction of VR and there is no need for information of exact reaction model and mathematical assumptions for temperature integral, which can raise systematic errors in the kinetic analysis. Finally, the kinetic parameters of VR pyrolysis were determined based on the results of Friedman analysis and distributed activation energy model (DAEM), and VR pyrolysis behavior was well expressed with the kinetic parameters obtained from DAEM analysis.