Selective separation of solvent from deasphalted oil using CO₂ for heavy oil upgrading process based on solvent deasphalting

The solvent deasphalting (SDA) process is a heavy oil upgrading process in which deasphalted oil (DAO) is extracted from heavy oil feedstock by precipitating asphaltene using an excess amount of alkane solvent (C3-C6). After the extraction, solvent recovery should be carried out for separating the solvent from the DAO in order to recycle the expensive solvent. In the conventional solvent recovery method, the mixture of solvent and DAO is heated to evaporate the solvent, which requires massive heat energy, resulting in reduced process efficiency. In this study, CO₂ is applied for the first time to selectively separate solvent from DAO at a relatively low temperature. The experimental results in a batch separator indicate that the temperature required for high solvent recovery of over 80% decreases from 200 °C to 40 °C when using CO₂ compared to the conventional method. The theoretical approach using Hansen distance calculation based on the Hansen solubility parameter (HSP) was used to verify the mechanism of solvent separation using CO₂. The results suggest that the increase in the interaction between CO₂ and solvent causes the separation of solvent from DAO, leading to an increase in solvent recovery. Also, numerical simulation results show the possibility of continuous operation for solvent recovery using CO₂.