This study focuses on understanding the impact of phase behavior, particularly solid phase behavior, on heavy oil partitioning processes in upgrading operations. Multiphase behaviors for the model systems Athabasca Bitumen Vacuum Bottoms (ABVB), a 525+°C fraction containing 32 wt % asphaltenes, + pentane, heptane and dodecane are investigated using a variable volume X-ray view-cell. The mixtures exhibit complex fluid phase behaviors with asphaltene solidification. Two three-phase LLV zones, L1L2V and L2L3V, were found for ABVB + pentane mixtures. The L1L2V zone is expected since it is close to the vapour pressure curve of pure alkane, a typical characteristic of asymmetric mixtures. However the L2L3V zone, found at temperatures T > 230°C for 40∼45 wt % ABVB + pentane mixtures and T = 20∼340°C for 50 wt % ABVB + pentane mixtures, was unexpected. The pressure range of the L2L3V region was very narrow and this zone has great potential for developing selective separation processes. Existing processes such as Residuum Oil Supercritical Extraction processes are currently operating in L1L2V zone. Solids when present can be completely dispersed, completely settled, or remain partially dispersed and partially settled. In addition, adherent deposits, including liquids, are observed at T < 200°C over a broad range of conditions.
Composition analysis for specific phases revealed that mineral matter is easily and quantitatively separated from ABVB by adding sufficient amounts of an alkane solvent to create a second liquid phase, while selective removal of nickel, vanadium, sulfur and nitrogen from ABVB + pentane mixtures is not realized. Chemical reactions coupled with multiphase behavior are required to selectively remove heavy metals. Saturate-Aromatics-Resins-Asphaltenes (SARA) analysis indicates that the rejected phases contain saturates, aromatics and resins while the extracted phases contain asphaltenes, suggesting aromatics, resins and asphaltenes constitute a compositional continuum with respect to both molar mass and polarity.
The X-ray view-cell technology was also enhanced during this study. Detection of precipitated phase/phases and apparent phase density measurements were improved. A new phase density calibration method using a beryllium insert as an internal standard was developed and automated. Software was prepared to process experimental data.