Density and Viscosity of Visbroken Bditumens and Their Fractions

To design visbreaking processes for bitumen upgrading, it is necessary to predict the product properties. This study examines the impact of visbreaking on the density and viscosity of two bitumens, a vacuum bottom and a deasphalted oil. The oils were visbroken at different combinations of temperature and space time (with conversions up to 38%) by using an in-house continuous visbreaker. In all cases, the gas yields were below 1.5 wt %, and no coke was detected. The products were separated into distillates, saturates, aromatics, resins, and asphaltenes (DSARA). The density and viscosity of the oils and each of their fractions were measured directly or indirectly from measured whole oil, maltene, and residue properties over temperatures from 20 to 150 °C, depending on the fraction. The product density was modeled with a volumetric mixing rule, and the viscosity was modeled with the Expanded Fluid model. Existing correlations for the input DSARA property parameters as a function of conversion were updated. The models with the updated correlations and a new tuning procedure were evaluated by using measured feed properties, conversion, and product compositions as inputs. The average deviations in the modeled product densities and viscosities were 2.2 kg/m3 and 28%, respectively. The models were further tested using default feed properties, and product compositions correlated to conversion. This approach eliminated the need for measured product composition and properties and had minimal impact on the accuracy of the updated models.