Continuous visbreaking of heavy oil in medium and high-pressure steam environments

Abstract

Continuous visbreaking of heavy oil in a tubular reactor was studied under pressurized steam environments at 10 MPa (MPS) and 18 MPa (HPS). Within the operating range considered, heavy oil and pressurized steam exhibit a liquid-vapor two-phase structure. During the transition from the MPS environment to the HPS environment, the dissolution of water into the oil phase is promoted, thereby reducing the viscosity of the oil phase. According to the lumped reaction kinetics analysis, the reaction behavior of the lumped component VR2 with a boiling point higher than 700 °C determines the visbreaking efficiency in the early visbreaking stage to a large extent. Dealkylation of VR2 and condensation of the lightest lumped component show sensitive responses to improved diffusion in the oil phase. At 400 °C and a space time of 37 min, visbreaking in HPS environment can achieve a viscosity reduction rate of 90%. Meanwhile, the asphaltene content of the product is lower than the feedstock value.