Slurry prepared with up to 12% of solids and DAO obtained from a proprietary solvent deasphalting process were evaluated under dynamic conditions. Six different solid concentrations were evaluated in an experimental flow loop at six different mixture velocities. All experimental points exhibit Reynolds numbers <1400 (laminar flow) and homogeneous flow pattern. The obtained slurry viscosity is significantly lower than the viscosity of original heavy oil (three orders of magnitude lower) and comparable to viscosities obtained when diluting oil with naphtha at 70:30 oil/naphtha ratios, but without the additional increase in volumetric flow rates and pipe size. The slurry exhibits a Newtonian behavior for all solid concentrations studied, with no yield strength, which means no significant additional pump discharge pressure is required for re-start operations for this particular issue. However, an increasing pump discharge pressure can be required after a prolonged shutdown due to a viscosity increase with time caused by progressive re-dissolution of asphaltenes. Slurry morphology and viscosity are time dependent, as solid phase dispersed in DAO progressively return to their colloidal state. After 24 hours, slurry viscosity increases up to 45% when compared to the initial stage for the maximum solids concentration of 12%, to a maximum value of 0.16 Pa.s, which is still three orders of magnitude lower than viscosity of original heavy oil. Asphaltenes re-dissolution is a relatively slow phenomenon as asphaltenes kinetics is slow. However, additional studies are required to assess long-term stability of slurry, to properly address requirements for re-start operations after prolonged shutdowns. The pressure drop in the pipeline can be estimated using a simple Darcy factional pressure drop model, considering the suspension as a homogeneous phase, with an absolute average error of 11%.
Heavy oil transportation as a slurry
2013
10 Seiten, Bilder, Tabellen, 10 Quellen
Conference paper
English
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