Rheology of Middle Distillate. I. Role of Composition

The rheological behavior of middle distillate (250-375°C) fraction, obtained from the waxy Bombay-High Off-shore crude oil, and its five narrow sub-fractions of 25°C interval each, i.e., Fr 1 (250-275°C), Fr 2 (275-300°C), Fr 3 (300-325°C), Fr 4 (325-350°C), and Fr 5 (350-375°C), have been studied below their ASTM pour point temperatures. The rheograms (the shear stress vs. rate of shear) of the fraction and sub-fractions, at various temperatures below their pour points, are recorded on a Haake RV-12 Co-axial Rota Viscometer fitted with a NV sensor and a temperature programmer (PG-20) and attached with a programmed heating/cooling system. From these rheograms the flow parameters like plastic viscosity, apparent viscosity, and yield stress are obtained and their variations with temperature and shear rate have been studied in terms of compositions of the fraction/sub-fractions. These results might be useful in devising methodology for overcoming the wax separation phenomenon from middle distillates at low temperatures.