(403i) Electrical Treatment of Waxy Crude Oil to Improve Low Temperature Flowability

Wax precipitation from crude
oils caused by temperature reduction greatly increases the apparent viscosity
of oils and thereby poses challenges to the safety and efficiency of their transportation.
In the present work, we demonstrate that the apparent viscosity of waxy crude
oil at temperatures near the pour point could be significantly reduced by
applying a direct electric field parallel with the direction of the oil flow
for only one to two minutes. A novel apparatus (Figure 1) was assembled that
can electrically treat waxy crude oil and simultaneously measure the
rheological property of the treated oil, and a method was developed to calculate
the viscosity variation by using non-Newtonian fluid mechanics and rheological
principles. Lower treatment temperatures (Figure 2) and higher electric field
strengths (Figure 3) provided greater viscosity reduction. We also observed that
the performance of electrical treatment depends upon the shear rates, with a
lower shear rate generally resulting in a greater viscosity reduction. Notably,
a viscosity reduction of 70% was obtained after the crude oil, that has a pour
point of 17 ^oC, was
electrically treated at 18 ^oC and 0.8
kV/mm for 90 s. Besides,
the energy consumption of the electrical treatment was estimated to be less
than 1% of that of the conventional heating method to achieve the same
viscosity reduction performance. Thus, we herein demonstrate a technology for
improving the flowability of waxy crude oils at low temperatures in an
energy-efficient manner.

Figure
1: Schematic
diagram of the electrical treatment apparatus

Figure
2: Effect of treatment temperature on viscosity reduction at different shear
rates

Figure
3: Effect of electric field strength on viscosity reduction at different shear
rates