Crude Oil Fouling: Fluid Dynamics, Reactions and Phase Change

Abstract

In the present study, the fluid dynamics and phase behavior of crude-oil fouling in a closed-end heat-exchanger is studied. The deposition process associated with fouling is assumed to be due to two routes: asphaltene precipitation, and a two-step chemical reaction. The SAFT-γ Mie theory is employed to describe the phase behavior of an asphaltene-containing crude oil system, which comprises pseudo-components (C13 ∼ C20+). The predicted phase equilibrium constants are used to quantify the asphaltene precipitation rate. A computational fluid dynamics framework is then used to simulate the fouling process, accounting for the multiphase flow dynamics, heat transfer, and the two deposition routes. Fouling is simulated due to the two routes individually and in concert. In the latter case, it is found that the interaction of the two routes is due to the fouling layer adhering to the heat- exchanger walls, which influences heat transfer from the hot walls to the cooler oil in the bulk. The delicate interplay between heat transfer and fluid dynamics, which accompanies the flow, leads to enhancement and suppression of chemical reaction- and precipitation-driven fouling, respectively, and an overall rise in the fouling rate.