Hydrodynamic Perspective on Asphaltene Agglomeration and Deposition

In this work, we propose a detailed numerical model for asphaltene agglomeration and deposition, as induced by a resolved turbulent liquid carrier phase flow, in which transport, breakup, and re-entrainment are also taken into account. Asphaltene phase separation is represented by the appearance of adhesive primary particles, which bond upon collision and act as a precursor to agglomerate formation. Deposition is considered using a novel approach in the context of agglomerate structure resolving simulations: the attractive particle-all interaction is modeled by a damped harmonic oscillator, whereas the deceleration of depositing particles occurs with a characteristic relaxation time. In the absence of deposition, agglomeration and breakup give rise to a statistical steady state. Universal scaling relations, valid for a large range of Reynolds numbers, accurately predict the mean agglomerate mass in this steady state. We show that the shape of the agglomerates is insensitive to the breakup mechanism considered and that the fractal dimension is similar to experimental values reported in the literature for asphaltenes. It is found that the properties of the agglomerates change when two-way coupling is considered instead of one-way coupling, but not when large-eddy simulations are conducted instead of direct numerical simulations. When particle wall interactions are included, deposition predominantly occurs close to the region where asphaltene phase separation takes place. The morphology of the deposit layer is shown to depend upon the local concentration and the mobility of the deposited particles; we also present how these features depend upon the parameters of the deposition model.