We have developed and applied an Eulerian-Lagrangian model for the transport, formation, break-up, deposition and re-entrainment of particle agglomerates. In this paper, we focus on agglomeration and break-up. Simulations were carried out to investigate what changes in the turbulent flow are inflicted by the presence of the agglomerates. Also, the dependence of the properties of the agglomerates on the Reynolds number of the flow and on the strength of the bonds between the primary particles is studied. The presence of the agglomerates attenuates the turbulence and thereby lowers the Reynolds stresses. As a result, the flow rate increases at constant pressure drop when agglomerates are formed (up to a certain dimension). If the agglomerates surpass this dimension, long-distance viscosity effects become dominant and a flow rate decrease occurs. The characteristics of the agglomerates are largely insensitive to the Reynolds number, provided the flow is turbulent. The agglomerates have an open and porous structure, and a fractal dimension of 1.8-2.3. Their mean mass scales exponentially with the strength of the internal bonds. Contrary to assumptions that are typically made in engineering models in the literature, agglomerates do not preferentially break into two fragments of similar size.

We present a model for the formation, break-up, deposition and re-entrainment of solid particle agglomerates in turbulent flows. The turbulent flow of the liquid carrier is represented through Direct Numerical or Large Eddy Simulations. The structure of the agglomerates, which are formed by inter-linked spherical primary particles, is explicitly taken into account in this model. While firstly still ignoring deposition and re-entrainment, we present results on the properties of the agglomerates formed both in channel flow, and in flow in a cylindrical pipe. The collision rate of the agglomerates is found to be under-predicted by the Saffman & Turner collision kernel by up to a factor of 10. We also present results on the modification of the turbulence due to the presence of the agglomerates. Furthermore, results on the deposition and re-entrainment rate of the agglomerates, as well as on the additional streamwise pressure drop induced by the deposition are presented. Ultimately, the results obtained this way are used to construct improved engineering models for predicting asphaltene deposition during crude oil production.This research was carried out in the context of the Integrated Systems Approach to Petroleum Production (ISAPP) Knowledge Center. ISAPP is a joint project of the Netherlands Organization for Applied Scientific Research (TNO) and Delft University of Technology, sponsored by ENI, Petrobras, and Statoil.