Experiments and modeling for investigating the effect of suspended wax crystals on deposition from 'waxy' mixtures under cold flow conditions

Solids deposition in the hot flow and the cold flow regimes from wax-solvent mixtures was studied experimentally using a cold finger apparatus. The deposition experiments were conducted with a 10 mass% wax-solvent mixture, at an agitation speed of 250 rev min(-1), with a constant coolant temperature of WAT - 12 degrees C, at 9 wax-solvent mixture temperatures (from WAT + 6 degrees C to WAT - 10 degrees C), and for 17 deposition times (from 2 s to 48 h). The deposit growth was very rapid during the first few minutes of the deposition process, which is typical of thermally-driven processes. In all experiments, the deposit mass increased during the initial 24 h, after which the deposition process reached a steady-state. The results of these deposition experiments are shown to validate the predictions from a steady-state model as well as an unsteady-state model, which has been used in the past for simulating wax deposition behaviour in a pipeline under laminar and turbulent flow conditions. Furthermore, experiments were performed to investigate the effect of wax crystals on the deposition process in the cold flow regime. This was accomplished by repeating the deposition experiments with filtered wax-solvent mixture, i.e., following a filtration step to remove the suspended wax crystals. A comparison of the deposition results, from the experiments with unfiltered and filtered wax-solvent mixture, showed that the suspended wax crystals do not affect the deposit mass or thickness.