Counterintuitive Effects of the Oil Flow Rate on Wax Deposition

The experimental trend of a reduced deposit with an increasing flow rate has been observed in a series of wax studies. Despite the fact that many previous studies intuitively attribute the reason to the "shear removal", the role of heat and mass transfer was frequently overlooked as the true explanation. In the current study, the Michigan Wax Predictor (MWP) was applied to elucidate this trend by analyzing the growth rate of the wax deposit in a series of flowloop experiments from first principles. The model was able to predict the experimentally observed decrease in deposit thickness with an increasing oil flow rate without any adjustable parameters. It was found that three effects exist to affect wax deposition when the oil flow rate is changed, and each one can either increase or decrease the growth rate of the deposit. These effects focus on the heat- and mass-transfer phenomena at the oil-deposit interface. In addition, this study also revealed that the dynamics of the competition between all of these three effects can vary as time progresses and that the overall behavior of the wax deposit growth is eventually determined by the most dominant effect of the three. These results have provided important insight for the effects of the oil flow rate on wax deposition.