Solids Deposition from Two-Phase Wax-Solvent-Water "Waxy" Mixtures under Turbulent Flow

The deposition of solids from two-phase waxy mixtures (comprising a multicomponent paraffinic wax dissolved in a multicomponent solvent and water) was studied under turbulent flow conditions in a flow -loop apparatus, incorporating a cocurrent double pipe heat exchanger. The deposition experiments were performed with 6 mass % wax solutions, containing 0, 5, 10, 15, 20, 25, and 30 vol % water, at different flow rates over 5600 < Re < 25 300, and at different hot and cold stream temperatures. In the bench-scale apparatus, the deposit was formed rapidly such that a thermal steady state was attained within 10-20 min in all experiments. The water content of the deposit was found to be not related to the water content of the waxy mixture. The deposit mass was found to decrease with an increase in Re, the waxy mixture temperature, and/or the coolant temperature. The deposit mass also increased as the water content of the waxy mixture was increased to about 10 vol % and decreased thereafter. The deposition data, analyzed with a steady-state heat-transfer model, indicated that the liquid-deposit interface temperature was close to the wax appearance temperature of the waxy mixture. The average thermal conductivity of the deposit was estimated to be 0.38 W m(-1) K-1. Overall, the results of this study confirm that the deposition process from waxy mixtures is primarily thermally driven.