Measurement of the Liquid−Deposit Interface Temperature during Solids Deposition from Wax−Solvent Mixtures under Static Cooling Conditions

Abstract

The liquid−deposit interface temperature for solids deposition was measured under static cooling (i.e., without any induced shear stress) from prepared mixtures of a petroleum wax (C20−C40) and a multicomponent paraffinic solvent (C9−C16) at different coolant temperatures. Two designs for the cooling of wax−solvent mixtures were developed for monitoring the temperature at fixed radial locations in a cylindrical vessel. The wax−solvent mixture was cooled from a temperature higher than its wax appearance temperature (WAT), and the movement of the liquid−deposit interface was obtained from the rate of change of temperature at different radial locations. The deposit-layer thickness increased more rapidly with a larger heat-transfer area and a lower coolant temperature. The interface temperature was observed to be equal to the WAT of the wax−solvent mixture, and it decreased slightly when the liquid-region temperature became less than the WAT of the original mixture (causing the precipitation of wax crystals). The results of this study support the constant-interface-temperature assumption made in the heat-transfer approach for modeling solids deposition from waxy mixtures, but not the increasing-interface-temperature assumption in the molecular-diffusion approach.