Measurement of the Liquid-Deposit Interface Temperature during Solids Deposition from Wax-Solvent Mixtures under Sheared Cooling

The liquid-deposit interface temperature for solids deposition was measured under sheared as well as static cooling from prepared mixtures of two petroleum waxes and a multicomponent paraffinic solvent (C-9-C-16) at different coolant temperatures. The interface temperature and location were obtained from the rate of change of temperature at fixed radial locations in a cylindrical vessel, while maintaining the coolant temperature below the wax appearance temperature (WAT) of the wax-solvent mixture. In addition, precipitation-filtration experiments were performed on several wax-solvent mixtures at a temperature below the respective WAT, which confirmed that the WAT of the filtrate was 1-2 degrees C less than the precipitation and filtration temperature. For all sheared- and static-cooling experiments, with both wax samples, the interface temperature throughout the deposit-growth process was found to be equal to the WAT of the liquid phase. The results of this study validate the constant-interface-temperature assumption made in the heat-transfer approach for modeling solids deposition from waxy mixtures but do not support the increasing-interface-temperature assumption in the molecular-diffusion approach.