Investigation of solids deposition from wax-solvent mixtures under static, sheared, and 'cold flow' cooling conditions

This study presents a procedure developed to measure the liquid--deposit interface temperature during solids deposition from wax--solvent mixtures under static and sheared cooling conditions using a novel batch deposition apparatus. Batch deposition experiments were carried out with two types of multi-component waxes, using different wax concentrations, coolant temperatures, and different size of cooling surface area. All experiments showed the interface temperature throughout the deposit layer growth process was equal to the wax appearance temperature (WAT) of the liquid phase. Results from static cooling deposition experiments compared well with predictions from a mathematical model based on the moving boundary problem formulation. In addition, precipitation--filtration experiments were developed and performed on several wax--solvent mixtures at temperatures below the respective WAT. The WAT of all filtrates was found to be 1--2°C less than the precipitation and filtration temperature.;A novel bench-scale flow-loop apparatus was developed to investigate the role of heat transfer during deposition from wax--solvent mixtures under 'cold flow' conditions. Experiments were carried out with 3 and 6 mass% wax--solvent mixtures, at different mixture flow rates, coolant temperature, and mixture temperature. The deposit mass increased with a decrease in the coolant temperature and an increase in both the wax concentration and mixture temperature. Solids deposition during 'cold flow' did not occur when the difference between the liquid--deposit interface temperature became equal to the coolant temperature. Predictions from a steady-state heat-transfer model showed good agreement with the 'cold flow' deposition experimental data.