Solids deposition from multicomponent wax-solvent mixtures in a benchscale flow-loop apparatus with heat transfer

The deposition of solids from mixtures of a paraffinic wax (C-20-C-40) dissolved in a multicomponent solvent (C-9-C-16) was studied under laminar flow conditions. A novel benchscale flow loop was developed, which consisted of a jacketed heat-exchange section for solids deposition on the inner surface of an aluminum tube. Experiments were performed to investigate the effects of the wax-solvent mixture composition, hot and cold stream temperatures, flow or shear rate, deposition residence time, and hydrodynamic entry length on the deposition process. The data were analyzed with a pseudo-steady-state heat-transfer model, which validated the solids deposition process to be controlled primarily by heat transfer. The mass of deposited solids was related to the ratio of temperature difference across the deposit layer and the overall temperature difference. Gas chromatography (GC) analyses of the deposited layer showed significant shifts in the carbon number distribution. The C20+ content of the deposit layer was observed to be higher, by similar to 70%-200%, than that of the corresponding wax-solvent mixture.