Deposition and aging of waxy solids from paraffinic mixtures.

摘要

Wax deposition from a paraffinic wax (C20--C40) dissolved in Norpar13 (a paraffinic solvent, C9--C16 ) was studied. A flow loop was developed where the flow of wax-solvent mixtures was achieved using a submersible pump attached to a sealed tank which was submerged in a water bath. The flow loop consisted of a novel jacketed heat exchange section where wax deposition took place on the inner surface of an aluminum tube section. The effects of tube entry length, mixture composition, flowrate, time, and hot and cold fluid temperatures on wax deposition were studied. Experiments were performed for several wax-Norpar13 mixtures (7--15 mass%) over durations of 1, 2 and 4 hours.;A heat transfer model was used to confirm that the deposition of solids is controlled primarily by heat transfer and that the temperature at the wax-solvent deposit interface is the Wax Appearance Temperature (WAT). A dimensionless ratio of the temperature difference across the deposit layer and the overall temperature difference, thetad, was related to the amount of wax deposited.;The composition of wax deposits was analyzed using GC to study its aging or 'hardening' process. The wax deposit aging involved a change in its composition as well as the solid-to-liquid phase ratio. A relative wax content parameter, Gammaw, was used to relate the wax content of the deposits with the wax content of the wax-solvent solution. Gamma w produced a trend of increasing wax content with decreased deposition that fit all the concentrations studied.