000			02057nab a2200181 4500
005			20260520000831.0
008			260224s2009 xxu
245	0	0	_aCharacteristics of wax gel formation in the presence of asphaltenes
260			_a _b _cmar./abr. 2009
270			_a2009-08-07 ; 2009-08-07
300			_a5 p. ; 1289-1293
520			_aResúmen del autor: When pipelines are shutdown, waxy crude oils tend to form gels, which tend to plug the lines and stop flow. Restart requires sufficient pressure to overcome the yield stress of gelled oils. This study examines the yield strength of well-characterized waxy model oils at temperatures below the pour point. First, the yield stresses of model oils were determined by the vane method at different temperatures. Yield stress values were strongly dependent upon wax amounts and compositions, as expected. The extent of increase in yield stress values with temperature was greater for model oils that had a higher percentage of wax. The x-intercept values obtained from yield stress versus temperature were interpreted as no-flow points, which could be used as alternative measures of pour points. Second, the role of asphaltenes was examined in the evolution of the yield stress as the oil is cooled below the pour point. Asphaltene additions resulted in pour-point reductions, of up to 4 °C for additions of asphaltenes up to 0.1% (w/w). Small amounts of asphaltenes (0.01%, w/w) also played a significant role in yield stress reduction. The concept of steric hindrance and asphaltene aggregation was adapted to explain the yield stress reduction at the different asphaltene concentrations. At lower temperatures, as more wax came out of solution, the slope of the yield stress versus temperature line went back to the slope of the asphaltene-free oil, indicating the dominance of the wax networks at higher wax concentrations.
773	0		_tEnergy & fuels _g23
942			_cARTICULO
100	1		_aOh, Kyeogseok _941746
100	1		_aDeo, Milind _941747
999			_c170268 _d170268