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Effects of Polymers on the Structure and Deposition Behavior of Waxy Gels

Jack F. Tinsley1, Robert K. Prud'homme1, Xuhong Guo1, Douglas H. Adamson2, and Heather D. Dettman3. (1) Dept. of Chemical Engineering, Princeton Unversity, A-215 E-Quad, Olden Street, Princeton, NJ 08544, (2) Princeton Institute for the Science and Technology of Materials (PRISM), Princeton Unversity, 70 Prospect Ave., Princeton, NJ 08540-0211, (3) National Centre for Upgrading Technology, 1 Oil Patch Drive, Suite A202, Devon, AB T9G 1A8, Canada

Deposits of waxes in crude oil transport lines are a physical gels whose formation poses a significant industrial challenge. Recent work has examined the effects of thermal history and shear history on the rheology and microscopic structure of waxy gels [1], but not the effect of polymer additives. Other work has examined the dynamic behavior of waxy oils without polymer additives [2]. This present work considers the effects of polymers on the rheology and deposition behavior of waxy. Three sets of polymers with controlled crystallinity were tested: poly(ethylene butene) (PEB), ethylene-vinyl acetate co-polymers (EVA) and maleic anhydride co-polymers (MAC). Additions of the polymer at 50 to 800 ppm reduced the yield stress of the waxy gel up to three orders of magnitude, depending on the polymer type. Effects of polymer micro-structure are discussed. Deposition tests performed on a laboratory-scale deposition cell showed varied results depending on the polymer. Results are discussed in terms of amount of solid in the deposit (from gas chromatography, GC), the carbon number distribution of the deposit (also from GC), the microscopic morphology of the deposit and the cloud point of the solution.

[1] Ramachandran Venkatesan, Ph.D. Thesis, University of Michigan, 2004, Ch VI; Singh et al. J. Rheology 43 (1999) 1437-1459.

[2] Singh et al. AIChE J. 46 (2000) 1059-1074; Parthasarathi, P. and A. K. Mehrotra Energy & Fuels 19 (2005) 1387-1398.