Selective Inhibition of Paraffin Deposition under High Flow Rate as a Function of the Crude Oil Paraffin Type and Content by Fluorescence Depolarization:  Polypropylene and High-Density Polyethylene

Abstract

High-density polyethylene (HDPE) and polypropylene (PP) were studied to identify tailor-made materials for walls of pipelines and ducts for crude paraffinic oil that inhibit paraffin depositions. The interfacial interaction was investigated from 50 to 70 degrees C and as a function of the n-C(36)H(74) paraffin concentration added to the paraffinic crude oil. The static and the dynamic interfacial tensions were observed, respectively, by traditional contact angle measurements and by fluorescence depolarization of the natural fluorescent probes of the crude oil, flowing at a high rate. The static interaction showed a low dependence on the n-paraffin content for both surfaces. For PP, it decreased slightly as the n-paraffin concentration increased, evidencing an increase in the liquid-liquid interaction. The dynamic interfacial tension with PP clearly decreased as temperature and n-paraffin concentration increased, the latter effect being attributed to the PP methyl groups hindering the interaction between the n-paraffin and the PP main chain. For the flow on HDPE, the interaction proved to be highly dependent on the n-paraffin concentration and temperature. It increased as n-paraffin was added and temperature decreased. The former effect is attributed to the alignment of the n-paraffin chains within the high rate flowing liquid and the similar molecular geometry of the n-paraffin and the linear polymer surface (almost without branches), which increases the number of sites available for interaction. PP proved to be more suitable for transportation of crude oil rich in paraffins with more than 36 carbon atoms, while HDPE was more suitable for those with smaller paraffinic chains.

Theoretical Study of the Prohibited Mechanism for Ethylene/Vinyl Acetate Co-polymers to the Wax Crystal Growth

“…11 For instances, high-density polyethylene and polypropylene were studied to identify tailor-made materials for walls of pipelines and ducts for crude paraffinic oil that inhibit paraffin depositions. 12,13 Copolymers of alkyl acrylates [14][15][16] have been found to act either as wax growth inhibitors or promoters with different degrees of polymerization. Poly(ethylene-butene) random copolymers were reported to co-crystallize with waxes into thin platelets so as to modify the wax crystal morphology through microscopy and calorimetric studies 17,18 and small-angle neutron scattering (SANS) techniques.…”

“…Owing to the wide variety of oil components, many kinds of polymers were developed as PPD additives to affect the flow property of oil via adjusting the precipitation of wax crystals , C opolymers of alkyl acrylates − have been found to act either as wax growth inhibitors or promoters with different degrees of polymerization. Poly(ethylene−butene) random copolymers were reported to co-crystallize with waxes into thin platelets so as to modify the wax crystal morphology through microscopy and calorimetric studies , and small-angle neutron scattering (SANS) techniques .…”

Effects of paraffin chain size on the oil outflow investigated by a combination of thermal lens and laser-induced fluorescence spectrometries

“…In the past, several research groups dedicated time and effort to investigate the physicochemical mechanisms that lead to the formation of paraffinic deposits, as well as to develop methods to prevent the formation of these crystals and the consequent stagnation of oil production and transport [2][3][4][5]. Several techniques have been used to determine the properties such as thermal diffusivity, heat capacity, (paraffin) molecular diffusion coefficient, and kinematic viscosity, with the aim of developing alternative methods to characterize the types of oil [6][7][8].…”

Wettability under Imposed Flow as a Function of the Baking Temperatures of a DGEBA Epoxy Resin Used in the Crude Oil Industry

“…They may be used either as coatings or linings for metallic ducts or as massive ducts. Although they cannot stand high temperatures and their low mechanical resistance is a concern, they have the advantage of impeding the formation of paraffin deposits − and a much lower corrosion rate than unlined metallic ducts. They are already being used to recuperate condemned metallic ducts by insertion of a plastic layer as inner lining, thus reducing the costs of welding and equipment maintenance or replacement.…”

“…Recently, it was observed that θc could not discriminate between the interactions with polyethylene surfaces with different branching degrees. 16 It was also shown 3,4,[17][18][19][20] that θc characterization cannot be applied straightforwardly to interactions between walls and liquids flowing at high rates as it becomes unreliable due to not taking into account flow effects within the liquid like molecular chains orientation.…”