Electrical Transport Processes in Heavy Hydrocarbon Fluids

Scarcely any information is available about electrical transport in heavy petroleum oils, which, in addition to having large and complicated hydrocarbon molecules, also contain heteroatoms (especially N, OH, and S) which should affect the transport processes. Petroleum conductivity is an important Parameter for a number of commercial particulate separations processes based on electrophoresis, but information on the mechanism is lacking. Furthermore, the heteroatoms will affect the orientation polarizability in ac electric fields; the presence of permanent dipoles may affect the viscoelastic properties of these oils. The response of heavy oils to applied electric fields proved to be quite similar to that of polar polymers. There is a glass transition, followed by a rapid but frequency-dependent increase in the dielectric permittivity. At higher temperatures , a true dc component is modelled as the translation of charges among the ir-orbitals of the polynuclear aromatics in the oil; no permanent electrochemical effects were observed. Although the oil does not possess a long-chain structure with identifiable repeat units like a polymer, the close resemblance of the dielectric data of the oil to that of polymers may well imply that the oil is not simply composed of an entirely random mixture of unaffiliated molecu1es.