An examination of additive-mediated wax nucleation in oil pipeline environments

As part of a wider study probing the molecular-scale factors important in controlling wax crystallisation processes, the effect of additives on the surface and bulk nucleation of wax crystals from hydrocarbon solution phases was examined. Bulk: nucleation data obtained in the absence and presence of two growth inhibiting additives indicated an increase in the meta-stable zone width (MSZW) on addition of both inhibitors, and differences in their kinetics of inhibition. Complementary studies of surface nucleation using a pipe blocking apparatus revealed a lowering in the temperature at which blockage occurred on addition of inhibitor to the model oil, and existence of fractional crystallisation observed in the bulk phase was confirmed. The hydrodynamic dependence of the nucleation process provided added information on how the inhibitors and wax would perform. in a field situation, with a strong dependence on shear rate. (C) 1999 Elsevier Science B.V. All rights reserved.