Uma modelagem fundamental para a deposição de parafinas em tubulações

Abstract

Operations of production of crude heavy oil in offshore platforms tend to present problems on maintenance of productive flow due to the deposition of paraffin in the walls of pipelines. Paraffin is the denomination of long chains of hydrocarbons that are formed at high pressures and low temperatures, and that by imprisoning molecules in its interior are characterized by being chemically stable. Therefore, once the paraffin is formed, its removal is extremely difficult. The subject is commonly treated as a problem in the production of petroleum because the diameters of the pipes are reduced. Consequently, more energy is required to move the same amount of oil through the system. There are several deposition mechanisms of paraffinic residues, the most important being molecular diffusion. The present work proposes the elaboration of a mathematical and numerical model to estimate the deposition of paraffin in pipelines by the mechanism of molecular diffusion. The mass concentration gradients are dependent on a temperature gradient. The deposition as function of time was obtained through the solution of differential equations derived from the principles of mass conservation, energy, and the constitutive relation of mass diffusion. profiles of paraffin mass concentration were presented along the pipe radius and the presence of paraffin was found to be concentrated near the pipe.