The presence of fine (submicron) particles in hydrocarbon streams is problematic due to their undesirable impact on product quality and their gradual deposition and fouling effects on equipment. By forming large aggregates that are subject to gravity settling, these particles can be removed. However, the particles are often coated with carbonaceous matter that may negatively influence their aggregation. In this study, submicron silica particles were coated with a layer of hydrocarbon materials, and then suspended in different types of organic solvent to examine their settling rates. The experiments showed that the coating caused quite different settling regimes in different types of solvent. A mathematical model was proposed to study the kinetics of the settling process. The results were used to evaluate the performance of current settling units. A specific modification was suggested to improve the efficiency of particle separation. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.