Stability of Crude Oil-in-Water Enlulsions

Abstract

Abstract A coulter counter was used to measure the droplet-size distribution of crude oil-in-water emulsion. The stability of the emulsion was determines by the decrease in oil concentration and the change in specific surface with time. All experiments core carried out at room temperature with initial oil to water volume ratios of 0.005 and 0.01. Six different types of crude oil were investigated. All of them behave similarly. Creaming was found to be pre-dominantly responsible for the instability of the emulsions. However, all the emulsion finally attained stability with an oil concentration or between 10−2 and 10−3 % volume, a specific surface of around 3 × 10 cm2/g and a droplet size belong 4 μm. Introduction WHEN CRUDE OIL SPILLS onto the surface of water, it spreads out into a layer the thickness of which depends on material properties and environmental conditions. Unless the spillage has been close to shore or the water is exceptionally calm, two types of emulsions will likely be formed(1) The oil-in-water emulsion, having droplets of oil dispersed in the water phase, is caused by the action of currents, wind, tides and waves and may be rendered stable by such hydrophilic groups a. - COO-, - OH, - CHO, - OSO3 and SO H which occur naturally in the crude. The water-in-oil emulsion consisting of droplets of water enclosed in sheaths of oil, is stabilized by the presence of various resinous and asphaltic materials which also occur naturally in crudes. The latter type of emulsion now generally referred to as "chocolate mousse", is known to be extremely stable(2,3). However, knowledge of the stability of the former, which is a useful input in assessing the effects of an oil spill has not yet been reported. The present work investigates the stability of crude oil-in-water emulsions by making use of a Coulter counter. Experimental Materials: Six different types of crude oil were used in this investigation. Their origin and physical properties are given in Table 1. The water was deionized, distilled and filtered twice using a Gel man membrane filter with a pore size of 0.2 μm. A 3% sodium chloride solution also filtered twice with the Gelman filte, was used as the diluent for the Emulsion and, at the same time served as the electrolyte solution for the Coulter counter. All the glassware employed was thoroughly washed and rinsed with filtered water. Traces of oil remaining in the glassware due to a previous experiment were removed by benzene and hot water. Preparation of Emulsions: The crude (oil-in-water Emulsions were prepared using a Virtis 45 homogenizer as follows. The homogenizer falsely was first filled with 200 ml of water the crude oil was then pipetted in and the mixture was homogenized for 10 minutes at the medium speed (approximately 10,000 rpm). The emulsion as immediately transferred into a cylindrical separatory funnel and samples were withdrawn from the bottom at selected time intervals.