Abstract
The oil tank can form a considerable amount of sludge deposition after continuous accumulation, which cause a seriously negative impact on both the storage capacity and the safe operation of the oil tank. Therefore, it is important to anticipate the rate of sludge deposition in advance so that proper measures can be planned to remove this heavy layer on the bottom. This paper proposes a method using a relatively simple formula for predicting the sludge deposits. The sedimentation mechanism of wax and asphaltene is introduced and summarized from both the micro and macro aspects, the factors causing the interaction between particles and the influence on coalescence were analyzed. We applied our prediction methods to calculate the sludge deposition of four oil tanks in Mo-he Station and compared our results with the data measured by experiments. The results show that our method had a good general accuracy to experimental data and can be used directly for on-site engineers to anticipate real sludge height before measuring the oil level inside the tank.
Highlights
Particle sedimentation is the movement process of solid in liquid due to various forces
Due to the existence of sedimentation balance, the number of particles that can settle in each batch of oil is limited, and the settlement of wax and asphaltene in the oil tank did not attract much attention from researchers as they do for the case of pipeline wax/asphaltene deposition
For the wax dominated sediments, the results showed that the paraffin content and average carbon content in the sediments were higher than those in the crude oil products, because the sediments contained oil residue, asphaltene and a small amount of inorganic salt particles
Summary
Particle sedimentation is the movement process of solid in liquid due to various forces. Asphaltene and wax can coalesce and separate. When they aggregate to a certain particle size and density, they settle under the action of gravity, which is more obvious under weak convection and shear force. After a long period of time and continuous accumulation, a considerable amount of sediment can be formed at the bottom of the tank. This effect seriously affects the storage capacity of the oil tanks, and the economic benefits, weakens the buffer capacity of the oil tank and brings challenges to the operation and maintenance. If sludge deposition can be anticipated in advance, it can help the oil company to better determine the cleaning period of the sludge and to ensure the safety of the whole oil transportation system, so that maximum benefit can be possibly obtained
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