During the transportation and storage of heavy, highly viscous oil products, especially at low temperatures, serious problems arise due to the accumulation of oil sludge on the surface of oil technological equipment, in tanks and pipelines. Paraffin deposits reduce the useful cross-section of pipelines and, as a result, significantly complicate the pumping of oil products with a simultaneous increase in electricity consumption, lead to increased wear and tear of equipment, losses of oil products, and deterioration of the environmental condition. Periodically, after the cleaning of tanks and other containers, oil sludge and contaminated soil accumulate and are stored in various technological storage facilities, sedimentation ponds, barns, on specially equipped sites and sludge accumulators, which occupy large areas and poison the environment.
It is possible to prevent the crystallization of paraffin by heating oil products, but this method leads to unnecessary costs and is economically unjustified. In some cases, this procedure is not possible at all. Decreasing the temperature of paraffin crystallization is achieved by mixing high-paraffin oil products with low-paraffin oil or with solvents, which also leads to additional resource and time costs.
In practice, enterprises use the simplest methods – burying such waste or burning it in landfills.
During storage and preparation of hydrocarbon mixtures for transportation in order to avoid clogging of pipelines and technological equipment, it is suggested to take into account the values of their main indicators (density, viscosity), depending on the ratio of components.
The process of paraffin formation, including the features of the structure of paraffins as a result of phase transitions during temperature reduction is analyzed in the paper. Mathematical models of thermodynamic and kinetic calculations of the phase equilibrium of the "solid-liquid" system have been developed. It was established that in order to shift the equilibrium in the "fuel oil-paraffin" system towards the liquid side, it is necessary to reduce the ratio of the activities of the solid and liquid phases by introducing a substance with a lower solubility parameter than that of the sediment-forming components.
Additives have been synthesized to increase the stability and improve the structural and mechanical characteristics of oil dispersion systems. Phase transitions were studied using the example of fuel oil depending on the temperature with the addition of a plant-based depressant additive.
The results of the research of the effect of the plant origin additives on the aggregative stability of oil dispersed systems, which is caused by the presence of asphaltenes, are presented. The stability factor of the system is determined. Acceleration of the sedimentation process by centrifugation showed a significant decrease in the difference in the average diameter of the particles in the upper and lower layers of the centrifuge after the introduction of plant-based additives, which is evidenced by a decrease in the difference in the sample optical density of the upper and lower layers of the centrifuge.
Methods of obtaining natural and biosynthetic surfactants of various compositions based on rapeseed oil: diethanolamides, mono- and diglycerides of fatty acids, their sulfosuccinates and phosphatides have been proposed and worked out. Infrared spectroscopy confirmed the completeness of chemical transformations and the formation of target functional groups. The effect of adding natural and biosynthetic surface-active substances on low-temperature properties of oil fuel and tribological characteristics of lithium grease was analyzed. The expediency of using these substances as depressant additives to oil fuel in the amount of 0.25-0.5% by weight has been experimentally confirmed. (the pour point of oil fuel was reduced by 12ºС) and as anti-seize additives for lubricants (the diameter of the wear spot after adding the additives decreased from 0.8 to 0.38 mm).
A number of existing dispersants of asphaltenes in oil dispersed systems – oil soluble surfactants of various nature – were considered. The use of surfactants of plant origin – phosphatide concentrate and sodium sulfosuccinate – as asphaltene dispersants is proposed. The process of flocculation of asphaltenes on model mixtures of asphaltenes with toluene and precipitants, as well as the influence of the proposed additives on the aggregative stability of the mixtures, was studied. The starting point of flocculation (onset) of each mixture was determined by the photocolorimetric method.
