Rheology of Heavy Oils

The problems of heavy oil rheology, accompanied by physical phenomena of the formation and destruction of coagulation disordered structures and aggregates as a result of the hydrodynamic interaction of particles (asphaltenes, paraffins, resins, and solid-phase particles) contained in the oil, which significantly affect its properties and flow, are considered and analyzed. Rheological models of viscous-plastic heavy oils are considered and developed, consistent with a variety of experimental data. New rheological models for viscous-plastic heavy oils are proposed, which make it possible to generalize many existing models. It is noted that the variety of rheological models for heavy oils is determined by the conditions for the formation of disordered structures in the bulk of the oil flow. For heavy oils, a nonlinear equation for filtration in porous media is proposed, depending on the shear stress, pressure gradient, effective viscosity of the oil, and a number of other parameters. An analytical solution to this equation is proposed, which is consistent with the experimental data. Models for the settling rate and drag coefficient of particles in heavy oils are proposed. Applied problems of rheology aimed at improving the rheological properties of heavy oil during their processing as a result of creating a recirculation scheme at an operating oil refining unit are considered

Rheology of Structured Oil Emulsion

This study is devoted to the rheology of oil emulsions, accompanied by both the formation and destruction of the structure. The presence of particles of a dispersed phase in an oil emulsion, including asphaltenes and resins, determines the formation of coagulation structures as a result of interaction and collision of particles. In this regard, to study the formation of coagulation structures, analytical solutions to the mass transfer equations are proposed, based on which the coalescence and fragmentation frequencies of the droplets are determined. Models and analytical solutions of the equation for the thinning of an interfacial film between droplets with their coalescence in the volume of an oil emulsion are proposed taking into account the Marangoni effect and the effect of asphaltene content. The thickness of the adsorbed layer on the droplet surface was estimated. Many empirical and semiempirical formulas have been proposed for determining the dependence of viscosity on the content of water and asphalt-resinous substances in oil. Based on the solution of the Fokker-Planck equation, the evolution of the distribution function of droplets in time and size in an oil emulsion is studied

Applied Problems in the Rheology of Structured Non-Newtonian Oils

The rheology problems of non-Newtonian oil, accompanied by the physical phenomena of formation and destruction of coagulation structures and aggregates, significantly affecting the flow are considered and analyzed. Also are considered issues of hydrodynamic interaction of particles leading to the formation of disordered structures, which significantly change the rheological properties of non-Newtonian oil. It has been noted that the formation of coagulation structures depends on energy dissipation, viscosity, stress or shear rate, and the size of the particles forming the structure. With increasing asphalt-resin content in the oil, the probability of particle collision increases, increasing the rate of formation of various disordered structures up to a framework that nullifies the rate of oil flow. Applied problems of rheology, including dissolution kinetics of asphalt-resinous substances in aromatic hydrocarbons and improving rheological properties of the oil, rheology of structured non-Newtonian oils in gas lift method of production, as well as possible ways to create new technologies for processing non-Newtonian oils were considered

Study of electrochemical deposition of Ni-Mo thin films from alkaline electrolytes

The process of co-deposition of Ni with Mo from alkaline electrolytes was studied by taking linear and cyclic polarization curves of Pt electrode at various concentrations of initial components and potential scan rates. Solutions of Na2MoO4∙2H2O and NiSO4∙7H2O were used as sources of ions of the main components in NH4OH electrolyte. It was found that co-deposition of nickel with molybdenum goes through the oxide formation stage, and a solid solution of these two metals is deposited on the cathode surface. The film obtained at constant current on Ni electrode under optimal conditions was found amorphous, but additional thermal treatment at 500 °C for one hour made it polycrystalline. This was confirmed by peaks in X-ray diffraction patterns, corresponding to NiMoO4, Ni, and MoO3. The proposed electrolyte and electrolysis conditions allow to obtain thin films with molybdenum content ranging from 17.1 to 50.9 at.%. The co-deposition of Ni with Mo is limited by diffusion of these ions to the cathode surface. The knowledge of the mechanism of co-deposition of Ni and Mo will make possible a selection of optimal conditions for deposition of alloys of the required composition with satisfactory electrocatalytic properties

Studying the electrochemical deposition process of molybdenum from aqueous solution of molybdate ions

In this study, the tracing of the electroreduction process of molybdate ions in aqueous media at different conditions is achieved for obtaining molybdenum metal in a simple and easy way. The kinetics and the mechanism of the electroreduction of molybdate ions are studied using cathodic polarization technique. It is observed that, the speed of the electroreduction process depends on the speed of the change of the cathodic potential sweep as well as on the temperature of the electrodeposition bath. Moreover, it is observed that, at the potential range from the stationary potential (Est = 0.25 V) to −0.7 V, the electroreduction of molybdate ions occurs into two steps. Moreover it is observed that, after −0.7 V the electroreduction process of molybdate is accompanying with evolution of hydrogen

Electrodeposition of Bi-Se thin films involving ethylene glycol based electrolytes

The work is devoted to the electrochemical deposition of Bi-Se thin films from ethylene glycol-based electrolytes. The studies have been carried out by potentiodynamic and galvanostatic methods under various conditions, using Pt and Ni electrodes. By recording cyclic and linear polarization curves, the potential range of deposition of thin Bi-Se films on Pt (-0.75 to -1.2 V) and Ni (0.2 to -0.85 V) electrodes was determined. A comparison of the polarization curves of two electrodes showed that co-electrodeposition of Bi and Se occurs in approximately the same potential range. In order to find the optimal mode and composition of the electrolyte, the effect of various factors (concentration of initial components, temperature, etc.) on the process of co-electrodeposition of Bi with Se was studied. In addition, the samples of Bi-Se thin films obtained on Ni electrodes using the galvanostatic method were studied by scanning electron microscope (SEM) and X-ray phase analysis. The results of X-ray phase analysis confirmed the formation of thin Bi2Se3 films with and without additional heat treatment step. Elemental analysis of obtained films carried out by EDS shows that films contained 62.79 wt. % Bi and 37.21 wt. % Se

Electrochemical behaviour of selenite ions in tartaric electrolytes

In recent years, a great interest has been emerged on electrochemical preparation of semiconductor films based on selenium. Therefore, a study of electrochemical reduction of selenium could be very important. In this work, the kinetics and mechanism of the electrochemical reduction of selenite ions on the Pt cathode have been studied in the electrolyte containing selenious and tartaric acids. The study shows that electroreduction of selenite ions from tartaric electrolytes proceeds in two stages. The effect of various factors on the cathodic reduction of selenium ions has also been studied. The effective activation energy was calculated using the polarization curves of the temperature dependence of the electroreduction process of selenite ions. It was established that the process of electroreduction under investigation is proceeding by mixed kinetics, at first by concentration and then by electrochemical polarization

Thermodynamic Study of Tl6SBr4 Compound and Some Regularities in Thermodynamic Properties of Thallium Chalcohalides

The solid-phase diagram of the Tl-TlBr-S system was clarified and the fundamental thermodynamic properties of Tl6SBr4 compound were studied on the basis of electromotive force (EMF) measurements of concentration cells relative to a thallium electrode. The EMF results were used to calculate the relative partial thermodynamic functions of thallium in alloys and the standard integral thermodynamic functions (-ΔfG0, -ΔfH0, and S0298) of Tl6SBr4 compound. All data regarding thermodynamic properties of thallium chalcogen-halides are generalized and comparatively analyzed. Consequently, certain regularities between thermodynamic functions of thallium chalcogen-halides and their binary constituents as well as degree of ionization (DI) of chemical bonding were revealed