Theoretical Foundations of Chemical Engineering最新文献

The possibility of emergence of oscillatory conditions during a chemical process in a flow reactor with spatial inhomogeneity is analyzed. The mathematical dynamic model of the reactor takes into account molecular and convective heat- and mass-transfer processes. The problem is solved in a one-dimensional approximation under single-step chemical-reaction conditions. An analytical expression for the stability criterion of the steady-state conditions is obtained provided that the diffusion and temperature conductivity coefficients are equal. The sequence of actions upon determining the critical conditions for the stability of the system is shown. A series of numerical experiments is performed to verify the emergence of oscillatory regimes at different parameter values corresponding to real conditions in the reactor.

Conventional fuels are the transportation sector’s major occupants since they provide more power and efficiency with harmful environmental pollution. Researchers have focused on alternative and suitable solutions over a decade, considering the depletion of conventional fuels and environmental pollution. The present work is trying to explore an alternative solution resulting from Calophyllum inophyllum seed oil. This oil is extracted mechanically from seeds and the acid value is found to be very high. Acid esterification of oil is done with diluted H₂SO₄ to reduce the acid oil value of oil to make the oil suitable for the transesterification process. Here, a less expensive and abundantly available CaO catalyst is synthesized from wastages of gas industries. Further, the independent factors of transesterification, such as the molar ratio of methanol and oil, type and concentration of the process catalyst, process temperature, stirring rate and process time need to be optimized to get maximum biodiesel yield through the process. The process is optimized by Response Surface Methodology (RSM) through Box Behnken Design with minimum experimental runs. The optimization results show that optimum values are 9 : 1, 50°C and 3 wt % of molar ratio of methanol and oil, process temperature and concentration of catalyst, respectively. During this process, the Analysis of Variance ANOVA table was also employed to identify the significance and fitness of the model.

The work considers the hydrodynamics in contemporary packed film devices with tubular and plane channels and laminar and turbulent gas- and liquid-flow patterns in a downflow cocurrent regime. Weak hydrodynamic interaction between the phases and no velocity circulation in the gas phase are assumed. The solution is found by the approximate Schlichting method. The distribution of velocities in the phases, the thickness of the downflowing film, and the sizes of the inlet hydrodynamic areas in the liquid and gas are determined.

The study concerns waste of the fuel and energy complex, ceramic samples, and the phase composition of ceramic samples. The fuel energy complex is one of the main sources of pollution of the natural environment. Usage of waste of the fuel and energy complex in ceramic masses for manufacturing ceramic materials is favorable for the formation of mullite, anorthite, hematite, cristobalite, and wollastonite in the products.

Thermal engineering experiments were carried out with laboratory water-to-water tube-in-tube heat exchangers of the same design parameters with smooth and profiled inner tubes. The tubes were profiled by confuser–diffuser constrictions of the flow section of the inner channel, which were formed by the deformation of their walls and placed along the length at a step that was constant and equal for all profiled tubes. The obtained results showed a dependence of the heat transfer enhancement in the tube channel on the Reynolds and Prandtl numbers, with the dependence on the latter being much stronger than that on the former, at least in cases where the heat carrier is water.

Pilot-plant testing of a laboratory technology for producing alkaline titanosilicate sorbent from the current titanium-containing technogenic waste from the enrichment of the Khibiny apatite–nepheline ore shows that this technology can be modeled on an enlarged (pilot-plant) scale. The parameters of the main technological operations in systems of various salt compositions are checked and optimized. For example, in the ammonium sulfate systems, a two-phase precipitate is formed, which consists of phases similar to the minerals zorite and ivanyukite at their weight ratio of about 1 : 0.8–1.0. A one-phase precipitate in the form of ivanukite crystals is formed in the sulfate system. A study of the technical and sorption properties characterized in the tests of sorbents finds that the absorption of the Cs⁺ cation is due to the substitution for the Na⁺ cation in the interframework space of the crystal. The Sr²⁺ cation is also substituted for Na⁺ and is additionally deposited on the sorbent particles due to the alkaline reaction of its surface. The sorption capacities of powder and granules for Sr²⁺ are, on average, 170 and 160 mg g^–1, respectively; and for Cs+, 275 and 245 mg g^–1, respectively. Tests will be continued as pilot batches of the sorbent with stable structure and properties are produced for testing in specialized organizations.

The current work focuses on the synthesis of the biodegradable film made from Sodium alginate (S.A), and then the addition of magnesium oxide nanoparticles (MgO-NPs) was synthesized by sol-gel technique. Glycerol which is a plasticizer is used to enhance the tensile strength (TS) and film expansion due to a decrease in intermolecular forces in the polymer chain. With the addition of olive oil (OE), the functional properties of control films were improved, which results in a lowering of water solubility, and moisture content but the tensile strength slightly decreased. The opacity, moisture absorption, and solubility of the film, thickness, tensile strength (TS), elongation (EB), ultraviolet-vis spectroscopy, scanning electron microscope (SEM), transmission electron microscopy (TEM) were used to characterize sodium alginate biofilm with the addition of MgO-NPs (SA1) and without the addition of MgO-NPs (SA2). But considering all other factors, the film (SA1) revealed a slower rate of degradation than the film (SA2). The film’s TS and opacity are enhanced by MgO-NPs addition, while moisture content (WVP), solubility, and elongation at break are decreased.

The synthesis of molybdenum powders with a highly developed surface by reducing molybdenum oxides with magnesium vapor in the temperature range of 600–750°C under dynamic vacuum conditions (0.01 kPa) and residual argon pressure of 0.5–10 kPa in a reactor is studied. During the MgMoO₄ and CaMoO₄ reduction, mesoporous molybdenum powders with a specific surface area of up to 31.8 m² g^–1 are obtained. The average size of the metal crystallites is 16–25 nm.