Theoretical Foundations of Chemical Engineering最新文献

Phase equilibria are studied in sections of the systems NaCl–CO(NH₂)₂–H₂O, CaCl₂–CO(NH₂)₂–H₂O, and NaCl–CaCl₂–CO(NH₂)₂–H₂O at temperatures from 0 to –57°C. The features of the mutual influence of the components on the temperatures of the eutectics in the systems and on the deicing ability of urea–salt mixtures are determined. It is found that the introduction of urea into the systems CaCl₂–H₂O and NaCl–CaCl₂–H₂O gives rise to low-temperature eutectics with crystallization temperatures of –54 and –57°C, which are promising for the development of low-temperature deicing agents on their basis.

An analytical model of a solid–liquid heterogeneous reaction to form a gas phase was presented. The model is based on the analysis of the main parameters that have the most significant effect on the intensity of the reaction. The formation of gas–liquid dissipative structures in the form of alternating flows of reacting phases that perform relaxation pulsations was shown. The formation, detachment, and movement of bubbles were described with a satisfactory adequacy. The dynamics and conditions for the formation of a gas bubble on a solid reaction surface were characterized. Relationships were obtained for estimating the mass-transfer coefficients, which correlate with experimental data. The developed analytical model of the heterogeneous reaction will give a better insight into the essence of the melting processes in ore-thermal furnaces, which will make it possible to make changes to these processes using qualitatively new parameters of their characteristic reactions. Analysis of the hydrodynamics with the formation of the gas phase by analytical and numerical methods suggested the type of the flow of the liquid phase. Typical was the presence of hydrodynamic structures that determined the ordered movement of the liquid phase with various methods of supplying the gas phase. The values of critical mass-transfer parameters were determined. In contrast to the boiling process, a crisis of the heterogeneous reaction is impossible because of the shielding of the reaction surface.

To predict and evaluate the carbon footprint in the gas phase, furnace fuel oil oxidation in excess air (alpha factor 1.3) was studied over a wide temperature (T = 298–3000 K, P = 0.1 MPa). Equilibrium thermodynamic parameters (entropy, enthalpy, and internal energy) and the concentration distributions of C-, S-, N-, O-, and H-containing components and active particles in the gas phase were determined. Based on the total concentration distribution of C-, S-, N-, O-, and H-containing components and active particles in the gas phase, the weight content of carbon was calculated. Taking into account the chemical matrix of the furnace fuel oil–air system and the weight content of carbon, the man-made load of carbon in the gas phase was found. The results of the work made it possible to evaluate the carbon footprint in the gas phase because of the combustion of fuel, in particular, furnace fuel oil in air. Reduction of the man-made load of carbon oxides (CO, CO₂) in the gas phase was achieved by modifying and burning furnace fuel oil in the form of oil-in-water (reverse) emulsions in E-1/9M industrial boilers.

The article presents new details of an algorithm and compares the results of calculating the heat and mass transfer of water and air in spray apparatus for the regimes of cocurrent and countercurrent of phases, taking into account the early crisis of drops drag and the accompanying crisis of heat and mass transfer. The mathematical model used is based on nonstationary differential equations for the flow of a compressible medium, supplemented with the equations of heat and mass transfer from drops to the gas. The known explicit Lax–Wendroff scheme is used in difference analogs of the equations of continuity and phases flow. The distributions of phases velocities and temperatures, and densities of water vapor in air and saturated vapor near the surface of drops in the two-phase flow are calculated to compare the co- and countercurrent flows of phases through the cylindrical apparatus. In particular, the calculations determined the dependences of the average temperatures of the gas and the liquid over the outlet section of the apparatus for each phase on the gas flow through it.

The article discusses the main methods and technologies of three-dimensional printing. The basic principles are presented for technologies that are implemented in powder, polymerization, and extrusion methods of additive manufacturing. The main applications of additive technologies in medicine, pharmacy, and chemical engineering are considered. Based on the review made, conclusions were drawn about the existing problems and limitations that do not allow the integration of additive processes into industry. In addition, the prospects for the development of additive technologies in these applications are considered.

Abstract

The interaction of tungsten mineral raw materials with a mixture of NH₄HF₂ and (NH₄)₂SO₄ upon heating was studied. It was determined that, first, at temperatures up to 200°C, the incoming components are fluorinated to form complex and simple fluorides. A further increase in temperature is accompanied by the decomposition of ammonium sulfate to form NH₄HSO₄, which leads to the conversion of fluorides into sulfates and of the tungsten ammonium fluoride complex into tungstic acid H₂WO₄. It was shown that water leaching of the product of the decomposition of tungsten-containing mineral raw materials with a mixture of NH₄HF₂ and (NH₄)₂SO₄ makes it possible to extract tungsten from mineral raw materials in the form of the commercial product WO₃.

The coagulation ability of organic and inorganic quaternary ammonium salts is assessed comparatively. It is found that the replacement of a hydrogen atom in ammonium chloride with an alkyl radical decreases the consumption of the coagulation agent. The best results are achieved when tetraethylammonium chloride is used as a coagulant. The resulting rubbers and vulcanizates meet the requirements according to their main indicators.