Theoretical Foundations of Chemical Engineering最新文献

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.

In a cascade of mixer–settler extractors, both countercurrent extraction process and chromatographic process can be performed. In the chromatographic mode, the organic phase is not removed from the extractors, but circulates between the mixing and settling zones in each unit. In this work, a theoretical analysis was made of the separation in a cascade of mixer–settler extractors in the liquid–liquid chromatography process and the countercurrent liquid extraction process. Conventional chromatographic separation processes and processes with the recycle of the aqueous phase were considered. The prospects of using the principles of chromatography in extraction technologies to obtain pure and ultrapure products on an industrial scale were shown.

The process of perfluoro(7-methylbicyclo[4.3.0]nonane) (MBCN) purification from an industrial mixture of decalin or naphthalene fluorination products is considered. According to experimental data, distillation separation allows us to concentrate MBCN to a fraction with the target-component content of more than 0.950 wt. fr., after which the process efficiency begins to decrease quickly; upon reaching a concentration of 0.975 wt. fr., separation practically breaks down (the value of the separation coefficient ({{K}_{{{text{sep}}}}}) → 1). The process of purification of MBCN by the method of heteroazeotropic distillation using acetone (Aс) as a separating agent is proposed, the process being realized on a batch semi-industrial distillation column. The method makes it possible to intensify significantly the final stage of purification and to increase the MBCN content from 0.950 to more than 0.998 wt. fr., the mass fraction of the enriched fraction sampling comprises more than 0.85 of the load and the product yield being above 88%. The values of the separation coefficients between the distillate and the bottom product and the coefficients of enrichment for the target and impurity components are given; for the MBСN–Aс binary system, data on the liquid–liquid phase equilibrium and heteroazeotrope characteristics are determined.

Ethyl acetate can be obtained directly from ethanol by dehydrogenation and this is respected as a promising process. This work explores the design and control of pressure-swing distillation systems for separation of ethyl acetate/ethanol during the ethyl acetate production process. Rigorous steady-state and dynamic simulations are implemented using commercial simulators Aspen Plus and Aspen Dynamics. The dynamic simulation results reveal that the control structure CS1 are unable to maintain the bottom products at their quality specifications while control structure CS2 can only hold the quality specification of ethanol from the bottom of atmospheric column with feed flow rate disturbance. The dynamic responses of dual temperature control (CS3) work pretty well for this partially heat-integrated pressure-swing distillation, even for large feed flow rate and composition disturbances. Effectiveness of dual temperature control with QR/F ratio fixed control structure for feed flow rate disturbance is investigated and results indicated a better performance.

Studies of the electrodialysis separation processes under pulsed current have faced problems related to the lack of a mathematical description of the electric mass-transfer processes, taking into account unsteady current modes. The main problem when describing electric mass-transfer processes is the presence of two driving forces, namely the electric potential gradient and the concentration gradient. The objective of the present work is creating a criterion equation describing charge transfer, derived by analogy with the derivation of the substance-transfer equations. As a result, a convective electrical conductivity equation is derived, which expresses in general terms the charge-density distribution in a moving flow. The obtained equation allows us to derive the criteria of electrical similarity, namely the electrical Peclet and Prandtl numbers. The obtained electrical numbers are compared with the classical criteria in terms of their dimensionalities. Using the obtained numbers, the Nusselt number for electric mass-transfer processes is derived, which takes into account the substance transfer both due to the concentration gradient and due to the potential difference, as well as the influence on the electrodialysis separation process of the operating and limiting current density and the geometrical parameters of the plant.

Lithium–titanate anodes are increasingly being used in the manufacturing of lithium-ion batteries due to their advantages in charge/discharge speed and safety of use relative to graphite anodes. The addition of titanium to the battery composition, along with the high content of cobalt and lithium, results in a further growth of their cost, and the reprocessing of such batteries becomes an extremely topical problem. In the framework of the present article, a comparative analysis of the hydrometallurgical reprocessing of batteries containing a lithium-titanate anode and a nickel–manganese–cobalt cathode by leaching with mineral acids (sulfuric and hydrochloric acids) is performed. In the work, the dependences of the leaching degree of the metals from real samples of the anode and cathode in their mixture on the mineral acid concentration, auxiliary additives, and solid : liquid ratio are demonstrated and the temperature and kinetic dependences for this process are obtained. Based on the results of qualitative and quantitative analysis of the leaching solutions, conditions for processing of the leaching process are proposed for further extractive separation. It is demonstrated that two-step successive leaching with hydrochloric and then sulfuric acid with the release of titanium concentrate is optimal. An important aspect of the work is the study of the joint leaching of the cathode and anode, since in the known processes of mechanical processing the stage of their separation is absent.

Changes in the structure, diffuse reflectance spectra, and solar radiation absorption coefficients a_s of the BaSO₄ powder modified with SiO₂ nanoparticles are studied under successive exposure to electrons and solar spectrum quanta in different sequences. The maximum changes Δa_s in the absorption coefficient of the BaSO₄ powder in the two successive irradiation modes are approximately equal. Irradiation by solar spectrum quanta causes the greatest changes both under the initial exposure and after irradiation by electrons. Regardless of the successive irradiation mode used, defects accumulate mainly in the UV and visible spectral ranges.

The chemical composition of rocks from the Kanzafarova open pit mine is determined by inductively coupled plasma atomic emission spectroscopy; their petrochemical properties are estimated. On the basis of the obtained data, the mineral composition is estimated, permitting the raw material to be referred to the family of basalt basic volcanic rocks of normal alkaline suborder 45 ≤ SiO₂ ≤ 52; 0.5 ≤ (Na₂O + K₂O) ≤ 5. This is also confirmed by the results of X-ray phase analysis. Calculation of the coefficient of acidity of the rock allows it to be recommended as a raw material for the production of mineral fiber.