Theoretical Foundations of Chemical Engineering最新文献

Abstract—New methods for the synthesis of NASICON of the composition Na_{1 + x}Zr₂P_{3 – x}Si_xO₁₂ (0 ≤ x ≤ 3) were presented. In the work, the method of pyrolysis of organic solutions was used, which takes a minimum time to synthesize the material. Various options for the composition and heat treatment of precursors were considered. The effect of rosin on the pyrolysis process and the phase composition of the final products was discussed. The optimal conditions for the synthesis of the low-dimensional monoclinic polymorph Na₃Zr₂Si₂PO₁₂ with homogeneous composition were determined.

The behavior of rare-earth elements and major impurities during the nitric-acid decomposition of a lean yttrofluorite concentrate by the method of sorption conversion is studied. The decomposition conditions providing satisfactory extraction into the sorbent for rare-earth elements, especially yttrium and yttrium group lanthanides, are determined.

Using the dependences C(REE) = f(τ), fundamental differences in extraction of rare earth elements (REEs) from phosphate raw materials of sedimentary and igneous origin were identified, which consist in the extremal and monotonic plateauing behavior of the kinetic curves, respectively. The discovered features of nitric acid extraction of rare earth elements will make it possible to evaluate the prospects for integrated processing of raw materials and optimal conditions for their recovery from multicomponent systems.

The efficiency of using heat pumps in extractive rectification schemes with partially coupled heat and material flows is studied on the example of separating an allylic alcohol–allyl acetate mixture of various initial compositions with n-butylpropionate as a separating agent. A comparison of schemes with heat pumps and schemes with a traditional two-column scheme of extractive rectification is carried out according to the criteria of reduced energy costs and total annual costs. It is established that with increasing concentration of allylic alcohol in the feed, the energy and economic efficiency of the scheme with a heat pump on the main column of the complex with partially coupled heat and material flows increases. The energy efficiency of the side-section heat-pump circuit decreases with increasing allylic alcohol content in the feed, and the economic efficiency of this circuit increases slightly. The energy efficiency of the scheme in which heat pumps are simultaneously used on the main column and on the side section depends little on the composition of the feed, while the economic efficiency of this scheme increases with increasing concentration of allylic alcohol. For all considered power compositions, the maximum savings in energy costs (by 45.9–49.1%) compared to the traditional two-column scheme is provided by the schemes in which heat pumps are simultaneously used on the main column and on the side section, and the maximum reduction in total annual costs (by 11.7–27.9% with a service life of 20 years) is achieved with the scheme with a heat pump on the main column of the complex with partially coupled heat and material flows.

Abstract—The flotation of impregnated copper-nickel ores is studied using humate agents as depressors, which are obtained from oxidized brown coal by extraction with alkaline reagents. The effect of the humate agents on the flotation of some iron-bearing minerals (pyrite, pyrrhotine, chalcopyrite) among the sulfide ores, as well as the sorption of humates with minerals, are studied. The humate agents are found to have a depressing effect on both nonmetallic minerals and sulfides.

Abstract—Phase equilibria in Ca(NO₃)₂–C₃H₆(OH)₂–H₂O system sections and anti-icing properties of calcium nitrate–propylene glycol compositions with a component ratio from 1 : 3 to 3 : 1 are studied, and the temperatures and composition of eutectics with ice and the melting capacity of nitrate–propylene glycol compositions at temperatures of –5 and –10°C are determined. The compositions characterized by good anti-icing properties are identified.

The interaction of perovskite concentrate with nitric acid under atmospheric conditions and at an excess pressure was studied. High efficiency was achieved in the separation of components in the form of a solid phase (hydrated precipitate of titanium and rare metals) and a liquid phase containing calcium, rare-earth metals, and thorium. It was shown that the conditions of the acid treatment of the resulting precursors determine their structure and composition, which, in turn, determine the directions of their further processing to obtain final products. In particular, it was established that an increased pressure in the reaction zone causes rutilization of the hydrated precipitate, and therefore its further processing to produce titanium dioxide and rare metals should be carried out by chlorination.

An approach based on the gas-phase processing of secondary wastes in an HNO₃ (vapor)–air or NO_x–H₂O (vapor)–air atmosphere with further Mn and Cr leaching with water is proposed for Mn and Cr extraction from the secondary wastes of metallurgical plants (fly ash from the ore-dressing plant of the Norilsk Combine and rock refuses from the Punda Gourda Nickel Production Combine of the Cuban State-Owned Commercial Caribbean Nickel Company). It is shown that the preliminary treatment of secondary wastes in a nitriding atmosphere at a temperature of 400–425 K for 5 h makes it possible to leach Mn from the volume of secondary wastes. For the fly ash from the ore-dressing plant of the Norilsk Combine and the rock refuses from the Punda Gourda Nickel Production Combine of the Cuban State-Owned Commercial Caribbean Nickel Company, the degree of Mn extraction with water is less than ~33 and ~65% of their total content in the wastes, respectively. The degree of Cr extraction is less ~2% in all cases.