Hydrogen Production in Oil Refineries

A source of hydrogen is one of the conditions for refining crude oil in existing and future refineries. In refining medium-sulfur crude oil, the hydrogen produced in catalytic reforming of naphtha cuts is sufficient for hydrotreating of straight-run light cuts. In refining of high-sulfur crude oil with catalytic reforming in standard conditions, an insufficient amount of hydrogen is produced for these purposes, which makes it necessary to use special units or to stiffen the reforming conditions for its production.     

Stabilization of crude oil in hydrocyclones with treatment of casing-head gas to remove hydrogen sulfide

A method is proposed for stabilization of crude oil and condensate in hydrocyclones to create closed systems for exhaustive preparation of feedstock. Hydrocyclones are small, simple in layout, and highly efficient units that allow enhancing operation of the primary crude oil preparation system and equipping units in block-aggregate layout. Pilot-industrial tests of crude stabilization processes using centrifugal forces and preparation of gas to remove hydrogen sulfide demonstrate the possibility of industrial introduction of the new technology.Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 1, pp. 12 – 15, January – February, 2005.     

A Challenge toward Novel Quaternary Sulfides SrLnCuS3 (Ln = La,Nd, Tm): Unraveling Synthetic Pathways,Structures and Properties

We report on the novel heterometallic quaternary sulfides SrLnCuS₃ (Ln = La, Nd, Tm), obtained as both single crystals and powdered samples. The structures of both the single crystal and powdered samples of SrLaCuS₃ and SrNdCuS₃ belong to the orthorhombic space group Pnma but are of different structural types, while both samples of SrTmCuS₃ crystallize in the orthorhombic space group Cmcm with the structural type KZrCuS₃. Three-dimensional crystal structures of SrLaCuS₃ and SrNdCuS₃ are formed from the (Sr/Ln)S₇ capped trigonal prisms and CuS₄ tetrahedra. In SrLaCuS₃, alternating 2D layers are stacked, while the main backbone of the structure of SrNdCuS₃ is a polymeric 3D framework [(Sr/Ln)S₇]_n, strengthened by 1D polymeric chains (CuS₄)_n with 1D channels, filled by the other Sr²⁺/Ln³⁺ cations, which, in turn, form 1D dimeric ribbons. A 3D crystal structure of SrTmCuS₃ is constructed from the SrS₆ trigonal prisms, TmS₆ octahedra and CuS₄ tetrahedra. The latter two polyhedra are packed together into 2D layers, which are separated by 1D chains (SrS₆)_n and 1D free channels. In both crystal structures of SrLaCuS₃ obtained in this work, the crystallographic positions of strontium and lanthanum were partially mixed, while only in the structure of SrNdCuS₃, solved from the powder X-ray diffraction data, were the crystallographic positions of strontium and neodymium partially mixed. Band gaps of SrLnCuS₃ (Ln = La, Nd, Tm) were found to be 1.86, 1.94 and 2.57 eV, respectively. Both SrNdCuS₃ and SrTmCuS₃ were found to be paramagnetic at 20–300 K, with the experimental magnetic characteristics being in good agreement with the corresponding calculated parameters.     

Stator current fault diagnosis of induction motor bearings based on the fast Fourier transform

Monitoring of the technical state of induction motor bearings is one of the important indicators of reliable and efficient operation of industrial electrical drives. This article considers the problems of fault diagnosis of induction motor bearings with a squirrel-cage rotor by stator consumption current. Test results on an experimental test bench with an electromagnetic powder brake are presented and analyzed. Experiments were carried out during tests of the induction motor at the rated mode with an operable bearing and alternately with two faulty bearings with defects at the inner and outer parts of cages. The characteristic harmonic components of stator currents appearing during operation of the induction motor with faulty bearings are presented. It is revealed that an anticipatory diagnosis of induction motors by stator current makes it possible to reveal the air-gap eccentricity due to the operation of an electric motor with a damaged bearing. Control of the technical state of bearings is important both during at the stage of manufacturing machines, in particularly for powerful and crucial mechanisms, and during their use. The basic features of monitoring the bearings are revealed, and recommendations for diagnosis by stator currents are presented.     

Magnon BEC in Antiferromagnets with Suhl–Nakamura Interaction

From atomic physics one knows the phenomenon of Bose–Einstein condensation (BEC), where a macroscopic ensemble of particles occupy coherently a single state. Similar phenomena were observed for different types of quasiparticles in condensed matter. Here we present the results of investigations on the BEC of elementary magnetic excitations—magnons—in antiferromagnets with a dynamical frequency shift.     

Quaternary Selenides EuLnCuSe3: Synthesis,Structures, Properties and In Silico Studies

In this work, we report on the synthesis, in-depth crystal structure studies as well as optical and magnetic properties of newly synthesized heterometallic quaternary selenides of the Eu⁺²Ln⁺³Cu⁺¹Se₃ composition. Crystal structures of the obtained compounds were refined by the derivative difference minimization (DDM) method from the powder X-ray diffraction data. The structures are found to belong to orthorhombic space groups Pnma (structure type Ba₂MnS₃ for EuLaCuSe₃ and structure type Eu₂CuS₃ for EuLnCuSe₃, where Ln = Sm, Gd, Tb, Dy, Ho and Y) and Cmcm (structure type KZrCuS₃ for EuLnCuSe₃, where Ln = Tm, Yb and Lu). Space groups Pnma and Cmcm were delimited based on the tolerance factor t’, and vibrational spectroscopy additionally confirmed the formation of three structural types. With a decrease in the ionic radius of Ln³⁺ in the reported structures, the distortion of the (LnCuSe₃) layers decreases, and a gradual formation of the more symmetric structure occurs in the sequence Ba₂MnS₃ → Eu₂CuS₃ → KZrCuS₃. According to magnetic studies, compounds EuLnCuSe₃ (Ln = Tb, Dy, Ho and Tm) each exhibit ferrimagnetic properties with transition temperatures ranging from 4.7 to 6.3 K. A negative magnetization effect is observed for compound EuHoCuSe₃ at temperatures below 4.8 K. The magnetic properties of the discussed selenides and isostructural sulfides were compared. The direct optical band gaps for EuLnCuSe₃, subtracted from the corresponding diffuse reflectance spectra, were found to be 1.87–2.09 eV. Deviation between experimental and calculated band gaps is ascribed to lower d states of Eu²⁺ in the crystal field of EuLnCuSe₃, while anomalous narrowing of the band gap of EuYbCuSe₃ is explained by the low-lying charge-transfer state. Ab initio calculations of the crystal structures, elastic properties and phonon spectra of the reported compounds were performed.