Papers by Keyword: Dissociation

Abstract: Kinetics of the siderite ore roasting in the air, helium and hydrogen flows has been studied in a gasometrical unit with continuous mass variation logging. We have derived the expression for determination of an apparent degree of calcination and identified its dependence on the size of the prill, the heat treatment duration, and gas-phase composition. Using a generalized chemical kinetics equation, we have obtained a formula for calculation of the decomposition period for siderite ore samples. It has been found that calcination rate increases with the temperature rise, irrespective of the sample size and atmospheric composition. Calcination process has been studied at low temperatures. We have demonstrated that it is feasible to describe the process of siderite ore thermal dissociation by a first-order kinetics equation. We have obtained the expression to calculate the duration of this process depending on different parameters. Using a generalized chemical kinetics equation, we have obtained a formula for checking the expressions that describe the experimental data. We have studied kinetics of the reduction of roasted ore samples at various temperatures using different sizes of the samples. The obtained results have been applied for optimization of the design values and operating conditions of the siderite ore roasting in shaft furnaces. These will also be used for designing a shaft furnace consisting of a calcination zone, reduction zone (metallization zone) and metallized product cooling zone, which will increase iron content in the end-product to 65-70%.

Abstract: We have studied the influence of oxidation-reduction reactions on the structure and strength behavior of the Kachkanar fluxed pellets both in their initial condition and during reduction. It has been discovered that at heating rates and temperatures found in industrial units the roasted pellets that are not oxidized to a full extent and are characterized by zonal structure do not meet the requirements imposed for the blast-furnace smelting raw materials. To develop a process that would ensure high metallurgical properties, we have analyzed the hematite dissociation reaction. It was found that the temperature and the content of slag-forming oxides influence this reaction. A sinter pot was used to carry out the research and determine metallurgical properties of partially dissociated pellets. The obtained results helped to develop a process to dissociate hematite at lower temperatures with calcium ferrosilicate melt. Such pellets are reduced at the temperatures of over 700^оС, which prevents their destruction in blast furnaces.

Abstract: The concept and a new method for the shielded development of bottom gas hydrates have been proposed, the technological phases and constructive elements of their implementation have been substantiated. The research provides for the realization of the idea suggesting the simultaneous dissociation of the vast areas of a gas hydrate deposit, management of the targeted process of the penetration of methane recovered from gas hydrates into water space and its accumulation under the extensive gas-collecting shield wherefrom it is removed by bottom pipe transportation facilities. To do hydraulic fracturing, a well is drilled into the plane of the junction of the surface of a gas hydrate deposit and the rocks of a roof, the open system of fissures in the rocks of a roof is made through which produced gas is released to a gas-collecting blanket in a water.

Abstract: H₂S adsorption and dissociation on MoP(010) were investigated using density functional theory (DFT) together with periodic slab models. Several different possibilities for H₂S, SH, S and H adsorption were considered. Our results show that the H₂S, SH and H prefer to adsorb at bridge site, while S adsorbs preferentially at hcp and bridge sites. Additionally, the optimum co-adsorption configurations for SH/H and S/H were determined. The results indicate that the co-adsorbed species repel each other slightly on MoP(010) surface. Finally, the potential energy profile of H₂S dissociation on MoP(010) surface was given out. The dissociation energy barriers of the S–H bond scission exhibit that H₂S prefers to dissociate on MoP(010) surface. When compared with MoP(001) surface, the obvious differences in H₂S decomposition arise demonstrate that the MoP-based catalysts are structure-sensitive.

Abstract: A one-dimensional model of an elasto-plastic theory of dislocation fields is developed to model planar dislocation core structures. This theory is based on the evolution of polar dislocation densities. The motion of dislocations is accounted for by a dislocation density transport equation where dislocation velocities derive from Peach-Koehler type driving forces. Initial narrow dislocation cores are shown to spread out by transport under their own internal stress field and no relaxed configuration is found. A restoring stress of the lattice is necessary to stop this infinite relaxation and it is derived from periodic sinusoidal energy of the crystal. When using the Peierls sinusoidal potential, a compact equilibrium core configuration corresponding to the Peierls analytical solution is obtained. The model is then extended to use generalized planar stacking fault energies as an input and is applied to the determination of properties of planar dislocation cores in crystalline materials. Dissociations of edge and screw dislocation cores in basal and prismatic planes of Zirconium are shown.

Abstract: Thermal stability of the sintered samples of uranium mononitride was investigated in high purity helium atmosphere at 1900° – 2300°С. Thermogravimetry analysis of samples showed that the weight loss in uranium nitride consists of two stages. On first stage decomposition of uranium mononitride and nitrogen release starts. On the second stage additional active evaporation of uranium metal happens. During heating of the samples, nitrogen was registered by mass spectrometry. Microstructure of the samples after high temperature tests showed irregularly distributed spherical particles of uranium metal.

Abstract: Using the CIS (Configuration Interaction with Single Substitute) method, we calculated structure of cycloheptanone ion excited state and frequency of vibration. Comparison can be seen from the table 3, the path formed by the debris path C lowest energy structure, so the stable structure of C₄H₅O⁺ fragmentation can be shown in path C. It is the parent ion 1C-7C, 4C-5C fracture formation, one of 9H and 10H migration. 11H and 12H migrated from 3C to 4C, formed C₄H₅O⁺ fragmentation. It mainly through the fifth excited state occur the dissociation process.

Abstract: Using the CIS(Configuration Interaction with Single Substitute) method, and 6-31+G (d, p) basis set, we calculated the frequency of excited state of cyclopentanone ion molecule. Studies on the possible way of obtain CH₃⁺ small fragments by cyclopentanone ion. Judging from mass peak, there is ion fragments of CH₃⁺, through the theoretical calculation, we have get that the fragments CH₃⁺ by the dissociation products of C₅H₈O⁺ is the same to the fragmentation of the time-of-flight mass spectra excited by femtosecond laser. It can be preliminary judgment that C₅H₈O⁺ cleavage fragments may have CH₃⁺ fragments in this vibration mode.

Abstract: Our theoretical study aims to analyze the Way of Obtain C₄H₆O⁺ macro ion by C₇H₁₂O⁺ Excited State and gives out a result with proved and directed significance for the corresponding experiments. Using the CIS(Configuration Interaction with Single Substitute) method, we calculated the frequency of cycloheptanone ion excited state. It is the parent ion 1C-7C, 4C-5C fracture, generates C₄H₆O⁺ pieces. It mainly through the fifth excited state occur the dissociation process.

Abstract: Theoretical study aims to the way of obtain C₄H₆O⁺ fragments laser-induced by cyclicketone ion (C₇H₁₂O⁺) excited state, and gives out a result with proved and directed significance for the corresponding experiments. According to the analysis of C-C key vibration mode, mainly considering the C-H bond cleavage, H atom migration formed fragments, We can get the possible ways of C₄H₆O⁺ fragments are: 1C-7C, 4C-5C broken, formed C₄H₆O⁺ fragments, 2C-3C, 6C-5C broken, formed C₄H₆O⁺ fragments.