Yousef Mohassab

Structures, preparation and applications of titanium suboxides

The crystal structure, physical and chemical properties, and applications of titanium suboxides (TinO2n−1, n = integer greater than one) have recently attracted tremendous attention. In this paper, the structure and physical properties of titanium suboxides are summarized, and recent progress in their synthesis methods and applications in catalysis, environmental, electronic and optoelectronic devices and batteries is reviewed. The presence of two Ti3+ and (n − 2)Ti4+ provides TinO2n−1 with several possible configurations of cations in the crystal, various charge-ordered states and electronic structures which lead to their versatile physical properties, such as conductivity, magnetic and optical properties. A series of TinO2n−1 has been synthesized by redox reduction of different titanium sources of TiO2 and other raw materials. Notably, Magneli phase titanium oxides (typically n is between 4 and 6) have played very important roles in Pt-catalyst support, organic degradation, coatings and supports in various electronic and optoelectronic devices. Undoubtedly, titanium suboxides are expected to become indispensable materials in future.

Computational Fluid Dynamics Simulation of the Hydrogen Reduction of Magnetite Concentrate in a Laboratory Flash Reactor

A three-dimensional computational fluid dynamics (CFD) model was developed to study the hydrogen reduction of magnetite concentrate particles in a laboratory flash reactor representing a novel flash ironmaking process. The model was used to simulate the fluid flow, heat transfer, and chemical reactions involved. The governing equations for the gas phase were solved in the Eulerian frame of reference while the particles were tracked in the Lagrangian framework. The change in the particle mass was related to the chemical reaction and the particle temperature was calculated by taking into consideration the heat of reaction, convection, and radiation. The stochastic trajectory model was used to describe particle dispersion due to turbulence. Partial combustion of H2 by O2 injected through a non-premixed burner was also simulated in this study. The partial combustion mechanism used in this model consisted of seven chemical reactions involving six species. The temperature profiles and reduction degrees obtained from the simulations satisfactorily agreed with the experimental measurements.

Analysis of the Hydrogen Reduction Rate of Magnetite Concentrate Particles in a Drop Tube Reactor Through CFD Modeling

A computational fluid dynamics (CFD) approach, coupled with experimental results, was developed to accurately evaluate the kinetic parameters of iron oxide particle reduction. Hydrogen reduction of magnetite concentrate particles was used as a sample case. A detailed evaluation of the particle residence time and temperature profile inside the reactor is presented. This approach eliminates the errors associated with assumptions like constant particle temperature and velocity while the particles travel down a drop tube reactor. The gas phase was treated as a continuum in the Eulerian frame of reference, and the particles are tracked using a Lagrangian approach in which the trajectory and velocity are determined by integrating the equation of particle motion. In addition, a heat balance on the particle that relates the particle temperature to convection and radiation was also applied. An iterative algorithm that numerically solves the governing coupled ordinary differential equations was developed to determine the pre-exponential factor and activation energy that best fit the experimental data.

Determination of Total Iron Content in Iron Ore and DRI: Titrimetric Method Versus ICP-OES Analysis

The determination of reduction degree in a DR process is sensitive to the total iron in the ore and DRI. An accurate and high throughput analysis method for total iron has been developed. Titration of the solution after tin(II) chloride reduction of ferric ion is a widely used method foriron analysis. However, it is a multistep method that requires many chemical reagents and much time. In this work, an ICP-OES analysis method with higher or equivalent accuracy compared with the titrimetric method was developed. This method has much higher throughput and demands fewer chemical reagents compared with the titrimetric method. In this paper, a comparison of the two methods is presented.

Calcined Nanocrystaline Layered Double Hydroxides For The Removal of Arsenate and Arsenite

This work studies the removal of arsenic (V), arsenate, and arsenic (III), arsenite, from aqueous solution using calcined Quintinite-3T. The two adsorbents Quintinite-3T was prepared, calcined at different temperatures, and characterized by XRD, BET, and SEM. The surface area of the calcined Quintinite-3T was 193.4 m2/g. The particles size ranged from 12 to 56 nm for the uncalcined Quintinite-3T and from 24 to 42 nm for the calcined Quintinite-3T. Kinetic analysis, adsorption isotherm, and factors affecting the adsorption were investigated. Calcined Quintinite-3T retained As(v) and did not release it back to water even after an entire month.

Reduction Kinetics of Hematite Concentrate Particles by CO+H2 Mixture Relevant to a Novel Flash Ironmaking Process

The kinetics of hematite concentrate reduction by mixtures of hydrogen and CO of various compositions has been investigated as part of the development of a flash ironmaking process at the University of Utah. This process produces iron directly from iron oxides concentrates by the gas-solid flash reaction based on the partial oxidation of natural gas, resulting in a significant reduction in energy consumption and greenhouse gas emission. The reduction kinetics of hematite concentrate of an average particle size 21.3 µm by the above mentioned gases in the temperature range 1423 to 1623 K (1150 to 1350 °C) was investigated. Hematite concentrate particles can be reduced to > 90% by any of these reductants in several seconds of residence time typically available in a flash reactor. The activation energy ranged from 214 kJ/mol for hydrogen to 231 kJ/mol for CO.

Effect of Water Vapor on O2? Content in Ironmaking Slag

In principle, slag basicity can be expressed as the concentration of free oxygen (O2−) in the slag system. This free oxygen content is equilibrated with different silicate anions in addition to other components in the silicate-based slags. X-ray photon spectroscopy (XPS) and scanning electron microscope equipped with energy dispersive spectrometer (SEM-EDS) were used to investigate the effect of water vapor on the free oxygen content in ironmaking slags. It was found that water in the gas atmosphere plays a significant role in the silicate anion equilibria. Water decreases the amount of free oxygen in the studied slags, with the free oxygen expressed as percentage of the total oxygen decreasing in the order of the following gas mixtures: CO+CO2 (44%,

Flash Ironmaking from Magnetite Concentrate in a Laboratory Reactor: Experimental and CFD Work

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