Search

Molten slag has different properties depending on its composition. The relationship between its composition, structure, and properties has been the focus of attention in industrial manufacturing processes. This review describes the atomistic scale mechanisms by which oxides of different compositions affect the properties and structure of slag, and depicts the current state of research in the atomic simulation of molten slag. At present, the research on the macroscopic properties of molten slag mainly focuses on viscosity, free-running temperature, melting point, and desulphurization capacity. Regulating the composition has become the most direct and effective way to control slag properties. Analysis of the microevolution mechanism is the fundamental way to grasp the macroscopic properties. The microstructural evolution mechanism, especially at the atomic and nanoscale of molten slag, is reviewed from three aspects: basic oxides, acidic oxides, and amphoteric oxides. The evolution of macroscopic properties is analyzed in depth through the evolution of the atomic structure. Resolution of the macroscopic properties of molten slag by the atomic structure plays a crucial role in the development of fundamental theories of physicochemistry. [ABSTRACT FROM AUTHOR]

The shape of shaft furnace is a crucial feature of direct reduction processes, as it affects both particle and gas flow during production. However, current knowledge on the impact of furnace shape on particle flow is limited. Herein, the discrete element method is employed for numerical simulations, in which two different methods of varying the wall angle (i.e., changing the radius or the height) are utilized to investigate the effect of wall angle on the flow behavior of particles in a shaft furnace. The effect of wall angle under different combinations of radius and height on the transformation of the particle flow pattern is innovatively examined, compared to previous studies on charging particles and internal furnace conditions. It is demonstrated in the results that the wall angle of the shaft furnace has a significant influence on the transformation of particle flow mode, with a reduction in the wall angle facilitating the transformation of particle flow mode to mass flow. Furthermore, it is shown in the study that different methods of changing the wall angle have varying effects on the transformation of particle flow mode. [ABSTRACT FROM AUTHOR]

In recent years, with the attention given to hydrogen reduction‐related technologies, the parameter indicators of direct reduction in the shaft furnace have gained importance. Herein, the numerical simulation of the particle flow field in the shaft furnace is investigated with the help of discrete element method (DEM) model. In contrast to the subregional modeling and the single particle shape study of the previous studies, this study innovatively uses the real shape of the particles and the overall structure of the vertical furnace for modeling. The transient characteristics of solid particle flow under ten lump ore ratios and three shapes are considered. The results show that the mass fraction and the shape of lump ore have little effect on the particle falling speed, but have a significant effect on the particle segregation behavior. In addition, the void ratio responds to the permeability condition in the furnace, which is also influenced by the lump ore proportion and shape. [ABSTRACT FROM AUTHOR]

FeO and Fe2O3 represent similar but different effects on the structure and properties of aluminosilicate system. Molecular dynamics was conducted to clarify the influences of FeO and Fe2O3 on the structure and properties of SiO2-CaO-Al2O3-FeO (Fe2O3) systems. The bond length and coordination number (CNs) of Si-O bond are almost not affected by FeO (Fe2O3), but FeO and Fe2O3 have opposite effects on the CNs of Al-O bond. The more the Fe3+ ion is, the closer the CN is to 4. The ability of Fe3+ ions to reduce bridging oxygen (BO) is greater than that of Fe2+ ions, while non-bridging oxygen (NBO) and free oxygen (FO) show an opposite trend. In the same way, the influence of Fe atomic numbers of different valence on BO, NBO and FO is similar to that of FeO (Fe2O3) on BO, NBO and FO. The total diffusion coefficient and viscosity of the system increase with the addition of iron oxide. [ABSTRACT FROM AUTHOR]

Precisely predicting the hopper discharge rate and trajectory is of great significance for industrial processing of granular materials. This study uses the DEM (Discrete Element Method)-based open-source software LIGGGHTS to analyze the flow behavior of spherical particles in six cone-shaped hoppers with different outlet shapes (circle, triangle, square, rectangle, pentagon and hexagon) with the various opening area. It was found that the particle flow velocity and mass flow rates are mainly determined by the outlet areas, while the outlet shape have an obvious influence on the particle trajectory which determines the stagnation area in the hopper. The results of the present study can provide meaningful guidance for the optimization of industrial hopper structure design and control. [ABSTRACT FROM AUTHOR]

[Display omitted] • Microstructure evolution mechanism of graphene oxide deflagration phenomenon. • Functional group desorption process of GO pyrolysis at high temperature. • Hybridization statistics and graphitization degree analysis of C atoms in GO. • C-O bond length statistics and structural analysis in graphene oxide. • The release process and quantity statistics of gas molecular of GO pyrolysis. An in-depth understanding of the structural evolution of graphene oxide (GO) at high temperatures is of crucial importance for tuning the properties of GO and synthesizing graphene-related materials from GO, which still has many unknown structural changes at the atomic scale. In this work, the overall structural change process and the local structural evolution mechanism during the high-temperature pyrolysis of GO were investigated by the ReaxFF molecular dynamics simulation method. The detonation process of GO was explored for the first time at the atomic simulation level, and the detonation point of GO was found to be positively correlated with the C/O ratio, which is highly consistent with previous experimental results. The bonding pattern between C-O in GO was sorted out, and the desorption mechanism of functional groups during pyrolysis was explained in detail by analyzing the ratio of sp2 and sp3 hybridized C atoms. In addition, the effects of temperature, C/O ratio and functional group type on the small molecule pyrolysis products were also investigated. The present study provides strategies to tune GO structure by pyrolysis at high temperature. [ABSTRACT FROM AUTHOR]

Polymerization degree theory and traditional charge compensation theory are the most fundamental principles to understand the structure and properties of oxide melts. It can well explain the behavior characteristics of acidic oxides and basic oxides in a melt. However, the amphoteric behavior of oxides cannot be explained well by these two theories. Herein, the octahedral connection mode and the behavior of the amphoteric transition of TiO 2 are analyzed by molecular dynamics simulation, and then, a calculation model which can quantitatively calculate the amphoteric transition of the oxide is established by analyzing a large number of data. On the basis of the model, a novel theory of supply and demand is put forward, which can explain the amphoteric transition behavior of oxides very well. To a great extent, the supply and demand theory makes up for the deficiency of the atomic structure theory of oxide melts and provides mechanism explanation and model prediction for the oxide amphoteric transformation behavior., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)