In order to investigate and analyze the effect of MgO gangue on the surface adsorption and oxidation behavior of magnetite, the physicochemical properties of substances in the magnetite oxidation process are investigated in this study by using thermogravimetric experiments, density functional theory, and ab initio molecular dynamics methods (AIMD) methods. The oxidation mechanism of magnetite and the inhibition mechanism of magnesium oxide on the oxidation properties of magnetite are elucidated. The results of the thermogravimetric experimental study show that the initial oxidation temperature of magnetite tends to increase with the increase of MgO content. At the same time, the presence of MgO leads to the migration of oxidation reactions to the high‐temperature region. AIMD study shows that the presence of the gangue element Mg prolongs the adsorption and dissociation time of O2 molecules on the surface and reduces the interfacial chemical reaction rate of Fe3O4. Moreover, the chemical bonds formed in the system after doping Mg atom are more stable, which is not conducive to the migration of oxygen atoms between Fe3O4 crystal structures, thus affecting the comprehensive oxidation performance of minerals.
This study aims to investigate the effect of water on the properties of cast in situ foamed concrete with a dry density of 300–800 kg/m3 (100 kg/m3 is a gradient). Firstly, the shrinkage deformation with the curing time and the volumetric moisture content is studied by the drying shrinkage test and improved drying shrinkage test. Secondly, the influence of volumetric moisture content on mechanical properties is assessed. At last, the effects of immersion time and immersion type on the mechanical properties of foamed concrete are studied by considering the water-level conditions. The achieved results show that the shrinkage deformations increase with the curing time for the drying shrinkage test and the improved drying shrinkage test, while the variations are different. The shrinkage deformation increases with the decrease of volumetric moisture content for six dry densities of foamed concrete. Besides, it gradually changes in the early stage, while it changes fast in the later stage. The compressive strength and elastic modulus decrease with the increase of volumetric moisture content for each density. For the water-level unchanged condition, the compressive strength and elastic modulus initially decrease and then slowly increase with the increase of the immersion time. For the water-level changed condition, the compressive strength and elastic modulus of foamed concrete decrease with the increase of immersion time for each dry density, and the rate of early attenuation is high, whereas the rate of later attenuation is limited.
Adopting conventional sintering process of vanadium-titanium magnetite concentrates has such problems as low tumbler index and RDI due to the high-TiO 2 content, coarse granularity and poor hydrophilicity. In this experiment, vanadium-titanium magnetite (VTM) is treated by the composite agglomeration process to prepare blast furnace burden and the resulting sinter performance is compared with conventional sintering process. Compared to the sinter with VTM proportion of 15wt%, the productivity and RDI+3.15 of the CAP product with the same VTM proportion are 0.45t/ (m 2 •h) and 6.39% higher, respectively. The effects of pelletized feed proportion (PFP), pelletized feed size and pelletized feed basicity on agglomeration indexes of CAP are also studied. The results show that the optimal PFP, pelletized feed size and pelletized feed basicity are 15wt%, 5~8mm and 0.9, respectively. Vanadium-titanium magnetite composite agglomeration process not only improves the quality and quantity indices of sinter, but also optimizes the melting and dripping properties.
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