贫赤铁矿高压辊磨产品湿式预选研究

采用柱状磁介质研究了介质棒间隙、直径及背景磁场强度对贫赤铁矿高压辊磨产品湿式强磁预选效果的影响,并对磁场中不同直径的单矿物颗粒进行了受力分析.研究表明:减小介质棒间隙、增加介质棒直径和提高背景磁场强度均能降低预选尾矿的品位和产率,提高回收率.在同一背景磁场强度下,随着直径的增加,介质棒对粗颗粒的捕收磁力增加,对细颗粒的捕收磁力减小;对于实际连生体矿粒,考虑到矿粒重力和黏滞阻力的影响,增大介质棒直径在有利于粗矿粒捕收的同时并不影响细矿粒的捕收;减小介质棒直径有利于细矿粒的捕收,但对粗贫连生体矿粒的捕收能力下降.     

Quasi-2D Monte Carlo simulations of the regime change in the aggregates of magnetic cubic particles on a material surface

We have investigated the aggregate structure of a suspension composed of magnetic particles with a cubic geometry by means of Monte Carlo simulations. From the viewpoint of application to the technology of surface modification, we have considered a quasi-two-dimensional suspension in thermodynamic equilibrium. As the magnetic interaction strength is increased, the effects of the thermal energy are reduced and the particles tend to aggregate together. These aggregates of cubic particles are not chain-like, but are designated as closely packed clusters. An applied magnetic field tends to enhance the formation of clusters along the field direction but does not significantly regularise the internal structure of the cluster. This is mainly due to the preference of a face-to-face contact configuration for the alignment of particles with cubic geometry. The regime of the internal structure of aggregates has a significant effect on the characteristics of the alignment of the magnetic moments with regard to the external magnetic field direction. Our simulations indicate that larger closely packed clusters are formed with increasing volumetric fraction, whereas the internal structure of the closely packed clusters is not found to be significantly influenced by the change in the volumetric fraction.     

Effect and mechanism of siderite on reverse flotation of hematite

The effects of siderite on reverse flotation of hematite were investigated using micro flotation, adsorption tests, and Fourier transform infrared spectroscopy. The flotation results show that interactions between siderite and quartz are the main reasons that siderite significantly influences the floatability. The interactions are attributed to dissolved siderite species and fine siderite particles. The interaction due to the dissolved species is, however, dominant. Derjaguin-Landau-Verwey-Overbeek (DLVO) theoretical calculations reveal that adhesion on quartz increases when the siderite particle size decreases and that fine particles partly influence quartz floatability. Chemical solution calculations indicate that the dissolved species of siderite might convert the surface of active quartz to CaCO₃ precipitates that can be depressed by starch. The theoretical calculations are in good agreement with the results of adsorption tests and FTIR spectroscopy and explain the reasons why siderite significantly influences reverse flotation of hematite.     

基于镍基修饰的铁矿石载氧体煤化学链燃烧实验

使用1 kW_th串行流化床反应器,研究了以铁矿石为载氧体以及对铁矿石进行镍基修饰情况下煤化学链燃烧特性,对两种修饰方法(机械混合和浸渍)进行了对比评价。结果表明,铁矿石载氧体具有良好的反应性能和稳定性,是实现煤化学链燃烧的一种比较理想的载氧体。向矿石中机械添加少量NiO/Al₂O₃载氧体,能够有效改善其反应活性,提高系统CO₂捕集率;采用浸渍法修饰的铁矿石载氧体煅烧后,总体微观孔隙结构变差,导致煤气化产物与载氧体间的反应无法充分进行,系统CO₂捕集率显著下降。浸渍修饰的方法和过程需要进一步的研究和改善。     

磁种磁团聚强化淀粉对微细粒赤铁矿的抑制

针对赤铁矿反浮选过程中,淀粉对微细粒赤铁矿抑制作用较差的问题,通过浮选试验、EDLVO理论计算、粒度分布和SEM分析,研究了利用磁种磁团聚强化淀粉对微细粒赤铁矿的抑制作用.结果表明,随着赤铁矿的粒度降低,淀粉对赤铁矿的抑制作用变差.添加磁铁矿可强化淀粉对微细粒赤铁矿的抑制作用,随着磁铁矿粒度的增加,强化抑制作用越明显.不同粒级的磁铁矿与微细粒赤铁矿间均存在引力作用,可使磁铁矿与赤铁矿发生磁团聚,且磁铁矿粒度越大,引力作用越强.磁团聚作用增加了微细粒赤铁矿的表观粒度,从而强化了淀粉对微细粒赤铁矿的抑制作用.     

Evidence from Mössbauer spectroscopy of neo-formation of magnetite/maghemite in the soils of loess/paleosol sequences in China

Samples of four different loess/paleosol couplets of a loess sequence in Huangling (China) have been studied with ⁵⁷Fe Mössbauer spectroscopy. Each sample was separated into strongly, weakly and very weakly magnetic fractions. The iron mineralogy of the strongly magnetic fractions of both loess and soils consists of magnetite/maghemite and hematite together with some silicates. The soils contain some additional small-particle maghemite. From the spectral behaviour a similarity in terms of morphology and crystal chemistry for hematite throughout the whole section could be inferred. The ratio of iron in magnetite and maghemite to that in hematite differentiates well between the loess and soil samples. These results strongly suggest the neo-formation of magnetite/maghemite in the soils.     

Influence of the starting materials on the catalytic properties of iron oxides

The effect of iron nitrate, sulfate and chloride on the catalytic properties of hematite toward ethylbenzene dehydrogenation has been studied. Iron nitrate has been the best precursor to prepare the catalysts.     

Iron oxide pigmenting powders produced by thermal treatment of iron solid wastes from steel mill pickling lines

Phase changes of iron containing solid wastes from steel mill pickling lines after thermal treatments were investigated aiming the determination of the appropriate conditions for its transformation to be useful for industrial raw materials. Above 275°C, the thermally treated wastes contain a mixture of α-Fe₂O₃ (hematite) and γ-Fe₂O₃ (maghemite) in different proportions, depending on the maximum heating temperature of the thermal treatment. Increasing the maximum temperature the maghemite participation is decreased through its transformation to hematite. Above 850°C hematite is the main constituent, suggesting that thermal treatment of the wastes in this temperature will give a product that could be used as red iron pigment.     

The effect of the starting material on the thermal decomposition of iron oxyhydroxides

The effect of the iron precursor on the thermal decomposition of iron oxyhydroxides was studied by DSC, DTA and TG in this work. Samples were prepared from iron nitrate, iron sulfate and iron chloride and the thermal curves obtained were analyzed by specific area measurements, X-ray diffraction and Mössbauer spectroscopy. It was found that the iron oxyhydroxide precursors affect the temperatures of the hematite formation as well as the textural properties of the final hematite producing particles with different diameters as following: iron sulfate (3.3 nm)相似文献