Selective enrichment of iron particles from complex refractory hematite-goethite ore by coal-based reduction and magnetic separation

Study on Extraction Valuable Metal Elements by Co-Roasting Coal Gangue with Coal Gasification Coarse Slag

Coal gangue (CG) and coal gasification coarse slag (CGCS) possess both hazardous and resourceful attributes. The present study employed co-roasting followed by H2SO4 leaching to extract Al and Fe from CG and CGCS. The activation behavior and phase transformation mechanism during the co-roasting process were investigated through TG, XRD, FTIR, and XPS characterization analysis as well as Gibbs free energy calculation. The results demonstrate that the leaching rate of total iron (TFe) reached 79.93%, and Al3+ achieved 43.78% under the optimized experimental conditions (co-roasting process: CG/CGCS mass ratio of 8/2, 600 °C, 1 h; H2SO4 leaching process: 30 wt% H2SO4, 90 °C, 5 h, liquid to solid ratio of 5:1 mL/g). Co-roasting induced the conversion of inert kaolinite to active metakaolinite, subsequently leading to the formation of sillimanite (Al2SiO5) and hercynite (FeAl2O4). The iron phases underwent a selective transformation in the following sequence: hematite (Fe2O3) → magnetite (Fe3O4) → wustite (FeO) → ferrosilite (FeSiO3), hercynite (FeAl2O4), and fayalite (Fe2SiO4). Furthermore, we found that acid solution and leached residue both have broad application prospects. This study highlights the significant potential of co-roasting CG and CGCS for high-value utilization.

Effect of Co-Reduction Conditions of Nickel Laterite Ore and Red Mud on Ferronickel Particle Size Characteristics and Grindability of Carbothermic Reduction Products

The carbothermic co-reduction of nickel laterite ore and red mud realized the simultaneous reduction of nickel, iron in laterite ore, and iron in red mud at high efficiency. Nickel and iron in nickel laterite ore and iron in red mud were recovered in the form of ferronickel. The size characteristics of ferronickel particles and grindability of carbothermic reduction products are essential for obtaining good technical indicators. The influence of co-reduction conditions on ferronickel particle size and relative grindability was investigated by a carbothermic reduction test, particle size analysis, and relative grindability determination. The mean size of ferronickel particles increased and the proportion of coarse particles grew with improving carbothermic reduction temperature, increasing appropriately anthracite dosage, and prolonging carbothermic reduction time. However, the relative grindability of carbothermic reduction products deteriorated when reduction temperature was improved and the reduction time was extended. The relative grindability was negatively correlated to the ferronickel particle size. The carbothermic reduction temperature had the most dominant effect on the ferronickel particle size and relative grindability, followed by the anthracite dosage and reduction time. More nickel-bearing and iron-bearing minerals were reduced to metallic state with raising reduction temperature and increasing appropriate anthracite dosage. The fine ferronickel particles agglomerated and merged into bulk ferronickel grains with a prolonged reduction time. The results will provide theoretical guidance for the recovery of nickel and iron by co-reduction of nickel laterite ore and red mud.

Clean Utilization of Limonite Ore by Suspension Magnetization Roasting Technology

As a typical refractory iron ore, the utilization of limonite ore with conventional mineral processing methods has great limitations. In this study, suspension magnetization roasting technology was developed and utilized to recover limonite ore. The influences of roasting temperature, roasting time, and reducing gas concentration on the magnetization roasting process were investigated. The optimal roasting conditions were determined to be a roasting temperature of 480 ℃, a roasting time of 12.5 min, and a reducing gas concentration of 20%. Under optimal conditions, an iron concentrate grade of 60.12% and iron recovery of 91.96% was obtained. The phase transformation, magnetism variation, and microstructure evolution behavior were systematically analyzed by X-ray diffraction, vibrating sample magnetometer, and scanning electron microscope. The results indicated that hematite and goethite were eventually transformed into magnetite during the magnetization roasting process. Moreover, the magnetism of roasted products significantly improved due to the formation of ferrimagnetic magnetite in magnetization roasting. This study has implications for the utilization of limonite ore using suspension magnetization roasting technology.

Mineral and Technological Features of Magnetite-Hematite Ores and Their Influence on the Choice of Processing Technology

Analysis of the current technical solutions for the processing of iron ores showed that the high-grade ores are directly exposed to metallurgical processing; by comparison, low-grade ores, depending on the mineralogical and material composition, are directed to beneficiation including gravitational, magnetic, and flotation processes or their combination. Obtaining high-quality concentrates with high iron content and low content of impurities from low-grade iron ores requires the maximum possible liberation of valuable minerals and a high accuracy of separating features (difference in density, magnetic susceptibility, wettability, etc.). Mineralogical studies have established that the main iron-bearing mineral is hematite, which contains 69.02 to 70.35% of iron distributed in the ore. Magnetite and hydrogoethite account for 16.71-17.74 and 8.04-10.50% of the component, respectively; the proportion of iron distributed in gangue minerals and finely dispersed iron hydroxides is very insignificant. Iron is mainly present in the trivalent form-Fe₂O₃ content ranges from 50.69 to 51.88%; bivalent iron is present in small quantities-the FeO content in the samples ranges from 3.53 to 4.16%. The content of magnetic iron is 11.40-12.67%. Based on the obtained results by the investigation of the features of magnetite-hematite ores from the Mikhailovskoye deposit, a technological scheme of magneto-flotation beneficiation was proposed, which allows producing iron concentrates with 69% of iron content and less than 2.7% silicon dioxide for the production of pellets with subsequent metallization.