This study presents the results of the solid-state reduction of iron–manganese ore from the Keregetas deposit (Kazakhstan) using hydrogen as a reductant. The findings demonstrate that hydrogen is an effective and environmentally friendly reducing agent, enabling selective reduction of iron. The investigated iron–manganese ore exhibits a complex mineralogical composition comprising oxides of Fe, Mn, Si, and aluminosilicate complex phases. X-ray diffraction (XRD) analysis of the raw ore confirmed the presence of goethite, hematite, quartzite, and MnO2 as the primary mineral phases. Oxidative roasting induced the dehydration of goethite and its conversion to hematite, along with the formation of Mn2O3 and Mn3O4 phases. The detection of Mn7SiO12 indicates interaction between manganese and silica under high-temperature oxidation conditions. Reduction experiments were conducted in an RB Automazione MM 6000 laboratory furnace at temperatures ranging from 700 to 1100 °C, with a holding time of 60 min and a hydrogen flow rate of 0.5 L/min. Results revealed high selectivity of hydrogen reduction: at 700–800 °C, iron and arsenic were predominantly reduced, as evidenced by the emergence of a metallic Fe-containing phase, while oxides of Mn, Si, Ba, and Al remained in the residue. Increasing the temperature to 900–1000 °C resulted in partial reduction of manganese. At 1100 °C, a decrease in the intensity of the metallic phase was observed, likely due to sintering of ore particles and reduced gas permeability. The reduced metal and oxides were readily separable by melting. These findings provide a basis for developing processing schemes for beneficiation and hydrometallurgical treatment of iron–manganese ores from Kazakhstan.

This study investigates the behavior of phosphorus during high-temperature smelting of hydrogen-reduced high-phosphorus oolitic iron ore from the Lisakovsk deposit. The preliminary reduction was carried out at temperatures ranging from 600 to 900 °C using hydrogen, aiming to selectively reduce iron to the metallic phase while retaining phosphorus in the oxide form. The resulting reduced products were subjected to wet magnetic separation and liquid-phase separation. It was found that neither method provides effective separation of phosphorus from iron: phosphorus partially enters the magnetic fraction and, during smelting, transfers into the metallic phase. To confirm the mechanism of phosphate reduction by metallic iron, a control experiment was conducted, in which a mixture of reduced iron and raw ore was smelted at 1650 °C. Microstructural and elemental analyses confirmed the redistribution of phosphorus into the metallic phase. These findings indicate that effective separation of iron and phosphorus cannot be achieved by reduction roasting alone and highlight the need for further studies on slag formation conditions and phase separation kinetics.

Processing of titanium-containing ores with extraction of all the major elements is an urgent task of minerals rational use. It is shown that none of the existing processing schemes allows extracting of all the major useful elements at the same time from titanium-containing iron ores, i.e. – iron, titanium and vanadium. This problem can be solved using selective extraction of these elements based on new ideas about electronic reduction mechanism. Propagation of the process of solid-phase selective reduction of iron with the powder of carbon-containing material deep into the layer of grains of ilmenite concentrate from the surface of its contact was experimentally studied. The results of determining the amount of metal phase released as it moves away from the concentrate – reducing agent contact boundary are presented. Based on the results concerning amount of precipitated metal phase, a conclusion was made about diffusion processes in a layer of concentrate grains contacting only between themselves, limiting process of iron reduction. It is shown that near the plane of contact of solid reducing agent with the layer of concentrate grains, the rate of iron reduction is higher than the rate of high iron content phase precipitation from ilmenite. In depth of ilmenite concentrate layer, process of iron reduction is preceded by formation of iron-containing silicate phase from concentrate grains, where iron is reduced earlier than in ilmenite grains. Formation of iron-containing silicate phase contributes ilmenite grains sintering. It was concluded that in the concentrate layer in contact with solid reducing agent layer in absence of contact of each ilmenite grain with solid reducing agent, the point contact of grains and presence of voids between them in the layer do not prevent propagation of reduction process in the layer of grains contacting with each other only.

Processing of titanium-containing ores together with the extraction of all the major elements is currently an urgent problem for the usage of mineral produ

The results of theoretical analysis and experimental studies of selective solid-phase Fe reduction from an ilmenite concentrate by carbon or hydrogen are presented. It is shown that hydrogen reduces Fe with a higher rate at a relatively low (900 °C) temperature, what allows to obtain soft iron and titanium dioxide concentrate, which are easily separated by melting and are commercial products. Hydrogen is practically not dissolved in solid iron, and is easily removed from the unit due to the gaseous state, what eliminates titanium reduction and formation of its lower oxides when the temperature rises at the stage of separation of the reduction products. Fe reduction by carbon at an acceptable rate and at a higher (above 1100 °C) temperature is accompanied by reduction of titanium to lower oxides, while energy consumption for reduction increases by 2.25 times. The scheme is proposed for processing of ilmenite concentrate in a non-agglomerated form – selective reduction of iron with hydrogen in a multi-hearth furnace, with consequent separation of reduction products into soft iron and titanium dioxide concentrate in a plasma furnace.The study was supported by the Russian Science Foundation (grant no. 23-29-10119, https://rscf.ru/project/23-29-10119/).

The thermodynamic modeling method was used to determine the temperature of beginning of reduction of iron, vanadium, silicon, and titanium in ilmenite concentrate by carbon or hydrogen at different amounts of reducing agent in the system. The amount of excess carbon relative to the stoichiometry of the iron reduction reaction does not affect the temperature of reduction beginning, but determines their reduction degree and the amount of carbides formed. The amount of hydrogen in the system significantly affects the temperature of reduction beginning: with an increase in water amount, this temperature of each element decreases, but to a different extent. The wider temperature range of beginning of reduction by hydrogen and the quantitatively unequal effect of temperature create more opportunities for controlling the solid-phase selective reduction by hydrogen in comparison with carbon. In contrast to the carbothermic process, the solid-phase reduction of titanium by hydrogen is negligible at relatively low temperatures, at which titanium is reduced by carbon and forms carbides. The low solubility of hydrogen in solid iron excludes its influence on the behavior of elements at the stage of separation melting of solid-phase reduction products. This makes it possible to carry out reduction in hydrogen flow by changing the temperature and amount of hydrogen in the reducing gas mixture, and to control the processes of selective solid-phase reduction of elements. The use of hydrogen at the stage of solid-phase reduction makes it possible to selectively reduce iron with the storage of titanium oxides in the oxide phase in form of TiO₂, and after separation of the reduction products by melting, to obtain the products in demand (carbon-free iron and TiO₂ concentrate).