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The development of manufacturing technology of Sn-bearing stainless steel inspires a novel concept for using Sn-bearing complex iron ore via reduction with mixed H2/CO gas to prepare Sn-enriched direct reduced iron (DRI). The thermodynamic analysis of the reduction process confirms the easy reduction of stannic oxide to metallic tin and the rigorous conditions for volatilizing SnO. Although the removal of tin is feasible by reduction of the pellet at 1223 K (950 °C) with mixed gas of 5 vol pct H2, 28.5 vol pct CO, and 66.5 vol pct CO2 (CO/(CO + CO2) = 30 pct), it is necessary that the pellet be further reduced for preparing DRI. In contrast, maintaining Sn in the metallic pellet is demonstrated to be a promising way to effectively use the ore. It is indicated that only 5.5 pct of Sn is volatilized when the pellet is reduced at 1223 K (950 °C) for 30 minutes with the mixed gas of 50 vol pct H2, 50 vol pct CO (CO/(CO + CO2) = 100 pct). A metallic pellet (Sn-bearing DRI) with Sn content of 0.293 pct, Fe metallization of 93.5 pct, and total iron content of 88.2 pct is prepared as a raw material for producing Sn-bearing stainless steel. The reduced tin in the Sn-bearing DRI either combines with metallic iron to form Sn-Fe alloy or it remains intact.

High-iron content manganese ore resources are becoming the mainstream raw ores for manganese extraction due to the depletion of high-grade manganese ores. Our previous research has reported the optimization parameters for the sintering of high-Fe manganese ore (abbr. high-Fe Mn-ore) fines. This study further investigated the consolidation behavior of high-Fe Mn-ore sinters with natural basicity. Sintering pot tests showed that the high-Fe Mn-ore sintering required high coke breeze dosage (about 9.9 wt.%). The CO content of the outlet flue gas (7.5 vol.%~8.0 vol.%) in the high-Fe Mn-ore sintering was higher than that in the ordinary iron ore sintering (1.0 vol.%~2.2 vol.%). XRD and SEM-EDS analyses indicated that the major mineral phases in the sinters included Fe-Mn oxides (FexMn3-xO4), ferrotephroite ((Fe,Mn)2SiO4), Ca-,Al-,Mn-,Fe- bearing silicate melts, and a small quantity of hausmannite (Mn3O4) and free quartz (SiO2). Optical microstructure and SEM images showed that the Fe-Mn oxides, Ca-, Al...

REE-Nb-Fe ore is a typical refractory resource rich in valuable elements. In this article, coal-based reductive roasting followed by magnetic separation is proposed to recover rare earth element (REE), niobium (Nb), and powdered metallic iron (Fe) concentrate from a REE-Nb-Fe raw concentrate containing 31.9% total iron grade (TFe), 3.2% rare earth oxides (REO), and 2.9% Nb2O5. Sodium sulfate is employed to enhance the reduction of iron oxide and to facilitate the growth of metallic iron grains. A magnetic fraction with TFe of 89.3%, iron metallization of 95.8% and iron recovery of 91.5% is obtained by magnetic separation after the raw concentrate is reduced to 1100°C for 120 min in the presence of 15 wt.% sodium sulfate. The contents of rare earth and niobium in the nonmagnetic fraction are enriched to 5.4% (REO) and 4.6% (Nb2O5) with recoveries of 96.1% and 95.8%, respectively. The TFe in the nonmagnetic fraction obtained after the separation is decreased to 4.8% accordingly. The reactions between sodium sulfate and SiO2/Al2O3 enhance the reduction by destroying the mineral structure. The separation of iron from rare earth and niobium is highly improved as metallic iron grains grow markedly when roasted in the presence of sodium sulfate.

Reduction roasting-acid leaching process was utilized to process high-iron-content manganese oxide ore using black charcoal as reductant. The results indicate that, compared with the traditional reductant of anthracite, higher manganese extraction efficiency is achieved at lower roasting temperature and shorter residence time. The effects of roasting parameters on the leaching efficiency of Mn and Fe were studied, and the optimal parameters are determined as follows: roasting temperature is 650 °C, residence time is 40 min, and black charcoal dosage is 10% (mass fraction). Under these conditions, the leaching efficiency of Mn reaches 82.37% while that of Fe is controlled below 7%. XRD results show that a majority of MnO2 and Fe2O3 in the raw ore are reduced to MnO and Fe3O4, respectively.

Manganese oxide ore is one of the most important resources. Owing to the depletion of high-grade ores, attention has turned to low-grade ones containing multiple elements such as iron, silicon, and aluminum. Conventional processes for extracting manganese are characterized by high production costs, intensive energy consumption, heavy environmental issues, or high co-leaching of impurities. In this study, selective sulfation roasting–water leaching is proposed for recovering manganese from iron rich low-grade manganese oxide ores using SO2 as reductant. Thermodynamic analysis indicated that manganese dioxide is readily transformed to sulfate. However, the sulfation of ferric oxide only occurs in the presence of both SO2 and O2. The thermodynamic stability region for MnSO4 and Fe2O3 demonstrated selective sulfation of manganese dioxide is feasible. The experimental validation for sulfation roasting and water leaching revealed that 90.6% of manganese and only 3.5% of iron were extracted when sulfation roasting was conducted at 500 °C for 60 min with SO2 partial pressure (SO2 / (SO2 + N2)) of 0.5%–1.0% (Vol.), and the leaching process was performed at 50 °C for 15 min with liquid-to-solid ratio of 5. This process is able to recover manganese from various low-grade manganese oxide ores.

It is generally known that the large formation amount of calcium ferrite is favorable for the iron ore sintering. The effects of sintering temperature and O2 content of inlet gas on the calcium ferrite formation characteristic of typical iron ores, including hematite, limonite, specularite and magnetite, were investigated. And the effect of O2 content on the microstructure of the roasted briquettes was also studied in detail. The results show the amount of calcium ferrite initially increases then decreases with the increase of the sintering temperature. The temperature of maximum calcium ferrite generation amount is determined as follows: for hematite and limonite it is 1275 °C, whereas for specularite and magnetite, 1250 °C. The maximum contents of calcium ferrite for hematite, limonite, specularite and magnetite under the optimal sintering temperature are 73%, 82%, 67% and 63%, respectively. Increasing O2 content of the airflow is advantageous to the formation of calcium ferrite. Relatively, the effect of O2 content on the calcium ferrite formation of magnetite is the most pronounced, while O2 content of inlet gas has little effect on the calcium ferrite formation of limonite.

Sodium stannate is widely used in the electroplating and tin alloy industries. The traditional sodium stannate production processes suffer a variety of disadvantages including long flowsheet, high production cost and strict requirements for the equipment. In this study, a novel process for preparing sodium stannate is developed by roasting tin dioxide and sodium carbonate in CO/CO 2 mixed gas followed by leaching the intermediate products in a diluted sodium hydroxide solution. The effects of roasting and leaching parameters on the leaching efficiency of Sn were investigated. The Sn leaching efficiency reaches 85.6% under the optimal experimental conditions: roasting temperature of 875 °C, CO content of 15%, roasting time of 15 min, Na 2 CO 3 /SnO 2 mole ratio of 1.5, liquid-to-solid ratio of 4 cm 3 /g, leaching temperature of 40 °C, leaching time of 60 min, and stirring speed of 300 rpm. Sodium stannate trihydrate (Na 2 SnO 3 · 3H 2 O) having a purity of 95.8% is successfully produced from cassiterite concentrates with a SnO 2 content of 76.4% through the new process, which is superior to the traditional approach for producing the industrial first-grade stannate.

Lead-rich molybdenite is a typical rhenium-bearing molybdenum resource in China, which has not been efficiently utilized due to its high contents of lead and gangue minerals. In this study, hydrochloric acid was used for preliminarily removing lead and calcite from a lead-rich molybdenite concentrate. Oxidative roasting-ammonia leaching was then carried out for separation of rhenium and extraction of molybdenum. The hydrochloric acid leaching experiments revealed that 93.6% Pb and 97.4% Ca were removed when the leaching was performed at 95 °C for 10 min with HCl concentration of 8 wt. % and liquid-solid ratio of 5 (mL/g). The results of direct oxidative roasting indicated that 89.3% rhenium was volatilized from the raw concentrate after roasting at 600 °C for 120 min in air. In contrast, the rhenium volatilization was enhanced distinctly to 98.0% after the acid-leached concentrate (leaching residue) was roasted at 550 °C for 100 min. By the subsequent ammonia leaching, 91.5% molybdenum was leached out from the calcine produced from oxidative roasting of the acid-leached concentrate, while only 79.3% Mo was leached from the calcine produced by roasting molybdenite concentrate without pretreatment.

In recent years, the comprehensive utilization of low-grade manganese oxide ores has received much attention due to the shortage of high-grade manganese ore resources. In this study, low-grade manganese oxide ores were treated by reduction roasting using chemically pure sulfur as a reductant. Then, the roasted samples were subjected to sulfuric acid leaching to extract manganese (Mn). The effects of roasting temperature, roasting time, S/Mn mole ratio, sulfuric acid concentration, leaching temperature, stirring rate, leaching time and liquid-to-solid ratio on the Mn and Fe leaching were discussed. The leaching efficiencies of 95.6% for Mn and 14.5% for Fe were obtained under the following optimized conditions: 550 °C of roasting temperature, 10 min of roasting time, 0.50 of S/Mn, 1.0 mol/L of sulfuric acid concentration, 25 °C of leaching temperature, 200 r/min of stirring rate, 5 min of leaching time and 5:1 of liquid-to-solid ratio.

Low-grade manganese oxide ore is generally characterized by high iron content. In this work, sulfidation roasting of an iron-rich manganese oxide ore with elemental sulfur was characterized. The experimental results indicated that manganese dioxide can be selectively reduced over iron oxide by using elemental sulfur. The manganese phases in roasted product included low-valence manganese oxide, manganese sulfide and manganese sulfate, while those of iron mainly depended on the sulfur addition. Iron oxide would only be reduced or sulfidized at larger sulfur additions. The effect of roasting temperature and S/Mn mole ratio on the phase transformations was also investigated; extractions of Mn/Fe by sulfuric acid were evaluated. An extraction of Mn greater than 95% was obtained while that of Fe was controlled less than 10% under the optimal conditions.