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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.

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.

In order to reduce SO2 emission in the iron sintering process, the flue gas circulation sintering (FGCS) process has been recommended and put into practice. In this process, flue gas containing low SO2 concentration is recirculated to the sintering process, achieving the concentration of SO2 content in the off-gas, which is favorable for current flue gas desulphurization processes. In this study, SO2 behavior in different sintering zones was investigated under the simulated experimental conditions. In the moisture condensation zone and sinter mixture zone, SO2 of recirculated flue gas is absorbed by the moisture and slaked lime of sinter mixture; in the drying and preheating zone, part of SO2 in circulating flue gas is absorbed by dry slaked lime in sinter mixture under low temperature conditions, and SO2 is generated by oxidization of sulfides and re-released by decomposition of sulphurous acid; in the hot zone, SO2 in circulated gas is partially absorbed by the molten phases, newly crystallized minerals such as calcium ferrite and dissociative CaO; in sinter zone, part of SO2 is absorbed by residual CaO in sinter under the condition of humid circulated flue gas, which results in unfavorable increase of residual S in the up layer sinter.

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.

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.

Sn-bearing iron ore containing small amount of Zn, Pb and As is one of the typical complex polymetallic ores in China. This kind of ore is not extensively utilized due to the complicated relationships between iron and other associated nonferrous metal minerals. Excessive contents of these elements would adversely affect the metallurgical operation as well as the quality of steel products. In this study, reduction behavior of Sn was detailedly investigated using H2 or mixed H2/CO as reductant. The results revealed Sn volatilization was improved in the presence of H2 than individual CO/CO2 atmosphere. Simultaneous volatilization of these elements was realized by roasting under weak H2/CO reducing potential, and metallization reduction was advantageous for further Zn volitilization. A metallic pellet (DRI) with Fe metallization greater than 90%, residual Sn, Zn, Pb and As content of 0.054%, 0.012%, 0.0045% and 0.09% was prepared via a simulated reducing gas of coal gasification.

Reduction disintegration of sinter significantly affects the coke consumption and productivity of blast furnace smelting. As we know, the reduction disintegration index (RDI+3.15) of sinter obtained from titanomagnetite concentrate is relatively worse than those from ordinary iron ores. In this study, the effect of sintering parameters, mainly involving coke breeze dosage and basicity on sintering indexes was investigated using titanomagnetite concentrate as raw material in an experimental-scale pot. Subsequently, RDI+3.15 of the sinter was detected according to the Chinese standard of GB/T13242-91. The results show that RDI+3.15 rises with the increase of coke breeze dosage, while it decreases with increasing basicity from 0.5 to 2.0 and then increases in the basicity range of 2.0–3.0. Finally, the microstructure of sinter before and after reduction was studied. And the mechanism of reduction disintegration was preliminary revealed by analyzing the morphologies and distributions of minerals in the sinter.