Roasting Of Ore Research Articles

Influence of Sodium Salts on Reduction Roasting of High-Phosphorus Oolitic Iron Ore

ABSTRACT The reduction roasting followed by magnetic separation process is considered to be a suitable method to treat the high-phosphorus oolitic iron ore. Currently, the dephosphorization mechanism of additives such as CaCO3, Ca(OH)2, Na2SO4, and Na2CO3 on the reduction roasting of the iron ore in which phosphorus occurs in apatite have been thoroughly studied. The effect of sodium salts (Na2CO3, NaCl and Na2SO4) on reduction roasting and magnetic separation of high-phosphorus oolitic iron ore containing phosphorus in iron oxides was investigated, and the mechanisms of sodium salts were expounded using XRD and SEM-EDS. The results show that the dephosphorization ability of sodium salts was in the order of Na2SO4> Na2CO3> NaCl>no sodium salts. Na2CO3 and Na2SO4 transferred Fe3PO7 from the iron oxides to nepheline, which upgraded the separation of iron and phosphorus. However, NaCl did not inhibit the reduction of phosphorus in the iron minerals. In addition, Na2CO3 strengthened the reduction of iron oxides. However, a small amount of wustite failed to be reduced to metallic iron with the addition of NaCl, and troilite and wustite formed hindered the reduction of iron minerals after adding Na2SO4.

Thermal Decomposition and Kinetics of Pentlandite-Bearing Ore Oxidation in the Air Atmosphere

The roasting of sulfide ores and concentrates is one of the most important steps in pyrometallurgical metal production from primary raw materials, due to the necessity of excess sulfur removal, present in the virgin material. Pentlandite is one of the main sources for nickel pyrometallurgical production. The knowledge of its reaction mechanism, products distribution during oxidation and reaction kinetics is important for optimizing the production process. Raw pentlandite-bearing ore from the Levack mine (Ontario, Canada) was subjected to oxidative roasting in the air atmosphere. A chemical analysis of the initial sample was conducted according to EDXRF (Energy-Dispersive X-ray Fluorescence) and AAS (Atomic Adsorption Spectrometry) results. The characterization of the initial sample and oxidation products was conducted by an XRD (X-ray Diffraction) and SEM/EDS (Scanning Electron Microscopy with Energy Dispersive Spectrometry) analysis. Thermodynamic calculations, a phase analysis and construction of Kellogg diagrams for Ni-S-O and Fe-S-O systems at 298 K, 773 K, 923 K and 1073 K were used for proposing the theoretical reaction mechanism. A thermal analysis (TG/DTA—Thermogravimetric and Differential Thermal Analyses) was conducted in temperature range 298–1273 K, under a heating rate of 15° min−1. A kinetic analysis was conducted according to the non-isothermal method of Daniels and Borchardt, under a heating rate of 15° min−1. Calculated activation energies of 113 kJ mol−1, 146 kJ mol−1 and 356 kJ mol−1 for three oxidation stages imply that in every examined stage of the oxidation process, temperature is a dominant factor determining the reaction rate.

Hydrochloric Acid Decomposition of the Niobium–Rare-Earth Slag Produced by Reducing Roasting of the Rare-Earth Ore from the Chuktukon Deposit

Hydrochloric Acid Decomposition of the Niobium–Rare-Earth Slag Produced by Reducing Roasting of the Rare-Earth Ore from the Chuktukon Deposit

NEURAL NETWORK MODELING AND OPTIMISING OF THE AGGLOMERATION PROCESS OF SULPHIDE POLYMETALLIC ORES

During the operation of the lead-zinc production while processing of polymetallic ores, problems arose related to the quality of products and the efficient use of equipment – agglomeration furnace and crushing apparatus. Previously, such issues were resolved due to the experiences and based on mathematical modeling of processes. The mathematical model for optimizing unnecessary such operating mode is a difficult program. Performing calculations is required a fairly large investment of time and resources. Therefore, the program of the mathematical model for optimizing the operating mode of the agglomeration furnace and the crushing device for sinter firing was replaced with a neural network by implementing the process of training the network based on the results of calculations on a mathematical model. The results obtained showed that neural network models were more accurate than mathematical models, which made it possible to solve production optimization problems of great complexity. The use of neural networks for modeling technological processes has made it possible to increase the efficiency of product quality control systems and automatic control systems for the roasting of sulfide polymetallic ores.

Mineralogical characterization and speciation of sulfur, zinc and lead in pyrite cinder from Bergvik, Sweden

Roasting of sulfide ores to produce sulfuric acid began on an industrial scale in the middle 1800′s and is still used extensively worldwide. The residual, pyrite cinders, have commonly been disposed in the environment where they pose a potential and serious threat to aquatic life. In this project, two profiles in a pyrite cinder deposit in Bergvik, Sweden, have been sampled and a comprehensive mineralogical characterization have been carried out. The objectives were to investigate the composition and morphology of pyrite cinder grains and the speciation of sulfur, Pb and Zn in the solid phase. Scanning electron microscopy showed pyrite cinder grains with a core of the ore minerals pyrite and sphalerite enclosed in layers of iron oxides/hydroxides (mainly hematite). XANES analysis, supported by X-ray diffraction analysis, SEM-EDS and bulk element analysis, showed that content of the residual sulfur in the cinder is mainly sulfides, 55–80%, predominately sphalerite. The remaining mass of sulfur is assumed to be adsorbed or precipitated as secondary sulfate minerals, predominantly associated with the grain surfaces. Calculated saturation indexes indicated barite, anglesite and perhaps aluminite. EXAFS spectroscopy indicated that about half of the Zn was bound to O and half was bound to S. LCF analysis of EXAFS spectra indicated that the main Zn species were sphalerite (40–50%) and franklinite (10–20%). The remaining Zn was associated with iron oxides/hydroxides and Zn minerals like hydrozincite or possibly zinc oxides. SEM-EDS analysis showed Pb precipitate located on both the surface of the grains and in the interior as inclusions. The analytical interpretation indicated anglesite.

Oxidation Roasting of Fine-Grained Carbonaceous Gold Ore: The Effect of Aeration Rate

The oxidation roasting of carbon-bearing micro-fine gold can eliminate or weaken the robbing effect of carbonaceous materials and clay, and destroy the encapsulation of micro-fine gold. The micropores produced by gas escaping during the roasting process are conducive to the diffusion of leaching agents, thus enhancing the cyanide leaching of gold. In this paper, the influence of the aeration rate during roasting on the leaching rate of fine-grained carbonaceous gold ore and its mechanism were studied using thermodynamic calculations, crystal structure analysis, surface chemical groups and bonds analysis, microporous structure analysis, and surface morphology detection. Under suitable roasting conditions, the carbonaceous and pyrite in the ore are oxidized, while carbonate minerals such as dolomite and calcite as well as clay minerals are decomposed, and the gold-robbing materials lose their activity. The experimental results have theoretical and practical significance for the popularization and application of oxidation roasting technology of fine carbon-bearing gold ore.

Extraction of Sc from Sc-Bearing V–Ti Magnetite Tailings

In this study, a magnetic separation–shaking table gravity separation process was used to treat Sc-bearing V–Ti magnetite tailings, and the Sc2O3 content in the Sc concentrate was enhanced from 0.0039 to 0.0061%. The majority of the Sc in the Sc concentrate originates from augite, hornblende, and aluminosilicate. Magnesium chloride and the Sc concentrate were placed in a roasting furnace for chloridizing roasting, causing the partial chlorination of Sc to ScCl3. Sc was extracted from the roasted ore using hydrochloric acid leaching. Sc extraction indices demonstrated 95.12% Sc2O3 leaching efficiency and 0.0011% Sc2O3 content in the acid leaching residue, clearly indicating the extraction of Sc. No noticeable peak of Sc was observed in the spectrum of the acid leaching residue. Most of the Sc in the roasted ores was dissolved as Sc3+, and it entered the liquid phase. The main minerals in the acid leaching residue were Mg2SiO4, CaTiO3, and Fe2SiO4.

Sustainable Utilization of GCP Sludge as a Reductant in the Reduction Roasting of Low-Grade Manganese Ore to Recover Mn and Fe Values

Sustainable Utilization of GCP Sludge as a Reductant in the Reduction Roasting of Low-Grade Manganese Ore to Recover Mn and Fe Values

Experimental study of historical processing of cobalt arsenide ore for colouring glazes (15-16th century Europe)

Cobalt was used since the early antiquity to tinge glass and glazes in blue. The presence of arsenic in blue decorated glazes since ~1500 onwards and absence beforehand, observed in Europe, might be related to the processing of the ore: roasting of the cobalt mineral (saffre) and obtaining a glass adding sand and potash (smalt) or as by-product of other metallurgical processes, e.g. silver smelting slag. We have replicated the roasting of cobalt arsenide ore (CoAs3) and the processing of silver smelting as described in historical treatises following the transformations by in situ variable temperature SR-XRD, PIXE and SEM. Our laboratory tests have proved that roasting cobalt arsenide ore either alone or mixed with fluxes (PbO, CaF2), CaCO3, SiO2 and kaolinite was unable to remove the arsenic completely. Roasting cobalt arsenide ore (saffre) alone explains the presence of arsenic in the cobalt blue glasses and glazes after 1520. The product obtained as described by Agricola contains less arsenic forming calcium arsenates, lead arsenates (Pb5(AsO4)3F, Pb8As2O13) and calcium lead arsenates (Ca,Pb)5(AsO4)3(F,Cl,OH) with an hedyphane structure, while cobalt is incorporated into a glassy matrix. As the physical separation of the arsenic free cobalt vitreous phase does not seem possible, these processes can explain the variable content of arsenic shown by the historical blue glazes but not the arsenic free glazes. In this case, the use of an arsenic free cobalt ore such as linnaeite is the most likely source.

Reduction roasting and bioleaching of a limonite ore

Two of the main challenges presented by the implementation of nickel laterites atmospheric acid leaching are: (i) high acid consumption and (ii) high final iron concentrations in the PLS. In the current work, a novel process was devised by applying pyrometallurgical and bio-hydrometallurgical operations. The experimental set-up comprised the reduction of a nickel limonitic ore with hydrogen gas in a rotary kiln, at 900 °C, until all the goethite was converted to metallic iron. Subsequently, the reduced sample was bioleached by mesophilic microorganisms grown on Fe2+ (Acidithiobacillus ferrooxidans) at 5% solids, 32 °C, and pH < 3. The results showed that an increase in the Eh values, promoted by the bacteria, resulted in the leaching Fe, Ni and Co, therefore a dissolution of 92% of the nickel and 35% of the cobalt was observed in experiments carried out with 35 Kg H2SO4/(ton of the reduced ore). The iron concentration in the liquor generated under these experimental conditions was below 5 mg/L owing to the fact that Fe3+ precipitated as jarosite. The experimental conditions applied also resulted in low acid consumption and the final total iron concentration was also reduced in the leach liquor (< 200 mg/L), which were considerably lower than the values reported for the HPAL process.

Definition of conditions of selective iron reduction from iron-manganese ore

The article presents thermodynamic modeling results of reduction roasting of ferromanganese ore with a high phosphorus content in the presence of solid carbon. The modeling was carried out using TERRA software package. Influence of the process temperature in the range 950 – 1300 K and carbon content in the amount of 8.50 – 8.85 g per 100 g of ore on reduction of iron, manganese and phosphorus was investigated. With these parameters of the system, iron is reduced by both solid carbon and carbon monoxide CO to the metallic state, and manganese is reduced only to MnO oxide. The degree of phosphorus reduction depends on the amount of reducing agent. With an excess of carbon relative to the reduction of iron, all phosphorus is converted into metal at a temperature of 1150 K. Phosphorus is not reduced at temperatures below 1150 K and such amount of carbon. The process of solid-phase reduction of iron from manganese ore with the preservation of manganese in the oxide phase was researched in laboratory conditions. Experimental results of direct reduction of these elements with carbon and indirect reduction with carbon monoxide CO are presented. The experiments were carried out in the laboratory Tamman furnace at a temperature of 1000 – 1300 °C and holding time of 1 and 3 hours. Results of the research of phase composition of the reduction products, as well as chemical composition of the phases are considered. The possibility of selective solid-phase reduction of iron with solid carbon to the metallic state was confirmed. Iron in the studied conditions is reduced by carbon monoxide CO and passes into magnetic part. During the magnetic separation of the products of ore reduction roasting with solid carbon and carbon monoxide CO, the non-magnetic part contains oxides of manganese, silicon and calcium. The work results can be used in development of theoretical and technological foundations for the processing of ferromanganese ores, which are not processed by existing technologies.

A Comparison of Direct Concentrating Solar Thermal Treatment of Manganese Ores to Fossil Fuel Based Thermal Treatments

In South Africa, the world’s largest land-based manganese reserves occur in an area coincident with high annual solar irradiance. The use of direct concentrating solar thermal treatment, as opposed to fossil fuel based thermal treatment, reduces the CO2 emissions associated with thermal treatment of manganese ores greatly and could open new processing opportunities when scaled up. The application of direct concentrating solar thermal treatment of manganese ores is compared to other thermal treatment methods. The evaluation is based on the results of exploratory on-sun experiments conducted in 2019. Pellets prepared from manganese ores, bentonite binder and charcoal were treated with concentrating solar radiation. The solar treated samples were analyzed to determine changes to their mineralogy with X-ray diffraction and scanning electron microscopy. In addition, the solar treated pellets were tested to determine their compressive strength. The pellets did not pass the strength requirement of 500 N/pellet to qualify as feed for submerged arc furnaces. Results from these experiments were then further compared with other thermal treatments of manganese ores such as calcination, nodulizing, pelletizing, sintering and reductive roasting to evaluate the feasibility of applying concentrating solar thermal treatment in these treatment options. The direct concentrating solar thermal treatment was found to strengthen manganese pellets sufficiently to be considered dried and preheated for pelletizing but not cured. Temperatures were achieved suitable for calcination or reductive roasting of manganese ores, where agglomeration is not required.

Technical and Economical Substantiation of the Technology of Joint Pyrometallurgical Processing of Oxidized Nickel Ores and Sulfide Copper Ores

The technological scheme of processing of nickel and copper ores from the Urals deposits is substantiated, including calcination of oxidized nickel ore with limestone, partial oxidative roasting of sulfide copper ore, blending of calcines with coke, and melting of charge to obtain copper-nickel matte. The implementation of the scheme will increase the complexity of possible uses of raw materials and ensure a high environmental protection level. A feasibility study was carried out for the organization of industrial enterprise, which entailed the joint processing of oxidized nickel ores and sulfide copper ores with a capacity of 700,000 tons per year of a mixture of initial ores, including 400,000 tonnes of nickel ore and 300,000 tonnes of copper ore (dry weight). Finished products are: copper-nickel matte, containing not less than, wt.%: 3.3 Cu, 4.7 Ni, 0.6 Co, 1.5 g/t Au, 2.6 g/t Ag; granular slag containing, wt.%: 0.01–0.02 Ni, 0.01–0.02 Cu, 0.01–0.06 Co, 13–16 Fe, 44–50 SiO2, 13–14 MgO, 4–5 Al 2O3, 9–11 CaO; and technical grade sulfuric acid (mass fraction of monohydrate not less than 92.5 %). The planned enterprise is expected to produce the following annual volumes of finished products (not less than): 94,900 tonnes of matte; 512,300 tonnes of granular slag; and 235,500 tonnes of technical grade sulfuric acid. The estimated period of project implementation is 13 years. The total amount of investment costs is 1407 million roubles, current costs for the annual production program are 3820 million roubles. The financial results of the investment project are characterized by the following indicators: net profit is 5,735.5 million roubles, net discounted income is 1546.6 million roubles, the profitability index of discounted investments is 2.1, the internal rate of return is 36.4 %, and the discounted payback period is 5.5 years. The results indicate the viability and economic efficiency of the project.&#x0D; Keywords: ore, processing, sulfides, oxides, copper, nickel, cobalt, smelting, extraction, products, economy, indicators, efficiency

A sustainable reduction roasting technology to upgrade the ferruginous manganese ores

Reduction roasting of manganese ores is a known process; however, it is not yet commercialized mainly due to various techno-economic issues. The current research work presents results of a large-scale plant trial performed at a commercial Direct Reduced Iron making plant to upgrade low-grade ferruginous manganese ores (Mn: 25–32%, Mn/Fe: ∼1). Trials were carried out using a lot of 2000 of tons low grades ferruginous manganese ores of three different types. Experiments were designed to test 3 levels of two different variables for each type of ore. Raw material feed rate (3, 4.5, and 6tph) and feed coal proportion (25, 29,33% of ore) were the prime process variables. Process settings were identified and fixed to limit the occurrence of undesired chemical reactions to restrict the formation of complex MnxFe3-xO4 phases and dilution of reducing atmosphere. Ores were crushed into 0–15 mm size, reduce-roasted at 950 °C in a rotary kiln, crushed into <3 mm size, and passed through a magnetic separator. The technology can enhance the Mn content of the ores by > 15 units (Mn: 30%→46%) and can bring down the Fe content by > 15 units (Fe: 27%→12%) in the produced ore concentrate. The developed process could achieve product yield ∼50% and Mn Recovery>70%. The Mn-rich concentrate was successfully converted into extrusion briquettes and consumed in a submerged arc furnace for ferroalloy making. The iron-rich by-product was successfully used as a sinter mix for steelmaking process. Techno-economic evaluation and sensitivity analysis have also been carried out. Studies indicated that roasting of ferruginous manganese ores at a commercial Direct Reduced Iron plant is an adaptable and sustainable solution to upgrade the low-grade Mn resources in the dynamic global Mn ore market.

Effect of Thermal Oxidation Pretreatment on the Magnetization Roasting and Separation of Refractory Iron Ore

ABSTRACT The effect of thermal oxidization pretreatment (TOP) on the magnetization roasting and separation of refractory iron ore was investigated. The TOP of raw samples was performed in a muffle furnace at 750°C for 30 min. The magnetization roasting and separation experiments of the raw samples and TOP samples were performed, which revealed that TOP could decrease the optimal CO concentration required during the magnetization roasting process by 10% and increase the iron recovery by about 10%. Analysis results of X-ray diffraction (XRD), scanning electron microscope (SEM) and vibrating sample magnetometer (VSM) showed that there were many pores and cracks in the TOP samples, which were advantageous to the subsequent magnetization roasting, and promoted the sufficient conversion of specularite and siderite to magnetite, increasing the iron recovery significantly.

Nonoxidative Microwave Radiation Roasting of Bastnasite Concentrate and Kinetics of Hydrochloric Acid Leaching Process.

Herein, a new clean extraction technology for the decomposition of bastnasite concentrate by utilizing the microwave radiation is proposed, which prevented Ce(III) from being oxidized to its tetravalent form. The process includes microwave radiation roasting to nonoxidatively decompose the bastnasite concentrate, mechanism analysis of Ce(III) not being oxidized to Ce(IV), hydrochloric acid leaching of the nonoxidative roasted ore, and kinetics analysis of the leaching process. The experiments were carried out concentrating on the effect of roasting temperature and holding time on the decomposition rate of the bastnasite concentrate and the oxidation rate of cerium and the effect of acidity, liquid–solid ratio, leaching temperature, and stirring rate on the leaching kinetics of the nonoxidative roasting ore. When the roasting temperature is 1100 °C, the holding time is 20 min, and the m(C)/m(REFCO3) ratio is 0.2, the results show that the leaching efficiency of rare earths can reach 85.45% under the conditions 3 mol/L HCl, 90 °C, 60 min, 9 mL/g liquid–solid ratio, and 300 rpm stirring rate. The X-ray diffraction and scanning electron microscopy analyses of the samples before and after acid leaching show that the rare earth oxides were completely leached and Ce(III) was not oxidized to its tetravalent form. The apparent activation energies of leaching rare earths were calculated as 14.326 kJ/mol, and the HCl leaching process can be described by a new variant of the shrinking-core model, in which both the interfacial transfer and the diffusion through the product layer influenced the reaction rate. Furthermore, a semiempirical rate equation was created to describe the leaching process of the nonoxidative roasted ore.

Selective reduction of iron and phosphorus from oolitic ore

Possibility of selective solid-phase reduction of iron from oolitic ore has been experimentally confirmed. Solid phase reduction was carried out at temperatures of 850 and 1000 °C in CO atmosphere and in the mixture with solid carbon. Distribution of iron and phosphorus was investigated with scanning electron microscope. It was found that at temperature of 1000 °C minimum amount of phosphorus (up to 0.3 %) is transformed into the metallic phase at reduction by carbon monoxide. Upon reduction in mixture of ore with carbon, phosphorus content in metal phase reaches 1.0 – 1.3 % evenat temperature of 850 °C. Thermodynamic modeling of the processes occurring during reductive roasting of oolitic ore was carried out depending on temperature (1000 – 1400 K) and amount of carbon in the system. It is shown that reduction temperature and degree of phosphorus reduction vary depending on ratio of CO and CO2 in the gas phase. At temperatures below 892 °C, phosphorus is not reduced and all iron is in metal phase. With an increase in amount of carbon in the system, phosphorus appears in metal phase. With an excess of carbon in the system, all phosphorus is in metal phase at temperature of 892 °С. Thus, with a certain amount of carbon in the system and, correspondingly, with a certain ratio of CO and CO2 in gas phase, selective reduction of iron is possible without phosphorus reduction even at temperature of 1100 °С. Comparison of experimental results with results of thermodynamic calculation confirms possibility of se selective reduction of iron without phosphorus reduction only by carbon monoxide.

Pelletization of synthesized magnetite concentrate obtained by magnetization roasting of Indian low-grade BHQ iron ore

In India, the use of iron ore pellets in the blast furnace, electric arc furnace, or sponge iron production is continuously optimized, considering different aspects of the production chain from the run of mining (ROM) to metallic iron depending upon the industrial need and ore availability (recent aggressive iron ore mining auction 2020 in India). The scarcity of high-grade iron ore resource and availability of the considerable quantity of low-grade iron ore fines, banded hematite quartzite (BHQ) ore in mines (mostly in Bihar, Odisha, Madhya Pradesh, and Karnataka), has to lead the way to beneficiate and utilize the concentrate as pellet feed for the steelmaking process. Banded iron ore such as BHQ is one of the potential resources of iron having a total iron content, i.e., Fe (T) of 35–48 wt%, which is lying unutilized in most of the Indian iron ore mines. The challenge before the policymakers and researchers is to think of a sustainable process technology to utilize these iron ore resources wisely. The conventional beneficiation of this type of siliceous BHQ iron ore resource having low iron content is not advisable. Therefore, pelletization of synthesized magnetite concentrate obtained from the magnetization roasting of BHQ emerged as an alternative energy-saving and ore conserving process that may be scaled up and commercialized for low-grade banded iron ores. The pelletization of magnetite concentrate is an independent heat hardening process; thereby requirement of anthracite coal fines as a fossil fuel additive to maintain the temperature gradient from core to the periphery of the pellet can be avoided. Physical properties such as cold crushing strength (CCS) and porosity of the pellets were optimized to study their suitability in the steelmaking process. In this regard, characterization studies of the pellets were performed using X-ray diffraction (XRD), scanning electron microscope (SEM), optical microscope, and X-ray micro-computed tomography to understand the microstructural properties of the pellets. The CCS of 255.8 kg/pellet and porosity of 25.42% were achieved at the optimized induration temperature and residence time of 1250 °C (50 °C to 80 °C less than conventional hematite pellet induration) and 10 min, respectively. The properties studied are encouraging and comparable with the pellet prepared from the natural magnetite/hematite ore.

Selective Reduction of Iron and Phosphorus from Oolitic Ore

The possibility of selective solid-phase reduction of iron from oolitic ore has been experimentally confirmed. Solid phase reduction was carried out at temperatures of 850 and 1000°C in a CO atmosphere and in a mixture with solid carbon. Distribution of iron and phosphorus was investigated with a scanning electron microscope. It was found that at a temperature of 1000°C a minimum amount of phosphorus (up to 0.3%) is transformed into the metallic phase upon reduction with carbon monoxide. Upon reduction in a mixture of ore with carbon, the phosphorus content in the metal phase reaches 1.0–1.3% even at a temperature of 850°C. Thermodynamic modeling of the processes occurring during reductive roasting of oolitic ore was carried out depending on temperature (1000–1400 K) and amount of carbon in the system. It is shown that reduction temperature and degree of phosphorus reduction vary depending on the ratio of CO and CO2 in the gas phase. At temperatures below 892°C, phosphorus is not reduced, and all iron is in the metal phase. With an increase in the amount of carbon in the system, phosphorus appears in the metal phase. With an excess of carbon in the system, all phosphorus is in the metal phase at a temperature of 892°С. Thus, with a certain amount of carbon in the system and, correspondingly, with a certain ratio of CO and CO2 in the gas phase, selective reduction of iron is possible without phosphorus reduction even at a temperature of 1100°С. Comparison of experimental results with results of thermodynamic calculation confirms the possibility of selective reduction of iron without phosphorus reduction only by carbon monoxide.

Pyrolysis behavior of a green and clean reductant for suspension magnetization roasting

The use of siderite as a green and clean reductant for the suspension magnetization roasting of refractory iron ores was proposed. In this study, the behavior of siderite, which was pyrolyzed into magnetite and CO, was investigated using chemical analysis, vibrating sample magnetometer, X-ray diffractometry, Mössbauer spectroscopy, scanning electron microscopy, and gas composition analyzer. The roasted product, which contained 15.88% CO and presented a saturation magnetization of 57.10 A m2/kg was obtained at the roasting temperature of 620 °C and the roasting time of 10 min. The pores and cracks of the particles developed gradually and their sizes increased continuously, which rendered the structure of the particles loose and led to a decrease in the amount of energy required for grinding. Approximately half of the amount of FeO, produced via the pyrolysis of siderite was oxidized to magnetite using CO2, and the content of residual FeO in the roasted product was 18.5% by the volume. Particularly, the complete reaction of the roasted product with CO2 increased the saturation magnetization of the product by 16.44%, from 57.07 A m2/kg for the initial roasted product to 66.45 A m2/kg for the final roasted product, and also generated a certain amount of CO. Our study demonstrated that the traditional magnetization roasting of single siderite greatly wasted a large amount of natural reductant (CO). This innovative use of siderite could improve the quality of the roasting products and reduce the consumption of fossil fuels and CO2 emissions.