High Phosphorus Oolitic Hematite Research Articles

Red mud as a green dephosphorization agent: Co-reduction with high phosphorus oolitic hematite for iron extraction and dephosphorization

The large utilization of red mud (RM) presents many challenges due to its high alkalinity, which is attributed to the presence of CaO and Na2O. High phosphorus oolitic hematite (HPOH) is a typical refractory ore for Fe and P separation. During the direct reduction of HPOH to produce direct reduced iron (DRI) and achieve simultaneous dephosphorization, sodium or calcium salts are typically added as dephosphorization agents. This study investigated the feasibility of using RM as a green dephosphorization agent. Co-reduction of RM with HPOH was conducted to prepare DRI. By adding 60 % RM and using a reductant dosage of 17 %, a DRI with 90.89 % Fe and 0.095 % P was obtained. The corresponding total iron recovery was 87.79 %. This indicated that the addition of RM facilitated effective simultaneous iron extraction and dephosphorization. The co-reduction mechanisms were analyzed using X-ray diffraction (XRD), thermodynamic analysis, and scanning electron microscopy combined with energy dispersive spectroscopy (SEM–EDS). In the absence of RM, the reduction of fluoroapatite occured, leading to the incorporation of P into metallic iron. However, with adding RM, albite and anorthite were generated, hindering the reduction behavior of fluoroapatite and reducing P content in DRI. Thus, RM effectively served as a green dephosphorization agent in the co-reduction process.

Dephosphorization study on hydrogen reduction-melting separation of high-phosphorus oolitic hematite

In order to clarify the dephosphorization mechanism of DRI (Direct Reduced Iron) derived from hydrogen reduced high-phosphorus iron ore during the electric arc furnace melting process, slag was prepared using reagent-grade powder based on the gangue mineral composition of high-phosphorus oolitic hematite. By incorporating varying amounts of CaO, FeOx, and reduced iron powder, experiments simulating the dephosphorization of melting separation slag from DRI with different basicity and metallization rates were conducted at 1873 K. The results show that phosphorus in the iron primarily exists in the form of Fe–P–O spherical slag inclusions and FexP, while in the slag, phosphorus mainly resides within the silicate phases. As the amount of CaO added increases, there is a significant decrease in the phosphorus content within the slag inclusions, and the P-containing compounds in the iron gradually shift from FexP and Fe3(PO4)2 to FeO. As the dephosphorization capacity of the slag increases, the distribution of phosphorus-rich phases in the rapidly cooled slag becomes more extensive. When the basicity increases to 3, the phosphorus-rich phases in the slag transition to 2CaO·SiO2 and 3CaO·SiO2. When the basicity is fixed at 2.5, regulating the metallization rate can control the FeOx content in the molten slag, thereby enhancing the dephosphorization ability of slag. The results show that under conditions of a DRI basicity of 2.5 and a metallization rate of 85%, slag/metal separation can produce low-phosphorus iron with 0.022 wt% P, achieving a dephosphorization rate exceeding 95%.

Effect of Na<sub>2</sub>CO<sub>3</sub> and CaCO<sub>3</sub> on deep dephosphorization by the direct reduction of high-phosphorus oolitic hematite

The direct reduction–magnetic separation process based on coal is considered to be one of the most important methods that can effectively utilize high-phosphorus oolitic hematite. In this study, the mechanism of the effects of CaCO<sub>3</sub> and Na<sub>2</sub>CO<sub>3</sub> on the dephosphorization of high-phosphorus oolitic hematite during the direct reduction process was investigated using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results showed that Na2CO3 and CaCO3 reacted with Al<sub>2</sub>O<sub>3</sub> and SiO<sub>2</sub> during the direct reduction process, inhibited the generation of hercunite (FeAl<sub>2</sub>O<sub>4</sub>) and fayalite (Fe<sub>2</sub>SiO<sub>4</sub>), and promoted the reduction of metallic iron (Fe). Furthermore, the reaction inhibited the reduction of apatite and prevented the generation of FeP<sub>2</sub>. Na<sub>2</sub>CO<sub>3</sub> could change the form of phosphorus in the gangue from Ca<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub> to Na<sub>2</sub>Ca<sub>4</sub>(PO<sub>4</sub>)<sub>2</sub>SiO<sub>4</sub>. Increasing the dosages of Na2CO3 and CaCO3 in the dephosphorization agent and increasing the content of Na<sub>2</sub>CO<sub>3</sub> in the dephosphorization agent were beneficial to the growth of metallic iron particles, and increasing the dosage of Na<sub>2</sub>CO<sub>3</sub>, CaCO<sub>3</sub> in the dephosphorization agent had more significant effects on metallic iron particles than increasing the content of Na<sub>2</sub>CO<sub>3</sub> in the dephosphorization agent. The research conducted in this study is expected to provide a basis for the effective exploitation of complex and refractory iron ores.

Calcium Carbonate as Dephosphorization Agent in Direct Reduction Roasting of High-Phosphorus Oolitic Iron Ore: Reaction Behavior, Iron Recovery, and Dephosphorization Mechanism

Calcium carbonate, renowned for its affordability and potent dephosphorization capabilities, finds widespread use as a dephosphorization agent in the direct reduction roasting of high-phosphorus oolitic hematite (HPOIO). However, its precise impact on iron recovery and the dephosphorization of iron minerals with phosphorus within HPOIO, particularly the mineral transformation rule and dephosphorization mechanism, remains inadequately understood. This study delves into the nuanced effects of calcium carbonate on iron recovery and dephosphorization through direct reduction roasting and magnetic separation. A direct reduction iron (DRI) boasting 95.57% iron content, 93.94% iron recovery, 0.08% phosphorus content, and an impressive 92.08% dephosphorization is achieved. This study underscores how the addition of calcium carbonate facilitates the generation of apatite from phosphorus in iron minerals and catalyzes the formation of gehlenite by reacting with silicon dioxide and alumina, inhibiting apatite reduction. Furthermore, it increases the liquid phase, enhancing the dissociation of metallic iron monomers during the grinding procedure, thus facilitating efficient dephosphorization.

In-Situ Investigation of Phosphorus Transformation and Distribution During Gas-Based Reduction of High-Phosphorus Oolitic Hematite

In-Situ Investigation of Phosphorus Transformation and Distribution During Gas-Based Reduction of High-Phosphorus Oolitic Hematite

Direct Reduction of High-Phosphorus Oolitic Hematite: Quantifying Phosphorus Migration and Recovery

Direct Reduction of High-Phosphorus Oolitic Hematite: Quantifying Phosphorus Migration and Recovery

Iron recovery and dephosphorization behaviors from high-phosphorus oolitic hematite by gas-based direct reduction and magnetic separation

Iron recovery and dephosphorization behaviors from high-phosphorus oolitic hematite by gas-based direct reduction and magnetic separation

Mechanistic insight into phosphorus migration pathways from oolitic hematite using in-situ observations during roasting and reduction process

Oolitic hematite is a promising alternative resource, in facing the iron ore downgrading. As oolitic hematite is often rich in phosphorus, an efficient separation of iron and phosphorus is necessary, in terms of utilizing both elements. Therefore, a close insight into the transformation of phosphorus-bearing minerals in the unique oolitic structure during the reduction process is important. To capture the real-time transformation of the apatite ring in the oolitic structure, in-situ observations under roasting, and CO/carbon reducing conditions were adopted by high-temperature confocal laser scanning microscopy. The results indicated that the apatite ring was transformed by four stages during the roasting process from 25 °C to 1400 °C: stabilization, defluorination, partial melting, and complete melting, which was: Ca5(PO4)3F → Ca3(PO4)2 → Ca3(PO4)2 + P2O5 liquid → P2O5 liquid. Under the CO reduction, the partial reduction of the phosphate at 1400 °C generated a Fe-Plow alloy. While the carbon reduction promoted iron phase absorption of phosphorus, forming Fe-Phigh alloy at 1400 °C. In addition, interfacial phenomena between apatite and slag melt were observed, and the dissolution of apatite (Ca/P molar ratio) into the slag melt was affected by the Fe/(Al + Si) molar ratio of the slag. Finally, using inverse error function methods, the diffusion coefficients of P and Ca increased significantly from the roasting to CO reduction and then to carbon reduction. These findings can benefit to understand phosphorus migration mechanisms, improving effective dephosphorization strategies for high-phosphorus oolitic hematite.

Research on efficient utilization of high-phosphorus oolitic hematite for iron enrichment and dephosphorization by hydrogen mineral phase transformation

Research on efficient utilization of high-phosphorus oolitic hematite for iron enrichment and dephosphorization by hydrogen mineral phase transformation

An innovative study for pretreatment of high-phosphorus oolitic hematite via high-temperature heating: phase, microstructure, and phosphorus distribution analyses

To investigate the effects of heating pretreatment on the distribution of phosphorus elements, phase transformation, and microstructure evolution mechanisms of high-phosphorus oolitic hematite (HPOH), particularly from the Tindouf regions of Algeria, several analyses, including HSC Chemistry software, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Image-Pro Plus software, specific surface area, pore size distribution (BJH), and N2 adsorption–desorption isotherms. The results show that the conventional heating pretreatment has a significant effect on the phase and microstructure of HPOH. Cracks appeared within mineral phases and around the interphase boundaries owing to the co-promotion of different thermal expansions of minerals and dehydration and chemical reactions via the heating treatment of ore samples. As the pretreatment temperature increased within the studied range, increases in crack perimeter (from 8.062 to 87.236 μm), percentage of crack area (from 0.135 to 7.988 %), and BJH desorption average pore diameter (from 6.1788 to 23.4384 nm) were observed. The specific surface area and pore volume decreased from 23.2054 to 1.0661 m2/g and 0.0237 to 0.0017 cm3/g, respectively. In addition, the distribution of phosphorus did not change or repartition during the heating pretreatment period in the mineral phases.

Effect of Raw Material Particle Size on the Direct Reduction Process of High-Phosphorus Oolitic Hematite

Effect of Raw Material Particle Size on the Direct Reduction Process of High-Phosphorus Oolitic Hematite

A New Route to Upgrading the High-Phosphorus Oolitic Hematite Ore by Sodium Magnetization Roasting-Magnetic Separation-Acid and Alkaline Leaching Process

In this paper, an innovative method is proposed to upgrade iron and remove phosphorus from high-phosphorus oolitic hematite ore by the sodium magnetization roasting–magnetic separation–sulfuric acid and sodium hydroxide leaching process. The process parameters of sodium magnetization roasting, acid leaching, and alkaline leaching were optimized. The results show that by only adopting traditional magnetization roasting–magnetic separation, an iron ore concentrate containing 57.49% Fe and 1.4% P2O5 at an iron recovery rate of 87.5% and a dephosphorization rate of 34.27% was produced, indicating that it is difficult to effectively dephosphorize and upgrade iron by the conventional magnetization roasting–magnetic separation process. The obtained rough magnetic concentrates were then subjected to acid and alkaline leaching steps, and the final product, assayed at 64.11% iron and 0.097% P2O5, was manufactured successfully. Moreover, the added NaOH could promote the mineral phase reconstruction of aluminum- and silica-bearing minerals during magnetization roasting and intensify the upgrading of iron as well as enhance the growth of iron grains.

Synchronous enrichment of phosphorus and iron from a high-phosphorus oolitic hematite ore to prepare Fe-P alloy by direct reduction-magnetic separation process

Synchronous enrichment of phosphorus and iron from a high-phosphorus oolitic hematite ore to prepare Fe-P alloy by direct reduction-magnetic separation process

An alternative and clean utilisation of refractory high-phosphorus oolitic hematite: P for crop fertiliser and Fe for ferrite ceramic

High-P oolitic hematite is recognised as one of the most refractory mineral resources because of the special oolitic structure. Conventional selective reduction roasting is characterised by high energy consumption and large greenhouse gas emissions. In this study, a clean utilisation of refractory high-P oolitic hematite via phase reconstruction was proposed to make the P for crop fertiliser and Fe for ferrite ceramic. Phase reconstruction indicated that the oolitic and finely disseminated structure was dramatically changed by the oxidisation roasting with Mn ore at 1100°C–1250 °C. After reconstruction, 85 wt%–90 wt% Fe and Mn were concentrated in the magnetic ferrite phase whilst 90 wt%–100 wt% P, K, Ca, Si, Mg, and Al impurities were enriched in the nonmagnetic P-bearing tailings. After separation, the separated Mn ferrite and P-bearing tailings after activation could be used as ingredients in ceramic and fertiliser production. The as-purified ferrite showed good electromagnetism performance whilst almost all nutrients in the P-bearing tailings were activated via high-temperature melting and water quenching and can thus be readily absorbed by the crop roots. Moreover, the phase reconstruction mechanism and feasible granular fertiliser preparation from P-bearing tailings were discussed. All elements in the high-P oolitic hematite were utilised without emission of greenhouse gases.

Reaction Characteristics and Existing Form of Phosphorus during Coal-Based Reduction of Oolitic Iron Ore

It is particularly significant to investigate the reduction behavior and existing form of phosphorus in metal and slag phase during coal-based reduction for the efficient development and utilization of high-phosphorus oolitic hematite. The reduction behavior of phosphorus minerals and their existing form in the metal and slag phase during the coal-based reduction of high phosphorus oolitic hematite were systematically investigated using HSC software simulation, thermodynamic calculation, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectrometry (EDS). The results show that after Fe2O3 was reduced to metal iron, the reduction of apatite was promoted by providing the most inclined enrichment site of phosphorus (metallographic phase). Phosphorus existed mainly in two forms in the metal phase—one was in the form of Fe3P compound at the boundary of the metal phase, and the other was in the form of solid solution in the metal iron. There were two forms of phosphorus in the slag phase—one was incompletely reacted apatite, and the other was formed as CaO–SiO2–P2O5 solid solution. In the early stage of coal-based reduction, phosphorus in the slag phase mainly existed in the form of apatite, while in the later stage, it mainly existed in the form of CaO–SiO2–P2O5 solid solution.

Strengthening iron enrichment and dephosphorization of high-phosphorus oolitic hematite using high-temperature pretreatment

The efficient development and utilization of high-phosphorus oolitic hematite is of great strategic significance for the sustainable supply of iron-ore resources in China. In this paper, the mechanism of high-temperature pretreatment for enhancing the effect of iron enrichment and dephosphorization in the magnetization roasting-leaching process was studied by X-ray diffraction (XRD), vibration sample magnetometer (VSM), scanning electron microscopy and energy dispersive spectrometry (SEM-EDS). Compared with the process without high-temperature pretreatment, the iron grade of the magnetic separation concentrate after high-temperature pretreatment had increased by 0.98%, iron recovery rate had increased by 1.33%, and the phosphorus content in the leached residue had decreased by 0.12%. High-temperature pretreatment resulted in the dehydration and decomposition of hydroxyapatite, the dehydration of limonite and the thermal decomposition of siderite, which can produce pores and cracks and weaken the compactness of the ore, improve the magnetization characteristics of roasted ore, and strengthen the iron enrichment and dephosphorization during the magnetization roasting and leaching process.

Effect of Different Additives on Reaction Characteristics of Fluorapatite During Coal-Based Reduction of Iron Ore

In the coal-based reduction of high phosphorus oolitic hematite, it is particularly important to study the mechanism of phosphorus regulation during the formation of iron metals for the efficient development and utilization of iron ore. In this study, the thermodynamics of the coal-based reduction process of fluorapatite in different mineral systems, effect mechanism of the reduction degree, kinetics, mineral composition, and morphology of structural evolution samples were systematically investigated using FactSage software, single factor analysis, the isothermal method, X-ray diffraction (XRD), scanning electron microscope (SEM), and an energy dispersive spectrometer (EDS). Thermodynamic analysis indicates that the effect of the SiO2–Fe2O3–C system on reducing the initial reduction temperature of fluorapatite was stronger than that of the Al2O3–Fe2O3–C system. The effect mechanism of the reduction degree demonstrates that increasing the dosage of silica, iron oxide, carbon, reduction time, and reduction temperature could promote the reduction reaction of fluorapatite under certain conditions. Dynamics analysis shows that the best kinetic mechanism functions of the SiO2–Fe2O3–C system and the Al2O3–Fe2O3–C system were A1/3 = 1/3(1 − α)[−ln(1 − α)]−2 and A1/2 = 1/2(1 − α)[−ln(1 − α)]−1, respectively. The activation energy and pre-exponential factor of the reduction kinetics equation in the system containing silica were significantly lower than that in the system containing alumina, which explained that the catalytic effect of silica on the reduction of calcium fluorophosphate was far greater than that of alumina. XRD and SEM/EDS analysis indicate that the solid–solid reaction of alumina, silica, iron, and fluorapatite occurred during the reduction process, while calcium aluminate, calcium silicate, and calcium oxide were formed at the contact point. Among them, iron could absorb P2 gas so that it played a greater role in promoting the reduction of fluorapatite. Increasing the reduction temperature and prolonging the reduction time were beneficial to the reduction of fluorapatite.

Enhance the carbothermic reduction of high phosphorus oolitic hematite with borax

The reduction of high phosphorus oolitic hematite, especially for the accumulation and growth of iron played an important role in subsequent magnetic separation, the influence of borax on which was studied. It was indicated that the mass loss percent was up to 31.11% and the metallization ratio was up to 90.10% when the temperature was 1000 °C and the amount of borax was 6%. SEM and EDS analysis shown that borax could destroy the oolitic structure of the oolitic hematite and decrease melting point of the reduced sample. During the process of reduction, the phases of fayalite (Fe2SiO4), hercynite (FeAl2O4) and kyanite (Al2SiO5) were disappeared, and then the low melting point of sodium salt was formed. The amount and average particle size of iron metal of the reduced samples increased with the increase of borax additive.

The function of blast furnace dust as reductant on simultaneous reduction of high-phosphorus oolitic hematite

ABSTRACT A simultaneous reduction process followed by magnetic-separation is presented in this study for effective utilization of blast furnace dust and recovering of iron from blast furnace dust and high-phosphorus oolitic hematite. The function of blast furnace dust in simultaneous reduction of high-phosphorus oolitic hematite is also investigated by mole ratio, and SEM-EDS analyses. The reduction-reaction system of blast furnace dust as reductant is prone to occur direct reduction reaction, but the reduction-reaction system of coal as reductant is liable to indirect reduction reaction. Direct reduction can contribute to the improvement of iron recovery and obtain a DRI with low [% P] in the process. The P-bearing minerals were mainly distributed in fluorapatite and gangue, and adhere to metallic iron particles of briquettes when indirect reduction occupied a large proportion in the reduction-reaction system, which cannot contribute to obtain a DRI with low [% P] in the magnetic-separation process.

Recovery of Iron, Chromium, and Nickel from Pickling Sludge Using Smelting Reduction

This paper reports the recoveries of iron, chromium, and nickel from pickling sludge using coal-based smelting reduction. The influences of slag basicity (CaO/SiO2, which is controlled by high phosphorus oolitic hematite iron ores), reduction temperature, reduction time, and the C/O mole ratio on the recoveries of Fe, Cr, and Ni are investigated systematically. The experimental results show that high recoveries of Fe (98.91%), Cr (98.46%), and Ni (99.44%) are produced from pickling sludge with optimized parameters for the smelting reduction process. The optimized parameters are a slag basicity of 1.5; a reduction temperature of 1550 °C, a reduction time of 90 min, and a C/O mole ratio of 2.0. These parameters can be used as technical support for the recycling of pickling sludge with pyrometallurgy.