Magnetite Pellets Research Articles

Desulfurization Behavior of Magnetite Pellets Reduced by Isothermal Pure Hydrogen

The desulfurization behavior of magnetite pellets reduced by pure hydrogen at isothermal temperature is studied, the mechanism of self‐oxidation desulfurization is put forward, and the thermodynamic theoretical calculation and experimental verification of this mechanism are carried out. The feasibility of the reaction between iron sulfide and Fe3O4 is analyzed by HSC Chemistry 6.0 software. Additionally, a thermal gravimetric analyzer is used to further study the thermal behavior of pellet material under Ar atmosphere from 400 to 1400 K. The results show that the removal of sulfur in the isothermal reduction process of pure hydrogen does not depend on hydrogen phase diffusion and reduction temperature. During the heating process, self‐oxidation desulfurization occurs in the system, and the self‐desulfurization reaction is more inclined to Fe3O4 + FexSy → FeS + SO2. Under the experimental conditions, the temperature range of self‐oxidation desulfurization under conventional thermal field and microwave field is 700–1100 and 370–1140 K, respectively, and the desulfurization rate is 92.9% and 95.8%, respectively. The key to improving desulfurization by microwave radiation is that iron sulfide has good wave‐absorbing characteristics.

Preheating Characteristics of Magnetite Pellets Under Microwave Irradiation

Preheating Characteristics of Magnetite Pellets Under Microwave Irradiation

Experimental study on parameters optimisation of adding vanadium-titanium magnetite to iron ore pellet

Vanadium-titanium magnetite has coarse particle size, small specific surface area, poor surface hydrophilicity and low strength when being made into pellets. However, vanadium-titanium magnetite pellet also has a certain application requirement due to its large reserves and high comprehensive utilisation value. Therefore, this article investigated the effects of water ratio, bentonite ratio, vanadium-titanium magnetite ratio, CaO ratio and roasting temperature on the strength of pellets. The results showed that better parameters of green pellets were obtained as follows: the water ratio was 9%, the bentonite ratio was 2.5% and the vanadium-titanium magnetite ratio was 25%. There was no obvious relationship between the CaO ratio and green pellet strength. Better preparation parameters of roasted pellets were as follows: water ratio was 9%, bentonite ratio 2%, vanadium-titanium magnetite ratio 25%, CaO ratio 1% and roasting temperature 1300°C. This provides guidance for the effective use of vanadium-titanium magnetite.

Preparation of Oxidized Pellets of Vanadium Titanium Magnetite and Direct Reduction Behavior in Hydrogen‐Based Shaft Furnace

Herein, the optimized process parameters for the preparation of vanadium‐titanium magnetite (VTM) pellets are determined, and an efficient and green utilization technology for VTM based on the integration of oxidation roasting‐hydrogen‐based shaft furnace direct reduction is established. The results indicate that the preferable VTM oxidized and pre‐reduced pellets can be prepared by preheating at 925 °C for 18 min and roasting at 1200 °C for 25 min, followed by the reduction temperature of 1050 °C at the reduction atmosphere of 4% CO2 and H2/CO = 8. The corresponding compressive strength of the preheated and roasted pellets is 516 N per pellet and 2028 N per pellet, respectively. In addition, the LTD+6.3 and LTDUP of roasted pellets are 80.86% and 93.90%, and the corresponding reducibility index, reduction swelling index, and the reduction sticking index are 0.0428, 2.32%, and 2.50%, respectively. All of which meet the production requirements of hydrogen‐based shaft furnace.

Investigation of Basicity on Compressive Strength and Oxidation Induration Mechanism of Vanadium–Titanium Magnetite Pellets

Currently, the typical charge structure for blast furnace smelting of vanadium–titanium magnetite (VTM) is the addition of acidic pellets, high‐basicity sinters, and lumps. To increase the percentage of pellets entering the blast furnace, it is necessary to transfer the basicity burden to the pellets. In this study, the effect of basicity on the phase transition and oxidation hardening mechanism of VTM pellets is investigated. In the results, it is indicated that when the preheating temperature is 950 °C, the preheating time is 15 min, the roasting temperature is 1260 °C, and the roasting time is 15 min, with the basicity (CaO/SiO2) increasing from 0.08 to 1.3, the compressive strength of pellets shows a trend of “increasing first and then decreasing,” with the highest value reaching 3159 N pellet−1 at basicity of 0.5. As the basicity increases, calcium ferrate can be generated by CaO in the liquid phase with Fe2O3 in addition to silicate with SiO2, which will increase the amount of the liquid phase. With the increase of basicity, the oxide‐bonded induration is gradually weakened, and the slag‐bonded induration is gradually enhanced. A moderate amount of liquid phase can play the role of bonding and filling, thereby improving compressive strength.

Effect mechanism of manganese on hydrogen-based reduction behavior of magnetite pellet

In the ironmaking industry, using hydrogen energy as a reducing agent or fuel instead of fossil energy has emerged as the primary development direction in future. This study investigates the action mechanism of Mn3O4 in manganese-bearing magnetite pellets during hydrogen-based shaft furnace direct reduction (HSFDR). The findings indicated that with the increase of Mn3O4 addition, the content of MnxFe1-xO and Mn-rich silicate phases in the reduced pellets gradually increased, while the metallization rate of pellets decreased. With the augmentation of Mn-rich silicate phases, numerous metallic iron particles were wrapped by them, which resulted in the loss of clear boundaries between the metallic iron particles and the silicate phases. Concurrently, the MnxFe1-xO inhibited the growth of metallic iron whiskers, altered their growth structure, and reduced the reduction swelling index (RSI) of pellets. This study provides theoretical and practical insights into the hydrogen-based shaft furnace reduction of manganese-containing magnetite pellets.

Leaching characteristics and solidification mechanism of vanadium in preparation of titanium-containing pellets using spent SCR catalyst

The spent SCR catalysts produced from flue gas denitrification are hazardous to the environment and human health. This study proposed a harmless strategy for utilizing the spent catalysts for manufacturing magnetite pellets, in which the mechanical properties of the spent catalyst pellets and the distribution of vanadium during heating were studied. The leaching characteristics and solidification mechanism of vanadium in magnetite pellets were investigated. The results confirmed that the pellets with 10 wt% spent catalysts have mechanical properties satisfactory for application as an ironmaking feedstock. After preheating and roasting the pellets, 91.2 wt% vanadium in spent catalysts was solidified. The leaching ratio of vanadium in spent catalyst pellets was less than 1 % under different pH, liquid-to-solid ratio, and leaching time conditions. Raman, XPS, XRD, and SEM analyses confirmed that the V2O5 started to liquefy at 700 °C, and 8.8 wt% of V2O5 was volatilized into the flue gas at 700–950 °C. The remaining vanadium oxides reacted with iron oxides to form FeVO4, Fe2VO4, and FeV2O4 at 700–1250 °C, leading to its consolidation in the pellets. The treatment of spent catalysts by the pelletizing process is a new technology with the advantages of low investment cost and controllable environmental risk. This new technology could not only solve the problem of spent catalysts utilization in the iron and steel industry but also provide a reference for the treatment of spent catalysts generated from flue gas denitrification in thermal power generation, waste incineration, and other industries.

Softening-melting Properties of High-chromium Vanadium–titanium Magnetite Pellets with Different Basicity

Softening-melting Properties of High-chromium Vanadium–titanium Magnetite Pellets with Different Basicity

Effect of alumina occurrence form on metallurgical properties of hematite and magnetite pellets

Effect of alumina occurrence form on metallurgical properties of hematite and magnetite pellets

Influence of magnetite concentrate morphology on oxidation and sintering rates of pellet during induration

This study investigates the influence of the morphology of concentrate on the oxidation and sintering rates of magnetite pellets during induration and its impact on the indurated pellets' quality. Various morphologies of concentrates were obtained by ball milling (BM) and high-pressure grinding rolls (HPGR). Pelletizing and induration processes were carried out at different temperatures and times. After a comparative study of the physical characteristics of concentrate powders, the effect of morphology was evaluated through thermal behavior during induration. The physical, microstructural, and strength properties of pellets were also investigated. The HPGR concentrate had angular and elongated-shaped particles with a broad particle size distribution, while the BM particles had a more rounded morphology, and their size distribution was narrower. Results showed that BM and HPGR magnetite pellets are oxidized between 270 and 950 °C. HPGR pellets oxidize slower than BM pellets. Cold compressive strength (CCS) was increased by induration time, although porosity was reduced. HPGR pellets had less porosity than BM pellets; however, their CCS was significantly higher. For pellets indurated at 1200 °C, the difference in CCS between HPGR and BM pellets increased with an increment in the induration time and reached 80 kg/pellet in 20 min. The microstructural analysis took place on the concentrate powder and pellets fracture surface. It was found that HPGR powder sinters faster than BM powder due to its angular shape and broad particle size distribution.

Effect of TiO2 on compressive strength and microstructure of high basicity iron ore pellets

ABSTRACT High basicity (basicity 2) magnetite pellets containing TiO2(1–7%) were studied in the laboratory. Ca(OH)2 is used as a flux for the production of raw balls. The raw balls were made from laboratory-scale balls and discs, preheated at 900°C and roasted at 1220°C for 15 min. The phase composition, thermal decomposition performance, microstructure, and element distribution of preheated and roasted pellets were systematically analysed by XRD, TG, and SEM-EDS. The results show that suitable TiO2 content can promote the oxidation of magnetite, but the content should not exceed 5%. With the increase of TiO2 content, the compressive strength of preheated pellets first increases and then decreases, while the liquid content in roasted pellets decreases, while the porosity increases and the compressive strength decreases. The reason is that the formation of calcium titanate inhibits the formation of calcium ferrite liquid phase, and its continuous aggregation obstructs the crystallization of haematite, resulting in high porosity and lower compressive strength. The increased weight loss of the pellets is due to the breakdown of calcium hydroxide. According to the above experimental results, a schematic diagram of oxidation mechanism is given, which provides a theoretical basis for the study of titanium-containing pellets with high basicity.

Effect of Ce on microstructure evolution of oxide scale for CLAM steel exposed to LBE containing 10−6 wt% oxygen at 500 ℃

Lead-cooled fast reactor (LFR) is one of the six types of fourth-generation advanced nuclear reactors, and the corrosion with liquid lead-bismuth eutectic (LBE) to structural materials is regarded as a major obstacle restricting the development of LFR. This study focused on the surface morphology of oxide scale, aiming to illustrate the evolution law of oxide scale and the mechanism of Ce effect on oxide scale. China low activation martensitic (CLAM) and Ce-containing CLAM (Ce-CLAM) specimens generated roughly circular and slat-like magnetite islands respectively, but their magnetite pellets had similar growth trends from small to large sizes. Ce delayed the evolution of magnetite, enhanced the adhesion, continuity and integrity of oxide scale for Ce-CLAM specimen. The mechanism model of Ce effect on the evolution of magnetite and the scale growth model of the two kinds of specimens were proposed.

Reduction and subsequent carburization of pre-oxidation magnetite pellets

Reduction and subsequent carburization of pre-oxidation magnetite pellets

Effects of High-Oxygen-Level Process Gas (40% O<sub>2</sub>) on the Temperature and Strength Development of a Magnetite Pellet Bed during Pot Furnace Induration

Effects of High-Oxygen-Level Process Gas (40% O<sub>2</sub>) on the Temperature and Strength Development of a Magnetite Pellet Bed during Pot Furnace Induration

Phase transformation and slag evolution of vanadium–titanium magnetite pellets during softening–melting process

Blast furnace process is the main approach for utilizing vanadium–titanium magnetite (VTM) and VTM pellet is an important burden due to its excellent performance. In this paper, the softening–melting behavior of VTM pellets was investigated. The softening, melting temperature interval and permeability index were obtained as 75 °C, 181 °C and 507 kPa·°C, respectively. Ti–bearing components in pellets were transformed in the order of Fe2TiO5 → Fe3-xTixO4 → FeTiO3 → MgxTi3-xO5 and TiC. Hematite was reduced stepwise to metallic iron entering metallic fraction while most of titanium entered the slag phase. Wustite was an important component during slag evolution. The slag phase mainly consisted of spinel, silicates and wustite, in which the FeO content gradually decreased during the slag evolution process. Anosovite and silicate were the main phases in the slag fraction at the dripping temperature of 1441 °C. Titanium carbide (TiC) was also verified, which was an unfavorable product for the slag properties.

Effect of Humic Acid Binder on Oxidation Roasting of Vanadium–Titanium Magnetite Pellets via Straight-Grate Process

The oxidation roasting of vanadium–titanium magnetite (VTM) pellets with a new composite binder was investigated using a pilot-scale straight-grate. The evolution of the chemical and phase composition, the compressive strength, and the metallurgical properties of the fired VTM pellets were investigated. Under a preheating temperature of 950 ∘C, a preheating time of 18 min, a firing temperature of 1300 ∘C, and a firing time of 10 min, the compressive strength of the fired pellets was as high as 2344 N per pellet. The fired pellets mainly consisted of hematite, pseudobrookite, spinel and olivine. The total iron content of the fired pellets was 0.97% higher using 0.75 wt% humic acid (HA) binder instead of 1.5 wt% bentonite binder. These properties are beneficial for the production efficiency and energy efficiency of their subsequent use in blast furnaces. Moreover, both the softening interval and the softening melting interval of the HA binder pellets were narrower than those of the bentonite binder pellets, conducive to the smooth and successful smelting of the VTM pellets in a blast furnace.

Enhanced process route to produce magnetite pellet feed from copper tailing

The majority of copper mines generate a large quantity of tailings after their concentration processing. The flotation tailings are, in general, either piled up or stored in dams, although most copper tailings have a huge potential for by-products production leading to improve sustainability and profitability of operations. This paper describes a study aiming at producing a by-product magnetite pellet feed from IOCG (Iron oxide copper–gold) industrial copper processing tailings, located in northern Brazil. The mineralogy of copper tailings indicates around 14% of magnetite in its head composition, making its concentration of economic interest also allowing a considerable reduction in the amount of tailing disposal. The proposed route of this study is composed of hydrocyclones, low and high fields magnetic separation followed by silicates reverse cationic flotation. The complex mineralogy of IOCG deposits leads to the need for regrinding the rougher magnetite pellet feed to a P80 of 20 µm to achieve the desirable magnetite liberation. A saleable magnetite pellet feed within a high chemical quality (Fe > 64.1 wt%, SiO2 < 2.5 wt%, and Al2O3 < 2.0 wt%) and specific surface area of 2600 cm2/g was obtained. The results have shown a total mass recovery of 9.5% and 63% of magnetite recovery. Moreover, it was generated a non-magnetic rougher tailing with low magnetite and high quartz contents that might be used as a by-product as aggregated material in the construction industry and as soil remineralizer. An investigative flotation optimization is being undertaken and will be further published as a continuation of the present work.

Pelletization of hematite and synthesized magnetite concentrate from a banded hematite quartzite ore: A comparison study

A compressive pelletization study, for the utilization of an Indian Banded Hematite Quartzite ore, is presented in this communication. Iron ore concentrates have been generated utilizing the conventional beneficiation process and also by the approach of reduction roasting-magnetic separation. The Fe contents of the hematite and the synthesized magnetite concentrate were found to be 64.22 and 63.80%, respectively. The influence of different factors on the respective physical, chemical, and metallurgical properties of the fired pellets, generated through both the routes, have been compared. The pellets prepared from the synthesized magnetite attain the threshold Cold Crushing Strength (CCS) of 50 kg/pellet at a lower temperature of 1050 °C in comparison to hematite pellets (1100 °C). Also, the threshold CCS of 250 kg/pellet is attained by synthesized magnetite pellets at a lower temperature of 1250 °C compared to hematite pellets (1360 °C). The fired synthesized magnetite pellets also achieve the desired metallurgical properties i.e., Reduction Degradation Index (RDI), Reducibility Index (RI), and Swelling Index (SI) at par with the hematite pellets. Moreover, unlike the hematite pellets, the synthesized magnetite pellets do not need the addition of external carbon during the pellet making.

Evaluation of concentrated solar thermal energy for iron ore agglomeration

The iron and steelmaking industry is actively seeking to reduce its overall carbon footprint with major research and investment directed towards fossil fuel-free steelmaking. In this paper, we present a novel iron ore agglomeration process that produces a Lime Magnetite Pellet (LMP) feed using concentrated solar flux as the energy source that significantly reduces the CO2 emissions compared to existing pellet making processes. The process has been tested under laboratory experiments inside a solar simulator-electric furnace hybrid reactor setup. A detailed mass and energy balance analysis of the process was conducted for estimation of the emission reduction as well as for estimating the solar flux requirement at various percentages of fuel to solar flux substitution. The preliminary economics of the solar-based LMP process was also investigated. The estimated capital cost of a 2 Mtpa (million tonnes per annum) plant was between AU$165 M and AU$142 M assuming a solar reactor thermal efficiency of 50% and 80%, respectively. The payback period was likely to be 15–20 years (50% efficiency) and 7–9 years (80%). At current achievable reactor efficiencies, a solar-based LMP process is not economically attractive. However, with further development in reactor design, heliostat cost reductions and improvements in thermal storage performance, a solar-based LMP process could potentially be commercialised.

Influence of basicity on metallurgical performances of fired super high-grade magnetite pellets in hydrogen-rich gases

Influence of basicity on metallurgical performances of fired super high-grade magnetite pellets in hydrogen-rich gases