Roasting Of Ore Research Articles

Phase transformation assisted reduction roasting of low-grade iron ore via industrial biomass as a reductant

Phase transformation assisted reduction roasting of low-grade iron ore via industrial biomass as a reductant

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.

Micropores formation and effects in the magnetization roasting of limonite ore

As an abundant iron ore resource, limonite (mainly composed of goethite, hematite, lepidocrocite and other iron minerals) ore is seldom utilized due to its complex compositions, which has led to it lack mature processing methods. Magnetization roasting and magnetic separation is a promising method to process limonite ore. In this paper, the influence of microscopic pores on the reduction roasting of limonite ore was studied. X-ray diffraction, vibrating sample magnetometry, optical microscope, scanning electron microscopy, and the Brunauer-Emmett-Teller method of surface area analysis were used to study the dehydroxylation mechanism. The results indicated that goethite transformed into hematite, and the crystal structure of partly hematite probably changed when the dehydroxylation temperature increased from 600 °C to 1000 °C, making the sample more magnetic, the saturation magnetization increases significantly from 0.29 to 3.20 A·m2·kg−1. Simultaneously, SEM and BET showed the surface property has a big difference after roasting, more and more pores were generated with the temperature increased, then the specific surface area of the sample decreased from 75.94 to 0.59 m2·g−1. The reduction experiment results showed the dehydroxylation temperature has a significant effect on the reduction efficiency, the reduction time increased from 4 to 12.5 min with the temperature increased. This study has implications for the utilization of limonite ore using magnetization roasting technology.

A kinetic comparison between in situ hybrid microwave and conventional magnetising roasting of low-grade iron ore composite pellet

This article aims to comprehensively summarise the essential aspects of reduction kinetics in magnetising roasting of low-grade iron ore–coal composite pellets in the hybrid microwave and conventional furnace. The influence of crucial process parameters like temperature, time, and heating methods, including traditional and hybrid microwave heating, is explored. Investigating the impact of low-grade iron ore and coal quality on reduction kinetics is conducted to identify optimal heating methods for upgrading low-grade iron ore to blast furnace grade through magnetising roasting. The study uses diverse gas–solid reaction models to assess the reduction mechanism (Fe2O3 to Fe3O4). Results indicate the success of the contracting volume model for microwave heating, while conventional heating transitions from phase-boundary chemical control to diffusion control. XRD confirms magnetite dominance post-reduction, while scanning electron microscopy analysis establishes microwave crack-assisted efficiency over conventional heating for ease of reduction. A comparative study of apparent activation energy reveals the hybrid microwave method's four-fold lower (36.71 kJ/mol) than conventional resistance heating (156.19 kJ/mol). This underscores the potential of microwave heating for enhanced reduction kinetics and low-grade iron ore material processing applications.

Characterization of fluidized reduction roasting of nickel laterite ore under CO/CO2 atmosphere

Characterization of fluidized reduction roasting of nickel laterite ore under CO/CO2 atmosphere

A Study on Inert Magnetization Roasting of Low Grade BHQ Ore and its Beneficiation

A Study on Inert Magnetization Roasting of Low Grade BHQ Ore and its Beneficiation

Study on the Migration and Release of Sulfur during the Oxidizing Roasting of High-Sulfur Iron Ore

In China, most of the high-sulfur iron ores have not been fully developed and utilized due to the lack of breakthrough progress in the research on the sulfur migration and the desulfurization mechanism during the roasting process. This study will focus on revealing the release and fixation mechanisms of sulfur during the roasting process to achieve the transformation of desulfurization from terminal treatment to process control. Experimental results show that as the roasting temperature increases, the release rate of SO2 also increases, reaching the maximum release rate at 900 °C. Simultaneously, it is found that at the same roasting temperature, the release rate and amount of SO2 under the O2/N2 atmosphere is significantly greater than that under the pure N2 and air atmospheres. Meanwhile, X-ray diffraction (XRD) is utilized to explore the phase composition of the roasted product and the sulfur release mechanism. In addition, the adsorption energy, stability and electron transfer of SO2 on the CaO surface are calculated through density functional theory (DFT), and the optimal adsorption active site perpendicular to the O atom (O-top) is also determined. Finally, the sulfur fixing agent CaO is used to study the SO2 fixation mechanism. When the concentration reaches 10%, the sulfur fixation efficiency reaches more than 80%. Therefore, this work will present basic knowledge and systematic guidance for the sulfur migration and release of high-sulfur iron ore under the oxidizing roasting process.

Effect of Power and Exposure Time on the Microwave-Assisted Roasting of Refractory Gold Ore

Reserves of high-grade gold ore worldwide are decreasing, and some industries have started processing refractory gold ore. Refractory gold ore contains sulfide minerals such as pyrite (FeS2), chalcopyrite (CuFeS2), galena (PbS), and sphalerite (ZnS). Gold in refractory ores occurs as fine-size gold-bearing sulfide minerals. In this study, the microwave-assisted roasting method has been investigated as a pretreatment for a refractory gold ore. This method can provide rapid heating radiation, cause micro-cracks, and trigger the decomposition of sulfide minerals. The presence of additive helps in the oxidation of sulfide minerals. The microwave-assisted roasting was carried out using variations in microwave power and time. Microwave power between 300 - 600 watts significantly affected the increase in roasting temperature and weight loss of refractory gold ore. The highest temperature reached 567°C in roasting at 800 watts for 30 minutes. The optimum condition for microwave roasting was achieved at 400 watts of power with a roasting time of 30 minutes. Metals extraction of Cu, Zn, Pb, and Fe reached 97.2%, 82.7%, 16.1%, and 2.1% in water leaching.

Limonite deposit at the Mikniškiai settlement site (South Lithuania)

A cemented limonite deposit and sunken features recorded at the Mikniškiai settlement site (mid-1st century BC – early 3rd century AD) have been interpreted as potential signs of shallow opencast ore mining. Inhabitants of this area of Lithuania maintained close relations with the Bogaczewo culture, through which knowledge of iron metallurgy spread. However, the archaeometallurgical investigation revealed that the tested samples represent natural bog ore that was insufficiently Fe-enriched material for iron smelting. There were no attempts to increase the iron content by proper pre-processing of the ore. Moreover, the archaeological investigation revealed no traces of ore roasting and not a single piece of iron slag was found at the site. This implies that to assume the occurrence of ore-rich sediments in the vicinity of Iron Age settlements as an indication of iron bloomery might be premature and the circumstances of their discovery allow more than one alternative interpretation.

Utilization of Waste Straw Biomass in Suspension Magnetization Roasting of Refractory Iron Ore: Iron Recovery, Gas Analysis and Roasted Product Characterization

The straw-type biomass, as a green and alternative reductant for the suspension magnetization roasting (SMR) of iron ores, is proposed. The roasted products are investigated at a roasting temperature of 750 °C, the roasting time of 7.5 min and the biomass dose of 25%. The iron phase results indicate that hematite ores were reduced to magnetite by the biomass, and the magnetization transformation increased from 0.64 A·m2·g−1 to 36.93 A·m2·g−1. The iron ore microstructure evolutions of holes and fissures are detected by SEM-EDS. The biomass pyrolyzed to form CO2, CO, CH4, H2O, H2, C=O, benzene skeleton, C-Hand C-O compounds at 200–450 °C, while the mass loss of the magnetization roasting process occurred at 450–750 °C by using TG-FTIR. The GC/MS results showed that the organic gases preferred to produce the O-heterocycles at 329 °C while the hydrocarbons were dominant at the high temperature of 820 °C for the hematite ore and biomass mixture. The gas composition analysis explained that the reducing gaseous products (CO, CH4 and H2) were used as a reductant and consumed obviously by hematite ore in the SMR process. The innovative utilization of biomass waste was effective for iron recovery of hematite ore and contributes to the reduction of greenhouse gases and the protection of the environment.

Insight of Reduction Roasting of a Low-Grade Goethitic Indian Iron Ore in a Rotary Kiln: Process Optimization and Characterization

Insight of Reduction Roasting of a Low-Grade Goethitic Indian Iron Ore in a Rotary Kiln: Process Optimization and Characterization

Recovering cobalt from cobalt oxide ore using suspension roasting and magnetic separation technique

Cobalt ore is a scarce resource in China, often associated with iron ore, and it is well known that its separation and effective recovery are extremely difficult. In this paper, cobalt oxide ore is used as raw material and reduced by suspension roasting method at the atmosphere of H2. Magnetic separation is carried out to obtain cobalt (Co) and Fe concentrate. The experimental results show that the optimal magnetic separation performance of cobalt oxide ore is achieved at 650 °C and 30 % H2 concentration. The Co and Fe concentration are obtained synchronously with the grade of 7.32 % and 62.13 % respectively. X-ray diffraction (XRD) and scanning electron microscope (SEM) reveals that the phase of cobalt oxide ore in H2 roasting process is transformed into CoO→Co and Fe2O3→Fe3O4. The surface of the sample appears cracks after roasting. The vibrating sample magnetometer (VSM) test reflects the magnetic changes of minerals that the optimum roasting condition leads to an increased magnetism. The specific surface and fracture structure are analyzed to illustrate the specific surface area and pore volume of the particles decrease and the average pore size increases as the roasting temperature increases. In general, reduction roasting of cobalt ore makes it possible to recover Co and Fe simultaneously, following by magnetic separation. The beneficiation efficiency is improved along with the reduced cost.

Slags from roasting of antimony ore in the Brioude-Massiac (France) area used as aggregates: An early example of circular economy.

Towards the end of the 19th century and the early 20th century, France was the world's largest producer of antimony, especially due to the rich deposits in the Brioude-Massiac area. Even though all the mining and smelting activities are long gone, there are still some remains of those activities. The most original of those is the use of roasting slags as aggregates in former plant walls or industrial building. They are macroscopically characterised by a black or red colour with a vesicular aspect similar to natural pozzolanas. Common petrography and mineralogy tools have been used to characterise those slags: optical mineralogy, scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD). To gain an insight into their mineral complexity, a QEMSCAN map has been produced. The mineralogy is typical of high-temperature slags: cristobalite, quartz, mullite, fayalite-forsterite series and spinel. The antimony content is quite high, up to seven percent, under the form of various antimony oxides and native antimony.

Decomposition of monazite in Bayan Obo rare earth ore by roasting of Na2CO3 pellets

To resolve the issue of rotary kiln agglomeration during the sodium carbonate roasting of dolomite rare earth ore, this study introduces an oxidation-sodization pellet roasting method for decomposing mixed rare earth concentrates. The focus of this paper lies in understanding the bonding and roasting mechanism of sodium polyacrylate as a binder to dolomite ore and examining the process index of Na2CO3 pellets roasting-acid leaching using X-ray diffraction (XRD), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), and zeta potential analysis. The results indicate that sodium polyacrylate facilitates the bonding of sodium carbonate to monazite via adsorption of positive and negative charges, and upon roasting at 750 °C for 1.5 h to obtain rare earth oxides. Under conditions of a hydrochloric acid (HCl) concentration of 9 mol/L, a reaction for 60 min, a solid-to-liquid ratio (g:mL) of 1:5, and reaction temperature of 90 °C, the leaching rates of rare earth elements and thorium (Th) reached maxima of 85.14% and 95.53%, respectively. The process results in a yield of 47.61% for fluorine (F) and 89.25% for phosphorus (P). This research forms a foundation for the sodium carbonate roasting decomposition of mixed rare earth concentrates.

Enhancement of magnetization roasting of hematite ore by high voltage pulse discharge

High voltage pulse discharge (HVPD) is a new type of crushing technology with good application. Existing studies have focused on the crushing characteristics, with less reports on follow-up work. This study magnetization roasts hematite ore after mechanical crushing and HVPD, analyzing the difference in the roasting effect between the two crushing methods by establishing a new system of HVPD-magnetization roasting. For a roasting temperature of 500 °C, roasting time of 30 min and number of pulses of 100 times, the grade and recovery of magnetic separation concentrate obtained from HVPD products after secondary separation were 64.69% and 82.05% respectively, which were 0.28 and 1.96 percentage higher than those of mechanical crushing. X-ray diffraction (XRD), vibrating sample magnetometry (VSM), Brunauer-Emmett-Teller (BET), scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS) were used to analyze the process and showed that the specific surface area, pore volume and average pore size of the HVPD products were improved. Grain boundary fracture and burn marks were present in the HVPD products.

Enhanced activation roasting of cobalt-rich copper sulfide ore for efficient extraction of cobalt assisted by sodium sulfate

The strategic position of cobalt is increasing with the advancement of global electrification. In order to solve the problem of low extraction of cobalt in ordinary activated roasting, the process of enhanced activation roasting assisted by sodium sulfate was proposed. The feasibility of the process was verified theoretically by thermodynamic predominance area calculation and thermal behavior comparison. The optimal roasting and leaching conditions were determined and the average extraction of cobalt was increased by nearly 10% than ordinary activated roasting. The reaction mechanism of enhanced activation roasting was discussed, indicating that Na2SO4 was not only conducive to the oxidation reactions, but also promoted the migration of valuable components. The thermal kinetics analysis also proved that Na2SO4 had inhibitory effect on the decomposition of sulfates. The proposed technology could realize utilization of cobalt-rich copper sulfide ore and effective extraction of cobalt and copper.

Effect of CaO on Fluorine in Spent Cathode Carbon during Nickel Laterite Reduction

Large amounts of solid waste-spent cathode carbon (SCC) was produced in aluminum electrolysis process. At present, landfill and storage methods are widely used, which will not only cause great harm to the environment, but also cause a lot of waste of resources. Nickel and iron were recovered from laterite nickel ore by reduction roasting-magnetic separation using SCC as reducing agent. The fluorine in SCC was fixed in roasted ore by adding CaO. The feasibility of the method was verified by thermodynamic analysis and experiments, and the optimum conditions for CaO addition were determined. The recovery of nickel and iron reached 91.23% and 89.63% respectively when the addition of SCC was 14 wt. % and CaO was 8 wt. %. Adding 8 wt.% CaO under the condition of SCC as reducing agent can change the viscosity of roasted ore and promote the aggregation of ferronickel particles. The concentration of soluble F- in roasted ore was reduced and fixed in roasted ore in the form of insoluble calcium fluoride. Under the condition of adding 8 wt.% CaO, the fluorine fixation rate was 95.99%, and the concentration of F- in roasted ore was only 31 mg·L−1.

Evasion of Gaseous Elemental Mercury from Forest and Urban Soils Contaminated by Historical and Modern Ore Roasting Processes (Idrija, Slovenia)

Considerable amounts of gaseous elemental mercury (Hg0) can be released into the atmosphere from Hg-enriched substrates, such as those from former mining areas, posing a potential environmental threat. In this work, Hg0 fluxes at the soil–air interface under natural vegetation covers were measured in various locations within the Idrija Hg mining area (Slovenia) and its surroundings. Sites were selected in order to compare Hg0 fluxes from both forest soils heavily impacted by historical ore roasting and urban soils characterised by a different degree of Hg enrichment due to the natural occurrence of Hg in rocks or recent mining and roasting processes. Replicate measurements at each site were conducted using a non-steady state flux chamber coupled with a real-time Hg0 analyser (Lumex RA-915M). Moreover, topsoil samples (0–2 cm) were analysed for Hg total concentration and speciation. Cinnabar was the predominant Hg form in almost all the sites. Despite Hg0 being undetectable in soils using thermo-desorption, substantial emissions were observed (70.7–701.8 ng m−2 h−1). Urban soils in a naturally enriched area showed on average the highest Hg0 fluxes, whereas relatively low emissions were found at the historical roasting site, which is currently forested, despite the significantly high total Hg content in soils (up to 219.0 and 10,400 mg kg−1, respectively). Overall, our findings confirm that shading by trees or litter may effectively limit the amount of Hg0 released into the atmosphere even from extremely enriched soils, thus acting as a natural mitigation.

Fluidized magnetization roasting of refractory siderite-containing iron ore via preoxidation–low-temperature reduction

Fluidized magnetization roasting of refractory siderite-containing iron ore via preoxidation–low-temperature reduction

Kinetics and mechanism of oxidizing roasting of sulfide copper-cobalt ore

The aim of the study was to examine the chemistry, kinetics and mechanism of oxidizing roasting of a typical sample of sulfide copper-cobalt ore. The research object was sulfide copper-cobalt ore with the following main minerals: pyrite, pyrrhotite, chalcopyrite, sphalerite, tremolite, silicon dioxide, talc, siderite and calcite. The methodology involved high-temperature X-ray phase analysis (100–900°C), thermogravimetry, differential scanning calorimetry and mass spectrometry of the released gas (30–1100°C, heating rate – 5–20°C·min-1, air flow rate – 30 cm3·min-1). The chemistry, kinetics and mechanism of oxidizing roasting of sulfide copper-cobalt ore with a particle size of <0.1 mm were studied. It was found that the process can be represented as a set of seven elementary reactions: five exothermic reactions (at 398–445, 394–488, 440–498, 433–549 and 451–562°C), corresponding to the intense combustion of iron, copper and zinc sulfides, and two endothermic reactions (at 651–664 and 743–927°C), associated with the decomposition of residual copper and iron sulfates. Kinetic analysis (Kissinger and Augis-Bennett methods, identification of the reaction model by reference function and iterative optimization) of differential scanning calorimetry data in connection with the above reactions showed that the limiting stage of the latter is nucleation and crystal growth. The values of activation energy, pre-exponential factor and Avrami parameter ranged between 140–459 kJ·mol-1, 1.41·104–3.49·1031 with-1 and 1.0–1.7, respectively. It was established that crystallization of the products of elementary reactions is accompanied by an increase in the number of nuclei; new phase nuclei can be formed both on the surface and in the bulk of ore particles. The crystal growth is one-dimensional and is controlled by a chemical reaction at the interphase boundary or by diffusion of reagents. The results obtained can be applied in the practice of oxidizing roasting of sulfide ores and concentrates.