Production Of High Carbon Ferromanganese Research Articles

Evaluation of solar thermal pretreatment of carbonate-rich manganese ores in high-carbon ferromanganese production through dynamic process modelling

The necessity of reducing greenhouse gas emissions to limit the impact of anthropogenic climate change means that all industrial processes should investigate their options towards decarbonization. Iron, steelmaking, aluminium, and cement production produce the most industrial emissions. Although most research focuses on decarbonizing these industries, minerals processing industries must be decarbonized to achieve net zero emissions goals by 2050. Incorporating renewable energy sources and avoiding the combustion of fossil fuels are two ways to reduce greenhouse gas emissions. This paper reports on the results from a dynamic process model developed to investigate the feasibility of concentrating solar thermal pretreatment of manganese ores to pretreat carbonate-rich manganese ores for increased ferromanganese smelter productivity and reduced greenhouse gas emissions. The results indicate that pretreated ores reduce the energy requirement for smelting significantly for some ores and lowers total carbon dioxide emissions by 13 to 19% compared to the traditional smelting route. A high-level economic evaluation shows that solar thermal treatment is financially viable for low cryptomelane, high braunite ore that is common in the Kalahari Manganese Field.

Eco-friendly low-carbon manganese ferroalloy production for cleaner steel technologies

Global steel production, a major contributor to anthropogenic carbon dioxide, heavily relies on manganese, a key ingredient that significantly impacts the carbon footprint during the production of high-carbon ferromanganese. A single-step generation of low-carbon ferromanganese (LC-FeMn) from manganese ore in an electric arc furnace (EAF) was investigated. The theoretical and experimental investigations helped to balance the required and supplied energy. The process sustainability was predicted based on the enthalpy of the reaction. Pre-reduction of manganese ore decreased energy consumption in the smelting process and saved raw materials costs. The simulation studies revealed a significant effect of lime and silica on the slag-metal equilibrium. It further confirmed the best-reducing condition with the basicity 1.5–1.77 by smelting tests in EAF. Experimental results showed an optimal charge mixture comprising appropriate ratios of ore:SiMn:lime ratio, producing a standard-grade product. Simultaneous melting and smelting sensibly used the exothermic heat, consuming 410–880 kWh/ton, much lower than the international benchmark, i.e. approximately 2000 kWh/ton. The characterization of resulting slags corroborated the advantages of the manganese ore pre-reduction on the energy and reductant consumption, alloy grade, and slag characteristics. The present study's findings can potentially contribute to the ongoing low-carbon initiatives of steel.

The effect of petrographically determined parameters on reductant reactivity in the production of high-carbon ferromanganese

In pyrometallurgical processes, metal oxides are reduced from molten slag through carbothermic reduction. It is of interest to evaluate the reactivity of the carbonaceous materials towards substances such as slag. Characterization techniques such as coal petrography can provide insight into the influence of feed coal properties and how they potentially dictate reductant performance. This study aimed to compare the petrographically determined organic composition of coal to reductant reactivity. Two South African medium-rank C bituminous coals and one anthracite sample were investigated together with high-carbon ferromanganese industrial slag. The reductant reactivity tests were conducted at 1500°C in a muffle furnace to assess the potential of carbonaceous reductant in reacting with the main slag components. SEM-EDS was applied to understand the extent of MnO (and to a lesser extent, SiO2) reduction from the slag. Coal 2, consisting of a greater proportion of vitrinite (59.5 vol% on a mineral matter-free basis and 54.7 vol% including mineral matter) was the most reactive reductant. The anthracite sample, with the highest inert maceral proportions (71.8 vol% including mineral matter and 76.8 vol% on a mineral matter-free basis), was the least reactive reductant.

Extent of Ore Prereduction in Pilot-scale Production of High Carbon Ferromanganese

Three pilot-scale experiments have been conducted at SINTEF/NTNU in a 440 kVA AC electric furnace to demonstrate the process operation, energy requirements and CO2 emissions in the production of high carbon ferromanganese alloys. Comilog, UMK and Nchwaning (Assmang) ores blended with other materials, such as sinter and flux, thus achieving different charge mixtures have been utilized in the experiments. In the prereduction zone, higher manganese oxides in the ore are reduced to MnO through solid-gas exothermic reactions and at a temperature around 800oC, the unwanted endothermic Boudouard reaction is also active. As such, the total coke and energy consumption is highly dependent on if the prereduction occurs by CO gas or solid C. The pilot furnace has been excavated after each experiment and the extent of prereduction of the ore has been investigated by collecting samples from specific regions in the prereduction zone. In addition, material, and energy balance calculations for the three pilot experiments have been calculated using HSC Chemistry software. The HSC material and energy balance calculations have shown that the slag/alloy ratios, metal analyses, carbon consumption and the overall energy consumption are mainly affected by the composition of the charge mixtures. The relationship between the specific carbon consumption, the off-gas CO2/(CO2+CO) ratio and energy consumption to produce 1 tonne of HCFeMn alloy is discussed for the three different pilot-scale scenarios.

MnO reduction in high carbon ferromanganese production: practice and theory

ABSTRACTThe SAF (submerged arc furnace) process is most widely used for industrial production of high carbon ferromanganese. Most plants use ore feed in the form of lump ore (−75 mm +6 mm), but long term supply is limited, and large quantities of ore fines are generated in ore mineral processing. Therefore development of alternative processes using ore fines (−10 mm) is important. The AlloyStream process is one such process developed to use a feed material mixture of fine ore, coal and flux. This process development provided a unique opportunity to correlate MnO reduction process theory to pilot plant production practice represented in minerlogical observations from furnace heap samples.

Dissipation of Electrical Energy in Submerged Arc Furnaces Producing Silicomanganese and High-Carbon Ferromanganese

Submerged-arc furnace technology is applied in the primary production of ferroalloys. Electrical energy is dissipated to the process via a combination of arcing and resistive heating. In processes where a crater forms between the charge zone and the reaction zone, electrical energy is dissipated mainly through arcing, e.g., in coke-bed based processes, through resistive heating. Plant-based measurements from a device called “Arcmon” indicated that in silicomanganese (SiMn) production, at times up to 15% of the electrical energy used is transferred by arcing, 30% in high-carbon ferromanganese (HCFeMn) production, compared with 5% in ferrochromium and 60% in ferrosilicon production. On average, the arcing is much less at 3% in SiMn and 5% in HCFeMn production.

Phase Characterization of High Basicity Manganese Slags

Slag chemistry applied in the AlloyStream process differs from that used in the production of high carbon ferromanganese in the submerged arc furnace. In process development of the AlloyStream process, several pilot plant and demonstration plant campaigns were completed. Slag samples were selected from the samples collected at each tap, throughout the four month pilot plant campaign. Phase characterization of these samples is reported here, and the results are interpreted in terms of the slag chemistry operational options in the AlloyStream process.

Smart ore blending methodology for ferromanganese production process

This study is carried out to develop a smart ore blending methodology for high carbon ferromanganese production units. Geometallurgical characterisation of the ores collected from 10 different mines has been carried out to estimate variation in their aptness for the alloy production process. An evolutionary algorithm-based methodology has been adopted for ore blending to maximise the total manganese content of the ore blend under applied physico-chemical constraints. Analysis provides various blends of the same chemical composition but of different geometallurgical ranks. An artificial neural network model has been developed to predict the operational parameters such as slag and metal composition. This method allows the operator to visualise the impact of combinations of different ore blends on slag–metal composition as well as on electric power and coke required for smelting reduction of ores in the submerged arc furnace. It was observed that best blends could reduce power and coke consumption by 100 kWh ton−1 and 30 kg ton−1, respectively, but optimum values can be established in long run considering conservation of natural resources.

Microscopic Study of Carbon Surfaces Interacting with High Carbon Ferromanganese Slag

The interaction of carbon materials with molten slags occurs in many pyro-metallurgical processes. In the production of high carbon ferromanganese in submerged arc furnace, the carbothermic reduction of MnO-containing silicate slags yields the metal product. In order to study the interaction of carbon with MnO-containing slags, sessile drop wettability technique is employed in this study to reduce MnO from a molten slag drop by carbon substrates. The interfacial area on the carbon substrate before and after reaction with slag is studied by scanning electron microscope. It is indicated that no Mn metal particles are found at the interface through the reduction of the MnO slag. Moreover, the reduction of MnO occurs through the contribution of Boudouard reaction and it causes carbon consumption in particular active sites at the interface, which generate carbon degradation and open pore growth at the interface. It is shown that the slag is fragmented to many micro-droplets at the reaction interface, potentially due to the effect on the interfacial energies of a provisional liquid Mn thin film. The rapid reduction of these slag micro-droplets affects the carbon surface with making deep micro-pores. A mechanism for the formation of slag micro-droplets is proposed, which is based on the formation of provisional micro thin films of liquid Mn at the interface.

Slags in Production of Manganese Alloys

AbstractThe paper analyses the equilibrium partitioning of manganese and silicon between slag and alloy during the production of high carbon ferromanganese (HC FeMn) and silicomanganese (SiMn) using FACTSage software. The results of this modeling are compared with industrial and experimental data and used to elucidate the nature of the reduction processes. In production of HC FeMn, molten slag co‐exists with a monoxide phase (Ca,Mg,Mn)O in which MnO is the major constituent. Analysis of industrial data shows that slag and monoxide are close to equilibrium, but manganese slag–metal partitioning is far from equilibrium. It is evident that the rate of MnO reduction from the slag is slower than the rate of MnO dissolution into the slag. A previous laboratory study confirmed that MnO reduction from HC FeMn slag is slow and that equilibrium is not reached. In the production of SiMn, the charge consists of manganese ore, ferromanganese slag, quartzite, and fluxes. Excavation of industrial furnaces has revealed the presence of quartzite in the reaction zone, so there are four condensed phases in the reaction zone; molten slag, molten SiMn alloy, quartzite, and coke. FACTSage modeling showed that during the production of SiMn, manganese, and silicon partitioning between the metal and slag is close to equilibrium at 1600°C. The concentration of silica in SiMn slags is much lower than the silica‐saturation value. It can be concluded that the reduction of silica from these slags is faster than the dissolution of quartzite into the slag.

Characterization of Egyptian Manganese Ores for Production of High Carbon Ferromanganese

This work aims at studying the reactivity of Egyptian manganese ores to be used in the production of ferromanganese alloys in submerged electric arc furnace. Ores with different manganese content (high-medium and low) were selected and characterized by X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM). The main mineralogical compositions in the three ores are pyrolusite (MnO2) and hematite (Fe2O3). Porosity of selected Mn ores was determined. The reactivity of the different ores was carried out through pre-reduction of the selected ores using thermobalance at 900°C and 1100°C and mixture of CO and CO2 gases. The reduction process was done until steady weight. The reduced ores were examined using XRD and SEM. The results showed that pyrolusite in high and medium ores are converted completely to MnO at 1100°C. However, the ore with low manganese content was converted to MnO and Mn3O4. Consequently, it is clear from the results that Mn ores with high and medium MnO2 content are more reactive than those with low MnO2. Therefore, high MnO2 content Mn ores are preferable to get good economic impact during the production of high carbon ferromanganese.

Characterization of Egyptian Manganese Ores for Production of High Carbon Ferromanganese

This work aims at studying the reactivity of Egyptian manganese ores to be used in the production of ferromanganese alloys in submerged electric arc furnace. Ores with different manganese content (high-medium and low) were selected and characterized by X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM). The main mineralogical compositions in the three ores are pyrolusite (MnO2) and hematite (Fe2O3). Porosity of selected Mn ores was determined. The reactivity of the different ores was carried out through pre-reduction of the selected ores using thermobalance at 900°C and 1100°C and mixture of CO and CO2 gases. The reduction process was done until steady weight. The reduced ores were examined using XRD and SEM. The results showed that pyrolusite in high and medium ores are converted completely to MnO at 1100°C. However, the ore with low manganese content was converted to MnO and Mn3O4. Consequently, it is clear from the results that Mn ores with high and medium MnO2 content are more reactive than those with low MnO2. Therefore, high MnO2 content Mn ores are preferable to get good economic impact during the production of high carbon ferromanganese.

Parameters Affecting the Production of High Carbon Ferromanganese in Closed Submerged Arc Furnace

This study has been performed to investigate the different parameters affecting on the production of high carbon ferromanganese in closed submerged arc furnace. The analysis of industrial data revealed that using manganese ores with low Mn/Fe ratio necessitates higher amount of Mn-sinter in the charge. Using Mn-blend with higher Mn/Fe ratio reduces the coke consumption and this leads to reducing the electrodes consumption. The recovery of Mn ranges between 70 and 80 %. Much higher basic slag has slight effect on Mn- recovery. However, as slag basicity increases, the MnO- content of slag decreases. The manganese content of produced HCFeMn depends mainly on Mn/Fe ratio of Mn-blend. For obtaining HCFeMn alloy containing minimum 75%Mn, it is necessary to use Mn-blend with Mn/Fe ratio of higher than 6. A model for determination of the amount and composition of off-gases has been derived based on the chemical composition and material balance of the input raw materials and the produced alloy and slag. By using this model, the amount of off-gases was found to increase by increasing both Mn-blend and coke consumption.

Factors Affecting Silicomanganese Production using Manganese Rich Slag in the Charge

Silicomanganese is widely used as a complex reducer and an alloying addition in the production of various grades of steel due to its economic and metallurgical advantages. It is also used as a semi‐product in the manufacture of medium‐ and low‐carbon ferromanganese and metallic manganese. Manganese‐rich slag, resulting from high carbon ferromanganese production, has the advantages of high manganese content, high Mn/Fe ratio, low excess oxygen, low phosphorus content, low fine content and low cost. Such slag seems to be very attractive to use as raw materials for the production of silicomanganese alloys. In the present study, experimental heats were designed and carried out to optimise the factors affecting the production process of silicomanganese using manganese rich slag in the charge. The results of pilot plant experimental heats showed that the optimum metallic yield and recoveries of manganese and silicon are obtained with an initial slag basicity, (CaO + MgO) / (Al2O3), of 1.8 by using dolomite as fluxing material and charging quartzite and fluorspar in percentage of 25% and 4% of the blend, respectively. The results also showed that an amount of 30% of coke in excess of the stoichiometric amount should be added. These results are relative for the specific high Al2O3 ores used.

Production of high carbon ferromanganese using manganese rich slag in the charge

The possibility of replacement of the high cost sinter manganese ore by manganese rich slag for the production of high carbon ferromanganese was experimentally demonstrated. The experimental heats were designed and carried out to optimize this replacement through the adjustment of different production parameters. The results of pilot plant experimental heats showed that replacement of 50% of the sinter in the blend (or 25% of the blend) by slag containing 32% Mn and operation under slag basicity 0.9 and low (MgO)/(CaO) ratio of about 0.2‐0.3 are the optimum conditions to attain the highest manganese content in the produced ferromanganese, the highest manganese recovery and the highest metallic yield. The industrial application of reusing manganese slag clarified the economic efficiency of charging manganese slag up to 20‐25% of the blend in reducing the production cost due to reducing the cost of manganese ores. Charging of 20‐25% manganese slag reduces the cost of manganese ores and the total production cost by about 13 and 6% respectively, comparing with the conventional technology (without using manganese slag in the blend).

The Physico-Chemical Properties of Slags Associated with the Production of High-Carbon Ferromanganese

Published information concerning the physico-chemical properties of liquidus temperature, electrical conductivity and viscosity for the slag system MnO–MgO–CaO–Al2O3–SiO2, is reviewed. The effect of each oxide on the different physico-chemical properties is shown, and the effect of these slag properties on the production processes is explained. The gangue oxides contained in manganese ores influence the final composition of production slags thereby affecting the production process and this is illustrated through the physico-chemical properties of the slags produced. Résumé Nous avons passé en revue l'information publiée concernant les proptiétés physico-chimiques telles que: température du liquidus, conductivité électrique et viscosité du système MnO–MgO–CaO–Al2O3–SiO2, On montre l'effet de chaque oxyde sur les différentes propriétés physicochimiques et on explique l'effet de ces propriétés des scories sur les procédés de production. Les oxydes contenus dans la gangue des minerais de manganèse influencent la composition finale des scories de production et par là même affectent les processus de production. Ceci est illustré à travers les propriétés physico-chimiques des scories produites.

The Physico-Chemical Properties of Slags Associated with the Production of High-Carbon Ferromanganese

Published information concerning the physico-chemical properties of liquidus temperature, electrical conductivity and viscosity for the slag system MnO–MgO–CaO–Al2O3–SiO2, is reviewed. The effect of each oxide on the different physico-chemical properties is shown, and the effect of these slag properties on the production processes is explained. The gangue oxides contained in manganese ores influence the final composition of production slags thereby affecting the production process and this is illustrated through the physico-chemical properties of the slags produced. Résumé Nous avons passé en revue l'information publiée concernant les proptiétés physico-chimiques telles que: température du liquidus, conductivité électrique et viscosité du système MnO–MgO–CaO–Al2O3–SiO2, On montre l'effet de chaque oxyde sur les différentes propriétés physicochimiques et on explique l'effet de ces propriétés des scories sur les procédés de production. Les oxydes contenus dans la gangue des minerais de manganèse influencent la composition finale des scories de production et par là même affectent les processus de production. Ceci est illustré à travers les propriétés physico-chimiques des scories produites.