Ferrochrome Production Research Articles

Value Extraction from Ferrochrome Slag: A Thermochemical Equilibrium Calculation and Experimental Approach

The valorization of slag from the production of high-carbon ferrochrome is a challenge for ferrochrome producers. The recycling of high-carbon ferrochrome slag was explored through the smelting route to recover Fe–Si–Al–Cr alloys and reengineer the residual slag for alumina-enriched refractory material. In this research, the focus was to reduce the SiO2% and enrichment of Al2O3% in the final slag and recover the metallic value in the form of a complex alloy containing Fe, Si, Cr and Al. The manuscript consists of a thermochemical simulation of the smelting of FeCr slag followed by smelting experiments to optimize the process parameters such as temperature and the addition of coke, cast iron and alumina. An experimental investigation revealed that the maximum recovery of Si (57.4% recovery), Al in the alloy (20.56% recovery) and Al2O3 (85.78% recovery) in the slag was achieved at a charge mix consisting of 1000 g of FeCr slag, 300 g of alumina, 200 g of cast iron and 300 g of coke. The present study also demonstrated the usefulness of prior thermochemical calculations for smelting metallurgical wastes such as slag from high-carbon ferrochrome production for value creation and reutilization purposes.

Analysis of the ecological footprint of mining machines in the phase of material extraction and processing in LCA

Sustainability in the mining industry continues to be a challenge. Although there is research in this area, there are still no solutions supporting the assessment of environmental impact in this sector. Therefore, it is important to look for and conduct various types of analyses that will be useful in this area. Therefore, the objective of the research was to analyse the ecological footprint of mining machines in the first phase of the LCA life cycle (obtaining and extracting materials). The analysis was based on the example of a hydraulic actuator, which is considered crucial to control machines in the mining industry. The ecological footprint burdens analysed included direct and indirect land take, sequestration of carbon dioxide (CO2) emissions, and the use of nuclear energy. Life cycle assessment was carried out using the OpenLCA software with the ecoinvent v3.10 database. It has been shown that the largest amount of emissions occurs during off-site treatment of nonsulphide waste, cogeneration of heat and energy (hard coal), production of ferrochrome, high carbon, 68% Cr, and heat production in an industrial furnace using hard coal. It is proposed to carry out improvement activities that will first contribute to reducing the main environmental burdens. Then, it will be possible to significantly reduce the negative environmental impact of the hydraulic actuator's extraction and processing of materials. The results from the analysis may be useful not only for products from the mining industry but also in other areas of activity using this type of machine.

STUDY OF FERROCHROME SMELTING TECHNOLOGY USING BRIQUETTES WITH VARIOUS CARBONACEOUS REDUCERS

This study explores the ferrochrome smelting technology using briquettes with various carbonaceous reducers. The research addresses the significant challenge of dust and fine fractions of raw materials generated during the metallurgical industry's crushing, beneficiation, storage, and transportation processes. Briquettes were produced and tested by agglomerating chrome ore dust with carbonaceous reducers for their mechanical properties and effectiveness in smelting processes. The study concludes that carbonaceous reducers' ash content significantly affects the chrome ore-containing briquettes' thermal stability and electrical conductivity. Low ash content was associated with better performance in the smelting process. Using briquettes with various carbonaceous reducers offers a flexible approach to charge composition, depending on specific production needs and the availability of reducers. The results highlight the potential for improved environmental impact, reduced material losses, and enhanced efficiency in ferrochrome production.

STUDY OF THE MODES OF RECOVERY AND DESTRUCTIBILITY OF CHROME BRIQUETTES UNDER CURRENT AND THERMAL LOADS

For an objective assessment of the recoverability of the resulting oxidized materials and deciphering the physico-chemical characteristics of their reduction processes occurring during the smelting of carbonaceous ferrochrome, special studies are needed. In this regard, the kinetics of the briquette reduction process has been studied in this article, which is extremely important for understanding the mechanism of carbothermic reduction in order to improve metallurgical technologies using coated materials. During the study, 6 different variants of briquettes with chromium ore and various types of carbon reducing agents were studied, such as China coke, Shubarkolsky special coke, Borlinsky coal and Shubarkolsky coal. The degree of chromium reduction was studied in the Tamman furnace by thermogravimetric method at temperatures of 1200; 1300; 1400; 1500; 1600 ° C for 1 hour. This article also provides calculations to determine the degree of reduction of chromium and iron using the Yander and Gistling-Brownstein equations. Of the six briquette variants, the best results in studying the kinetics of reduction of chromium ore raw materials were obtained using briquettes № 1, 3, 5. The study emphasizes the critical importance of understanding the reduction and destructibility modes of chromium briquettes to optimize the melting processes of carbon ferrochrome. The conclusions from this study are key to the development of both scientific understanding and practical applications in the metallurgical industry. This article summarizes the main results and meanings of the authors’ research, emphasizing its contribution to improving the efficiency and quality of carbon ferrochrome production through the systematic study of reduction behavior in chrome ore briquettes. Keywords: ferrochrome, chrome briquettes, coal, coke, degree of reduction, Yander equation, Gistling-Brownstein equation.

EXTRACTION OF CHROME FROM FERROCHROME PRODUCTION SLAG USING THE SULFURIC ACID METHOD

Currently, the development of industrial waste recycling processes that reduce the anthropogenic load on the biosphere and ensure the rational use of natural resources is an urgent task. Technogenic waste from ferrochrome production contains chromium, which is one of the most toxic components of industrial waste. To extract chromium from them, the most acceptable method is acid leaching. The purpose of the work is to study the influence of temperature, process duration and H2SO4 concentration on the extraction of chromium from high-carbon ferrochrome slag into a sulfuric acid solution. Using mathematical planning of a 3-factor experiment, experiments were carried out to extract chromium from the slags of high-carbon ferrochrome production. The H2SO4 concentration was varied from 5 to 95% by diluting the concentrated acid. The duration of the process ranged from 10 to 180 minutes at S:L = 1:30, the temperature varied from 22 to 90 °C. Results and discussion. The maximum transition of chromium into acid occurs at a temperature of 76-90 °C and a process duration of 145-180 minutes. The degree of extraction reaches 97.9%. The smallest amount of chromium, about 20 mg/L, passes into the weakly concentrated H2SO4 solution, the degree of leaching is low and equal to 20.6%. When using 50% H2SO4, the highest degree of transition of Cr (94.8%) from ferrochrome slag to sulfuric acid occurs at a high temperature of 90 °C in 150-180 minutes. Deeper extraction of chromium cations into acid occurs at 80-90 °C. The maximum content of Cr3+ in the acid is achieved in 46-107 minutes and amounts to (0.33-0.68)%. Conclusions. It was revealed that with increasing process duration and increasing temperature, the degree of extraction increases. The maximum transition of chromium into acid from high-carbon ferrochrome slag occurs at a temperature of 76-90 °C and a process duration of 145-180 minutes. The degree of extraction reaches 97.9%. An increase in the temperature of the process of leaching chromium from VUVC with concentrated sulfuric acid initiates the extraction of chromium from the raw material.

Preliminary study of the technology of vacuum-thermal production of low-carbon ferrochrome

Preliminary study of the technology of vacuum-thermal production of low-carbon ferrochrome

Investigation of the Mechanical Behaviors of Sustainable Green Reactive Powder Concrete Produced Using Ferrochrome Slag and Waste Fiber

Reactive powder concrete (RPC) is a new generation concrete with high strength, used in special structures, and its use is increasing day by day. In this study, instead of using high-strength aggregates typically used in RPC, wastes released in ferrochrome production were used. In addition, the possibility of using fibers obtained from end-of-life automobile tires (ELT), instead of the micro steel fibers typically used in RPC, was investigated. Thus, sustainable green reactive powder concrete (GRPC), the material which is obtained from waste materials except the binder and chemical additive, has been developed. As ferrochrome wastes, olivine, serpentine, rum, slag, and pure waste were used as powder and aggregate in GRPC. Firstly, in GRPC without fiber, the physical and mechanical properties of ferrochrome wastes were examined by using different ratios. Then, the optimum mixture was selected, and different ratios of industrial steel and ELT fiber were added to this mixture. As a result, the compressive strength of GRPC using olivine and pure waste (ferrochrome slag) is close to the reference RPC. However, it is 28% more economical. The flexural strength of the samples with a 4% addition of industrial or ELT fiber increased by 182% and 213%, respectively, compared to the reference sample without fiber. With the use of 4% ELT fiber (by volume) in GRPC, the flexural strength increased by 11% compared to the use of industrial steel fiber. In terms of cost, with the use of ferrochrome waste and ELT fiber, GRPC was 48% more economical. When examined in terms of the flexural and compressive unit strength cost, GRPC was approximately 41% more economical. As a result of this study, high-performance concrete with high mechanical properties that is economical, sustainable, and environmentally friendly has been produced by evaluating the use of waste materials.

Enabling CO2 neutral metallurgy for ferrochromium production using bio-based reducing agents

The metallurgical industry is a major source of anthropogenic greenhouse gas emissions. This study explores the replacement of fossil-reducing agents with potentially CO2-neutral bio-based reducing agents. Since reducing agents remove oxygen bonded with metal oxides present in the ore, they are a necessity for the production of metallic elements. The investigated metal is chromium, a major part of stainless steel, and therefore a highly relevant element for the transition from a fossil-based energy system to a renewable one. The state-of-the-art smelting reduction and pre-reduction process followed by subsequent smelting using various reducing agents are investigated in this article. The obtained products, metallurgical efficiencies, energy consumption and off-gas generation were compared. While the products produced with bio-based reducing agents are comparable with the reference trials using metallurgical coke regarding the major components in the metal, the concentration of detrimental phosphorus is significantly higher using bio-based reducing agents. The metallurgical efficiency of the process is comparable to the usage of bio-based reducing agents and coke. However, the energy consumption and the generation of off-gas is higher, when coke is replaced by bio-based reducing agents.

Environmental characterization of ferrochromium production waste (refined slag) and its carbonization product

This paper presents the results of research on the method of utilization of self-disintegrating slags of refined ferrochrome production by autoclave carbonization in carbon dioxide environment. The work has a complex character, including earlier laboratory studies of the slag carbonization process under different conditions, as well as studies of chemical and mineralogical composition of initial waste slags taken from the slag dump and samples of bricks subjected to carbonization. The composition of slags and obtained products was investigated by XRD, DTA, DTG and XRF analyses, which showed that the main phases of the studied samples are dicalcium silicate, montichelite, periclase, magnesiochromite, calcite. Thermal analytical studies showed that magnesium carbonate is present only in the samples of artificially carbonized material. Also, the process of carbonate formation in the thickness of bricks during forced carbonization was investigated. As a result, it was obtained that with increasing CO2 pressure, the amount of bound carbon in the products increases proportionally in all layers. It was determined that the amount of CO2 absorbed during carbonization can reach 20 % of the mass of the initial slag. Stale slag can be used simultaneously as a carbon dioxide absorber and as a building product.

Prediction of burden distribution and electrical resistance in submerged arc furnaces using discrete element method modelling

A computational model of a submerged arc furnace (SAF) used in the production of ferrochrome is presented. The model's intended use is to investigate the extent to which intrinsic and extrinsic properties of the raw materials affect burden distribution and electrical resistance within the furnace. The model is built on the discrete element method and calculates the mechanical interactions of particle distributions resulting from the flow motion of typical raw materials used in the smelting of chromium ore. This model excludes the effects of thermodynamics, furnace chemistry, and heat transfer. It illustrates how the consumption of materials (chromite pellets, flux, and reductant) is affected by changes in electrode length, reductant fractions, and reductant sizing and density during the formation of a reductant bed. The resistance calculation algorithm developed by Mintek was applied to construct networks developed from particle contacts, which can quantitatively generate estimates of the electrode-to-electrode and electrode-to-bath electrical conduction conditions.

Құрамында бор бар силикохромды қолдану арқылы төмен көміртекті феррохромды балқыту процесін термодинамикалық модельдеу

The TERRA program for calculating multicomponent heterogeneous systems, based on the principle of maximum entropy, was used to study systems with a complex chemical composition, in which the task of numerical modeling is chemical and phase transformations play an important role. The effect of charge composition and temperature on the chemical and phase composition of melting products was studied, the degree of transition of charge elements into metal was determined, and optimal conditions for obtaining the alloy were found. The thermodynamic analysis of the ferrochromium production process showed that in order to approach the real process of low-carbon ferrochromium smelting, it is necessary to take into account the degree of silicon use by introducing oxygen into the working fluid to oxidize excess silicon according to the calculation. On the basis of the performed thermodynamic analysis, it is also shown that the choice of the process temperature (1750-1800°C and more) is associated with the kinetic conditions of melting, the melting temperature of the formed metal and slag. Therefore, it is expected that the presence of boron oxide, in addition to stabilizing slag from decomposition, will reduce its melting point, and the early appearance of the liquid phase due to low-temperature boron phases will ensure a shift in the reduction reactions of chromium with silicon to the low-temperature region. All these provisions will be implemented during high-temperature experimental work on the development of technological parameters.

Study of direct alloying of steels by carbon reduction of Cr2O3 under vacuum

Currently, steel is mainly alloyed by adding ferrochrome alloys in the production of chromium-containing steels. However, the production of ferrochrome consumes a lot of electricity and produces a large number of additional products that are extremely harmful to the environment. For the consideration of the above problems, the experiment studied the reduction behavior of Cr2O3 using carbon powder as the reductant under different ambient pressures, different reductant dosages, and different initial oxygen contents in the molten steel. The results show that CO bubbles can be formed by decreasing the air pressure and increasing the amount of reductant, thus the reduction rate and reduction efficiency of Cr2O3 can be increased. It was found that the ambient air pressure mainly affected the reduction rate of Cr2O3, and the fastest reduction rate of Cr2O3 was found in vacuum environment. The reductant dosage has great influence on the reduction rate, reduction efficiency, density and size of inclusions of Cr2O3. Addition of carbon powder with a carbon-to-oxygen molar ratio of 2 will significantly improve the reduction rate of Cr2O3. The yield of [Cr] in steel can reach more than 95 %. In addition, the density of inclusions in steel is stabilized below 0.2/mm−2. The addition of carbon powder with nc:no ≤ 1.0 significantly reduces the reduction rate of Cr2O3 due to the decrease of carbon concentration in the steel. The density of inclusions in steel also increased significantly up to 210.4/mm−2. The initial oxygen content in the molten steel had little effect on the reduction of Cr2O3. However, the reduction rate of Cr2O3 is lower in steel with high oxygen concentration than in steel with low oxygen concentration. Under the optimum reduction conditions-nc:no = 2.0, initial oxygen content of 3 × 10−4, and ambient air pressure of 50 Pa. The yield of [Cr] in steel can reach 96.85 %, the total oxygen content can be reduced to 1.6 × 10−5, the density of inclusions is 0.04/mm−2, and the size of inclusions is below 1.8 μm.

Energy and Exergy Analyses of a Submerged Arc Furnace used for Ferrochrome Production

Energy and Exergy Analyses of a Submerged Arc Furnace used for Ferrochrome Production

Hydrogen-based pre-reduction of chromite: Reduction and consolidation mechanisms

The pre-reduction of chromite plays a vital role in the production of ferrochrome, offering advantages such as reduced carbon consumption and improved production efficiency. In this study, the feasibility of a hydrogen-based pre-reduction process for chromite was examined, and the mechanisms of reduction and pellet consolidation were discussed. The results demonstrate that the degree of Fe metallization and the degree of iron oxide deoxidation increase with higher reduction temperatures, longer durations, and increased H2:CO ratios. Notably, the degree of Fe metallization reached a substantial value of 85.9% under pure H2 conditions at 1300 °C for 3 h. The strength of the pellets exhibits an initial increase followed by a decrease as the degree of Fe metallization increases and the Fe2+ degree decreases. This phenomenon is attributed to a decrease in the Fe2+ degree, leading to an increase in the melting point of the binder phases and subsequently resulting in a significant reduction in pellet strength. However, the average strength of pellets reduced at over 1200 °C is higher than 1000 N. The reduction process of chromite can be divided into four stages, metal Fe is primarily reduced from the Fe3+ site, followed by reduction from Fe2+ in the (Mg, Fe) (Cr, Fe, Al)2O4 structure. Only a small amount of Cr can be reduced, forming Fe–Cr metal. According to thermodynamic calculation, H2 offers a thermodynamic advantage over CO as a reducing agent. H2 exhibits higher reactivity and a greater affinity for oxygen compared to CO. These factors contribute to the superior performance of H2 in the reduction of chromite.

PROSPECTS FOR THE EXTRACTION OF CHROMIUM FROM SLAG FERROCHROME PRODUCTION BY ACID METHOD

In the Republic of Kazakhstan, there is a noticeable upward trend in the volume of industrial waste, including from the production of ferrochrome. The problems of man-made pollution of the natural environment are becoming more acute every year, and are beginning to take on a global dimension. Technogenic ferrochrome production waste contains chromium, which is highly toxic and carcinogenic, which poisons water, soil, negatively affects the activity of all living organisms. Slags contain a significant number of valuable components used in various industries, and above all, chromium, which is irrevocably lost during storage. The main task still remains the development of industrial waste disposal processes that reduce the anthropogenic load on the biosphere and ensure the rational use of natural resources. The purpose of the work is to justify the choice of the method of processing the slags of the ferrochrome production. Conclusions: The analysis of the modern scientific and patent literature on acid processing and utilization of chromium-containing slags from the production of refined and high-carbon ferrochrome has been conducted. It should be noted that the described methods of various methods of processing ferrochrome production slags, despite their availability, are characterized by a multi-stage nature and do not allow complete processing of ferrochrome production slags in Kazakhstan. Currently, there is an excess of sulfuric acid production in Kazakhstan, so it becomes advisable to use sulfuric acid as a reagent for leaching chromium from slag from the production of ferrochromium. It can be expected that in sulfuric acid under certain conditions, such as heating, a sufficiently high degree of extraction of chromium (III) will be achieved in slags from the production of high-carbon chromium and in refined ferrochem slags.

Physical and Chemical Studies of Smelting Products of Calcinated Composite Pellets Produced from Chromium Production Waste

This study presents the results of the enlarged laboratory research on the melting of calcined composite pellets for ferrochrome obtained from fine-dispersed conditioned chrome concentrate containing 50.3% Cr2O3. This is a product of the gravitational beneficiation of waste sludge tailings from the Dubersay tailings dump at the Donskoy Mining and Processing Plant (DMPP) of JSC “TNC Kazchrome”. The composition of the charge for obtaining composite pellets consisted of 88.5% of chrome concentrate, 3% of mineral part of refined ferrochrome slag (RFC), 4% of ferruginous diatomite, 3% of coke and 1.5% of liquid glass. The initial charge was pelletized on a laboratory pelletizer to a size of 6–10 mm, dried at room temperature for 24 h and fired at 1200 °C for 60 min at a heating rate of 15 deg/min. On the basis of the developed composite annealed pellets, studies on the production of high-carbon ferrochrome at different melting temperatures were carried out. The results showed that with an increase in temperature from 1750 to 1850 °C, the iron–chromium phase in the composition of the alloy increases from 45.2 to 50.1%, the chromium carbide phase decreases from 23.7 to 11.3% and the chromium–iron phase increases from 7 to 11.2%. The carbon content in the alloys at temperatures from 1750 to 1850 °C varies from 7.2 to 8.94%, respectively. The maximum chromium content of the alloy is 64.82% with a melting point of 1850 °C; this alloy can be classified as FeCr60C90LP grade ferrochrome according to the international Chinese standard, which has no more than 0.03% phosphorus and no more than 0.1% sulfur.

Chemical beneficiation of chromite ore to improve the chromium-to-iron ratio for ferrochrome production

Ferrochrome (FeCr), a relatively crude alloy comprised primarily of iron (Fe) and chromium (Cr), is vital for the production of stainless steel. FeCr is produced from chromite ore, the most important source of virgin Cr units. FeCr producers are only paid per mass unit of Cr content in the FeCr, i.e. in US¢/lb contained Cr, according to the current global FeCr markets pricing structure. Consequently, FeCr producers transport a large fraction of their product weight, i.e. the Fe content of the FeCr, without any benefit. The Fe content in the FeCr produced depends on the chromite spinel Cr/Fe ratio. Therefore, the selective removal of Fe from the chromite spinel using different combinations of chromite pre-oxidation, pre-reduction, and sulphuric acid leaching was investigated. The Cr/Fe ratio of the case study ores could be increased from 1.57 up to ∼23.4. However, Cr recovery decreased significantly under experimental conditions to achieve such high Cr/Fe ratios. More desirable Cr/Fe ratios of >2 up to ∼4.28 were achieved while maintaining Cr recoveries of >90%.

Analysis of Electrical Energy Consumption in a Novel Direct Current Submerged Arc Furnace for Ferrochrome Production

Analysis of Electrical Energy Consumption in a Novel Direct Current Submerged Arc Furnace for Ferrochrome Production

An Overview of Currently Applied Ferrochrome Production Processes and Their Waste Management Practices

Ferrochrome (FeCr) is the main source of virgin chromium (Cr) units used in modern-day chromium (Cr) containing alloys. The vast majority of produced Cr is used during the production of stainless steel, which owes its corrosion resistance mainly to the presence of Cr. In turn, stainless steel is mainly produced from Cr-containing scrap metal and FeCr, which is a relatively crude alloy between iron (Fe) and Cr. The production of FeCr is an energy and material-intensive process, and a relatively wide variety of by-products, typically classified as waste materials by the FeCr industry, are created during FeCr production. The type and extent of waste generation are dictated by the smelting route used and the management practices thereof employed by a specific smelter. In some cases, waste management of hazardous and non-hazardous materials may be classified as insufficient. Hazardous materials, such as hexavalent Cr, i.e., Cr(VI), -containing wastes, are only partially mitigated. Additionally, energy-containing wastes, such as carbon monoxide (CO)-rich off-gas, are typically discarded, and energy-invested materials, such as fine oxidative sintered chromite, are either stockpiled or sold as ordinary chromite. In cases where low-value containing wastes are generated, such as rejects from ore beneficiation processes, consistent and efficient processes are either difficult to employ or the return on investment of such processes is not economically viable. More so, the development of less carbon (C)-intensive (e.g., partial replacement of C reductants) and low-temperature pellet curing processes are currently not considered by the South African FeCr smelting industry. The reasoning for this is mainly due to increased operation costs (if improved waste management were to be implemented/higher cost reductants were used) and a lack of research initiatives. These reasons result in the stagnation of technologies. From an environmental point of view, smelting industries are pressured to reduce C emissions. An attractive approach for removing oxygen from the target metal oxides, and the mitigation of gaseous C, is by using hydrogen as a reductant. By doing so, water vapor is the only by-product. It is however expected that stable metal oxides, such as the Cr-oxide present in chromite, will be significantly more resistive to gaseous hydrogen-based reduction when compared to Fe-oxides. In this review, the various processes currently used by the South African FeCr industry are summarized in detail, and the waste materials per process step are identified. The limitations of current waste management regimes and possible alternative routes are discussed where applicable. Various management regimes are identified that could be improved, i.e., by utilizing the energy associated with CO-rich off-gas combustion, employing a low-temperature alternative chromite pelletization process, and considering the potential of hydrogen as a chromite reductant. These identified regimes are discussed in further detail, and alterative processes/approaches to waste management are proposed.

CO2-Minimized Ferrochrome Production Utilizing Silicon Wafer Cutting Slurry as an Alternative Reductant

Direct emissions due to the use of carbon-based fossil-reducing agents contribute to the overall CO2 emissions of pyrometallurgical production processes. This study investigated the replacement of fossil coke by silicon-rich cutting waste from the solar wafer cutting process to produce ferrochrome in an electric arc furnace. Laboratory test work and thermochemical simulation were carried out to examine the product quality at various additions of cutting waste and lime. The experimental trials resulted in products in accord with international standards, however, adjusting the slag composition by the addition of lime was necessary, otherwise high silicon contents in the alloys were obtained. Due to the highly exothermic reaction of silicon with iron- and chromium oxides, the silicothermic reduction results in a decreased specific electric energy consumption compared to the carbothermic reduction according to the thermochemical simulation. Low phosphorus and sulfur contents in the alloy might result in premium prices, aiding the economic viability of the process.Graphical