Search Results (76)

Barro Alto processes nickel laterite ore using rotary kilns and six-in-line rectangular electric arc furnaces. This study evaluated the briquetting of ferronickel ore to reduce kiln fines, improve furnace charge permeability, and enhance process safety. Binderless briquettes were produced from screened ore at two size fractions (−6.3 mm and −12.5 mm), with moisture contents of 16% and 24%, cured under closed and open conditions. The physical and metallurgical properties of the briquettes were assessed using ISO standard tests. The results confirmed successful agglomeration of the ore into binderless briquettes. Screening the run-of-mine (ROM) ore improved the feed quality, increasing the NiO grade from 2.0% to 2.2% in the −6.3 mm fraction. The briquettes from the −6.3 mm ore at 16% moisture exhibited the highest green strength (559 N). Higher moisture content reduced the briquette strength and increased both the reduction disintegration and decrepitation indices. The decrepitation index increased from 0.33% to 0.61% for the −6.3 mm briquettes when the moisture increased from 16% to 24%. The reduction levels were 33.4% and 39.2% for −6.3 mm and −12.5 mm briquettes with 16% moisture, respectively. This study concludes that optimal performance was achieved using −6.3 mm ore, 16% moisture, and open curing, thereby balancing reduction efficiency and mechanical stability. Full article

This study presents the results of laboratory experiments on the processing of lateritic nickel ores mixed with coal and CaO, followed by the use of the obtained product for the smelting of nickel-containing ferroalloy by the metallothermic method. The study analyzed the thermodynamic effects of complex reductant concentration (silicon- and aluminum-containing alloy) on the reduction degree of nickel and iron. An experimental process resulted in a product containing Ni_total (2.60%) and Fe_total (60.52%), obtained through reduction roasting of lateritic nickel ore mixed with coal and an addition of 20 g of CaO at a temperature of 1150 °C. Under laboratory conditions, a nickel-containing ferroalloy was successfully obtained using the product after reduction roasting and a complex alloy as the reducing agent. The following optimal process parameters were determined: reductant consumption of 20 g per 100 g of the reduction roasting product, smelting temperature of 1600 °C, and slag basicity (CaO/SiO₂) of 0.5. In this case, a nickel-containing ferroalloy with 72% iron, 15% nickel, and up to 5% chromium was successfully obtained through silicon and aluminum reduction using a complex alloy. A microstructural analysis of the nickel-containing alloy was conducted using an electron probe microanalyzer (JXA-8230) in combination with scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results showed that silicon and iron were the dominant elements in all particles. Nickel was detected at concentrations of up to 15.02 wt. %, while chromium reached 3.47 wt. %. Depending on the silicon concentration, the nickel-containing ferroalloy is recommended for corrosion-resistant steel production (Si < 5%) and as a reducing agent for ferronickel production (Si > 5%). Full article

In modern nickel mineral processing operations, the aim is to separate pentlandite from gangue minerals. One of these gangue minerals, pyrrhotite, contains up to 1 wt% Ni but is disposed of as waste, i.e., as tailings. Declining sulfide ore grades and increasing nickel demand have led to renewed interest in extracting nickel from pyrrhotite tails. One proposed process is thermal concentration, which aims to recover the nickel as a ferronickel alloy via thermal treatment at temperatures greater than 900 °C. Achieving these temperatures requires substantial energy input as the reactions involved are highly endothermic. In the present research, microwave radiation was used to process a reaction mixture consisting of a concentrate of pyrrhotite tails, iron ore, and metallurgical coke. The fundamental property that determines the interaction of microwaves with a material is complex permittivity. It was found that the reaction mixture had very high real and imaginary permittivities, making it a good candidate for microwave treatment. An input power of 800 W of microwave radiation (2450 MHz) was then employed to heat various reaction mixtures for thermal treatment times of 120, 300, and 600 s. The ferroalloy grades (6–7.5 wt% Ni) were comparable to those produced by conventional heating and to those obtained by other authors using conventional heating techniques. The microwaved samples had increased metallization of nickel, which was attributed to increased melting due to the higher internal temperatures. Full article

Saprolite ores in nickel laterite deposits are pyrometallurgically processed to produce Fe-Ni alloy and Ni matte. The key to achieving the highest recovery degrees from nickel ore in electric arc furnaces and producing top-quality ferro-nickel alloys lies in maintaining optimal carbon consumption and carefully controlling the composition of the slag. This research work focused on finding the optimal smelting procedure for extracting ferro-nickel from calcined nickel ore. Comparing experimental data to the results of thermodynamic modeling using Factsage 8.2 software was a key part of the study. The nickel smelting process, which involved a carbon consumption of 4 wt.%, resulted in ferro-nickel with an Fe/Ni ratio of 4.89 and slag with a nickel content of just 0.017%. The structure and properties of nickel slag in the MgO-SiO₂-FeO system were investigated by observing the changes in the MgO/SiO₂ ratio. This study found a significant nickel recovery degree of 95.6% within the optimal M/S ratio range of 0.65 to 0.7. When the M/S ratio exceeds 0.7, iron-rich magnesium silicates (Mg_xFe_ySiO_2+n) are generated within the slag. These compounds are released downwards due to their higher specific weight, restricting the movement of small metal particles and contributing to increased metal loss through the slag. Optimized slags could revolutionize smelting, increasing metal recovery while minimizing environmental impact. Full article

This study aimed to develop optimized alkali-activated concrete using ferronickel slag for high-temperature applications, focusing on minimizing environmental impact while maintaining high compressive strength and slump. A response surface methodology, specifically the mixture design of experiments, was employed to optimize five components: water, FNS-based alkali-activated binder, and three aggregate sizes. Twenty concrete mixes were tested for slump and compressive strength before and after exposure to 600 °C for two hours. The optimal mix achieved 88 MPa compressive strength before heat exposure and 34 MPa after, with a slump of 140 mm. An upscaled version with improved workability (210 mm slump) maintained similar unheated strength but showed reduced post-heating strength (23.5 MPa). Replacing limestone with olivine aggregates in the upscaled mix resulted in 65 MPa unheated and 32 MPa post-heating strengths. Life Cycle Analysis revealed that the optimized ferronickel slag alkali-activated concrete’s CO₂ emissions were 77% lower than those of ordinary Portland cement concrete of equivalent strength. This approach demonstrated the applicability of mixture design of experiments as an alternative design methodology for alkali activated concrete, providing a valuable performance-based design tool to advance the application of alkali-activated concrete in the construction industry, where no prescriptive standards for alkali-activated ferronickel concrete mix design exist. The study concluded that the developed ferronickel slag alkali-activated concrete, obtained through a performance-based mixture design methodology, offers a promising, environmentally friendly alternative for high-strength, high-temperature applications in construction. Full article

Various studies have reported the use of alkali-activated composites to enable sustainable development in the construction industry as these composites eliminate the need for cement. However, few studies have used ferronickel slag aggregates (FSAs) as an aggregate material for alkali-activated composites. Alkali-activated composites are environmentally friendly and sustainable construction materials that can reduce carbon dioxide emissions from cement production, which accounts for 7% of global carbon emissions. In the construction industry, various research was conducted to improve the performance of alkali-activated composites, such as changing the binder, alkali activator, or aggregate. However, research on the application of ferronickel slag aggregate as an aggregate in alkali-activated composites is still insufficient. In addition, the effect of ferronickel slag aggregate on the performance of alkali-activated composites when using calcium-based or sodium-based alkali activators has not been reported yet. Thus, this study prepared ground granulated blast-furnace slag-based alkali-activated composites with 0, 10, 20, and 30% FSA as natural fine aggregate substitutes. Then, the fluidity, micro-hydration heat, compressive strength properties, and resistance to chloride ion penetration of the alkali-activated composite were evaluated. The test results showed that the maximum temperature of the CF10, CF20, and CF30 samples with FSA was 35.4–36.4 °C, which is 3.8–6.7% higher than that of the CF00 sample. The 7 d compressive strength of the sample prepared with CaO was higher than that of the sample prepared with Na₂SiO₃. Nevertheless, the 28 d compressive strength of the NF20 sample with Na₂SiO₃ and 20% FSA was the highest, with a value of approximately 55.0 MPa. After 7 d, the total charge passing through the sample with Na₂SiO₃ was approximately 1.79–2.24 times higher than that of the sample with CaO. Moreover, the total charge decreased with increasing FSA content. Full article

Ferronickel slag (FNS) is a byproduct produced during ferronickel alloy manufacturing, primarily used in the manufacturing of stainless steel and iron alloys. This material is produced by cooling molten slag with water or air, posing significant disposal challenges, as improper storage in industrial yards can lead to environmental contamination. This study investigates the chemical and mineralogical characteristics of reduction ferronickel slag (RFNS) and its potential use as an alternative aggregate in hot mix asphalt (HMA). The research is based on the practical application of HMA containing RFNS in an experimental area, specifically the parking lot used by buses transporting employees of Anglo American, located at the Codemin Industrial Unit in Niquelândia, Goiás, Central Brazil. Chemical analysis revealed that RFNS primarily consists of MgO, Fe₂O₃, and SiO₂, which are elements with minimal environmental impact. The lack of significant calcium content minimizes concerns about expansion issues commonly associated with calcium-rich slags. The X-ray diffractogram indicates a predominantly crystalline structure with minerals like Laihunite and Magnetite, which enhances wear and abrasion resistance. HMA containing 40% RFNS was tested using the Marshall methodology, and a small experimental area was subsequently constructed. The HMA containing RFNS met regulatory specifications and technological controls, achieving an average resilient modulus value of 6323 MPa. Visual inspections conducted four years later confirmed that the pavement remained in excellent condition, validating RFNS as a durable and effective alternative aggregate for asphalt mixtures. The successful application of RFNS not only demonstrates its potential for local road paving near industrial areas but also underscores the importance of sustainable waste management solutions. This research highlights the value of academia–industry collaboration in advancing environmentally responsible practices and reinforces the contribution of RFNS to enhancing local infrastructure and promoting a more sustainable future. Full article

Knowledge of the phase equilibria in the MgO–CaO–SiO₂–Al₂O₃ slag system is crucial for the nickel laterite smelting process. The phase equilibria of this slag system were experimentally investigated, focusing on the olivine and tridymite/cristobalite primary phase fields, using high-temperature equilibration and quenching methods, followed by Scanning Electron Microscopy–Energy Dispersive X-Ray analysis. The phase equilibria of the MgO–CaO–SiO₂ slag system at 1400 °C and 1500 °C were first determined in the absence of ferronickel alloy. The phase equilibria between 1400 °C, 1450 °C, and 1500 °C were then determined under a reducing condition, i.e., at equilibrium with ferronickel alloy and solid carbon. Finally, the effect of Al₂O₃ addition on the liquidus and solidus compositions in the slag system under the reducing condition was investigated at 1400 °C and 1450 °C. Comparisons between the experimentally constructed diagram, previous data, and FactSage-predicted phase diagrams have been provided and discussed. The present study identified the liquid slag both in the absence and presence of ferronickel alloy and solid carbon, as well as in the presence of Al₂O₃ impurity, within the formation boundaries of olivine and tridymite/cristobalite solids. Identifying the liquid slag area is essential to ensure that the nickel laterite smelting slag can be tapped from the furnace. Full article

The concentrations of cadmium, copper, lead, zinc, nickel, and chromium in samples of sediment, water, and Typha angustifolia plants in the stream of the Drenica River were determined to assess the level of pollution. According to sediment analysis results from seven locations, the concentrations of Cu, Ni, Zn, and Cr exceeded the permitted limits according to WHO standards from 1996. In the plant samples, the concentrations of Cd and Pb were above the allowed limits according to GD161 and ECE standards, and according the WHO standard, the water quality in the Drenica River is classified into the first, second, and third quality categories. The results of this study show the bioaccumulation coefficient in Typha angustifolia plants, and it was found that the most bioaccumulated of the metals is Cd, with a bioaccumulation coefficient (BAF) greater than 1. The pollution load index (PLI), enrichment factor (EF index), Geoaccumulation index (Igeo), potential ecological risk factor (Eif), and potential ecological risk index (RI) were used in combination to assess the degree of pollution and the environmental risk presented to the freshwater ecosystem of the Drenica River. The results show that the Drenica River is mainly polluted by Ni, Cu, and Cr, reflecting substantial impacts of anthropogenic activities, including sizeable industrial effects, the development of urbanism, agricultural activities, and the deposition of waste from a ferronickel factory in the area. Full article

The use of ferronickel slag powder (FNSP) as a cementitious additional material has been supported by numerous reports. FNSP concrete has the same shortcomings as ordinary concrete, including low hardness. In this study, in order to make FNSP concrete more durable, end-hooked type steel fibers were incorporated. To understand how various elements affect the mechanical properties of steel fibers, an experiment was carried out on the mechanical properties of steel FNSP concrete (SFNSPC). FNSP’s principal ingredients, with a particle size distribution ranging from 0.5 to 100 μm and a sheet-like powder shape, are CaO, SiO₂, Al₂O₃, MgO, and others, according to tests conducted on the material’s microstructure and composition. Then, eighteen mix proportions were developed, comprising six distinct FNSP replacement rate types and three distinct steel fiber content types. Crucial metrics were evaluated and analyzed, including the relationship among the toughness, tensile strength, and compressive strength as well as slump, splitting tensile strength, compressive strength, and uniaxial compressive stress–strain curve of SFNSPC. The results showed that the slump of SFNSPC under different FNSP replacement rates decreased with increasing steel fiber volume. Steel fibers have a small but positive effect on SFNSPC’s compressive strength; nonetheless, as FNSP replacement rates increased, SFNSPC’s slump gradually decreased, though not by much. These results show that FNSP is a viable alternative cementitious material in terms of strength. Specifically, the splitting tensile strength of SFNSPC improves with an increase in steel fiber content, and the pace at which SFNSPC strength drops with an increase in the FNSP replacement rate. With varying mix proportions, the stress–strain curve trend of SFNSPC remains mostly constant, and steel fibers improve the compressive toughness of SFNSPC. After adding 0.5% and 1.0% steel fibers, the toughness index of concrete with different FNSP replacement rates increased by 8–30% and 12–43%, respectively. Full article

This study’s aim is to fully characterize ferronickel slag from New Caledonia, considered a multiphase mineral containing amorphous material. The methodology consisted of combining chemical, mineral, and morphological characterization techniques, such as ICP-AES, TGA, Q-XRD, microscopy, spectroscopy, etc. The ferronickel slag consisted of 44 wt. % forsterite, with the inclusion of iron as a substitution for magnesium (Mg_1.8Fe_0.2SiO₄), 1.7 wt. % chromite and 54 wt. % amorphous phase containing iron, magnesium, aluminum, and silica (Mg/Si = 0.4; Fe/Si = 0.2; Al/Si = 0.1). This material was slightly reactive in a cementitious medium, thus limiting its use as an SCM in the construction sector. The ferronickel slag was then subjected to an attrition-leaching carbonation process at 180 °C and a partial pressure of CO₂ of 20 bar. The obtained product, carbonated at 80% of its capacity, was also characterized. It was composed of carbonates (37% of magnesite and 4% of siderite), remaining forsterite (7 wt. %), chromite (1 wt. %), and 50% of an amorphous phase, mainly composed of silica and aluminum. The complete characterization of those products helped in understanding the chemistry of the carbonation process and finding valorization paths for the carbonated products in the construction sector. The carbonated product may be used either as an SCM in blended cement or as a precursor of magnesium–silicate binders. Full article

The smelting process of Ferronickel in Indonesia produces a significant amount of waste in the form of Ferronickel Slag (FNS), with an annual accumulation of up to 13 million metric tons. Previous studies have shown promising strength results for concrete utilizing FNS as a fine aggregate. This study aims to analyze the mechanical properties of three reinforced concrete (RC) beams measuring 15 cm × 25 cm × 300 cm, each containing FNS as a 50% substitute for fine aggregate. The RC Beams underwent experimental testing using a four-point loading scheme under semi-cyclic loading conditions. Test results show the beams’ capacity had reached up to 8 ton-f and their load–displacement responses show promising results. Digital Image Correlation (DIC) analysis facilitated the observation of surface deformation evolution due to loading, aiding in the identification of concrete crack patterns. Due to semi-cyclic loading, cracks on the beams’ surface were experiencing a crack opening and closing phenomenon, where the propagations of cracks ceased or reclosed throughout the unloading process. Moreover, the opening of residual cracks was also captured by DIC analysis. The experimental finding was validated by finite element analysis. The RC beam numerical model was created using the Timoshenko Multi-fiber element in CAST3M software version 2022. Mazars concrete and elastoplastic steel damage model were used as constitutive laws for numerical modeling. The model’s load–displacement response demonstrated satisfactory agreement compared to the experimental monotonic loading result. However, the model had limitations regarding the simulation of residual displacements of beams due to semi-cyclic loading. Full article

Currently, the global shift towards green energy is at the forefront of efforts introducing a new era, thus rendering exploration for critical raw materials essential. To this purpose, the utilization of advanced machine learning methods in remote sensing has emerged as a rapid and cost-effective approach. This study proposes a new methodology, utilizing Sentinel-2 satellite data, to distinguish ferronickel (Fe-Ni-) laterite from bauxite across pre-mining, mining, and post-mining occurrences worldwide. Both ores contain mineral raw materials such as nickel, iron, cobalt, and alumina and their discrimination is generally macroscopically challenging, especially when their locations are often in geographical proximity. The proposed method is based on Support Vector Machines (SVM) classification using spectral signatures of known Fe-Ni-laterite and bauxite-bearing pixels in Greece, Cuba, and Jamaica. The highest classification accuracies are obtained by combining b12 with b6 or b7 spectral bands. Comparisons with specific ore mineralogies show that b6 and b7 are strongly linked to the ferric phase, while b12 is mainly associated with the argillic mineralogies, the latter probably being the key discriminating factor between the two ores. From laboratory chemical analyses, we also establish that b12 and b6 or b7 are strongly associated with Al₂O₃ and Fe₂O₃ content correspondingly. The proposed method is accurate, it has reduced prospection costs, and it can facilitate the initial screening of broad areas by automatically characterizing whether an ore is bauxite or Fe-Ni-laterite. This underscores the methodology’s significance in ore differentiation and exploration within the context of green energy endeavors. Full article

Ferronickel slag is the solid waste slag produced by smelting nickel–iron alloy. After grinding ferronickel slag into powder, it has potential chemical activity. It can partially replace cement and reduce the amount of cement, and is conducive to environmental protection. The mechanical properties of soil cement were investigated through the compressive strength test and inter-split tensile test of ferronickel slag powder soil cement with different dosages. To further study the mechanism of ferronickel slag powder’s action on soil cement microscopically, the microstructure of soil cement was analyzed by using a scanning electron microscope and nuclear magnetic resonance equipment. The results of the study show that the incorporation of ferronickel slag powder can enhance the compressive and tensile strength of soil cement. The best performance enhancement of ferronickel slag powder was achieved when it was doped with 45% of its mass. The hydration products of soil cement increased with the increase in the doping amount, but the excessive doping of ferronickel slag powder would lead to a weakening of the hydration reaction and a decrease in the strength of the soil cement. At the same time, ferronickel slag powder plays the role of filling the void of soil cement. With the increase in ferronickel slag powder, the large pores inside the soil cement are reduced and the structure is denser. Full article

This paper presents a study on the combined use of two by-products, namely quarry dust (QD) and ferronickel slag (FNS), as a full substitute for natural sand to improve the greenness of concrete production. Quarry dust was used in increments of 25% to a maximum of 75% substitution, where nickel slag was used as the remaining proportion of fine aggregate. All the combinations of quarry dust and nickel slag were found to be compliant with AS 2758.1 and they showed notably better grading than 100% sand. In this research, standard concrete tests, such as the slump test for fresh concrete, and compression, tensile and shrinkage tests for hardened concrete, were conducted. Scanning electron microscopy and X-ray diffraction analysis were also conducted for microstructural investigation. The results concluded that the combinations of quarry dust and nickel slag in concrete as a whole substitution of sand provide similar results for these properties. Specifically, 25% quarry dust with 75% nickel slag proved to be the most promising alternative to sand, with compressive and splitting tensile strengths of 62 and 4.29 MPa, respectively, which were 16% and 20% higher than those of the control mix. Also, lower drying shrinkage was observed for this combination compared to the control mix. The higher strength is attributed to the rough texture and angular shape of both quarry dust and nickel slag providing a better mechanical interlocking. The validity of this result has also been confirmed through image analysis of micrographs from various specimens. In microstructural investigations, specimens with QD and FNS exhibited fewer voids and a more compact surface compared to the control specimen. This shows the potential for further research into the use of quarry dust and nickel slag in the production of green concrete. Full article