Steelmaking converters increasingly face challenges from the use of higher phosphorous ores in the Blast-Furnace and the need to reduce their environmental impact on all aspects, including the volume of generated solid residues. According to CSN's 2023 integrated report, approximately 648.000 tons of steelmaking slag were produced at its plant in Brazil in 2023. Although part of this volume is used as road ballast, this destination does not consume all of the production, making it necessary to study sustainable routes for the use of this by-product. One possibility of reducing the total amount of slag generated in the melt shop while maintaining or improving the converteŕs ability to dephosphorize is to recycle specially adjusted recovered slag mixtures, adding them to the converter to enhance early formation of a fluid slag. In this work, we use a recycled slag mixture regularly produced at CSN, with 40% CaO and around 24% total Fe + MnO. Two aspects of this slag mixture were evaluated to estimate its potential as an early addition to the converter, replacing part of the usual lime addition. First, we investigate storage and handling properties, including the slag mixture stability with time. Then, the effect of the early addition of this recycled slag product to the converter is evaluated. After preliminary studies, tests were performed in a total of 255 heats, (corresponding to a total of 530,000 tons). In these tests, additions of the recycled slag varied in the range of 500–3000 kg/heat. The results of these heats were compared both with standard heats and heats to which an addition of sodalite was made to improve dephosphorization. The comparison included dephosphorization results, slag behavior in the converter and overall lime consumption. The results indicate that the use of the recovered slag mixtures has no effect on stable converter operation, produce effective dephosphorization, and form slags with the desired basicity and theoretical viscosity. With excessive additions of the recycled slag, flame formation was observed during the end of the blow: to prevent potential cooling problems of the gas collection equipment, the addition was limited to 1300 kg/heat. In this scenario, a potential decrease in lime consumption of 2 kg/t of steel was observed. The yearly estimate of the use of this technique would result in savings of 9000 tons of lime, and consequently the generation of CO 2 associated with lime production, and the corresponding reduction in the amount of solid residue.

Steel slag is a significant environmental liability generated by pyrometallurgical processes. Residue generation, such as granulated blast furnace slag and basic oxygen slag (BOF), is intrinsic in steel production. Blast furnace slag, generated in the carbothermal reduction of iron ore, is almost entirely used as a supplementary cement material in Portland cement. BOF slag, produced in the conversion of pig iron into steel in a basic oxygen converter, is still not consolidated or valued for reuse. This research proposes the reuse and valorization of BOF slag combined with blast furnace slag in clinker-free cement production. Cement formulations were produced with different slag and gypsum contents, ranging from 80 to 90% blast furnace slag, 10 to 20% gypsum, and 10 to 15% BOF slag. All formulations were evaluated for compressive strength at ages of 3, 7, 14, 28, 91, and 180 days of curing. At the initial ages, the cement formulations exhibited high resistance. On the 3rd day, the cement formulations reached up to 10 MPa, and on the 7th day, 40 MPa. At late ages, the best-performing formulation, ECO2, showed, after 28 days of hydration, a compressive strength greater than 50 MPa, and at 180 days, a compressive strength greater than 80 MPa. It was possible to understand that BOF slag acts in cement alkaline activation with pH increase, more or less actively due to the presence of lime, portlandite, and calcite.

Fluorine-based mold fluxes are critical for continuous casting of peritectic steels, controlling heat transfer and preventing cracks. However, environmental and health concerns associated with fluorine have spurred the search for alternative flux compositions. This study applied a factorial design to explore the effects of Na2O, TiO2, B2O3, and fluorine on key properties such as viscosity, crystallization temperature, and melting behavior. Analytical methods, including viscosity measurements, differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM-EDS), combined with thermodynamic modeling, were used to evaluate performance. Four formulations were selected based on factorial design results. Sample A, with high Na2O, exhibited intense crystallization of merwinite (Ca3MgSi2O8) and perovskite (CaTiO3). Sample B, incorporating B2O3, had reduced crystallization and suitable viscosity (2.97 Pa·s). Sample C, with a slightly higher fluorine content than Sample B and without B2O3, presented balanced low viscosity (1.75 Pa·s) with a moderate crystallization tendency. Sample D, free of fluorine and B2O3, showed high viscosity (4.58 Pa·s) and significant crystallization. These results demonstrate that fluorine-free fluxes with properties comparable to fluorine-based compositions can be developed, offering a sustainable alternative for steelmaking. Industrial trials are necessary to validate their performance under operational conditions.

The search for binders with a lower environmental impact has grown, especially for those with reduced clinker content or even for formulations not used due to the high CO2 emissions associated with their production. In this context, the steel industry, which generates a significant amount of waste and co-products, especially steel aggregates, such as blast furnace slag and basic oxygen slag, can be a source of raw materials for cement plants. For this reason, in search of an innovative alternative with low environmental impact, in this work, a clinker-free cement was developed by mixing waste from steel and civil construction. The results of this study demonstrated the possibility of producing a Portland clinker-free cement, using only solid waste, through a mixture of steel slag from blast furnaces, basic oxygen slag and gypsum residue from civil construction, presenting hydraulic properties compatible with national cement CPIII-32 and CPII E-32, and the European cement CSS 32.5 N. The cement mixtures were also characterized as resistant to sulfate attack. It was found that the basic oxygen slag acted as an alkaline activator, thus enhancing the hydration process of the mixture of blast furnace slag and gypsum.

The reuse of industrial waste is an important tool to contribute to the sustainable development of different sectors. It is known that most companies do not have reuse policies, making the final disposal of waste in landfills or even inappropriately. In this context, the objective of this work was to study the reuse of the waste from the production of electrofused alumina in red ceramic. Initially, the electrofused alumina waste was characterized, being subsequently used in ceramic bodies to evaluate the properties of linear shrinkage, water absorption, open porosity and flexural rupture strength. Extruded specimens with dimensions of 120 × 30 × 20 mm3 were produced, being fired at temperatures of 750–1050 ºC. The waste was used in contents of 0–10

Basic oxygen furnace slag is considered a potential material for the replacement of natural aggregate in Portland cement concrete due to its similar physical characteristics. Therefore, in the present work, the slag was analyzed by Nitrogen sorption porosimetry, elemental analysis, mineralogical analysis, and volume stability. On the other hand, concrete mixtures were manufactured with basic oxygen furnace (BOF) slag aggregates and characterized mechanically and morphologically. The results showed superior compressive strength due to interfacial improvements in the slag aggregate. Statistically, there was no differentiation between the reference concrete and the slag concrete mixtures for tensile strength. Additionally, due to the porosity and low stiffness presented by the slag, the concrete elastic modulus showed a slight decrease. The replacement of sand with BOF slag as fine aggregate in Portland cement concrete presents itself as a sustainable alternative for the elimination and valorization of this environmental liability.

Explosive spalling is a major concern when drying refractory concretes. For safety, empirically defined overestimated slow heat-up curves are used in industry. Polypropylene fibres reduce spalling; however, they are inconvenient for certain castables due to properties deterioration, such as slag penetration. There is neither a generally accepted methodology to define monolithic refractories dry-out schedules nor agreement about a mathematical model to predict spalling phenomena. This paper presents original numerical and experimental results of castable drying investigation using slow heating. Modifications in experimental methods were made to reproduce refractory lining boundary conditions. A conservative fully implicit finite volume method in three-dimensions was developed to predict pressure and moisture migration. The influence of the methods used to characterize the properties needed for the mathematical model was discussed. The combined analyses suggest that the first holding time used was not productive for drying; however, its effect on curing must be reviewed.

PDF | A caracterização e seleção apropriada dos refratários podem levar a melhorias no desempenho do revestimento refratário, implicando nos seguintes benefícios: uniformização do perfil de desgaste e, consequentemente, redução do consumo específico de refratário e aumento da disponibilidade do equipamento para operação. Neste trabalho são apresentados e discutidos os resultados de caracterização de tijolo refratário de MgO-C para a linha de escória de panela de aço. As principais técnicas de caracterização utilizadas para caracterização de amostras de tijolo antes e após uso foram difratometria de raios X (DRX) e microscopia eletrônica de varredura (MEV) com auxílio da espectroscopia de energia dispersiva de raios X (EDS). Através das análises das amostras post-mortem os principais meios de degradação dos refratários de magnésia-carbono são por dissolução química intergranular da escória nos grãos de MgO e consequentemente dispersão dos grãos para o banho de escória.

In this research, a study was carried out on the application of glass packaging in different granulometries in red ceramics. The raw materials underwent chemical, mineralogical, physical, dilatometric, thermal and microstructural characterization. Specimens were produced using a ceramic mass (0%) and incorporated up to 30% of glass waste in powder form, in granulometry 40,100, 200 and 325 mesh. Specimens produced by uniaxial pressing (35 MPa) and fired at different temperatures (800-1050 degrees C). After firing, the properties of linear shrinkage, water absorption and flexural strength were evaluated. The microstruc-ture was evaluated by optical microscopy. Analyzing the results, it is possible to observe that the raw materials have similar chemical composition and their application in ceramic materials is a highly viable option, and can also act as a flux, improving properties, in addition to reducing the firing temperature. The incorporation of waste reduced the water absorption and significantly increased the resistance of the pieces, mainly in the gran-ulometry of 200 mesh and 325 mesh. In addition to improving the quality of red ceramics, incorporating glass from powder packaging is a highly advantageous alternative for recy-cling, as glass can take thousands of years to decompose in the environment.(c) 2023 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Given the current huge generation of solid waste worldwide, alternative and innovative methodologies for incorporating these materials should be encouraged elsewhere. In this context, the objective of this research is to evaluate the use of glass waste as a substitute for sand as raw material in ceramics. Formulations containing from 0% to 20% of glass waste were produced, thus replacing natural sand. Extruded and calcined specimens were produced at temperatures of 800, 900 and 1000 °C. The characterization results demonstrated the compatibility and their potential for the glass waste for improving the properties of ceramics. Results of density, water absorption and flexural strength improved when 20% of glass waste was added due to the porosity reduction, provided by the formation of a liquid phase and then by a sintering, promoted by the glass waste. This resulted in coherent properties with ceramic applications in the form of tiles and blocks, at a calcining temperature of 800 °C. On the contrary, results without glass did not reach the necessary parameters even at 1000 °C. In conclusion, the feasibility of using glass waste has been proven, which, in addition to improving the material’s properties, provides economy benefits for the ceramic industry, with the calcination process at milder temperatures.

The contradictory properties required of castable refractories makes selecting castable refractories for industrial applications challenging. This paper seeks to describe the material selection for a blast furnace blowpipe application that is subjected to sudden temperature changes and must prevent heat loss. Three commercial high alumina castables containing andalusite or mullite from different manufacturers were characterized. Thermal shock damage resistance was evaluated using thermal shock damage resistance theory and experiments. The castables' coefficient of thermal expansion was estimated using quantitative X-ray diffraction. Crack propagation resistance was measured using the work-of-fracture technique. Thermal shock damage was experimentally evaluated by measuring the modulus of elasticity and rupture prior to and after thermal cycles. Ultimately, the microstructure of the castables was related to the thermal shock damage behavior by estimating the aggregate size and the fracture toughening mechanisms using light optical and scanning electron microscopes. Heat loss was evaluated by calculating the blowpipe shell temperature using a one-dimensional steady-state heat conduction model. The best commercial castable refractory for blowpipe showed high thermal shock damage resistance and low thermal conductivity. The results in this study agreed with thermal shock damage resistance parameters and showed a correlation between coarse microstructure with large aggregate and higher thermal shock damage resistance.

Abstract: This paper compares the thermal shock damage resistance and the slag corrosion resistance of a high-alumina and an alumina-containing andalusite refractory castable. Thermal shock damage resistance was analyzed through thermal cycling and thermal shock damage resistance parameters. Thermal shock cycling damage was analyzed using the dynamic modulus of elasticity (E) and the modulus of rupture (MOR) before and after the thermal shock cycles. The alumina-containing andalusite castable showed superior thermal shock damage resistance in both parameters. The high-alumina castable showed a higher resistance to slag corrosion. These results were linked to material selection for specific industry applications.

Abstract This is a study about the synthesis of SiC from rice husk. The SiC production was carried out in two stages, the first one being the rice husk carbonization under vacuum, at the temperature range from 270 to 650 °C, and the second stage was the pyrolysis of the carbonized rice husk, at the temperature range from 1300 to 1800 °C and 120 min isotherms. The rice husk was characterized by X-ray fluorescence, and the reaction products were characterized by X-ray diffraction and scanning electron microscopy. The temperature influence on pyrolysis was demonstrated. SiC formation occurred in samples treated over 1600 °C, while at lower temperatures, it was possible to observe the secondary formation of cristobalite, tridymite, and quartz. In this study, it was possible to calculate the yield of SiC production as a function of the pyrolysis temperature of the carbonized rice husk.

A ciclos a melhor alternativa econômica e ambiental. trabalho objetivou incorporar resíduo gerado na etapa de eletrofusão da alumina em cerâmica vermelha. Para isso, as matérias-primas foram caracterizadas quimicamente e determinada sua distribuição granulométrica. Foram confeccionados corpos de prova laboratorialmente por extrusão e sinterizados a 850, 950 e 1050 °C. Após, as peças cerâmicas foram submetidas aos ensaios de densidade aparente, absorção de água, porosidade aparente, retração linear de queima e tensão de ruptura a flexão. Apesar do efeito deletério do resíduo, foi demonstrada a viabilidade em sua utilização como matéria-prima para a indústria cerâmica, visto que as propriedades situaram-se dentro dos limites e recomendações para produtos de cerâmica vermelha. Abstract The introduction of waste in other production process has emerged as the best economic and environmental alternative. This work aimed to incorporate the residue generated in the electrofusion step of alumina in red ceramics production. For this, the raw materials were chemically characterized and their granulometric distribution determined. Laboratory specimens were made by extrusion and sintered at 850, 950 and 1050 °C. Afterwards, the ceramic products were submitted to the tests of apparent density, water absorption, apparent porosity, firing linear shrinkage and rupture stress. Despite the deleterious effect of the residue, it was demonstrated the viability in its use as raw material for the ceramic industry, since the properties were within the limits and recommendations for red ceramic products.

This work has as its objective to evaluate the effect of mold flux waste incorporation in a red ceramic body. The mold flux waste came from an industry of additives for continuous casting of steel, in the municipal area of Guaratinguetá, State of São Paulo, Brazil. Initially, the mold flux waste was characterized in terms of chemical composition, particles size distribution, X-ray diffraction, specific surface area and scanning electron microscopy. Clay mixtures were prepared with additions of 0, 5, 10 and 20wt.% of mold flux waste. Red ceramic specimens were produced by extrusion and then fired in an industrial furnace at 750, 850, 950 and 1050ºC. Some physical and mechanical properties were evaluated. The results indicated that mold flux waste addition optimized the plasticity of the clayey body, increased the flexural and compressive strength and reduced the values for water absorption. The specimens with 5wt.% of mold flux waste, at 1050ºC firing temperature, presented the best results for the properties evaluated, indicating a higher packing for this composition. The incorporation of mold flux waste allowed improvements in the clayey body, producing better quality materials and being an appropriate way of disposal.

The natural aggregates of the construction industry are the most exploited mineral inputs in the world and their demand expands with increasing infrastructure. To ensure the conservation of natural aggregates, it is imperative to study alternative aggregates, such as wastes generated by steel mills. LD mill slag is the main residue of the steel refining process. In the context of the excessive extraction of natural aggregates, the use of steel residues can be justified due to its crystalline structure of high resistance to abrasion and hardness. Thus, in this work the characteristics of LD steel slag for the use as concrete aggregate were evaluated, as well as the effect generated in Portland cement concrete by the use of LD slag in substitution of natural sand in proportions 0%; 25%; 50% and 75% by weight. The slag concretes studied showed significant improvements in the compressive strength, similar to the reference behavior in the tensile strength, and a significant reduction in the modulus of elasticity as a function of the porous structure presented by the slag. As well as the aggregates presented expansive behavior in alkaline cure.

The indirect selective laser sintering (SLS) process consists of a powder-based additive manufacturing (AM) technique. Recently, an attempt was carried out using the indirect-SLS method on ceramics to obtain complex geometric parts without the need to fabricate tools or molds. In this context, the ceramic particles employed in indirect-SLS must be coated with a polymer layer and retain spherical format. Currently, several processes of encapsulation and balling up of ceramic particles are available, among which thermally induced phase separation (TIPS) is noteworthy. The present study describes the synthesis, via TIPS, of spherical micrometric alumina particles coated with polyamide 12 to be employed in indirect-SLS. Dimethyl sulfoxide (DMSO) was used as a solvent to obtain these particles. After encapsulation, the agglomerates were characterized according to granulometry, microstructure, thermal behavior, and flowability. The obtained results delineated the ideal conditions to synthesize agglomerates with adequate flowability, particle size profile, and similar thermal behavior to that verified for PA-12, a currently used material in SLS printing. Based on the results of the present study, it is possible to confirm the effectiveness of the TIPS technique in obtaining ceramic polymer-coated spherical particles that are suitable for use in AM processes via indirect-SLS.

The technological process of clinkerization is responsible for a high consumption of energy and the release of carbon dioxide (CO2) to the environment. It is estimated that the cement industry generates, for every tonne of cement produced, around 0.7-1 tonne of CO2, in order to be responsible for 5% of CO2 global emission, while in Brazil, this corresponds to 1.4%. This study reused the basic oxygen furnace slag, submitted to different cooling processes, for the partial replacement of clinker. Formulations of CPIII portland cement were prepared with substitution of 5.4% by weight of clinker by basic oxygen slag with 53 and 71% amorphous phase. The compressive strength was evaluated at ages 3, 7, 28 and 91 days, determined setting times, hot and cold expansibility. The addition of basic oxygen furnace slag, regardless of the crystallinity degree, provided the cement gains in the initial and final mechanical strength. By adding slag with 71% amorphous phase, the cement presented 29 and 40.4 MPa of compressive strength after 7 and 28 days, respectively; while with the addition of slag with 53% amorphous phase, the cement strength exhibited 31.9 MPa after 7 days and 41.4 MPa after 28 days. The use of BOF slag, as a partial clinker substitute, allows it to reduce pollutant emissions and to achieve a higher energy efficiency without affecting the cement physical-chemical properties. (C) 2017 Elsevier Ltd. All rights reserved.