REM - International Engineering Journal, Volume: 75, Issue: 1, Published: 2022
  • Lessons learned from leading diverse teams Editorial

    Coelho, Jório
  • Finite element computational development for thermo-mechanical analysis of plane steel structures exposed to fire Civil Engineering

    Neves, Natan Sian das; Camargo, Rodrigo Silveira; Azevedo, Macksuel Soares de

    Abstract in English:

    Abstract This article presents a numerical formulation based on finite element procedures for application in nonlinear thermo-mechanical analyses of steel planar structures under fire condition. The mechanical properties of structural elements degrade when subjected to high temperatures, resulting in significant reductions in strength and stiffness. Under these conditions, the structures present complex behaviors associated with nonlinear models, requiring an advanced mathematical analysis. As such, a computer program called NASEN has been developed to investigate the behavior of steel structures subjected to fire, considering the effects of geometric and material nonlinearity, as well as the thermal gradients acting on the cross-section. The solution strategy is based on sequential coupling of numerical processes. Initially, the two-dimensional thermal field is determined, followed by an assessment of structural behavior. In each solution step, corrective processes are implemented to ensure convergence of the temperature and displacement nodal vectors. Numerical experiments are performed in order to evaluate the accuracy and capacity of the computer program. Results are compared with experimental tests and computer simulations found in pertinent literature. The program shows good agreement with reference solutions, indicating its accuracy and applicability for the cases studied.
  • Thermal characterization of soil-cement bricks using mining tailings Civil Engineering

    Gomes, Ana Cláudia Franca; Cordeiro, Carol Cardoso Moura; Callejas, Ivan Julio Apolonio; Rocha, Sônia Denise Ferreira

    Abstract in English:

    Abstract Soil-cement bricks are earth construction materials that have been gaining prominence due to their environmental advantages. The Brazilian Technical Standard NBR 8491 establishes physical and mechanical procedures to characterize these bricks. However, the thermal characterization is an important assessment, since it is related to the building’s thermal performance. The objective of this study is to thermally characterize a panel of soil-cement bricks produced with mining tailings. For such, its absorptance (α) was evaluated using the ALTA II spectrometer, and its thermal transmittance (U) and thermal resistance (RT) through the hot box method (ISO 9869). The results enabled the calculation of the thermal capacity (CT), thermal lag (φ) and solar factor (FSO) of the panel, which were compared to the Brazilian Technical Standards NBR 15575-4 and NBR 15220 for Bioclimatic Zone 8. As a result, the soil-cement body panel showed values of α = 0.71, U = 2.47 Wm-2K-1, CT = 273.4 kJm-2K-1, φ = 6.02 h and FSO = 6.81%, meeting the requirements established in the first standard, but failing to attend the second. To comply with the Brazilians specifications, it is suggested to paint bricks with lighter colors focusing on decreasing its absorptance value. Thus, soil-cement bricks may be an environmental alternative to dispose of the waste generated during the mining process, contributing to sustainability.
  • Steel desulfurization on RH degasser: physical and mathematical modeling Metallurgy And Materials

    Silva, Antonio Marlon Barros; Peixoto, Johne Jesus Mol; Silva, Carlos Antônio da; Silva, Itavahn Alves

    Abstract in English:

    Abstract Due to the high-quality steel demand, especially for ultra-low Sulfur steel, RH desulfurization has been practiced. Based on this, mathematical and physical modeling have been applied to study steel desulfurization by reagent addition in the RH degasser vacuum chamber. The main result of cold modeling, using water and oil emulating steel and slag, respectively, was to assess the influence of density difference between the continuous and disperse phases on oil droplet behavior. It is shown that its flow tends to be more restricted near the down snorkel when the density difference increases. Moreover, these results provide the basis for CFD modeling validation, which enabled the determination of slag drop residence time inside steel on RH and the average value of the rate of dissipation of turbulent kinetic energy inside the RH ladle. These two parameters were used to develop a kinetic model, which reaches a good agreement with industrial trial results available in literature. The optimum desulfurization degree of 31.44% was achieved for a gas flow rate of 90 Nm3/h, according to the kinetic model. This value can be useful in some steel grade production, where the required S content is less than 10 ppm. Even in common steel grade production, if some punctual chemical adjustment is necessary, this technique is also useful. The main kinetic parameter for steel desulfurization is the steel circulation rate. For best results, it should be reduced in the desulfurization stage, and after that, the normal operation can be resumed, so that the production cycle is not affected.
  • Comparative evaluation of three classical sizing methods of vibrating screens Mining

    Sales, Cristiano Geraldo; Galery, Roberto

    Abstract in English:

    Abstract The sizing of vibrating screen machines can be done by various methods, most of them based on the classic method of Allis Chalmers (ACM). Due to the wide diffusion and applicability, the Peter King (PKM) and Karra (KM) methods present great technical relevance as well. The objective of this study was to evaluate and compare the results of the screen surface areas, calculated by these three methods, and the real areas of the industrial machines. The study was based on data generated in 11 real industrial screening operations, being possible to evaluate the deviations of the areas calculated by the mathematical methods in relation to the real areas of the industrial machines. Results have shown that although all methods have restrictions on their use, PKM has the smallest deviations compared to the real dimensions of the industrial machines for four screening conditions. All these conditions showed screen apertures from 4.76mm to 19mm, moisture from 2.12% to 3.3%, Gneiss as feed material and deviations smaller than 13%.
  • MLA and optical microscopy as complementary techniques to the iron ore geometallurgical studies Mining

    Rodrigues, Rafael de Souza; Brandao, Paulo Roberto Gomes

    Abstract in English:

    Abstract Mineral liberation is an important variable to be considered in the iron ore geometallurgical studies, especially since it provides information leading to the understanding of the ore’s behaviour in the beneficiation process, mainly when harder ores are concerned. Nowadays, the professionals and researchers in the mineral industry have been using complementary techniques for mineralogical characterization. In this way, Mineral Liberation Analyser (MLA) and optical microscopy are amongst the most efficient and important tools in these studies. Together, these techniques can provide information leading to the development of geometallurgical models, including the degree of quartz liberation, mineral modal composition, mineralogical association and particle and mineral size distribution, as well as the spectrum of mineral liberation either by free surface or particle composition. The purpose of this study is to compare the degree of quartz liberation in four different iron ore types observed in optical microscopy and MLA. It also assesses the influence of mineral liberation in the quality of the resulting concentrate, according to the SiO2 content. All the results of the various quartz liberation degrees, determined by both MLA and optical microscopy were very close, as well as the correlation between the mineral liberation and the ore’s response in the flotation process. The investigation provided evidence that the mineral liberation study is an important tool in the prediction of the ore’s behaviour in the beneficiation process.
  • Optical sorting technology for waste management from the Boukhadra iron ore mine (NE Algeria) Mining

    Rouaiguia, Issam; Bounouala, Mohamed; Abdelmalek, Chiraz; Idres, Abdelaziz; Benselhoub, Aissa

    Abstract in English:

    Abstract Mining processes in the iron ore mine of Boukhadra, Tebessa (NE Algeria) generated thousands of tons of mining wastes every year, which represents a real threat to the environment, leading to hazardous effects for the resident population of the region. The aim of this study is the selective sorting of the Boukhadra mining wastes for valorization. This will facilitate the recycling of the mineral substances (limestone, iron, marls) on the one hand and it makes it possible to minimize the volume of stocks and their environmental impacts on the other hand. To do this, and taking into account the chemical properties of wastes, we recommend an optical separation management using a color camera and a microprocessor linked to the ejection system (valve or pump), the color measurement tests performed on Boukhadra waste rocks samples using Matlab codes converted from Algorithms showed that each rock has a specific color (Red Green Blue value) or RGB. For this purpose, the use of three optical separators that sort according to algorithmic commands (RGB interval) will contribute to the separation of the Boukhadra mining wastes and consequently simplify their reuse.
  • Strain analysis in diametral compression test through digital image correlation Mining

    Silva, Ângelo Quintiliano Nunes; Galery, Roberto

    Abstract in English:

    Abstract In the search for alternatives to obtain more information from rock tests and to make them more accessible, this study applies the Digital Image Correlation technique (DIC 2D) in a diametral compression test called Brazilian Test, comparing the result measured by an extensometer with the result obtained by DIC. Rock tests provide information about rock characteristics applicable to several engineering areas, such as mining and construction. In tests using strain gauges to measure strain, the equipment is expensive and there is a risk of breaking the instrument due to the contact with the specimen. However, tests measuring strain through the DIC technique may be more accessible, using open source software and lower cost equipment when compared to the cost of the extensometers. The results of this study demonstrate that the DIC technique enables: 1) complementing the information of diametrical tests obtained using strain gauges, for example, supporting the visualization of crack propagation; and 2) in some cases, replacing the use of extensometers, as far as a variation is tolerated.
  • Short-term mine scheduling targeting stationary grades Mining

    Toledo, Augusto Andres Torres; Marques, Diego Machado; Costa, João Felipe Coimbra Leite; Capponi, Luciano Nunes

    Abstract in English:

    Abstract In short-term mine planning, mining scheduling is generally defined by designing dig-lines, allocated on benches. The mined ore will be sent to stockpiles, homogenization piles, or a concentration plant. The process to design dig-lines is usually done manually, whereby multiple simultaneous mining fronts are time-consuming and labour-intensive. The manual design of dig-lines tends to produce high variability of the grades throughout certain periods. Due to the limited time to manually multiple test dig-line design alternatives in short term planning, it is impossible to ensure production under stationary mean grades and variance. This article proposes an alternative to design short-term dig-lines, through an optimization process that joins and sequences the blocks in the block model over weeks or months, ensuring low variability of grades among periods. The methodology proposed generates multiple random paths starting at seed-points representing the locations and numbers of shovels previously selected by the mine planner. It tests multiple polygons representing a set of first dig-lines, comparing them with others, and keeping the dig-lines of low variability closer to a specific ore grade probability distribution, discarding the rest of the iterations. The process is repeated for the next dig-line. The block grades' probability distribution of all iterations is compared to a reference-grade histogram, and the iterations with the grade histogram more adherent are selected. Union-find and genetic algorithms were used to optimize the dig-lines aiming at the possible stationary grade distribution. The mean and variance of the reference model are 2.13% and 0.64%2, respectively. The mean for the automated draw dig-lines is closer to these values than the ones manually drawn. The method ensures more constant quality and quantity of ore production along a period planned, matching a target grade probability distribution. The methodology is illustrated using SiO2 values at a major iron ore mine.
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