Scielo RSS <![CDATA[Rem: Revista Escola de Minas]]> vol. 68 num. 3 lang. en <![CDATA[SciELO Logo]]> <![CDATA[Editorial]]> <![CDATA[Influence of growth ring orientation of some wood species to obtain toughness]]> Wood toughness is a mechanical property of interest in structural design where the load impact must be considered, finding a strong application in bridges, however, not an integral part of the mechanical properties commonly investigated in the characterization of this material. This study aimed to investigate with the aid of variance analysis, the influence of growth ring orientation to obtain toughness for Angelim Saia (Parkia pendula), Eucalyptus grandis, Pinus elliottii and Corymbia citriodora wood species, considering three different positions, so that the orientation causes tensile strength in fibers near the pitch, near the bark, and in the radial direction. The results of the statistical analysis revealed that there was no significance in the orientation of the growth rings to obtain the toughness of the wood species investigated, where the highest values were for Corymbia citriodora and the least values were for Pinus elliottii. <![CDATA[Maps of deformations in a cantilever beam using particle image velocimetry (PIV) and speckle patterns]]> PIV (particle image velocimetry) has been spreading in studies that use the movement of particles to monitor the displacement of an object or the flow of a fluid by means of velocity vectors using optical techniques and second order statistics. PIV is also known as laser speckle velocimetry when associated with speckle patterns. This technique has been used in works involving fluids, in general, building a map of velocity vectors representing the flow under analysis. This paper presents an approach by using PIV associated to speckle patterns for deformation measurements in a cantilever beam (ASTM A36 steel), one of the most common examples used in civil engineering, without the introduction of external particles. Results showed that the difference between PIV associated to speckle patterns and the analytic displacement values is increased along the beam length for a load of 1.96 N as an evidence of sensitivity of the proposed measurement method. This indicates that PIV is also capable for detecting displacement fields associated with laser speckle patterns in solid mechanics generating a map of deformation as an additional option for non-destructive tests. <![CDATA[The kimberley process certification system - KPCS and diamond production changes in selected African countries and Brazil]]> After more than a decade since its creation, the KPCS is undergoing questioning as to efficiency in combating the irregular trade of diamonds, among the countries with significant production for the global market, mainly Angola, the Democratic Republic of the Congo and Zimbabwe. Governments and institutions are considering it to be conducive to serious violations of human rights. In Brazil all activities of the sector have been reduced drastically. It is estimated that there has been a loss in Brazilian production, after implementation of the KPCS rules, in the order of 8.1 million Kts, valued at more than $ 2.0 billion. <![CDATA[Thermal processes for lead removal from the funnel glass of CRT monitors]]> The disposal of CRT monitors increases each year, generating millions of tons of waste containing various types of materials. The glass present in CRT tubes displayed about 20%-25% of lead oxide. If improperly disposed of, this glass can be leached directly in nature or may cause environmental contamination, especially with lead. Because of this leaching possibility, this waste is classified as Class I solid waste, according to the NBR 10004. Thermal processing of these glass tubes was seen as an alternative to remove lead from the glass matrix. Parameters such as reaction time, percentage of reducing agent, the reaction temperature, and atmospheric environment of the system were analyzed in this work. It was concluded that it is possible to remove the lead from the glass matrix by thermal processing. The removal of 92% of the lead from the glass was obtained at 800°C, a vacuum of 1.3 kPa, with 5% carbon as a reducing agent, and 18 hours of thermal processing. <![CDATA[Evaluation of the milling efficiency increase of AISI 52100 steel using niobium carbide addition through high energy ball milling]]> The AISI 52100 is a tool-type steel and is more often used in industry for the production of bearings. After the end of its life cycle, it is discarded or remelted, but both processes are considered expensive. Thus, the possibility of reusing this material through the powder metallurgy (PM) route is considered advantageous, since it transforms a waste into another product. To obtain the starting powders, the AISI 52100 steel scrap was submitted to a process of high energy ball milling, which was milled pure and with 1 and 3 % of niobium carbide (NbC) additions. Those additions were performed with the intention of increasing the milling efficiency of the steel, through formation of a metal-ceramic composite with a ductile-fragile behaviour. To determine the morphology and particle size, scanning electron microscopy (SEM) and particle size distribution tests were used. The results indicated that with the carbide addition, a significant increase in the milling efficiency was achieved, being possible to obtain nanoparticles after 20 hours of milling time. <![CDATA[The influence of tundish heating and purging on inclusion formation]]> Steel with high cleanliness requirements require an accurate control of the non-metallic inclusions, such as its quantity, morphology, chemical composition and size distribution. The continuous casting tundish has a fundamental role in steel cleanliness, avoiding its reoxidation by air and ladle slag that retain inclusions, as well as aiding the removal of those same inclusions along the continuous casting (Sahai, 2008). To perform the study, IF steel samples were collected in RH at the start, in the middle and at the end of the continuous casting of the tundish's first heat in three different conditions of tundish processing, alternating between heating and purging. These samples had their inclusions characterized by MEV/EDS using the ASCAT (Automated Steel Cleanliness Analysis Tool) technology. The results showed that more than 90% of the oxide inclusions generated in that type of steel are Al2O3 and AlTi. It was also observed that there is an increase of steel inclusions originating from RH in the tundish and that area fraction and average inclusionary density decreases along the continuous casting in two of the processing conditions. <![CDATA[Three-dimensional reconstruction of compacted graphite in vermicular cast iron by manual serial sectioning]]> Microstructural characterization is an important tool to optimize the properties of engineering materials. Metallography is a common technique, but it provides two-dimensional images from (sometimes complex) three-dimensional microstructures. Three-dimensional reconstruction of microstructures provides more precise informa tion on the morphologies of the material microconstituents, providing more accurate control over their physical and mechanical properties. The main barrier for the dis semination of this technique is the extensive time dispended to obtain a record of in numerous metallographic polished planes and the 3D image reconstruction procedure. The present work shows a practical example of three-dimensional reconstruction of the graphite phase in a compacted graphite cast iron executed by "manual" technique and using optical microscopy. <![CDATA[Iso-velocity maps. A vibration control tool in quarries]]> Urban growth around mining areas has brought problems such as neighborhood's discomfort due to blasting vibrations, which can cause structural damage to the houses, dust and atmospheric overpressure. In Brazil, environmental restrictions are increasingly rigorous and seismic monitoring is required as an environmental control measure. This study aims to analyze a methodology for application of iso-velocity maps in quarries located in urban areas and evaluate options for building iso-velocity maps. This work was performed in a quarry located in the State of São Paulo and four blastings were monitored. All blastings had similar features and they were evaluated in the same bench. For each equation, directional, scaled-distance parameters were estimated and different iso-velocity maps were made and compared. It is concluded that geophone disposition must adjust to the monitoring purposes. Eight to fifteen aligned geophones are adequate for a scaled-distance curve. Sixty-four or more geophones, spatially and homogeneously distributed, can generate an iso-velocity map concerning a single blasting. High variability of rock mass features seems to prevent obtaining good results when the seismographs are not homogeneously distributed surrounding the blasting. <![CDATA[Influence of Mn<sup>2+</sup> ion in reverse cationic flotation of iron ore]]> This paper presents the study results of Mn2+ ion influence on reverse cationic flotation of iron ore at pH 10.5. A small influence was observed on all response variables evaluated: mass recovery, Fe metallurgical recovery, grade of Fe and SiO2 in obtained concentrates for dosages of MnCl2 from 600 g/ton. The conditioning of pulp with ethylene diamine tetraacetic acid - EDTA complexing agent (720 g/ton) in presence of MnCl2 (600 g/ton) at natural pH, before the addition and conditioning with corn starch (400 g/ton) and amine (50 g/ton) at pH 10.5, produced a concentrate with 63% Fe, 5.1% SiO2, which is similar to results obtained in flotation test without manganese species present in pulp. <![CDATA[Mine surveying works for the purpose of excavating the remaining reserves of bauxite in the deposit of "Podbracan"]]> Mining projects for mineral resource mining contain in certain cases specific technical and technological solutions, these being the result of the mine’s characteristic spatial position and the geometry of the ore deposit, existing mining works, structures, and terrain relief etc. For the purpose of completion of the mining project, it is necessary to carry out a series of mining and surveying tasks during the pre-project and project stage of mining, as well as during the construction of mining facilities and excavation of mineral resources. Specific features of the project concerning excavation of the remaining reserves of bauxite in the deposit of "Podbracan", and in this way the forthcoming mining and surveying works, are displayed by the integration of the underground mining project into the existing mine chambers, infrastructure structures on the terrain surface and into the open pit. Large number of mining and surveying works will follow the completion of this project, but in the meantime, this paper shows the a priory accuracy assessment of the spatial position of the point, it being the exit point to the existing bench of the open pit at the elevation +420m. <![CDATA[Processes for phosphorus removal from iron ore - a review]]> This paper aims at reviewing literature on the occurrence of phosphorus in iron ores from the mines around the world. The review extends to the phosphorus removal processes of this mineral to meet the specifications of the steel industry. Phosphorus is a contaminant that can be hard to remove, especially when one does not know its mode of occurrence in the ores. Phosphorus can be removed from iron ore by very different routes of treatment. The genesis of the reserve, the mineralogy, the cost and sustainability define the technol ogy to be applied. The articles surveyed cite removal by physical processes (flotation and selective agglomeration), chemical (leaching), thermal and bioleaching processes. Removal results of above 90% and less than 0.05% residual phosphorus are noticed, which is the maximum value required in most of the products generated in the processing of iron ore. <![CDATA[Evidences of the influence of the detonation sequence in rock fragmentation by blasting – Part I]]> Drilling and blasting are fundamental operations in the mining cycle and consti tute an important component of the mining costs. Rock fragmentation can in principle be managed by means of two options: by increasing or reducing the specific consumption of explosives, or by modifying the drilling pattern. The choice of one or other type of control depends on the relationship between the unit costs of drilling and explosives, and on technical restrictions or regulations imposed by different reasons. It is then necessary to identify the link between the blast design and some factors affecting the downstream processing of the product. This paper analyzes the theoretical basis aimed at evaluating the main parameters involved when organizing a production blast in open pit quarries. In particular, a method developed through the analysis of the results in a large number of limestone open pit quarries in Italy is described and commented. The first experimental results in Brazil have been obtained by applying this method at the Experimental Mine of the Research Center of Responsible Mining of the University of São Paulo. Experimental methods and results will be analyzed and discussed in the second part of this paper. <![CDATA[Bioflotation of apatite and quartz: Particle size effect on the rate constant]]> This work deals with the fundamental aspects of apatite and quartz bioflotation using R. opacus bacteria as a bioreagent. It was observed that the flotability of both minerals depends on the pH value and the mineral particle size. The maximum flotability of both minerals was presented at a pH value of 5, achieving values of 90% and 14% for apatite and quartz, respectively, after seven minutes of flotation. The kinetics analysis showed that the smaller the apatite particle size, the lower its bioflotation rate value. On the other hand, the smaller the quartz particle size, the higher its bioflotation rate value. The first-order kinetic model better fitted the experimental data of both minerals, and a logarithmic relationship between particle size and kinetic rate constant was observed. <![CDATA[Analysis of the economic feasibility of a mining project due to the presence of natural underground cavities]]> The legislation for the protection and conservation of caves is recent in Brazil. In 2008, the Decree 6.640 was enacted and in 2009, the Normative Instruction Nº 2 by the Brazilian Environment Ministry (MMA, Portuguese acronyms) was published. Mining operations cause a significant impact on the caves when they are present in or next to the mineral body. The impacts include the suppression of cavities and impacts on physical and bio-speleological stability of the caves. On the other hand, the actual legislation causes a significant impact on the mineable reserves when cavities are present. This article aims to assess the impact of the natural cavities on the feasibility of a mining project, based on the federal legislation, as well as to propose alternatives to combine mining activity with cave protection. For this research, three scenarios of open pit for a hypothetical ore body were considered for the assessments. This paper presents the results achieved for the three and comments on the necessity of researches to conciliate the conservation of the natural underground cavities with the mining activities. <![CDATA[The NoBLOCK Technology A Major Breakthrough in Wet High Intensity Magnetic Separation (WHIMS)]]> Since its introduction in 1963 by G.H. “Jones”, WHIMS MS has proven to be, worldwide, a major technology for separating several types of ore fines from their contaminants. Unfortunately, despite its superb characteristics, even if the best operational procedures are followed, one main issue lasts. It is the blocking of the matrix gaps by oversized particles. Protection screens have been employed to wipe out this blockage, though only partially effective. Creative methods and tools have been developed to facilitate and speed up the cleaning process. But, in fact, along 50 years, the matrix blockage nightmare lingered defying the minds involved with Whims operation. The recent environment demands and the need to reduce costs by recovering ore ultra-fines currently being disposed in tailing ponds, further posed a new challenge. Reportedly these ore ultra-fines, typically below 75 microns, demand smaller gaps for its recovery than today’s bottom limit 1.5 mm. The blockage issue worsens even more and to solve it, Gaustec Magnetism, after two years of research and test work, finally succeeded in developing The Brand New NoBLOCK® Technology presented here.