DEMIN - Departamento de Engenharia de Minas

URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/510

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Remediation alternatives for an abandoned gold mine contaminated with mercury in Brazil.
(2022) Miranda, José Fernando; Lima, Hernani Mota de; Curi, Adilson; Luz, José Aurélio Medeiros da; Destro, Elton
Heavy metal contamination of soils has generated two major problems, namely, loss of land value and health risk for people near contaminated sites. Studies on soil remediation are typically conducted on a pilot scale under very controlled conditions. This is a misleading approach, once the complexity of the actual biogeochemical soil conditions may causes inefficiency in full scale real-world application. In addition, environmental impacts of remediation practices themselves are often ignored, which may make them unfeasible. In 2002, an occurrence of mercury in an abandoned old gold mine was detected in a rural area of Descoberto, Brazil. In 2014, the State Public Prosecutor required from the responsible State Environment Agency, a remediation project to the area. This study compares alternatives for remediation of the contaminated area. Also a historical approach on mercury amalgamation in gold mining in the region, in order to estimate the amount of mercury remaining in the site. The geochemical characterization of the contaminated area was performed to describe the contamination process. The results were compared with the remediation proposal advocated by the Brazilian Ministry Public, and some alternatives for decontamination of the area were studied. The electrokinetic method has displayed the lowest overall unit cost, between US$ 120.00/t and US$ 260.00/t. The residual Hg concentration after four cycles of the electrokinetic technique was estimated at 1.28 mg (Hg)/kg (soil), slightly higher than the intervention value for agricultural soil, which is 1.20 mg (Hg)/kg (soil).
Separação magnética de ustulado de minério de ferro hematítico.
(2022) Neuppmann, Pedro Henrique; Luz, José Aurélio Medeiros da
A ustulação objetivou o aumento da eficiência da separação magnética de um minério de ferro hematitico. O percentual de coque, o tempo de ustulação e a temperatura foram analisados em vários níveis baseados na literatura prévia. A caracterização da amostra foi feita para avaliar a densidade da amostra e o tamanho tanto da partícula de minério como de coque. A análise termogravimétrica indicou transformação de hematita para magnetita por picos característicos de perda de massa. A transformação hematita-magnetita fornece forte contraste na suscetibilidade magnética entre minerais portadores de ferro e ganga, esta composta basicamente por quartzo. Os resultados demonstraram o incremento no magnetismo e fotografias comprovaram o caráter magnético da amostra ustulada. A melhor condição obtida foi com 35 minutos, 10 % de coque (em massa) e 1,023 K (750 oC). A eficiência foi aumentada em 5.3 % sob campo de 0.93 T e 240.3 % sob campo de 0.06 T, aumentando a seletividade da separação magnética até sob baixo gradiente magnético. Esta rota poderia ser aplicada com sucesso aos rejeitos de minério de ferro em campo de baixo gradiente, naturalmente após análise econômica cuidadosa, na qual a quantificação de passivos ambientais (principalmente resultante de sua não implementação) é incluída.
On bed porosity of multisized spheroidal particles.
(2022) Prado, Diogo Rodrigues; Luz, José Aurélio Medeiros da; Milhomem, Felipe de Orquiza; Paracampos, Marcos Paulo Salomão
In numerous instances of engineering the problem to quantify the porosity of polydisperse systems arises. Despite its great importance, the theoretical predictability of the bed porosity is still problematic. In the field of ceramics, classically, Furnas' studies on porosity are quoted, where he has studied void fraction resulting from blending two distinct particle sizes in various proportions. Less often, ternary diagrams plotting porosity isovalues for spherical particles beds are used to characterize ternary mixtures of distinct monosized particulate systems (usually in ceramics industry). Although similar studies using polydisperse systems have been conducted, a lot of improvement is yet to be achieved. This article falls in this context and aims at contributing to this field of technical and economic impact. Synthetic samples with controlled particle size distribution were used. The resulting porosity of those glass beads random packs (mimicking several size distributions described by Rosin–Rammler equation) has been experimentally determined under a standardized compaction level. The main result was to obtain an equation for the porosity forecast for bead beds inside spheroidal containers, as a function of the sharpness parameter, n, from Rosin–Rammler distribution. An accurate extrapolation to systems well described by the Whiten sigmoidal distribution was achieved as well. A generalization of the Ergun equation is presented at the end of the article, as an application example.
Microwave aquametry according to ASTM D4643-17 for moisture determination in iron ore tailings.
(2022) Cordeiro, Juni Silveira; Eloi, Danilo Manata; Araújo, Sirlan; Brito, Hermando; Luz, José Aurélio Medeiros da
The gradual increase in the exploitation of iron ore leads to a need for the disposal of tailings from its processing. One of the key features of a granular system stacked is its moisture content. This work aimed at evaluating the use of microwave oven to determine the moisture content (following the ASTM D4643-17 standard) of iron ore dewatered tailings, for fast assessment of the geotechnical condition of every stacked layer on disposal areas. The preconized method has showed good agreement with the conventional oven method (standard assay), resulting in linear equation with coefficient of determination of 0.9953. However, the recommended method has shown less accuracy in the range of low moisture values (below 5 %), which does not represent a critical disadvantage from the point of view of geotechnical safety. The economic impact of the method advocated here will be great, since the movement of large volumes of tailings in limited areas leads to customary downtime, often resulting from waiting for confirmatory analytical results to practice within the safety limits.
Long-term evolution of heap surface of paste tailings under erosion.
(2022) Branches, André Miranda Brito; Lima, Hernani Mota de; Luz, José Aurélio Medeiros da
Many mines are moving from conventional tailings storage facilities to filtered tailings disposal systems. The benefits of these systems include increased water recovery, reduced size of containment landfills, improved facility safety, and reduced environmental impact. In geotechnical terms, the challenges are to find the correct way of waste disposal: whether in piles of dry sandy tailings or co-disposal waste rock. The long-term evolution of the surface of fine and sandy tailings stockpiles is a matter of concern. The goal of this study was to quantitatively evaluate the temporal evolution of a paste tailings pile, using a computational model of landscape evolution. For this, SIBERIA, a simulator of the evolution of landscapes under the action of runoff and erosion, was used. The effect of erosion on a trunk-pyramidal tailings pile with about 21% of slope after long periods of decommissioning (100 and 250 years) was studied. The SIBERIA modelling data considered the surface roughness and the average diameter of the sediment particles and the typical properties of iron ore tailings. The results indicate that for a lower Manning roughness coefficient and larger average apparent diameter of the sediment particles (or clods), the lower the sediment transport will be and, therefore, in the long term, the greater will be the integrity of the tailings pile.
Multivariable control strategy for a bucket wheel reclaimer.
(2022) Freitas Júnior, Luiz Rogério de; Luz, José Aurélio Medeiros da
Mining operations are generally done by large machines working in very harsh environments and historically having shy embedded technology. The use of control strategies, in many cases, dramatically increases the operating efficiency without large financial investments. In this context, this paper presents the method of choice and practical application of a multivariable control strategy for a bucket wheel ore reclaimer. This strategy adopts PI and PID controllers following a type override strategy acting on the manipulated variable: the slewing angular velocity. This manipulated variable was chosen because its actions affect the controlled variable very fast, so, allowing correcting disturbances in an adequate time. In addition, a fuzzy type controller was implemented to act on a second manipulated variable: the translation step. The second manipulated variable aims at taking the first one (angular speed) out of saturation states. When working together, these controllers seek to increase the equipment and process performance, taking into account, however, their operating limitations. Finally, a statistical analysis of results was performed in order to validate the feasibility of the implanted strategy when compared with the method previously in operation.
Microflotação de hematita e quartzo com óleo de manga.
(2022) Milhomem, Felipe de Orquiza; Gomes, Bruna de Oliveira; Luz, José Aurélio Medeiros da
A flotação é uma das técnicas mais empregadas no processamento mineral, e no caso do minério de ferro, é utilizada amina como coletor de ganga. Um dos problemas desse reagente é a baixa tolerância a finos, tornando difícil o processamento de minérios mais complexos ou da tentativa de recuperação de minerais-minério presentes em rejeitos. Assim, este estudo verificou o comportamento de hematita e quartzo na microflotação com uso de sabão de óleo de manga como coletor, nas concentrações de 2,0; 5,0 e 75,0 mg/L. Ensaios dos minerais separados foram realizados em célula de Fuerstenau, com 11,00 g de amostra e em pH 7,0; sem deslamagem. Além dos valores de recuperação dos minerais, também foi estudada a cinética do processo, através do modelo retangular de Klimpel. O quartzo teve recuperação próxima a 25 % nas três concentrações estudadas, e a hematita apresentou recuperação de 65,85 %, na concentração de 75,0 mg/L de coletor. Quanto à cinética, o parâmetro cinético da hematita em 75,0 mg/L teve valor de 3,19 [1/min], e o quartzo teve valor de 1,48 [1/min] na mesma concentração. Isso demonstra potencial do óleo de manga como coletor de hematita.
Diagnosis of the production cycle in the small shaft sinking.
(2022) Luz, José Aurélio Medeiros da; Silva, José Margarida da; Neuppmann, Pedro Henrique
Shaft sinking is a classic activity in underground mines. In shafts with small cross-section or in mines with low mechanization indices it is common to use hand pneumatic drills and blasting by explosive gelatin in cartridges, employing natural draft or flexible ducts with axial fans for gases and fumes exhaustion, muck removal by hand shoveling into hoistable dumping buckets. System of this type has been studied here, consisting of a rectangular cross- section shaft (3.7 m x 2.0 m), with final depth of 94 m, excavated in order to obtain samples for a pilot-scale mineral processing testwork, before the open pit mine’s industrial startup. The shaft had a concrete collar and its walls were supported by wooden sets spaced 1.5 m and 25 mm thick wooden planks as liners. This shaft has been excavated in schist rocks belonging to the metamorphosed hydrothermal deposit of copper and gold located in Chapada (municipality of Mara Rosa, Brazil). Daily production worksheets covering one month campaign were statistically analyzed, encompassing the entire cycle of mining operations, namely drilling, charging and blasting, fumes exhaustion, mucking, wall and face trimming and scaling, and assemblage of support system. Operation downtimes were also quantified. Statistical analysis of productivity indices allowed the detection of critical points of the operation and the establishment reference for similar mining operations.
Selective flocculation and floc-flotation of iron bearing mineral slimes.
(2022) Bretas, Pedro Lopes; Rodrigues, Otávia Martins Silva; Luz, José Aurélio Medeiros da
The mineral processing of friable iron ores usually generates ultrafine (smaller than 15 μm) particles, normally called slimes, which usually have a high iron grade and are usually disposed into tailings dam. The traditional mineral process techniques for iron ore do not work efficiently with ultrafines; however, selective flocculation is an alternative to concentrate that fraction. The physical-chemical treatment of iron ore slime was studied here, on a bench scale, based on the scientific foundations of selective flocculation and flotation. Samples of slimes from two Brazilian iron ore processing plants (CEII and VGII) and industrial process waters were used in the tests. Complexometric titration of calcium and magnesium indicated that the process waters were adequate for selective flocculation. Only selective flocculation, even under optimum conditions, did not achieve good results. However, its use prior to flotation led to promising results. The VGII sample has stood out, for which the final concentrate achieved 60.1 % of Fe, the mass recovery was 64.5 % and 13.5 % of Fe in the tailing, resulting selectivity index of 6.58, only with one stage of selective flocculation and one stage of flotation.
Electrical profiling of vibration-induced dewatering of sand.
(2021) Reis, Jonathan Leandro Martins; Luz, José Aurélio Medeiros da; Vardanega, Fábio
Electrorresistive profiling of moisture inside a quartz sand bed on a pilot-scale vibrating screen was treated here. As electrode or probe configuration for resistivity measurement is concerned, the classical Wenner α array was used, requiring equal electrode spacing, and correct penetration depth and alignment. Here, the influence of small variations in penetration depth and lack of probe collinearity on the moisture readings, using a digital earth resistance tester and copper wires as probes, was evaluated. The penetration depths studied were 50 mm and 55 mm. In turn, the electrode misalignment tested was 10 mm. The only factor that has caused statistically significant effect in measurements was probe penetration depth, at least under the range tested here.

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