José Aurélio Medeiros da Luz

Conversibilidade entre distribuições probabilísticas usadas em modelos de hidrociclones

This article presents a conceptual analysis on the relationship between the sharpness parameter m, of the Rosin-Rammler distribution, and the parameter a, its correspondent in the Whiten logistic distribution function. The solids split curve is approximated by a Rosin-Rammler distribution function in the Plitt model for hydrocyclone, while, alternatively, the logistic distribution function is adopted for the partition in the Lynch-Rao model. The results show that the two parameters can be related to the following equation, achieved by nonlinear regression analysis: a = 34,555 x exp [-3,9/ m0,5984]

Análise granulométrica por técnicas que se baseiam na sedimentação gravitacional: Lei de Stokes

Sizing and size particles distribution is very important in materials technological characterization. In general the particles have irregular shape, so the methods used to determine the particle size are based on geometrical similarity, like equivalent diameter that are determined by techniques that use the Stokes law. This law is applied only in laminar flow. With nowadays technological development is possible to analyze sizes until 0.1 mm using the sedigraph analyzer that apply the Stokes law plus the X-ray absorption by dispersion of particles in water environment. In order to use correctly these methods it is very important that the material have to be pure or if there are more than one phase the density of those should be very close. So the calculation of particles size present will be correct.

Seletividade na cominuição de mesclas de dolomita e quartzo

This article is a sequence of another one and displays results in the selective comminution of binary mineral mixtures. The selectivity of dolomite and quartz grinding rates under different proportions was studied. The called global grain contrast indicator (IGCG) was used to improve the analyses of the behavior of these minerals under comminution, using theoretical size distribution curves, fitted to the Hills sigmoidal function. The results have suggested the optimum grinding times, within the tested range. The results presented here have validated the development of a neural network-based predictive model for grinding system simulation (a multilayer perceptron using backward propagation with moment), which will be approached in another article.This article is a sequence of another one and displays results in the selective comminution of binary mineral mixtures. The selectivity of dolomite and quartz grinding rates under different proportions was studied. The called global grain contrast indicator (IGCG) was used to improve the analyses of the behavior of these minerals under comminution, using theoretical size distribution curves, fitted to the Hill’s sigmoidal function. The results have suggested the optimum grinding times, within the tested range. The results presented here have validated the development of a neural network-based predictive model for grinding system simulation (a multilayer perceptron using backward propagation with moment), which will be approached in another article. Keywords : Selective comminution, binary mix, grinding, artificial neural network. Attention: Soon, you will be able to read (or download) the complete article (contents) by accessing Scielo’s homepage.

Cumulative impact assessment on air quality from multiple open pit mines

Both open pit mine and smelter projects can have significant impacts on a variety of environmental resources. Among these, air quality of the surroundings is a key issue. Additionally, the environmental assessment of projects demands integrated approach taking in account all pollution sources. Therefore, specific focus has been put on the methodology for assessing impacts on air quality. This paper proposes an integrated index of environmental impact aiming to quantify the air quality impact of industrial operations around an urban area, in case of scarcity of in situ acquired data. This proposed pollution index is demonstrated by a case study conducted in the municipality of Congonhas, Brazil, in which contributions of five open pit mines and two smelters were studied. To achieve the pollution index, the wind rose and distances from the centroids of effective areas to the urban nucleus itself were considered, taking into account the wind projection areas from windward impacting sources on the leeward impacted urban site. The proposed index also includes the squared wind speed (proportional to the kinetic energy transferred in uplifting dust from ground surface). The method proposed is considered suitable for impact assignment for each one of the air pollution sources in the neighborhood of studied area. Some fluid dynamic aspects of airborne particulate matter are also studied by proposing a new equation for threshold saltation speed.

Pluvial percolation in pyrite-bearing coal stockpiles

Acid mine drainage is a main environmental problem linked to coal and sulfide ore mining. Its treatment usually involves alkalinization and subsequent precipitation and immobilization of the dissolved species. Rainfalls over stockpiles can cause a very similar phenomenon. This work aimed to study the effluents from such a leaching process in steam-coal stockpiles Brazilian coal with a high pyrite content was used. The effluents have been chemically characterized. Effluent clarification by aggregation and settling in an attempt to simultaneously deplete heavy metal content was studied. Settling experiments were carried out with coal suspensions, in order to evaluate the efficiency of inorganic and polymeric reagents in the process.

Caracterização da parcela magnética de minério fosfático de carbonatito

Abstract The characterization of the magnetic fraction of atail from phosphate rock processing was done. Sampleswere from Tapira, in Minas Gerais, Brazil. The mainphysical, chemical and mineralogical properties, aswell as this material response to separation processeswere determined. The first part of this work encompassesthe mineralogical characterization (determination ofparticle size distribution, X-ray diffraction, Mossbauerspectroscopy, optical microscopy and scanning electronmicroscopy). In the second part, concentration tests bymagnetic separation, flotation and acid leaching werecarried out. The iron-bearing material is composedpredominantly of magnetite, hematite and ilmenite. Wetlow intensity magnetic separation has reached ironrecovery above 96 %. As far as flotation is concerned,fatty acid soap from vegetal oil (Hidrocol) as a collectorfor silicates and apatite was better than amine. Attritionor scrubbing prior to conditioning seems not to affectflotation performance in this case. Acetic acid hasextracted only 0.41 % of the phosphorus, andhydrochloric acid has depleted 73.05 % of thephosphorus in the samples under leaching.

Caracterização tecnológica de resíduos de pedreiras de quartzito da região de Ouro Preto/MG

Abstract Quartzites from Taquaral Hill at Ouro Preto - inthe State of Minas Gerais - have been exploited forconstruction and ornamental purposes for decades.Until now, the rudimentary way to exploit and refinethese weatherized rocks has produced, a large amountof residuals distributed in a broad size distributionrange. This work aimed to characterizes the sand anddebris from the mining operation, which are depositeddownhill. Three samples were studied and it becameevident that this debris can be used as sand in the civilconstruction and foundry industries. Also, afterremoving the impurities (F 2 O 3 , Al 2 O 3 e TiO 2 ) by highintensity magnetic separation and froth flotation, it canbe used in the glass industry, which is of social,economical and environmental interest. Keywords : Waste technological characterization,quartzite sands. Mineracao Caracterizacao tecnologica de residuos depedreiras de quartzito da regiao deOuro Preto/MG (Technological characterization of the residuals from aquartzite quarry of Ouro Preto/MG)

Modelamento matemático de peneiramento vibratório (Parte 2): simulação

Screening is a unit operation where probabilistic mechanisms take place in an intensive way. This work presents an alternative screening model. The final product is a software system called SimPeneira (experimentally validated) developed in order to simulate scenarios in industrial screening and to quantify the impact of parameters such as: screen opening, length, effective area, material flow speed, vibration frequency and amplitude. The system can also size screens using the classical sizing procedure (with modifications).

Modelamento matemático de peneiramento vibratório (Parte 1): dimensionamento clássico

Flow splitting in screens is strongly dependent on probability distribution of particles passage through the screen openings. This probability is influenced by operational conditions and the particle size to opening ratio. A software system called SimPeneira was developed to perform sizing of screen using the classical sizing procedure (with changes) and also to simulate several scenarios in industrial screening, quantifying the impact of operational parameters. This article describes the first part, embracing the sizing pack.

Feasibility project for implementation of conveyor belts in an iron ore mine. Study case: Fabrica Mine in Minas Gerais State, Brazil

This article objectifies the implementation of a conveyor belt in an iron ore mine. The mine operational costs of the company Vale S.A. have a tendency to increase in coming years. This increase is related to the rising price of labor, fuel, tires, maintenance costs and large transport distances. Meanwhile, environmental impacts also need to be reduced. The case study of the Fabrica mine operated by VALE in the city of Congonhas, in Minas Gerais State of Brazil, was chosen aiming for a comparative study between the employment of big trucks and the deployment of conveyor belts. The decision for the best alternative would be made by an economic analysis of the incremental cash flow. After the economic evaluation of the project, economic and environmental gains were expected for the alternative of conveyor belt deployment.