Roberto Galery

The effect of the dispersion degree on the floatability of an oxidased zinc ore

Abstract Most of the Brazilian zinc deposits consist of the so-called “calaminic” ores (silicates and 7carbonates). Considering that the Italian reserves at Sardinia are now exhausted, the ores from Vazante - MG may be considered unique. Earlier studies of microflotation in a modified Hallimond tube indicated that the dispersion degree of the pulp should control the flotation behaviour of these ores. Dispersion tests were then performed in a sedimentation tube with samples of calaminic zinc ores from Mineracao Areinse. Bench scale flotation testwork was carried out under the best dispersion conditions, following traditional cationic flotation. The major objective of the present investigation was the establishment of correlations between slurry dispersion, desliming and flotation. It was verified that an adequate slurry dispersion is not enough for a high selectivity, a combination of desliming and dispersion being required. The performance of the dispersing agents and the magnesium grade in the concentrate depend on the pulp percent solids. The most efficient dispersing agents were determined for the three samples under investigation.

Charge Behavior Analysis in Ball Mill by Using Estimated Torque

The aim of this paper is to present a method to analyze the dynamic of the charge in a ball mill. The method is based on the mill torque estimated from angular position and motor electrical signals. The estimated torque signal obtained from a Luenberguer velocity observer is bandpass filtered to isolate the mill-filling-related component. The root-mean-square value of this component, used as an indication variable, is correlated to vibration signal measured through an accelerometer in order to check the validity of the proposed method. The proposed method does not need any sensor be installed directly on the mill and requires only sensors usually available for motor control purposes in frequency inverter drives.

Recobrimentos de poli (tereftalato de etileno) depositados em aço por aspersão térmica a partir de pós obtidos em diferentes condições de moagem

Resumo: Neste trabalho foram analisados recobrimentos de poli(tereftalato de etileno), PET, depositados em aco carbo- no atraves da tecnica de aspersao termica a combustao, e produzidos a partir de pos oriundos de processos de moagem, em moinho de bolas e de facas, de garrafas de PET pos-consumo. Algumas condicoes de moagem foram testadas, tendo- se obtido pos com diferentes caracteristicas morfologicas. As caracteristicas morfologicas dos pos e dos recobrimentos foram avaliadas por microscopia optica e eletronica, tendo-se observado que o recobrimento apresentava bolhas, prova- velmente devido a degradacao do polimero. Alem disto, os recobrimentos produzidos, bem como as amostras de po, foram caracterizados por espectroscopia na regiao do infravermelho, por calorimetria exploratoria diferencial e atraves da determinacao de viscosidade intrinseca em solucao. Os resultados obtidos mostraram que e possivel a producao de aco carbono recoberto com PET atraves da tecnica de aspersao termica, sendo que o grau de degradacao, a morfologia e a distribuicao granulometrica dos pos utilizados influenciaram significativamente as caracteristicas e propriedades dos recobrimentos formados. Palavras-chave: Poli(tereftalato de etileno), aspersao termica, analise termica, viscosidade intrinseca. Thermally Sprayed-Coated Carbon Steel Produced Using PET Powder Obtained under Different Grinding Conditions Abstract: The main purpose of this work was to study the production of a thermal spray coated poly(ethyleneterephthalate) (PET) steel. PET coatings were made of a thin grinding waste produced by a PET recycling company, and of a PET powder, which was obtained by grinding post-consumer beverage bottles. Some grinding conditions, using a ceramic ball mill, were studied. Scanning Electronic Microscopy (SEM) and optical microscopy (OM) were used in the study of powder and coating morphologies, and this analysis showed that PET coating presents bubbles due to polymer degrada- tion. PET powder and coating characteristics were investigated using Differential Scanning Calorimetry (DSC) and measurements of intrinsic viscosity. It was observed that the powder morphology and the degradation and size distribu- tion of the PET powder affect significantly the characteristics and properties of coatings.

Charge behavior analysis in ball mill by using estimated torque

The aim of this paper is to present a method to analyze the dynamic of the charge in a ball mill. The method is based on the mill torque estimated from angular position and motor electrical signals. The estimated torque signal obtained from a Luenberguer velocity observer is bandpass filtered to isolate the mill-filling-related component. The root-mean-square value of this component, used as an indication variable, is correlated to vibration signal measured through an accelerometer in order to check the validity of the proposed method. The proposed method does not need any sensor be installed directly on the mill and requires only sensors usually available for motor control purposes in frequency inverter drives.

Effects of hematite surface characteristicson filtration process

In iron ore pelletizing plants a range of process parameters such as particle size distribution, specific surface area, and moisture, must be controlled to achieve optimized operation conditions. Particle size distribution and specific surface area are controlled during the grinding operations. Moisture, however, is controlled during filtration of the ground products. This work investigates the relationship between particle morphology, filter cake moisture and filter capacity. The samples were taken during the filtration tests and referred to three different blends presenting distinct mineralogical features and similar chemical compositions in order to investigate the effects of only the hematite surface characteristics. Six types of morphology are distinguished: granular hematite, tabular hematite, martitic hematite, polycrystalline hematite, hematite-goethite aggregates and goethite. For each filtration test, the filter cloth product was characterised. The characterisation analysis revealed that blends containing martitic hematite concentration above 11.45 percent increased substantially the filter capacity. However, it had also caused an increasing in final moisture content that reached values around 10.0 % compared with industrial moisture specification that can vary on the range of 8.5 to 9.5 %.

Impact of grade distribution on the final pit limit definition

Geologic modeling is an important step in determining the benefits and final pit dimensions for mining operations. Geostatistical models and distance-based functions are the main methods used to estimate the grade behavior. However, these two methods, despite their similar mean values, differ in spatial variability. The objective of this article is to prove, by comparing the two methodologies, that models with different spatial variability using the Lerchs-Grossmann algorithm will output subtly different final pit dimensions and scheduling. Furthermore, with the direct block schedule (DBS), these differences can be considerable. The tests compared the methodologies using the following three models: inverse distance (ID), ordinary kriging (OK) and turning bands simulation (TBS). The results demonstrate that the Lerchs-Grossmann algorithm is only slightly sensitive to the spatial variability of the grade; however, DBS requires the model populations to be better defined because of its greater sensitivity to spatial variability.

Classical and stochastic mine planning techniques, state of the art and trends

Determination of the best possible ultimate pit for an open pit mine is a fundamental subject that has undergone a highly evolutionary process, reviewed in this study, since the correct choice carries substantial economic impact for the industry. The correct choice can be very beneficial for project analysis, whereas an incorrect choice has the potential to mask huge financial and economic future losses that could render a project unfeasible. The advent of computers in the 1960s allowed sophisticated analysis for the selection of the best ultimate pit determination, under specific modifying factors such as economic, social, environmental, and political, but only in deterministic situations, i.e., when the problem and variables for the ultimate pit determinations were considered deterministically and almost always based on average values. Techniques such as the Lerchs– Grossman algorithm and mixed-integer programming are among many standard tools now used by the mineral industry. Geological uncertainty and the associated risks as well as the need to consider the appropriate time to mine a block during a mine operation have a significant impact on the net present value of the resulting ultimate pits. Stochastic aspects embed a probabilistic component that varies in time and are now under intense investigation by researchers, who are creating algorithms that can be experimented with and tested in real mine situations. One can expect that once these algorithms demonstrate their efficiency and superior results, they will readily dominate the industry.

Simulations of Vertimill Pilot Scale tests for Itabirite

The Minas-Rio Project is the biggest project from Anglo American in the world and considers Vertimill in the regrinding circuit to adequate the particle size distribution to feed slurry pipeline that will pump the ore from Conceicao do Mato Dentro in Minas Gerais State to Acu Port in Rio de Janeiro State, Brazil. A Vertimill pilot test campaign was carried out at Metsos pilot plant facility located in York city, Pennsylvania State, USA, to provided information to sizing the industrial grinding circuit. The main objective of this work is proposing a way to simulate the industrial Vertimill using the population balance model, normally used to simulate ball mills. The simulations were based on the selection and breakage functions determined from the laboratory tests using a batch ball mill. The simulations were performed using a Vertimill model implemented in the ModsimTM plant-wide simulator. The results of simulations shows that was possible to simulate the pilot tests, with good accuracy, considering simple laboratory tests with small quantities of samples.

Financial Compensation for the Use of Mineral Resources at the Minas Gerais State – Brazil

The Financial Compensation for the use of Mineral Resources - CFEM, is a compensation for the mining activity in the municipalities where it is allocated. This study shows the importance of CFEM in the State of Minas Gerais - Brazil, where the mining activity is very important. The importance of CFEM is on its application on the counties, as it must be used in projects that bring improvements on the life conditions of the population. Usually, the HDI – Human Development Index of the municipalities where mining projects are developed is higher than the HDI of the State in which such projects are located. However, the correct management of this compensation must be reconsidered focusing on the development of local communities. It is important to highlight that, besides CFEM, the mining companies develop many other projects related to culture, education, sports, among others in the communities where they are located, bringing benefits for the population. With the new mining code, some changes in CFEM are expected, mainly in its calculation and in the percentages of some mineral resources taxes. Besides, a better distribution of the values is being considered, mainly associated to surrounding counties which are also affected by the mining activities. Thus, CFEM is understood as an important compensation for the mining activity that can bring many benefits if well applied and managed.

Simulation of a ball mill operating with a low ball charge level and a balanced ball size distribution

The optimization of industrial grinding circuits has been successfully performed using mathematical models that describe the industrial scale data from breakage parameters determined in laboratory grinding tests. The test material studied here is a gold ore ground in a closed ball mill circuit with hydrocyclone classification. Several sampling campaigns were carried out aiming to produce mass balances and provide material for laboratory tests. The parameters determined in the laboratory tests were used to predict, by simulation, the circuit behavior with a low ball charge level and a balanced ball size distribution.