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By José Hamilton Resende Tavares, Késsius Bortolan Menezes, Mariana Vieira de Moura

Sampling and its representativeness is of significant importance in process control and decision making in the mineral sector. In this way, the present work seeks to compare different methodologies for the sampling of the iron ore from Anglo American. Through a sample of 120 kg, representing the industrial flotation circuit feed, samples obtained by the method of long pile, random sampling and rotary sample divider were analyzed, being the latter adopted by the company. In this case, after sampling, the material obtained through each method was subjected to the same sequence of characterization tests and the difference between the results statistically analyzed. Through such analysis it was observed that the random sampling method showed high values of variability and is therefore considered as unsatisfactory when compared to the other methods tested. In addition, rotary sample divider also showed parameters slightly superior to the long pile method. This study confirms the importance of appropriate sampling systems and procedures systems in the pursuit of reliable results.

Oct 3, 2019

By Jackson Teixeira de Oliveira, Douglas Batista Mazzinghy, Vanderson Eney de Matos, Alexandre Camilo Leles de Figueiredo

This work studied the effect of different ball sizes in the secondary grinding stage of Samarco. The Moly-Cop Tools 3.01 spreadsheet was used for models calibration and simulations, considering grinding balls topsize of 15, 20, 25, 30 and 35mm diameters. A normal specific selection function up to the largest fed ore particle size (840μm) was obtained. The higher generation of fines and compliance with particle size specifications (+ 74μm and -44μm) proved to be more favorable for smaller ball sizes. The specific energy consumption was lower for the 15mm ball (10.7kWh/t), increasing up to the 35mm ball (13.0kWh/t). Although smaller diameter balls seem to be the best option for the size specifications, some factors may limit their use, such as: the higher generation of specific surface area; and the amount of ball purge in the discharge of the mills.

Oct 3, 2019

By Walter Valery, Kristy Duffy, Alex Jankovic, Peter Holtham

Hatch’s Mine to Process Optimization projects integrate mining and processing strategies, minimizing operating costs and maximizing overall profit. The methodology involves ore characterization, blast audits, plant surveys, analysis of historical data, and integrated modelling and simulation of mining and processing. Blast designs are tailored according to ore type and the downstream process is optimized for the changed feed. This approach has increased throughput and minimized costs for many operations worldwide. The implementation of this methodology at an iron ore operation that faced challenges with increasing mining strip ratio and ore body mineralogy changes is presented in this paper. The larger stripping ratio increased mining costs and constrained the run-of-mine (ROM) delivery to the process plant. Process performance was affected as the ore mineralogy shifted from predominantly hematite to include greater proportions of magnetite. The project objective was to minimize overall cost per ton mined and processed and maximize profit. Tailoring the blast designs according to ore type and process optimization increased the throughput of all process lines. This provided the potential to shut down one of the five processing line, aligning the mine and plant capacity and significantly reducing the processing costs.

Oct 3, 2019

By Luís Marcelo Tavares, Henrique Dias Gatti Turrer, Luciana Pereira Alves

Desliming is a method of classifying mineral particles, which aims at removal of slimes so as to prepare the slurry to downstream concentration processes. It is a common item in mineral processing flowsheets, being mostly carried out in hydrocyclones, in which separation is result of complex fluid flow and its interaction with the mineral particles. When dealing with particles contained in size ranges relevant to desliming, the challenge in describing the process is even greater. The work deals with the fitting of the Narasimha-Mainza model of classification in hydrocyclones to data from desliming an itabirite iron ore, for prediction of feed slurry flowrate, corrected cut size and short-circuit to the underflow. As such, tests were conducted at both pilot and industrial plants in KREBS 2.7” and 4” cyclones operating under a variety of conditions. In the validation of the model, deviations between the predicted and measured values were lower than 34% for feed slurry flowrate, less than 22% for corrected cut size and less than 18% for short-circuit for underflow.

Oct 3, 2019

By Junio Simões Pereira, Carlos Magno Nascimento, Frederic Yann Armache Braga, Luiz Cláudio Monteiro Montenegro

Given the current scenario experienced by Brazilian mining industry, the study and development of technologies that enable a more secure and controlled disposal of tailings has gained significant relevance. Among the various alternatives and disposal methodologies, Anglo American has been developing tests on three study fronts: dewatering polymers, hydrocyclone dewatering and pulp filtration. The first two fronts are intended to optimize the way of occupying the existing tailings dam. The filtering is intended to reduce the mass transfer to the reservoir, extending the life time of the existing structure. The studies were divided into laboratory, pilot and industrial phases, aiming at proving applicability and scheduling for a definitive future installation. Until this moment, all tests have demonstrated gains and potentials of applicability.

Oct 3, 2019

By Silvio Pereira Diniz Maranha, Evandro Costa e Silva

The disposal of coal tailings in an economically and environmentally sustainable way can be considered one of the biggest challenges for coal producers due to their physical, chemical and mineralogical characteristics and the significant annual volumes generated. The processing and utilization of coal fines is recognized as one of the great technical challenges of this industry. These challenges become even greater when it comes to the use of tailings from coking coals. This is due to the potential changes in their various properties, variability of these characteristics along the deposits, the handling and dewatering aspects of the products and the granulometric restrictions imposed by the coking plants for the coals to be handling and coking. This work presents the current stage of project development for the use of a metallurgical coal fines dam, addressing the general concept of the project, the exploratory sampling program and the characterization of the tailings for process and product development purposes after processing. It aims at the characterization and the carbonization tests for product development, the mining method considered, product alternatives, suitable to the market, to be generated and the next steps.

Oct 3, 2019

By Thamiris Auxiliadora Gonçalves Martins, Isabela Falconi Brandolis Alves, Viviane Tavares de Moraes

Reverse flotation process is a method used for remove impurities from the most abundant iron ore; the itabirite. In this process, amines surfactant are used which may prevent the reuse of water in processes. The Fenton oxidative processes and the synthesis of nanoparticles are highlighted in catalysts application and in organic substances degradation. This study performed the synthesis of copper nanoparticles (CuNPs) to employ them as catalysts of the modified Fenton reaction to degrade an amine surfactant used in reverse flotation and compared with the classic Fenton (Fe2+) reaction. CuNPs were synthesized by chemical reduction, pH 11 with copper sulfate and ascorbic acid. They were characterized by UV-Vis, DRX and DLS and Zeta potential. The nanoparticles had diameters of 125.00 to 17.22nm and stability during 50 days. The tests were prepared with 180mg/L of amine and 1890mg/L of H2O2 in 150 minutes. The degradation was assessed by UV-Vis and FT IR. The results showed that CuNPs degraded 84% of the surfactant while Fe2+ reached 89%. In this way, both processes can be used for surfactant degradation, although the CuNPs method is easier to operate at neutral pH.

Oct 3, 2019

By José Pancrácio Ribeiro, Rafaella Bicalho da Rocha, Cláudio Henrique Ribeiro

For more than five years, GAUSTEC, along with large Mineral Industry companies, has sought solutions to concentrate flotation tailings and fines by using High Intensity Magnetic Separators (WHIMS). In 2014, GAUSTEC launches the world's largest magnetic separator, the GHX 1400, with capacity up to 1400t/h. By 2015, it launches NoBLOCK® technology, a protection for magnetic separators against clogging. Finally in 2017, it launches two technologies that, together with the previous two, revolutionize the market for magnetic separation, the BigFLUX® Matrix and SuperWHIMS® technology. This article aims to show all these technologies together and to show the efficiency of the same ones already employed in mining companies.

Oct 3, 2019

By Luana Lessa Pacheco, Antônio Vitor Magalhães Cota

With the sharp fall in commodity prices, the terms cost reduction and higher productivity have become subjects that are constantly addressed in the daily life of companies, since these factors represent a question of survival of the organizations. To achieve this, the search for continuous improvement of our processes in order to guarantee space in the market is a reality and necessity, so it is important that companies know their processes in detail and have the maturity to make decisions based on data and facts. Thus, this work aims to apply the Six Sigma methodology to investigate which are the variables that most influence the transportation process, carried out by large trucks, increasing their specific consumption of diesel, which is the second largest expense of a company. mining in the city of Mariana MG. The goal of the project was to reduce diesel consumption in the large transport fleet by 7.4%, from 0.32 l / t (average carried out from Feb / 16 to Jan / 17) to 0.30 by February 2018 , with an estimated gain of R $ 4.2 million. The results achieved exceeded the established target, reaching a 10% reduction in specific diesel consumption, totaling a projected real gain of R $ 6.4 Million, in addition to the reduction of 1,710.52 t of CO2 in the atmosphere.

Oct 3, 2019

By José Francisco Cabello Russo, Késsius Bortolan Menezes, Henrique Dias Gatti Turrer, Denílson Rodrigues de Araújo

With the start-up of the Minas-Rio system, Anglo American, in Conceição do Mato Dentro, MG, in 2014, a methodology was also implemented and certified to perform the tests to obtain the results of TML (Transportable Moisture Limit). Such a parameter provides the maximum moisture content contained in the material that could be transported without the risk of the cargo liquefaction process, which could lead to incidents such as the tipping of ships carrying iron ore concentrate in bulk on the deep water. This means that when loading a ship, the moisture content of the material to be transported should not be higher than the TML reference value, obtained in a physical test and intrinsic to the material. Should this occur the charging may be rejected. From 2014 a downward trend was observed for this reference parameter in the Minas-Rio system, with results approaching the moisture of the filtered product, bringing risks to the operation of the project. In this way, an investigation of the possible causes for understanding this downward trend was required.

Oct 3, 2019

By Leonardo Camilo dos Reis, Edmilson Fernandes Dadomi, Claudio Silva de Paulo

In the hot strip mill production, one of the factors that may affect the productivity is the occurrence of failure due to the geometry of the strip at the exit of the rolling mill, because the tip of the strip can turn-down or turn-up. This study had the objective of evaluating the behavior of the strip when leaving the working rolls, through numerical simulation, aiming to know the influences of the main variables that govern the formation of the turn-down. The methodology consisted in performing the computational simulation of the strip mill and to vary the operational and geometric parameters that could influence the process. The results showed that the rolling of hot strips of HSLA material with final thickness varying between of 3 to 6 mm and a reduction of 6.6% to 11.0% in the last stand of a hot strip mill, tends to bend towards the roll with larger diameter, higher friction coefficient , higher temperature and lower limit of material flow. It was observed that the variation in diameter is the main factor that contributes to the formation of the curvature of the front-end of strip. Based on these results, several measures were implemented in the industrial line, with a significant reduction in the occurrence of turn-down.

Oct 2, 2019

By Antônio Donizetti Giuliano, Fernando Codelo Nascimento, Viviane Tavares de Moraes, Cilene Cláudia Diógenes, Erivan Cardoso Rocha

Nos lagos ornamentais geralmente tem-se a dificuldade em controlar o crescimento de algas, pois existe a incidência de luz e a disponibilidade de nutrientes provenientes da ração fornecida aos peixes, os quais propiciam o crescimento e o desenvolvimento das algas. Uma alternativa de tratamento é o processo oxidativo avançado (POA) existente, a ozonização, com o objetivo de propor um processo de tratamento de água para controlar a proliferação de algas em um lago ornamental sem prejuízos à comunidade aquática, vivente no lago. A metodologia utilizada foi o estudo de caso do lago que envolveu as seguintes etapas: construção do lago ornamental; definição do sistema de tratamento; monitoramento de parâmetros como: a demanda bioquímica de oxigênio (DBO), a cor, o pH, a temperatura, a amônia (NH3) e o oxigênio dissolvido (OD) do lago durante três meses; aplicação do ozônio para controlar a proliferação de algas e monitoramento dos mesmos parâmetros durante o processo de ozonização. Dentre os principais resultados encontrados citam-se: a redução de 170 unidades de Cobalto platina (PCU) da cor esverdeada da água do lago; descimento de 60% da DBO; aumento de 16% da concentração de OD e a redução de 80 a 100% da concentração de NH3, eliminando assim odores desagradáveis e melhorando a qualidade da água. Por meio dos resultados obtidos conclui-se a aplicação de ozônio em lagos ornamentais é uma alternativa para a manutenção aquática e melhoria da qualidade da água..

Oct 2, 2019

By Rafael Fernandes Reis, Leonardo José Silva de Oliveira, Rodrigo Seara Martins

Alterações na cristalização dos pós fluxantes durante o processo, devido variações de composição química pelas reações metalúrgicas na interface metal/escória ou pela incorporação de compostos exógenos, afetam o fluxo de calor no molde de lingotamento contínuo. Um dos compostos importantes é o ZrO2, proveniente do desgaste da válvula submersa. A proposta do trabalho foi investigar o efeito deste composto, utilizando simulação laboratorial, na cristalização do pó fluxante e no fluxo de calor do molde. Os resultados demonstraram que quando há o incremento do teor de ZrO2 o fluxo de calor na região do menisco também se eleva. Tal efeito é crítico para formação de defeitos, uma vez que a região do menisco é crucial para a solidificação inicial do aço.

Oct 1, 2019

By Woo, Hur, Kim, Ki Nam, Seung Min, Kyoung Sik

Tandem cold mill (TCM) is a process to obtain flatness as well as thickness desired by the customer by rolling hot-rolled coils continuously. The final stand of the TCM plays the most important role of flatness control, which usually uses the real-time measurement at the exit. However, as the material property increases, it is not easy to handle flatness with only the final stand. In order to overcome such a limitation, we propose a feedback control method to strengthen flatness control for non-final stands. The proposed method was tested in an actual production line, and the effect is proved for 45K or less steel grade.

Oct 1, 2019

By Marcelo Rebellato, Beatriz Pereda, Beatriz Lopez, Pello Uranga

The classical application of Nb microalloying in the development of thermomechanical processes for flat products has been related to its suitability to enhance strain-induced precipitation and get a pancaked austenite prior to transformation. As new steel grades or new lay-outs are being developed, more complex metallurgical conditions need to be evaluated. In this context, Nb microalloying, alone or combined with other microadditions, needs to intervene in a more controlled way in additional steps of the thermomechanical process, besides its conventional strain-induced precipitation role. For example, the hardenability enhancement associated with Nb to properly achieve lower temperature transformation products, demands a proper balance of the Nb amount precipitated during rolling and the one remaining in solid solution. Similar effects are also sought when the final available Nb is used to increase strength through precipitation hardening. This manuscript evaluates how changes in the rolling strategies affect the interaction between Nb(C,N) precipitation and austenite recrystallization at different steps of the rolling process. As the possible interactions between parameters intervening simultaneously are quite complex, the application of microstructural models helps to properly define the best austenite conditioning combined with the convenient amount of Nb in solution, as a function of the final property requirements. Along the manuscript, several strategies will be discussed for the case of hot rolling of flat products comparing both normal and coarse initial austenite grain sizes.

Oct 1, 2019

By Wellington Bruno Silva de Jesus, Esaú Gomes Souza, Luiz Gabriel da Silva Nascimento, Jeovan Ramos Nascimento, Deibson Silva da Costa

O estudo desse trabalho foi voltado para a solidificação unidirecional da liga Al-9%Ni usando um dispositivo em que sua câmera interna não permite a existência de gradiente de temperatura para outra direção que não seja o sentido da solidificação. Após o processo de fusão e solidificação foram coletadas amostras de posições aleatórias ao longo do lingote para serem realizados os procedimentos metalográficos, ensaio mecânico e microscopia óptica e de varredura. A macroestrutura se mostrou predominantemente colunar vertical, e a microestrutura se mostrou dendrítica nas regiões mais próximas a extração de calor tendo seu espaçamento cada vez menor, o que influenciou no aumento da dureza. Observa-se também através de análise de microscopia eletrônica de varredura a presença de uma grande quantidade de fibras de Al3Ni, que também contribuíram para o aumento da resistência da liga.

Oct 1, 2019

By Dagoberto Brandão Santos, Kairo de Barros Guimarães, Túlio Magno Füzessy de Melo

The effect of the cooling conditions on the microstructure and hardness of a Dual Phase hot-rolled steel 800 MPa strength was investigated. Simulations of the cooling conditions using a dilatometer were carried out from samples of a hot rolled coil with variations of the intermediary temperature from 620 to 740°C, isothermal holding time between 1 and 10 s and coiling temperature between 50 and 400°C. In addition, two CCT (Continuous Cooling Transformation) diagrams were developed to evaluate the effect of the isothermal holding time on the phase transformations of the remaining austenite. It was observed that the intermediary temperature has a strong influence on the kinetics of the phase transformation, as well as the isothermal holding time influences the amount of ferrite formed and, consequently, the final microstructure and hardness of the material. The coiling temperature did not cause significant changes in the amount and morphology of the ferrite, but a gradual replacement of martensite with bainite was observed, which, in addition to the self-tempering effect, contributed to the hardness reduction.

Oct 1, 2019

By Samuel F. Rodrigues, Clodualdo Aranas Jr., Fulvio Siciliano

The application of thermo-mechanical control processing (TMCP) in hot rolling of steels has become a common routine since the last 60 years. The understanding of the physical metallurgy behind TMCP played a major role in the early developments. Physical and numerical simulation works are performed firstly to derive the fundamental metallurgical knowledge and secondly to conceive existing TMCP practices. In this paper, a summary TMCP techniques is presented. The occurrence of dynamic transformation of ferrite in the austenite region is shown by means of synchrotron light diffraction methods. This phase transformation mechanism is taken into consideration and its effects on TMCP are proposed in an exploratory way.

Oct 1, 2019

By Xihuai Gong, Hongshuang Di, Jianping Li, Ning Yan

In this work, we investigated the effect of the rolling process (warm-rolled or cold-rolled) on microstructure evolution and mechanical properties of 9Mn steel. After intercritical annealing at 670°C for 10min, both cold-rolled and warm-rolled microstructures are composed of ultra-fined austenite and intercritical ferrite. The austenite in warm-rolled sample includes two types of morphology, namely equiaxed and lamellar, which exhibits a wide distribution of grain-size. The incomplete recrystallization or recovery behavior of ferrite in warm-rolled and annealed sample results in higher yield strength and shorter yield point elongation. Moreover, the warm-rolled and annealed sample extends the TRIP-related work hardening over a broad strain range, resulting in a better combination of ultimate tensile strength and total elongation.

Oct 1, 2019

By Stephanie L. Kaster, John G. Speer, Blake M. Whitley

Niobium-microalloying technology has been increasingly applied in a wide range of steel applications over the past half-century, to increase strength, control microstructure, enhance properties and enable a variety of applications. To achieve desired performance levels, thermomechanically processed microalloyed steels are widely supplied by the steel industry for high volume applications in hot-rolled plate, sheet and structural steels. However, in steel long products and forgings, the final properties are often generated by downstream users, after heat-treatment, surface hardening, forging or wire drawing. Two examples are presented highlighting advancements associated with Nb-microalloying, to enhance microstructures and properties developed during thermomechanical and/or downstream processing. In the first example, a 0.02 wt. pct. Nb addition was made to a medium-carbon bar steel intended for induction-hardening applications requiring fatigue and fracture resistance in bending and torsion. The Nb addition as well as thermomechanical bar processing led to beneficial refinement of both the pre-induction and post-induction microstructures. In the second example, a 0.01 wt. pct. Nb addition to a high-carbon wire rod was found to refine the pearlite colony size and interlamellar spacing, and increase the hardness.

Oct 1, 2019