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By ANGELA NAIR AVELAR, Reiner Neumann, PAULO R. G. BRANDÃO

The understanding of the influence of the different types of apatite on the performance of mineral processing of igneous phosphate ores is still a challenge due to the difficulty to explain why some types of apatite floats in the froth flotation cell and others do not under the same conditions. Three types of apatite were identified by means of cathodoluminescence (CL) images in flotation concentrate and tailing samples from the Catalão mine: predominantly blue apatite, followed by green apatite and less frequently yellow apatite. The chemical composition of these types of apatite was determined by electron microprobe analysis (EPMA) and LA-ICP-MS. Blue and green apatite respond well to the process, thus remaining in the concentrate, while yellow apatite remained in the tailings. Yellow apatite is the one bearing the lowest P2O5 content and the largest anionic and cationic sites substitution, followed by green apatite, whereas blue apatite is the most homogeneous, with highest P and Ca grades and lowest substitution level. A negative correlation of the amount of phosphorus with fluorine was observed. Furthermore, impregnation of iron oxide-hydroxides in the yellow apatite was also observed. Therefore, the low flotation behaviour is due to low crystallinity coupled with impregnation onto its surface.

Jan 31, 2022

By Timothy Batchler, Khaled Mohamed

Standing supports have been used in coal mines for decades to enhance roof support capability. Sometimes standing supports are used as a tool to resist the lateral movement of spalled ribs. Researchers from the National Institute for Occupational Safety and Health (NIOSH) are conducting a testing program for different types of standing supports (steel and timber) to investigate the effect of lateral loading on their vertical loading capacities and the factors affecting their lateral loading capacities. In this paper, the mine roof simulator (MRS), at the NIOSH Pittsburgh research facility, was used to determine the response of steel props to vertical and horizontal loadings. Finite element models (FEMs) were developed and verified using the tested steel props. To justify the testing program for testing standing supports with end-conditions of rock-like materials, the verified prop models were used to study the effect of a wide range of roof and floor materials (gray shale, shale, and claystone) on the critical buckling loads of the steel props. Also, several lateral loading scenarios were evaluated in which the steel props were laterally loaded at different heights. The critical buckling load for steel props setting up against a claystone roof and floor was found to be one-half of that shown by the MRS test where roof and floor platens are made of steel. Minimum prop performance was observed when the lateral load was applied at the mid-height of the steel prop, especially at small lateral displacement (less than 2 in).

Sep 10, 2022

By VIVEK KASHYAP, Evody Tshijik Karumb, PATRICK TAYLOR

The partial reduction of zinc ferrite to zinc oxide and iron (II, III) oxide can enhance the leaching rate of zinc. Zinc ferrite has often been found as a major component of zinc residues and electric arc furnace dust. The Waelz process is an existing process for zinc ferrite processing, which requires a temperature of more than about 1200 °C to produce Waelz oxide containing ZnO. Since zinc residues have been deemed as a potential way for the extraction of zinc and other critical metals, it is important to analyze the reaction kinetics in the temperature range of interest. This manuscript discusses the chemical kinetics of zinc ferrite reduction by hydrogen gas. Several researchers studied the reduction of zinc ferrite with CO; however, unlike CO, the use of H2 gas as a reductant allows partial reduction of zinc ferrite even at low-temperature range (400–600 °C). Thermogravimetric analyses (TGA) experiments were performed in the temperature range of 300–700 °C with 10% and 30% H2, and the data obtained was analyzed using the isoconversional method of kinetic analyses. The standard models used for isoconversional kinetic analysis were chosen from literature and experimental data were fitted to determine the controlling mechanism and calculation of kinetic parameters of reduction of zinc ferrite. The rate of reaction was found to be increasing with an increase in temperature and partial pressure of H2 gas. The reaction could be divided into three stages, where reaction interface contraction was found to be the controlling mechanism at the initial stage of reaction. As the reaction proceeds, product layer thickness increases, and thus, diffusion was found to be the controlling mechanism. Roasting products obtained from TGA experiments were also characterized using a scanning electron microscope (SEM) to verify critical morphological details.

Jul 26, 2022

By Michael David Harmse, Wiehan Adriaan Pelser, Jean Herman van Laar, Cornelius Stephanus Lodewyk Schutte

The South African deep-level mining industry is characterised by high operating costs and narrowing profit margins. Compressed air is commonly the largest consumer of energy in these mines, and any inefficiencies reduce profitability. Various methods aiming to optimise the compressed air networks have been implemented without an ideal economic dispatch strategy due to the lack of compressed air storage. In this study, a genetic algorithm was developed to evaluate the financial benefit of converting underground haulage to act as an air receiver (compressed air storage). By converting inactive haulage of 1.17 km in length into a volumetric air receiver, an annual monetary benefit of R2.5 million ($163 200) can be achieved, with a payback period of fewer than eight months. However, implementing the ideal size air receiver would result in an annual monetary benefit of R7.67 million ($500 700).

Jul 11, 2022

By Rudrajit Mitra, Erik Hulthén, TOBIAS HARTMANN, ELISABETH CLAUSEN, Aarti Sörensen

There has been an ongoing debate on how to transform engineering education to better prepare students for today`s professional world that is characterized by increasingly complex problems and challenges that engineers are tasked with upon entering the industry. Within the conceive–design–implement–operate (CDIO) framework, entrepreneurship education presents a valuable pedagogical approach to foster the necessary skills of the students through integrated, hands-on, active learning experiences. While numerous publications have addressed possibilities of how experiential, problem-based, project-based and active learning can be integrated into engineering curriculum, there has been hardly any attention on mining engineering with respect to adopting this approach. This paper will address the possibilities of integrating entrepreneurship education into mining engineering programs in particular. This paper will enhance and foster discussion among academics from mining engineering on how to integrate elements of entrepreneurship education on a course, program and departmental level to infuse value creation experiences across the curriculum.

May 25, 2022

By Aimee A. Woolsey

Enterprise Unmanned Traffic Management is a holistic system concept evolving from technological developments in radio frequency where dynamic tracking can be added into current and emerging platforms. This is done through inexpensive RF sensors capable of real-time and cooperative, non-GPS tracking enabling digital visualization of assets, including unmanned aerial systems (UAS). The RF sensors are low size, weight, and power (SWaP), creating efficiencies in energy and material consumption while transmitting positions in real-time and at long ranges. Multiple UAS and other unmanned vehicles can be visualized for risk mitigation in operations,

Oct 17, 2022

By C Rutter, N Shea, K Kolobe

The Henderson mine, a panel cave mine in Colorado, has undergone multiple ventilation system changes to meet dynamic airflow needs. This paper explains the ventilation designs for different production panels, the challenges faced, and the modifications made to optimize the ventilation systems. The study highlights the importance of a robust ventilation system for safe and productive mining.

Mar 2, 2022

By LUKAS FAHLE, Andrew J. Petruska, JURGEN F. BRUNE, Gabriel Walton, Elizabeth A. Holley

Adverse ground behavior events, such as convergence and ground falls, pose critical risks to underground mine safety and productivity. Today, monitoring of such failures is primarily conducted using legacy techniques with low spatial and temporal resolution while exposing workers to hazardous environments. This study assesses the potential of novel simultaneous localization and mapping (SLAM)-based light detection and ranging (Lidar) data quality for rapid, digital, and eventually autonomous mine-wide underground geotechnical monitoring. We derive a comprehensive suite of quality metrics based on tests in two underground mines for two state-of-the-art mobile laser scanning (MLS) systems. Our results provide evidence that SLAM-based MLS provides data of the quality required to detect geotechnically relevant changes while being significantly more efficient for large mine layouts when compared to traditional static systems. Additionally, we show that SLAM-specific processing can achieve an order of magnitude better relative accuracy relevant for change detection than quality metrics derived from traditionally deployed tests would suggest while reducing SLAM drift error by up to 90%. In collaboration with an operating block cave mine, we confirm these capabilities in field tests on a mine-wide scale and, for the first time, demonstrate methods of rockfall detection using MLS data. While more work is required to investigate optimal collection, processing, and utilization of MLS data, we demonstrate its potential to become an effective and widely applicable data source for rapid, accurate, and comprehensive geotechnical inspections.

Aug 16, 2022

By Hugo E. Camargo, Amanda S. Azman, Brian Kim

Repeated noise exposure and occupational hearing loss are common health problems across industries and especially within the mining industry. Large mechanized processes, blasting, grinding, drilling, and work that is often in close quarters put many miners at an increased risk of noise overexposure. In stone, sand, and gravel mining, noise is generated from a variety of sources, depending on the type of ore being mined as well as the final consumer product provided by that mine. Depending on the source of noise generation, different strategies to reduce and avoid that noise should be implemented. The National Institute for Occupational Safety and Health (NIOSH) has evaluated the noise profile at three operational surface stone, sand, and gravel mines. A-weighted sound level meter data as well as phase array beamforming data were collected throughout the mines in areas with high noise exposure or high personnel foot or vehicle traffic. Sound level meter data collected on a grid pattern was used to develop sound profiles of the working areas. These sound contour maps as well as phase array beamforming plots were provided to the mines as well as guidance to modify work areas or personnel traffic to reduce noise exposure.

Jan 6, 2022

By Kanhaiya Mishra, Phanil. K. Mandal, S. K. Behera, P. S. Paul, Prashant Singh, C. N. Ghosh

The techno-economic and social benefits of cemented paste backfill (CPB) resulted in its wide acceptance by the mining industry. The Ordinary Portland Cement (OPC) remains the key binder but to diminish its economical constraints, suitability of alternate binders has been examined worldwide. The present study aimed to investigate the effect of partial replacement of OPC with fly ash on the CPB’s strength and to determine the most optimal mix to achieve the required strength (1 MPa at 28 days of curing) at the most cost-effective way using the Bayesian network (BN). The CPB mixes were prepared at 72 wt.% solid concentration with mill tailings (87–91%), OPC (6–13%), and fly ash (0–4%), and instantly after mixing, fresh (slump, bleeding, density) CPB properties were measured. The strength was tested at 7, 14, 28, and 56 days of curing and initially analysed through traditional model. The traditional models follow the aleatory principle and are considered not appropriate for geotechnical engineering. Hence, the BN model was developed and tested. The reliability of two classifiers in learning model structure was compared which gives Naïve Bayes as the highest reliable tool. The CPB’s strength is most sensitive to the OPC content. The most consistent mix(s) is mill tailings: 87–88%, OPC: 9–11%, fly ash: 1–4%. Adding fly ash at 89–91wt% mill tailings possesses high failure probability of the CPB. The collinearity test indicates that the fines percentage and chemical composition of CPB’s ingredients are highly correlated with its slump, bleeding, and strength development.

Jul 14, 2022

By Ihsan Berk Tulu, Haochen Zhao, Deniz Tuncay

This paper proposes a new method to estimate the percentage of load carried by the gob in underground coal mines using a new parameter that introduces the site-specific overburden geology. The new parameter was defined as the total strong layer thickness (tstr) that represents the strength and stiffness of the overburden with a single value. Twelve field measurement case studies from 11 different U.S. longwall mines with different overburden geologies were used to develop the new methodology. 2D numerical models of these case studies (and additional parametric runs with different panel widths) were verified against field measurements such as surface subsidence and stress. Statistical analyses using the model results were conducted for a loading model with the new tstr parameter as one of the variables. The new methodology was found to have a coefficient of determination (R2) of 85% when compared to the field measurements and the parametric models. The method was then tested for practical implementation for pillar design. The percentages of load carried by the gob as estimated by the new method were implemented into the LaModel program, that is commonly used in the coal industry. The results obtained from LaModel were compared to the available field stress measurements, and the new method implemented into LaModel was found to give successful results.

Jul 18, 2022

By Peter Zhang, Todd Minoski, Gabriel Esterhuizen, Jack Trackemas, Berk Tulu, Morgan Sears

Longwall mining is a highly productive and efficient coal mining method used in the USA. During longwall retreating, the belt entry must be maintained stable, and any roof fall in the belt entry would jeopardize mine safety and substantially interrupt the continuous production of coal in the longwall face. Past experience of longwall mining has shown that belt entry stability was the greatest challenge in longwall ground control, and the occurrence of roof falls in belt entries was largely associated with high horizontal stress. To properly support the roof in the belt entry, it is important to understand how longwall-induced horizontal stress changes affect roof stability in belt entries and to strategically install supplementary support to prevent any potential roof falls. Researchers from the National Institute for Occupational Safety and Health (NIOSH) performed horizontal stress measurements in the immediate roof of the belt entries for two Pittsburgh seam longwall panels oriented unfavorably to high horizontal stress. Hollow inclusion cells (HICells) were installed in the immediate roof at the intersection in each of the belt entries, and stress changes were monitored as the longwall face was approaching and passing the intersection. Numerical models were set up to calculate the longwall-induced horizontal stress changes in the roof at the monitoring sites. With the verified model, investigations were made of how horizontal stress is concentrated and relieved in the belt entry roof near the face under different panel orientations. Both measurements and modeling results showed that high horizontal stress is concentrated in the roof in the belt entry within about 15 m outby the face when a longwall panel is unfavorably oriented to the major horizontal stress. The study demonstrated that longwall-induced differential horizontal stress can be used as an indication of the degree of horizontal stress concentration. Roof support strategies are discussed on how to maintain the stability of belt entry under high horizontal stress concentration.

Jun 14, 2022

By Jessica M. Wempen, William G. Pariseau, Dallan J. Coons, Michael K. McCarter, Erik C. Westman

The abstract discusses the importance of proper pillar sizing in underground mining for safety and efficiency. It highlights the use of theoretical models, geotechnical measurements, and numerical modeling in predicting pillar behavior. The research focuses on using seismic tomography to image stress changes in a yield pillar at a longwall mine as the longwall face approaches. The study aims to compare the stress distribution imaged using tomography with theoretical models, geotechnical measurements, and numerical models.

Mar 18, 2022

By Julio Aníbal Morales Pereira

Sabe-se dos problemas associados com as inclusões não metálicas, os quais afetam não somente a operação de fabricação, como também a qualidade do produto final. Por esses motivos, muitos estudos têm sido realizados para melhorar o controle do tamanho, quantidade, forma, distribuição e composição das inclusões. Especificamente para as inclusões de espinélio MgO·Al2O3, ainda é preciso melhorar o entendimento dos fenômenos sobre a formação e modificação destas inclusões para um melhor controle ao longo do processo de fabricação do aço e obter maior limpidez inclusionária nos aços. Assim, neste trabalho, foram revisados tópicos reportados na literatura relacionados com: a formação, influência da composição da escória e modificação com cálcio das inclusões de espinélio.

Aug 16, 2017

By Raphaella Hermont Fonseca Murta

O ensaio não destrutivo por ultrassom é amplamente utilizado para detectar e dimensionar descontinuidades no interior do material. A técnica TOFD (Time Of Flight Diffraction [do inglês]) foi a técnica ultrassônica utilizada. Entretanto, a classificação do tipo de descontinuidade, a partir dos sinais ultrassônicos obtidos durante uma inspeção requer um profissional altamente capacitado. Esta tarefa pode ser realizada por algoritmos de reconhecimento de padrões, capazes de processar rapidamente uma grande quantidade de dados. Nesse trabalho, foram simulados três tipos de descontinuidades em juntas soldadas: falta de penetração, poro e trinca, utilizando-se o Método dos Volumes Finitos (MVF). Em seguida, foi aplicado o método de reconhecimento de padrões K-vizinhos mais próximos (K-NN – K-nearest neighbors [do inglês]), para verificar como esses dados são separados. Esse trabalho é um passo inicial para o emprego de simulação numérica do ensaio ultrassônico para produzir sinais simulados e utilizá-los no treinamento de ferramentas de reconhecimento de padrão, a serem futuramente testados com sinais ultrassônicos experimentais. O K-NN classificou bem os sinais simulados. Conseguindo uma taxa média de acerto de aproximadamente 84%.

Oct 30, 2017

By W. J. González

With the increasing demand for minerals and the decline in the quality of ore reserves, technologies to maximize recovery are critical to a mine?s economic success. Many mining waters exhibit the potential to form hardness-based inorganic scales, which inhibit effective mineral recovery. Often, a continuously-fed chemical deposit control program is implemented by the mine site to inhibit these scales. The use of retractable scale coupons is the current industry standard for monitoring these programs; however, a key drawback to their use is the limited, and sometimes untimely amount of information they provide. A proprietary fouling analyzer has been developed that can be used to continuously monitor the formation of inorganic scales in mining process streams. Consequently, it can be used to continually, and more effectively, communicate the efficacy of an antiscalant program, thereby providing the ability to compare different scale control programs and to optimize their feedrates. Case studies presented validate the applicability of this technology to help optimize mineral recovery.

Feb 23, 2014

By Alberto Moreira Guerreiro Brito

Componentes tubulares de parede fina têm aplicações em diversas áreas industriais, na forma de trocadores de calor, amortecedores de impacto, sistemas de fixação, absorvedores de energia, pré-formas para outros processos de conformação mecânica, etc. Neste trabalho é apresentado um estudo de natureza teórico-experimental envolvendo o processo de expansão de extremidades de tubos. Busca-se determinar os parâmetros que governam o mesmo, suas limitações e se a conformação em matriz pode ser uma alternativa viável a processos mais complexos, como por exemplo, hidroconformação. É feita a caracterização do material (uma liga de alumínio ABNT 6061) através do levantamento de curvas de escoamento, perfis de microdureza Vickers, e deformabilidade quanto ao surgimento de trincas e de instabilidade plástica (flamblagem). Ao final são conduzidas simulações através de elementos finitos e experimentos do processo de expansão. São variadas características geométricas dos tubos e das ferramentas e o estado do material (diferentes tratamentos térmicos).

Aug 8, 2018

By Ivo Filipovic

The steel melting process in an Electric Arc Furnace is a complex set of tasks, coping with highly dangerous hazards as fire, explosions, uncontrolled reactions, hot metal projections and gas or dust emissions. Melt shops are dangerous working areas for operators, recording statistics with a high frequency of injuries. In the past years, without dedicated safety equipment, there wasn't a real attitude to the risk prevention. The paper describes the available technological packages to eliminate the manned activities on the melting floor, with the aim to prevent accidents and keep furnace operators safe. The technological packages suite extends the automatic control of the EAF melting process to all the operations from charging phase to tapping. Plus, the integration of the most frequent operations by automated specialized tools effectively minimizes power-off times, enhancing reliability and improving the transformation costs.

Aug 17, 2017

By Alessandra Regina Machado Schifino

Neste trabalho foi realizado um estudo comparativo entre as normas utilizadas para validação da solda aluminotérmica em trilhos do tipo Premium – Vignole dos modelos TR, utilizada em reparos de trilhos ferroviários. As normas a serem comparadas são: ABNT (Associação Brasileira de Normas Técnicas), AREMA (American Rail Way Engineering and Maintenance of Way Association) e a Norma Europeia (British Standard – Railway Aplication Track – Auminothermic Welding of Rails). Esta comparação será realizada para avaliar a relevância da variação dos parâmetros utilizados em cada uma das normas e quais fatores devem ser analisados em mais de uma norma para que não haja dúvidas se os trilhos estão aptos para serem colocados em operação. Através da realização dos ensaios mecânicos e metalúrgicos, sugeridos pelas normas, encontra-se defeitos causados por diversos fatores, tais como: processo de fabricação, mau uso dos trilhos, falhas operacionais na soldagem, de preenchimento, de solidificação entre outros. Utilizando-se deste conjunto de informações será possível validar as soldas aluminotérmicas testadas.

Oct 30, 2017

By MARCELO TADEU TOMAZELA LIMA

Os aços inoxidáveis são largamente utilizados nos mais diversos segmentos da sociedade, tendo como principal característica a resistência à corrosão. Existem muitos estudos sobre o comportamento destes aços, que se apresentam com diferentes composições, estruturas e propriedades, mas algumas características ainda precisam de muito estudo, como exemplo a interação do metal com o hidrogênio. O hidrogênio nos metais é estudado há muitas décadas pela sua alta capacidade de mobilidade intersticial, todavia seus mecanismos de fragilização são pouco compreendidos e propostos em algumas teorias. O presente trabalho busca caracterizar os efeitos do hidrogênio em um aço inoxidável ferrítico tipo AISI 409 quando tensionado em ensaios de achatamento comparativamente entre amostras hidrogenadas e não hidrogenadas. Os testes no material de base evidenciaram que o hidrogênio age na perda de ductilidade deste aço inoxidável, apresentando facetas de clivagem ao ser tensionado. Os resultados obtidos sugerem que a fragilização por hidrogênio representa um risco e um desafio à Indústria, reforçando a necessidade de desenvolvimento de pesquisas e estudos para minimização dos efeitos do hidrogênio nos metais.

Oct 30, 2017