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By Xinyang Wang

It is believed that sulfur and volatile matter con-tents in coals are the main intrinsic properties to cause the self-heating of coal. Their oxidation at lower temperatures than that of fixed carbon to initiate coal's self-heating should be quantified. This study is aimed to improve the previous mathematical model developed by the authors for studying the coal's propensity for spontaneous combustion. It enhances the model's ability to consider the effects of sulfur, volatile matter and moisture contents in the coal three important factors affecting the coal's self-heating process. Sulfur exists in coal primarily in the form of pyrite which will be oxidized rapidly under suitable conditions. Volatile matters, higher in low rank coals, are more easily to be oxidized. Heat of water condensation provides initial energy for low temperature oxidation. Heat release rates for pyrite oxidation and moisture condensation are built in the model. Finally, the simulation results in terms of time versus temperature on pyrite oxidation and moisture condensation are validated with the adiabatic testing data respectively.

Jan 1, 2013

By B. C. Paul, R. Q. Honaker, M. Huang

Froth flotation is now, the most commonly used method for cleaning fine-coal fractions in coal-preparation plants. Past research and industrial practice have demonstrated that froth flotation achieves excellent separation efficiencies for fine coals having only a small fraction of middling particles. However, the efficiency of froth flotation decreases sharply as the concentration of middling particles increases. This is due to the flotation of high-ash particles that have a small amount of hydrophobic coal present at the surface. Because gravity-based processes are much more efficient for the treatment of middlings, the application of centrifugal washing for fine-coal cleaning was studied with an emphasis on the primary cleaning of fine-circuit feed. Results are shown of a parametric study that used a semibatch Falcon centrifugal concentrator. The results of the study revealed that separation performance is a function of particle size, bowl geometry, feed solids content and feed rate.

Jan 1, 1996

By A. T. Iannacchione

Unfortunately from 1991 through 1995, 44 miners were fatally injured in the stone industry. Of these 12 occurred at underground mines from a total work force of less than 2,000 miners. Nine of these 12 miners were fatally injured in falls of roof or rib. A safer environment for the miners can be achieved by evaluating the nature of the hazardous ground and by developing more efficient and effective ground control strategies. Roof and rib conditions in the underground stone industry were observed and assessed at 33 mines in Illinois, Indiana, Kentucky, Maryland, Missouri, Pennsylvania, and West Virginia (Figure 1). Hazard assessment indicated that those ground failures occurring under moderate to substantial overburden ( > 30 m [100 ft]) were caused by stress concentrations and geologic structures. Ground failures near the surface are caused by solution (water) processes. Selection of the mining horizon and mine layout decisions tremendously influence ground stability.

Jan 1, 1997

By Chester A. Rowland

La conminución de Ios minerales es, generalmente, una etapa de preparación de la alimentación para las subsiguientes etapas del proceso. La molienda, fase de conminución de productos finos, requiere una gran inversión de capital y frecuentemente es el área de máxima utilización de potencia y de materiales resistentes al desgaste. La molienda se produce normalmente en tambores rotativos que utilizan un medio de molienda que se pierde en la misma, al elevarse con la rotación del tambor, se rompe el mineral por combinación de los efectos de impacto, atrición y abrasión, hasta producir el producto especificado. El medio de molienda pueda ser: - El propio mineral (molienda autógena - primaria y secundaria). - Medio no metálico, natural o fabricado (pebbles) - Medio metálico (barras o bolas de acero) Este capítulo tratará de molinos de barras y bolas que utilicen medio metálico de molienda.

Jan 1, 1982

By Ron Robinson, Trevor Harrison

The planning, installation and commissioning of the first scheme of controlled recirculation of air flow in a section of coal mine in Great Britain is described, together with the proposals for a second installation. The work updates a previous paper (Robinson and Harrison, l986) on the subject. The special problems of ventilating the increasingly distant faces of the undersea mines in the North East Area of the British Coal Corporation are discussed and the alternative solutions stated. The advantages of using a system of controlled recirculation of air are proposed together with the safety features considered necessary. Design and installation details of the recirculation fans and a new booster fan are described.

Jan 1, 1987

By Jan M. Mutmansky

Simulation is a general term which commonly appears in the technical literature and which can have different meanings to different people. One interesting definition (9)* applicable in an engineering context is the following: "Simulation is the use of a model to study a problem." In most cases, the model referred to in the above definition is a simulation model constructed in a computer language and implemented on a computer in order to solve the problem under consideration. The application of computer simulation models to the study of problems in materials handling and earthmoving has been successful in the past. Generally speaking, this method has been used where the system to be studied has many variables and where the ability to predict the outcome of the system under different sets of conditions is difficult. The prime reason for using such a model is to evaluate the numerous likely ways of operating any particular system without the necessity of actually conducting full-scale field tests. The simulation model presented here is such an application made to the process of tunneling and, in particular, to the process of tunneling with a boring-type tunneling device. At first glance, the process of tunneling may not appear to be particularly complex and susceptible to study by a computer model. However, a close analysis of the tunneling process will reveal that it is rather complicated as a result of limitations placed upon the system by restricted space in the tunnel, geologic variations along the tunnel

Jan 1, 1972

By Liming Yuan, Wei Tang, RICHARD THOMAS, JOHN SOLES

Lithium-ion battery pack fires pose great hazards to the safety and health of miners. A detailed experimental study has been conducted at the National Institute for Occupational Safety and Health (NIOSH) Pittsburgh Mining Research Division (PMRD) to investigate the effectiveness of different fire suppression systems on Li-ion battery pack fire extinguishment. Tests were conducted in a well-ventilated container. Two sizes of battery packs (12 V, 24 V) were heated by heater strips to trigger thermal runaway and fire. Water mist with different flow rates, ABC powder, type D dry chemical, and water mist with F500 additives were used as the fire suppression agents. Multiple thermocouples were installed on the battery packs to measure the temperature evolution during the tests. The results indicated that the water mist with F500 additives is the most effective suppressant among the agents tested. Dry chemicals, however, do quench the fire for a moment, but cannot prevent re-ignition of the battery since they do not provide enough cooling. The findings of this paper can be used to develop safer battery fire suppression techniques in mining environments.

May 4, 2023

By Lim Thi Duong, Du Duy Bui, Thuat Ngoc Pham, Chuc Ngoc Pham, Que Anh Nguyen, Hoa Anh Bui, Chi Thi Ha Nguyen, Hoan Thanh Nguyen, Bac Quang Nguyen, Kien Trung Nguyen, Dung Trung Doan, Nhiem Ngoc Dao

The microstructures and kinetics of a rich iron ore ( TFe = 65.84%) of Na Rua mine, Vietnam, used for the iron production were investigated in this study. Thermal behaviors of iron ores were well-examined by heating microscopy, thermogravimetric analysis, and differential thermal analysis. After being pelletized and then oxidatively fired at 500–1200 °C for 2 h, the pellets fired at 1200 °C (P1200) displayed a hard and dense structure with a decent compressive strength of 317.9 kg/pellet whereas those fired at 500 °C (P500) had a soft and spongy structure. The reduction of iron pellets conducted in a flow of a 60–100% CO2/ Ar gas mixture at 900–1100 °C showed significantly higher efficiency than the reduction using coal. The spongy pellets showed superior performance for the reduction in the CO/Ar gas mixture compared to the dense ones, compatible with the production of sponge iron. When mixed with an amount of coal, P1200 designed for iron production in the blast furnace demonstrated an impressive reduction activity compared to P500 and previous studies. The kinetics of pellet reduction was determined by the diffusion of substances through the solid product layers having the mathematical model of 1 − 2 3 f − (1 − f )2∕3 = kt . The microstructures of pellets during the oxidative firing and reduction were also examined by X-ray diffractometry; scanning electronic microscopy; energy-dispersive X-ray spectroscopy; and Brunauer, Emmet, and Teller method.

Jun 7, 2022

By C. A. Holley

The generation of coal fines is a growing problem which has serious environmental and resource recovery Impact. Several methods of agglomeration are studied including the production of briquettes for the consumer market. Simplified process flow diagrams, "order of magnitude" plant capital cost and operating costs are presented.

Jan 1, 1986

By D. P. Patil, B. K. Parekh

Water is the mainstay for beneficiation of fine size coal and minerals; however, it is also the least desirable constituent in the final product. The basic concept of the novel process described in this paper is based on the differential surface heat conduction/ absorption capacity of individual particles, which differs for different species of minerals. When a mixture of fine material is exposed to a radiant energy source, the various solids present in the mixture will absorb heat energy depending on their heat-conducting properties and there will be a difference in the surface temperature of the particles. When this differentially heated solid mixture is placed on a moving belt, which is coated with a low temperature melting resin, the hotter component of the mixture will stick to the belt and relatively cooler particles will stay free on the belt and fall off at the end of the belt run. Experiments were conducted with pyrite, coal, and quartz of 6 × 18 mesh particle size. The goal of the test program was to find the optimum conditions at which there exists a required temperature difference between minerals and coal particles by controlling the operating system variables. Preliminary tests results showed that there is a potential for separating mineral matter from coal using the thermo-adhesive separation technique.

Jan 6, 2022

By III Sadler

Processing bauxite and clay ores to reduce Iron content to levels low enough for the ores to be suitable raw materials for such products as refractories and abrasives has long been regarded as a diffi9ult problem. Standard magnetic separation processing of the untreated ore has been attempted by previous investigators with only limited success due to the finely divided state and weak magnetic susceptibility of the iron minerals (hematite, geothite, etc.) present in these ores. The new process described in this paper consists of calcining the finely crushed ore at 500 to 800 C and then reducing (with hydrogen, carbon monoxide, etc.) the iron oxides present to magnetite or elemental Iron. The magnetic susceptibility of iron in these forms is enhanced 40-to 100-fold over that of hematitie and is readily removed by simple magnetic separation. Starting with a 2.7% Fe20s Alabama bauxite ore, a 1.5% Fe20s product was produced in one pass through a Davis tube magnetic separator with 95 + % recovery of the iron-free bauxite fraction and a 20% Fe20a magnetic product. These findings suggest that with the addition of light calcination, reduction and magnetic separation steps to the conventional refractory grain production process, the large U.S. reserves of high-iron bauxites could be used.

Jan 1, 1990

By Max Friedemann, Franziska Günther, Helmut Mischo

Ensuring adequate ventilation is a critical aspect of safety in underground mining operations. In small-scale mines in particular, key ventilation parameters such as temperature, humidity, and air velocity are often measured manually and only at infrequent intervals, typically using analog instruments. As a result, real-time monitoring of environmental changes, timely detection of hazardous situations, and demand-driven ventilation control are not feasible. This presentation discusses the selection and evaluation of modern digital ventilation measurement devices, including handheld instruments with digital data logging capabilities and continuously operating sensors with potential for real-time data transmission. The investigations focus on the challenges posed by underground environments with extremely high humidity levels, which can adversely affect sensor performance and electronic components. The results are based on testing conducted at the Research and Teaching Mine of TU Bergakademie Freiberg—an underground ore mine characterized by humidity levels exceeding 95%. Findings include assessments of measurement accuracy, reliability, and practical applicability under these demanding conditions.

Feb 22, 2026

By SUHAINA ISMAIL, NORLIA BAHARUN, SHAIK ABDUL RAHMAN, WAN NUR SYAFIQAH ANUAR, MOHAMMAD REZAEI ARDANI

Refractory gold ore contains sulfide minerals like pyrite, chalcopyrite and sphalerite that are difficult to be directly leached by cyanidation or by lixiviants such as thiourea and halides. In such cases, it is necessary to perform oxidative pretreatment of the ore to oxidize the sulfide matrix, and gold particles can be exposed to the solution during the leaching process [1]. In recent years, hypochlorite and chloride solutions have been introduced as alternative materials for hydrometallurgical methods of gold extraction instead of cyanide solution [2]. A previous study by Hasab et al. [3] reported that the gold dissolution rate in hypochlorite solution was higher than in the cyanidation process, due to the presence of hypochlorous acid (HOCl) as a strong oxidizing agent. In a hypochlorite leaching system, the change in pH can influence the presence of oxidant species in the solution: the hypochlorite ion (OCl−) is stable in pH greater than 7.5, HOCl can be found in pH between 4.0 and 7.5, and aqueous chlorine (Cl2 (aq)) is the predominant oxidant when pH is below 4.0. As HOCl is the most effective oxidizing agent for gold extraction, pH should be maintained in the range of HOCl stability [4].

By S. G. McDowell

This paper discusses the utilization of automation to increase productivity of continuous miners. Automation techniques are used during the design stage to decrease the time required and ensure the accuracy of the design. This is followed by automated manufacturing processes to reduce manufacturing time and improve the quality and consistency of parts. Combined, the result is a more reliable machine which can provide ongoing production capability. With the use of automation to enhance operator effectiveness and monitoring machine condition the productivity of machines is also improved.

Jan 1, 1991

By Enrico Pavese, Tim Kearney, Stefan Lemke

Watertightness is of central importance in hydraulic and underground structures but has always been associated with a risk, as demonstrated by the very high impact that water inflows have on the damage of linings and infrastructure (Howard, 1991; Sandrone and Labiouse, 2011). Concrete is vulnerable to groundwater and chemical contaminants in the soil. These can leach into the pores and cracks of the concrete and degrade its integrity, causing spalling and corroding the reinforcing steel. Moisture migrating into the building can also degrade structural elements over time and lead to mold and other hazards to occupants’ health. In this connection, the demands placed on the setup and detailed design of the seal depending on the negative influence by water on the one hand and on the other hand on the function of a construction in view to its watertightness classification. Thus, the reliable functioning of a seal is of particular significance in the case of traffic tunnels, which are not easily accessible for all subsequent repairs after the construction in seepage water and especially when located in a pressure water zone (risk–cost assessment). Requirements for the long-term efficiency and quality of underground structures have increased in recent decades. Today, the standard lifetime requirement for an underground infrastructure project is 100 to 120 years and, in some cases, even higher. This calls for high increased attention to the durability of the whole structure and of each individual element. Standards, which started as application guidelines given by the manufacturers, are available in the market since the 1980s and are constantly adapted to the current developments in various technical committees. Differentiations are made between: Manufactures application guidelines, case studies or published articles Test standards for the laboratory to guideline the testing procedures (air temperature, type of test equipment, dimensions, test speed, test duration, concentration, type of liquids, monitoring, tolerances, interpretation of results, documentation, etc.), developed by committees based on material and laboratory experts Application standards, which include test standards but also the related minimum performance requirements (values) for material, processing, and quality assurance (practical tolerances), developed by committees based on a wide range of experts (e.g., designers, construction companies, applicators, manufactures, owners, test institutes, quality engineers) and therefore also based on a wide field of experience, different views and up-dated case studies. In the following there are some examples of guidelines and published information’s, ranked according to the year of issue, which are relevant for the development of waterproofing specifications in the tunnel industry:

Jun 13, 2023

By Steven Keim, Steven Stansfield, Kevin Andrews

Geotechnical, geological, and hydrogeological fieldwork and data collection for the mining industry is often conducted by younger, less-experienced staff members. In many cases, fieldwork personnel are recent college graduates or are otherwise relatively new to the mining industry. Due to busy schedules, staffing shortages, project budgets, and in some cases, poor management, new fieldwork hires often do not receive thorough training. In the past and the present, many workers in the mining industry learn(ed) by “doing.” While this is still considered to be the most practical approach and the easiest way for a company to determine the skill set of an employee, there is always some risk involved in the “feet to the fire” method. The reality is that field personnel are often collecting data on which major operational decisions will be made or on which regulators will base enforcement decisions. Inadequately trained or inexperienced field personnel may collect inaccurate data or fail to recognize key conditions that may influence decisions made by regulators, design engineers, mine managers, and corporate leaders. Even the best engineers may come to incorrect conclusions if they are starting with poor input data. Decisions based on inaccurate data often result in delays, budget issues, unsafe conditions, or even worse consequences. This paper provides numerous mining industry examples of incidences where inaccurately collected field information did, or could have, resulted in major adverse consequences. The paper also offers some simple approaches to minimizing the potential for such problems.

Jul 1, 2023

By W. H. Jang

Although surface chemistry fundamentals of semi-soluble minerals have been studied by many researchers, detailed understanding of these systems is still incomplete. In-situ FT-IR/IRS techniques have recently been used to successfully describe the adsorption of carboxylates at semi-soluble mineral surfaces. However, the wetting characteristics of these adsorbed films require further consideration. In this regard, the hydrophobicity and stability of transferred Langmuir-Blodgett (LB) monolayers of fatty acids at fluorite and calcite surfaces has been studied by contact angle measurements with polar and apolar liquids. Generally, it was found that the transferred LB monolayers of fatty acids at a calcite surface are unstable whereas such monolayers transferred at a fluorite surface are stable, as revealed from advancing and receding contact angle measurements. These results are believed to be due to the incomplete reaction of fatty acid monolayer at the calcite surface. In addition it was found that a closely packed well-ordered stearate monolayer with good hydrophobicity, equivalent to that of a transferred LB monolayer, can be formed at fluorite surfaces by spontaneous adsorption and self-assembly from aqueous solutions.

Jan 1, 1995

By A. R. Laplante

A novel methodology to estimate gold recovery by gravity is presented. The methodology makes use of a population balance model which represents gold liberation, breakage and classification behaviour and applies pre-concentration and recovery performance curves to gravity-recoverable gold to predict overall recovery. Derivation of the necessary parameters is explained and demonstrated using data from an actual gravity circuit and one projected application. The methodology makes it possible to estimate the performance of circuits with large gold circulating loads and relatively low unit recoveries (e.g. jigs), or with high recoveries on a bleed of the circulating load (e.g. Knelson concentrators).

Jan 1, 1994

By J. A. Botín

Investment decision for large mining projects imply an enormous financial risk and therefore, require a more complex risk evaluation methodology taking into account all sources of uncertainty from each process in the project value chain. Generally, the main sources of risk are those related to uncertainty on grade and other techical variables of the orebody. In this study, conditional simulation is applied to develop a risk management model to quantify and to manage financial risk associated to uncertainty on the grade of the orebody. The model was validated in case study on a real porphyry copper orebody in Chile.

Feb 23, 2014

By Eric Lundgren

The mining paradigm is changing on the continent of Africa. Jessica Kogel?s closing statement from her September 2013 President?s Page (ME, September 2013, pp. 6) has never been more appropriate, ?Africa is shaping up to be the next mining powerhouse, and there is huge opportunity for local communities, national governments and private industry to work together to create a win-win situation for all.? Supporting this notion, attendance at numerous industry conferences around the world demonstrates the shift toward a more sustainable, more environmentally conscious extractive model. But questions remain: How effectively is the industry making this transition, and how willing are companies to learn from the experiences of others? The international development community, as we like to call ourselves, is going through a parallel shift. We are experiencing our own funding crisis; governments are not as flush with resources as they were pre-economic meltdown. But more importantly, after a half century of implementing development programs, we must admit that while some of our programs have been fantastically successful, too many still fail to achieve the goal of poverty alleviation for the world?s poorest. Moving forward, we are forced to recognize that achieving success in scale and sustainability is not always accomplished from our work alone. As the director of international programs for Africare, a nonprofit with more than 40 years of experience implementing community-based development programs in Africa, I can report that our organization is changing the way we think about successful development partnerships. Africare recognizes that for too long the mining sector and nonprofits have been at odds, choosing noncommunication as a ?solution? to the problem. Both sides now recognize that this standoff is outdated, and Africare, specifically, is ready to cross the proverbial line. We see the potential benefits of mining for local communities and, when done responsibly, the opportunity to properly manage Africa?s resource boom as a benefit to all. There are challenges in this conversation. Many mining professionals view nonprofits as whistle-blowers, ready in a pinch to speak to news sources and complain about poor operational standards. Those are advocacy organizations, and while their role is important, they are not the only nonprofits interested in mining operations in developing countries. Organizations like Africare, with decades of experience implementing poverty reduction programs, approach this differently. We know we can work with mining companies to promote economic opportunity in the communities where mining operations are occurring. We recognize that the conversation is difficult, and we are open to discussions about how we can bring our unique experience to bear on the problems faced by mining companies in carrying out their investment programs.

Jan 1, 2014