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By J. Mark Richardson

The use of an integrated software package to simulate and optimize the performance of mineral processing circuits is illustrated by three examples. Each represents application of the software and associated techniques to optimization of an existing plant. In the first example, a South-western U. S. copper company employs the method to simulate and improve performance in crushing, screening and SAG milling. A second copper producer evaluates equipment changes and flowsheet alternatives in a closed-circuit ball mill-cyclone operation. A Southeastern U. S. aluminum refinery optimizes performance of a dry milling and classification circuit for production of carbon particles used in anode casting. Graphical and tabular data describe the circuits simulated and the results achieved in each example.

Jan 1, 1990

By J. Rostami, J. Brune, S. Slouka

Respirable dust poses long-term health issues to personnel working in mining and civil projects where mechanized mining and tunneling machines are used for hard rock excavation. Machines, such as longwall shearers, roadheaders, or continuous miners, use consumable picks to cut rock. However, rock dust is generated in the work environment each time the pick tip contacts the rock surface. Additionally, the generated dust can be reintroduced into the air further down in production, such as at transfer points. The purpose of this study is to characterize respirable dust particles generated at the pick tip at two stages of pick wear: new and moderately worn. Understanding dust characteristics in terms of concentration, size distribution, and particle shape throughout the life-cycle of the pick will provide a basis to mine and tunnel operators for changing out picks to mitigate dust generation at the source. This paper discusses the dust characteristics generated from preliminary full-scale cutting tests in a laboratory of an igneous rock block cut with conical picks at new and moderately worn levels of wear. The moderately worn pick generated a size distribution that favored smaller particle sizes compared to the new pick. The moderately worn pick also generated more overall dust, as the concentration level in mg/m3 was over double the amount of the new pick. Lastly, both picks generated particles that had similar aspect ratios and roundness measures.

May 18, 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 Jürgen. F. Brune, CLAIRE STREBINGER, ADITYA JUGANDA, Gregory E. Bogin Jr

The abstract highlights the risk of methane gas explosions in underground coal mines and the potential of computational fluid dynamics (CFD) modeling to simulate such events and assess their impact on mine ventilation. The study focuses on developing CFD models for large-scale explosions in longwall mines, specifically simulating methane gas explosions resulting from face ignition during coal cutting. The research demonstrates the integration of a combustion model into a longwall mine ventilation model and shows how the availability of explosive gas mixtures significantly affects flame propagation and explosion pressure.

Mar 27, 2022

By A. M. El Shafey, Ahmed W. Hussein, Ibrahim M. Gaafar, Mona M. Fawzy, Mohamed Diab, Mohamed S. Abu El Ghar

The Quaternary stream sediments of the Diit area, southern Red Sea coast, Egypt, were mineralogically studied for their content of economic heavy minerals. The study area covered approximately 450 km2 and included three main parts: Wadi and Delta Diit, as well as Diit lens. The mineralogical investigation revealed that these sediments contain considerable amounts of placer ilmenite, magnetite, zircon, sphene, apatite, garnet, and rutile. Also present, in minor or trace amounts, are uranothorite, monazite, xenotime, fergusonite, khatyrkite, and gold. The magnetic fractionation tests, supplemented with the XRD and SEM mineral analyses, indicated the presence of Fe-oxide minerals as wuestite, hematite, and maghemite accompanied with magnetite as products for hand magnet separation. Ilmenite separation was carried out using a high intensity magnetic separator at a current of 1 A, while the paramagnetic minerals (e.g., garnet, pyroxene, amphibole, epidote, monazite, xenotime, and fergusonite) were separated as magnetic fraction at a current of 3 A. The non-magnetic minerals (e.g., zircon, apatite and rutile, uranophane, uranothorite, gold, and khatyrkite) were obtained at 3 A current. On a mineralogical and geochemical basis, the present work suggests that Diit stream sediments should be considered as a potential source for Ti, Fe, Zr, Zn, and Cu after the physical upgrading processes for concentrating the minerals carrying the aforementioned economic elements.

Jan 21, 2022

By Menglong Bian, Xiaotong Dong

Thermal damage is an urgent problem faced by deep mining. High-temperature rock mass, hot water and electromechanical equipment are the sources of the thermal damage. The increase in air temperature in mine tunnel is the result of fluid–solid coupling heat transfer from various heat sources. This paper takes a roadway with hot water and a mine car as the research object. Based on the Fluent, Static Structural and Steady-State Thermal modules in ANSYS, the thermal-fluid–structure coupling analysis in the roadway is carried out. It is found that the hot water has a significant effect on the thermal environment of the mine. Under the experimental parameters, the maximum heat flux density and equivalent elastic strain at the interface between the hot water and the rock are 9789.3 W/m2 and 0.00054532 m/m, respectively. The heat flux distribution in the rock area near the mine car does not change much, and the equivalent elastic strain value in this area is high. After the air is heated in the hot water area, the temperature curve changes gradually and then rises steadily. By changing the inlet air temperature parameter, it is found that the lower the inlet air temperature, the better the cooling effect, and the change of the inlet air temperature can change the air temperature field in the roadway as a whole. By changing the parameter of inlet air speed, it is found that higher wind speed brings better cooling effect, but with the increase in wind speed, the cooling effect of roadway thermal environment is very limited. When the wind speed increases from 5 m/s to 10 m/s, the air temperature of most measuring points drops by more than 2℃; when the wind speed increases from 15 m/s to 20 m/s, the air temperature of most measuring points drops below 0.7℃. After the wind speed reaches a certain value, the cooling effect of ventilation is very limited.

May 5, 2022

By A. Bhatanagar, D. Makhija, A. K. Mukherjee, R. K. Rath, P. Dixit

Characterization and beneficiation of dry iron ore processing plant reject fines of Khondbond region, India, was investigated. Different characterization techniques viz. size analysis, size-wise chemical and density analysis, X-ray diffraction analysis, sinkfloat analysis, thermo gravimetric analysis, scanning electron microscopy, and QEMSCAN were carried out. Based on characterization results, two process flow sheets comprising wet screening followed by conventional gravity concentration and two stage classification with different beneficiation routes were used to recover the iron values from reject fines containing 58.73% Fe, 5.54% Al2O3, and 6.6% SiO2. Finally, suggested flow sheet comprising of two stage classification and advance gravity concentration followed by the combination of grinding, classification, and froth flotation produced iron concentrate of 2.36% Al2O3 with 75.8% yield which can be used in sinter/pellet making.

By Gregory Rumbaugh, Christopher Mark

Recent pillar collapses have caused five large airblasts in underground U.S. limestone mines. One of these events injured three miners, but all of them put many other miners at risk. To better understand the hazards, Mine Safety and Health Administration (MSHA) conducted a comprehensive review of the international literature on airblasts. More than 40 airblast cases have been documented, in a wide variety of minerals. Experience shows that miners that are in the direct path of the air as it moves towards the mine exits are at the greatest risk. The paper describes a risk management methodology that can be used to evaluate the level of hazard throughout the mine and aid in the selection of controls to reduce the risk. The paper concludes with a detailed case history of an actual pillar collapse and airblast.

By M. R. Shahan, W. R. Reed, J. P. Rider

Roof bolter operators may be exposed to high respirable dust concentrations on continuous miner sections with blowing face ventilation when bolting is performed downwind of the continuous miner. One solution to reduce the high respirable dust concentrations is to use a canopy air curtain (CAC) to deliver clean air from a filtered blower fan directly to the bolter operators under the canopies. The influence of CAC installation in the airflow and dust dispersion around the location of the roof bolter operator can be evaluated by using computational fluid dynamics (CFD). This study, performed by the National Institute for Occupational Safety and Health (NIOSH), considers two scenarios: (1) a roof bolting machine in the center of the entry for installation of the fifth row of bolts from the face, and (2) a roof bolting machine positioned close to the face for the installation of the last row of bolts. In both scenarios, the bolting machine is placed in an environment which contains 6.0 mg/m3 of respirable dust and is ventilated by a blowing curtain with 3000 cfm (1.42 m3 /s) of air. This environment is used to simulate the roof bolter machine operating downstream of a continuous mining machine. Two operation positions are simulated at the same bolting location: dual drill heads in the inward position for two inside bolts and dual drill heads in the outward position for two outside bolts. The influence of the CAC on airflows and dust dispersion is evaluated with the CAC operating at 250 cfm (0.12 m3 /s).

By C. J. Slaughter, S. P. Harteis, L. L. Chasko, D. W. Alexander

The Department of Health and Human Services (HHS), National Institute for Occupational Safety and Health (NIOSH), Office of Mine Safety and Health Research (OMSHR), with the assistance of cooperating underground mining operations and state agencies, has conducted research exploring devices and technologies that could be used to assist miners navigating through smoke and dust resulting from a fire or explosion. Recent events in mines confirm that smoke and dust can enter and contaminate mine escapeways, creating an atmosphere with severely reduced visibility. This reduced visibility results in substantially increased escape times, possible disorientation or confusion, and increased stress levels, and may prevent evacuation altogether. Tools or devices that assist miners in navigating through smoke-filled areas void of lifelines could make the difference in successful escape from the mine. This paper presents the results of OMSHR research to identify and evaluate tools and devices that could provide meaningful information to evacuating miners in areas with limited visibility and without the benefit of a lifeline.

Jan 1, 2011

By A. D. Ajak

A complete mining cycle involves digging, loading, hauling and dumping of the materials. Moving the ore from the pit to the crusher or to the waste dump requires access routes, which are termed haul roads. These roads have to be designed, constructed and maintained. A review of the literature indicates a common consensus among researchers that there should be a balance between haul road economics and safety of the road users. However, there is no universally accepted theory on the design of haul road geometry and, in particular, road dimensions. The current industry practice is based on empirical data and rules of thumb developed by engineers. Therefore, this paper will use the overlooked and less valued branch of mathematics, arithmetic progression, to derive a road width equation. It is beyond the scope of this paper to discuss all road design components. The focus will be on the geometric aspects, which more often have a direct impact on road safety. In this paper, the current design practices and techniques for haul road geometrics design will be explored, using arithmetic progression to formulate road width equations, case examples to apply the equation and then validating the results with conventional techniques that have confirmed the reliability of road width equations, thus eliminating use of tables during design.

Jan 1, 2012

By R. J. Thompson

Well-designed and maintained haul roads are the key to minimizing truck haulage onroad hazards and costs, as well as increasing productivity. In practice, however, designing and managing a haul road for optimal performance is often difficult to achieve, especially when resources assigned to design and construction are constrained. By understanding how a road design is developed from geometric, structural, functional and maintenance considerations and, critically, the interplay between these components in design and operation, optimal performance can be achieved. This paper briefly summarizes the evolution of mine haul road design, from the seminal USBM work of Kaufman and Ault in 1977, through to current geometric, structural, functional and maintenance management design components. These augmented design and management guidelines have been developed over the past decade, both in response to the requirements of mine operators for safer and more efficient haulage systems, the truck manufacturers’ requirements for a more predictable and controlled operating environment and the recognition of human factors as a significant contributor to haulage accidents. While the human factor is the most problematic to address in a road design, the paper shows that the more that is known about human error, the better a road can be designed to accommodate those actions or non-standard practices that would, on a poorly designed road, invariably escalate an error into an accident.

Jan 1, 2010

By Xianyang Qiu, Xiuzhi Shi, Chen Xie, Xiaofeng Huo, Yanhai Wang

In upwards medium-deep hole cut blasting, many confinement effects exist due to the small number of free surfaces, which is mainly provided by an empty hole. If the cut blasting effect cannot meet expectations, then subsequent blasting construction will be seriously affected, and large security risks to operators in the stope can be induced. The number of free surfaces is directly related to the layout of the cutting borehole. Therefore, it is necessary to optimize the layout of the first round of cutting boreholes. Theoretical analysis, numerical simulations, and field tests were used to study the formation process of cut blasting and optimize the layout of the first round of cutting boreholes. Based on the blasting parameters in the field, LSDYNA software was used to establish cut blasting models with four kinds of borehole layouts in the first round. The RHT constitutive model was used to simulate the rock-breaking effect. The numerical results show that the cut blasting effect is optimal when Nos. 3, 5, 7, and 9 are charge holes and Nos. 1, 2, 4, 6, and 8 are empty holes. In addition, the greater the number of empty holes, the larger the release space and the better the cut blasting effect. The uniformity of the empty hole distribution, namely, the uniformity of the release space, also affects the cut blasting effect. The field results indicate that a good cut blasting effect can be achieved by optimizing the borehole layout.

Sep 7, 2023

By W. G. Pariseau

Joints may be taken into account when using numerical modeling as an aid to mine design by embedding joints in the model. When using the popular finite element method, say UT3PC, a pre-analysis step is necessary, Step 0. This step is for the computation of equivalent properties of a representative elementary volume of jointed rock (REV) in the model. This Step 0 is taken before Steps 1, 2 and 3 for specification of a rock properties file, generation of the mesh, and model analysis are taken. A brief explanation of equivalent properties and several examples aid in explaining the details of Step 0. Focus is on procedures, input files, and output to show ease of computation. Theoretical details are relegated to references (e.g. Pariseau 2022). Comparisons of safety factor distributions about example mine excavations with direct scaling from mine observations then offer some insights concerning equivalent properties, especially strengths.

Feb 1, 2023

By E. R. Bauer

In response to the mandates in the MINER Act of 2006, NIOSH conducted refuge alternatives research that included characterizing the utility, practicality and survivability of refuge chambers and outby safe havens. NIOSH also prepared and delivered a report to Congress in late December 2007 that summarized the findings of the research, included recommendations concerning the design and performance specifications for refuge alternatives, and focused on specific information that could inform the regulatory process on refuge alternatives. This document highlights NIOSH's research and recommendations concerning refuge alternatives, survivability evaluations of refuge chambers, and presents a brief review of the current deployment of refuge chambers in underground coal mines in the U.S. The research has lead to the conclusion that refuge alternatives have the potential for saving the lives of mine workers if they are part of a comprehensive escape and rescue plan, and if appropriate training is provided. DISCLAIMER: ?The findings and conclusions in this report have not been formally disseminated by the National Institute for Occupational Safety and Health and should not be construed to represent any agency determination or policy.?

Jan 1, 2009

By James H. Allen

The air lift method of pumping water is discussed. A review of several large diameter hole drilling projects that used reverse circulation air lift techniques is presented. Proposals are made for reverse circulation flow rates for slow rates of bit penetration (5 fph) as well as reverse circulation flow rates for faster rates of bit penetration (10 fph). The Ingersoll- Rand air lift equations are modified for rotary drilling operations. By establishing minimum reverse circulation flow rates and utilizing the modified air lift equations, the establishment of minimum circulation equipment sizes and a more definitive requirement for improved bit body design should result.

Jan 1, 1976

By R. J. Sheets

In 2009 the Gold Quarry open pit mine, located 11 km northwest of Carlin, Nevada, USA, experienced multiple large-scale slope instabilities of the upper east highwall that reduced gold ore extraction for nearly 18 months. The slope instabilities occurred within a weak, consolidated sedimentary sequence that exhibits strength characteristics that are transitional between soil and rock. Instability initiated as mining exposed the lower clay-rich sub-units of the Carlin Formation (Fm.). This deformation created preferential flow paths that allowed groundwater from the upper sandy sub-units to infiltrate low permeability clay-rich sub-units, thereby enhancing deformation of the slope toe which in turn destabilized the upper portion of the highwall. The outcome was a 160 m high slope instability that had a lateral run-out of 850 m. The effort to return the pit to ore production required both the geotechnical and hydrogeological investigations and the preliminary remediation mining activity to be concurrent. This approach required the development of detailed safety procedures and a requirement to modify the remediation design as new results were obtained. An initial challenge was to mitigate a near vertical, 90 m headscarp with blast induced, localized slope failures. Back-analyses applying numerical modeling indicated that the failure surface did not coincide with initial interpretations based on field observations; drilling results eventually confirmed this alternative failure geometry. The final remediation design incorporated shallower slope geometries and an approximately 3 Mt buttress along the base of the Carlin Formation and bedrock contact to reinforce the lower clay-rich sub-units. The outcome is a stable highwall within the Carlin Fm. following nearly ten years of repeated slope instability, and an example of the necessity to conduct appropriate geotechnical and hydrogeological studies during the early stages of a new layback evaluation or new open pit development.

Feb 23, 2014

By F. F. Peng

A unique collector dispersion techniques was developed and used to improve the flotation rate and recovery of coarser and ultrafine coal-rich particles in the froth flotation processes. In this novel collector dispersion method, the collector such as hydrocarbon-oil is gasified and transported by gas phase (air stream) into the pulp. In addition to the excellent mode of collector dispersion, the collector-encapsulated air bubbles are generated in the pulp. This approach alters the surface properties of air bubbles and provides the fast rate of flotation compared to that of direct liquid collector addition froth flotation. Using gasified kerosene as the collector, the effect of altering surface properties of bubbles on the recovery of larger and finer coal-rich particles of -1.7 mm (-12 mesh) and -600 µ m (-30 mesh) raw coal samples were studied. The Redstone seam coal obtained from Northern Central region of West Virginia was used in this work. The effect of particle size on oil-coated bubble flotation rate and recovery were also evaluated. The conventional froth flotation test with a liquid form of kerosene addition was also conducted for comparison purpose.

Jan 1, 1991

By P. R. Taylor

The ability to process complex precious metal sulfide concentrates containing antimony and arsenic, in an economic and environmentally safe manner, is an important problem facing the mining industry in the united states. Preliminary experiments have been performed to evaluate the possibility of treating a complex sulfide concentrate to recover antimony and precious metals while fixing the arsenic and sulfur as calcium arsenate and calcium sulfate. The process involves the oxidation of the antimony and arsenic minerals in the presence of soda ash (to collect the sulfur dioxide and to keep the antimony and arsenic from forming volatile compounds), the selective leaching of the arsenic from the roast calcine with a heated caustic solution, the precipitation of the arsenic and sulfate with calcium hydroxide and/or calcium chloride, the reduction of the residual antimony (collecting the precious metals), fuming of the metal to form a marketable antimony oxide, and crucible reduction of the residue to obtain a gold and silver dore. Experiments have been performed to evaluate the first stage of this process. Batch experiments were performed using synthetic concentrates of stibnite and arsenopyrite. Variables that were studied included: mixture weight fractions, temperature, gas flow rate, oxygen partial pressure and time. All of the off gas dust and sulfur containing gases were collected and analyzed. The roast solid residue was subjected to arsenic leach tests and the leach solutions were subjected to arsenic and sulfate precipitation tests.

Jan 1, 1993

By D. Malhotra

The effect of some of the reagents, namely hydrocarbon oil, Syntex (sulfated coconut oil surfactant), pine oil, sodium silicate, and lime, used at the Climax mill on the recovery and grade of molybdenite and gangue minerals has been investigated experimentally using factorially designed test approach in the laboratory. The results of the investigation are presented in two dimensional plots. The lower additions of lime (equivalent to a pH of 8 to 8.5) were desirable for maximizing recovery subject to constraints on grade. Higher additions of pine oil improved recovery, but only at the expense of grade. A mathematical model of the objectives of an operating plant was formulated and optimum reagent conditions obtained.

Jan 1, 1977