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By R. Du Plessis, J. D. Miller, D. G. Kotlyar

The low potential hydrophobic state of pyrite in amyl xanthate flotation with nitrogen is of particular interest with regard to the N2TEC flotation technology currently being used for the recovery of auriferous pyrite at Newmont’s Lone Tree Plant in Nevada. The N2TEC system had been found to operate satisfactorily, but cyanide in the flotation mill water appeared to be responsible for a loss in pyrite recovery. This supposition was confirmed with laboratory experiments and a program was initiated to study flotation chemistry variables by electrochemically controlled contact angle measurements. Experimental results show that activation of pyrite in such cyanide solutions can be achieved more effectively with lead than with copper. Subsequently, based on these fundamental studies, significant improvement at the Lone Tree Plant was achieved by lead activation, in which case the recovery increased to expected levels. The effect of activator is particularly significant not only with respect to pyrite depression by residual cyanide, but also with respect to collector (PAX) consumption and the initial state of the pyrite surface. Each of these issues is being studied in detail and research progress is discussed herein.

Jan 1, 2002

By K. S. Gritton

The implementation of advance control systems brings with it the expectation of improvements in process performance and controllability. Specifically, expectations include a shift in the mean value of the gross measure of process performance, and/or a decrease in process variability. When determining statistically-defensible measures of these benefits care must be taken to preclude process parameters from biasing the determination. Specifically, the effects of ore type, shift personnel, water availability, etc., must all be separated from the effect on performance of the advanced control system. Methods are presented for separating the effects of process control from other process parameters. Examples of the required data analyses are also presented.

Jan 1, 2001

By P. Conrad

Experience has shown that, since the passage of the Surface Mining Control and Reclamation Act, over-compaction of spoil during the reclamation process has severely limited tree growth on reclaimed land. Researchers at the University of Kentucky have conducted a ten-year investigation at a surface mine in eastern Kentucky that monitored the changes in selected spoil physical characteristics for various reclamation and compaction alleviation methods. More specifically, research plots were developed for reforestation that employed three different levels of compaction and two different methods of ripping for overly compacted spoil. Each year measurements were made in the field of dry bulk density, using a nuclear density gage, and maximum penetration depth, using a recording cone penetrometer. In addition to good correlation between tree growth and selected spoil characteristics, the data demonstrated a gradual convergence of the measured spoil characteristic data over the study period.

Jan 1, 2008

By T. McKeon, G. Luttrell

Spiral separators are commonly used to upgrade sand-sized particles in both the coal and mineral processing industries. Many plants utilize multiple stages of cleaning and/or scavenging spirals to improve recovery and/or final product grade. Field studies suggest, however, that the layout of industrial spiral circuits is often less than optimal. This oversight can usually be attributed to a failure by plant designers to consider fundamental process engineering rules that govern the layout of complex separation circuits. This article reviews some of these important rules as specifically applied to multistage spiral circuit design. Two industrial case studies, one involving the upgrading of heavy mineral sands and a second involving the cleaning of fine coal, are presented to illustrate the impact of good design protocols on spiral circuit performance.

Jan 1, 2007

By S. M. Jasinski

Peat is a natural organic material of botanical origin. Peatlands are situated predominately in shallow wetland areas of the Northern Hemisphere. Commercial deposits are formed from the gradual decomposition of plant matter under anaerobic conditions for about 5,000-years. In 2004, peat was harvested in 16 states. Florida, Michigan and Minnesota accounted for more than 80 percent of the U.S. production. Reed-sedge was the dominant variety of peat harvested in the United States, comprising almost 80 percent of the output. This was followed by humus, hypnum moss and sphagnum moss.

Jan 1, 2005

By B. Samanta

This paper highlights the use of an innovative mine production scheduling scheme for grade-control planning tasks that take into consideration grade-model uncertainty. The scheduling exercise has been carried out with the help of a multiobjective genetic algorithm (MOGa) for the production scheduling operations. The underlying motive behind the use of MOGa has been the generation of a set of pareto optimal solutions to meet the goals of the target-grade specifications for the considered multiple grade attributes. Several new concepts related to MOGa formulation, in particular the mutation operation and the convergence criteria of this algorithm, are proposed in this paper. The modeling of grade uncertainty into the scheduling outputs has also been incorporated through a set of conditional simulated grade maps. The proposed scheme of production scheduling operations has been applied for the grade-control planning operations in an iron ore mine to meet the targeted grade specifications of iron, silica and alumina, and a risk analysis has been performed to this end.

Jan 1, 2013

By J. C. Cawley

This National Institute for Occupational Safety and Health study was conducted to focus future research on the most significant electrical problems in the mining industry. Data from 1,926 mine electrical accidents (including 75 fatalities) that occurred between 1990 and 1999 were studied. Coal and metal-nonmetal operator- and contractor-reported data are presented. All data used in this analysis were MSHA closeout data, except 1999, which were preliminary data. Electricity was the 4th leading cause of death reported in mining despite being the 14th leading cause of injuries. Electrical shock, not electrical burns, caused 70 of the 75 electrical fatalities reported. About one-half of mine electrical accidents and fatalities occurred during electrical maintenance. Suggestions for mitigating electrical hazards are proposed.

Jan 1, 2002

By Richard Gertsch, Jack Eloranta, Leslie Gertsch

An ongoing research program is characterizing the ore qualities that most affect mine and mill processing of iron. Current practice uses assays of magnetic iron and silica, but additional qualities are needed for advanced process control. If additional qualities can be measured from core, blastholes, or process samples, they can be modeled and controlled similarly. What qualities, other than assays, hinder or facilitate beneficiation at each processing step, and how can they be measured in the mine/mill ore stream? This paper describes preliminary determinations of the effects of ore chemistry, hardness, blasthole drill performance, fragmentation control, and grindability on mill performance.

Jan 1, 2005

Things are going well in the mining and construction industries world-wide. So good are things that from April 23 to 29 more than 500,000 visitors involved in those two industries attended the bauma 2007 Trade Show in Munich, Germany. Bauma is an international trade fair for construction and mining equipment that took place at the New Munich Trade Fair Center. It is hosted by Munich once every three years. This year was the most successful bauma ever and further strengthened the shows position as the world leader in the field.

Jan 1, 2007

By S. Strömberg, A. Jokilaakso

Two complex copper concentrates and one arsenical nickel concentrate were oxidized in simulated flash smelting conditions using a laminar-flow furnace. The concentrates contained tetrahedrite as Sb-bearing mineral and arsenopyrite and gersdorfite as As-bearing minerals. At high temperatures and low oxygen potentials, Sb tended to vaporize, but with high oxygen potentials it was captured in mixed oxide phases with copper and iron. Arsenic was found to follow antimony in copper concentrates, although with less sharp contrast between low and high oxygen potentials. In the nickel concentrate studied, arsenic was found to vaporize from the gersdorffite particles and, subsequently, condense on the other particles.

Jan 1, 1998

By Kai Wang, Chao Xu, Qiang Fu, Tong Yang, Chunyu Zhao, Wei Zhao

The stress of a coal seam is an important factor that affects the permeability of the coal seam and then affects the coalbed methane (CBM) drainage. In China, adjacent coal seam mining is an important method to reduce stress, which increases the permeability of the coal seam. However, in the process of mining adjacent coal seams, many coal pillars remain, which causes stress concentrations and results in a decrease in permeability. Therefore, it is important to study the influence of coal pillars on the stress of adjacent layers and its distribution and evolution in the floor rock. This paper took the Shendong Baode Coal Mine as a case study and investigated the influence of the coal pillar on the stress and permeability of coal seam #11. The results show that under a coal pillar, the relationship between the vertical stress of different floor depths and the width of the coal pillar can be divided into a negative correlation zone, transition zone, and positive correlation zone. The change in the coal pillar width does not affect the pressure relief range or the degree of pressure relief in the adjacent coal seams below the goaf. The field measurements show that after the mining of panel #81,505, the permeability coefficient of coal seam #11 under the goaf increased from 0.1434 to 26.3545 m2/( MPa2*d), increasing 182.7 times, and the drainage mixing volume of boreholes #1 and #2 increased from 1.24 to 1.52 m3/ min. While the permeability coefficient of coal seam #11 from 12.5 m in the coal pillar has only increased by 2.6 times, the drainage volume of boreholes #3 and #4 did not change significantly.

Nov 19, 2022

By H. Walqui, G. Rajala, G. Suardini

The Empire mine began operations on 1963. Low grade Magnetite ore is processed to produce iron pellets for blast furnace feed. Three expansions were added to the original plant and several equipment upgrades have been completed to improve the plant performance as the ore characteristics have been changing through the life of the mine. Size reduction is carried out by two grinding stages, the first one using autogenous grinding and the second one using pebble mills. Pebble crushing is also used to break the critical size fraction and increases primary grinding capacity. This paper describes changes in the configuration of the grinding circuits that have helped increase plant throughput and reduce power consumption by more efficiently utilizing assets available. Understanding the different components of the size reduction circuits and plant sections has allowed shifting part of the load from one section of the plant to another without affecting plant throughput.

Jan 1, 2007

By L. A. Ruth

Vision 21 is a government/industry/academia cost-shared partnership to develop the technology basis for integrated energy plants that will, early in the 21stcentury, result in the deployment of ultra-clean plants that produce electricity and “opportunity” products. Vision 21 plants will use fossil fuel feed-stocks in combination with other domestic resources, e.g., biomass, municipal waste, and petroleum coke. Opportunity products could include transportation fuels, steam, high-value chemicals, synthesis gas, and hydrogen. Performance targets for Vision 21 plants, example plant configurations, and the key technologies that will be needed are described.

Jan 1, 2000

By T. R. Ellis

Australia’s mineral valuation code continues to evolve, while mineral valuation standards are also being written for Canada and Southern Africa. The author is leading a task force for writing the extractive industries addition to the International Valuation Standards. Meanwhile, the International Accounting Standards Board is continuing the development of an extractive industries addition to its International Financial Reporting Standards, with an emphasis on valuation reporting. This paper analyzes the need, content and ownership for a U.S. minerals appraisal standard in the context of both these developing international standards and also existing U.S. regulations and appraisal standards. The author provides many questions for research and debate.

Jan 1, 2003

By M. M. Rajkovich

Just prior to the close of the century, the Federal Mine Safety and Health Review Commission issued its long-awaited decision in Berwind Natural Resources, et al v. Secretary of Labor, to usher in the new millennium. The case arose as a result of a mine explosion in Eastern Kentucky resulting in MSHA’s issuance of 225 citations, not only to the contractor, but to four affiliated entities of Berwind Corporation. While an Administrative Law Judge dismissed those citations as to three of the Berwind entities, both MSHA and the remaining Berwind entity appealed the case to the Commission. Although the Commission effectively left intact the Administrative Law Judge’s decision, it announced a new theory of liability that would apparently be applied in the future, namely the Unitary Operator Theory. This presentation will provide an in-depth look into the Berwind decision and explore the means under which MSHA might impose liability for contractor violations upon other entities in the future.

Jan 1, 2001

The occlusion of unliberated gold particles in silicates and sulfides in crushed/milled ore dictates the recovery that can be expected. The grade of this occluded gold in cyanide leach residues shows a consistent, general relationship to the head grade of the ore, irrespective of mineralogy or geographical location. The residue grade almost invariably increases with the head grade, but not in proportion to it. This phenomenon appears to stem from the nature of the geological events originally responsible for creating the ore deposits. A statistically-based technique for determining the true head grade-tail grade relationship from gold plant operating data is described. The effect is illustrated with results from several worldwide gold milling operations analyzed over the last 35 years.

Jan 1, 2008

By J. Kim, H. Cho

The objective of the experiment was to investigate the efficiency of hindered-settling column in recovering carbon from anthracite. Two types of Korean anthracites were prepared for feed materials. Each sample was crushed and classified by size, and washability analyses were performed. Separation efficiency was evaluated under various operating conditions using a laboratory scale hindered settling column. Results showed that the carbon recovery was higher for the smaller sizes, but the purity of the product was better for the larger sizes. In, overall, 2-0.21mm particles of 40-45 % ash could be processed into about 20 % ash products.

Jan 1, 2002

By J. Herbst, J. Groppo, A. Noble, R. Q. Honaker

"Coal and coal byproducts produced annually contain a sufficient amount of rare earth elements (REEs) to meet current U.S. demand. The REEs exist in the form of minerals, ion-adsorbed elements associated with clays, and chemically bonded elements within the organic coal matrix or host mineral. Researchers at three universities collaborated to evaluate the effectiveness of existing physical and chemical concentration processes for the recovery of the REEs. The efforts found that physical separation processes can increase the total REE content in the thickener underflow material collected from a Central Appalachian coal cleaning facility from around 300 ppm to values greater than 17,500 ppm on an ash basis. Leaching followed by solvent extraction was found to be the most effective to recover the REEs from coarse middlings materials collected from multiple coal basins, as indicated by recovery values exceeding 80 percent. Based on material characterization data and process evaluations conducted for several potential feed coal sources, economic recovery of the REEs will require byproduct production of both clean coal and REE concentrate using a process flowsheet that is unique for each source. IntroductionRecent studies initiated by the National Energy Technology Laboratory showed that U.S. coals contain significant amounts of rare earth elements (REEs), suggesting that rare earth minerals (REMs) and/or REEs can be produced as byproducts (Ekmann, 2012). According to the report, the richest source of REEs is the Central Appalachian coal. At present, there are 208 coal preparation plants located in the region consisting of areas within the states of West Virginia, Kentucky, Pennsylvania, Virginia, Alabama and Tennessee, with a total capacity of 166,495 t/h, or more than 1 Gt/y (Fiscor, 2014). If only a portion of these plants are retrofitted with advanced separation processes, the U.S. coal industry would become a significant producer of REE concentrates as byproducts. An inherent advantage of becoming a byproduct producer of REEs is that no mining cost needs to be part of the production cost."

Jan 1, 2017

Soil erosion is strongly related to soil hydraulic properties. Understanding how surface coal mining impacts those properties is important in developing effective management practices to control erosion during reclamation. Soils from undisturbed areas, roughly graded mine spoil, replaced topsoil before seeding, and revegetated areas at the Rosebud Mine in Eastern Montana were evaluated to determine impacts on soil hydraulic properties. Field and laboratory studies were conducted to determine soil hydraulic properties, including particle-size distribution, organic matter content, and saturated hydraulic conductivity. WEPP simulations and risk analyses were performed on the soil hydraulic property data to determine the impacts of changes on soil erosion. The hydraulic properties of the soils in each representative area have significant differences due to the mining and reclamation practices at the mine. WEPP simulations show that the potential for soil erosion increases due to mining activities disturbing the soil. WEPP simulations also indicate that the potential for erosion may return to pre-mining levels over time with effective revegetation practices.

Feb 27, 2013

By R. B. Crookston

This paper presents the status and mining method chosen by each of the active underground oil shale projects in the united States today. Potential improvements in equipment and methods on the near-term horizon are discussed. The problems and potentials that lie in the long-term future of oil shale mining are examined in light of the demands which must be met by this developing technology.

Jan 1, 1981