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By J. Grubb

"The undertakings described in the paper titled “Study on correlation of quantified coal rank with self-heating temperature” by Wang and Luo in the November 2015 issue of Mining Engineering (Wang and Luo, 2015) are mathematically sustainable and an acceptable extension of work performed by Smith and Lazzara (1987) for the U.S. Bureau of Mines. The paper is not an accurate explanation of the currently accepted leading practice for determining the propensity of a coal seam for spontaneous combustion. The paper could lead a practitioner to an oversimplified conclusion on how to determine the propensity of a coal seam to spontaneously combust.The spontaneous combustion of coal is a complex and not fully understood reaction. What is understood is that many more factors other than selfheating temperature (SHT) and coal rank are required to sufficiently evaluate the risk of spontaneous combustion in a particular coal seam. A superficial assessment can lead to an improper response to the risk. Some statements on the next steps through an appropriate literature search would have made the authors’ conclusions more credible.The SponCom 2.0 software, updated by the National Institute for Occupational Health and Safety (NIOSH) in 2011, provides a path for evaluating the susceptibility of a coal seam to spontaneous combustion. In addition to proximate and ultimate analyses to establish coal rank, and therefore an estimate of SHT, the program includes the history of heatings, friability, seam thickness, overburden thickness, rider seam presence, pyrite presence, face and butt cleat densities, geothermal source presence and other geological features in the assessment. Mining conditions including floor heave, rib sloughage and rate of advance are also assessed to conclude a propensity for spontaneous combustion."

Jun 1, 2016

By Francis Martino

There are numerous techniques and predictive models used by geologists and mining engineers to define coal reserves and plan mines. The traditional reserve estimation methods commonly used include the isopach, triangular, polygonal, inverse-distance weighting, weighted-moving-average, and trend-surface methods. Geostatistically-based estimation techniques are now being examined by many geologists and mine planners as a superior alternative to these traditional methods. With today's coal mine development costs often exceeding $100 million, and power generation $1 billion, it is logical that a technique that can indicate the degree of confidence associated with a reserve estimate (fuel supply), and thus also the degree of risk, is highly desirable to the coal producer, the financiers, and those desiring to commit to coal utilization under short or long-term supply arrangements.

Jan 1, 1983

By Edward R. Mueller

As an alternative to a million dollar, sensor based, computer dispatching system, Cyprus Pima Mining Company has installed a home¬made analog computer. The device is used in conjunction with a standard radio-dispatching system; it is inexpensive and very simple to build and operate. It enables the dispatcher to make near opti¬mum dispatching decisions and to identify all off schedule haulage trucks. Since installation, Cyprus Pima has experienced significant increases in pit productivity.

Jan 1, 1977

By H. Polat

Relatively large amounts of such hydrocarbons as fuel oils are often needed in flotation of low rank coals. The amount of oil can be decreased considerably by using surfactants as promotors. The reagents which are good candidates as surfactants to promote hydrophobicity can also act as emulsifying and wetting agents. Since the physical and chemical variables influence various sub-processes in different ways, their influence on the performance parameters is complex. The results of laboratory tests are presented to show that the dual role of reagents can be judiciously exploited to increase both the recovery and grade of clean coal. The mode and order of reagent addition is critical in enhancing their efficacy as flotation promotors. The results demonstrate the benefits of proper conditioning of the pulp prior to flotation.

Jan 1, 1997

By E. L. Michaels

Laboratory and pilot scale tests have been made to deter- mine the utility of heavy media separation, particularly a cone type separator, as a means of recovering aluminum from shredded municipal solid waste. The effect of the method of shredding on the behavior of aluminum in a heavy media system was deter- mined. Two-stage pilot scale heavy media separations were made with size fractions of shredded refuse. Recoveries of aluminum, as well as other components of the refuse, were measured and medium losses were determined. The experimental results indicate that with certain reservations a heavy media cone system can be utilized for aluminum separation and recovery from shredded and air classified municipal solid waste. Observations made using two-stage heavy media separation in a drum unit are included. Qualitatively, the results from the two types of separators are similar.

Jan 1, 1974

By J. C. Gathje

The Robinson copper ores were mined for many years from pits containing varying ore grades, sulfide and oxide ore types, and differing mineralogy. The ores also contain gold and molybdenum values, and their recoveries are an integral part of the flowsheet development. Metallurgical responses were characterized using a standard flotation procedure. Further studies investigated primary and regrind particle sizes, reagents, and other variables. The metallurgical testing was supported by mineralogical studies. Results demonstrated a high degree of metallurgical success for flotation. Final copper concentrates ranged in grade from approximately 28 to 30% copper and copper recoveries were 89 to 95% based on laboratory and pilot plant data.

Jan 1, 1992

By T. V. Subrahmanyam

Unlike coarse particles (40-50 µm), the fines (<10 µm) have low collision efficiencies with gas bubbles in flotation process. Among the alternative methods for recovering the fines are their aggregation with coarse particles (carrier flotation) and flocculation of the fines alone (shear-flocculation), prior to flotation. In any case, hydrophobic aggregation is the mechanism involved though the technique is known by different names in literature. This paper deals with theory and state-of-the-art of particle aggregation. To illustrate the dependence of aggregation on particle hydrophobicity, charge and, in turn, the sheer force, the results of quartz-DDACI and galena-xanthate systems are considered. In the flotation of complex ores selectivity is achieved by chemical control and aggregation of particles of the same species is analogous to that; however, more work is necessary on ores for a better understanding of the pulp chemical aspects from the view point of selectivity in aggregation. For a few ores, the results of earlier workers confirm improved recoveries of fines by aggregation prior to flotation.

Jan 1, 1997

By J. F. Fitzpatrick

This paper examines the cost elements associated with changes to gold mining practice over the last decade that result from the changes in environmental regulation and the heightened governmental and public awareness of environmental issues. The main experience base is Pegasus Gold Corporation&apos;s flagship mine, Zortman/Landusky, located in the Little Rocky Mountains of Phillips County, Montana. This operation was among the first mines that were permitted under the 1974 Montana Metal Mining Reclamation Act. In 1974, the Montana Metal Mine Reclamation Act was enacted, creating a permit system for metal and industrial mineral mines for the state of Montana. The act established the content of mine permit applications and defined parameters for the reclamation of mining disturbances. The Act can be viewed as implementing legislation for Article 9, Section 2, of Montana&apos;s Constitution, which provides that "all lands disturbed by the taking of natural resources shall be reclaimed." Pegasus Gold Corporation&apos;s Zortman/Landusky mine was among the first mines permitted under the new Act. In 1978, the initial permit applications were submitted for Zortman and Landusky, and a full Environmental Impact Statement was prepared by the Montana Department of State Lands; permits were issued in 1979. When opened later that year, the anticipated mine life for the combined Landusky and Zortman operations was approximately 18 years, based upon a proven and probable ore reserve of 43.2 million tons. Zortman/Landusky was the first large-scale heap leach gold mine in the United States. Its distinguishing feature was, and remains, a remarkably low ore grade, now .016 oz/ton. The ore is economic because it requires neither crushing nor agglomerating to leach effectively. Approximately two years after the initiation of the state&apos;s regulatory process, the Federal Land Policy Management Act (FLPMA) was enacted, establishing a mine regulatory framework for lands under the administration of the Bureau of Land Management.

Jan 1, 1992

By Ronny J. Sadri

Under contract to the Department of Energy, Fluor Mining & Metals, Inc. and Bonner & Moore Associates developed a group of computer models that can be used to simulate single seam dragline operations. These models have been subsequently modified by Fluor for use in multi-seam dragline mining situations. The single seam model analyzes the digging, spoiling, and walking patterns of draglines to identify possible parameter changes to increase productivity. Parameters such as key-cutting, panel width, digout length, and bench height, etc., are analyzed in this process. The models were tested using data from four operating mines. Field demonstrations were performed to correlate computer optimization results with field data. Productivity was greatly enhanced at one mine site by a change in some of the operating parameters. The multi-seam study has as its objective the development of a broad- based mine planning tool which would be used to identify and quantify the different procedures employed in multi-seam dragline mines to increase their productivity. The major problem identified in multi-seam mining is the sequencing of the different stripping and mining operations. The multi-seam model has the same capabilities as the single seam model. In addition, it models up to four seams with three partings per seam. It allows the operation of several draglines at different levels, and analyzes the effect of ramps, rehandling, and ancillary mining equipment.

Jan 1, 1982

By David Jenkins

Grefco Inc. operates two diatomite mines in the western Santa Ynez Mountains. The larger of the two mines, the Palos Colorados Mine, is located approximately seven miles southeast of Lompoc. The Miguelito Mine is located about two miles south of Lompoc on the west side of the Miguelito Canyon. Diatomite from the Palos Colorados and Miguelito mines is trucked to the Grefco plant at Lompoc for processing (Figure 1). HISTORY Grefco, Inc. evolved from the originating Dicalite Company which in 1929 began operations at the Walteria plant in the Palos Verdes Hills south of Los Angeles. In 1942 Dicalite leased the Palos Colorados mine at Lompoc. In 1944 the Dicalite Company was purchased by Great Lakes Carbon Corporation.

Jan 1, 1995

By Thomas H. Dubaniewicz

(XP) enclosures to enclose electrical ignition sources to prevent propagation of an internal methane-air explosion to a surrounding explosive atmosphere. Researchers at the National Institute for Occupational Safety and Health (NIOSH) conducted a lithium-ion battery thermal runaway test within a modified MSHA-approved XP enclosure to assess thermal runaway containment. Thermal runaway produced jet flames emanating from the cover joint at several locations and distorted the cover joint and bottom plate of the enclosure beyond allowable limits. The test demonstrates that XP enclosures may not provide adequate explosion protection against lithium-ion battery thermal runaway. This paper suggests some approaches to mitigate the hazard.

Feb 1, 2024

By C. Leal

Modern production has as goal to reach high and uniform quality in their products. To success with this, it is essential to have a good knowledge of the different variables involved in the process. Investigation or analysis of a process or system has as references the measurements of the variables. These measurements are presented normally in form of data. These data are measured in intervals over time. The aim with measurement of the data in a process is to obtain information about the state of it in order to have it under control. Other goal is to know how the results are affected by the process variables to improve upon product quality, redunding manufacturing cost, better pollution control etc.

Jan 1, 1994

By L. Donovan Clark

The term "powder factor" is almost universally accepted as the measure of the efficiency of a blasting program. It represents the economics of blasting since it designates quantity of explosive (thereby providing quality control in rock fragmentation) in terms of the associated volume broken. It is the wide use of this concept that explains the interest shown in an approach to rock blasting preferred by A. W. and Z. W. Daw* in a treatise on 3 blasting (1) substantiating its use in the form, Q = CVW3 for single shot hole, where Q = quantity of explosive lb Cv = blasting coefficient W3 = unit volume of rock It is obvious that the term Cv could also be called the apparent powder factor should the equation be written in the form, Cv = Q/W3 (lb per cubic unit). However, while the approach was ingenious** and the practical applications straightforward, their original, rather limited experimental work, along with certain assumptions, was questioned.

Jan 1, 1970

By David E. Sims

Asarco has been using computer-aided open-pit mine design since 1966. The in-house developed program package includes drill-hole analysis programs, interpolation routines, and three-dimensional open-pit design programs. The financial analysis step after pit design required that a reasonably accurate schedule be produced so that a good cash flow model could assess the feasibility of a project. The manual method of scheduling was too time-consuming for feasibility work, so a computerized scheduler was required. Since no computerized mine scheduling programs existed, we requested proposals from consulting firms to develop such a program. The selection of a consulting firm, the formulation of the contract and design specifications required about three years to accomplish. The consulting firm, Systems Control Inc. (SCI), of Palo Alto, spent over one year doing the programming and testing alone. The details of the program development were reported in "Computerized Year-by-Year Open-Pit Mine Scheduling," SME-AIME Transactions, December 1974. In June of 1973 the program, which SCI dubbed Optimum Resource Extraction or ORE, was installed. Version 1 of ORE was utilized successfully on three separate properties over a period of two years. During this time it became obvious that some of the original design specifications were restrictive, and certain modifications were required. The ORE program was submitted for modification, and after one year version 2 was operational in May of 1976. The program now consists of approximately 20,000 lines of FORTRAN source statements grouped into 190 subprograms, and runs in a 450K region of Asarco&apos;s 370/148 in Cranford, NJ. The Tucson com¬puter (370/115) is tied to the Cranford computer via a 9600 baud leased T.P. line, for running mine scheduling and other large mine planning programs.

Jan 1, 1979

By Hussin A. M. Ahmed

Oxidized coals are difficult to float. Therefore, in this paper, a special flotation procedure was investigated for upgrading this type of coal. The procedure is called direct contact flotation. It relies on mixing dry coal either with pure (anhydrous) flotation reagent(s) or microemulsion. By applying the new direct contact flotation procedure, a coal yield reaching > 95% using anhydrous flotation reagents was achieved, but with relatively high consumption of reagents (up to 30 g/kg). This high reagent consumption may be attributed to the fines included in the flotation feed (100% less than 0.5 mm, with 40% less than 75 µm). On the other hand, the clean coal yield was found to be approximately 88% when mixing dry oxidized coal with microemulsion droplets from dodecane and dodecyl tetra (ethylene glycol) ether (C12E4) in water at a total reagent dosage of 10 g/kg. The direct contact of coal either with unhydrous reagents or microemulsion also provided a high flotation selectivity.

May 1, 2012

By R. D. Irvine

Enhanced concern for protection of the environment and attendant actions by environmental regulatory authorities in support of this concern are influencing to varying degrees the demand and supply of a range of industrial minerals in a number of jurisdictions. These influences take a variety of forms. In this paper, the author seeks to delineate certain broad trends which are occurring relative to industrial minerals and the environment and then, through a series of examples, outline opportunities, developments, and impacts respecting a number of industrial minerals produced and consumed in Canada and the United States.

Jan 1, 1995

By J. M. Keating, R. L. Wiegel

Those processing plants which depend on flotation for their mineral separations are always looking for reagents which are cheaper, more selective or in some other way may provide improved economic performance. This paper describes the rationale for and some results from applying a statistically based approach to reagent testing in those flotation plants which still rely on experienced operators for manual flotation control.

Jan 1, 1986

By N. B. Prenn

Case Studies in Open Pit Design Using Whittle 4D will be discussing the following four examples: 1) Optimization of process plant design using Whittle 4D as a sizing tool. In this case, the home office and project team had different views of the size of the final project. The home office wanted to reduce the size of the project to reduce capital expenditure, while the project team suggested a larger project. Whittle 4D was used to determine Net Present Value and Internal Rate of Return using the Whittle scheduler (FDAN) to schedule many alternatives, and calculate the NPV and return for each alternative. 2) Comparison of pit optimization methods: Lerchs-Grossman vs floating cone. Many pits are developed based on floating cone economics. A comparison of methods in one large gold mine resulted in the stripping ratio of the pit being reduced by 10% in the Whittle 4D optimization as compared to the floating cone optimization. 3) Pit optimization to determine if a new mill is justified. A large heap leach gold and silver mine needed to determine if a new mill was justified. The planning and scheduling would take several man months if completed without pit optimization and scheduling software. Whittle 4D software proved to be very effective in providing optimized pits and a mine schedule in a short time frame. 4) Pit optimization to determine how to mine and size. Open pit optimization determined where the underground operation should start, and whether the material should be processed by milling or heap leaching. One of our clients asked for help in determining where the pit should end and a new underground operation start. We used Whittle 4D to help determine where the pit should end and where to go underground. In addition the operation needed to determine how to process the material.

Jan 1, 1996

By Mahmoud Sepehrmanesh, Verya Nasri

The purpose of this paper is to outline the advantages and disadvantages of single tube and twin tubes for subway systems. Different aspects such as diameter of the tunnel (tunnel spaceproofing), configuration of subway line and stations, impacts on passenger safety and evacuation, ventilation system as well as rail system for each solution were evaluated and compared. In addition, a multi-criterion approach is established to facilitate the decision making for these two different subway systems. The practical example of a mega project has been discussed and the details of the decision-making process has been explained. This proposed multicriterion can be used to facilitate selecting the best subway system in any urban areas.

Dec 1, 2022

By Philip Lindstrom

Retreat mining, using yielding steel friction props, over a seven-year period has been successful at a uranium mine operated by Hecla Mining Company in southeast Utah. The support system allow good roof control, maximum profit, complete extraction, and good ventilation. Unusual subsidence observations were made in that some of the surface was raised rather than lowered, Longwall mining, commonly practiced in European coal mines, has a potential of broader application because of mechanization possibilities and better roof control and ventilation at greater depths.

Jan 1, 1964