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By James P. Rider, Robert P. Vinson, Fred N. Kissell, Jon C. Volkwein, Gregory J. Chekan, Jay F. Colinet

The Thermo-MIE personal DataRAM dust monitor (pDR) is a light-scattering instrument approved for use in gassy underground mines by the U.S. Mine Safety and Health Administration (MSHA). However, the use of lightscattering monitors has been inhibited by concerns about inaccurate readings resulting from changes in dust size distribution and composition, as well as concerns about the impact of moisture in the mine air. Because of this concern, the National Institute for Occupational Safety and Health (NIOSH) has evaluated the pDR using available data from laboratory tests and mine surveys. The data show that accuracy can vary widely from test to test and mine to mine. In most cases, the results can be improved by using a companion gravimetric measurement to adjust the pDR data.

Jan 1, 2005

By W. Robert Rose, Randall Pyper, Carlos Mirabal, Jaime Eguivar

In 1984, work was started to determine the viability of heap leaching silver-containing waste dumps from Cerro Rico near Potosi - Bolivia, at an elevation of 4300 meters (14 100 it.). The result today is an unusual heap leach utilizing fine crushing, grinding, and agglomeration to process 1000 tonnes per day of ore containing 200 g/tonne silver. The unique metallurgical, economic, and political factors will be discussed which led to the decision to build a heap leach rather than a conventional agitation leach plant. Capital and operating costs will be given along with some of the uncommon process design and equipment problems encountered while developing the operation.

Jan 1, 1990

By J. G. Groppo, J. G. Justice, B. K. Parekh

Removal of particulates and/or metal ions from mineral/coal processing waste water is a necessity from the environmental point of view. This paper describes application of a novel AC- electrocoagulation technique to remove the particulates as well as metal ions using AC power. A series of laboratory tests conducted on a stable black water sample obtained from a sub-bitminous coal operation provided a clear supernatant (-10 NTU) from the suspension. The process also shows promise in removal of up to 90 percent of phosphate ions and other metal ions (copper and nickel) from solution. A preliminary economic evaluation of the process will also be included.

Jan 1, 1992

By Ruifeng Li, Yanghui Ren, Hua Gao

"Since entering the new century, China’s coal industry has witnessed the rapid development, and provided a reliable energy supply for the national economic and social development. But after the “golden decade” of rapid development, the coal industry now is facing overcapacity, low industrial concentration and production efficiency, high pressure of production safety and environmental protection and other prominent issues. Based on defining the connotation of highly-efficient recovery of coal resources, this paper established the relevant 8 indicators to reflect the highly-efficient recovery level of coal resources, summarized the present situation of China's coal resources recovery and the main problems, analyzed the development environment of China's coal industry under the new situation, and finally put forward the strategic measures to promote highly-efficient recovery of coal resources in China.1. Background Coal is the main energy in China. Since entering the new century, China's coal industry has made significant progress, and the level of production safety, resource recovery rate and mining mechanization increased significantly, which provided a reliable energy supply for the rapid development of the national economy. However, due to the changes of China's economic environment, slow growth of energy demand and other factors, some prominent contradictions in the coal industry have significantly restricted the healthy development of the industry. The first problem is serious overcapacity. In the past few years, 16 industries including coal, electric power, chemical and others have invested in coal mines. It is reported (Han 2016) that only during the nine years from 2005 to 2014, the fixed assets of coal industry increased totally more than 3.3 trillion RMB, which brought a large number of production capacity. Affected by the slowdown of economic growth and energy structure adjustment, Chinese coal demand has reached the peak platform and caused the overcapacity of coal supply, so shutting down the backward capacity is the most important task in the future. The second problem is the low efficiency of coal production. There are about 4.3 million coal mine workers in China, and the annual coal production per capita is less than 900 tons, while it was reported (EIA 2016) that the annual production per capita in the United States is more than 10 thousand tons. The third problem is that the green coal resources are not rich. Among the 1.53 trillion tons proven reserves, only about one third are green coal resources in accordance with the principle of ""safety, technology, environment and economy"". The coal resources with high quality and easily mining conditions are not abundant."

Jan 1, 2017

By S. J. Jung

The stability of underground openings for deep mines is critical, since incorrect orientation or geometry of shaft, stope, and accessways often results in the failure of openings due to high stress concentrations. Current state-of-the-art procedures for the design of underground openings are largely based on rules of thumb, experience, and trial and error. Rules of thumb are invariably based on the past experience of the designer and may not remain optimal as the depth and complexity of mine workings increase. Often, as conditions change, and as the interaction between geology, in-situ stress conditions, and mine openings grows more complex, the cost of maintaining structural integrity becomes prohibitive. Existing design procedures for deep mines are rapidly becoming inadequate as mines are worked at greater depths. For example, in the Coeur d' Alene Mining District, several million dollars are spent for inspection, repair, and maintenance on a regular schedule, largely as a result of inadequate design. In these types of situations, it is of critical importance that a new design methodology be developed for the layout and design of underground openings.

Jan 1, 1994

By Felicia F. Peng, Lili Li

The dispersion model of nonideal flow was applied to describe the hydrodynamic state within the flotation column. Residence time distribution (RTD) data of a laboratory flotation column were measured to determine the parameters of the model. The effects of operating variables and column geometry on the Peclet number which reflects the extent of axial dispersion were investigated and a semi-empirical expression of Pe was formulated. The dispersion model was validated for the column flotation of ultrafines coal. Under the conditions of sufficient aeration rate and frother addition, a good agreement between the measured recoveries and predicted data was obtained. The dispersion model with first-order flotation rate process of the flotation column developed in this study is useful in predicting the collection zone recovery of fine coal, and for the flotation column scale-up.

Jan 1, 1995

By G. Vijaya Kumar, B. Srinivasa Rao, G. V. Krishna Rao

The paper outlines the ventilation practices prevailing in coal mines of Singareni Collieries Company (South India). The high annual average surface temperature and relatively steep geothermic gradient results in virgin strata temperatures in the region of 38- 42°C creating environmental problems in the working places. Expensive methods of air cooling can not be employed as the mines are small, and production and productivity do not justify the costs of artificial cooling of mine air. Controlled recirculation of mine air -- the unconventional technique being tried with success in some coal mines in U.K. has been analysed for improving the environmental conditions. The analysis shows that the method is safe, cost effective and can be applied with very little extra equipment.

Jan 1, 1991

By John R. Marks

Few if any mines in North America have used exhaust air to remove heat at temperatures above the stope reject temperature. In contrast, the South African mining industry has long taken advantage of this heat removal method. The Homestake Gold Mine in Lead, South Dakota, has reached the point where a large air-conditioning upgrade is needed. Since existing air and water resources are being utilized about as well as practically possible, it was recently decided to install an 8.1 MW(R) (2300 ton) plant in the deepest mining division. Two horizontal bulk air spray coolers will distribute the coo1th to active workings via controlled recirculation. The heat will be rejected to exhaust air in four parallel cooling towers. The number and size of these large direct-contact heat exchangers prompted an investigation into South African planning techniques.

Jan 1, 1987

By N. I. Aziz, B. Srinivasa Rao, R. N. Singh

The control of respirable dust and its subsequent exposure to miners is essential for improved safety in longwall mining. The extensive variation in face conditions and operations of longwall make numerical modelling an attractive approach in both the development and evaluation of dust control devices. Three dimensional finite element computational fluid dynamics code FIDAP was used to model air velocities and the effect of dust control techniques on dust concentrations at a typical longwall face. The effect of shearer body on airflow characteristics in a longwall face was analysed with both antitropal and homotropal ventilation systems. Path traces of particles introduced near the shearer drums was also simulated. Initial modelling results were validated using field trial results at three operating longwall faces. Results of simulations tallied very well with the field results.

Jan 1, 1993

By A. S. Ibrado, D. W. Fuerstenau

The adsorption of the cyano complexes of Ag(I). Cu(l), Hg(II), Cd(II), and Zn(II) on activated carbon was investigated as a function of pH and correlated with the speciation diagram for each metal. The results show marked changes in uptake with pH, closely resembling the predominance profiles of their neutral and singly charged cyano complexes. Multicharged negative complexes are repelledby the negatively charged carbon surface. The sensitivity of activated carbon to the charge of the adsorbing species indicates that silver adsorbs as an anion, not chemically bound to the coadsorbing counterions. For the same reason, activated carbon is selective to metals that preferentially form neutral and singly charged cyano complexes, namely gold and silver.

Jan 1, 1990

By Richard A. Brown, Robert D. Norris

By-product metals can be a significant source of revenue for a mining operation if their recovery can be accomplished without negatively impacting primary metal recovery. The main problem encountered in separating primary and secondary metals is to selectively control the solubility of the individually important metals with¬out affecting their ultimate recoverability As a class of hydrometallurgical chemicals, peroxygens have a versatility which permits the selective recovery of individual metal species. Peroxygens function as more than simple oxidants. They are effective solubility control agents and have proven utility in complexation, precipitation, dissolution, extraction, oxidation and reductive processes Peroxygens have been used commercially to recover by-products vanadium, uranium, molybdenum, and cobalt and have proven experimentally to recover rhenium, gold, silver, manganese and zinc

Jan 1, 1983

By D. B. Jenkins, D. R. Taylor

Treatment of bentonite clay with mineral acids yields a modified clay product of high surface area and acidity that exhibits enhanced adsorptive and catalytic properties. A highly specialized segment of the clay industry based on this process has evolved into a worldwide business with a capacity of about 500 kt/a. This paper will present data on the chemistry, mining, manufacturing, and applications for acid-activated clays.

Jan 1, 1988

By A. I. Makhin, S. M. Sablukov, V. K. Sobolev, V. A. Larchenko, V. S. Shchukin

The kimberlites of northern Europe are related with a large crustal block having a northwest-southeast orientation. Kimberlites penetrate the Archean formations of crystalline basement, Late Proterozoic rocks, which are overlapped by Middle Carboniferous and younger deposits. The kimberlites bodies include pipes, dikes and sills of Upper Devonian age. Within the region, rocks of two magmatic series form diamond-bearing kimberlites. Aluminum rocks form a new type of diamond-bearing rock that is not found in other diamond provinces. Kimberlites of this region are characterized by highly developed deuteric alterations, a low content of associate minerals, the presence of two diamond generations and an increased content of jewelry-grade diamonds.

Jan 1, 1997

By Richard B. Muter

In determining the layout or combination of unit operations to be utilized in a modem preparation plant, several factors must be taken into account. Among these are the washability data, size consist data, the particular market or markets for the coal, the mining method used, the degree to which the coal must be prepared, expected fluctuations in raw coal and markets, and the overall economics of the process. In addition, there are the health and safety aspects of coal utilization and preparation. Chapter 1 of this book discusses the characteristics of coal and coal markets, while Chapter 2 deals with the design of preparation plants. Once the unit operations for a particular plant have been decided upon, these arrangement may be depicted by using a flowsheet. A coal preparation plant flowsheet is a two-dimensional graphical representation of the sequence of operations, the arrangement of machinery, and the flow of materials for a particular coal cleaning operation. The flowsheet is usually qualitative in nature, becoming more quantitative as material balances, water balances, numbers and sizes of various pieces of equipment, etc. are added. The usual convention in preparing a flowsheet is to show the feed flowing from left to right, starting at the top left and working down as in an all-gravity process. Various symbols are used for each unit operation as depicted on a flowsheet, and Fig. 14-37 is a compilation of the commonly accepted international standard symbols for each unit operation. Fig. 14-38 through Fig. 14-40 are flowsheets of various coal cleaning processes as published in the January 1976 issue of Coal Age. Each process has its own unique features which, among others, depend upon the coal being cleaned, the coal market, and the mining operation. Fig. 14-38, for example, is a flow diagram for a jig plant preparing steam coal from two strip mines located a few miles apart. In addition to the jig washer, cyclones are used to treat the finer size coal. Fig. 14-39 is a flowsheet of a heavy media plant using a heavy media washer for + %-in. (+6.3-mm) coal, froth flotation for -28 Tyler mesh (-0.6 mm) material, and dewatering phase units (dwp) for Y, in. x 28 Tyler mesh (6.3 x 0.6-mm) cleaning of steam coal. In addition, thermal drying, centrifuge drying, and the use of vacuum disk filters and thickeners for dewatering are depicted. Fig. 14-40 is a flowsheet of a plant producing metallurgical coal. In addition to the heavy media and froth flotation circuits, a tabling circuit is also employed. These flowsheets are intended to give the reader an example of how the various unit operations for coal cleaning may be linked together. Figs. 14-41 and 14-42 illustrate the conversion of block diagrams into an IS0 prescribed set of symbols.

Jan 1, 1991

By V. Srajer

The loading and hauling equipment simulation model was developed to satisfy, the requirements and need of the mining industry in western Canada. It is expected the model will be used to determine the' impact of various combina¬tion of loading and hauling equipment, company policies and maintenance procedures, haulage requirement, to evaluate possibilities, of the use of truck monitoring and dispatch systems, and to access loading and hauling equipment productivities. To evaluate the model, and to access its capabilities in addressing the above requirements, the model was validated. The validation was based on the following: 1. Running the model in-house to evaluate its structure, 2. Running the "test case" by timing models developed elsewhere to compare the results of simulation, 3. Soliciting of model critique from outside agencies, and 4. Comparison of calculated data with real time study data. The presented paper provide overview of the validation processes and summarize" results obtained during comparison and evaluation studies.

Jan 1, 1989

By D. C. Seidel, W. K. Tolley

Supercritical water alters the structure of common sulfide minerals by partially removing sulfur from the mineral structure. This discovery has been applied to the treatment of pyritic gold ores to improve precious metal recovery without generating or utilizing environmentally sensitive products such as S02, chlorine, or cyanide. Pretreating pyrite concentrates in supercritical water under mildly oxidizing conditions provided by certain metal oxides or oxygen improved gold leaching using thiourea. The pretreatment differs from chlorination or roast pretreatments in that elemental sulfur rather than sulfuric acid is the major product. A pyritic ore containing 58 g/mt Au was pretreated with oxygenated supercritical water at 24 MPa and 400°C, then leached with 20 g/L thiourea. With pretreatment, gold recovery was 90%; by contrast, gold recovery was below 10% without pretreatment.

Jan 1, 1990

By L. E. Krys, K. D. Harrison, C. G. Anderson

Since 1984, nitrogen-species catalyzed pressure leaching has been utilized at Sunshine Mining and Refining Company for the recovery of precious metals from a refractory sulfide concentrate. The process operates without the use of cyanide. The plant is now the only industrial-scale commercial application of this technology. Since the inception of the process, changes have been implemented to improve efficiencies and throughputs. Two of these changes, the replacement of nitric acid by sodium nitrite and a concentrate regrind, have recently been implemented. This paper discusses the development and potential mechanisms involved in these recently patented plant-process changes. A companion publication (Anderson et al., 1996) covers the plant integration and potential applicability of the technology.

Jan 1, 1997

By Kai Nielsen

In underground mining coarse muck and large boulders lead to ineffective utilization of costly mining equipment, and extra expenses and delays caused by secondary blasting. Cost analysis in some Norwegian mines shows that these extra expenses may amount to 10% or more of total mine operating costs. A computer model has been developed for sensitivity analysis of underground longhole stope blasting. The basic idea of the model is : When increasing the blasting energy input and fragmentation costs, the fragmentation will be better. This will lead to cost savings for loading, hauling, secondary blasting and primary crushing. The blasting design giving the lowest overall costs will indicate the optimal practice. The model has been used with data from several underground operations in Norway. An example run with typical costs shows that the costs for drilling, blasting and secondary blasting are the most significant parameters in the optimization process.

Jan 1, 1986

By M. Josick Comarmond, John J. Jeffery, John W. Bennett

Oxidation rates of sulfidic mine wastes measured at a range of size scales have been collected from a number of sources. The results suggest that well-designed laboratory columns, under controlled conditions, provide comparable information on oxidation rates to that obtained from field test piles. It has been found in the cases presented that laboratory measurements of oxidation rates of a particular material type can be applied with confidence to the same materials in the field. It is recommended that a further study be undertaken to measure the time-dependence of the oxidation rate for a range of particle sizes and different materials. This study would provide measurements against which models of oxidation rate as a function of time and particle size can be tested, to give confidence in the use of models to describe dump behaviour in the longer term.

Jan 1, 2000

By R. V. Ramani, S. Tan

A computer-oriented systems simulator (CMHS) has been developed for analysis of continuous materials handling systems. Special emphasis has been placed in the model on several features that are unique to these systems. These features include periodic pattern of material arrival from several sources, several types of material to he transferred, material dispatch processes, intermediate storage capacities, and multiple material destinations. Both the deterministic factors of the continuous material handling system, such as the physical decomposition of the system and the scheme and schedule of its operation, and the stochastic factors, such as variations of material arrival, material pattern on the conveyor, and availabilities of the system elements, are considered in the simulator. The application, of the model is demonstrated through a study of an underground conveyor belt network serving long- wall and continuous miner sections.

Jan 1, 1990