Search Documents

By A. G. Fonseca

The effects of coal cleaning, coal combustion and flue gas particulate removal systems on the partitioning of 12 trace elements were investigated. This study was prepared to help document the fate of trace elements in modern coal preparation plants and coal-fired utility boilers. The coal cleaning data were obtained from several coal preparation plant operations. The CONSOL 1. 5 MM Btu/hr pilot combustion and electrostatic precipitator (particulate removal system) test facility was used to develop the combustion systems data. A comparison with the very limited amount of published data from utility boilers is presented.

Jan 1, 1993

By I. E. Odom

The physiocemical properties and industrial uses of the clay mineral montmorillonite are reviewed. Montmorillonite is the most abundant species of the smectite clay mineral group and is the predominant mineral composing bentonite deposits. The crystal structure, chemical composition, exchangeable ion type, and small crystal size are responsible for several unique properties, including a large chemically active surface area, a high cation exchange capacity and interlamellar surfaces having unsual hydration characteristics. The type of exchangeable ion Na, Ca and/or Mg has a major influence on industrial and chemical uses of montmorillonite because of their hydration characteristcs. Natural occurrences of Na montmorillonite in commercial quantities are geographically limited, but Ca-Mg montmorillonite deposits are known world wide. Foundry, well drilling, pelletizing and civil engineering constitute the major uses of montmorillonite, but the total array of uses of montmorillonite exceeds that of any other mineral.

Jan 1, 1986

By D. D. Gertenbach

"The successful commercialization of a pressure oxidation (POX) process for recovering metal values, including gold, copper, zinc, nickel and molybdenum, is the result of a carefully planned development program. The initial task involves developing one or more conceptual flowsheets, including the POX autoclave and downstream purification and recovery steps. A laboratory program is completed to determine the technical viability of the flowsheets, define the operating parameters for each step and provide information for an initial economic assessment of the process. The process is then confirmed during a continuous pilot plant program, providing engineering design data and other information for the commercial design. A well-thought-out development program has been shown to be critical for reducing the risk of commercializing POX processes. Experiences developing POX processes for refractory gold ores and copper concentrates are briefly discussed. IntroductionPressure oxidation (POX) has become a common commercial operation for processing sulfide-bearing feedstocks. These feedstocks include gold ores and concentrates; copper concentrates; nickel concentrates and mattes; zinc concentrates; and molybdenum concentrates. Drivers for the development and commercialization of POX processes include:• The high cost for pyrometallurgical processing of sulfide ores, much of which is attributed to environmental controls.• The motivation to implement safe and more environmentally attractive alternatives for sulfide ores.• The need to process increasingly difficult ores with complex mineralogy.• Improvements made over the last 25 years in POX equipment design and experience operating commercial POX plants.Although the capital and operating costs for commercial POX processing can be high, this technology is capable of rapid oxidation of most sulfides and arsenic minerals in the feed, with little noxious gases and environmentally stable iron arsenate and other iron compounds in the POX residue (Marsden and House, 2006).In POX operations, sulfides are oxidized to either sulfates or elemental sulfur in an autoclave at elevated temperature and pressure with oxygen gas. An example is the overall oxidation reactions of chalcopyrite when sufficient oxygen is present, shown in the following reactions:"

Jan 1, 2016

By Robert W. Bruhn

Ground movements associated with high extraction underground coal mining, such as pillar retreat and longwall, are sometimes large enough to disrupt the ground water regime as well as damage buildings and other surface structures. A U.S. Department of Energy/Bureau of Mines- sponsored subsidence study currently underway at Kitt Energy Corporation's Kitt No. 1 Mine near Philippi (Barbour County), West Virginia has provided an opportunity to monitor the ground water response above a mine panel during both developmental and pillar retreat mining. The initial findings concerning ground water effects presented in this paper indicate that total extraction mining produced significant water level declines in deep-lying strata but had little effect on water bevels at shallower depths.

Jan 1, 1985

The Cadia Mine is located 25kms South West of Orange in the central west of New South Wales (NSW), Australia (Figure 1). Orange is a major regional centre with a population of 35,000 people. Cadia has a history of mining and exploration dating back to 1851 and shortly after the first Australian gold rush at Ophir, north of Orange. Newcrest Mining commenced an exploration program at Cadia Hill in 1992. This identified a substantial zone of copper and gold mineralization. Subsequent resource definition drilling defined an orebody with a mineable reserve of 200 million tonnes of ore with an average gold grade of 0.74g/t and 0.17\ copper. A full feasibility study commenced in 1994, approvals to proceed with development were granted in September 1996 and the processing plant was commissioned in July 1998. The project came in on budget at A$440 million and on time, 24 months from design to construction. The estimated operating cost at the time of commissioning was A$8.85/t of mill feed.

Jan 1, 1999

By William H. Lehr

A 4200 ton-per- hour marine transfer terminal, where river and oceangoing vessels simultaneously exchange cargos of coal and phosphate rock, is now in operation near the mouth of the Mississippi. Its materials handling machinery includes a bucket ladder barge unloader; a rope operated clamshell bucket unloader; a coal loader; and a rail mounted bucket wheel machine. The design and operation of this equipment is described as are the docks and conveying, breasting and barge-haul systems in use at the facility. Design considerations imposed by soil and river conditions, geography, operating needs and investment requirements are discussed. The economic significance of design and shipping innovations introduced by this facility is noted.

Jan 1, 1967

Since the beginning of the computing age, technical software packages have not been developed to address only programming specialists but have been dedicated to process engineers. For process analysis, BRGM is developing and commercializing three packages: ? sampling software: ECHANT 2.0 for Windows ? material balance calculation: BILCO 2.0 for Windows ? steady-state simulator for plant design, adaptation and optimization: USIM PAC 2.1 for Windows This paper deals in a first part with the main features of these three packages. In a second part, advanced models are presented for SAG/ AG mills and flotation columns. An industrial case of application is shown for each of them.

Jan 1, 1997

By Philip R. Whitney

Precipitation of hydrous manganese/iron oxides in streams can be readily observed in much of the northeastern United States, and is apparently a common phenomenon in other glaciated areas (1,2,3,4). Deposition occurs when Mn-enriched ground or surface water enters the stream environment and encounters conditions of higher Eh and pH. The preferred location for deposition is in shallow, fast-flowing segments of stream; the oxides usually form as coatings on detrital material. The experimental studies of Hem(5) and a considerable amount of work on marine and lacustrine manganese nodules(6,7,8) suggest that given an appropriate substrate, deposition of manganese oxides may occur even when the water is undersaturated in Mn with respect to the oxides, due to catalysis by organisms or by silicate, carbonate, or ferric hydroxide surfaces. Once begun, manganese oxide deposition is autocatalytic (9). Studies of the distribution of oxides in various size fractions of stream sediments indicate that the thickness and prevalence of the coatings commonly increases with increasing particle size in the coarse sand and gravel size ranges. Figures 1 and 2 show a fairly typical distribution of leachable metals over nine size fractions from 62 microns up to 8-16 mm. The leaching solution used was neutral ammonium citrate with hydroxylamine hydrochloride, which effectively removes the oxide coatings without significantly attacking most silicates, carbonates or sulfides. Figure 1 shows metal content as ppm of the total sample; figure 2 shows' the same data as micrograms of metal per square millimeter of surface area.

Jan 1, 1975

By Robert Stefanko

The results of a recent study on the influence of continuous and conventional mining techniques on the size consist and wash- ability characteristics of coal are presented. Eight samples, four each from continuous and conventional mining sections were collected. Each sample was screened in seven size fractions, and each size fraction was totally fractionated at five gravities. The data thus collected was statistically examined for the influence significance of mining techniques, size, and gravity on the quality of the mined product. The paper presents the sample collection method, data gathering and analysis procedures, and major conclusions. The study revealed that there are pronounced differences in the products from the two mining systems and that conventional mining yielded a better product in terms of size-consist, and yield, ash, and sulfur in both the raw and washed products. The results of the study are significant in regard to consideration of resource utilization and conservation, and environmental impacts.

Jan 1, 1974

By R. H. Roberts

The Environment Weipa is located at 12° south latitude on the west coast of Cape York Peninsula, North Queensland, Australia. The climate is tropical with most of the 1 600 mm. average annual rainfall falling between November and March. During the short winter months (May/ August) the weather is clear and pleasant, with temperatures seldom exceeding 27°C.Throughout the remainder of the year, conditions are frequently oppressive due to consistent high ambient temperatures accompanied by high humidity. The terrain is of low relief, and generally not more than 6 to 10m. above mean sea level adjacent to the coast. The coastline features numerous short estuaries which discharge run-off from the heavy rains collected by creeks and rivers. The whole area is covered by an open forest, the predominant species of which is Eucalyptus tetradonta. These eucalypts have only limited commercial value and are heavily infested with termites. Despite the fact that Weipa is close to the location of the first reported sighting of the Australian coastline by a European (William Janz - 1606), it remains very isolated. There is no developed road or rail connection to centres of population, so that transport of practically all products, personnel and materials to and from Weipa is by sea and air. Cairns (population 49 000) is 580 km. by air and 670 nautical miles by sea; Brisbane, the

Jan 1, 1977

By Wayne L. Johnson

The depth capability of engineering seismographs has been greatly increased by the use of signal enhancement, a technique in which seismic waveforms created by repeated impacts are digitized, stored, and summed. Summation amplifies the signal and partially cancels background noise. This gives a clearer picture of the wave aid makes it possible to determine the travel tune of signals from 'eater depth. Signal enhancement combined with continuous display of waveform, permanent recording of waveform, and precision digital readout of travel time has opened new fields of application in mining and engineering. Recent work has clown that replacement sulfides can be distinguished seismically from country rock at Bistee, Ariz. Work on the Iron Range of Minnesota indication,: that, by using a 300 pound weight as the source, the Biwabik iron Formation can be traced down dip to several hundreds of feet traverses over known areas show that reflections can sometimes be identified. Reflection, if identified preclsely, give a mere accurate estimate of depth and buried topography. Comparison of ( ) and weight drop have given some understanding of low wave amplitude varies win; source candid

Jan 1, 1971

By William G. Pariseau, Mark K. Larson, Heather E. Lawson

Rational design based on engineering fundamentals is essential for the layout of safe, stable shafts and tunnels. Shafts and tunnels including winzes, raises, adits, and crosscuts are lifelines to the underground and must be secure. The contribution of this paper describes a significant extension in existing software previously developed for five important design problems in strata-bound mines such as coal, trona, salt, potash, and some large, lead-zinc mines. This extension in software allows analysis to proceed in three easy steps: (1) preparation of a strata properties file, (2) generation of the finite element model, a mesh, and (3) finite element program execution. Circular, elliptical, and rectangular shaft sections are available for a single shaft, twin shafts, and shafts in a row. Spacing of twin shafts and shafts in a row is a free parameter (pillar width). Tunnel shapes are the same as shafts but include the conventional arched back section. Dipping strata of variable thickness, depth and orientation relative to the excavation of choice are allowed. The analyses are three-dimensional. An elastic-plastic material model based on associated rules of flow and an N-type yield condition for isotropic, transversely isotropic, or orthotropic rock are used for all strata. Example analyses from several hardrock mines are provided to illustrate the three-step process including mesh plotting and plotting of selected results. The goal of this software is to advance mine design technology for improved miner health and safety.

By Michael Murphy, Gamal Rashed, Brent Slaker

Pillar stability continues to be a significant concern in multiple-level mining conditions, particularly for deep mines when pillars are not stacked or the thickness of interburden between mining levels is thin. The National Institute for Occupational Safety and Health (NIOSH) is currently conducting research to investigate the stability of pillars in multiple-level limestone mines. In this study, FLAC3D models were created to investigate the effect of interburden thickness, the degree of pillar offset between mining levels, and in situ stress conditions on pillar stability at various depths of cover. The FLAC3D models were validated through in situ monitoring that was conducted at a multiple-level stone mine. The critical interburden thickness required to minimize the interaction between the mining levels on top-level pillar stability was explored, where the top level mine was developed first followed by the bottom level mine. The model results showed that there is an interaction between numerous factors that control the stability of pillars in multiple- level conditions. A combination of these factors may lead to various degrees of pillar instabilities. The highest degree of local pillar instability occurred when pillar overlap ranges between 10 and 70%. On the contrary, the highest degree of stability occurs when the pillars are stacked, the underlying assumption is that the interburden between mining levels is elastic (never fails). Generally, for depths of cover investigated in this study, the stability of top-level pillars shallower than 100 m (328 ft) or with interburden thicknesses greater than 1.33 times the roof span—16 m (52.4 ft) in this study—does not appear significantly impacted by pillar offset. The results of this study improve understanding of multiple-level interactions and advances the ultimate goal of reducing the risk of pillar instability in underground stone mines.

Jul 27, 2022

By J. K. Pandey, ebashish Mishra, D. P. Mishra, N. K. Mohalik, S. K. Ray

The increasing demand for coal and depletion of shallow depth reserves are pushing towards deeper mining. In deeper coal mines with multiseam workings, the problem of ventilation surges many folds primarily related to air quantity requirement, heat, humidity and spontaneous heating/fire in goaved (gobbed) out areas. The paper describes the design of a new approach to improve the ventilation system of a real-life deep underground coal mine with multiseam workings. For this, the ventilation problem of one deep underground coal mine 6&7 pits Bhutgoria Amalgamated Colliery of Tata Steel Ltd. with multiseam workings has been studied in detail to determine an appropriate solution. A ventilation survey of the mine and computer simulation of the ventilation network has been carried out to reach a practical solution. Ventilation survey results have been analysed to develop a representative ventilation network of the mine for both qualitative and quantitative analysis. Further, computer simulation of the ventilation network of the mine has been performed to virtually verify the application of a highcapacity booster fan in the present ventilation circuit without disturbing the vulnerable areas. Field validation is also carried out after the implementation of the solution in the mine to determine its efficacy. Thus, the findings of this paper can be directly applied for the installation of booster fans to achieve the required air quantity in deep underground coal mines with multiseam workings having spontaneous combustion liabilities of upper seam goaved out areas.

Jun 2, 2022

By Denis Tepavac, Mark Trim

Structural performance of fiber reinforced concrete (FRC) depends on its ability to carry tensile forces after cracking. Australian Standards AS5100-2017 and AS3600-2018 are the only available design standards that establish a test procedure to determine strength and toughness of an FRC in direct tension. Direct tensile testing of fiber reinforced shotcrete samples was performed to determine if the model and guidelines in AS5100/3600 were applicable to shotcrete; all previous testing was from cast samples. In addition to direct testing, micro CT-scanning was also performed. The paper presents tests performed, results, and how the tests could be used on future projects. In addition, a brief summary is provided of the guiding structural mechanics used for estimating residual tensile strength and test methods utilized to verify those estimates.

Jun 13, 2023

By B. T. Lusk, Q. Q. Huang, R. Q. Honaker, K. A. Perry

Rock dust is applied in underground coal mines to prevent the propagation of coal dust explosions. It is applied either dry or wet. Both methods have advantages and disadvantages, but the formation of caked rock dust particles is cited as a significant concern for wet applications. We conducted a study to evaluate the effect of modifying the rock dust particle surfaces to repel water and each other by the addition of oleic acid and sodium oleate. At a sodium oleate dosage of 1 kg/t, a contact angle of 112o was measured, indicating strong surface hydrophobicity and thus the ability to repel water. Fourier transform infrared spectroscopy (FTIR) studies indicated a chemisorption mechanism, which is necessary for long-term stability of the surface modification. The dispersibility of the modified rock dust samples was elevated by the application of both oleic acid and sodium oleate, thereby indicating a significant reduction or elimination of the detrimental effect of caking. Tests in an explosion chamber showed an 82.8 percent reduction in the dust explosion potential relative to untreated rock test applied by the wet technique.

Jan 1, 2015

By Smart Chika Obiora, Anthony Chukwu

Mining and processing of raw materials is one of the earliest activities of man for survival and development. The products are used for making jewelleries, metal tools, and for exchange of goods and services. However, despite the benefits of mine recoveries, it’s negative and long term effects on the environment and lives remain the point of discussion throughout the world. This study summarizes findings of researches in active/abandoned lead–zinc mines in Enyigba and Ishiagu mining districts including social surveys in the localities surrounding the mines in order to ascertain the effects on the inhabitants. Lead–zinc mining in Enyigba and Ishiagu, southeastern Nigeria has lasted for decades and has affected the socio-economic well-being of the host communities. There are evidences of soil, water, and plants contamination by Pb, Zn, Cd, and Mn in these mining communities. The mining activities also affect the overall social development of the host communities. These effects include retardation in educational development, health care provision, unemployment, and access to potable water supply. Others are rise in poverty level, social amenities, sanitary/hygiene level, high cost of living, and fertility rate. Possible mitigation strategies such as to liaising with relevant government agencies in collaboration with mine owner, mine workers, and host communities can ameliorate these negative effects and promote environmental sustainability.

Feb 24, 2023

By Pei‑liang Xu, Jun Wang, Xi Zhang, Deng‑pan Qiao, Tian‑yu Yang

The surface backfill, serving as the operational platform for continuing mining in upward slicing and filling stopes, is required to possess sufficient strength and thickness. Currently, there are limited model methods for determining the strength and thickness of the surface fill body. By analyzing the mechanical actions on the surface backfill, it is determined that its stability is mainly influenced by the combined effects of normal and tangential uniform loads under full-load conditions of trackless equipment. Assuming a circular contact surface between the tire of the trackless equipment and the surface backfill, and utilizing solutions from elastic mechanics theories such as the Boussinesq and Cerruti solution, the stress and displacement distribution of the surface fill body were obtained. Based on the maximum vertical stress condition, where the surface backfill body undergoes maximum deformation while still in an elastic state, and considering the stress–strain relationship, a model for the strength and thickness of the surface backfill has been established. According to the research findings, the design for the strength and structural parameters of the surface backfill has been developed to meet the full-load operation of the Atlas ST7 scooptram, with a compressive strength of 1.32 MPa and a thickness of 0.5 m. Numerical simulation analysis results indicate that the stress and displacement of the surface backfill align with theoretical analysis results. Practical results from industrial application in the western section of the Dahongshan Copper Mine demonstrate that the designed strength and thickness of the surface backfill meet the operational requirements for trackless equipment, resulting in significant engineering application effects and economic benefits. The research findings hold significant importance for advancing the theory of backfill mining and have high applicability and promotional value for similar mines.

Mar 24, 2024

By J. G. Davis

The St. Peter Sandstone is typically a well-sorted, friable, ultra-pure, fine- to medium-grained, quartzose sandstone with silica content higher than 99 weight percent in places. The sand grains are well-rounded, highly spherical and characteristically frosted. Their size typically varies from 2 millimeters diameter (No. 10 U.S. Standard Sieve Series size) to less than 0.08 millimeters diameter (No. 200 U.S. Standard Sieve Series size). A freshly exposed surface of the formation is commonly white with shades of pink and green. Weathered surfaces are a dirty gray or brown and are case-hardened at many localities. Bedding is characteristically indistinct, and the formation usually appears massive throughout. The rock is cross-bedded and ripple-marked locally. The formation is generally porous, permeable and rarely fossiliferous in Missouri. The St. Peter is continuously present in the subsurface in the northern half of the state and along the southeastern edge of the state. The St. Peter crops out in a narrow band that starts in western Montgomery County and runs southeastward, along the Missouri River, to just west of St. Louis and continues south, just west of the Mississippi River, through Scott County. The outcrop belt varies from less than one mile wide to over ten miles wide, and it is over 150 miles in length. The formation dips into the subsurface radially away from the outcrop band. A notable isolated outcrop occurs in Lincoln County to the north of the main outcrop band. The St. Peter is discontinuously present in the subsurface along a band in the west-central portion of the state. It is not present at the surface or in subsurface in the remainder of the state. The formation averages 80?100 feet thick. There is an estimated 3.8 trillion short tons of St. Peter in Missouri. Sieve analyses on drill cuttings indicate three subsurface locations in northeastern Missouri where the St. Peter is greater than 10 percent by weight of sand falling in the 20?40 U.S. Standard Sieve Series size range. The St. Peter was first produced in Missouri in the 1870s for the manufacture of glass. Since that time it has been used as a paint additive, filler material, polishing compound, filtering media, and recently it is commonly used as a fracture proppant in oil and gas wells. The St. Peter is currently quarried and produced in Missouri from four sites located in St. Louis, Jefferson and Perry counties. In the same area there are at least nine abandoned historic mine sites.

Feb 27, 2013

By W. K. Connor, O&apos

The Bureau of Mines is investigating the Co and Mn resource of the West-Central Arkansas District, including field investigations, mineralogical characterization, beneficiation, and hydrometallurgical tests. The deposits occur within the Ouachita Mountains and are con-trolled structurally, occurring along the axes of anticlines making up the mountain ridges. Brecciated novaculite is cemented with a mixture of Mn oxides, primarily cryptomelane and psilome-lane. Cobalt is concentrated within a particular Mn oxide phase, lithiophorite. Chemical analyses on head samples reported up to 25 pct Mn and 0.17 pct Co. Magnetic separation yielded products with up to 41 pct Mn and 0.22 pct Co at recoveries of 95 pct Mn and 93 pct Co.

Jan 1, 1991