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By Xuchen Fan, Chenyang Zhou, Yuemin Zhao, Liang Dong, Chenlong Duan

A gas–solid fluidized bed using magnetite particles is an effective methodology for coal beneficiation in the field of dry coal cleaning. Broadening the size range of magnetite used in the bed decreases medium preparation cost. In this study, a tapered fluidized bed was used to investigate a magnetite particle size range of −0.5 + 0.074 mm. The results showed that a tapered fluidized bed effectively strengthens mixing of magnetite with a wide size range (−0.5 + 0.074 mm). The results of beneficiation experiments indicated that with increasing tapered angle, separation efficiency increased and then decreased. The highest separation efficiency was obtained at a tapered angle of 10°. The optimal results showed that the ash content of the concentrate decreased from 31.82% to 12.33% with a probable error of 0.11, which indicated that a tapered fluidized bed was efficient to improve fine coal beneficiation performance.

By Karan S. Keith, Haydn H. Murray

The sorptive and impervious nature of clay materials was recognized long before modem technology allowed us to understand the physiochemistry of clays. In Cyprus, around 5000 BC, sorbent clays were used for fulling woolen cloth. One of the earliest recorded uses of clays as an impervious liner was more than 3200 years ago in the construction of a bitumen-sand-gravel-clay liner built along the embankment of the Tigris River at Assur. Today one of the most common applications for clay minerals in the environmental industry is for use as impermeable barriers to fluid transport. Clay minerals are fine in particle size and thus have large surface areas, which, as a result of intermolecular forces and ionic substitutions, make them excellent materials for both ion exchange and ion sorption. Therefore it was logical to consider certain clay materials for applications in the environmental industry, where they can act as physical and chemical traps for potential contaminants. Certain bentonites have historically been used as sealants for fluids (Grim, 1962), and other clays have been used as sorbents for both water and oil (Haden, Jr., 1972). Prior to the 1980s, disposal of the nation's municipal, commercial, chemical, and nuclear wastes was largely indiscriminate and poorly regulated. This created environmental pollution problems, especially with respect to groundwater contamination. Promulgation of federal regulations like the Resource Conservation and Recovery Act (RCRA) and the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA - commonly known as Superfund) have forced a more careful and costly approach to waste disposal. The US Environmental Protection Agency (EPA) is the government body charged with enforcing and ensuring compliance with federal regulations governing toxic waste production, storage, and disposal. Widespread application of geotechnology to the design and construction of waste containment systems and to pollution remediation has become necessary due to such laws and because of increasing use of the subsurface environment for the disposal of hazardous wastes. In the United States nearly 1.8 kg of trash is disposed of per person per day, which amounts to nearly 181 Mt per year. This amount is more than double the waste produced in 1960, and these numbers are expected to continue to increase. Canada produces approximately 1.68 kg of waste per person per day. The EPA estimates that in the United States 64% of our garbage is landfilled, 18% recycled, and 18% incinerated. Even with continued increases in recycling and incineration efforts, the EPA projects that the United States will still need 82% of today's landfill capacity in the year 2000. Data on the exact number of landfills in the United States and Canada is conflicting in part because of changing definitions of what constitutes a landfill and because of inadequate record- keeping by some states and provinces. An estimate of the number of municipal solid waste (MSW) landfills in the United States in 1990 to 1991 ranged from 4 462 to 10 467 with an average estimate of 6 600. In Canada the number of MSW landfills reported varied from 5 493 in a 1982 survey to 1 766 reported in a 1991 National Solid Wastes Management Association (NSWMA) survey (Repa and Sheets, 1992b). A properly operated MSW landfill on average requires 1 hectare of land per year per 25 000 people (Coates, 198 1). In addition to MSW facilities, there are also waste disposal facilities needed for hazardous waste and low level and high level radioactive waste. In 1983, approximately 266 Mt of hazardous waste was generated in the United States, almost 50% of this by industrial production. About 68% of the hazardous waste generated in the United States and Canada and almost 50% generated in Europe are still landfilled (Egger, 1987). In 1985, approximately 51 000 m3 of commercially produced low level radioactive waste was disposed of in radioactive waste disposal sites across the United States (Jungling and Greeves, 1989). By 1987, the US defense program had produced approximately 10 000 t of high level nuclear waste. In addition, there were approximately 14 000 t of spent fuel assemblies from commercial nuclear power plants in temporary storage; the amount is expected to nearly triple by the year 2000. Presently most commercial spent fuel assemblies are stored in water-filled pools at nuclear power plants. Defense waste is stored on federal reservations in surface and underground steel tanks (Anon., 1987). Under federal law nearly all waste disposal and containment sites are required to have a liner or barrier and a cover system design that meets federal- or state-approved hydraulic conductivity requirements for the type of waste that the site will receive. When approved materials, necessary for constructing the waste containment structure, are not available on site, one of the most economical ways to meet these requirements is through the use of clay, soil/clay, or clay/geotextile materials. In a 1991 survey by NSWMA of its members and other select private sector facilities, 81% of the surveyed landfills had some type of liner system. About 75% of these liners were clay materials (either recompacted or natural). The remaining 30% were using flexible membrane liners as part of a liner system. Clay liner materials are most commonly used in the South, Midwest, West-central, and South-central regions of the United States. About 93% of the landfill facilities had closure plans, and of these 91 % were using clay materials in some way for the final cover material (Repa and Sheets, 1992a). Waste barriers and containment structures take several basic forms, and they are used in a variety of different applications: 1) cutoff walls, 2) soil or soil/clay-admix liners, 3) geosynthetic bentonite-clay/geotextile membranes, 4) radioactive waste containment barriers, and 5) synthetic geomembranes. This chapter will discuss the first four of these categories. The field of synthetic geomembranes, although a related topic, is beyond the scope of

Jan 1, 1994

By Jenna Wundrack, Evan Thibaud

The advanced cryogenic treatment is a post-manufacturing metallurgical process that involves subjecting off-theshelf materials to extremely low temperatures, significantly improving wear resistance and reliability. These case studies explore whether the claims of Enrich Bits & Tools benefit metals and their specific in-field application to drill bits in the blasting industry. This paper reviews the application of the treatment to button drill bits for enhanced wear resistance in two operations. The first is a civil construction project with highly abrasive rock. To confirm the remarkable benefits of the treatment, a second case study was performed. This case study utilized measure-while-drilling technology in consistent rock characteristics to reduce variables in the field study.

Feb 1, 2024

By D. Sotiropoulos

In the recent years, the mining sector is looking for specific indices, taking into account economic, environmental and social criteria, in order to meet the sustainable development requirements. In the present study traditional and environmental sustainable indices used in the Agios Dimitrios Power Plant, Northern Greece, are compared to those of ESKOM Company, South Africa, taken as reference. These indices are referred to, a) the solid fuels consumption, such as lignite, and, b) the emissions to the atmosphere, such as SO2, NO2 and dust. Last five years data show a remarkable improvement of all indices in the Agios Dimitrios Power Plant. Although the lignite used in this Power Plant is by far of poorer quality than that used by ESKOM - net calorific value 1272 and 4638 kcal/kg, respectively - dust emissions in both Power Plants are similar (52 and 31 g/kWh, respectively). The SO2 and NO2 emissions are very low in Agios Dimitrios compared to those of South Africa, respectively 1.92 and 7.91, and 1.74 and 3.61 g/kWh. This is mainly due to natural desulfurization (by the lignite?s calcium content) and the low NOx burners.

Jan 1, 2003

By Wolfgang Pietsch

DR iron') is a generic term for metallized product that results from the direct or solid state reduction of iron ore. In direct reduction, iron oxides are reduced to metallic iron in the solid state without an intermediate melting step. MIDREX ® Iron is the DR iron material produced in the MIDREX ® Direct Reduction Process. Except for some thermal and mechanical degradation, the external physical form of as-reduced DR iron is the same as the feed material. Chemically, oxygen associated with iron is removed leaving a very porous structure. Figure 1 is the scanning electron micrograph (SEM) of the internal surface of a MIDREX Iron pellet obtained from a Swedish oxide pellet during reduction at 760 °C. Figure 2 is the SEM of a polished and etched cross-section through the same pellet showing the amount of intraparticle porosity. As a result of this high porosity, apparent density of DR iron is relatively low, typically a¬round 2 g/cm3, and specific surface is extremely high, typically around 1.0 m2/g or more. Both density and specific surface depend on the raw materi¬al and the operating conditions of the direct reduction plant. Normally, more than 97% of the available iron is reduced into metallic iron with the rest mainly in the form of wustite (FeO). During direct reduction, the gangue in the iron remains essentially unchanged. Removal of oxygen and the corre¬sponding reduction in weight result in a slightly higher percentage gangue in the product than in the raw material.

Jan 1, 1976

By R. S. Olsen

Intensely altered rock has had a large effect on slope stability as slopes increase in height at Island Copper mine. Traditionally used, fracture-controlled rock slope stability design techniques have been supplemented with analyses of failure modes which include failure along curved surfaces typical of soil materials. A rock mass rating (Pa) system has been developed that addresses the lower end of rock mass strengths. Rock masses are rated in terms of fabric integrity, alteration, fracturing intensity and gouge strength. Rock mass classes have been defined using statistical frequency distributions of rock mass rating values. Strength values have been assigned to the various classes from shear testing, back analyses of failures and engineering judgment.

Jan 1, 1987

By Bruce D. Hanson

A computer model capable of simulating the basic production system in a variety of underground mining methods has been developed at the Twin Cities Mining Research Center. This Bureau of Mines paper describes the simulation of the basic production system at the working face, which includes drilling, blasting, mucking, and roof bolting. The model is event-oriented; that is, the status of the system is updated at the occurrence of an event. All event or activity times, including failure and repair of equipment, are treated as stochastic variables. A location dimension, in addition to the time dimension, is used, allowing the simulation of multiple location systems. To aid the user in determining the efficiency of his system, the model provides several reports. An event or activity report gives the frequency of occurrence total active time, and cumulative delay statistics for each event. An equipment report delineates the availability and utilization of all equipment. A production report provides information on various performance measures such as tons produced and holes drilled. The cost report gives the cost of various elements in the system. Operating data from an actual mining situation were used in validating the model. In addition to the description of the model, examples of simulation experiments which were performed on a room-and-pillar mine system are given. Use of the model to determine methods for improving the efficiency of the system is discussed.

Jan 1, 1974

By H. V. S. Tingley

My topic today is future trends in compensation for the mining industry. I seldom get the chance to speak about a subject of such immediate interest to an audience, so I would like to make the most of this opportunity by telling you that everybody in this room will become rich beyond his wildest dreams in the next few years. I would like to open my talk that way, but in compensation, like everything else, there is a great gap between dreams and reality. Back to reality. When we talk about compensation, we?d better define our terms because the compensation is really an umbrella for five basic types of payment made to management personnel. Slide 1 identifies these elements of compensation.

Jan 1, 1980

By Michael Deutscher, Jozef F. Zurawski

Part of Capital Improvement Project SE-754 tendered by New York City Department of Design and Construction included installation of a 96-in. (2.47 m)diameter sewer by pipe jacking methods. The pipe selected by the Contractor, EIC Associates, Newark, New Jersey, was a glass-fiber-reinforced thermosetting resin pipe installed in two reaches: 72 m (235-ft.) and 222 m (728-ft.). The machine selected for the excavation was an open face shield. This paper describes the set up of the tunneling operations, subsurface conditions, progress of excavation, pipe performance and other details of the project including unexpected difficult ground conditions that were encountered during excavation and how these conditions were overcome.

Jan 1, 2003

By G. Thorsen

An alternative way to the normal practice of precipitation of jarosite, goethite, or hematite for removal of iron from zinc sulphate process liquors/ is to employ the techniques of solvent extraction. The process presented avoids the addition of any external alkali for the extraction of iron by integrating the leaching and solvent extraction steps in a hydrometallurgical zinc plant. By starting the leaching of zinc from the solid zinc calcine material with an organic solution of an acid liquid cation exchanger, the organic phase is loaded with the organic zinc salt from the direct reaction with zinc oxide. The residue from the organic leaching is transferred to a hot acid leach circuit where the remaining zinc oxide and the zinc ferrites will dissolve form¬ing an aqueous sulphate solution of zinc and iron. In the subsequent solvent extraction of iron from this aqueous leach solution, iron is exchanged with zinc from the organic phase. The commercial carboxylic acid Versatic 10 (Shell) is highly efficient for this integrated process of leaching and solvent extraction. The resulting iron-loaded organic phase is heated to 150-200 C in the presence of water whereby the iron will be directly precipitated from the organic phase as iron oxide of high purity and the regenerated organic acid is recycled to the organic leaching step for reloading with zinc.

Jan 1, 1980

By Robert Cook, Valeria Zarate, Jason Hallowell

The long hole open stoping (LHOS) method is widely used in underground mining. While methods to predict stable stope geometries are well established, the ability to maintain a stable back often assumes effective ground support across the full stope span. The efficacy of the support strategy is dependent on rock jointing, quality, density, top cut width and height, and the type, amount, and orientations of bolts installed. However, it is becoming increasingly common for operators to assume narrow top cuts in service of wider stope spans with minimal bolting coverage. Failure to account for the required top cut drift size and support requirements can ultimately lead to raveling type instabilities along stope shoulders that result in back collapse. A new method has been developed to evaluate the minimum top cut dimension necessary to accommodate wider stope spans with various rock bolting configurations. Due to the economic impacts of top cut development and support, this is a critical consideration in the accurate costing and scheduling of a LHOS operation. Tables 1 lists the acronyms are used throughout this paper.

Feb 1, 2025

By E Marambio, R Brändle, G Fischer, G von Rickenbach, L Burgos, R Luis Fonseca

Ground support systems must provide safe and effective designs for underground excavations under high stress conditions. These systems must be capable to resist dynamic impacts and yielding during the loading process. In this context dynamic testing of the reinforcement and retaining elements that compose the ground support system are required to study and improve the behaviour of these elements under dynamic load events. During the last years, Geobrugg has been working on the improvement of retaining products by testing them in a large-scale impact test facility located at Walenstadt, Switzerland. The test facility is composed of a double level platform with a square-shaped pyramidal trunk geometry, in the upper level housing a loading mass that drop from a height up to 5m. The loading mass is guided by one central steel pipe, and the impact occurs in the sample to be tested located at the lower level in a slab with an area of 3.6m × 3.6m where the ground support system is installed. During the last years, this innovative facility has been used to test several configurations of ground support systems. The results of these tests have enabled to improve the understating of the behaviour of ground support systems under dynamic loads. In this manuscript, the arrangement, measurement, results, and the preliminary analysis of a single impact dynamic test performed during 2021 of a ground support system with a high-tensile steel wire mesh MINAX 80-4.6 is presented.

Apr 26, 2022

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 J. Iannicelli

Spray drying is the principal drying method used in the production of over six million tons annually of beneficiated kaolin in Georgia. Thirty-three dryers in the Georgia Kaolin belt comprise the highest concentration of large tonnage spray dryers in the world. The steady growth of spray drying in the U.S. kaolin industry is paced by advances in design and development of large spray dryers which have led to large scale new applications in mining and related industries.

Jan 1, 1982

By David I. Dr. Hoyer

The Hicom mill is a conical mill in which a ball or autogenous load tumbles within a high-intensity acceleration field. An autogenous Hicom mill with a power density of about 1100 kw/m3 and a volume of just 4 litres reduced a 50 m quartzite feed to 90% passing 38 microns at a feed rate of 160kg/h (in closed circuit with a hydrocyclone). Batch tests have identified fracture, chipping and abrasion breakage mechanisms at pebble sizes of 5 to 50 mm. The special behaviour of the load in Hicom mills was exploited to develop a novel technique for estimating steady state autogenous load size distributions.

Jan 1, 1992

By Charles H. Wells

This paper presents a review of the state of the art in coal preparation plant instrumentation and a discussion of automation practice that could be applied based on current mineral beneficiation experience and demonstrated foreign technology in coal washing plants. Specific e-mules of applications of remotely controlled slurry values, pneumatic and electronic field transmitters, computers for control and data logging, and on-line analytical instrumentation are given. A program, to demonstrate this technology is described.

Jan 1, 1980

By Linda J. Dahl

The U.S. Department of the Interior, Bureau of Mines is developing a process to selectively extract manganese from oxide ores as part of its in situ leach mining research program. The Bureau is conducting site characterization studies of two manganiferous iron-formation deposits which include: drill core, regional stratigraphic relationships from the existing geologic database, ore body geometry, geologic structure, hydrologic conditions, proximity of ore minerals to the leach fluid paths, surface subsidence potential, and data collected from laboratory leaching experiments. This information is being used to evaluate the technical, environmental, and economic feasibility of in situ leach mining of manganese for these two deposits. This paper will focus on the stratigraphy, mineralogy, ore textures, fractures, permeability, and porosity as they relate to in situ leach mining.

Jan 1, 1992

By George D. Lessner

I'm sure that everyone at this meeting is aware of the current problems facing the U.S. metals mining industry. Prices are depressed and expected to remain depressed for quite some time. On the other hand, industrial minerals, including talc, are doing quite well. The profitability of industrial minerals has sparked considerable interest on the part of many companies in expanding into industrial minerals. Our company is one of those actively seeking to expand its position in industrial minerals. It is appropriate that the A.I.M.E. asked me to speak to you regarding entry into the talc business. So how do you get into the talc business? Earlier speakers have explained how to locate, mine, process, and market talc, so you have the "how ton.

Jan 1, 1984

By George H. Klein, B. Kent Merritt, Anthony Crisci

During the past decade, over 114-km (71-mi) of 0.25-m (10-in) to 3.7-m (144-in) finished diameter tunnels have been driven below Metropolitan Houston as part of a major program of water and wastewater improvements. This large effort has seen the introduction of midwestern technology with over 18-km (11-mi) of man-entry pipe jacking and European and Japanese technology with over 21-km (13-mi) of microtunneling. Owing to the high water table; a stratigraphy consisting of stiff fissured clays containing numerous layers, channels, and lenses of water-charged sands and silts; and active faults, many challenges existed for designers and contractors alike.

Jan 1, 1991

By Rod L. Norfleet

Cemented tungsten carbides are a sintered powder - metallurgical product essential to modern industry. Because of their moderate unit price and our dependence upon foreign sources for the component raw materials, a growing recycling industry has developed in the United States. There are two basic approaches taken to recycling cemented carbides; those which leave constituting materials unaltered or direct-reuse and those which separate the constitutes back to the raw components. To separate the carbides back to their raw components usually requires expensive chemical processing and is thus confined to the lower value materials such as grinding sludges. The direct-reuse methods recycle cemented carbides back to an intermediate level, a powder capable of being recompacted and resintered into a functional end-product. The three most commonly used methods of direct-reuse recycling, the coldstream process, bloaching and the Bernard or zinc process, are reviewed,

Jan 1, 1984