Search Documents

By R. W. Culbertson

During the 1920's, approximately 11,000 small gasifiers were in operation in the United States. They converted about 15 million tons of coal per year into low Btu gas. In some cases, hot raw gas was used for applications such as firing open hearth furnaces or brick kilns. In other cases the gases produced in the gasifiers were cooled, cleaned and desulfurized for various utility and industrial purposes. The steel industry was by far the largest user. The most important fact was that the conversion of coal to a usable fuel gas was demonstrated to be commercial. During the late 1940's and early 1950's, this form of energy was largely replaced by natural gas as the pipeline net work was expanded. Producer gas was no longer economically competitive. Over the past twenty-five (25) years, government controls on the interstate price of natural gas have maintained this situation. At present only three commercial small coal gasifier plants are still in operation in the United States. These facilities are operated by the Glen-Gery Corporation which is located in eastern Pennsylvania; the National Lime and Stone Company which is located at Carey Ohio; and Holston Defense Corporation which is located at Kingsport, Tennessee. There are, however, numerous operating gasifiers in other parts of the world. Recent events indicate that this situation is changing. The quantity of domestic natural gas available to the interstate market has been declining at the same time that demand for all forms of energy has been increasing. The current potential market for gas with a heating value ranging from 100 to 500 Btu per cubic feet has been estimated at sixteen (16) quads (16 x 1015 Btu) per year. This is expected to grow to twenty (20) quads by the year 2000.

Jan 1, 1978

By Rainer Antretter

While respirable crystalline silica (RCS) dust that arises in industrial production mostly emanates from point sources and can be well mitigated, the extraction of dust is much more difficult in underground construction, since locally generated dust spreads widely. Analysis of dust measurements shows that RCS values are difficult to predict, and effective dedusting systems are required to comply with permissible exposure limits (PEL) in breathed air. Dedusting systems are effective near the tunnel face, while dedusting of working areas away from the tunnel face is difficult or even impossible. In general, there is little temporal influence on the tunnelling work—except for drill and blast excavation—which makes it necessary to remove the deduster and ductwork from the face area. Concurrent work in the tunnel is affected by the backflowing air mass of ventilation and therefore the quality of this air mass must be considered. The use of personal protective equipment (PPE), e.g., dust filter masks, is considered the least-desirable safety measure available. However, for certain individual operations in the tunnelling process, the use of PPE cannot be avoided, especially if other technical mitigation measures are not possible. In tunnels with small cross sections for example, dedusting systems often cannot be accommodated and PPE must be used instead. This raises the question of whether the use of PPE can be avoided by designing appropriate excavation cross sections and allowing for the implementation of technically engineered mitigation measures. The paper highlights problems with dedusting measures and shows possible ways to achieve OSHA compliance.

Jun 13, 2021

By J. S. Lewis

Beneficiation and physical and chemical processing of non-terrestrial materials borrow strongly from terrestrial experience, but also involve the necessity of handling literally un-Earthly feedstocks, reagents, and environmental conditions. The present state of scientific and engineering understanding of the processing of non-terrestrial minerals, gases and hydrocarbons is reviewed with the production of rocket propellants, life-support fluids, structural metals, and refractories as the goal.

Jan 1, 1992

By Blake M. Paterson

The increasing global demand and lower price of gold has resulted in more advanced gold extraction techniques. One trend is the use of oxygen in place of air in the leaching process, which is proven to significantly enhance recovery of gold ore refractory in such techniques as CIP and CIL. This has resulted in a search for more reliable and cost efficient paradigms of oxygen supply. Many gold mines already realize the heightened recovery rate achieved with oxygen. Previously this benefit had only been available to the largest consumers of oxygen, near oxygen production facilities. Requirements of (1) to (20) metric tons per day have traditionally been supplied with expensive, delivered, liquid oxygen. Since many mines are located in remote areas, it is difficult to secure cost effective and continuous supply of liquid oxygen. However, the benefits of On-Site Oxygen Production combined with a self-generated bulk reserve supply are now available to mine sites. This paper explains and discusses the use of on site Pressure Swing Adsorption (PSA) oxygen production, coupled with a cryogenerator to liquefy oxygen for storage. This package offers continuous oxygen supply to mining sites in even the most remote corners of the world.

Jan 1, 1997

By Lloyd M. English

Accurate knowledge of the gas content of coal seams has always been important, according to the work of W. P. Diamond and J. R. Levine, 1981, but is becoming increasingly important for several reasons: Excessive gas emissions in the mine can create explosion hazards. Depletion of shallower coal reserves is forcing underground operations to greater depths where coal gas content is often greater. Natural gas prices and the need for new energy sources make naturally occurring coal gas a potential resource of economic interest. Information on coal gas content will impact mine designs, mine ventilation system specifications, and the effectiveness of methane control procedures used. Accurate resource assessment is needed for projecting and designing potential gas utilization enterprises. The emphasis upon methane hazards in mining operations, and upon potential methane utilization, has led us to improve upon the procedures used to determine coalbed methane levels.

Jan 1, 1984

By J. Kretschmann, K. Sakamornsnguan

"Sustainable development is an influential ethical concept in modern mining management. However, the concept is not culturally neutral because it is based on Christian, Western values. These values can be very different from traditional values in emerging mining countries like Thailand, where Buddhist values are dominant. When applying the concept of sustainable development, these differences should be taken into account. Different values imply different interpretations of ‘good mining’. They have a significant impact on how mining operations are evaluated, perceived, operated and managed. This paper attempts to integrate Buddhist principles with approaches of the sustainable development concept. When local values are appreciated and maintained, mining companies and their external stakeholders can identify objectives and approaches that match with their own values and contexts. Practices based on this integrated ethic can help to promote sustainable mining and to minimize communication risks for enterprises in mining countries like Thailand. INTRODUCTION The objective of this paper is to integrate Buddhist principles to the application of sustainable development concept to mining activities. The structure of this paper is divided into four parts. An introduction provides basic information about Thailand, its mining industry and the role of Buddhism on the past development. The second part compares the differences between the sustainable mining framework and the implications of Buddhist principles on mining. In the third part, the core Buddhist teachings are integrated into the sustainable mining framework. This is followed by conclusions in the last part. THAILAND, BUDDHISM, AND MINING Thailand is a constitutional monarchy state in Southeastern Asia with a population size of around 65 million [1]. Its GDP in 2013 was 391 billion USD [2], predominantly deriving from manufacturing (38%), trade, transport and communication (24%), agriculture (8%) and mining and construction (4%). Still the largest part of the Thai workforce (39%) is working in the agricultural sector. The remaining part of the workforce is equally distributed across services, manufacturing, and mining and construction sectors. [3]"

Jan 1, 2015

By F. S. Knoll

Electrostatic separation is one of the most misunderstood physical processes used to beneficiate minerals. Nonetheless, millions of tons of titanium ores, iron ores and other minerals are processed every year economically, efficiently and safely. Over the past ten years major advances in electrostatic separation and its application have occurred. New processes include dewatering clay slurries, separating halite and sylvite, and shape separation of vermiculite and gangue minerals. Electrostatic separation techniques are based on one of two methods, electrophoresis or dieleccrophoresis -- processes involving charged and uncharged particles respectively. In some cases, the combination of these two techniques has proven quite useful. The purpose of this paper is to provide a basic understanding of the physical processes collectively called "electro- static separation" in order to enhance one's ability to define and consider new possibilities in mineral processing and other fields.

Jan 1, 1984

By Paul R. Smith

The theoretical requirements for the flotation d large particles are discussed. A flotation machine is described which has components which meet many of the theoretical requirements for the flotation of large particles. The machine's salient features include multiple fine-bubble attachment, froth level feeding, quiescence, shallow depth, and short flotation time. Test conditions and results are presented for the laboratory flotation of 10 mesh phosphate, 4 mesh potash, and 1/2 inch coal. In addition, test conditions and results of pilot plant flotation of minus 14 plus 35 mesh phosphate and minus 14 plus 150 mesh phosphate are also presented.

Jan 1, 1969

By E. D. Gálvez, L. A. Cisternas, A. López-Valdivieso, F. Lucay

"The floatability of molybdenite fines in saline solutions was investigated through microflotation studies using a modified Hallimond tube. In addition, the effect of pH and gypsum precipitation from calcium ions (Ca2+) and sulfate ions (SO4 2-) ions in saline water on the recovery of the molybdenite was analyzed. It was found that the floatability of molybdenite fines significantly increased with the ionic strength of the saline solutions and is independent of pH above 0.5 mol/L ionic strength. The high floatability of molybdenite in saline solutions is explained as being due to the low electrostatic repulsion between bubbles and the edges of molybdenite particles, which is exceeded by interactions due to van der Waals and hydrophobic forces. The precipitation of Ca2+ and SO4 2- ions as gypsum had a detrimental effect on the natural floatability of molybdenite because of gypsum crystal attachment on the faces of the molybdenite particles. This precipitation phenomenon may be initiated in copper–molybdenite flotation circuits that use recycled saline water, like seawater containing Ca2+ and SO4 2- ions.IntroductionWater availability is a significant factor in mining projects. Water, particularly fresh water from rivers and underground water, is becoming a scarce resource for mining operations and new projects. Under these circumstances, the use of water with high concentration of salts in flotation plants is becoming increasingly important (Cisternas and Moreno, 2014). The use of seawater has been studied as a sustainable solution for many mining companies in dry areas located near the sea. Notably, using seawater in mining operations is how mining companies in Chile have coped with the problem of water resources (Cisternas and Gálvez, 2014). In 1930, small plants in Chile used seawater to float chalcopyrite from high-copper-grade ores. In 1975, the results of tests in pilot plants for the flotation of copper minerals with seawater were reported. It was found that froth formation in seawater at pH 9.5 was suitable to make the rougher circuit work properly, even without frothers. The Cenizas mining group successfully floated chalcocite, bornite and chalcopyrite in the Las Luces plant in Taltal in Chile using seawater (Moreno et al., 2011). Minera Centinela (Antofagasta Minerals S.A. Chile) is currently processing porphyry copper ores using a seawater mixture consisting of 20 percent fresh seawater and 80 percent recycled water. Lower consumption of flotation reagents was reported in both seawater and salt water. In addition, studies performed with synthetic seawater showed that certain frothers increase the froth volume, whereas others decrease it. Additionally, the froth produced with seawater carries a high amount of gangue, and low-quality concentrates are obtained, requiring more cleaning stages."

Jan 1, 2015

By M. E. Mellado

In this paper, we present an a posteriori validation of a heap leaching analytical model using sensitivity analysis. The model is suitable to represent the process of heap leaching of solid reactants from porous pellets and is based on a combination of the leaching kinetics at two levels: particle and heap. The validation is simple, and a sensitivity analysis can easily be performed. The simplicity of the analysis provides insight into the control and optimization of the heap leaching process without strong mathematical complexities. The model and the corresponding sensitivity analysis include the effects of heap height, particle sizes, flow rates and several operation-design variables. Using a case study, we discuss the importance of model validation based on sensitivity analysis. We also comment on several choices for optimizing the process. We had three goals in this work: a posteriori validation, highlighting the importance of model validation and providing insight into optimization choices. We can conclude that the model has good internal logic and there are no extra variables; i.e., all of the variables in the model are necessary.

May 1, 2012

By C. Heckman, M. S. Moats, A. Luyima, W. Cui

"Nucleation and growth of copper on 316L stainless steel from synthetic acidified copper sulfate was studied in the absence and presence of chloride ions and/or organic additives – HydroStar® 4208, DXG-F7® and Cyquest® N-900 – using a potentiostatic technique. The current–time data obtained at 0.16V versus the SHE were analyzed using nucleation and growth models. Scanning electron microscope (SEM) images of deposits produced at 300 A/m2 show that the addition of 20 mg/L chloride ions increased the size and reduced the number of copper nuclei. Potentiostatic current–time data from the electrolyte without organic additives, and confirmed by SEM images, indicate progressive nucleation with two-dimensional growth under diffusion control. None of the organic additives studied at a concentration of 2.5 mg/L with 20 mg/L chloride changed the nucleation and growth mechanism, but the additives increased the number and reduced the size of copper nuclei, leading to more uniform coverage of the stainless steel substrate.IntroductionElectrowinning of copper is an important process in the manufacture of high-purity copper metal. Approximately 20 percent of the world’s refined copper is produced from acidified copper sulfate solutions by electrowinning (Schlesinger, Sole and Davenport, 2011). In many plants, copper is electrodeposited on AISI 316L stainless steel substrates for a period of 6-7 days, after which the copper is stripped from the blanks. Even though the deposition time for a commercial copper electrowinning circuit is around one week, it is critically important to control the nucleation, growth and nature of the initial deposit (Sun and O’Keefe, 1992).Deposit morphology and structure are influenced by the real current density at the electrode surface. The real current density across the cathode surface is made uniform by proper design of the electrowinning cell and electrodes and careful operational practice. Even with good design and control, some current maldistribution occurs. The outcome of severe current maldistribution is poor deposits that affect product quality and/or increase energy consumption. To combat current maldistribution and create a larger operating window in terms of current density, temperature and copper concentration, small amounts of organic smoothing agents – traditionally, guar products – are added to copper electrowinning electrolytes. Moreover, these additives inhibit the growth of copper nodules and lead to improved deposit quality by producing bright, smooth and dense cathodes.Recently, the use of polysaccharides, such as HydroStar 4208 and DXG-F7, and polyacrylamides, such as Cyquest N-900, has been reported in commercial electrowinning tankhouses as replacements for guar (Ashford, Clayton and Sandoval, 2012; Robinson et al., 2013; Sandoval, Morales and Bernu, 2010). However, little information has been published on the effect of these new organic additives, especially regarding the nucleation and growth mechanisms of copper electrodeposits in their presence."

Jan 1, 2016

By C. N. Speltz

The cost of transportation of industrial minerals is frequently higher than the cost of the product. Where a minc, industrial mineral plant. or customer is served by a single railroad, that single railroad, because of lack of competition, may increase rates and/or provide inadequate service so that the economics of that mine, plant or customer are adversely affected, or so that the level of service precludes satisfactory performance. Transloading of industrial minerals from rail-to-truck or truck-to-rail in order to improve economics and sales of product is not new. However, transloading to reduce freight costs or improve inadequate service caused by a lack of competition in the rail industry, is a relatively new concept brought on by the recent mergers of many of the main line railroads, both in the eastern and western United States. For example, with completion of the Burlington Northern/Santa Fe and the Union Pacific/Southern Pacific mergers, the western United States has only two mainline railroads. The industrial mineral producer, in order to reduce the cost of transportation, or increase the level of service, must evaluate potential transloading opportunities in light of higher prices and reduced service brought on by reduced railroad competition.

Jan 1, 1998

By Alan R. Johnson

Because of the competitive nature of the iron ore pelletizing industry, commodities required for the production of pellets are continually being scrutinized to minimize their usage and offset rapidly escalating costs. In the Tilden pellet plant, the usage of one commodity, bentonite, has been reduced from over twenty-four pounds per long ton of pellets to as low as eight pounds per long ton. The evolution of bentonite usage from plant start-up to the present time is described.

Jan 1, 1984

By J. Singh

Recently, a Maryland bank became the overnight owner of a toxic waste site through a foreclosure. The original property owners had operated a crash and garbage business on the site and obtained loans for their business venture through the bank. In 1980, their son purchased the property from his parents with mortgage monies obtained from the bank. Failing to make his loan payments, the son defaulted on the mortgage. The bank foreclosed on the property and eventually purchased the property at a foreclosure sale. Shortly after the bank's purchase of the site, toxic wastes were found on the property--the result of disposing solid wastes on the site for 10 years. The bank declined responsibility for contaminating the site and consequently for its cleanup. The Environmental Protection Agency (EPA) took corrective actions to clean up the site. EPA then handed the bill to the bank, citing the Comprehensive Environmental Response Compensation and Liability Act (CERCLA) of 1980 (more commonly known as "Superfund"). CERCLA imposes liability on the current owners and operators of hazardous waste sites.

Jan 1, 1988

By Ken E. Baylis

Current over-capacity in coal production provides assured and relatively low-cost supplies to coal importers. At the same time, it is of serious concern to coal producers who invested considerable sums in the expectation that overseas demand would continue to grow rapidly. This paper assesses the reserves available for export, the export facilities, the coal supplies which can be put through them, and the market prospects for the future. It assumes, rightly or wrongly, that there will be no major and prolonged disruptions in supply from any major sources of coal. COAL RESERVES FOR EXPORT Economically recoverable reserves in the non-communist world amount to about 470 billion tonnes. These are sufficient to sustain current production levels of 2 billion tonnes a year for 235 years.

Jan 1, 1984

By Corby G. Anderson, Sheikh Abdul Rezan Sheikh Abdul Hamid, Sanjith Udayakumar, Ahmad Fauzi Mohd Noor, Teuku Andika Rama Putra

Chemical and mineralogical characterization of Malaysian monazite, a phosphate mineral, bearing rare earth elements separated from the tin tailings originated from Ipoh, Perak, Malaysia, was performed in this paper. The study aims to collect detailed information on the chemical composition, crystal phases, and microstructure of the mineral monazite concentrate that would aid to optimize the subsequent hydrometallurgical processes for high-efficient separation of thorium and other associated rare earth elements. A systematic characterization study of the concentrate was conducted using techniques such as optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS), and Fourier-transform infrared spectroscopy (FTIR). These techniques analyzed the morphological details on the surface, elemental analysis, and mineral association assessment and identified the surface functionalization groups. The bulk composition and the mineral phases in which the elements are present were studied by wavelength-dispersive X-ray fluorescence (WD-XRF) and X-ray diffraction (XRD) studies respectively. The XRF analysis confirmed the presence of Ce, La, Nd, Pr, and Y (rare earth oxides: REO’s ~ 60 wt.%) while thorium dioxide (ThO2) accounted for 7 wt.% of the total composition. Traces of Ca, K, Al, Fe, Ti, and Mn were also confirmed by SEM elemental mapping. The XRD results confirmed that the concentrate was primarily composed of monazite (Ce, La, Nd, Th (PO4)) along with minor impurity phases of quartz. Automated mineralogical analysis was used as a confirmatory tool to corroborate the preliminary evidences. Based on the particle size distribution analysis supported by SEM, the majority of monazite grains were found to be present in the size range of 170–210 μm. Strong bands of PO4 and SiO4 were observed in the IR spectra corresponding to the phospho-silicate matrix of the REE mineral.

By James M. Peay

This paper discusses the recently completed organizational development research project, which was addressed to the underground mining industry. The three specific purposes of the project were as follows: (a) to determine whether Organizational Development approaches are feasible in the mining industry, (b) to provide a demonstration that Organizational Development methods can successfully contribute to the safety of underground mines, and (c) to compare the efficacy of classical Organizational Development methods, which are highly trainer- intensive, with trainer-nonintensive management development approaches. The term "Organizational Development" (OD) is here broadly defined as a management intervention for the purpose of assisting an organization with the solution of problems, which are seen by the organization as important. More specifically, we can define OD as a planned effort to improve the effectiveness of an organization through (a) team building and problem solving, which concentrates on the issues of immediate concern to the organization, and (b) efforts to improve organizational communication at all levels of the organization.

Jan 1, 1983

By Thomas Novak, Philip Johnson, Richard L. Sanford, Lloyd A. Morley

Macintosh use in mine-planning applications lags DOS machines since many users have made significant investments in hardware and training for other environments. Macintosh use is becoming more pronounced in many other industries, and com soft-ware is of at least the quality of that available for DOS machines and many workstations. This paper describes attributes of the Macintosh computer family as related to many mine-planning problems and solutions including software, memory considerations, workstations, DOS compatibility, and networking.

Jan 1, 1993

By Guillermo Krstulovich

Pillar strength is a fundamental variable in the design of room and pillar mining. A number of researchers have investigated the strength of mine pillars by loading cubical, cylindrical and rectangular model pillars to failure in a compression testing machine (1). Several of these researchers have observed an increase in the compressive strength of model pillar with an increase in friction at the platen-specimen interface (2, 3, 4, 5). It has been postulated that the friction prevents lateral expansion of the specimen, thereby exerting a confining pressure at the interface. Seldenrath and Gramberg in their work with cylindrical specimens of limestone and marble noted that the effect of clamping the ends of the specimens, i.e., to restrict lateral movement of the specimen face, was to increase the compressive strength about 10% for marble and from 50-75% for the limestone, as compared to the same type of specimens when tested with the end planes free (6). No attempt was made to determine the confining pressure exerted by the clamps. In recent years, Bureau of Mines has conducted an extensive study, similar to Seldenrath and Gramberg's, with dog bone specimens. The confining pressure exerted by the clamps was determined and an increase in the compressive strength with increasing confining pressure noted (7, 8).

Jan 1, 1970

By Norman F. Schulz

The technical excellence of separation achieved in a mineral concentration process, or any other process where two constituents of any kind are physically separated from each other, is expressed uniquely and quantitatively by the Separation Efficiency: ES = (R ? Rg) where R is the percentage of the valuable constituent and Rg the percentage of the waste appearing in the concentrate. The Separation Efficiency meets all the usual requirements of a true efficiency and is independent of the nature of the process used. It can be visualized as the percentage of the feed material that, in effect, actually undergoes complete separation while the rest of the feed is distributed randomly and unchanged into the two separation products.

Jan 1, 1969