Search Documents

By I. Chatterjee, M. Misra

The principle of microwave drying of fine coal is based on the selective absorption of microwaves by water. Coal is a poor absorber of microwaves. As a result, water can be removed from fine coal by selectively heating water molecules. One of the difficult problems during microwave heating is the exact determination of temperature in the core of the materials. The electromagnetic energy absorption in coal/water mixtures during microwave drying is controlled by several factors including the dielectric properties of the constituents. In this paper, electromagnetic and thermal models of coal are presented that can predict the energy absorption and temperature distribution during microwave drying.

Jan 1, 1992

By S. Zendejas-Mendivil, E. Pérez-Segura

The Cananea porphyry copper-deposit is the site of the second largest mining operation in Mexico. Mineralization is related to quartz-monzonite Laramide stocks that intrude volcanic and volcaniclastic Mesozoic rocks. The ore deposit is a stockwork and breccia-pipes system with Cu-Mo sulfides and pervasive quartz-sericite hydrothermal alteration. A study was made of the arsenic distribution in the mine and the ore-dressing plants. The arsenic (As) in the mine is related to a feldspathic quartz-porphyry type rock associated mainly with the breccia pipe structures (100-700 ppm As in the Veta 7 Breccia). There is vertical zoning, with As decreasing in the deepest part of the breccias. This As mineralization corresponds to a later sulfide hydrothermal stage. The concentrates are made of Cu, Fe and Mo sulfides and some minor quantities of As minerals. The most important copper minerals are chalcocite-covellite, bornite and chalcopyrite. Some of these minerals have 390-880 ppm As. The main As mineral is enargite[ [Cu2.97Fe0.06(As0.90 Sb0.01Pb0 01 )0.92 S4 051 and there are traces of stibioluzonite-luzonite I Cu, .95(Aso.4vSbu.49)0.9rfS4.07-Cu2 93(Aso.H4Sba.10)0.94S4.13] and of another stibioluzonite mineral type with substitution of As by Bi[Cu,96(Ascr,,'Sb0ccrB'OJ3jI~6S] These minerals contribute 80% of the As in the concentrates.

Jan 1, 1992

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 Paul Madsen, Bade Sozer, Thomas Hennings, Eileen Test

The Rondout Bypass Tunnel in New York has two access shafts. The upper sections of the shafts are lined with steel pipe to resist a substantial net internal water head . Initial design included a ¾-inch-thick cement mortar lining (CML) for all three components. Because of concerns with CML application on large-diameter pipes, the protective lining was redesigned for shotcrete application. This paper discusses the details of that design, mock-ups, and shotcrete application.

Jun 13, 2023

By Christian F. Baiz

A new agenda has risen. Born out of governments' policies and world economies, the years ahead will carry with them reduced growth. For inflation dependent and capital intensive industries, such as metals and mining, as well as most other natural resource industries, a period of long-term contraction in outmoded and costly capacity will evolve. This will be supplanted by new, lower cost capacity in some cases, but only if the total cost of production, including cash operating and debt service costs comes in at or below current market conditions. The industrial outlook can be characterized as bearish. As one major U.S. bank economist put it, mining companies planning their five-year forecast from 1984 out, should take the current market conditions and straight-line them to the end of the decade. With low growth and low inflation, the real price of metals will remain flat or slightly declining. As a result, capital funding will be problematic. The low cost producer, that is one with low cash costs and low principal and interest costs per unit of production, will succeed.

Jan 1, 1984

By XUEWEN WANG, Changda Zhang, Huaguang Wang, Mingyu Wang, Bin Hu

The copper smelting process produces plenty of copper slag every year, which is a hazardous solid waste, but a secondary resource. In the present study, the extraction of copper, nickel, and cobalt from copper slag was investigated through the process of sulfation roasting–water leaching and the process of sulfation roasting–sulfate decomposition roasting–water leaching respectively. Compared with the process of sulfation roasting–water leaching, the process of sulfation roasting–sulfate decomposition roasting–water leaching is a better choice, which could not only get almost the same leaching of copper, nickel, and cobalt as the former process, but has a lower leaching of iron and aluminum. For the process of sulfation roasting–sulfate decomposition roasting–water leaching, the leaching of Cu, Ni, and Co reached up to 74.2%, 71.1%, and 69.6% respectively, under the optimal conditions including sulfation roasted with 80 wt% sulfuric acid addition at 200 °C for 60 min and sulfate decomposition roasted at 650 °C for 60 min, followed by water leached at 90 °C for 30min with a liquid–solid ratio of 2 ml/g. The leaching of Fe and Al was only 4.9% and 17.6%.

May 4, 2020

By Mohammad Irshad, Larry H. Heflin

INTRODUCTION The planned 166 kilometer (103 mile) Metro rapid rail transit system in Washington, D.C. is being designed and constructed by the Washington Metropolitan Area Transit Authority. At the present time, 112.6 kilometers (70 miles) of this system is in operation and contains 21 route-kilometers (13 miles) of rock tunneling, and 14.5 route-kilometers (9 miles) of soft ground tunneling. An additional 2.4 kilometers (1.5 miles) of single track tunnels in rock are planned and 6 additional contracts will consist of some 8 kilometers (5 miles) of twin tunnel, resulting in 16 additional linear kilometers (10 miles) of single track tunnel in soft ground. The Authority plans, upon its evaluation and the recommendation of the General Engineering Consultant, to include an alternative design incorporating the convergence confinement method of construction known as the New Austrian Tunneling Method (NATM), for Sections E-5, E-6e and E-8a of the E-Route. The Metro system is constructed in a variety of geological conditions and crosses the boundary of two major geographic provinces. Rock tunneling is to the west of this "fall-line" boundary, soft ground tunneling to the east. The soft ground tunneling portions of Metro construction lie in the coastal plain which consist of a

Jan 1, 1987

By Gennaro Gerald Marino

In this paper the main subsidence- ground-structure interactions and an overview of the response of surface structures to subsidence ground movements are presented. The purpose of the paper is to augment our understanding for more effective application of available data as well as to highlight the essential site conditions in building response. The data presented general1 y applies to houses to structures up to 2-3 stories high and no more than several hundred feet in length. Superstructures of these buildings are supported by exterior (wood-frame or masonry) bearing walls with the interior floor loads carried by essentially one row of interior columns. This paper is not directed towards the response of tall buildings, steel-framed structures, or building types commonly associated with schools, churches, libraries, etc.

Jan 1, 1986

By M. S. Duffy

To exploit the mineral resources of fine grained ore bodies the minerals processing industry is turning to fine grinding technology, of which tower milling has become an established part. However, compared to other mills relatively little is known about the operating mechanisms in tower mills. In all milling processes one of the keys to understanding how they work is in knowing how their grinding media move. To investigate the ball motion in tower mills a glass unit was therefore constructed and measurements taken of the movement of the grinding media. This paper describes the results from this study.

Jan 1, 1998

By TOMI GIORGIO DE, Ricardo Tichauer

Mineral exploration is a key factor for success in the mining industry. However, exploration best practices are often ignored in small-scale mining. This works presents the Tichauer-DeTomi Matrix, a methodology that measures the level of compliance of exploration programs in small-scale mining with the industry best practices. The matrix has been applied to three projects in Brazil: an artisanal gold mine in the state of Pará, a small-scale manganese project in the state of Bahia, and a small-scale manganese project in the state of São Paulo. The application of the matrix resulted in indexes that represent the level of maturity of the exploration program in each project and indicate priority actions for reduction of the geological uncertainty. Therefore, the Tichauer-DeTomi Matrix has shown potential to be a useful tool for assessment of geological uncertainty in small-scale mining. As a risk indicator, it may contribute to promoting investment in small-scale mining and development for communities that depend on this activity around the world.

By John Rajala

The Otjikoto Gold Mill was commissioned during November–December 2014 as Namibia’s first new gold producer in 30 years. Its operations consist of surface mining with a modern gravity/carbon-in-pulp mill for ore treatment and gold recovery. The initial mill design capacity was 2.5 Mt/a. Its capacity was expanded after nine months of operation to 3.1 Mt/a, and process performance has significantly surpassed design expectations. After startup, the Otjikoto Mill’s throughput and gold recovery ramped up quickly, with both parameters exceeding design after only two months of operation. The robust process performance continued into 2019, with key performance indicators (KPIs) eclipsing design values in almost every aspect of mill operation. The Otjikoto Mill’s gold recovery is exceptionally high, exceeding 98 percent every year following startup, especially considering the low-grade nature of the deposit.

By Keith G. Wallace, Justus B. Deen, Daniel J. Brunner

This paper describes the impact of natural ventilation pressure (NVP) on the Nuclear Waste Isolation Pilot Plant in New Mexico (WIPP). The WIPP site is a U.S. Department of Energy underground facility for the disposal of low level radioactive transuranic defense generated waste. Because the facility is designed for the storage of nuclear waste, special design considerations are necessary to ensure containment of potential radioactive releases. The main design considerations which influence the ventilation system are the requirements of separate air splits for mining and storage operations and of air filtering before atmospheric discharge in the event of a radioactive release. The leakage between the two air splits must always be from the mining area to the storage area. The transient effects of natural ventilation pressures, caused by seasonal and diurnal surface temperature changes, impact the ventilation characteristics throughout the facility. This paper discusses the measurements taken to quantify the changes in NVP and the engineered systems designed to mitigate against the effects of NVP.

Jan 1, 1991

By P. Verhoeven, G. Hefter, P. M. May

The dissociation (ionisation) constant of hydrogen cyanide, pKa(HCN), has been measured by high precision glass electrode potentiometric titrations in saline solutions containing up to 5 mol/L sodium chloride. The dissociation constant of water that is necessary for the calculation of pKa(HCN) has also been measured. In saline solution, and in contrast to literature values, pKa(HCN) changes considerably at both high and low ionic strengths as a result of changes in activity coefficients. In addition an equation is presented, using literature data, that describes the variation of pKa(HCN) with temperature up to 150°C. The significance of the changes in pKa(HCN) for optimising the pH of alkaline cyanide gold recovery streams is briefly discussed.

Jan 1, 1991

By Robert E. Haun

Retech's Plasma Arc Centrifugal Treatment (PACT) system is a thermal technology that uses heat generated by a plasma torch to treat hazardous waste containing metals and/or organics. Metal bearing solids and soil are melted by the process, and organic contaminants are thermally destroyed. The molten material forms a hard, glass-like leach resistant mass after cooling in a mold. This paper discusses plasma processing in general and presents some results of treating mineral processing wastes using the plasma arc centrifugal treatment process.

Jan 1, 1995

By K. V. Viswanathan, P. Sornasundaran, S. E. El-Mofty

Dolomite is found to undergo preferential dissolution in aqueous solutions and this is found to be strongly dependent on the solid to liquid ratio (SIL). Electrokinetic studies done under the sump conditions revealed that the mineral surface charge is also affected markedly by the solid content in the suspension. Conditioning of the dolomite at low SIL ratios for short time intervals showed preferential dissolution of calcium leading to a magnesium-enriched dolomite surface. At higher SIL ratios and longer conditioning times, calcium depletion from the solution and a calcium-enriched dolomite surface resulted. The results are discussed in terms of surface precipitation and/or bulk precipitation and surface conversion of dolomite to the calcium-enriched phase (calcium carbonate and/or magnesian calcites).

Jan 1, 1990

By Colonel Oattis E. Parks

The quantity of coal recovered by diamond coring techniques is not sufficient in many instances to make meaningful coking and/or ash fouling tests. Quantities in excess of that obtained by conventional coring techniques, usually in amounts exceeding 500 pounds, has been designated bulk sampling. During the past three years, AMAX Coal Company has utilized five methods of bulk sampling. It was our desire to obtain a bulk sample that was diagnostic of the seam by the most expedient and economical method. From the beginning all of our efforts have been directed to methods which would extract the required coal from slim boreholes which provide quick and inexpensive access to the coal seam, regardless of depth, terrain and accessability. In our efforts and investigation several large diameter cores have been taken from thick coal seams at relatively shallow depths in easily drilled rocks. On the other hand, for deeper thin seams multiple large diameter coring is more expensive and time consuming. It is somewhat less expensive when multiple cores are taken from a single slim borehole utilizing deflection coring, although considerable skill is necessary.

Jan 1, 1973

By T. Gollaher

The use of paste thickeners for mineral tailings has gained increasing acceptance by the mining industry throughout the world and in the U.S. during the last five years. Advantages of water recovery and environmental sustainability are the driving forces for paste as an alternative to conventional thickening and the slurry pond. This paper presents a summary of the differences between paste and conventional tailings thickeners, along with recent examples of full-scale paste thickener installations.

Jan 1, 2010

By F. J. Hurst

Phosphate rock, which is a prime source of phosphate used in fertilizer manufacture in the United States, contains uranium. In general, the uranium content of the rock increases with the phosphate content and most high-grade phosphate deposits (>30% P2O5) contain 0.01- 0.02% U3 8. The large tonnages of rock being mined represent a significant potential source of uranium that lends itself to recovery as a by-product of the wet-process phosphate industry. For example, in 1953, the U. S. Geological Survey estimated that recoverable phosphate reserves in the U. S. totaled about 5 billion tons and contained 600,000 tons of uranium. I This estimate did not include any rock from North Carolina which has since been estimated at about 2 billion tons. For the most part, the known, economically mineable U. S. reserves - estimated at about 7 billion tons - are concentrated in a few areas: 43% in the western states of Idaho, Montana, Utah and Wyoming; 28% in each of Florida and North Carolina and less than 1% in Tennessee. In the past, Florida has supplied about 80% of the total U. S. production, practically all of which is land pebble phosphate. All forecasts indicate increased production rates from North Carolina and the western states.

Jan 1, 1976

By John R. Wright

This paper reviews the increased use of mechanization in order to develop lateral headings efficiently and economically. Particular emphasis is placed on the role of the Electric-Hydraulic Drill Jumbo in achieving this goal. Also, the use of modified mining equipment to suit various operating conditions is discussed.

Jan 1, 1981

By Byron R. Berger

Epithermal Ag-Au deposits form at low to moderate temperatures in near-surface environments. Historically, these deposits have been the source of high-grade ores. Increases in the market prices for gold and silver make lower-grade ores economically viable when available in large tonnages. Both the high-grade and bulk-tonnage ores are a consequence of the same processes, and general models of epithermal systems can be useful in the search for new precious-metal resources. A detailed study of deposits at Round Mountain, Nevada; Balei, Russia; Creede, Colorado; Guanajuato, Mexico; and Chanarcillo, Chile, indicates that the hydrodynamics of the fluid systems as determined by fracture geometries, the permeability, and composition of the host rocks are the key factors in the creation of both high-grade and bulk-tonnage epithermal deposits. End-member models that explain the range of observed deposit characteristics are: (1) the hot-springs deposition model; (2) the stacked-cell convection model (where mineral deposition occurs laterally along the interface of two partially separated fluid reservoirs); and, (3) the closed-cell convection model (where deposition occurs in vertical zones due to the relatively unimpeded vertical flow of hydrothermal fluids). Boiling and fluid mixing appear to be agents of precious-metal deposition with the self-sealing of the hydrothermal system being an important adjunct to boiling. Imaginative application of model concepts in exploration has led and can lead to the discovery of new high-grade and/or bulk-tonnage precious-metal deposits.

Jan 1, 1982