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By E. S. Peterson, M. K. Harrup, K. A. Dolbeare, J. E. Wey

Efficient methods for the removal of copper from heap-leach solutions without mobile organic phases are a current mining industry need. To satisfy this need, a selective, high-capacity, durable solid material is required. The Idaho National Engineering and Environmental Laboratory (INEEL) developed a set of materials based on current solvent-extraction chelates that provide selective copper concentration in the presence of high concentrations of iron. In contrast to conventional solvent extractions, the author's strategy anchors the chelators to a nonpolymeric solid substrate through the use of a custom-designed linker molecule. The fundamental synthetic routes to these materials have already been established, and attachment to the solid surfaces have been achieved in an efficient manner. The author's continuing research is focused on the optimization of the synthetic pathways to these solid materials and the evaluation of their copper-capturing capabilities.

Jan 1, 2003

By P. E. Nielsen, T. L. Loga, B. B. Mauko

A numerical model is presented which simulates the dynamic fracturing process for a circular geometry fracture in a uniform stress medium. The dependence of crack aperture and net pressure in the crack upon various dominant parameters of the fracturing process is discussed. An analysis of a 75% nitrogen foam fracture in a coal seam at 5600 feet (1707 m) is also presented. The analysis is based upon the discussed parametric trends, the job records of treatment parameters, and a Nolte plot of net downhole pressure. It is interpreted that fracturing with water, in pre-foam fracture pump tests, resulted in significant fracture height growth. However, the subsequent foam fracture had reduced height growth due to the high effective viscosity of the foam and due to the higher magnitudes of elastic modulus and stress in the bounding rock strata with respect to the coal.

Jan 1, 1986

By S. S. Hsieh

As part of a program to address the long-term need to ensure adequate supplies of domestic phosphate raw materials, the Tennessee Valley Authority (TVA) has conducted considerable research on dolomitic phosphate rock beneficiation. The discovery that alkyl diphosphonic acids act as phosphate mineral depressants led to the development of several processes involving a carbonate flotation step for the effective beneficiation of these problem ores. Most recently, a partial deoiling process in which the reagent consumption is greatly reduced has been developed. The reduction is achieved because part of the initial feed is beneficiated without passing through the separate carbonate flotation step. Using this method, a phosphate product containing 30.6-30.9% P2O5 and 0.7-0.8% MgO was obtained from a Florida dolomitic phosphate pebble that contained about 23% P2O5 and 2.0% MgO. The P205 recovery was 80.8-86.5%.

Jan 1, 1991

By Paul H. Lu

This paper proposes a novel method, "integrity factor approach," of mine-pillar stability evaluation based on in situ triaxial-loading measurement. The pillar integrity factor is defined as the quotient resulting from division of integrated total pillar strength across the critical dimension by the integrated total pillar load across the same dimension. The integrity factor is dynamic, while the conventional safety factor is static. With this approach, the pillar stability can be evaluated at any stage of mining progress during panel operation. It automatically considers the progressive failure of the pillar and post-failure strength without the need to clearly define the boundary between yielded and intact zones of the pillar. Based on two case studies, the integrity factor approach is shown to be a practical, effective technique for evaluating stability of conventionally designed pillars. It is suggested that a more realistic estimate of in situ pillar strength could be made based on the combination of in situ triaxial-loading measurements and laboratory true triaxial compression tests, rather than through the traditional combination of biaxial-loading measurements and conventional triaxial compression tests.

Jan 1, 1986

By Flavio Moreira Ferreira

In mining industry, one of the simplest methods to smooth the standard deviation of a given ore controlled property is to build longitudinal blending piles. The effect of homogeneization is obtained due to the fact that an entire cross-section of the pile is reclaimed at each time. The variance of the pile output is the sum of the internal cross-section slice variance plus the reclaimed slice variance. While the first term is a tipical short-term parameter and is absorbed by the process, the second one may be or may not be absorbed. The goal of designing blending piles is to minimize the reclaimed slice variance. Conditional Simulation as described in this paper, is an alternative method to do it. It is devised to design longitudinal blending piles, taking into consideration economical, geometrical and statistical parameters of the ore to be blended, in order to estimate the resulting effect. It presents advantages in relation to other methods for its adaptability and flexibility in simulating pile performances.

Jan 1, 1992

By R. Cooper, K. De Wet, A. Janwong

"Horsehead Metal Products is a zinc refinery in Mooresboro NC treating crude Waelz Oxide (WOX) to produce Special High Grade Zinc by a hydrometallurgical process, comprising leaching, zinc solvent extraction/electrowinning (SX/EW), melting and casting and bleed treatment. Cadmium removal by zinc dust cementation plays an essential role in the bleed treatment circuit to prevent a build-up of cadmium in the circuit. Silica, although not present at significant levels in the WOX feed material (approximately 0.3%), had a significant impact on the efficiency of cadmium cementation with zinc dust, most likely due to the passivation of zinc dust particles with silica gel. Solid/liquid separation efficiency by filter press was also impacted. The silica levels were mapped throughout the circuit in an attempt to identify the source of the silica issues. Adjustments including using PLS as feed to cementation, pH control in WOX leaching and neutralization have been introduced to mitigate the issues created by silica gel in the circuit. INTRODUCTION Located in North Carolina, Horsehead Metal Products Inc. is a hydrometallurgical zinc refinery processing Waelz Oxide (WOX) to produce Special High Grade (SHG) zinc. The flowsheet, known as the Modified Zincex® process, consists of leaching, solvent extraction, electrowinning, melting and casting and bleed treatment as illustrated in Figure 1. Cadmium cementation, part of the bleed treatment process, provides an essential bleed of cadmium from the circuit, as metallic cement. The Cadmium cementation circuit consists of agitated cementation reactors, a zinc dust addition system, filter presses, agitated purification (releach) reactors and a cadmium concentrate filter press Silica can be found in several forms in acid leaching. The first form is fine silicate particles. The size of the particles can vary from one to twenty microns (1). Fine silicate particles can lead to the formation of crud in solvent extraction circuits (2, 3). At Mooresboro, crud has been observed in Depletion, which is part of the solvent extraction circuit. Silica content in the solution in this section is high. The second form of silica is monosilicic acid Si(OH)4, which begins to polymerize almost immediately upon being leached into solution. Monosilicic acid polymerizes to silica gel or a silica precipitate dependent primarily on supersaturation (5). Factors that influence the rate of polymerization include temperature, sulfuric acid concentration / pH, hydrofluoric acid concentration, seeding, and dissolved salts concentration such as zinc and aluminum in the solution (4, 5, 6). In sulfate systems, silica solubility is reported in the range of 150 to 450 ppm of SiO2 (3, 5, 7)."

Jan 1, 2016

By M. C. Roberts

The consumption of industrial minerals, like most other commodities produced from the earth, depends on the demand for the goods and services that use these materials. Minerals are not generally used directly by final consumers (table salt is a notable exception) but instead are used to either make products that are then purchased by customers, or the minerals are used to make industrial products that eventually contribute towards producing other goods and services. Therefore the demand for industrial minerals in most uses is derived from the ultimate demand for goods and services by consumers. The problem for producers of industrial minerals is that the demand for their mineral product fluctuates greatly in response to the changes in the production of goods and services over the course of the business cycle. In this respect, the producers of industrial mineral are innocent victims, subject to market fluctuations outside of their control. Because the demand for most minerals depends on the demand for the product and because minerals typically make up a minor portion of the costs of producing the product, changes in the price of the mineral often do not influence demand for it to a significant degree in the short run. This is described as a very low price elasticity of demand, as shown by the steep slope of the hypothetical demand curve in Figure 1. This demand curve shows that changing the price of the mineral does not alter the quantity demanded very much, but shifts in the demand curve will be the important determinant of the quantity of the mine.ra1 that is sold. The shifts are caused by the changing demand for the products using the mineral over the course of the business cycle.

Jan 1, 1994

By Frank J. Hirner

Economic open-pit and surface mining often call for ever increasing volumes of lower grade materials. So it is important, often critical, to develop precise expense and production estimates for the large electric mining shovels now in use. An electric shovel's basic application is to "shovel up" material, starting at ground level with the dipper moving up into a working face or bank. It's impractical to dig below ground level with a shovel, except briefly or in unusual circumstances. The shovel working face is "the bank," whether the material is dug from natural bed or blasted. The shovel's digging attachment, the boom and dipper handle, is built in standard and long range configurations. A standard digging attachment is normally used for loading into haulage equipment. The long range attachment is normally used for side or hack casting to a spoil pile. It is also used fir loading into haulage equipment placed above shovel ground level, as in some coal loading applications. Shovel clipper size and hauler capacity should he matched so that a hauler can he loaded in three to four shovel work cycles. Five cycles is usually the limit of good practice. If fewer than three cycles are required, the hauler is too small. More than five cycles indicates possible excess harder waiting time for loading, or shovel waiting time for too few haulers. Full dipper loads, including the last dipper or ''pass, " are essential for economical shovel and hauler match. Consistent need for a final partly full dipper to fill the hauler shows an improper match between the two.

Feb 1, 1981

By D. Gu

Breakage of rock by machine is one of the major methods of excavation. With the development of modern engineering techniques, the advantages of using this method have become even greater. Improving efficiency and reducing the cost of rock breakage is the main goal of mechanizing the rock-breaking operation. For a given stratum, the efficiency of a machine excavation depends, to a large extent, on the design and method of application of the tools used. In a planetary cutter head, the subcutter heads move like planets around the main drive shaft. The general structure of the cutter head is shown in Fig. 1. As shown in this illustration, the main drive shaft (1-1) is connected to the tie bar (1) and, thereby, to a gear(5) that meshes with a fixed-gear ring(2). The subcutter head (4) is rigidly connected to the gear (5) by the subcutter-head axis (2-2). When the main drive shaft (1-1) rotates, the subcutter head (4) rotates around the axis (2-2), under the action of the tie bar and with the help of sleeve pipe (3).At the same time, axis (2-2) also rotates around the main shaft (1-1). As shown in Fig 1, is the angle between the main shaft and the subcutter-head axis.

Jan 1, 1995

By Vincent J. Murphy

INTRODUCTION Geophysical applications to engineering projects are usually considered for reconnaissance exploration, and for some preliminary design phases. Recent experience indicates a growing need and a greater number of requests for measurements during construction. This is particularly true where seismic velocity values are related to strength properties of rock. Typical project objectives during construction are: dike and tunnel realignments required by surprise conditions encountered during foundation preparation; checks on grouting effectiveness which require velocity measurements before and after grouting; and dynamic moduli measurements along the walls of tunnels and deep excavations. This paper considers one of the on-site seismic applications that is rather simple and straightforward, and yet has few references in the literature. The specific objective is the measurement of seismic velocities (both "P" waves and "S" waves) for determining the thicknesses and dynamic moduli values of loosened zones of tunnel wall rock. PRE-EXCAVATION SEISMIC METHODS The seismic methods suitable for engineering project studies are well known and especially suited for routine site reconnaissance; these are illustrated in Fig. 1. The seismic refraction profile with a

Jan 1, 1997

By Rodney H. Sergent

After being forgotten or ignored for nearly 100 years, the ability of bromine chemistry to extract gold from ore has been rediscovered. While bromine chemistry is similar to chlorine, there are some important differences. Bromine in its elemental form is a dense, fuming, red liquid. Elemental chlorine is a gas and requires a substantial amount of equipment to handle, store and deliver to solution. Bromine has an advantage in its ability to rapidly and completely oxidize heavy metals to water soluble halide salts. The first patent for use of bromine chemistry for gold extraction was issued in 1881 (1). By 1895, work done in Colorado concluded well roasted ores required approximately 1-1/2 lbs/ton of elemental bromine for superior extraction of metals (2)). At that time, bromine was deemed to be cost effective vs. chlorine even though it was more expensive on a pound basis than chlorine. The advent of cyanide technology virtually eliminated both chlorine and bromine from consideration for leaching of ores. Cyanide was so inexpensive that it made deposits requiring unique technologies unattractive for mining. Only since the deregulation of gold price has bromine/chlorine technology been considered for those ores not amenable to cyanide. While chlorine has found its way into the pretreatment steps, bromine is just beginning to realize its niche in the marketplace.

Jan 1, 1998

By B. J. Sauer

Misapplication of ac induction motors for mine crusher and mill applications has long been a frustration for the driven equipment supplier and the mine operator. Proper selection of ac induction motors is critical to providing efficient production. This paper focuses on the selection of ac induction motors for gyratory crusher, conecrusher and grinding mill applications. The criteria for motor selection includes: proper enclosure, driven equipment torque requirements, bearing life, temperature rise, starting requirements, ambient temperature, altitude and accessory requirements.

Jan 1, 2002

By Ted M. Noskiewicz, James A. Ramsay

INTRODUCTION During the various stages of an underground project from inception through design and construction, probably the single factor of most interest and concern is the nature of the ground. The ground conditions more than any other item govern costs and feasibility; and although the methods available for assessing the ground have become increasingly reliable during the past thirty years, it is still very difficult in many cases to predict the behaviour of soil and rock during and after excavation. To help in this ground evaluation process, we have frequently supplemented the boring program with one or more large diameter inspection holes; and during the past eighteen years, seventeen of these holes have been constructed on tunnel projects which we have designed. There are references in the literature to similar inspection holes (1); however, as far as we are aware, no detailed description of them has been published. The behaviour of soil or rock during and after excavation and the effect of ground water on tunneling operations are of vital interest to tunnel designers and contractors. A comprehensive geotechnical investigation is therefore among the early and most important tasks carried out on a tunnel project and the backbone of every geotechnical investigation is the boring program. A series of borings, typically 50 to 100 mm (21 to 4 in) diameter, are drilled from which soil samples or rock core are recovered and the ground water observed.

Jan 1, 1979

By N. P. Reddy, Y. J. Wang

This paper describes an experimental setup for multiple fan ventilation systems at the ventilation laboratory of the West Virginia University Department of Mining Engineering. Housed in a 30-ft x 70 -ft room, the experimental setup consists of three 18-in., variable-speed, axial flow fans; an 18-in. -diam, fiberglass tubing; associated fittings for arranging networks; and a picot-tube measuring and data-acquisition system. The fiberglass tubing and fans can be organized into non-planar networks of two or three fans. The setup is mainly designed for studying the characteristic curves, operating points and fan stall for multiple fan ventilation systems.

Jan 1, 1993

By Thomas E. Weyand, Wolfgang Baum

PMET is engaged in the development of reuse operations for process wastes from the natural resources industry. Most of the current remediation practices with mining wastes are concentrated on stabilization techniques. Once stabilized, valuable resources are no longer readily available for recovery and reuse. Additionally, stabilized materials, unless protected from weathering influences, pose lingering liability for the generator.

Jan 1, 1992

By Jorge Martinez

The Muck Valley Hydroelectric Project in Northeastern California required construction of a 3.65 meter tunnel through 6,623 meters of mixed volcanic flow deposits within a critical time frame. As Engineer and Construction Manager for the Project, Morrison-Knudsen Engineers invited bids for both Drill and Blast as well as Tunnel Boring Machine methods, selecting a contractor proposing a TBM designed and built specifically for this project which could excavate a wide variety of materials and maintain acceptable progress rates to complete the work within schedule. Tunnel lining as required included shotcrete with metal fibers and full circle concrete.

Jan 1, 1989

By Thomas E. Krakowski

INTRODUCTION This paper presents a method of calculation of internal moments and thrusts in tunnel liners of any material. The method is intended for hand calculation, but as it is numerical in nature it can be programmed for use in computers. The information required for design or analysis is presumed active internal and external pressures, the effective moment of inertia and cross-sectional area of the tunnel liner, the liner's modulus of elasticity, and the coefficient of subgrade reaction of the material surrounding the tunnel. Starting with active external and internal pressures and following the procedure described herein using the structural properties of the liner and surrounding medium, external passive reactions and internal moments and thrusts are calculated. The method is intended for use by design engineers. GENERAL Experience has shown that flexible tunnel liners have less internal bending stresses than those calculated using classical structural theory applied to free-standing arches. In fact, liners which are very flexible in relation to the surrounding soil or rock have virtually no bending moments when compared to free-standing arches supporting equal active loads. In order for this phenomenon to occur, the original active pressure diagram must be "modified" by additional external reactions (passive pressures) from the surrounding material, so that the thrust line within the lining follows the centroid of the tunnel arch more closely than that of a similar free-standing arch. These passive pressures are reactions developed through outward deflection of the tunnel liner. Thus, the outward moving portions of a

Jan 1, 1979

By Victor F. Hollister

Skam deposits considered as porphyry copper deposits have been classified into three basic prospecting models: (I) the skam deposit associated with a mineralized intrusive (Pima-Mission), (2) the deposit associated with a barren igneous stock (Ertsberg), and (3) mineralized rock that seems to have no clear association with apluton (Phoenix). Pima-Mission, Christmas, and many other copper-bearing skarns developed in carbonate sequences near mineralized intrusives form an important part of the deposit. Historically, copper derived from the mineralized intrusion accounts for less than half of the metal produced by most porphyry mines, as most mineralization occurs in the intruded rocks. Skam mineralization is an important part of wall-rock metal deposition, because carbonate sequences are preferentially replaced by sulfide and skarn minerals. Exploration for skam mineralization is an important phase of porphyry copper exploration. Impure carbonate beds can become better host rocks for skam deposits than pure carbonates, and these in particular should be included in porphyry-exploration programs if the impure strata are cut by the stock. Skam deposits can also form near stocks that are barren of sulfide. In this model, the two best ore guides are strata favorable for mineralization (usually impure carbonate beds) and the intrusive contact. Faults can also act as important ore controls. Some skarn deposits form that have no clear genetic connection with a stock, although intrusive rocks are known in the district. In such cases, the best ore guides are strata and district-wide faulting. Dikes and sills are also common and mineralization can locally prefer their contacts even though the igneous rocks are barren. Skam minerals are influenced by the chemical composition of the carbonate. Forsterite, brucite, tremolite, and talc are common in skams developed in dolomitic beds. Skams derived from calcic beds often contain wollastonite, calcite, stilbite, or idocrase. Diopside, however, is a common accompaniment of copper sulfide in skam regardless of the original composition of the carbonates. Tremolite and possibly other amphiboles and chlorite can occur significantly in the zinc-lead portion of skams. Gamets occur in magnetite, copper, and zinc-lead zones of skams, but are not as diagnostic as diopside for the copper zone or tremolite for the zinc-lead zone. A general desciption of skam-deposit mineralogy can be used to construct prospecting models of porphyry copper skams. An abstract of such a description follows.

Jan 1, 1991

By E. F. Divers

Adequate ventilation of coal mine working faces is the most important technique for controlling respirable dust and methane. Choosing the right technique presents some tough questions. US Bureau of Mines research has shown that to control respirable dust, you must contain the dust near the face, keeping rollback (turbulence) to a minimum. For methane, the most effective approach has been to use a blowing brattice, or tubing, and to create turbulence and disperse the face methane, allowing it to pass over the machine and into the return. It is immediately apparent that the two approaches may counteract one another, thus complicating the decision as to which system may be best for a given situation. At present. Bureau research has developed two successful machine-mounted face ventilation systems to meet these different needs and allow deeper cutting. The fan- powered dust scrubber is designed to control dust primarily associated with blowing face ventilation systems. The spray- fan controls methane on exhaust-ventilated sections.

Jan 1, 1987

By Brian Hester

Many Third World African countries are well-endowed with minerals - especially gold and diamonds - while only a few have important base metal deposits. For decades since colonial rule, political and economic conditions discouraged interest by Western capital. Influence from Soviet Bloc countries, however, has declined with the move toward multi-party rule. And the left wing orientation, once widely favored by Third World African countries, has almost disappeared. With International Monetary Fund (IMF) encouragement, these Third World African countries now encourage representational government and solicit western finance to expand their industries. Mining is especially encouraged. The North American mining industry is following the same trail as other capital intensive industries and looking abroad for opportunities. The Prospectors and Developers Association of Canada released figures that show exploration expenditures in that country were halved between 1987 and 1990. Figures for the United States are not so easily found but every indication points to a downward trend. While total annual expenditures on US exploration by corporations as a group are either declining or remaining constant, expenditures away from North America is increasing. Gold exploration expenditures in 1991 by the major companies tracked by Minerals Economics Group were less in the United States than for Latin America and the Southwest Pacific combined. The same study showed as much was spent in the Republic of South Africa and "Other" areas combined as in the United States. Expenditures by major corporations in these "Other" areas amount to only 5.2% of their total budget. Third World Africa is a major component of these "Other" areas.

Jan 1, 1993