Search Documents

By David C. Sanders, Rodney H. Sergent, Victor C. Storhok, Batric Pesic

In the past, considerable work has been done on the applica­bility of bromine chemistry in the extractive metallurgy of gold. While the research in this area spanned from the understanding of fundamental dissolution chemistry to the demonstration on a pilot plant scale, no work was done on the fate of discarded leach residues with respect to the stability of accompanied heavy met­als. Because the leach residues were the discharge products of halide/halogen systems, the general perception was that the con­tained heavy metals would be more susceptible to dissolution than in typical sulfate systems, thus causing increased environ­mental problems. A long-term study was performed to obtain the information on the stability of heavy metals contained in the leaching residues after bromination. The study involved the leach residues of three different ores, as well the precipitates prepared from the synthetic solutions (not presented here). The conclusion of this study is that the stability of solid residues produced by bromination leaching was same as the sta­bility of leach residues produced by leaching in the sulfate sys­tems. Also, contrary to the past expectations, the presence of bromide ions in the test solutions (up to 1 g/L NaBr) did not enhance the solubility of heavy metals (Cu, Zn, Pb, As) beyond the solubilities found in the sulfate systems.

Jan 1, 1998

By I. Tsolas

This paper presents the use of the Jaggi-Freedman model for deriving composite environmental sustainability indicators at the mine level (i.e. indicators which focus on both the environmental and economic dimension of the sustainable development) using environmental, economic and/or integrated indicators (i.e. indicators which inter-relate two dimensions of sustainability). The derivation of composite environmental sustainability indicators by means of the Jaggi-Freedman model concerns the South-Field lignite mine of Public Power Corporation (PPC) in Western Macedonia. In the light of the results of the present paper it is evident that the performance of South-Field mine, during 1986-1990, was the exclusive domain of large production yearly activities. The considerably low indicators? scores during the 1986-1987 period are attributed to the increased environmental impacts and electrical energy consumed. The merit of this framework is that it can be used both internally, for benchmarking purposes and externally, for sustainability reporting.

Jan 1, 2006

By Andrew P. W. Briggs, Corale L. Brierley

A considerable economic and technical knowledge base has been amassed with the successful and sustained operation of commercial minerals bioleaching/biooxidation plants to extract copper from chalcocite ore and enhance precious metal recovery from sulfidic refractory ores and concentrates. Economic evaluation ofbio-processing must consider the value of the ore, the sulfide-sulfur requiring oxidation to achieve significant metal recovery, the time required for the biological process and, in the case of precious metal feed-stocks, the down-stream reagent consumption. Of these considerations oxygen requirement for the biologically-catalyzed oxidation of sulfide minerals is the prevailing determinant in the capital and operating costs of aerated, stirred-tank reactors for processing concentrates and bio-heaps for processing ores. Oxygen requirement is dictated by the amount of sulfide-sulfur requiring oxidation to achieve desired metal recovery. The testwork program to evaluate a project for application of biooxidation/bioleaching must be designed to insure that factors critical to economic assessment are fully quantified.

Jan 1, 1997

By James P. Dorian, James M. Otto

The value of exported nonenergy minerals from the less-developed countries has increased substantially between 1970 and 1985, but their market share relative to world exports has remained stagnant. Of the top twenty minerals exporters, only four are developing countries. Production capacity in the developing countries is shown to be less sensitive to demand downturns than capacity in the developed countries. Two approaches to the management of cyclical minerals demand are given using examples from India and Papua New Guinea. The authors conclude that pro¬tective policies implemented by developing nations have, barring a few exceptions, relatively little impact on the chronic nonfuel minerals oversupply problem.

Jan 1, 1989

By David J. Hammel

This chapter will summarize some of the important applications in the geotechnical (pit slope, spoil pile and tailings stability, and hydrology), the environmental (including reclamation), and equipment selection and analysis areas. Virtually all aspects discussed are applicable both for planning of new mines and for evaluating existing operations. Probably the most influential item which has affected the areas discussed in this chapter and possibly most areas discussed in this book is and will continue to be, in the next decade, the myriad federal and state environmental, safety, and reclamation regulations affecting new mine development and continued operation of existing properties. Computer applications have been and will continue to be instrumental in assisting in planning to meet the challenges of the requirements dictated by these regulations.

Jan 1, 1979

By Robert A. Robinson, Steven R. Thompson, Harvey W. Parker

The Mt. Baker Ridge Tunnel, under construction in Seattle, will be the world's largest-diameter soil tunnel with an inside diameter of 19.2 m (63 ft) and an effective outside diameter of about 24.4 m (80 ft). The five-lane highway tunnel will be constructed using a "stacked-drift" scheme in which an articulated or "flexible" tunnel lining consisting of 24 concrete-filled drifts is constructed to form a horizontal compression ring followed by removal of the soil core. Geotechnical factors, including variable strength hard fissured soils, high horizontal stresses, potentially unstable sands, and prior slope instabilities, significantly influenced the innovative design and construction approach.

Jan 1, 1983

By R. S. Conti

The US Bureau of Mines (USBM) has developed an inflatable feed-tube seal (IFTS) for high-expansion foam generators. The IFTS is a lightweight, portable, rectangular inflatable bag that can be used by firefighters to rapidly seal large openings, such as those in underground mines, and to simultaneously provide a feed-tube for a high-expansion foam generator. Thus allows fire fighting foam to freely flow to the fire site and control or extinguish the fire. Studies indicated that a high-expansion foam plug will travel 183 m (600 ft) down an entry with a 4.5% rise in elevation, before leakage of foam from around the inflatable partition.

Jan 1, 1996

By C. K. Nworu, L. O. Asuquo, C. O. Nebo

Selective flocculation studies of Agbaja iron ore with starch-type and nonionic polyacrylamide-type flocculants has been conducted to determine the effect of flocculant type. The results indicate that corn starch was slightly better than cassava starch in selectivity performance. Cassava starch was in turn better than Superfloc 16, while the poorest results were obtained with commercial starch. Sodium humate shows better dispersive capability, and thus enhanced flocculation results, than sodium silicate. Pulp pH affects the zeta potential, polymer chain configuration and hence selective flocculation. Overall results indicate that recovery and separation of this very fine grained iron oxide by selective flocculation is feasible.

Jan 1, 1995

By Alexander Filimonov, Yury Bloshteyn

Ventilation of gas mines keeps necessary sanitation and hygienic conditions for labor in mines and increases the safety by dilution and removal of hazardous and dangerous gases in accordance with the safety rules. Several different concepts exist at the present time to design mine ventilation control systems. But technical ideas have been developed inadequately and technological solutions have not been investigated experimentally enough to build a serviceable system. This paper presents a new concept of high- efficiency mine ventilation process control system (MVPCS). The methods of modern system engineering (Kalman, 1969) are used to establish its functional and algorithmic structure. A three level hierarchical principle of system building is considered.

Jan 1, 1991

By Harold D. Taylor

Cone fitting is a procedure which can be used to estimate the short range, linear portion of a variogram. Rather than combining data over windows In different directions and fitting by hand, cone fitting estimates the variogram in all directions at once using a multiple regression approach. The method automatically provides estimates of nugget effect, anisotropy, and initial slope of the variogram. This paper presents the results of simulation studies which have been carried out. These studies Indicate that the method works well and that it may be particularly useful for small data sets. The simulation studies also indicate that the local variogram may differ greatly from the theoretical variogram.

Jan 1, 1986

The new generation of computer environment provides mineral processing plants with convenient tools to store and retrieve or to analyze on-line process variable values as given along time by the various sensors installed in the plant. The paper describes the application of classical tools, such as time series analysis, to retrieve the hidden information contained is such data. The concepts used in single signal processing (autocorrelogram, power spectrum, ARIMA descriptors) and multi-signal processing (cross-correlogram, cross-spectrum) are briefly reviewed. Some examples are given to illustrate their application (sampling, data filtering, process behaviour prediction, process evaluation, data synchronisation). Examples are taken from mixing, flotation and leaching processes.

Jan 1, 1990

By A. G. Journel

The regionalization of tungsten grades at the deposit represents an ideal case for anisotropic hole-effect variogram modelling. The modelling technique is presented step-by-step and the consequences of the model on block kriging are indicated.

Jan 1, 1982

By Wendi H. Cooksey

This paper examines two comminution circuits on a hypo­thetical gold ore deposit with both small-scale (1,000 short tons per day) and large-scale (35,000 short tons per day) production rates. The most appropriate circuit is dependent on the highest economic performance with a combination of crushing and grinding equipment to achieve the desired product size. The selected circuit is dependent on costs associated with project cri­teria, equipment selection and ore characteristics. Factors influ­encing the selection of the comminution circuit require system­atic evaluation to optimize plant performance and maximize eco­nomic return. The small-scale circuit economics responded best to three-stage crushing followed by a single-stage ball mill. The large-scale plant favors a primary crusher followed by SAG milling and ball milling. The conclusions from this paper indi­cate that each project must be evaluated separately to determine the most economic means of reducing the size of the ore.

Jan 1, 1998

By Ing. H. Kellerwessel, Ing. M. Esna-Ashari

This paper refers to the new crushing and grinding process, invented by Professor Schonert (Ref. 1), Clausthal, Germany. The process is known as high pressure particle bed comminution or interparticle crushing. Several papers already describe fundamentals of the process, the equipment used, results of lab size and large scale tests and the first results of commercial operations (Ref. 2 to 7). Of course, we will treat the topic from the perspective of a downstream gold ore upgrading or leaching process. Some recently executed testwork indicates that the process provides special advantages in this field. To describe the process generally, in view of the already existing publications.

Jan 1, 1998

By Cuong V. Trang, Christopher A. Fleming

There has been greatly renewed interest throughout the gold mining industry over the last few years in cyanide recovery from gold and silver plant tailings. This interest has been spmred by two factors. Firstly, the increasing cost of destroying cyanide to levels that meet more and more stringent regulations for tailings impoundment or discharge to the environment. Secondly, many gold ore bodies suffer high cyanide consumption costs as a result of the presence of base metals (principally copper) that react with and consume cyanide during the gold leach. In most cases, the cost of recovering and recycling this cyanide from the tailings is signif­icantly lower than the cost of purchasing new cyanide. When this cost benefit is added to the lower costs of tailings detoxification, a compelling case can frequently be made for cyanide recove1y. A number of processes for recovering cyanide from gold plant barren solutions or pulps have been developed. Most of the processes require that the recoverable cyanide is first converted to the highly toxic hydrocyanic acid gas (HCN) and fears surrounding the handling of this compound have probably presented the great­est impediment to implementation of these processes.

Jan 1, 1998

By Eugene F. Casey

As indicated on the official conference program, this presentation in not a formal one, but a synopsis of the activities of a newly created Sub-committee of the Research Council on Underground Construction, which involves itself with small diameter tunnels. Because there is a dire need to develop a system of excavating small horizontal openings at shallow depths without interrupting traffic, it was hoped that a more progress report could be reported at this time. Because of ecological and environmental considerations, laws are being passed which mandate that all utilities be placed underground. In urban areas the excavation of trenches in which these utilities are placed has been done by disrupting the normal flow of traffic, thereby creating complete chaos. In addition, it always seems that the Companies involved have no coordination, since one company completes its installation and another one begins. Certainly, utility tunnels can be driven at greater depths to house main feeder and trunk lines, but there still remains the problem of installing distribution lines for house services. The definition of a "mini" tunnel, is a tunnel whose excavated size is approximately 48 in. or less. The objectives of the Committee are to "stimulate the development of systems and equipment to build tunnels in these size ranges which will reduce costs, time and surface disruption from current systems."

Jan 1, 1974

By Paul D. Dupree

Introduction Trapper mine is a dip-line strip coal mine, located about 10 km (6 miles) southwest of Craig, CO. The mine provides the Craig Generating Station, operated by Colorado-Ute, with about 2 Mt (2.3 million st) of coal annually. The Trapper mine is situated on a hillside that climbs in elevation from 2 to 2.5 km (6500 to 7400 ft) at average grade of 15%. The coal seams dip at about 16% down-grade and they outcrop near the top of the hillside. They exceed maximum stripping depth in 1 to 1.7 km (3500 to 5500 ft) of pit length. Stripping in the three existing pits is performed with three Page 752 23 m3 (30 cu yd) walking draglines. Two of the pits are currently being cast blasted. Until the active cut, the Derringer pit was cast blasted only where the lower mined seam exceeded stripping capabilities and the pit was a single seam operation. Now, a 9-m (30-ft) interburden bench has been incorporated into the stripping plan. This bench protects the first seam of coal from shear when the overburden is cast blasted. The cast blasted section of the 1.6 km (53,000 ft) long pit has been increased from the 457 m (1500 ft) casted previ¬ously to 1 km (3500 ft). High speed films show the coal losses due to shear of the blast are minimal. The pit width in Derringer pit is 61 m (200 ft). This is necessary for efficient spoil side stripping of a relatively thin interburden in the two-seam section of the pit. The Enfield pit is entirely cast blasted. The single seam pit is 46 m (150 ft) wide, 1.1 km (3600 ft) long, and varies from 15 and 46 m (50 and 150 ft) in overburden depth. The overburden strata at the mine consists of medium-hard layers of sandstone, shale, and

Jan 1, 1987

By Randall E. Hughes, John F. Burst

This chapter describes the nature and occurrence of the principal clay minerals that are used as ceramic raw materials, explains how these raw materials are used to produce finished goods, and summarizes positive and negative trends that will affect future demand for raw materials and products in the ceramic industry. The term ceramics was derived from the ancient Greek keramikos (a clay jar). A ceramic product is a material that has been fired to at least 468.3°C (Mitchell, 1983). In addition to being one of our earliest manufacturing and construction materials, ceramic products are among the earliest records of civilization. The enduring significance of ceramics is shown by the fact that, even today, the manufacture of whitewares, brick and related red-fired wares, refractories, and engineered ceramics continues to be a major sector of the US economy. A wide range of materials can be made into ceramic products, although relatively few earth materials make up most of the ceramics in today's markets (Table 1). Most ceramic products are made from clay or a related material. The long history of clay use in the ceramics industry stems from its variable and sometimes unique physical and chemical properties, as well as its ubiquitous occurrence and relatively low cost. Clay is important to ceramics because of its plasticity, moldability and filterability, chemical content, color. refractoriness, solubility. corrosion resistance, electrical properties, and other properties that result from the essentially two dimensional morphology of the individual clay mineral platelets. Because of their basic relationships to the chemical and physical properties of clays, the chemical and mineralogical content have been the subject of continuous studies over the past few decades. Advances in knowledge about the chemical, mineralogical, and physical properties of clays are responsible for most of the advances in processing. The need to remove off-colored contaminants, minerals with low melting points, and soluble salts has resulted in beneficiation by wet processing methods such as water washing. Water washing is restricted to kaolins, although low cost methods of water washing have been extended more recently to ball clays in Europe. High intensity magnetic filtration and flotation technologies have noticeably improved the quality of kaolins and broadly expanded their use in the ceramics industry. In addition to products for construction (e.g., brick, tile, sewer pipe, field drain pipe, cement, fiberglass, roof granules, and paint) and manufacturing (e.g., refractories, kiln furniture, sanitary ware, pottery, and dinnerware), clays are used in calcined form as ceramic fillers, carriers, extenders, and grogs. Ceramics suppliers are under economic pressure in several of these product areas. Manufacture of refractories in America has declined as steel production has decreased. Similarly, dinnerware and tile production have declined because of foreign competition. Fortunately, new uses for clays,

Jan 1, 1994

By Wayne Stange

Due to the availability of user-friendly microcomputer based packages, the use of simulation is increasing.. Users have however encountered problems inherent to the structure of sequential-modular simulators. These are the difficulties associated with estimating parameters for arbitrary' models and the solution of design and optimization problems. The implementation of an optimization routine in the simulator MicroSim has facilitated the solution of such problems. The literature indicates that more efficient numerical techniques for solving optimization problems than those presently used in MicroSim are available. These techniques, together with user-interfaces which allow such problems to be specified easily by users, will result in the development of simulators much more powerful than existing ones.

Jan 1, 1989

By J. W. Choung, J. A. Finch

Acid rock drainage (ARD) is a recognized environmental challenge facing mining industries. An ambient temperature ferrite (ATF) process has been investigated for treating ARD. Most nonferrous metal and calcium ions present in typical ARDs were found to be detrimental to the ATF process. Three approaches were examined, including C02 aeration, addition of complex agents and use of magnetic seeds. By introducing magnetic seeds in the ATF process, the interferences were minimized and all the precipitates formed with lime neutralization were magnetically recovered from a simulated ARD. The residual concentrations of major metal ions in the treated water were environmentally acceptable. The XRD pattern confirmed the spinel ferrite crystal structure of the products

Jan 1, 2000