Search Documents

By James L. Whitlock, Amy E. James

During the past twenty years, numerous advances have been made in the technologies used to pretreat sulfidic refractory gold ores. These advances have included improved equipment design, increased gold recoveries, and reduced operating and capital costs. More recently, treatment of refractory gold ores has primarily been accomplished by pressure oxidation (POX), roasting, chlorine oxidation, or biooxidation. In addition to improving the time-proven processes of pressure oxidation and roasting, new and innovative approaches to biooxidation pretreatment of both concentrates and whole ores have been developed. Selecting the appropriate biooxidation technology depends on the nature of the refractoriness in the ore, economic gold recovery, plant design operating parameters (such as desired tonnage), site climatic conditions, and operating and capital costs, as well as several other deciding factors. The objective of this paper is to outline the biooxidation processes and technologies currently available for the recovery of gold from refractory sulfidic ores, to discuss the critical factors that affect plant design and operation, and to provide the metallurgist with a practical guide to choosing the appropriate biooxidation technology for a particular ore or concentrate.

Jan 1, 1999

By Gary Johnson, Bill Mackenzie

The Paddy's Flat plant of Dominion Mining Limited was commissioned in March 1988 with a design throughput rate of 700,000 tpa. The plant now treats ore at an annualised rate of over 2,000,000 tpa. The only major capital improvement to the plant has been the addition of a pebble crushing circuit. Whilst significant changes in the average hardness of the ore being fed to the plant have obviously occurred, a number of processing innovations have been necessary to enable these throughputs to be maintained. The treatment of ore types with a wide variety of physical properties has been a feature of the operation of the Paddy's Flat plant. The leaching characteristics of the ores are relatively straight forward, and it has been possible to considerably enhance the rate of gold extraction from the ore. Reserves of soft surface ore have been increased which has created the opportunity to improve the profitability of the operation by increasing throughput to considerably above the design level, without having to increase the capital investment in the plant.

Jan 1, 1992

By V. I. Lakshmanan, Chris Dodson

Refractory gold ores or concentrates are pretreated in general by physical, chemical and biological oxidative pretreatment processes prior to cyanidation for the economic recovery of gold. The thermal treatment processes generally include fluid bed pro­cessing(!>, chemical with pressure<') or atmospheric (Caro's< ·'>, 3 Nitrox1')) pretreatment leaching and physical with ultrafine grinding!"). Roasting and aqueous pressure oxidation pretreat­ment methods have several commercial applications (Homestake, Barrick) and biological oxidation methods have recently found industrial applications in Africa. The roast pretreatment methods to treat refractory sulphide ores or concentrates transform iron sulphides generally to a porous iron oxide matrix assisting the lixiviant cyanide to effectively diffuse the calcine for cyanidation and hence with improved gold recovery. Jha and Kramer<') made an extensive review of roasting chemistty and practice to tt·eat refract01y gold ores. Industrially two stage pretreatment roasting is generally employed. During the first stage roasting is carried out under oxygen deficiency conditions to provide a low arsenic calcine, mainly magnetite and in the second stage magnetite is trans­formed to haematite under oxidizing conditions.

Jan 1, 1998

By A. Anderson, G. May, C. Kubank, S. Meik

The Kori Kollo operation is owned by Empresa Minera Inti Raymi S.A., a Bolivian mining company. Inti Raymi is an eighty-five percent owned subsidiary of Battle Mountain Gold Company (BMGC). The remainder of Inti Raymi is held by Zeland Mines S.A., a Bolivian mining company. The project is located near the village of La Joya, approximately 220 km south of La Paz, and 40 km north west of Oruro on the Bolivian altiplano. Inti Raymi started a heap leach operation in 1985. By 1988, following several expansions, 4,000 tonnes per day of oxide ore were being treated. At this time drilling was started to delineate the larger sulfide orebody. A feasibility study for the development of this deposit was completed in 1990, and following project approval, the engineering design was started later that year. During this period orders were placed for the major items of mechanical equipment. In July 1991, Minproc Engineers Inc. was awarded a firm price contract to design and construct the 14,000 tonne per day sulfide ore process facility.

Jan 1, 1993

By A. Kyriazopoulos

Quarrying is an important activity as it significantly contributes to the economy of a country. This activity presupposes the destruction of the natural vegetation, the removal of the surface soil and deposition of inactive materials. The lack of fertile soil in these disturbed areas is usually a problem for the plant cover establishment. The purpose of this study was to investigate the potential of the establishment of ten herbaceous plant species to inactive quarries with the use of limited amount of fertile soil. The research was conducted in the area of the quarries of the cement manufacture company ?TITAN?, Thessaloniki, Greece. On a terrace of one of the quarries, a 2 cm layer of fertile soil was placed. In early October 2007, the herbaceous species, Lolium rigidum, Festuca arundinacea, Bromus inermis, Agropyrum desertorum, Phalaris aquatica, Dactylis glomerata, Medicago sativa, Medicago lupulina, Sanguisorba minor and Phacelia tanacetifolia, were seeded separately. The first results indicated that among the tested species Dactylis glomerata, Festuca arundinacea and Phacelia tanacetifolia had the highest establishment capability.

Jan 1, 2008

By C. J. Pritchard

I commend the authors on examining an interesting method of shaft lining and attempting to improve safety in a dangerous environment by remotely installing the shaft lining. It is important, though, to not trade off shaft lining safety for long-term mine safety by lining an intake shaft with combustible material. In many operations, the mine utilities are installed next to the lining of the intake shaft, supplying a possible ignition source if damaged or overloaded. Although the polyurethane studied in the paper is of relatively high density, no mention is made of the flame retardency of the samples. When exposed to heat, small amounts of polyure¬thane will melt and bum but are extinguished when the heat source is removed. If large surface areas of combustible polyurethane - a tunnel or mine shaft - are exposed to ignition heat sources that are not removed or extinguished early, an uncontrollable, fuel rich fire may result with high carbon monoxide levels, low oxygen concentrations, and greatly increased burning rates that can have devastating effects on the ventilation system and miners&apos; safety.

Jan 1, 1990

By Thomas E. McNider

On July 20, 1990, a Spontaneous Combustion Control Plan was approved by MSHA for Jim Walter Resources, Inc. No. 5 Mine. The mine operated under the plan for twenty-nine shifts before MSHA revoked the plan. A total of fifty-five seals were constructed during the process of implementing the plan. The major difficulty in applying the control concept resulted from problems controlling leakage at the numerous seals. The number of seals was a direct consequence of attempting to merge the traditional bleeder system, used in all the Blue Creek Mines, with the bleederless system Jim Walter Resources proposed as a means of controlling the spontaneous combustion hazard. This paper discusses Jim Walter Resources experience with spontaneous combustion control and the new safety standard which applies to underground coal mines that demonstrate a history of spontaneous combustion and how this standard would apply to our No. 5 Mine. The new Ventilation Standards were published in the Federal Register on May 15, 1992, and scheduled to go into effect August 16, 1992.

Jan 1, 1993

In order to analyze and quantify distinct environmental properties in the vicinity of sites, the Site-Specific Natural Resources Information System (SARIS) has been developed based on a Geographic Information System (GIS). SARIS is one of the fundamental databases of a collaborative research program aiming at the resource orientated analysis of metallic raw material flows with aluminum and copper serving as exemplary case studies. The spatial database incorporates all present production sites of ore extraction, refining and smelting. Environmental data for each location were derived from global digital survey data covering land cover, soils, morphology, climate, topography and population density. The main application of this database is the characterization of environmental safeguard objects, which may be affected by the activity of concern. This site-specific environmental impact assessment is used to determine the relevance of environmental issues based on the distribution pattern of sites in a global framework. The derived results are used to suggest a tailored indicator approach to measure progress and performance of industrial developments relative to the predetermined site-specific conditions.

Jan 1, 2003

By Martin H. Col, Thomas W. Steele

The ability to make a good profit in the mining industry is becoming more and more difficult. Typically, grades are lower, sites are more remote, and environmental restrictions are getting tighter than ever before. While the price of the materials P.roduced, such as gold and silver, have stayed flat or declined, the external costs (goods and services) have increased. Increasingly difficult environmental restrictions have increased the lime and costs of develoJ?in9 new deposits, while often placing restrictions on a mme s production rate. Environmental costs for mine closure and site reclamation also make it very difficult to show a long-term profit while mining. Typically, the answer to this cost/price squeeze has been technological innovation. The whole concept of heap leaching low-grade gold ore is one innovation that provided some very goocf profits to the mining companies; but, today, those profits are being eroded by the continuing cost/ price squeeze. This paper will discuss material handling in a heap leach stacking operation and the alternatives of trucks, grasshopper conveY.or systems and mobile conveyor systems.

Jan 1, 1992

By Robert H. Merrill

The art of rock mechanics has been applied in various forms since early man first used caves for housing and fashioned rocks into weapons, tools, and utensils. The development of the science of rock mechanics has occurred in a slow but steady fashion due to the complexity of the materials, geometries, and loading conditions involved. It encompasses a great diversity of topics ranging from techniques for rock destruction to those required for rock strengthening or support, and as such enters daily into the life of the mining engineer. Although today rock mechanics can be confidently used in competent geologic structures, the degree of confidence diminishes as the structures become more complex and the number of geologic defects become more numerous. Even so, the principles still give a better estimate of the structural behavior of underground openings than ever before, and the persons responsible for design and control draw freely and often on the subject. For the most part, the civil engineer will spend more time and money on pre-design than the mining engi-

Jan 1, 1982

By D. S. Bird

Kennecott Utah Copper began a modernization program in 1986 that was aimed at expanding and updating mining and ore process facilities at the company’s Bingham Canyon copper mine and concentrator near Salt Lake City, UT. Major components of the project included installation of an in-pit crusher, a transfer conveying system and a new ore concentrator with a design capacity of 70 kt/d (77,000 stpd). The Copperton concentrator was commissioned in February 1988. The grinding circuit is one of its principal features. It consists of three identical lines, each with a 10.4-m- (34-ft-) diam x 4.6-m- (15-ft-) long semiautogenous grinding (SAG) mill and two 5.5-m- (18-ft-) diam x 8.6- (28-ft-) long ball mills. The SAG mills are driven by two 4.5-MW (each) (6000-hp) variable- speed dc motors through a clutch-pinion gear-ring gear assembly. The ball mills are driven by 4.1-MW (5500-hp) synchronous motors coupled through a typical clutch-pinion gear-ring gear system.

Jan 1, 1995

By James J. Snodgrass, David E. Siskind

The Bureau of Mines investigated the effects of vibrations from underground blasting in four rock types to define blast parameters that affect vibration amplitudes and to establish means of predicting expected vibration levels. Previous studies of surface blasting indicated that charge weight per delay period had a major influence on vibration amplitudes. Dividing the distance from the blast by the square root of the charge weight scaled the effect of various charge weights, however, and allowed vibration data for a particular site to be represented by a propagation equation of the form v = K(D/W ½ )-n (1) where v = particle velocity, D = distance from the blast, W = maximum charge weight per delay period, and K and n = empirically determined site constants. For square-root scaling, particle velocity and acceleration data from the underground sites appear to follow a similar propagation law. The subsurface data are in good agreement with those of the surface studies and provide a basis for engineering estimates of vibration amplitudes in many different rock types.

Jan 1, 1974

By A. Bascetin, A. Nieto

One of the most difficult problems in mining operation is how to determine optimum cutoff grades of ores at different periods over the lifespan of the mine that will maximize the net present value (NPV) of the mine. Cutoff grade optimization maximizes the NPV of a project subject to capacity constraints in the mine, mill and the market.. This paper describes the determination of a cutoff grade strategy based on K. Lane’s algorithm adding an iterative optimization factor calculated for every year during the live of the mine to maximize the project’s NPV. The introduced algorithm is a windows based program developed at Virginia Tech which coded in visual-basic within a spreadsheet environment (Excel). The resulting cut-off windows based program is a user-friendly tool which calculates interactively different mining cutoff grade scenarios. The benefits of the methodology are demonstrated using a hypothetical case study. The authors have observed an improvement of the total NPV using this iterative approach using a year by year optimization factor.

Jan 1, 2007

By Kent G. Homewood

The well-being of any company is directly related to the well-being of its employees and to the effectiveness with which the personnel resource is managed. In an era when personnel management has steadily become more complex, there is an increased awareness of employee information systems at all levels of management due to: (1) regulations enacted by federal, state, and local government agencies; (2) technological advances within the mining industry which have resulted in the requirement for highly skilled personnel; (3) increasing concern for the confidentiality of employee information; and (4) management&apos;s need for information for planning purposes to control costs and for early recognition of trends and potential problems. In the past it was sufficient to maintain records manually. Today computers are necessary to provide information on short notice and effectively manipulate large volumes of&apos; data. This discussion will describe the following aspects of employee information systems: (1) collection and maintenance of information, and (2) applications which include employee health, salary administration, management re- sources, and labor negotiations.

Jan 1, 1979

By B. J. Arnold

Coal blending inherently means homogenizing a mixture of coals so that the properties of the blend meet some specifications for maintaining power plant performance and emission requirements. In practice, however, coal blending is, at best, coal mixing. The degree of blending sophistication required depends on the reason for coal blending in the first place. If it is to maintain fuel characteristics that will diminish the chance of slagging and fouling, then some swings in variability may be tolerated at some power stations. However, if emissions limits are the issue, then more sophistication may be needed. Emissions limits are becoming stricter with requirements to meet averages for shorter time frames (hours and days instead of weeks and months). These restrictions require closer control over the quality of the blend being fed into the bunkers at the station. Even scrubbed units should have a consistent quality of fuel as feed so that sorbent additions can be minimized. To meet these challenges, engineers must consider available equipment and control techniques and the properties of the parent coals when evaluating new blending systems.

Jan 1, 1994

By Peter Hornby, Maurice Craig, Franklin G. Horowitz, Don Bone

We have developed a high-performance, flexible scheme for interpolating multi-dimensional data. The technique can reproduce exactly the results obtained, for example, from Ordinary Kriging and related techniques in 3D, or from Thin-Plate Splines (Briggs&apos; minimum-cuwature algorithm) in 2D. Moreover, com- pared to traditional implementations of these algorithms, our method enjoys large computational-cost savings. The new approach produces an interpolation that obeys a Partial Differential Equation (PDE). The PDE may arise from physically based arguments, but its form can vary widely. It might be specified only implicitly (as through a Model Variogram), or be nonlinear (although a performance penalty could then apply). While a formal equivalence between Kriging and Splines has been known for some time (Matheron, 1980), the present derivation, from radial basis functions, further illuminates this connection. Thus, for example, we can make explicit the PDEs that underlie some of the Model Variograms most often used in Geostatistics. Besides its practical utility, the work thereby ac- quires a theoretical interest.

Jan 1, 1996

By William Wraith

The availability of computer resources and data management technology, together with the prudent use of scientific management concepts, has made it possible to achieve important improvements in the control of maintenance and materials activities in the mining and minerals processing organization. The introduction of minicomputers and. the greatly improved efficiency of computer systems in general have put the use of computer technology within the reach of even the smaller mining companies which probably could not have afforded them just five to ten years ago. A number of progressive companies have implemented computer-based maintenance, purchasing, and supply inventory control systems. Using modern safety stock, demand forecasting, parts reliability analysis, and other control concepts, these new systems have helped minimize production losses by reducing the frequency and severity of supply shortages and unplanned repairs. At the same time, these systems are helping to conserve scarce capital resources by better utilization of supply inventory investments, reduced expenditures for maintenance, less frequent equipment replacements due to improved maintenance reliability, and greater capacity utilization of existing facilities.

Jan 1, 1979

By D. Krzyszton, P. Czaja

Mining explosions in rocks originate stress waves of great intensity, which crush the surrounding rocks and are then propagated as a seismic wave. Seismic waves are the cause of dynamic loading of pillars and their subsequent destruction. In calculating safe dimensions for inter-room pillars, not only the stresses conditioned by overburden pressures should be taken into consideration, but also the dynamic stresses caused by explosion. This is of particular importance for pillars with great specific acoustic impedance which have been destroyed mainly by the reflected seismic wave. It is possible to take dynamic loading into consideration in the calculation of pillars when the parameters of the propagation wave, the dynamic elastic constants of rocks, the strength properties of rocks, the strength properties of rocks subjected to dynamic loads and the parameters of the blasting charge are known. An example of the calculation for the safe width of an inter-room pillar subjected to the seismic effect of an explosion is given and the possibilities of reducing the dynamic loading of pillars are discussed.

Jan 1, 1982

By R. M. Damodaran

The flotation performance of Florida phosphate rock was evaluated in terms of the mixing behavior of reagents and particulates during anionic conditioning of phosphate slurries. The various conditioning variables that influence mixing, namely, solids loading, agitation speed and conditioning time, were investigated to determine their effect on reagent coating of the particles. The phosphate recovery was used to monitor the conditioning efficiency. The mixing characteristics of the phosphate feed were evaluated in terms of the ratio of the mixing power (P) to the minimum power (Pm) required to keep the slurry in suspension. It was found that mixing conditions govern the conditioning time required to obtain a high recovery. Reagentization was slower at lower P/Pm ratios. At higher P/Pm ratios, the flotation recovery was optimized, and the agitation speed was found to have no significant effect. Optimum mixing conditions were obtained for a74 wt% slurry at an agitation speed of 450 rpm (47 radians/sec). Under these optimum mixing conditions, the collector dosage required for an improved recovery was lower and the conditioning time was shorter.

Jan 1, 1997

By Joe W. Cotton, Thomas A. Wheeler

This paper briefly covers theories behind caking of crystalline salt particles, and methods of its prevention. The main factors that influence the extent of caking are humidity, storage pressure, temperature variations, and length of storage time. Careful adherence to control- ling these variables are more critical than the addition of even the most efficient anticaking reagent. The principle characteristics that a successful anticaking reagent must possess are: high retention at the temperature of application, good coating of reagent on the particle surface, capability of in- creasing the hydrophobicity of the particle, reducing the surface tension of liquids, and/or creating of a barrier between particles that prevent contact between particles, and modifying the crystal structure of the salt between the particles. Methods to evaluate the reduction of caking tenacity with the application of various anticaking reagents, reagent volatility and reagent degradation in plant and laboratory scales are discussed. Various types of anticake reagents used today in industry are organic active and inactive reagents, inorganic inert and inorganic salt crystal modifying re- agents.

Jan 1, 1986