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By Y. Zimmels, C. Feldman

Closed-circuit grinding processes are considered in the context of a reactor-separator circuit that involves multifraction streams and products. Because grinding circuits are low-efficiency, capital-intensive operations, modeling to maximize their economic return is appropriate. An attempt to develop and test such a model is presented in this work. The model relies on process simulation for both the mill and the separator, in conjunction with constraints imposed by product specifications. The grinding process was simulated using breakage functions, which provided complete data on the feed and product of the mill. A cyclone bank used as the separator was also simulated using known models. The overall process model provided a complete simulation of the multistream grinding and separation process. The process model was then incorporated into an economic model that predicts grinding cost, subject to process constraints, for a given set of operating variables. The model facilitates economic optimization of the grinding process as it relates to process variables and process hardware.

Jan 1, 1993

By Jack W. Murphy, Kent J. McGrew, Rudolph H. Jacobson

Introduction Maximization of profit consistent with environmental protection is the principal goal of new applications development for any conventional or in-situ mining technique. Efficient evaluation of all the parameters that contribute to mining costs and production hinges on proper design and evaluation of testing programs and data. The program discussed herein utilizes several field and laboratory procedures to estimate ore deposit characteristics and optimize lixiviant compositions. The ore characteristics and lixiviant compositions are then used in a long path leaching test (stream tube test). The stream tube test data are analyzed by mathematical models with computer assistance to predict such well-field rate parameters as target metal production, lixiviant consumption, and restoration. When these predicted rates are combined with market values for target metals, capital expenditures, prices of lixiviant chemicals, and other economic variables such as labor costs, power rates, licensing fees, and others, an assessment of the relative feasibility of various proposed mining plans is possible. The flowsheet in Figure 1 illustrates this process.

Jan 1, 1984

By Steven G. Vick

Not too long ago a mill superintendent, when asked where his tailings were being disposed, could simply shrug his shoulders and point to the open end of the thickener discharge pipe. This “out of sight, out of mind” approach to tailings disposal is a practice of the past. Today there are very few planned hardrock or energy-related mining facilities where tailings disposal has not been identified as the major area of impact and controversy. In fact, development of some ore bodies has been stymied altogether by lack of suitable sites or methods for tailings disposal. The bottom- Iine result is that tailings disposal often controls the permitting lead time and has a significant influence on construction cost (up to 2070 in some cases) of new minemill complexes. The following article, the first in a series of three, explores technical background and historical perspectives on siting and design of tailings impoundment facilities.

Jan 6, 1981

By C. Ek

Tailings originating from the gravity concentration of a gold ore containing about 14 g/t Au have been treated by various beneficiation methods. These tailings have been screened on the 147 and 74 micron sieves and the two coarsest fractions have been separated on shaking tables with unsatisfactory results, but the concentrates have been examined in polished sections for mineragraphic analysis. Very simple flotation flowsheets have been applied to collect most of the gold, recovery and grade varying with the regrinding time in a ball mill. Cyanidation tests have shown that this type of treatment is also applicable to such tailings.

Jan 1, 1991

By Archie W. Fletcher, R. J. Wesely, Nathaniel Arbiter, A. D. Zunkel

In contrast to pyrometallurgy's six thousand year history in the production of metals, that of hydrometallurgy is of relatively recent origin. The earliest reference to it at all was in the 16th century, with the first applications to copper in the 17th and 18th. In the 19th century, increased demands for pure metal resulted in development of electrolytic refining, and early in this century electrowinning. The rapid growth in wpper production in the present century, paricularly in the United States and Chile, stimulated the development of new technology for leaching, and for the recovery of copper from leach solutions. Solvent extraction has become a major factor during the past quarter century by permitting novel leaching technology which produces dilute or complex solutions. In addition, solvents other than sulphuric acid, and chemical methods for precipitating copper metal are now of increasing interest. These are trends which should grow in importance in the future with the need to process lower grade and more complex materials. The evolution of copper hydrometallurgy is reviewed briefly and key factors in recent major developments are presented with details of specific operations and with trends for the future indicated. The relative importance of copper hydrometallurgy is compared to that of pyrometallurgy in the light of probable changes in ore supplies and character.

Jan 1, 1993

By A. C. Burrow, R. P. King

A dynamic model that predicts the variation of carbon content with time in the argon-oxygen decarburization (AOD) process has been developed. The model recognizes three distinct zones in the AOD vessel: the tuyere region in which the blown oxygen reacts very rapidly with the metal components in the molten alloy; a region in which bubbles of inert gas and oxide drop lets rise through the molten alloy; and a zone in which the slag layer can interact with the molten alloy. The process is dynamically controlled by the rate at which dissolved oxygen, produced on the surface of rising oxide droplets, and dissolved carbon diffuse through the molten alloy to react at the surface of the rising bubbles. The rate at which carbon and oxygen react on the bubble surface is assumed to be intrinsically very fast. Predicted decarburization rates compare reasonably well with rates measured in the AOD vessel at Middleburg Steel and Alloys. The model has been developed primarily to allow development of a time-optimal blowing stategy for the AOD vessel.

Jan 1, 1990

Some basic terms used in cost management and accounting include: - Cost. A sacrifice made to acquire goods or services, measured by the price paid. Technically, the sacrifice is called a cost until the benefits from the goods or services have expired, at which time the sacrifice is called an expense. In this text, the terms "cost" and "expense" are used interchangeably. - Revenue. An increase in the value of the firm resulting from the sales of goods and services. - Income. The excess of revenues over costs for a specified period. The term is often used with modifiers to indicate specific quantities on an income statement (e.g., pretax income; net income). - Activity. A measure of production work. Traditionally, physical production volume (tons of ore or units of product) has been used as the measure of activity. Other measures include direct labor hours, equipment operating hours, and quantity of materials or supplies consumed. - Responsibility center. A segment of an organization that is responsible for a specified set of activities. In mining, individual operating divisions can be treated as responsibility centers, known as profit or cost centers. Departments within a division are generally treated as cost centers. - Cost center. A portion of an organization having responsibility for achieving specified levels of cost. - Profit center. A portion of an organization having responsibility for achieving specified levels of profit (revenues and costs).

Jan 1, 1999

By G. Meiers, M. O’Kane

Dry cover systems as a closure option for management and decommissioning of waste rock and tailings is a common prevention and control technique used at numerous sites around the world. Numerous site-specific factors control the long-term performance of dry cover systems. Site-specific climate conditions are one of the key factors to consider when determining the objectives of a dry cover system because these conditions will significantly influence long-term performance. There are advantages and disadvantages of characterizing the site on an annual basis as generally a “dry” site (annual potential evaporation greatly exceeds annual precipitation), or generally a “wet” site (annual precipitation meets or exceeds annual potential evaporation). The field performance monitoring data and discussion presented herein illustrates the caution that is required when using these “annual” criteria for characterizing site climate conditions. Numerous sites exist where precipitation exceeds potential evaporation on an annual basis; however, the site typically experiences hot, dry summer months where evaporation greatly exceeds rainfall. These dry summer conditions have a strong influence on long-term performance. In contrast, sites where potential evaporation exceeds precipitation on annual basis, typically experience periods of the year when a moisture surplus occurs, which also impacts on long-term performance. This paper uses soil-atmosphere cover design modelling and field performance monitoring from sites in Canada, Australia, and the United States to demonstrate the importance of considering site-specific climate conditions when predicting long-term cover system performance.

Jan 1, 2003

By Songlin Ye, Frank Su

"Recycling valuable metals from waste streams has become increasingly important to the mining and smelting industry in China due to resource depletion and environmental concerns. Predicated on multiple large scale metal recovery operations designed by BQE Water at active mines in the Jiangxi Province of China, this paper presents a case study demonstrating recovery of zinc and copper from the waste stream at a major gold smelter in the Shandong Province of China. One of the issues facing the smelter is the lack of a cost-effective and robust process to recover zinc from the acidic process waste stream. As such, significant amounts of zinc-containing wastewater are neutralized with lime, resulting in not only the loss of zinc metal but also the generation of large volumes of sludge. In the case study, a sulphide precipitation process is chosen to selectively recover zinc and copper from the wastewater, in the form of commercial grade metal concentrates that can be sold as regular concentrates at the going market price. In the current project phase, over 2,500 tonnes of zinc metal and 40 tonnes of copper metal can be recovered on an annual basis. This not only generates revenue to offset waste treatment costs, but also eliminates significant amounts of sludge that would otherwise require storing and further disposal if the metals are not recovered.Introduction / Background With resource depletion becoming a global concern and environmental regulations becoming increasingly strict, companies in the mining and smelting industry are actively seeking technologies to maximize resource recovery and provide concurrent minimization of waste residue production from operational activities. Mining and smelting companies have typically used lime neutralization as the primary method to reduce metal concentrations from mine waters prior to reuse or discharge to the environment. However, this process creates large volumes of metal laden sludge with long-term liabilities in the form of ongoing storage and management (Zinck et al 1997). Recovering metals of value from mine water not only reduces sludge volumes and the costs of associated liabilities, it produces a commercial grade metal concentrate that can be sold to generate revenues to offset treatment costs. ChemSulphide® is a sulphide precipitation process developed by BQE Water that has been successfully applied at mine sites in the Jiangxi Province of China to remove and recover copper from acid mine drainage. The success of these copper recovery water treatment plants demonstrates both the economic and environmental benefits of recovering residual metals from mine water and provides reference for the copper and zinc recovery project at a gold smelter in the Shandong Province that is the subject of this case study."

Jan 1, 2017

By Tom C. Palanglo, Norbert Maerz

Control of crushing and grinding circuits ideally requires continuous particle size measurements on both in- and outgoing streams. Until recently, size distributions could only be obtained by screening methods, which were neither cost effective, frequent enough, nor timely. Input streams are often composed of large fragments, making screening prohibitive. Optical image processing systems, such as the WipFrag System, have been developed to the point that they are an extremely valuable tool to characterize, control, and fine-tune the comminution process. Although accuracy is less than that of screening, measurements are precise enough to detect relatively small changes in size distributions.

Jan 1, 2000

By John L. Habberstad, Robert R. Thompson, George B. Wallace, Robert C. Bates

INTRODUCTION Rock bolts are one of the most common mine support systems in use today with approximately 90 to 95 million used annually in the nation's coal, metal and non-metal mines. By far the largest majority of these are steel bolts with mechanical expansion shell anchors. Many theories have been advanced to explain the ground control achieved through the use of rock bolts. Most of the theories are applicable to a specific set of circumstances, geology, geometry, rock properties and in-situ stresses. Examples are those which relate the beam building or strata-hanging theories of ground support used in the rectangular openings of a coal mine(l). In tunneling and most metal mining, either circular or horseshoe shaped openings are normally used. Here, bolts may be used to develop a radial stress around the opening, which adds stability to that opening, or merely pin blocks of rock back into more stable ground so that they cannot slip. In most cases, the bolts are torqued to a specified value to seat the anchor and to achieve the pre-load or tension that is desired. To be effective, however, this tension cannot be lost through bolt slippage or creep frequently caused by blasting, moisture attack or raveling of the rock surrounding the drill hole, etc. Furthermore, in soft rock or in oversized holes, sufficient anchorage cannot be achieved with the mechanical anchor, and in very brittle rock the concentration of forces produced by the expanding anchor might cause a crack to propagate from one drill hole to the next. Mechanically anchored bolts are also short lived in mines or tunnels having a corrosive seepage. The steel in these installations can fail

Jan 1, 1974

By J. Ragot, D. Maquin, N. Heraud

Acquisition of coherent and representative data about the state of processes remains a major problem of process control. This paper proposes an approach that ensures coherence in measurements on an operational industrial process. The basic technique employed relies on balance equilibration of resource mass flow. An interesting particularity of the set up is the ease with which it can be adapted to check productivity or detect sensor failures. In the case of sensor failure, it suffices to examine the evaluations before and after balance equilibration. The algorithm was tested by means of computer simulation using data from an industrial metallurgical flowsheet.

Jan 1, 1992

By Gerald P. Kelton

Hydrocyclones have emerged as successful classification devices In closed circuit grinding applications However, their use for ultrafine particles separation is a relatively new application For ultrafine particles separation In small diameter (51 mm or smaller) cyclones, the cyclone diameter, feed pulp density or viscosity, pressure drop, and configuration play an important role Most often commercial application of the small diameter cyclones suffers from plugging problems resulting from the presence of fibres, wood chips, paper scraps, etc This paper describes important design features of small cyclones, followed by examples of case studies of commercial application of these cyclones

Jan 1, 1983

By C. I. Everson

The Elkhorn mining district is located 35 kilometers southeast of Helena, Montana, on the southeast edge of the Boulder Batholith. Geologically the district consists of a folded sequence of Paleozoic limestones and shales which have been thermally metamorphosed and altered by monzonite to diorite intrusives related to the Cretaceous Boulder Batholith. For the most part, the skarns are associated with metasomatic: replacement of calc-silicate hornfels, diorite and marble by iron rich, dark green pyroxene, garnet, sulfides, the district contains excess of 30,000 Kg.

Jan 1, 1992

By W. K. Tolley, D. G. Kotlyar

Silver is an economically important component of many complex, massive sulfide ores. The beneficiation of this type of ore is now almost entirely accomplished by flotation. Silver recovery is often low, and little is known about the flotation behavior of the silver-bearing minerals. Floatability studies were conducted using silver-bearing tetrahedrite and lead-zinc ore. The effects of xanthate-collector concentration, conditioning time, potentiostatic control of the mineral potential and control of the pH on mineral floatability were evaluated. The floatability of the silver-bearing minerals was shown to depend on collector concentration and mineral potential. The effect of controlling the mineral potential during the flotation process is discussed.

Jan 1, 1996

By H. S. Ten Eyck

The major underlying threat to man's successful survival and happy existence on this planet is our own prolification. This poses an even greater threat to the future of civilization than continued wars and even "The Bomb" itself. Just the predictions of the world's population trend are awesome and demand our serious thought. This trend has been given the now well-known term, "The Population Explosion" - and this is literally what is taking place throughout most of the countries around the globe. Today, the world's resources support approximately 3.3 billion people. Based on the present world population growth rate of 2.1 percent, there will be another 65, million just one year from today. Such an increase in one year means that the world will add a greater population than that of Mexico and Canada combined. Projecting at this remarkable, but unchecked, growth rate, 6.7 billion people will be competing for survival by the end of this century.

Jan 1, 1966

By Tony Weeks, J. Loah, Ian Mcgaffin

PT Newmont Minahasa Raya (PT NMR) operates a 700,000 tonne per annum open cut gold mine in the Minahasa region of North Sulawesi. The operation commenced production in the second quaiter of 1996 and is expected to produce an average of 150 000 to 180 000 ounces of gold per year for the mine life. The deposit is predominately refractory in nature and requires a complex treatment route incorporating dry milling and whole ore roasting followed by conventional cyanidation and adsorp­tion of the gold onto activated carbon. Gold is eluted from the carbon to produce <lore bars assaying approximately 94 percent gold. A scrubbing system for the removal of mercury from the roaster off gases was commissioned in late 1997. Due to the location of the operation, close to the coast and in seismic region with high rainfall submarine tailings placement (STP) was the preferred method of tailings disposal. Prior to dis­posal into the ocean the tailings from the CIP plant are detoxified in a three stage detoxification circuit to treat cyanide, arsenic and mercury. This paper reviews some of the design and operational fea­tures of the whole ore treatment process employed at the Minahasa Gold Mine.

Jan 1, 1998

By Gretchen K. Hoffman, George S. Austin

Soil amendments or soil conditioners generally carry the con- notation of being useful for problem soils or soils needing special treatments to produce maximum yields. Many different materials have been utilized, both inorganic and organic. Only the most commonly used and those that appear to have potential to become commonly used will be discussed. Soil productivity depends on many factors. Soil amendments mainly modify physical characteristics and microbial action, and/or change the pH of a soil, rather than directly supplying plant nutrients. They give soil the needed physical properties to allow plant growth, fight erosion, or save water. Some soil amendments provide nutrients in addition to altering the physical, biological, or chemical characteristics of soil. The term "soil amendment," as it is used by Soil Science Society of America, allows soil amendments to be materials other than those used primarily as fertilizers (Anon.,1987). Soil amendments as fertilizers of any type will not be considered here because this aspect is more relevant to the previous chapter entitled "Agricultural Materials: Fertilizers" in this volume. Several inorganic soil amendments have been used since the early 20th century to alter the character of soil: limestone, lime, and similar calcium-rich carbonates and oxides for acid soils, and calcium sulfate (gypsum) and native or uncombined sulfur for alkaline soils. The use of these amendments (limestone, lime, gypsum, and sulfur) or their equivalents has been studied and documented in many basic soils tests (McCaslin and Boyle, 1980). Perlite and vermiculite are considered in separate chapters and only a brief statement of their use as soil conditioners will be made in this chapter. Peat is the principal natural organic soil amendment, but manure, both as a fertilizer and soil conditioner, is used in every part of the world. In less-developed countries, manure is the primary soil fertilizerlconditioner. An organic-rich material designated as "humate" has been marketed as a soil amendment for many years and will be addressed in this paper. Other materials are discussed by the Soil Science Society of America in its Special Publication 7, "Soil Conditioners" (Stewart, 1975). They include bitumen emulsion, polyacrylamide, polyvinyl acetate, polyvinyl alcohol, bentonite, nonionic surfactants, and natural mulches. Zeolites can be added to the list of miscellaneous soil amendments (McCaslin and Boyle, 1980), as can calcium chloride (Pressler and Pelham, 1985), sulfuric acid, ferric and ferrous sulfate, aluminum sulfate, ammonium polysulfide, calcium polysulfide, and ammonium bisulfite (Stromberg and Tisdale, 1979). Sludge will not be considered as a soil amendment because it has properties more consistent with fertilizers. All these "other materials" account for a very small amount of the volume and value of soil amendments used and will be only briefly discussed.

Jan 1, 1994

By J. A. Meech, C. A. Harris

Expert Systems are being used in the Mineral Industry with ever­increasing frequency. A major advantage of these systems over conventional computer programs is that the knowledge and intelligence of human experts can be captured directly onto a computer for transfer to novices or other lesser experts. These programs allow rapid construction of process models that are not well-understood in fundamental terms, but for which good operational reasoning exists. In addition, user-friendly access to "high-tech" knowledge can be provided to unsophisticated personnel who otherwise might be turned off by unintelligible jargon. As such, these systems can be important training tools for new operators. This paper describes the features of Expert Systems that relate to gold processing plants. Applications include grinding circuit control, supervisory control of reagent addition and pulp density, monitoring and control of CIP/CIL carbon inventories and the operation of carbon stripping and regeneration facilities. A consultative Expert System is described that provides advice on laboratory cyanidation testwork

Jan 1, 1992

As mentioned in chapter 8, one of the objectives of the budget is to provide a mechanism for ongoing measurement and control of the production operation. The budget shows expected performance. Actual results are compared to this benchmark to evaluate past performance and to direct future activities. The variances between budgeted and actual results identify specific activities that did not perform as expected (whether negatively or positively). Managers who use variance analysis are essentially applying a management- by-exception philosophy. Individual organizations will determine variances that reflect their own processes and managerial interests, but these variances all follow the approach outlined here. Firms will also vary in the extent to which variances are reported. Some firms use a few variance measures for the overall production organization whereas others calculate variances for individual departments or even individual work areas. As mentioned in chapter 5, it is important to distinguish between controllable and noncontrollable costs when using budgets for control and evaluation.

Jan 1, 1999