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By J. A. Chermak

Piles of sulfide-bearing overburden, ore, and tailings have the potential to generate acid drainage (AD) when exposed to an oxidizing environment. Laboratory column experiments were conducted using acid-generating overburden material with an added surface amendment of limestone and/or lime. Artificial rainwater was introduced and allowed to drain through the columns. Results showed that the limestone and/or lime reacted with the acidic rock, resulting in the precipitation of a hardpan layer of gypsum and amorphous iron oxy-hydroxide at the surface. The hardpan layer significantly reduced the effective permeability of the column. Based on this study, hardpan layers can be created as chemical caps to significantly reduce the infiltration of rainwater and snowmelt into acidic overburden or tailings material. Unlike traditional capping methods (for example, clay and high density polyethylene (HDPE) covers), chemical caps are self-healing.

Jan 1, 1996

By Scott W. Harrison, Richard E. Aaseng

In 1993 Ispat Inland Mining Company began mining its Laurentian ore reserve, which has six distinct ore types that are extremely variable. Initially batch processing was necessary to optimize mining equipment utilization. The variability as found in the ground was compensated for in plant operation, which proved ineffective. When the last of the six ore types was introduced in 1997, production, quality, and cost were seriously impacted. In-pit blending was the solution developed by the process management team to provide the plant feed required to economically process all six ore types in the Laurentian reserve.

Jan 1, 2000

By W. S. Hannan

History Leaching of sulfide ore was first attempted by the Phelps Dodge Corporation about 1900 at Bisbee, Arizona, when Dr. James Douglas conducted experiments in an attempt to apply the leaching techniques then in use at Rio Tinto, Spain. Although this initital attempt was unsuccessful, research work was continued which culminated in successful leaching operations at Tyrone, New Mexico, in 1917 and at Bisbee beginning in 1920. Leaching has continued intermittently since that date, with material from the Lavender Pit being leached today. The Lavender Pit Leach Dump Stripping for the Lavender Pit was started in 1951, with mining operations on stream in 1954 and continuing to the present. All material removed from the pit has been classified as waste, leach material, milling ore, or direct smelting ore, depending upon grade and degree of oxidation. Lavender Pit leach material has been stockpiled in a single dump, called No. 7 Dump. This dump covers an area of approximately 135 acres and average about 300 feet in height. The dump has been deposited over a period of 20 years by truck haulage and contains several layers, each of which has a permeable boulder layer at the bottom and a compacted layer at the top. Leaching of Lavender Pit material was started in 1956 and has proceeded simultaneously with dump construction. Former leach pond areas and haulage surfaces have been ripped with D-9 tractors before deposition of succeeding layers of ore.

Jan 1, 1972

By R. L. Pearson

The 1987-88 Denver Brown Cloud Study was performed to determine the sources of the particle cloud which forms over Denver each winter. The study was organized under the leadership of Colorado Governor Roy Romer , EPA Region VIII and the Greater Denver Chamber of Commerce. The study was sponsored by over 40 organizations representing governmental agencies, the natural gas industry, the coal industry, utilities, oil companies, railroads, the motor vehicle industry, and other Denver area companies and organizations. The cost of the study was $1.5 million which was raised almost entirely from private sources. The study team was headed by Dr. John Watson of the Desert Research Institute of the University of Nevada. Dr. Watson is a recognized expert in conducting studies of this type.

Jan 1, 1990

By M. Khandrika, B. K. Parekh

Column flotation has proven to be the most effective technique for the flotation and recovery of ultrafine coal. The commercial application of columns in the coal industry is steadily increasing (Parekh et al., 1990; Yoon et al., 1992). For the flotation of coal or mineral air is used for generating bubbles. Using a conventional flotation cell, Miller and Mishra (1985) compared froth flotation behavior of fine coal using air, nitrogen and carbon dioxide gas. They concluded that carbon dioxide gas provided a higher rate of recovery and a lower ash content. The objective of the present study was to investigate the effect of various gases such as compressed air, nitrogen, argon, and carbon dioxide on the column flotation of fine coal.

Jan 1, 1999

By R. J. Snoby, P. Grotjohann

In processing heavy-mineral sands, the low feed concen¬tration and respective high value of the desired minerals require high-capacity production and sharp classification/ separation techniques to reduce the specific production costs. This paper describes the new allfux® separator, which can economically accomplish these criteria. The separator is a two-stage process that combines rising current and fluidized-bed technology. This allows for the treatment of ex¬tremely high mass flows in a single unit. This paper reports on test work performed on coal, iron ore and heavy minerals.

Jan 1, 2000

By Xu Xiaohe, Zhou Jiandong, Luo Shihui, Zhang Liqun

Recently, the research and applications of ES (Expert Systern) have been put forward actively in many mining fields in China. After various ES applications or instances are introduced, the paper has especially focused on the exclusive properties of a mining system different from any other system and the problems of the existing mining ES applications. And a synthesis methodology has been introduced in order to develop a applicable ES application

Jan 1, 1996

By F. D. Wang

This paper presents an innovative mining method with the application of the water jet. The basic principle of this mining method is to mine a thin panel slice with a water jet system and to allow the roof to deflect elastically and subsequently to be supported by the coal floor without artificial roof support. Through the sequential mining of layers from top to bottom, the entire seam is extracted and the roof rests upon the mine floor. The advantages of this method are that the safety of underground operation can be greatly increased and the surface overburden disturbance will be markedly reduced. . An economic evaluation of such a system is presented for the total cost estimated per ton of coal mined at the face. This evaluation is then compared to that of a continuous mining section utilizing a room and pillar mining method.

Jan 1, 1991

By J. Y. Kim

Silver contained in zinc calcines undergoes several phase changes as it proceeds through the leaching circuit of a roast-leach-electrowin zinc plant. In the present study, the flotation response of silver from leach residues prepared under a variety of carefully controlled operating conditions in the pilot plant has been examined. Flotation of neutral leach residue is shown to be technically viable and to merit consideration for those plants without a high acid leach circuit, but having significant silver values in the feed. Residue leach conditions must be kept slightly acidic to promote the formation of Ag2S, (Ag, CU)2S and Ag2S rims on residual unroasted sphalerite, while simultaneously avoiding the hydrolysis of soluble iron which depresses silver recovery and grade. Factors to be considered during integration of a flotation process into an electrolytic zinc plant are discussed.

Jan 1, 1990

By D. Bogunovic

The objective of this research was to conduct field-scale experiments at an operating surface coal mine in order to determine the impact of the bucket fill factor on dragline production rate and energy consumption. Data collected from a dragline monitoring system were recorded in a specifically designed software tool and the relationship among these parameters was established. an algorithm for the determination of the ?best? fill factor was developed and integrated in the software. It was determined for the analyzed dragline in the mine that energy consumption in the digging phase can be reduced by 36% and production rate can be increased by 1.4% for a bucket fill factor of about 80%, a fill distance of 19.8 m (65 ft) (i.e., 3.1 bucket lengths) and a bucket fill time of 15 sec. the method developed and applied in this study may help dragline operators to determine the fill factor that will increase production rates and reduce energy consumption in specific surface coal mines. Mining Engineering, 2011, Vol. 63, No. 8, pp. 48-53. Official publication of the society for Mining, Metallurgy and Exploration, Inc.

Jan 1, 2011

By Ji Changsheng

In a large surface mine design, different kinds of mining equipment can be selected. Even though the major purpose of capital investment is to get more profit from mining activities, there are some other complicated factors which influence the selection of mining equipment must be considered as well. A fuzzy evaluation model with fuzzy set theory is proposed in the paper to make a good selection of mining equipment in which different kinds of factors including quantitative and nonquantitative ones can be taken into account at the same time. With the model, mining equipment selection of a large surface mine can take into consideration not only economic factors but also some other factors which play important role in mining system.

Jan 1, 1996

By M. J. Laurila

On-line analyzers have made possible the use of Fuzzy Logic Control (FLC) for local control applications in coal preparation plants. This includes FLC control of complete circuits such as heavy media vessels, cyclones and froth flotation. These circuits can be controlled in real time in a feedback control loop with an on-line analyzer. Control strategies can be readily developed using Statistical Process Control (SPC) techniques which are first applied off-line in manual mode through the use of control charts and then this process is brought on-line using FLC in conjunction with an on-line analyzer to fully automate the circuit. This paper outlines the types of control strategies employed and presents examples of automatic verses manual control.

Jan 1, 1997

By C. W. Chiaretta

Utah Power and Light Company's Deer Creek Mine had been developed to a point where mine ventilation efficiency had declined to an unacceptable level. Problems identified were ventilation of inactive areas, excessive leakage, and restrictions in the return and intake air ways. Mine management implemented an intensive mine ventilation improvement program to alleviate future problems with respirable dust in the working sections and diesel equipment emissions. Program objectives included sealing of inactive areas of the mine, rehabilitation of high resistance areas, and construction of additional intake and return aircourses. Applications of computer modeling techniques are used to predict the effects of ventilation changes and improvements. Improvements are then prioritized to achieve the largest efficiency increases first. Actual real time assessment of the mine environment and ventilation changes are accomplished with a mine wide monitoring computer system. The Deer Creek ventilation improvement program has more than doubled the ventilating efficiency of the mine.

Jan 1, 1990

Current scrubber capacities vary from 1.89 to 4.72 m3/s (4,000 to 10,000 cfm), and there is interest in using scrubbers with capacities up to 6.61 m3/s (14,000 cfm). This paper describes research to compare the effectiveness of blowing and exhausting face ventilation systems using high-capacity scrubbers with flows up to 6.61 m3/s. Tests were conducted in a surface ventilation gallery with exhaust and blowing systems operating under similar conditions. The mining machine was equipped with a machine-mounted scrubber. Methane gas was released at constant flow at the mining face and measured at several face locations. Effectiveness of exhausting and blowing systems was compared by determining average face methane concentrations. For each operating condition tested, blowing ventilation was more effective than exhausting for controlling face methane levels. Raising scrubber flow to 6.61 m3/s reduced methane levels for both blowing and exhausting systems.

Jan 1, 1996

By J. Iannicelli

A variety of domestic bauxites have been beneficiated to meet refractory grade standards by use of high intensity, high gradient, wet magnetic separation. Besides reducing the iron content to less than 2%, the Ti02 content of the bauxite was also reduced. The beneficiation can be accomplished by means of a simplified wet process flow sheet with an estimated cost comparable to that of water washed, filler grade kaolin. The process has been carried out on a small pilot plant and then scaled to produce 25 tonnes of calcined refractory bauxite meeting National Stockpile Specifications.

Jan 1, 1984

By C. C. Harvey

Asia is experiencing a growth market for industrial kaolins for use in ceramics, paper, plastics and other market sectors. Export and import data for the Asian countries reflects this growth with the Peoples Republic of China as the major exporter of clays and Japan the major importer. The growth in tonnage and product sophistication of kaolins produced on Belitung in Indonesia is typical of developments that are taking place in many locations in Asia. This region therefore presents opportunities for mineral processors and a challenge for the exploration geologist, the mineral processing engineer, the mineral economist and the marketing specialist.

Jan 1, 1996

By David J. Dunn

Mill liner design is an important factor in grinding. Testing and selection of the optimum liner profile for a given set of mill operating conditions can improve mill capacity, liner life, and liner wear rate At a time when mill avilability is at a premium, production costs are going up, and lead time for mill liner castings is a year or more, the mill liner that grinds best, lasts longest, and costs least is a necessity for economic mill operation. In testing four mill liner profiles for 13' x 12' overflow ball mills, Climax found that an improved design increased mill tonnage by 3 tons per hour while reducing finish grind by 1.7% + 100 mesh, reduced liner wear rate, and almost doubled liner life.

Jan 1, 1976

By A. P. Grobbelaar

Andalusite is a member of the sillimanite group of minerals consisting of andalusite, kyanite, and sillimanite. These minerals are the structural polymorphs of Al,Si05 (the anhydrous silicate of aluminium) and although chemically similar, they differ in physical properties due to their different crystal structures. For further information on the sillimanite group, see the chapter on Kyanite and Related Minerals that follows. The minerals are generally the products of the metamorphism of alumina-rich sediments and are found in schists, gneisses, or hornfelses, which have undergone either regional or thermal metamorphism from their original form. Sedimentary deposits may also form since the minerals are chemically and physically resistant to breakdown. When heated to a sufficiently high temperature the sillimanite group minerals convert to mullite with a resultant volume expansion and the liberation of silica. Due to the stability of the mullite formed, its high hot strength and resistance to chemical and physical erosion, they are widely used in the manufacture of refractories and special ceramics (Table 1). The reaction can be represented as follows: [ ] The worldwide use of these minerals depends to a large degree on their availability (Fig. 1). Andalusite, with its lower conversion temperature and the lowest volume expansion on being heated is the natural choice as a raw material to produce energy-saving refractories without prior calcination. The Republic of South Africa holds by far the largest minable andalusite deposits of the world, estimated at some 70 Mt of known in situ reserves. The only other large commercial production of andalusite comes from France, with known reserves of about 5 Mt. Potential new deposits are known from China, Ireland, Australia, and South America. World consumption of andalusite in special performance refractories has risen from less than 10 ktpy in 1960 to nearly 300 ktpy in 1990, which is due to cost effectiveness in many industrial applications compared to other conventional refractory products. Andalusite-based refractories have traditionally been used in Europe, South Africa, and the Far East; usage in America was limited in the past due to relatively high delivery costs and availability of other local refractory minerals. However, there is a significant trend towards greater use of andalusite in North America, thus opening new markets and replacing other traditional refractory raw materials. GEOLOGY Andalusite occurs in metamorphosed rocks of clay-like com- position, as in the andalusite-hornfelses in thermal aureoles (contact metamorphism), formed under conditions of high temperatures and low stress, and in regional metamorphic rocks, such as the andalusite-schists. These schists are mostly unconnected with definite igneous intrusions but were presumably also formed at high temperatures and under low stress. Andalusite can also appear in alluvial deposits associated with the primary deposits. At depths of 10 to 20 km, temperatures of up to 450°C might be expected. Another result of increasing depth is an increase of pressure due to the load of the rock cover. The load stresses involved in metamorphism is generally believed to lie in the range 0 to 10 000 bars. During contact metamorphism the increase in temperature is brought about by the injection of magma. The temperature reached in the country rock at some distance from the igneous body will always be less than the initial temperature of the intrusion, which is presumably less than 1 200°C, and will vary with time and distance from the contact. A simple metamorphic reaction involving dehydration of an aluminous sediment can be: [ ] At higher temperatures sillimanite would form at the expense of andalusite, while kyanite would be the mineral formed at higher pressures, as can be seen in the phase diagram of A12Si05 (Fig. 2).

Jan 1, 1994

By Lucien Duckstein

The purpose of this paper is to give recommendations for utilization of water resources in a mining region, considering also water supply and environment; the case study of mining for coal and bauxite under the karstic aquifer of the Transdanubian mountain of Hungary is used to illustrate the approach, which consists in formulating a static multiobjective control model and solving it by compromise programming. The three activities of regional mineral resource exploitation, water supply and environmental protection are represented by different objectives which cannot be expressed in commensuerable units. Thus, a solution which is optimal for one objective is usually far from being optimal with respect to the other two objectives. As a result, we are not seeking an optimal solution for the conjunctive regional system, but a good compromise, trade-off or "satisfactum" (1), (2).

Jan 1, 1979

By Al. Valero, A. Domínguez

This paper appraises the energy requirements for mineral production through an exergy approach taking into account the long-term decline in ore grades. In this context, the exergy required for restoring resources from the dispersed state of the so called Crepuscular Earth into the physical and chemical conditions in which it was delivered by the ecosystems in light of the available technology, is known as exergy cost. The exergy cost is the point of reference in order to evaluate in a single variable, characteristics such as composition, concentration (ore grade) and the state of technology. The ratio between the exergy cost and the minimum thermodynamic cost required to accomplish the same process is called unit exergy cost and provides a measure of the irreversibility of the analyzed processes. Otherwise, the ore grade is one of the main issues which affects directly the costs associated with mining the ore. Hence, the unit exergy costs to produce minerals from progressively lower ores grades by the current technology is analyzed. The unit exergy cost curves are presented for some important minerals such as aluminium, chromium, cobalt, copper, gold, lead, manganese, nickel and zinc, in order to know the trend when the ore grade decreases.

Jan 1, 2011