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By Alfredo Dammert

The paper presents the results of a model built at the World Bank in order to analyze the aluminum industry. Bauxite demand for the year 2000 is estimated as a function of alumina refineries' requirements and of non-metal uses for bauxite. Bauxite supply by countries or regions depends on economic factors such as investment costs, operating and transportation costs, as well as on tariffs and levies. Various scenarios are considered as a result of varying the assumptions of the model.

Jan 1, 1984

By E. Ozberk, J. B. Hiskey, M. J. Collins, B. J. Scheiner, M. E. Chalkley, I. M. Masters

Conventional zinc concentrates generally contain 5 to 10% Fe, while bulk concentrates can contain up to 20% Fe. As a result, the disposal of iron bearing residues is an integral part of zinc refining operations. The quality of iron residues must comply with ever changing and increasingly stringent environmental legislation. Zinc has been recovered from sulphide concentrates by a hydrometallurgical route for almost one hundred years. The disposal of iron was a major difficulty for the industry for many decades and was directly responsible for low overall zinc recoveries. The introduction of the jarosite process in the mid 1960's allowed for the treatment of neutral leach residues and the precipitation of iron in an easily filterable form. Subsequently, three additional iron precipitation processes have found commercial application in the zinc industry: the goethite process; the paragoethite process; and the hematite process. The Sherritt Zinc Pressure Leach Process has been developed for integration with existing roast leach electrowin zinc plants, or as a stand alone facility for the treatment of a wide variety of zinc bearing feed materials. It is essential that these processes allow for the disposal of iron residues in an environmentally acceptable form. This paper describes the integration of the Sherritt Zinc Pressure Leach Process with commercially proven iron precipitation processes. The results of laboratory testwork and data from operating plants are presented.

Jan 1, 1993

By W. W. Koczkodaj, J. Partyka

Beat exchange in an open air-water system is considered. The system incorporates a vertical cooling tower, and a horizontal multi-stage spray chamber with unlimited number of stages. Mixing of two streams of both water and air is permitted. A spread-sheet implementation estimates temperatures of outgoing water and air for given mass flow of water and air, factor of merit for heat exchangers, barometric pressure, wet- and dry-bulb temperatures, and the temperature of incoming water.

Jan 1, 1987

By N. L. Parduhn

Populations of Bacillus cereus spores are elevated in soils over four subsurface gold deposits in the western United States. Large deposit-to-background ratios of B. cereus populations were obtained in soil traverses over the Minnesota vein deposit, Empire District, Colorado (maximum 50:1); the Shasta (maximum 3,500:1), and Evening Star maximum 18,000:1) vein deposits, Shasta County, California; and the Hog Ranch disseminated gold deposit (maximum 40,000:1) in Washoe County, Nevada. Small increases in the concentration of toxic metals in the soil may be responsible for the elevated spore populations. The observed elevation of B. cereus spore populations near these gold deposits indicates that the method should be further investigated as a potential exploration tool.

Jan 1, 2013

By A. Frederick Banfield

Various modeling techniques are available for describing ore deposits on the computer. Multiple seam coal deposits can be quite successfully modeled by using the variable block modeling method. In essence, this type of model provides an efficient method for storing the relevant data required for calculating ore reserves and for performing the mine planning. The main advantages of the variable block model over other methods for modeling irregular block or tabular deposits are: 1) The amount of data that has to be stored is minimal, i.e., the most efficient use of computer space is made since only the pertinent seam and topographic geometries need to be stored. 2) The computer logic necessary for calculating ore reserves and performing mine sequencing is relatively simple as compared to the logic that would be required for the three-dimensional block model. 3) A variable block model can be created either by starting from raw drill-hole data or by digitizing cross sections that contain the geologic interpretations. 4) Updating individual or multiple blocks can be performed with relative ease. 5) Display of the model is relatively inexpensive and easy to perform. The objective of this chapter is to describe a developed procedure as used in applying the variable block model to a specific multiple seam coal deposit. The general sequence of operations includes: (1) develop the computer model, (2) design the open-pit limits, (3) compute reserves, and (4) develop a long-range mining plan. The programs developed for this application are an expansion of MINTEC's MEDSYSTEM software. It should be noted that this is just one of many possible applications of the developed variable block model.

Jan 1, 1979

By K. Hanumantha Rao, K. S. E. Forssberg, H. R. Manouchehri

The fundamentals of electrical separation, the electrical properties of minerals, the principal methods used for charging minerals and their mechanisms, the effective factors controlling the acquisition of charges by minerals, the general configuration of commercial electric separators and the forces operating during electrical separation of minerals are reviewed and presented.

Jan 1, 2000

By C. D. Wittreich

The results of an engineering study of fiber-reinforced cemented tailings are presented. These tests were conducted to evaluate the potential for using fibers to increase the strength of cemented tailings used as backfill for ground support in the undercut -and - fill mining method in a mine subject to high horizontal stresses and rock bursts. Stress-strain measurements indicate that fibers not only increase the peak compressive tensile and flexural strengths of cemented tailings, but limit reductions in residual strength following failure. Results also show the effect of water content, fiber type, fiber density, and curing time on strength.

Jan 1, 1987

By Eugene E. Brucker

In recent years, there has been increased interest in construction problems presented by karst topography. Twenty-five years ago, karst areas were by-passed for development. Today, the high cost of land and population pressures are requiring utilization of karst areas. Areas exhibiting karst features can be satisfactorily developed so that construction can proceed in a normal manner; or the areas may be left undeveloped and the underground drainage system abused by improper use causing or contributing to structural collapse, excessive erosion, and a grave threat to the stability of land development and the environment. The term "karst" is a comprehensive term applied to areas underlain by soluble rock that possess a topography formed chiefly by the dissolving of rock and the diversion of surface waters to underground routes. There are four features which contribute to the maximum development of karst. 1. A soluble rock, preferably limestone, must be present at or near the surface of the ground. Occasionally, dolomite will suffice.

Jan 1, 1970

By Michael Li

Unsaturated flow and solute transport were studied in three large columns measuring 1.5 m diameter x 2 m height, loaded with up to 3.7 t of oxidised waste rock, which was excavated from the Stratmat pile at Heath Steele Division, Noranda Inc. and contained elevated concentrations of zinc in the pore water. The bottom of each column was partitioned into 37 squares, each of which was drained independently. Following rain simulations at the top of the rock bed, the drainage in each drain port was monitored for volume and physicochemical parameters at pre-determined intervals. This paper describes some of the observations resulting from the experiments. The main conclusion of the study is that unsaturated flows in waste rock are heterogeneous, and flow channelling is ubiquitous. The results imply that the transport of solutes from oxidised waste rock to its toe drainage is subject to various controlling mechanisms, including geochemical equilibrium control and successive pore water dilution control.

Jan 1, 2000

By J. H. Tylczak, R. Blickensderfer

Impact and abrasion properties of various commercial US grinding halls were evaluated and compared by the Bureau of Mines, US Department of the Interior. Laboratory tests were conducted on balls obtained from eight major US manufacturers. The halls included forged steel, cast steel, and alloyed white cast iron and were subjected to repeated impacts until they broke or until 300,000 impacts were exceeded. Pin abrasion tests also were conducted. The results showed wide differences in impact lives, ranging from a few thousand to over 500,000 impacts. The life of inferior commercial halls was increased five to six times by a laboratory tempering heat treatment. For halls that did not break, the major impact wear mode was spalling and ranged from an average rate of 0.28 to 4.46 mg per impact. The softest halls (steel) had excellent impact resistance but low abrasion resistance. The abrasion resistance of the steel halls generally increased with hardness. The alloyed white cast irons had about twice the abrasion resistance of the steel halls. Users should become aware of the wide variations among commercial halls, and ball manufacturers should be aware that their product can he improved.

Jan 1, 1990

By R. Larry Grayson

A menu-driven, linear-programming- based, user friendly computer program was developed to assist mine managers in determining optimal longwall panel dimensions for a given set of operating conditions. A sensitivity analysis must be performed by varying key mining and configurational parameters over an expected, practical range during the optimization process. Results from analysis of a base case mine indicated that no single combination of longwall panel length and face width is optimal for all operating situations. Each mine manager must therefore look closely at his operating situation and determine the proper dimensions to minimize total mining cost.

Jan 1, 1989

By Don W. Murphy, Don M. Larsen

Advanced process control has been implemented at the Jerritt Canyon Mill. Plant production prior to 1997 was limited by grind circuit capacity. The installation of additional mill horsepower and an optimizing supervisory control system achieved a throughput increase in excess of 12 percent. The controller application utilized a seamlessly integrated fuzzy logic expert system for real-time mill control coupled with a neural network predictor for closed-loop feedback of particle size constraints. In late 1998, a second supervisory controller was installed to operate the fluidized bed roasters. The second controller optimized roasting conditions, increased plant throughput and improved metallurgical recovery.

Jan 1, 2000

By M. J. Sapko

The Bureau conducted, through joint funding with the Colorado Mining Association, large scale oil shale rubble fire tests to investigate flotability characteristics and different methods of extinguishment. Ignition of large rubble piles was easily accomplished. Foam blankets could be used to control surface flames. The results of these large scale tests confirmed that water was effective in extinguishing deep seated oil shale fires but not particularly efficient. It took up to 1.7 times as much water to extinguish a fire as anticipated on the basis of a simple cooling model, assuming 100 pet utilization.

Jan 1, 1989

By W. G. Pariseau, S. C. Schmelter

The destabilizing effect of water pressure on rock-mass stability is examined quantitatively by the finite element method. A coupled code that accounts for the simultaneous effects of rock-mass deformation and transient fluid flow is used for this purpose. The traditional soil-mechanics assumption of an incompressible fluid is shown to be untenable for the analysis of porous, fractured rock slopes. A Mandel-Cryer effect, whish is a transitory but elevated and potentially destabilizing water pressure following a cut, was not observed.

Jan 1, 1999

By V. P. Petrov, V. S. Znamensky

There are a great number of asbestos deposits in the USSR, and some are quite large. The main deposits of chrysotile asbestos are shown in Fig. 1. The Bazhenovo deposit, which is located in the Sverdlovsk region, is the largest and has been mined since 1889. Systematic studies of asbestos deposits were begun from the very be- ginning of Soviet government and are most often connected with the names K.E. Tarasov, P.M. Tatarinov, B.J. Merenkov, N.D. Sobolev, F.V. Syromjatnikov, V.N. Lodochnikov, V.P. Petrov, V.P. Eremeev, L.A. Sokolova, V.R. Artemov, and V.F. Dybkov. Investigations by these people and others helped the USSR be one of the most important producers of asbestos in the world. In this chapter, the main asbestos deposits of the USSR are explained in a general outline from the point of view of their genesis, common features, and differences that must be taken into account for forecasting, exploration, and the mining of asbestos. All chrysotile asbestos deposits of the USSR were formed from magnesium rock as a result of comparatively low grade temperature, hydrothermal alteration, and free crystallization of fibrous chrysotile in open cavities that served as catalysts. Chrysotile, a widely distributed rock-forming mineral, is not in general an important mineral for industry as it is a long fibrous and main vein variety. However, it must serve for geologists as an important prospecting criteria. And, the geologist should search for the mineral not only in places of possible chrysotile generation, but in places where asbestos may be crystallized in its long fibers. The Soviet geologists distinguish chrysotile asbestos deposits in two groups: (1) ultrabasic rocks and (2) sedimentary dolomite terranes, taking into account how the maternal rock was affected by hydrothermal solutions. The largest deposits are related to ultrabasite. In dolomite, the largest deposits are small and their asbestos contains almost no iron, which makes it a better filler for insulating plastics. There are a few types of asbestos deposits within the limits of the ultrabasic group, the largest being a Bazhenovo type to which the deposits of the Urals are attributed. This Bazhenovo asbestos is characterized by the most complete zonality of disposition for various kinds of asbestization. These types of deposits are, for the most part, the only ones presently working in the USSR. The Bazhenovo deposit is connected to the gabbro-peridotite intrusive belt that is about 180 km long and is broken into a number of fault blocks as shown in Fig. 2. Granitoid veins of intruded rocks are found along the deepest faults, and were sources of hydrothermal solutions that affected the maternal rock. The nearest granitoid vein, ultrabasite, is substituted by listwanite that consists of quartz, talc, carbonate, and some other essentially talcous rock. The next zone of hydrothermal alteration is composed of serpentine. The boundry between serpentinite and unaltered ultrabasite is as irregular, diffuse, and rough as the boundaries between all other zones. Nearer the vein of granitic rock, ultrabasite is entirely serpentinized into massif serpentinization that penetrates through cracks and fissures. There is an unaltered ultrabasite space between fissures, and the biggest block is preserved unaltered in the central part of the massif. The Soviet geologists call this ultrabasic sopka. Preservation of the unchanged blocks is of great importance for deposit formation as volume changes are impossible during the process of asbestization and serpentinization. It may be confidently said that asbestization in Bazhenovo type deposits is possible only when alteration of ultrabasite has not completely occurred. Under conditions of massif volume, a very big mass of substance must be carried out of the ultrabasite for the progressive stage of serpentinization. However, in the regressive stage,

Jan 1, 1986

Over the last two decades, the mining industry has spent considerable time and effort in installing sophisticated control systems (including expert systems) to regulate and improve the performance of AG/SAG mills. Yet the need for these systems is often overlooked – unmeasured and uncontrolled variation in the feed material. With AG/SAG mill technology replacing rod and ball mills as primary grinding equipment, the need for careful and thoughtful feed preparation has gone. To maximise mill throughput, operations need to better understand the ore characteristics affecting AG/SAG mill performance. Industrial operating data will be used to illustrate these ideas and concepts. It is often quite surprising which ore characteristics that are the most influential on mill throughput.

Jan 1, 2004

By Joseph L. Walker

INTRODUCTION In looking over the diversity of the papers that are being presented during this meeting on The Industrial Practice of Fine Coal Processing one cannot help but be impressed with the progress the industry has made in beneficiating fine raw coals, and in the number of innovations that are under study to increase recovery and to improve the quality of the finest size particles produced at a preparation plant. Those who are not in our industry, who look at the technical program, might be confused, when they see that the papers include such topics as cleaning to zero and heavy media cyclone cleaning 28M x 100M; application and performance of fine coal jigs, tables, hydrocyclones, spirals, and flotation; filtration, dewatering and thermal drying; and ancilliary aspects such as fines handling, instrumentation and process control plus screening and liberation. This is an observation and not a criticism of the diversity of papers being presented. The program fits within the parameters of fine coal preparation as the term "coal preparation" is defined, but perhaps not as the term "fine coal" is defined. Admittedly these definitions are sometimes loose. However, each should be made more definitive if a meaningful fine coal preparation overview is to be possible. COAL PREPARATION DEFINED In the opinion of the writer, the term "coal preparation" should be defined as including all work activities that are performed on all components of a run-of-mine coal from the time it leaves a surface reserve or an underground portal, until all components are either ready for shipment or are stowed on, or in the earth in an environmentally acceptable manner. This definition excludes the work that is performed to improve coal quality or handleability inside the mine or pit. This work is commonly called "face" or "pit" preparation. FINE COAL DEFINED The term "fine coal" means different things to different people. In the past, anthracite finer than No. 3 Buckwheat (3/16 in.) was considered fines which often were discarded from the breaker as an unsalable by product; and bituminous coals finer that about 1/4 in. (slack) were either discarded or sold at cost to prevent an accumulation of "no bills" which referred to a product having no immediate sale. Although a standard definition of "fine coal" is yet to be accepted by the industry, a designation of coals by particle-size range has evolved through the wide use of three-circuit flowsheets, wherein the optimum size range by washer type determines the size fractions: a coarse-coal circuit for the plus 3/8 in., a -11- coal circuit for the 3/8 in. x 28 Mesh, and a fine-coal circuit for the remaining 28 Mesh x 0. Logically, the term "fine coal" should refer to some resultant size fraction or some top size by zero. This definition should include a 28 Mesh x 0 feed to a flotation cell but should exclude a 28 x 100 Mesh size fraction fed to a heavy media cyclone. Failure to include the resultant sizes in the definition precludes accounting of the full range of particle sizes present in the feed to the plant. Since the 28 Mesh x 0 fraction is treated in the final circuit of the three discreet washing circuits, now almost always used in U.S. commercial applications, and since it contains all of its resultant sizes, in the writer's opinion, it should be designated "fine coal". FINE COAL CLEANING Cleaning coal fines, which in the past was at best marginally profitable, is now an essential part of coal preparation strategy for a number of reasons : 1. Raw coals now cost more to produce and

Jan 1, 1988

By Michael Francis, Chris Darton

More than 55 km of tunnels have been constructed by TBM in the last 12 years to refurbish and upgrade the high voltage cable network in London. These include a tunnel of 20km length using EPBM machines in both clay and granular soils. Route selection was made with reference to subsurface structures, existing ground conditions, using suitable shaft locations addressing environmental concerns. The complex interfaces to manage included obtaining of consents to the coordination of multiple suppliers. The paper describes how all these challenges have been met successfully and how technology has been employed to provide for safe construction and operation in the congested urban environment.

Jan 1, 2003

By Robert Sutton, Milan Sjaus

Conveyor pulleys are an important and integral component of a conveyor. Conveyors work in sequence to make up conveyor systems. Each conveyor system is only as reliable as its crudest component. If the pulley fails, then the whole material handling system stops. So what is the effect of this downtime? What are the costs of repair? How much are we willing to pay to solve the problem? What should we spend to prevent an unscheduled shutdown? Do we use the technological improvements at our disposal or do we ignore them to satisfy immediate cost savings? This study will focus on the cost of pulleys relative to the total conveyor cost, the cost of downtime, the maintenance costs and the costs for resolution of the problem. Some philosophic and design concepts are injected for illustration and discussion.

Jan 1, 2000

By R. Bruce Tippin

The silicates represent the largest and most common group of minerals on earth. Yet in spite of the chemical similarities, numerous mineral processing plants worldwide are operating successfully to yield varied commercial products for numerous uses. The silicates that are commercially produced in the United States by flotation include quartz, feldspar, mica, spodumene, talc, kaolin, and wollastonite. The operation of several plants and the conditions affecting mineral separation by flotation are described. Because the process is usually dictated by the desired market, specifications for the most common products are provided. Potash is a basic fertilizer component, along with phosphate and nitrogen. Potash is typically produced from underground evaporite beds or recovered from natural brine solutions. Flotation of potash is unique in that it is processed in a saturated salt solution. The potash flotation process is outlined and several commercial operations are described.

Jan 1, 1999