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By K. S. Eric Forssberg, Lennart Ryk

The paper discusses coal utilisation in Sweden. All hard coals have to be imported from other countries. Peat from domestic sources is used as a complement. Environmental legislation and taxation on fuel and emissions are severe. This situation affects the procurement, preparation, handling and use of coal. The paper presents: • R&D projects concerning deep cleaning of thermal coal. • Handling and treatment of coal used in PFBC boilers and for blast furnace injection • Dust prevention for coal and peat briquettes. Procurement of coal emphasising quality and environmental issues.

Jan 1, 1995

By V. Rajaram

A mine fire or roof collapse may necessitate the reversal of main fans to isolate the fire or provide an escapeway. Hence, to assist the mine operator in estimating the flow and pressure during reversal, Engineers International Inc. conducted a laboratory and field study of the reverse performance characteristics of main mine fans. Laboratory tests were performed using a 2.4-m (96-in.) diam vane axial fan to establish the forward and reverse performance characteristics under controlled conditions. Subse¬quently, a field test was conducted in a Colorado oil shale mine during which two 2-m (79-in.) diam fans were reversed. The data obtained indicate that reverse performance characteristics depend on the blade angle and the hub-to-tip ratio. The quantity in the reverse mode ranged from 30% to 65% less than in the forward mode, and the static pressure was directly proportional to the square of the quantity.

Jan 1, 1987

By J. A. Cervantes

A statistical model for assessing the risk of ground subsidence in abandoned mine areas is presented. The model is based on the relationship that exists between .the frequency and the location-of subsidence events in a given area and the physical conditions of the ground. These conditions can be described by a series of geological, mining, and physical variables. The model suggests the existence of regions in the multidimensional space of variables which are associated .with increases or decreases in the frequency of subsidence events. Regions associated with an increase in the frequency of subsidence events correspond to regions of higher risks, and vice versa. Risk assessment is based on the ability to express the limits of these high and low risk regions in the, space of variables, and on the ability to express the degree of membership of blocks of land within any of these regions. The theoretical framework for the model is extracted, from discriminant analysis. Risk is quantified by the probabilities of membership of blocks of land into any of these regions. Risk maps are produced by displaying membership probabilities in. appropriate contouring levels. The model has been applied in two urban areas where subsidence of the ground has been active in the past. The two areas are Penn Hills, near Pittsburgh, and Scranton/Wilkes-Barre in northeastern Pennsylvania. In this paper, only the results for the Scranton/Wilkes-Barre area are presented. Those for the Penn Hills area have been presented elsewhere (Cervantes, et al, 1990). In the- Scranton/Wilkes-Barre area, geostatistical estimates of variables likely to affect the stability of the ground were made using samples from 53 drillholes. The estimates were made for 2000x2000 ft squared blocks of land covering the study area. Discriminant functions were computed from the estimated variables and used to establish regions for classifying blocks of land into one of these two populations: 1) blocks not likely to have a subsidence event, and ii) blocks likely to have one or more subsidence events. The same, discriminant functions were used to compute membership probabilities for blocks of land to tall within any of these two populations. These probabilities were contoured to produce a risk map. The risk map produced compares well with the location of the subsidence events which have occurred to date in the area.

Jan 1, 1992

By N. Zouridakis

Radon is an established lung carcinogen and remains the most important environmental radiation exposure. It was estimated that inhalation of radon and its short-lived decay products accounts on average for about one half of the effective dose equivalent from all natural sources of radiation. Radon contained in household water can transferred into room air as a result of agitation or heating. An indoor air concentration of 400 Bq/m3 is obtained if the radon concentration in household water is 4 kBq/L. A typical concentration of radon in ground water is about 1000 times lower than this concentration but sometime elevated concentrations of some kBq/L in ground water are reported. In this work a Liquid Scintillation counting system is used to obtain fast and accurate measurements of radon (222Rn) in water samples from Argolida, Greece.

Jan 1, 2007

By R. Houot, C. Leschevin, G. Gillet

In mineral processing, conventional magnetic separators are equipped with traditional magnetic circuits (magnetic iron yoke with copper coils or iron-clad solenoid) that develop magnetic fields of less than 2 T'. For minerals of low magnetic susceptibility, use of these circuits has many disadvantages. Only a separator with a superconducting magnet can contribute to solving the problems and produce a high magnetic field. This paper presents and describes a magnetic separator having a superconducting magnet with integrated closed circuit for helium liquefaction. The system generator and maintenance are simplified by extensive automation realized by a versatile program- mable autocontrol unit. A comparative study if the results on concentration and purification of different raw materials with the new and with conventional separators is described.

Jan 1, 1987

By J. David Lowell

The discovery of the Kalamazoo (Arizona) ore body was a comedy of errors and coincidences and luck -as most discoveries probably are. The story began in early 1965 when Quintana Petroleum decided to diversify from petroleum into minerals and decided to do this by the route of minerals exploration. Quintana Petroleum is owned by the Cullen family of Houston and has Geen successful over the years in discovering oilfields. In 1965, the president and general manager was Corbin J. Robertson, son-in-law of Harry Cullen, founder of the company and a famous Texas wildcatter. But, in 1965, Quintana's financial advisors suggested that the company go into several mineral commodities, including copper, with Tucson, AZ, as the jumping-off point for copper exploration, and with a geological consultant (me) as the point man. The stage was now set! (See Fig. 1, location map of the San Manuel District, Arizona.)

Jan 1, 1991

By R. M. Bowen

To help solve problems associated with the optimization of complex coal preparation systems, a mathematical model has been assembled which can simplify calculations pertaining to the core of the plant, i.e. the coal cleaning section. It uses algebraic expressions, derived by fitting hyperbolic equations to Mayer curves, to calculate optimum settings for a specified array of coal cleaning units and feeds. This is done without search procedures, and with usually only minor iteration of a simple calculation to specify optima within 0.02% of specified product ash contents. The key to the calculation is a relationship derived via the analytical geometry of conic sections facilitating easy application of the incremental ash theory of separations. The model has been assembled in a generalised form to cater for N processes in parallel, each giving M separations to produce P final products. Examples are given involving assessment of some complex circuit options.

Jan 1, 1986

By R. K. Mehta, K. N. Han, P. B. Queneau, V. Dieudonne

A study based on a statistically designed sets of experiments (central composite design) was conducted to determine the optimum conditions for leaching a subbituminous coal (7.0 % ash) from the middle Wyodak seam in mild sulfuric acid solutions. The statistical analysis was conducted with the ash content and ash removal as the dependent variables and with the coal loading, acid concentration, ferric ion concentration, and temperature as the independent variables. Treatment of the experimental data via a simple genetic algorithm (GA) revealed that acid concentration and temperature are the two most critical variables. Unlike the case with bituminous coal, the ferric ions addition shows no beneficial effect. The optimum "macro response" predicted by GA was verified experimentally; the ash content was reduced to 2.7%, which is close to the value predicted by GA. The ash content was further reduced to 1.7% in a two-stage leaching process devised by incorporating the optimization results with that of leaching kinetic studies.

Jan 1, 1993

By Greg Blerie

The requirements placed on belt conveyors grow increasingly complicated No longer is it sufficient for the conveyors to merely move material from "Point A" to "Point B. " Now these systems must be able to produce a specified flow, guaranteeing a plant can operate as scheduled without peaks and valleys in material flow and production rate. In addition, the conveying system must provide effective control, to minimize the problems and costs associated with the escape of fugitive material these problems include unscheduled shutdowns, premature equipment failures, regulatory headaches, poor neighbor relations, and health and safety issues. The key to accomplishing these goals is the loading and discharge of the conveyor belts. Fortunately, new designs for the chutes that accomplish conveyor loading and discharge can move material efficiently, without blockages and while minimizing the amount of dust generated This innovation is the development of engineered flow chutes

Jan 1, 2004

By I. Nishkov, L. Alexandrova

The kinetics of froth flotation and the three-phase contact (TPC) parameters are studied at temperatures varying from 20°C to 40°C. The material floated consists of glass spheres and a quartz particles with various diameters. Dodecylamine hydrocloride (DDAHCI) is used as a collector. The equilibrium three-phase contact angle is measured with a microscope technique using the modified Mingins-Scheludko method. Using a Wilhelmy method, the temperature effect on the surface tension of the DDAHCI solution is determined. The formation of the thin film on a polished plate of vitreous silica and the expansion of TPC is monitored by means of a metallographic microscope and recorded on a attached camera at different temperatures. The experimental data show an intensification of the flotation kinetics at 30 and 40°C in the case of small particles. Such an intensification is not observed with the larger particles. The cause for intensification of the flotation kinetics is sought for in the dependence of the TPC rate of expansion and induction time on temperature.

Jan 1, 1995

By D. R. Nagaraj

There are few organic ligands that can adsorb effectively on noble metals, especially gold, in aqueous media. Ligands containing sulfur and nitrogen donors are known to be the most effective. Dithiophosphorous acids, for example, are known to adsorb on gold under certain conditions and these, along with xanthates, are used traditionally to recover gold values by flotation from ores. These compounds, however, are not necessarily selective for gold since most of the associated sulfide minerals are also floated. Monothiophosphorous acids, on the other hand, were recently discovered to float gold values selectively from sulfide-containing ores in a mildly alkaline medium; thus the dicresyl monothiophosphate is now used commercially in a gold flotation operation in the U.S.

Jan 1, 1991

By John Waggoner, Steve Klein, John Townsend, Jay Arabshahi

The Riverside Badlands Tunnel is a 13 km (8 mile) long segment of the Inland Feeder Project. This 3.65 m (12 ft) finished diameter water tunnel presented many challenges that had to be overcome to take the project from concept to reality, not the least of which were the diverse ground conditions. Construction of the tunnel was carried out by a single tunnel boring machine (TBM) in one tunnel drive. The project is considered a success due to the accurate baseline established for the ground conditions; the approaches used to mitigate adverse conditions; and the appropriate use of TBM excavation methods, which achieved rapid advance rates despite the challenging ground conditions.

Jan 1, 2003

By Nikhil C. Trivedi, Robert W. Hagemeyer

Despite the apparently unflattering term filler, this group of industrial materials has become an essential component of many industrial products with varying degrees of sophistication. Mineral fillers are, by definition, inert materials included in a composition for some useful purpose. Included in this broad category are asbestos, barite, bentonite, natural calcium carbonates (limestone), clays, diatomite, feldspar, micas, silica, talc, and other industrial minerals. Also included in this category are synthetic mineral- derived materials such as aluminum hydrate, precipitated calcium carbonate, and pyrogenic and precipitated silicas and silicates. Mineral fillers are included in compounds to accomplish a variety of final results. Inclusion of fillers modifies physical characteristics such as hardness, brittleness, impact strength, compressive strength, surface texture, fire resistance, softening point, and electrical conductivity. Depending upon the performance characteristics of the particular filler used and the quantity of the usage (i.e., percentage added), these materials can enhance the physical and optical properties, price-performance, and appearance of the finished products. These enhancements in properties of the finished compounds are the result of properties of the fillers including chemical activity, purity, hardness, particle size, particle shape, particle size distribution, surface structure, color, density, and refractive index. This chapter will review the general usage of fillers, the rationale for their use, trends, and economic factors influencing those trends. Major using industries will be examined in detail with extensive discussion of major fillers used in those industries. The reader is referred to the appropriate commodity chapter for specific information on deposits and processing for industrial minerals. All of these same filler materials have additional significant uses based on their chemical composition or other characteristics. Cross-references for these will be found in other use chapters and summarized in commodity chapters. The chart in Table 1, updated from the 5th edition of Industrial Minerals and Rocks, illustrates the major mineral fillers (both natural and synthetic) and their more important end uses.

Jan 1, 1994

By J. Brent Hiskey

INTRODUCTION Metal electrodeposition processes are of fundamental technological importance to a number of fields. Electrorefining, electrowinning, electroplating, and electrogalvanizing have all been the subject of intense study for over a century. More recently, electrochem- ical deposition has played a critical role in advances in microelectronics and lately has been an enabling technology for the production of certain nanostructured materials. Electrometallurgists have most frequently been concerned with the structure and morphology of massive deposits. For example, in metal recovery steps such as electrorefining and electrowinning, deposits demonstrating adherent coarse-grained characteristics are most desirable. In the case of electroplating, a bright fine-grained, tenacious and strongly adherent deposit is required. The fabrication of microelectronic devices and the production of nanoscale structures such as nanoparticles, nanowires, and nanorods requires a keen understanding of early stage deposition effects. The initial stages of metal deposition, usually referred to as electroclystallization, are fundamentally linked to nucleation and growth phenomena. Early stage deposits are typically very ordered. Whereas, bulk metal deposition structures are much more ran- dom. In both cases, the discharge of a metal ion at an electrified interface is represented by simple cathodic reduction as follows: [ ] Me(H2O)xn[ ] is a hydrated metal ion residing in the bulk solution and Me is the metal atom occupying a crystallographic lattice position. A similar reduction reaction can be

Jan 1, 2005

By Linda Frederick

In July 1997, Krupp Canada obtained the contract to design and supply the conveyor system for Chile's Los Pelambres copper mine expansion project. Progress on the overland conveyor system is currently on schedule. It is a challenging task to convey copper ore from an open-pit mine located on a mountain site 3,000 m (9,840 ft) above sea level down 1,300 m (4,265 ft) to the processing plant at the valley floor below. The Los Pelambres conveyor system moves copper ore at a rate of 8.7 ktlh (9,600 stph) and at a speed of 6 ml sec (1,180 ftlmin) for 12,750 m (41,830 ft). The distance is divided in three conveyors, each 1,800 mm (71 in.) wide. The largest conveyor is 6 km (3.7 miles) long. To protect against avalanches and rockslides, the conveyors run through a 12-km- (7.4-mile-) long tunnel system. The lowest of the three conveyors is equipped with a shuttling head end. With this, the conveyor discharge point can be moved back and forth by 100 m (330 ft), allowing it to build up a longitudinal stockpile at its end. To meet the extreme design parameters, the limits of conveyor design had to be pushed to record-setting marks. For instance, the ST-7800 steel cord conveyor belt is the strongest belt ever installed in a conveyor system. A total drive power of 25 MW (33,535 hp), consisting of 10 2.5-MW (3,352-hp) drives, is included in the design plans. In loaded condition, the electric motors act as generators and feed electric energy back into the power grid. The motors are controlled by variable frequency inverters that provide an infinite adjustment of motor speed. This technology allows starting and stop- ping the conveyors precisely along predetermined acceleration and deceleration ramps. This is done so harmful belt jerking and stress waves can be avoided.

Jan 1, 1999

By Wayne Charlie, Joseph P. Martin

INTRODUCTION Typically, uranium mills produce slurred tailings which are transported by pipeline to a tailings impoundment. The slurried tailings contain about 250 solids (75% liquids) by volume and, depending on the milling process, have a high or low ph. Despite decanting water from the tailings pond and losses by evaporation and seepage, Staub (1978) estimates that for lined impoundments over half of the input water is stored in the tailings. As long as the impounded tailings remain in a loose and saturated state, potential hazards exist and include potential for short and long-term seepage from the impoundments and the potential for large scale release and movement of liquified tailings should an embankment fail. The breach of an earthen dam on July 16, 1979 at Church Rock, New Mexico, and the subsequent release of 100 million gallons of water and liquified uranium tailings, underlines the potential hazard. Loose saturated tailings also have a high potential of liquefaction during earthquakes (Charlie and Wardwell, 1979; Martin, Finn and Seed, 1978; and Mittal and Morgenstern, 1976). If the tailings could be dewatered, the liner's integrity would become less critical, longterm seepage and settlements would be greatly reduced. In addition, the potential for tailings liquefaction from an embankment failure or earthquake would be greatly reduced. This paper reviews the concept, criteria, and design of various proposed interior drainage systems to dewater the tailings after deposition. ADVANTAGES OF INTERIOR DRAINAGE The primary purpose of interior drainage systems for uranium mill tailings impoundments is dewatering the tailings as rapidly and as thoroughly as possible. The expected benefits of this new technology are: • Reduction of potential seepage losses by decreasing the hydraulic head. • Reduce earthquake liquefaction potential of the tailings by inducing non-saturated conditions and/or lowering the water pressure. • Reduce the potential for large-scale release and movement of tailings should an embankment fail. • Stabilize the tailings to permit early reclamation. • Recovery and potential recycling of tailings liquid. • Inhibiting long-term seepage out of the impoundment by inducing nonsaturated conditions to provide capillary suction in the tailings.

Jan 1, 1980

By Paul M. Bommer

Abstract. This cater presents the development of and results from a computer model of in-situ uranium leaching. This model uses a streamline-concentration balance approach and is useful with a vide range of reservoirs. It can be used with any type of veil system, in a reservoir with or without boundaries, and with any form of descriptive kinetics. The model also includes the effects of dispersion and consumption of oxidant by minerals other than uranium. The effects of areal sweep, variable uranium concentrations, variable permeability, and the presence of oxidant consumers on uranium production are shown and discussed.

Jan 1, 1979

By Gary N. Greenfield

This morning, gentlemen, I should like to discuss resin anchors of a type introduced to North America approximately 2-1/2 years ago. We shall also briefly review the basics of mechanically anchored rockbolts so that a general comparison may be made. Previous efforts with synthetic resins were aimed at aiding a mechanical Or "point" anchor, obtain a better purchase in the rock mass. Resin cartridges of the type to be described in this paper are capable of achieving point anchorage or full encapsulation of mine roof or rockbolts. Of significance, therefore, is that unlike a mechanical bolt, placed and tensioned, celtite rockbolts may be fully grouted and tensioned or left untensioned in the installation sequence. Our principle effort has been to offer this system to mining and civil engineers who have encountered difficult rock conditions and wish to reinforce strata to achieve a greater degree of permanence and safety.

Jan 1, 1972

By Malcolm Reeves

The heavy oil reservoirs of Alberta and Saskatchewan include sequences of unconeolidated silts and fine sands which respond in an unusual manner when subjected to the high temperature and pore-fluid-pressure associated with steam injection and other thermal enhanced recovery techniques. Apparent transient connections are suddenly established between producers and injectore and there is an associated enhancement in oil (and sand) production. These phenomena have been attributed to local fluidization and piping processes which are known to occur in situations where high pore-fluid-pressures prevent the mobilization of intergranular friction. These breakdown processes may be associated with the penetration of tongues of the heated reservoir fluids with suspended sand into the creep sensitive intact reservoir since the viscosity ratios are sufficiently high for viscous fingering instability of the fluid-fluid interface. A program of laboratory tests has been carried out to measure the strength characteristic of saturated oil sands at a variety of temperatures and fluid pressures. These tests suggest, that in common with the coarser Athabasca sands, the Waseca sands have very little cohesive strength and show the characteristic dilational failure response of dense sands. Some special tests, devised to determine the relative ease with which samples can be fluidized, confirm the expected susceptibility of the fine- sand silts. Both piping and fluidization can be readily induced at in-situ reservoir temperatures and pressures. Analysis of stresses around wellbores suggests that fluid-pressure gradients may be sufficient to initiate piping and that backward erosion along streamlines may link producers and injectors. Such pipes may act as well “adits” gathering oil from the heated reservoir and contributing to enhanced production rates. Mechanical breakdown of the reservoir by drilling, injection and production processes provides a consistent possible explanation for the sand-cut response of production wells.

Jan 1, 1986

By L. W. Pommier

In the field of minerals processing the concentration of valuable minerals normally takes place in suspensions of ore particles in liquids. The fluid resistance offered by Newtonian liquids to the movement of free settling spheres for the limiting cases of creep flow and turbulent flow is well described by Stokes' and Newton's Laws. However, these equations are not applicable to non-Newtonian fluids, since the relationship between applied shearing stress and resulting rate of shear is a non-linear function, and more than one viscosity parameter is necessary to describe their rheological properties. For this reason, the term "apparent viscosity," which has been commonly used to explain the flow resistance of the non-Newtonian systems including suspensions, may be misleading. A rigorous analysis of the mechanisms of momentum transport of solid-liquid systems is complex indeed. There are many variables that affect the properties of such systems, and precise limitations and assumptions are necessary in order to produce quantitative relationships for predicting their behavior. Very dilute suspensions of spherical particles in Newtonian liquids of identical density as the solids have been examined in the past (12); however, the study of suspensions in which there is a considerable difference in density, between the liquid and the suspended solids has been neglected.

Jan 1, 1968