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By S. N. Groudev

Intensive uranium mining activities at the Curilo deposit in Bulgaria has caused widespread contamination over a wide area. A number of receptors including soils and watercourses as well as the ecosystems in the area have been severely affected. Even today, 10 years after the cease of activities, acidic waters generated from the abandoned mining works, the low-grade ore and waste dumps contaminate soil, surface- and groundwater. The present paper describes in general the environmental status of the wider Curilo area and examines the potential of preventive and remedial measures that can be applied in situ to rehabilitate the site and restore the ecosystem. The main rehabilitation technologies examined include modification of the acid generation potential of the pollution sources, treatment of the acidic drainage by means of a natural wetland and in situ bioremediation the of contaminated soils. Finally, a number of efficient indicators are proposed so that the rehabilitation potential at Curilo and similar heavily contaminated sites is assessed.

Jan 1, 2003

By J. A. Herbst, A. E. Oblad, Y. C. Lo

The major cost in comminution is energy consumption, which can be as high as 50% of the operating cost. Improvements in plant operations have resulted in up to a 15% reduction in energy usage (kw-hr/t). These improvements have been made through the optimization of grinding efficiency and the use of expert model-based control systems. Optimization involves the determination of the levels of the critical-operating conditions that result in the most efficient breakage of ore in the mill. These optimal levels are identified through plant/laboratory test work and through computer simulation using advanced process models. Model-based expert control achieves the maximum performance from the grinding circuit by identifying the characteristics of the ore in the mill with an optimal on-line estimator. Using this information, the control system dynamically determines the operating point that will yield the optimal performance. Two industrial applications of grinding-circuit optimization and model-based control are presented to demonstrate the power of this new technology.

Jan 1, 1997

By Nancy C. Shaver, Alan Tapp

Leach pads of 272,000 tonnes (300,000 st) and 910,000 tonnes (1,000,000 st) with associated operating ponds have recently been constructed on sidehill locations with up to 20 percent slopes. The larger pad was designed in anticipation of ore heights up to 30 meters (100 feet). This paper describes site investigations and civil engineering design as well as construction experience associated with development of these pads. The leach pads were underlain by a double liner system consisting of 2 mm (80- mil) HDPE over compacted fine-grained tailings, with an intermediate leak detection layer. Both sand and geotextile drainage layers were used. Pad slopes were limited by the factor of safety against sliding on the HDPE liner. The sites for the facilities had been substantially disturbed by prior mining and construction activities. Natural conditions included peat layers and locally swampy ground. Site preparation included french drains to lower the water table and stripping of unsuitable subgrade materials.

Jan 1, 1987

By James R. Aggson, Verne E. Hooker, Dennis R. Dolinar

The stability of underground openings and mining systems is closely related to the in situ stress field. This paper presents a short discussion of the three-component borehole deformation gage and overcoring technique which the Bureau of Mines uses to measure in situ stresses, and a summary of stress data that the Bureau has gathered in the process of evaluating ground control problems. Specific ground control problems and stress distributions are discussed as examples.

Jan 1, 1982

By Stephen Young

The continuous monitoring of free cyanide levels is an important part of gold recovery operations. Accurate and up to the moment knowledge of the free cyanide concentration can result in substantial cost savings by allowing reduced concentra­tions with lower fluctuations, while maintaining or increasing gold recovery. Reduced free cyanide levels also result in lower detoxification costs at the mill discharge which translates into further savings while meeting environmental requirements. As can be seen from the upper curve in Figure 1 (which is based on in-service measurements), without accurate monitoring and control, cyanide concentration fluctuates during the produc­tion cycle, and is maintained at a high level to err on the side of caution. The lower curve illustrates the improved control permitted by the installation of a CY ANCOR, giving a more consistent concentration over the process cycle, and safely allowing use of a lower concentration.

Jan 1, 1995

By P. K. Naik, S. C. Das

Leaching studies of low-grade manganese ore containing 31.77% Mn and 23.71 % Fe from Nishikhal, India, were carried out using pyritiferous lignite as a reductant in sulfuric acid medium. The variables studied were quantity of lignite, sulfuric acid concentration and temperature. Regression equations for the extraction of manganese and potassium were determined from 23 full factorial design data. The experimental conditions for the extraction of manganese were optimized using the steepest-ascent method. It was found that 99.03% of the manganese could be extracted in three hours with an ore to lignite ratio of 1:1.8, a sulfuric acid concentration of 1.9 M and a temperature of 99°C. Key words: Leaching, Manganese ore, Lignite, Statistical design

Jan 1, 2003

In the hierarchy of performing mine planning tasks, production scheduling is naturally at the bottom. Yet good production scheduling is probably the most demanding and difficult task to achieve for various reasons. Being the last task in the mine planning hierarchy, a proper production schedule must not only conform to both the long-range and the short- range mine plans but also satisfy many practical details that are unique to day-to-day operations. For example, the averages which were good enough for both long-range and short- range mine planning are no longer good enough for production scheduling. Instead, the variations become the overriding concern. The answer must also be obtained quickly and on time, thus adding another dimension to the overall problem. Because of these considerations, many production scheduling problems have been begging for solution during the past decade. Many attempts were made to solve the production scheduling problems in the past using computers and the available operations research (OR) techniques, particularly among academic groups. However, it is probably true that, compared with the current full-time computer usage in long-range and short-range mine planning, very little computer usage is being made in production scheduling to date.

Jan 1, 1979

By John A. Bischoff, Francis S. Kendorski

A technique that has been used for inspection and appraisal of rock tunnels is described. It enables a rapid and complete record to be made of those factors necessary for the engineering assessment of the rock conditions surrounding a tunnel. Full understanding of the regional geology, and a careful recording of data concerning the principal geological and construction factors is essential basic data for a tunneling project, whether the tunnel is under construction or is already in service. A methodical recording of data concerning general geology, shears, fracture orientations, spacing, persistence, rock classification, water condition, shear frequency, excavation method, blasting procedure, and rock stabilization and support methods, combined with a photographic record, can be completed by experienced engineers and geologists at the rate of over 1000 feet of tunnel per shift.

Jan 1, 1976

By H. Wesley Peirce

Arizona embraces portions of two major western-U.S. physiographic-geologic provinces and a smaller, local one. These exert fundamental control over the geologic framework and associated earth-material resources and potential. The Mogollon Rim diagonally crosses the State and separates the Colorado Plateau Province to the northeast from the Transition Zone and Basin and Range Province to the southwest. More than 90 percent of the population, production of nonfuel minerals, agricultural land, and water resources are in the Basin and Range part of the State. In 1981 Arizona was ranked number one in the Nation with respect to the value ($2.56 billion) of nonfuel-mineral production. About 8.2 percent of this amount ($212.9 million) can be attributed to nonmetallic (industrial) materials. Although a diversity of nonmetallic substances is produced and some are exported, the bulk is utilized within the State and is directly related to market growth. Since 1950 there has been a fourfold increase in Arizona's population, a concomitant twelvefold jump in sand-gravel production (tons), and a twentyfold increase in "stone" production. New industries developed during this time include cement, salt (and storage of liquid petroleum gas products in solution cavities in salt), zeolite, hydrofrac sand, vitrified clay pipe, crushed marble products (teed additive, pool sand, roofing granules, etc.), and "rock" wool. Most of these newer industries serve out-of-State as well as in-State markets. In 1981 at least 225 industrial mineral or rock deposits were being worked to produce about 10 tons of material per Arizona resident per year. In 1980 the relative values of basic industrial minerals produced in the State, by major group, were cement and lime (51.6 percent); gravel (26.5 percent); sand (11.8 percent); stone (4.6 percent); and others (5.5 percent). Detailed knowledge of the nonmetallic rock-and-mineral content of most Arizona ranges and basins is lacking. Exploration opportunities in this sun-belt growth region appear encouraging.

Jan 1, 1987

By Paul D. Chamberlin

In the author's selenium report of 1994 (1), the literature was culled for selenium removal technologies that had a chance of producing effluents with <10 ppb of total selenium. Very few processes could achieve such low concentrations. The EPA dictates such low concentrations. Discharges to fishery waters must be <5 ppb total selenium. The federal max­imum contaminant level ( MCL) for drinking water is 50 ppb. The EPA regulations are for total selenium, not for the species, perhaps because an approved EPA assay method is atomic absorption and it cannot distinguish between species.

Jan 1, 1996

By Asa Weber

With continuing pressure from stockholders not only to maintain but to increase mineral revenues, producers have increased plant capacity. Depressed mineral prices have accentuated the trend toward higher production rates to maintain consistent cash flow, and these same trends have promoted the development of large-scale processing equipment. In addition to the need to handle increased throughput, larger flotation equipment can result in decreased capital-equipment and operating costs. The development of larger column and conventional flotation equipment relies, in part, on suitable scale-up procedures. To properly scale-up large flotation cells and columns, certain constraints and design parameters must be taken into consideration, including velocities in the vessel, residence time, solids suspension, and lip loading. This paper will review the design constraints and scale-up criteria for WEMCO® flotation cells. Scale-up criteria are augmented with computational-fluid- dynamics analyses and high-speed imaging techniques, as well as multiple regresesion analysis of in-plant operational data.

Jan 1, 1999

By Jacob D. Baker

Sulphur dioxide is a versatile gas which has many uses throughout Pulp & Paper, Chemical, specialty Chemical, Mining and other industries. During recent years, S0 2 consumption and distribution patterns have resulted in renewed interests for liquid S0 2 and on site gaseous S02 manufacturing facilities. one relatively new use for S0 2 in the Mining Industry is its use for cyanide detoxification. Our purpose in this paper is to describe the process steps, economics and general technical features of so 2 gas generation using a Jet Type sulphur Burning System.

Jan 1, 1991

The ever-increasing power (and decreasing cost) of computers has opened up substantial oppor¬tunities for &apos;Vision&apos;-based systems in both on-line and off-line control. This paper reviews image analysis applications in use at the Julius Kruttschnitt Mineral Research Centre (JKMRC) for: •blast and mill feed size monitoring; •AG/SAG mill model-based control; •mineral liberation; and •froth flotation control. The SPLIT™ image analysis system is being used to estimate muck pile and ROM feed sizings. AG/SAG mill feed sizing is being used in a dynamic model for mill control. A new generation mineral liberation analyzer has been developed with Philips Electron Optics. The Philips-JKMRC mineral liberation analyzer offers a substantial improvement in resolution and speed over previous developments. While on-line liberation control continues to be something of a pipe dream, measuring liberation "one shift behind" is now feasible. A robust instrument has been developed to measure flotation froth bubble size and velocity. The instrument also derives a parameter that allows different froth textures to be distinguished. The instrument has been used for on-line control in coal and sulfide flotation. For coal froth, an online ash estimate has been achieved at one site and is being tested at other sites. Overall, image analysis is finding many applications in mineral processing and control.

Jan 1, 2000

By Henry P. Ehrlinger III, Latif Khan, John M. Lytle

The primary purpose of this project was to produce and test coal concentrates made from coal preparation plant waste fines for use in a slurry-fed gasifier. Concentrates from several individual waste streams were examined to determine their amenability as feedstock for a slurry-fed, slagging, entrained-flow gasifier. The tests included analyses of the plant feed and product, material balances, and estimates of gasification reactivity and of pumpability. The following preparation plant fines were examined: • fresh rejects produced in a plant processing underground- mined Springfield Coal • fresh rejects produced in a plant processing underground- mined Herrin Coal • fresh rejects produced in a plant processing surface-mined Springfield Coal and Herrin Coal • Five-year old impounded fines rejected during processing of underground mined Herrin Coal. At high coal recoveries the Btu content of the concentrates was greater than the Btu content of the utility product from the plant. The coal recovered from fines was found to be entirely acceptable for gasification and pumping without additives.

Jan 1, 1995

By R. G. Reddy

Iron solubility&apos;s in spent pickling (HFHNO3 -H2O) solutions were determined as a function of HF and HNO3 acid concentrations. A chemical analysis of the industrial pickling solutions and sludges was performed. The stable phases observed in the sludges are FeF3.3H2O and (FeCr)F3.3H20. Pure Fe metal, AISI 316 stainless steel and AISI 416 stainless steel were used in this study. The results show, that the solubility of Fe increased as the concentrations of HF increased in the pickling solution at a fixed concentration of HNO3. A reasonable agreement between the experimental solubility data and the theoretical calculated data was obtained. X-ray diffraction analysis showed that the solid solubility product formed in the ternary solution containing pure Fe is mainly, at a high pH value, FeO(OH) compounds and, at a low pH value, Fe F3.3H2O compounds.

Jan 1, 1994

By J. H. Tylczak, R. Blickensderfer, D. J. Singleton

As part of its research on wear of mining and mineral processing equipment, the US Bureau of Mines evaluated the erosion-corrosion characteristics of 12 alloys in phosphoric acid waste water. Tests were conducted on 2- and 5-cm-diam specimen8 in 12- and 60-cm-diam ball mills by grinding phosphate rock in gypsum pond water with an initial pH of 1.6. For comparison, grinding tests also were conducted in tap water. Static corrosion tests in gypsum pond water also were carried out. For all alloys tested, the wear by erosion-corrosion was greater than the sum of erosion plus static corrosion. A low-alloy, high-carbon steel and a high-manganese, nitrided stainless steel were the most cost-effective materials

Jan 1, 1987

By R. Velkova, D. Bojinova

The objective of the present investigations is to establish the effect of the preliminary mechanical activation of phosphates on the degree of phosphorus extraction by bioconversion of Bulgarian and Tunisian phosphates using A. niger fungi and T: thiooxidans microorganisms. The influence of the phosphate concentrations, the type of the nutritive medium and the incubation times on the process of biological mobilization of the phosphates was studied. When the concentration of phosphates in the medium is twice as high, an equal and/or higher degree of phosphorus extraction can be achieved through the bioconversion of mechanically activated phosphates compared with non- activated phosphates under similar conditions. A maximum degree of 90+% phosphorus extraction in utilizable form was achieved at definite conditions.

Jan 1, 2002

By R. Q. Honaker

Recent research has shown that enhanced gravity separators provide the opportunity to effectively clean I mm x 37 micron coal. At Southern Illinois University, a detailed experimental program was performed on a continuous Falcon Concentrator, which was found to achieve separations at mass throughput capacity values in excess of 100 tonnes/hour. The apparent particle separation density for I mm x 73 micron coal was about 1.60 with relatively high efficiency (Ep = 0.12). Typical ash and sulfur rejection values of 85% and 70%, respectively, were achieved while recovering 85% of the combustible material. Metallurgical and efficiency data from the evaluation are presented in this publication.

Jan 1, 1998

By G. V. Krishna Roa, G. Vijaya Kumar

One of the main objectives while planning ventilation systems for mines with multiple fans is minimization of the total airpower consumption of the mine. Solution of this problem by conventional ventilation network analysis programs is tedious and time consuming, and may not yield optimum results in all the cases. The paper presents an algorithm for solving multiple fan networks by finding optimum combination of fan operating points for required airflow distribution in the ventilation system.

Jan 1, 1995

By David C. Sanders, Rodney H. Sergent, Victor C. Storhok, Batric Pesic

In the past, considerable work has been done on the applica­bility of bromine chemistry in the extractive metallurgy of gold. While the research in this area spanned from the understanding of fundamental dissolution chemistry to the demonstration on a pilot plant scale, no work was done on the fate of discarded leach residues with respect to the stability of accompanied heavy met­als. Because the leach residues were the discharge products of halide/halogen systems, the general perception was that the con­tained heavy metals would be more susceptible to dissolution than in typical sulfate systems, thus causing increased environ­mental problems. A long-term study was performed to obtain the information on the stability of heavy metals contained in the leaching residues after bromination. The study involved the leach residues of three different ores, as well the precipitates prepared from the synthetic solutions (not presented here). The conclusion of this study is that the stability of solid residues produced by bromination leaching was same as the sta­bility of leach residues produced by leaching in the sulfate sys­tems. Also, contrary to the past expectations, the presence of bromide ions in the test solutions (up to 1 g/L NaBr) did not enhance the solubility of heavy metals (Cu, Zn, Pb, As) beyond the solubilities found in the sulfate systems.

Jan 1, 1998