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By S. K. Mukherjee, A. W. Laurito, M. M. Singh, N. I. Jayaraman

This paper describes the application of foam to control respirable dust in a double-drum longwall mining section. The feasibility of injecting an adequate quantity of foam through the shearer drum was initially established in the laboratory. Thereafter, underground testing of the foam system to determine its effectiveness on an active operating longwall was conducted in a mine in West Virginia. The foam system proved superior to the water spray system. The details of the laboratory and field investigations, the results obtained, and the degree of acceptance of this system by the mining company are discussed in this paper.

Jan 1, 1987

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 Roland Heersink, Charles H. Wells

This paper discusses how a mill uses off-site data hosting approach to effectively utilize an entire suite of advanced applications to optimize daily operations, without incurring the overhead of on-site systems, staff and support. Details of the solution are provided, together with a live view of actual plant operations. Security and authentication mechanisms are also outlined so that users may gain an appreciation of the actual security of the remotely hosted data. A number of Web-hosted software applications provide direct connectivity to the database offering rapid and deterministic response times to clients. A 24x7 help-desk is available to authorized users from any Internet connected device. The paper shows how mill management advantageously use wireless PDA's to view what is going on at anytime and from anywhere. It concludes with a summary of how the approach is being used to speed decision-making and capture spot market opportunities.

Jan 1, 2002

By J. Engesser

A research project supported by the Minnesota Department of Natural Resources and the Iron Ore Cooperative Research Committee was undertaken to reduce the dissolution of fluoride into process water during taconite processing. Leach tests were conducted using rod mill feed samples and water containing varying concentrations of calcium and sodium. Laboratory liberation grinds were performed to evaluate fluoride rejection during grinding and magnetic separation. Tube furnace tests were conducted to evaluate fluoride volatilization during pellet induration. The results indicate that fluoride concentration of process water is a function of both calcium and sodium concentration in process water. It appears that less than 1 percent of the fluoride present in rod mill feed will dissolve in process water during grinding. More than 90 percent of the fluoride present in rod mill feed is rejected with tailings during size reduction and magnetic separation. The furnace tests demonstrate that bentonite and fluxstone (calcite and dolomite) addition to taconite concentrate during pellet production increases the amount of fluoride that volatilizes during induration. Lime hydrate addition to pellets decreases the amount of fluoride that volatilizes during pellet induration. During acid pellet production approximately three times more fluoride enters the water during induration-off-gas scrubbing than during grinding. When fluxed pellets are produced three to eight times more fluoride enters the water during off-gas scrubbing than during taconite grinding.

Jan 1, 2004

By L. Piga, G. Belardi, V. Alesse, N. Shehu, J. Freund

The physico-chemical interactions among minerals such as olivine, chromite and serpentine; the most commonly present ions in solution such as Ca and Mg; and flotation reagents such as EDTA and oleic acid were investigated. The study was conducted via release tests, electrophoretic measurements and microflotation of selected minerals coming from the Kukes deposit in Albania. The results were confirmed in beneficiation tests on two ores, one from the Kukes (Kalimash) deposit and the other from the Rizo deposit in Greece. It was demonstrated that, when Na-oleate is used as collector, chromite, olivine and serpentine can be separated at pH 2.5 and/or pH 5.5 when employing ethylenediamine tetraacetate (EDTA) on previously deslimed material. This approach ensures flotation concentrates with a Cr203 content better than 50% with a recovery of more than 75%.

Jan 1, 1998

By E. Topuz, M. J. McPherson, I. M. Konduri

The research is carried out to investigate the flow mechanics and effectiveness of face ventilation using induction fans, as an effort to provide a more efficient alternative to conventional auxiliary duct or brattice ventilation systems. The induction effects and plume longevity of fluid jets are being studied with the help of a plexi-glass model, using water as the fluid medium and creating a system that is dynamically similar to the flow in mine headings. This scaled model represents a typical 1.5m x 6m x 25m heading connecting to a crosscut. Reynolds Number criteria are used to obtain dynamic similarity of the flow in the designed model to simulate real mining conditions. The role of various parameters such as nozzle position in three dimensions, airway roughness, nozzle geometry, and flow rate in the jet are studied. During the laboratory tests, flow visualization techniques, coupled with still and video photography, were employed to identify the flow patterns. The results indicate that in typical coal mine headings, jet fans can produce effective face ventilation for distance up to 30 meters.

Jan 1, 1995

By Y. Nan

A new computer simulation model for the analysis of underground coal mine production systems in the Peoples Republic of China is presented. As a case study the model was used to analyse the railway system of an existing underground coal mine. Some results of this first application are given in this paper and some conclusions of common interest for underground rail haulage systems are discussed.

Jan 1, 1986

By F. F. Aplan, S. Chander, A. R. Alaboyun

Several aspects of the capture of hydrophobic dust particles by droplets in sprays have been studied. The particle capture depends on several sub-processes involving collision, adhesion and engulfment. The collision events between dust particles and a single droplet were observed with a high speed motion analysis system to determine the influence of a surfactant on the capture process. In the adhesive process it was observed that the dust particles are collected at the surface of the water droplet to produce a rigid film at high dust loadings. In the presence of the surfactant, however, the particles were engulfed inside the droplet keeping a fresh surface on the droplet available for capture of more particles. A theoretical analysis is presented to take into account the role of contact angle on the penetration of particles into droplets. A significant increase in collection efficiency was observed with decrease in droplet size.

Jan 1, 1991

By J. M. Dean, R. L. Grayson, R. D. Begley, G. L. Winn

Evidence has accumulated indicating that cultural change toward safer workplace behaviors is beginning to occur systematically in the coal industry. Through a range of programmatic mining company successes, enforcement and litigative actions, economic responses to competition and integrated efforts by federal and state agencies, a broader participation of safety and training professionals is being achieved to address prioritized workplace problems at mines. Small steps in workplace-related improvements have been realized already, but the trends in industry safety statistics, coupled with focused programmatic initiatives, indicate that more definitive and systematic steps are occurring to improve safe behavior in the workplace routinely.

Jan 1, 1998

By Robert G. Moorhead

Fine-coal screening can be one of the most critical operations in a modern coal-cleaning plant. The yield and quality of clean coal produced in fine-coal circuits is controlled as much by how efficiently 0.15 mm (100 mesh) particles are sized as on the performance traits of the fine-coal cleaning device itself. In addition, the increased interest in effective fine-coal sizing operations indicates that many operators have also discovered its importance in affecting the quality and yield of clean coal produced in fine-coal circuits. This paper describes the three most prevalently used fine-coal screening technologies and discusses their sizing mechanism, performance, and application.

Jan 1, 1988

By J. M. Mutmansky, A. Wang

This paper defines the elements of a basic economic model for decision making when considering a methane drainage system for an underground coal mine. A drainage system entails significant capital and operating expense; hence the decision to utilize drainage must be made carefully. The model outlines the basic structure of decision making and considers the costs and benefits when the methane is marketed and when the methane is vented to the atmosphere. The effects on mine safety and the dust levels in the mine are also considered, both in a general format and as economic variables. Sources of information for executing this decision making are provided for an actual mine decision.

Jan 1, 1999

By Palmer C. Sweet

By-products from mining and processing plants and coal-fired power plants are being utilized more as valuable resources in Virginia. Mining-related by- products are divided into two categories: those generated from mineral extraction and beneficiation, and those generated from mineral processing or from industrial plants. Materials from both categories are produced in Virginia, where by-products have been exploited for various uses in the past and/or present. These materials include coal- combustion products (fly ash and bottom ash), lime-kiln dust, flue-gas-desulfurization residue, rock fines, magnetite, Cold Spring clay (kaolin), Austinville tailings, soapstone rock, and calcium-carbonate paste. Some of these by-products have never been utilized, although several ideas have been investigated over the years.

Jan 1, 1999

By R. A. Metz, William H. Breeding

The remarks that follow are based substantially on experience covering 45 years, 80% of which has been in placer work, rather than on a review of available literature. Most commercial placers have been deposited by the action of water. The richer and more difficult-to-mine placers are those in the headwater areas where gradients are steepest. The most lucrative placers are generally in intermediate areas where volumes are greater, fewer boulders are present, and gradients are from 3% to 1-1/2%. The higher volume, lower grade placers are in the lower reaches of river systems where gradients are lower. Where gold-bearing rivers have discharged into the sea, wave action can concentrate values on beaches, past and present. Most of the rich, readily accessible placers were mined by our forefathers. Current opportunities exist: (1) in remote areas where infrastructure has been absent in the past, or development has been prohibited by adverse ownership - political or commercial; (2) in deposits that could not be mined by equipment available to our forefathers; (3) in deposits unidentified by our forefathers; (4) where the-price-of-product/cost ratio is substantially better than in earlier years; or (5) a combination of those factors. When I entered the placer business in the late 1930s, and subsequently, a prevailing opinion believed that glacial deposits should be avoided as irregular in mineral content and composition, and unrewarding to explore and develop; yet an operator has been mining a fluvio-glacial deposit profitably for the past 17 years. Rich buried placer channels, often called paleo-channels were worked in the last century, generally by hand methods, and under conditions that would be unacceptable today. Exploration and mining equipment now available make some of these channels attractive targets. Well-known examples are in California and Australia. The formation of a commercial placer requires a source of valuable minerals. Above primary deposits, there may be eluvial deposits formed by the erosion of gangue minerals and the concentration "in situ" of valuable minerals. Down slope from these deposits are the hillside or colluvial deposits, and below them are the alluvial deposits of redeposited material. Most of the great placer fields of the world are the result of several generations of erosion and deposition. Well-known examples are in California and Colombia. Gold is a very resistant and malleable material, and gold placers may extend for 64 or 80 km (40 or 50 miles) along a river system. Platinum is less malleable, but is very resistant to disintegration. Diamonds are extremely hard, and (especially gem diamonds) may be found over great lengths of a river system. Cassiterite is less resistant to disintegration, and tin placers seldom extend over two miles without resupply from an additional source or sources of mineralizaton. Tungsten minerals are generally more friable, and within a few hundred yards of the source disintegrate to the point that they are uneconomical to recover. Rutile, ilmenite and zircon placers generally result from the weathering of massive deposits, and may be encountered over extensive areas; most are fine grained and durable. What does a geologist or mining engineer look for in placer exploration? The old adage to look for a mine near an existing mine is still valid. You need a source of valuable mineral. Then you require conditions for concentration, which means a satisfactory gradient and/or other conditions that will permit heavy minerals to settle. Nicely riffled gravel, often called a shingling of the bars, is conducive to placer formation. Coarser gravel is logically associated with coarser gold. Excessive clay and/or high stream velocities in narrow channels can carry gold far downstream and distribute it uncommercially over a large area. When material is extremely fine, in situ weathering and concentration become more important. Placers frequently occur distant from lode mines, and one must remember that in a larger watershed the exceptional floods that occur once in a hundred or a thousand years can move great quantities of material long distances. The carrying power of water is said to vary with the fifth or sixth power of its velocity. I am not ready to disagree with Waldemar Lindgren and accept that many commercial placers are substantially enriched by the chemical deposition of gold from solutions; however, I have seen crystalline gold in clayey material quite distant from known sources of primary gold that is dif-

Jan 1, 1992

By J. M. Kruger

High-resolution ground-penetrating radar (GPR) was used to image the near-surface extent of two exposed Late Cretaceous kimberlites intruded into lower Permian limestone and dolomite host rocks in northeast Kansas. Six parallel GPR profiles identify the margin of the Randolph 1 kimberlite by the up-bending and termination of limestone reflectors. Five radially-intersecting GPR profiles identify the elliptical margin of the Randolph 2 kimberlite by the termination of dolomite reflectors near or below the kimberlite's mushroom-shaped cap. These results suggest GPR may augment magnetic methods for the delineation of kimberlites or other forceful intrusions in a layered host rock where thick, conductive soil or shale is not present at the surface.

Jan 1, 1997

By K. A. Natarajan, J. M. Modak, B. Saha

Nonliving waste biomass consisting of Aspergillus niger attached to wheat bran was used as a biosorbent for the removal of copper and zinc from aqueous solutions. Copper and zinc uptake by the biomass obeyed Langmuir isotherms. The binding capacity of the biomass for copper was found to be higher than that for zinc. The metal uptake, expressed in milligrams per grain of biomass, was found to be a function of: •the initial metal concentration (with the uptake decreasing with increasing initial concentration), •the biomass loading (with the uptake decreasing with increasing biomass loading) and •pH (with the uptake increasing with increasing pH in the range of L5 and 6.0). The metal uptake was significantly affected in the presence of a co-ion. The uptake of copper by the biomass decreased in the presence of zinc and vice versa. The decrease in metal uptake was dependent on the concentrations of metals in the two-component aqueous solutions. The effect of copper on zinc uptake was more pronounced than the effect of zinc on copper uptake.

Jan 1, 1997

By J. D. Miller, D. M. Catarious, F. L. Stanley

The quality of cleaned products from coal preparation plants is often variable due to natural fluctuations in the washability characteristics of the plant feed. To combat this problem, many modern plants have installed on-line analyzers that provide feedback for the real-time control of product quality via the adjustment of circuit cutpoints. Unfortunately, optimization studies show that this approach may actually lead to increased losses of saleable coal. This paper discusses the problems associated with the real-time manipulation of circuit cutpoints and suggests alternative modes of operation that are better suited for plant optimization. A case study involving an eastern U.S. coal plant has been used to compare the economic impacts of these different approaches for plantwide control.

Jan 1, 2000

By R. J. Hickson

From 1993 through 1999, Cyprus Amax Minerals successfully completed eight major construction projects around the world. Six greenfield mines were brought into production, an ongoing operation was completely modernized and an environmental issue was appropriately remediated. The projects stretched over three continents: from arctic Russia to the Atacama Desert, from sea level to an elevation of 4,900 m (16,00Oft), from city suburbs to remote wilderness and from a low of US$130 million to more than US$ 1billion. The operations included open-pit and underground mines, mill and leach facilities and involved gold, copper, molybdenum and coal. The diversity of these projects inspired Cyprus Amax to create a "best-practices” project-management protocol to steer corporate expansion in the new millennium. This paper summarizes these best practices, while highlighting the project-management pirfalls to avoid.

Jan 1, 2000

By D. R. Spears, D. A. Stanley

The US Bureau of Mines investigated the fundamental aspects of shear-flocculation using a rapid, in-situ particle size analyzer. Silica was stirred in the presence of an aliphatic amine to determine the effects of collector coverage, stirring speed and solids concentration on the kinetics of shear-flocculation. The results showed that shear flocculation is a two-stage process. In the first stage, which occurs during the first 1-2 min. of the reaction, the mean particle size increases rapidly, and in the second stage, an equilibrium is set up between the rates of floc growth and floc decay. Collector dosage affected the position of the equilibrium by altering the number of surface sites for particle-particle attachment. A minimum stirring speed was necessary for shear flocculation, which was dependent on solids concentration and collector dosage. This stirring speed was the minimum necessary for particles to overcome the electrostatic energy barrier, and that results in keeping the conditioned particles dispersed. Larger particles flocculated more rapidly. At very high stirring speeds, large flocs became unstable, resulting in a narrowed particle size distribution in the slurry.

Jan 1, 1995

By H. Pieterse, K. S. Fraser, J. R. Goode

The Goldstrike autoclave plant is designed for the pressure oxidation of 1363 t/d (1500 stpd) of refractory gold ore. The plant was commissioned in early February 1990 over a one week period - an unusually short period for a plant of this complexity. The rapid plant start-up is attributed to certain detailed design and control aspects of the plant. This paper discusses key features of the autoclave plant with emphasis on the design of the splash/flash system of heat recovery and the control systems. Commissioning and plant operations over the first three months are reviewed.

Jan 1, 1990

By D. M. Fritz

Environmental experts face large and rapidly-increasing volumes of raw data obtained from environmental monitoring stations. These professionals must compile and analyze the data in a systematic manner to cost-effectively understand and minimize the impacts of mining. The shift toward desktop computing, combined with the downsizing of company staffs, has now more than ever created a demand for a modern, PC-based application for the storage, retrieval, analysis and presentation of environmental data. This paper discusses the general requirements of such a system, and points out specific ways in which such industry-specific software can provide convenient and useful access to the data. The software used to illustrate these features is the HydroDat program, developed by Western Water Consultants, Inc.

Jan 1, 1996