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By L. Gertsch, R. Gertsch

Mechanical mining is steadily gaining in usage in the mining industry. A variety of machines are now being used, including tunnel boring machines, roadheaders, continuous miners, surface miners and augers. These machines have advantages compared to drill-and-blast mining methods, including increased safety, lower cost, uniform muck size and accurately sized openings. A century of experience with mechanical methods has paid dividends to the coal industry. Current trends guarantee eventual development of true general-purpose hard-rock mechanical mining machines. When several significant challenges have been met, mechanical miners will become integrated mining systems and will determine the design of mines.

Jan 1, 2002

By Y. Wang, E. Forssberg

Wet magnetic separation methods for the recovery of hematite and chromite fines and ultrafines were investigated. These methods included wet high-intensity and high-gradient magnetic separation, carrier or "piggy-hack" magnetic separation, magnetic field-induced aggregation and magnetic seeding. This investigation indicated that wet magnetic separation is more efficient for fines and ultrafines. This investigation also indicated that other methods can be used to enhance the particle aggregation and/or the magnetic response. The magnetic behavior of these minerals with respect to the magnetizing field, temperature and particle size is also presented.

Jan 1, 1995

By C. D. Harrison, G. S. Stallard

The 199O Clean Air Act Amendments specify national objectives for reducing sulfur dioxide emissions from coal fired power plants. System-wide reductions can be achieved by combining various emissions control technologies and allowances, or compliance credits, that can be purchased, sold or traded. As part of the Coal Quality Expert development project funded by the US Department of Energy and the Electric Power Research Institute (EPRI), Black & Veatch has developed an interactive computer tool, the Acid Rain Advisor (ARA). Through this program, integrated, system-wide compliance plans are generated by comparing the costs and emissions reduction benefits of emissions allowances and various SO2-control technologies (coal cleaning, fuel switching, scrubber retrofits, etc.)

Jan 1, 1993

By G. T. Adel, W. Z. Choi

A model describing size reduction and mineral liberation during grinding has been extended to include multiple classes of composite particles. The majority of the model parameters have been directly determined using computerized image processing equipment to analyze the products from batch grinding tests. A coarse-grained sphalerite ore from Tennessee, representing a nearly ideal binary mixture of sphulerite and dolomite, has been used to experimentally validate the model for the case of dry batch grinding. In all cases, excellent agreement has been observed between the model predictions and the experimental results.

Jan 1, 1988

By H. M. von Seebach, M. P. Trubeljal, L. G. Austin

Six US coals and a crystalline quartz were tested in an instrumented laboratory high-pressure grinding rolls machine equipped with 100-mm-diam. rolls. The machine was choke-fed to maximize the capacity. As expected, the specific capacity decreased with increased grinding pressure for each material tested. Among the six coals, there were significant differences in the critical angle of nip, the effective feed porosity and the variation of strain at the gap relative to the grinding pressure. Although a precise correlation was not obtained, the overall effect of these factors was that, at a given grinding pressure, the specific capacity increased as the Hardgrove grindability index of the coal increased. The relationship between the specific capacity and the grinding pressure for a given coal was independent of feed size down to 150 µm. However, smaller feed sizes produced anomalous results, and the flow within the feed hopper was restricted.

Jan 1, 1996

By R. W. Smith, M. C. Fuerstenau, G. X. Xang

Nonliving dried water hyacinth (Eichhornia crassipes (Mart.) Solms) roots were investigated for the biosorption of cadmium, lead and other heavy metal ions from aqueous solutions. Dried water hyacinth roots, when suspended in solution, strongly and rapidly sorb several different metal ions. Factorssuch as reaction time, pH, the initial concentration of metal ions, the presence of other metal ions and biomass concentration were investigated. The adsorption was shown to follow the generalized Langmuir adsorption equation. The relative affinity of the roots for lead is greater than that for cadmium. The batch sorption kinetics of the uptake of cadmium and lead can be described by an apparent first-order reversible reaction model. The roots could be regenerated after the metal ions were stripped. Successful desorption of Cd and Pb from the biomass by acidic CaCl2 solutions revealed that the metal uptake phenomenon is reversible, implying physical sorption of Cd and Pb.

Jan 1, 2000

By William H. Pomroy, Annie M. Carigiet

This U.S. Bureau of Mines report is an analysis of underground coal mine fire incidents occurring in the United States during the 15 years from 1978 through 1992. The fire data used in this analysis were obtained from Federal Mine Safety and Health Administration (MSHA) mine fire investigation reports. Fires were analyzed by year, state, coal bed thickness, mining method, evacuation measures taken, ignition source, burning substance, location, equipment involved, detection method, time of day, number of injuries and fatalities, and method of extinguishment. In all, 164 fires are reported, or an average of 10.8fires per year. The most common ignition source was electricity, the most common burning substance was coal, the most frequent fire location was the belt entry, belt conveyors were the most common equipment involved in fires, and water was the most common extinguishing agent.

Jan 1, 1995

By A. I. Makhin, S. M. Sablukov, V. K. Sobolev, V. A. Larchenko, V. S. Shchukin

The kimberlites of northern Europe are related with a large crustal block having a northwest-southeast orientation. Kimberlites penetrate the Archean formations of crystalline basement, Late Proterozoic rocks, which are overlapped by Middle Carboniferous and younger deposits. The kimberlites bodies include pipes, dikes and sills of Upper Devonian age. Within the region, rocks of two magmatic series form diamond-bearing kimberlites. Aluminum rocks form a new type of diamond-bearing rock that is not found in other diamond provinces. Kimberlites of this region are characterized by highly developed deuteric alterations, a low content of associate minerals, the presence of two diamond generations and an increased content of jewelry-grade diamonds.

Jan 1, 1997

By G. T. Adel

Hindered-bed separators are often used in the minerals processing industry to classify particles according to size and density. A new technology, known as the Eriez CrossFlow, was recently developed to overcome some of the limitations associated with hydraulic separators. The innovative feature of this unit is a novel feed presentation system that improves separation efficiency and capacity. In the present work, a detailed process engineering evaluation was conducted to determine the basis for the improved performance of this unit. The evaluation included controlled separation tests using well-characterized feeds, particle and liquid tracer experiments and mathematical modeling studies. Data obtained from this work show that the new separator is capable of maintaining good separation efficiencies at higher solid feed rates than traditional designs due to improved hydrodynamics in the separation zone. This paper reviews the operating principle of the Eriez CrossFlow separator, discusses the results of the tracer experiments and modeling studies and presents test data obtained from recent laboratory and plant trials. Key words: Size classification, CrossFlow separator, Hindered-bed separator, Hydraulic separator

Jan 1, 2003

By Lit-Mian Chan, David H. Carlson, John H. Johnson

This paper presents an apparatus and procedures to implement a methodology for controlling ambient air quality in a confined working environment, such as an underground mine, an underground storage area, or a tunnel. The air quality control methodology is directed at limiting the quantities of exhaust pollutants emitted by diesel-powered vehicles into the confined space by identifying vehicles that are excessive polluters. The methodology is based on tailpipe and ambient air measurements in the confined space, and the ambient air threshold limit values (TLVs) for the various diesel exhaust pollutants. The methodology consists of two computational methods; a deterioration criteria computational method to identify excessive polluting vehicles, and an engine performance computational method to determine engine performance and to provide information needed to diagnose engine faults. The methodology is designed for implementation in conjunction with a preventive maintenance program. The first part of the paper describes the mine air and tailpipe emissions measurement apparatus and techniques used to obtain data. This is followed by sections discussing the deterioration criteria and the engine performance computational methods. A section discussing some common engine emissions-related faults is also presented. Lastly, a proposed procedure to implement the methodology including a possible hierarchical structure for mine personnel involved to implement the procedures is presented.

Jan 1, 1993

The Peruvian mining industry has seen an explosion of foreign investment since President Albert? Fujimori's government was first elected in 1990. Since then, Peru has taken some large steps toward recovery, making it the envy of most other developing countries. A measure of political stability was gained in 1992 when Shining Path leader Abimael Guzman was captured. In addition, the country has taken on a huge privatization program, rewritten its foreign investment laws and has reined in its annual inflation rate from 1,700% in 1990 to about 8% by late 1997. Small wonder then that attendance at the XXIII Peruvian Institute of Mining Engineers conference reached a record level, many of whom are employed by some of the world's largest mining companies. About 2,700 mining industry professionals from all over the world attended the week-long event, held in late September in Arequipa. That was an increase from 1995s 1,600 attendees, that meeting also held in Arequipa.

Jan 1, 1998

By Ross D. Lawrence

Suggestions have been made that the appraisal of mining assets using discounted cash flow techniques should be based solely on proven and probable reserves in reliance upon the widespread international recognition of uniform resource definitions. Following a review of generally accepted valuation principles, a survey of the literature and, most importantly, a review of real transactions in the open market, it is clear that valuators should not be constrained by the growing acceptance of modern mineral resource codes. On the contrary, valuation practitioners should be encouraged to examine all classes of mineralization and, after making due allowance for risk, to utilize all mineral resources as a basis for determining fair market value.

Jan 1, 2002

By Roger J. Hornberger, Paul F. Ziemkiewicz, Dirk J. A. vanZyl, Gene E. Krueger, Harry H. Posey, Kim A. Lapakko, Charles H. Buckmam

The Acid Drainage Technology Initiative (ADTI) was initiated in 1995 by federal agencies, the National Mining Association and the Interstate Mining Compact Commission to identify, evaluate and develop cost- effective and practical acid drainage technologies. In 1999 ADTI was expanded through the addition of the metal mining sector group, which began organization efforts in 1998. ADTI addresses drainage quality issues involving metal mining and related metallurgical operations and acid drainage from coal mines, for abandoned, active, and future mines. ADTI is a technology development program. It is not a regulatory or policy development program. The guiding principle of ADTI is to build a consensus among industry, federal and state regulatory agencies. ADTI is focusing these efforts on technology development and technology transfer in the areas of mine drainage sampling/monitoring, prediction, avoidance/remediation and modeling.

Jan 1, 2000

By D. R. Maneval

The vast coal resources of North Slope, Alaska, can be expected to attract substantial interest because the nearly flat-lying coal beds of the coastal plain are specially amenable to surface mining. Mining on a scale large enough to justify coal development in this area could have severe environmental effects. The mitigation would be uncertain because large-scale coal mining and reclamation operations have not been carried out in the arctic. The deficiency of the scientific data base is another factor that requires consideration if coal mining has to develop in accordance with the objectives of PL 95-87. The objective of this paper is to establish the inter-relationship between the problems due to permafrost and factors in reclamation of post-mining land in order to find ways to transform nature in a rational and purposeful manner and to suggest specific reclamation approaches that may be appropriate in this region.

Jan 1, 1987

By Alva L. Kuestemeyer, Randall J. Scott

INTRODUCTION Pincock, Allen & Bolt, Inc. (PAH) has developed a series of cost models for Western U.S. Gold Mines. The models indicate the economic potential of developing gold properties at various production rates and ore grades. Various combinations of mining and processing methods are also analyzed. The conclusions shown in this paper are taken from PAH's 600 page study titled, "Capital and Operating Cost Models for Western U.S. Gold Mines." PAH decided to develop the cost manual as a result of our perception of the industry's need for such a document. It was our impression that exploration development decisions were being made on the basis of limited economic information. PAH has compiled a substantial database on unit cost information. That database and the engineering capabilities of the firm allowed us to develop a reasonably detailed analysis of capital and operating costs and overall development economics. The study has developed a series of algorithms for underground and open pit mining, processing, G&A, and infrastructure costs. The capital and operating cost data served as a basis for performing after tax discounted cash flow analysis for the various development alternatives. For the base case scenarios, a 15% DCFROR was assumed and the required ore grade was back calculated using the computer. The ore grade versus production rate graphs summarize the economics of developing gold projects in the Western U.S.

Jan 1, 1987

By Steven F. Hoerger

Newmont Gold Company is the largest producer of gold in North America. Accurate resource estimates are critical to planning the mining in a year of over 90,000,000 t (100,000,000 tons) of mill, leach and waste grade material, from which over 47 t (1,500,000 oz) of gold are recovered. Resource estimates are updated frequently to take advantage of new drilling, improved geologic understanding and additional production reconciliations. At Newmont Gold, indicator kriging is the primary method being used to create resource estimates. Indicator kriging (IK) is a well accepted method of resource estimation; however, many details of the IK process which are critical to producing a useful resource estimate have not been well documented. An IK model must have several characteristics in order to be a useful resource estimate: the model must take into account geologic features of the mineralization; model creation cannot require too .much time; the model must accurately reflect the effects of selective mining; the model must be stored in an easily accessible format; and the model must be useable with a variety of cutoff grades. This paper will show how Newmont Gold implements the IK process in order to achieve these goals.

Jan 1, 1992

By L. E. Krys, K. D. Harrison, C. G. Anderson

Since 1984, nitrogen-species catalyzed pressure leaching has been utilized at Sunshine Mining and Refining Company for the recovery of precious metals from a refractory sulfide concentrate. The process operates without the use of cyanide. The plant is now the only industrial-scale commercial application of this technology. Since the inception of the process, changes have been implemented to improve efficiencies and throughputs. Two of these changes, the replacement of nitric acid by sodium nitrite and a concentrate regrind, have recently been implemented. This paper discusses the development and potential mechanisms involved in these recently patented plant-process changes. A companion publication (Anderson et al., 1996) covers the plant integration and potential applicability of the technology.

Jan 1, 1997

By Lars Söderberg, Eric Sandström, Per G. Broman

INTRODUCTION Boliden Mineral AB currently mines sulfide ores in 18 mines and processes them in eight concentrators. Most ores are typically complex. Gold consti¬tutes a considerable part of the value of the ore reserves. The value of total production in 1984, distributed by different metals is shown in the pie chart below. Traditionally, gold has been recovered as a byproduct, or coproduct, along with silver in floated copper and lead concen¬trates. Gold-price trends over the past decade have prompted comprehensive efforts by Boliden to increase the recovery of gold in concentration processes. Gravimetric recovery of gold in the grinding circuit is one method that has led to quick results. This method supplements tradi¬tional recovery processes based on flotation. The development of a feasible circuit, and the results obtained by its application in the central concentrator at Boliden, in the northern Swedish province of Västerbotten, are reported below. GOLD MINERALOGY IN BOLIDEN ORES The gold content in Boliden Mineral's ores is primarily in the form of alloys with the elements silver and mercury. A minor quantity appears in an unalloyed form.

Jan 1, 1986

By Agne Rustan

Most of the mines in Sweden are metal ore mines in hard rock and none of these mines are classed gassy because there is no methane emission. The risk of methane explosions in Swedish mines is therefore very small. Since the 1960?s, in Swedish mines, there has been a change from electric and pneumatic loaders and transport machines to diesel. Today in almost all Swedish underground mines diesels are used. One of the most common complaint from the underground mine- workers is the exhaust gases from the diesel-vehicles. This is a strong motive for attempts to assure a more comfortable environment. Another motive for a better efficiency of ventilation under ground is the increasing cost of energy for fans and for heating the air during winter. For the largest mine in Sweden, the Kiirunavaara Mine, 36% of the energy for ventilation is used for preheating the air during the seven months when the temperature is below zero. The air quantities used for ventilation are large. In table 1 a comparison of the ratio between yearly produced ore and waste rock and installed fresh 'air capacity is shown. [ ]

Jan 1, 1980

By Michael L. Nave

Belt Conveyors are an important method for transportation of bulk materials in the mining industry. The control of the application of the starting torque from the belt drive system to the belt fabric affects the performance, life cost, and reliability of the conveyor. This paper examines applications of each starting method within the coal mining industry.

Jan 1, 1993