Search Documents

By Ulrich O. Lange

Coal is America's most abundant energy resource. Therefore, it IS logical to assume that coal must be produced in much greater quantifies in order to make the United States self-sufficient, as far as energy is concerned by 1985. However, there are a number of obstacles which have to be overcome in order to achieve such a great task. According to one of the most outspoken American Mining men, there are three major obstacles. Those are: (1 ) Mining technology (2) Public image of the coal mining industry (3) Governmental policy toward the mining industry The following will be dealing with Shortwall Mining, which is a very specific part of mining technology and which might influence the image of the coal mining industry as well as the governmental guidelines, at least to make it easier to live with those guidelines. During recent years the operation of coal mines has been more expensive than ever. Since 1970, the cost of producing coal increased by 30% and the productivity dropped by just about the same amount. Those are alarming signs.

Jan 1, 1975

By Kenneth L. Maloney

Ten small and intermediate-sized [11 GJ/hr to 264 GJ/hr (10,000 lb/hr steam to 250,000 lb/hr steam)] coal-fired boilers in the upper Midwest have each been tested on both a bituminous eastern coal and a subbituminous western coal. The purpose of this study was to determine the feasibility of substituting western subbituminous coal for eastern bituminous coal as a means of reducing the SO x emissions from this class of boiler and to demonstrate the feasibility of greatly expanded western coal utilization as a means of reducing the use of oil and gas. The scope of this study was such that the representative boiler types were tested on both eastern and western coal for a period of time sufficient to completely characterize their individual emission and operational characteristics.

Jan 1, 1977

The past decade has seen remarkable progress by the railroads both in equipment and concepts in the handling of dry bulk. materials. While such shipments have always been an important part of the traffic handled by the railroads I little was done to improve the efficiency of handling or toward attempted optimization of equipment design before 1960. Several developments at about that time turned attention to this important segment of railroad traffic. One was the construction of a successful coal slurry pipe-line. Another was the promise of substantial economy in electric power transmission by ultrahigh voltage systems and finally, came the growing technological and economic feasibility of nuclear fuel electric generating plants. Each of these developments was a threat to the coal traffic of the railroads --the most important single commodity they handled in terms of revenue and tonnage. By the mid-1950's I Southern Railway management had become most concerned with its growing investment in freight car equipment and the declining revenue productivity of the capital employed. Additionally I there was substantial concern with the loss of business and potential losses in the area of the railroad's greatest economic advantage --bulk commodity movements. In 1958 a small team was established to study this problem. They arrived at two conclusions. The first conclusion was that within limits of maximum gross allowable weight on rail the lowest unit net capacity cost of investment came at maximum allowable gross weight per car unit. The second conclusion was that with a high degree of utilization costs per weight unit transported could be reduced to the pOint where

Jan 1, 1971

By C. R. Everly

"The purpose of this paper is to review the most effective methods of reducing chloride transfer and chloride removal in the solution extraction and electrowinning (SX/EW) process. Elevated chlorides in electrolyte have various negative effects including a reduction in current efficiency, increased handling costs at rod plants and smelters, increased anode corrosion, cobalt losses due to increased electrolyte bleed, degradation of HDPE piping, and increased corrosion in the SX/EW plants. Historical controls that Sierrita has used to control chloride transfer, in order of effectiveness, have been chloride gasification at the EW that is directly correlated to amperage and chloride concentration in electrolyte, wash stage bleed and efficiency, width and velocity of aqueous bands, and electrolyte bleeds. Maintaining high bleed rates and high amperage settings has been a challenge with decreasing pregnant leach solution (PLS) grades, so keeping chlorides out of the electrolyte has become imperative. The effectiveness of reducing aqueous entrainment, optimizing wash stage efficiencies, and improving organic quality to reduce the transfer of chlorides to the electrolyte are illustrated in this study. INTRODUCTION The transfer of impurities from PLS feed streams to electrolyte in the Copper Solution Extraction process is a very common problem and is the reason that the wash stage exists in most SX operations. The main impurities affecting the SX process are iron, chloride, nitrate, and manganese. Elevated chlorides in the electrolyte have various negative effects including reduced current efficiency, increased handling costs at rod plants and smelters, increased anode corrosion, increased cobalt losses due to increased electrolyte bleed, degradation of HDPE piping, and increased corrosion in the SX/EW plants. Freeport-McMoRan Sierrita Hydromet is unique in that a high-chloride byproduct stream from the molybdenum process is pumped into the SX raffinate solution pond. This byproduct steam accounts for the majority of chloride introduced to the circuit, and over the years has built up to a point where 4000ppm chloride is consistently in the PLS feed to the SX. Concentrations of chloride over 70 ppm in electrolyte will result in downgraded cathode, so it is important to limit chloride carryover from SX as much as possible. Historically, Sierrita has been able to manage chloride levels with reactive techniques including increasing electrolyte bleeds and rectifier amps. Decreasing copper in PLS has made high amps harder to maintain, and increasing bleed rates have a direct impact on production goals."

Jan 1, 2015

By Walter E. Kramer

The advantages derived from the use of pellet burdens in blast furnaces are so great, that hematite ores are being converted into pellets in greater quantities each year. The conversion of these ores into pellets appears on the surface to be relatively simple. In reality, this is not so. Serious difficulties are encountered in drying these pellets that do not exist in the drying of taconite concentrate pellets. The ores that present problems are goethite and earthy hematites. Green pellets prepared from these ores have very law shock temperatures, 200-600° F. The shock temperature of a green pellet according to our definition is the highest initial temperature to which a green pellet may be exposed without suffering decrepitation. Decrepitation may involve spalling, fracturing or total disintegration. The poor shock properties of these green pellets result from the inability of the vaporized water to escape freely and easily as it is formed with¬out affecting the integrity of the pellet. As a consequence, the pellets must be carefully dried prior to induration. This careful treatment is costly. The slow drying process restricts productivity and requires larger furnaces than desired. The use of an additive to elevate the shock temperature of the green pellets would increase productivity. Bentonite is used in some pellet plants to improve balling but it raises the shock temperature only slightly. Nalco became interested in the shock temperature problem because of its activity in the development of organic pelletizing aids for taconite concentrates. The findings reported here are an outgrowth of our experimental work on the development of shock temperature additives.

Jan 1, 1967

By T. Faulkner, S. A. Richards

"The Scale-Distance formula is one of the primary means of determining the maximum amount of explosives that can be safely detonated at one time by a single delay. This paper describes a method of applying the Scale-Distance formula to the entire mining area using gridded surfaces. Using this technique, the operator can better determine the economic impact of nearby structures on the mine plan. INTRODUCTION As the surface mining of coal and stone encroaches near populated areas, precautions must be taken to minimize blast vibration damage to protected structures. The common method employed to minimize vibration damage is not to reduce the total amount of explosive in the hole (which would negatively affect fragmentation), but rather to introduce delays to reduce the amount of explosive detonated at any point in time. The Scale-Distance formula, an industry-accepted standard, may be used to calculate the maximum weight of explosive that can be detonated at one time without damaging the structure. This information may then be used to determine the number of delays required for each hole. Detonators make up a large part of the cost of blasting. At roughly $15 per detonator an additional detonator in the hole can be significant. It is normal to set off hundreds of holes at in one shot. An additional detonator in each hole can cost additional thousands of dollars per shot. The number of detonators is also a function of the depth of the holes and the hole spacing. Being able to accurately forecast the economic impact of blasting near structures improves a company’s ability to make informed decisions on how to approach property owners. Operators basically have three options when dealing with property owners: 1. Buy the property and blast without restriction 2. Negotiate with property owner for a waiver to allow unrestricted blasting 3. Comply with the legal blasting restrictions This paper proposes a method for the engineer to forecast for all points in the proposed mining area the impact of nearby structures upon the blast design. Being able to create a contour map and ultimately estimate the number of delays required for the entire forecasted mining area, the engineer can create accurate economic forecasts of the cost of blasting. The objective is to reduce the level of uncertainty in the forecast of the blast component portion of the forecast."

Jan 1, 2016

Approximately forty years ago, the military services began a realistic investigation of the problems involved with the replacement of high pressure gaseous systems with liquid oxygen systems. The program was temporarily discontinued because of numerous State-of-the-Art problems. Ten years later, interest in the liquid oxygen breathing concept was revived. Initial testing of this concept was completed in 1946. The ensuing years have seen the general acceptance of many cryogenic breathing systems for airborne applications. The inherent features of weight savings (approximately 70%) and space savings (approximately 80%) make it very desirable for high performance military aircraft. A typical aircraft system consists of a storage container with appropriate integrated control valving (the liquid oxygen converter), a heat exchanger, breathing regulator, and oxygen mask. Normally the liquid converter is located in the aircraft wheel well for easy access by ground crew personnel and the breathing regulator is mounted in the cockpit where the pilot can connect his oxygen mask. An aircraft system such as this will provide the pilot with eight hours of breathing oxygen after a 24 hour standby period. Early in 1960, the National Aeronautics and Space Administration sought a means of providing a cooling system for their personnel involved in fueling the rockets used in the space program. While fueling rockets N.A,S.A, personnel wore a completely enclosed butyl rubber suit and were susceptible to heat prostration. Using the concept of an aircraft system, Aro redesigned the container, heat

Jan 1, 1971

By David W. Wisecarver

The U.S. Bureau of Mines, in cooperation with U.S. Borax and Chemical Corporation and the Kennecott Copper Corporation, has investigated the use of the microseismic method to evaluate the stability of large, open-pit slope walls. The method is based on the phenomenon that stressed rock normally emits subaudible rock noises, and the number of rock noises per unit time (noise rate) and the magnitude of the rock noises (amplitude) increase as the stresses in the rock approach the failure stress of the rock. Therefore, the detection and recording of those rock noises serve as a semiquantitative method of predicting the incipient failure of rock. This report briefly describes the three different types of microseismic apparatus, the procedures, and the results of microseismic investigations in the slope walls of the Boron Mine near Boron, California, and the Rimbley, Liberty, and Tripp-Veteran open-pit mines near Ely, Nevada. Microsesimic noise rates in stable inactive mining areas are between 0 and 10 noises/ hour; the rates in stable active mining areas are between 10 and 50 noises/hour; and the rate in unstable areas is as high as 2500 noises/ hour. High microseismic noise rates in the Liberty Pit correlate with the time of nearby earthquakes, indicating that the earthquakes affected the slope wall. The results provide evidence that the microseismic tech¬nique is applicable to large pit walls, and that the wide band, wide range microseismic equipment appears to be suitable for open-pit investigations.

Jan 1, 1969

By K. Bounou, K. Komnitsas

"Risk quantification may be used as a sustainable development index in the mining industry, since it encompasses both economic and social factors. In addition, it may assist in the development of a framework, which is also indirectly related to sustainable development, to prevent accidents and improve health and safety standards. However, risk quantification in the mineral sector involves diverse activities and is considered a very difficult task. Although statistical data report accident severity rates, incident rates and accident frequency rates, none of these allow for accurate risk calculations. In this paper, two risk calculation formulas, which may be used to quantify risk, as well as to identify hazardous activities in a workplace, are proposed. Numerical examples are given based on statistical data available through the MSHA database. Also a combination of a decision/fault/event tree that allows risk quantification is presented."

Jan 1, 2005

By MARK J. VANARELLI

Estimating ground-water inflows in rock deep tunnels is critical to the safety of personnel constructing the tunnel and the cost of construction. This paper presents two case studies, including the Chattahoochee and Nancy Creek tunnels, for estimating steady-state ground-water inflows into deep rock tunnels. Statistical methods were applied to packer test data obtained from exploratory borings during geotechnical site investigations, and a semiempirical procedure was used to estimate ground-water inflows. The Chattahoochee and Nancy Creek tunnels are deep rock tunnels that exhibit radial flow conditions. For the radial flow condition, a statistical analysis presented in this paper indicates that the semiempirical procedure works well; however, variations in the procedure and/or an insufficient amount of testing could lead to underestimations of the inflow quantities. Modeling using Monte Carlo simulations was observed to be an effective tool for removing data distribution irregularities and incorporating high-end permeability data to derive reasonable ground-water inflow estimates.

By George K. McCord

It is a pleasure to participate in this Fall meeting of the Society of Mining Engineers to discuss energy conservation trends in the cement industry. Energy is the "life blood" of American industry, and the ability to use available energy resources efficiently may well determine the future of our nation and of its industries. The Federal Energy Administration has classified cement manufacture as one of several energy-intensive industries in the U.S. and has selected the Portland Cement Association to make a detailed study of possible energy conservation measures. Member companies of the Portland Cement Association represent about 85% of the cement producing capacity of the United States and 100% of Canadian capacity. Stated briefly, the purpose of the Association is to extend the uses of portland cement and concrete through research and development, market promotion, education, and public affairs work. PCA's general offices and research laboratories are located in Skokie, Illinois. Our staff of engineers, scientists, and research personnel make the PCA uniquely qualified to perform an energy conservation study of the kind requested by FEA.

Jan 1, 1975

By T. W. Martin

In 1973 the percentage of total coal production mined by surface methods in the United States again increased, reflecting a long term trend. Barely three decades ago less than 10 percent of the U.S. coal was produced in this manner. Last year surface coal mines produced 299 million tons, 50.7 percent of our nation's coal. At present there are about 2450 strip mines producing coal in 23 states. While accident rates for surface coal mines are less than underground coal mining rates, surface coal mining is certainly one of the more hazardous occupations. Figure 1 shows the injury rates (fatal and non-fatal accidents) of major U.S. industries. Note that surface coal mining is more hazardous than all other industries except contract construction. Accident rates are about the same as the contract construction industry which uses similar equipment. A limited amount of detailed data was available on elements of surface coal mining jobs and this lack of compiled information made it difficult to assess the significance of the conditions contributing to accidents and to make recommendations that would reduce accident frequency. Therefore as part of the Bureau of Mines continuing research efforts related to the health and safety of the coal miner, a contract was awarded to Theodore Barry and Associates of Los Angeles to conduct an "Industrial Engineering Study of Hazards Associated with Surface Coal Mines."

Jan 1, 1974

By E. D. Sehnke

The refractory materials industry provides the largest commercial market for nonmetallurgical grade bauxite. Refractory grade bauxite is prepared from bauxites having low iron, titania, and alkali content by calcining at temperatures near 1,650° C. Although there are substantial bauxite reserves in the world, premium grade bauxite ores suitable for use in refractory applications are limited to only a few specific sources, primarily in Guyana and the People's Republic of China. Consumption of bauxite for refractory use is closely associated with the production and consumption of primary metals, in particular iron and steel. Barring major disruptions within the principal producer nations, sufficient supplies of refractory bauxite will be available to meet world demand well into the next century, and raw material costs will continue to determine the availability of markets for bauxite-based refractory products.

Jan 1, 1992

By Michael J. Shulman

The DEAREX knowledge acquisition and engineering system is a teaching and exploration tool designed to facilitate the under- standing and development of expert systems by explorationists without the aid of a knowledge engineer and without recourse to expert system languages. To fulfill its objective, the DEAREX system considers the selection of exploration methods in desert areas. The system consists of three parts: 1. A tutorial which introduces the basic and selected advanced concepts of expert systems, 2. A sample program illustrating how an expert system works and can be used, and, most importantly, 3. A knowledge acqusition and engineering program which enables users to develop their own expert systems. The tutorial provides a brief and concise introduction to expert systems, a 10 rule exploration example which defines, explains and illustrates the basic concepts and design of expert systems, and a glossary of expert system terms including cross references. The sample program is a larger, self contained example of an expert system with some commentary illustrating addition- al expert system concepts and the role of the knowledge engineer in particularizing rules and ascertaining the knowledge base. Restricting itself to the selection of exploration methods in desert areas, the knowledge acquisition and engineering program questions the user and converts the answers into an expert system. Questions pertain to geology, infrastructure, availability of instrumentation, personnel, etc. Additional information may also included. In conclusion, some salient points concerning knowledge engineering toolkits, shells and knowledge acquisition capabilities such as contained in DEAREX are discussed.

Jan 1, 1992

By L. Clark

Despite near-record commodity prices, the mining industry continues to search for ways to maintain profits in these times of steadily increasing energy prices and steadily decreasing grades. The pressure is still on today’s miners to continuously improve their operations because they know that one day prices too will drop. Some, however, have seized the opportunity to employ systematic methods to reduce costs and increase the efficiency of their workforce and equipment. As a result, closer attention is being paid to scheduling and the value that could be added by defining the extraction sequence that maximizes the net present value [NPV] of a project. This paper will discuss the challenges faced by Newmont Mining Corporation [Newmont] at its operations and the application of sophisticated software tools and methods in its search of solutions to this problem.

Jan 1, 2007

By D. Marsh

The feasibility study for the Grasberg Block Cave mine, finalized in May 2008, indicated a production capacity of 160,000 tonnes per day. A rail haulage system was an integral part of the mine design. This paper describes the simulation process used in optimizing the design and discusses the key factors and variables that impact the capacity of the system. The final recommendations for the haulage level layout and associated equipment are also included.

Jan 1, 2010

By F. J. Susko

The Bureau of Mines applied a flotation model to the hydrodynamics of the Bureau-developed rapid flotation system. Rapid flotation is a process which separates the bubble-particle attachment and froth-pulp separation stages of the flotation sequence into two discrete unit operations allowing the operations to be individually optimized. Both an air-injected hydrocyclone and an in-line mixer were used as the bubble-particle attachment unit and a shallow-depth froth separator was used to separate the ore-laden froth from the pulp. A 10-L/min batch system was tested on a coarse coal feed sample. The system was tested using two different bubble-particle attachment units at various aeration levels in order to test the flotation model. The results of the flotation model reflect general trends observed in the experimental data.

Jan 1, 1993

By G. T. Lineberry, R. S. Mateer

Often only after years of "technical dormancy" do errors in published literature become apparent and meaningful. To prevent duplication of effort for future generations, the fol¬lowing corrections are offered. These errors were discovered during a recent study in which a computer program for mine hoist rope selection was developed (Lineberry and Mateer, 1988). In order of increasing gravity: Captions for Figs. 3 and 4 are transposed. • Purported to be a more accurate method of rope selection than the process of successive approximation, the direct method assumes linearity between a given rope's minimum breaking strength, T, and unit rope weight, Wv. Because of the sensitive location of the constant, K, in equation (8) for breaking strength, the significance of this nonlinearity is magnified. For a typical 6 x 37 class fiber core wire rope (Wire Rope Corp. of America, 1985), K actually varies from 43,650 to 52,190, depending upon rope diameter. Although the direct solution permits a rapid selection of hoist rope, an indirect (iterative) solution procedure is favored because of its im¬proved accuracy and ease of computerization. • Equation (8) for minimum breaking strength is in error. It should read:

Jan 1, 1989

By G. T. Lineberry, R. S. Mateer

Often only after years of "technical dormancy" do errors in published literature become apparent and meaningful. To prevent duplication of effort for future generations, the following corrections are offered. These errors were discovered during a recent study in which a computer program for mine hoist rope selection was developed (Lineberry and Mateer, 1988). In order of increasing gravity: Captions for Figs. 3 and 4 are transposed. Purported to be a more accurate method of rope selection than the process of successive approximation, the direct method assumes linearity between a given rope's minimum breaking strength, T, and unit rope weight, WV. Because of the sensitive location of the constant, K, in equation (8) for breaking strength, the significance of this nonlinearity is magnified. For a typical 6 x 37 class fiber core wire rope (Wire Rope Corp. of America, 1985), K actually varies from 43,650 to 52,190, depending upon rope diameter. Although the direct solution permits a rapid selection of hoist rope, an indirect (iterative) solution procedure is favored because of its improved accuracy and ease of computerization. Equation (8) for minimum breaking strength is in error. It should read:

Jan 1, 1990

By D. Bedell, J. Robitalle, D. Macgilliveray

Agnico Eagle (Cadillac Quebec, Canada) selected the new Eimco PEC E – CAT™ clarifier thickeners for their counter-current decantation circuit, which handles approximately 200tph leached gold/silver ore. The E-CAT is based on rakeless ultra-high rate thickening technology that originated in South Africa. Four 9m diameter and two 10m EIMCO E – CAT ultra high rate, rakeless thickeners were installed in the fall of 2000. Thickening and clarification performance has been excellent. Problems with level control have been resolved and the plant personnel continue to improve the operating control techniques. The CCD circuit is critical to the success of the operation and good recovery. Data will be presented showing the wash ratios and recovery achieved. A brief history of the operation and the decision to utilize the CCD system will be presented.

Jan 1, 2002