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By C. D. Kuchera

Ore crushing facilities at the Phelps Dodge Morenci Reduction Works became operational in January of 1942. This plant, with a capacity of 25,000 tons per day, was part of a project started some five years earlier with development of the Morenci Open Pit Copper Mine. In the following year, World War II's heavy copper demands prompted an 80% expansion in concentrating capacity to 45,000 tons per day resulting in a doubling of the secondary crushing plant. In the late 1950s and early 1960s, grinding capacity was again expanded to the present 60,000 TPD. This time the then 20 year old crushing plant was obliged to meet a 20% increase in production demand with no additional equipment. The ore, principally a medium hard monzonite porphyry, is dumped from 40 yard rail cars into an ore pocket over the primary crusher at a rate of approximately one car per minute. The primary crushing flowsheet, Figure 1, has remained essentially unchanged over the years. Equipment consists of a 40 by 16 foot grizzly set on a 40° incline and having 6" openings, a 60" gyratory crusher nomin¬ally set at 62" + 1" on the closed side and two 72" by 38' panfeeders which load crushed ore and grizzly undersize at a rate of 4,000 tons per hour onto a twin 54" belt conveyor system for delivery to the coarse ore bin. Ore is distributed across the bin by two single side discharge tripper cars. Bin capacity is extremely limited at 23,000 tons of which only 12,000 is available or "live".

Jan 1, 1975

By G. J. C. Young

In 1986 the city of Johannesburg celebrates its first century of existence. The fact that the city was founded to exploit the gold deposits which underlaid it, prompts this review of the gold process development in the mining industry of South Africa. Clearly a complete history of, the gold recovery process to date is not called for and it is proposed therefore to outline the most significant developments which have taken place since the middle 1930's, that is to say the last 50 years or so. Prior to this period the industry had seen the development of comminution processes employing cone crushing in closed circuit with vibrating screens followed by grinding in rotating mills and the gradual disappearance of stamp mills. The all sliming process was well established as a viable route and continuous dewatering in thickeners, continuous leaching and filtration were serious rivals for the earlier batch processes. Continuous processes for gravity concentration had also been developed and the recovery of gold from pregnant solutions employed cementation on zinc dust as opposed to shavings. Thus at the beginning of the half century under review the industry had adopted, or started to adopt, many of the processes still accepted as modern practice. However in some areas little change was evident this was especially so in the smelthouse where some thirty more years were to elapse before the hand stoked coal fired calcine and reverbatory furnaces were replaced by more environmentally acceptable electric furnaces. The most significant feature in recent history has been the mining of progressively lower grades of ore and the retreatment of tailings from earlier operations, much of the latter comprising tailings only a decade or even less in age. Notable among these operations are those on the East Rand near Springs in the Transvaal, in the Orange Free State at Welkom and more recently, massive reclamation of tailings close to the city centre itself. The carbon in pulp (CIP) process has been much publicised in recent years and all new plants erected during the 1980's have adopted this route for gold recovery. However the major proportion of tonnage milled in the industry is still subjected to the more traditional process of liquid solids separation by vacuum filtration. The discussion that follows will centre largely on the developments in the traditional process route, which for the sake of completeness is listed below: Comminution Dewatering Leaching Liquid solids separation Gold recovery Smelting

Jan 1, 1985

By Neil D. Donnell, O&apos

Bituminous sands of the Lower Cretaceous McMurray Formation in northern Alberta constitute the ore for the surface mining operation at Syncrude Canada Ltd. These sediments represent a complex succession of fluvial, estuarine and marine depositional environments. Grade prediction is realized through a combination of geological interpretation, computer modeling, and reference to past mining experience. Accurate forecasts of feed grade permit reliable predictions of volumes for removal to meet budgeted synthetic crude oil production. This planning facilitates efficient allocation of mining equipment and resources. The feed grade to the Extraction Plant is monitored at various points along the delivery system.

Jan 1, 1984

By Bernard J. Scheiner, R. J. Wesely, Cy E. Jordan, A. D. Zunkel, Gary M. Wilemon

The U.S. Bureau of Mines has investigated leaching of off-grade western United States phosphate deposits using sulfuric acid (H2SO4) in the presence of methanol. A combination of ore grinding followed by sulfuric acid in methanol leaching extracted over 80 pct of the phosphate. This leaching technique significantly limited the dissolution of iron, aluminum, and magnesium impurities and produced a phosphoric acid that was well within the desired limits for these impurities. The dissolution rate of phosphate rock in the sulfuric acid methanol system was significantly slower than the conventional aqueous sulfuric acid dissolution. Initially dissolution of the phosphate particle was controlled by the amount of surface area available to the sulfuric acid reactant. After about an hour of leaching, phosphate dissolution was slowed almost to a stop, limited by the rate of ion diffusion through the calcium sulfate barrier layer surrounding the unreacted phosphate particle. Consequently, the ore was ground below 38-pm to increase the particle surface area available and improve the overall dissolution kinetics and extraction. In addition, the sulfuric acid was slowly metered into the reactor to prevent any excess heat from the mixing of acid with the methanol from simulating the formation of methyl sulfates. The formation of methyl sulfate ultimately lowered the overall phosphate extraction by exhausting the supply of available sulfate ions for the dissolution reaction. Subsequent evaporation of the methanol from the product acid decomposed the methyl sulfates leaving undesirable sulfate ions in the product acid. Slow acid addition to the reactor provided high phosphate extraction and limited the amount of sulfate in the final product acid.

Jan 1, 1993

By Frank F. Aplan, G. Rinelli

INTRODUCTION Coal is a solid, combustible mineral substance resulting from the degradation and alteration of vegetable matter largely in the absence of air. In this natural process of coalification, some non-combustible mineral matter is always associated with the combustible material. Coal preparation or cleaning is the process of removing this inert mineral matter from the coal. Preparation is highly successful in removing the large fragments of inert material, but is not very effective in removing the fine inorganic mineral matter intimately associated with the coal. Of the 600 million tons of coal produced in the United States every year, approximately one-half is produced by coal cleaning methods (1). The bulk of this tonnage is cleaned by coarse or intermediate gravity preparation methods (5 inches to 28 mesh, Tyler). Fine cleaning, say, -28 mesh, is done by shaking tables, washing cyclones, and flotation, or, until recently, the fines were either incorporated into the clean coal or simply discarded--not infrequently, the latter. In 1972, only 13 million tons of raw coal were cleaned by flotation in the United States, and from this 8.4 million tons of clean coal were produced (1). The percentage of clean coal produced by flotation in Europe (England, West Germany, Poland, U.S.S.R., etc.) is substantially higher. However, coal flotation has grown rapidly in the United States from only a few plants in 1950 to 31 in 1960 (2) and 66 in 1970 (1). Virtually all new preparation plants incorporate flotation into their basic flowsheet. The essential difference between ore and coal flotation is that for ores the entire tonnage is ground to flotation size, whereas for coal

Jan 1, 1976

By Willard C. Lacy

Survival of the mining industry as a viable economic entity in the United States is being seriously threatened by declining grades of ore reserves, rising operational and capital costs, and increased governmental taxes, restrictions, and subsidizing of third world competition. Discovery of major high-grade deposits is becoming increasingly unlikely. International competitiveness of the U.S. deposits will depend upon 'Yankee Ingenuity', innovations in mining methods, metallurgical treatment, and financial arrangements, and a viable national strategy. This will require not only effective management for control of operations, but management that encourages breakthroughs in technology, financing, labor relations, and in public and governmental understanding. The mine geologist and the exploration geologist both have important roles to play in all aspects of this fight for survival of the industry.

Jan 1, 1984

By R. A. Matuszak

U.S. Government sponsored studies proclaim large reductions in surface mine productivity. Consulting studies place a large share of the blame on increased governmental regulatory activities and on inexperienced, improperly train people. Union rules, which allow indescriminate bidding for job openings, seem to be a major factor causing the lack of experience in spite of elaborate training programs.

Jan 1, 1982

By Jay F. Colinet

Coal workers’ pneumoconiosis (CWP), commonly known as black lung, is caused by the inhalation of respirable coal mine dust and is a disabling and potentially fatal lung disease with no cure. Historically, CWP has taken a tremendous human and financial toll on the U.S. coal mining industry. Recent health surveillance data indicate that CWP continues to occur at elevated levels. Respirable coal dust exposure must be controlled to prevent the development of CWP. The Pittsburgh Mining Research Division of the U.S. National Institute for Occupational Safety and Health (NIOSH) conducts laboratory and mine-site research to identify control technologies that can be used to successfully reduce respirable dust levels. Various technologies, using multiple methods of control, can be applied to reduce dust levels. An overview of CWP’s impact and a general methodology for controlling respirable dust in underground coal mines are discussed in this paper.

By Ihsan Berk Tulu, Ted Klemetti, Deniz Tuncay, Cicek Sena, Zhao Haochen

"Analysis of Longwall Pillar Stability (ALPS) and Analysis of Retreat Mine Pillar Stability (ARMPS) treat the pillar as a passive structure that is designed to carry overburden dead-weight. This dead-weight is calculated by simple rules based on the geometry of the mining, such as “tributary area theory,” “pressure arch theory,” and “abutment angle theory.” Although the pressure arch loading approach indirectly accounts for the generally stiffer overburden response of narrow and deep panels, it does not include the effect of specific geology of the overburden in load calculations. The relationship between successful pillar layouts and overburden geology can be incorporated into the load calculation by using the Ground Response Curve (GRC) approach.This paper introduces the GRC modeling methodology to investigate the effect of overburden geology and excavation geometry on load transfer mechanisms using seven field measurement case studies from four U.S. mines. It was also shown that the modeling methodology used to derive GRC in this study approximates mining-induced stresses and deformations within 5% of the values measured in the field.INTRODUCTIONFrith and Reed (2017) stated that current state-of-the-art pillar design methods ignore the overburden mechanics and use estimated dead-weight of overburden to compute pillar sizes. In the United States and around the world, overburden loading is typically estimated by simple geometric rules, generally with the tributary area theory (TAT). The specific overburden mechanics, structural competence of the overburden strata, geology, in situ stresses, and overburden/pillar interactions are typically ignored. However, these important mechanical responses affect the stability of the mine pillars and openings; therefore, they also affect the safety of the mine workers.Research conducted by the National Institute for Occupational Safety and Health (NIOSH) after the Crandall Canyon mine disaster (Esterhuizen, Mark, and Murphy, 2010) showed that small panel width-to-depth ratios and stiff-strong overburden result in a reduction of the observed pillar loads, much smaller than the TAT estimate. In fact, as a response to the Crandall Canyon disaster, Mark (2010) implemented a pressure arch loading approach into the latest ARMPS program to recognize the inherently greater stability of narrow panels at depth. The pressure arch approach is a first logical step to introducing non-tributary area loading into the practical ARMPS program. Although the pressure arch loading indirectly accounts for the generally stiffer overburden response of narrow and deep panels, it does not include the effect of specific geology and mechanical response of overburden in the load calculations."

Jan 1, 2019

By Brandon Barnes, Michael Haggerty

"Around Minneapolis and Saint Paul, Minnesota, the local geology includes the St. Peter Sandstone, which is easily minable and has facilitated construction of interceptor tunnels for storm water and sanitary tunnels since the 1800s. The elevation of the geologic units allowed gravity-driven flows from the downtown areas all the way to the Mississippi River. Through many years of service, some of these tunnels have experienced degradation and require maintenance. Additionally, increased stormwater surface runoff can result in internal pressurization of the tunnels, accelerating degradation. Because structural failure or collapse of any of these interceptor tunnels would create a significant repair challenge, the city of Minneapolis has been inspecting and designating tunnels in its system for periodic review and repair. One of these, the St. Mary’s/Hiawatha tunnel, was rehabilitated using a grouting program. A hydrologic model was also used to improve understanding of pressurization events during some storms, leading to construction of a near-surface pressure dissipation chamber to provide increased hydraulic capacity. BACKGROUND The St. Mary’s/Hiawatha tunnel in Minneapolis has three segments; the first two were constructed in 1942 and the third was added in 1987 (Figure 1). Segment 1 is approximately 4,700 feet in length and outlets to the Mississippi River. Segment 2 intersects Segment 1 approximately 3,500 feet upstream of the river outlet and continues for approximately 2,500 feet in a southeasterly direction. The third and newest segment is approximately 500 feet long. There are four different cross sections of tunnel along the entire system.Originally, tunnel construction often consisted of mining the St. Peter sandstone with a pressurized water lance and constructing wood lagging support (Payne, 1967). An underdrain was generally installed below the invert during construction; this resulted in localized dewatering and provided groundwater control during construction. Non-reinforced concrete liner sections were cast in place. Often void space existed between the tunnel liner and the native sandstone bedrock. These voids, particularly in the crown, prevent direct contact between the liner and the bedrock."

Jan 1, 2016

By Vas Choudhry

The eighties are likely to witness the first commercial-size coal-to-gasoline plant(s) in the U.S., although uncertainty regarding crude prices and cautious involvement of the Federal Government in the synfuels development are evident. The formation of The U.S. Synthetic Fuels Corporation with passage of the Energy Security Act is projected to pave the way for some of the projects on a moderate scale. The corporate objectives (1) are to provide funds for supporting a number of feasibility studies and loan guarantees for the construction of at least some commercial-size plants and the possibility of product price supports or purchase commitments. There are a number of coal conversion processes (2) currently under evaluation for producing either gaseous or liquid plus gaseous fuels, the other processes such as SRC I are for producing desulfurized deashed clean solid fuel for commercial use.

Jan 1, 1982

By X. Cai, L. Jiang, G. Fu

A process for recovering manganese from low-grade manganese oxide ore through a reduction acidolysis-selective leaching method is investigated. Two types of biomass, sawdust and straw, were used as reductants. Reduction acidolysis, using concentrated sulfuric acid, was used to disrupt the structure of the biomass, allowing the biomass to be hydrolyzed into monosaccharides. Analysis by X-ray diffraction revealed that Mn2O3 was reduced to MnSO4. Then, in the selective leaching process, iron was removed through the formation of goethite. The optimized experimental parameters are as follows: reductant to ore mass ratio of 0.4, sulfuric acid to ore mass ratio of 0.9, water to ore ratio of 0.5, aging time of 18 h, leaching temperature of 95 °C, leaching time of 90 min, and solution pH of 2.5 to 2.8. Under these conditions and using sawdust as the reductant, the manganese leaching efficiency and iron removal efficiency were 91.8 and 99.2 percent, respectively.

By Melvin W. Dadd

[One of the major problems in the purchase and sale of coal shipped in lake or ocean going vessels has always been the difficulty in obtaining a true analysis of the shipped coal?s quality because of faulty sampling by manual methods. As long as coal was sampled according to standards set up by ASTM methods designated D 492-48 there generally were no quarrels with the results obtained. However, due to varied weather conditions and because of the large number of cars sampled, there is no assurance that prescribed manual methods of sampling will always be followed. Because of this problem, the organization previously called American Coal Sales Association, now part of the National Coal Association, set up a committee compose of representatives from coal producers, coal shippers and coal consumers to study this sampling problem and to devise, if possible, a means of sampling on the high lift dumpers which could be automated so that a; true sample of the coal as loaded in the railroad car could be obtained.]

Jan 1, 1962

By D. W. Olson

Estimated world production of natural and synthetic industrial diamond was about 630 million carats in 2004. Natural industrial diamond deposits have been found in more than 35 countries, and synthetic industrial diamond is produced in at least 10 countries. About 80 percent of the global output was produced in Ireland, Japan, Russia, South Africa and the United States. Russia and the United States are the world’s leading producers of synthetic industrial diamond. In 2004, the two U.S. synthetic producers, one in Pennsylvania and the other in Ohio, had an estimated output of 250million carats. Also in 2004, nine U.S. firms manufactured polycrystalline diamond (PCD) from synthetic diamond grit and powder.

Jan 1, 2005

By M. L. Smith

The U.S. Bureau of Mines Cost Estimating System (CES) has been used for prefeasibility analysis and mine cost engineering since 1978. In the past, prefeasibility analysis with CES has involved the solution of regression equations. The new generation of CES uses an object-oriented expert system in a Windows? environment. Knowledge bases are structured around generic mine models which access shared knowledge bases for system design.

Jan 1, 1994

By V. C. Rogers, K. K. Nielson

INTRODUCTION An evaluation of the radiological health risks from uranium mining and milling requires the determination of several key parameters. As shown in Figure 1, the first step is the estimation of the radioactive source term. The radionuclides in the ore consist of the 238U decay series nuclides shown in Figure 2, the 235U series nuclides, and 40K. The 238U decay series isotopes dominate the source term, with the 235U series isotopes causing less concern and 40K remaining at background levels. [ ] Specifically, the risks from uranium mining and milling are mainly associated with 230Th, 226Ra, 222Rn, and its short-lived daughters. These radioisotopes are mainly alpha-particle emitters; hence, some dispersion mechanism is necessary to bring them into intimate contact with man so that they can be inhaled or ingested For water pathways, the leaching of the isotopes from [ ] the solid ore or tailings provides a measure of the amount of contaminant initially available to the environment. For the air pathway, dust-creation mechanisms such as blasting, crushing or general resuspension processes dominate for 226Ra and 230Th. However, 222Rn, being a chemically inert gas generated from the decay of 226Ra, can migrate through the ore, overburden and tailings over considerable distances. As shown in Figure 1, the next step in the pathway to man is environmental dilution and delay. For the water transport mechanism, the delay in the isotopes reaching an accessible water supply may be considerable (several thousand years or more), but for airborne nuclides the dispersion in the atmosphere is rapid and constitutes the main mitigating factor. Considerable ventilation is provided in underground mines to dilute and remove radon and its daughters in order to keep their concentrations low and thereby minimize their inhalation by miners. The rate of uptake by both the workers and the general public is often difficult to ascertain. It involves breathing rates, rates of water consumption and other poorly-defined parameters. The final steps are the risk estimators used to predict doses and cancer rates from the inhaled radon daughters and ingested or inhaled radium. Many

Jan 1, 1981

By L. G. Kirk

The Mississippi embayment ball clay region, including western Kentucky, western Tennessee, and northwestern Mississippi, accounted for more than 95% of the total U.S. ball clay production during 1985. Other producing states during the year were Texas and Maryland. The U.S. Bureau of Mines reported total domestic production for 1985 of 910,000 short tons. The United States exports approximately 20% of the annual ball clay production. Geologically, the ball clay deposits are sedimentary in origin and occupy the north- eastern flank of the Mississippi embayment. The commercial deposits have been confined to the Claiborne and Wilcox formations within mid to lower Eocene and upper Paleocene age strata. The deposits are lenticular in nature and highly variable in areal extent and thickness. They exhibit very abrupt lateral boundaries and are bounded laterally and vertically by unconsolidated sands, silts, and waste clays.

Jan 1, 1986

By A. P. Cook

Methane Rating has been developed from a need, in South Africa, for quick and simple measurement of coal face methane characteristics. It employs proven existing direct measurement methods, adapted specifically for rapidly advancing coal face conditions, to deal with the short term high release rates encountered during continuous miner coal cutting. The Rating is a comparative value, relative to the normal or average conditions encountered within a maintained data base. The seam gas content and the initial emission rate are plotted against each other on a graph, where they are compared with the average conditions to obtain the rating. The higher the seam gas content, and the higher the initial methane release rate, then the higher the Methane Rating, on a scale of 1 to 4. Methane being released from a newly mined coal sample is measured once underground, from a sealed gas-tight canister. The sample is returned, still sealed, to surface and milled to rapidly release the remaining methane. It is later intended that the milling process is also completed underground. Applications include the identification of changing methane conditions, outburst prone conditions, methane emission against advance, and mining in devolatilised coal.

Jan 1, 1998

By Kenneth G. Colman

Even though wet processes were used in coal preparation plants prior to 1941, dewatering coal was not a problem then because the finer sizes were uneconomical to recover and were considered waste. However, during the war years the scarcity of raw materials necessitated the utilization of every pound of natural resources and coal plants began seeking an economical mans of recovering fine coal. Early efforts to this end concentrated primarily on centrifugal dewatering devices. Such equipment produced good results but was relatively expensive. In 1944, a method was devised utilizing a vibrating screen fitted with a profile wire deck rather than the standard woven wire cloth deck. This machine came to be referred to as a dewaterizer. Results obtained with the dewaterizer approached those of the centrifugal equipment, but at a lower capital cost, Their use reduced either the number of centrifugal units required to follow the dewaterizers or the required energy input to heat dryers, In some cases they eliminated the need for any further dewatering equipment.

Jan 1, 1970

By Robert H. Raring

Viewed abstractly, a mill may be defined as a mineral processing facility located somewhere between the mine and the tailings storage area, Just how mining operations and the demands of tailings storage affect mill design is, the subject of this paper. At the outset, it will be readily acknowledged that no two installations can, or ever will be the same. At one extreme is the bucket line dredge where the distance between the ?mine? and the tailings area is measured in terms of tens of feet. At the other extreme, the large open pit copper mines are frequently spread across twenty, miles or so of countryside with the ore moving to the mill, as exemplified by the operations at Bingham Canyon, Ray, or Ruth - the "upstream" counterparts of Garfield, Hayden and McGill. In each of these cases, mill location was largely determined by requirements for tailings storage and/or water supply.

Jan 1, 1961