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By C. A. Oestreicher

For sulfide minerals, the presence of dissolved oxygen in the water phase is an influencing factor for separation by flotation. Klassen and Mokrousov(I:217l distinguish three stages of oxygen adsorption; namely, reversible adsorption, activated adsorption and, finally, surface oxidation. While contraversial, limited adsorption of oxygen is believed to improve the interfacial reactivity between collector and mineral. Intensive surface oxidation of sulfide minerals usually results in unsatisfactory flotation with collectors of the xanthate type. The influence of dissolved oxygen in the water phase has received consideration for sphalerite, galena, chalcopyrite, arsenopyrite, chalcocite, and covellite(2,3,4,5,6). However, the nature of surface oxidation products of sulfide minerals has received very limited investigation(6,7). Lightly oxidized galena promotes the adsorptive reaction of surfactant (xanthate or dixanthogen). Tolun and Kitchener(8) state that limited interaction occurs between galena and xanthate under relatively reducing conditions. And, that exposure to oxygen raises the electrochemical potential of the galena to that required for reaction with xanthate or dixanthogen. In the latter condition, the galena has an "effective flotation surface". On the other hand, intensive oxidation of galena reduces the chemical reaction with xanthate collectors (9) . Complete flotation with xanthate-type surfactants with increasing oxygen content in the water phase has been determined to have the following sulfide mineral sequence(3): galena, pyrite, sphalerite, chalcopyrite, pyrrhotite and arseno-pyrite. The work of Cusack(4) suggests that some threshold amount of oxygen is necessary for flotation to occur, but heavy oxidation hinders flotation with xanthates. According to Tolun and Kitchener(8) catalytic oxidation of xanthate to dixanthogen occurs. From infrared studies, Poling and Leja(IO,II) found that in the absence of oxygen in solution, xanthate ions do not adsorb either on

Jan 1, 1972

By E. J. Karges

The use of pulverized coal for generating power and performing industrial processes has made an important contribution to our industrial economy during the past half century. Actually, the burning of coal in powdered form is a subject that has held the attention of engineers for a century or longer. Its widespread use, however, is comparatively recent, As early as 1866 patents were granted to Messrs. Whelpley and Storer for a method of feeding pulverized coal into a furnace as an auxiliary to the grate fuel. In the many tests made during the subsequent years with various kinds of apparatus, the experimenters were handicapped in not getting the coal fine enough to obtain complete combustion and to prevent excessive formation of slag.

Jan 1, 1965

By E. R. Bauer

In response to the mandates in the MINER Act of 2006, the National Institute for Occupational Safety and Health (NIOSH) conducted refuge alternatives research that included characterizing the utility, practicality and survivability of refuge chambers and outby safe havens. NIOSH also prepared and delivered a report to Congress in late December 2007 that summarized the findings of the re-search, included recommendations concerning the design and performance specifications for refuge alternatives, and focused on specific information that could inform the regulatory process on refuge alternatives. This paper highlights NIOSH?s research and recommendations concerning refuge alternatives, survivability evaluations of refuge chambers and presents a brief review of the current deployment of refuge chambers in underground coal mines in the U.S. The research has lead to the conclusion that refuge alternatives have the potential for saving the lives of mine workers if they are part of a comprehensive escape and rescue plan and if appropriate training is provided.

Jan 1, 2009

By J. F. Burr, D. P. Snyder, G. W. Luxbacher

"The Mine Improvement and New Emergency Response Act (MINER Act) of 2006 (PL 109-236, 2006) established the Office of Mine Safety and Health, functioning as the Office of Mine Safety and Health Research (OMSHR) within the National Institute for Occupational Safety and Health (NIOSH) and provided authority for awarding contracts related to the development and implementation of new mine technology and equipment. The OMSHR external contracts program was formed in accordance with the MINER Act and has since issued more than 150 contracts focused on worker health and safety. Initial funding for this program was provided by the United States Congress through two emergency supplemental appropriations and was focused on emergency oxygen supply, communications and tracking, and refuge chambers (also referred to as refuge alternatives). Since the MINER Act, Congress has continued to fund the program through the annual NIOSH mining appropriation. The program was supplemented starting in 2009 with an academic capacity building program directed toward developing university tenure-track faculty and facilities and supporting graduate students in the area of mine ventilation. Ground control was added as an additional focus area in 2011. A short synopsis of each contract is published on the NIOSH Mining website (www.cdc.gov/niosh/ mining/researchprogram/contracts/index.html) and final reports are available in digital form on request. A summary of the progress OMSHR has made over the 10-year period since the Act was published previously (Snyder et al., 2016).External contracts are broadly classified by the following areas:• Communications and tracking.• Emergency response.o Self-escape and breathing air supply.o Refuge alternatives.o Escape and rescue.• Equipment safety.• Fires and explosions.• Ground control.• Mine environmental systems (mine ventilation and atmospheric monitoring).• Worker/workplace health and safety.Contracts are issued under a request for proposal (RFP), through a broad agency announcement (BAA) or under an interagency agreement (IAA). An RFP solicitation includes a specific problem description and a well-defined scope of work to guide the offeror in preparing a bid to conduct the research. Under the BAA several problem areas are described and the offeror develops the scope of work and deliverables for the proposed research. An IAA is very similar to an RFP except it is a contract between two federal government agencies."

Jan 10, 2018

By M. R. Shahan, C. E. Seaman, S. E. Mischler, T. W. Beck

"Float dust deposits in coal mine return airways pose a risk in the event of a methane ignition. Controlling airborne dust prior to deposition in the return would make current rock dusting practices more effective and reduce risks of coal dust-fueled explosions. The goal of this NIOSH study is to determine the potential of open-air water sprays to reduce concentrations of airborne float coal dust (<75 µm diameter) in longwall face airstreams. This study evaluated unconfined water sprays in a featureless tunnel ventilated at a typical longwall face velocity. Experiments were conducted for two nozzle orientations and two water pressures for hollow cone, full cone, flat fan, air atomizing, and hydraulic atomizing spray nozzles. Gravimetric samples show that airborne float dust removal efficiencies averaged 19.6 percent for all sprays under all conditions. The results indicate that the preferred spray nozzle is operated at high fluid pressures to produce smaller droplets and move more air. These findings can be used to select sprays and design spray arrays to control airborne float dust over the entire longwall ventilated opening. INTRODUCTION Coal mining processes produce airborne dust that naturally deposits on the floor, roof, and ribs of mine airways. These fine dust particles, termed float coal dust when smaller than 75 microns in diameter, are deposited in return entries of coal mines and can be re-entrained by pressure waves induced by methane-air explosions (Rice et al., 1911; Nagy, 1981; NIOSH, 2006). These particles are also those most likely to participate in coal dust-fueled explosions, which can potentiate and propagate explosions resulting in extensive damage. In order to meet compliance requirements of at least 80 percent incombustible content in the composition of material deposited in mine entries (CFR, 2016), coal mines apply an inerting agent, specifically, rock dust (Harris et al., 2009). Should methane be present in the mine atmosphere, the required fraction of incombustible content is further increased by 0.4 percent for each 0.1 percent methane. The removal of airborne float coal dust (AFCD) prior to deposition is an approach intended to make current rock dusting practices more effective by increasing the proportion of inert material to combustible material, resulting in a lower risk of coal dust-fueled explosions. Water sprays are both effective and widely accepted as a method for controlling underground coal mine dust. In fact, water sprays are considered to be the most economical and technically feasible means of reducing dust concentrations in underground coal mines (Courtney and Cheng, 1977; Barker and Humphreys, 1996). Sprays are used in several ways to control dust in mining processes: inhibiting dust formation, immobilizing dust to prevent it from becoming airborne, and capturing airborne dust (Cheng, 1973). Reductions in airborne dust concentrations have frequently been attributed to inertial impaction between water droplets and dust particles, forming larger agglomerates which then quickly precipitate out of the airstream (McPherson, 1993). Inertial impaction activity is generally accepted as the major capture mechanism for airborne particles larger than 0.5 µm in diameter. It is this mechanism that is evaluated in this study."

Jan 1, 2017

By Jan Wolf

The iron ore industry presently utilizes two types of de-posits. The first are the high grade deposits generally located in remote areas and, secondly, the low grade de-posits which are normally found nearer to the steel-making centers. The high grade deposits produce a direct shipping ore which has an iron content which may be close to the maxi-mum 70% of Fe. These deposits have reserves which are ex-pressed in billions of tons. The ore needs little or no up-grading and where this is performed is restricted to ore washing. With the large demand for iron ore pellets, plus a national drive to perform as much of the upgrading as possible in the native country, there is a trend to erecting pellet plants at the mine location~ Large iron ore suppliers such as Australia, Brazil, Venezuela and Liberia already have pellet plants in operation, and there are new plants projected or expansion projects under study. The low grade ores are mined at locations closer to steel mills such as in Minnesota, Michigan and Canada. These low grade ores require methods of beneficiation to obtain a commercially accept-able product with the modern beneficiation techniques it is no~, possible to produce iron ore pellets of 68% Fe and 4.5% silica from ores containing as low as 26% Fe. Figure 1 gives a general picture of the types of iron ores and their beneficiation. The final product of the high grade ore is a coarse concentrate, sinter product or pellets. The final product of the low grade ores is pellets and, in some cases, coarse concentrates.

Jan 1, 1971

By J. A. Luppens

Five years ago, Phillips Coal Company decided replacing mainframe/workstation programs with a new package of PC software was clearly the best solution for computer reserve modelling. The system chosen was actually three programs distinguished by their power, cost, flexibility and integration, and ease of learning and use. Phase I involves the use of the "StratiFact" program for borehole data management and seam correlation. This phase is probably the most neglected, yet critical aspect of reserve evaluation. Phase II employs the "PC/Cores" package for modelling and volumetrics. Phase m is "PC-Cut" which provides mine planning tools including an automated cut generator.

Jan 1, 1996

By Paul D. Tomlingson

The difficult and often harsh working environment of the mining industry can stress both personnel and equipment to the extreme. Often, the unintended consequences of this environment lead to confrontations between departments, as each goes about its tasks of mining, maintaining or supporting these activities. On occasion, the confrontations may result in criticism of other departments for perceived or real sins or omissions. The offended department may not be able to change the circumstances, but can only complain while frustration persists. The most effective solutions are the actions of the mine manager. By establishing mutually supporting roles of each department and specifying conditions for the interactive conduct of maintenance, the mine manager can better assure that the inherent problems of the mining environment are neutralized.

Jan 1, 2011

By C. K. Arthur, N. K. Dumakor-Dupey, B. A. Kansake, F. A. Kaba

Autonomous mining systems have been deployed for improving mine performance. However, there is a fear of job losses. Adoption of autonomous systems is envisaged to be resisted by major stakeholders in Ghana due to high illiteracy and unemployment. This paper assesses the preparedness of Ghanaian mining stakeholders for the adoption of autonomous systems to Ghana’s surface mining industry. Closed and open-ended questionnaires were administered to mine stakeholders. Respondents generally expressed unwillingness to accept autonomous systems into Ghanaian mines due to fear of increased unemployment. We propose setting up a mining education fund (MEF) for training stakeholders in autonomous mining systems. INTRODUCTION Mining contributes enormously to the sustenance and growth of global and national economies through the provision of raw materials, employment, revenues and foreign exchange (Carvalho, 2017; ICMM, 2017; Cordes et al., 2016; Solomon et al., 2008; Walser, 2000). The International Council on Mining & Metals (ICMM, 2014) reported that globally, formal mining employs approximately 2.5 million people. Many resource-rich countries, especially the developing ones, have experienced strong socioeconomic growth propelled by the discovery and extraction of valuable minerals. McMahon and Moreira (2014) reported a positive linkage between mining and sustainable development. They revealed that averagely, resource-rich countries have improved Human Development Index (HDI) scores than countries without mineral resources. Mining remains a crucial industry in Ghana’s economic development (Bermúdez-Lugo, 2016; Amponsah-Tawiah and Dartey-Baah, 2011). Over the years, mining has contributed significantly to the gross domestic product (GDP) of Ghana. In 2013, mining accounted for 1.7% of Ghana’s GDP and about 19% of government revenues (Ghana Chamber of Mines, 2015). The Ghana Chamber of Mines also reported that mining contributed over 50% of foreign direct investment, 37% of export earnings and 1.1% of direct employment revenues. The US Department of Energy (DOE) estimates that 65% of coal, 92% of metals and 96% of industrial minerals are mined using surface mining methods (DOE, 2007). Generally, mining is a capital-intensive venture, with high operating cost, hence there is a constant demand for mining companies to seek efficient cost reduction and production maximization strategies. One strategy being pursued keenly is automation, which is noted to improve productivity, and worker safety at minimal cost. According to Parreira (2013), mining automation involves direct teleoperation whereby workers remotely control the mining process using computers from a control room.

Jan 1, 2019

By R. J. Gray

Oxidation of coal can best be described as a process of deterioration, since most of the uses of coal, such as for fuel and by-product chemical and coke production, are adversely affected by coal oxidation, and the inclusion of oxidized coal in most coal products detracts from their value. There are probably many mechanisms of coal oxidation, and the ways oxygen molecules combine as complexes with coal macromolecules to form new substances have been dealt with and speculated upon by many workers1)* but are not dealt with in the present work. This study deals with tests and methods of detecting oxidized coal, with particular emphasis on the microscopically discernible changes that accompany the chemical and physical changes that affect the technological properties of coal during oxidation.

Jan 1, 1974

By J. M. Pachter

Property sales and acquisition are prominent features of today&apos;s coal industry. Before selling or buying a site, a company must know the property&apos;s economic net worth. Any evaluation of economic net worth would be inadequate if determinations of a property&apos;s environmental liabilities and costs were omitted. Short-term and long-term costs can result from liabilities related to reclamation, water treatment, subsidence, and hazardous waste disposal. A structured, interdisciplinary approach can aid in the delineation, summation, and scheduling of these costs and liabilities.

Jan 1, 1986

By Peter M. Fozzard

A review is made of the actual costs of recent foreign mineral exploration programmes in third world countries. Target identification leading to the selection of areas, or macro-targets, must follow a well planned and defined series of steps. Suggestions are made with respect to this inter-active project development work. Potential revenues in the broad sense will always determine the overall economics of exploration but clear objective philosophy, good planning and adequate financing are essential for exploration success. Considerable opportunities exist for making important foreign mineral discoveries and broad selected suggestions are made for the identification of exploration areas in relation to high-grade and precious metal mineralization.

Jan 1, 1984

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 W. Ellison

Worldwide development of commercial markets for FGD (flue gas desulfurization) gypsum is described and used as a basis for assessing potential overall market growth and regional demand foreseen in the U.S. during the 1990s. Diverse strategies are outlined for cost-effective substitution of this major supply from acid rain control retrofits (power plant scrubbers) for natural gypsum in the principal, existing markets: gypsum board and portland cement. Another focus of utilization forecasting is a key group of related. new-product advancements including floor screeds, mining mortars and various types of innovative construction products.

Jan 1, 1993

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&apos;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 Raymond T. Moore

The Federal Coal Mine Health and Safety Act of 1969 (FCMHSA) begins with this statement: "Congress declares that the first priority and concern of all in the coal mining industry must be the health and safety of its most precious resource -- the miner; . . ." At the Federal level this responsibility is shared by the Department of the Interior and the Department of HEW. The health research and standard setting activities under the Act are largely the responsibility of the Department of HEW, and with the exception of Title 4, Black Lung Benefits, have been delegated to our Institute, which I will refer to henceforth as NIOSH. In addition, we bear certain joint responsibilities with the Department of the Interior. These include dust sampling and respirator approval. To complete the picture, the Department of Labor has recently assumed Black Lung Benefit respon¬sibilities from the Social Security Administration under Title 4 of the Act.

Jan 1, 1974

By R. H. King

Suboleski and King (1990) analyzed the reasons for the dramatic increase in underground coal mine productivity during the last 10 years. This paper examines whether this increase can be extended. The paper forecasts whether the mix of technological, procedural and other factors that produced the increase will change in the future. The forecast is based on the base case and spreadsheet production model described in the previous paper.

Jan 1, 1991

A comprehensive understanding of the effects of autoclave configuration (batch, semi-batch, continuous) on the residence time necessary to achieve a target conversion is a prerequisite for design of commercial scale autoclaves. Particle size distribution, mineral and reagent concentrations, temperature and mixing also influence the conversion. This paper outlines the bases of using test data to predict performance of commercial scale autoclaves. Recommendations for coordinating test program design with selection of scale-up method are provided. Examples are given to illustrate the different levels of engineering effort needed to meet corresponding levels of design optimization and accuracy.

Jan 1, 1998

By G. J. S. Govett

Dwindling near-surface mineral reserves emphasize the need for the development of exploration techniques capable of greater depth penetration; geochemical techniques tradition- ally have been restricted to the search for deposits having at least a sub-outcrop expression. Rock geochemical techniques developed in Cyprus in 1967-1968 recognized anomalous conditions in volcanic rocks up to one mile from an ore de- posit. Research by the Exploration Geochemistry Group at the University of New Brunswick has shown that some massive sulphide deposits in New Brunswick have well-defined halos of major, minor, and trace elements in the host rocks extending up to 1,200 metres (4,000 feet) laterally along the same stratigraphic horizon, and up to 450 metres (1,500 feet) vertically in hanging wall rocks which apparently post-date mineralization; well-defined halos have also been found in foot- wall rocks. Some of these halos are readily identified as individual elements or as element pairs; others are so subtle as to be recognizable only through computer-calculated multivariate analysis. Research continues to extend the dimension of rock geochemical halos for regional exploration and for identification of more restrictive anomalous conditions which may closely define the location and extent of buried sulphide deposits.

Jan 1, 1975

By Richard W. Patton

With the advent of the Clean Air Act and the installation of flue gas desulfurization (FGD) equipment (scrubbers) on coal fired power plants, the management of solid wastes has taken on added importance. Aside from the large amounts of fly ash and bottom ash usually generated, large quantities of liquids in the form of scrubber sludge are also produced. These wastes must be disposed of within the constraints of land and water quality regulations. This paper describes the practices adopted by the electric utility industry in denting with this problem, including methods of generation and treatment, quantities and characteristics of the materials, and transportation and disposal practices. The paper also briefly describes final product characteristics and several applications for commercial utilization and land reclamation.

Jan 1, 1983