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By Michael Perch

The fact that coal is a complex organic material and heterogeneous in composition has made its study extremely difficult, particularly in regard to obtaining a fundamental concept of the processes involved in the formation of coke. It has been stated recently that coals are natural polymers and that in a complex reaction such as occurs during carbonization the differences between coals are quantitative and not qualitative. Such being the case, it would be expected, therefore, that a series of coals subjected to exactly the same conditions of coking would produce results that should be related quantitatively to the chemical analyses of the individual coals. In the past, however, this fact was not generally recognized and consequently many empirical test methods were devised for testing coals. The interpretation of the results obtained depended upon comparing a set of data with other data on coals of known characteristics. The testing procedure had to be con- ducted in precisely the same manner each time and not the least requirement in making the interpretation was experience. The test methods varied from those utilizing a gram of coal to the plant-scale tests in which one or more ovens were charged with the test coal. The aim had been principally to find some simple, inexpensive means by which the coke-making and other properties of coal could be predicted. It is not necessary to emphasize the importance of these endeavors, for anyone acquainted with the problems involved in the selection of coals for making coke is well aware of the time and expense involved in making a series of definitive tests.

Jan 1, 1949

By A. Boehm

Mineral selective flash roasting (Steiner process) in oxidizing atmosphere was tested successfully for the efficient low intensity magnetic separation of siderite from ankerite and other gangue minerals within the ore of the Steirische Erzberg, Austria. The calcium, magnesium and manganese containing siderite turns selectively into a ferromagnetic oxide phase while ankerite remains paramagnetic. The expulsion of CO2 increases the volume specific surface depending on the selected temperature. Unlike pure iron oxides absorbing SO2 below 530°C, the calcined siderite (enriched in the magnetic product of the Steiner process) acts as a sorbent for SO2 between 500 and 820°C. The effect was studied by thermogravimetric analysis and particle bed tests complemented with neutron thermo diffractometry (D20/ ILL). The energy input was simulated with the help of a tube furnace. The composition of the artificial combustion gas permeating the bed was close to that measured in pilot scale tests (6 % CO2, 12 % O2, 700 vpm SO2). The evaluation of data relating the SO2 variation in the off gas monitored by electrochemical cells to the actual phase composition revealed an intermediate ferrite phase as absorber. During the rapid decomposition in oxidizing atmosphere starting at 500°C the occurring siderite alters to a (CaO, MgO, MnO)Fe2O3 ferrite as an intermediate phase accompanied with sudden SO2 absorption. SO2 disintegrates the ferrite structure forming MgSO4 and MnSO4, taking Fe2O3 as a catalyst. Ankerite (enriched in the non magnetics of the Steiner process) starts to absorb at temperatures above 1000°C forming gypsum. The findings support the SO2 controlled operation of the Steiner process by ?autodesulfurisation?. It explains aspects of the SO2 implementation reactions within off gas recycling in Austrian sinterstrands. Keywords: magnetising flash roasting, neutron thermo diffractometry, SO2 absorption, siderite, ankerite

Sep 1, 2012

By David White

This paper is the result of a comparative study of ultimate coal analyses made and published by the United States Geological Survey. This study, at first casually undertaken to devise an acceptable classification of coals based on chemical analyses, was continued in connection with a microscopic examination of a number of the coals. The initial comparisons, made from a relatively small number of analyses, not only confirmed a previous conviction that the elimina- tion of oxygen incident to the development of a coal is economically far more important than has been generally suspected, but also showed that oxygen is very nearly as harmful as ash in coal. The immediate purposes of the present study were: (a) To deter- mine more definitely, from a comparative examination of a large number of ultimate analyses, the relative importance of oxygen as an impurity in various coals; (b) to illustrate the transition between various grades of coal of similar origin-transition mainly due to progressive devolatilization, brought about more or less directly by dynamic influences; (c) to ascertain the relative proportions of oxygen, hydrogen, and carbon in coking coals, especially with refer- ence to a theory tentatively framed to explain the coking quality; and (d) to forecast the probabilities of successfully treating a large number of coals so as to render them amenable, in a softened condition, to satisfactory study under the microscope. Although the hypothesis as to coking quality finds but partial support in the chemical analyses, its consideration has led to a method of predicting from an analysis with a fair degree of certainty whether any given coal will coke by the ordinary process. The unbroken transition between coals originally similar but now classed in widely different groups, whether of the same age or of different ages, as a result of dynamochemical action, appears demonstrated by the analyses as well as by field observation. This subject will not be

Jan 1, 1911

By D. P. Bishop, G. J. Kipouros, R. L. Hexemer Jr., I. W. Donaldson, W. F. Caley

Aluminum powder metallurgy (APM) is an advanced metal forming technology frequently employed to fabricate complex structural components in a near-net-shape fashion. Exhibiting nearly 100% material utilization, APM continues to rise in popularity. Recent research initiatives in this field have emphasized the development and processing of advanced 2xxx and 7xxx series alloys. In particular, APM equivalents to wrought 7075 and 2024 have been sought. An overview of work completed in this area is presented. Included are data on the various production stages (powder compaction, sintering, forging, and heat treatment) as well as the microstructure and mechanical properties of the finished products.

Jan 1, 2010

By J. F. Dorion

This paper presents the results of on-going investigations on the performance of support systems in Québec underground mines. The focus of these investigations is on site observations complemented by laboratory investigations. Of particular interest is deducing the corrosion rate, at selected mine sites, as determined by the installation of monitoring coupons.

May 1, 2009

By G T. Jemwa, F Rousseau, F J. Wolfaardt, J A. M Rademan, P W. Smit

Mining companies are increasingly faced with the challenge of reducing operating costs while maximising throughput and profitability. At the same time, the grade and quality of treated ores are becoming poorer and more variable, resulting in suboptimal process performance.It is now widely accepted that strategies to drive operational goals must revolve around improving plant availability, reliability and process efficiency. In particular, progress in plant automation and control systems has seen a trend towards unified frameworks for control and optimisation of mineral processing plants. These frameworks seek to seamlessly integrate different roles and tasks involved in process operations - IT, automation, plant maintenance and operations. An integrated solution framework for reducing process variability, increasing process efficiencies and maximising plant availability and reliability is discussed within the context of a typical milling circuit. The framework exploits a real-time analysis ægapÆ evident in production operations that prevents timeous identification of equipment and process failures. This is achieved by leveraging predictive analytics for equipment health monitoring, control loop monitoring and advanced regulatory control solutions towards enhanced process performance, improved asset management and regulatory compliance. The framework provides for early and actionable warnings on equipment and process degradation using real-time operational data.Resolving these problems can potentially avoid unplanned downtimes, process instabilities and other operational surprises, thus ensuring optimal plant throughput and optimal process behaviour for improved recoveries. Integrating control systems and plant automation with advanced analytics to analyse and optimise processes enables operations to achieve reductions in the variability of key process parameters. In addition, early detection of equipment malfunction or suboptimal process conditions leads to improved equipment availability and reliability. Ultimately, these operational gains reflect in profitability because of plant throughput and recovery gains. These benefits are demonstrated using data from a South African gold mining operation, where such an integrated asset and process health monitoring framework for process optimisation has been implemented.CITATION:Jemwa, G T, Wolfaardt, F J, Smit, P W, Rademan, J A M and Rousseau, F, 2013. Towards an integrated framework for asset and process health monitoring and optimisation on a milling circuit, in Proceedings World Gold 2013, pp 137-148 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

By E. Jong, E. Watkins

"The application of passive tracer gas sources in underground mines is particularly useful for long-term tracer studies as well as for studies conducted in permissible areas of underground coal mines. The use of passive perfluoromethylcyclohexane (PMCH) sources has been previously demonstrated in underground mines, but this new work details the testing of multiple, distinct tracer compounds compatible with passive sources. A description of their potential application in mine ventilation systems is also provided. Three tracer compounds are detailed: (1) PMCH, (2) perfluoroethylcyclohexane (PECH) and perfluoromethylcyclopentane (PMCP). The release rates of these tracers were examined over a 180-day period at multiple temperatures. The advantages and disadvantages of these sources are presented, along with potential applications in characterizing ventilation circuits, flow through gob and leakage. IntroductionThe use of tracer gases for ventilation applications is an established practice, with various past research projects conducted using sulfur hexafluoride (SF6). Tracer gas techniques have been applied to assess flow rates, dilutions rates and auxiliary ventilation system efficiencies with quick, reliable and accurate results (Suglo and Frimpong, 2002). Perfluorocarbon tracer (PFT) compounds are a new introduction to ventilation and air modeling applications in terms of ventilation flow characterization (Watson et al., 2007).PFTs are liquids that are characterized by low background presence in air, low reactivity, high detectability and low toxicity. A design was proposed, called a permeation plug release vessel (PPRV), to convert PFTs from a liquid to a gas and then release the gaseous tracer in a controlled manner. The initial concept was originally introduced by Brookhaven National Laboratory and refined later to become the PPRV. The PPRV functions by allowing the volatile PFT liquid to become a vapor in a controlled manner. The vapor diffuses through a permeable silicone stopper at a predictable rate proportional to temperature (Zhang and Cloud, 2006)."

Jan 2, 2018

By Robinson Leon-Diaz, Alberto Jaen-Toribio, Raymond Blanchard, Mike Deevy, Miguel Fuentes-Llanos

"Tunnels designed to NFPA 502 are required to withstand the RWS time-temperature curve, more specifically prevent progressive spalling and loss of strength of steel reinforcement. Fire boards or spray-on layers can be effective, however, these solutions have capital and whole-life cost implications. The use of “fire resistant” concrete based on a suitable aggregate with polypropylene fibers has also increased in recent years. This article presents a new methodology for thermal and structural analysis of segmentally lined tunnels, which permits the analysis of project specific fire curves and an assessment of different fire protection strategies. The effectiveness of fire boards is assessed along with whether “fire resistant” concrete alone is a viable means of achieving the required protection. Finally, since NFPA 502 recommends water-based fixed fire-fighting systems for Category C and D tunnels, we discuss the question of how a fixed fire-fighting system should be addressed within the structural design. INTRODUCTION Protecting road tunnels from structural damage and collapse is a key requirement for both life safety and business continuity. Where road tunnels are part of key highway corridors, protecting business continuity is a high priority for owners, operators and the Authority Having Jurisdiction. For existing tunnels, compliance with NFPA 502 may require upgrades with either passive fire protection and/or water-based fixed firefighting systems. For new tunnels, compliance with NFPA 502 requires a combination of good practice in design and fire testing. A water-based fixed firefighting system is a Conditionally Mandatory Requirement1 for Class C and D tunnels, i.e. all tunnels greater than 300m and 1000m long respectively. The basis for fire safety design of new tunnels and assessment of existing tunnels is the worst-case fire scenario. A number of factors, including but not limited to the following, influence this design fire scenario:"

Jan 1, 2016

The U.S. economy and, consequently, the demand for minerals grew at more moderate rates in 1995 compared with stronger performances the previous year. Demand for metals such as steel and copper was relatively stable. For example, the decline in steel consumed in motor vehicle manufacturing (reflecting lower vehicle sales) for the first half of 1995 was offset by an increase in steel consumed in construction during the same period. More detailed information on events, trends, and issues in the mineral and material sector Is presented below and in the commodity sections that follow. Overall Performance The value of processed materials of mineral origin produced in the United States during 1995 was estimated to be $395 billion, an increase of almost 10% compared with 1994. The estimated value of U.S. raw nonfuel minerals production in 1995 was $38 billion, about 7% more than in 1994. The value of U.S. minerals production has increased in 30 of the last 35 years.

Jan 1, 1996

By P. Kobylin, K. Haavanlammi, K. Valkama

"Base metals and precious metals can be recovered from a nickel matte or nickel concentrate using the Outotec nickel chloride leaching process. The raw material is leached with hydrochloric acid and the metals are recovered by solvent extraction, where ammonia is used to control the pH. Ammonium chloride is regenerated to ammonia and the side product of this step is calcium chloride solution. The regeneration utilizes either calcium oxide or calcium hydroxide. The calcium chloride solution is used to convert sulfuric acid into a hydrochloric acid solution while producing pure gypsum as a side product. The regeneration and reuse of ammonia and hydrochloric acid in this process will have a positive impact, from the point of view of both operating costs and environmental sustainability. This paper concentrates on the test work and technical concept development performed by Outotec to implement and develop chemical regeneration and recycling into a vital part of the nickel chloride leaching process.INTRODUCTION According to a nickel market analysis, the nickel market is expected to grow in the future. Main driver for this growth is the increase in stainless steel consumption as the living standards are equalizing globally. The expected increase in the amount of electrical cars and the need for nickel in the batteries of electrical cars also gives potential for the increased need for nickel in near future. At the moment the use of nickel in nickel-cobalt-manganese (NCM) and nickel-cobalt-aluminium (NCA) Li-ion batteries is in the range of 14 ktpa. It is estimated to increase to the level of 90 ktpa by 2025. In every era of the nickel industry, Outotec has been constantly developing new processes to create environmentally sustainable and economically viable processing routes. The Outotec® Nickel Matte Chloride Leaching process is a great example of a process that is flexible regarding raw material and could also treat nickel raw materials that are difficult for smelters. Outotec’s main options for pyrometallurgical nickel treatment include the Outotec® Direct Nickel Flash Smelting process (DON) and the Outotec® Ausmelt TSL process. The DON process is operated in Boliden Harjavalta Nickel Smelter in Finland. Ausmelt process is in use for example in Daye nonferrous plant in China. In the Outotec® Direct Nickel Flash Smelting Process, a sulphide nickel concentrate is processed in an Outotec Flash Smelting Furnace (FSF). Producing concentrates and processing them by Outotec Direct Nickel Flash Smelting to matte followed by hydrometallurgical refining offers a reliable route from concentrate to product. In the DON process, high-grade matte with low Fe content is produced in the FSF and the valuable metals in the slag are recovered in an electric furnace (EF). The Outotec® Ausmelt TSL process can use a large variety of raw materials (concentrates, secondary material and scrap metal) as feed. Fuel and oxygen are injected into the furnace through TSL (Top Submerged Lance) and this enables efficient smelting. Both Flash Smelting and TSL plants produce nickel mattes, which can be refined with Outotec hydrometallurgical processes."

Jan 1, 2017

By John J. Laffin

"IN THE BOOK that has been rated the best seller of all time, it is predicted that man will earn his livelihood by the sweat of his brow. Apparently man has accepted the statement as a challenge and has been attempting to refute it ever since, as he continues to transfer the workload to his inanimate servants - the many types of machines and other labour-saving devices that are available to assist or perform for him in the normal tasks of the day. The history of the evolution of the use of energy takes us back to primitive man, who existed in a very low energy environment, the only energy available being his own muscle power. Although man took a great leap forward when he discovered fire, which was used for lighting, heating and cooking, he still depended upon his own muscles for power. Early man's greatest achievement was probably the invention of the wheel, which permitted him to utilize the muscle power of animals. While still in a very primitive state when viewed from the perspective of the twentieth century, man, with fire and the wheel, had achieved a standard of life far exceeding that of his predecessors. Looking beyond the very basic elements of human energy, fire and the muscle power of animals, we find the next additions of energy coming from man's mastery of other elements of nature. The Phoenicians utilized the power of the wind and the Romans adapted the energy of falling water to the water wheel."

Jan 1, 1972

By Yinan Zhang, Y. Luo

Most of the reported coal spontaneous combustion events occur in surface and underground mines where low rank coals (i.e., subbituminous and lower for this particular studies) are extracted indicating their high propensities for spontaneous combustion. Low rank coals have high moisture content (15 to 45%) and are capable of absorbing more moisture in dried condition. However, it is hard to induce the initial stage of self-heating process for the low rank coal using the current laboratory R70 testing method — a method widely used in the coal industry. Like a sponge, dry low rank coals can absorb water vapor in the air while the heat contained in the moist air is transferred to coal and served as the required activation energy to initiate the coal self-heating process. In order to prove this theorem and quantify the effects, the R70 adiabatic oxidation testing method has been improved to introduce a controlled moist flow into the coal reaction vessel. Tests using the new method and its setup on low rank coals showed that the initial self-heating process of coal sample can be greatly accelerated by the added water vapor — impossible with the regular R70 method. Once the self-heating is sustained, the removal of air moisture can further accelerate the process.

Sep 17, 2021

By H S. Smit, P Lotz

Gold mining companies who are signatories of the International Cyanide Management Code (visit www.cyanidecode.org for further information) are required to measure WAD cyanide on-line and destroy WAD cyanide in excess of specified limits. Weak acid dissociable (WAD) cyanide refers to those cyanide species liberated at a moderate pH of 4.5 such as HCN(aq) and CN-, and the majority of Zn, Cd, Cu, Ni and Ag complexes with low dissociation constants. It is potentially toxic to humans and animals. Recognising and in response to the gold mining industryÆs need for an on-line WAD cyanide measurement device, Mintek recently developed the WAD Cynoprobe. The WAD cyanide analysis technique is based on the use of a ligand exchange reagent that liberates WAD cyanide from metal-cyano complexes. The ligand exchange reaction is represented by the following chemical equation: Metal(CN)X + yLigand <-> Metal(Ligand)y + xCN- The plant filtrate is treated with a ligand exchange reagent, to liberate WAD cyanide, before measuring the free cyanide concentration via amperometry. The instrument proved to be accurate and reliable in the laboratory as well as under industrial gold plant conditions during various trials. It has gained wide-spread commercial acceptance both locally and internationally. However, itÆs recent exposure to complex ore types have called for refinements to the analysis technique. It has been further developed to improve its precision and accuracy and to remove reagent and thiosulfate interferences. Its compatibility with the most commonly used destruction oxidants has also recently been investigated. The WAD Cynoprobe may be configured to measure both free and WAD cyanide concentration. Its fast analysis time, approximately 5 min, makes it suitable for use in the control and optimisation of the cyanide destruction and recovery process. Proper oxidant dosage control and monitoring of effluent concentration levels will ultimately result in less cyanide and post-destruction salts discharged into the environment.

Jan 1, 2008

The value of processed materials of mineral origin was estimated to have exceeded $310 billion in 1990. U.S. raw nonfuel minerals mine production in 1990 was estimated at $33 billion, a 3.1 % increase over that of 1989. The value of minerals production increased in all but 3 of the last 30 years. The metals component of production value has fluctuated much more than the industrial minerals component. This reflects the greater volatility of metal prices. In 1990, total employment in metal mining continued the increase that began in 1987. This growth was partially offset by a slight decline in employment in industrial mineral mining, resulting in an overall in-crease of 1.1 % to 179,100 in 1990. Continuing high (by historical standards) metal prices led to expansions at some mines, as well as opening or reopening of additional mines, resulting in increased employment.

Jan 1, 1991

By Milford L. Skow

This report summarizes the principal activities and results of 15 years of research by the Bureau of Mines, U.S. Department of the Interior, on methane control in coal mines. This research has investigated fundamental factors regarding the occurrence and movement of methane in coal beds, removal of methane prior to mining, and control of methane during mining. The report includes a bibliography listing the more than 150 publications resulting from the Bureau's methane control program as well as numerous other references, a section on methane recovery and use, a look at the upcoming Bureau of Mines research program, and a brief review of methane drainage practices in other coal-producing countries.

Jan 1, 1980

By D. W. Alexander

In 1993, CONSOL began investigating new methods of permanently filling coal mine shafts, which after ventilation is stopped, may contain a potentially hazardous atmosphere. Fill materials such as fly ash/cement can be pumped, are non-combustible and non-incendiary but tend to flow into the mine entries. A non-flowable mixture has been developed that minimizes the volume of fill used. The paper presents our recent shaft filling experience including fly ash material properties, mix designs, field problems, placement success, and gas testing techniques.

Jan 1, 1996

By M. Yamine, R. J. Ring, D. J. Waters

"An experimental program has been carried out by the Australian Atomic Energy Commission to compare the effectiveness of Caro's acid as an alternative oxidant to pyrolusite in the leaching of uranium ores from the Alligator Rivers region of northern Australia. Batch leaching tests on Ranger, Nabarlek, Koongarra and Jabiluka ores showed that uranium extraction was unaffected by choice of oxidant, but that Caro's acid reduced acid requirements by 15 - 25%. Lime requirements for neutralization of tailings liquors were reduced by 20 - 30%.The batch studies were extended to a four-stage continuous leaching circuit with a capacity of 400 gore h-I. Comparative leaching tests confirmed the reagent savings obtained in the batch tests. Following these encouraging laboratory results, lnterox Chemicals Pty Ltd carried out plant trials using Caro's acid. Reagent savings in the mill were similar to, or better than, those obtained in laboratory test work. The trials also established that Caro's acid has a number of operational advantages over pyrolusite.IntroductionUranium is most commonly extracted from its ores by leaching in sulphuric acid. Simple hexavalent uranium oxides and compounds are readily soluble but uranium in the tetravalent form is insoluble and must be oxidized for dissolution to occur. The most commonly used oxidants have been sodium chlorate and manganese dioxide. They act indirectly by maintaining iron as the ferric ion which oxidizes uranium by a surface electro- chemical reaction. An Fe3+ concentration of about 1 - 2 g L-I is usually considered adequate for the effective dissolution of uraninite(1)."

Jan 1, 1984

By Tim Chapman

This general report considers what promoters of deep basement projects want from their teams and whether they get it often enough. Most large projects are based on complex financial models where the funding is related to a future income stream. Project delays and cost over-runs can critically affect the financial model. Too often, delays and cost over-runs originate in the substructure and foundations. We must take positive steps to improve our industry's reputation for reliability.

Jan 1, 2006

By A. Adhikari, P. Tukkaraja, S. Jayaraman Sridharan

Shafts are critical components of the mine ventilation systems and contribute significantly to the mine ventilation pressure. Estimation of shaft pressure losses is an important aspect of mine ventilation planning and shaft frictional pressure losses are extensively studies. Shock losses contributed by shaft buntons are estimated using the interference factor model developed half a century ago. This study aims to develop a better performing prediction model for shaft buntons using state of the art experiment and numerical data, and machine learning techniques. Results show that the present prediction model is performing poorly, and the prediction performance can be improved by incorporating additional predictor variables. The Artificial Neural Network standardized Machine Learning model developed in this study is able to predict the shaft bunton shock loss with high accuracy (R2 = 0.956).

Jun 25, 2023

By Erik Sherer

Indonesia is poised to become a major player in the Pacific Rim thermal coal markets. Although the colonial Dutch developed numerous coal mines in the late 1800's for steamship bunkers and domestic fuel, Indonesia's coal industry has only recently begun to actively participate in the growing global marketplace. This export coal is primarily the result of the commercial development of coal mines in eastern Kalimantan by foreign contractors. From virtually no coal exports in the late 1980?s, Indonesia's coal industry has increased its exports to approximately 15 million metric tons (Mmt) in 1992. In 1992, Indonesia was the world?s sixth largest exporter of steam coal, By the year 2000, Indonesia projects that it will supply approximately 25 percent of the seaborne thermal coal requirements of the Pacific Rim countries. Although limited quantities of this coal may enter the European and U.S. markets, high qualities, low production casts, and favorable transportation rates will make Indonesian coals very competitive in the rapidly growing Pacific Rim markets. This study examines the Indonesian coal mining industry and compares it to the U.S. coal mining industry. This report is the sixth in a series of coal exporting country studies requested by the House Appropriations Committee. Previous studies examined the Colombian, Canadian, Australian, South African, Polish, and Venezuelan coal industries.

Jan 1, 1994