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By Raymond E. Zimmerman

The use of standard dense-media cyclones is well known, as they have been in use for many years. They are especially well suited for operating at low separating densities and for treating difficult coals containing a high percentage of near-gravity at the point of separation. Very few modifications of the basic design have ever been made. The author recently, however, has been interested in the development of a new type of dense-media cyclone that has been produced in Japan. He has observed the testing of this unit and has collected much data which he feels should be of considerable interest to coal preparation engineers. He feels that this unit, called the Swirl Cyclone, may be of substantial value as an alternate to the standard cyclones. It is certainly worthy of further investigation. There has been relatively little written in English-language publications on the Swirl Cyclone. It was briefly described at the Fifth International Coal Preparation Congress. I It has been described in a general manner by the author in two prior publications. 2, 3 This paper proposes to describe this device in more detail and at the same time submit technical data illustrating its wide characteristics.

Jan 1, 1977

By D. E. Healy

In 1989 an Autogenous Grinding Task Force was formed to study potential autogenous grinding circuits to replace the existing semi-autogenous grinding at the National Steel Pellet Plant located in Keewatin, Minnesota. Pilot plant test work performed by the Hanna Research Center (HRC) indicated that fully autogenous grinding with pebble extraction and crushing could feasibly be incorporated into the existing circuits. In 1990, one of the existing ten grinding mills was converted for an in-plant test incorporating pebble crushing. The full scale test work conducted in 1990 and 1991 verified the pilot plant projections with primary mill throughputs from the fully autogenous circuit utilizing pebble crushing being greater than throughput of the existing SAG mill circuits.

Jan 1, 1992

By Su Yang, Pang Shun, Xiaoding Xu, Guodong Yang, Hengfeng Liu, Meng Wu, Yuejin Zhou

By introducing the hydrochemical damage variable of coal gangue granular material, this paper analyzed the evolution law of gangue mechanical parameters with hydrochemical damage. By constructing a gangue damage model considering multifield coupling, the damage mechanism of gangue under multi-field coupling was revealed from the microscopical aspect, and the influence law of gangue damage mechanism on the dissolution of toxic substances under multi-field coupling was obtained: the conditions of Test 1 have the greatest influence on the porosity of coal gangue, and the damage of coal gangue is the greatest. Cu, Zn, Cd, and Pb are more easily leached under acidic conditions. The coupling effect of seepage, temperature, and chemical field can promote the formation of secondary voids, change the voids, and form migration paths in coal gangue. The kinetic model of toxic leaching of coal gangue under multi-field coupling can be well characterized by Elovich equation. The release mechanism of heavy metals is mainly manifested as delayed diffusion or dissolution in the early stage, diffusion and dissolution in the middle stage, and depletion in the late stage.

Nov 23, 2023

By Yi Luo, Jianwei Cheng, Mingming Li, Lei Xiao

Concealed thermal events in longwall gobs present safety hazards for underground coal miners and can significantly interrupt mining production. The probable causes for such thermal events range from coal oxidation at slightly above ambient temperature to smoldering fires due to spontaneous combustion of the broken coal left in the gobs. Locating such “hot spots” is the key step for planning and implementing mitigation measures to bring such thermal events under control. If a mine section, or even an entire mine, has to be sealed, understanding the status of the sealed mine atmosphere is important for the decisions guiding subsequent actions. The gas composition data obtained through the tube bundle mine atmospheric monitoring system is firsthand information of great value. Fire ratios proposed by various researchers and derived from gas composition data are useful in determining the fire status and even approximating the source locations (Timko and Derick, 2006). However, the applicability of each of these ratios under particular conditions should be carefully evaluated. The use of properly combined fire ratios can enhance the certainty of analysis. The explosibility of a sealed mine atmosphere deserves primary concern for safety reasons during seal construction, idle time and reopening of the sealed area.Mine atmospheric monitoring data from a longwall mine with flame fire have been analyzed. Efforts have been made to identify the possible causes, locations and statuses of these events using the obtained gas data, as well as other ventilation, geological and mining parameters. The effect of injected inert gas to control the events has also been quantified. The explosibility of the sealed atmosphere has been determined using two methods.

Jan 1, 2012

By Thad J. Bydlon

Uncertainty of future energy supplies has forced industrial nations to diversify both their energy mix and their energy sources of supply. As a result, U.S. coal exports have grown substantially during the past several years. Projected long-term worldwide economic growth suggests that a well-established trend has been set for increased foreign demand for U.S. coal. As export volumes increase the need for careful planning to prevent bottlenecks and to provide for the uninterrupted flow of coal increases. It also will place increased emphasis on identifying the most economic transportation alternatives. These planning and evaluation functions are greatly facilitated if a systematic method is available for modeling the complex interactions of a coal export system. One such model, developed by the Anaconda Minerals Company, is the Coal Export model.

Jan 1, 1982

By B. Goertz

Since the turn of the century the mining industry in the United States has had a number of serious mine explosions, fires and ground fall disasters that have led to a major re-evaluation of mine communication and rescue practices. One of the hindrances of current underground communication technologies is the potential of lost or cut connections when a serious accident, such as an explosion, fire, inundation or major ground fall, takes place. The Mine Improvement and New Emergency Response Act of 2006 (MINER Act)1 mandated that each underground coal mine in the U.S. must provide for two-way wireless, post-accident communications between underground and surface personnel as well as electronic tracking of underground workers One area that has gained renewed attention in the mining sector is Through-The-Earth (TTE) communication. TTE technology has a major advantage in that transceiver devices can be carried by miners and set up quickly during an emergency, since they require no wire connection to the surface. TTE technology uses ultra-low frequency (1 to 4 kHz) electromagnetic waves, requiring relatively large wire loop antennas and highly sensitive receivers. The signal bandwidth is narrow and the permissible antenna currents in coal mines are restricted, which has led to limited usability of TTE technology in the past, as evidenced in research studies conducted by the U.S. Bureau of Mines in the 1970s. Yenchek (2012)2 pointed out that recent advances in receiver and signal processing technology have enabled voice and text communication capabilities and much improved sensitivity that offers new possibilities for TTE communication in mining applications. One company that has been developing such technology is Vital Alert Communication Inc. Vital Alert has been providing TTE communications since 2003 with a growing focus on emergency response and portable systems. The company?s Canary® Go System is one such product that looks to provide reliable communication capabilities in a portable, user friendly unit that can be utilized both for normal operation and mine rescue scenarios. Researchers at the Colorado School of Mines (CSM) have tested the Canary Go TTE communications system in the CSM Edgar Experimental Mine to determine signal propagation distances, signal quality and aspects of practical application.

Feb 23, 2014

By Steven W. Hunt, Steven B. Fradkin, Roger J. Maurer

During the 1980s and 1990s, twenty deep shafts were constructed in Milwaukee to depths from 85 to 91 m (280 to 300 feet) through soil and weak rock thicknesses ranging from 37 to 69 m (122 to 227 ft). Adjacent compressible soils, settlement sensitive structures and high groundwater levels required that shafts be constructed without dewatering. Contractors attempted several methods of ground support and groundwater cutoff. Significant problems developed during construction of 11 of the 20shafts. One shaft collapsed; groundwater blow-ins occurred at five of the shafts; and seepage caused unfrozen windows at three of the freezewalls. Ultimately, combinations of grouting and ground freezing were utilized to complete all of the shafts into bedrock. This paper discusses the main design and construction challenges experienced and the lessons learned.

Jan 1, 2003

By J. T. Graves

Bauxite, dolomite, and magnesite are natural occurring minerals that are used extensively in the manufacture of refractory products. In addition, magnesia produced from seawater or brine finds its way into the production of refractories. All of these materials must be processed at high temperatures, 1500°C to 2200°C, to produce an intermediate raw material (refractory grain) , which can then be used in the final manufacture of refractory bricks and shapes. During the last 20 years, the major supply of refractory bauxite has been from Guyana, and at times the annual production has ranged up to 1,000,000 tons per year. More recently, China has become a major source of refractory grade bauxite by supplying over 300,000 TPY. Other sources of bauxite in lesser quantities have been Surinam, Brazil, and the U.S.A. During 1980, the estimated available world tonnage amounted to slightly more than 1,300,000 tons. The bulk of this material has been calcined in rotary kilns except for some of the Chinese production, which was treated in shaft kilns. Recent work has indicated that an excellent product can be produced in the Nichols Shaft Kiln using much less fuel than the conventional rotary kiln. Details of the Nichols Shaft Kiln will be provided later in this paper.

Jan 1, 1982

By E. J. Peuraniemi, J. T. Yli-Penttilä, A. Jokilaakso, K. M. Riihilahti

Dust formation and the reaction mechanisms of copper matte particles were investigated in simulated flash-oxidation conditions. The granulated and ground matte consisted of 72% Cu, 4% Fe and 21 % S (by weight). Experiments were conducted by using a laminar flow furnace with a reaction-gas composition ranging from 20% to 75% O2 (by volume) in nitrogen. The particle feeding was carried out by a single-particle method, and samples were quenched after a specified reaction time ([~] 0.05 to 0.4 s) in a cold water film. Experimental temperatures ranged from 800o to 1,300o C. Chemical analysis was used to determine the degree of oxidation, and optical and scanning electron microscopes, combined with energy dispersive analysis, were used for characterization of the reacted particles.

Jan 1, 1999

By Bruno Mattle, Max John

For tunnels with low overburden, the shotcrete lining is the main element of ground support, which is why shotcrete behavior is of prime importance. Following its application, shotcrete not only gains strength and stiffness with time but—if loaded at an early stage—it is also subject to creep which in turn leads to stress relaxation. For two-dimensional FE calculations, a computational modulus of elasticity of shotcrete is to be used. Based on parameter studies it was found that the modulus of elasticity of shotcrete depends on both shotcrete mix and ground behavior. While the Young’s Modulus used for young shotcrete may range from 1,000 to 7,000 MPa, the Young’s Modulus used for hardened shotcrete is best represented by a value of 15,000 MPa.

Jan 1, 2003

Bauxite mine rehabilitation is an important stage of today’s bauxite mining activities. To get an overall picture on those activities the International Aluminum Institute (IAI) has been carrying out Bauxite Mine Rehabilitation Surveys since 1991. The most recent survey from 2003 covers 70% of the world’s bauxite production and 23 corresponding companies from 12 countries. The survey activities show that nearly all operations refer to a sophisticated environmental management strategy. By setting up a review scheme based on the principles of the Global Reporting Initiative the compliance of this survey to aspects of Sustainable Development has been reviewed. The Clarification of a multitude of aspects based on the GRI guidelines helped to structure recommendations and relate them to the survey as such but also to the different stakeholders involved.

Jan 1, 2005

By T. D. Kaufmann

When Dr. David Gully solicited this paper last spring a few questions basic to commodity trade between the U.S. and world markets appeared perplexing. Why, for example, when the demand for aluminum was at a peak and when little expansion of capacity had taken place, was the dollar price half of what it had been at the previous peak? Or, why in 1984 when imports surged by 50% as the U.S. economy pulled out of its recession did the dollar not fall, but rather rose by 35%? And, why when the experts all seemed to agree that the dollar was grossly overvalued did the price of gold continue to decline? Surely these were extraordinary times for the mineral economist. When this paper was written in late July, 1985 the answers seemed clearer. The prices of many commodities were not low - the dollar in which they were denominated was too high. In other currencies many commodity prices were indeed high. The dollar was overvalued in trade terms by some 40% caused by an influx of short term coupon investments made by foreign money managers to take advantage of the higher short term interest rates in the U.S. relative to other international banking centers. With a decline in the relative difference in interest rates, an unhealthy buildup of foreign bank accounts and a perception that the dollar would fall, the dollar did start to decline rapidly.

Jan 1, 1985

By M. Rieber

The potential for the wide-spread commercialization of superconductivity, the disappearance of all resistance to a direct current (D.C.) electric flow, began in 1986-87 with the development by Bednorz and Muller at IBM's Zurich Laboratory of an yttrium -barium -copper oxide conductor which attained zero resistance at 90t:. Although the status of superconductivity is still pre-bench scale, it is useful to forecast its probable effects on the copper industry. I t should not be forgotten that at their inception, the impacts of transistors, semi-conductors, thin films and fiber optics on the electric/electronics sector of this industry, were largely underestimated. Superconductors are not metals, but a class of ceramics. They represent an efficiency increase of one or more orders of magnitude. If their development is to be a boon to the copper industry, rather than a reduction of metal demand through miniaturization or material substitution, vastly expanded copper containing electrical uses must be in prospect. In this paper the projected uses of high temperature superconductivity are examined, followed by the remaining problems to be overcome. Assuming success, a time horizon for maturation is estimated. The penalties for the non-recognition of new markets and material substitution are shown on the basis of past forecasts. Finally, the application of successful superconductivity to the copper industry over the forecast period is estimated.

Jan 1, 1990

By John P. Albers

During the 1950's and 1960's a program of geologic mapping of counties has been underway in Nevada by geologists of the U. S. Geological Survey and the Nevada Bureau of Mines. The aping has been done principally at reconnaissance scales, with more detailed work in local areas. Geologic maps are either published or open-filed for about a dozen counties at scales of 1:200,000 or 1:250,000. One by-product of the geologic mapping has been the recognition of about 80 Tertiary volcanic centers from which large or very large volumes of volcanic material ranging from rhyolitic to andesitic in composition have been erupted. For purposes of this discussion these are regarded as the major centers; the tally does not include hundreds and perhaps thousands of small rhyolitic domes and plugs and basaltic vents. About 15 to 20 of the 80 major centers are believed to be calderas ranging in diameter from 3 to 25 miles. Some have been described in the literature by geologists of the Nevada Test Site and others. However, the vast majority of the 80 centers have not been described in print, and we are indebted to our colleagues for locating them for us in many of the counties. Briefly, we would like to express our appreciation to the following people all members of the USGS unless identified otherwise: Robert Coast, who has identified the centers in Elko County; Ron Willden, Robert Yates, and

Jan 1, 1968

By Justin Jensen, Luis Moya, Jose Carlos Durazo, William Szolga, Tyler McCallum, Tim Doubleday

Sulfuric acid mist is an undesired by-product of the copper electrowinning process, caused by oxygen evolution at the anode which entrains droplets of the acidic copper electrolyte solution. As the oxygen moves to the surface of the cell, these droplets become aerosolized resulting in acid mist. The addition of chemical anti-misting agents to the copper electrolyte is a common mitigation technique. This paper details Syensqo’s laboratory development of a new environmentally friendly acid mist suppressant, ACORGA® EW98. The product exhibits excellent acid mist suppression and it is fully compatible with the adjacent solvent extraction process. Lab and pilot test results are reviewed ahead of future planned industrial trial testing.

Feb 1, 2025

By Tomek Ulatowski

This article discusses four principal areas relevant to financing direct reduction facilities: (1) Lenders' differing requirements with respect to projected cash flows; (2) The impact of leveraging on project viability; (3) The importance of appropriate debt structure; (4) The significance of accurate and complete capital cost estimates. The overall findings emphasize the inseparable connection between the project economics and its financeability, and particularly how direcly intertwined they both are in the project planning.

Jan 1, 1978

By Xingtian Hui

Due to variation in the geological natures of underground coal mines, especially when the entry?s roof/floor are soft and weak, it is vital to select an appropriate roof bolting system to ensure entry stability, coal production, and miner?s safety. No single type of roof bolting system perfectly fits for various types of openings, even within a mine. From the results of continuous research on roof bolting in the past 10 years, the authors used a novel concept of ?Self-screwed? mechanism to develop five types of roof bolting under a patented Self-screwed Tube Bolting System (STBS)©. This roof tube bolting system can be applied to meet different timing-strength requirements under varying mining conditions to increases the stability of mine workings. This paper outlines the structures and mechanisms of the five types of self-screwed roof bolting systems along with their unique characteristics, advantages and disadvantages, and limitations. Two case studies using a Self-screwed Tube Drilling Bolting (STDB)©, one of the five types of roof tube bolting systems, show the principles of mechanics, suitability and parameters for a mine entry and a subway?s construction/ supports in the surrounding soil layers and soft sands, respectively are presented. The results confirmed the time dependent anchorage capacity between predictions and on-site measurements. Currently, other types of the self-screwed tube bolting systems are also being applied to different coal mines in China to increase entry stability and meet safety requirements.

Jan 1, 2009

By Eugene L. Foster, Gilbert L. Butler

The successful demonstration of a precast segmented concrete liner in the Lexington Market Section of the Baltimore Regional Rapid Transit System (BRRTS) is an important step forward in our continuing efforts to control tunneling costs in the USA. In addition to its contribution to specific savings in future tunnels, this demonstration project has taught other lessons about the U.S. tunneling industry and about the process of "mainlining" new and improved technology into that industry. This paper will present an overview of the Lexington Market Demonstration Project from its beginnings to the present time. In addition, it will discuss other implications which have an important bearing on the extent to which tunnels will be used in future transportation systems in the USA. THE HISTORY Precast segmented concrete tunnel liners are not new. An unbolted version was reportedly used in New York City in the 1930's. The modern bolted configuration has been in use in foreign countries for more than 15 years. Indeed, consideration of the use of precast bolted segments below the water table in the USA dates back to the BART system in San Francisco in the 1960's. At that time, they were evaluated and it was concluded that the state of the art would not allow segments to be precast to the required tolerances. A secondary grinding operation would be required if water-tightness was to be assured, making them economically non-competitive with steel. Based

Jan 1, 1981

By John C. LaScola, Gerald L. Finfinger, Michael A. Trevits

Methane gas is an ever-present problem facing the underground coal mining industry. Mine operators are mandated by law to maintain safe concentrations of methane gas within the mine environment. Ventilation is the method of choice used by all mine operators to reduce gas concentrations. When gas emissions are such that ventilation alone cannot control the gas, methane drainage methods must be applied. In the 1970’s, there was a concern that unprecedented gas emissions would be experienced as mine operators began new developments in the deep and gassy Blue Creek and Pocahontas No. 3 Coalbeds. Such concern was well founded as significant gas volumes are being emitted as these mining operations mature. In 1971, the U.S. Bureau of Mines began to tabulate and track the change in mine emissions. These data were extracted from the underground coal mine quarterly air quality-quantity inspections performed by the Mine Safety and Health Administration. At that time, approximately 6560 Mm3/d (231.7 MMcfd) of gas were emitted from 430 underground coal mines. It was determined however, that the mines emitting less than 2832 m3/d (100 Mcfd) contributed only 2.1 percent of the total daily gas flow. In 1988, underground coal mines emitted 8350 Mm3/d (294.9 MMcfd) from 487 mines. This report evaluates the changing nature of U.S. mine gas emissions over the last 18 years.

Jan 1, 1991

By S. Hicks

This technical note describes an alternative procedure that can be used in linear programming calcula¬tions where the compliance limit of lbs S02/million Btu for the blending coal is subject to change. Dr. Mateer in his technical note titled "Coal blending for sulfur compliance" (ME, September 1994, p. 1103) defined an "excess sulfur" parameter that provides a valid constraint equation for a linear program optimization. The coals used by Dr. Mateer in his examples are shown in Table 1. To create the parameters for the constraint equa¬tions to blend to an SO2 content of 1.2 lbs S02/million Btu; the excess sulfur for Coal A was defined as Sulfur excess%o = 0.5 - 0.6-13,000/10,000 = -0.28 This equation was used to create the constraint equation -0.28A + 0.44B + 1.36C<- 0.0 Another way to create the parameters for the constraint equation is given below. In these equations: ? W is the total weight; ? A, B and C are the fractional proportions of each potential blend stocks; ? Sa, Sb and Sc represent the percent sulfur content of the blend stocks; ? Ha, Hb and He represent the calorific content of the blend stocks in Btu/lb; and ? H and S represent calorific and sulfur contents of the composite blend. The weight of blend to produce one million Btu is [ ]

Jan 1, 1997