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By W. C. Taylor

The present fuel situation indicates that, at least for the next 20 to 30 years, the burning of coal will be a main source of energy. All coal contains sulfur, which is converted to sulfur dioxide during combustion. The concentration of sulfur dioxide (SO2) in the resulting flue gas, for most coals, would exceed the limits established by the Environmental Protection Agency (EPA). Therefore, the sulfur must either be removed from the coal prior to its burning, or be collected from the stack gas before it reaches the atmosphere. There is currently a large amount of research devoted to methods of removing the sulfur from the coal before burning, or during combustion in fluidized beds with materials which trap the sulfur in the solid residue. The commercialization of these processes, however, is not expected in the near future. Flue gas desulfurization appears to be the best near term prospect of fulfilling current air quality control regulations. The lime/limestone wet-scrubbing methods are the most advanced flue gas desulfurization processes and will account for the majority of sulfur removal systems in electric power generation. There are currently at least 23 full-scale systems existing or under construction and 17 of these will use the lime or limestone wet-scrubbing process. (1)

Jan 1, 1974

By H. Vendette, N. R. Dando, A. Moras

The thorough analysis of results obtained from different testing campaigns performed on an alumina dry-scrubber pilot installation treating aluminum potline offgases, suggests a clear relationship between the emissions of gaseous fluoride and the fluoride saturation level of the alumina. The integration of this relationship into the development of a new generation of alumina dry scrubber represents an intriguing challenge regarding the design of more efficient air pollution control equipment. An innovative scheme challenging conventional industry practices was proposed. From theoretical simulations, the reduction in fluoride emissions can potentially be reduced by as much as 50% in the summer season. To validate this innovative approach, Solios in partnership with Alcoa Primary Metals, modified one of the Aluminerie de Deschambault's systems by adding new temporary equipment on the operating units and subjecting it to several test campaigns. This article presents the first results obtained in testing this new and innovative approach on alumina dry scrubbers used to capture fluoride emissions coming from aluminum electrolysis potlines.

Jan 1, 2006

By Jin Anshi, Wang Dai, Wang Zingshen

Both fire and gas problems in Fully Mechanized Sublevel Caving Coat Face are quite different from those in common fully mechanized coal face. Pouring N2into the goaf would be the best method to prevent fire in the goaf. In this paper how to determine parameters of pouring N2 is discussed. Comparing distributions of gases and temperature before pouring N2into the goaf with those after pouring N2 into the goaf, the effectivenesses of preventing the fire by pouring N2 into the goaf are testified. Some special gas problems appear in Fully Mechanized Sublevel Caving Coal Face, which are proved to be serious and interrelated with pouring N2 into goaf. Finally, a few methods adopted to deal with gas problems are described simply.

Jan 1, 1991

By Ian Bell

This paper investigates fragmentation in an aggregate quarry using the fragmentation-energy fan concept. Six blasts were monitored, located one behind the other in the same quarry area. The rock structure was blocky, the water level and the usage of explosives were variable within and between the blasts. The powder factor above grade was between 0.28 and 0.44 kg/m3 (0.47 and 0.74 lb/yd3). Fragmentation of the plant feed was measured using an online digital image analysis system and three belt scales. The oversize material that was not directly fed to the plant after the blast corresponds to 3‒9.3 % of the total. Data from image analysis was used to build the size distribution in the coarse range (fragments above 120 mm), and the passing fractions at 120 and 25 mm (4.72 and 0.98 in) obtained from belt scales data were used in the range 120‒25 mm (4.72 ‒ 0.98 in) . The non-dimensional percentile sizes between 10 and 90 % for each blast are described through power functions of the powder factor above grade; the model coefficients are statistically significant. From them, using the principles of the fragmentation-energy fan and the Swebrec distribution properties, the fragmentation can be expressed in terms of the powder factor by means of five parameters: the fan focus coordinates and the three parameters of a function of the exponents vs. the percentage passing. The model shows a good capability to describe fragmentation.

Jan 1, 2019

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 L. Alan Weakly

The Powder River Basin of northeastern Wyoming and southcentral Montana contains the largest strip minable reserve of compliance coal (0.27 kg or 0.6 or less Ibs of sulfur per million Btu) in the United States. In mining parlance, it is the mother lode. Wyoming's portion of the Basin is called the Southern Powder River Basin (SPRB). It has been the nation's top coal producer for the past nine years. And based on 1997 production statistics and estimated strippable compliance coal reserves, Wyoming should remain the nation's top producer for the next 51 plus years. In August 1994, ME featured 10 articles that covered all aspects of coal production in the SPRB. In this issue, five authors update the 1994 articles and provide a pre- diction of what the Basin will look like at the turn of the century. In addition to this article, the titles and authors of the other five articles include: ? "Geology of Wyoming's Powder River Basin coal field," by Gary B. Glass and Robert M. Lyman. ? "Coal quality challenges in the Powder River Basin," by Sharon Roness, Richard A. Turpin and Robert A. Young. ? "Markets for Southern Powder River Basin coal," by , Patti J. Best and Patrick W. Wright. ? "Evolution of mining equipment in the Powder River Basin," by Kenneth R. Miller and James L. Long. ? "Hauling coal into the 21st century," by Dave Willis and Will Cunningham.

Jan 1, 1998

By E. H. Hamilton

WHEN starting a series of experiments on the use of powdered coal in lead blast furnaces to replace coke, I realized that in copper smelting the problem is simpler because the sulfur recovers the copper in the form of matte. In lead smelting there are greater difficulties because a reducing atmosphere must be maintained in the active, zone corresponding to each tuyere in order to get the best recovery of lead. Therefore, the feed of powdered coal must be quite regular, uniform and under control. The molten products issuing from the taphole are the resultant of the work of all the tuyeres and it can readily be con-ceived that one part of the furnace may be forming slag with a higher lead content than the slag formed in other parts of the furnace. At first, we used only one tuyere situated on the back of the furnace. This was for the purpose of getting all of our regulations under the regular operating conditions. We tried every known system of feed and found they were not dependable and our present system was finally worked out, and so far as we know, is the only working system that will give uniformly good saving in lead blast furnaces. We placed a Bristol self-recording thermometer on the feed floor. This gives a 24-hr. continuous record of the temperature of the gases leaving the furnace. We put a self-recording gage on the "15-lb." air used in the injector. A second recording Bristol gage was put on the low-pressure air (40 oz.). I realized that it was necessary that we should know the exact weight of coal going into each tuyere and that it should 'be under observation at all times. L. W. Kirk was assigned to the problem and developed the open sight feed and the distributor, so that we now have the coal being fed into each tuyere in sight of the men in charge. We have an apothecary's balance beside the furnace, and the operator takes the pan and inserts it under the stream of falling powdered coal for one minute, and places the pan on the scale, the other scale pan having weights indicating the desired amount to be fed to each tuyere per minute.

Jan 10, 1922

23.1-SOURCE, POWER-SYSTEM ELEMENTS A. J. T HUM Basic considerations in providing power for mine production and collateral operations are: 1. Mining operations of any size normally use electric motors for driving all equipment except mobile service units. 2. The electricity for power may be purchased or self-generated, depending on the location, size and specific operating circumstances of the individual property. 3. The major elements of the power system will be the source, either an incoming transmission line from a utility in the case of purchased power or the power plant if self-generated. Energy for the power plant may be water, hydrocarbon fuels, waste heat or nuclear, which will govern the type of prime mover selected. 4. The electricity normally is generated in the form of alternating current and must be distributed to the points of usage. This usually requires a primary substation for transformation to suitable voltages and secondary substations at points of usage throughout the operations, The power is delivered from the primary to the secondary substations over transmission lines or cables, depending on distances, voltages and local conditions. 5. At the points of use, there will be starting and protective devices for each motor. In some instances, direct current will be needed and rectifiers of various types can be used to provide it. 6. The entire electrical system requires suitable switching and protective devices to prevent damage to the equipment in case of power failues or faults; also, in most cases, sufficient metering to establish the demand and amount of electrical energy consumed. 23.2-PURCHASED POWER A. J. THULI 1. Where public-utility or government-generated power is available, it usually is advantageous for the mine owner to purchase rather than generate. Purchased power generally will be cheaper and more reliable than operating a small generating plant except in some cases where waste heat is available as the source of energy and can be used to supply all or a portion of the power requirements. 2. If it is decided to purchase power, the owner usually must participate in the cost of constructing the connecting line from the closest existing utility line to his point of usage. If the connected load is less than 1,000 lip, it probably is best to let the utility provide the primary substation. For larger connected loads the owner can obtain a more favorable "primary voltage" rate if he provides the primary substation to receive the incoming power and transform it to the distributing and usage voltages. 3. The cost of purchased power usually is made up of a demand charge, deter¬mined by the maximum amount of power the customer takes during any 15-min period throughout a month, and a graduated energy charge for the kilowatt-hours consumed-that is, so much for the first block of energy based on the demand,

Jan 1, 1973

By A. Gutiérrez

At present, most ore milling is done in tumbling mills, consisting of huge cylinders turning on their horizontal axis. This rotational motion causes the ore charge and the grinding balls to interact by impact, compression and abrasion, to reduce the size of the ore. This method is very inefficient since only around 12% of the energy supplied is used for actual grinding, the rest being used in moving the large mass of balls and ore within the mill. This work aimed at better understanding the milling process by evaluating the movement of the load through the Discrete Elements Method (DEM). First, the number of bodies (balls and ore) moving inside the mill is determined, to correlate to the potential impacts that constitute one of the milling mechanisms. Then, the number of high energy impacts is evaluated to correlate to the bodies in motion. At this stage, a differentiation between grinding media and the ore, as well as between the types of contact taking place in the mill, has to be made. This latter issue is of great relevance since from the five identified contact types (ball-ball, ball-liner, ore-ore, ball-ore and ore-liner) only the last three actually contribute to the milling process, the other two causing structural damage to the mill.

Jan 1, 2007

By Colin C. Harris, Jie Zheng

While applications of stirred media mills for fine particle production have continued to increase, there is a lack of understanding of operating behavior and power requirement. Investigations in laboratory stirred media mills have been carried out with grinding media, limestone and yttria stabilized zirconia. The torque required to rotate impellers immersed in dense particulate media with supernatant versus impeller rotational speed displays four regions marked by sharp transitions: transition from static to dynamic friction; channel- ling; dispersing; and centrifuging. Equations, including dimension- less group correlations of power and modified Reynolds number, for relating power, speed, impeller and tank dimensions and design, media size and density, solid concentration, and other relevant variables have been established. Scale-up guidelines with respect to power consumption are also proposed. The best operating conditions for grinding limestone in the laboratory stirred media mill have been identified. Complexation by the polymer during ultrafine grinding of zirconia has been found to cause extraction of yttrium into solution with possibly significant changes in the surface chemical composition of the product.

Jan 1, 1995

The first part describes a model (the C model) based on the motion of the grinding charge. The charge is treated as a continuum, which allows analytical solutions to the equations that are developed. The C model is equally applicable to ball-, semi-autogenous and autogenous mills and contains a description of the power draw of both the cylindrical section and the cone-ends. Differences between the power draw of grate- and overflow-discharge mills are described from consideration of the different shapes and compositions of their charges. A large database of industrial mill data is used to demonstrate the accuracy of the model. Part 2 describes a simpler, empirical model (the E model) whose performance is based on that of the C model. The same database was used to assess the predictive capabilities of the E model. The model was shown to be only slightly less accurate than the C model despite its much simpler structure

Jun 18, 1905

By Michael F. Gleason

In 1986, Gold Fields began negotiations with a large Nevada electrical power utility to supply power for its Chimney Creek Mine In northern Nevada. After the long negotiations reached an impass over various costs associated with the power line, a decision was made by Gold Fields to generate its own power. Self-generation is not uncommon overseas, but it is rare for any but very large or very small operations in the United States. Surprisingly, under certain conditions a mine can generate its own power profitably and Gold Fields has found that the associated operating and maintenance problems are minimal. The following report details what factors went into this decision and how it works. Hopefully, it can serve as a guideline for those who may find themselves in a similar position.

Jan 1, 1990

By Thomas V. Falkie, Robert Stefanko

Recently The Wall Street Journal featured a series of articles titled "The Dirty Work-Brutal, Mindless Labor Remains a Daily Reality for Millions in The US.-Mining Coal, Shoveling Slag, Gutting Hogs Pays Bills But Can Drain Spirit, Hope." The article was devoted to describing how tough and dangerous is mining (and some other jobs) and how rough life is for miners and their families. Similarly during the past few years some psychiatrists and sociologists have devoted increased attention to the attitudes and life styles of miners. Unfortunately most of their approaches have been neither scientific nor objective, and very little good clinical research has been done on the subject.

Jan 1, 1971

By Arthur Green

A GROUP of 13 cities situated in Los Angeles and Orange counties in Southern California is engaged in constructing an aqueduct to carry water from the Colorado River at a point near Parker, Arizona, to a distribution point sear Riverside, California. The aqueduct will have a total length of approximately 241 miles, and is designed to deliver 1605 cu. ft. of water per second, or a little more than one billion gallons per day. The aqueduct crosses a barren, desert waste and the project includes approximately 91 miles of 16-ft. tunnel. The large amount of tunnel driving that has been done in this country in the past few years has resulted in some remarkable developments in equipment and methods. The building of the Colorado River Aqueduct, with its 91 miles of tunnels, has called on the best engineering knowledge in the country. New and better equipment has been designed for all phases of the work, and this equipment has been coordinated and adapted to the various conditions with a high degree of efficiency. The result has been that records for tunnel driving have been set under adverse natural conditions that exceed the estimates for progress under good conditions. All of the tunnels in the main aqueduct, except the Valverde and Bernasconi at the western end, have a finished diameter, inside the concrete lining, of 16 ft. Fig. 4 shows a section of the tunnel with the concrete lining in place. Fig. 5 illustrates the finished tunnel in three typical sections. The standard tunnel grade is 3.432 ft. per mile in the 16-ft. tunnels, but the Valverde and Bernasconi tunnels have a steeper grade and a finished diameter of 15 ft. 3 in. The rough bore of the large main aqueduct tunnels averages 12.95 solid cubic yards of material per foot of advance in timbered sections and 10.76 solid cubic yards per foot in unsupported sections.

Jan 1, 1936

By R. Hogg

Based on a simplified model for the motion of particulate materials in horizontal, rotating cylinders, approximate expressions have been derived relating the power consumption of a tumbling mill to its dimensions and speed of rotation and to the amount and nature of the charge. The basic assumptions underlying the model are that there is no slip between the charge and the mill shell, that the free surface of the charge remains essentially planar during rotation and that there is no transfer of momentum from the material flowing down the free surface back to the mill shell. The relationships formulated from this model have been shown to be in excellent agreement with experimental results taken from the literature. While the requirements of the model are most closer met at low speeds of rotation, the results appear to be valid even for speeds up to 70-80 percent of the critical speed. Poorer agreement between theory and experiment is found when the charge consists of relatively large particles (balls) and when the filling of the mill exceeds 50 percent of the available volume. Qualitative explanations of these deviations have been offered.

Jan 1, 1971

By Bailey H. W

Power supply for remote mining developments is compared with supply to the general public with the conclusion that the private power plant operator has many opportunities to minimise his costs which are not open to public utilities. The main features of diesel, gas turbine and steam power plant and the limitation upon their application which may be imposed by the fuels available and the local conditions at remote sites are outlined. Reference is made to the value of joint examination by the mining engineer, metallurgist and power engineer to decide how to make best overall use of capital, labour and energy in co-ordinating the design of power and process plant and in setting no more than adequate standards of reliability and efficiency. Fluctuations in world markets make it difficult to plan mining operations to a firm time base. Suggestions are made to minimise the financial risk in forward expenditure upon power plant which in large sizes due to longer construction time may have to be ordered before a final decision is taken upon the mining development it is to serve.

Jan 1, 1973

By Ashish Ranjan Kumar, Barbara Arnold, Luis Sanchez Gonzalez

The health and safety of miners is critical in the industry. Prolonged exposure to dust-laden air results in irreversible ailments like pneumoconiosis that have a severe impact on their lives. Operations use various personal protective devices (PPEs) to alleviate their exposure to respirable dust. Powered Air Purifying Respirator (PAPR) is one such device that uses high- efficiency filters and positive pressure masks to shield miners from airborne contaminants. Used in the medical and other industries, these respirators efficiently protected healthcare workers during the COVID-19 pandemic. Recently, the mining industry has shown a growing interest in adopting this PPE to ensure safe working conditions for the miners. We present an introduction to the PAPRs and discuss their dust capture efficacy in this manuscript.

Feb 1, 2025

By Alexander Filotti, Richard Kalson

"1. INTRODUCTION- WHAT IS P3 OR PPP ?The Public Private Partnership (PPP or 3P) is a project delivery scheme based on the government providing land and/or a concession agreement, and on a private entity providing the design, construction, financing, operation and maintenance of the project for an extensive duration of time (up to thirty years). At the end of the operation-maintenance period, the project is turned over to the public entity, which fully owns the project at all times. While there are many PPP delivery schemes used around the world, for the present paper, we are going to analyze the impact of the Design-Build-Finance-Operate-Maintain (DBFOM) scheme on the deep foundation specialty subcontractor. There are couple of reasons that the PPP delivery system started to be used and implemented not only by developed nations (e.g. United Kingdom, USA etc.), but also by the International Development Bank for delivering major infrastructure projects in developing nations. From the point of view of government agencies, some of the reasons to use PPP are the following:??The primary use of private capital in an era where borrowing and/or supplemental taxation represents too much of a political risk. Budget deficits and taxation limits are extremely hot topics in every election (national or local) and the level of education of the electorate in this area is making it more and more difficult for politicians to use borrowed funds and additional taxation finance sources for public projects. At the same time, we see an increase in the social expenditures of the government in parallel with a needed increase in expenditures on infrastructure due to aging and neglect.??Bundling the construction risks with the operational and maintenance risks naturally pushes the private entity to increase the level of innovation and communications in the primary phase ( the construction phase) in order to develop future process based upon the innovation and communications utilized in the operation and maintenance phase of the project. This is true if contractual incentives are properly structured because “all revolves around incentives. In a world of ‘incomplete’ contracts, where it is difficult to foresee and contract about uncertain future events, it is important to get the incentive structure right” (Grimsey and Lewis, 2004).??The transfer of very expensive risks such as differing site conditions, schedule, design, construction, maintenance and operation costs from the public authority to the private entity.??The timespan of development and construction of a PPP project is usually shorter than the traditional procurement process (e.g. “ the I-595 P3 provided capacity improvements fifteen years sooner than a conventional plan would have offered. In Maryland, an innovative expansion of the Seagirt Marine Terminal in the Port of Baltimore was completed two years ahead of schedule due to the P3 model. As a result, the Port of Baltimore is only the second port on the US East Coast to have unrestricted access to both a fully functioning 50-foot channel and 50-foot berth.”)"

Jan 1, 2017

By Mirko Jurkovic, Thomas Hueper, Jens Kempken

The high competition scenario pushes the steel producers business. Zero defect requirements from customers force the operators for additional efforts in process control and quality management. PQA® has been developed as an advanced process and quality management assurance solution. It is focusing on the analysis of process data, equipment information, inline quality measurement devices and trend analysis. The paper describes the structure of the advanced process and quality management assurance solution PQA®; it gives insights on the expert know-how, process and quality evaluation and points out the benefits like cost reduction, improvement yield and customer satisfaction increase.

Oct 1, 2019

By Philip S. Mathews

THE tremendous stimulus given to the mining industry by the gold and silver policy of the present administration has found the capital market for mines ill prepared to afford practical means of financing. Particularly has this been true of the host of abandoned high-cost producers and prospects which increased gold and silver prices have made potentially profitable. In a comparatively short time, experience has demonstrated abundantly that valuable properties have frequently failed to secure capital, while questionable properties have drawn to themselves and their promoters more of the public moneys than their prospects justify. Singularly enough the fault is usually attributable to faulty financing. Discussion and study of this problem are vital to the industry.

Jan 1, 1936