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By Eugene M. Trisko

Presentation Overview State-Of-The-Art Scrub/Switch Analyses > Allegheny Power System > PSI Energy UMWA Phase I Coal Interests > 16 Phase I Scrub Plant Coal Profiles > Coal Price/Emission Allowance Interaction Southern Company Case Study > 2+ Million Ton Phase II Allowance Purchases > 10+ Million Ton Phase I Coal Switch > Georgia PSC Proposed Fuel Price Cap > Shift/Avoid Georgia Scub Costs Through System Allowance Purchases

Jan 1, 1993

By J. F. Brune

This paper analyzes the explosion hazard resulting from the formation of methane-air mixtures in the mined-out gobs of underground longwall coal mines. Although direct examinations of the gob atmosphere are difficult due to the inaccessibility of these gobs, evidence from methane drainage practices and investigations of numerous mine explosions suggests that explosive methane zones can form within longwall gobs. Explosions and fires resulting from these methane accumulations have led to severe and fatal injuries to the miners. Most recently, this was demonstrated in the explosion of the Upper Big Branch Mine in West Virginia, where 29 miners lost their lives.The paper also reviews current research on numerical modeling of gas flows in longwall gobs and outlines how targeted injection of nitrogen into gobs can effectively reduce the volume of such explosive methane zones. The paper concludes that comprehensive monitoring of gas compositions, along the accessible fringes of the gobs along with inertization, improved ventilation schemes and further research are necessary to control this explosion hazard and make mining operations safe.

Jan 1, 2013

By Y. Luo

"Investigating abandoned mine subsidence is often a difficult task because many factors, both mining- and nonmining-related, can affect the possibility and the formation process of surface subsidence events over abandoned underground room-and-pillar mines. Among them, mine water frequently plays an important role in causing such subsidence events. However, mine water could also serve the purpose of preventing subsidence. The dewatering of abandoned room-and-pillar mines has been identified as the main cause for a number of serious mine subsidence events in the past.In this work, the mechanism of mine water to prevent surface subsidence over abandoned room-and-pillar coal mines was studied. Two mathematical models are proposed to quantify the potential effects of mine water on the structural stability of mine pillars, roof and floor as well as the potential for causing surface subsidence. The models are validated with an actual case. IntroductionThe potential for room-and-pillar mining operations to induce surface subsidence is mainly dependent on the recovery ratio in the underground mines that directly relates to the stability of pillars. Normally, if the recovery ratio is less than 50 percent, the mine pillars are sufficient to support the overburden strata without their collapse in a sufficiently large contiguous area. Consequently, there will be no surface subsidence. However, if the recovery ratio is greater than 70 percent, the pillars are too small to support the overburden strata and can cause immediate surface subsidence. In 1993, a mathematical model and program was developed and proposed (Luo and Peng, 1993) to predict surface subsidence caused by high-extraction, roomand- pillar mining. When the recovery ratio is between 50 and 70 percent, the mine pillars could be loaded near their critical condition and, therefore, the surface subsidence is uncertain to develop. If the surface subsidence did not occur immediately, mine water starts to fill the underground openings. If thick, clay-type rock layers are presented in the mine roof, floor or pillars, they can be considerably weakened by mine water and cause surface subsidence. The techniques to investigate subsidence events over inactive room-and-pillar coal mines caused by the weakening effects of raising mine water to the claystone immediate roof and floor were presented in Luo (2009, 2011)."

Jan 6, 2018

By C. F. Bonney

Spherical or oil agglomeration has been recognised for many years as a possible process for the recovery of mineraVmetal values. BP has investigated the potential of spherical agglomeration for a number of minerals as have other workers. Testwork has also been carried out by both BP and others on the selective agglomeration of fine coal. The spherical agglomeration of both minerals and coal depends on the use of an immiscible liquid e.g. a hydrocarbon which is added to a suspension of the solids in water. On agitation the oil is distributed over oleophilic/hydrophobic surfaces and particle impact allows inter-particle liquid bridges to form causing agglomeration. It is also possible to enhance the oleophilicity of the material to be recovered by the use of collectors similar to those used in froth flotation.

Jan 1, 1998

By P. I. James, M. R. Baker

This paper examines new copper production from waste-grade ore using Blue Planet Strategies’ DEMET™ (Dynamic Electrode Mining Effluent Treatment) technology, which aims to bridge the practical weak pregnant leach solution (PLS) processing gap in heap leach-solvent extraction/electrowinning (SX/EW) operations by electrochemically removing metals from weak streams and generating product streams strengthened in target metals in a functional analog to SX. Weak PLS treatment was studied and used to estimate the economic and production impacts for a representative hypothetical brownfield copper heap leaching and DEMET-augmented SX/ EW operation to utilize "waste ore." Copper removal at 86% plating efficiency to below 0.1 g/L copper with power consumption of 0.55 kWh/lb copper and product strengths of over 10 g/L copper are presented. Modeling yielded approximately $2/lb total copper production and = $1/lb treatment costs with an immediate operation gross margin increase of 12% for the augmented brownfield. Potential mine life extension with an average 38% gross margin on "waste ore" augmented production at copper values of $3.25/lb was also indicated.

Jan 1, 2014

Acid Mine Drainage (AMD) is the most serious environmental problem facing the Canadian Mineral Industry today. Acid Mine Drainage results from oxidation of sulphide minerals (e.g. pyrite or pyrrhotite) contained in mine waste or mine tailings. It is characterised by acid effluents rich in heavy metals that are released into the environment. A new acid remediation technology is presented in this paper by which metallurgical residues from the aluminium extraction industry are used to construct permeable reactive barriers (PRB) to treat acid mine effluents. It describes column tests performed to simulate a PRB using Bauxsol?, a chemically and physically treated bauxite refinery residue, as a reactive material. This experimentation shows promising results for the Bauxsol? PRB method in neutralizing pH and removing metals from acidic mine effluents.

Jan 1, 2006

By R. R. Fernández

The Newmont roasting plant in Carlin, Nevada, commenced operating in December 1994. Over the years, refractory ores and pyrite concentrates from different gold deposits constituted the feed to the facilities. Historical plant performance indicated that the roasting temperature was the main variable affecting the structural characteristics of the calcine, which in turn affected the recovery of gold by cyanidation. Gold recovery as a function of roaster temperature has been closely monitored since October 2000. The original design temperature was 550° C. Lower roaster temperatures of around 500° C resulted in a gold recovery increase of more than six percent. This increase was directly related to an increase of the surface area of the calcine. The implementation of an ?intelligent? process control system helped significantly in achieving steady low roasting temperatures, thus obtaining high gold recoveries of 92 to 93 percent. Under these conditions, several roasting campaigns with high-arsenic-containing ores were conducted, which resulted in a significant decrease in gold recovery. The reduced gold recovery was caused by the loss of surface area (e.g., porosity) of the calcine as the arsenic content of the roaster feed increased.

Jan 1, 2010

By Dominique Francois-Bongarcon

The world mining industry is facing a severe recession. Thus, it is time to recall the value of geostatistical methods which were formerly developed as a money-saving and productivity-increasing tool. The situation has worsened, but the techniques of geostatistics have dramatically changed. Up to millions of dollars can be saved during exploration with simple use of variograms; then, during reserves estimation with kriging methods; and finally, with the parameterization of reserves, when evaluating a project and optimizing its global mining parameters.

Jan 1, 1983

By Maurice L. Madden

An investigation was undertaken for a ground water discharge plan for the Chino mining complex near Hurley, New Mexico. Operations which impact ground water include dump leaching, storage reservoirs, and tailings seepage. The investigation included both hydrogeological data collection and laboratory analysis. A conceptual understanding of surface water and ground water was then developed. Surface water and ground water models were used to match existing conditions and predict the impact of operational modifications. The study concluded that runoff and resulting leach reservoir overflows were primarily responsible for the ground water degradation. Tailings seepage represents a smaller part of the impact.

Jan 1, 1984

By C. P. Blair

In discussing so-called "volume rates" for the movement of coal, I start from one basic premise: That it is the job of the railroads to devise rates which will move the traffic, while at the same time assuring a fair return on their investment. No matter how reasonable and nondiscriminatory freight rates may be, if they fail to attract and hold traffic to the rails, they are utterly useless - both to the carriers and the shipping public. And it will be my purpose here to show that under certain circumstances the use of volume rates by the railroads enables them. to hold traffic which would otherwise be lost, and to avoid needless dissipation of revenues, Properly employed, volume rates should benefit both the coal industry and the railroads, I do not, however, advocate the discarding of the carload as the basic rate-making unit. Far from it. Sound operating reasons dictate the making of rates based on car- loads, and the tradition of carload rates has a firm foundation in railroad operating costs, many of which vary directly with cars handled. In short, the carload was, Is and, in my opinion, will continue to be the basis for most rail rates on coal, as well as on other commodities. But change is an inevitable result of progress, and we should not be so bound by tradition that we are unwilling to try novel methods of ate making, should the circumstances require, The modern rate maker must, now and then, run the risk of being called an iconoclast if he is to keep up with the times. As T will point out, volume rates were for many years rejected by both the Interstate Commerce Commission and the railroads, But now both the Commission and the carriers have come to recognize that under proper circumstances and conditions volume rates are a powerful and effective tool.

Jan 1, 1959

By Dr. David R. Hargis

Finite-difference digital computer models can be used to evaluate the effects of proposed mine dewatering and depressuring operations on ground-water aquifer systems. The effects of proposed dewatering and depressuring operations can be simulated for both underground and open-pit mining in confined and unconfined aquifer systems. Design of dewatering and depressuring well arrays to accommodate proposed mining operations in a variety of hydrogeologic settings can be accomplished through judicious application of well-documented and tested computer programs that are widely available from government agencies and universities. The speed and flexibility of the computer models can provide an economical means for comparison of alternative mining plans, and can be used to determine the optimum mine plan with respect to dewatering requirements.

Jan 1, 1980

By T. W. Beck

Drilling into coal mine roof strata to install roof bolts has the potential to release substantial quantities of respirable dust. Due to the proximity of drill holes to the breathing zone of roof bolting personnel, dust escaping the holes and avoiding capture by the dust collection system pose a potential respiratory health risk. Controls are available to complement the typical dry vacuum collection system and minimize harmful exposures during the initial phase of drilling. This paper examines the use of a bit sleeve in combination with a dusthog- type bit to improve dust extraction during the critical initial phase of drilling. A twistedbody drill bit is also evaluated to determine the quantity of dust liberated in comparison with the dust-hog-type bit. Based on the results of our laboratory tests, the bit sleeve may reduce dust emissions by one-half during the initial phase of drilling before the drill bit is fully enclosed by the drill hole. Because collaring is responsible for the largest dust liberations, overall dust emission can also be substantially reduced. The use of a twistedbody bit has minimal improvement on dust capture compared with the commonly used dust-hog-type bit.

Jan 1, 2014

By Robert E. Mclvor

Classification system efficiency (CSE) is a simple metric that can be used to measure and increase ball milling circuit efficiency. It is defined as the percentage of the ball mill energy being used to grind target (oversize) particles. This paper describes CSE analysis conducted for a variety of operations with related improvements in circuit efficiency ranging from 3 to 30 percent. The achievable CSE for any given ball milling circuit is described, providing the means to determine the extent to which every plant can benefit from increasing grinding circuit CSE.

By Don S. McCoy, W. Joseoph Schlitt, Donald B. Swanson

Introduction Contract miners have long played an important role in the minerals industry. Historically, these were individuals who worked as underground miners and were paid by the ton or the day. These hardy types still ply their trade in the industry. However, today the term "contract miner" generally refers to an independent contractor who supplies the people and equipment needed to conduct surface mining operations for an owner or lease holder. At one time or another, contract miners have probably handled virtually every mineral commodity from sand, gravel, and stone quarrying to mining uranium and precious metal ores. In today's market, though, contract mining appears to be concentrated in just a few areas. These include precious metal mines, various types of solid fuel operations, and reclamation of abandoned mines. This article covers market areas, contract mining organizations and services, and their advantages and disadvantages. Gold and silver mines Although exact figures are not available, contract mining represents a significant element in the precious metals segment of US mining. For gold and silver, the growth in contract mining appears to be paralleling the overall growth in mining activity itself. Nevada is the largest gold producer in the US. The latest available data (1985) on open pit gold/ silver mines is summarized in Table 1 (Nevada Division of Mine Inspection, 1986). These figures show that contractors mined nearly half of the ore in 1985. Total tonnage mined, of course, was much higher for both owners and contractors. Assuming an average stripping ratio of 2.5 to 1, the total daily mining rate for the contractors was more than 145 kt (160,000 st). This translates into a contract mining rate of about 36 Mt/a (40 million stpy) based on 250 operating days a year. This approximate 50-50 split between owner and contractor also appears to hold for the future. Metals Economics Group (1987) published a survey of 51 short-range and 54 long-range precious metal projects being considered throughout the US. Contacts with owners, requests for proposals, and past corporate philosophies all suggest that about 55% of the open pit operations scheduled for the near-term will be contract mined. This represents an estimated 26 kt/d (28.5 stpd) of ore. A similar assessment of the long-term projects indicates that about 12 kt/d (13,000 stpd), or just under 50% of the open pit tonnage will be contract mined. There are several reasons why gold and silver represent such an attractive opportunity for contract miners. One is that many properties are owned or leased by individuals or partnerships that are essentially entrepreneurial. Many of these owners or lease holders have minimal mining experience. They must therefore either rely on contract mining organizations, sell an interest in the project to another mining company that will become the operator, or hire an experienced management team. For about the same reason, junior mining companies also represent good prospects for contracting. This is because most junior companies focus on exploration. They would prefer to spend their generally limited funds on drilling programs. Thus, they tend to minimize additional capital requirements by using contract miners or farming out the property to another mining company. Another good reason for using contract miners is the size of the deposit. Many properties are so small that their reserves will not support the capital expenditures

Jan 12, 1987

By Pieter-Jan Kleiterp

Highwall mining is a mining method to extract coal from a final boundary in opencut mining, trench mining or contour mining. This boundary may have been reached because of economic constraints (economic strip limit) or geographic constraints, such as spoil heaps and rivers. Coal is mined from visible, horizontal, or near-horizontal coal seams by making rectangular, parallel, unsupported drives with an unmanned cutterhead and coal transport system. This is controlled from a mining unit, or launch frame, positioned outside the drive, in front of the highwall. Removal of overburden is not required or is limited to small quantities only.

Jan 1, 2010

By C. Einberger

Groundwater Monitoring is typically required by regulatory agencies at potentially hazardous landfills or surface impoundments. Agencies have often required an arbitrary number of wells with limited evaluation of the effectiveness of the network to detect a leak. A Monitoring Efficiency Model (MEMO) has been developed to improve the design and cost effectiveness of monitoring well networks. MEMO 15 an analytical model that simulates the migration of hypothetical contaminant plumes from a site and quantifies the efficiency of alternative well network designs in detecting the plumes. The computed monitoring efficiency provides a quantitative measure of the well network adequacy based on hydrogeologic considerations. The model was recently used to design the groundwater monitoring well network for a heap leach pad at the proposed Beartrack Project.

Jan 1, 1993

By P. Kawahata

Newmont?s Twin Creeks Mine, located in northern Nevada, is producing gold ore from surface mining operations. The ore is currently processed at three different on-site facilities depending on ore type and grade. Processing facilities operate under stringent geochemical blending constraints that must be met from mine ore deliveries and off-site sourced ore. To analyze various strategic options, the technical team utilizes the mathematical optimization approach. However, due to the size and complexity of the operation, there are unique challenges in optimizing life-of-mine production scheduling. This paper describes those challenges and methods developed to take advantage of different scheduling software to effectively compensate each other and result in reasonable guidance. This paper also describes how those scheduling results are reflected in detailed mine plan and cost estimate work.

Jun 1, 2013

By E. C. Watkins

The fiber glass industry is an industry that. hopefully is still in its infancy and far from a mature business. Fiber glass, as will be discussed in this paper, deals with continuous strand glass as used in the textile laminate and reinforced plastics industries. More specifically, we are speaking of glass used for printed circuit boards, tapes, paper, cloth, pipes, tanks, boats, recreational equipment, roofing shingles, and automotive applications. Compared to the flat, container and decorative glass industries, we are very young. The early patents on fiber glass applications were issued in the 1930's. The type of glass most commonly used in the world and that discussed in this paper is designated as "E" glass. This is a boro-silicate type glass having specific chemical and electrical resistance and low thermal expansion properties.

Jan 1, 1986

By Bryan Ulrich

Knight Piésold and Co. hosted its annual roundtable discussion on March 17, 2011 at the Stockman Hotel and Casino in Elko, NV. The theme for Roundtable 2011 was, ?High density tailings, paste, and filtered tailings,? although the topic may well have been subtitled, ?Don?t prematurely rule out any technologies before they are given their day in court.? Bryan Ulrich, Knight Piésold?s local representative, as well as Tom Kerr from Knight Piésold?s office in Denver, CO, were on hand to help facilitate the discussion. Ulrich and Kerr are senior vice president and president of Knight Piésold?s U.S. practice, respectively. The event played host to more than 30 attendees from several western states. Attendees included personnel from a dozen mining properties and various corporate offices. There were also attendees from manufacturing and specialist consulting firms who have been providing services to various high-density tailings, paste and filtered tailings operations worldwide. It may be noted that the term ?filtered tailings? is used in this discussion. Alternative terms, such as ?dry stack? or ?dewatered tailings,? should be avoided whenever possible, as such terms tend to give a false sense about the nature of the material since these materials typically still retain a significant amount of moisture.

Jan 1, 2011

By B. W. Cavender

Capital investments are made for a variety of purposes, from providing incremental capacity at existing operations to developing and implementing new technologies intended to radically improve a company's capabilities. These projects generate very different business opportunities and create value in distinctive ways. For incremental improvements, the capital budgeting process assures at least a loose fit between short-term goals and readily available resources. However, the criteria used to evaluate capital projects often prevent a company from committing to more aggressive goals that lie beyond the firm's current abilities or resources. Such projects may not have clearly identifiable future cash flows, and the degree of interaction with other projects and the nature of the risk incurred may be difficult to estimate. Additionally, by focusing only on quantifiable benefits, the budgeting process often fails to recognize "soft" improvements such as increased operating flexibility or new knowledge generated by such projects. By rejecting these projects, the capital budgeting process may actually harm the company's future competitive position.

Jan 1, 1998