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By Richard Weinstein, Richard Snoby

There are many advantages to upgrading coal with dry jigging technology. The most obvious is the lack of process water, which eliminates the need for fines dewatering and slurry confinement. Dry jigging eliminates the clean coal moisture penalty associated with wet processing. Particulate emissions are virtually nonexistent due to inclusions of fabric dust collectors on all modern dry jig plants. Because of the environmentally friendly nature of dry jig plants, installation permits are often measured in days, not months. There has also been a fundamental advance in dry jigging efficiency. All of these advantages have renewed the coal industry’s interest in dry jigging. But air jigging is not right for every application. There are limitations due to particle size, particle shape, moisture and near gravity content. This article explores the evolution of dry jigging. It reviews parameters important for determining the suitability of dry jigging. It also compares historical performance data as measured by imperfection, against results from modern dry jigging technology. The article also presents data from modern dry jig installations.

Jan 1, 2007

By M. S. Safarzadeh

Over the last fifty years, the treatment of enargite concentrates has not received much attention primarily because of the availability of other clean concentrates suitable for processing with existing smelting and/or leaching technologies. As traditional copper ores have become scarcer, copper-arsenic ore deposits have garnered more interest. Arsenic release is a significant concern during the treatment of enargite by pyro or hydrometallurgical methods. Enargite is also very refractive in standard leaching procedures. Thus, economical treatment options for enargite concentrates are needed. Preliminary experiments have shown that the acid-bake leach process could be adapted and used for the treatment of enargite concentrates. In this study, low-temperature (100-400 ºC) sulfuric acid baking of an enargite concentrate followed by water-leaching has been evaluated. The results indicate the thermal transformation of enargite to copper sulfate during sulfuric acid baking, with most of the arsenic being released from the concentrate into the gas phase for baking at 400 ºC. The condition for maximum copper extraction (~100%) from the concentrate was found to be 400 ºC, sulfuric acid amount of 0.5 mL/g of concentrate, and 2 h baking time. Part of the arsenic was captured in the form of arsenopyrite (FeAsS). XRD analysis proved the presence of some arsenic in the form of claudetite (As2O3) in the baked concentrate. Acid baking of pure enargite behaved in similar fashion.

Jan 1, 2012

By David van Cleave, David L. Rome

Whether you buy your minicomputer from a manufacturer or another vendor, the first thing you must do is define your needs. With good planning, the initial cost will be low and your return on investment will be maximized over the long term. Involving all members of your staff who will he using the new computer in the planning phase is also important. Their participation will alleviate any potential concerns they may have about new equipment, and their suggestions will provide valuable input for your specifications. After you define your proposed system, survey available hardware and software. The survey will help you in the next step, preparation of specifications. The specifications, along with a quote request, are then sent to various manufacturers. Consider the Manufacturer When selecting your minicomputer, one important item to consider is the manufacturer. Remember, when you buy a computer, you're also buying the services of a computer company. A firm that makes a commitment to its customers and provides a product that is field tested before releasing it for sale is preferable. Examine the company's maintenance and support packages, since every machine requires preventive maintenance. Does your manufacturer or original equipment manufacturer (OEM) support service sites in your area? Has their service record been commendable? Will they provide training for your personnel and a supply of circuit boards so you can retain a degree of self-service autonomy? Three methods of buying a computer involve the manufacturer, an OEM, and the systems house. Buying direct from the manufacturer means you go straight to the source, using no middleman. This gives you maximum flexibility; you can consider every alternative and many possible combinations of computers, peripherals, and software until you find exactly the right system for you. The OEM buys computers direct from the manufacturer and builds them into his own computerized, special purpose product. He usually sells a complete package, including software and hardware, and often noncompetitive equipment as well (a scientific or engineering instrument, for example), designed for the mining market. Because he offers a packaged product, the OEM can often charge less for the system than if you put the pieces together yourself. In many ways, the OEM also provides a unique system. And while the OEM sells a packaged solution, he also usually has the special market knowledge necessary to modify the system to meet your unique needs, if necessary.

Jan 11, 1981

By J. Hines

Traditionally, fuel oil or diesel was the collector of choice in coal flotation, but in recent years these materials have come under increased scrutiny because of concerns about the toxicity of some components. In response to these concerns, Georgia-Pacific Chemicals LLC has commercialized a patent pending coal collector (Talon® 9400 reagent) that is 100% derived from the pulping of trees. This study presents a comparison of yields and recoveries for different coal collectors, including the one derived from the pulping of trees.

Jan 1, 2011

By M. S. Miller

With prevailing assumptions that plentiful domestic coal reserves will be available for meeting our Nation’s expectations for on future low emission, coal-fired power plants, major government funding in Clean Coal Technology, and Carbon Sequestration Programs continues to be aggressive. However, after more than a decade of cutbacks in funding for domestic coal-related programs and personnel, there is a growing concern that adequate quantification and qualification of our Nation’s coal reserves is increasingly being compromised. This paper will define the growing concerns and dichotomies that continue to increase, and address the decreasing number of fossil fuel mapping and assessment programs by Federal and State programs.

Jan 1, 2004

By Marianne Snedeker

In September 1985 we published a questionnaire asking about the content of MINING ENGINEERING and about your interests. By Dec. 10, our cutoff date, we had 430 responses, representing about 1.5% of the 28,238 people who received the September issue of ME. In the data that follow the tabulation and percentages are based on the number of individuals who responded to the particular question. About ME Through responses to the questionnaire, we were hoping to learn more about you, your interests, and how the magazine could better serve you. Those of you who responded told us something positive - you look at or read the magazine. Of the 430 respondents, 428 or 99.5% indicated that they had read or looked through the July and/or August issues. Those of you who refer to the magazine once are 207 or 48.5%. Those of you who refer to the magazine two or three times are 193 or 45.2%. Those of you who refer to the magazine four or more times are 27 or 6.3%. How much time do you spend reading the magazine? Of those responding to this question: 64 spent up to 1/2 hr 15.0% 224 spent up to 1 hr 52.6% 115 spent up to 1-2 hr 27.0% 23 spent more than 2 hr 5.4% In an informal survey among our staff, we determined that most people spend 1/2 to 1 hr reading magazines to which they subscribe at home. Does that match your experience? Many of you, 335 or 79%, clip your magazine for further reference. Also, many of you, 313 or 73.6%, do not pass your copy on to another reader, indicating that you are clipping it or receiving the magazine at home. Those magazines that are passed on reach: 1 person 3 0.7% 2 people 64 15.1% 3-5 people 34 8.0% 5 or more 11 2.6% Answers to what portions of the magazine you find useful indicated that the top three were Industry Newswatch, feature articles and Technical Papers; see Table 1. The "other" category included advertising - display, classified, Employment, and Professional Services - Washington Survey, New Products, Free Literature, book reviews, technology news, and Coming Events and Short Courses. We asked your appraisal of the technical level of the magazine. Of those responding, 39 or 9.1% indicated that it is too technical, 55 or 12.8% indicated it is not technical enough, and 335 or 78.1% judged it to have the correct technical level. In response to the question about whether you like to read an occasional feature that is not technically oriented, 21 or 5.1% said no, but an overwhelming 94.9% (393) said yes. Of the specific

Jan 1, 1986

By P. C. Fletcher, E. Kaya

The Bond grindability testing procedure has been standardized to measure the same grindability values, i.e. Bond work index (BWi), for the same ore when tests are performed in different laboratories or by different operators. This is accomplished by the standardization of mill dimensions, tumbling speed, grinding ball charge weight and distribution, sample ore charge weight in the mill and operating practice. The results of this investigation reveal that the Bond work index grindability values may differ substantially with different standard Bond ball mills. This paper will review the results.

Jan 1, 2002

By William D. Leech, Ronald E. Romley, Gary N. Sheppard

The Price Road Drainage Tunnel was constructed for the Arizona Department of Transportation (ADOT) in 1988 and 1989 to provide surface water drainage for the proposed outer Loop Highway (SR 117). The 5.4 km (3 mile) long, 6.6 m (22 ft) excavated diameter tunnel was driven through sand, gravel and cobbles utilizing an open face digger shield. Precast concrete segments were erected for initial ground support. A second-pass reinforced concrete final lining was placed, which was followed by contact grouting. This paper will consider the owner's representatives' view of the effectiveness of using precast concrete segments for this project. Topics discussed include segment design and erection, ground support, geotechnical instrumentation, segment erection verses contact grout interactions and tunnel production.

Jan 1, 1991

By K. Lapakko

One responsibility of the Minnesota Department of Natural Resources is to encourage the development of mineral resources within the state. A second responsibility is to ensure that mineral development does not adversely impact other natural resources, including the water resources of the state. One approach the Division of Minerals has taken to fulfill these responsibilities is to conduct cooperative research with the mining industry. To encourage mineral development the Division has cooperated with industry on projects related to exploration, mining, and mineral processing. To examine environmental issues the Division has worked in concert with iron ore, base metal, and precious metal exploration and mining companies, as well as the Western Governors' Association, US Bureau of Mines, US Bureau of Land Management, and the US EPA for the past 20 years. These projects were conducted to evaluate methods of predicting, preventing, controlling, and treating problematic mine waste drainages, as well as mine waste revegetation. This paper I) briefly summarizes cooperative projects conducted, 2) enumerates elements which have contributed to the success of cooperative projects, and 3) describes changes implemented for future projects at the Division's new field and laboratory research facilities, as well as at existing mine and plant sites.

Jan 1, 1998

By Nathaniel Arbiter

Flotation’s earliest patent was issued in 1860. However, the process was first applied commercially in Australia until 1904, and in Montana in 1911. Major advances followed both in reagent treatment and in cell design, with resulting process improvements. Mechanical cells have seen the widest use and with the major increases in plant capacities (Fig. 1) their volumes have also increased (Fig. 2). In 1991, the principal use for the process was to produce copper concentrates for smelting. It was applied to 243 Mt (268 million st) of copper ore. The total of all ores floated that year was 426 Mt (470million st). In 1997, US mines produced 257 Mt (284 million st) of copper ores for flotation, yielding1.75 Mt (1.94 million st) of copper.

Jan 1, 2000

Roof falls in coal mines typically occur in or around intersections and this has not changed in the last two decades. This research develops an improved scientific understanding of stress distribution and associated failure behavior around 4-way and 3-way coal mine intersections. Three-dimensional numerical analyses were performed to determine factors that influence intersection stability. The analyses used Hoek-Brown failure criterion. Failure zones around 3-way and 4-way intersections were developed. Intersection span and horizontal stress have a major influence on intersection stability. For the 4-way intersection, pillar corners across the intersection fail first and lead to progressive failure of immediate roof and floor layers. The mechanism of failure is similar for the 3-way entry but the shape and extension of failed zones differ. Coal ribs mostly fail due to tensile stress, while roof and floor strata fail due to shear stresses. Rib corners fail due to a combination of shear and tensile stresses. In addition to stress distribution; safety factor contours analysis was performed to assess stability of intersections.

Feb 27, 2013

By Douglas B. Silver

Traditional cycle theory would postulate that if you have a supply shortage relative to demand, the price will increase because buyers will incrementally increase the price they are willing to pay to ensure that their needs are fulfilled. As prices rise, more supply will be brought on and will eventually exceed demand. This supply excess will cause the price to decline as producers have to lower their prices to sell their goods. What is interesting is that cycles are simply volatility over time. Without the time factor, volatility simply goes up and down. When we add the time element, a cycle is created. This cycle can be big or small. In mining?s case, we are talking about a Super Cycle ? a big cycle. But a Su-per Cycle can be formed in two ways. It can form by either increasing the wavelength or the volatility. If these two elements are combined, a Super Cycle is formed. It is bigger than the normal cycle in terms of time duration and extent of volatility. A recent study (Fig. 1) conducted by Cuddington and Jarrett showed an interesting proof of Super Cycles and suggests that these cycles last between 15 and 30 years. So, what causes a Su-per Cycle? Is it a convergence of unrelated events or a consequence of related events? In a global community everything is related. Equilibrium theory would also take the position that a Super Cycle is a consequence of events.

Jan 1, 2008

By William M. Gleason

Hard times continued to plague the industry when the calendar rolled over to 2000. During 1999, the United States economy had grown vigorously, capping the longest economic expansion in United States history. However, the mining industry was not so fortunate. Commodity prices remained in a slump in the “new-economy” that was fueled by excitement and speculation about the power of the Internet during the infancy of the Information Age. Much of the investment money that once went to mining and exploration was now headed to the world of virtual gold mines. SME President Donald E. Ranta implemented new technology into his plans for SME. His two major goals were new membership growth and to foster the establishment of the comprehensive Internet presence for the Society’s technical information. His strategic priorities included enhancing the quality and quantity of publications, programs, meetings and short courses. “The Internet is the vehicle that will advance the priorities,” he said.

Jan 1, 2007

By Mark E. Smith

Oxide ores can consume enormous amounts of expensive sulfuric acid. The problem is amplified with increasing heap heights. One solution is to provide a thin liner and drainage system between each lift of ore, thereby intercepting the pregnant leach leach solution (PLS) after it exits the active lift. However, these liner systems require special attention to hydraulics, slope stability and geomembrane design criteria. Inadequate attention to the first two can result in reduced recoveries, increased acid consumption andsystem failures. The geomembrane selection criteria are different from the base liner, and optimizing its selection can have significant effects on the operation’s bottom line.

Jan 1, 1996

By M. H. Pelkki, R. J. Sweigard, P. W. Conrad, J. M. Ringe, D. H. Graves

Research has shown that excessive soil compaction is detrimental to the establishment of trees in reclaimed soils. Dry bulk density and penetration resistance are two soil parameters that can be used to indicate the level of compaction in reclaimed soils. It is believed that reclamation practices which minimize soil compaction will produce better results when forestland is the intended post-mining use. The University of Kentucky has developed reforestation test cells on reclaimed soils at a surface mine in eastern Kentucky to test this hypothesis. Each test cell has been planted with various species of trees, and since 1997, data have been collected at these test cells for soil average dry bulk density, average penetration resistance, average depth to refusal, and average survival rate of trees. These data have been correlated to determine the relationship between soil compaction and tree survival rate. It is believed that the two soil compaction parameters may ultimately be used to predict tree survival rates on reclaimed surface mined lands.

Jan 1, 2001

By P. A. Plunkert, D. E. Morse, L. McCartan, S. F. Sibley

The average annual growth rate of real gross domes-tic product (GDP) from the third quarter of 2001through the second quarter of 2003 in the United States was about 2.6 percent. GDP growth rates in the third and fourth quarters of 2003 were about 8 percent and 4 percent, respectively. Many other indicators reflected a rebounding U.S. economy — rising consumer confidence, higher retail sales, greater industrial production and more housing starts. Inflation also reached a 38-year low in 2003. The upward trends in many sectors of the U.S. economy in 2003, however, were shared by few of the mineral materials industries. Annual output declined inmost non fuel mining and mineral processing industries, although there was an upward turn toward yearend as prices began to increase (Table 1).

Jan 1, 2004

By Kerry Spickelmier

The only nickel smelter and the only active nickel mine in the United States is Glenbrook Nickel Co., a joint venture (50% each) of Cominco Resources International Ltd. and Cominco Ltd. In 1989, with the nickel price riding high between $2.30 and $2.70/kg ($5 and $6/lb), Glenbrook seized the opportunity to purchase and recommission a southwestern Oregon ferronickel smelter and the adjacent nickel-ore mine. This Douglas County site is only about 97 km (60 miles) due east of the Pacific Ocean, and California's border lies a similar distance to the south. Hanna Mining Co. had closed the operation in 1987. And the following year, the equipment had been largely stripped for salvage value. From November 1990 through August 1992, the mine supplied an average 5 kt/d (5500 wet stpd) of ore. Currently, with import ore supplying 40% of the smelter feed, the mine's daily tonnage averages 4.2 kt (4600 wet st). From November 1990 through August 1993, the mine has delivered 2.1 Mt (2.3 million st) of ore grading 1.22% nickel with an average moisture content of 26%. Buffaloed nickel? A nickel is not worth what it was in 1989 and neither is ferronickel, with recent prices hovering around $1.13/kg ($2.50/lb). To survive, Glenbrook has focused on increasing smelter production to lower its operating costs. And this strategy has triggered several bold moves: • a new, $30 million, port facility and • a 10-year importation contract for ore from New Caledonia, an island approximately 1000 km (625 miles) east of Australia. For a Glenbrook update, a May 25, 1993 visit was made to the company's Oregon operations - the mine and smelter near Riddle plus its new Coos Bay port facility. Unfortunately, as the rain came down that day, so did news of another temporary shutdown. The previous suspension had lasted from Dec. 20, 1992 until Feb. 22, 1993. Barely three months back to work on a wet May afternoon, more than 250 of Glenbrook's approximately 300 employees contemplated yet another shutdown, effective July 31, 1993.

Jan 1, 1993

By M. J. Gilbey

Cross passageways between adjacent tunnels in passenger rail or transit systems may be used during train fire emergencies to evacuate passengers to points of safety in the non-incident tunnel. Rescue trains can be brought into the non-incident tunnel to remove passengers to expedite evacuation times as compared to walking along bench walls to the nearest egress stairs. In cases of multiple train emergencies, the required ventilation capacities can result in high pressure differences between the incident and non-incident tunnels. These pressure differences can make it difficult or impossible for a normal person to open doors of a cross passageway between adjacent tunnels. If opened, the velocity of the airflow through an open cross passageway can reach levels high enough to impede passenger evacuation. This paper describes the analysis of this problem for a sample rail tunnel. A ventilation concept that mitigates the problems of high cross passageway door opening forces and high velocities through open cross passageways is presented.

Jan 1, 2009

By B. Oraee

Accurate estimation of equipment costs is a key factor in feasibility study and evaluation of design alternatives of mining projects. In this paper, capital and operation costs of backhoe loaders are estimated using multiple linear regression (MLR), based on principle component analysis (PCA). These cost functions are consisted of five independent variables; bucket size, digging depth, dump height, weight and horse power. The MLR is conducted in two steps. At the first correlation between independent variables is omitted using PCA technique. Thereafter, MLR functions are established using selected significant PCs and total cost functions are constituted as functions of initial variables. At the end, accuracy of functions are evaluated using mean absolute error rate method.

Jan 1, 2011

By T. W. Beck

Overexposure to respirable dust remains a widespread health hazard to roof bolter occupations in underground coal mines. Recently implemented mist drilling technology was evaluated for its effectiveness in controlling respirable dust exposures for roof bolting personnel. This work presents the findings from NIOSH field and laboratory studies comparing respirable dust levels on mist drilling roof bolter machines to dust levels measured on machines using a conventional vacuum drilling system. Gravimetric and instantaneous respirable dust samples were collected for multiple drilling cycles. These dust measurements were used to assess the potential dust control capabilities relative to conventional drilling. Controlled laboratory tests found 0.3 mg/m3 more respirable dust with mist drilling than with the conventional vacuum method. A separate field investigation of the two techniques observed higher dust levels around the mist bolting machine.

Jan 1, 2008