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Column flotation cells continue to gain acceptance in the coal industry for the treatment of high-ash streams containing clay slimes. Unfortunately, some industrial installations have failed to meet expectations due to improper scale-up, incorrect operation and poor ancillary circuit design. To overcome these problems, case studies have been conducted to fully define the capabilities of column cells for coal applications. These data have been used to develop generic engineering guidelines for column circuit design and operation. An economic analysis has also been conducted to illustrate the importance of key capital cost considerations. These analyses indicate that column cells are significantly more expensive than conventional machines, although this difference can be greatly reduced through the installation of very large-diameter columns.

Jan 1, 1999

By M. Peters, P. Schmäh

The development of renewable energies and a sustainable power grid are the challenges for future energy supply. Underground cables will replace the vulnerable overhead lines, because of their safety benefits. Due to the public environmental awareness, smart tunnelling and trenchless solutions are required for inner-city and cross-country installations of underground cables, as well as for crossings and the landfall sections to connect offshore wind farms to the transmission grid. Methods from the tunnelling and pipeline industry provide a high flexibility in the planning of alignments, including versatile tunnel concepts and the installation of protective pipes with E-Power Pipe and Direct Pipe.

Jun 13, 2023

By M. R. Shahan, W. R. Reed, J. P. Rider

Roof bolter operators may be exposed to high respirable dust concentrations on continuous miner sections with blowing face ventilation when bolting is performed downwind of the continuous miner. One solution to reduce the high respirable dust concentrations is to use a canopy air curtain (CAC) to deliver clean air from a filtered blower fan directly to the bolter operators under the canopies. The influence of CAC installation in the airflow and dust dispersion around the location of the roof bolter operator can be evaluated by using computational fluid dynamics (CFD). This study, performed by the National Institute for Occupational Safety and Health (NIOSH), considers two scenarios: (1) a roof bolting machine in the center of the entry for installation of the fifth row of bolts from the face, and (2) a roof bolting machine positioned close to the face for the installation of the last row of bolts. In both scenarios, the bolting machine is placed in an environment which contains 6.0 mg/m3 of respirable dust and is ventilated by a blowing curtain with 3000 cfm (1.42 m3 /s) of air. This environment is used to simulate the roof bolter machine operating downstream of a continuous mining machine. Two operation positions are simulated at the same bolting location: dual drill heads in the inward position for two inside bolts and dual drill heads in the outward position for two outside bolts. The influence of the CAC on airflows and dust dispersion is evaluated with the CAC operating at 250 cfm (0.12 m3 /s).

By M. Z. Mubarok, Z. T. Ichlas, A. T. Sugiarto, K. Sukamto

The use of ozone as an oxidant for the direct leaching of zinc sulfide (sphalerite) concentrate in sulfuric acid medium under atmospheric pressure was explored. The influence of acid concentration, feed gas injection rate, particle size distribution, stirring speed, temperature and slurry density on zinc extraction efficiency was examined. The experimental results showed that the leaching efficiency depends on all of these operating parameters except for stirring speed. It was found that essentially complete dissolution of zinc from the concentrate with the present method can be achieved in only about seven hours under the conditions of sulfuric acid concentration of 2 mol/L, particle size smaller than 74 µm, slurry density of 50 g/L, stirring speed of 420 rpm and feed gas injection rate of 1 L/min at ambient temperature. The experimental results suggest that the dissolution reactions produce independent elemental sulfur that is readily floated and can be easily separated rather than forming a layer on the surface of the reacted particle, as usually observed in a system with ferric-sulfate as oxidizing agent. It was therefore determined that the dissolved ozone play a key role in improving the rate of zinc dissolution from the concentrate. Analysis of the leaching kinetics indicate that the leaching rate follows the shrinking particle model, and the overall dissolution rate of zinc is controlled by a surface reaction.

Introduction The US mineral industry in 1983 participated in the recovery from the recent recession. Compared with 1982, the value of raw nonfuel mineral output rose 8% to $21.2 billion. The $218 billion worth of goods processed from this crude mineral output represented a 9% increase over 1982. Even in real terms, these figures reflect growth. Demand for nonfuel mineral materials, of course, depends on the overall state of the economy, which steadily improved each quarter in 1983. Of particular importance to the mineral industry were surges in key mineral-consuming sectors such as construction and automobile manufacturing. New housing starts rose one-third, to 1.7 million units, while automakers turned out about 35% more cars (6.8 million) and 25% more trucks (2.4 million) than in 1982. These are significant increases, even considering recent trends toward smaller, lighter vehicles, and multiple-unit housing. A comeback for the mineral industry, however, is bound to proceed unevenly, particularly at the beginning. Traditionally, the industry lags behind the rest of the economy during a recovery, and some mineral products respond to overall economic improvement more quickly than others. This pattern has been repeated many times and the industry is used to it. Mineral executives know it is best to be patient and cautious during the first stages of an economic upturn. Many experts say that it may take extraordinary toughness, patience, and caution this time around. Steel Improves Raw steel production - a major indicator of both material use and mineral production - rose 14% to 77 Mt (85 million st), stimulating a 7% rise in domestic iron ore production to 39 Mt (38 million It). Still, the iron ore industry operated at less than half capacity, with most major mines remaining closed for part of the year. Iron ore imports dropped 24% to 10 Mt (11 million st), so demand was partly met by withdrawals from stocks. Despite the increase in steel production for 1983, output remained far below levels of just a few years ago. For example, 1983 production was still 29% less than in 1981. Raw steelmaking capacity actually declined about 10% during the year to 122 Mt (135 million st). The industry continued to cite steel imports, especially those from developing nations, as a major cause of domestic capacity loss. As long as steel production remains weak, steelmaking metals suffer. Domestic producers of bulk ferroalloys of chromium, manganese, and silicon operated at about one-third capacity in 1983, with six of the 19 companies involved being closed all year. The US mined no manganese or chromium, and very little nickel, although the country's only nickel mine did resume production in November. Molybdenum production, at 13.6 t (15 st), was only about one-third as much as in 1982. The major molybdenum mines, Climax and Henderson in Colorado, remained closed all year. To meet demand, molybdenum stocks were halved to 19 t (21 st). Mine shipments of tungsten, another mineral tied to steel production, dropped 30% to 1.1 kt (1,200 st) of contained metal. One of the most positive responses to the general economic recovery came from the aluminum smelting industry. By the end of the year, it was operating at about 79% capacity, compared to 59% in January. Nevertheless, the 3.3 Mt (3.64 million st) of primary aluminum produced represented only a slight increase over 1982. Total bauxite imports were about 27% below 1982 levels. Production of magnesium metal rose 11% to 100 kt (110,000 st). But titanium was more typical of other

Jan 5, 1984

By Kang-Hyun Lee, In-Mo Lee, Byung-Kyu Kim, Parkm Jinho, Seoung-Won Lee

"In this study, the TBM Resistivity Prediction (TRP) system is developed for predicting the location, thickness, permittivity ratio and electrical conductivity of anomalous zones ahead of tunnel face using the measured resistivity of the ground. The applicability of the developed system was verified by performing field tests at a construction site in which an EPB-shield TBM is used for tunnelling work. In the first field test, it was found that the rock around the tunnel face had the same resistivity and permittivity with the rock ahead of the tunnel face indicating no anomaly ahead of the tunnel face. In the second test, a stronger zone 5-m thick was predicted ahead of the tunnel face based on lower permittivity than that of the rock around the tunnel face. The ground condition assessed by the newly developed TRP system matched well with that either predicted from geophysical exploration or directly obtained from drilling boreholes or from daily observed muck conditions. INTRODUCTION During tunneling work, the emergence of unpredicted zones of relatively weaker or stronger ground can lead to delays in construction work or an increase of construction cost. Predicting anomalous zones ahead of tunnel face in advance can thus prevent time and economic loss. For these reasons, various methods to predict the ground condition ahead of the tunnel face have been studied and developed. Prediction methods using various kinds of equipment include tunnel seismic prediction, ground penetrating radar, electromagnetic surveys based on electronic antennas, and electrical resistivity surveys conducted by analyzing electric currents in the ground ahead of the tunnel face (Ryu et al. 2008). However, most of the prediction methods are only applicable to conventional tunneling job sites, which feature free access to the tunnel face. In mechanized tunneling projects, accessibility to the tunnel face is very limited because the tunnel face is occupied by the TBM."

Jan 1, 2016

By A. A. Compoli

Injecting water under pressure to wet the coalbed in advance of mining reduces mining-generated respirable dust. Owing to economic and geological barriers, water infusion for longwall dust control in the United States is currently limited to the Pocahontas No.3 Coalbed in Virginia. Water is pumped into the coalbed through underground boreholes drilled horizontally from the headgate toward the tailgate side of retreat longwall panels. This paper theorizes that the barriers to widespread utilization of water infusion for longwall dust control could be overcome by long-duration, low-pressure water infusion through vertical gob gas boreholes. Currently, 43% of the 72longwall mines in the United States employ vertical gob gas boreholes. Computer coalbed reservoir simulation suggests that one vertical surface borehole could infuse the same longwall panel area as four horizontal boreholes in the current water infusion system for longwall dust control in the Pocahontas No.3 Coalbed.

Jan 1, 1995

By B. P. Spigarelli

To meet the growing need for CO2 capture and storage technology, Michigan Technological University is researching CO2 capture and storage using carbonate solutions. The objective of the present study was to increase the absorption rate of CO2 into the carbonate solution without reducing the absorption capacity of the solution. This approach used a polypropylene glycol methyl ether (PPGME) as a surfactant to chemically alter the gas bubble size. Experiments were conducted to study the absorption rate of CO2 at varying surfactant concentrations of 0, 0.12, 0.24, 0.36 and 0.48 g/L. Results showed that as the concentration of surfactant increased in solution, the absorption rate also increased. The CO2 absorption rate increased from 3.45 mmol/min CO2 at 0 g/L PPGME to 3.92 mmol/min CO2 at 0.48 g/L PPGME. This amounted to a 14% increase in the CO2 absorption rate with no decrease in absorption capacity of the solution.

By J. A. Burger

Research in the eastern U.S. has shown that productive mine soils and forests can be restored using the following guidelines: (1) cooperation among the mine operator, landowner, and regulatory authority in developing the mining permit; (2) replacing topsoil or creating a desirable medium in which trees are planted; (3) loosely grading non-compacted topsoil; (4) using native and non-competitive domestic ground covers that quickly protect the site; and (5) planting a proper silvicultural mix of crop trees for their commercial value along with nurse trees for wildlife and soil improvement.

Jan 1, 2002

By R. L. Hudak, R. F. Randolph, A. S. Azman

The mining workforce experiences high rates of hazardous noise exposure and hearing loss. However, previous studies have identified specific behavioral and attitudinal barriers that keep miners from effectively acting to prevent their own hearing loss. The National Institute of Occupational Safety and Health (NIOSH) has developed several new hearing loss prevention tools and interventions that specifically target these barriers to prevention. The NIOSH Hearing Loss Simulator addresses motivation to take action and knowledge about the consequences of noise exposure. The QuickFit earplug test device and QuickFitWeb online hearing protection tester address barriers to effective earplug and earmuff use by verifying at least 15 decibels of protection. The NIOSH Roll-Pull-Hold technique helps miners obtain better protection through an easy-to-remember set of steps that improves attenuation by nine decibels. The “Inquiring Ears Want to Know” fact sheet helps miners to understand audiograms and to use them to maintain their hearing health. Each of these interventions can be used within the context of a comprehensive hearing loss prevention program.

Jan 1, 2010

By Stanley Noss

One need be neither an historian nor technologist to recognize that activi¬ties related to the conversion of coal to other usable energy forms have been active for nearly fifty years. The degree of such activity and its evolution to significant commercial proportions has, however, fluctuated widely with world circumstance. For the past decade there has existed both a consistent technology evolution effort in classic R & D proportions, and a mainstream commercial acti¬vity but in rather modest proportions when viewed from the vantage point of world energy needs. But the chain of events wherein it became increasingly obvious that we were in energy trouble irrespective of world politics, spurred alternative energy source activities in the fossil fuels areas. The oil embargo of 1973-1974 made the obvious even more so and provided additional emphasis for the need of such alternatives. Yet the preponderance of these added expenditures and activities (with one notable exception which is the subject of this discussion) has been focused on the intended identification of the best or ultimate process by means of analytical and modest empirical means, whereas our circumstance dictates a bold, higher-risk effort to prove the viability of coal conversion as an industry on a real-time, real-size, real-economics basis. With such proof on hand, industry demands in all related areas will provide the stimulus, motivation and environment for all processes. There is both need and room for many who will compete for a meaningful segment of this new industry which can grow at a rate never seen before in our growth history. The single program in the world today oriented specifically toward the goal of proof of industry viability is the Energy Research and Development Administration's CBF (clean boiler fuels) Program for which COALCON is proud to be the prime contractor.

Jan 1, 1976

By Steven I. Majtenyi

INTRODUCTION The heavy risk inherent in all underground construction projects contributes significantly to the high cost of transportation tunnels. First, the knowledge of this risk leads the engineer to design conservatively. Second, the cost overruns are still common with a high proportion of them originating from corrective measures needed when unforeseen problems develop during excavation. These unforeseen problems includes - encountering unexpected objects, materials and water conditions - experiencing an unforeseen behavior of the materials - damaging property beyond the expected range of influence of the tunnel construction. To minimize these expenses, more emphasis is being placed on well planned and interpreted site investigation programs in the final design and planning stages of the project. It is well known that the cost of a planned excavation is less than the cost of dealing with the same conditions when they are encountered unexpectedly. Therefore, the objective of site investigation is to provide a complete set of reliable data for designers and contractors that is continuous along the projected tunnel alignment. Two alternatives axe available to achieve this objective; - for shallow tunnels, it is often feasible to generate continuous data by drilling appropriately spaced, vertical bore holes and applying sensing techniques for interpolation (1, 8). - for deep tunnels, or certain urban tunnels under existing structures, closely spaced, vertical bore holes are not feasible except for narrow zones at the portals. In such cases direct horizontal penetration may be required that may be complemented by radial sensing to extend the range of information.

Jan 1, 1976

By Eudes Prado Lopes

The Mineral Resource Exploration Company - CPRM - a part-private, part-government concern jurisdictioned to the Ministry of Mines and Energy of Brazil, was founded in 1969 for the purpose of promoting the exploration of mineral and hydric resources throughout Brazil. The political-administrative framework within which it was conceived and created considering that an economic and financial balance to be maintained in all its fields of activity, CPRM set out right from the start to organize itself to perform -three basic lines of action, which can be summarized as follows: As a Service Company, to carry out those services requested by government agencies and by the private sector through of service contracts; As a Mining Company under the Brazilian Mining Code, aiming at supplementing private initiative, not beyond the field of mineral exploration;

Jan 1, 1975

By M. Schultz

The cost of remediation often drives the selection of the preferred remedial alternative at hazardous waste sites. The use of probabilistic cost/risk analyses can aid in predicting costs of remedial alternatives. Three types of information are discussed in performing cost/risk analyses: (1) data on the quantity of contamination versus the contaminant concentration; (2) unit costs of remediation for the remedial alternatives; and (3) risk to contaminant concentration relationships. Cost/risk evaluations are performed on a site-by-site basis, to account for combined risks of different contaminants and differences in quantity to be remediated versus contaminant concentration. The cost/risk analysis produces a graph of risk versus cost for each of the remedial alternatives. These costs are then compared to facilitate selection of a preferred alternative. An example of comparison of alternatives is illustrated for a historic coal gasification site.

Jan 1, 1992

By Enrico Pavese, Tim Kearney, Stefan Lemke

Watertightness is of central importance in hydraulic and underground structures but has always been associated with a risk, as demonstrated by the very high impact that water inflows have on the damage of linings and infrastructure (Howard, 1991; Sandrone and Labiouse, 2011). Concrete is vulnerable to groundwater and chemical contaminants in the soil. These can leach into the pores and cracks of the concrete and degrade its integrity, causing spalling and corroding the reinforcing steel. Moisture migrating into the building can also degrade structural elements over time and lead to mold and other hazards to occupants’ health. In this connection, the demands placed on the setup and detailed design of the seal depending on the negative influence by water on the one hand and on the other hand on the function of a construction in view to its watertightness classification. Thus, the reliable functioning of a seal is of particular significance in the case of traffic tunnels, which are not easily accessible for all subsequent repairs after the construction in seepage water and especially when located in a pressure water zone (risk–cost assessment). Requirements for the long-term efficiency and quality of underground structures have increased in recent decades. Today, the standard lifetime requirement for an underground infrastructure project is 100 to 120 years and, in some cases, even higher. This calls for high increased attention to the durability of the whole structure and of each individual element. Standards, which started as application guidelines given by the manufacturers, are available in the market since the 1980s and are constantly adapted to the current developments in various technical committees. Differentiations are made between: Manufactures application guidelines, case studies or published articles Test standards for the laboratory to guideline the testing procedures (air temperature, type of test equipment, dimensions, test speed, test duration, concentration, type of liquids, monitoring, tolerances, interpretation of results, documentation, etc.), developed by committees based on material and laboratory experts Application standards, which include test standards but also the related minimum performance requirements (values) for material, processing, and quality assurance (practical tolerances), developed by committees based on a wide range of experts (e.g., designers, construction companies, applicators, manufactures, owners, test institutes, quality engineers) and therefore also based on a wide field of experience, different views and up-dated case studies. In the following there are some examples of guidelines and published information’s, ranked according to the year of issue, which are relevant for the development of waterproofing specifications in the tunnel industry:

Jun 13, 2023

By William Gleason

There was a time, not too long ago, when the most daunting challenges facing those in the mining and mineral processing industries could be solved through better technologies and better practices. But now the challenges that come from the actual acts of mining and processing are just part of the bigger picture. SME?s Colorado Section of the Mineral Processing Division (MPD) hosted its 63rd annual meeting at the Broadmoor Hotel in Colorado Springs, April 25-27 and, while the conference had its fair share or mineralolgy and processing presentations that were heavy on the technical side of things, this year?s conference was also focused on the issues of permitting, regulation compliance and legislative issues. The so-called ?softer? issues, that, if not addressed, can lead to very real and very hard challenges. Under the theme ?Mine your own business - permits, startups, expansions and resources,? even the most dedicated metallurgists were drawn into the discussions of politics and legislation, and how those issues affect their business. Fittingly, Colorado Mining Association (CMA) president Stuart Sanderson was honored with the Arthur C. Daman Lifetime Achievement Award. Sanderson, an outspoken proponent for the mining industry in Colorado and beyond, also presented the keynote address to the lunch crowd where he spoke about framing public opinion toward mining and the efforts of the CMA to move the public opinion dial in a direction more favorable to mining. Sanderson explained that Colorado, once a Republican stronghold, turned after 2002 and now is controlled by Democrats who are traditionally less supportive of the mining industry. Sanderson said the deciding factor in the power shift was money, as supporters of Democrats outspent Republicans in the most recent election cycles. CMA has done its part to keep mining going in the state with a broad marketing campaign that was outlined by Sanderson.

Aug 1, 2013

By William L. Carter

Through your presence here this morning and your membership in the Society of Mining Engineers, you have shown that you are interested in keeping abreast of the latest technology and mining procedures, want to be part of the continuing progress made by those in your profession, and are looking for ways to participate in expanding your professional and personal experiences and skills. All of these factors are part of your continuing education, the need for peer identification or recognition, and the desire to make a specific contribution to strengthening your profession. However, you may be here with or without your company support and financial backing, unless you are self-employed. Whether you are here for the above reasons, or for many others, your presence reflects a recognition of the importance of participating in the organizational structure of your profession.

Jan 1, 1981

By Erik Westman, Brandon Stables, Benjamin Mirabile

"Standing support is often used in conjunction with underground retreat mining. Knowledge of the load-displacement behavior of standing support and loading induced by the mine opening is critical to proper support selection. The NIOSH STOP database contains load-displacement laboratory test data for most commonly used standing supports. Hydraulic load cells currently used to measure in-situ loading of standing supports have exhibited leakage under load, producing irregularities within the dataset. An improved hydraulic load cell eliminates leakage and produces more consistent data.INTRODUCTIONA hydraulic load cell, more commonly known as a flat jack or JackPack, is a device installed to determine the loading characteristics of the roof-to-floor supports. These standing or roof-to-floor supports include, but are not limited to pumpable cribs, cans, wooden cribs (4-point, 9-point, etc.), metal props, wood timbers, concrete donut cribs, and other variations of these standing supports.Flat jack devices have been used previously to determine the loading of such roof to floor supports. The most commonly used load cell for standing supports is based on a design intended for pre-stressing standing supports, not load measurement. Preloading helps to keep the supports, such as timbers props and cribs, in place during the dynamic loading associated with blasting (Barczak and Tadolini, 2004).Flat Jacks are manufactured in various shapes and sizes depending on the application; common shapes are square and round that are 25.4 mm (1.0 inch) thick when collapsed, as shown in Figure 1. These load cells are produced in South Africa and can be formed into several different shapes depending on the application (Barczak, 2003). The sheet metal that makes up the bladder is comprised of 19-gauge or 1.11 mm (0.04 inch) thickness; the top and bottom pieces of sheet metal are resistance-seam welded around the perimeter. There are two different ports installed on one of the bladder skin corners of the flat jacks; these ports allow fluid to fill the unit, and the other port has a relief valve. The fill port is comprised of a check valve. The pressure relief valve is located in the second port; preset to 1,724 kPa (250 psi), the pressure relief valve keeps the load cell from bursting. Bursting of these load cells typically causes a small tear in the metal skin allowing the fluid to leak out without a large catastrophic failure.The effective inflation range of these load cells is between 25.4 mm (1.0 inch) to 254.0 mm (10.0 inches) thick. Different types of fluids can inflate these load cells but the most common and easily accessible fluid for testing applications is water. Water pressure from the mine supply line can inflate these load cells to the desired load. Depending on the pre-stressing requirements, a pneumatic powered pump, hydraulic pump, or hand pump may be required to inflate the load cells."

Jan 1, 2019

By Wayne W. Murdy

Since 1993, Newmont has been actively growing through the development of three major foreign mining operations with a fourth under construction. The first project, Yanacocha in Peru began operating in October 1993 at a time when political and business risk in that country was considered high. In 1995, Newmont began operating the Muruntau Joint Venture in Uzbekistan, the first of its kind in the CIS. In early 1996, Newmont started operating the Minahasa mine in Indonesia. Now, in early 1997, Newmont is undertaking the construction of a $1.9 billion project in Indonesia and is completing a feasibility study with our partner for the development of a gold operation in Mexico. All of these projects have been considered "risky" by most standards, and Newmont has been very successful in all of them through risk mitigation programs including utilizing strong and successful in-country partners, concentrating on developing a strong national workforce with minimal expatriate employees, utilizing World Bank, EBRD and IFC financing and building and maintaining strong ties with host governments. This paper describes in more detail, some of the risk mitigation programs that Newmont has used to successfully grow the company through development of major foreign mining operations.

Jan 1, 1997

By David Beck, Eko Wibowo, Hendri Silaen, Andres Sugiyanto, Karl Llewelyn

PT Freeport Indonesia’s Deep Mill Level Zone mine is one of the deepest block cave mines in the world and is in mountainous terrain in West Papua, Indonesia. The mineralization is hosted in a skarn deposit in a structural setting that is complex at the footprint, mine and regional scale. Large seismic events and significant episodes of rapid rock mass deformation are potentially critical geotechnical risks during this ramp-up stage of mining. Understanding the interaction between stress, strain, rock mass strength and geological structures is essential to minimize the hazard and engineer control measures to help ensure the safety of the employees while achieving production targets. This paper discusses how the seismicity and excavation damage have been shaped by the interactions between the mine and geological features, and how this affects strategic mining decisions. Additionally, the paper presents a summary of the mitigation measures used for mining the DMLZ in the safest and most productive way. These include improvements to geotechnical characterization of rock mass and structure, dynamic ground support designs, production scheduling for desirable cave propagation and a seismic monitoring system with re-entry protocols.

Apr 26, 2022