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By H. Sevim

In long-term open pit production planning, a series of nested and maximum-value pits is usually generated first. These pits are then considered as possible pushbacks over a number of planning periods. To determine the best pushback in each planning period, the pits are evaluated for their technical and economical feasibilities under certain production constraints. Parameterization is a commonly used technique to generate a series of pits. In almost all cases, however, some of the consecutive pits generated by this technique are too far apart from each other. This is called the "gap" problem. It may make the entire pit series useless for production planning purposes. A new pit gener¬ating algorithm has been developed to overcome the gap problem. Through this algorithm, a series of nested maxi¬mum-value pits can be generated with a controllable size increment. The logic of the algorithm is illustrated through a small hypothetical case. Its capability of generating maximum-value pits that are as optimal as those generated by parameterization and its advantages over parameteriza¬tion are presented through an actual gold deposit case.

Jan 1, 1996

By Jorgen Elbrond

The capacity calculation of complex transportation systems involving variable activity times such as encountered in the mining industry are often worked out by means of simulation, which reconstructs waiting times and cycle times. The queuing theory, which mathematically calculates waiting times, has been used mainly to describe the, phenomena. This is due partly to the difficulties encountered in modelling complex systems and partly to the difficulty of reconciling the required time distribution laws with the real phenomena by means of the queuing theory. It is, however, obvious that formulas for capacity calculations would be preferable to simulation procedures because of their higher calculation speed, shorter and more flexible programs and shorter programming work. The calculation procedure presented in this paper is composed of some rather simple models, which are based on the queuing theory, and on some probabilistic and some deterministic considerations. The models are supported by observations, and to some extent by simulations. It has been attempted to find all the components of the cycle time and to include them in a comprehensive model. It is the intention to demonstrate that even quite complex mine transportation systems can be treated by means of the queuing theory with the advantages mentionned above and, without sacrificing the precision of the estimates. The speed of calculation of a wide range of parameter combinations is such that the procedure can be used extensively by a project engineer in the search for optimal modifications of the entire transportation system.

Jan 1, 1979

By J. J. Bartels

The phosphate rock review did not arrive in time for publication in the. June issue. The world phosphate industry continued its slide in 1992 from the already depressed levels in 1991. The industry is locked into a 30-year fertilizer price low due to the worldwide fertilizer glut. Domestic production and imported, marketable phosphate rock decreased 1%, while domestic consumption increased by 1 % last year. The US Bureau of Mines reported a decrease in the domestic phosphate rock value from $25.42/t in 1991 to $23/t in 1992 ($23.06/st to $20.80/st). The diammonion phosphate (DAP) product price also dropped in value from $138/ t in January 1992 to $11 0/t in December ($125/st to $99.70/st). Continued declines in DAP prices is forcing the US fertilizer industry to develop cost-saving programs and reorganizations. Layoffs in 1992 resulted in a 7.6% decrease in the Florida phosphate workforce. Since 1980, the Florida workforce has declined by 35%. Small phosphate companies were forced to close operations or were sold to larger phosphate companies. Federal and state environmental regulations for byproduct waste disposal methods are being studied. The Environmental Protection Agency (EPA) approved phosphogypsum use in agri¬cultural and research applications as long as the radium 226 concentration is lower than 10 pci/g. The EPA is also reviewing regulations concerning air emissions at fertilizer plants. Industry publications reported the possibility of continued company sales and mergers in 1993. Industry expectations are optimistic while waiting for an upturn in the market. The US phosphate industry consolidation into three or four major companies should evolve into a stronger world market force.

Jan 1, 1993

By W. R. Reed, S. Klima, J. Driscoll, T. W. Beck

"Tests were conducted to determine properties of four foam agents for their potential use in longwall mining dust control. Foam has been tried in underground mining in the past for dust control and is currently being reconsidered for use in underground coal longwall operations in order to help those operations comply with the Mine Safety and Health Administration’s lower coal mine respirable dust standard of 1.5 mg/m3. Foams were generated using two different methods. One method used compressed air and water pressure to generate foam, while the other method used low-pressure air generated by a blower and water pressure using a foam generator developed by the U.S. National Institute for Occupational Safety and Health. Foam property tests, consisting of a foam expansion ratio test and a water drainage test, were conducted to classify foams. Compressed-air-generated foams tended to have low expansion ratios, from 10 to 19, with high water drainage. Blower-air-generated foams had higher foam expansion ratios, from 30 to 60, with lower water drainage. Foams produced within these ranges of expansion ratios are stable and potentially suitable for dust control. The test results eliminated two foam agents for future testing because they had poor expansion ratios. The remaining two foam agents seem to have properties adequate for dust control. These material property tests can be used to classify foams for their potential use in longwall mining dust control. IntroductionAbout one-half of U.S. underground coal is produced by longwall mining, which allows for mining high volumes of coal but generates significant amounts of coal mine dust. This can lead to overexposures for longwall miners and possibly occupational respiratory diseases, including black lung and silicosis, which have no cure and can be disabling or fatal. The only method to avoid these occupational illnesses is through elimination of exposure to respirable coal mine dust and crystalline silica (quartz). The current occupational exposure limit for respirable coal mine dust is 1.5 mg/m3 during each shift that a miner is exposed in the active workings of the mine or in mine facilities (Mine Safety and Health Administration (MSHA), 2015a). When respirable quartz is present, the mine must maintain average concentrations at or below 0.1 mg/m3. If the mine exceeds the 0.1 mg/m3 respirable quartz dust concentration, then the applicable respirable dust standard is reduced, calculated as 10 divided by the percent quartz present (MSHA, 2015b)."

Jan 1, 2018

By D. R. Spears, D. A. Stanley

The US Bureau of Mines investigated the fundamental aspects of shear-flocculation using a rapid, in-situ particle size analyzer. Silica was stirred in the presence of an aliphatic amine to determine the effects of collector coverage, stirring speed and solids concentration on the kinetics of shear-flocculation. The results showed that shear flocculation is a two-stage process. In the first stage, which occurs during the first 1-2 min. of the reaction, the mean particle size increases rapidly, and in the second stage, an equilibrium is set up between the rates of floc growth and floc decay. Collector dosage affected the position of the equilibrium by altering the number of surface sites for particle-particle attachment. A minimum stirring speed was necessary for shear flocculation, which was dependent on solids concentration and collector dosage. This stirring speed was the minimum necessary for particles to overcome the electrostatic energy barrier, and that results in keeping the conditioned particles dispersed. Larger particles flocculated more rapidly. At very high stirring speeds, large flocs became unstable, resulting in a narrowed particle size distribution in the slurry.

Jan 1, 1995

Ground falls (roof and rib) have historically been responsible for about 50% of all fatalities in bituminous underground coal mines. In some recent years, the number of ground fall fatalities has approached zero, indicating that significant progress has been made. On the other hand, last year?s Crandall Canyon twin mine disasters, in which 9 miners perished in violent coal bumps, provided a stark reminder that complacency is premature. One important success has been a great reduction in the number of miners killed inby roof supports. Throughout the 1990?s these accounted for nearly half of all roof fall fatalities, but there have just been two inby incidents in the past 5 years. Progress has also been made in pillar recovery. Safer mining technologies have reduced the number of fatal incidents, but some recent failures have underlined the need for careful management of the retreat mining process. On the other hand, more than 400 miners continue to be injured each year by rock falling from between supports, and 100 more are injured by rib falls. Together, these two categories also account for a large percentage of recent ground fall fatalities. Available technologies such as roof screen, rib bolting, and inside control roof bolters could dramatically reduce injury and fatality rates if they were used more widely. Further advances in these areas will likely be the next big advance in ground control safety. Disclaimer: The findings and conclusions in this report have not been formally disseminated by the National Institute for Occupational Safety and Health and should not be construed to represent any agency determination or policy.

Jan 1, 2009

By Michael Vitale, Lee W. Abramson, Daniel McMaster, Andrew J. Thompson

"Performing risk analyses on tunnel projects has become common place and on many projects it is required from an owner or regulatory perspective. After the project is planned, designed and constructed, the data concerning identified risks, assumptions, costs, probabilities and mitigations is generally long forgotten and buried in some file somewhere. A study was performed comparing predicted risks versus actual events on four recently constructed rock tunnel projects in New York, Ohio, Georgia and California. Probabilities and costs for selectively common risks on tunnel projects have been studied and re-evaluated. Conclusions are presented that can guide future projects and the veracity of the tunnel risk analyses performed. INTRODUCTION Tunneling is a risky business. More than ever, attention is being paid to the risks associated with tunneled facilities and implications on project or program cost and schedule. Questions about why tunneling projects notoriously exceed budget numbers abound. Evaluations in retrospect and going forward have focused on the wide breadth of inherent risks associated with tunneling. More and more, these risks are being identified, studied and managed to a higher degree. As more and more scrutiny pervades the industry, little value is being obtained and leveraged on future projects. The industry seems to be headed in a direction of making the same mistakes over and over. The notion of risk evaluation has been around for decades and received wide notoriety with the U.S. Space Program and ambitious projects in the energy industry such as hydropower and nuclear power in the 1960s and 1970s (Stewart and Melcher, 1997). This led to the evolution of tunnel risk analyses with more rigorous identification of the unique risks in tunneling projects impacting cost and schedule. As tunneling risks became more readily identified, more attention has been paid to the frequency and impact of the occurrences unique to tunneling (ITIG, 2012). Currently, few tunnel projects are being planned, designed or constructed without a formal risk register that identifies the risks, mitigates the risks and quantifies the probable impacts of risks that cannot be mitigated. In hind sight on many recent projects, events that brought projects to “its knees” were not addressed in risk assessments or were not dealt with to adequately mitigate the risk of these events."

Jan 1, 2016

High pressure grinding mills have been successfully introduced in the industry. They offer the possibilities for capacity increase of existing plants and reduction of operating costs. Further metallurgical advantages in gold and copper are possible. The plants in operation are running in different applications and modes of operation. They can be installed in a combination with SAG and ball mills or in a stand-alone mode. In combination with other grinding mills, it has to be investigated how the HPGR can be installed to reach the full efficiency. This paper describes the possibilities to implement high pressure grinding rolls and shows by case studies the potential of savings which could be reached

Jan 1, 1996

By K. H. Boss

In modern iron pelletizing plants fuel consumption has been optimized to such an extent that only minor savings can be expected in the future. Inspite of this fact, different process parameters were studied with a mathematical model and firing tests. The influence on fuel consumption and productivity was established. Furthermore, the adoption of simplified firing patterns was investigated, in particular for coal firing. In view of high costs of oil and natural gas, only substitution of these fuels by coal can substantially reduce production costs. In existing plants partial replacement of oil and gas can be achieved by addition of coal to the iron ore feed and by firing the pellets with pulverized coal. Two systems have been developed for the Lurgi- Dravo travelling grate process which enables coal to completely replace oil or gas. This paper describes in the first part the potentials for fuel savings available in the Lurgi-Dravo process. In the second part, different techniques for the use of coal as fuel in iron or pelletizing plants and in particular the recently developed Lurgi Multistage Coal Injection and Combustion Process (LMC) are discussed. Combined with the LMC process, a wide variety of iron ores and coals - also with high ash contents - can be used in the Lurgi-Dravo travelling grate process.

Jan 1, 1983

By Robert W. Bartlett

Pretreatment of sulfidic refractory gold ore by biooxidation in coarse-crushed ore heaps is a promising new technology, especially for low-grade ores that cannot afford pressure leaching or roasting. An algebraic equation for determining the economically optimum biooxidation of the sulfide minerals in the ore is provided that is based on the empirical biooxidation rate constant for the ore, the project's financial discount rate, the ore grades of both refractory and non-refractory gold, and the gold price. Then, the economically optimum duration of bioheap pretreatment, t$, is determined from its logarithmic relation to the optimum fractional extent of ore biooxidation, F$, through the ore's biooxidation rate constant. In doing so, it is assumed that the ore is adequately crushed and amenable to bioheap pretreatment and that the cumulative oxidation of the ore with time is known from ore testing so that the rate constant can be determined.

Jan 1, 1995

By A. K. Sinha

Modern mine ventilation systems have grown rapidly in recent years both in tern of its complexities as well as its value for human health and safety. Although computer models are now available to help the design and operation of mine ventilation systems, considerable differences often exist between the computer based predictions and practical results. Research conducted to compare computer result with practical measurements made in ventilation circuits simulated in a physical model seems to confirm such differences. It is concluded that although a mine ventilation computer model is a very powerful tool, it can be utilized to its full potential only after more reliable input data are developed.

Jan 1, 1985

By R. B. Inturi, R. G. Reddy

Solid-state reduction of roast Movat chromite ore with carbon was carried out as a function of the C/FeO ratio at temperatures ranging from 800°C to 900°C. The reduction was studied using thermogravimetric analysis (TGA). A two¬stage mechanism consisting of the reduction of FeO with carbon monoxide and the regeneration of CO by the oxida¬tion of carbon with CO2 was proposed. The rate-controlling step is the carbon oxidation reaction. A kinetic equation, that of random nucleation, was proposed. The activation energy for the reduction was determined to be 55,800 J/mole and is compared to those activation energies determined for other chromite ores.

Jan 1, 2000

By Tim Neil, O&apos

Acid rain legislation, the new tax package, excess coal capacity, the effects of low oil prices, how to increase coal exports: These were among the items discussed at the May 4-7, American Mining Congress coal convention in Pittsburgh. Some 2000 people attended the convention, which also offered 15 technical sessions. As always, the state of the domestic coal industry might be characterized as "long-term promise, short-term problems." And one of these problems is acid rain. Acid rain The proposed acid rain legislation in Congress could be the most costly piece of environmental legislation ever written. In its present form, the measure could cost the nation up to $110 billion over the next 15 years. Rep. Henry Waxman's (D-CA) bill, HR 4567, would mandate large reductions in sulfur dioxide emissions from coal-fired power plants. The bill has more than 150 Republican and Democratic cosponsors. Ed Addison is president of the Southern Co., one of the nation's largest utilities and users of domestic coal. Addison noted that America's electric utility industry buys and uses nearly 85% of the coal consumed in this country. He said Waxman's bill would drive up prices of low-sulfur coal, raise electric rates, and force miners out of work in high-sulfur coal regions. In repeating a standard coal industry response, Addison said the Clean Air Act is doing the job. In recent years, while coal use has gone up, S02 emissions have gone down. Current air pollution standards are producing cleaner air, he said. Despite concern over HR 4567, the bill's future is uncertain. Several coal industry executives and analysts predict the bill will die under weight of opposition from coal, utility, and steel interests. But the acid rain issue is gaining momentum. Future legislation of some kind is likely. Meanwhile, research continues to develop clean coal technology to deal with the S02 problem. Commercialization of these front-end technologies currently lags public sentiment for acid rain legislation. Ground water runoff and contamination is another area where future legislation would seem likely. Already, one bill has been introduced in Congress. A second is being drafted. The impact of such legislation may be significant according to Bruce Leavitt, a hydrogeologist with Consolidation Coal Co. He said if current proposals are adopted, there will be more federal, state, and local government involvement in ground water regulation. In any event, the coal industry can expect to see more emphasis on preventing acid mine drainage and on water replacement, according to Leavitt. He urged those in the coal industry to present information about mining and ground water. That is needed to prevent misdirected state and federal programs, he said. Another coal industry concern is excess capacity. The industry has the mines, equipment, and employees to produce 15% more coal than at present. Problem is, the markets are not there. Slower-than-predicted growth in electric utility coal use has kept sales sluggish. There are also tax uncertainties. Congress is considering repeal of the investment tax credit and elimination of black lung payments and excise taxes as deductible expenses. One analyst estimates the coal industry would lose $1.1 billion in five years, if the changes are approved. In addition, there are the usual concerns about excessive governmental regulations involving safety and environmental matters. Bill Kegel, for example, said these regulations mean extra costs and delays in developing mines. Kegel is president and chief executive officer of the Rochester & Pittsburgh Coal Co. More than half the electrical power in the US is generated by coal-fired plants. That percentage could slip by a couple of points as nuclear generators come on-line the next few years. About 1990, though, we will see the end of US nuclear plant construction. No new nuclear plants have been scheduled since 1978. So any growth in electric power use should benefit the coal industry. BethEnergy - High Power Mountain During 1985, BethEnergy - a Bethlehem Steel Corp. - subsidiary developed High Power Mountain, a 1.8-Mt/a (2-million-stpy) surface mine in West Virginia. Construction saw movement of more than 3 hm3 (4 million cu yds) of earth. A computerized 544 t/h (600 stph) heavy media cyclone prep plant and a 3.6-kt/h (4000-stph) railroad loadout facility were built in six months. And a 5.6-km (3.5-mile) railroad spur and loop bridging a major highway were constructed. Larry Willison of BethEnergy noted the project's ambitious construction schedule. It was forced by the need for the project to be market driven and - lacking available capital - externally financed. BethEnergy did several things before obtaining with Detroit Edison a market for 0.9 Mt/a (1 million stpy) of coal. Willison said his company prospected and proved the eastern half of its 8-km2

Jan 7, 1986

By Hitch M.

Many mining wastes, especially those from the metal mining industry, have traditionally been treated as a matter of little or no value and in practice a cost burden. Some wastes, due to their reactivity characteristics, have emergent values that go beyond purely economic and into the environmentally beneficial realm. This paper discusses the changing paradigm of mine waste management. Such fundamental parameters such as cut off grade, and strip ratio, are positively impacted by the revaluation of waste rock material. Mine rock waste can now be seen as a commodity of value, similar to the underlying ore being mined and influences the economic performance of suitable projects. This valuable material can be used for industrial purposes including acid neutralization as well as the capture and long-term disposal of anthropogenic carbon dioxide. The Turnagain Nickel project, located in northern British Columbia serves as an example of how waste rock material can become an important matrix for carbon capture and sequestration and can benefit economically from it. By producing material that has emergent economic value as well as carbon capture and sequestration capabilities, the sequestration matrix producer is a beneficiary of new carbon credits that have a market value and is looked upon favourably by regulatory authorities and affected stakeholders.

Jan 1, 2010

By Jerry C. Tien

China?s remarkable levels of economic growth during the past three decades have lifted almost 300 million people out of poverty. This amazing achievement has placed an increasing demand on energy and minerals, especially coal, which supplies 68.7 percent of China?s energy (June 2011). It is estimated that China mined more than 3 Gt (3.3 billion st) of coal in 2010, three times as much when compared to merely 10 years earlier. Such an impressive achievement does not come without major costs ?? including concerns with mine safety and an increasing number of occupational illnesses due to fast growth. This article reports on one of the major safety concerns in China?s coal mining, dust and dust control practices, and known cases of caol worker?s pneumoconiosis affiliated with prolonged exposure to excessive coal dusts. The exact size of China?s mining industry is not known, but it is estimated the coal industry is at least five-million people strong, and the metal and nonmetals industry probably employs another three million people. To meet increasing energy demand, China mined more than 3.1 Gt (3.4 billion st) of coal in 2010 from its 15,000 plus coal operations1, most of which are small- to medium-sized operations with annual coal productions ranging from a few thousand tons to 300 kt (330,000 st). These small coal operations are typically in remote areas, inadequately engineered, poorly ventilated and still using rudimentary drilling and blasting mining methods employing antiquated mining equipment and, presenting safety concerns, i.e., methane and dust explosions.

Jan 1, 2011

By R. B. Hopler

Explosives R&D has historically been motivated by coal mining. Whether to solve safety problems or to improve productivity and cost, the result has been the same: better explosives products and initiation systems. This process continues at an accelerated pace today due to the tools presently available to the explosives and mining industries.

Jan 1, 1993

By A. L. Coello Velázquez

The subject of this paper is particle population balance models (PBM) that describe mineral impact crushing behavior; it is mainly concerned with the selection and fragmentation distribution function due to their importance in this context. The data obtained by Datta (1999) by applying impact pendulum testing to single limestone particles, used by Austin (2002, 2004a and 2004b) to obtain the principal parity of fragmentation functions, were processed in order to compare them with the results of other authors, such as Nikolov (2002 and 2004) and Vogel and Peukert (2003 and 2005) so as to increase knowledge of impact crushing. From this data it has been possible to obtain the performance models of the principal parameters of fragmentation function, thereby reducing the number of experiments necessary to model the impact crushing process. The authors also propose a simplification of the selection function model posited by Austin (2002).

Jan 1, 2011

By E. Baliktsis

We have searched and analyzed several modern technologies aiming at the best applications of environmental management, the studying of quarrying ? mining as well as the excavation sites ? utilization ? rehabilitation. We have used long-range reflectorless laser surveying systems, so as to achieve the fastest and most accurate surveying of the extractive work sites. We also used them, in order to collect field data, measure distances, surveying monitoring stations and environmental parameters ? data. Furthermore these systems can make the field work quite faster, more reliable and credible and have low cost in collecting data even in dangerous and non-approachable areas. We have used and processed on the field data in G.I.S. applications, in order to create 2-D and 3-D digital ground models. These G.I.S. applications present the existing relief and the management of the final stage of the area. The suggested techniques and works needed, for reclamation and utilization of the areas, could be tried, evaluated and well presented. The evolution and utilization of these ?smart? modern tools for the effective environmental management of quarrying ? mining ? extractive activity sites, will be presented by using case histories from the Hellenic territory.

Jan 1, 2002

By Richard Crowell, James Gillaspie

A concentrate biooxidation process was successfully demon­strated in the field in a remote part of northwestern Mexico. A 275 tonne (300 st) biooxidation heap was constructed using GeoBiotics' proprietary GEOCOAT™ coated concentrate process. The pyrite/chalcopyrite/sphalerite concentrate was bioox­idized in the heap for 60 days. Cyanide leach recovery of the con­centrate increased from 68% gold recovery at a cyanide consump­tion of 1.6 kg NaCN/g Au (llO lbs/oz) in the as-received concen­trate, to 94% gold recovery at a cyanide consumption of 0.37 kg NaCN/g Au (27 lbs/oz) in the biooxidized concentrate. The heap was constructed at a rate of7 tonnes (7.5 st) concentrate per hour, using typical heap leach equipment and easily scalable methods. Heap operations demonstrated that energy dissipation in the humid summer environment was easily controlled by low pressure aeration and management of solution chemistry and application. Observations of the demonstration heap appear to support the presence of reflux of moisture within the biooxidation heap.

Jan 1, 1998

By F. W. Brackebusch

Paste backfill is a pumpable, flowable, non-Newtonian fluid consisting generally of mine tailings and cement. Paste is prepared from dilute slurries of tailings. This is done by dewatering the slurries with conventional thickening or filtering. Backfill with a paste consistency is prepared by mixing dewatered tailings with cement and water to obtain the desired consistency of medium slump concrete. The paste is pumped with concrete pumps over relatively long (1 km or 0.6 mile) horizontal distances. More commonly, though, it flows by gravity down a mine shaft and then horizontally to the void being filled. Alternatively, cement can be added near the end of the pipeline. A certain proportion of fine particles <20 µm (<625 mesh) must be present in pastes but particles of aggregate can be added without significantly affecting the flow characteristics. Detailed testwork is necessary to design a system to prepare and place paste backfill. Testwork must determine dewatering characteristics, strength of mixes and friction in pipelines. Plants must be well engineered and controlled with PLCs because high quality control is necessary to prevent plugged pipelines and excessive pressures. Relatively small amounts of cement (3% to 5%) produce stiff backfill material 1.5 to 3.5 MPa (217 to 507 psi). The advantages of paste backfill in a mining operation include reduced mine dewatering, labor and materials savings, reduced tailings impoundment requirements, good support properties and reduced spills underground. In certain cases where more than 30% of the weight of the ore is sold as a product, the entire tailings stream can be placed underground. Paste technology can he used for surface or underground placement of tailings.

Jan 1, 1995