Search Documents

By Magno Rodrigues Ribeiro, Alexandre Cabral Stelzer, Cacio José da Silva, Leonardo Nogueira Ferri, Marcelo Ciminelli Mendes, Christophe Bouché, Marco Aurélio Soares Martins, Evenilson Soprani Lopes, José Xavier da Silva Filho, Sérgio Luiz Dalvi

Since 2001, CVRD is carrying out a modernization project in it’s pelletizing plant’s automation systems, that comprehends instrumentation, control and information systems. In addition, the project includes implementation of advanced control systems, using artificial intelligence techniques, including fuzzy logic, expert systems and dynamic physical models, to increase production, reduce fuel and energy consumption and improve quality. This paper reports CVRD’s experiences in carrying out an optimization project.

Jan 1, 2005

By G. T. Lineberry

Reduced clearance is one of the most important characteristics of encumbered space in underground coal mining. Another key variable is the maximum velocity at which a piece of mobile mining equipment can operate in this limited space. Typical velocity- clearance curves for different mine transportation systems are developed and characterized. Applications of the relationships are examined, emphasizing their significance in the design and control of mine materials handling systems.

Jan 1, 1983

By Frank W. Schmechel

The subsidence monitoring program at the Old Ben No. 24 Mine was planned in 1976 as part of the on- going demonstration of longwall mining. The construction and installation of the network of surface subsidence monuments was started in Play of 1976 and completed four weeks later after which an initial reference survey was made of all surface monuments. Mining of the first longwall panel started in September of 1976 and was completed in May of 1977. Mining of the second panel started in August of 1977 and is continuing at this time. The Automatic Data Acquisition System (ADAS), which is the subject of this paper, was installed over the second panel on March 29, 1978 near the panel center (Figure 1) and approximately 104 meters (370 feet) in front of the face position at that time. Mine No. 24 is located approximately 5 kilometers (3 miles) Northwest of Benton, Franklin County, Illinois. Coal is being mined from the Illinois (Herrin) No. 6 seam which is at a depth of about 189 meters (620 feet) at the site. The Herrin No. 6 is up to 2.7 meters (9 feet) thick in the mine but a constant thickness of 2.1 meters (7 feet) is being mined by the demonstration longwall with both roof and floor coal being left for stability. Although the seam is flat laying at the mine, it dips north- ward regionally. Topographically, the surface over the demonstration panels is essentially flat and low laying with several areas of standing water. The Rend Lake Dam (United States Army Corps of Engineers) is about 305 meters (1000 feet) north of the demonstration site.

Jan 1, 1979

By William A. Macaitis, Frank E. Dalton, Leo R. DiVita

The Metropolitan Water Reclamation District of Greater Chicago's Tunnel and Reservoir Plan (TARP) is a multi-purpose urban public works project with a total cost of $3.7 billion. Currently 51 miles of TARP tunnels are completed and operational and 34 miles are under construction. The excavated TARP tunnels have been constructed in rock utilizing 29 tunnel boring machines, ranging in size from 6.5 to 35.3 feet in diameter.

Jan 1, 1993

By T. C. Eisele

The use of column flotation was considered for the ?reverse flotation? of iron ore, where the gangue (quartz) was recovered in the froth product. This use of the froth for carrying the gangue mineral rather than carrying the valuable concentrate significantly changes the operational requirements of the column. The objective of this work was to determine which of several column flotation technologies would be most suitable for this type of flotation operation. Studies were carried out using both the Jameson column and the Deister column. Comparative results are presented that show the capabilities of both column types in this application relative to conventional Wemco flotation cells. Columns were demonstrated to have grade-recovery performance superior to what could be achieved with conventional cells. Two-stage flotation with the columns could produce a concentrate that was up to 70.2% Fe at 87.5% iron recovery, compared to 70.4% Fe at only 77.7% iron recovery for four stages of flotation in conventional cells. It was shown to be particularly important to operate the columns to recover a maximum of the quartz gangue into the froth. It was noted that there are often problems in scale-up of laboratory columns to plant scale, because the increase in height and the decrease in the ratio of height to diameter at the larger scale allows more axial mixing and bubble coalescence, both of which degrade the column performance. Horizontal baffling was shown to improve column performance by reducing axial mixing and breaking up large bubbles, and so the use of such baffles in the reverse flotation application was investigated.

Jan 1, 2007

By R. Leithner

The need/wish to sequestrate CO2is based on the assumption of the International Panel of Climate Change (IPCC), that CO2 maybe the major driver in climatic changes, i.e. especially the anthropogenic CO2emissions due to the combustion of fossil fuels like coal, oil and natural gas will increase the atmospheric CO2-content, which will lead to higher temperatures in the atmosphere. The 0.03% CO2in the atmosphere have a 22% share of the natural greenhouse gas effect of 33 K necessary for life on earth. The main share of 62% has the water vapour in the atmosphere. Only if one concentrates on the greenhouse gas effect of the gases beside water vapour, CO2 becomes most important with 58% influence. In addition there are other influences on the climate like: • Eccentricity of earth’s orbit, precession of orbital plane, obliquity and precession of earth’s rotation axis (Milankovitch’s theory) • Sunspots and magnetic field of the sun • Changing streams in the ocean • Volcanic activities • Distribution of continents on the surface of the earth • Impact of meteorites • Change of insulation by interplanetary dust [Muller, R.A. 2000] etc. To answer the question, if the CO2-content in the atmosphere has an important or exclusive influence on the earth atmospheric mean surface temperature, one should look into history. Figure 1shows the mean temperature of the atmosphere and the atmospheric CO2-content time histories 1 billion years back; no correlation can be found between them. Nevertheless a lot of countries have committed themselves to reduce their CO2-emissions.

Jan 1, 2004

By Robert S. Hendricks

LOCATION AND HISTORY The Lakeshore Copper property is located on the Papago Indian Reservation approximately 30 miles South of Casa Grande, Arizona. This major porphyry type deposit was discovered by El Paso Natural Gas Company in 1966. Following an extensive diamond drilling program, El Paso invited several mining companies, including Hecla, to examine the property with a view towards participation. Hecla's examination, and the attendant feasibility studies, led to agreements, which were finalized in September 1969, whereby Hecla would acquire a 50% interest in the property, and would act as operator. The Lakeshore deposit covers an area approximately 3,000 feet in width by 6,000 feet in length. It consists of an upper zone of disseminated copper oxides, averaging approximately 100' in thickness overlying a zone of disseminated copper sulfides up to 1,000 feet thick. Near the base of the disseminated ore is a blanket like zone of high grade copper sulfides, referred to as the tactite ore body. The mine is being developed to produce approximately 6,500 tons per day of oxide ore and 9,000 tons per day of sulfide ore. This represents a total daily production rate of 15,500 tons per day, which will be achieved by underground mining methods using rubbertired dieselpowered mining equipment. DEVELOPMENT LAYOUT The mine is being developed by two parallel 15° decline tunnels. The declines were collared 5,000 feet southeast of the ore body, and are being driven in a northwestery direction, to pass beneath the tactite ore zone. The declines will constitute the primary means of access to the underground workings. One decline (north

Jan 1, 1997

By G. Papantonopoulos

Natural stones are extensively used for construction purposes since the dawn of human civilization, due to their unique aesthetical and technical characteristics. Their production and consumption has been continuously increasing over the past twenty years worldwide at an annual rate of 8.8%. European countries lead the race of per capita consumption, with Switzerland being in the first place with a consumption of 144.7 m2 per hundred inhabitants followed by Greece, Spain, Portugal, Belgium and Italy. On the other hand, during the period 2001-2002 the generated stone wastes were 110 million tones according to EU data, from which only about 5 million tones were recycled or re-used mainly in the construction industry. These stone wastes the non-natural wastes such as oils or chemicals coming from the equipment and machinery employed for stone extraction and processing, are disposed in the environment, posing serious environmental threat. To achieve sustainable development of the stone sector appropriate methods that will prevent or reduce waste generation and disposal have to be identified and applied. In this work an extensive study of the stone waste management techniques applied in Europe is carried out, in order to identify the Best Available Techniques (BAT) that can be used according to the type of generated wastes and the waste management hierarchy: Waste minimisation, Re-use, Recycling and Disposal. The identification of BAT was performed based on 14 Sustainable Development Indicators (SDI), which were grouped into three categories: environmental, economic and social. The developed final list of BAT includes waste minimisation techniques, eco-management schemes, in-situ treatment and appropriate storage and selection.

Jan 1, 2007

By Randhir Sehgal

If the primary purpose of a control system is to assure a fixed-quality product at maximum yield, the real issue involved in control of the fine coal cleaning circuit in a plant is to demonstrate that control is technically feasible and economically beneficial . This paper suggests that it is not easy to do so in most cases. Fine coal, defined here as the 28 mesh x 0 fraction of the plant feed, is generally cleaned using a combination of hydrocyclones and flotation. Both of these processes are relatively insensitive to changes in operating variables. Further, the fines fraction general 1 y forms no more than 20% of the plant feed and, at times, is as low as 10%. The instruments to measure flow rates, densities, and product qua1ity (ash, sulfur, etc.) are not sufficiently accurate to allow effective responses to changing state variables and product quality. It is sufficient to run the fine coal circuits at maximum recovery, and the control of product quality and optimization of yield should be achieved by controlling the coarse coal circuits and measuring the quality of the entire clean coal leaving the plant. This contention is made with particular reference to U.S. plants cleaning coal for the utility industry and should be viewed in this context only. It is explicitly admitted that this strategy is mathematically non-optimal in the sense that all size fractions are not necessarily cleaned at equal elementary ash, and would result in a loss of yield. However, under the conditions of conventional coal cleaning practice, this is a sensible approach.

Jan 1, 1988

By Stephen Utter

One function of mining is to supply oil shale of the required grade and characteristics to surface retorts. The mining methods must he safe, efficient, and environmentally acceptable. Although the Bureau of Mines no longer conducts research on methods of mining fossil fuels, including oil shale, its many years of activity in that field resulted in a significant body of findings. This article summarizes some of these findings, with respect to oil shale mining. The large areal extent of Green River formation oil shales and the diversity of geologic, hydrologic, topographic, and other conditions, preclude the use of any one single mining and waste management technique. Instead, in most instances, methods and equipment will be chosen to meet site-specific conditions. Such methods include conventional surface mining (open-pit and strip), underground mining (room-and-pillar, sublevel stoping, caving) and in situ extraction (true in situ from surface drill holes and modified in situ from underground retorts containing rubblized oil shale). Combination or hybrid systems may prove suitable. Both surface and underground backfilling of spent shale waste may be practiced. Tremendous amounts of oil shale must be mined, processed, and the waste shale properly disposed of in order to meet projected industry production goals. For example, about 1.4 tons of oil shale averaging 117 L of shale oil per ton are required to produce one bbl of oil. A plant with a daily production of 8 dam' (50 000 bbl) of oil would thus require some 68 kt of raw shale daily. This is more than the average daily production from any underground mining operation.

Jan 1, 1981

By P. Malozemoff

Discussion by P. Malozemoff I have no objection to using mathematics in the value appraisal of properties. The factor that is not emphasized in the paper is that very few important properties have a lifetime that reflects the initial ore reserves of the property divided by the rate of production adopted. In the majority of cases, major properties mine out several times the initial reserves. How much more will be mined out is not known, and only exceptionally gifted geologists can predict that additional reserves will be found. There is the further factor of metals price, which, over the long term, is not predictable. Another factor vitiating making calculations on initially established ore reserves is the speculative nature of exploration success. In my judgment, the life of a property, in addition to an established ore reserve, should include ample time for exploration to find additional reserves. The likelihood of additional reserves is based on the geological promise of the general area where the mine is established. This is especially important because of various risk factors associated with small orebodies, the economic life of which is about five to seven years. In underground mines, it is not economic to develop reserves beyond a certain depth, so the life of initially established reserves must be limited. In these cases, it is especially important to have a good geological understanding of the orebody and its continuity. To accommodate these concepts and present proof of economic soundness for a mining enterprise, a mathematical analysis should yield a life long enough to allow exploration and the development of additional reserves that would ensure a longer mine life and a more profitable result.

Jan 1, 1994

By M. J. McPherson, P. Mousset-Jones, J. Banik, F. Calizaya

Friction factors or coefficients of friction used to estimate the resistances of mine airways are, in the main, estimated from empirical measurements made in other airways considered to be of a similar geometry and type of lining. A somewhat more analytical approach, although still based on empiricism, is to estimate the ratio of the average height of the asperities to the hydraulic mean diameter of the airway (e/D ratio) and then to employ the Moody Chart or one of the equations that have long been established to represent the [coefficient of friction v Reynolds number curves] on that chart. Unfortunately, the Moody Chart and corresponding equations are based on pipes of uniformly distributed (sand grain) roughness whereas the asperities that exist on the surfaces of mine openings are frequently highly irregular both in their size and distribution. This is considered to be a major cause of discrepancies that have been found between coefficients of friction by the Moody Chart and those actually measured in mine airways. The work described in this paper examines an alternative method of estimating coefficients of friction for rough natural surfaces with uneven sizes and distribution of surface asperities. The technique utilizes the relatively recent developments in fractal analysis. A fractal dimension is determined from the topography of the surface. This has been correlated to coefficient of friction for a scale model of a mine airway. Further work is being carried out in actual mine airways. However, at this time, it appears promising that the fractal method may allow coefficient of friction to be predicted for given types of strata and method of roadway drivage.

Jan 1, 1993

By James Wm. White

Computer-based mine management systems are being used in many surface mines to assign haul trucks, track equipment and manage information. Advances in digital communications allow these systems to be used in underground operations. Underground mine management systems help maximize production by providing gains in equipment and manpower use, drawpoint equalization in block caving operations, preventive maintenance and safety. Current systems use allocated or "locked" train and load-haul-dump (LHD) dispatching. Allocated dispatching rarely optimizes open pit product' on. But it offers an efficient mode of operation underground and where options are more limited. The primary objectives of underground mine management systems are to maximize production and mini¬mize contention time through allocated train, truck or LHD dispatching, traffic control, equipment monitoring and comprehensive reporting. The main components of an underground mine management system include: ? A central computer (personal computer or worksta¬tion) in a central control center. It sends instructions to train, truck or LHD drivers and allows dispatcher interaction. ? A field computer system (FCS). This consists of a touch-screen graphics console (GC) and mobile hub - on each train, truck or LHD to receive and display instructions from the central computer and accept driver input. ? A data radio network based on leaky feeder (data, voice, video) or microcell radios (data only) and advanced token-ring technology. This passes information between the central computer and the FCSs. ? Radio frequency (RF) tags mounted at boxes, weigh bridges, tips and rim tunnel main haulage ways to locate trains or LHDs (Luke, 1993). Such a management system must be in place before implementing computer-based dispatching (Vagenas, 1991) for production optimization.

Jan 1, 1997

By Jed H. Mosgrove

One of the most interesting of all the subjects required of persons studying the different facets of coal mining is coal mine gases. Some mine gases have been a real problem since the very beginning of underground mining, and in the early days there was insufficient knowledge to cope with them. The history of mining shows that until about the last 50 years, much work was done primarily by the hand methods which are primitive by today's standards. Miners had to contend with gases without the aid of enclosed lighting, permissible mine machinery, sophisticated testing devices, and high-pressure ventilating fans. In early days the miners were not educated about the different mine gases nor did they have the technical equipment to determine the actual composition of the deadly atmospheres they encountered. They simply applied a descriptive term to each gas or mixture of gases depending on its effect on a person or the surrounding atmosphere. The gases or mixtures of gases were then referred to as "damps," a term which was probably derived from the German word "dampf," meaning vapors or gases. The more common damps encountered were : Blackdamp A condition of the atmosphere in which a miner's light would be extinguished and in which breathing would be difficult, sometimes even resulting in suffocation. An atmosphere deficient in oxygen which could contain a combination of any of the mine gases Firedamp A flammable mixture of methane and air which would either burn or explode when ignited. White Damp A mixture of gases containing carbon monoxide, most often found in mines during fires or after explosions.

Jan 1, 1981

By Michael Gay, W. H. Hansmire, G. Rippentrop, V. S. Romero

The new Tren Urbano heavy rail transit project in San Juan, Puerto Rico has one very significant part, the Río Piedras Contract, being constructed underground. This paper will give an overview of the tunneling work that started construction in1997. Design-Build procurement for tunneling is addressed. The new and modern transit system in San Juan will be 17.2 km (10.7 mi)long and have 16 stations in its first segment of construction, which is due to open in 2001. The line connects the city center district of Santurce to the outlying suburban municipality of Bayamón. All construction is being done under design-build contracts as a demonstration project funded by the Commonwealth of Puerto Rico and the Federal Transit Administration (FTA). The Río Piedras Contract is completely underground and involves practically all types of construction in soft ground. One station is built as cut-and-cover at the University of Puerto Rico. One portion has twin tunnels to be driven with an Earth Pressure Balance Machine (EPBM) and lined with one-pass precast concrete segments. Another has four short tunnel drives at a turnout that will be constructed with an initial support of shotcrete and lattice girders (i.e., the New Austrian Tunneling Method of construction). The most complex construction is the Río Piedras Station, which is being built as a stacked drift with a total of 15 individual tunnel drifts. After being sequentially excavated and concreted, they will form the arch of the 19 m (62 ft.) wide by 16 m (53 ft.) high cavern station. This structure is excavated in soil with less than 5 m (16 ft.) of cover to overlying historic buildings.

Jan 1, 1999

By Anthony S. Spearing

The vast majority of the estimated 100 million rock anchors installed in mines in the USA per year use resin cartridges (Tadolini and Mazzoni, 2006). About 4.5 million per annum of these are bolts with a mechanical shell that if properly installed become effective active supports on installation. In addition, cable anchors (mostly passive) are installed with typically 4 ft of effective resin anchorage length sometimes with mechanical shells, which further makes the installation more difficult. This is because the cable (even with a stiffener tube) is not very rigid. When installing bolts with mechanical shells and cable bolts in the holes, the back-pressure can be so high that the installation is unsuccessful often creating a ?spinner? (an un-tensioned bolt) at best or buckling the bolt thus requiring another bolt/cable to be installed, or leaving a poorly functioning unit. The installation problems can create a significant potential safety hazard and waste time and money. Using a purpose designed test rig that physically inserts different rock anchors into pipes with resin and measure the back-pressure developed with time during the insertion/ installation. The test installation procedure is designed to mirror that used underground by rockbolt operators in coal mines. In addition a computer model has been calibrated that can predict the approximate back pressure of new anchor and resin combinations acting as a screen before physical testing. This research has lead to an understanding and quantification of the insertion back-pressures and this already resulted in improved prototype designs that could lead to more reliable mechanical shell and resin bolt installations.

Jan 1, 2009

By Tracy Braun, Dan Lampshire

Over the past decade, heap leaching at Cortez has evolved from a rather small operation producing around 30,000 ounces per year of gold to an operation scheduled to produce over 400,000 ounces in 2004. Evolution and expansions in the heap leach operations are discussed including plant design criteria and some of the design features in the various facilities. Operating parameters and production forecasting are also discussed.

Jan 1, 2005

By J. N. Economopoulos

The mining industry is becoming increasingly aware of environmental issues and has made big forward steps in the field of environmental management. Legislation, social pressure and competition introduced changes in the industry?s policies and practices in order to conform to the new standards of environmental performance. The paper addresses the need for an integrated and systematic approach to the issues of environmental management within the mining industry.

Jan 1, 2002

By Leonard A. Eros

In many mining applications it is not practical to use gravity takeups. In these situations hydraulic takeups are often utilized. Performance specifications are often compromised by designs which have inherently high internal friction and inefficient hydraulic designs. This results in performance which does not match the requirements of the conveyor system. A computer model has been built to check unit efficiencies and field measurements have been taken which verify the results.

Jan 1, 1993

By Gordon R. Wicker, Peter V. Avotins, Steven S. Ahlschlager

Laterite ore slurries exhibit Bingham plastic behavior and can be characterized by the magnitude of their yield point and Bingham viscosity. These two parameters are affected by ore composition, solids concentration, and temperature and are used to predict the pressure drop in pipelines and heat transfer coefficients in shell-and-tube heat exchangers. In cycloning of laterite slurries, the calculated cut size is corrected by factors obtained from the rheological parameters.

Jan 1, 1979