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By J. A. van Huyssteen, P. H. Radcliffe

With the profit squeeze of recent years and indeed the survival of many mines at risk due to low gold prices and declining grades, many inventive solutions have been found of increase production and decrease cost. One of these is the application of process auditing methodology which is essentially a tool to determine systematically whether a process is delivering optimally and, if not, to identify the basic causes. Then a prioritized action plan can be developed with the client. Our experience has shown that problems are seldom what they appear to be and that most processes can operate far more efficiently with relative little effort. A process auditor requires good facilitation skills to overcome initial suspicion, and for sustainable solutions client involvement is essential. Process auditing as it is being applied in Anglogold has evolved over many years to reach its current format. The lessons learned and insights gained in the process are shared here with the reader.

Jan 1, 1999

By Warwick Hoffmann, Robin Batterham, David Conochie

CRA has been actively involved in developing a bacterial oxidation process for the treatment of low grade, refractory gold resources. Success in this application is dependant on the design of large, energy efficient reactors. It was identified at an early stage, that the conventional, bottom sparged bioreactor is inherently inefficient because air must be compressed to a pressure above that at the bottom of the tank. This inefficiency increases as the size of the reactor increases. CRA has developed a novel approach to the aeration problem. In this, venturi aeration is used to aspirate air into a liquor stream. The stream is then reintroduced at the top of a draft tube bioreactor. The advantages found with this technique include · low energy requirements and high oxygen utilisations. From results at the 30 m3 scale, we predict an energy usage of -500 kWh/t sulphur oxidised at a scale of 1000 m3.

Jan 1, 1993

By David R. Wayman

This paper summarizes environmental compliance and related issues associated with underground construction and tunneling operations, whether new work or rehabilitation. Underground construction and tunneling operations have (in most cases) both an underground and surface component. Since many of the major tunneling projects occur in urban areas, often is areas inhabited for several decades or centuries, environmental problems may already exist in a project area, though that may not yet have been formally recognized. Large projects often attract more than their fair share of regulator attention. This paper addresses the issues with the greatest potential to be encountered by underground constructors, with the emphasis on minimizing contractor liabilities, both in the short- and long-term. Minimizing contractor liability begins with understanding bid documents, contract provisions and necessary means of protection, and carries through project execution by responsible control of hazardous materials, avoidance of media contamination, proper waste disposition, as well as compliance with other environmental requirements.

Jan 1, 1999

By M. Cambridge

The extractive industries are currently, and will continue to be, major contributors to the world economy, particularly in the developing world where economic growth is dependent upon a sound supply of primary materials. However, tailings dam and other mine failures have been very much a feature of recent anti-mining publicity, particularly in Europe, and thus instrumental in inhibiting new mine developments. Although, superficially, the record of dangerous incidents might support the anti-mining position, closer inspection suggests otherwise. This paper reviews the failures which have occurred over the last 50 years and demonstrates that, though poor practice is an ongoing problem for the industry, the record is one of improvement in both design and practice. Examples are provided of significant events which have led to dramatic advances in design and operation. The paper assesses the improvements made in technology and practice, and concludes that historic events must continue to form the underlying basis for design and operation of future mining projects.

Jan 1, 2005

By Owen Kreilis

By the time coal was discovered in Newcastle, Australia in 1791, it was already a most important industrial commodity in European countries. Coal was the first mineral to be discovered in Australia and the first to be mined. Today, coal remains Australia's most important mineral in terms of local use and international trade. The first mechanized longwall in Australia began operation in 1963. It contained self-advancing hydraulic supports and was installed at Coalcliff Colliery, located in the Southern Coalfields of New South Wales. After nine months and production of 53 kt (58,000 st), the unit was withdrawn, largely because of uncontrollable roof weight and with the problems of airborne dust and large coal still unsolved. Basically, roof support was insufficient. The European design of the Coalcliff longwall was inadequate for Australian conditions. Another type of support with modifications was installed and began operation at Kemira Colliery at Wollongong, New South Wales, in 1964.

Jan 1, 1995

By S. L. Bessinger

The need for improved safety and productivity brought about the introduction of longwall mining to the Appalachian coal fields. These same forces continue to drive developments in modern longwall equipment and mining practices. Current initiatives to improve productivity and safety are focused on automation and the effects of scale in equipment design. Longwall roof-supports, shearers and face-conveyors have changed significantly. Panel layouts have evolved to include larger total tonnages and provide for more rapid development of gate-entries. These advancements have improved longwall productivity and new production records are continually being set. Roof supports Reliability is implicit in the quest for automation. It is impossible to automate equipment if it is not reliable. To a large degree, this has been the problem with longwall shield automation efforts. The "electronic control" of shields depends on the proper functioning of electronic equipment, electrohydraulic valves and full-flow service valves onboard every support.

Jan 1, 1995

By Vladimir L. Konyukh

Robotics is topical for mining owing to deterioration of miner's safety as a depth of winning, limited functions of traditional mechanization and automation, rise of miner's labor cost. Mining robot is an autonomous mining machine with a free programmable control that provides a multifunctional use of working head. After analysis of world publications the database “Technological applications of robotics in mining" has been built. In most cases robots are suggested for imitation of miner's motions. The following shapes of robotics had been classified for mining: technological robot as a flexible controlled mining machine, remote manipulator, mine rescue robot. The problems of both non-repeated environment recognition and telepresence without direct visibility must be solved. The more a robots integration is the less investments and the more efficiency are. Computer simulation of robotics-based mining is founded on a base of 6 robots functional models, Petri nets and library of 30 robotized technologies. There are some examples of mine robotization in the paper.

Jan 1, 1996

By Eleanora I. Robbins, Motoaki Sato

Many problems associated with acid mine drainage (AMD) are caused by the complex way molecular oxygen (O2) oxidizes reduced matter at surface temperatures. In aqueous solution, O2 kinetically "prefers" to go through the formation of hydrogen peroxide (H2O2) as an intermediate. Being innately unstable, H2O2 is quickly decomposed back to water and oxygen in the presence of dissolved Fe and Mn, both catalysts for the decomposition. Direct addition of H2O2 to AMD produced similar results. Ozone (O3) is a much faster and stronger oxidizer than either O2 or H2O2. In the laboratory, O3 rapidly precipitated Mn, Fe, Ni, Co, Pb, and Ag even in acidic solutions. The experiments indicate that AMD can probably be processed with ozone and metal oxides/hydroxide recovered in flow systems using only septic-tank-size reactors and small sedimentation ponds.

Jan 1, 2000

By M. ]. [Mohkam

The paper describes the features of the problems encountered and the countermeasures taken for two different tunneling projects. Where, slurry shields were used to excavate, in soft heterogeneaous water-bearing grounds, tunnels passing at very low cover beneath existing foundations of H.T. electric pylons, underground structures and major utilities. In order to avoid any ground failure and/or damage to the existing structures, one option was ground treatement by grouting or freezing technics. However, it was judged that, based on previous experiences, excavation with slurry shield could be carried on securely using an appropriate slurry enriched with polymers and applying a well determined pressure at ground face. A three dimensionnal limiting equilibrium analysis model was used to determine proper confinement pressures. And, the appropriate slurry compositions were stabilished based on laboratory test results. The tunnels were excavated successfully, no ground failure was experienced, and the maximum settlement recorded (on pylons) didn't exceed 3 mm.

Jan 1, 1991

By Clyde M. Pearce

This paper describes the facilities at Pointe Noire, Quebec that Wabush Mines utilizes for the receipt, distribution, stockpiling and shipping of iron ore concentrate and pellets. The main topics to be covered will be: 1. - General description 2. - Concentrate receiving facilities 3. - Conveying circuits 4. - Stockpiling 5. - Vessel loading GENERAL DESCRIPTION The map of the eastern Quebec - western Labrador area as shown in Appendix #1 shows the location of Wabush Mines properties. You will note the Scully Mine located at Wabush Lake, Labrador, 235 miles north of the town of Sept-Iles, Quebec. Our neighbors, the Iron Ore Company of Canada have their properties further north at Shefferville, near by at Carol Lake and at Sept-Iles. To the Southwest, our other neighbors, Quebec Cartier Mining, have their iron ore processing facilities and their terminus on the St-Lawrence at Port Cartier. Concentrates are prepared at the scully Mine by mining, crushing, grinding, concentrating, drying and high tension separation for shipment by rail to Pointe Noire, Quebec. Pointe Noire is situated across the bay from the town of Sept-Iles, Quebec on the North Shore of the St-Lawrence River. The concentrate consists of 66% iron, 2 ¼ percent silica and practically no moisture, permitting the use of specially constructed railroad cars and handling facilities to convert the concentrate into pellets, the final product.

Jan 1, 1967

By Jim W. Rosteck, Anthony Del Vescovo

In December of 1992, the City of New York, Department of Environmental Protection, solicited bids for Contract 543B. The low bidder was a joint venture of Schiavone Construction Co., Inc. and the J. F. Shea Co., Inc. When completed, the project provides a 4.88 meter diameter water tunnel 8,840 meters long. This paper presents a case history of the equipment and construction methods utilized for this, the first portion of the New York City Water Tunnel constructed by use of a tunnel boring machine.

Jan 1, 1997

By R. J. Jula

The process of treating granular activated carbon for return to service in the recovery of gold in Carbon in Pulp and Carbon in Leach circuits has been investigated. Carbons from four U.S.A. mines, one Canadian mine and one South African mine were characterized before and after regeneration. The use of thermal gravimetric analyses demonstrated the presence of inorganic compounds on the surface of the carbon. Thermal regeneration was investigated using factorial' analysis to determine the effect or interaction of furnace temperature, retention time and the use of supplemental steam. The operation of acid leaching prior to or after gold elution was investigated. The effect of water quenching, regenerated carbon was also studied. From the data obtained in this investigation, guidelines are given for effective regeneration operation.

Jan 1, 1985

By A. Vaillant

Classifiers that are used to separate granular materials into a coarse and a fine stream, are considered. Fundamental Equations are presented which apply to all, such Classifiers and all feed size distributions. The practical, real Classifier is compared quantitatively with the perfect. Classifier. A Formula is introduced for the Real Classifier Selectivity, that defines what portion of each particle size is sent to the coarse outlet duct. This selectivity function is characterized by three Parameters, one of which (b) is a numerical measure of the sharpness of classification. A new dimensionless variable (J) appears in Equations and Graphs for recirculating load, product size distribution and specific surface in the classified product. This variable combines the effects of sharpness of separation, Classifier setting and fineness of a Rosin-Rammler Type feed to the Classifier. Classifier efficiency is defined, based on Specific Surface.

Jan 1, 1967

By V. Enns, E. Soprovich, J. H. G. Laflamme

A mineralogical and geochemical characterization study was carried out on arsenic-bearing Ketza mine tailings to complement a column extraction test program with the purpose of assessing the potential of arsenic mobilization from the tailings. Two types of tailings samples (i.e., exposed tailings from the impoundment area and water covered tailings samples) were subjected to column tests under standing water cover and with no water cover but weekly flow-through flushing. The tailings have a uniform size distribution. The samples are characterized by high Fe2O3 (44.0 to 68.2 %) and As (3.7 to 4.4w%) concentrations. Ferric hydroxides are the dominant species that are mostly amorphous or cryptocrystalline. Arsenopyrite, scorodite, an Fe-Ca arsenate hydrate phase, an Fe-Bi-As phase and ferric hydroxides are the arsenic-bearing minerals. Arsenic is essentially contained in Ca-As goethite, Fe-Ca arsenate hydrate phase and scorodite. Goethite, although containing low levels of arsenic, could be a significant arsenic-bearing phase because of its high abundance. There does not appear to be any significant chemical or mineralogical difference between the original exposed tailings and the material left underwater with no flow-through for over a year. There are differences in terms of CaO, Fe2O3, SiO,, As, goethite, scorodite, calcite and dolomite concentrations between the exposed tailings and the column material after undergoing approximately two-year flow-through and aggressive leach tests. These differences are likely to be resulting from a combination of different column test conditions and sampling or heterogeneity of the material.

Jan 1, 1998

By Donald J. Olson, Thomas J. Lutzenberger, John Ramage

The North Shore Inline Interceptor, Phase IA tunnel is a 8,550-meter (28,000-ft) interceptor tunnel currently being constructed by Traylor Bros./Frontier-Kemper, Joint Venture, using a 9.8-meter (32-ft - 4-in) diameter Robbins tunnel boring machine (TBM). This tunnel is being driven in Silurian age dolomite approximately 91.5 m (300 ft) below ground surface. Significant water inflows were encountered when the tunnel drive penetrated the thinly-bedded Waubakee Formation. Flow increases approaching 0.75 cu m per min per 30 m of tunnel (200 gpm per 100 ft) have occurred in this formation. After driving approximately 2,285 m (7,500 ft) of tunnel (200 m full face in the Waubakee Formation), total flows exceeded 12 cu m per min (3,200 gpm) with about 5.7 cu m per min (1,500 gpm) entering the tun¬nel from the 200 m (600 ft) of exposed Waubakee Formation. Additional water control measures consisting of increased pumping capacity, increased water treatment capacity, surface grouting ahead of the tunnel, grouting ahead of the tunnel face and panning to improve the working environment for installation of tunnel support, were implemented to deal with the large water inflows. Currently (January 24, 1989), 3,400 m (11,000 ft) of tunnel has been driven, total water inflows are in the range of 11.7 cu m per min (3,100 gpm) with only 6.8 cu m per min (1,800 gpm) inflow from about 1,220 m (4,000 ft) of tunnel driven full face through the Waubakee Formation.

Jan 1, 1989

Lingering effects of the 1990 oil shock that included overbuilding and corporate and individual financial distress caused the Gross Domestic Product to fall slightly to $5.67 billion (US billion = l09). With 254 million people - 697,000 in mining and petroleum - the US has more than 100 million dwelling units and 190 million licensed motor vehicles. New private housing starts fell 15% to one million units. New car production fell 11 % to 5.4 million units. Truck and bus production fell 8% to 3.4 million units. The inflation rate was 3%, while the prime rate of interest was 8.5%. The Producer Price Index (1982 = 100) changed as follows: -fuels and related products and power down 1% to 8l, • metals and metal products down 2% to 120, • chemicals and allied products up 2% to 126, and • non-metallic mineral products up to 2% to 117. Energy Imports of crude and refined petroleum, costing $50 billion, fell 5% to 2.8 billion bbl. Domestic petroleum production rose 1% to 3.6 billion bbl. Petroleum supplied about 39% of US energy, natural gas 24% and coal 22%. The National Energy Strategy was announced in February 1991. Its purpose is to encourage domestic production of fossil fuels and nuclear and renewable energy and to stimulate efficiencies in use. Congress continued to debate the strategy and took no action. Coal production fell 3% to 902 Mt (994 million st). About 60% of that came from surface operations. Seventy-eight percent of the total was used to generate electricity and 3% was coked.

Jan 1, 1992

By M. L. Smith

SAG mill throughput is often a bottleneck in increasing metal productivity. Improved size distribution control in the mill feed can be used to increase mill production. This can be accomplished by controlling blast fragmentation as a function of energy input and rock characteristics. Such an approach requires the integration of rock fragmentation and comminution modeling. The optimal mill feed size distribution is determined by adapting a population balance comminution model to a measure of rock hardness or fragility which is also relevant to the rock fragmentation that is achieved by blasting. The relation between the size distribution and fragility of the feed and of the mill's product and the critical size in a SAG mill is examined.

Jan 1, 1993

By Mark L. Bricker

The Jim Bridger Coal Mine, operated by Bridger Coal Co., is located in Sweetwater County, WY about 56 km (35 miles) northeast of Rock Springs. Bridger Coal is a joint ven¬ture between Nerco Coal Corp, the operator, and Idaho Energy Resources Co. The permit boundary encompasses more than 81 km'- (20,000 acres) on the western side of the Continental Divide. Since the mine began opera¬tions in 1974, it has produced about 82 Mt (90 million st) of coal while moving about 344 hm3 (450 million cu yd) of virgin earth. Annual production averages 4.5 Mt to 6.4 Mt (5 million to 7 million st) of run-of-mine coal. Coal is consumed on-site by the Jim Bridger Power Plant, a 2000-MW generating station. Electricity is transmitted to the Pacific Northwest power grid that includes Oregon, Idaho and northern California. Geology The mine is located on the northeast flank of the Rock Springs uplift. This is a broad, asymmetrical anticlinal feature about 97 km (60 miles) long and 56 km (35 miles) wide with a north-trending axis. This uplift separates the Green River Basin to the west and the Great Divide and Washakie Basins to the east. Precambrian rocks on the apex of the uplift are estimated to be 5200 m (17,000 ft) above the Precambrian rocks in the Green River and Washakie Basins. Normal faults with generally less than 30-m (100-ft) vertical displacement cut through the uplift. The dip of strata on the flanks is generally between 3° and 15°.

Jan 1, 1991

By George E. Valadão, Iván A. Reyes, Mizraim U. Flores, Armando C. Araujo, Rubén H. Olcay

Dewatering tailings to higher grades than paste produces a stable deposit that typically does not require retention dams and is called a “dry stack.” A proposal of different dewatering techniques applied in the fine tailings produced after final desliming phase, obtained from the treating of phosphatic ores, is the main objective of this work. The dewatering techniques evaluated were column thickener, deep cone classifier, and hyperbaric filtration. Calcite and dolomite were the main mineral contained in the phosphate tailings and these have a very fine granulometry; the tailings presented different behaviours related to the dewatering technique applied. The test column thickener and deep cone classifier with the best operational parameters found to obtain a maximum percentage of solids in mass were ~ 71% and ~ 67%, with values of yield stress ~ 200 Pa and ~ 100 Pa, respectively. In the hyperbaric filtration, a cake with ~ 10% moisture was obtained. This indicates that the transportation conditions are not the same. The overflow turbidity levels obtained from column thickener and deep cone classifier test did not exceed the value 100 NTU, whilst for the filtrate of the hyperbaric filter obtained values ~ 800 NTU. It was possible to preliminary estimate the recovery direct of water, considering each dewatering technique for final disposal of the tailings. The best dewatering techniques obtained were in the following order for the disposal in phosphate fine tailings dams; the hyperbaric filter showed an excellent dewatering capacity with productions rates around 160 kg h− 1 m− 2 for moisture cake of 10%, followed by the column thickener and deep cone classifier with paste ~ 71% of solids (W/W) and high-density slurry ~ 67% of solids (W/W), respectively.

Dec 23, 2023

By B. K. Mishra, R. K. Rajamani, R. Venugopal, P. Songfack

Millsoft is a computer-simulation software that predicts the performance of large industrial grinding mills. This software surpasses all other tumbling-mill analysis techniques available today because it is based on fundamental laws of physics instead of empirical correlations. Graphical user interface (GUI) forms simplify the specification of the following design and operating parameters: mill diameter, length, speed, charge density and size distribution, lifter material and geometry. All of these parameters are taken into account in the discrete element numerical technique that constitutes the essence of the simulation software. In turn, the software produces a visual animation of grinding-charge motion, predicts mill power and gives the distribution of impact energy. In this paper, a case study of an 8.5-m-(28 ft-) diam SAG mill is used to illustrate the application of Millsoft for mill design and trouble shooting.

Jan 1, 2000