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By H. Ban

Triboelectrostatic separation tests were performed on a bench-scale, analytical separator using coal, coal combustion fly ash and mineral samples. Fractions of separated samples were collected and analyzed to characterize the performance of the separation. Particle size distribution and morphological characteristics for these samples were analyzed by optical microscopy, and scanning electron microscopy (SEM). It was found that smaller size fractions of a fly ash sample had better separation than the full sized parent fly ash sample, indicating interference or particle-particle interactions during the separation process. It was also observed experimentally that small kaolin particles attach to the surface of large silica spheres, causing charge neutralization and subsequent low separation efficiency.

Jan 1, 1997

By F. Forbes

For many years, the Machinery Division of Dravo Corporation has been designing and constructing bins and hunkers as part of overall plant facilities. We have designed bins to handle a variety of materials including coal, coke, iron ores and concentrates, sintered and pelletized ores, calcined and raw limestone, bentonite, alloys for BOF shops, and even cast iron chips from machining operations. We, along with everyone else in this business, have had our bin problems. The bins either plug, rathole, segregate, wear out, flood the discharge device, or overload it. Surprisingly, sometimes they have worked. As engineers, it has long concerned us that something as important as bin design should be so imprecise and that it has been so conspicuously avoided in research and in literature. In past years, rule-of-thumb design criteria had been to keep the sides of the bins as steep as possible and the outlets of the bin as large as possible. This criteria led to the design of bins with 600 to 700 side slopes and table feeders which were very large. Unfortunately, this meant trying to fit tall, skinny bins into a layout where minimum building height was required for obvious economic reasons. Like everyone else in the industry, we found that this design procedure was expensive and ineffective.

Jan 1, 1968

The stability of mine roofs in permafrost zones is determined mainly by temperature and ice content. The deformation resulting from creep and temperature dependent physical properties of frozen rockmass is the dominant component of total deformation. Roof bolts can consolidate the roof and control its deformation. In this paper, a finite element model for analysis of the effects of roof bolting in a frozen rockmass is presented. The model includes the variables normally encountered when analyzing the effects of roof bolting in rocks. It also accounts for properties unique to frozen rockmass, creep deformation and the change in Young's modulus with changing temperature. The model shows that, as bolt spacing decreases, there is a trade-off between increased roof stability from increased mechanical support and decreased stability from increased conduction of heat into the frozen roof. This result was expected, and shows that, for a given set of rockmass conditions, including ice content, temperature, particle size, etc., there is an optimum bolt length and bolt density for minimum roof deflection.

Jan 1, 1996

By R. L. McNearny

A comparison study was conducted between an actual physical model and a numerical model based on the physical model of the block cave mining method. Results from the numerical analyses closely simulated the blocky behavior of the physical models, including bridging and interlocking of the simulated orebody during draw. The draw-down patterns and the rate of draw developed during numerical modeling also closely simulated the physical models. An unexpected result from the numerical modeling was the development of a zone of downward deflection which preceded the development of the zone of material movement.

Jan 1, 1997

By B. H. Johnston, B. N. Doyle

Introduction In 1983-84 Kidd Creek Mines Ltd. in Timmins, Ontario, started up the second commercial zinc pressure leaching plant based on the Sherritt Gordon Mines Ltd. direct pressure leach process. The first plant using this process was that of Cominco Ltd. at Trail, B.C. (Parker, 1981; Martin and Jankola, 1985). The Kidd Creek plant was constructed to take advantage of the extra capacity that the existing purification, cell house, and casting sections had in comparison to the roasters and acid plant. In addition, pressure leaching offered flexibility in other areas such as treatment of low grade concentrates. The process design package and the detailed design of the autoclave system was carried out by Sherritt. The detailed design for the rest of the plant was done by Cambrian Engineering Ltd. under the direction of Kidd Creek. The construction and commissioning of the plant has been described earlier (Johnston, 1983). This paper describes, briefly, the application of the direct pressure leaching process for zinc concentrates and the integration of the pressure leaching plant into the main zinc plant at Timmins. It discusses some of the startup problems and changes made to the plant. The damage following a fire inside the autoclave is also described. The subsequent repair and recommissioning of the autoclave has enabled Kidd Creek to demonstrate the originally sought advantages of pressure leaching and to take advantage of their extra cell house and casting capacity to produce more zinc. Process principles The development of the direct pressure sulphuric acid leach of zinc sulphide concentrate at temperatures above the melting point of sulphur and at elevated oxygen pressure has been described in detail in a number of papers (Martin and Jankola, 1985; Johnston, 1983; Veltman and Bolton, 1980; Kawulka et al., 1975; Veltman et al., 1977). The most significant aspect of the process is that sulphidic sulphur is converted to elemental sulphur in reactions that can be simply described as follows. ZnS + H2SO4 + 1/2 O2 ZnSO4 + S° + H2O (1) FeS + H2SO4 + 1/2 O2 FeSO4 + S° + H2O (2) The rates of these reactions increase with temperature. However, at temperatures above the melting point of sulphur, 12°C, the presence of a surface active agent is necessary to prevent the occlusion of the sulphide particles by elemental sulphur and the consequent termination of the leach. The zinc that is dissolved according to reaction (1), after purification of the zinc sulphate solution, is recovered by electrowinning. The iron that is put into solution according to reaction (2) is further oxidized to the ferric state and subsequently, as the acidity decreases, precipitates as hematite or as complex basic sulphates. MINERALS AND METALLURGICAL PROCESSING Examples of this are shown below. 2FeSO4 + H2SO4 +1/2O2 - Fe2(SO4)3 + H2O (3) Fe2(SO4)3 + 6H2O - Fe2O3.3H2O + 3H2SO4 (4) 3Fe2(SO4)3 + 14H2O - 2(H3O)Fe3(SO4)2(OH)6 + 5H2SO4 (5) (hydronium jarosite) The conventional zinc process involves concentrate roasting to produce zinc oxide and sulphur dioxide. The zinc oxide is leached in spent electrolyte and the sulphur dioxide is converted to sulphuric acid. The pressure leaching process can, therefore, be used to replace conventional concentrate roasting, sulphuric acid manufacture, and atmospheric leaching with one unit operation. Integration of pressure leaching into the Kidd Creek flowsheet A block flowsheet of the Kidd Creek zinc plant, with the new pressure leach plant integrated, is shown in Fig. 1. The original plant, which was constructed in 1972, is based on standard electrolytic zinc plant technology. Concentrates are dead roasted to remove sulphur. Sulphur dioxide is treated to produce sulphuric acid. Calcine is leached in two stages using cell-house electrolyte. Iron is precipitated as jarosite and solutions are purified to remove copper, cobalt, nickel, and cadmium to provide feed for a partially mechanized cell house. Zinc is plated from solution, and the resulting cathode is melted, cast, and sold (Johnston, 1983). The integration of the pressure leaching plant into the main zinc plant is relatively simple. As shown in Fig. 1, a fraction of the zinc concentrate and spent electrolyte are fed to the pressure leach autoclave, while part of the calcine from the roaster is used as a neutralizing agent in the oxidation step along with. the jarosite leach solution. The main exit stream from the pressure leaching plant is the slurry discharged from the oxidation step, consisting of neutral zinc sulphate solution, unreacted calcine, and precipitated iron oxides. This slurry is transferred to the neutral leach step in the main zinc plant. The leach residue from the pressure leaching step, consisting of basic iron sulphate and elemental sulphur, is washed and impounded along with the jarosite residue produced in the main plant.

Jan 1, 1987

By Mark J. Zdunczyk

Short Mountain Silica mines the Clinch Formation, an orthoquartzite, for silica sand. The operation is located near Mooresburg, TN, about 80 km (50 miles) northeast of Knoxville. Short Mountain is a local geographic name given to an area of resistant sandstone (Fig. 1). The area is part of the Clinch Mountain system that extends from eastern Tennessee to southwestern Virginia. The thick sandstone unit is more technically called a quartz arenite (orthoquartzite) that forms most of the mountain. In 1980, a Knoxville resident brought the Clinch Formation - Short Mountain in particular - to the attention of the large silica-sand producers as a potential silica-sand mine. Working with a local contractor who owned several hundred acres on Short Mountain, the Knoxville resident contacted interested companies. Many silica companies reviewed the property including Ottawa Silica Co., Pennsylvania Glass Sand Co. (both now US Silica Co.),Unimin Corp.,The Morie Co. and others. AFG Industries was the main market for the glass sand product from this potential mine. It had two plants, both within trucking distance from the site. All the silica sand producing companies, however, declined to develop the site. A few years later, Unimin Corp. decided to drill and evaluate the deposit. From that evaluation, Unimin leased the property but later dropped it. The relatively limited market for the Short Mountain product as well as Unimin’s recent acquisition of Carolina Silica were reportedly instrumental in the company’s decision to let go of the lease. Several other companies-unrelated to the silica sand industry - looked at the site but no one was interested in developing it. In 1986, J.D. Nicewonder, owner of coal mines in Virginia and Kentucky, was approached to investigate the site. Nicewonder began to develop the site with the intent to produce glass sand to supply AFG Industries. In May 1988, the first shipment of sand was trucked to AFG Industries.

Jan 1, 1992

It is well established that the results of emulsion flotation in which water-insoluble oily collectors are utilized depend critically on the emulsification of the collector and on its conditioning with the pulp prior to flotation. The flotation tests carried out with magnesite and fluorite using sodium oleate as collector confirmed acidic and alkaline ranges of good flotation. While the flotation results in the acidic solutions depend strongly on the conditioning time and can be very much improved when longer conditioning times are utilized, the tests in the alkaline environment do not exhibit any significant dependence on conditioning. The results obtained with sodium salts of myristic and lauric acids confirm these findings. The observed effects provide additional evidence for the role of the colloidal species which appear in the acidic solutions of weak electrolyte type surfactants, such as fatty acids. The flotation properties of sodium oleate in the pH region in which it appears in the form of oleic acid droplets are mainly determined by the properties of such droplets. The flotation in this pH region closely resembles an emulsion flotation.

Jan 1, 1993

By S. M. S. Azghdi, K. Barani

The effect of microwave treatment on the surface roughness and wettability of chalcopyrite (CuFeS2 ) and on the chemical composition of its surface was studied. The microwave source was a conventional multimodal oven with frequency of 2.45 GHz and maximum power of 900 W. Pure chalcopyrite specimens and purified chalcopyrite concentrate were used in this study. Analysis using atomic force microscopy showed a decrease in the surface roughness of the chalcopyrite after microwave radiation. This decrease may be due to oxidation of the surface and formation of iron oxide. Moreover, the surface wettability of the chalcopyrite mineral increased with increasing duration of microwave radiation, which was in good agreement with the micro-flotation mass recovery results. The increased wettability of the surface may be attributed to the decreased surface roughness by microwave radiation. Analysis using scanning electron microscope/energy-dispersive X-ray spectroscopy indicate that after microwave radiation, the contents of sulfur and iron increased whereas that of copper decreased on the surface of the chalcopyrite, significantly changing the average atomic number of the chalcopyrite surface.

By C. E. Jordan

Under its program of advancing minerals technology, the Federal Bureau of Mines has developed a laboratory apparatus for continuous separation of minerals according to their dielectric properties. The unit consists of a rotating wire grid drum electrode and a fixed curved wire screen electrode positioned 3 mm apart. By applying high voltage across the electrodes, which are immersed in a dielectric fluid medium, a high-gradient electric field is produced. The high-dielectric-constant minerals are attracted and conveyed through the separator by the rotating drum electrode, whereas the low-dielectric-constant minerals settle through the fixed electrode. In typical tests, a sample of Montana chromite ore containing 43 percent chromite was concentrated to 72 percent chromite with 90 percent recovery.

Jan 1, 1977

By Joseph M. Chelini

The report shows the sensitivity that nine different cash-flow factors have on the discounted rate of return calculated from feasibiliity- studies on potenital open-pit orebodies of silver, copper, and uranium. Cash-flow factors of "grade", "market value", and "recovery" are. the most sensitive. This verifies the need of reliable estimates for these factors. The cost of evaluation of "preproduction cost" is the least sensitive. This gives credence to the fact that more consideration should be given to compiling sufficient data, as the largest financial losses are not in the cost of evaluation but rather in the abandonment of an unprofitable mining operation after a commitment of capital is made on the basis of an incomplete evaluation. Sensitivity analysis of cash-flow factors enhances evaluation programs by disciplining the collection of data and allowing more realistic distribution of evaluation monies.

Jan 1, 1971

By D. Carr, C. Anderson, M. Deal, C. Larson

"Construction of the OceanaGold Haile operation’s process plant in Kershaw, South Carolina is currently under way, with ore through the mill expected in late 2016 and commercial production expected in early 2017. The process is designed to treat 6,350 tonnes per day with minor upgrades required to achieve 8,270 tonnes per day. Plant optimization during detailed engineering, combined with a focus on de-risking the process, has resulted in numerous process changes since the initial design. This paper describes the plant optimization and de-risking, it also presents a proven commissioning strategy modelled after OceanaGold’s Didipio operation, whilst identifying potential expansion opportunities. INTRODUCTION Haile Gold Mine is located in Kershaw, South Carolina, approximately 50 miles south of Charlotte, North Carolina. Gold was first discovered at the site in 1827, and the property has been through several operating periods since. The last operation employed heap leaching from 1985 through 1992. Since then, the property has been closed and fully reclaimed. Romarco Minerals acquired the property in 2007, and began an exploration program that delineated 2.02Moz. of gold in reserve at an overall grade of 2.06 g/t. OceanaGold acquired Romarco Minerals and the Haile Operation in October of 2015. OceanaGold operates under a risk management philosophy in all aspects of operation, both corporately and at each individual business unit, and has implemented numerous process changes to eliminate or mitigate risks identified in the initial design of the processing circuit, and provided increased opportunity for optimization and expansion. This paper describes the plant optimization and de-risking, it also presents a proven commissioning strategy modelled after OceanaGold’s Didipio Operation, and identifies potential expansion opportunities. INITIAL PROCESSING CIRCUIT DESIGN An extensive metallurgical test work program was undertaken by Romarco Minerals and third party laboratories during the initial design phase of the Haile project [1]. This preliminary test work provided the technical information as a basis of plant design. The initial flow sheet for the Haile processing circuit is shown in Figure 1 (see APPENDIX). The plant is designed to process 6,350 tpd (7,000 stpd) on an annualized basis. The process begins with a jaw crusher followed by a SAG and ball mill grinding circuit to reduce particle size to P80 74 µm. A flash flotation cell treats 50% of the cyclone underflow in the ball mill circuit. Grinding circuit product is sent to a rougher flotation circuit to recover gold-bearing pyrite. The flotation concentrates from flash and rougher flotation are reground to P80 13 µm using stirred media detritors (SMD’s). The rougher flotation tail is pumped to the carbon-in-leach (CIL) circuit for gold recovery. The reground concentrate is pre-aerated prior to being pumped to the CIL circuit. The CIL circuit is a hybrid circuit with eight tanks. Tank 1 leaches the pre-aerated concentrate only, and tanks 2 through 8 leach the combined flotation tailing and tank 1 discharge. The carbon strip circuit is a standard pressure Zadra system, followed by electrowinning, and refining using an induction furnace. CIL tailing passes through a cyanide recovery thickener prior cyanide destruction and then pumped to the tailing storage facility (TSF)."

Jan 1, 2017

By G. C. Tipper, A. P. Deane, A. G. Myers

SCHEME DESIGN London’s Heathrow Airport, as the world’s busiest international airport, is missing one vital aspect - a dedicated rail link which connects directly to the city. All this is about to change with the construction of Heathrow Express - a fast, high quality rail service between the airport and the centre of London. It was recognised in the mid 1980s that if Heathrow was to accommodate the forecast growth in passenger numbers and the resulting increase in road traffic, a dedicated airport rail service would be vital. The main access into the centre of Heathrow is via a road tunnel with a direct link to the M4 motorway. The airport has introduced a number of traffic management schemes, but these can only achieve so much benefit. Growth in air passenger traffic is predicted to continue at an average of 4% per annum well into the next century and it was clear that significant investment was needed. Heathrow Express at a cost of over £350 million will provide this when it starts its service in June 1998. The business case for the scheme is based on a rider ship of around 15% of air passenger traffic. The initial Heathrow Express service will be based on four trains per hour, up to 8 car train lengths, providing a high speed non-stop service between the airport and central London in just 16 minutes. Initially a joint venture between the British Railways Board and Heathrow Airport, by mutual consent of the two parties, Heathrow Airport recently purchased the British Railways Board share making this one of the largest private sector rail projects currently under construction in the UK. Leaving Paddington, the main rail terminus in West London, Heathrow Express trains will travel 12 miles on the newly electrified line to airport junction, north of the airport. At this point they will leave the mainline to enter a 5 mile tunnel section that runs underneath the heart of the airport. The railway companies are responsible for track work, signalling and electrification of the 12 mile main line section including a grade separated junction over the main tracks for the Great Western Railway which links London and South Wales. Heathrow Airport is re-

Jan 1, 1997

By Tyler A. Dawson, Ryan P. Butler, Timothy Gualandri, Jason R. Edberg

"In the early 1920’s, the City of Tulsa, Oklahoma constructed an approximately 8,238-foot long tunnel, the Tiawah Tunnel, through bedrock. Voids behind the concrete tunnel liner were detected via probe drilling in early 2000 as part of an interior visual condition assessment. In 2012 and 2015, conditions along the entire tunnel were efficiently assessed through geophysical investigation using ground penetrating radar (GPR) along the inner tunnel crown and at various select locations within the tunnel. Fifty-seven (57) potential voids, extending up to 19 inches in depth and 12 feet in width, were detected with 1,000 MHz GPR and confirmed through probe drilling with approximately 80% accuracy. GPR proved to be an efficient and reliable technology for void detection behind concrete tunnel lining. This paper highlights the geophysical investigation and how geophysical efforts were combined with other investigation efforts to definitively determine the presence of voids outside of the tunnel lining.INTRODUCTION The city of Tulsa, Oklahoma has a population of about 400,000 people. The original source of water for the city was the Arkansas River. The first pumping operation provided untreated water to homes and businesses in 1904. The residents of Tulsa found this water to be unacceptable due to the high levels of salt and gypsum present. As the city grew, land and storage/treatment facilities were acquired in order to obtain and distribute a more suitable raw water. The raw water needs for the city are currently satisfied by transport and treatment of about 100 million gallons per day (MGD) of water from surface water sources. Water is transported many miles from Spavinaw/Eucha and Oologah lakes to Yahola Lake and the Lynn Lane Reservoir (totaling over 3-billion gallon capacity). From here, the raw water is treated and transported to the various customers (City of Tulsa 2015). The Tulsa Metropolitan Utility Authority (TMUA) is responsible for the operation and maintenance of the raw water transport system."

Jan 1, 2016

By C. Duke

The water treatment industry has historically been involved with reducing or inhibiting the inherant scale forming or fouling tendencies of natural waters associated with large industrial cooling water systems. Fouling is an extremely complex phenomenon. From a fundamental point of view, it may be characterized as a combined momentum, heat, and mass transfer problem. Chemical reaction kinetics is involved, as well as the solubility characteristics of salts in water and corrosion technology. It is a routine practice to over size pumps, piping and heat exchangers to compensate for fouling.

Jan 1, 1983

By Omid Frough, Hossein Changani

Application of Tunnel Boring Machines (TBMs) is one of the main solutions to achieve a safe and high-performance method of construction in hard rock and soft ground tunneling. In order to adequately assess the progress and potential impacts of the tunneling operations with the TBM, it is required to record a series of data during the tunneling and process of the data to evaluate the TBM performance. Applying the right machine parameters during the excavation not only delivers an optimum penetration rate, but also prevents extra downtime due to over excavation or wear of cutting tools. In this paper, the effect of machine and operational parameters on TBM downtimes has been studied and supported with the real examples of TBM operation data.

Dec 1, 2022

By Theodore H. Budd, Douglas J. Heinz

This report concerns the successful construction of Contract No. 287 of the Northeast Side Relief Sewer System for the Metropolitan Sewerage District of the County of Milwaukee. The contract involved the construction of approximately 3316 meters (10,880 feet) of tunnel concrete lined to 1.83 meters (72 inch) internal diameter; 30.48 meters (100 feet) of 1.83 meters (72 inch) reinforced concrete pipe jacked-in-place; a river crossing of approximately 107 meters (350 feet); 197 meters (647 feet) of 1.83 meters (72 inch) reinforced concrete pipe in open-cut; several diversion and flow monitoring structures; and miscellaneous manholes and appurtenances. The contract proposal, which was extremely prescriptive, did allow alternative methods of primary support consisting of precast reinforced concrete segments, steel liner plates, steel ribs with wood lagging, and combinations thereof in designated areas. The specifications required the contractor to designate which support scheme it intended to use. The specifications also required compressed air as a means of ground water control for approximately 2316 meters (7600 feet) of tunnel. The alternative selected in the bid proposal was the support method consisting of steel ribs and wood lagging for 2263 meters (7425 feet) of tunnel and steel liner plates for the remaining section. Shaft supports, by specification, were designed to be steel liner plate with steel ribs varying in size from 4.27 meters to 6.10 meters (14 foot O.D. to 20 foot O.D. ).

Jan 1, 1983

By MATTHEW HART, THOMAS BAMFORD, Kamran Esmaeili, MICHAL KOWALCZYK, FILIP MEDINAC

Improved haul road conditions can positively impact mine operations resulting in increased safety, productivity gains, increased tire life, and lower maintenance costs. For these reasons, a monitoring program is required to ensure the operational efficiency of the haul roads. Currently, at Bald Mountain mine, monthly site severity studies, ad hoc inspections by frontline supervisors, or operator feedback reporting is used to assess road conditions. These methods are subjective and provide low temporal resolution data. This case study presents novel unmanned aerial vehicle (UAV) technologies, applied on a critical section of haul road at Bald Mountain, to showcase the potential for monitoring haul roads. The results show that orthophotos and digital elevation models can be used to assess the road smoothness condition and to check the road design compliance. Moreover, the aerial mapping allows detection of surface water, rock spillage, and potholes on the road that can be quickly repaired/removed by the dedicated road maintenance team.

Sep 15, 2020

By S. B. Patton, T. Novak

To fully utilize a ventilation simulator as a planning and production tool, the network database must keep pace with mining progress. By using AutoCAD's™ attribute-definition function, the branch data and node coordinates can be stored as part of the branch-diagram file and updated with the drawing. Attributes are drawing entities that contain text which can he extracted in a standard spreadsheet format or as an ASCII text file. The data can be subsequently loaded into a ventilation simulator. This paper presents the methodology for using AutoCAD's™ attribute feature in a ventilation simulation format.

Jan 1, 1995

By J. W. Jang

The wear behaviors of grinding media with different chemical compositions and microstructures in wet grinding of a quartz-pyrrhotite mixture was investigated under various environments. The marked ball wear tests showed that the wear rate could be minimized by a suitable combination of martensite and ferrite within the same ball. A ball composed solely of hard martensite exhibited increased wear under an oxygen environment, while balls composed of both soft ferrite together with hard martensite exhibited decreased wear due presumably to the difference in their passivation? behaviors. The galvanic interactions between the two phases as well as among these phases and an electroactive mineral were investigated through electrochemical measurements under abrasive conditions in a slurry. The rates of formation of passive films controlled the corrosion currents of the high chromium steel media. Corrosive wear and its effect on flotation are discussed using the passivation kinetics model thereby developed.

Jan 1, 1989

By R. L. Lewis

A simple method for estimating the steady-state water quality of a pit lake is presented. The steady-state concentration of a conservative chemical constituent in a pit lake is shown to be a simple function of inflow rate, evaporation rate, and inflow concentration. An analytical method is presented for estimating the equilibrium ground water inflow rate for use in water quality predictions. The time required to reach chemical steady-state is estimated using an iterative mass balance model. Mine operators should find the methodology useful for planning and screening-level regulatory applications where conservative estimates of pit lake water quality are desirable.

Jan 1, 1998