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By Jack D. Melin

The commercial development of the Liwell Screen is a result of a thorough search for a non-blinding and highly efficient screening device capable of handling even the most difficult-to- screen feed materials. A proprietary development of Hein, Lehmann A.G. of Duesseldorf, West Germany, the Liwell Screen utilizes a unique flexible deck motion for sizing a variety of sticky, high surface moisture feed materials including raw coal and lignite at separations ranging from 3/4-inches (19mm) down to 10 mesh (1.5 mm).

Jan 1, 1983

By William Bogan, Mark Vaivoda, Richard Daniele

Many factors must be considered when performing engineering and construction work for a major minerals project. Dravo's Afton copper smelter in British Columbia illustrates some of the E&C factors considered when setting up this new operation. In March 1978, Afton Mines Ltd., a Tech Corp. subsidiary, began blister copper production at the world's first integrated copper ore mining, milling, and smelting operation to use Top Blow Rotary Converter (TBRC) process smelting technology. This key TBRC smelting element is licensed by INCO Ltd. to Dravo Corp. The TBRC process uses a single vessel of modular design. It rotates for mixing and provides complete processing capability, from concentrate through blister copper. The Afton facility is about 16 km west of Kamloops, a town in south-central British Columbia. To make its operation as economic as possible, Afton officials considered several options for the copper smelter, the first in modern times in the province. Inability to extract precious metals-primarily gold-from the concentrates ruled out hydro-metallurgical processes. The final choice was between a conventional electric furnace/ Peirce-Smith converter combination and the TBRC process. The TBRC process was chosen for its versatility in processing the various Afton concentrates and grades and its 40% lower capital cost compared to the electric furnace converter system. The TBRC smelter -including concentrate slurry receiving, drying, storage, smelting, off-gas cleaning, and copper casting-had an installed cost of about $25 million. In December 1974, a pilot program was conducted by Teck, Dravo, and INCO at INCO's Port Colborne, Ontario, research facility. The pilot program demonstrated the TBRC's ability to smelt, convert, and clean copper slags. After the successful pilot effort, Dravo performed additional research to find an effective fixation system for high grade, intermittent SO2 gases. Once the go-ahead was given, design and procurement for the Afton copper smelter was provided by the Denver Division, Dravo Engineers and Constructors. Commonwealth Construction, Vancouver, constructed all Afton facilities. Afton's single furnace smelter is designed to produce 25-kt/a blister copper in 363-408 kg cake form. The product is sold to England for electrolytic refining. The TBRC process is only one of several innovations proposed by Dravo and chosen by Afton to insure the most modern smelter in North America and meet all British Columbia's environmental restrictions. Conventional smelting methods use a separate furnace for each process step. The TBRC process employs but one furnace. The Afton TBRC vessel measures 6.4 m in length and 4.3 m in diameter. The furnace is supported on a set of motor-driven rollers. These permit the vessel to rotate at variable speeds to 40 rpm. Rotation provides good mixing, high reaction rates, and effective heat transfer from the refractory sides to the molten bath resulting in a low thermal gradient. The furnace can tilt through a full 360° for charging, firing, and pouring. Smelting at Afton is accomplished in sequential fashion. Flotation concentrate and limestone flux are initially charged to the hot, empty vessel. Using the water-cooled, oxy-fuel lance, the initial charge is smelted. Once sufficient molten bath is obtained and slagging completed, the metallic concentrate is charged. Materials are charged through the water-cooled, variable position additive chute mounted on the TBRC

Jan 10, 1980

By A. Konya

"INTRODUCTION Underground Mining and Construction projects face several challenges unique to the underground environment compared to the surface environment. The goals of an effective blasting program are the development of a blast pattern that minimizes cost, maximizes face advance, and provides the desired fragmentation and face profile. In addition to these , mines must consider the very real operational problems that occur such as drill deviation, ground vibration, and deadpressing or sympathetic detonation of explosives. These operation problems lead to increased costs and decreased production in the mine, hurting the bottom line. Combined with these problems, underground blasts can be difficult to monitor and evaluate due to tight spaces, dust during the blast obscuring video, and the need to evacuate the immediate area with no clear line of sight to observe performance. This creates an environment which most mines know that blasting can be improved in their underground operations, yet most are hesitant to change due to fears of the shot freezing, misfires occurring, and questions about how to achieve a proper design. The explosive companies and shot service providers also offer limited assistance or knowledge in the underground blasting realm, unlike with surface blasting, leaving many underground operations in the dark. It is for these reasons that most underground operations are operating decades behind the current technologies and incurring significant costs, both real and hidden, from there blasting operations. This paper discusses philosophical changes to designs that need to be made for effective design and modifications of underground blast patterns to prevent deadpressing and precompression of modern explosive products (Konya, Konya, & Worsey, Modern Blasting Method Selection, 2017). While numerous different methods of underground heading development exist, there are two types that are used in a majority of mines around the world, these are the burn cut and the V-cut. The burn cut is a parallel cut that has holes that go straight into the face and are primarily used in smaller opening (due to ability to pull deep rounds with smaller room widths) and metal mines (helps in ore dilution and greater fragmentation). The V-Cut is a cut that uses angled drilling towards the center of the face (in the traditional method) and is primarily used in underground aggregate operations due to its cheap cost but larger fragmentation sizes and greater throw of the muckpile. This paper will discuss these two forms of cuts specifically with the understanding that modifications to these can be applied to other parallel and angled underground heading techniques. BURN CUT The burn cut is one of the older forms of underground blasting, where a part of the blast (burn) of a shot is heavily loaded with additional empty (relief) holes with the goal of smashing (aka burn) and pushing/blowing all the material in the burn out to provide relief for subsequent blastholes. The relief holes in the burn cut provide a parallel relief for the holes that are firing to break too creating a second plane of relief, however these are extremely small and can cause many problems if a design is improper."

Jan 1, 2018

By J. G. Groppo

Froth flotation has been shown to be an effective method for reducing Loss-on-Ignition (LOI) of ponded or landfilled fly ash. Reduction of LOI is required for many fly ashes, particularly those produced from low-No, burners, in order to meet ASTM requirements for use as a mineral admixture in Portland cement concrete. An additional ASTM requirement, fineness, is critical in determining end use applicability, and in many cases, classification of fly ash is necessary to produce an acceptable product. Hydraulic classification has been shown to be a simple, cost-effective method for classification of a variety of minerals including silica, phosphate, mica, coal, etc. and has shown to be similarly effective on fly ash. The combination of froth flotation and hydraulic classification facilitate the production of a high quality pozzolan that meets or exceeds ASTM specifications. This combination has been rigorously evaluated and results of pilot-scale testing are presented. Pilot scale testing was conducted on fly ash from two active utility storage ponds and demonstrated that high quality, consistent pozzolan could be produced using APT's Fast Float? Technology. Along with the pozzolan, additional production of aggregate for masonry mortar and a low sulfur, medium Btu fuel were also demonstrated. The Fast Float? process incorporates several simple unit processes to ensure pozzolan consistency; classification controls particle size distribution which is critical to achieving early strength, flotation controls the grade with respect to L.O.I. (Loss on Ignition) while dewatering controls the moisture content.

Jan 1, 1998

By Ehsan Alavi, Brian Hagan, Colin LaVassar, Glen Frank, Derek Dugan, Rick Capka, Lisa Mori

"Tunnel face instability is one of the most common issues in EPB tunneling. The evaluation of an ideal face support pressure is a critical element in the design and construction phases of EPB tunneling. In this study, measured tunnel face pressures in three EPB tunneling projects (University Link U230 and U220 projects and the Northgate Link Extension N125 Project) for Sound Transit in Seattle, WA are compared with the calculated analytical methods. This comparison shows that the analytical methods generally overestimate the required tunnel face support. The best practice for managing the face pressure in EPB tunneling operation is discussed based on the experience gained through these projects. Furthermore, the algorithm that is developed for identifying ground loss in these projects is addressed. INTRODUCTION Earth pressure balanced tunneling relies on using muck within the chamber to support the face. Muck is pressurized by controlling the advance rate of the tunnel boring machine and the speed of the screw conveyor. Target face pressure is typically calculated by using the geotechnical assumptions in the geotechnical baseline report. The concept behind EPB tunneling is that the application of sufficient face support pressure will prevent tunnel face instability and the resultant over excavation. Tunnel face instabilities caused by a lack of sufficient face support can lead to ground loss and surface settlement (Anagnostou & Kovári 1996, Kirsch 2010). A certain support pressure must be achieved to counteract water and earth pressure with an adequate factor of safety. While the water pressure can be predicted accurately, the determination of the resultant earth pressure on the face is less precise. This becomes manifested in the relatively high partial safety factors on the earth pressure."

Jan 1, 2016

By J. L. Ellenberger, P. W. Jeran

A deep longwall coal mine was instrumented with a three-dimensional microseismic system in order to help determine the exact strata mechanics associated with the rock failure, redistribution of stress and the associated gob formation from the longwall. Overall, 5,000 well calibrated seismic events were recorded during the mining of the panel. Analysis of these events showed a close correlation between the seismic activity and advance rate, and that the majority of the recorded seismic activity occurs in the immediate area of the advancing longwall face.

Jan 1, 2002

By David R. Klug, Chris Gause, Troy L. Page

The Inter-Island Tunnel is one of two undersea tunnels which are part of the Boston Harbor Clean-Up Program. The tunnel is 7.7 km (25,160 ft) long, bored to a 4.3 m (14 ft) diameter in the Cambridge Argillite Formation and was finished to a 3.5 m (11.5 ft) diameter final concrete lining. The owner is the Massachusetts Water Resources Authority (MWRA) who is a regional authority responsible for overall design and construction. The tunnel's primary purpose is the transport of untreated effluent from Nut Island facility in Quincy, MA to the new treatment plant at Deer Island. Two sludge lines are installed for the transport of sludge from Deer Island to Nut Island. During construction the contractor encountered fault zones, fractured strata, and soft ground tunnel sections which liberated more ground water than was originally anticipated by the project designer. Ground water was controlled during mining and the placing of the final lining. The final lining of cast-in-place concrete had to be backfill grouted to cut off water inflows and provide contact for equal tunnel loading which is critical in long-term design. This paper deals with an engineered backfill grouting system which was the first of its type to be used in North America. It discusses the geological conditions encountered, the design criteria used in the evaluation process, and an indepth review of the various system components. It demonstrates how contractors can use knowledgeable and professional industry suppliers to solve difficult construction problems.

Jan 1, 1999

By Michael Bourassa, Sonja Felderhof, Normand Champigny, Steve Vaughan

Introduction -Comparison of International Reporting Standards (Sonja) -Legal and Due Diligence Requirements for Reporting (Steve) -Flexibility to Recognize International Reporting Standards (Michael) -Obligation of SRO’s to Discipline (Michael) -Impact of Sarbanes Oxley on Reporting (Normand)

Jan 1, 2003

By Yves Picot

Construction of new installations was recently completed in the Port of Tubarao, Brazil, With this expansion the port, operated by Companhia Vale do Rio Doce (CVRD), has become the largest iron ore port in the world, with an annual throughput capacity of 60 million long tons. GROWTH OR IRON ORE EXPORTS Since its formation CVRD has steadily increased the shipment of iron ore to overseas markets. Starting with less than 100,000 tons in 1942, the yearly export volume grew to 1,500,000 tons in 1951, 5,000,000 tons in 1961 and 25,000,000 tons in 1971. The number of different grades of ore also increased during this period. Production of high grade pellets, starting in 1970, further increased the number of ore products to be shipped. In the same period the size of ore carriers increased twenty-fold to over 250,000 DWT.

Jan 1, 1974

By B. Listerud, G. Zhan, M. A. Jones

Barrick Goldstrike Mines Inc. (BGMI) operates the Betze-Post openpit and the Meikle and Rodeo underground mines. Because the majority of the orebody is located below the water table, mining at BGMI requires a significant dewatering program. BGMI has a comprehensive dewatering and water management system that experienced a peak dewatering rate of 4,400 L/s in the mid 1990s. Changes to the hydrologic/hydrogeologic system caused by the mine dewatering have been monitored by an extensive network of groundwater monitoring wells and surface water monitoring stations, which cover about 1,550 km2. In addition to the monitoring program, a new tool, called Interferometric Synthetic Aperture Radar (InSAR), has also been used to enhance the evaluation of changes. Finally, a groundwater flow model has been developed that successfully simulates and predicts aquifer responses in the mine area and region. The well-calibrated flow model has served as a reliable tool to develop dewatering and mining plans, and project post-closure hydrologic conditions in the region. This paper introduces the BGMI dewatering and water management system and the means used by BGMI to evaluate and anticipate hydrologic responses in the region. The water management and analysis system has been and continues to be an integral part of managing ongoing operations, planning and pricing out future activities and evaluating the long-term effects of mine water handling.

Jan 1, 2011

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 J. R. Cooper

Since man began beneficiating ores, a limited number of factors influenced the type of treatment. The ore itself has always been a factor. The first form of concentration was probably hand sorting, and the grade of concentrate and recovery had to be considered from the start. The cost of labor as a factor in mill design did not attain importance until the period following World War I. Power was one of the cheapest commodities available, and consequently power consumption was ignored. That no longer holds true. The present work does nothing to simplify the work of the metallurgist, or designer. On the contrary it adds another element to the design considerations. And while this report concentrates on power consumption, the mill designer must take the other factors into account as well. This study is based on a compilation of data supplied by a number of Western United States copper operations, as well as information from equipment manufacturers. Although its conclusiones apply to other minerals and geographic areas, the information is more precise, when applied to similar ores. The discussion has been divided into sections covering crushing, grinding, and flotation as these are the principal power consuming functions.

Jan 1, 1977

By Paul C. Schmall

In recent years, several geotechnical methods have been successfully applied to ash pond closure. These include modified dewatering techniques with wellpoints and wells to physically drain the material, soil mixing to create a soil-concrete material for improved accessways as well as improved ground structures within ponds to act as barriers or gravity dams, and geotechnical instrumentation to serve as an early warning of the potential for liquefaction. Given the parallels between fly ash and sluiced in place mine tailings, the application of fly ash remediation method to mine tailings shows significant potential, as illustrated in this paper.

Feb 1, 2024

By E. L. Schrader

Statistical Process Control (SPC) is a cooperative arrangement between a component or raw materials supplier and a manufacturing customer. The supplier must analyze his own manufacturing process and determine, predict, and control those variable elements in the circuit which affect finished product characteristics according to the customer's specifications. The results include: control of fluctuations in product characteristics to a narrow range, close communication between supplier and customer, and an increased responsibility for quality control placed on the supplier. In the mining and. processing of airfloated kaolin some unique problems arise with the SPC concept: 1) The SPC system was designed for manufacturing facilities that did not have to deal with natural variations in their raw material; 2) The airfloat process is relatively simple and offers limited opportunity to change processing steps or "fine tune" a circuit for special product needs; 3) Determining adequate sampling frequency for a plant which processes hundreds to thousands of tons per day is statistically difficult; and, 4) Due to the variety of customer industries served, different SPC programs must be set up to deal with widely varying specifications. For airfloated kaolin, SPC is "in line" process control, not after the fact "quality" control. The emphasis must be on statistically valid sampling of the kaolin ore and complete monitoring of its path through the beneficiation circuit.

Jan 1, 1987

By David A. Rice, Scott A. Shuey, William K. Tolley

The U.S. Bureau of Mines (USBM) is developing new dewatering technology to permit the recycling of iron values contained in wet steel plant sludges. In laboratory tests, Q-BOP fume sludge was dewatered to 12% moisture by displacing water with acetone in a plate-and-frame pressure filter. Acetone is reclaimed through distillation at lower cost than conventional thermal drying of the sludge. The projected additional energy requirement for acetone treatment of the sludge, including acetone recovery, is $5 to $7 per dry ton.

Jan 1, 1995

By M. J. Blattman

The problem of measuring the amount of rock removed during a given time interval is faced by most milling operations. Many methods have been developed with varying degrees of success, dependent upon the mining method and the availability of usable data. The Rosebud Mine has been in production for nearly two years, employing several techniques to estimate monthly production from underground production stopes. The use of three-dimensional solids generated from survey data has greatly improved the reliability and confidence of monthly production reports. The authors will summarize the methodology currently being utilized at Rosebud.

Jan 1, 1999

By Christopher Haycocks

Successful ground control is an essential part of all viable underground mining operations. To a large extent ground conditions influence the choice of mining methods, percentage and cost of extraction, and often the degree of safety that can be achieved. Utilizing the computer for ground-control planning offers great potential under many diverse conditions as not only are computations facilitated, but also details of the often complex geologic and structural framework of the mine can be readily stored and retrieved. Two basic approaches have been developed for applying the computer in solving ground-control problems. The first uses an analytical method, such as the finite element technique, for solving a specific problem. The second is more general and involves storage of geologic data and application of general design equations. The latter has found wide application in stratified deposits. It is the purpose of this chapter to describe both approaches as they are used for improving the ground-control aspects of mine planning.

Jan 1, 1979

By T. Knuutinen, M. Klemetti, P. Mörsky

This paper presents a comparison study done at VTT's new pilot plant facilities in Outokumpu, Finland, for chromite ore. The ore was ground in a rod mill -, a ball mill - and high pressure roller mill - ball mill circuit in the capacity range of 0.5 - 3.0 t / h. The main grinding characteristics are discussed and the quality of the products are compared from the mineralogical point of view. The benefits of high pressure roller mill comminution for further mineral processing of chromite is also discussed.

Jan 1, 1995

By S. Bentley

"Everyone has a general idea what mixing means, but describing the mixing process is not so simple. The objective of any mixing process is to distribute and blend the materials with different characteristics, different quantities as evenly as possible resulting in a homogenous mixture. Introducing proportional movement with the optimal intensity into the materials achieves effective homogeneous mixing results. A simple one directional movement with inadequate acceleration of the materials would obviously not achieve the same mixing results. This would be more like stirring than mixing. The amount of relative movement that is introduced is a decisive factor. Circumstances for successful mixing involve distribution of all materials, and achieving the highest probability that all recipe particles located in a specific position at the beginning can be found at any random location in the mixing chamber at the end of the process. This is the only way to ensure that a consistent result is achieved every time mixing is repeated.THREE-PART CYCLE The mixing cycle occurs in three phases; charging the mixer, the mixing process, and discharging. The sequence in which the individual materials to be mixed are filled into the mixer can have a huge impact on the efficiency of the mixing cycle. The mixing cycle overlaps the charging process and the discharge cycle follows the mixing cycle. To achieve optimum results, effective discharging methods should be taken into consideration to avoid risks of segregation. Costs for energy and wear should be as low as possible and finally, it is very important that the mixing cycle takes place as quickly as possible. In concrete or paste backfill production, selecting the best mixing technology is crucial for both the quality of the final product to be blended and the efficiency of the production process. The optimum mixing system is one that rapidly disperses all ingredients evenly throughout the mixing trough and completely surrounds all the course or fine aggregate particles with the slurry cement particles. Specific for paste production it’s the mixers job to also break-down unconditioned tailings to achieve consistent paste viscosity or measured spread. Many paste and concrete formulas also involve small quantities of chemical additives which also must be evenly distributed effectively. The time required per mixing cycle as well as the costs of energy, wear and maintenance will determine the economy of the concrete production."

Jan 1, 2015

By Norman E. Breslow, John A. Montgomery, Sanford W. Horstman

Reconstruction of historical exposures to silica dust is required in an ongoing cohort mortality study of workers in the diatomaceous earth (DE) industry. However, historical data were collected using three different sampling methods. This study was conducted to derive empirical quantitative relationships from linear regression equations between the three methods: standard impinger, total mass, and respirable mass. Dust from one diatomaceous earth processing plant was sampled simultaneously by all three methods. Results from 61 clusters of the three sampling devices indicate that the phcle size distribution of the dust varies with the two parent products sampled. baghouse product and main product. The relationships between particle counts and respirable mass are: Respirable mass (mg/m3) = 0.064 (mppd) impinger count for baghouse product dust, and respirable mass (mg/m3) = 0.018 (mppcf) impinger count for main product dust. The relationships between particle counts and total mass are: Total mass (mg/m3) = 0.837 (mppcf) impinger count for baghouse product, and total mass (mg/m3) = 1.21 (mppcf) for main product dust. In all four euuations, the intercept did not differ significantly from zero, and the correlation coefficients ranged from 0.90 to 0.95. Results are compared with data from four previously published studies.

Jan 1, 1991