Search Documents

By B. Anameric

Considerable effort has been directed towards understanding the carbothermic reduction mechanisms of self-reducing, fluxing dried green balls to produce pig iron nuggets. Given the geometry of the situation, some investigators believed that the shrinking core model was applicable. Hence, this study involved investigation of the applicability of the shrinking core model to pig iron nugget production. The experiments involved heat treatment of dried green balls utilizing either a laboratory-scale resistance box furnace or a gas-fired muffle furnace at various furnace temperatures and residence times. The products were analyzed for the following: (i) preferred reaction pattern, (ii) distribution of the metallized areas, (iii) % iron content variation in the pig iron nuggets from surface to center, (iv) carburization pattern and (v) physical and chemical properties of the pig iron nuggets. It was determined that the reduction of iron oxide occurred simultaneously throughout the sample and not beginning at the surface and propagating inward; thus the shrinking-core model was not applicable. Heat transfer and gas diffusion from surface to center were not the rate-limiting steps for reduction and carburization reactions.

Jan 1, 2011

By T. Rudolph, M. Pawlik, J. Benndorf, X. Yin, J. F. Brune, P. Goerke-Mallet

The long and often undefined period in the post-mining phase challenges geo-monitoring with its various responsibilities, like the detection of environmental changes, ground movements and water management. Modern methods of geo- and environmental monitoring observe numerous aspects using active and passive sensors with multispectral, hyperspectral and microwave sensors, with diverse spatial dimensions and spatiotemporal resolutions from satellites, Unmanned Aerial Vehicles (UAVs), in-situ sensors. Data integration, together with on-site knowledge and experience, provides the basis for comprehensive modeling, which improves the understanding of the environmental changes and their related causes, which is an essential step for public acceptance. In this paper, we aim to give a brief overview of various geo- and environmental monitoring methods.

Mar 2, 2022

By J. A. Herbst

In spite of potential theoretical and economic advantages of large-diameter ball mills, many manufacturers elect not to build these mills owing to what is perceived as an excessively large design risk. This risk results from the fact that traditional predictions for mill-scale-up to large diameters are not always accurate. It is apparent that alternative methods of analysis and scale-up are required. Recent studies have shown that detailed population balance models which account for important grinding subprocesses, i.e., grinding kinetics, material transport, and classification, are capable of predicting the performance of small- and intermediate diameter mills (up to 4.3 m (14 ft)) from small-scale batch tests. These same models are used in the current study to predict the performance of a "borderline" large ball mill (4.7x5.5 m) at Asarco's Sacaton operation, a ball mill (5.0x5.8 m) at Kennecott's Chino operation, and one of the world's largest ball mills (5.5x6.1 m), at Cities Service Pinto Valley operation. Model parameters required for scale-up have been estimated in a 380-mm diameter batch mill. Predictions are compared with the results of detailed plant sampling in the three plants. For the Sacaton and Chino operations, the error of the predictions was found to be less than 2.5%, while the corresponding error for the Pinto Valley operation was less than 2.7%. It is concluded that proper representation of the major subprocesses of grinding in the model equation is the key to achieving accurate scale-up. Of special importance is the need to account for the size distribution of the grinding media and the influence of the size distribution environment in the mill on grinding kinetics.

Jan 1, 1983

By J. E. Sepulveda

Tar sand deposits in the. Stare of Utah contain more than 25 billion barrels of in-place bitumen, Although thirty times smaller than the well-known Athabasca tar sands, Utah tar sands do represent a significant domestic energy resource comparable to the national crude oil reserves (31.3 billion barrels), The term "tar sand" refers to a consolidated mixture of bitumen and sand, Based upon a detailed analysis of the physical and chemical properties of both the bitumen and the sand, a hot-water extraction process for Utah tar sands is currently being developed in our laboratories at the University of Utah. This process involves intense agitation of the tar sand in a hot caustic solution and subsequent separation of the bitumen by a modified froth flotation technique., Experimental results indicated that, for a given tar sand sample, percent solids and caustic concentration were the two most important variables controlling the performance of the digestion stage, These variables were identified by means of an experimental, factorial design, in which coefficients of separation greater than 0.90 were realized. Although preliminary in nature, the experimental evidence gathered in this investigation seems to indicate that a hot-water extraction process for Utah tar sands would allow for the efficient utilization of this important energy resource.

Jan 1, 1978

By Richard B. Berg

Chlorite veins in the Silver Star district (40 km southeast of Butte) were of little interest to those who were mining gold and silver in the late 19th century. It wasn't until 1975 that unusually pure magnesian chlorite of the variety clinochlore was identified from a ?talc? claim in this district. In 1977 tests by Cyprus Industrial Minerals showed that this chlorite was suitable for use in ceramics. Mining begun in that year continues. These replacement veins of chlorite in Precambrian quartzofeldspathic gneiss differ from the metalliferous veins to the northwest in both attitude and mineralogy.

Jan 1, 1982

By Richard F. Hammen

Mineral extraction from sulfide ore deposits usually leads to the combined action of oxygen and water on the newly exposed ore. The result is acid mine drainage, a low pH solution of various metal sulfate salts and sulfuric acid. Paradoxically, the valuable metals dissolved in acid mine water are a liability because they are too toxic for discharge but too dilute to recover economically. The expense of compliance with water quality release standards has reduced the profitability of many mining operations. Solid phase extraction (SPE) columns have been developed to extract metals from acid mine water. These columns are designed to remove the toxic elements from water and recover the metals as purified fractions. This article describes the results of a Phase 1 bench-scale project to test the performance of the SPE columns. The tests were conducted with water collected from the abandoned Berkeley Pit copper mine in Butte, MT.

Jan 1, 1993

By Stefan Mede

Robot Supported Moulding—this is the name of Herrenknecht Formwork’s entry to the world of automated segment production. What had been considered impossible for a long time, has been achieved by Herrenknecht experts together with the Swiss company Marti AG: unmanned segment production on the working line. The moulds open and close autonomously with the help of a hydraulic system. A robot cleans and greases the moulds at one work station and inserts the injection sockets at another. The next step will include further automation and digital networking of all processes from production to installation in the tunnel.

Jun 13, 2021

By B. Anamaeric

Economic, environmental and operational disadvantages of the traditional blast furnace process has led to the development of direct smelting reduction processes, including those that utilize self reducing/ fluxing dried greenballs as iron oxide feed materials. This is mainly due to improved carbothermic reduction, carburization and reaction kinetics. In this paper, the morphological changes of the greenballs as they transform to pig iron nuggets are examined over time at a constant temperature of 1,400° C. The products produced after each treatment were characterized using optical microscopy, scanning electron microscopy/energy dispersive spectroscopy and point counting/image analysis. The changes in the percent metallized area, wustite dendrite and slag matrix content of the structures were calculated. It was determined that the transformations were initially controlled by dissolving and containment of iron oxides in the molten slag and their consequent reduction to iron, followed by coalescence of the metallized areas. The final transformations were controlled by the carburization of the metallized areas.

By D. A. Elgillani

Oxidation potentials have been measured in the presence of various concentrations of cyanide, ferrocyanide, and ferricyanide and ethyl xanthate at various values of pH and related to flotation response. Eh-pH diagrams are constructed and show that the formation of surface ferric ferrocyanide is probably responsible for depression when cyanide is added. The influence of cyanide in the depression of pyrite with xanthates as collector has been the subject of many investigations (1,2,3,4,5,6), and from these studies several theories on the mechanism of depression have evolved. Wark and Cox (7) and Gaudin(8) have suggested that the depressing effect is due to a competition of cyanide ion with xanthate ion for the surface. Cook and his colleagues (9,10,11) have explained this phenomenon in terms of competition between hydrocyanic acid and xanthic acid. Sutherland (12) has shown that both of these theories describe accurately the relation between pH value and cyanide addition at constant collector addition but fail to describe the relationship, between pH value and the amount of collector required to cause flotation. Taggart(12) suggested that depression in these systems is due to the formation of a reaction product between ferric ion at the pyrite surface and ferrocyanide ion derived from solution. Majumdar(4,6) has attempted to prove this hypothesis by measuring the contact angles of pyrite in the presence of 25 mg/liter ethyl xanthate and different concentrations of potassium ferrocyanide and ferricyanide. In all cases the contact angles were quite high up to pH 10; these results indicate that pyrite should not be depressed by either potassium ferrocyanide or ferricyanide. In view of these facts, Majumdar has assumed that the compound Fe(CN)2 forms at the surface.

Jan 1, 1968

By S. T. Murray

The European industrial minerals industry and its markets are largely self-sufficient. The companies who are members of the Industrial Minerals Association (IMA-Europe) number around 150 contributing 5 billion Euros to the EU?s GDP and range in size from global publicly quoted corporations to small family owned private companies. Their means and capability to implement sustainable development vary considerably. However the leading companies provide an excellent set of best practices, which IMA as a trade association with recognised core competencies in the field of sustainable development is ideally placed to promulgate throughout its membership. As an active participant in the EU Voluntary Scheme for SDI reporting IMA is not only working to increase the level of response to the SDI questionnaire but is also developing with its members a new sustainable development charter which its members will voluntarily adopt as a guiding principle for their implementation of sustainable development This work will be a consultative process involving all IMA?s section members as well as other trade associations, NGOs and MEPs. Public awareness of the benefits of minerals and their contribution to sustainable development has been raised by IMA?s awareness campaign now being followed by a more targeted programme aimed at MEPs. Further work in the future will consider product stewardship and life-cycle analysis. IMA is already positioning itself with the help of its members to assimilate the minerals industry of the accession territories in the sustainable development process.

Jan 1, 2003

By C. A. Young

Cyanide is a toxic species that is found predominantly in industrial effluents generated by metallurgical operations. Cyanide's strong affinity for metals makes it favorable as an agent for metal finishing and treatment and as a lixivant for metal leaching, particularly gold. These technologies are environmentally sound but require safeguards to prevent accidental spills. Various methods of cyanide remediation by separation and oxidation, including photolytic advanced-oxidation processes, are therefore reviewed. Reaction mechanisms are presented throughout the paper. The methods are compared in regards to their effectiveness in treating various cyanide species: free cyanide, thiocyanate, weak-acid dissociables, and strong-acid dissociables.

Jan 1, 1996

By Henning Schwarz, Faisal Al Arifi, Anas Almousa

"The Riyadh Metro Project forms part of a complete new public transport system integrated in the urban planning and development of the fast growing capital city of the Kingdom of Saudi Arabia. The Design & Build project consists of 176 km of a new metro network with 57 km of double track single tunnel infrastructures, spread over six metro lines. During the design phase, geological, hydrogeological, geotechnical and geophysical site investigations were undertaken to chart the, previously uncharted, underground construction space. Different TBM solutions were selected for implementation taking due consideration of the ground conditions of each metro line. The results obtained from deep excavations for underground stations and analysis of the TBM tunneling data will be used as key input for future tunneling projects in the Riyadh and the Kingdom of Saudi Arabia. The present paper details the design conditions and presents the solutions for large diameter tunnels in karstic limestone. INTRODUCTION The High Commission for the Development of Arriyadh was established in 1974 as the organizational, planning, executive and coordinating body responsible for the development of Riyadh. Arriyadh Development Authority (ADA), established in 1983, is the High Commission’s executive, technical and administrative arm. The ADA is responsible for implementing the High Commission's organizational, planning, executive and coordinating decisions and missions (ADA 2015). One of the remits of the ADA is the preparation and execution of a transport plan for the city. The metro network is planned to be the backbone of the public transport system developed as part of the King Abdulaziz Project for Riyadh Public Transport in Riyadh. With six lines and a total length of 176.5 km (Table 1) and 85 metro stations, the metro network will cover most of the densely populated areas, public facilities, and the educational, commercial and medical institutions. The network will connect the King Khalid International Airport, the King Abdullah Financial District, main universities, Riyadh downtown and the public transport center. The public transport plan includes a future bus network with 22 lines on 1200 km and 6765 stops that will be the main feeder for the Riyadh metro network; it will also be the main mode of transportation within and around Riyadh districts (ADA 2015)."

Jan 1, 2016

By G. L. Mowrey

One critical element of the U.S. Bureau of Mines (Bureau) autonomous mining research program is the development of a reliable coal interface detection (CID) system. Several candidate CID concepts currently being investigated by the Bureau include vibration, passive infrared, radar, and natural gamma radiation (NGR). To establish which CID sensor technologies need to be developed for a given seam, coal and adjacent rock samples (i.e., immediate roof and floor) are being collected from selected major coal seams in the U.S. and are being analyzed in terms of NGR and other geophysical measurements. Results of the NGR measurements indicate that, in general, all shale and shale-like materials (e.g., drawslate, slate, and fireclay) have higher NGR readings than the coal seam. Consequently the NGR method appears to be a potentially useful CID tool, provided that the immediate roof and floor are both composed of a high percentage of shale-type material.

Jan 1, 1990

By David Mast, Irwan Halim, Seung Han Kim

Nowadays more infrastructure tunnel projects are procured using design-build method. In this environment, the Owner’s engineer would typically provide performance requirements for the design-builder, and the Contractor’s designer would work with the contractor to design the tunnel lining based on the Contractor’s means and methods and manufacturing process. This paper will describe the typical requirements provided by the Owner based on its design objectives, and the means and methods by the Contractor that would significantly impact the design. Project examples and recommendations for Owner’s requirements will be provided that can optimize the design and still achieve the Owner’s performance objectives.

Jun 13, 2021

By M. Akser

Ilmenite, rutile, and zircon deposits of commercial importance have not been reported to-date from Turkey. However, information from recent reconnaissance activities indicates the possibility of an economically viable heavy-mineral deposit along the Black Sea coast of Turkey in the vicinity of Ormanli, northwest of Istanbul. Consequently beach and sand dune samples were collected from that area for additional analysis. Laboratory methodologies, designed to simulate standard industrial heavy-mineral plant practices, were used to analyze and evaluate the samples. Based on the analyses, and current market needs, none of the deposits in the Ormanli area qualify as a commercial heavy-mineral deposit.

Jan 1, 1995

By D. Donison

The practice of blasthole mining is typically applied in competent ground conditions, primarily because of the open stope dimensions. At Magma Copper -Superior Mine, a field pilot project was completed examining a variation of blasthole mining in poor ground conditions. The results were very encouraging not only from a technical viewpoint, but also productivity viewpoints. This paper describes the pilot project and the resulting implications.

Jan 1, 1994

By D. W. Gunkle

Processing of various ores and materials in a reducing atmosphere has been done for many years. However, the typical device currently used is a large, often high maintenance, expensive piece of equipment; the rotary kiln. While it is a very reliable and a proven technology, the rotary kiln also has its limitations. It is limited by its ability to process very fine materials without creating a huge dust loss to the air pollution control equipment. This leads us towards the development of an alternate technology; the Gas Suspension System. Gas suspension preheating of various materials has been in commercial use since the early 1950's, but recently has been expanded to include Gas Suspension Reduction. Laboratory experience has proven successful on several materials; Nickel Laterite Fines, Iron Ore Fines, Fluorspar, and Clays. The gas suspension reduction system has many advantages over the conventional reduction kiln when processing fines. They are; lower cost, more fuel efficient, able to process fines, less real estate required, etc.

Jan 1, 1998

By Jan Van Greunen, Mark Vanderzee, David Haug, Geoffrey Hughes, Yiming Sun, Roozbeh Geraili Mikola

"The Sanitation Districts of Los Angeles County is planning to construct a new, approximately 7-mile-long (11.3 km) effluent outfall tunnel to be excavated by TBM and lined with precast concrete segments. Anticipated net operating pressures within the tunnel are expected to approach 3 bar. To counteract joint opening and exfiltration leakage, an approach has been investigated to post-tension the precast concrete tunnel lining with steel tendons. The tunnel alignment crosses several seismically active fault zones, at which installation of steel pipe is proposed as a secondary inner lining to mitigate potential offset displacements. This paper discusses the tunnel lining design approach and methods used to address these unique challenges.INTRODUCTION The Sanitation Districts of Los Angeles County (Sanitation Districts) is planning to construct a new 18-foot-diameter (5.5 m), approximately 7-mile-long (11.3 km) tunnel from the Joint Water Pollution Control Plant (JWPCP), located in the City of Carson, to the existing White Point outfall manifold structure at Royal Palms State Beach (RPSB) (Figure 1). The project is part of the Sanitation Districts’ Clearwater Program, which will improve overall system reliability through the repair and replacement of the existing aging infrastructure. The existing system includes two 6-mile-long (9.7 km) tunnels, 8- and 12-feet in diameter (2.4 and 3.7 m), and four ocean outfall pipes with a maximum capacity of approximately 675 million gal/day (MGD) (2.6 billion L/day). Addition of the new parallel tunnel will increase overall capacity to accommodate peak wet weather wastewater flows of up to 1,262 MGD (4.8 billion L/day) and will allow inspection and repair of the existing tunnels. The new outfall tunnel will be excavated using a pressurized face tunnel boring machine (TBM). Shafts at the north (JWPCP Shaft) and south (RPSB Shaft) ends of the proposed alignment will connect the tunnel to the existing wastewater treatment plant and existing ocean outfalls manifold and during construction act as launch and receiving shafts for the TBM. The tunnel will be excavated from north to south as a single heading."

Jan 1, 2016

"The Ohio River Bridge East End Crossing Tunnel requires a 75-year service life of its cast-in-place reinforced concrete lining. This twin-tube 3-lane (each tube) highway tunnel is about 55-ft wide and 30-ft high. Since unified tunnel service life prediction methodology does not exist in the US, challenges occurred during the design-build phase of this project. These challenges include the methodologies in determining the reinforced concrete’s degradation mode, the lining’s surface chloride concentration level, the reinforcing steel’s critical chloride threshold value for corrosion, how to verify the concrete’s diffusion coefficient, and the durability impact from concrete crack width. This paper presents a methodology in verifying the proposed concrete mix can achieve the service life requirements. This methodology can be adopted for service life prediction for future tunnels to be built in the US. INTRODUCTION The Ohio River Bridge East End Crossing (ORBEE) Tunnel is part of a Public Private Partnership project, which connects transportation network between Louisville, Kentucky and southern Indiana. Located in Louisville, Kentucky, the twin-tube highway tunnel provides northbound and southbound lanes of the Kentucky approach to a new bridge across the Ohio River. Tunnel lengths are approximately 1,675-ft and 1,685 for the northbound tube and the southbound tube, respectively. Connected by two cross-passages, both tubes have a roadway width of 40-ft, for 3-lane traffic, and a vertical clearance of 26.5-ft.The tunnel was constructed by drill and blast method with shotcrete and rock dowels as initial ground supports. The final tunnel lining system includes: •,Nominal 16” cast-in-place reinforced concrete lining, with 2” and 3” concrete covers over reinforcing steel for its extrados and intrados, respectively. •,20” cast-in-place reinforced concrete invert slab, with 4” and 3” concrete covers over reinforcing steel on its top face and bottom face, respectively. •,PVC waterproofing system around tunnel perimeter, excluding invert slab. •,Perforated PVC groundwater collection pipes on both sides of the tubes and one below the invert slab of each tube."

Jan 1, 2016

By J. F. Mack, P. R. Michael, J. M. Shapaka, S. J. Self, M. W. Richmond

"On October 11, 2000, an estimated 306 million gallons of water and coal waste slurry drained from an impoundment in Martin County, eastern Kentucky into an adjacent underground mine. Approximately 230 million gallons of the water and slurry discharged from two underground mine portals and affected over 75 miles of streams in Kentucky and West Virginia. In response to this and several other similar events, the U.S. Office of Surface Mining Reclamation and Enforcement (OSMRE) commissioned an oversight study that evaluates how well state and federal regulatory programs established under the Surface Mining Control and Enforcement Act are ensuring that impoundment operators are minimizing the potential for impoundment-basin breakthroughs. The study focuses on slurry impoundments constructed in the hollows of Appalachia where numerous coal seams and steep topography combine to result in a large number of mined seams intersecting and underlying impounding facilities. Factors under consideration include: (1) full accounting of all mineable coal seams intersecting and underlying the impoundment; (2) identification and accurate location of underground mines close enough to the impoundment to potentially affect its stability; (3) assessment of the stability of coal barriers between the impoundment basin and adjacent mines, and stability of roof rock and pillars in mines subjacent to the structure; (4) determination of the flowability of the impounded slurry when expanding or undermining the facility are being considered; and (5) measures undertaken to reduce breakthrough potential when necessary. The oversight study began in 2012 after program-evaluation criteria were defined in an OSMRE technical position paper. The study is scheduled to be completed in 2017. BACKGROUND The Surface Mining Control and Reclamation Act (SMCRA) authorizes the disposal of coal mine waste by constructing a coarse coal mine waste embankment across a valley and pumping the fine coal mine waste (slurry) into the resulting basin (Figure 1). A concern shared by many engineers, geologists, and mine inspectors familiar with coal mine waste slurry impoundments is related to the common occurrence of underground mine workings adjacent to or beneath the impoundment: the potential for slurry “breakthroughs” into mine works and subsequent breakouts into the surface waterways (Figure 2). On October 11, 2000 a combination of coal refuse slurry and water from the Big Branch impoundment in Martin County, Kentucky broke through into an underground mine and subsequently discharged into the receiving streams. The location of the point of breakthrough, pathways of slurry/water flow within the mine workings, and two points where the liquid exited the mine are shown in Figure 3. An estimated 306 million gallons of water and coal refuse slurry drained from the impoundment into the adjacent underground mine. Approximately 230 million gallons subsequently discharged from the underground mine at two portals."

Jan 1, 2015