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By T. Gupta, T. Ghosh

Rare earth elements (REEs) and their compounds are essential in a multitude of mundane and sophisticated applications such as renewable energy technologies, catalysts, medicine, and defense applications. The global supply deficit could be attributed to the destabilization of REE market that has, as a result, incentivized indigenous production of REEs. Cost-effective and environmentally benign opportunities are being explored for the production of REEs from non-conventional mineral sources including coal and coal by-products to stabilize the supply chain. Coal from Healy coal mine and Wishbone Hill deposits in Alaska have been quantified for REEs and were found to possess elevated total REE concentrations as compared to world average levels (60– 70 ppm). The objective of the study was to concentrate the REEs in the froth phase by froth-flotation of the fine size fraction (< 75 μm). A Box-Behnken design of experiment was employed to ascertain the main and interaction effects of operational parameters on response variable by analyzing 3D response surfaces. Experiments were carried out to maximize REE recovery and concentration by modeling and optimization of three operating variables (frother dosage, pulp density (% solids), and collector dosage). Based on the results, the optimum flotation conditions for maximum recovery at an elevated concentration of REEs in the froth fraction was obtained at 4.2% solids and 32.7 ppm of frother dosage for Healy sample and 10% solids and 37.9 ppm of frother dosage for Wishbone Hill coal sample. The quadratic relationship between the input and response variable was found to be independent of collector dosage suggesting good surface hydrophobicity and floatability of the two coal samples.

By Wayne Green

The Regional Municipality of York, located north of the City of Toronto in Ontario, Canada, has experienced unprecedented growth during the past decade, with new home construction averaging 15,000 units per year. This rate of growth is planned to continue well into the future with a projected growth of more than 500,000 new residents by 2031, combined with a tar-get of more than 300,000 new jobs to provide a sustainable economic base for the region. It should be noted that York region has been designated as one of the key growth centers by the province of Ontario, aimed in part to meet the housing and employment needs of Canada?s growing population. York Region is a mix of urban and rural areas and is one of the most desirable areas to live in Southern Ontario. York region offers an attractive lifestyle, with its nine municipalities and the amenities created by the many rivers, streams and protected greenbelt areas that encompass more than 69 per cent of the region?s area.

Jan 1, 2010

By D. M. Avant, S. M. Pickering

A variety of grades of very white muscovite mica are now being produced from sedimentary sands and clays in Central Georgia. The mica is naturally concentrated near the base of the lens-shaped kaolin deposits and also disseminated in associated quartz sands. The same weathering and bacterial alteration processes which have transformed the kaolins from dark organic muds to white pigment-grade industrial clays have also removed discoloring iron from the micas and developed unusually white muscovite. Further, chemical alteration has removed some potassium from the muscovite atomic structure, resulting in an easily delaminated mica which can be cleaved to unusually fine, high bulking, high aspect ratio products. The peculiar alteration history of these sedimentary micas enables production of some of the whitest, finest particle size, and thinnest aspect ratio muscovite mica products on the world market today. Raw mica feed is obtained from kaolin and sand processing by-products, and also from beneath the useful base of abandoned kaolin mines. The processed ultrafine and filler grade muscovite mica products are used for paint, plastics, cosmetics, mold release, thermal and electrical insulation, epoxy, and dry wall joint cement markets.

Jan 1, 2002

By R. Zunich, E. Rybinski, M. Grondin, B. Flintoff

It is uncommon these days to read a business magazine or newspaper without finding a reference to Knowledge Management (KM), and its critical importance to corporate success. One definition of KM is: “getting the right knowledge to the right people at the right time and helping them to put information into action in such ways that strive to improve organizational performance.” In the minerals processing industry we could assert that we have been practicing this for years through effective operator training. In most cases we would probably be wrong. Training has certainly filled the need of addressing safety and basic operational issues, but we must collectively focus on education (learning), and the difference, as measured in outcomes, is not at all subtle. This paper briefly examines the history of training and education in the mining industry, and looks in more detail at the impact of one company’s approach to empower its workforce, while keeping the ultimate goal clearly in mind: “The great end of knowledge is not knowledge, but action.” (T.H. Huxley)

Jan 1, 2001

By Roberto J. Guardia, Tim Shell, Robert A. Robinson, Steve Rodolf

Our aging infrastructure includes numerous tunnels that provide easy access through topographic and societal obstacles. These tunnels are renewable resources that require periodic maintenance and rehabilitation to extend their useful lifespan to hundreds or even thousands of years. However, as with any structural rehabilitation project, tunnel liner rehabilitation requires an inordinate amount of evaluation and care due often poorly documented original construction and subsequent repair construction methods and materials. This paper documents the investigation, planning, design, and construction efforts of the rehabilitation of a 74-year old, 216-meter (713 foot) long two-lane highway tunnel in moderately fractured to highly sheared basalt on the Oregon coast. The tunnel consists of four sections lined originally with timber and subsequently overlaid with concrete, and three unlined sections.

Jan 1, 2005

By Doug Harding

The Niagara Tunnel Project (NTP) is a 10.4-km- (6.5- mile-) long, 14.4-m (47.5-ft) bored tunnel that will run under the city of Niagara Falls from the Upper Niagara River to the Sir Adam Beck power station. The completed project will enhance the capacity of the Sir Adam Beck power station by adding 500 m3 /sec (17,657 cu ft/sec) of water through the tunnel. The project uses the world?s largest hard-rock tunnel boring machine (TBM) at 14.4 m (47.5 ft) in diameter to excavate the tunnel. Features of the project include the use of a high performance (HP) main beam TBM, state-of-the-art ground support and tunnel logistics systems. A continuous conveyor is used for muck transport from the TBM to the disposal area In June 2004, the Ontario government announced that Ontario Power Generation (OPG) had been given approval to proceed with the third tunnel under the city of Niagara Falls ? the first two tunnels were constructed in the 1950s using drill-and-blast techniques. The third tunnel, appropriately named the Niagara Tunnel Project (NTP), consists of a 10.4-km- (6.5-mile-) long TBM-bored, concrete-lined tunnel with a finished diameter of 12.5 m (41.1 ft). In August 2005, OPG the selected of Strabag of Austria, one of the largest construction companies in Europe, as the contractor to build the NTP at a price of C$600 million. In September 2005, Strabag selected The Robbins Co. of Solon, OH to design, manufacture and deliver a new 14.4- m- (47.5-ft-) diameter high performance, state-of-the-art main beam hard rock TBM to be used in the excavation of the tunnel. To meet the aggressive construction schedule as requested by OPG/Strabag, the TBM needed to be sup-plied as ready-to-bore within a 12-month period after the contract was awarded to Robbins.

Jan 1, 2008

By H. K. Lin

Deepwater discharges of sulfide flotation tailings have been practiced for several decades. Oxygen penetration and organic matter content in such environments are the two major factors that determine their reduction-oxidation condition and hence the rate of sulfide mineral dissolution under such discharge environments. In this study, the effects of solution redox potential and pH on the dissolution of some heavy metals from sulfide flotation tailings were examined. Zn, Pb and Cu concentrations in solution were all higher at a higher redox potential and lower pH. Dissolved Zn concentrations reached 100 ppm even at a low redox potential of 105 mV and near neutral pH after 33 days. Pb concentrations were below 2 ppm at 105 mV and near neutral pH after 165 days. At 105 mV, the Cu concentrations were below 0.2 ppm at near neutral pH after 165 days. At pH 2.3, the Fe concentrations were higher at 420 mV than at 105 mV. But at pH 6.8, the Fe concentrations were lower at 420 mV than at 105 mV, due to the oxidation of Fe2+ to Fe3+ and the subsequent precipitation of ferric hydroxide. Arsenic concentrations in solution were all less than 0.002 ppm. For Zn, Cu and Fe, no significant differences were observed between the tests in solutions prepared using seawater and those using distilled water. However, Pb concentrations reached higher levels in solutions prepared using seawater.

Jan 1, 2009

By Jayant Khambekar

In a typical mining operation, run-of-mine (ROM) ore is crushed and screened to achieve a desired particle size distribution and then fed to processing equipment for further refining. For an operation to be profit-able, the ore handling system from the mine face to final product loadout must be reliable. However, the handling system components do not always perform as expected and production problems related to material flow occur. These problems include flow stoppages, limited live storage capacities, uncontrollable flow, segregation, spillage and dust emissions. These result in lost production, excessive maintenance, safety and environmental issues, and even structural failures, in some cases. Flow patterns Flow problems and their solutions can be best understood by first learning how bulk solids flow. As bulk solids discharge by gravity from a storage system, primarily two types of flow patterns can develop: funnel flow and mass flow. Figure 1 shows a schematic of these two flow patterns. In funnel flow, only a portion of the material is in motion during discharge, which flows toward the outlet through a channel that forms within the stagnant material. Funnel flow occurs when a hopper is not sufficiently steep and smooth to ensure flow along the walls or when the outlet is not fully effective. In mass flow, all of the material is in motion whenever any is discharged ? there is no stagnant material. Mass flow occurs when the hopper is sufficiently steep and smooth to ensure flow along the hopper walls. Shallow valleys are not permitted and the outlet must be fully effective. A third type of flow pattern, called expanded flow, can develop when a mass flow hopper (or hoppers) is placed beneath a funnel flow hopper or bin. The mass flow hopper is designed to activate a sufficiently large flow channel in the funnel flow hopper to avoid flow problems due to a rathole. The flow pattern in which a bulk solid discharges from a storage system strongly influences the flow problems that may occur in that facility.

Jan 1, 2009

By I. Yildirim

Water contact angles of talc powders were determined from the values of the heats of immersion measured using a flow microcalorimeter. The results were used to calculate the contact angles using a rigorous thermodynamic relation. In the present work, the calculation was carried out using the temperature coefficient of the contact angles determined experimentally using another method. The results obtained in the present work on several different talc samples are compared with those obtained using other methods.

Jan 1, 2001

Several of the larger copper projects recently built have included a molybdenum byproduct circuit as part of the overall project due to the favorable molybdenum market conditions and overall economic contribution to the project. This paper provides a summary of moly plant flotation practices across a number of both recent projects and historical ones. Modern Molybdenum flotation flowsheets predominantly incorporate self-aspirated cells and forced air cells with nitrogen addition. The paper provides insight into the process considerations, capital and operating costs associated with both of the cell types. It also reviews metallurgical aspects and important safety aspects. Other aspects including instrumentation and degree of automation are also discussed along with overall plant design.

Feb 27, 2013

By T. McKeon

Gravity separators are commonly used in multistage cleaning and scavenging circuits to improve the quality and/or recovery of the final concentrate. Unfortunately, studies suggest that many industrial plants are poorly designed in terms of equipment layout. This shortcoming can often be attributed to a failure by engineers to make use of fundamental process engineering tools for circuit design. One of the most important of these is linear circuit analysis. This powerful tool makes it possible to mathematically compare the relative efficiencies of circuit configurations in advance of experimental testing. This article provides a basic review of the linear circuit analysis concept and discusses some of the key insights it provides for the layout of multistage circuits. An industrial case study is provided to show the tremendous impact that this process engineering tool can have on the design of multistage spiral circuits in a heavy mineral wet plant.

Jan 1, 2005

By Hugh R. Rhys

The question of the desirability of recovering cullet from MSW in order to recycle it into the manufacturing of glass containers remains a controversial one. The main factors appear to be: 1. The position of the Glass Container Manufacturers Institute (GCMI), as the trade association for most container manufacturers, is that post-consumer cullet is a vital source of raw material. Present requirements are for: a) Flint cullet b) Non-flint cullet of known mix proportions c) Mixed unsorted cullet of known mix propertions c) Mixed or non-flint cullet of unknown mix proportions. A market balance for these products exists, and this might somewhat limit the outlets for (b), (c) and (d), or severely limit the outlet for (d) alone. 2. The color specifications are rather strict. With cullet admixtures of 20% of the melt or more, and the use of decolorisers in a flint furnace discouraged because their action is reducing in a process which requires an oxidising environment, color contamination in a flint furnace is serious.. For amber and green furnaces (reducing) it is less serious, but in order that the quantity of decolorisers may be controlled, the color balance (as a measure of the Fe and Cr content) of the admixtured cullet should be known. 3. Why not simply color analyze, either by a continuous on-stream or off-stream: photo-electronic analysis, or by systematic batch sampling (with some kind off electronic surveillance of the mainstream) and just send mixed, color measured cullet to only amber and green furnaces? The flint would-be simply included in the mix. This is probably technically feasible, but is subject to the market limitations noted in point1.

Jan 1, 1975

By V. L. Ketellapper

This paper discusses the technical issues and stakeholder collaborative processes which resulted in achieving a balance between the reclamation of abandoned mine sites, providing affordable housing, and preservation of open space at the French Gulch Site. Through this process, it was discovered that mine site reclamation would need to be conducted in conjunction with two priorities for community sustainable development: providing affordable housing for locals who work in the resort town of Breckenridge, and open space preservation. It was found that conducting these activities concurrently would result in providing resources necessary to complete mine site reclamation. The first phase of the affordable housing development is almost completed. This development resulted in redevelopment of mining impacted lands and was recognized by the U.S. Environmental Protection Agency (EPA) with a National Smart Growth Award in 2002.Negotiations are also underway to preserve the remaining 1,800 acres of land held by the mining company as open space. This transaction will in turn provide resources to address water quality issues associated with mine discharges.

Jan 1, 2004

By R. H. Grau

NIOSH’s Pittsburgh Research Laboratory is currently involved in research to identify silica dust generation in underground metal/nonmetal mines. The ultimate goal of this research is to develop control technologies to reduce worker exposure to respirable silica dust. Commodities and job classifications with the highest silica dust exposure have been identified through analysis of the Mine Safety and Health Administration (MSHA) compliance dust sampling database. Dust surveys were conducted in an underground limestone and gold mine to investigate silica dust sources, generation levels, and controls being used. A summary of the mining operations, sampling procedures, resulting data, and suggested methods to improve the dust control will be provided.

Jan 1, 2002

By F. Burat

Large reserves of feldspar ore exist in the Aegean region of Turkey. The main colored impurities in these ores are iron- and titanium-bearing minerals such as anatase, rutile, sphene and ilmenite. In this study, a potassium feldspar ore containing mainly quartz and coloring impurities was subjected to beneficiation tests involving magnetic separation and flotation, which were applied either separately or in combination. Bench-scale flotation experiments using cationic collectors G-TAP and Flotigam V-4343 and using HF and H2SO4 as modifiers were employed to separate feldspar from quartz and to remove part of the titanium impurities. The best results were achieved with a combination of high-intensity wet magnetic separation and flotation. A feldspar concentrate containing 16.28% Al2O3, 10.75% K2O, 2.84% Na2O, 69.97% SiO2 and 0.16% Fe2O3 was produced. A quartz concentrate containing 2.30% Al2O3, 0.48% K2O, 0.42% Na2O, 0.07% Fe2O3 and 96.20% SiO2 was also obtained

Jan 1, 2007

By Joseph J. Zaluski, J. Steven Gardner, Marco M. Rajkovich

The telephone rings at 3:20 a.m. An exasperated voice on the other end says, “There has been a mine explosion at Mine No. 5 and we have not heard from three units of men.” Twenty-three minutes later, the phone rings again and another panicked voice says, “There is something wrong at the slurry impoundment, the pool level has just dropped five feet and we are trying to figure out what is wrong” Thirty minutes later, the mobile phone rings. An excited security guard says, “We have reports of thick black water running down the right fork and left fork of Straight Creek and both seem to be rising in the banks.” If this is not enough excitement, the mobile phone rings again. A stressed company official says, “I just heard a report that black slurry is running out of the portals of XYZ Co. No. 2 Mine, which is adjacent to our No. 5 Mine.” Is this all some kind of dream or nightmare? More importantly, though, if this happens, what do you do? Most people think: “It can’t happen to me.” But mine explosions do happen, slurry impoundments can rupture and creeks can flood with black water causing damage to others, including competitors. A mine’s response must be quick, cool-headed, calculated and effective. This article examines the issues, concerns and ramifications of this hypothetical disaster. The authors then present a systematic crisis-management response.

Jan 1, 2004

By J. de Bakker

It hardly needs to be repeated that if coal is to continue as America’s premier source of cheap energy, it is absolutely necessary that the carbon dioxide from its combustion somehow be sequestered. A promising method proposed to accomplish this is the “indirect” carbonation of serpentine in a concentrated magnesium chloride brine. Indirect carbonation could be also applied to precipitate magnesium in lateritic nickel processing: this would not only solve magnesium-control problems in laterite hydrometallurgy, but also reduce its energy requirements and create CO2-sequestration credits. Fifty-five percent of the electricity generated in the United States comes from coal-fired power plants, and American coal reserves can last over 500 years at 1990-level consumption1. Coal is therefore both abundant and cheap: it could (and in fact probably will) continue to be an affordable source of energy, both for producing electricity and as a feedstock for liquid hydrocarbon production by Fischer-Tropsch reactions. As a result, it is important to find a workable method of permanently sequestering CO2.

Jan 1, 2007

By A. Mahmoudkhani

Primary cementing is the process of placing cement in the annulus between the casing and the formations exposed to the wellbore. Portland cement was first used in 1903 in the Lopoc Field in California for well cementing. Since then, the major objective of primary cementing has always been to provide zonal isolation in oil, gas and water wells, i.e. to exclude fluid(s) in one zone from another zone in the well. To achieve this objective a hydraulic seal must be created between the casing and cement and between the cement and the formations, while at the same time preventing fluid channels in the cement sheath. This requirement makes primary cementing the most important operation performed on a well. Without complete isolation in the wellbore, the well may never reach its full producing potential. The industry knowledge on cements relies heavily on empirical data, but the chemistry, physics and structure of cement are not fully understood yet. The strength of concrete can be increased essentially by reducing its porosity through optimizing the size distribution of its components and filling the residual porosity of the hydrated cement phase with inorganic fillers. This approach has successfully utilized in different ways and several technologies for placing high performance oil and gas well cements have been developed over the last few decades. There are reasons to believe that the next source of improvement will lie in the fine-tuning of the hydrates themselves and of the different parameters that drive short (ionic?covalent bonding) and long (ionic correlation) interactions.

Jan 1, 2012

By J. D. Miller, C. L. Lin

Appropriate software and hardware necessary to adapt a x-ray CT analyzer for determination of coal washability has recently been developed and sucessfully tested for well characterized samples under laboratory conditions. Evaluation of the CT-based analyzer under simulated on-line conditions is also presented to verify the on-line capabilities of the newly developed x-ray CT analyzer for the control of coarse coal cleaning circuits. The investigation shows that the data obtained from CT washability analyses compare favorably with experimental sink-float data. Further, image frequency was considered to evaluate the CT-Based coal washability analyzer for simulated on-line conditions. Specifically the number of observations (image spacing) needed for accurate sampling and the total time required to perform the calculations for a representative data set were determined.

Jan 1, 2001

By P. Sangurmath, C. Gundewar, M. Riyazulla, V. Vasudev, N. Shadaksharswami

Dharwar craton in the southern Indian shield, comprises the Neoarchaean foreland in the west and a relatively younger accretionary complex composed of granitoids and intervening gold-bearing volcano-sedimentary belts. The Hutti schist belt hosting a major gold producing mine is situated in the northern part of the eastern Dharwar craton. It is a horse-shoe shaped structure comprising predominantly of pillowed metabasalt of tholeiitic composition with minor amounts of clastic sediments and felsic volcanic rocks. The belt is intruded on all sides by circular to tabular bodies of granites and granodiorite. Important gold deposits are located at Hutti, Hira-Buddini and Uti villages. Felsic volcanics in the Hutti belt occur as tabular bodies of quartz porphyry and breccia. Two of the gold-bearing reefs in the Hutti mine, Viz., Middle and Strike reefs are intimately associated with tabular sub-vertical sheets of mylonitic quartz-feldspar porphyry intruding pillowed metrabasalt. In Uti mine area, the felsic volcanics occurs as a tabular body. At Hira-Buddini, the felsic volcanic occur as a irregularly shaped sheet in pillowed metabasalt. Mineralogical and geochemical studies suggest that the felsic volcanic rock in Hutti mine area is a rhyolite and at Uti and Hira-Buddhini it is of dacite composition. Scheelite occurs as veins, veinlets, stringers and blebs along fracture planes of felsic volcanics in the Hutti mine area, whereas at Uti and Hira-Buddini it is insignificant. On the basis of spatial association of metabasalt and felsic volcanics and on geochemical grounds, we interpret that the felsic volcanics might have originated by the partial melting of basalt. REE patterns of the granite, granodiorite and metabasalt of Hutti are similar to each other indicating that they could be co-magmatic. However, REE in the Hutti felsic rocks is significantly higher than in Uti and particularly Hira-Buddini mine areas. The two felsic volcanic samples drawn away from the mineralized zone from all the three mine areas were analyzed for tungsten. In Hutti one sample assayed 0.15% and another 0.062%. At Uti, in one sample it assayed 0.056% and another less than 1 ppm, whereas at Hira-Buddini, it is less than 1 ppm in both the samples. The spatially associated basalt analyzed 23 to 235 ppm tungsten, whereas granites and granodiorites have very low (<1 ppm) tungsten. Therefore, the source of tungsten in the felsic volcanics of Hutti area could be traced to metabasalt. The absence of significant amount of tungsten in the felsic volcanic of Hira-Buddini could be attributed to the lack of REE enrichment compared to REE in Hutti and Uti felsic volcanics.

Jan 1, 2007