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By T. P. Dolley

Domestic production of industrial sand and gravel in 2004 was about 29 Mt (32 million st), a 6-percent increase from 2003. This increase was buoyed by a robust construction sector of the U.S. economy. U.S. apparent consumption was 30.3 Mt (33.3 million st) in 2004, an in-crease from 2003. Imports were about 490 kt (540,000 st) in 2004, an 11-percent increase from 2003. Imports of silica are generally of two types. They include small-quantity shipments of very-high-purity silica or a few large shipments of lower grade silica that were shipped only under special circumstances (such as very low freight rates).

Jan 1, 2005

By D. G. Klaren

Self-cleaning fluidized bed heat exchangers are conquering the world for reason that they are able to solve any severe fouling problem in indirect heat transfer due to the circulation of cleaning particles through the tubes of vertical shell and tube exchangers. In most cases, these particles consist of chopped metal wire. Moreover, self-cleaning fluidized bed heat exchangers perform with excellent heat transfer at very low liquid velocities, which makes completely new designs of shell and tube configurations possible. Further, self-cleaning fluidized bed heat exchangers show a strong shear thinning effect in non-Newtonian liquids. All the above characteristics make the self-cleaning fluidized bed heat exchanger an ideal tool for the indirect heating of laterite nickel slurry in High-Pressure-Acid-Leach (HPAL) plants. Preliminary tests and evaluations of these heat exchangers have shown that the performance and price of these heat exchangers used for the production of nickel and cobalt from a laterite slurry, cannot be matched by existing conventional heat exchange systems. This article explains the principle, design, lay-out and enormous advantages of the self-cleaning fluidized bed heat exchange technology in a plant suitable for an annual production of approx. 45,000 ton nickel and 4,500 ton cobalt from laterite slurry through high pressure'acid leaching.

Jan 1, 2002

The use of belt air in underground coal mines has been a continuous discussion since it was first introduced in the Federal Coal Mine Health and Safety Act (Coal Act) of 1969. Although the Coal Act prohibits the use of belt air to ventilate active workings, there were two exceptions prior to the 2004 Final Rule. There have been several major studies/rule-proposals by MSHA since 1985 and the most recent of which is the Technical Study Panel (TSP) established by the Mine Improvement and New Emergency Response (MINER) Act of 2006 to study the use of belt air and related issues. This paper reviews the history of belt air use, its associated controver-sies, and more specifically, the 20 recommendations unanimously approved by the TSP.

Jan 1, 2009

By L. Franko, S. Klima

Wet-drum magnetic separators are used extensively for upgrading iron ore and for magnetite recovery in dense-medium circuits. In this study the performance of a continuous, laboratory wet-drum magnetic separator was evaluated with and without the application of ultrasonic energy when processing dense medium slurries. Test variables included magnetic-to-nonmagnetic ratio, solids concentration, and nonmagnetic materials. The results indicate that under certain conditions, the purity of the magnetic material increased after ultrasonic treatment.

Jan 1, 2001

By F. Schreiter

The Ore Mountains in Germany have a history of more than 850 years of underground mining activity. This has created a situation where thousands of old mine shafts and adits are due for rehabilitation. While no long-term stable rehabilitation was executed in previous centuries, those abandoned mine sites which date back to the uranium mining boom from 1945 to 1962 were rehabilitated immediately after mine closure according to state-of-the art technology. Over the years, however, it has become obvious that most of these sites are not long-term stable and thus it has become necessary to rehabilitate them a second time. Technical University Bergakademie Freiberg is carrying out a research project on the optimization of this process. 70 mine site rehabilitation projects, the technology and the materials used have been assessed. A technical guideline for future rehabilitation projects, based on the outcomes of this assessment, is under development with the goal to make it easier, faster and more economical to select and apply suitable designs and construction materials for dams, plugs and other rehabilitation structures in former uranium mines.

Feb 27, 2013

By Jack Bedder, Nils Backeberg

"Native antimony metal is rare and antimony generally occurs together with gold, lead, copper and silver. There are more than 100 antimony minerals, although the sulfide mineral stibnite is the main economic mineral.Antimony enters the supply chain either as a result of mining (primary production) or recycling (secondary production). China has by far the largest antimony resources and is, as a result, the world’s center for antimony mine production. While China remains the leading primary producer, accounting for 69 percent (80.5 kt or 88,700 st) of the global 117.5 kt (129,000 st) in 2017, market consolidation and regulatory inspections across China leading to closures of facilities have caused a significant decrease in Chinese output from 115.8 kt (127,600 st) in 2015 (81 percent of global production).Tajikistan and Russia are the next largest producers of antimony after China, both ramping up production in recent years. Russia could significantly increase its supply of antimony if Polyus moves ahead with supplying 10-12 kt/a (11,000–13,200 stpy) of contained antimony from gold tailings. Australia and Bolivia are also significant mine producers outside China. The value of the different ores varies based on the metal content of the concentrates, with the most valuable gold-bearing ores sourced from Australia’s Costerfield Mine and the least valuable mercury-bearing ores sourced from the Anzob Mine in Tajikistan. On average, Bolivian and Russian ores trade at an intermediate value between those from Costerfield and Anzob. Nearly all of the rest-of-world production is exported to China, where the ores and concentrates are processed into antimony ingots and oxides.Antimony ingot production is not as widespread as is the case with antimony mine production, owing to the high levels of pollution that are associated with antimony smelting. It is for this reason that smelting has been largely confined to China and other Asian countries ,such as Vietnam and Myanmar, where environmental legislation has historically been less stringent. Tajikistan has become a growing producer of antimony ingot since 2014, coming from the commissioned metallurgical plant at the Anzob Mine.Antimony oxide production is undertaken on four continents with China being the biggest producer. There is also a considerable amount of oxide production in Europe (mainly Belgium and France), which relies on imported antimony metal feedstock, mostly from China.A new antimony project under construction by Strategic and Precious Metals Processing (SPMP) in Oman made progress in 2016 and 2017, and after producing first metal in April 2016 in test facilities, was set to be commissioned in the first quarter of 2018. Commissioning had been moved back to June 2018, with a potential ramp-up to 2-3 kt/a (2,200 to 3,300 stpy) of antimony metal by the end of 2018. SPMP is also reviewing producing antimony oxide as part of its flow sheet."

Jan 7, 2018

By D. He

In China, the total reserves of vanadium, reported as V2O5, in stone coal is 118 Mt (130 million st). Recovering vanadium from such a large resource is very important to China?s vanadium industry. The technology now being used to recover vanadium from stone coal has the following two problems in the leaching process: a low recovery of vanadium and high acid consumption. To resolve these problems, a new leaching technology is proposed. The effects of factors such as H2SO4 concentration, liquid-solid ratio, temperature and time, and the types and additions of additives were studied. By adding 1.5% (by weight) CaF2 and leaching the roasted residue of stone coal with 5.4% (by weight) sulfuric acid at 90°C for 12 hours at a liquid-solid ratio of 2 mL/g, the leaching degree of vanadium reached 83.10%. This proposed leaching technology gives a feasible alternative for the processing of roasting residue of stone coal and can be applied in the comprehensive utilization of stone coal ores in China.

Jan 1, 2008

By Paul Eger

The use of wetlands to treat mine drainage has become increasingly common, particularly as more information is available on their operation and construction. However, the lifetime of each system is still, at best, an estimate. Treatment lifetime depends on the types of processes that provide the majority of the metal removal. Anaerobic systems (vertical flow systems) rely primarily on sulfate reducing bacteria, which reduce sulfate to sulfide and generate alkalinity. Metals can be precipitated as sulfides, and acidity is neutralized. These systems can remove over 90% of the metals and increase pH from around 4 to over 7. The bacteria will remain active as long as the system remains anaerobic and contains an adequate supply of sulfate and small chain organics. Although estimates of lifetime made on the total carbon in the system suggest that lifetime should exceed 20 years, data from field and laboratory studies show that the rate of sulfate reaction decreases with time, and that after several years rates decreased substantially. To maintain acceptable treatment, either additional organic material must be added or the total metal and acid load to the system would need to be reduced substantially. Aerobic systems (overland flow wetlands) can effectively remove metals from neutral mine drainage by reactions with organic material in the substrate. Over 90% of the copper and nickel have been removed in aerobic systems treating mine drainage in Minnesota. The primary removal processes in these systems include adsorption, ion exchange and complexation, which are finite; removal will cease unless new removal sites are generated. Two wetlands built in Minnesota have been successfully treating mine drainage for 12 years. At one of the wetlands, the annual production of new removal sites has been estimated to be equal to the annual metal input, and, as a result, metal removal should theoretically continue indefinitely.

Jan 1, 2005

By Michael J. Lehnen

Slurry diaphragm walls are commonly used as both temporary excavation support walls, and permanent structural walls, for circular shafts and long rectangular structures (such as underground subway stations); however, they are not commonly used for more compact rectangular or square shafts. In these instances, a second wall is typically cast inside the slurry walls to form the permanent structure. This paper discusses the approach used on the Silicon Valley Rapid Transit Project in California to analyze these compact rectangular types of structures for static and seismic loading, and to determine whether or not slurry walls can be confidently used as both the temporary and permanent walls for two tunnel ventilation shafts.

By Chen-Luh Lin, Jan D. Miller, Sindhoora Puvvada

The depletion of good-quality phosphate resources, coupled by a need to supply acceptable products at a rapid rate, while meeting the specifications of fertilizer chemical plants, is of significant concern to the phosphate industry, particularly the production of concentrates with tolerable dolomite content. Tremendous efforts have been made in the past to develop an efficient and economical process that can effectively reject dolomite. However, dolomite removal continues to plague the phosphate industry due to several process-specific challenges being encountered with various beneficiation technologies. In this regard, detailed characterization of phosphate reserves is crucial to understand textural limitations and help design appropriate strategies to achieve quality products. In this paper, the development of procedures to establish dolomite rejection/francolite recovery curves for gravity preconcentration of pebble phosphate from Central Florida is described using high-speed X-ray computed tomography (HSXCT). The developed procedure is illustrated with the analysis of high MgO pebble phosphate samples (10.39 mm × 1 mm) received from South Pasture and Four Corners locations operated by the Mosaic company. The rejection/recovery curves were calculated for each sample for five different particle size classes to observe the trend in rejection/recovery with variation in particle size. In order to evaluate the reliability of the HSXCT data, analysis using the high-resolution X-ray computed tomography (HRXCT) technique was performed on one particular sample (FC-3-1). Finally, to assess the separation efficiency, the HSXCT and HRXCT rejection/recovery curves obtained were compared to experimental gravity preconcentration results reported in the literature. In this way, liberation limitations for gravity preconcentration in the processing of pebble phosphate have been established based on X-ray computed tomography analysis.

By N. P. Widodo

The ventilation measurements by tracer gas method at Pongkor gold mine show that effective diffusion coefficient, E, at straight airways indicated a similar range of measured one by the laboratory experiments which can be estimated by Taylor equation. On the other hand, E of the curved airways in the mine was estimated as larger than that of the straight ones (1.5 to 32 times than that obtained by the Taylor equation and these have been compared with the data measured in Kushiro coal mine, Japan). The curved mine airways, with small curvature against airway radius and complex velocity profile, possibly give concentration ? time curves with long tailings, thus those airway conditions could make larger E. Laboratory experiments of gas diffusion by a pulsed injection of small amount gas, into straight and curved airways, have been conducted in order to investigate a range of E in mine airways. The plots of E against Reynolds number show that the present laboratory results of straight-long airways are almost close to one calculated by Taylor equation. On the other hand, the values of E measured at curved single-direction airways were smaller than that of the straight airways, which may be due to effects by secondary vortexes flow in the curved airways.

Jan 1, 2009

By Jose A. Delgadillo

The hydrocyclone problem has been a challenging task for the last 30 years. In the 80’s and 90’s Computational Fluid Dynamics solution to this problem began to appear. These were unsuccessful due to over simplification. In the past 3 dimensional solution with ?-e model and Reynolds Stress Model have been published. In this paper RSM and ?-e models are compared with velocity profiles measured in 75 mm and 250 mm diameter hydrocyclones. It is shown that results are not satisfactory with RSM or ?-e and that a model called Large Eddy Simulation is needed to describe velocity profile evolution and size classification.

Jan 1, 2005

By Brendan Demich, Joseph McGuire, Emily J. Haas

Near misses recorded and reported by workers can provide awarenessto the potential causes of injury and prompt safety management initiatives. Although most companies require near-miss reporting, it is unclear what the value of these reports are, if any, and how they influence subsequent actions or controls to reduce on-the-job risks. Researchers at the National Institute for Occupational Safety and Health (NIOSH) conducted a case study with an aggregates company in which near-miss reports were analyzed at each of their locations over an entire quarter during the summer of 2018. Within that quarter, workers recorded 249 near misses. Of those, 167 were valid near misses that occurred at work. Researchers coded the reports using a qualitative 5 × 5 risk matrix. Of the 167 near misses, 19% were deemed low risk, 25% moderate risk, 30% high risk, and 26% critical risk. Several patterns in the near-miss incidents were documented, including classification of incidents and common corrective actions referenced (i.e., elimination/substitution, engineering control or redesign, work process/procedures, and personal protective equipment). The analysis provides insight into ways that risk communication and management programs can be improved to reengage workers and their situational awareness on the job.

By D. Bedell, J. Robitalle, D. Macgilliveray

Agnico Eagle (Cadillac Quebec, Canada) selected the new Eimco PEC E – CAT™ clarifier thickeners for their counter-current decantation circuit, which handles approximately 200tph leached gold/silver ore. The E-CAT is based on rakeless ultra-high rate thickening technology that originated in South Africa. Four 9m diameter and two 10m EIMCO E – CAT ultra high rate, rakeless thickeners were installed in the fall of 2000. Thickening and clarification performance has been excellent. Problems with level control have been resolved and the plant personnel continue to improve the operating control techniques. The CCD circuit is critical to the success of the operation and good recovery. Data will be presented showing the wash ratios and recovery achieved. A brief history of the operation and the decision to utilize the CCD system will be presented.

Jan 1, 2002

By R. D. Sharpe

Gypsum wallboard manufacturers in the United States shipped 3.18 billion m2 (34.2 billion sq ft) of wall-board products during 2004 versus 2.93 billion m2 (31.5billion sq ft) in 2003. Following a historic high production of gypsum wallboard products in 1999, production decreased in 2000. But it has steadily increased during2001 through 2004. Wallboard production in the United States increased about 8.6 percent in 2004 from 2003. Following several years of a “building boom” of new wallboard plants and the expansion of the manufacturing capacity of several existing plants, 2004 was a relatively quiet year. However, several new plants and capacity expansions were announced or are in progress during 2004.

Jan 1, 2005

By J. P. Ducarme

Numerous fatal/nonfatal accidents involving underground workers struck by powered machinery occur yearly, with continuous miners and roof bolters involved in the majority of these accidents. In an attempt to reduce these accidents, researchers at the the National Institute for Occupational Safety and Health (NIOSH) Pittsburgh Research Laboratory conducted studies of operator interactions with the motions of continuous mining machines and roof bolter boom arms. These operators generally perform their tasks in close proximity to the equipment in confined workspaces, often employing awkward postures. Since experiments with human subjects using the actual equipment were not feasible due to safety concerns, researchers opted to conduct controlled experiments in laboratory settings. Utilizing motion capture technologies and computer simulations, the studies collected data on equipment and operator movement in a range of seam heights and working postures. This article details the results of these studies to examine operating speeds based on usage and seam height.

Jan 3, 2010

By N. Ahmed

The collection of hydrophobic particles in the froth phase in flotation has been studied. A continuous flotation cell was developed, in which the froth phase could be isolated from the pulp zone. Hematite particles, d80 = 87 µm, were floated in the pulp, using a conventional oleate collector, while glass spheres of similar diameter, d80 = 82 µm, were introduced in wash water added to the froth. Four samples of glass spheres, with contact angles between 0 and 82 degrees, were used. The results indicate that the efficiency of collection of the hydrophobic particles in the froth can be very high. The process is strongly influenced by the hydrophobicity of the particles and the surface area available for attachment in the froth. Recommendations for the flotation of particles in the froth phase are made, especially regarding the desirable hydrophobicity as reflected in the contact angle, the froth depth, the solids concentration in the feed to the froth, the air rate and the wash water rate.

Jan 1, 2001

By Rolf Birger Pedersen, Alden Ross Denny

"Synthetic Aperature Sonar (SAS) is a powerful tool for ultra-high resolution marine survey. The Kongsberg HiSAS system deployed on the HUGIN AUV has a rangeindependent resolution of 3x3 cm for sonar image and ~10x10cm for the interferometric bathymetry product [1]. This resolution is achievable for areas up to 50 km2 on a single survey mission providing huge multi-attribute datasets. This technology, originally designed for military and oil-industry applications, has the potential to revolutionize scientific seafloor mapping. The extreme resolution of this technique allows for deposit mapping in and around seafloor hydrothermal systems, including the discovery of extinct venting structures. By clearly distinguishing between volcanic and hydrothermal landscapes based on features below the resolution of conventional multibeam systems, SAS enables an entirely new level of hydrothermal deposit survey. Additionally due to the extreme resolution of this survey technology, repeat survey and change detection should allow centimeter-scale changes in deposit morphology to be routinely detected over an entire hydrothermally venting region. In collaboration with the EU funded MIDAS project, the Centre for Geobiology at the University of Bergen will deploy the HUGIN AUV this summer at two distinct shallow venting systems on the Arctic Mid-Ocean Ridge system. The AUV will collect repeat bathymetry at the Jan Mayen Vent Field, and extend the SAS coverage to include newly discovered venting sites. We will present the preliminary findings of this expedition, including the first deposit estimations made from full-resolution SAS mosaics."

Sep 1, 2014

Oil sands processing generates huge volumes of slurry, known as tailings, that is being stored in tailings ponds. The volume of produced tailings is a very important factor in oil sands surface mine planning, because the available area for dam construction is limited to the lease areas. On the other hand, oil sands operators cannot leave mine sites without reclaiming the tailings ponds. Since most of the reclamation material is generated in either oil sands mining or processing, it is reasonable to include reclamation material requirement as part of long-term mine planning. In this paper, an integrated optimization framework is proposed to maximize the net present value (NPV) of the produced oil sands, with respect to tailings capacity constraints and reclamation material requirements. A mixed integer linear programming (MILP) model is developed to find the optimal solution for long-term mine planning problem. A sample bitumen processing flow sheet is used to formulate the volume of produced tailings, based on Clark hot water extraction method. To verify the proposed model, it is coded in Matlab and run using CPLEX. Run results for real-case oil sands dataset show that the optimal production schedule meets material requirements for reclamation, tailings volume is within tailings capacity range in all periods and the production schedule follows the predetermined horizontal direction.

Feb 27, 2013

By M. Radwan, S. Shimada, S. Z. El-Tawil, K. A. El-Barawy, Y. Miyamoto

This study presents the results of synthesizing monolithic siliconoxynitride, Si2N2O, ceramic from a mixture composed of reclaimed silicon and natural desert sand by using the nitriding combustion synthesis method. Single-phase Si2N2O powder was prepared by the combustion of a mixture composed of silicon and pulverized sand in 3 MPa nitrogen gas. The combustion reaction completed in 2 min and the combustion temperature reached 1577°C.The as-synthesized Si2N2O powder is agglomerate of fine particles with sizes < 5 µm and has various morphologies; rod-like and irregular crystals, irregular kinking, hollow crystals and grown pseudo-hexagonal prismatic crystals. Porous Si2N2O compacts (24.5–47.1% porosities) were fabricated from the synthesized Si2N2O powder at different calcia-alumina additives (5–20 wt%) by normal sintering at 1500°C for 1 hr in N2atmosphere.They showed superior oxidation-resistance at high temperatures up to 1500°C in an oxidizing atmosphere of Ar/O2/H2O(70/20/10 kPa).Near-full dense Si2N2O compacts were also successfully fabricated from the synthesized Si2N2O powder with 5 wt% oxide additives by using the spark plasma sintering at 1600°C.DenseSi2N2O had good mechanical properties (18.7 GPa Vickers hardness, 3.3 MPa.m1/2fracture toughness and 363 MPa strength) and excellent chemical and oxidation resistance.

Jan 1, 2004