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By K. Whiting

In October 1993, the first two of a series of full scale passive biological treatment cells were constructed to treat mine drainage from the Burleigh Mine (located approximately 48 km west of Denver, Colorado in the Clear Creek/Central City Superfund Site). The two cells are each 19-21 m long, 10.7 m wide and 1.2 m deep. Each cell contains approximately 216 cubic meters of substrate (composted manure) and is designed to treat 60 L/min of mine flow. One cell is designed as an upflow reactor and the other cell is designed as a downflow reactor. The differences in flow hydraulics and treatment efficiencies will be tested in these two cell for approximately nine months before the remaining cells are built to treat all the discharge. The substrate material was selected based on a series of bench scale tests. During the tests, the amount of metals removed was determined. The design flow rate was based on a sulfide generation rate of 400 nanomoles of sulfide generated per cubic centimeter of substrate per day. Metal removal results for the first three months of operation of the two cells will be presented and compared to results of bench and pilot studies at other sites.

Jan 1, 1994

By S. B. Castor

Although production generally satisfies demand for rare earths, new markets may make undeveloped resources, particularly those rich in yttrium, more interesting. A Precambrian carbonalite orebody at Mountain Pass, California, has been the world's largest rare earth producer. Minor rare earth production comes from titanium placer mining in Florida and uranium mining in Canada. Prior to operations at Mountain Pass, North American production was mostly from placer deposits that constitute large, low-grade rare earth resources. Newly discovered North American rare metal resources in peralkaline igneous rocks are potential yttrium producers. Most of these resources are in a continent-wide belt of anorogenic magmatic rocks approximately coeval with mineralization at Mountain Pass. Other untapped rare each resources in North America are generally light rare earth-dominated and small or of low grade.

Jan 1, 1991

By A. C. Smith, J. H. Rowland III

The Mine Improvement and New Emergency Response Act of 2006 (MINER Act) established a Technical study panel (the Panel) to provide recommendations on the utilization of belt air and new technology that may be available for increasing the fire resistance properties of conveyor belt used in underground coal mines. The Panel Report recommended use of the belt evaluation laboratory test (BELT) as the method for testing and approval of flame resistant conveyor belts used in underground coal mines. The research conducted to establish the correlation of the BELT with large-scale belt fire flammability tests was done using 91 - 107 cm (36- to 42-in.) wide conveyor belt. Due to today’s coal haulage capacity, the mining industry is using 183 cm (72 in.) and wider conveyor belts. The U.S. National Institute for Occupational Safety and Health (NIOSH) conducted a study to determine if the BELT will also qualify wider belts as fire resistant for use in underground coal mines. This paper describes the results of recent experiments comparing results from using the BELT and the large-scale tests for six different belts.

Jan 1, 2011

By Paul D. Tomlingson

Numerous worthwhile benefits accrue to the industrial organization that is supported by a maintenance organization performing at a world class level. That organization will be favored with consistently reliable production equipment. It will be assured of meeting production goals. Its product will exceed marketplace standards. Its customers will see them as a quality organization. Its employees will enjoy job satisfaction and the plant will realize continuing profitability. Every industrial plant aspires to achieve ?world class? status knowing it can compete favorably with the best, most profitable organizations in the world. The trick is to achieve the attributes that qualify your organization for world class status. But there are no world class maintenance organizations. Rather, there are world class industrial organizations that include a world class maintenance organization. Maintenance, by itself, is a service provider, dependent on the support and cooperation of other departments. When that service is exceptional, it is made that way because maintenance is operating in a plant environment that requires it to be exceptional. Managers have created an environment in which maintenance can be exceptional. The plant, mine or facility manager must acknowledge from the start that maintenance is not a stand-alone effort of a plant maintenance department. It will require the joint efforts of all plant departments. Quality material support and full cooperation from operations, for example, are among the essential requisites for effective maintenance and achievement of world class maintenance status. When attributes such as these are reinforced by dedicated plant managers, profitability soon follows.

By Amar Prakash, V. M. S. R. Murthy, Ajoy Kumar Singh, Avinash Paul, John Loui Porathur

Weak, layered, and fragile rock mass formation, if not supported properly, is subject to roof failure thereby affecting safety and productivity in underground coal mines. Though Central Mining Research Institute – Indian School of Mines Rock Mass Rating (CMRI-ISM RMR) based well-defined support design guidelines are established, still occurrence of roof failures in underground coal mines is a real matter of concern for mining engineers and researchers. Numerical modeling techniques are successfully used by several researchers by simulating rock mass condition for stability assessment of mine openings. The analysis becomes crucial in case of weak and fragile rock formation. The present research envelops the determination of 31 cases of rock load by CMRI-ISM RMR under different geo-mining conditions followed by the development of modified Rock Mass Rating (RMR), i.e., rock mass rating dynamic ( RMRdyn) by incorporating P-wave velocity as a new parameter. The rock load determined using RMRdyn and numerical models was correlated and found in close agreement. In addition, the deviation in rock load determined by all the three approaches, i.e., CMRI-ISM RMR, numerical modeling, and RMRdyn, was compared with the actual field data. The percentage deviation obtained in RMRdyn and numerical modeling is less compared to CMRI-ISM RMR.

Sep 1, 2023

By W. K. Hitchcock

Anecdotal evidence suggests that re-entering a sealed heating poses a significant hazard, whereby the original heating is rejuvenated at an accelerated rate forcing withdrawal and re-sealing of the area. Bulk-scale laboratory experiments using a two-metre column confirm these mine site observations. A high volatile bituminous coal from New South Wales, Australia was allowed to develop a significant hot spot before being inerted with nitrogen and allowed to cool. Air was then allowed back into the coal after the nitrogen was turned off and a hot spot developed almost immediately at the same location as the original hot spot before it quickly migrated towards the air source within a day. Two more re-entries were simulated. Each successive re-entry developed a broader hot spot and took longer to reach thermal runaway. These results clearly show the behaviour that can be expected when trying to recover a section of an underground coal mine that has been sealed due to a spontaneous combustion event.

Jan 1, 2009

By R. Kahrger

This paper is written to convey the latest developments in compact bucket wheel excavators (BWE's) operating in medium-hard rock and will serve to indicate that BWE and compact machines in particular do in fact have application in materials other than loose sandy soils and soft rock. A recently run extensive three month field test in hard marl, which was previously considered too hard and difficult to be handled by a BWE, is used as an example to explain some of the design requirements and problems associated with digging harder materials.

Jan 1, 1990

By Xun Zhang, Hang Qiu, Andrea R. Gerson4, Shaomin Lei, Yubiao Li, Yu Meng, Zhenyu Pei, Min Lin

Efficient separation of trace muscovite from the surface/interface of quartz grains was accomplished during oxidizing calcination and catalytic pressure leaching of the hydrothermal quartz. Experimental results suggest that 98.97% or more of the muscovite was separated when quartz sand was calcined at 900 °C for 5 h and then leached by hydrochloric acid and ammonium chloride solutions as substitutes for leaching agents containing fluorides. The chemical processing techniques show high selectivity in purifying quartz sand by transforming mineral muscovite into active structures during oxidizing calcination, and then dissolving the active substances during catalytic pressure leaching

By Yun-tao Xin, Yu Yi, Kang Yan, Gang Li, Xiao-dong Lv

This study investigated the selective removal of arsenic from high-arsenic dust in alkaline systems and the effects of different leaching conditions. The results indicated that the liquid–solid ratio, NaOH concentration, and sulfur dosage had a significant influence on the process. The leaching efficiency of arsenic reached 99.57%, while that of lead was as low as 0.03% under appropriate conditions. In particular, the addition of sulfur can effectively promote the leaching of arsenic and reduce the dissolution of lead in the solutions. An artificial neural network was used to model the leaching process. It consisted of a back-propagation artificial neural network model with a “6–10–2” structure that could effectively simulate and predict the value with more than 99% accuracy. Based on the difference in weights of the different parameters in the neural network model, the relative importance of the parameters related to arsenic and lead leaching efficiency was obtained, which followed the order of NaOH concentration, liquid–solid ratio, sulfur dosage, temperature, time, and stirring speed.

Jul 29, 2021

By Mustafa Kumral, Yuksel Asli Sari

Underground mining operations are sensitive to price fluctuations because they usually perform with a narrow profit margin compared to open-pit mining. Furthermore, the economic evaluations regarding operation are based on estimated or simulated grades rather than actual values. These bring a high degree of uncertainty to the viability of an operation. Hence, mine planning that accounts for uncertainty is crucial for underground mining operations. As an underground mining technique, sublevel stoping has geotechnical, curing time, seismicity, cost minimization, and production requirements. A new mixedinteger linear program is proposed that considers the uncertainty associated with net present value using chance-constrained programming. The net present value (NPV) maximization objective is transformed into a multi-objective maximization problem where one objective is to maximize the mean NPV, and the other objective is to maximize the negative standard deviation multiplied by a scalar called risk or reliability level. The balance between the two objectives was maintained by this scalar and was selected based on the reliability level of the project. A case study was conducted with varying reliability levels, and sequences were generated. It was shown that the expected net present value increased at higher reliability levels, and the overall value of the objective function decreased as the reliability level increased. In other words, the variance component penalized the value of the objective function. Moreover, it was observed from the case study that at lower reliability levels, stope grade order bears similarity to the extraction order.

Aug 4, 2023

By Florence Munter

This paper provides a discussion of the various federal and state laws governing water quality as related to mining operations. The specific laws addressed are the Clean Water Act, and the Arizona Mined Land Reclamation Act. Topics that will be addressed are mine water and process water discharges, storm water discharges, pollution prevention, dredge and fill, spill prevention control and countermeasure plan, and surface water protection. Proposed changes to the laws and regulations will be discussed. Compliance strategies will be suggested to prevent potential noncompliance and enforcement.

Jan 1, 1996

"Metallurgical process development in greenfield projects must define the comminution flowsheet and establish the equipment sizes that are required to deliver the project design criteria. These are critical steps that heavily influence the financial performance of the project, requiring a detailed understanding of the ore properties of the project resources and the best practice methods to size comminution machines. This paper reviews current practices for determining the ore characteristics relevant to comminution circuit design. Particular attention is given to the design of sampling and testing programs, and the methods commonly applied to size crushers and mills for conventional size reduction applications in mineral processing. IntroductionMetallurgical process development in greenfield projects requires the selection of a comminution flow sheet and must establish the equipment sizes required to deliver the project design criteria. This necessitates a detailed understanding of the ore properties that define the project resource. For brownfield projects the same objectives may apply for plant expansions, or the project objective may be simply to define the capacity and operating cost of an existing facility for a new ore source. The process development phase in either instance will typically comprise the following key activities:• Geometallurgical classification and sampling of the ore deposit or deposits.• Determination of comminution energy requirements.• Benchmarking similar projects.• Identification of flow sheet options.• Equipment selection and sizing.This paper is concerned specifically with process development testing and will as such focus on the first two activities on the list: sampling and testing of the deposit. The discussion will focus on testwork programs to support the design of comminution circuits commonly in use in mineral processing today, specifically crusher, tumbling mill and stirred mill technologies.It is important that any testwork program is designed giving consideration to the types of flow sheets that are viable for the project, and the data that will need to be generated to support the final equipment sizing. Designing a testwork program to only provide information about one particular type of flow sheet will not allow sufficient information to be generated for a rigorous trade-off analysis of options, and may therefore preclude financial optimization of the project. Testing programs should be designed to collect sufficient data to ensure that any backtracking at a later stage to fill in missing information is minimal."

Jan 1, 2016

By S. J. Root

The mineral processing industry supplies raw materials to a wide variety of manufacturing sectors. Large companies such as Ford, Microsoft, and Johnson&Johnson have pledged carbon neutral supply chains in the coming decades, leaving suppliers to reevaluate their energy sources [1–3]. National Renewable Energy Lab [4] has partnered with over 700 organizations with similar goals in mind. The energy needs are broad in scope in the mineral processing industry. Generation IV of nuclear reactors, which is currently under development in both the private and public sector includes a class called microreactors like the small modular reactor XEnergy plans to install at Dow Chemical’s Gulf Coast facility by 2023 [5]. As the name implies, these are smaller than the utility scale nuclear power plants in operation today, and are intended to be more versatile. A specific reactor core design, along with modules could be selected to fit a certain application without needing to design a greenfield power plant. Basic water cooled designs could easily supply shaft work, electricity, and low grade process heat to a facility. More advanced designs, such as molten-salt-reactors and high-temperaturegas-reactors can achieve higher temperatures needed for ore roasting. Similarly, these reactors could produce hydrogen by high temperature electrolysis to use as combustion fuel and reducing atmosphere in blast furnaces.

Feb 1, 2023

By H. EI-shall

Bench top centrifuge is used to study the consolidation behavior of phosphatic clays. A mathematical model (based on first order kinetics) is developed to describe the relationship between the void ratio (at any time) and the effective stress. Permeability of the sediment as a function of the void ratio is also described. The obtained data are compared with that obtained by other consolidation testing methods. Centrifuge results indicate that consolidation data may be developed in a short period of time (hours) as compared to days or weeks when other techniques are used.

Jan 1, 1995

By Mustafa Fener, Masoud Rostami, Sair Kahraman, Behnaz Dibavar

Roadheaders are commonly used in coal mines for roadway excavations. The prediction of roadheader performance is necessary for the planning of roadway projects and the estimation of costs. Recently, a new rock mass cuttability classification (RMCC) system has been introduced for roadheaders used in coal mines. In this study, the validity of the RMCC system was investigated for different types of roadheaders and different coal mines. Four different coal mines were visited, and the performance measurements of different axial and transverse roadheaders were carried out during the excavation of roadways. Uniaxial compressive strength, volumetric joint count, the strike and dip of joints, joint aperture, the Cerchar abrasivity index, and water ingress were determined in field and laboratory studies to calculate the RMCC index. The analysis of the data demonstrated that the correlation coefficients between the net cutting rates and the RMCC indices were higher than 0.94, suggesting that the RMCC system was valid. It was concluded that the RMCC system could be reliably used for the evaluation of roadheader performance in coal mines.

Jun 21, 2023

By Alejandro Sanz, Juan Luis Magro, David Mazeyrie

The Hampton Roads Bridge-Tunnel Expansion Project (HRBT), initiated by the Virginia Department of Transportation (VDOT), will add two new 1.5-mile TBM bored tunnels to the two existing immersed-tube tunnels between artificial islands, part of the connection between Norfolk and Hampton under the Hampton Roads Harbor in Virginia, USA. The new bored tunnels will be built by Hampton Roads Connector Partners (HRCP), a joint venture of Dragados USA, Vinci Construction, Flatiron Constructors and Dodin Campenon Bernard. This paper covers technical discussions that led HRCP to select a Variable Density TBM to address the challenges of this tunnel project, including but not limited to (i) the diameter of the bore: a 46 feet (14.04 m) diameter machine that constitutes the second-largest TBM ever used in the United States; (ii) shallow ground-cover under the water table; (iii) challenging and varying geology along the alignment, with mixed-face conditions and different types of ground modification zones; and (iv) the high TBM operating pressures required—all these and other challenges in a sensitive marine environment.

Jun 13, 2021

By E. Berrezueta

Automatic digital phase imaging should yield unbiased and representative characterizations of gold ores. However, this is not a simple tusk due to low gold grade, fine grain size, possible complex mineralogy, nugget effect, etc. Using the same sections of a gold-rich ore, a critical test was performed using an optical microscope (OM) and an electron microscope (EM). In general, the two methods are consistent and useful for ore processing. There are some minor differences, such as the detection of very fine gold grains is enhanced by EM. Key words: Digital imaging, Gold ores, Mineralogy, Electron microscopy, Optical microscopy

Jan 1, 2003

By M. A. Greenwood

The total value of coal, FOB mine, consumed in the United States was $21 billion in 1985. Roughly $6 billion was spent to transport coal from the mine to the consumer by rail. This indicates the impact railroad transportation has on the competitiveness of U.S. coal as an energy resource. Actually, this is just the tip of the iceberg. When you consider the largest U.S. reserve of coal, the Powder River Basin, which is possibly the lowest cost coal in the U.S., or maybe even the world, the transportation cost is the overriding factor in developing competitive pricing. Rail transportation costs from Powder River can be multiples of 2, 3, or even 4 times the cost of coal FOB mine. About sixty percent of all U.S. coal is shipped by rail. In the case of Powder River Basin coal and many other reserves there are no current alternatives to rail. Are there feasible alternatives to rail transport?

Jan 1, 1986

By M. Guney, A. R. Bell

In Mindola mine on the Zambian Copperbelt, there is a plan to extend the current production level of 1.2-1.5 km (3,900-4,900 ft) with five additional production levels. Research work indicated that the present total heat output of 38.6 MW will inevitably increase to 63.2 MW in 25 years. Estimated WB and DB temperatures, representing the total heat generation in stope faces and development headings during these same periods are predicted to increase to 33.8/40.2°C (93/104°F) and 35.3142.10C (95/108°F) respectively. It is assessed that the nominal refrigeration capacity needs to be progressively increased to 9, 000 MW.

Jan 3, 1984

By Steve Kral

The third edition of the Underground Construction Association of SME?s (UCA) Cut-ting Edge series of conferences focused on a challenge every underground construction and tunneling project faces: controlling ground water. The conference, held in New York City in November, is a partnership between the UCA and The North American Tunneling Journal. It featured more than 20 technical presentations by professionals from around the world. Each described specific challenges unique to their projects and the solutions employed. More than 175 professionals attended the two-day conference that included an exhibition featuring 17 companies. In addition to the technical program, the Cutting Edge conference featured a site visit to the $10.4 billion East Side Access Project. Sponsors of the meeting included Soil Freeze, Traylor Bros., Kiewit, Skanska, Moretrench, Aecom and The Robbins Co.