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By R. DasGupta

The dissolution behavior of gold in ammoniacal solutions at 75°C has been investigated. The variables investigated include concentration of lixiviants, pH of the solution and various oxidants. The anodic dissolution of gold was studied in the absence of oxidants using the potentiodynamic polarization technique. The cathodic reaction of oxidants was studied on a platinum electrode. Tafel polarization tests were also performed to determine the dissolution rate. The overall dissolution of gold in ammoniacal solutions was examined using a mixed potential theory. A comparative study on the role of cupric am mine, oxygen, hydrogen peroxide, sodium hypochlorite as oxidants for the dissolution of gold in ammoniacal solutions has been carried out.

Jan 1, 1996

By J. A. Marts

Reservoir properties including porosity and permeability distributions in longwall coal mine gobs have direct application to modeling the flow patterns and gas distributions in the gobs. Proper assessment of these distributions is required to assess gob gas hazards such as spontaneous combustion and explosive methane mixtures and to optimize gob gas venthole operation and nitrogen inertization. Determining the reservoir properties is difficult given that the gob is inaccessible and direct measurements cannot be easily taken. Several techniques have been used by previous researchers and will be discussed. This paper will present the methodology used to model the gob compaction by simulating the sequential extraction of coal. Two Western US coal mines were used for case studies. By determining volumetric strain, the porosity and permeability distributions in the gob can be calculated. The geo-mechanical model predicts an axisymmetric volumetric strain distribution with a steeper slope near the start-up room and a shallower slope near the active face.

Feb 23, 2014

By D. P. Tao, J. G. Groppo, R. Killmeyer, W. W. Wen, B. K. Parekh

Economical dewatering of ultra-fine (minus 74 m) clean coal slurry produced in column flotation to a 20 percent or lower moisture level will be an important step in successful implementation of the advanced fine coal cleaning processes. The main objective of the present study was to evaluate efficiency and effectiveness of three dewatering techniques, namely, hyperbaric, vacuum and screen bowl centrifuge, in dewatering of ultra-fine (D50 ~ 25 m) clean coal slurry produced by the `Ken-Flote' columns operating at the Powell Mountain Coal Company, St. Charles, Virginia. he hyperbaric filter using 3 bar pressure and 165o cake formation angle, provided a filter cake with 23.6percent moisture with a throughput of 800 Kg/m2-h and air consumption of 868 Nm3/t (460 scfm/t). The vacuum filter with 30 percent submergence provided a filter cake with 27.8 percent moisture with a throughput of 122 Kg/m2-h. The screen bowl centrifuge provided a dewatered product containing 32.9 percent moisture at a feed rate of 450 Kg/hr, however, the solids capture was only65 percent. Addition of 1 Kg/t of a cationic surfactant provided filter cakes with 19.1 percent, 23percent, and 34 percent moisture using hyperbaric, vacuum, and centrifuge, respectively. Similarly, addition of 0.5 Kg/ton of copper chloride lowered filter cake moisture to 20.7 percent and 24.8percent, using hyperbaric and vacuum. With the centrifuge no improvement in filter cake moisture was noted. However, use of 80 Kg/ton of `orimulsion' in the centrifuge provided dewatered product containing 26 percent moisture, and the solids capture increased from 65 to 95 percent. The dewatered product appeared dry and was easily handleable.

Jan 1, 1999

By Alain S. Kivava, Olawale K. Aromolaran, Charles Nzolang, Anthony T. Bolarinwa, Georges M. Kasay

Rare earth elements (REEs) are crucial in high-tech and green technologies. The Democratic Republic of Congo (DRC), rich in mineral resources, shows potential for REE deposits in carbonatites, pegmatites, and placers. This paper reviews global REE resources, highlights potential REE targets in Africa, and emphasizes the need for further research and exploration in the DRC to unlock its REE potential.

Feb 4, 2022

By John H. Bassarear

The never ending search for lower unit costs led Pima Mining Company's management to study various alternatives shortly after Expansion III was completed. It soon became apparent that a considerable amount of ore assaying 0.35% copper had to be moved in order to maintain mill feed at the desired 0.54% copper content, which is the overall grade of the ore reserves. Detailed investigations revealed that for a period of 8 - 10 years, about 14,000 tons per day of 0.30 - 0.40% copper ore would pass by the crusher en-route to the low grade stockpile. This ore is very hard, very clean and has to be mined at a relatively uniform rate. A six month pilot plant run testing autogenous and semi-autogenous grinding gave very encouraging results. Since no mining costs need to be charged to the extra tonnage (it had to be mined anyway) the only major costs would be against milling. The decision to proceed was made in August 1970 and Fluor-Utah was retained as the prime design construction contractor. Ore was first put through the new mill on December 29, 1971. By March of 1972 design tonnage of 14,000 TPD had been attained. The first three expansions at Pima Mining Company, 20 miles south of Tucson, increased mill capacity from 3,000 TPD to 36,000 TPD. These expansions included a separate, conventional, three stage crushing plant plus additions to the existing concentrator that primarily duplicated the then current flowsheet. Expansion IV, however, consisted of an entirely new and separate primary crusher and a completely new mill building located about 2,000 feet southeast of the 01 d concentrator. The new mill, using semi-autogenous grinding, produces scavenger and rougher flotation concentrates that are pumped to the old mill for regrinding, cleaning, thickening and filtration.

Jan 1, 1973

By R. R. Rollins

Field data combined with theoretical derivations were used to design a surface mining operation using explosive casting. Calculated casting results varied from 44 to 65% depending on bench height. This model was then applied to field tests at an eastern, contour, coal stripping operation. Results from five experimental casting shots are summarized and compared to conventional mining methods. The overburden material removed by casting ranged from 35 to 65% with an average of 50%. Fragmentation was improved and it was demonstrated that this procedure is economically attractive with a resultant cost savings of $.59/m3 or $5.93/t of clean coal.

Jan 1, 1987

By Zhian Liang, Xiong Huang, Weixin Wu, Lifeng Cui, Zhuanhua Wei, Guoyao Li, Xiao Ni, Junrong Wang, Shuiping Zhong

ZJ 201 (modified starch) is a non-toxic, odorless, and biodegradable polymeric depressant, which selectively depressed galena in batch flotation tests while chalcopyrite was not significantly affected. In a plant trial, copper-lead separation was successful for the first time without using dichromate. Moreover, the plant process could be changed to sequential Cu-Pb flotation using ZJ 201 for higher grade lead concentrate. A copper concentrate was obtained with a Cu grade of 24.91% and a Pb grade of 5.11%, which recovered 76.6% of the copper from the original ore; a lead concentrate was also obtained with a Pb grade of 21.90% and a Cu grade of 5.31%, which recovered 52.6% of the lead. In addition to the effective copper-lead separation observed in the plant trial, another improvement observed is that gold was recovered mostly in copper concentrate, which could be sold for higher prices. Au grade reached 230.64 g/t, and its recovery reached 65.8% in the copper concentrate. Au grade in lead concentrate was only 18.90 g/t.

Aug 27, 2021

By Rainer Antretter

"THE CHALLENGE The 14km long, Arlbergtunnel, closed for public traffic during summer 2015, receiving a comprehensive and substantial renovation from 2015 to 2017. The main works discussed here, carried out during 2015, comprise 37 drill and blast SEM/NATM emergency escape tunnels from road level to the ventilation duct plenum have to be constructed as well as eight additional lay-by niches and three transformer tunnels. This presentation comprises the construction ventilation design, designed according to national regulations, suitable for 150 employees working 24/7 simultaneously at more than 40 single working sites lined up along the tunnel. The ventilation-system chosen was utilising two existing shafts for intake/discharge and a cross passage to surface, to handle a total fan power of 1.600kW. DESCRIPTION OF RENOVATION WORKS Linking Tyrol and Vorarlberg, two Federal States of Austria, the Arlbergtunnel is a single tube two-way road tunnel with vent duct plenum, constructed in the mid-1970s. According to latest EU legislation, additional escape exits have become obligatory. The existing seven cross passage links to the adjacent Arlberg Railway Tunnel, with average spacing of about 1.500m constructed in 2007, an additional upgrade to shorter escape spaces of approx. 400m was now required to comply with the updated legislation. Additional transformer tunnels, lay-by niches and small niches for emergency maintenance use, cleaning and other purposes, as well as a the installation of a new fire main in the invert, coupled with the simultaneous replacement of virtually the entire power and signaling cables, generated several dozen small and large single sites distributed along the 14km of tunnel.Purpose of the 37 walkable emergency escape tunnels is to reach the “upper deck” of the Arlbergtunnel, the vent duct plenum. These have an 180deg curve in plan, inclined at 10% and approx. 60m (65yd) long tunnels, excavated using drill and blast method starting from road level and working upwards to the level of an “intermediate soffit”, the vent duct plenum in the crown of the tunnel. The vent duct plenum is separated into a fresh air part and an exhaust air part, shown in Figure 1. The escape tunnels end with a pressure door in the fresh air section of the ventilation duct plenum. From there illuminated signs show the shortest escape route to the safe area between the road tunnel and the railway tunnel, as shown in Figure 2."

Jan 1, 2016

By J. MCGUIRE, E. J. Haas, B. Demich

Near misses can enhance awareness of the potential causes of injury and prompt safety management initiatives. Although most companies require near-miss reporting, the value of these reports and how they influence subsequent actions or controls to reduce on-the-job risks are unclear. Researchers at the U.S. 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. 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 S. Dawson

The Republic of South Africa has become a major producer of opencast coal in recent years. Opencast production commenced in 1970 and by 1977 some 10 million run of mine tonnes were being produced annually, Since then surface mine activity has increased to more than 60 million tonnes which represents approximately one third of the total annual South African? coal production. Whilst a substantial portion of this production is exported, the majority is used in the domestic market, The largest consumer, being the South?\ African Electricity Commission (Eskom), produces most of South Africa's electricity using coal fired power stations,

Jan 1, 1990

By S. Al-Thyabat

In this work, the floatability of Jordanian phosphate slime (-38 µm) was evaluated in a batch column flotation cell, 100 cm high and 5 cm inner diameter. Flotation was conducted using sodium oleate as a collector and methyl isobutyl carbinol (MIBC) as frother. Rougher flotation yielded concentrate assaying 29.19% P2O5 with 90.29% recovery at the following flotation parameters: 2.6 cm/s superficial gas velocity, 20 ppm frother dosage, 0.205 mM collector concentration and 40% weight solids. It was also found that conditioning with the same collector dosage but with a different solids weight percent gave different flotation results. However, pulp collector concentration was the key operating parameter; increasing collector dosage at the same solids weight percent decreased flotation recovery by 3%, while increasing solids weight percent at the same collector dosage increased phosphate recovery by 18%.

Jan 1, 2011

By Yi Yang, CHENGLONG XU, HAORAN LI, YALI FENG, JINRONG JU

This study presents a method for recovering valuable metals and synthesizing anhydrite from steel slag using sulfuric acid leaching and solvent extraction. The process achieved high leaching efficiencies for V, Ti, Fe, and Mg, and produced anhydrite with 93.09% purity. The leachate was further processed to separate and recover V, Ti, Fe, and Mg using selective stripping and precipitation methods, offering a sustainable approach to steel slag utilization.

Jan 22, 2022

By P. M. Hawley

In April 1975 Kaiser Steel Corporation and the United States' Department of Energy entered into a cost-sharing agreement for the demonstration of shield-type longwall supports on three consecutive longwall panels at Kaiser's York Canyon' Mine in New Mexico. Under this agreement the Department of Energy supplied 117 Hemscheidt 320 HSL caliper-type shield supports and hydraulic pumps for the duration of the demonstration. The purpose of the demonstration was to educate the U.S. coal mining industry as to the benefits in production, productivity, health and safety, and increased coal extraction afforded by shield-type longwall mining systems and to provide the industry with a working model. A detailed description of this demonstration is given in U.S. Department of Energy Publication No. DOE/ET/12530-T1, entitled "Demonstration of Shield-Type Longwall Supports at York Canyon Mine of Kaiser Steel Corporation," hereafter referred to as the York Canyon Report.

Jan 1, 1984

By Pierre Filiatreault, Brian Straight, Stephanie Thibeault, Devin Castendyk, Londie Cameron

"Working on or near water at active, closed or abandoned mine sites is inherently dangerous. Between 1996 and 1999, the U.S. Mine Safety and Health Administration (MSHA) reported 17 fatalities involving drowning at U.S. metal, non metal and coal mines (MSHA, 2000). Openpit mines which fill with water following mine closure, called pit lakes, present numerous risks to environmental monitoring teams including: a) drowning, b) hypothermia, c) falls to the ground from the top of high walls, d) collapse of unstable access roads, e) rock falls and avalanches from pit walls, f) avalanchegenerated tsunamis traveling across the lake surface and g) rapid degassing events.Some pit lakes are simply not safely or easily accessible for ongoing monitoring. However, the routine collection of water samples from the entire water column on a regular basis is needed to monitor the evolution of water quality over time, verify the accuracy of numerical predictions and, ultimately, manage lake water chemistry and ecological risks. For pit lakes with surface water discharge, regular monitoring is used to appropriately design and adjust water treatment plants in order to produce acceptable site discharge water quality.As a product of these risks and the need for water samples, mining companies spend considerable expense on pit lake safety as part of monitoring programs. This includes training personnel for on water duties and hazards, purchasing or hiring specialized equipment and personnel (such as boats, boat operators, personal floatation devices and cold-water clothing called mustang suits), stabilizing pit walls and maintaining safe access roads to the lake surface and employing spotters who can directly communicate with emergency medical services to watch sampling activities because cell phones and radio signals can be blocked by pit walls. Some sites utilize redundancy to prepare for unexpected incidents and accidents. For example, one Canadian mining company requires two boats on the water during pit lake sampling events, with a third boat on the shoreline, gassed and ready to go. In addition, water samplers are required to hold Marine Emergency Duties training to ensure the entire boat crew is sufficient and competent for the safe operation of the vessel in the event of an accident."

Jan 7, 2017

By D. D. Schlepp

There is a continuing debate about the influence of circulating load and classifier efficiency on the capacity of the circuit. Specifically, the effects of preferential classification, bypassed fines, and the sharpness of classification will be examined. Horizontal cyclones have also proven to be very successful in a number of operations but their impact on the circuit capacity has not been clearly defined.

Jan 1, 1990

By Willard C. Lacy

INTRODUCTION A program to insure adequate talent for development and management of our mineral resources entails two equally important and interrelated aspects: 1) attracting and retaining promising student talent, and 2) providing a first-rate education for those entering careers in mineral science and engineering. Manpower shortages have eased in many areas of engineering, particularly in those areas dependent directly or indirectly upon government contracts in space and war programs. However, in the minerals industry the needs still remain critical. As increasing concern over preservation of the environment has developed, the political and social reaction was to seek out major offenders, to look for "whipping boys" -- and the mineral industry was, and had been, an offender. It was there for everyone to take pictures, it couldn't be covered up, and the Department of the Interior lashed away in the beautiful and popular brochures: Quest for Quality, The Third Wave, The Population Challenge, and Surface Mining and Our Environment (Ravaged Land). The Sierra Club, the Field and Stream magazine, TV, and daily news media added their lashes. In the minds of our social-conscious youth the mineral industry took on the image of "exploiters" of natural resources; "polluters" of streams, lakes, and the atmosphere; "despoilers" of wilderness areas and scenic beauty -- a plague to combat, rather than an exciting challenge that entailed exploration of the remote, conquering of the primitive, and developing of the undeveloped. Enrollments declined and many traditional mineral engineering curricula were abolished or Integrated into other stronger engineering departments to meet student-faculty ratio requirements.

Jan 1, 1971

A knowledge of airway friction factor (K-factor) is necessary to designing mine ventilation systems for least cost and optimum effectiveness. The friction factor used must be accurate and reliable to estimate correctly roadway resistances and pressure sources for required flows. Though the resistance to flow offered by mine airways has been an object of study over the last half century, no accurate relation has yet been established from which the prediction of the resistance of a projected airway can be made. In Kentucky, only limited and incomplete data on local K-factors are available. Therefore, there is a need for field investigations to determine these values in-situ for existing mining conditions. The author describes a study concerning K-factor that was carried out in ten coal mines, located in eastern and western Kentucky. The results of these investigations are presented in both tabular and graphical form.

Jan 1, 1991

By T. J. Lien

AMAX Coal Company's Belle Ayr coal dryer is the first industry attempt to commercialize sub-bituminous coal drying which has been the subject of laboratory and pilot plant tests for almost two decades. This paper presents the historical background, construction, start-up and operation of this adaption of fluidized bed coal drying technology to Powder River Basin coal. The flowsheet and operational problems encountered during plant start-up are discussed together with general material balance and product quality.

Jan 1, 1990

By B. K. Parekh

Economical dewatering of ultra-fine (minus 74 m) clean coal slurry produced in column flotation to a 20 percent or lower moisture level will be an important step in successful implementation of the advanced fine coal cleaning processes. The main objective of the present study was to evaluate efficiency and effectiveness of three dewatering techniques, namely, hyperbaric, vacuum and screen bowl centrifuge, in dewatering of ultra-fine (D50 -25 m) clean coal slurry produced by the 'Ken-Flote' columns operating at the Powell Mountain Coal Company, St. Charles, Virginia. he hyperbaric filter using 3 bar pressure and 1650 cake formation angle, provided a filter cake with 23.6 percent moisture with a throughput of 800 Kg/m2-h and air consumption of 868 Nm3/t (460 scfm/t). The vacuum filter with 30 percent submergence provided a filter cake with 27.8 percent moisture with a throughput of 122 Kg/m2-h. The screen bowl centrifuge provided a dewatered product containing 32.9 percent moisture at a feed rate of 450 Kg/hr, however, the solids capture was only 65 percent. Addition of 1 Kg/t of a cationic surfactant provided filter cakes with 19.1 percent, 23 percent, and 34 percent moisture using hyperbaric, vacuum, and centrifuge, respectively. Similarly, addition of 0.5 Kg/ton of copper chloride lowered filter cake moisture to 20.7 percent and 24.8 percent, using hyperbaric and vacuum. With the centrifuge no improvement in filter cake moisture was noted. However, use of 80 Kg/ton of 'orimulsion' in the centrifuge provided dewatered product containing 26 percent moisture, and the solids capture increased from 65 to 95 percent. The dewatered product appeared dry and was easily handleable.

Jan 1, 1999

By Verya Nasri, Mehdi Bakhshi

"Fiber reinforcement has emerged as an alternative to steel bars in precast concrete segments due to advantages such as saving cost and reducing production time while developing a more robust product with improved handling and long-term durability. ACI recently drafted a new report as the first design guideline on FRC tunnel segments to provide specific guidance for this emerging technology. ACI document offers general information on the history of FRC precast segments from tunneling projects throughout the world; a procedure for structural analysis and design based on governing load cases, and a description of the material parameters, tests and analyses required to complete the design. This paper summarizes the design considerations in this ACI guideline prepared by the authors of this paper as the main contributors. Application of this guideline to design of a tunnel with an internal diameter of 5.5 m (18 ft) results in elimination of steel bars.INTRODUCTIONPrecast concrete segments are installed to support the tunnel excavation behind the Tunnel Boring Machine (TBM) in soft ground and weak rock applications. The TBM advances by thrusting off the completed rings of precast concrete segments that provide both the initial and final ground support as part of a one-pass lining system. These segments are typically designed to resist the permanent loads from the ground and groundwater as well as the temporary loads from production, transportation and construction. Tunnel segments are generally reinforced to resist the tensile stresses at both the Serviceability (SLS) and the Ultimate Limit States (ULS). With traditional rebar, a significant amount of labor is needed to assemble the cages and place the rebar, which results in higher production costs.Fiber Reinforced Concrete (FRC) can be used to enhance the production, handling, and placement of precast concrete segments. This is because of the uniform dispersion of fibers throughout the segment to include the concrete cover, which is very advantageous for resisting the bursting and spalling stresses. These stresses develop as a result of the high loads induced on the segments during the TBM jacking process. The presence of fiber in the concrete matrix helps mitigate against unintentional impact loads during segment handling and tunnel construction operations."

Jan 1, 2016