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By R. I. Pennington, J. L. Vanderbeek

Investigations have been conducted at Chino Mines Co. into the effect that SAG mill recycle material (critical size) exerts on SAG mill throughput and specific energy requirements. Tests were conducted on laboratory, pilot, and plant scales to evaluate the merits of alternative treatment options. Removing critical size material from the SAG mill circuit has been shown to improve new feed rates by 84% with a reduction in specific energy (kWh./t) of 88%. Test results obtained to date are presented.

Jan 1, 1987

By A. E. Isaacson, T. H. Jeffers

The U.S. Bureau of Mines (USBM) is investigating arsenic removal from dilute waters using a biological precipitation/chemical adsorption system. The method includes (1) inoculating water with ferrous salts to increase hydrogen sulfide generation by indigenous sulfate-reducing bacteria, (2) utilizing the hydrogen sulfide to precipitate the bulk of the arsenic as arsenic sulfide, and (3) using beads containing ferric oxyhydroxide to remove the remaining arsenic. This approach was applied to a contaminated water containing 13 mg/L As. Arsenic extractions up to 99% were achieved. The use of sulfate-reducing bacteria is particularly warranted in this situation since most of the required nutrients are present in the water. Based on successful initial efforts, planning is underway to conduct a pilot-scale test at the site.

Jan 1, 1995

By Carl P. Maronde, William P. Barnett, Patricia A. Rawls

The commercial deployment of advanced fine-coal cleaning technologies depends on cost-effective approaches for efficient separation and ancillary operations in handling, dewatering, drying, and transporting coal fines. As a result of two solicitations under the High-Efficiency Preparation component of the Department of Energy Coal Preparation Program, several projects were initiated for testing and evaluation of emerging technologies and equipment that address operational difficulties associated with coal fines. This paper will update the status of those projects and discuss how the technologies they represent can ameliorate some problems associated with coal fines in today's preparation plants.

Jan 1, 1995

Careful financial analysis of capital investments has always been a vital task in mining which is one of the most capital intensive sectors of the economy. Furthermore, mining costs have leapt ahead at an astonishing rate in recent years not just due to accelerated inflation, which affects everyone, but also due to the imposition of enormous costs of enviromental regulation and the continuing decline in ore tenor. Not only have unit costs risen, but the amount of effort expended to recover a pound of metal has increased due to the inexorable decrease in ore grades. New low-margin, high-volume mining investments place increasing importance on sound financial planning. Owing to the enormous investments involved, a greater share of individual corporate resources is committed to these projects than is normally the case in other industries. Thus, the consequences of failure are extremely grave, and a close examination of all inputs to the evaluation equation is clearly indicated.

Jan 1, 1979

By D. L. Jones, S. Knoerr, J. Mansanti

The Buckhorn Mine in Nevada currently treats oxide ore using heap leach methods, but exploration has identified sulphide reserves which are refractory in nature. Preliminary testwork was conducted on the sulphide material to screen potential pre-cyanidation treatment methods. Processes evaluated included pressure oxidation, biological oxidation, nitric acid oxidation and roasting. An initial economic and process analysis of the results concluded that roasting was the only viable process, and only if the roaster off-gases were converted to soleable sulphuric acid. Further economic analysis indicated that roasting of the whole ore was more attractive than pre-concentrating by flotation, followed by roasting of the concentrate. These results were generalized to show that for high sulphur ore a roaster/acid plant combination is more attractive that either of the other options, ie. pressure leaching or bioleaching, provided the by-product acid is soleable.

Jan 1, 1990

For all the attention given to mining activities in Central and South America, Mexico, Indonesia and Papua New Guinea, it is sometimes easy to forget the activities taking place in one of North America's most important and largely untapped regions -Alaska. The Alaskan minerals industry employed about 3,406 people during 1995. That is a 23% increase from - - 1994. It also contributed about $719.8 million to the state's economy during 1995, a 10% increase. During the past few years, Alaska has seen significant increases in exploration and mining activity. Fairbanks Mining, an arm of Cyprus Amax, began producing gold during 1996 at its Fort Knox Mine, as did Nevada Goldfields' Nixon Fork gold mine. Kennecott's Greens Creek lead-silver-gold mine also reopened and USMX began operations at its Illinois Creek gold mine. In addition, several impressive exploration projects were under way in Alaska. Placer Dome reported good results at Donlin Creek project in southwest Alaska. Likewise, Newmont Exploration is getting serious about its True North gold project. And Nerox is nearing production at its Jonesville coal project in Alaska's interior. In November, about 400 miners gathered in Anchor- age for the Alaska Miners Convention. Throughout the conference and exhibition, attendees listened to updates on these precious- and base-metal and coal exploration and mining operations. They also learned that the state wants more miners to head north and help develop its natural resources. Alaska is ripe for a smelter The mining industry -Alaska's miners in particular - has a powerful ally in Sen. Frank Murkowski (R-AK). He is the chairman of the Senate Energy and Natural Resources Committee. During his luncheon address, Murkowski said it appears that it is economically feasible to extend the Alaska Railroad to northwest Alaska, taking advantage of the large coal and hard-rock mineral tracts in the Ambler mining district. He also renewed his push for building a major smelter in Alaska to process ore that would come from the Ambler mining district. Murkowski believes that Alaska's economy can be expanded by extending the railroad from Nenana to the Point Lay coal fields to open coal development. Along the way, the railroad would pass through the Ambler district, helping to develop the hard-rock deposits. An outgrowth of this additional mineral development, Murkowski said, could be a new smelter in Alaska. It could use power from the Tyee hydroelectric facility near Wrangell or from the Makushin geothermal project near Unalaska. Either site, he added, offers access to plentiful, relatively low-cost power, at tidewater to facilitate ore deliveries to the Pacific Rim. The Congressional Research Service has determined that there are enough mineral deposits and coal beds to make it possible to finance the extended railroad, he said. The 1,200-km (744- mile) rail extension would cost about $4.2 billion. The North Slope of Alaska contains up to 3.6 Tt (4 trillion st) of coal, Murkowski said, that contains less than 0.25% of sulfur and less than 4% moisture. It aver- ages 12,300 Btu in heat content. "That is a tremendous resource," he said. The Ambler mining district, meanwhile, has at least eight identifiable hard-rock deposits, Murkowski continued. These contain zinc, lead, copper, nickel, chromium, tin, barite, gold and silver. "All eight of these can generate ore concentrates at rates similar to Red Dog's cur- rent 725 ktla (800,000 stpy)" of zinc, he said.

Jan 1, 1997

By Subash Chander, B. Arnold

Many developments have occurred in coal flotation with regard to increasing recovery from the flotation circuit and its impact on overall coal preparation plant recovery. This includes innovative design of flotation circuits, equipment modification and development, methods of enhancing the use of reagents, effect of slimes, and recognizing the effect of water chemistry. This paper will review recent advances and present some guidelines to improve process efficiency.

Jan 1, 2005

By Agne Rustan

INTRODUCTION This work is a continuation of the preparatory study by Rustan and Stöckel 1979 (3) and (4) of the possibilities to introduce automatic mine ventilation in Swedish mines and construction works. The preparatory study has been financed by the Swedish Board of Technical Development. In the study it was recommended that an automatic step by step control of the fans near the working place due to diesel exhaust emission would be the best solution. A more advanced alternative would be to regulate the fresh air continuously in proportion to the contamination. The latter alternative has been studied by Boliden Mineral Co in the Udden mine. In this study it was found that the air supply could be regulated continuously but it was very important where the sensors feeling the contamination were placed. An intense study of the environment underground is now being planned by our division together with specialists from the National Board of Health and Safety, The Swedish Work Environment Fund, LKAB and the local Governmental Inspection of the Workers Safety. Different gases, radon, dust, airspeed, moisture temperature and pressure is planned to be measured continuously and correlation between the parameters is going to be established to decide the best measurement parameters for regulating the system. The best situation of sensors is also going to be studied. Despite this work hasn't been done yet this paper covers some of the problems which could be encounted with continuous regulation. In this report the environment has been studied during the test with step by step regulation of fans by radio. Diesel vehicles are the largest polluters under ground in Swedish mines and we have therefore suggested that the large diesel vehicles should regulate the fans. The goal of this study has therefore been to find how active diesel vehicles should be able to start and stop gallery fans at both intake and return air. In this paper different methods for activating fans are discussed. Then the best methods are chosen and tested in the mine. In this study we have found that changes of temperature is a cheap and effective method to start and stop cross cut fans in sublevel caving and radio signals seem to be an attractive system for start and stop of gallery fans. This work has been done in close collaboration between LKAB in Kiruna and the University of Luleå - Division of Electronics and Division of Mining and Rock Excavation. A reference group for the project has been established with ventilation experts from the mines, representatives for the local mine worker's unions and authorities from the local Governmental Inspection of the Workers Safety. VENTILATION SYSTEM STUDIED In the project the ventilation system at LKAB in Kiruna has been studied. The mining method used is sublevel caving with 9-13 m slice height. The air is heated winter time over ground by hot water heat exchanger. The main fans are pushing air down to a main distribution level along the 4000 m long and about 100 m wide orebody. From the distribution level, air is taken through shafts down to the sublevels, where it is pushed through the levels by local gallery fans on both intake and return side, see fig 1. The air ( ~ 8 m3/s) is moving freely through the gallery head. The cross cuts are ventilated with smaller fans, diameter 500 mm, and flexible duct, see fig 2. The aim of this study has been to study how to start and stop gallery- and cross fans and examine the environment when the fans are stopped . In Sweden there are no regulations telling that a minimum of air amount must be supplied. Instead the hygienic limits must be fullfilled.

Jan 1, 1981

By Randall Smith, Leslie Stayner

At the request of the Mine Safety and Health Administration, a quantitative assessment of the risk of lung cancer associated with occupational exposures to diesel exhaust was performed. This assessment was primarily based upon the results from a study of the effects of chronic inhalation exposure to diesel exhaust in Fischer-344 rats (previously reported by Mauderly et al., 1987). An adaptation of the Armitage-Doll multistage model, which allows for an age-dependent effect of exposure, was used to model the tumor response data. This model was fitted to all tumors (benign and malignant), and to malignant neoplasms alone. Estimates of unit risk (potency) were derived based upon a linear approximation to the results from the multistage model. A biologically equivalent dose was developed to scale the results from airborne exposure in rats to humans, which was adjusted for differences in weight, ventilation rate, deposition fraction, and the percentage of time actually exposed. Comparisons are made with risk estimates derived from modeling other rat inhalation bioassays and from applying different models to the study by Mauderly et al. (1987). We emphasize that our risk estimates are based upon a series of assumptions and carry a great deal of uncertainty. In particular, uncertainties regarding the effects of exposure on lung clearance mechanisms, the deposition rates in humans, and the relevance of our exposure index limit our confidence in these risk estimates. Because of these uncertainties, this risk assessment would best be viewed as an exploratory effort. Key words: Diesel, lung cancer, risk assessment

Jan 1, 1991

By Allyn J. Steward

The 14,350 m (47,000 ft) Mount MacDonald Tunnel is nearing completion. North America's longest railroad tunnel is being advanced from each end by two contractors. This presentation outlines techniques employed by the Manning Kumagai Joint Venture, working from the west portal. Rapid construction was achieved by simultaneous installation of cast in place arch-wall lining and drill and blast excavation. Extensive planning, judicious choice of equipment and efficient crews combined to shorten the original schedule. Manning Kumagai was also awarded the tunnel mid-section as a separate contract. This includes construction of an underground chamber and structure for a unique permanent ventilation system.

Jan 1, 1987

Cost reduction programs can focus on total cost or unit cost, but unit cost is usually the principal objective. The production cost per unit is: [Unit cost = Total cost Production volume] Consequently, any activity that reduces the total cost or increases the production volume will reduce the unit cost. Production volume is increased by (1) maximizing the availability of the production equipment and (2) maximizing equipment performance during periods of operation. Most operations managers routinely focus on volume because the factors influencing volume are generally well understood and congruent with the managers' technical skills. In fact, production volume (as a percentage of maximum achievable capacity) is widely recognized as one of the most significant measures of operational performance.

Jan 1, 1999

By Hee-Young Chung, In-Mo Lee, Jeongjun Park, Hangseok Choi, Seok-Won Lee

"When using a Tunnel Boring Machine (TBM) during tunneling work, unexpected ground conditions can be encountered that are not predicted in the design stage. These reduce the stability of tunnels, and can result in considerable economic losses. This paper analyzes the potential risk events that may occur due to risky ground conditions. A resistivity survey is utilized to predict the risky ground conditions ahead of the tunnel face during construction. The potential risk events are evaluated considering both the occurrence probability and the impact. A TBM risk management system that can suggest proper solution methods for potential risk events is also developed. Multi-Criterion Decision Making (MCDM) is utilized to determine the optimal solution method to handle risk events. Lastly, an actual construction site, at which a risk event occurred during tunnel construction, is analyzed utilizing the Earth Pressure Balance (EPB) Shield TBM, to verify the efficacy of the proposed system.INTRODUCTION The Tunnel Boring Machine (TBM) method has been widely adopted in numerous tunneling projects because, as a mechanized tunneling method, it is also environmentally friendly, exhibiting minimal noise and vibration when compared with conventional tunneling method. In addition, it provides considerable economic benefits that allow for a high advance rate for long drives during construction. However, the TBM method has a limitation, as it is unable to deal with unexpected situations during construction, as the system is not capable of moving backwards. This leads to delays or even stoppages, and a corresponding increase in construction costs due to the need to arrange for alternative equipment and solutions. It is essential to retain systematic management in order to prevent or deal with unforeseen consequences such as the collapse of a tunnel face, ground surface upheaval or settlement, and construction delay due to water leakage during construction. Therefore, a systematic risk management system that is applicable during the construction stage of the TBM tunnel should be developed, taking into account the predicted risky ground conditions ahead of the tunnel face in advance."

Jan 1, 2016

By Hamid Maleki

Mine seismicity is influenced by the mechanical properties of both near-seam rocks and overburden and the prudent selection of mining methods and mine layout designs. Using finite-difference modeling, experience in many U.S. mines and measurements of the pressure arch width, the author has reviewed the engineering design factors that control seismicity in room-and-pillar retreat operations for stiff stratigraphic conditions in deep western U.S. mines. By back analyzing the overburden response in now understood to have been inadequately designed historic room-and-pillar mine, the overburden collapse mechanism is addressed as well as the need for improvements in designs including panel and barrier pillar widths, and sequence of retreat.

Jan 1, 2009

By Jiro Yamatomi, Susumu Takemura, Osam Sakai, Hiroshi Shimotori, Yoshio Otsuka

The Toyoha Mine is operated under extremely high rock temperature. The geothermal heat is 10 to 20 times more active than the average of the Japanese Islands. The highest temperature ever observed in exploration drill holes is 242°C that must be equivalent to those of the geothermal fluids utilized for power generation in Japan. In order to improve the underground climate, the mine has a plan to introduce paste backfilling and to effectively reduce the heat flows from the mined out stopes. The surface flow test was carried and the second test is being arranged in underground.

Jan 1, 2001

By C. J. Veal, C. I. House, S. R. Bellamy

INTRODUCTION Coal gold agglomeration (CGA) is a new concept in gold processing. It involves the recovery of oleophilic (oil-loving) gold grains by causing them to adhere selectively to the surfaces of coal oil agglomerates. Under optimum conditions very high recoveries of gold. can be achieved. The agglomerates are recycled to build up gold loading to typically 1000 - 5000 g/tonne. Bullion can be produced by burning the loaded agglomerates with subsequent recovery of gold from the highly loaded ash either by dissolution/electrowinning or smelting. A wide-ranging programme of laboratory testwork has been performed to investigate the response of different ore types to the process. This has shown CGA to be most applicable to ores in which the gold is liberated or easily liberatable, relatively coarse (ca 500 µm) and fine (<5 µm) gold grains being recoverable with equal ease. The best opportunities for CGA seem to be: • placers containing fine gold not recoverable by gravity concentration • low grade gravity concentrates to avoid multiple magnetic/gravity separation stages and amalgamation • free milling ores where the gold can be liberated at a reasonable ore particle size eg >d80 50 µm • tailings past or present from gravity concentration plants. CGA testwork ranging in scale from laboratory to pilot plant on tailings produced by gravity concentration in the 19th century Australian gold rush has already been reported (Bonney, C F, 1988; House, C I, Townsend, I C and Veal, C J, 1988). An economic appraisal for a Canadian free milling gold ore has also been published (Buckley, S A, House, C I and Townsend, I G, 1989). This paper describes results of a detailed laboratory programme to assess CGA as a means of recovering gold from a beach sand deposit in New Zealand. The area from which the samples were taken consists of quarternary interglacial marine, lagoonal, fluvial and eolian deposits. The heavy minerals present are predominantly ilmenite and garnet and small concentrations of gold. In certain locations the sands and gravels are consolidated by a limonitic cement. In the 19th Century some parts of the deposit were mined and the ore processed using stamp milling and gravity concentration. Gold recoveries were low, probably below 50%, due primarily to the fine size of the gold grains, the flaky nature of the gold and also imperfect liberation by the stamp mills. Our laboratory testwork was divided into three parts: i) Preliminary studies on an initial sample to assess the feasibility of treating the ore by CGA ii) Extended studies on further samples from various locations in the deposit to confirm predictions from (i) iii) Conventional gold recovery techniques. EXPERIMENTAL PROCEDURES All CGA tests were performed by agitating a slurry of ore in water in a 0.6 dm3 pyrex beaker fitted with four vertical baffles. When required, potassium amyl xanthate collector was added and the slurry conditioned for 5 min. Coal (ex BP Coal Australia&apos;s Tahmoor Colliery) previously ground to a d80 50 µm was added followed by a commercial grade of gas oil (density 840 kg/m3). The agglomeration time was 30 min. The agglomerates were separated from the tailings by screening, both were then dried and analysed for gold by fire assay. This test procedure provides a reasonably accurate estimate of gold recoveries that might be expected from our 1 tph pilot plant. Ore samples were ground either dry in an agate ring disc mill or wet in a steel batch tumbling

Jan 1, 1989

By Robert Mullen, Patrick K. Sollars

In 1994, Cyprus Twentymile Coal Company and Scandura formed a joint task force charged with the purpose of developing the highest rated fabric belt for underground longwall coal mining. This paper details the development efforts and concepts utilized by Cyprus and Scandura to meet the challenging demands of Twentymile Coal&apos;s East Mine District (EMD). The finished panel consisted of a 5,500 meter (18,000 feet) conveyor with 245 meter (800 feet) of drop over the first 3,660 meters (12,000 feet) and 245 meters (800 feet) of lift out-by over 1,830 meters (6,000 feet). The panel was designed with an operating capacity of 4,500 tph (5,000 stph) and 4.1 m/s (800 fpm) belt speed.

Jan 1, 1998

By T. S. Golosinski

This article reviews current contract mining practices in Australia. Various types of contracts are reviewed, including partnering arrangements and alliances between the contractor and the mine owner. Applicability is also discussed of various types of contracts to specific mining situations, as is their effect on overall mine performance.

Jan 1, 1998

By Arun Kumar Singh

Wide variation in the nature of the coal seams and the surrounding rock mass of the Indian coalfields and very little information about the associated stress fields were observed to be the major hurdles in the straight forward application of a continuous miner (CM) based mechanised depillaring approach. Due to various techno-economic reasons, a considerably large number of coal seams have been developed and are standing on pillars in India. The development of pillars is done as per Indian coal mines regulation, which results in pillars of relatively large size. In fact, the large size of the pillars provides stiff natural support to control caving of the massive overlying strata. However, the size of these pillars is not conducive for the single pass pillar stripping technique and, therefore, there is a need for pillar splitting before pillar extraction/retreating. Splitting of the pillar may reduce the competency/stiffness of the pillar, which creates a chance of overriding during final extraction below a massive roof stratum. This paper first discusses the existing coal mining scenario in India followed by a brief presentation of geo-technical details of pillar extraction at the three sites where a CM has been introduced for depillaring/pillar retreating in the country to date. Based on past rock mechanics experiences with conventional depillaring faces, stability issues of the pillars, fenders, and stumps in and around the depillaring face are discussed. This may prove to be an important factor in the success of future CM faces. It is recognized that the application of the modern strata movement monitoring techniques may improve operation safety by providing valuable qualitative and quantitative information that can be used to improve the design of modern concepts like roof bolt based breaker line support during pillaring.

Jan 1, 2009

By Jamal Rostami, Ataollah Rahbar, Jürgen Paulzen

"Uma Oya Multipurpose Development Project is located in South West Sri Lanka. This project, among many components, involves a 14 km headrace tunnel in very hard and abrasive igneous rocks. The tunnel is under construction by a 4.4 m diameter double shield TBM. The headrace tunnel has already reached 5km milestone and has passed through some reaches of tunnel in very strong intact rocks with no joints. Low penetration at high thrust load has caused frequent stoppages for cutter change leading to low utilization and advance rates due to low cutter life. The original machine was dressed with 27, each 432 mm (17 inch) diameter, 19 mm (3/4 inch) tipped disc cutters. However, various cutter diameters of 432-457 mm (17-18 inch) and cutter tip widths 13 to 19 mm (0.5-0.75 in), have been tried to see if cutter life and penetration rates could be increased. This paper will review the history of the project, the geology of the site, along with TBM performance and cutter life. It will focus on frequency of different cutter failures encountered in various ground conditions. Also, results of using variation of cutter diameter and tip width to cope with the hard rock conditions and their results in increasing machine productivity will be discussed. This allows for better understanding of parameters controlling disc wear/life and leads to better cutter management for more efficient operation of hard rock TBMs in similar conditions. INTRODUCTION The Uma Oya Multipurpose Development Project (UOMDP) lies in the south-eastern part of the central highland region of Sri Lanka. The Multi-Purpose Project Of Uma Oya is planned to convey water from Uma Oya to Kirindi Oya Basin for hydroelectric energy generation includes Puhulpola RCC Dam on the Uma Oya river, Dyraaba RCC Dam on the Mahatotilla Oya river, a conveyance tunnel from Uma Oya to Mahatotilla Oya (L=3750m), a long feeder tunnel from Mahatotilla Oya to Kirindi Oya river. The feeder (or power) tunnel Lot consists of a 15554 m long headrace tunnel (HRT), the surge shaft and tank on the upstream of the vertical shaft, a 650 m vertical shaft with steel lining, and an underground powerhouse and a 3650m tailrace tunnel (TRT)."

Jan 1, 2016

By Roe-Hoan Yoon

INTRODUCTION In 1960, coal accounted for 49% of the world energy consumption, an amount that was reduced to 29% in 1973 because of the availability of cheap oil. At that time, it seemed that oil would remain available for a long time in unlimited quantities. However, this situation changed drastically in 1973/74 when a series of closely spaced price increases from $3 per to $12 per bbl by mid-1974 hit both industrialized and developing countries. Another sharp price increase in 1979/80 to the $34 to $38 per bbl level also hit the world economy hard and, at the same time, set in motion powerful technology development forces for increased coal utilization. At this point, the price of coal was approximately $1.50 per MM Btu, while that of oil approached $6.00 per MM Btu. This huge price differential offered an incentive for developing new coal technologies including liquefaction, gasification, fluidized bed combustion, coal-water mixture (CWM), etc. The CWM technology was of particular interest to the utility industry, which consumes more than 80% of the coal mined in the US for power generation. In this technology, a powdered coal is mixed with water to produce a stable slurry that can be stored for an extended period of time without settling and is readily pumpable. Various reagents in the amount of approximately 1% by weight of the coal are added to inhibit sedimentation during storage and to reduce the viscosity for atomization in burners. The coal loading is in the range of 50 to 80% solids, depending on the particle size and its distribution. With very fine particles, it is difficult to increase the coal loading above 50%, and a binomial distribution helps increase the coal loading. The presence of water consumes a relatively small amount of the heating value of the coal during combustion; for a coal-water slurry containing 30% water, less than 5% of the calorific value of coal is usually consumed due to evaporation. The major advantage of burning coal as a slurry is that many of the oil-burning furnaces can be converted to coal-burning with a minimum retrofit cost. Considering the substantial price margin between coal and oil, the pay- back period for retrofit costs can be relatively short. Nevertheless, the retrofit cost can be further reduced if low-ash coals are used as feedstocks for CWM; there will be savings in the capital cost of installing bag filters or electrostatic precipitators that are designed to remove the ash from the combustion gases. Furthermore, the use of low-ash coals can minimize derating of boilers because the velocity of the combustion gases can be maximized without creating erosion

Jan 1, 1991