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By William Gleason

"On April 4, 2017, the largest earth-pressure-balance tunnel boring machine (TBM) ever built finally completed its 2.7-km (1.7-mile) journey beneath Seattle, WA, nearly four years after it began boring the SR-99 tunnel that will eventually replace Seattle’s Alaskan Way Viaduct.By now, readers of this publication are familiar with the ordeal that began on Dec. 6, 2016, when the machine overheated and shut down. Until that point, the TBM, named Bertha, had grabbed headlines for being the largest in the world with a 17-m (57.6-ft) diameter face. But after the incident that stopped the progress, the headlines suddenly stopped focusing on the engineering marvel of the tunnel project and began asking what went wrong. Just 300 m (1,000 ft) into the tunneling journey the machine was stuck, unable to move forward and impossible to retract.The project’s contractors, Seattle Tunnel Partners,(STP JV) – a design-build consortium comprised of Dragados - USA, Tutor Perini, say a 20-cm (8-in.) steel well-casing buried in the path of the machine caused the problems that halted the TBM. The Washington State Department of Transportation (WSDOT) disagrees, and the issue over who ultimately pays for the repairs is now with the courts.Eventually, engineers determined the best way to get Bertha back to work was to dig a 36-m (120-ft), deep concrete lined shaft pit in front of the machine and lift the 1.8-kt (2,000-st) cutterhead out for repairs. The repairs took two years but eventually the machine resumed mining in January 2016. In April 2017, the TBM finished building the tunnel, breaking through at the tunnel’s north end near Seattle’s Space Needle, with little to no ground surface movement measured on the entire alignment.While the cause of the TBM breakdown and who should pay for repairs was debated above ground, the work below ground continued. David Sowers, deputy program administrator, engineering and program management with WSDOT, told Mining Engineering during the 2017 Cutting Edge Conference in Seattle that in addition to the technical marvel that the tunnel became, the fact the parties involved were able to work through the unprecedented challenge is a great example of how to overcome challenges on massive projects."

Jan 12, 2017

By P. V. R. Bhaskar Sarma, P. K. Sahoo, G. Roy Chaudhury

A process was developed to treat an ammoniacal leach liquor containing zinc using Di (2-ethyl hexyl) phosphoric acid (D2EHPA) as the extractant. The objective of this work was to develop a process package for the treatment of complex sulfide leach liquors. Zinc extraction could not be carried out directly from the ammoniacal solution in mixer-settler units because of crud formation and low extraction efficiency. After neutralizing the free ammonia with H2SO4, the extraction efficiency was only about 40%, due to the high concentration of (NH4)2SO4. To decrease the (NH4)2SO4 concentration, the free NH3 was steam stripped, and the resultant liquor was subjected to zinc solvent extraction. An extraction efficiency of 98% could be achieved by controlling the equilibrium pH. Stripping studies were also optimized after removing ammonia from the zinc-loaded organic. A continuous 100-hr operation that included extraction, scrubbing and stripping, was carried out successfully.

Jan 1, 1995

By Robert A. Jankowski, John J. McClelland, Charles Babbitt

The purpose of this study was to develop guidelines to enable mine operators to maximize longwall dust reductions, while optimizing the use of ventilating air and shearer water consumption. A recent investigation by Foster-Miller Incorporated, under a Bureau of Mines contract, quantified the effect of increased face airflow and shearer water supply on face dust concentrations. A 70 pct reduction in respirable dust levels was achieved at the shearer operator's position during tail-to-head cutting by an incremental increase in average face air velocity from 83.8 m/min (275 fpm) to 123.4 m/min (405 fpm), while holding shearer water consumption constant. A 60 pct reduction was achieved through an increase in shearer water pressure and flow from 9.1 kg/cm2 (130 psi) at 0.19 m3/min (50 gpm) to 19.7 kg/cm2 (280 psi) at 0.28 m3/min (75 gpm), holding airflow constant. The combined effects of increasing both parameters produced an 85 pct reduction. Optimal usage of ventilating air and shearer water consumption can be achieved by defining a "point of diminishing returns" above which further increases no longer reduce dust concentrations, proportionately .

Jan 1, 1987

By Jugal Kar

Yilgam Star treats a gold bearing ore which has an association with pyrohotite and pentlandite (Fe,Ni)9S8 Nickel behaves similar to gold in cyanide solution, it leaches in cyanide to form a number of species. It adsorbs like the noble metals on carbon. During smelting Nickel causes significant problems in the crucible as the melting point of nickel is much higher (1452 °C) than gold (1040 CC). The crucible became overheated, holed and increases furnace downtime. To overcome such dif­ficulties an investigation was carried out to reduce the amount of nickel on steel wool during stripping. Yilgam Star has got I.P.S. high pressure zadra stripping system which works on 400 kpa, at 140 °C. The trend of gold and nickel profiles has been observed with varying caustic concentrations. The gold and nickel profile has been monitored with the addition of cyanide in the stripping liquor. It has been ascertained that at lower caustic levels the nickel ion remains in solution and is subsequently not electro­won. The cyanide concentration of0.4% (Wt/Vol) keeps nickel ion in solution and induces metallic nickel to produce nickel ion as NiCN.

Jan 1, 1995

By YU. F. Vasyuchkov, K. Vasioutchkov, B. M. Vorobjev

Introduction It is now believed that, even with the environmental protection measures now being taken, the further application of traditional coal-mining and electric power-generation technologies will inevitably cause further irreversible damage to the global ecosystem. Further improvements in conventional coal-mining technologies, both surface and underground, are expected to have only limited impacts on the economical, ecological and social aspects of coal mining. In countries with a developed coal industry, coal reserves with favorable conditions at shallow depths are rapidly being depleted. Therefore, in the future, more coal will be mined from deeper levels, resulting in higher operational costs and lower labor productivity. The solution to this problem is to be found in developing, promoting and implementing unconventional coal-mining and advanced clean-coal technologies. This paper presents an unconventional concept that has been suggested by the authors. The basic goal is to achieve coal-methane energy resource conservation and to remove barriers to energy efficiency through the adoption of integrated, ecologically clean, innovative technology. The following principles form the foundation of this concept: Energy resource conservation: This principle concerns the exploitation of actual and potential coal-methane reserves in the most effective way with the lowest possible losses and with the application of the most energy-efficient electric power-generation technology. Energy conversion: Energy conversion means the conversion of solid coal to synthetic fuel gas (in situ or in-cycle), the conversion of methane bounded within the coal matrix to free-flowing drained meth¬ane, the conversion of solid coal in situ to a coal/water mixture (slurry), and the conversion of these gas fuels into electric power. Technological and managerial integration: This prin¬ciple means an integration of coal-gas methane min¬ing operations and electric power generation into one commercial mine-to-product enterprise with electric power as the final product. Thus, coalbed methane drainage and coal gasification (both in situ and in-cycle) integrated with a combined cycle of electric power generation constitutes a highly integrated coal-gas methane energy-generation system. The system can be materialized in the form of a local integrated coal-gas electric power complex (LICGEPC). General features of the new concept The coal-gas-methane electricity concept is actually a synthesis of the following four technological components: Coalbed methane drainage. This technique and its utilization attained recognition after commercial operations were proven successful in the San Juan and Black Worriers coalfields in the United States. Worldwide, extensive field experiments and research-and-development activities are being carried out in the area of coalbed methane exploitation and utilization. Recently, coalbed methane drainage for power generation has been undergoing intensive research and development. At the Harworth Colliery in the United Kingdom, a combinedcycle power plant has been built that uses coalbed methane. The plant has an installed capacity of 15 MW Also, Germany, Australia, the CIS and China have conducted various experiments and industrial tests on the use of coalbed methane power generation. Underground coal gasification. Another unconventional technological approach is underground coal gasification (UCG). A number of semi-commercial, demonstration and pilot projects have been undertaken in Russia, the Ukraine, Uzbekistan, the United States, the United Kingdom, Italy and Belgium to demonstrate the technical and economical viability of coal gasification in situ. In Uzbekistan, the Angren coal-gasification station has been in full-scale commercial operation for two decades. The operation supplies a power plant with synthetic coal gas. Under sponsorship of the US Department of Energy's Morgantown Energy Technology Center, large-scale laboratory tests simulating coal gasification in situ were successfully completed by the

Jan 1, 1999

By Robert H. Oliver

Flowsheet flexibility in new 750 TPH coal cleaning plant provides three unusual capabilities. Two compartment drum coarse H.M. washer can be adapted to provide two stage separation. Coarse section of plant can be operated without fine section when washing surface mined coal. Fine section can operate with flotation cells bypassed if strip coal oxidation kills the froth. Plant can be fed by belt from bulk storage, front end loader from storage piles and truck from the mines. Raw coal and each of four washed products can be fed by belts to three separate loading points on two separate railroads.

Jan 1, 1979

By D. Pappas

Over the past decade, the number of contractors working in underground coal mines has nearly doubled; however, the effect this has had on the industry's injury rates has been the subject of much speculation. The confusion exists because the U.S. Mine Safety and Health Administration (MSHA) database does not assign contractor hours to the individual mining operations where they worked. To better understand the safety record of the contractor segment of the industry, the National Institute for Occupational Safety and Health (NIOSH) undertook a comprehensive analysis of the data contained in the MSHA database. The first part of the study compared overall contractor and operator trends from 1983 to 2009 related to employment, hours worked and injury rate. One unexpected finding was that the larger contractors tended to have higher injury rates than the smaller ones. The second part of the study directly addressed the role of contractors on the safety record of 10 large underground coal mines. A detailed analysis provided both injuries and estimated contractor hours worked at these mines for the period 1992-2007. Comparison between the estimated contractor injury rates and the reported operator injury rates at these mines indicated that the contractor injury rates were significantly higher at most of the operations studied. However, the industry-wide data indicates that contractor and operator injury rates have converged since 2005 and are now equivalent. Mining Engineering, 2011, Vol. 63, No. 11, pp. 73-79. Official publication of the Society for Mining, Metallurgy and Exploration, Inc.

Jan 1, 2011

By W. C. Yates

Lack of visibility from large, open-pit haulage truck cabs has become a serious safety problem. Anaconda conducted a research program to develop a low cost system to alert haulage truck operators to small vehicles present in blind areas. Several systems were developed and tested. As open-pit haulage truck size has increased, so has the size of the blind areas. Mine utility vehicles, pickup trucks, and cars are concealed within these blind areas and become safety hazards. Figure 1 shows the typical blind areas of a 136 t (150-ton) haulage truck. The areas of greatest concern are at the rear center and front right corner of the truck. In these "no visibility" areas many small vehicles have been crushed by large haulage trucks at various mine sites. In most instances, the occupants escaped the vehicle before it was destroyed. But injuries and death have occurred. In most cases, the accidents were attributed to negligence or carelessness by the small vehicle driver. The limited visibility problem still exists, though, and a solution is needed. Initial Solution The usual plane mirror on the driver's side and the convex mirror on the right front of the haulage truck allow only limited rear visibility. The typical, right side convex mirror is generally small and difficult to locate at a glance. This convex mirror also presents an image that distorts distance perception. These mirrors are of¬ten broken and immediate replacement not demanded or made. The US Bureau of Mines, in a contract with M.B. Associates, San Ramon, CA, developed an improved visibility system. It consisted of a larger, left view mirror and unique, blind area viewer. The large 230 x 690 mm (9 x 27 in.) left mirror has a small convex spot mirror near the bottom. The entire unit can be quickly replaced if broken. The large size provides a full view of driver orientation features such as the rear tire and the top of the load bed. The right 300 x 410 mm (12 x 16 in.) mirror has a convex surface and is quite rugged. The 510 mm (20 in.) spherical radius presents the operator with some distance distortion, but objects in its view are easily seen. The "blind area viewer" consists of a modified fresnel lens that allows the driver to "look around the corner." Installation of three of these lenses on the front of each haulage truck is rec¬ommended for adequate blind area coverage. This system significantly increases an operator's field of view and allows viewing of objects within about 3 m (9.8 ft of the truck. Many open-pit mines are nor mounting on smaller vehicles a long whip with a flag and lamp or both. This increases vehicle visibility to haulage truck operators. The whip is permanently attached to the mine vehicle. It can also be magnetically attached to transient vehicles. The whip system. though, is inadequate for visibility in the critical rear and right front blind areas. Alternate Solutions All of these visibility aids as¬sume an attentive driver. In addi¬tion, areas such as the rear blinc, area are not covered. Based on the inadequacy of existing visibility systems, Anaconda made a com mitment to further the truck de¬tection technology. The best ap¬proach was considered to be ar active system. It would notify the haulage truck operator that an en¬croaching vehicle is present. Sev¬eral systems were considered, in¬cluding ultrasonics and elec¬tromagnetics. For the ultrasonic system, com mercial and in-house design were looked at. Designing an( building transducers with the spe cific beam shape to match the haulage truck blind spots re¬quired a major technological breakthrough. False alarms ap¬peared difficult to prevent en¬tirely. They were caused by pass¬ing, trailing, or leading vehicles a., well as nonthreatening objects. As a result of these problems, the ul¬trasonic technique was not pur sued. An alternative, an electro

Jan 7, 1982

By Bruce H. Mason

Lightweight aggregates are classified as those minerals, natural rock materials, rock-like products, and byproducts of manufacturing processes that are used as bulk fillers in lightweight structural concrete, concrete building blocks, precast structural units, road surfacing materials, plaster aggregates, and insulating fill. Other uses include architectural wall covers, suspended ceilings, soil conditioners, and other agricultural uses (Mason, 1989). One unusual agricultural use recently reported was for bedding on a crocodile farm on the south coast of Natal. It seems that female crocodiles became upset because there was no vermiculite in which to lay their eggs due to the late arrival of a consignment of vermiculite. The vermiculite was being used as a substitute for river sand to nest crocodile eggs (Griffiths, 1989). The various lightweight aggregate materials may be classified into four groups as follows: 1. Natural Lightweight Aggregate Materials-prepared by crushing and sizing natural rock materials, such as pumice, scoria, tuff, breccia, and volcanic cinders. 2. Manufactured Structural Lightweight Aggregates-prepared by pyroprocessing shale, clay, or slate in rotary kilns or on traveling grate sintering machines. 3. Byproduct Lightweight Aggregates-prepared by crushing and sizing foamed and granulated slag, cinders, and coke breeze. This group of lightweight materials, with the exception of slag, has become less significant and will not be discussed in this chapter. Other lightweight aggregates are beginning to appear in the marketplace. Some are the result of manufacturing processes on industrial byproducts and/or waste products, such as fly ash and incinerator residue (Bigner, 1992). 4. Manufactured Insulating Ultralightweight Aggregates-pre- pared by pyroprocessing ground vermiculite, perlite, and diatomite. The application of diatomite in brick and in extruded and aggregate forms has declined in recent years (Kadey, 1983) and will not be considered in this chapter. Lightweight aggregates for structural concrete and concrete masonry units, according to the American Society for Testing and Materials (1986) consist of "aggregates of low density used to produce lightweight concrete, including: pumice, scoria, volcanic cinders, tuff and diatomite; expanded shale, clay, slate, perlite, vermiculite or slag; and end products of coal or coal combustion" (Mason, 1989). Lightweight aggregates are distinguished from other mineral aggregate materials by their lighter unit weights-1 281 to 1 602 kg/m3 or less for loosely packed lightweight aggregates-as com- pared to 2 002 kg/m3 or more for crushed stone, sand, gravel, air-cooled slag, and other common mineral aggregates. The specific gravities of these lightweight aggregates are also used to classify them for use in concrete; they range from the extremely light materials, used for insulative and non-structural concrete to expanded shale, clay, slate, and slags used for structural concrete. Vermiculite and perlite are sometimes referred to as super light- weights. Insulating concrete (non-load bearing) weighing as little as 240 kg/m3 can be made with these aggregates. Natural aggregates such as pumice, pumicite, and scoria are normally made into concrete weighing about 400 to 480 kg/m3. Expanded shale, clay, and slate produced in a rotary kiln make structural concrete ranging from 1 201 to 1 842 kg/m3. Expanded shale and clay produced by sintering make concrete that ranges from 1 442 to 1 922 kg/m3. Air-cooled slag produces concrete ranging from 2 162 to 2 403 kg/m3. The low density lightweight aggregates are used primarily for insulating purposes. They have relatively low compressive strength. The middle density aggregates are used for insulation and for fill. Those at the upper end develop excellent compressive strength and are used in many structural applications (Anon., 1971). In recent years, the production of lightweight aggregates in the United States for all uses (including insulation and construction materials) has averaged about 19 Mtpy (Table 1). The production and consumption of lightweight aggregate is closely tied to the fortunes of the construction industry and the need to construct energy efficient buildings. Recent years have seen the production of lightweight aggregate approach the levels of the early 1970s. The period of 1979 to 1981 was a low point in production levels. The low levels of production were caused by significantly higher plant energy costs due to the large amounts of fuel and energy used in the production of most types of lightweight aggregate. Lower levels of construction activity also affect production levels. This chapter focuses on the use of natural lightweight aggregates and manufactured insulating ultralightweight aggregates, and on both the production and use of manufactured structural light- weight aggregates. Some additional comments are made on byproduct materials. Separate commodity chapters on vermiculite, perlite, pumice, and volcanic cinders are elsewhere in the volume. Discussion of the commodities covered elsewhere in the book will be limited to observations on their utilization and relation to other lightweight aggregate materials.

Jan 1, 1994

By S. Yap, F. J. Sotillo, L. P. Irwin, F. M. Utsey

Slimes, especially clays, are detrimental to several processes in the Mining Industry. The efficiency of classification, clarification, gravity separation, and flotation decreases significantly in the presence of slimes and clays. This problem is particularly critical in the Phosphate and Sulfide Industries. To reduce the effect of slimes in mineral processing, several desliming techniques and chemical additives are used, such as sodium silicate, sodium carbonate, sulfuric acid, tripolyphosphate, hexameta phosphate, etc. Lately, the Mining Chemical industry has shift to more “Specifically Developed” reagents that offer the most efficient and cost effective performance, mainly using organic polymers. For this purpose, the Mining Chemical Industry needs to understand the crystal chemistry of minerals, the chemistry of the aqueous media, the interactions in solids-aqueous-gas interfaces, the rheology of the system, and the plant operation conditions and parameters. This paper describes the use of surface chemistry fundamentals on the design of an organic polymer capable of modifying the rheology of clayish slurries of a phosphate ore. The change in the rheological characteristics of the clayish phosphate slurries allow fine ore particles to settle faster by reducing the slurry viscosity. Thus, abetter separation of the ore from the slimes is possible using gravitational or centrifugal forces. As examples of the application of this reagent, industrial and pilot plant tests on desliming using tanks and hydrocyclones are presented. These tests showed the reduction of 32%-36% in ore losses for different phosphate ores during desliming operations, and the increase of cyclones desliming efficiency to 80%. Tests were also carried out to improve the rejection of unwanted iron bearing slimes in phosphate feed. These tests demonstrated that it is possible to reduce by 0.25%-1.23% Fe2O3content in the flotation feed product. As a result, significant economical benefits are observed with the use of this new technology without any adverse effect on down stream operations, such as clay settling or phosphate flotation.

Jan 1, 2003

By E. B. Graves

I have been asked to talk to you this morning about phosphate marketing and distribution. In discussing this I will attempt to answer such questions as: What is phosphate? Where do we get it? What form is it and how do we sell it? How do we distribute it? How is it applied? And last, but not least, What about the future? To start with, phosphate is one of the three primary plant nutrients. It is the element essential for root structure of plants. Plants, like humans, need a balanced diet. Thus, the amount of phosphate required by individual plants is, in part, related to how much of the other nutrients are used. Virtually all soils contain a certain amount of available phosphates. Back at the turn of the century the most common source of additional plant nutrient, including phosphates, was from cattle manure. The use of chemical fertilizers is something that has grown significantly during the last half century, and in particular, the last 20 years.

Jan 1, 1977

By William Mayrsohn

IMTRODUCTION The marketing aspects of a new precious metals property is often not considered until the mine actually begins production. At this point in time it is often too late or too expensive to change the mine's final product and not enough time to do an effective marketing program. MINE PRODUCT The rule for determining the mine's final product: The higher the gold and silver content, the greater return of metal at the lowest post-mining cost. . Dore Bullion: Most advantageous Advantages: - Highest return of metal. - Lowest refining cost per ounce of gold and silver. - Very compact and easy to ship in small quantities. - Easy to assay. - Assays between mine and refiner are comparable. - Melt losses are very small at the refiner. - Outturn of gold and silver 20-30 days for quick cash flow. - Gold/silver refiners can return or purchase metal soon after arrival at a nominal financing cost.

Jan 1, 1987

By Liu Cheng-si

Basing on a brief assessment of the conventional theory of ventilating air distribution, its methods of calculation and practical application, this paper makes an approach to the controllability of different aircourses of a ventilation network and further points out that it is possible for the positions of control to extent into the natural distribution subnetwork of the ventilation network, which was been long considered as a restricted zone. This important discovery makes the regulation of the ventilation system more flexible and diversified, thus attaining quantitative distribution of ventilating air as well as a cost benefit. Because it has been impossible to solve the problem mentioned above by conventional theory and its relevant methods of calculation, the author, based on applying graph theory on the structure, characteristics, and requirements of controllability of the ventilation network, presents a new controllable subgraph concept and the means for determining the rational quantity for control devices of the ventilation network. The solution of all the control alternatives and methods of obtaining all the parameters for the solution of various alternatives have been derived. The economic benefit and the optional positions of the control devices have also been approached. Specific calculation examples are a1 so included in this paper. Along with the conventional theory and its methods, it can be seen that the new theory presented makes a great change in the control aspects of the ventilation network, with the number of possible alternatives increasing in an astonishing manner. Among the alternatives, some may be safer, more economical or technologically superior than those obtained from conventional theory. Thus, the new theory may provide an immense improvement in the choice of a ventilation system.

Jan 1, 1987

By G. Paul Anderson

Personnel at Utah Copper Division's Bingham Canyon Mine use current computing technology to compile pertinent production statistics and mining plans. Within hours after the day's work has been completed, concise reports summarizing the previous day's production statistics, actual production vs. budget statistics, the location of shovels relevant to the mining plan, the performance of equipment, equipment next scheduled for maintenance, etc. are available at the terminals located throughout the mine. Also, engineering personnel us e computerized systems, directly from their offices, to assist them in the timely development of mining plans. Timely and concise reporting and planning capabilities such as these assist mine personnel in their efforts to review mining progress and equipment performance, and as such they are in a better position to detect adverse trends early and to seek appropriate resources or make changes in plans or practices.

Jan 1, 1977

By W. R. Reed, G. J. Joy, B. Kendall, A. Bailey

"Testing of the roof bolter canopy air curtain (CAC) designed by the U.S. National Institute for Occupational Safety and Health (NIOSH) has gone through many iterations, demonstrating successful dust control performance under controlled laboratory conditions. J.H. Fletcher & Co., an original equipment manufacturer of mining equipment, further developed the concept by incorporating it into the design of its roof bolting machines. In the present work, laboratory testing was conducted, showing dust control efficiencies ranging from 17.2 to 24.5 percent. Subsequent computational fluid dynamics (CFD) analysis revealed limitations in the design, and a potential improvement was analyzed and recommended. As a result, a new CAC design is being developed, incorporating the results of the testing and CFD analysis.IntroductionExposure to respirable coal mine dust can cause coal workers’ pneumo-coniosis (CWP), also known as black lung. If silica is present in the dust, the miner may develop silicosis in addition to CWP. CWP and silicosis are occupational respiratory diseases that are ultimately fatal and have no cure. The only method of prevention is to eliminate exposure to respirable coal mine dust and crystalline silica, or quartz. The occupational exposure limit on a Mining Research Establishment (MRE) basis for respirable coal mine dust had been 2 mg/m3 during each shift that a miner is exposed in the active workings of the mine or in mine facilities. Under recently enacted legislation, this standard was changed in August 2016 to 1.5 mg/m3 for a full working shift (The Office of the Federal Register, 30 CFR 70.100, 2015). When respirable quartz is present, the mine must maintain its average concentration at or below 0.1 mg/m3. If the mine exceeds the 0.1 mg/m3 respirable quartz dust concentration, then the applicable respirable dust standard is reduced, calculated as 10 divided by the percentage of quartz present (The Office of the Federal Register, 30 CFR 70.101, 2015).The sources of exposure to respirable coal mine dust for roof bolting occupations include infrequent maintenance and cleaning of the vacuum dust collection system and operating the bolter downwind — in the return air — of the continuous miner (Good-man and Organiscak, 2003). Recent studies have demonstrated that vacu-um dust collection systems are effective in capturing bolter-generated dust if maintained and operated correctly and if proper face ventilation techniques are used. However, most expo-sure to respirable coal mine dust for a roof bolter occurs when the roof bolter machine is operated downwind of the continuous miner (Potts, Reed and Colinet, 2011; Colinet, Reed and Potts, 2013). Because of this higher exposure downwind of the continuous miner, the roof bolter is often limited to working downwind of the miner only once during a production shift."

Jan 1, 2017

By Donald W. Gentry

Mine valuation is a multifaceted, interdisciplinary process by which the economic viability of an old, existing, or new mining property or venture is determined. The problems associated with arriving at a representative and accurate value for a mining property are complex and numerous, and the procedures utilized in determining these values vary from simple, back-of-envelope calculations to sophisticated mathematical manipulations requiring computer modeling and analysis. Regardless of the complexity or the degree of sophistication associated with any particular project, the evaluation process must ultimately provide management with two basic types of information. First, the evaluation process should indicate whether or not the mining project is economically viable after careful consideration of all engineering, environmental, geologic, and other variables pertaining to the project. Second, the evaluation process should provide management in- formation on the relative attractiveness of the project when compared to other alternatives. In some cases, it may be extremely difficult to supply this information for a project directly. Nonetheless, the evaluation process should and must present all information necessary in a format which can be incorporated into the decision-making process as expeditiously as possible.

Jan 1, 1979

By Hsu-Hui Hsing

In several previous studies from this laboratory (1-4) the autophobicity concept of Zisman and co-workers (5, 6) has been extended to gas phase adsorption processes. Low molecular weight alcohols adsorb on silica or alumina to yield novel isotherms in that monolayer adsorption occurs at low relative pressures indicative of strong bonding, but subsequently multilayer adsorption is quite sparse and diminishes with molecular weight of the alcohol. Such isotherms fit no standard classification scheme, however, in the vacinity of monolayer coverage alcohol isotherms give an excellent fit to the Langmuir or B. E. T. , Type I model (7). Monolayer adsorption is relatively irreversible and it is thus possible to prepare these chemisorbed layers and perform subsequent adsorption studies thereon. All indications are that the adsorptive properties on such films is radically different from that on the underlying alumina (4, 8) and in one study finite contact angles for hydrocarbon fluids were observed. One perennial conceptual difficulty is that there is no observed upper bound to the adsorption isotherm which would be necessary for autophobic adsorption to occur. The cause for this has been studied, and it is currently believed that adsorption is complicated by reversible capillary condensation at contact points between powder particles. The evidence for this is that large particle powders give less "apparent" adsorption at high relative pressures and in one very tedious study adsorption on planar sheets, oxidized aluminum displayed similar reduced uptake at high relative pressures when compared with high specific surface area powders (3).

Jan 1, 1974

By McDonald E. Wrenn, Narayani P. Singh, Victor E. Archer, Ceno Saccomanno

Fourteen uranium miners' lungs from Colorado plateau were collected at autopsy and the concentrations of 238U, 234U and 230Th were determined by radiochemical procedures utilizing solvent extraction - alpha spectrometric techniques. The uranium and thorium isotopes are in near equilibrium with average concentrations of 238U, 234U and 230Th being 89.3, 95.2 and 91.1 pCi/kg respectively. The combined average radiation dose rate to lung from these three isotopes is about 24.2 mrad/year at death excluding the unmeasured contribution from the 226Ra and daughters. The average concentration of 230Th is about 65 times higher than the mean concentration of 230Th in lungs of non-miners dying at comparable ages from the same region.

Jan 1, 1981

By Wendell H. Wiser

A comparison is presented of coal pyrolysis at temp¬eratures ranging from 4090 to 497°C and thermal dissolution of coal in tetralin at temperatures ranging from 350° to 450,°C, both utilizing a Utah high-volatile bituminous coal. The initial coal pyrolysis reactions are second order with an enthalpy of activation of 35.6 kcal per mole. The fraction of total product yield produced under second order conditions ranges from 67% at 409°C to 96% at 497°C. The process then gradually deteriorates to a first order reaction in the later stages with enthalpy of activation of 4.1 kcal, per mole. The initial reactions of solution of coal in tetralin are second order with an enthalpy of activation of 28.8 kcal per mole. The fraction of total product produced under second order conditions ranges from 63% at 350°C' to 94% at 450°C. The dissolution process then gradually changes to first order in the later stages with enthalpy of activation of 15.6 kcal per mole. A model is presented which relates the two processes and explains, the significance of the above similarities.

Jan 1, 1967

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