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By Gülhan Özbayoglu, Yusuf Ziya Akgök

The effect of cooling rate on the flotation behaviour of copper slags of flash smelter plant in Samsun was investigated. Fresh molten slag was solidified in laboratory scale in three different ways. All the samples were characterized by chemical and mineralogical analyses. The chemical analyses showed that samples prepared from fresh slag had 0.9 to 1 % Cu with 40 % Fe and 30 to 32 % SO2. Old pit slag samples contained between 1 to 3% copper. Microphotographs showed that rapidly cooled slags showed fine size distributions, e.g. the copper grains in granulated slag had sizes in 1-2 microns. On the other hand, the size of copper grains in slowly cooled slags increased above 40 microns. Flotation tests carried out by using potassium amyl xanthate and Flotanol-C showed that slowly cooled slag reduced the copper losses in the tailing and improved the grade of concentrate. Under the light of laboratory investigation, the pit dimensions of Samsun Plant have been modified which resulted in a pronounced improvement of the grade and recovery of concentrate produced at Samsun slag flotation circuit.

Jan 1, 1995

By Staff

GENERAL DESCRIPTION The Lucky Friday mine is located in Mullan, Sho-¬shone County, Idaho. The mining method is horizontal slice cut-and-fill (with timbering for support or un¬timbered) using hydraulic sand. Cemented sand fill at a 1:17 ratio is used in sill pours and at a 1:7 ratio for the final 152 mm (6 in.) capping in successive stope floor pours. Annual production with 100% cut-and-fill mining is 167 829 t (185,000 st). The average depth of mining is 1296 m (4250 ft) and the average travel time to the stope is 45 min. GENERAL ORE BODY REQUIREMENTS AND LIMITATIONS Size The ore body is 396 to 488 m (1300 to 1600 ft) long on strike, 1421 m (4660 ft) on dip, with an average width of 2.3 m (7.5 ft). Dip varies from vertical to1.2 rad (70°) Ground Conditions, Ore Value, and Production Requirements The ore body contains quite strong argentiferous galena and quartz. The hanging wall and footwall are strongly sheared and fractured. Ore value is $211/t ($192/st).

Jan 1, 1982

In the early days of minimal environmental protection awareness and unreasoning economy development pressures, little attention was paid to growing environmental concerns in Fuxin colliery, especially the air pollution problem due to the long term mining activities. In order to determine air quality concentration levels, a new technique for synthetic assessment of ambient air quality by using the extension of matter-element method is proposed in this paper. The air pollutants data such as Sulphur Dioxide (SO2), Carbon Monoxide (CO), Nitrogen Oxides (NOx), Total Suspended Particulates (TSP), Particulate Matter (PM10), and dustfall collected at four different air quality monitoring stations located in four districts of Fuxin colliery is used. The results obtained indicate that TSP, PM10, dustfall and SO2 are the predominant pollutants. Other pollutants such as CO and NOx are also detected in Fuxin colliery. The air pollution comes mainly from industrial emissions, mining activities and the abandoned gangue stockpiles. Compared to those applied to other mathematical assessment methods, it is demonstrated that the extension of matter-element model is quite appropriate for air quality assessment.

Jan 1, 2006

By Thomas F. Stinson

Energy-producing states see severance taxes as attractive sources of increased revenues for otherwise tight budgets. Consumers in energy-poor states, however, protest that current rates are excessive and have moved to obtain a reduction. The US Supreme Court heard two cases questioning such taxes during its 1981 term, and Congress, in each of its last two sessions, has seriously considered measures placing a ceiling on severance tax rates. Although discussions usually focus on coal severance taxes levied by Montana and Wyoming, ramifications of changes in national policy are much larger, potentially affecting mineral taxes in all states. Severance taxes yield substantial revenues in some states, as illustrated in the accompanying table. In fiscal 1980, Texas collected more than $1.5 billion from such taxes, while Louisiana, Alaska, and Oklahoma collected $525 million, $507 million, and $436 million, respectively. Oil and natural gas production were the major items taxed. While the table shows only the 10 states with the largest severance tax collections, a total of 17 states had severance tax receipts exceeding $10 million in 1980. The enormous increases in severance tax revenue between 1970 and 1980 can be seen from the table by comparing columns A and B. For the 10 states shown, revenues increased from $650 million to $3.8 billion during that period, due to a combination of higher prices, increased production, and new or increased taxes. In most states, increases in prices and production were more evident than higher tax rates. Although the revenue increase is impressive, it understates the extent of changes occurring during the past decade. Since tax collections are shown for fiscal 1980, the full impact of the decontrol of domestic oil prices is not evident. Also, taxes on natural gas reflect controlled prices. When full de-control of natural gas occurs, significantly higher revenues can be expected in gas-producing states, even if tax rates, production, and world prices remain constant. These increases in severance tax revenues, coupled with further increases expected to accompany natural gas decontrol, have produced fears that a substantial transfer of income is taking place from residents of energy-poor states to those living in energy-rich areas. Others worry that increased severance tax revenues will be used to substitute for a substantial portion of state taxes that would have otherwise been collected from firms and individuals. The resulting improvements in tax climate, it is thought, may encourage firms and workers to migrate to energy-producing states. While these issues are often portrayed as pitting energy have-nots against the haves, such is not entirely the case. Much of the original impetus for limits on coal taxes came from Texas residents, the state collecting the most severance tax revenue. One way of gaining perspective on these concerns is by examining severance taxes per capita and as a percent of state tax collections (see columns C and D in the table). When this is done, Alaska, where 1980 taxes on oil and gas production totaled more than $1300 per capita (and 35% of all state tax collections), stands out as a special case. There, the state was able to eliminate some individual taxes, place revenues in a permanent trust fund, and consider offering a rebate of some previous income

Jan 4, 1982

By J. A. Finch, B. J. Huls

Accurate level detection is required to make full use of level in optimizing control strategies for flotation columns. Techniques based on pressure and electrical conductivity are compared. Pressure and conductivity profiles give good agreement on level. Level calculated from single and multiple pressure values became more accurate using, in order, one, two and three sensor locations. The level estimate remained in error, however, because, unlike the collection zone, froth zone bulk density varies with height. A conductivity probe continually updating the conductance profile is a practical method of obtaining an accurate level.

Jan 1, 1990

By S. D. Thompson, L. Adler

This study reviews and analyzes the empirical methods available for designing the capacities of coal mine gathering belts. The analyses lead to recommendations concerning the application and implementation of each empirical method. Operations research techniques, mainly simulation models, are also briefly mentioned, and a few recommendations are made concerning their selection and application. The objective of the study is to provide a reliable basis for the practicing engineer to properly select, apply, and implement a capacity design method.

Jan 1, 1988

By LeEtta M. Shaffner, John R. Marks

INTRODUCTION In the last twelve years, underground stoping methods at the Homestake Gold Mine have evolved from open cut-and-fill with jacklegs, cribbed raises and electric slushers to ramp-based mechanized cut-and-fill (MCF) and vertical crater retreat (VCR) with dieselpowered loaders, trucks and drill jumbos. The evolution was swift. Unfortunately, ventilation practices have had trouble keeping pace. Stope ventilation is still too dependent on auxiliary fans and coolers. A single large MCF stope might contain up to eight headings, each of which requires significant ventilation resources when a diesel loader is present. Air is shortcircuited all too frequently through mined-out VCR panels. These factors and the recent rapid decent of the center of mining prompted a study to improve ventilation practices and to more accurately project future requirements. BACKGROUND In 1992, the underground portion of the Homestake Gold Mine produced 8336 kg of gold from 1407 ktons of ore (268,000 oz from 1,551,000 st). The ore is hosted in low to medium grade meta-sediments. Stoping took place from 420 to 2347 m below the surface (1400 to 7700-ft levels). The weighted center of mining was 1662 m deep (5450-ft level) in 1990 and is projected to be 1890 m (6200-ft) in 1993. The deepest level is 2440 m (8000-ft) where the virgin rock temperature (VRT) is 56.1°C (133F). The mine is ventilated by 504 m3/s (1,069,000 cfm) measured at mid-exhaust-circuit density. The air-conditioning system includes an 8.1 MWR (2300 ton) controlled recirculation plant, a 2.0 MWR (580 ton) chilled water plant, a 1.0 MWR (290 ton) exploration drift refrigeration plant, 28 spot-coolers totaling 3.4 MWR (960 tons) and 35 spray coolers totaling 1.5 MWR (420 tons). The mine employs 117 diesel units with a total nameplate rating of 7961 kW (10,672 hp). These units include twenty-four 1.5m3 (2-yd) loaders, twenty-six 2.7m3 (3.5-yd) loaders, fourteen 3.8m3 (5-yd) and two 7.6m3 (10-yd) trucks, and assorted utility vehicles and drill jumbos. THE STUDY In April 1991, the University of Nevada-Reno (Mackay School of Mines) and the South Dakota School of Mines and Technology cooperated with Homestake on an MCF study. Mackay instrumented a stope with thermocouples, air velocity meters and hygrometers (Duckworth, 1992). South Dakota Tech conducted a finite-elements computer analysis of a back-filled MCF stope with/without light-weight shotcrete insulation on the sidewalls and back (Chellam, 1992). Homestake conducted an empirical analysis of deep-level MCF stoping. This paper describes the Homestake study. Twenty-three of the forty MCF stopes deeper than 1800 m were surveyed at least once during the last quarter of 1992. The stopes not included were being cable-bolted or back-filled. Figure 1 shows the complexity of one of the ramp-based stoping areas included in the survey. This particular stope has six separate production headings. A baseline wallrock heat load was derived for each stope or heading from psychrometric calculations. Broken ore, waste rock fill and fissure water were noted when present and the effects included in the baseline heat load. Other heat sources often mentioned in the literature such as metabolic heat from workers, heat from explosives and small electric loads were neglected. Fan heat was considered part of the ramp & crosscut heat load and thus not included in the study. Diesel heat was addressed separately. RESULTS Survey results, plotted as the heat flux against VRT, are shown in Figure 2. The equation for the regression line is: W/m2 = 2.1236*VRT - 75.405 The 0.31 correlation coefficient is poor which implies that the results should be used cautiously. Previous experience strongly suggests that differences in productivity are most likely responsible for the scatter in data points. A rapidly advancing stope will have a

Jan 1, 1993

By T. E. Durney

In the Fall of 1987 The Wellmore Coal division of The United Company installed a fines separation circuit in its #20 plant near Big Rock, Va. The addition of the fines circuit included a bank of classifying cyclones and two flotation units; one a conventional 4 cell, 34 m3 Wemco cell, the other an 2.4 meter diameter by 7.6 meter tall, 28.3 m3 column flotation cell. The new fine coal separation circuit is depicted in Figure 1. The column flotation cell is manufactured by the Deister Concentrator Company, Inc., under the trade name Flotaire. The Deister Flotaire column cell utilizes a counter current flow arrangement and a different means of generating air bubbles than that of conventional mechanical flotation cells found in coal processing plants. Other features include diffusers for additional air supply and a froth washer. This cell is one of the few commercial scale column cells processing coal.

Jan 1, 1990

By M. J. Howes, C. A. Nixon

INTRODUCTION A safe heat stress control strategy for an underground mine has three elements: Application of an environmental measure which reflects physiological strain with sufficient accuracy for the range of conditions encountered underground. Acceptance of a functional relationship between the environ- mental measure and human performance which is used to optimise the environmental conditions achievable with either ventilation or ventilation and refrigeration. A management control strategy based on the environmental measure which is designed to ensure that work in environments where excessive physiological strain may occur is prevented and corrective action is initiated. The environmental measure that reflects physiological strain is the link between the three elements and, since the turn of the century, the discussion of the merits of various indices has been prolific. One problem in selecting a suitable measure or index is the ease with which it can be physically obtained relative to accurately reflecting the physiological strain. For example, wet bulb temperature is simple to measure and, for a particular mining sys- tem, it may adequately represent physiological strain, however, it would not necessarily provide the same relatively safe measure in a different mining system. The acceptance of a measure which can be universally applied has been confounded by both development and predisposition. That is not to say that there is only one "correct" measure and all others are unsuitable. It is self evident that if the application of a particular index has resulted in adequate control, then that mea- sure is correct for that situation. However, an understanding of the limitations is necessary to ensure that adequate control is maintained as mining conditions change. Almost 100 years after the question of heat stress in mines started to be dealt with in a collective manner, an analysis of the available information is leading towards a general strategy to control this problem. In the paper, the developments in heat stress assessment are briefly examined and followed since the earliest published observations on the effect of heat in mines (Haldane, 1905), efforts to determine a relationship between an environmental measure and human performance are reviewed and summarised and the benefits of control strategies such as acclimatisation and shortened shifts are discussed as they relate to Mount Isa Mines. The results of testing the prototype air cooling power instrument are discussed and a heat stress control strategy outlined. HEAT STRESS AND AIR COOLING POWER The operation of the human engine is analogous to other engines where the conversion of chemical energy from the oxidation of fuel to useful mechanical energy is not 100% efficient. In a diesel engine it is about 33% and in a human engine less than 20% resulting in at least five times as much heat produced by the meta- bolic process as useful work done. Metabolic energy production is related to the rate at which oxygen is consumed and is about 340 W for each litre of oxygen per minute. Using measured oxygen consumption and an average body surface area of 2.0 m2, the approximate metabolic energy production associated with different mining tasks is (Morrison et al. 1968):- • Rest, 50 W/m2 • Light work, 75 to 125 W/m2 (machine, LHD or drill jumbo operators) • Medium work, 125 to 175 W/m2 (airleg drilling, light construction work) • Hard work, 175 to 275 W/m2 (barring down, building bulkheads and timbering) • Very hard work, over 275 W/m2 (shovelling rock) Heat balance is achieved when the rate of producing heat (the metabolic heat production rate) is equal to the rate at which the body can reject heat mainly through radiation, convection and evaporation. Heat exchange between the lungs and the air in- haled and exhaled is normally less than 5% of the total and there- fore usually ignored. Any heat not rejected to the surroundings will cause an increase in body core temperature. Since heat stress is related to the balance between the body and the surrounding thermal environment, the main parameters required to be known when determining acceptable conditions are those associated with the heat production and transfer mechanisms. These can be summarised as follows: Metabolic heat production rates (M - W) Skin surface area (A3) (and effects of clothing) Dry bulb temperature (t[ ]) Radiant temperature (t[ ]) Air velocity (V) Air pressure (P) Air vapour pressure (e [ ]) The rate of heat transfer to or from the environment depends on the equilibrium skin temperature t, and the sweat rate S,. These in turn depend on the response of the body to the imposed heat stress and the effect of thermoregulation (Stewart, 1981). Thermoregulation The body contains temperature sensitive structures which send impulses to the brain at a rate depending on the temperature. Both hot and cold signals can be differentiated and the thermoregulatory response ahivated according to which signal pre- dominates. If "cold" signals are dominant, body heat loss is re-

Jan 1, 1997

By D. T. McMurray

INTRODUCTION Shabanie mine, situated some 180 km east of Bula¬wayo, has been a producer of chrysotile asbestos for more than 50 years. The ore bodies occur in serpentinized dunite, which overlies talc-carbonate schist. A zone of relatively competent rock of varying thickness occurs between the schist and the ore bodies, which are gen¬erally less competent. The hanging wall of the ore bodies is economic, and the hanging-wall serpentine carries a variable subeconomic amount of fiber. It is important to note that, in general, the ore body competence is less than that of the foot and hanging-wall formations. Historical After surface operations ceased, cut-and-fill stoping was used to win ore from underground; this was success¬ful until the increasingly stoped-out area caused insta¬bility in the stope pillars and back. Consequently, dur¬ing the early 1950s, a gradual change to cave-mining methods was made, the ore being won by hand lashing in drawpoints, situated in the basement of the stope blocks, and passed through orepasses under gravity to the haulage level some 13 m below. About this time, interest was focused on the sub¬level caving method in use in Swedish iron ore mines: it was felt that it might be applied economically to the Shabanie ore bodies. Accordingly, in 1958, an experi¬mental stope block was laid out in which sublevel inter¬vals and extraction tunnel spacing were 9 m. The tun¬nels (ring drilling drives) were oriented on strike-in contrast to the Swedish system, in which crosscuts that retreat from hanging to footwall are used. The advantages of the method were quickly appre¬ciated by the operating personnel and, despite the in¬evitable teething troubles pertaining to the introduction of any new mining method, it was not long before sub¬level caving was providing a high proportion of the mill feed. The disadvantages also became apparent at an early stage, however, and, from that time to the present, continuing modifications have been made to mining lay¬outs in an effort to improve ore recovery. GENERAL DESCRIPTION OF METHOD The mine is served by a vertical hoisting shaft, in which two skips, a man cage and a service cage, provide adequate capacity for production requirements. The rock hoist is a Ward Leonard control hoist, in which two electric motors drive a common gearbox. The man winder is driven by an a-c motor. Several auxiliary shafts provide secondary egress and intake and return ventilation. Main haulage levels are above (Fig. I a and b). Blasthole fan patterns are drilled by drifters of 100 mm bore, drilling 41-mm holes; when a sufficient strike length has been drilled, a slot is cut in the upper¬most sublevel and the rings are broken into the slot. Initially, a limited tonnage is drawn, since it is essential to ensure that the hanging wall caves behind the retreat¬ing stope face. Once this has been established, maxi¬mum tonnage can be drawn, as described later in this chapter, under the heading "Draw Control." The broken rock is loaded by 0.14 and 0.20-m3 load¬ers into cocopans (rocker-dumping type of tipping truck), which are hand trammed to orepasses, discharg¬ing on the haulage where 11-t electric trolley locomo¬tives haul 3.95-m3 Granby cars to the main shaft bins. As is evident from Fig. 1, the layout is simple, the block is brought rapidly into production, there is a high degree of selectivity and flexibility, and the result is a low-cost high-productivity mining method. DEVELOPMENT Main haulages are developed at 3.2 x 3.2 m, and once the service winze connections have been completed the development of the sublevels is undertaken. The footwall drives are cut first, to obtain access to the block. These ends are of the standard section, 2.4 x 2.8 m, and from them crosscuts at intervals of 70 m are driven through the ore body to the hanging wall. These crosscuts are used to supplement the geo¬logical information previously obtained from diamond core drilling, and they provide additional and more de¬tailed data on fiber percentages and lengths, structural features, and other relevant criteria which are used to build up the geological assessment of the area and to classify it in terms of the geomechanics rock classification (Laubscher and Taylor, 1977). The crosscuts also allow the necessary orepasses to be sited conveniently so that tramming distances from the loading points are not excessive. Development Drilling Once the skeleton development has been completed, the extraction headings are developed at 2.4 x 2.4 m as shown in Fig. 1. Standard development practice is to use crews of a machine operator and his helper, equipped with air-leg mounted jackhammers, to drill rounds of 1.8 m with integral tungsten carbide tipped drill steel. The round drilled is a normal drag round, as shown in Fig. 2, but considerable attention is paid to the drilling of the perimeter holes to use effectively the

Jan 1, 1982

By Pinar Eksert, Hakan Akcin

Investigations show that injuries and fatalities in mining workplaces in developing countries are increasing. In Turkey, the number of workers killed in occupational accidents in the Zonguldak Hard Coal production region per 100,000 tons of coal production is 2.83 in the private sector and 2.03 in the public sector. For this reason, it is important to conduct risk analyses in terms of occupational health and safety and to implement measures quickly. Risks are evaluated with reactive and proactive approaches. Because hazards and events are often unpredictable in high-risk areas such as coal mining, it is not practical or meaningful to plan proactively in advance for every possible situation underground, especially psychosocial risks. However, it is important to develop protective strategies and measures for unexpected events or to take a reactive approach to prevent future incidents or accidents and to identify psychosocial risks. Therefore, reactive risk assessments based on the tactics and strategies of criminology can be conducted and spatiotemporal geographic information system (GIS) techniques can be utilized, enabling managers in mining workplaces to correct assessments.

Oct 1, 2024

By Kent G. Homewood

The well-being of any company is directly related to the well-being of its employees and to the effectiveness with which the personnel resource is managed. In an era when personnel management has steadily become more complex, there is an increased awareness of employee information systems at all levels of management due to: (1) regulations enacted by federal, state, and local government agencies; (2) technological advances within the mining industry which have resulted in the requirement for highly skilled personnel; (3) increasing concern for the confidentiality of employee information; and (4) management's need for information for planning purposes to control costs and for early recognition of trends and potential problems. In the past it was sufficient to maintain records manually. Today computers are necessary to provide information on short notice and effectively manipulate large volumes of' data. This discussion will describe the following aspects of employee information systems: (1) collection and maintenance of information, and (2) applications which include employee health, salary administration, management re- sources, and labor negotiations.

Jan 1, 1979

On longwall coal faces in some Japanese coal mines more than half of the air coming from the intake gate road flows into the caved goaf and the air heated by the hot waste rocks in the goaf comes out through the latter half of the face. This still constitutes a major heat problem in spite of the introduction of gate and face air coolers. Therefore, in order to establish effective measures to improve the environ- mental conditions, it is essential to obtain information pertaining to the air flow pattern on the face as affected by the goaf conditions and the air flow regulating measures taken at the intake side of the face. Experiments for this purpose were carried out using a coal face model. The model was reduced to a scale of 1110th of the real face measuring 100 m long and 2.2 m high, equipped with self-advancing supports. The model design was also conceived to accomodate eventual modifications of the space of the caved goaf as imposed by the actual conditions.

Jan 1, 1980

By J. A. McKeown, B. M. Sanders, A. Dadgar, R. H. Sergent

This paper describes the leaching of gold with Geobrom® 3400 from a very rich (6.2 kg/tonne) black sand concentrate and its subsequent recovery by ion exchange resins and solvent extraction. The dissolution of gold from black sand ranged from 94 to 96%. Gold loadings and recoveries of nearly 100% were achieved by both ion exchange and solvent extraction methods. The kinetics and equilibrium of loading gold onto ion exchange resins and its elution from the resin were studied. The commercial ion exchange resins PAZ®- 4, DOVEX®- 21K, and Amberlite® XAD- 7, and Great Lakes Chemical experimental GLR-30 were evaluated in this work. Diethylene glycol dibutyl ether was used in all the solvent extraction work for gold recovery from Geobrom leach solution. The consumption of Geobrom was about 130 kg per tonne of the concentrate processed. Therefore, the cost of lixiviant to extract 3.11 x l0-2 kg of gold from the black sand was only about $1.00. Based on the electrochemical regeneration of bromine, the economics of bromine process vs. cyanidation were investigated.

Jan 1, 1990

By Keith Whiting

The Little Boulder Creek molybdenum deposit is in central Idaho, in the White Cloud Range about 3.2 km (2 miles) northeast of Castle Peak, the highest peak in the range. The elevation of the deposit is about 2591 m (8500 ft). The deposit is accessible only by helicopter or by a 12.9-km (8-mile) trail from the county road along the East Fork of the Salmon River. The nearest towns are Clayton [25.7 km (16 miles) northeast], Stanley [33.8 km (21 miles) northwest], and Ketchum [45 km (28 miles) south-southeast]. The principal known deposit at Little Boulder Creek is called the "North Zone." In this zone, the molybdenite occurs both in stock- work veinlets and disseminated through metamorphosed quartzite of Pennsylvanian age. Pyrite is ubiquitous, averaging perhaps 0.05%. Scheelite and/or powellite are present in trace amounts. An intrusive quartz monzonite stock, probably of Cretaceous age, bounds the deposit on the west. A steep fault which drops Tertiary age Challis volcanics into contact with the mineralization limits the deposit on the east.

Jan 1, 1991

By Norm Greenwald

The Environmental Protection Agency ("EPA") has been attempting to develop a federal regulatory program for mine waste under Subtitle D of the Resource Conservation and Recovery Act since 1986. Recent regulatory and legislative events are now bringing this goal closer to reality. This paper discusses the mining industry's perspective on a number of the issues currently being addressed at EPA's Policy Dialogue Committee and in Congressionally-sponsored negotiating sessions.

Jan 1, 1992

By D. F. Doerr, E. Blalock, D. R. Bush, K. D. Cohen

"BACKGROUND The design, development, fabrication, and test of a cryogenic supply for a refuge alternative is part of a larger effort funded by the National Institute for Occupational Safety and Health and managed through a Space Act Agreement with the National Aeronautics and Space Administration at the Kennedy Space Center, FL to create cryogenically based life support equipment responsive to the needs of miners as required by the Miner Act of 2008. This work is done by a joint contractor/NASA team. In particular, the Cryogenic Refuge Alternative Supply System (CryoRASS) serves to provide a respirable air source to miners confined for 96 hours in a mine refuge alternative. This system stores liquid air in a zero-loss cryogenic reservoir (Dewar) until an emergency requires use. The system does not require electric power when in use by miners. Because of the very cold nature of the liquid air, considerable heat stress relief and reduction of humidity is provided in addition to the required replenishment of oxygen. Moderate dilution of CO2 also occurs.INTRODUCTION The design of this new cryogenic refuge alternative supply system (CryoRASS) uses NASA/Kennedy Space Center technology as a development baseline. The design stores cryogenic (liquid) air that is warmed in an air handler box and the resulting gaseous air is introduced to the chamber that not only causes air circulation, but relies upon environmental and human heat to expand the liquid air to a gaseous state. Therefore, the primary benefits of the liquid air source, besides atmosphere maintenance (oxygen), is refuge cooling and dehumidification. This results in reduction of human heat stress and this occurs without the need for electrical power in the refuge chamber. This reduction is a major factor in ""apparent heat"" and the human perception of comfort. Another benefit with introduction of ""air"" vs only ""oxygen"" is the dilution of carbon dioxide. The volume of new air will displace existing refuge air and this air laden with humidity/CO2/low O2 passes out of the refuge relief valves. These RVs should be strategically placed to vent stagnant air preferentially. An initial system test was conducted in our Florida facility in a production 10-person hard chamber for 96 hours. Last year (2014) the system was tested with a 23 person inflatable refuge alternative in Bruceton. For this test, the CryoRASS air handler was redesigned to offer superior characteristics when installed in a Built-in-Place refuge alternative. This report describes the results of the modified system being tested in the Pittsburgh Experimental Mine while attached to a 30 person refuge for 96 (+/-) hours."

Jan 1, 2016

By M. J. DeMarco

Beginning in late 1985 and continuing through 1987, Bureau of Mines personnel investigated longwall chain pillar and entry design in two-and three-entry gate-road systems at a deep underground coal mine located in central Utah. To evaluate their respective stability characteristics, four chain pillars and two longwall panels within the two separate entry systems were instrumented with Bureau of Mines hydraulic borehole pressure cells to continuously monitor vertical and horizontal pillar and panel stresses through adjacent panel retreat. In addition, supplemental entry closure information was obtained from sites located in the vicinity of the instrumented pillars. The findings presented in this report demonstrate the practicality of evaluating mine pillar stability using in situ methods and support three significant conclusions regarding ground control aspects of the investigated two-entry system: (1) Total areal entry loading was considerably less for the two-entry system, as opposed to the three-entry system, (2) a smaller percentage of opened ground in the two-entry system contributed to a marked reduction in roof falls, and (3) lower areal loading in the two-entry system suggests improved ground conditions when mining the underlying seam.

Jan 1, 1988

By R. D. Grove, M. F. Elliott, R. L. Weigel

The control of Florida phosphate flotation plants is largely based on the visual observations of experienced operators, both in recognizing good and bad froth conditions and in making judgments about the composition of feed, concentrate and tailing streams. Chemical analyses lag the process by at least two hours and therefore only assist in recalibrating the operators' vision when major deviations occur. An image analysis system has been developed by IMC Agrico Company (IMCA) to improve upon the accuracy and precision of the composition estimation process. It still relies upon the operator taking a representative sample, but provides a measurement in about 15 minutes after that sample is obtained. This paper describes the system and its use and presents comparative results for various process streams.

Jan 1, 1993

By A. Griffiths

The? use of hydrogen peroxide to detoxify gold mill waste waters containing cyanide and other toxic substances is already an established technology. Recent advances have extended the range of application of hydrogen peroxide treatment to include the removal of complex iron cyanides, the simultaneous removal of cyanide and toxic metals down to very low levels and treatment of barren bleeds, CIP' pulps and tailings pond discharges. Three treatment plants are described here. Each was installed at a gold mine in North America in 1987 and each illustrates a different application of hydrogen peroxide. The need for individual design of the detoxification plant to fit particular requirements is shown by the examples chosen.

Jan 1, 1988