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By J. B. Stockton, D. J. Robbins, E. T. Woodburn

Batch flotation data in an equilibrium cell show that beneficiation improves with froth drainage. The limiting lamella thickness in a well- drained 3-phase coal froth appears to be determined for ultra-fine particles (-45µm) by the d90 particle size. The froth stability is considered to depend on the existence of a very thin liquid film between the outer surfaces of the d90 particles and the bounding bubble interfaces of the lamella in which the particle is held. The dependence of the coalescence rate of bubbles in these froths on the residual surfactant concentration in the lamella liquid is then consistent with stability analyses for two-phase foams.

Jan 1, 1988

By E. Bane Kroeger

Plane failure in rock and soil slopes is usually caused by the intersection of a discontinuity plane with a slope face. Normally, these discontinuities are weaker than the surrounding intact rock and provide a surface along which movement can occur. The discontinuities are typically analyzed to determine the stability of a particular slope. One problem that arises when evaluating the stability of a planar feature is that the method for planar analysis is two-dimensional and has difficulty dealing with planes that are oblique to the slope face. Several researchers have stated in the past that planar failures are a special case of wedge failure. Wedge failures occur when two planar discontinuities intersect in an unfavorable manner. Sliding can occur along the intersection of the planes. Wedge failures are very common in rock slopes and can often be problematic. Wedge stability analysis methods are typically three-dimensional and can analyze planar features that are very oblique to the slope face. Wedge failure analysis can also be used to determine the stability of planar features with good success. One advantage to using wedge analysis over plane analysis is that a tension crack can be both non-vertical and oblique to the slope face in the wedge analysis. This allows the engineer to more closely match field conditions. It also negates the need for the engineer to have two separate software packages to analyze a single slope, saving both time and money.

Jan 1, 2002

By Robert Snow, Yingxue Yu, Howard Hanson, Patrick Zhang

One of the major current efforts by the Florida phosphate industry to reduce deep aquifer water consumption is to use 100% recycle water for flotation. This measure alone could save billions of gallons of deep well water annually. However, this also results in higher suspended solids (slimes) in flotation water, causing poor process performance particularly for amine flotation. Polymers could play a major role in allowing the industry to use high-turbidity recycle water for amine flotation without compromising its impact on the Florida economy. The enhancement of rougher flotation by polymers may also have potential. Most importantly, dramatic efficiency improvement may be realized by floating silica first. Adding polymer to flotation feed and/or water is perhaps the most economically viable way of reversing the Crago "double float" process, in order to reduce operating costs and increase phosphate recovery. This paper presents both laboratory and pilot flotation data showing the effect of different polymers on collector dosage and flotation recovery. There appeared to be an optimal range of polymer concentration beyond which the benefits do not offset the drop in phosphate recovery. The effect of poly mer is slime-level dependent. Pilot testing data show that the "Reverse Crago" process (floating silica first followed by phosphate flotation) can outperform the Crago process.

Jan 1, 1999

By M. Shen, T. D. Wheelock

The important characteristics of a gas-promoted oil agglomeration process for cleaning coal particles in an aqueous suspension were determined. Numerous agglomeration tests with scale-model mixing systems of different sizes with controlled amounts of air were conducted. The tests were conducted on high- and mediumvolatile bituminous coals using either i-octane or hexadecane as an oily agglomerant. The performance of the system was characterized by employing the minimum time required to produce spherical agglomerates (tE), the mean agglomerate diameter (dp), coal recovery and product ash content. Among these parameters, tE was found the most useful. It is a key parameter in the scale-up of an agglomeration mixing system. This parameter was found to depend on a number of system and operating variables. By controlling these variables and conducting further agglomeration tests with mixing systems that varied in size, an appropriate size scale-up rule was established.

Jan 1, 2002

By C. Flores, R. Y. Wan, M. C. Fuerstenau, T. S. Jordan

Most oxidized manganiferous silver ores contain manganese associated with silver and are not amenable to conventional silver extraction methods, including direct standard cyanidation techniques. However, it is known that dissolution of the manganese might yield a suitable material from which silver can be recovered by conventional methods. In the segregation process, which involves heating the ore with a small quantity of salt and with a source of reducing agent to 680°C - 800°C, the silver is volatilized, migrates and is reduced to metallic silver particles. Conventional cyanide leaching is applied to the resulting calcine. Laboratory investigations have been conducted on a manganiferous silver ore analyzing 0.02 % Cu, 0.09 % Pb, 0.33 % Zn, 12.55 % Mn and 187 g/ton Ag to study the influence of roasting temperature and time, quantity of salt and quantity of coke on silver extraction by the application of segregation roasting followed by cyanidation. Cyanide leaching tests were carried out at room temperature on the segregated calcines produced by using an alkaline cyanide solution containing 2.0 lb/ton of NaCN at pH 11 for 72 hours. The results indicated that 97.8 % of silver extraction can be attained at 850°C, with 2.0 % salt, 1.0 % Coke and 30 minutes of roasting time.

Jan 1, 1993

By Pierre Mousset-Jones, Felipe Calizaya, Malcolm J. McPherson

The objective of this study is to provide potential users of booster fans in coal mines with the necessary information on monitoring and control of fans and environmental factors. The guide-lines listed in this paper were formulated based on the current practice of mine monitoring, the U.S. Code of Federal Regulations on environmental monitoring, and the United Kingdom's National Coal Board recommendations on the use of booster fans. The principles involved in the design of booster fans as well as the provisions needed to guarantee a safe operation of these units, are illustrated by means of an example problem. The example includes a summary of costs for two ventilation systems: a conventional surface fan system and a fully automated booster fan alternative. A comparison of these costs showed that significant gains may be attained by selecting a combined surface-booster fan strategy over a conventional surface fan alternative.

Jan 1, 1989

By R. C. Bryan, D. B. Jamison

This paper describes a procedure for minimizing the operational costs associated with blending sodium in coal at a surface mine in the Powder River Basin. Mine site blending is performed by adjusting daily production rates for high- and low-sodium pits. These adjustments are designed to produce a consistent sodium value called the blending target. The mine's contractual limit for sodium is sufficiently close to the field average value that any decrease in the sodium blending target may result in an opportunity cost, if the number of potentially minable tons is reduced. Conversely, any increase in the blending target may result in a higher sampling cost if more information is required to keep the blend within contractual limits. Blending parameters were defined using a geostatistical block model of sodium content that was based on analyses of hundreds of in-pit sample holes. Variograms for these data were used to compute the marginal costs of opportunity and sampling for a series of hypothetical in-pit drilling patterns. These marginal costs provided a basis for selecting optimum values for key parameters such as the blending target, production variance and in-pit sampling density. The benefit of implementing these optimized parameter values is that operational costs of sodium blending will be minimized over the long-term. At the mine where this procedure was developed, each dollar spent to increase the sampling density to the optimum value was shown to generate a $10 savings in opportunity cost.

Jan 1, 1991

By Eric C. Schwamberge, Clem A. Pelletier, Deborah L. Muggli, George W. Poling

The Pit Lake at Island Copper has evolved into a 3-layered meromictic system. Acid Rock Drainage (ARD) is collected and injected into the lake at 220 m depth via 2 diffuser systems. In situ dye studies were conducted during 2 differing hydrological regimes in order to determine the behavior of the ARD plume within the Pit Lake. Results indicated that when runoff from the waste dumps was low, the injected ARD remained within the bottom half of the intermediate layer of the Pit Lake, initially below depths of 90 m. However, when runoff from the waste dumps was high, the injected ARD at -220 m depth rose through the intermediate water column layer rapidly, but did not breach the top pycnocline at -10 m depth. Overall, the system is currently performing as a mixing bowl with a strong boundary or cap at the upper pycnocline. maintaining mixing below the 10 m depth water level.

Jan 1, 2000

By D. S. Holmes

Biological processes for metal solubilization and ore beneficiation are in widespread use today. There are also some promising new applications of biotechnology in the areas of metal concentration and toxic metal cleanup. Recent progress in genetic engineering promises both to revolutionize the existing biological process and to expedite the adoption of the new biological applications. But before it can do so effectively, progress must be made in many areas of fundamental research and in biochemical engineering. These issues are addressed with special reference to the biotechnology of semi-enclosed containers (bioreactors), dumps, heaps, in situ and under- ground leaching, and with respect to the biotechnology of metal concentration. Finally, certain biological considerations for bacterial strain improvement are discussed.

Jan 1, 1987

By V. T. McLemore

The Steeple Rock district in New Mexico is a major epithermal gold-silver district that exhibits district zoning. Five types of ore deposits occur within the district: •base-metal veins (with gold and silver) form the center of the district and occur along the Carlisle fault, •gold-silver veins along northwest-trending faults and outward from the base-metal veins, •copper-silver veins along the margins of the district, •fluorite veins along the margins of the district, and •manganese veins along the margins of the district. Areas of older acid-sulfate alteration occur throughout the district and also exhibit the following zoning: massive silica/chert zone (inner), silicified zone and clay zone (outer). This alteration overlies regional alkali-chloride (propylitic to argillic to sericitic) alteration. Synthesis of available data suggests the acid-sulfate alteration is related to a shallow, but older, epithermal hot-springs system. Subsequently, younger epithermal veins formed along faults.

Jan 1, 1996

By William P. Diamond

Production trends have been analyzed for 82 gob gas ventholes on 7 longwall panels in the Lower Kittanning Coalbed, Pennsylvania. Cumulative production from individual holes was found to vary considerably, ranging from 0.03 x 106 m' to 10.1 x 106 m3. Peak production rates were generally about 0.03 to 0.06 x 106 &/d, but rates over 0.10 x 106 m3/d were observed. The variability of gas production from individual holes can be attributed to several factors including: completion practices and problems, the extent of fracture development in the strata above the extracted panel, water production, and location on the panel. Of particular significance, is hole location. Holes on the ends of the panels, where overburden strata are in tension due to the support of the surrounding pillars, were generally the highest and longest producers. This observation led to the experimental placement of gob gas ventholes in the zone of tension along the margin of a panel, instead of in the traditional centerline location which is in compression. Analysis of gob gas production data indicates that the experimental near-margin holes produced 77 pct more gas than did centerline holes on the same panel.

Jan 1, 1995

By Davidtz. John C.

INTRODUCTION The effectiveness of collector type on sulfide mineral flotation is generally determined by the amount and type of functional groups of collector molecules that interact with surface and water at the mineral/collector/water/gas interface. The final interfacial state when bubble contact takes place is preceded by chemical and physical reactions that involve these gas/liquid/solid interactions. These interactions differ not only for different minerals, solution and gas composition, but also for different collector molecules. The purpose of this paper is primarily to summarize the developments and status of short (C2-C6) and long (C12) chain, aliphatic collectors that contain three sulfur atoms in their polar function. These are trithiocarbonates (TT'Cs). For purposes of comparison, similarities in molecules containing 0, N and S are compared. Mostly short chain ionic collectors molecules of dithiocarbonates (DTCs) and TT'Cs were compared. The studies, largely bench scale flotation and plant testing, were carried out on ores containing Cu, Ni, Au, and PGM's. Studies of long chain 'ITC collectors are reported on Ni, PGM and auriferous pyrite ores containing uranium. Under starvation dosage conditions, surface activity coefficients of short chain collector molecules and interacting water were calculated. Based on the UNIFAC group contribution method of activity coefficient calculations, the Gibbs Excess Free Energy

Jan 1, 2005

By V. E. Suter

Anyone with geothermal experience can readily attest that geothermal operations are a natural extension of oil and gas operations. A geothermal company and an oil company need the same type of people to do the same kind of work. In the geothermal industry, geologists and geophysicists define prospects through surface geology, analysis of surface seeps, magnetics, gravity, and resistivity surveys - techniques similar to those used in the petroleum industry. In addition, shallow (250-ft) temperature gradient holes often are used in geothermal operations. Landmen take geothermal leases that are patterned after oil and gas leases. Exploratory drilling is done with the same drilling contractors and same drilling rigs, with minor modification. Drilling foremen and drilling engineers share the same objective of making the most hole, in the shortest time, at the least cost, with a proper completion. Petroleum engineers test the wells, design the completions, determine the reserves, make economic calculations, work with the tax assessor, and manage the reservoirs. Production engineers build roads, locations and pipelines, install gas/liquid separators and meters, and operate production and injection facilities. A contract to sell steam to a public utility is required. Various governmental regulations, permits, environmental concerns, and public affairs pose similar problems in both industries. Also required of both are top management people who are acquainted with geologic risk, prepared to accept million dollar dry holes, willing to bid competitively at lease sales, and able to invest large sums based on a technology not yet fully proven. Successful geothermal development requires in-depth financial ability similar to that required for petroleum development. A high capital investment is required early for leases, geological and geophysical work, and exploratory and confirmation drilling. After

Jan 9, 1980

By George E. Aiken, B. R. Jr. Waples

INTRODUCTION In this paper the author will attempt to bridge from the paper work of design and engineering to the reality of implementation. Certain facets of construction are constant to a successful project, no matter the level of technical complexity. Basic to timely, low cost construction are the people assigned to the project. Construction is not accomplished by robots, computers, or speeches; but rather by people. People do however require the avail- ability of equipment and communications to properly complete the work. ORGANIZATION Good organization is the basic requirement of a well implemented construction project. For this paper the author will suggest an organization chart as well as an activity listing that together support the construction activities. There is little difference in the activities or functions needed to construct a small plant or a large one. It is a matter of how much time an individual has to spend on an activity that determines the structure of an organization. The difference between a large and small plant construction job is often described as the multiple hat versus the single hat philosophy. As an example, a resident construction manager on a small job might be the manager, the field engineer, the scheduler, the estimator, and the procurement manager. At some time during a construction

Jan 1, 1986

By M. J. Richards, T. X. Ren

Determination of the state of an underground fire plays an important role in fire fighting, rescue and reopening operations. This is normally achieved by the analysis and interpretation of fire gases taken from the fire zone. However, drawing conclusions from gas analysis is not an easy task and needs specialist skills, expertise and experience that are usually beyond the knowledge of the officials in a mine. The complexities of a mine fire and the uncertainties of available information often make effective fire fighting decisions difficult if not impossible. This paper describes a knowledge based expert system that can aid in the diagnosis of sealed coal mine fires. Using a commercially available shell, the expert system has been designed to accommodate a series of diagnostic rules replicating the reasoning logic that would be used by human experts. The system allows the diagnosis of explosibility of the fire zone and trends of various fire ratios to be easily visualised for decision making. By continuously analysing the incoming information, the system is able to provide a rapid assessment of the situation of a sealed mine fire prevailing under specific mining and geological conditions. In addition, short term trends in fire behaviour can be predicted and possible fire control actions recommended. An example is given and shows how this system can be used as an analytical tool in various ways to assist the combating of coal mine fires. Further development of the system is discussed.

Jan 1, 1993

By R. L. Grayson, S. S. Peng

Sampling of respirable dust and analyses of samples have been partially completed for a longwall panel. Physical and compositional properties which have been characterized include: 1. Respirable mass concentration, 2. Mineral composition, 3. Particle size distribution by mineral, 4. Particle shape distribution by mineral, 5. Particle angularity distribution by mineral, and 6. Respirable size distribution. Analytical techniques used in the characterization of samples are described, and results are reported with emphasis placed on relationships between the various characteristics and worker locations. Details of existing mining conditions, equipment arrangements, dust control methods and operating system parameters are presented.

Jan 1, 1986

By W. DR. Fritz

Technical progress depends on strategic objectives and a concept showing how to benefit from the effects of novel techniques in an innovation process and how to implement them creatively in harmony with manpower capabilities. With the invention of prime movers, it was initially power engineering which dominated the development of industrial history before it was replaced by production techniques resulting from the more widespread use of machines. With the advances in the field of data processing and with the introduction of novel communication techniques, it is information technology- which today is having an ever increasing impact on technological progress. The main objectives of information technology in this context are a positive influence on the ?time? factor as well as the provision of tools to handle the complexity governing many operational processes through a concentration of information for the decision-making process. The German hardcoal industry became aware of the chances inherent in these new technological possibilities for the optimization of operational sequences and of decision-making and planning processes as a potential for success at an early stage and it has worked out a purposeful concept for their implementation.

Jan 1, 1992

By E. Peuraniemi, S. Strömberg, S. Jyrkönen, A. Jokilaakso

Several sulfidic raw materials have been flash oxidized in a laboratory furnace in oxidizing atmospheres at temperatures of 500-1100°C. Chemical analysis was used to determine the oxidation degree, and optical and scanning electron microscopy combined with energy dispersive analysis were used for characterization of the reacted particles. The studied materials included both Cu and Ni concentrates and mattes. In fixed conditions, the temperature dependence of sulphur removal rate was found to be equal for all the copper concentrates studied. Nickel concentrates and Cu- and Ni-mattes were, however, found to be less reactive. Most of the particles were found to spheroidize and to fragment to small droplets under intensively oxidizing conditions. The product particles were frequently found to be iron oxide cenospheres or dense spheres with a composition of mixed Cu-(Ni-)Fe oxides.

Jan 1, 1998

By Thomas J. Rudolphi

Efficient transport of bulk materials by belt conveyor systems is an important engineering design issue, especially as conveyors become longer and power requirements increase. It is well known within the industry that the parasitic energy loss of a belt conveyor, due to the indentation of the idlers into the belt backing material can be upwards of half the total energy required to drive it on a horizontal flight. Other loss sources includes the rolling resistance of the idlers, belt/roller misalignments, material trampling, frictional and acceleration losses on loading, etc., but energy absorbed by indentation of the belt backing as it passes over each successive idler is the dominant power consuming factor. INDENTATION LOSS MODELS Models to predict the rolling resistance of a cylinder (idler) on a viscoelastic foundation (backing material) have been available for some time. As a contact problem, it is nonlinear (contact length or indentation depth is a dependent on the load and vice versa) in load/deformation response. Rubber backing material is generally assumed to behave as a linear viscoelastic solid, even though it is known that most rubber compounds retain linearity only at very low strains. Because completely general solutions are impossible, practical solutions require simplifying assumptions. Those assumptions relate naturally to two separate pans of any analytical model: I. The deformation model-aspects of the problem relating to the geometry, boundary conditions and kinematics of how the material deforms. 2. The material model-aspects of the problem relating to the material properties, or constitutive relationships, i.e., the stress/strain relationships.

Jan 1, 2008

By J. W. Langhans, B. D. Blake

The U. S. Bureau of Mines has been investigating the application of thiosulfate to recover gold directly from low grade refractory carbonaceous ores for the past four years. Statistical experimental methods were used to determine the effects of various leaching parameters on both gold extraction and thiosulfate consumption. Seven variables were investigated, including thiosulfate, copper, ammonia, sulfite, and sulfate concentrations, leaching time, and leaching atmosphere. This information was used in face-centered cubic (FCC) surface response experiments to define the optimum leaching conditions for a low grade ore. Two models were generated from the data to predict gold extraction and thiosulfate consumption as a function of the leaching parameters. The models predicted a gold extraction of 67 pct and reagent consumption of 2 kg [S2032/mt ore at 0.25 M S2032-, 0.0014 M Cu2+, 0.27 M NH,OH, 0.00625 M SO;-,] and leaching for 16 h. Actual tests resulted in 62 pct gold extraction with 0.93 kg S2032- consumed/mt ore. Subsequent column leaching tests have further demonstrated the viability of applying this technology to recover gold from carbonaceous ores without first pretreating the material. Gold extractions in the column tests ranged from 69 to 78 pct with thiosulfate consumption ranging from 0.4 to 5.4 kg/mt ore. These results compare to <5 pct gold extraction using standard cyanide leaching conditions.

Jan 1, 1996