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By R. C. Fox

The geophysical aspect of reconnaissance marks the beginning of extensive computer applications supporting development of a mine. Although there are some storage and retrieval applications in geology, and some statistical analysis in geochemistry, large-scale compilation, reduction, and interpretation of mineral resource data are initiated in reconnaissance geophysics. The reasons for this fact are quite simple. Geophysics is oriented toward quantitative evaluation of areas of interest, and methods of data collection are automated to the extent that large amounts of analog and digital information are recorded. The large volume of data must be interpreted in a reasonable time. Furthermore, some modeling problems involving complex numerical solutions could not be attempted without the computer. Therefore, the computer is essential to the success of an exploration project using geophysics. For example, aeromagnetics is a common technique for reconnaissance examination of areas associated with sulfide systems and porphyry deposits. An area covering 161 X 161 km (100 X 100 miles) may be flown with a 1.6-km (1-mile) line spacing yielding 10,000 line miles (16,093 km) of data. If only 10 measurements are recorded per mile, 100,000 data points, including location and magnetic field intensity, must be reduced and stored for quantitative interpretation. Computer applications often represent a significant investment in manpower and hardware. It is desirable, therefore, to initiate an engineering approach to the application of computers to geophysics. By this it is meant that computer programs and systems should be formulated, developed, and implemented in a disciplined manner such that their usage is dependent only on the application and not on the individual doing the programming. In other words, computer application, development, and usage should evolve beyond the personal gadget phase to an important applied technology. Geophysics has evolved over the past two decades in a course parallel to computer hardware development. During the sixties, the computer became large enough and fast enough that complex models required by geophysics could be solved. Automation also relieved the geophysicist from routine manual calculations. During the seventies, computing power in¬creased and applications expanded from two-dimensional problems to three-dimensional modeling. Moving into the eighties, as computer hardware costs will significantly decrease, the major expense of computing will be the manpower required to develop, implement, and use an application; therefore, improved programming techniques and applications software engineering methods will be used to optimize and preserve this investment. This chapter presents a general overview of computer methods in geophysical reconnaissance; it is divided into two parts: geophysical methodology and software engineering.

Jan 1, 1979

By William R. Wayment, Wayne S. Cusitar

INTRODUCTION The process of mining removes valuable and eco¬nomically recoverable minerals from the earth. In the case of hard-rock mining, this process involves breaking and removing ore, while leaving the waste rock or host rock as intact as possible. Prior to mining, ground stresses exist in the ore and the host rock as a result of weight and tectonic forces; for the purposes of this chapter, the ore is considered to support the host rock on both the hanging and footwall sides. Two basic phenomena accompany mining. First, the hanging walls and footwalls tend to move together as the ore is removed. Second, high stress gradients de¬velop in the rock periphery of the opening; the magni¬tudes of the stress gradients vary widely, depending upon the local geometry and conditions. At various times, mining methods have used square¬set timbers, waste-rock backfill, alluvial sand fill, and tailings backfill materials, with or without cement, to replace the loss of support caused by the removal of the ore. Cut-and-fill mining has evolved to use hydraulically placed tailings for the backfill. In the stope, this fill provides massive support to the walls, thereby reducing stresses in the back. It also provides a floor from which men and machines can work to drill and blast, to haul ore, and to scale and bolt the back. In many cases, the addition of cement provides a competent free-standing wall when the fill is exposed during mining of adjacent stopes or during pillar recovery operations. In most cases, the use of fill does not eliminate standard tem¬porary or local roof control measures such as roof bolts and wire mesh. Fill Characteristics It is important that backfill used for ground support be of maximum stiffness in relation to wall closure. The stiffness of the fill is related to its placement bulk density or void ratio. In the case of cemented tailings, this is enhanced by the cement bonds. During stope closure, individual fill particles experience rotation and crushing at point contacts, but they are subject to little relative translation. The stiffness approaches infinity as the void ratio approaches zero, until the ground forces reach equilibrium, and closure stops. The gradation of particle sizes and minimal segregation resulting from good hy¬draulic placement both contribute to a high degree of early stiffness in the closure history of classified tailings backfill. This also implies that the fill should be resistant to creeping under high static loads. All mines experience shock loading situations such as blasting, and many mines experience rock bursts that can apply sudden and very high loads to the fill. Certain conditions of void ratio, particle size, and moisture con¬tent can result in mass fluidization of unconsolidated fill during such shock loading. Two key factors in avoid¬ing fluid behavior are the provision of a well-drained fill through desliming or classification and the achievement of a small degree of consolidation through the addition of cement in ratios as lean as 40 to 1 (2.4% cement). The acceptance of classified mill tailings as backfill material has been enhanced by its relative economy, including its source, preparation, delivery, and stope distribution. Transportation from the backfill prepara¬tion plant on the surface into the stope usually can be accomplished with low power consumption, with low labor costs, with few capital costs, and at high tonnage rates. An additional benefit is a reduction of the storage volume required for surface disposal of the tailings stream, with a resultant improvement in the environ¬ment. The costs of placing cemented tailings backfill generally range from $1.65 to $6.61/t ($1.50 to $6.00 per st) of fill depending upon the cement ratio used. Scope This chapter examines a major backfill program at a mine and mill complex where the backfill facilities are included as a part of the original planning. The backfill preparation plant is intended to make maximum use of remote controls and automation. The logistics asso¬ciated with material storage, handling, and metering in the plant are outlined. Important considerations in specifying equipment for typical service conditions are discussed. The fill delivery system is described, includ¬ing the boreholes, level lines, and stope distribution lines. Stope preparations for fill confinement and drain¬age are described, as are the techniques of placement and distribution. Methods of controlling and directing the flow of drainage water and slimes are presented, along with the facilities and equipment for clarification, pumping, and sludge removal. As shown in Fig. 1, the fill program encompasses most aspects of the mining and refining facilities, so the discussion is brief in each area. The preparation of backfill of a uniform and con¬trollable quality is presented here as a material handling problem. The balance of the presentation concentrates on the logic of the system, the costs where meaningful (in 1977 US $ unless otherwise specified), and some operating "tricks" that have contributed to system per¬formance and reliability. SURFACE PREPARATION PLANT A backfill preparation plant is required on the surface. This plant generates suitable fill material from the stream of mill tailings. Among the functions of the plant are: 1) Slimes are removed to improve the percolation characteristics of the fill; typically, particles finer than 325 mesh are removed from the tailings. 2) Tailings and sand storages are provided so that the steady stream of tailings produced by the mill can be accepted. Provision is made to accommodate the cyclic high-volume demand from the mine. 3) The plant stores the cement and contains meter¬ing and mixing facilities to provide fill of a controllable and uniform quality. 4) The hydraulic backfill delivery system is a part

Jan 1, 1982

By Julián Ortiz C., Clayton V. Deutsch

Indicator simulation allows specification of different continuity of high and low values through the use of grade thresholds. The sequential implementation of indicator simulation has been widely used, but the problem of order relation deviations remains a significant drawback. A new procedure for "Hierarchical Indicator Simulation" is introduced that avoids order relations and offers greater flexibility than the conventional sequential approach. The new implementation simulates all locations at the largest threshold and then considers decreasing thresholds in turn. All nodes with grades that are above the previous threshold are excluded from the domain of the current threshold and therefore, they are not used as conditioning data. The probability of being above or below the threshold is calculated using simple indicator kriging using all conditioning data in the domain, thus the covariance structure is preserved. The theoretical framework of this new approach is fully developed. Practical implementation details are discussed. Application to a copper deposit shows the advantages and drawbacks of the method. Finally, the possibility of incorporating multiple-point statistics is discussed.

Jan 1, 2002

By John D. Batty

With the emergence ofbiooxidation as a viable process for the pre treatment of refractory gold ores, so have the number of publica­tions on this topic increased dramatically. To a novice in the field of biooxidation, the infonnation presented is often confusing and sometimes even incorrect. Infonnation has also been published that is misleading in that it highlights a particular feature of a process that is either totally irrelevant or of no consequence to the ultimate goal viz. achieving the maximum economical gold recovery. To assist a potential user of biooxidation in evaluating the available published infonnation some guidelines or considera­tions for some of the more important aspects are given, as well as some extracts from publications that demonstrate the manner in which information has been presented.

Jan 1, 1996

The definition of sustainable development is often taken from the so-called “Brundtland” report, requiring that activities of the current generation not detract from the potential welfare of future generations. Mining is often held up as unsustainable in this regard, since the extracted resource is non-renewable. Yet Brundtland’s definition of sustainable development also requires that the current generation address the disparity in welfare across the globe, a facet of Brundtland’s report that most have ignored. This paper examines the impact of mining on the welfare of the poor, empirically assessing mining’s contribution to this second facet of sustainable development.

Jan 1, 2004

By W. B. Greer

The performance of seals in boreholes, shafts, and tunnels is an important concern in mine safety, in the control of effluents from operating and abandoned mines, and in the underground containment of hazardous wastes (Einarson and Abel, 1990; Mining Waste Study, 1988). Despite the clear need for effective seals, few documented test results are available concerning the performance of in-situ seals. Some evidence indicates that horizontal or near-horizontal holes are especially difficult to seal properly (Kelsall and others, 1982). This research involved the installation, extensive hydraulic testing, removal, and post-test examination of a l0-cm-long by 10-cm-diameter cement grout seal in a near-horizontal borehole in limestone. The work was performed in an underground mine on Marble peak in the Santa Catalina Mountains, Arizona. A test hole was diamond cored in the re-crystallized limestone of the Escabrosa formation. The hole is 33.24 m long, 10 cm in diameter, and dips at 10.4 degrees. The hole extends between two drifts and thus is accessible from both ends.

Jan 1, 1992

By K. Norrena, E. Magri

An important problem in mine operations is the classification of material as waste, low-grade stockpile and ore. This classification must often be made with blasthole data that are widely spaced and that have sampling errors. Geostatistical-simulation techniques combined with basic economic principles allow a procedure for classification that maximizes the expected profit. Geostatistical-simulation methods (Gaussian, indicator or annealing-based) allow the integration of hard and soft data in the creation of alternative, equally probable realizations of the mineral grades. At each location, for each realization one calculates the "profit" if the block were to be classified as ore or waste. The optimal classification is the one that maximizes expected profit (a maximum profit selec¬tion or MPS procedure). In this paper, the authors discuss the theoretical justification of the method and implementation details. The use of blasthole data from different types of mineral deposits, that is, different levels of continuity, are considered. The authors also show the efficacy of the procedure with different levels of sampling error. The increased revenue due to the MPS procedure and improved sampling is shown. The paper shows the geostatistical-simulation procedure and the uncertainty in block grades that result from incomplete and imperfect sampling. The optimal classification is presented. Optimal block classifications are transferred to realizable dig limits by hand-drawing polygonal boundaries. The results of the proposed method are compared to classification based on kriging. Limitations and areas of future work are identified.

Jan 1, 2000

By Fang-tu Wei

The purpose of developing this system is to monitor the operating status of the fully mechanized mining system in order to raise it's reliability. The completely mechanized coal mining system is a complex dynamic system, involving many sub-systems. It is the key of the mining process as well as a connected system composed of each working procedure. Any hitch in breaking, loading or transporting will interrupt the mining process. The analyses of the operating data has proved that the reasons causing the interruption of the extracting processes mainly come from the inner of coal face. Hence, after the installation of the MINOS system in England, the delays of belt conveyor sub-system were reduced. But the production increment was not as much as expected.

Jan 1, 1986

By John Frostiak

The Campbell gold operation of Placer Dome Inc. produces an arsenopyrite-sulfide concentrate that must be treated by roasting, biooxidation or pressure oxidation to obtain high gold recoveries. Pressure oxidation is a proven process that also meets Ontario's stringent environmental regulations. A comparison of biooxidation and pressure oxidation was completed early in 1990. Placer Dome selected pressure oxidation as the preferred process to replace the roaster. The commercial plant design was based on technology supplied by Sherritt Gordon. In July of 1991, the existing roaster operation was shut down and a new pressure oxidation plant was commissioned. The Campbell Red Lake Mine, in Balmertown in northwestern Ontario, is the first plant in Canada to use Sherritt Gordon's pressure oxidation technology to recover gold from a refractory ore body. A similar process has been used at Sao Bento in Brazil since 1986. The Porgera complex in Papua New Guinea also uses Sherritt's technology. At the Campbell Mine, gold occurs as either free gold or is encapsulated with sulfide minerals, mainly arsenopyrite, pyrite and pyrrhotite. These sulfide species are recovered from the ore by crushing and grinding to 80% -75. µm (200 mesh), followed by flotation. About 40% of the gold in the ore is recovered by gravity separation. The remainder reports to the ground slurry feed to flotation. The flotation concentrate averages about 55 to 60 t/d (60 to 66 stpd). A typical analysis is shown in Table 1. Before the installation of the pressure oxidation plant, the flotation concentrate was treated in a two-stage, fluid bed roasting circuit. Roaster off-gases passed through two parallel sets of cyclones, followed by electrostatic precipitators. Arsenic trioxide was captured in a four-chamber baghouse before the gas was discharged to a stack. The arsenic trioxide was sold or conveyed to an underground storage vault. The roasted calcine was fed to a gravity separation circuit and then subjected to cyanide leaching. Gold was recovered from the filtered leach solution in a Merrill-Crowe zinc precipitation circuit.

Jan 1, 1992

By Deepak Malhotra

INTORDUCTION Mining operations are unique In that they handle large volumes of water (millions of gallons) daily. The water contains dissolved metals, processing chemicals, organics, and other contaminants, There are several sources of water contamination at mine sites: mines, mills, tailings ponds, and Industrial/utility complexes. Utility waste water generally represents a very small portion of the total process water utilized in a normal milling operation and hence will not be addressed in this paper. Mine drainage can represent a significant amount, thus having an Impact on the recovery of metals, especially In Industrial minerals operations, and may have to be treated separately. The National Pollutant Discharge Elimination System (NPDES) effluent limits are becoming more stringent, thereby requiring mining operations to treat process water prior to discharge to the environment. The general trend Is to move toward a closed-loop waste system and treat only that small fraction of process water which Is to be discharged to public lands. The following section discusses the reasons for waste water treatment and the existing and emerging technologies for meeting NPDES effluent limits. REASONS FOR WATER TREATMENT Due to the diverse nature of the mineral Industry, process/waste water contamination problems as well as processing flowsheets are site specific. However, certain generalizations can be made specific to processing of different minerals: • Acid mine drainage Is a problem at sulfide/coal mines. • Cyanide contamination of water Is a problem at gold processing plants. • Organics can be a problem at mines using flotation oils. • Tolling ponds are generally acidic at sites processing industrial minerals such as silica sand and feldspar. The cost for water treatment Is viewed as an added cost of production. Hence, large mines are moving toward dedicating personnel to management of water resources in order to minimize waste water for treatment. Very often, mines having closed-loop water systems will treat waste water for reasons other than meeting NPDES regulations. These Include situations where process requirements dictate use of high-quality water for separation of minerals, neutralization of acid mine drainage water, and portable water for the mill. WATER TREATMENT TECHNOLOGIES Water treatment process has to be cheap and simple because It has to process large volume, and It does not directly add to the bottom line, namely revenue. The water treatment process development has to be site specific because the contaminants In the water vary from site to site. and discharge limits for water vary from state to state. The current technologies for wastewater treatment have been divided Into the following three areas: • Removal of heavy metals • Cyanide destruction • Scale control A brief summary of the current technology In each area Is discussed below. Removal of Heavy Metals The physical and chemical processes for heavy metal removal are summarized in Table 1. The most common and cheapest approach has been the precipitation of hydroxides at high pH followed by sedimentation and thickening of solids. The remaining solids can be removed by filtration. The pH is adjusted back to neutral, and the water Is discharged. This process is most commonly used wastewater treatment technology in the mining industry. The basic processes can be modified by combining other operations in order to meet the objectives of the specific site as illustrated In the following examples: • AMAX's Mt. Emmons treatment facility uses Lectro Clear® process where the precipitated solids are removed by electroflotation. • AMAX's Climax Mine water treatment plant used Ion exchange columns to meet the discharge limits on molybdenum.

Jan 1, 1992

By A. E. Foscolos

British Petroleum (BP, 2005), indicates that world reserves for oil to be 1198 billion barrels, for natural gas the equivalent of 1156 billion barrels of oil and for coal the equivalent of 3219 billion barrels of oil. If we take into consideration the mean aver-age annual increase in demand of the last three years for oil, 2.6%, for natural gas, 3.9%, and for coal, 6.6%, then their respective reserves? lifespan are calculated to be 27, 34 and 38 years. Without taking into account their annual increase in demand, lifespan increases to 38, 67 and 161 years respectively. Since zero increase or perpetual increase in energy demands on finite resources is unrealistic the selection of the most suitable energy commodity for power generation rests upon the law of supply and demand of each commodity. This defines its price hence its selection for the production of cheap electricity. When the ratio of supply to demand is less than one, peak production is achieved. Any further increase in demand results in price increase to quench its demand. The Association for Oil and Gas Peak (ASPO) has calculated that when oil demand exceeds 84 million barrels/day, Peak Oil Production will be attained thus prices will start to increase in order to even demand with supply. Correspondingly, Gas Peak Production is expected to take place when demand exceeds 9.1 or 10.2 billion cubic meters/day. Peak Oil production has been calculated to take place in the current year, 2006, while Gas Peak production is estimated to take place between 2020 and 2025 provided that gas will not cover the energy deficit created from the lack of oil otherwise Gas Peak production could arrive as early as 2010. The use of coal for power generation is considered a better alternative than oil and gas if new combustion technologies with an energy efficiency of 43%, Germany, and 47%, Denmark, are adopted. These not only extend the lifespan of coal reserves but reduce also CO2 emissions by 25% and 31%, respectively. In the very near future CO2 sequestration and fixation in deep geological strata will eliminate its emissions thus rendering the use of coal the cheapest feedstock for power generation.

Jan 1, 2006

"Above ground, elevated belt conveyors with span >200m between support points can cross valleys, rivers, forests and buildings with minimal footprint. The Cable Bridge Conveyor is a new type of suspension bridge based belt conveyor system that has long span between support points. It combines typical belt conveyor and the improved simple suspension bridge to form a conveyor bridge. The improved simple suspension bridge places a widened bridge deck directly on suspended cables, without the need for high truss towers. The benefits include reduced cost and increase aerodynamic stability compared to conventional suspension bridges. The Cable Bridge Conveyor’s compatibility with current belt conveyors allows the versatility in application. INTRODUCTION Belt conveyor is a ubiquitous material handling system. Conveyors can be placed directly on ground or elevated above ground by support structures. Considerations of cost, design, environment, civil work, safety and process requirements are all factors in choosing the ground based or elevated conveyors (1). The ground based conveyor has the lowest structural cost, where the conveyor is laying on an existing road. Maintenance access is easy and straight forward. Compared to the ground based conveyor, the elevated conveyor can cross existing buildings and structures, give passage to traffic beneath the conveyor, has smaller footprint, and requires less civil work to pass mountainous areas. The drawback of the elevated conveyor is higher structural cost, which can be compared with savings in civil work and other benefits. Conventional elevated conveyors are supported by rigid truss type structures, with typical span of 15m to 25m between concrete support bents or steel trestles. Triangular truss, using steel pipes instead of hot rolled steel sections, is more efficient. The typical span of triangular truss supported conveyor is around 30m to 40m, while the weight is about 10% less than conventional box truss with shorter span (2). Long span elevated structure based on suspension bridge is another step forward in increasing the distance between support bents, reaching 100m~400m and beyond. The very wide distance between support points of an elevated conveyor offers unique benefits. The conveyor can cross rivers, valleys, highways, forests and other obstacles with minimal footprint and reduced civil work. The versatility from long span conveyors makes bulk material transportation over previously impossible terrains now a feasible option."

Jan 1, 2015

By R. J. Sweigard

Differential settlement on reclaimed land presents a particular problem when the land is to be used for row crops. The poorly drained depressions caused by differential settlement restrict crop yield resulting in additional costs to alleviate the problem. Potentially more serious is the threat of failing to meet target yields due to settlement: related reductions. Because the mechanism by which the problem occurs is not well understood, a physical model study was conducted to investigate the importance of several factors. Although the importance of such factors as the relative amounts of rock and unconsolidated overburden in the undisturbed condition and the size distribution of rock fragments were considered, the analysis concentrated on the causes of settlement in the reconstructed soil layer above the rock spoil.

Jan 1, 1989

By Ian Farrell, Josh Stowe, Eric Wingeard

Tailings transport system design is generally based on identifying the minimum and maximum process boundary conditions for pump selection and pipeline sizing. The approach is robust and well-proven. However, the approach has the potential to skew selections to operating scenarios that have a very low likelihood of occurring, such as the combination of high solids throughput and low tailings solids concentration. The approach can result in a tailings transport system design that is overly conservative. A probabilistic method-based approach captures the independent variability of design inputs and the combined likelihood of outcomes. This approach identifies the process conditions that have the highest likelihood of occurrence and are most applicable to equipment and pipeline selections. An outline of a probabilistic-based approach to tailings transport system design and the resulting selections is provided in this article. The probabilistic-based system design is compared to the outcomes from the traditional approach. The benefits and challenges to this approach are discussed and recommendations for utilizing this approach for tailings transport system design are provided.

Mar 31, 2021

By S. Mathur

Oxide particles are commonly used as fillers in plastics, paper, rubber etc. (particulate composites). The successful fabrication of such composites is dependent upon the adhesive strength of the filler particles to the matrix. The compatibility of the matrix and the filler particles is generally enhanced by adsorption of surface modifiers such as surfactants and polymers at the particle-matrix interface. In order to develop a scientific basis for selection of appropriate modifiers it is necessary to understand their adsorption mechanism(s). Specifically, adsorption of polymeric additives is attributed to a combination of chemical and electrostatic interactions, hydrogen bonding and van der Waals forces. Hydrogen bonding has been suggested to be the primary adsorption mechanism for non-ionic polymers. However, a literature survey of Poly(ethylene oxide)(PEO)-oxide system suggested PEO, a non-ionic polymer, to be substrate specific. A systematic study was undertaken to investigate the adsorption mechanism(s) of a PEO on oxide particles. It was determined that strong Bronsted acid sites on the surface interact with the ether oxygen, a Lewis base, of PEO to induce adsorption. In this work characterization of PEO binding sites on oxides is reported and the mechanism(s) of PEO adsorption discussed.

Jan 1, 1997

By R. J. Rice, K. F. Denning

Effect of iron on the removal of arsenic, mercury and selenium from gold mining effluents. Arsenic, mercury and selenium are common trace elements in gold tailing effluents that require removal before the water is either recycled or returned to a receiving body. One of the better methods of removal of these elements is the use of iron salts whereby, the metal is trapped on the freshly precipitated hydrolyzed iron oxides either by adsorption or enmeshment of the fine particulate and hence, removed from solution. The metal removal is effected by iron to metal ratio, pH, temperature etc. Pilot plant tests have shown that mercury can be reduced to < 5 ppb Hg, while full scale tests on arsenic and selenium have achieved levels of < 50 ppb As and < 10 ppb Se in well controlled systems.

Jan 1, 1993

By S. Bhagwat

Coals capable of emitting 2 lbs SO2/106 Btu heat input must be defined as high sulfur coals. This is because electric utility plants built after 1971 may not emit more than 1.2 lbs SO2, and those built before 1971, and regulated under the State Implementation Plans (SIP), may exceed the 2 lbs S0 limit only under closely defined restrictions concerning ambient air quality and prevention of air quality deterioration. Coals produced in Kentucky, Illinois, West Virginia, Ohio, Pennsylvania, and Indiana account for 77% of SO2 pollution potential and are, therefore, the subject of this investigation. These coals have suffered market share losses in the 10 years from 1974 through 1984. This is due to their sulfur content as well as their lack of price competitiveness with low sulfur western and imported coals. Kentucky and West Virginia have been able to increase their compliance quality coal production substantially, but other states have largely been unable to do so because of nonavailability of low sulfur coal deposits. Assuming that the current relative productivity and cost competitiveness of coal producing states will not change significantly by 1994, this paper makes two projections of coal production in the selected states. In scenario I, the current clean air regulations are assumed to apply until 1994, and coal production in the selected states is projected to in¬crease by about 6% in 1994 compared to 1984. In scenario II, it is assumed that acid rain legislation will be implemented, which will adversely affect the markets for high sulfur coals. Coal production in the selected states under this scenario is projected to decline about 10% between 1984 and 1994, jeopardizing up to 13,000 mining jobs. The author concludes that better coal quality and greater cost competitiveness are both essential to stem the market losses and to regain strength.

Jan 1, 1988

By T. Bednarski, T. McCallum, L. Moya, B. Gay

"Molybdenum recovery by solvent extraction has gained interest partly due to advances in concentrate leach technology. Historically, both molybdenum and rhenium have been produced using amine-based extractants with the ability to co-extract both metals. Alternatively, a phosphinic acid-based extractant (CYANEX® 600) can be used depending on the flow sheet. CYANEX® 600 selectively extracts Mo leaving Re in the raffinate, which is a valuable feature in plants which require rejection of the rhenium from the molybdenum circuit. CYANEX® 600 piloting results are reviewed and compared to commercial experiences with an amine-based extractant. INTRODUCTION Molybdenum is most commonly found as molybdenite (MoS2) in primary porphyry deposits (about 59% of global reserves) and copper porphyries (about 39% of molybdenum reserves)[1]. Recovery from molybdenite traditionally involves flotation (concentrates typically containing 85 – 95% MoS2) followed by roasting to produce MoO3. Solvent extraction is also used to recover molybdenum from acidic aqueous solutions resulting from scrubbing of roaster and smelter off gasses and leaching of molybdenite (uranium ores). Molybdenum is also frequently found in low concentrations in copper leach inventories[2]. More recently, pressure oxidation has gained interest to treat molybdenite concentrates. Molybdenum Chemistry The chemistry of molybdenum is complex with a series of extractable species existing dependent on the pH and oxidation state as shown in Figure 1.Under strongly basic conditions, molybdenum primarily exists as MoO42- while under strongly acidic conditions MoO22+ becomes the predominant species. In between, a number of isopolymolybdates such as Mo7O246- and Mo8O264- are dominant. Equations (1) – (3) demonstrate some of the proposed molybdenum equilibrium reactions[1]."

Jan 1, 2017

By John D. Smart, John W. Sager

The following paper is an evaluation of the instrumentation programs on recent Corps of Engineers tunneling projects. The authors have first-hand knowledge of the NORAD Cheyenne Mountain Complex (NCMC) Expansion Project. Information on the other projects comes from conversations with those directly involved in the instrumentation programs and from referenced reports. The specific objectives of this paper are: (1) to state the purposes of the instrumentation programs, (2) to discuss the benefits gained from the instrumentation, and (3) to present conclusions from this study that will provide guidance to those planning instrumentation on future projects. Presentation of detailed descriptions of the projects and instrumentation data is limited to that necessary to the accomplishment of the above objectives. NCMC EXPANSION PROJECT The NCMC is located at a depth of approximately 800 feet in Cheyenne Mountain near Colorado Springs, Colorado. For the current expansion project new chambers were mined to accommodate a new diesel power plant and associated cooling and air handling equipment. During 1971 some 55,000 yd3 of granite were mined through existing access tunnels for this expansion. A model of the new excavation is shown in Figure 1. The light shaded areas are new openings, and the dark areas are portions of the existing operating complex. The large chamber to the right is the power plant chamber and has a span of 67 ft, a height of 50 ft, and a length of 172 ft. The other large chamber on the lower level is the cooling tower chamber and has a span of 38 ft, a height of 45 ft and a length of 185 ft. The small chamber on the upper level has a span of 20 ft and is 27 ft high and 140 ft long. Other major excavations are the 18 ft diam air tunnel

Jan 1, 1997

By B. Moudgil, Hassen El-Shall

Particle shape and size distributions are among the most important parameters that affect the filtration efficiency of phosphogypsum in wet- process phosphoric acid production. Cost-effective enhancement in filtration rate is desired by phosphoric acid producers for higher plant capacity and lower operating costs. In this regard, numerous research efforts have been carried out in different laboratories as well as in pilot and plant testing. Nevertheless, changes in phosphogypsum crystal shape and size distribution deserve special attention. In this study, the results obtained in the presence of Crysmod and Hiflo-S5 surfactants are discussed. The influence of such additives on crystal morphology and size distribution are studied under different sulfate contents (supersaturation). The obtained data are correlated with process efficiency parameters such as filtration rate, digestion of rock, and recovery of phosphate values. Up to 60% increase in filtration rate is obtained. In addition, an increase in digestion efficiency and P205 recovery is achieved due to addition of surface active agents. The observed beneficial effects are explained in the light of the changes induced in crystal habit, size, and size distribution.

Jan 1, 1999