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By Danforth R. Hale

The pressure of military use of quartz resonators led to efforts to Grow high, grade quartz crystals in Germany and in Great Britain during 19)3-25, and was responsible for a series of U.S.A. Signal Corps contracts beginning in 1946 with the Clevite Corporation (as the former Brush Development Company), Bell Telephone Laboratories, Antich College, and others. The technique of growing crystals from the melt, such as KI, NaBr, was already commercially inuse Quartz could not be so grown, since its utility depends on the form stable below 573°C, and, even if it could be grown from an extraordinarily viscous melt, the higher form passing through this transition becomes twinned. Again, several crystals were being grown commercially from water solutions; quartz, however, is listed in the common literature as being insoluble in water. Fused quartz, or vitreous silica, was chosen as raw mater¬ial by the European experimenters because of its thermodynamically lesser stability than quartz, and various alkaline solutions were tried for the purpose of enhancing the solubility.

Jan 1, 1964

Zirconium chloride is of great commercial importance as starting materials for production of ZrO2, Zirconium metal and other Zirconium compounds from its main resources (Zircon Sands). The present study concerns with preparation of pure ZrO2 from Zircon by direct chlorination technique. Different parameters affecting the chlorination process are studied viz. carbon, chlorine flow rate temperature and time. The chlorination extent is determined from the loss in weight and chemical analysis of reaction products. The maximum chlorination extent -92% are achieved at 1100°C for 30 min. Zirconium oxide is produced from the collected zirconium tetrachloride either by calcination at 900°C or by hydrolysis in water in presence of RCI with a purity = 99%. Evaluations of the products of the process are investigated microscopically and by X-ray diffraction. The apparent activation energy of the chlorination of Zircon is determined to equal 36 kJ/mole.

Jan 1, 1997

By Ralph H. Light

The recent surge in demand for uranium in the United States, accompanied by a significant increase in price, has resulted in exploration, mining, and milling of lower grade ores than have been exploited in the past. To sustain production levels of uranium with lower grades of feed requires larger tonnage mill operations. Also, because of recent environmental regulations, mill operations must be prepared to properly contain large tonnages of tailings, and recycle, treat and discharge, or evaporate mill effluents. Thus, the advent of lower grade ores, larger tonnage mills, and environmental considerations has made the cost of milling a critical factor in today's uranium production economics in the United States. Three basic milling methods are employed for extracting uranium from ores: 1. Acid leach, countercurrent decantation, and solvent extraction. 2. Acid leach, resin-in-pulp, and Eluex. 3. Alkaline leach, solid-liquor separation, and precipitation. Vanadium often occurs as a valuable by-product in ore deposits located in the Uravan mineral belt in Western Colorado. Also, lesser amounts of vanadium may occur in ores from South Dakota, New Mexico, and Utah. Vanadium is usually extracted in the acid leach solution with uranium and recovered by solvent extraction after recovery of the uranium. By-product recovery of uranium from phosphoric acid and porphyry copper dump leach solutions is now receiving considerable attention. Pilot plant studies are under way and construction of commercial plants is in progress.

Jan 1, 1977

By Dongjie Zhang, Shuxin Liu, Jianduo Wang

Broken rock mass and unreasonable stope structure parameters can cause excessive ore loss and dilution in sublevel caving; this is the main problem faced by caving mining in recent years. This paper proposes a stope structure parameter optimization method suitable for steeply inclined medium-thick broken ore bodies and evaluates the reliability and effectiveness through case studies. To solve the problem of large ore loss and dilution in the high-end wall sublevel caving method of Xilinhot fluorite mine, it is necessary to select proper stope structure parameters. Based on the theory of random media, an end-wall ore drawing experiment was carried out, and the bulk flow parameters needed to optimization of stope structure parameters were determined. In the experiment, it was found the draw-out body of high-end wall ore drawing showed a fine top and a thick bottom; the granular media had good fluidity. The reasonable caving step is determined to be 1.2 m instead of the 1.6 m originally used. Through the optimization experiment of the mining route position along the vein, the study found that the best route position is different with the ore body inclination. When the inclination angle of the ore body was 90°, the reasonable route was located in the center of the ore body. When the inclination angle of the ore body was between 85° and 90°, the route moved from the center of the ore body to the footwall at a rate of 22.5%. When the inclination angle of the ore body was between 80° and 85°, the route moved to the footwall at a rate of 54.8%. When the inclination angle of the ore body is not greater than 80°, the route should be arranged on the boundary of the footwall. Field application results showed the dilution rate reduced by 7.66% and the recovery rate increased by 7.31%. Field test results verify the effectiveness and applicability of the optimized stope structure, which corroborates the effectiveness and applicability of the optimized stope structure.

Mar 10, 2022

By J. J. Wallaert

The decreasing supplies of natural gas and low-sulfur crude oil available for electric power generation in the United States will unquestionably shift the emphasis to nuclear and coal fired steam power plants in the immediate future. Failure to do so will ensure our dependence on mid-east low sulfur crude oil comprising some 70% of the known world reserves, and imported liquid natural gas. By contrast, the United States has 43% of the known world reserves of anthracite, bituminous and semi-bituminous coal and 48% of all known coal reserves of the world including lignite. It is evident, therefore, that coal is alive and well and will continue to be a significant energy source for the production of electricity for many years. Of course, concern for our environment and the development of new technologies will ultimately curtail the utilization of coal for the generation of bulk power, but information released by the National Electric Reliability Council and the Federal Power Commission is worth repeating. In the year 1972 the total capacity of generating units in the United States was 379,552 Mw of which 149,974 Mw, or 39.5% of the total, was produced by coal fired steam turbines which consumed 344,700,000 tons of coal. New capacity additions planned or in construction show that in the year 1981 our total generating capacity will be 843,503 Mw, of which 257,995 Mw, or 30.6% of the total, if from coal only. Translating this increase into terms meaningful to the bulk material handling industry suggests that ten years from now the utility industry will require 590,000,000 tons of coal per year - a monumental task - if we are to sustain our current demand rate for power.

Jan 1, 1973

By Davar Abi-Zadeh, Cillian Brown, Deepak Kandra

"Grout backfill strategy for a particular subsurface concrete tunnel (~4.9km long, 3.5m in diameter, carrying 20” gas pipeline) was based on achieving 1:100 slope of the fill in order to progressively fill the tunnel, in a series of 350m section. Grout rheology, particularly its non-Newtonian and thixotropic behavior, determines the final fill slope for given backfill strategy. The objective of this study was to simulate the two-phase grout mix backfill process using Computational Fluid Dynamics (CFD) and determine the slope of the fill to validate and optimize the backfill strategy. Three dimensional CFD study showed that for a 500m long tunnel section with a single injection point of grout, given its rheology, it will likely keep flowing without filling the 500m section height wise. Design optimization for filling was carried out using two dimensional studies to make the backfill process “slope independent” by incorporating a 2.5m high bulkhead at ~1,000m. INTRODUCTION As part of a gas field development a 20” onshore gas pipeline is required from the landfall site to the processing terminal some 8km inland. At the landfall site the gas pipeline is routed in a ~5km underground tunnel underneath a bay. For operational reasons and planning consents as well as to mitigate environmental impact based on an environmental impact study, once the gas pipeline and the associated services and spares have been installed, the subsurface gas tunnel will be fully grouted. There will be no permanent access to the tunnel after construction is completed and the site compounds have been reinstated once works are complete. One of the key requirements is that “full grouting of the tunnel” is desired. The grouting material used is a non-Newtonian and thixotropic fluid mixture of bentonite, cement, plasticizer, retarder/stabilizer and water. The tunnel is filled progressively in 350m sections using a combination of existing and new pipework assuming the grout rheology will yield a fill slope of 1:100 in a 350m section. The proposed grouting system used one pump at the grouting compound to pump the grout into the tunnel using the existing tunneling pipework. For the longer runs a second booster pump was used in series to pump the grout to its final discharge location. The filling process is controlled via a system of flow meters, pressure transmitters and a tunnel CCTV system."

Jan 1, 2016

By K. Tempel

In December of 1999, Newmont Mining Corporation’s Eastern Nevada Operations commissioned its commercial biooxidation facility. The commercial biooxidation facility is a refractory gold whole ore heap process that uses bacteria to assist with the oxidation of sulfide minerals thus liberating occluded gold for further processing by cyanide for gold extraction. Before the commercial biooxidation facility was started, a decade of research went in to developing this state-of-the-art process. During final design and construction of the commercial facility a decline in gold price necessitated cost saving and project scope changes. As a result, the biooxidation process experienced many challenges. Some of the more significant challenges include poor heap permeability due to haul truck stacking, unhealthy bacteria population due to a lack of solution aeration, and insufficient biooxidation time because of limited pad space and high carbonate content in the ore. This paper discusses the many challenges encountered and addressed during the first 2-3 years of commercial biooxidation operation.

Jan 1, 2003

By V. Herman, B. Knorr, D. Whalen

"Edge effect is a condition widely observed in High Pressure Grinding Roll (HPGR) operations that gives rise to reduced comminution at the edges of the roll surfaces. This effect is caused by a reduction in the local crushing pressure at the edges of the rolls resulting from the sliding friction between the static cheek plates and HPGR feed material. Practically, this has an impact on equipment sizing, as the edge effect leads to coarser particles reporting to downstream equipment in open-circuit operations and increased circulating load and diminished HPGR circuit capacity in closed-circuit operations.To address this, Metso's HRC™ HPGR incorporates an Arch-frame to maintain a parallel relationship between the rolls and allow for the use of a flanged roll design. We conducted a series of pilot-plant tests with a 750 mm by 400 mm HRC HPGR to compare the performance of the flanged roll design against that of a traditional cheek plate arrangement under similar operating conditions. The edge effect was found to be significantly reduced with the flanged roll design. Based on the pilot-plant results, the implications for circuit design, energy efficiency and overall plant performance in a full-scale application were investigated and discussed.IntroductionGlobal trends such as lower ore grades and rising operating costs are driving the market toward more energy-efficient mineral processing solutions, most notably in comminution circuit design. High pressure grinding rolls (HPGRs) have been recognized as an energy-efficient solution relative to more conventional circuit designs. The basic operating principle of HPGRs, in which a fairly uniform pressure is applied to a bed of material in the compression zone, lends itself to this improved energy efficiency (Morley, 2006). Studies have estimated that savings of 10-15 percent are possible when comparing an HPGR circuit with a traditional SABC circuit (Rosario and Hall, 2008). While HPGRs offer a more energy-efficient solution than tumbling mills, there is still room for improvement in many aspects of the design. Edge effect, in particular, is one such aspect that limits the effectiveness of the machines. Edge effect is the impaired performance at the edge of the rolls due to a reduction in crushing pressure (Morley, 2010; van der Meer, 2010). As described in our prior work (Knorr, Herman and Whalen, 2013), edge effect is caused by the interaction between the ore entering the crusher and the relatively static cheek plates positioned at the edges of the rolls. As the material is drawn into the crushing zone, the sliding friction between the ore and the cheek plates inhibits the ability of material to be effectively drawn into the compression zone at the edges of the rolls. This reduces the crushing force in those edge regions relative to the center of the roll where material is being drawn into the compression zone at a higher rate. In addition, the cheek plates of a traditional HPGR design are held in place by spring-loaded brackets that are adjustable to manage the clearance. This spring-loaded cheek plate design prevents full compression of the material in the edge regions of the roll as there is relief at the outer edges."

Jan 1, 2016

By William C. Cox, Ronald E. Heuer, Jean-Michel Loignon

The Gatineau shaft described in this paper was an excavation of about 38 m diameter and 21 m depth constructed in Gatineau, Quebec, across the Ottawa River just north of Ottawa, Ontario. A large sewage lift pumping station-was to be constructed in this excavation. Subcontractor for the shaft excavation and initial support was Beaver Underground Structures Ltd., of Dorval, Quebec. Mr. William C. Cox of Beaver conceived the idea for the support system used in this excavation, and was responsible for the construction activities. Initial analysis and design concepts for the lining system were developed by Mr. Ronald E. Heuer. Detailed lining design and construction monitoring were the responsibility of Mr. Jean-Michel Loignon. Geologic conditions indicated by two borings within the shaft area are illustrated in Fig. 1. The shaft excavation would be in the sensitive Leda silty clay. The clay is of stiff to very stiff consistency, with an insitu vane shear strength averaging about 115 KPa (2400 psf) and a reported low value of about 87 KPa (1820 psf). Low strength values were from the middle of the clay layer, with higher strengths at the top and bottom. Average shear strength at the level of the base of the excavation was about 137 KPa (2860 psf). Remolded vane shear strength averaged about 20 KPa (420 psf), with a reported low of 13 KPa (270 psf). Based upon average strength values, the clay sensitivity is 5.8. The clay has an average water content of 53% (range 43 to 66%), which is near its liquid limit (average 56%). The clay unit weight is about 1760 kg/m3 (110 pcf). Underlying the shaft site at shallow depth is limestone bedrock within which the piezometric head is approximately equal to the original ground surface elevation. For shaft support, a -cast-in-place concrete wafer system was considered, but was discarded because of time restrictions imposed by concrete placement and curing. The support system selected utilized liner plate with light steel walers closely spaced. The light rib

Jan 1, 1983

By L. D. Patts, S. J. Janisko, E. G. Cauda, A. D. Bugarski, G. H. Schnakenberg, J. A. Hummer

Filtration systems with disposable filter elements (DFEs) are used in the underground coal mining industry to control particulate matter emissions from diesel-powered permissible and nonpermissible coal mining equipment. This study was conducted in underground mine conditions to evaluate three types of high-temperature DFEs used in those filtration systems. The DFEs were evaluated for their effects on the concentrations and size distributions of diesel aerosols and concentrations of nitric oxide (NO) and nitrogen dioxide (NO2). Those effects were compared with the effects of a standard muffler. The experimental work was conducted directly in an underground environment using a unique diesel laboratory developed in an underground experimental mine. After an initial DFE degreening period, the filtration system with all three DFEs was found to be very effective at reducing total mass concentrations of aerosols in the mine air. The effectiveness of DFEs in filtering aerosol mass was found to be a function of the engine operating conditions. The efficiency of the new DFEs significantly increased with operating time and buildup of diesel particulate matter in the porous structure of the filter elements. A single laundering process did not exhibit substantial effects on the performance of the DFE elements. The effectiveness of DFEs in removing aerosols by number was strongly influenced by engine operating mode. The concentrations of nucleation mode aerosols in the mine air were found to be substantially higher for DFEs when the engine was operated at high-load modes rather than at low-load modes. Initial heating of certain DFEs resulted in visible white smoke and substantially elevated aerosol number concentrations. The effects of the DFEs on the total concentration of nitrogen oxides (NOX) were found to be minor. The NO2 fraction was found to be generally lower for the DFEs than for the muffler. The engine-out NO2 fraction of the total NOX was found to be substantially higher for low-load modes than for high-load modes..

Jan 1, 2011

By R. Weinstein, R. Snoby

There are many advantages to upgrading coal with dry jigging technology. The most obvious is the lack of process water, which eliminates the need for fines dewatering and slurry confinement. Dry jigging eliminates the clean coal moisture penalty associated with wet processing. Particulate emissions are virtually nonexistent due to inclusions of fabric dust collectors on all modern dry jig plants. Due to the environmentally kind nature of dry jig plants, installation permits are often measured in days, not months. Coupled with all these advantages there has been a fundamental advance in dry jigging efficiency. All of these advantages have renewed the coal industry’s interest in dry jigging. But, air jigging isn’t right for every application. There are limitations due to particle size, particle shape, moisture, and near gravity content. This paper explores the evolution of dry jigging; reviews parameters important for determining the suitability of dry jigging; compares historical performance data as measured by imperfection, against results from modern dry jigging technology; and presents actual data from modern dry jig installations.

Jan 1, 2006

By K. Burke, G. Zhan, A. Mayer

A cover with capi1lary barrier effects (CCBE) is being constructed an the AA leach pad at the Barrick Goldstrike mine near Carlin, Nevada. The purpose of the cover is to eliminate/minimize infiltration of meteoric waters into the leach pad. Laboratory and numerical analyses indicate that Carlin Formation siltstone (TCS), a locally available material, has the necessary hydrologic characteristics when placed on the leach pad to act as a CCBE. A pilot study was conducted on a mall-scale test cover placed on the AA leach pad to examine the cover performance under irrigated conditions. The preliminary test results demonstrate that the designed cover is capable of preventing meteoric water infiltration.

Jan 1, 2002

By Francis F. Pitard

The presence of elements, minerals, or chemical compounds in materials at very low concentrations is becoming a constantly increasing concern for several segments of the Industry. Some trace elements or chemical compounds may be considered as hazardous, some are simply considered as undesirable In complex processes where they could be constantly recycled and end up as the major factor of decreasing quality for some valuable products. In some other cases, the presence of a trace element or mineral may be highly desirable because of its economical value: precious metals are falling into this category, they probably were the first trace elements to draw our attention. Tremendous quantity of money is spent for analysis at the trace level, also the analytical "tool" has been considerably improved during recent years, but still the sampling aspect of the problem remains obscur for many, and because of it, large quantity of analytical efforts become meaningless. Not only the absence of sampling strategies is badly affecting the representativeness of a large majority of samples, but furthermore for the same reasons, many laboratories are failing In their endeavor to prepare reliable standard reference materials. The reason of this failure has its roots in the unability to estimate effectively the sampling characteristics of the element, mineral, or compound of interest, not to mention the unability to perform precise and accurate complete analysis, so essential for the instrumental analyst (1). In this paper a strategy to perform a better sampling operation is recommended. SELECTION OF A PROBABILISTIC APPROACH AS SOON AS PRACTICALLY POSSIBLE It Is essential to differentiate probabilistic sampling from non-probabilistic sampling. As Illustrated in Figure 1, the sampling operation Is a selection process which could be performed In two different ways: I. A probabilistic selection process according to which all elements of a lot of material to be sampled are submitted to the selection with a same probability of being selected. 2. A non-probabilistic selection process according to which all elements of a lot of material to be sampled are submitted to the selection with different probabilities of being selected.

Jan 1, 1986

By Charles A. Maliszewski, James M. Galvin, Gerhard Urschitz

With obvious signs of deterioration, the double track, historically registered Bergen Tunnels as part of the commuter rail system in New Jersey waited for rehabilitation for a long time. Serious water in filtration not only caused operational and safety hazards for the electrified rail line but also deteriorated and structurally compromised the tunnel lining. An innovative rehabilitation program was developed to enlarge the tunnel and to provide a new waterproofing system and final lining. For the rock excavation and support New Austrian Tunneling Method (NATM) principles were utilized, while water tightness was achieved by installing a PVC membrane waterproofing system followed by a reinforced cast-in-place final lining. Experienced on-site supervision generated additional savings during construction by streamlining support elements based on geologic conditions encountered.

Jan 1, 2003

By K. J. Shoop

This study investigates the use of a horizontally-baffled column (7.6 cm inside diameter by 344.2 cm high) to reduce the ash content of a high ash bituminous coal. Tests were carried out to determine how the baffled column responded to changes in feed rate, reagent dosage, and feed quality, and to compare its performance with a conventional column installation in an operating plant. In this paper, the results of this investigation will be reviewed and discussed.

Jan 1, 1997

By Paul Shimizu

BHP Robinson contracted Minnovex Technologies to implement a Comdale Expert System at their greenfields operation in Ely, Nevada. The expert system has resulted in a significant increase in tonnage. Other benefits have also been realised, including a reduction in operation upsets (having a positive effect on downstream processes, i.e. flotation) and reduced production variances between crews. The expert system is written in a unique manner using trend based logic with minimal hard limits. The result is a robust system that requires minimal operator supervision while producing very high results. The development, success and acceptance of the system can be attributed to the strong team that was assembled for this project. The team not only consisted of BHP Metallurgists and Minnovex but most importantly included operations.

Jan 1, 1998

By Xuebin Liu, Yi Shang, Can Zhou, Hongqiu Zhu, Junbo Du

In the neutral leaching process of zinc hydrometallurgy, the pH value directly affects the leaching rate of zinc calcine. However, due to the complex mechanism of the leaching process and frequent fluctuation of working conditions, it is difficult to control the pH value by manual control. Therefore, this study proposes a fuzzy control method based on rule extraction under multiple working conditions, and analyzes the pH control performance. Firstly, the different operating states are classified according to process mechanisms and the Pearson method. Secondly, under the framework of the active learning algorithm, the approximate linear dependence (ALD) method is introduced to iteratively select samples with rule information in the original sample set for manual annotation. Then, the support vector machine (SVM) method is used to extract fuzzy control rules in different working conditions. Finally, a fuzzy rule set is established according to the samples mapped by the support vector. The simulation results based on industrial data show that the proposed method has better control performance than conventional fuzzy control and proportional–integral–derivative (PID) control.

Apr 1, 2024

By A. S. Ibrado, D. W. Fuerstenau

The adsorption of the cyano complexes of Ag(I). Cu(l), Hg(II), Cd(II), and Zn(II) on activated carbon was investigated as a function of pH and correlated with the speciation diagram for each metal. The results show marked changes in uptake with pH, closely resembling the predominance profiles of their neutral and singly charged cyano complexes. Multicharged negative complexes are repelledby the negatively charged carbon surface. The sensitivity of activated carbon to the charge of the adsorbing species indicates that silver adsorbs as an anion, not chemically bound to the coadsorbing counterions. For the same reason, activated carbon is selective to metals that preferentially form neutral and singly charged cyano complexes, namely gold and silver.

Jan 1, 1990

By R. J. Hickson

From 1993 through 1999, Cyprus Amax Minerals successfully completed eight major construction projects around the world. Six greenfield mines were brought into production, an ongoing operation was completely modernized and an environmental issue was appropriately remediated. The projects stretched over three continents: from arctic Russia to the Atacama Desert, from sea level to an elevation of 4,900 m (16,00Oft), from city suburbs to remote wilderness and from a low of US$130 million to more than US$ 1billion. The operations included open-pit and underground mines, mill and leach facilities and involved gold, copper, molybdenum and coal. The diversity of these projects inspired Cyprus Amax to create a "best-practices” project-management protocol to steer corporate expansion in the new millennium. This paper summarizes these best practices, while highlighting the project-management pirfalls to avoid.

Jan 1, 2000

By J. C. Yingling

An approximate analytic- model is developed for minerals liberation when comminution processes are applied to multi-component ores, i.e., ores that include grains of multiple mineral species. The model employs a one-dimensional representation of ore texture similar to that employed by King (1979) and Klimpel and Austin (1983). The spatial texture representation is viewed as being generated by a stationary semi-Markov process. Associated semi-regenerative processes are defined that can be used to establish, approximately, the joint distribution of particle size and composition, where composition refers to the identities and relative proportions of mineral species included within the particle. Numerical predictions made by the model are compared to size and composition distributions observed in previous experimental studies.

Jan 1, 1992