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By D. G. Krige

I read the paper “The jackknife approach” with interest. There appears to be a widespread misunderstanding of the kriging variance as a measure of the error variance of the kriged grade estimate of an ore block. Virtually all mineral deposits display skew frequency distributions and are subject to the well-known proportional effect. Thus, it is usual to find in an ore body, when subdivided a really into subpopulations, that the variances of the grades (or the total sills of the variograms) for the subpopulations will be correlated with the corresponding mean grades (usually linearly with the squares of the mean grades). Thus, the variogram will be stationary.

Jan 1, 1996

By R. P. Fischer

Traditionally, molybdenum and vanadium have been used chiefly as alloy metals in steel. They impart similar characteristics to most steels, and to some extent one can be substituted for the other. In the United States during the 1950's the production of steel increased about 5 percent, and the reported consumption of both of these alloy metals in steel increased some 40 percent. In Europe during the 1950's the production of steel in¬creased nearly 100 percent. Data on the actual consumption of these alloy metals in European steels are not available, but production and trade records show that the European supplies of molybdenum increased about 150 percent and those of vanadium about 350 percent during the 1950's. If most of the molybdenum supplies in Europe are being added to steel, as seems likely, then the European steel industry has nearly caught up with the United State in the rate of consumption of molybdenum in steel. The vanadium supplies, on the other hand, are puzzling--unless Europe is adding mach more vanadium to steel than is done in the United States, it seems reasonable to assume that other uses are consuming moderately large quantities of this metal or that appreciable amounts of it are being transshipped from Europe. To the extent that a changing volume of supply signifies a changing pattern of use, the increased demand for molybdenum and vanadium in Europe should be of interest to domestic producers and consumers of these metals.

Jan 1, 1964

By Lyle A. Hale

The subject area known as upper Dry Valley is located 15 miles due east of Soda Springs in Sections 14 and 23, Township 9 South, Range 44 East, Caribou County, Idaho. The railroad extending from Soda Springs to its terminus at El Paso's Maybe Canyon mine is 8z miles to the north in lower Dry Valley. Initial data derived from trench work in 1962 revealed a variety of econom¬ically significant alterations of the phosphatic beds related to the rather unique geomorphic development in the northern part of phosphate lease 1-012989. It was apparent that such conditions, while valid for near-surface beds in a strike direction, would be misleading if projected to the proposed depth limits of strip mining. Consequently, a subsurface mapping program was initiated in 1963 to determine: (1) the depth and horizontal extent of weathering and related phe¬nomena, (2) the depth, thickness, and quality of ore beds and intervening strata, and (3) structural geology as a guide for mining procedures. Successful use of a scintillometer in 1956 to detect the subcrop position of phosphate beds in the Smokey Canyon area of southeastern Idaho led to the conclusion that gamma radiation surveys of drill holes could be a useful aid in subsurface mapping. The objectives of this paper are: (1) briefly to describe geologic features characteristic of the phosphate lease area and (2) to demonstrate the practical application and theory behind gamma radiation logging as an effective tool in the economic evaluation of a phosphate lease.

Jan 1, 1969

By T. Marcher, C. Mathiesen, M. Allende, S. Bauer

"A unique pumped hydro storage facility using the ocean as a lower reservoir, combined with solar PV to create consistent, clean power will be presented: the Espejo de Tarapacá Project is comprised of a 300 MW seawater pumped storage hydroelectric plant using the Pacific Ocean as its lower reservoir and an existing natural concavity at the desert as its upper reservoir. The plant site is located in Chile’s northern coast 90 km south of Iquique. The site is characterized by a rocky shoreline and about 600 m of flat terrain moving inland, with an abundance of rock outcrops, after which there is a steep 700 m cliff. The power house and all waterways will be underground. The main focus is to present the rocks being expected in the underground works. As one of the actual most tectonically active regions of the world the seismic activity is particularly relevant and will be outlined in the presentation. INTRODUCTION Valhalla Energy is an independent Chilean-owned power development company. It focuses on the development, ownership and operation of renewable power projects. Valhalla was founded in 2011 with the goal of developing Chile’s natural renewable energy resources and strategically diversifies the country’s energy matrix away from an overdependence on imported fossil fuels. Valhalla began developing pumped storage hydro projects to provide scalable, clean, competitive, and reliable electricity by combining Chile’s superior solar resources with the country’s unique and extensive coastline suitable for storage.The capacity for renewable energy supply is driven by two distinct and unique natural characteristics found in northern Chile: (1) the abundant and reliable solar irradiation in the Atacama Desert and (2) a coastal site that benefits from a steep cliff and a natural concavity both within a relatively small land mass (see Figure 1). There are several potential sites in the northern part of the country that can be developed. The “Espejo de Tarapacá Project” is the first one to be built and subject of the present paper."

Jan 1, 2016

By D. R. Taylor

The use of clay granules as carriers for pesticides dates from the early 1940's and by the present day represents a business conservatively estimated at between 200 -300 thousand tons / year in the U.S. alone. Aside from economic and specific target pest efficacy advantages, the use of clay granules as pesticide carriers also delivers a number of environmental benefits which will be reviewed. Topics to be discussed will include: I) drift control (versus liquid sprays), 2) mobility (in the environment), 3) worker safety, and 4) transportation (spill) safety.

Jan 1, 1999

By B. Anamaeric

Economic, environmental and operational disadvantages of the traditional blast furnace process has led to the development of direct smelting reduction processes, including those that utilize self reducing/ fluxing dried greenballs as iron oxide feed materials. This is mainly due to improved carbothermic reduction, carburization and reaction kinetics. In this paper, the morphological changes of the greenballs as they transform to pig iron nuggets are examined over time at a constant temperature of 1,400° C. The products produced after each treatment were characterized using optical microscopy, scanning electron microscopy/energy dispersive spectroscopy and point counting/image analysis. The changes in the percent metallized area, wustite dendrite and slag matrix content of the structures were calculated. It was determined that the transformations were initially controlled by dissolving and containment of iron oxides in the molten slag and their consequent reduction to iron, followed by coalescence of the metallized areas. The final transformations were controlled by the carburization of the metallized areas.

By A. W. Laughlin

Analytical costs are a major part of exploration programs in developing nations which may lack adequate laboratories. Laser-Induced Breakdown Spectroscopy (LIBS), a variant of atomic emission spectroscopy, can reduce exploration analytical costs and can provide the analytical results in <1 minute. CPI is now marketing battery-powered, backpack mounted analyzers, using LIBS to analyze for many elements of interest to the explorationist. LIBS is well suited to the analysis of elements in industrial minerals. Limits of detection in ppm for some of these are: Li-1, Be-2, Na-100, B-33, Sr-10, Ba-300, Cs-1, K-500, Fe-500, Mg-500, and Ti-500.

Jan 1, 1999

By Thomas A. Simpson

Hydrogeological techniques were used to solve problems of slope stability in open-pit mines of the Eufaula bauxite district, Alabama. Geologic and hydrologic data were evaluated and used to design a system of dewatering wells to enable the operators to mine bauxite more efficiently and economically. Walls of open-pit mines in the district were subsequently stabilized by the operation of the dewatering system. Three open-pit mines, each at varying stages of the mining process, of the A. P. Green Refractories Company, were used to develop a sequential series of guidelines that indicate how to effectively remove ground water from the formations surrounding the ore bodies in the district. The use of sound engineering principles in well design, in combination with the correct interpretation of the pit hydrology provided the basis for solutions of the slope- stabilization problem aided in the economical removal of bauxite from mines of the district.

Jan 1, 1975

By I. E. Odom

The rare magnesium-lithium clay mineral hectorite occurs at many places in the McDermitt caldera of Nevada-Oregon. Commercial development of several high purity deposits began in 1986. The hectorite was precipitated in a lake environment formed after collapse of the McDermitt caldera. Hectorite beds and lenses are associated with volcaniclastic sediments, limestones, dolomites, zeolites and locally sandy bentonites. The high purity deposits appear to be associated with hydrothermal areas. The hectorite consists of extremely small flake-shaped crystals, and Ca is the predominant exchangeable ion. Its color ranges from white to light green. Commercial uses developed to date include high brightness magnesium aluminum silicate products, organophilic clays, pulp retention, and ceramics. The MAS is used as a suspending agent, binder, stabilizer and thixotrope in aqueous solutions for cosmetics, household cleaners, pharmaceuticals and miscellaneous industrial applications. Organoclays are used in printing inks and paints.

Jan 1, 1992

By D. G. Chedgy

This article presents a novel design, called the Climax High Capacity Processor (HCP), for pre-combustion cleaning of coal. This design is particularly suitable for the plant capacities of 400 -660 TPH. The HCP is different from the conventional designs with an equivalent throughput in three major aspects: 1) the use of one large capacity HM cyclone to separate coarse and intermediate raw coal in a single circuit; 2) the elimination of the conventional secondary magnetics recovery system by use of the high efficiency Climax magnetic separators; 3) the use of "single line" piping with a minimum requirement of ancillary devices. In comparison with conventional designs with similar capacity, the HCP plant costs much less in capital investment, operation and maintenance.

Jan 1, 1997

By B. DANIEL MARJAVAARA, I. A. SOFIA LARSSON, ANNA-LENA LJUNG

The flow field and coal combustion process in a pilot-scale iron ore pelletizing kiln is simulated using a computational fluid dynamics (CFD) model. The objective of the work is to investigate how the thermal effects from the flame affect the flow field. As expected, the combustion process with the resulting temperature rise and volume expansion leads to an increase of the velocity in the kiln. Apart from that, the overall flow field looks similar regardless of whether combustion is present or not. The flow field though affects the combustion process by controlling the mixing rates of fuel and air, governing the flame propagation. This shows the importance of correctly predicting the flow field in this type of kiln, with a large amount of process gas circulating, in order to optimize the combustion process. The results also justify the use of down-scaled, geometrically similar, water models to investigate kiln aerodynamics in general and mixing properties in particular. Even if the heat release from the flame is neglected, valuable conclusions regarding the flow field can still be drawn.

Apr 20, 2021

By James A. Decker

Hanna has developed three production planning systems to help the mine engineers determine the sequence of mining from available ore supples. The Production Scheduling System was developed to give the staff a tool for long range planning by sequencing the removal of blocks from an open pit property. It was needed to determine the year of removal for each block so that the optimum present-valued pit limits could be established by our pit design program. Since in this type of planning short term grade control is less of a factor than it is in daily or monthly planning, the system gives the program greater control and more latitude in block selection. It permits only full blocks to be taken.

Jan 1, 1984

By Donald M. Hausen

Microscopic evaluation of trace quantities of metalliferous phases in flotation products requires counting large numbers of particles. Particle counts of many thousands may be required for precision, but not obtained practically by conventional microscopic techniques. A less tedious microscopic method for evaluating trace sulfides in mill tailings was developed for the O&apos;okiep Mining Company in South Africa. Hundreds of thousands of particles were evaluated by this method called "gross-counting." Gross-counting consists of counting microscopic fields rather than point-counting individual particles. Total counts are calculated by multiplying the average number of particles per field by the total number of fields examined over the entire mount. Total gross-counts range from about 20,000 particles for +200 to 100,000 or more for -400 mesh size material in lucite mounts. Sulfides and metallic particles in each field are identified and tallied along with field counts. Totals for each type of metallic particle are divided by the total gross-count to give volume percent which is corrected to weight percent by specific gravity factors.

Jan 1, 1969

By CEM SENSOGUT, OZER OREN, YASAR KASAP

The mining sector, which is important in terms of raw-material and energy supply, is seen as a sector with high number of fatal accidents compared to other sectors. In this century of heightened occupational health and safety awareness, it is important to review past accident statistics and analyze current deficiencies using the information in inventory. Although there are many studies assessing occupational accidents occurring in the mining sector, there are few studies using the nonparametric linear programming method. There are many input and output parameters related to occupational health and safety. Nonparametric linear programming method has been found to be useful because it provides simultaneous evaluation of these input-output parameters, does not require functional form in the analyses and provides guidance on the improvement needed by the related parameter. However, this method analyzes data using a single period of time and does not take into account any changes in efficiency over time. In the literature, there is no study in which the change of occupational accidents occurring in mining and even other sectors over time is examined and the Malmquist total factor productivity index (MPI) is used. Within the scope of the present study, the aim was to examine the change of occupational accidents occurring in Western Lignite Corp. in Turkey, where underground and surface production methods are applied, between 2005 and 2018. It is the first time MPI is used to examine the change of occupational accidents over time. The DEAP 2.1 computer program written by Coelli [1] was used in the solution of the models [2].

By J. Kou

The adsorption process, density and structural property of the oleate layer adsorbed onto a hydroxyapatite (HAP) surface at six different concentrations and three pHs (pH 8, 9 and 10) have been studied using the technique of quartz crystal microbalance with dissipation (QCM-D). The present study demonstrated the versatility and accuracy of the QCM-D for surface adsorption characterization. The real-time measurements of frequency and dissipation shifts with a hydroxyapatite-coated sensor revealed changes in the hydroxyapatite surface during the entire adsorption process. Chemisorption and surface precipitation of sodium oleate were also observed on the surface of hydroxyapatite through the use of Fourier Transform infrared spectroscopy(FTIR). Chemisorption dominated at low concentrations and high pH values and formed a rigid and thin adsorption layer. Surface precipitation of calcium oleate and micelles dominated at concentrations higher than critical micelle concentration (CMC) and lower pHs and formed a thick but dissipated adsorption layer with a high hydration level. Three distinct adsorption behaviors were identified from the different slopes of ?D-?f plots. The adsorption density was less than a monolayer at concentrations <0.164 mM, but increased significantly at concentrations higher than 0.821 mM at all three pHs. The critical concentration at pH 8 was 0.33 mM, which was lower than at pH 9 (0.821 mM) and pH 10 (3.3 mM).

Feb 1, 2012

By Langtry E. Lynd

The titanium dioxide pigment industry in the United States has always relied to varying degrees on imported titanium concentrates. Dependence on foreign ilmenite was especially high (generally over 85% of consumption) until 1942, when large-scale U.S. production of ilmenite began, and has since ranged from 12% to 47%. Rutile import reliance was generally in the 45% to 80% range until the early 1960&apos;s, when increased use in the chloride pigment process raised dependence on imported rutile to over 90% in most years since 1963. Import reliance of zircon, obtained almost entirely as a byproduct of titanium mineral production, has generally ranged from about 30% to 65% of consumption. This paper will examine the history of U.S. sources of these heavy mineral commodities, and will discuss the potential U.S. future supply in view of changing industrial uses and processes and the anticipated development of new heavy-mineral-sand processing operations, such as those at Richards Bay in the Republic of South Africa and in Sierra Leone.

Jan 1, 1978

By Joseph M. Zigich

The Anaconda Minerals Company operates a molybdenite and copper producing mine and mill facility near Tonopah, Nevada. Included with the milling facility is a ferric chloride leach plant for removal of copper mineralization from the molybdenite concentrates. Discussed are the engineering and construction schedules associated with the leach plant. The chemistry associated with the process along with a description of the process flow, equipment, and operating parameters are contained in the paper.

Jan 1, 1983

By P K. Kaiser, D A. Malovichko

Highly stressed excavations in hard brittle rock may fail by self-initiated, triggered or dynamically loaded strainbursts (Moss and Kaiser 2021). The low-frequency part of seismic radiation associated with strainbursts is described by a crush-type seismic source mechanism with a significant negative (implosive) isotropic component and a ‘pancake-shape’ CLVD deviatoric component. The seismic source is co-located with the excavation damage site. For such strainbursts, the ejection velocity is primarily related to the depth of strainbursting, the rock mass bulking characteristics, the duration of the bulking process, and the effectiveness of the support system. For dynamically loaded strainbursts, the displacement and energy demand may be augmented by the impact of the stress wave from a distant seismic event. This article describes the failure process and factors contributing to rock deformation and energy demands for support design. Case examples are used to demonstrate the dependence of rock displacements, rock ejection and energy demand on the factors described above. A seismic source model is proposed to assess the depth of strainbursting and the duration of the related bulking process by using seismic monitoring data. The implications for support design are briefly discussed.

Apr 26, 2022

By Zhe Wang, Tichang Sun, Yongqiang Zhao, Zhengyao Li

Coal-based reduction followed by magnetic separation is a promising technology for processing refractory iron ores. Analysis of the size distribution of metallic iron particles is an effective approach for exploring the mechanisms of coal-based reduction. As metallic iron particles exhibit very complex shapes compared with nature ores, approaches for measuring and characterising metallic iron particles still remain unclear. In this study, the size of metallic iron particles was measured and characterised using manual point-counting by optical microscopy technics and image analysis. The effects of CaF2 as an additive on behaviour of the particle size distribution (i.e. mean size and cumulative frequency distribution) were also determined. Results indicate that CaF2 had a significant effect on the growth of metallic iron particles. When the CaF2 dosage increased from 0 to 8%, the mean size according to the area method increased from 9.03 to 16.28 μm, while the promotion effect gradually weakened and generated many fine metallic iron particles when the CaF2 dosage exceeded 8%. An increase in CaF2 dosage also led to cumulative distribution curves gradually shifting to the right mainly because F− can break the crystal structure of each phase during the carbothermic reduction of titanomagnetite and reduce the stability of the lattice structure, thus reducing the melting point and accelerating the growth of metallic iron grains. Compared to different measuring methods, the area method is a more suitable approach for measuring and characterising the size of metallic iron particles.

Sep 18, 2020

By Seokwon Jeon, Ho-Young Jeong

"Various numerical methods have been tried to estimate the cutting forces of a TBM disc cutter. In this study, SPH/FEM coupled method was newly employed to improve the traditional FEM analysis. The disc cutter and rock were modeled by Lagrange and SPH codes, respectively. The numerical cutting test was carried out for representative Korean rocks with different cutting conditions. The results show that the cutting forces obtained from numerical simulation had a good agreement with those from LCM tests, and that applying SPH method to rock cutting model has advantages and improvement compared to traditional FEM method. Erosion criterion and erosion limit were not required to simulate the rock fragmentation process, and the cutting forces from the numerical simulation was more stable and accurate. The results indicate that the numerical simulation can be successfully used to estimate cutting performance of a TBM. 1. INTRODUCTION Various numerical studies have been carried out to accurately simulate the limitations of linear cutting machine (LCM) tests. Numerical modelling methods have advantages comparing with full scale tests in terms of cost and time involved. Many numerical methods have been used to simulate rock cutting process by different cutting tools and the studies are summarized in Table 1.In 2D simulations listed in Table 1, because they do not take account of rolling force and horizontal rolling mechanism of a disc cutter, indenter was selected as cutting tool in their modelling. For these reason, 2D modelling is not suitable for rock cutting modelling using a disc cutter. In contrast, 3D numerical models can take account of the indentation process by thrust force and penetration processes controlled by rolling force."

Jan 1, 2016