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By James A. Clum

The shift to lower grade iron ores, e.g., magnetic taconites, resulted in a shift towards agglomeration practices which could effectively deal with the fine particle sizes generated in the liberation and concentration processes. If the iron bearing particles are not extremely fine, e.g., -1/2 in + 100 mesh, sintering is an adequate means of agglomeration.(1) For the more dispersed ores which result in fine concentrates (more than 80%,-325 mesh), the fine particles must be agglomerated by mechanical means before final hardening, e.g., pelletizing.(1) In the pelletizing process, the essentially mechanical step of balling is extremely critical since the strength of the pre-fired pellet determines the firing conditions. The ability of the proper amount of moisture to hold together a ball of the very fine ore concentrate particles has long been recognized. It is a charac¬teristic of the reaction at the interface between the ionic solid of the ore concentrate and the polar water phase which overlays the solids. The strength in such moisture laden balls, the green strength, is a strong function of the water content (Figure 1) and thus deteriorates rapidly for either a small excess or a small deficiency of moisture. For purposes of commercial practice, the control of green ball handling properties by accurate control of ball moisture is too demanding. Moreover, as the ball is heated towards its hardening tempera¬ture, e.g., 1300'C, there is a substantial drying reaction which would lead to such a low dry strength of the ball that it would not support its own weight much less the weight of other balls in a firing furnace.

Jan 1, 1976

By R. W. M. Lai

In flotation or hydrometallurgical leaching of minerals, the cumulative metals recovery for a given process condition generally approaches a maximum value or an asymptote as the process time increases. This paper discusses the experimental methods of identifying and obtaining the asymptote of metals recovery through kinetic studies. In flotation, the kinetic asymptote of metal recovery, or ultimate recovery, is a function of grinding and collector dosage, but within a realistic variable range, is not a function of pH or temperature. However, variations in grinding, collector dosage, pH and temperature, all exert noticeable effects on flotation kinetics. Frothers generally have a minor affect on the asymptote, but have a major affect on flotation kinetics. The asymptote from batch flotation is found to be identical to that of a continuous flotation. In hydrometallurgical Leaching, the asymptote of metal recovery for a given leaching system is a function of such variables as temperature, particle size, and acid concentration.

Jan 1, 1983

By Joseph Githiria, Khadija Omar Said

Mineable material is defined using cut-off grade either as geological or economic cut-off grade. Both geological and economic cut-off grade affects the output generated in an open-pit mining operation. It distinguishes the amount of ore sent to the mill for processing and waste to the dump. This consequently affects the overall profits generated from the operation hence the need for cut-off grade optimization. There are several mining parameters that are considered in a typical cut-off grade model. They include economic, geological, and operational parameters. They have a significant effect to influence the cut-off grade selected in mining operations at any given period. Some of the parameters are stochastic in nature by having a random probability distribution that may not be predicted precisely. When selecting cut-off grades in a mine operation, the mining engineers must consider the dynamic nature of the operational parameters in order to maximize the net present value of the project. Modifying Lane’s cut-off grade model which was developed in 1964 to incorporate the stochastic parameters in the approach helps improve the net present value as shown in the paper. The modified Lane’s approach is developed into a stochastic computer-aided application code-named NPVMining. Using NPVMining, selected stochastic parameters are considered in this exercise to show the effect on the output (net present value). The selected parameters (price and grade-tonnage) are varied by ± 10%. NPVMining has a graphical user interface that makes it easy to use and displays results in a user-friendly way. It gives the user the choice to manipulate the data depending on the study being undertaken or any other factor affecting the specific mine. This paper analyses the effect of each of the selected mining parameters on cut-off grade using NPVMining to show the significance of monitoring their variance.

Jun 25, 2023

By Felicia F. Peng

Using a fuzzy logic controller, a signal applied on the processes may be generated through a linguistic protocol expressing an operator's intuitive control strategies. In this work, fuzzy logic controller and PID controller imposed upon the feedback liquid level control systems for a stirred tank are studied and compared. The construction factors including the shape of membership functions, number of fuzzy variables, number of inputs, number of rules, and different defuzzification methods are considered in design and formulating the fuzzy logic control strategies and algorithms. From the analysis of the strategies and control performances, an optimum controller may be generated by making use of the best combination of these fuzzy construction factors.

Jan 1, 1997

By C. Clark, J. Johnson, M. Stepan

"Shotcrete and mesh are often installed to control ground deformation, falls and ejection between bolts. The combination of mesh and shotcrete forms a panel or plate that is typically bent by ground extruding between restraining rockbolts. The ground pressure applied (that is, the resistance of these panels to bending) over large ground deformations is important for maintaining ground support safety. This paper describes a new test device that measures this resistance and its evolution over large deformations. Mixes of shotcrete, mesh and other components that can maintain significant support pressure are desired, a characteristic described as the “toughness” of support. Results show toughness depends largely on how shotcrete is integrated with other components. Shotcrete strength is less important. INTRODUCTION Ground control safety often depends on supporting, or at least containing, the ground between the rockbolts. Shotcrete and mesh, in various combinations and with other components, are often called upon to do this (Figure 1). Applications are especially common in mines with squeezing ground or seismic loading. The support pressure maintained during ground deformation is key to the performance of these systems, and to protecting miner safety. However, the toughness of a design is difficult to estimate. Researchers at the Office of Mine Safety and Health Research (OMSHR) responded to this deficiency or “gap” by designing a full scale test device, described in this paper, and beginning a testing program. Some initial results from this program are reported to demonstrate test capabilities.BACKGROUND - TOUGHNESS Mining in ground that fails from the combination of in situ and mining induced stress is commonplace. Ground support elements are installed to reinforce such ground and preserve mine safety. Typically, the strength of support is considered key, and is used to prevent or halt yielding. However, ground movements driven by creep of weak ground or seismic loading may be impossible to halt altogether. In these cases, it is essential that support is able to yield with the ground in a safe manner while maintaining confining pressure that mobilizes the strength of rock in the immediate perimeter of the opening. In addition, it’s usually desirable to contain ground between rockbolts to protect miners from loose rock that might fall or be ejected. Shotcrete and screen are often employed, sometimes together and in combination with other support elements, to accomplish this function. A key characteristic of such a system is its ability to maintain support pressure through large ground deformations, a characteristic often called “toughness” – especially in support systems incorporating shotcrete. Toughness can be quantified as the work done during deformation (e.g. force x displacement)."

Jan 1, 2015

By W. Rocher

The Minera Ojos Del Salado (?MINOSAL?) concentrator is located 20 kilometers southeast of Copiapo, Chile and processes copper ore provided by its Santos and Resguardo mines at a capacity of 4,200 tip (4,620 stpd). Phelps Dodge acquired the majority interest in MINOSAL in 1982. The principal incentive for this purchase was the exploration potential of the property. At that time, the concentrator plant was a small, antiquated installation with a capacity of 674 t/d (740 stpd). In 1982, the majority of the ore was produced from the Santos and Resguardo mines, but custom ores of copper, silver, and gold were also treated. The acquisition occurred at a crucial time in the copper business, since the price had fallen to nearly $0.50 per pound. In 1985, Phelps Dodge purchased the outstanding interest in MINOSAL and acquired 100% of the property. Today, after numerous improvements and two expansion projects, the concentrator is an interesting combination of old and new equipment. The regrind mills, for example, have been in service for about 50 years, while the ceramic concentrate filter represents the latest technology.

Jan 1, 1993

By A Pettersson

LKAB owns and operates two of the largest underground mines in the world in Northern Sweden. In Malmberget, with a production capacity of about 30,000 t/day of iron ore, the current main 815 m haulage level is rapidly approaching the end of Its life and plans are being made for its replacement on the 1000 m level. Due to the separation of the orebodies, trucks have been chosen for transporting the ore from the orepasses to the crushers. The trucks currently in use have a capacity of 120 tons. To increase the efficiency of the loaded haul, the new main level will have a favorable slope from the drawpoint locations to the crushers. From the new level the crushed ore will be transported by conveyor to the 815 m level for hoisting to the surface. The paper discusses the planned mining and transportation system.

Jan 1, 1998

By M. Karmis

"The process of coal mining, as indeed of the mining of any stratified mineral, is inevitably followed by some degree of sinking of the superjacent strata and consequently of the surface." Royal Commission on Mining Subsidence, Second and Final Report, London, 1927. INTRODUCTION The above statement was used to describe mining subsidence in the classic report of the "Royal Commission on Mining Subsidence," published in 1927. In fact, this phenomenon has been recognized in Britain since the early fifteenth century, as revealed from court records of disputes and litigations related to property damage above mine workings (Shadbolt, 1978). The first attempts to investigate and analyze the mechanisms associated with mining subsidence, however, date back to the 1800's and were pursued by Belgian Engineers. This research effort was initiated as a result of the widespread movements and subsequent structural damage suffered by the City of Liege in the 1820's. The most notable achievement of the Belgian school of that era was he publication of Gonot's treatise "Loie de la Normal" in 1871 (Gongt, 1871).

Jan 1, 1982

By N. Duru

"Gravity concentration is still a challenging area in the mineral industry. This is mainly because of the fine size valuable mineral losses to the tailings during its application. But the recent developments in centrifugal separation methods and their mutual application with conventional separation techniques has increased mineral recoveries. In this paper, field application of conventional gravity separation methods with the combination of 2” diameter hydrocyclone cluster unit and a multi gravity separator (MGS) was discussed. Additionally, particle size distribution and chromite content of the plant streams is presented and initial laboratory test results were compared with the actual plant data throughout the paper. As expected, field data showed derivations from the laboratory tests but the combination of MGS and conventional gravity separation techniques resulted in gravity separation of -0.1 mm chromite particles. INTRODUCTION The purpose of this mineral processing plant project was to investigate the possibility of upgrading chromite ore from 12% to 48% Cr2O3 and having final tailings assay as 2% Cr2O3. For this reason, initially a set of laboratory gravity separation studies were conducted to evaluate the performance of combination of 2” diameter hydrocyclone cluster and multigravity separator. After obtaining successful results from the laboratory work, a feasibility study was initiated. Economical results of the feasibility study showed that an achievable high net present and return on investment values. Following the investment decision; engineering, equipment procurement, construction of the processing plant was completed in eighteen months. This paper focuses on the initial laboratory test work results, operational data of the 2” diameter hydrocyclones and MGS units; resulted chromite recoveries. Processed ore has the chromite associated with serpentine and olivine minerals. The chromite particles are generally in round shapes with sizes between 50 µm to 1600 µm and average size of 450 µm. The microscope images of the chromite and associated formations are presented on Figure 1.Chromite is formed in mixture with iron oxides, with varying amounts of magnesium, aluminum. The average chemical composition of the representative drill core samples of the ore deposit is given on Table 1."

Jan 1, 2017

By Lawrence A. Roe

This paper describes research and development efforts leading to a wet process for the beneficiation of Western talc ores in which the values are primarily present as soft, platy talc mineral. The mineralogy of the ore, as it relates to the logic of utilizing an uncomplicated, attrition-scrubbing sedimentation process is described. Bench-scale laboratory testwork and a pilot-plant test program are described. The pilot-plant program included production of several tons of products. The thickened talc slurries were very difficult to dewater prior to the drying step. Dewatering difficulties were overcome by use of a high-speed centrifuge. The centrifuge cake was dried either by tray, flash or spray drying. The successful use of one high-grade talc product as titanium dioxide extender in paper is discussed. The talc product has extremely low abrasion values, an important characteristic for minerals used in paper manufacture. It is concluded that this wet process for soft talc ores is capable of producing high-purity talc products for paint, paper, cosmetics and other industrial uses re-quiring very pure soft talc.

Jan 1, 1972

By B. J. Scheiner

The Federal Bureau of Mines has developed a chlorine-oxygen leaching technique for the recovery of metal values from lead-zinc sulfide concentrates. Lead, zinc, copper, cadmium, and silver extractions are in the 95- to 99.9-percent range. During leaching, the zinc, copper, cadmium, and silver are solubilized as metal chlorides, and lead is converted to insoluble lead sulfate. The iron contained in the concentrate is converted to insoluble iron oxide, and a majority of the sulfide is converted to elemental sulfur Minor metals such as copper, cadmium, and silver are recovered by precipitation with zinc dust. Zinc is then recovered from the purified zinc chloride solution by evaporation to dryness; the lead is recovered from the leach residue by brine leaching and crystallization to produce lead chloride. Recovery of zinc and lead metals by fused-salt electrolysis of the chlorides is being studied separately.

Jan 1, 1975

By M. C. Rockwell

There are approximately 1,800,000 t of discarded dolomitic-limestone tailings from the Gays River lead/zinc mining operation in Nova Scotia. Neutralization effectiveness similar to an agricultural grade limestone and low contents of residual metals make the tailings a suitable source' of soil conditioner material for the local market. However, the fine particle size, 98% passing 147µm, and a high moisture content make their handling and application difficult. Agglomeration of the tailings into relatively small hard pellets was investigated and difficul¬ties were overcome. Pellets with a range of pH values and various amounts of soil nutrients and moisture content less than 10% were obtained, from tailings containing 20% initial moisture, through the addition of less than 15% selected materials.

Jan 1, 1985

By S. Guo

In this paper, a model for the resin anchor bolt system is developed in which the smooth bar is modeled by using one-dimensional truss elements and the resin annulus is modeled by using axisymmetric elements. These two submodels are combined together and then incorporated into the' existing computer code ROOFBOLT. After this development, all of the components in the resin anchor bolt system including smooth bar, bearing plate and resin annulus can be correctly modeled.

Jan 1, 1995

By D. K. Grubbs

Anorthosite is an abundant, domestic source of alumina with reserves in individual deposits ranging from a few billion to hundreds of billions of tons. While anorthosite contains less alumina than does kaolinite, its CaO and Na20 contents are significantly higher (Figure 1). Alumina can be produced from anorthosite by alkaline, soda-lime sinter or acid processes. CaO and Na20 are advantageous because they are reactants consumed in alkaline processes. Acid processes require high calcium plagioclase feldspars (bytownite-anorthite) to obtain high alumina extraction because the lower calcium plagioclase feldspars (andesine-labradorite) are not as readily dissolved during digestion. The layered Raggedy Mountain Gabbro group in the Wichita complex in southwest Oklahoma is a high calcium anorthosite that could be processed by acid, sinter, or alkaline methods. Chemical grade limestone in the Arbuckle Group is located within 45 km of the anorthosite (Figure 2).

Jan 1, 1980

By R. Q. Honaker

Although the fundamental principles of hindered bed classifiers are relatively simple, the complex interactions between the operating parameters provide a degree of difficulty that hinders the ability for on-line plant optimization. Thus, a dynamic population balance model was developed for determining the hindered settling velocity of particles varying in density and size. The steady-state results of the model include partition curves as a function of particle size and density as well as metallurgical data. A statistical comparison of the simulation results with those obtained from industrial units reveal a high level of accuracy with adjusted R2 values greater than 0.95.

Jan 1, 1999

An appropriate scale-up methodology is very useful for ball mill design and optimization of the grinding circuit. To date, the scale-up is based on the selection and breakage function method using lab mill data. However, a major drawback of that approach is that the charge motion in a lab mill is vastly different from that in a large industrial mill. Therefore, in the methodology proposed here, first the energy of individual collision in the mill is computed employing the discrete element method (DEM). Then the breakage of particles as a function of collision energy is studied in a separate experiment. Together, this information constitutes what is known as collision energy based population balance method. The appropriateness of this method is shown for 38-cm ball mill.

Jan 1, 1998

By Kadri Dagdelen

The classification of selective mining units (SMU) and the assignment of grades to those classified SMU are very important in open pit mining, especially for precious metal mining. When the classification is done, the true values of the SMU grades are unknown. These unknown SMU grades are mostly estimated analyzing the geologic data and blast hole assays. To classify the SMU's based on the estimate of SMU grade, without considering uncertainty associated with unknown SMU grade, yields incorrect decision in sending material to appropriate destination. In this paper, a method is developed to classify SMU's considering the uncertainty associated with unknown SMU grades. By using this method, traditional estimate of SMU grade is replaced with conditional probability distribution of SMU grade. The decisions about the destination of a given SMU are performed by minimizing the loss due to misclassification. Also, the asymmetric loss function by penalizing the overestimation and the underestimation unequally is used in assigning grades to classified SMU's. A case study is carried out to apply the traditional ore control techniques and proposed method in classification of SMU's and the assignment of the grades in a hypothetical gold mine.

Jan 1, 1999

By A. Datta

An appropriate scale-up methodology is very useful for ball mill design and optimization of the grinding circuit. To date, the scale-up is based on the selection and breakage function model using lab mill data. However, a major drawback of that approach is that the charge motion in a lab mill is vastly different from that in a large industrial mill. Therefore, in the methodology proposed here, first the energy of individual collision in the mill is computed employing the discrete element method (DEM). Then the breakage of particles as a function of collision energy is studied in a separate experiment. Together, this information constitutes what is known as collision energy based population balance model. The appropriateness of this model is shown for different batch grinding mills.

Jan 1, 1999

By W. J. D. Stone

Many of the common valuable minerals have a magnetic susceptibility which is sufficiently high to render them amenable to magnetic separation. In addition,, many minerals which form the unwanted constituents of an ore can be removed by magnetic means. Magnetic separation in general has suffered seriously from, the lack of a high intensity wet separator. It is only recently that such a separator has become available to the industry. Prior to this, high intensity magnetic separation has been limited to the use of the dry techniques. Since the introduction of the Jones Wet High Intensity Magnetic Separator, extensive test work has been conducted to investigate possible applications. From the investigations conducted and the discussions that have taken place in the industry, it is apparent that the important mineral characteristic of magnetic susceptibility is not receiving the attention that it deserves. Applications for high intensity wet separation are being found in areas hitherto not considered.

Jan 1, 1963

By James H. Harmon

As the trend to deeper mines, producing from marginal ore bodies, continues, mine hoists and their associated equipment will become more sophisticated, complex, large and expensive. Over the past two decades, mine hoisting equipment and systems have moved from steam engines to static rectification of ac to dc, and electronic controls are the standard. It is the intent of this section to present what is currently available in the field of mine hoisting equipment and systems. Because the present engineer has been exposed longer and more intensively to such things as computers, electronic devices, and machine design, no attempt has been made to make this a layman's article. Contributions from the electrical design and application engineer, gearing and hearing design engineers and other specialists have been incorporated. Some material will be devoted to electrical drive systems, rectifiers and gearing design among others. These items are inherent in the design of a mine hoisting system and the subsequent selection of the correct, most reliable and most economic system. The mine hoist can be a bottleneck between the underground mine and the surface mill. Correct selection of the right type of hoist is imperative. In this vital link between mine and mill, crude estimates of hoist capacity are not good enough, and the mining engineer must design and select the right hoisting system to meet the design specifications. 15.1-MINE HOIST TYPES There are two basic types of mine hoists available anywhere in the world today: the drum hoist on which the hoist rope is actually stored during the hoisting cycle, and the friction (Koepe), which merely passes the rope over the wheel during the hoisting process. Drum and friction hoists are "generic" terms which describe the two basic categories. Within each category are variations, as below. 15.1.1-DRUM HOISTS Drum hoists, as noted, actually store the hoist rope on the drum much the same as line on a fishing reel. To accomplish this task, the drums are so designed to store, in one or more layers, the footage of wire rope equal to the total maximum hoisting distance plus sufficient rope for cutting and inspection at regular intervals and for holding to the drum (see Fig. 15-1). Usual practice in hoist drum design is to allow three turns of hoist rope for holding on the drum and three turns for inspection cuttings. 1. Single-Drum Hoists-Fig. 15-2 shows a typical single-drum hoist as manufactured by most U.S. heavy-mining-equipment companies. With the exception of some very minor features, this design configuration is standard throughout the U.S.A. Fig. 15-3 is a plan view of a typical single-drum mine hoist. This particular hoist has a single-motor drive and a double-reduction set of gearing.

Jan 1, 1973