Search Documents

Mechanism of Modified Sodium Silicate on Fluorite Ore Flotation

Sep 13, 2010

By J. B. Oosthuizen

Mechanical rock breakers are used in block caving operations to reduce the size of ore fragments which are too large to pass through grizzlys at the load-haul-dumper tipping points. Several layouts of grizzly, rock breaker and ore pass are possible. The authors evaluated three different layouts at the Premier Mine Division of De Beers Consolidated Mines. The first layout consisted of a 15m surge bin before the breaker, which was located 15 m below the production level. The second layout had a 43 m longs urge bin, with the breaker located 43 m below the production level. The third layout did not have a surge bin, the breaker was located on the production level and operated at the tip. The ore throughput, availability and utilisation, delays, costs and operational experience with each system are discussed. It was found that the rock breakers did not represent a bottleneck in the ore transfer system and a surge bin did not significantly improve the production capacity. The mine has decided to make use of rock breakers situated on the production level, breaking rocks at the tip.

Jan 1, 1997

By L. Bircumshaw

Paper written on project work carried out in partial fulfilment of BSc (Eng) (Chemical) degree This paper details the formulation of a mathematical model for the simulation of a primary bioleach reactor, with specific reference to the leaching of pyrite. The model is based on the direct reaction mechanism, where the leaching of pyrite is said to occur via a two-step process. The process involves the formation of ferrous?iron through the chemical leaching of pyrite and subsequent bacterial oxidation of ferrous-iron back into ferric-iron. At steady state the rate of chemical leaching and bacterial oxidation are linked by the ratio of ferrous-iron to ferric-iron in solution. The extent of conversion of pyrite in the reactor system is described using the segregated flow model, with the exit age distribution of the solid phase being described by the Tanks-in-Series model. The final phase in model formulation involves the inclusion of steady state material balances on the bacteria and fluid phase components. The model is compared to pilot plant data and laboratory data for two different types of pyrite concentrates, with simulation results showing that the model is in good agreement with the data. Author key words: Bioleaching; pyrite; primary reactor; modeling; segregated-flow model; tanks-in series model.

Jan 1, 2006

By S. Kelebek, E. Yalcin

"Two composite samples of a gold-bearing ore from North Western Quebec (Barry Township) were tested to assess their grindability, recovery by flotation and Knelson concentrator as well as extraction using cyanidation.Work index values (BWi) for two composites were found to be 10.4 and 11.0 kWh/tonne, respectively. Flotation tests involved feed samples for which the particle size ranged from a P80 value of 205 ?m to 53 ?m, which resulted in gold recoveries of 91.8% to 95.8% (at gold grades of 130 to 140 g/tonne). Cyanidation tests indicated gold extraction levels ranging from 94.2 to 97.5%. Higher, recoveries were obtained at finer grind sizes and higher cyanide strengths. However, the grind size had a bigger impact on gold leaching. Gold grade and recoveries obtained with the Knelson concentrator device were lower than those obtained by flotation. Mass recoveries to concentrate products strongly depended on the fluidization pressure used. High gold recoveries can be obtained generally at low water pressures of 3 to 4 psi. Higher water pressures produced more selectivity at the expense of higher gold losses.It can be concluded that the gold ore samples tested have good characteristics due to moderate levels of energy requirement, high gold recoveries and extraction rates attainable.INTRODUCTIONBench scale testing of ore samples is an important step in the long series of metallurgical and economic studies involved in bringing new ore bodies into production (Coleman, 1980). Through a laboratory testing program, the behaviour of an ore in a particular process on a larger scale can be established. In an exploratory manner, this testing can be helpful for classification of ores in terms of “good ore” or “problematic ore” by providing preliminary information on recoverability of target minerals. Potential problems if any can be assessed by further investigation of products (e.g., middlings) obtained as a result of testing. A detailed bench scale experimental program in the metallurgical laboratory can also provide the background work for flowsheet development. Depending on the simplicity or complexity of the ore to be tested and type of details required from a testing program, the amount of samples required in the mineral processing laboratory can vary from several kg to more than one hundred kg depending on how detailed the metallurgical testing program is."

Jan 1, 2008

By Kimberlee Falkenstein, Volha Kibitkina, Jessica Steeves

A series of experiments were conducted to obtain site specific constants for the vibration produced by a single charge and by more charges detonating in sequence, using short delay intervals. All charges were placed in relatively long boreholes in granite without a free face other than the ground surface. The boreholes were filled with water to provide good coupling with the rock and to provide identical confinement for all the blasts. Vibrations were recorded close to each blast in the vertical direction by uniaxial high frequency geophones and far field using a triaxial geophone.

Jan 1, 2013

By C. Balci

Specific energy is defined as the amount of work required to break a unit volume of rock and is used to predict the performance of mechanical miners. It is obtained from full-scale rock cutting experiments, which require large block samples, experienced personnel and expensive equipment found in only a few research centres in the world. Estimation of the optimum specific energy, at which a given geological formation is excavated at optimum cutting geometry in the most energy efficient manner, from mechanical rock properties to predict the performance/efficiency of roadheaders is the basic aim of this study. The mechanical rock property tests require only core samples, which are easier to obtain and to test. In this context, full-scale rock cutting tests are performed on 23 different rock, mineral and ore samples including sandstone, claystone, tuffite, chromite, trona and copper collected from some operating mines in Turkey. The optimum specific energy values are obtained for each sample. Physical and mechanical property tests are performed on the core samples obtained from the same samples to determine uniaxial compressive strength, indirect (Brazilian) tensile strength, static and dynamic elasticity moduli, Schmidt hammer rebound values, density, and Cerchar abrasivity index. The relationships between the optimum specific energy and the mechanical rock properties are analysed using statistical methods. The results indicate strong relationships between the optimum specific energy and the mechanical rock properties. The strongest relationships are found by using uniaxial compressive strength and tensile strength. The performance models developed in this study are in good agreement with the empirical models previously developed for roadheaders and can be used reliably for prediction purposes. Keywords: Mechanical excavation, roadheader, performance prediction, rock cutting, optimum specific energy, mechanical properties of rocks.

Jan 1, 2004

By Jack Touseull

On November 15, 1972, the Bautsch mine, a lead-zinc mine in Paleozoic dolomites, experienced a massive rock failure involving 3 to 5 million tons. Because this failure was large and extended to the surface, it was included in the Federal Bureau of Mines investigations on "Massive Rock Failures." Analysis of the rock mechanics and mode of failure revealed that failure at the Bautsch mine was the result of the interrelationship of many factors. Factors related to the failure were found to be external and internal to the mining environment. Unlike internal factors, external factors were not apparent and, therefore, many external factors were investigated; some of which are not normally considered in rock mechanics analyses. External and internal factors determined to be of significant importance were: (1) precipitation, (2) fractures, (3) plastic clay layer, (4) topography, (5) rock alteration, (6) bedding, and (7) mining zone dimensions. Because of the conditions at the mine, failure could have been predicted without extensive instrumentation. Application of basic geologic and engineering principles to the internal and external factors could have predicted failure. Alternately, failure would, in all probability, have been delayed by years if, after 1962, mining had been curtailed in the area of failure.

Jan 1, 1980

By Christian Flores

El proceso que se enfrentó en Tambomayo tuvo su principal complejidad en llevar un proyecto en etapa de exploración hacia la construcción de una a unidad productiva la cual permita obtener resultados económicos y trabajar con altos estándares operacionales en el que prime la seguridad y un buen clima laboral, acompañado al hecho de que la empresa cuenta con una cultura operativa tradicional, lo que género que las principales dificultades para la toma de decisiones es que se tengan que ir derrumbando paradigmas operacionales y de esta manera ser un agente de cambio para el logro de los objetivos.

Sep 1, 2017

[ ]

Jan 1, 1938

The following paper on the development of processes for the treatment of crude ore, accumulated dumps of tailing and slime at Broken Hill, has been prepared by a committee of the Broken Hill Branch of the Australasian Institute of Mining and Metallurgy, with the object of recording, in chronological order, the developments of the various processes which have led up to the metallurgical practice of the present day.

Jan 1, 1930

By Kirsten Corin, Belinda McFadzean, Cyril O’Connor, Jenny Wiese

The Bushveld Complex of South Africa contains almost 90% of the world’s reserves of platinum group minerals (PGMs). In the flotation of PGMs, there are significant challenges arising from the need to treat ever-decreasing grades of the relevant ore deposits. The major challenge in the flotation of these ore bodies is the control and management of the gangue minerals, particularly silicates such as orthopyroxene, plagioclase feldspar, and pyroxene which are often rimmed with talc which makes them naturally floatable. It has been shown that various polysaccharide depressants such as CMC and guar have different properties in terms of depressing the gangue minerals. Since the PGMs are often associated with sulphides, copper sulphate is widely used as an activator in PGM flotation but can inadvertently activate the gangue minerals as well as reduce the recovery of PtTe2 which accounts for up to 40% of the Pt in the Platreef ore body. Depressants also reduce the mass of solids reporting to the froth and can thus destabilise the froth. This effect on the froth can be mitigated by using higher frother dosages or water of higher ionic strength. Reducing chromite recovery is of critical importance since high levels may negatively affect the downstream smelting process. Chromite recoveries can however be reduced through the application of gravity separation or reducing entrainment through reduced water recovery. In summary, due care needs to be taken to carry out site test work to develop an optimum ratio of collector, frother, activator, and depressant to ensure that the highest grades and recoveries of the PGEs are obtained while reducing depressant dosage as much as possible.

By Carl-John Grävare

This paper deals with some of the systems and equipment that are being developed and/or are in use in Scandinavia. The main subject is the development of loading tests on the piles using monitoring equipment. This paper also describes ground improvement using lime-cement columns, expander body piles and steel core piles.

Jan 1, 2000

By Fred Breu, Ronald E. Heuer

INTRODUCTION The Point Lepreau nuclear generating station was constructed in the late 1970's and early 1980's by the New Brunswick Electric Power Commission. Point Lepreau is a small peninsula on the north shore of the Bay of Fundy, about 55 km west of St. John, New Brunswick. Cooling water for the plant was to be obtained from and discharged into the Bay of Fundy by the system of shafts and tunnels illustrated in Fig. 1. The design engineer for the cooling water system was Albery, Pullerits, Dickson and Associates, Ltd., Toronto. Ferrera-Resco Ltd, Windsor, Ontario, was contractor for construction of the cooling water shaft and tunnel system, which was done between 1976 and 1979. The senior author was project manager for Ferrera-Resco, the junior author served as consultant to Ferrera-Resco on evaluation of certain geotechnical questions which arose during construction. SITE CONDITIONS Geology Except for limited overburden soils at the onshore shaft sites, the tunnels and shafts were constructed entirely in Triassic conglomerate, sandstone, and siltstone, with some shale interbeds. The bedding strike averaged about N6°E, The dip was to the west at about 30° along the Discharge Tunnel and 40° along the Intake Tunnel. Rock along the Intake Tunnel was mostly sandstone and siltstone and more thinly bedded, with RQ D generally in the range of 50 to 60%. Rock along the Discharge Tunnel tended to be coarser sandstone and conglomerate and more thickly bedded, with higher RQ D averaging about 80%. In addition to bedding joints, two other joint systems were identified

Jan 1, 1985

Fines and unnecessarily small rock fragments are created by as many as four identifiable breakage mechanisms which operate close to the charged section or sections of the blasthole. The peak blasthole pressure (Pb) should not exceed that value at which the rock starts to fail in compression. Excessive Pb values can be prevented by carefully selecting:1. the composition, density and/or diameter of the charge, and2. the initiation/priming system.The percentage of fines increases with:1. increases in the charge diameter:blasthole diameter ratio, burden distance, blasthole diameter, effective sub-drilling and size of blast, and2. decreases in blasthole spacing, stemming height and the length:width ratio of the blast block.Decked charges tend to reduce the percentage of fines.Excessive fragmentation is more evident in buffer blasting and sinking cut shots than in blasts fired to a clean free face. Initiation sequences which give effective burdens considerably less than drilled burdens encourage the minimization of fines, as does an inter-row delay time which promotes good progressive relief of burden.The wastage of explosive energy in creating fines is most pronounced where fully-coupled, energetic charges are fired in weak and/or highly porous rocks. This is especially so where forward movement of the strata is impeded by buffer rock, excessive burden distances and/or inadequate inter-row delay times.

Jan 1, 1979

By T. Watanabe, S. Hayashi, M. Hayashi, K. Nagata, H. Fukuyama

Chemical states of fluorine in CaO-SiO2-CaF2glasses in a composition range of CaO/SiO2=0.5?1.3 and 5?25 mol%CaF2have been investigated by 19F solid-state NMR with and without MAS. The isotropic chemical shifts of the glasses are close to those of cuspidine crystal (59.4 and64.3 ppm with respect to C6F6) and CaF2crystal (58.6 ppm). The fluoride ions are coordinated with four or less than four calcium ions in this composition range. The chemical shifts move to the lower frequency with an increase in the CaF2content, whereas those are not affected by theCaO/SiO2ratio. The ionic distance between calcium and fluoride ions increases with an increase in the CaF2content. The chemical state of fluorine is not disturbed by the degree of polymerization of the silicate network. Comparing the MAS and static NMR spectra, the second moment attributed to 19F-19F dipole-dipole interaction has been estimated. The values of the glasses range over 3.1?7.3107Hz2andthose are larger than the calculated value of cuspidine crystal. This indicates that fluoride ions form Ca-F clusters in the glasses and that the size of clusters increases with increasing the CaF2content. Keywords: chemical state of fluoride ion, CaO-SiO2-CaF2glass, solid state 19F NMR spectroscopy

Jan 1, 2004

Jan 1, 1970

The following Inventory was prepared to provide mineral deposit data to the U.S. Army Corps of Engineers for use in the Resource Development Navigation Study in Alaska. The inventory was prepared using data contained in the U.S. Bureau of Mines Minerals Availability System (MAS) database. The Alaska portion of the database contains Information on over 7,000 mineral locations and deposits throughout the state. When MAS was established In 1975, database entries were originally compiled from literature searches by both Bureau personnel and contractors. Deposit data are obtained/maintained through Information gained from a variety of sources, Including published and unpublished Bureau of Mines reports, records, and files; U.S. Geological Survey (USGS) Bulletins, Professional Papers, and other reports; technical and professional Journals; State and other Federal agency publications; data generated during field examinations; and information obtained from knowledgeable individuals. Because of the size of the data base, many of the data have not been significantly modified since initial entry. Each deposit on the MAS data base has a sequence number of the following form:

Jan 1, 2011

By G. F. Sowers

Excavation bracing is a special structural system. It is built from the top down. The design is controlled by the economical construction of another structure as well as by the movement of the ground beyond the limits of its construction. It serves a number of purposes, all subordinate to the construction of the principal structure. Despite its importance, bracing design and construction is frequently overlooked in project planning, causing delays and expensive changes. Thoughtful planning, good design and resourceful, innovative construction can improve construction safety and save time and money.

Jan 1, 2010

By M Edwards

The paper outlines the successful application of some of the on-belt technologies available from Scantech International Pty Ltd and how these have provided benefits in a number of mining and mineral processing operations. Effective process control requires real time analysis so quality can be fed back to the previous process and fed forward to a subsequent process. A range of on-belt analysers that allows for full stream, continuous, non-contact analysis of conveyed materials is available to achieve this. Real time results can provide timely information for effective process control. Benefits of on-belt analysis systems become more evident once the true variability of material quality and moisture content in conveyed flows is measured. To obtain economies of scale in mineral processing operations large material flows are achieved using conveyors. The cost and effort to sample representatively increases as conveyor flows increase. One sample may represent a few tonnes or up to 10 000 tonnes of material. The turnaround time between sampling and availability of sample analysis data does not allow real time process control. Tonnage flow rate, moisture content and elemental or mineralogical composition are required to perform effective process control of most conveyed streams. Tonnages can be effectively measured using belt weighers. The analyses derived from small samples supplied by conveyor-based sampling systems contain high variability. On-belt, continuous analysers see all the material and, through short term compositing of analyses, supply less variable results. Real time analysis helps operators develop a better understanding of material variability. Analysers can be effectively utilised to improve the consistency of product quality through bulk sorting and blending control. Many existing users of the technologies have gained competitive advantages through their ability to supply a more consistent quality product to the market.

Jan 1, 2008

By H. R. Thorpe

A floating gold dredge operating in coarse alluvial gravels of the Grey River on the west coast of the South Island, New Zealand, generated high concentrations of clay and colloidal particles in the dredge pond, which entered the groundwater system. Sampling was carried out at depths down to 20 m and it was found that variation of the length of the flow path occurred because of the movement of the dredge towards the piezometers. The alluvial gravels, the suspended sediments, the groundwater system and the water chemistry were all studied. Sediment concentrations were found to be highly variable with depth, but the relative concentrations in the depth profile were generally consistent as the flow distance shortened. The sediments were extremely fine and travelled further through the gravels than predicted. Comparison of field results with the available theory of deep filtration in clean beds of porous media gives some basis for estimating the behaviour of fine sediments in other alluvial systems

Jun 19, 1905