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By C. H. Herty

The results of a study of the open-hearth process from the physicochemical viewpoint are given. This study includes experimentation in small laboratory furnaces and in standard 100-ton furnaces. The behavior of manganese, carbon and phosphorus are quantitatively explained. The action of "residual" manganese is discussed with reference to its relation to iron oxide dissolved in the metal. The solubility of CO in steel and its relation to dissolved FeO and carbon is given. The equation for phosphorus elimination has been tested out on a 200-ton furnace and the results are given in the text. The effect of temperature and slag composition on the elimination of metalloids in the basic open-hearth process has been qualitatively understood since the early days of steel making. The quantitative effect has, however, only recently been brought to attention. The effect of slag composition has received more attention than that of temperature, primarily because the range of finishing temperatures in the basic open-hearth process is small compared to the large variations found in the composition of the slag at different periods during the process, and to the variations occurring with the use of raw materials of different degrees of impurity. The effect of slag composition on the elimination of metalloids has been studied by Styril from the thermochemical standpoint. This method is open to serious errors, in that thermochemical data at 2900' F. are very inaccurate and in many cases completely lacking. Feild2 has calculated equilibrium constants from the rate at which the metalloids are eliminated. The effect of slag viscosity on rate of elimination will affect the constants calculated by this method. Whitely,a Colcough4 and others have used slag compositions as the basis for calculation of constants by which the extent of elimination may be calculated.

Jan 1, 1926

By D. Berberick

On January 5, 2012, the Mine Safety and Health Administration ordered the closure of the Silver Shaft, the primary underground access to Hecla?s Lucky Friday Mine, for removal of built up backfill material that accumulated over time on the shaft walls and furnishings. Lucky Friday and Cementation USA personnel worked quickly to identify the most effective means to get the mine back into production. The team developed a fast-track procurement and refurbishment plan utilizing shaft sinking winches, headframe modifications, a partial shaft sinking Galloway, and modified cages to not only complete clean-off of buildup, but also replace pipe brackets, shaft steel, and power and communications cables as needed in the 1,860 m (6,100 ft) deep shaft within 14 months.

Feb 23, 2014

By Dimitrios Fillippou

Magnesium hydroxide is used in a number of industrial applications, from the neutralisation of acid effluents to the production of pharmaceuticals. High-quality magnesium hydroxide powders can be produced by hydrating slow-reacting magnesia in dilute magnesium acetate solutions. The process of magnesia hydration shows many similarities with a typical hydrometallurgical leaching operation; however, its kinetics are crucial not only for process design and control, but also for the production of powders with a desirable particle morphology. This article shows the results of an experimental work whereby industrial heavily-burned magnesia powders were hydrated in 0.01 to 0.1 mol/L magnesium acetate solutions at temperatures ranging between 333 and 363 K. Examination of the magnesium hydroxide produced and the analysis of the kinetic data suggest that the hydration of heavily-burned magnesia in magnesium acetate solutions is a dissolution-precipitation process controlled by the dissolution of magnesia particles. The activation energy was estimated to be 60 kJ/mol, while the reaction order with respect to magnesium acetate concentration was found to be about one.

Jan 1, 1999

By Charles C. Dahl, Gordon C. Presley, Andrew E. Nevin, Bruce A. Kennedy

How does SME-AIME cope with profound changes in technology, markets - and most importantly - in employment patterns facing its membership today? This is the question that prompted the Society's Board of Directors to appoint a Long-Range Planning Commission (LRPC) (see ME, Feb. 1984, pp. 118 and 128). This is also the question addressed most particularly by the LRPC's Scope Committee. The Committee started its deliberations by asking such basic questions as "Who are we?" and "What is our business?" The Scope Committee then reviewed the findings and recommendations of other more specialized committees to develop and integrate their concepts of the Society's business for the next 10 years. The policy-making suggestions of the LRPC were reviewed and acted upon by the Board of Directors at its open meeting in Los Angeles on Feb. 26, 1984. At the Oct. 23-26, 1984 SME Fall Meeting in Denver, the Board will again review LRPC recommendations. In answer to the question "Who are we?" the Scope Committee proposed description, which was accepted by vote of the board of directors: . . A technical and professional organization that consists of individual members, namely those mining engineers, metallurgists, geologists, earth scientists, economists, managers, educators, and other professionals concerned with all facets of exploration, production, distribution, and using of mineral commodities. "These mineral commodities include all metals; industrial minerals, including construction materials and fertilizers; coal, oil shales, tar sands, and other mined fuels. Among the earth's mineral resources, only wellpumped oil and gas lie outside the Society's specific purview. "Traditionally, SME members work in the fields of engineering, technology, exploration and discovery, development, construction, mining, quarrying, beneficiation and processing, handling and transport, equipment manufacturing, sales and marketing, data processing, safety, land reclamation, environmental protection, taxation, administration, and management of these elements. "Members practice their professions in industry, in universities and research institutions, and in government. They may be operators, manufacturers, sales persons, contractors, consultants, analysts, researchers, educators, advisors, regulators, or members of supporting staffs. "The members of the Society are leaders in dedication to their crafts, in innovation, and in the pursuit of excellence. Among their numbers they count the most distinguished of engineers, applied scientists, and managers. "The Society is based in the United States, is active on a worldwide basis, and is open to nationals of any country. Certain qualifications must be met for attaining and maintaining membership." Purpose of the Society As to the question "What is our business?" the Scope Committee restated our purpose in light of current practice and the constitution of AIME and the bylaws of AIME and SME. The Board of Directors accepted the following proposed purpose of SME: "To further the professional development and well-being of its members by publishing and distributing technical writings, news, and information; by sponsoring meetings of members; by providing forums for discussions and for continuing education; and by fostering communication on the subjects within its purview. "The Society assists educa-

Jan 4, 1984

By H. Y. Sohn

The purpose of this article is to analyze critically and quantitatively the effect of chemical equilibrium on the overall rates of fluid-solid reactions. It is shown through a mathematical analysis that a reaction with a small equilibrium constant (a positive standard free energy of reaction) is more likely to be rate-controlled by pore diffusion or mass transfer than a reaction with a large equilibrium constant. The overall reaction rate of the former also tends to be slow. Furthermore, the apparent activation energy of such a reaction approaches the standard enthalpy of reaction (M-f'), rather than the true activation energy of the chemical reaction. The Law of Additive Reaction Times developed by the author is shown to apply to equilibrium-limited fluid-solid reactions and to be useful in quantitatively analyzing the behavior of such reactions.

Jan 1, 2003

By A. A. Bustos

A model was developed to simulate the blow-by-blow operation of the converting process. From the weights, compositions and temperatures of all converter feeds the model calculates the composition and tonnage of both converter matte and slag as well as bath temperature at the end of each blow. The development of the model and its application to the converter aisle operation are described. There is good agreement between model predictions and observed results. At the present time the model is being used to investigate different converting schemes and their effect on pay metal recoveries, slag chemistry and temperature of the bath. Future work involves the use of the simulation model as a process control tool for the converting operation.

Jan 1, 1988

By Raffaella Granata

The paper deals with the remediation of two areas formerly utilized for the disposal of hazardous wastes in a petrochemical plant. The works, designed on the basis of the criteria of maximum safety and minimum environmental impact, consisted in the confinement of the contaminated soil and groundwater within surface caps and perimetrical cut-off walls embedded in the underlying clay layer. The cut-off wall is 0.8 m thick and has a maximum depth of 33 m: it was designed to guarantee, as a minimum, the level of safety for a landfill for hazardous wastes, in accordance with the applicable National Standards. It was constructed with self-hardening mud and with the installation of an HDPE geomembrane. The HDPE liner of the cut-off wall was then sealed to that of the capping to obtain the complete encapsulation of the contaminated soil. A system of piezometers allows the monitoring of the cut-off efficiency measuring the fluctuations of the groundwater table and testing the chemical contents. Some wells installed within the contaminated areas will contribute to guarantee the full efficiency of the system in case of state of emergency, controlling the water-table level inside the confined areas.

Jan 1, 2006

By Leslie C. Thompson

The heap leach process used for recovering gold from oxide and sulfide ores is operated as a closed circuit system in which the cyanide process solutions are continuously recy­cled. In a well-designed operation there is little or no dis­charge of cyanide to the environment. Spent leached ore residues are water washed to remove most of the trace cyan­ides and precious metals remaining after completion of cyan­ide leaching. After the washing step, small amounts of cyanide, metal-cyanide complexes and nitrates remain in the residue. Most of the cyanide and nitrate residue constituents exist in the pore water of the spent ore rather than in the solid mineral fraction. More than 90% of the complexed cyanides in a freshly washed ore residue are present as free cyanide or weakly complexed metal-cyanides. Natural volatilization and decom­position rapidly remove most of these easily dissociable cyanides from the spent ore. Only the stable, strongly com­plexed metal-cyanides, such as gold, cobalt or the ferrocyan­ides and other constituents such as nitrates have a long term persistence in the spent ore residue (Towill et al). Despite washing and natural removal mechanisms, spent ore has the potential to act as a point source of com­plexed cyanides and nitrates for soil and groundwater con­tamination if inadequately contained (Huiatt et al). The groundwater contamination is caused by the leaching of the soluble cyanide compounds and nitrates from the pore water of the residue.

Jan 1, 1990

By Daniel S. Gwinner

The tolling, or processing for a fixed fee, of aluminum drosses to recover the metal units is a common practice in the Aluminum Industry. The Dross Toller is acting for the owner, and since most dross processes result in material going to landfill, it is important for the owner of the dross to insure that the toiler is processing the material and handling waste disposal in an environmentally responsible manner. The paper discusses the Dross Toiler Audit Program, first from the Reynolds Metals Company perspective. Included are the reasons the company deems it necessary to audit and a description of the items covered during the audit. Finally, there will be a discussion of the audit from the Tollers perspective - what the Toiler can expect when the auditor arrives.

Jan 1, 1995

By Joao Felipe Costa, Jair C. Koppe, Andre Zingano, Cleber Gomes

"Run-of-mine Brazilian coal has high ash content and low calorific power. Therefore, the coal must be washed to achieve the power plant specifications for burning coal. A large amount of waste results from the coal preparation, and it must be disposed of in waste piles or waste dams, depending on the material size. These waste disposals are the cause of serious environmental problems, not only in the short and medium terms, but mainly in the long term, due to the risk of provoking acid drainage or spontaneous combustion. Waste disposal requirements also demand large areas. Other problems include the pillar and roof stability in abandoned and mined out areas, building of edifices on the old and active mines, and mining under urban areas. To solve these problems simultaneously, backfilling the entries in mined out areas began with two objectives: to understand the mechanical behavior of the filling material and to model the backfilling of room-and-pillar coal mine entries through numerical simulation. Laboratory tests were performed for different filling material (with and without cement) to determine its mechanical properties and failure criteria. Based on this study, it was possible to conclude that the backfill method is a good strategy to improve the ground stability in room-and-pillar coal mines for the long term, especially for weak coal seams, and to reduce the quantity of material on waste piles on the surface.INTRODUCTIONRun-of-mine (ROM) Brazilian coal has high ash content and low calorific power. Therefore, the coal must be washed to achieve the power plant specifications for burning coal. Two types of waste are associated with power plants that bum coal for energy generation: 1) the waste from the coal preparation plant and 2) the ash from the power plant after coal burning.The Brazilian coal ash content in the ROM coal is between 45 and 55%. The clean coal is 20 to 30% ash for 4,500 kcal/kg (18,000 BTU). The coal preparation plant recovery is only about 35%. Santa Catarina State (SC) produces about 7 million tons/year of ROM coal, which results in a total of 4.5 million tons of waste. This is a large amount of waste that must be disposed of in waste piles or waste dams, depending on the material size. The waste and ash content is represented by silicate materials, such as clay and sand, and by sulfide materials, like pyrite and organic sulfur (between 1and5%)."

Jan 1, 2010

By AIME AIME

IN an address before the New York Section. A.I.M.E., Oct. 20, Alex L. ter Braake, speaking on the tin industry of the Netherlands East Indies, interjected a few remarks, at the chairman's request. on the mineral stock-piling project now before Congress in a bill sponsored by Senator Scrugham. The full text of Mr. ter Braake's paper was published in the Nov. 6 issue of the American Metal Market. Following mention of the buffer stock scheme as applied in the tin industry, Mr. ter Braake continued:

Jan 1, 1943

Refractory gold concentrates often contain submicroscopic gold that is encapsulated within the crystal matrix of iron sulfide minerals, such as pyrite, pyrrhotite and arsenopyrite. To recover the gold, the host mineral must generally be broken down chemically by oxidative processes, such as roasting, pressure oxidation or bacterial leaching, which expose the gold for subsequent recovery by leaching in cyanide solution. The focus of attention in these pretreatment processes is usually the oxidation of the sulfides to elemental sulfur, sulfur dioxide gas or sulfate ions. Less attention is paid to the deportment of iron and the changes in its oxidation state, although this can have a profound effect on gold and silver liberation, as well as downstream operating costs. Iron sulfide minerals break down completely during pressure oxidation, and dissolve in the sulfuric acid solution that is gener-ated from oxidation of the sulfides. This dissolution liberates the tiny gold particles that were originally trapped in the sulfide crystals, and gold recovery during subsequent cyanidation is usually very high (>95%). Iron goes into solution in the oxidation process, initially as ferrous sulfate, but this compound is rapidly oxidized to ferric sulfate, which then hydrolyzes and reprecipitates. The form of the precipitate varies depending on the operating conditions in the autoclave and the presence of certain metal cations. When the acidity in the autoclave is quite low (<20 g/L H2SO4) and the temperature is high (>200°C), the formation of hematite is favored. When the acidity is high (>20 g/L H2SO4) and the temperature is relatively low (160 to 200°C), the formation of basic iron sulfate is favored. If the ore or the leach solution contains significant levels of certain cations (such as Na+, K+, NH4+, Ag+ or Pb2+) and the acidity is high (>20 g/L H2SO4), jarosite compounds are favored. Hematite is the desired iron product in the autoclave discharge, for both metallurgical and environmental reasons, but it is difficult to operate an autoclave under the conditions required for effective liberation of gold without converting some of the iron to basic iron sulfate and/or jarosite. These compounds fall into a category of iron compounds known generically as iron hydroxy sulfates, all of which can cause significant processing and environmental problems in the downstream gold process. This paper deals specifically with basic iron sulfate: the conditions under which it is formed in an autoclave, the problems that are caused by its presence in the feed to a cyanidation plant and possible remedial strategies that can be adopted, both in the autoclave and downstream.

Jan 1, 2010

By J. T. Eash, W. S. Crowell, E. M. Wise

The practice of dentistry, particularly the construction of artificial dentures and "bridges," involves a unique and difficult application of the precious-metal alloys. Appliances used in the mouth are continuously exposed to corrosive agencies which can hardly be described as mild, and must remain free from tarnish and be substantially immune to corrosion. Limitations with respect to space and weight demand high physical properties, while complexity of form requires ease of working. The high corrosion resistance required necessitates the use of alloys of high precious metal content. The usual expedient of resorting to mechanical working to produce the requisite strength and stiffness cannot be utilized because of the frequency of annealing and soldering operations. To meet these difficult conditions manufacturers of dental goods were early led, unknowingly perhaps, to the production of precipitation-hardening or temperable alloys. The excellent properties of iridium-platinum may have suggested the addition of platinum metals to the conventional gold-silver-copper alloys to produce greater strength and hardness. It was found that such quarternary alloys retained their high physical properties after passing through the usual soldering process; i. e., heating to 750° to 800" C. and cooling naturally in the air. Later it was discovered that they could be softened and rendered more ductile by heating to the same temperature and quenching in water. These early examples of precipitation hardening, for years the common knowledge of dental practitioners and laboratory technicians, escaped the attention of the scientific world and discovery of the transformation which was responsible for this hardening was disclosed by the Russian investigators of the system Au-Cu, Kurnakow, Schemtschushny and Zasedatelev~,(~)$ although the optimum conditions for securing good properties in aged alloys were not given attention.

Jan 1, 1932

By M. E. Nicholson

IN order to understand how alloying elements influence hardenability through their effect on the rate of pearlite nucleation, it is advantageous to use a model to describe the mechanism of pearlite nucleation. The model which currently is most widely accepted has been described, among others, by Mehl et a1.1-3 and by Hultgren.4 Pearlite nucleation involves both the nucleation of ferrite and cementite.4,5 Cementite nucleates first, followed rapidly by the formation of ferrite at the cementite-austenite interface. The conclusion that cementite is the first phase to form during the process of pearlite nucleation is based, in part, on the observation that proeutectoid cementite is continuous with pearlitic cementite and that the orientation relationship between proeutectoid ferrite and austenite is not the same as that between pearlitic: ferrite and austenite.6,7 Recently, Smith" has suggested that the dissimilarity in orientation relations, instead of indicating the pearlite nucleation sequence, may be evidence that pearlite is nucleated in a grain adjacent to the one in which it is growing. Also, Modin9 as shown that ferrite in pearlite may be continuous with proeutectoid ferrite, and he has also shown that proeutectoid cementite is not always continuous with pearlitic cementite. Thus, it appears that the conclusion that cementite always initiates the pearlite nucleation process is open to serious question. The author believes that important evidence on the question of how pearlite is nucleated exists in the rates of pearlite nucleation of different steels. The following is a review and analysis of this evidence. If the nucleation of pearlite is considered as requiring the nucleation of both cementite and ferrite, then the time to nucleate pearlite consists of the time to nucleate the first phase to form, plus the time to nucleate the second phase at the advancing interface of the first. In the absence of a visible proeutectoid constituent, the second phase must be nucleated very soon after the first. If cementite is the first phase to form, the time to nucleate pearlite will be approximately equal to the time to nucleate cementite. Since the nucleation rate of a phase precipitating from solid solution increases with the degree of supersaturation, it would be expected that the rate of pearlite nucleation should increase with increasing carbon content. Digges10 has shown that the reverse is true. He determined the quenching velocity necessary to suppress pearlite formation in plain carbon steels as a function of carbon content. His results showed that pearlite formation could be suppressed with lower quenching velocities as the carbon content of the steel increased, at least up to 1.25 pct C, the highest carbon content he studied. Thus, it would appear that in plain carbon steels, in which pearlite is formed at the nose of the C-curve, the hypothesis that cementite nucleates first does not predict the observed change in nucleation rate. The validity of the current model of pearlite nucleation may be tested also by determining whether or not it predicts the relative influence of alloying elements on the nucleation of ferrite and pearlite. This can be done best by a consideration of the changes in a TTT diagram produced by a change in alloy content. Hultgren4 suggests that the general shape of a TTT diagram, as well as what constituents will form from austenite, can be predicted from the relative nucleation rates of ferrite and cementite. This is illustrated in the schematic diagram for a hypoeutectoid low alloy or plain carbon steel shown in Fig. 1. The C-curves for ferrite nucleation and for cementite nucleation are represented by AA&apos; and CC&apos;, respectively, and the start of ferrite formation and pearlite formation are represented by AX and BC respectively. Adopting the current theory, Hultgren suggests that between X and C pearlite forms directly from austenite, since cementite nucleates more rapidly than ferrite in this temperature range. Conversely, at temperatures above Tx, ferrite is the first to nucleate and proeutectoid ferrite is formed. As proeutectoid ferrite grows, austenite becomes enriched in carbon, so that the cementite nucleation rate is increased. As a result, pearlite nucleation above temperature Tx is accelerated, beginning along BX and not along C&apos;X. Temperature T, represents the temperature at which the nucleation rate of ferrite equals that of cementite. By extending this type of reasoning, using the principle that the nucleation rates of ferrite and cementite increase with increasing supersaturation of austenite with respect to these phases, it should be possible to predict the influence of carbon content on the shape of the isothermal transformation diagram. For a slightly higher carbon content than that of Fig. 1, the curve A A&apos; representing the beginning of ferrite formation should be moved to the right, whereas the curve CC&apos; representing the beginning of cementite formation should be moved to the left. For hypoeutectoid plain carbon and low alloy steels, this prediction does not agree with existing data. Instead, as the carbon content is increased, the pearlite curve moves to the right along with the ferrite curve and always appears to join it tangen-tially. This behavior is demonstrated by the TTT-curves of a series of manganese steels" shown in Fig. 2. In this figure, TTT-curves for four alloys containing 0.20, 0.40, 0.60, and 1.20 pct C are superimposed. The curves are identified in the figure legend. The letters F, P, and C are used to indicate the start of ferrite, pearlite, and cementite formation, respectively. In these steels, it appears that the nucleation of ferrite and of pearlite are related processes. As a result of the foregoing evidence, it is proposed that the formation of pearlite be considered as follows: Either ferrite or cementite may nucleate from austenite, then grow until the remaining phase is nucleated at the interface between the growing phase and austenite. (The growth of the first phase to form is assumed to be accompanied by a composition change in the adjoining austenite.) According to this model there are two modes of nucleating pearlite: 1—where cementite initiates the succession

Jan 1, 1955

By J. E. Dutrizac

The mineral forms of silver, lead and cadmium in the zinc concentrates and the various roaster products made by the Kidd Creek Division of Falconbridge Inc. have been elucidated. In the concentrates, all three elements occur mainly in sulphide form, either in solid solution in the principal ore minerals or as discrete mineral grains. During roasting, Ag, Pb and Cd are preferentially concentrated in the hot cyclone and ESP dusts of the roaster train. Silver is converted to <0.5 µm grains of silver metal and to Ag2S04 which dissolves in or impregnates silicates. Lead is converted to Pb-bearing silicates or to PbS04 and PbO which are present either as tiny free grains in ZnO or as an intergrowth with lead silicate. Lead is also a minor constituent of the ferrite phase. Cadmium occurs mostly as cadmium-bearing zno and ZnFe2o4 , but a significant amount also reports as Cd-bearing silicates or zinc sulphate.

Jan 1, 1990

By H. Y. Sohn

The purpose of this article is to analyze critically and quantitatively the effect of chemical equilibrium on the overall rates of fluid-solid reactions. It is shown through a mathematical analysis that a reaction with a small equilibrium constant (a positive standard free energy of reaction) is more likely to be rate-controlled by pore diffusion or mass transfer than a reaction with a large equilibrium constant. The overall reaction rate of the former also tends to be slow. Furthermore, the apparent activation energy of such a reaction approaches the standard enthalpy of reaction (Mf&apos;), rather than the true activation energy of the chemical reaction. The Law of Additive Reaction Times developed by the author is shown to apply to equilibrium-limited fluid-solid reactions and to be useful in quantitatively analyzing the behavior of such reactions.

Jan 1, 2003

By D. F. Malan, R. P. Els

The limit equilibrium model, used in displacement discontinuity codes, is a popular method to simulate pillar failure. This paper investigates the use of physical modelling to calibrate this model. For the experiments, an artificial pillar material was prepared and cubes were poured using the standard 100 mm × 100 mm civil engineering concrete moulds. The friction angle between the cubes and the platens of the testing machine was varied by using soap and sandpaper. Different modes of failure were observed depending on the friction angle. Of interest is that significant loadshedding was recorded for some specimens which visually remained mostly intact. This highlights the difficulty of classifying pillars as failed or intact in underground stopes where spalling is observed. The laboratory models enabled a more precise calibration of the limit equilibrium model compared to previous attempts. Guidelines to assist with calibration of the model are given in the paper. The limit equilibrium model appears to be a useful approximation of the pillar failure as it could simulate the stress-strain behaviour of the laboratory models.

May 3, 2023

By C. E. Doran

Since the early 1990s the underground mining industry has embarked on a vigorous program of improving process and eliminating costs. A leading development in this program has been the implementation of leaky feeder radio systems as an enabling infrastructure for future automation. El-Equip Inc. has led this development with more than 175 mines implementing mine-wide radio infrastructures for voice and data. In this paper, we describe the implementation of a digital radio network which supports existing installations through to an automation infrastructure employing full digital cellular communications with mobile video roaming capabilities. We outline the evolutionary path from existing low speed data communications links through to 155 Mbps and beyond.

Sep 1, 2001

By M. Barsky, E. Barsky

A study was conducted to elucidate the relationship between the hovering velocity and the particle settling velocity. The experiments were carried out in a water medium on five materials ranging in density from 1.070 to 4.000 kg/m3. Analysis of the results with allowance for the distribution of stream velocities over the cross section of the pipe revealed that the final settling velocity of the particles was equal to their local hovering velocity (on the stream axis), and not to the average velocity of vertical flow as is generally believed. It therefore follows that the kinetic structure of the stream must be taken into account when constructing theoretical models of the process for purposes of computation. In addition, the optimal stream velocity is not always equal to the hovering velocity and in fact is governed by other factors as well. Illustration is provided by the results of a study conducted in a vertical cascade classifier comprising eleven identical stages. The feed material was introduced at each stage successively beginning with the topmost (i* = 1 ) and ending with the lowermost (i* = 11). First, the stream velocity that yields optimum separation conditions at each stage of the cascade (i.e. k=50%, k being the yield of a given size class in the fines for a single stage) was sought. Subsequently the conditions of optimal separation for the instrument as a whole were determined (i.e. F(x) = 50%, F(x) being the yield of a given size class for the entire instrument). The results of the study are presented in the table.

Jan 1, 2003

By Kurt RP Petersen, Hendriena van der Walt

With the decline in fine diamond production from the Argyle mine in Australia, there is a greater emphasis on efficiently treating the finer size fractions through a DMS circuit. Although it is generally well understood that smaller diameter cyclones are more appropriate for this application, practical results do not necessarily meet this expectation. In this paper the operational performance of particular sized cyclones throughout the group was compared. Based on the results there is evidence that under certain practical operating conditions, small cyclones are not necessarily best for fine size particle treatment, particularly given the production pressures faced by all mines. However, there seems to be considerable merit in using larger sized cyclones, which tend to exhibit less performance variability, irrespective of operation conditions.

Jan 1, 2006