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By Ken Deter

My recent experience has been with wet tropical environments, which address a different set of concerns than Nevada, for example. Spraying rather than drips are required in most cases just to assist the water balance requirement, and my comments address those situations. Most tropical operations are faced with both extremely wet and very dry seasons, with some having multiple cycles during the year. A heap leach operation must address the rate of solution building up within the ponds and how long the volume must last until the next rainy season. It may be easier to construct sufficient pond volume to permit yearlong operation than by discharging excess solution now, and searching for water later. Pond capacity requirements can help with the following: Consider using the solution that could be locked up in the pads during leaching to assist water balance problems. Spray excess solution continuously onto spent ore that would not be normally be sprayed again to "soak up" the excess solution, and stop spraying when the water balance is low, allowing the solution in the spent ore to return back into the system-with or without cyanide added. In a multiple lift system, if intermediate HDPE liners are planned for solution grade control, have drips placed before the HPDE liner is in place. The drips can distribute excess precipitation throughout the lower lifts to control the water balance, while the most current lifts are being leached and sent directly for the preg pond. With only 2 million tonnes (2.2 million tons) of spent ore involved, up to 200,000 cubic meters (53 million gallons) of solution could be moved into or out of the water balance system, if proper methods are designed and installed. That is equivalent to one meter (40 inches) precipitation falling on a 200,000 square meter (2.2 million square feet) pad area. You may even get a little bit more gold recovered as the solution drains from the earlier pads, as well.

Jan 1, 1999

By Caibin Wu, Ali Lei, Ningning Liao, Jingsheng Ye

"The particle size distribution characteristics of ground product can influence the quality of the classification overflow and the next beneficiation indexes in an ore concentrator. Usually, the size distribution of ground product is considered to be determined by that of new ball mill feed. However, based on large amounts of data from industrial grinding circuit surveys, this paper has clearly shown that the size distribution of ground product should be determined by the size characteristics from classification underflow unless the circulating load was small, because the new feed is an important component and occupy a dominant position of mixed ore from belt feed and classification underflow. On the other hand, the correlation coefficient of the size distribution between ground product and classification underflow can be more than 0.99 when the relevance principle and its method are used. Meanwhile, their P80 value also keeps a synchronous correlation. The greater the capacity of classification underflow is, the higher the correlation of size distribution between the ground product and the mixed feed is. Furthermore, the correlation coefficient of the size distribution between ground product and classification overflow which is from primary or secondary can be 0.96. It is another discovery that the correlation coefficient is related to the type of classifier. The coefficient of size distribution of overflow and underflow from hydrocyclone is superior to that of spiral classifier, which can explain the reason why the hydrocyclone is widely used to replace the spiral classifier in concentrator.INTRODUCTION It is well knows that ball mill circuits closed with cyclones or spiral classifier such as a primary grinding circuit, a secondary grinding circuit and SAB mill have become an industry standard. Which grinding process employed will be determined by the P80 value of ground products. When the primary closed circuit ball mill or SAB that it is different throughout between the two processes was employed, a grinding fineness with -200mesh under 68% will be available. However, the secondary grinding circuit with the fineness of -200mesh above 80% can be conducted. Of course, the grinding fineness is determined by the grain size characteristics of the mineral."

Jan 1, 2018

By P. G. Roden, G. A. Maki, P. J. Fullmann

"In October 1984, Rocanville Division began using a stacking system to handle potash mill tailings. Previous to this date, mill tailings were slurried to the top of the tailings pile and allowed to debrine while flowing mobile stackers. The stackers consist of cyclone packs to debrine the tailings and drag conveyors with screw discharges to deposit the tailings onto the existing pile. The paper will deal with the various aspects of the project from conception to its present state. Key Words: stacking, mobile stackers, Linatex Separators, potash mill tailings, reclaim brine ponds, settling ponds, tailings pile. IntroductionPrevious to 1984, when the stacking project was first implemented, potash mill tailings were handled as follows. Mill tailings were first debrined to approximately 65% solids using a cyclone cluster. The cyclone underflows were then introduced onto a vacuum scroll filter table. Here the tailings were further debrined and discharged into the disposal tank where the tailings were reslurried with reclaim brine and pumped to the tailings disposal site. At the disposal site the slurry was discharged onto the tailings pile and by a natural settling process the tailings were debrined with the brine ultimately collected in the reclaim brine ponds. The shape and profile of the tailings pile was controlled by building salt dikes to control the flow of the discharged tailings slurry. As the tailings pile grew in height, booster pumps were added to the disposal system."

Jan 1, 1986

By G. H. Pardue, L. H. Gollwitzer, J. H. Moran, R. L. Morris

Experimental and theoretical studies of casing-borne signals have provided data on the attenuation efect, compressive strength and shear modulus for different types of cement. These data resulted in the establishment of a definite relationship between the cement compressive strength and the Cement Bond log reading. The relationship is influenced by the casing dimensions, but is independent of the type of cement and the curing conditions. The theoretical analysis provides a mathematical statement of the phenomenon and shows that the attenuation rate is basically a function of the shear modulus of the cement and the thickness of the casing. The lab tests provided a connection between the shear modulus and the compressive strength, and permitted a comparison of the experimental and theoretical work. The results of the experimental and theoretical study have provided means of quantitative interpretation of the Cement Bond log. This interpretation is made more convenient with the use of a nomograph. INTRODUCTION Past interpretation of Cement Bond logs has been essenlially based upon a qualitative comparison between the log response in the zone of interest and the responses in the "fully cemented" and the "uncemented" intervals. Most of the variables influencing the magnitude of the signals were recognized in an earlier paper'; however, insufficient laboratory data were available at that time for quantitative evaluation of these variables. Early attempts to use the numerical amplitudes of the signals without full knowledge of their significance resulted in erroneous comparisons between various types of cement. An extensive program was undertaken to evaluate, both experimentally and theoretically, the attenuation phenomenon and to study the effects of the more common variables. A major objective of the experimental program was to obtain data on the relationship between cement-bond-tool response and physical property standards used by the industry so that practical interpretation methods could be devised. The studies included a comparison of attenuation rate with these properties as a function of time, temperature and pressure, using common sizes of casing. The main result was that a definite relationship was established between the compressive strength of the cement in inti- mate contact with the casing and the response of the cement bond tool. For a given casing thickness, regardless of the type of cement or the curing conditions used, the attenuation rate is a function of the compressive strength. A theoretical analysis showed that the attenuation rate for casing-borne signals should be a function of (among other things) the shear modulus of the cement and the thickness of the casing. The relationship between the compressive strength and shear modulus for curing times similar to those encountered in the field was determined from laboratory tests. Using this relationship, the computed attenuation rates showed reasonable agreement with the measured attenuation rates. The purpose of this paper is to report the results of the experimental and theoretical investigations and to present the first practical method for a quantitative interpretation of Cement Bond logs based on known variables. This method is applicable where the casing-borne signal is not affected by high-velocity formation arrivals. DESCRIPTION OF LOGGING TOOL The Cement Bond logging tool shown schematically in Fig. 1 has been described previously.' The tool consists of two sections: acoustic and electronic. The acoustic section contains a transmitter and a receiver, usually spaced 3-ft apart. Sonic energy emittted by the transmitter travels through the casing and is detected at the receiver. The electronic section measures the amplitude of the

By S. Banisi, J. Marois, A. R. Laplante

"This paper compares the behaviour of gold and ore in the grinding circuit of Hemlo Gold Ltd. Particular attention is given to grinding kinetics, classification behaviour, and liberation. For grinding kinetics, laboratory grinding of gold flakes and silica, 840-1200 um in size (14/20 mesh), was also performed to provide a standard for comparison and to study in a controlled environment the mechanisms of breakage, folding, smearing and impacting.Grinding kinetics were characterized at laboratory scale with breakage and selection functions. The breakage function showed that 75% of gold disappearing from the 840-1200 um class reported to the 600-840 um; this figure is much higher than for silica ( 46%) or most other minerals, and implies that comparatively fewer fine fragments are produced from the breakage of gold flakes, on account of gold's malleability. The selection function of silica was four times that of gold. At plant scale, the ratio of the selection function of ore and gold increased from 6 for at 50-100 um to 20 at 500-1000 um.Observation of original flakes and their fragments with the scanning electron microscope showed that the main mechanism of ""grinding"" from the 840-1200 um to the 600-840 um class was folding rather than actual breakage. This was confirmed by a measure of individual flake weight. The postulated breakage cycle is that relatively globular flakes become increasingly serrated through grinding; they can then regain their original shape through folding and reflattening into cylindrical and spherical shapes, as the majority does; however, some fragments will at this point undergo actual breakage. Photographic evidence is presented to support the proposed mechanisms.Smearing of gold unto silica was observed when silica was ground after a gold, and embedding of silica into gold flakes when gold was ground after a silica. Both mechanisms occur whenever gold and harder minerals are jointly ground, and result in ""unliberation"" of gold. It is postulated that smearing of gold onto other minerals plays an important role in explaining how gravity recovery can increase overall gold metallurgy, especially when used ahead of flotation.Classification of gold in the primary hydrocyclones takes place at a much finer cut-size than ore, 20 vs. 57 um. This and the slower grinding kinetics result in high gold circulating loads in the primary loop, 6700%, and a gold content in the primary cyclone underflow (PCUF) is twenty four times that of the ore. The gold size distribution for primary cyclone overflow is much finer than that of the ore, although they are essentially similar in the PCUF.Liberation, or more accurately ""gravity recoverability"", was assessed with a 7.5 cm (3"") Knelson concentrator. It varied between the thirties for the primary mill discharge and two cyclone overflows, to highs of 89 to 92% for the PCUF and secondary mill discharge, 89 and 92%, respectfully."

Jan 1, 1991

By N. R. Zehr

El presente texto describe los problemas de desague y ventilación que corresponden al túnel Graton en Casapalca. En ese sentido, Antonio Raimondi menciona que probablemente fue Gratón, el primer túnel de desagüe en Casapalca: «la veta de San Antonio es drenada mediante túnel socavado hace poco tiempo y recientemente terminado. Esta conecta con áreas de trabajo situadas por debajo de las ya inundadas de modo que, para efectuar el desagüe, solo tendrá qµe perforarse en plano inclinado. Los túneles Graton tendrán poco más de 11 km, los cuales pueden perforarse desde accesos en el Valle del Río Rimac, poco más arriba del pueblo de San Mateo, en un punto denominado "Carbonyacúpalabra" quichua que significa «agua de carbón». Asimismo, estos túneles gemelos se terminarán bajo el pozo de la mina Aguas Calientes de Casapalca. Una vez terminado, una perforación servirá para desaguar las áreas de trabajo y la otra, para la respectiva ventilación.

Jan 1, 1969

By Diego Pacheco Wermuth

O presente trabalho apresenta os resultados do estudo e aproveitamento de cinzas leves da queima de carvão mineral em termelétrica, como reforço para o Compósito de Matriz Metálica de cobre. Foram estudados diferentes percentuais de cinzas leves como reforço para o cobre, sendo misturados estes pós através de misturador “duplo v”, compactando os pós em diferentes pressões e sinterizando os corpos de prova obtidos pela compactação. A amostra sinterizada que apresentou a maior dureza entre todos os corpos de prova sinterizados, atingindo 89 HV, foi utilizada como base para a formulação e obtenção de novos corpos de prova, que foram estudados sob condições de moagem dos pós por moinho de bolas e moagem de alta energia. A fabricação do compósito seguiu os padrões industriais do processo de Metalurgia do Pó, como a mistura e moagem dos pós, compactação dos pós e sinterização em atmosfera controlada. Foi realizado o estudo das propriedades mecânicas do compósito formado por cobre e cinzas leves, que comprovou o aumento da dureza para 122 HV. Este trabalho proporciona uma nova aplicação para as cinzas leves, utilizando estes resíduos de usinas termoelétricas como matéria prima para reforço mecânico na composição de peças à base de cobre na indústria metalúrgica.

Aug 17, 2017

By George B. Clark

The "Munroe effect" of shaped explosive charges was discovered by Charles E. Munroe more than 50 years ago (in 1888), but it was not until World War II that it was put to any practical use. Both Allied and Axis armies used the principle effectively in bazooka projectiles, artillery projectiles and in fixed shaped charges. The first two were used primarily to combat tanks and other armor and the latter to assault pillboxes and other fixed concrete emplacements. Many engineers and others who saw the military application of the jet effect of shaped charges believed application would be possible in many industrial fields where blasting is used, such as mining and quarrying. Some work has already been done on the problem of making shaped charges applicable to mining operations. Experimentation conducted at the National Tunnel and Mines1 was directed primarily along the lines of use of shaped charges for secondary blasting in connection with long-hole stoping methods. Experimentation initiated earlier and conducted by the author2 at the University of Utah on a more scientific basis was directed at revealing the basic principles of the functioning of shaped charges, as well as the feasibility of using them in mining operations after the principles of their operation had been clearly defined. It was found that: (I) a given design of charge required an optimum standoff to make it most effective, either in penetrating solid rock or steel (see Fig 3); (2) for a given design of charge there exists an optimum ratio of charge diameter to charge height above which the increase in effectiveness of the charge decreases rapidly (see Figs 4 and 5); (3) partial confinenlent has the effect of making charge performance much more consistent; (4) the higher power and higher velocity explosives tested are much more effective than relatively low-strength explosives; and (5) shaped charges may be adaptable to mining operations in secondary breakage and drilling blasting holes. Fig I is a diagrammatic sketch of the action of a shaped charge for two types of cavities, while Fig 2 shows the approximate manner in which the jets are believed to be formed when an explosive wave encounters the cavity, approaching it from the top. The experimentation already completed has laid the foundation for further research in the study of shaped charges. Standoff effects, effect of the strength of explosives and other features have been fairly well established. Such elements in the design of shaped charges as (I) geometry of cavity liners, (2) relative horizontal dimensions of explosive column, (3) effect of various metals and alloys in cavity liners, (4) percentage studies of jet energies, and

Jan 1, 1949

By Fernando Guevara

Many smelting and slag-cleaning furnaces operate with cooling systems designed to freeze a slag layer over the refractory to protect it. The fluid flow and heat transfer conditions associated with the freeze layer and mushy zones are poorly understood. These phenomena were simulated with a small-scale room temperature, 2-dimensional model, using an aqueous solution of calcium chloride to simulate the slag. Reasonable similarity with conditions encountered with copper and nickel smelting systems was achieved (Pr 50 and Ra 108, in the laminar-turbulent transition). Measurements of the freeze layer development and velocities were made with the Particle Image Velocimetry (PIV) technique. Direct Numerical Simulations (DNS) were also made of the unsteady fluid flow and heat transfer problem. It was found that the solidification process is well described using an improved model for high molecular viscosity in the mushy zone. Solid front growth, isothermal profiles, velocity profiles and heat transfer through the walls showed good agreement between the PIV and DNS results. Experimental and numerical velocity profiles close to the freeze layer show a parabolic behaviour in the vertical velocity profile which is completely different from the calculation of heat transfer using a sharp interface model. The reason for this is attributed to the effects of the mushy zone with a high viscosity and high shear stresses acting on that area.

Jan 1, 2006

By Pollard P. J

Australia is well endowed with both tin and tungsten resources, and is currently a significant producer of both commodities for the international market. The intensity of exploration activity for both metals has been rather sporadic, reflecting the changing market situation. Thus tin has experienced three major boom periods around 1880, 1907 and 1983, while tungsten prices peaked around 1917, 1953, 1970 and 1977. During the earlier periods, the major discoveries were located utilising simple prospecting techniques involving creek travers- ing and stream sediment panning. The resulting location of tin alluvials quickly led to the discovery of adjacent primary deposits. The major tungsten deposits were composed of quartz- wolframite, which was readily visible as mineralised float both within the drainage systems and on scree slopes. Thus by the early 1900s most of the currently significant deposits had been located. More recent exploration approaches have combined these tradi- tional methods with the development of exploration models based on evolving genetic concepts. Within tin systems the emergence of province styles of clas- sification combined with enhanced perceptions of tonnage-grade characteristics and improved geological models has enabled more effective exploration strategies. Province classification at the inter- national scale demonstrated a clear relationship between deposit type and geological environment and thus considerable attention was given to the range of provinces present within Australia. Tonnage-grade diagrams enabled the refinement of economic per- spectives, while detailed models provided the basis for localised search parameters.

Jan 1, 1988

By A. Cichowicz

In this study, techniques used to design earthquake-resistant structures are applied to the deep-level mining environment. Earthquake engineers seek to identify the cause of potentially damaging resonance, and design or reinforce structures to reduce these effects. Similar techniques have been used to analyse the dynamic behaviour of the rock mass surrounding a stope in a deep South African gold mine. A three-dimensional seismic array installed in a stope at TauTona Mine (previously Western Deep Levels, East Mine) provided an opportunity to examine the evolution of the wave field close to an underground opening. A set of three-component geophones installed in a borehole above the panel revealed the development of surface waves as wave fronts reached the excavation, and an array of vertical component geophones fixed to the hangingwall provided a two-dimensional map of site effects. While the collected data do not include damaging seismic events, quantitative analysis enabled phenomena which could lead to damage, to be recognized. In the vicinity of the excavation, the energy of the seismic signal is generally transformed from high frequency to low frequency. It was found that seismic events with relatively high corner frequency (150 Hz?200 Hz) usually excite several modes of vibration (30 Hz to 110 Hz), while events with low corner frequency (30 Hz?50 Hz) do not always excite higher modes of vibration in the structure. This implies that the rock mass around the excavation is a complex medium, and should be studied using the multi-degree-of-freedom model. A strong structural effect (due to the excavation shape) was revealed as a low frequency coda wave (at 40 Hz and 60?70 Hz), well developed on the skin of the hangingwall. A strong site effect was revealed by changes in signal properties between hangingwall geophones, exhibiting strong resonances around 160 Hz and in the range 200 Hz to 300 Hz.

Jan 1, 2000

By Robert H. Hafner, Irvin R. Kramer, Stewart L. Toleman

IN his paper on the calculation of hardenability from chemical composition, Grossmann1 discussed the effect of most of the alloying elements used commercially. The purpose of the work reported in this paper was to determine the effect of several other elements on hardenability-arsenic, antimony, beryllium, cobalt, columbium, germanium, tellurium, tin, aluminum, and titanium-and to extend the range of composition of some of the elements studied by , Grossmann-chromium, copper, manganese, molybdenum, nickel and silicon. EXPERIMENTAL METHODS To determine the effect on hardenability, suitable amounts of the alloying elements were added to experimental heats and the hardenability determined by means of end-quenched hardenability specimens. The steels were melted in a high-frequency induction furnace with a basic crucible, using ingot iron as a base for some of the heats and S.A.E. 1015 for others. The alloying additions were made as ferroalloys or as metal, depending on the ' alloying element. Hundred-pound heats were split and poured into square, tapered, cast-iron ingot molds with hot tops. Aluminum was not used as a deoxidizer in most of the heats. The ingots were homogenized for 12 hr. at 1260°C. (2300°F.) , and forged into rounds of 1 ½ in. diameter. These bars were normalized twice from 840°C. (1550°F.) before machining into Jominy bars. The composition of the steels was deter- [ ] mined in most cases by samples taken from the end-quench hardenability specimen. As suggested by crafts,2acid-soluble

Jan 1, 1943

By Stewart L. Toleman, Robert H. Hafner, Irvin R. Kramer

In his paper on the calculation of harden-ability from chemical composition, Gross-mannl discussed the effect of most of the alloying elements used commercially. The purpose of the work reported in this paper was to determine the effect of several other elements on hardenability—arsenic, antimony, beryllium, cobalt, columbium, germanium, tellurium, tin, aluminum, and titanium—and to extend the range of composition of some of the elements studied by Grossmann—chromium, copper, manganese, molybdenum, nickel and silicon. Experimental Methods To determine the effect on hardenability, suitable amounts of the alloying elements were added to experimental heats and the hardenability determined by means of end-quenched hardenability specimens. The steels were melted in a high-frequency induction furnace with a basic crucible, using ingot iron as a base for some of the heats and S.A.E. 1015 for others. The alloying additions were made as ferroalloys or as metal, depending on the alloying element. Hundred-pound heats were split and poured into square, tapered, cast-iron ingot molds with hot tops. Aluminum was not used as a deoxidizer in most of the heats. The ingots were homogenized for 12 hr. at 1260°C. (23oo°F.) and forged into rounds of I½ -in. diameter. These bars were normalized twice from 840°C. (I55o°F.) before machining into Jominy bars. mined in most Cases by samples taken from the end-quench hardenability spedmen. AS suggested by Crafts,2 acid-soluble (8

Jan 1, 1944

By Robert H. Hafner, Irvin R. Kramer, Stewart L. Toleman

In his paper on the calculation of harden-ability from chemical composition, Gross-mannl discussed the effect of most of the alloying elements used commercially. The purpose of the work reported in this paper was to determine the effect of several other elements on hardenability—arsenic, antimony, beryllium, cobalt, columbium, germanium, tellurium, tin, aluminum, and titanium—and to extend the range of composition of some of the elements studied by Grossmann—chromium, copper, manganese, molybdenum, nickel and silicon. Experimental Methods To determine the effect on hardenability, suitable amounts of the alloying elements were added to experimental heats and the hardenability determined by means of end-quenched hardenability specimens. The steels were melted in a high-frequency induction furnace with a basic crucible, using ingot iron as a base for some of the heats and S.A.E. 1015 for others. The alloying additions were made as ferroalloys or as metal, depending on the alloying element. Hundred-pound heats were split and poured into square, tapered, cast-iron ingot molds with hot tops. Aluminum was not used as a deoxidizer in most of the heats. The ingots were homogenized for 12 hr. at 1260°C. (23oo°F.) and forged into rounds of I½ -in. diameter. These bars were normalized twice from 840°C. (I55o°F.) before machining into Jominy bars. mined in most Cases by samples taken from the end-quench hardenability spedmen. AS suggested by Crafts,2 acid-soluble (8

Jan 1, 1944

By Clarence P. Linville

In an article published in the Iron Trade Review,' I gave a convenient arrangement for the installation of wet and dry bulb thermometers for use in making moisture determinations in the air being blown into a blast furnace, and also gave a chart for use in obtaining moisture values from the thermometer readings. The data from which this chart was prepared were obtained from the tables in use by the U. S. Weather Bureau.2 The work of Carrier3 has shown that these tables are somewhat in error. He has recalculated the values for moisture as referred to wet and dry bulb thermometer readings, and he has prepared a psychrometric chart from the values thus obtained. This work has placed the subject of psychrometry upon a correct scientific basis. I think it is proper that we should recognize the importance of his work and give him credit for one of the most interesting and valuable researches that have been published in recent years. Blast-furnace men are not ready to use, as he suggests14 a value expressed in grains of water accompanying a pound of dry air. However convenient this may be for heating and ventilating work and other engineering problems, there are several reasons for preferring the use of a value expressed in grains of water in a cubic foot of mixed air and water vapor, in connection with combustion phenomena and the effects of moisture on blast-furnace operation. Previous papers presented to the Institute have used such values and we have

Jan 1, 1914

By F K. Altuntov

The study presented in this paper is based on the Kiirunavaara underground mine located in the northern part of Sweden. The deposit is mined using the sublevel caving (SLC) mining method. This paper briefly reviews the alternative SLC layouts, as well as presents challenges for the application. In Kiirunavaara currently, the traditional SLC design is employed, however, continuous improvement of material transportation systems used in mines generates a need for investigation of the current and future production area layouts in sublevel caving mines. When identifying the potential benefits of the alternative production area layouts, the production targets and effects must be further investigated to understand the benefits and potential effects. In this study, several different layouts have been investigated and evaluated. The designs include different development configurations and orepass infrastructure moved further away from the orebody and still require further investigation.

Mar 29, 2023

By M. Stephton, L. A. Cornish, R. Süss, N. B. Maledi, J. H. Potgieter, L. Chown

In today?s gas turbines, the emphasis is on saving energy and reducing the amounts of pollutants emitted. This can be attained only by designing alloys with higher melting points and the capability to retain mechanical integrity at increased temperatures. The development of nickel-based superalloys (NBSAs) has reached its limit, as the alloys are operating at critical temperatures close to their melting points. Further increase in the operating temperatures will result in dissolution of the strengthening phases and even melting. Recent trends are towards developing materials that are adequately strong but have much higher melting points and corrosion resistance than the NBSAs that are currently in use. Studies conducted on Pt alloys with similar structure to the NBSAs have presented mechanical results that are promising. This has led to further development of these alloys as a replacement for NBSAs. The operations of gas turbines are usually limited by hot corrosion, which could lead to catastrophic failures. Increased temperatures have an adverse effect on the corrosion of the alloys by making the environment more aggressive. Hence, during a material selection process, the corrosion behaviour of any selected material for a highly specialized application such as gas turbines needs to be assessed. Generally, coatings are applied to combat degradation by salt deposits, hence coated and uncoated NBSAs were selected as benchmark alloys. Corrosion mechanisms and kinetic studies of the Pt alloys were conducted. High temperature hot corrosion (HTHC) tests were conducted at 950°C for540 hours. Analysis of the corrosion products was conducted using a Raman spectrometer, scanning electron microscope with energy dispersive X-ray spectroscopy (EDS) optical microscopy, and X-ray diffraction study of the phases that formed. Both coated and uncoated NBSAs failed under the test conditions. Samples were covered with a porous non-adherent greenish layer which is characteristic of NiO. Pt alloys displayed superior corrosion properties compared with the benchmark alloys.

Jan 1, 2006

By R. D. Grove

The control of Florida phosphate flotation plants is largely based on the visual observations of experienced operators, both in recognizing good and bad froth conditions and in making judgments about the composition of feed, concentrate and tailing streams. Chemical analyses lag the process by at least two hours and, therefore, only assist in recalibrating the operators' vision when major deviations occur. An image analysis system was developed by IMC Fertilizer to improve the accuracy and precision of the composition estimation process. It still relies on the operator taking a representative sample, but provides a measurement in about 15 minutes after that sample is obtained. Background The search for a quick and inexpensive technique for estimating phosphate flotation stream composition continues. There have been attempts at using "wet chemistry," nuclearmagnetic resonance, neutron activation, X-ray diffraction and other techniques reported on in the past several years. None of these have yet found its permanent place in the flotation plants of the Florida phosphate industry. IMC attempted to use wet chemistry to provide 7.5-minute estimates of final concentrate insol and tailings BPL. This was aborted after 36 months of plant operation due to the high operating costs for chemicals and an operator. There was also no significant economic improvement in the plant's operation. Another factor was the necessity to limit these crude analyses to only a few process streams, which were insufficient to achieve improved plant operation.

Jan 1, 1993

It should be stating the æbleeding obviousÆ to say that the most efficient method of recovery must be used during the testing and evaluation phases of an orebody. Furthermore, the company will be literally throwing away money by not using the most efficient recovery plant during mining. This is especially true in the case of a low concentration/high value commodity such as diamonds. Unfortunately, this economic recovery criterion is not always the driving force. Some inexperienced companies think that they can preserve capital by using cheaper, and generally less efficient, recovery plants to mine their product. This philosophy is invariably a fallacy. Furthermore, it is also important to use the correct sized plant for the proposed task. It is no use trying to use a small testing plant to treat large quantities of ore, as this may result in loss of recovery efficiency. The converse is equally true.

Jan 1, 2004

By Juan Sodi, John F. Elliott

The standard free energy of ReS2 has been measured in the range of 1050° to 1250°K using H2/H2S mixtures and a slight variation of the method described by Hager and Elliott.1 The result is: The experimental method and apparatus were modified slightly for this study. Measurements on Cu2S were made to verify the application of the method to the work on ReS2. THE EXPERIMENTS AND RESULTS Briefly, the experimental method consisted of exposing a chip of copper or rhenium at a known temperature for 8 hr to a slowly flowing gas stream at the same temperature in which Ph2S and PH2 were known. The chip was withdrawn quickly from the hot furnace, and subsequently it was inspected for the presence of a sulfided surface. In the experiments described here, there was no ambiguity in any case as to the presence or the absence of the sulfide. At a given temperature, gas compositions for sulfidization were explored systematically until two compositions were found whose values of ?G°, Eqs. [I] and [2], were within approximately 100 cal of each other, one of which was sulfi-dizing and the other was not. These are termed the "straddle" compositions and it is assumed that the equilibrium composition lies between them. The chief modification to the apparatus, which is shown schematically in Fig. 1 of Ref. 1, was to support the metal specimen on a small alumina boat which could be moved along the reaction tube, 6 mm ID, by platinum wires. An appropriate seal at each end of the reaction tube permitted the sample to be moved from the cold end of the tube into the hot zone in 2 to 3 sec, and the sample could be withdrawn equally rapidly. Thus, it was possible essentially to quench the specimen from the reaction temperature with the reaction gas or helium flowing and without danger of breaking the reaction tube. The usual practice at the end of the experiment was to switch the gas system to the helium tank, flood the reaction chamber with helium, and pull the sample out of the hot zone. The purpose of the modification was to permit study of the sulfidization of copper without the complication of the back-reaction between the gas and the specimen as the latter cooled during slow withdrawal of it from the hot zone; this was a problem in the earlier work.&apos; A further improvement located the tip of the temperature-indieating thermocouple and the specimen precisely at the hottest part of the furnace. A carefully calibrated thermocouple, with its tip at the position of the specimen and with other conditions duplicating those of an actual experiment, showed that in the temperature range of 900° to 1122°C the temperature of the specimen differed from that of the tip of the indicating thermocouple by less than 0.5°C. The two positions were 0.5 cm apart. The reaction gas was prepared from ultrahigh-purity hydrogen (<l ppm O2, <0.5 ppm H2O) and CP grade hydrogen sulfide (99.5 pct H2S). High-purity helium (99.995 pct He) was used. All of these gases were purchased from the Matheson Co. All flow meters were recalibrated by the soap-bubble method with hydrogen, H2S, helium, and several gas compositions used during the study. These calibrations gave a linear relationship with a slope of 1.0 for the plot of log flow rate vs log pressure drop across the flow meter, in accordance with the Hagen-Poiseuille equation. The analysis of the gas was determined in the same manner as was reported previously. Good checks were obtained between the composition of the gas established by the flow-meter settings and by chemical analysis of the gas taken after the mixing bulb and ahead of the furnace. The pressures of H2S, H2, S2, and HS in the equilibrium gas at temperature were calculated from the following data :3 The pressures of the species S and S8 were negligible for the conditions of the experiments.3 There was no sign of vaporization of ReS2 either by weight loss or deposits in the reaction tube. Thus it is not possible to account for the apparent volatility of the compound reported by Juza and Biltz.2 The inlet gas composition and the calculated equilibrium ratio of PH2 S/PH2 for the "straddle" points of each experiment are shown in Table I. The specimens of metal for the experiment were small clippings of annealed copper (99.9+ pct) sheet 0.005 in. thick that was obtained from Baker and Adamson and of "high-purity" rhenium (99.9+ pct) sheet 0.005 in. thick that was purchased from Chase Brass and Copper Co. A specimen was removed from the apparatus; inspected for the presence of the sulfide, and then stored in a sealed vial. A fresh clipping was used in each measurement. The condition of the surface of each specimen after the experiment is noted in Table I.

Jan 1, 1969