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By Tom Liu

This paper is a fundamental study of bubble-particle collision efficiency in turbulent flows. A CFD-based microscale scheme for the prediction of turbulent bubble-particle collision efficiency in a 3D isotropic turbulent flow is developed, and in this way, turbulence effects on particle-bubble collision efficiency are taken into account for the first time. By comparing the computed results with experimental data from the literature, the CFD simulation is shown to correctly predict the bubble-particle collision efficiency in a quiescent environment. The CFD method was then applied to the investigation of bubble-particle collision efficiency in a turbulent flow, and the simulation results are shown to be qualitatively consistent with the real observations. The predicted collision efficiency can be used in a multiscale modelling scheme, which would account for all control variables in a flotation cell, such as impeller structure and tip speed, air nozzle structure and air flow rate This study indicates how microscale simulations of bubble and particle behaviours, coupled to macroscale CFD simulations of flotation cells, can provide a powerful tool predicting the flotation rate in a real flotation cell.

Jan 1, 2014

By A. Ahmed, A. Fathy, M. Eissa, K. El-Fawakhry, A. El-Mohammady

Silicomanganese is widely used as a complex reducer and an alloying addition in the production of various grades of steel due to its economic and metallurgical advantages. It is also used as a semi-product in the manufacture of medium- and low-carbon ferromanganese and metallic manganese. Manganese-rich slag, resulting from high carbon ferromanganese production, has the advantages of high manganese content, high Mn/Fe ratio, low excess oxygen, low phosphorus content, low fine content and low cost. Such slag seems to be very attractive to use as raw materials for the production of silicomanganese alloys. In the present study, experimental heats were designed and carried out to optimise the factors affecting the production process of silicomanganese using manganese rich slag in the charge. The results of pilot plant experimental heats showed that the optimum metallic yield and recoveries of manganese and silicon are obtained with initial slag basicity,(CaO + MgO) / (Al2O3), equals 1.8 by using dolomite as fluxing material and charging quartzite and fluorspar in percentage of 25% and 4% of the blend, respectively. The results showed also that an amount of 30% of coke in excess of the stoichiometric amount should be added. These result are relative for the specific high Al2O3 ores used.

Jan 1, 2004

By Robert A. Cortese, Henry E. Perlee

Coal dust and float coal dust, produced during normal mining operations, in underground coal mines, are carried from the point of origin downstream by the ventilating air, where it deposits on the surfaces of the mine entry. In an explosion, this dust is lifted from the surfaces by the aerodynamic disturbances and, if of sufficient quantity, can continue to propagate the explosion. To prevent the surface coal dust from contributing, it must be inerted, typically by spreading pulverized limestone, i.e., rock dust, over the coal dust surface. To facilitate the dusting operation, the National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Laboratory(PRL), developed an automated system that continuously monitors the accumulation of coal dust. This system could activate a rock-dusting machine that disperses rock dust into the ventilation air when dangerous deposits accumulate and deactivate the machine when sufficient inert has been deposited on top of the coal dust. The system consists of a microprocessor-controlled optical float dust deposition meter. This device measures the light intensity reflected from a deposited layer of dust. A standard cap lamp is used as a fixed-position light source. From the reflected light signal, the microprocessor determines the hazard level of the deposited layer and performs the appropriate action. Full-scale studies conducted in the Experimental Mine at PRL's Lake Lynn Laboratory, using alternating thin layers of rock dust and coal dust, successfully demonstrated the operation of the device. Based on the statistical data from these studies, a mathematical model was developed to predict long-term error in total rock dust content using this inerting procedure. Downwind dust dispersion was also examined to provide optimum placement of the dust sensors and to determine the need for better rock dust dispersion techniques.

Jan 5, 1998

By Robert Stefanko

The results of a recent study on the influence of continuous and conventional mining techniques on the size consist and wash- ability characteristics of coal are presented. Eight samples, four each from continuous and conventional mining sections were collected. Each sample was screened in seven size fractions, and each size fraction was totally fractionated at five gravities. The data thus collected was statistically examined for the influence significance of mining techniques, size, and gravity on the quality of the mined product. The paper presents the sample collection method, data gathering and analysis procedures, and major conclusions. The study revealed that there are pronounced differences in the products from the two mining systems and that conventional mining yielded a better product in terms of size-consist, and yield, ash, and sulfur in both the raw and washed products. The results of the study are significant in regard to consideration of resource utilization and conservation, and environmental impacts.

Jan 1, 1974

By William A. Apel

Several different strains of bacteria have been shown capable of reducing hexavalent chromium, Cr(VI), to Cr(III), a less toxic, .. more readily recoverable form of Cr. This paper examined the Cr(VI) reduction efficacies of 3 different Cr(VI) reducing bacteria: Pseudomonas f1uorescens LB300., Pseudomonas aeruginosa PAOI, and Pseudomonas aeruginosa PAOI (pCROI) It was demonstrated that all three bacterial stratns reduced Cr(VI) primarily during their exponential growth phases while using glucose as their carbon and energy source. Significant differences in the three organisms' Cr(Vl) reduction capabilities depending on initial Cr(VI) concentrations were also demonstrated. P. aeruginosa PAOI showed superior Cr(VI) reducing capabilities over the. entire range of Cr(VI) concentrations tested while the Cr(VI) reduction capabilities of the other two strains were increasingly inhibited as Cr(VI) concentrations increased.

Jan 1, 1991

By B. van Beek, J. H. Zietsman, A. Lexmond, N. J. Andrew

"In platinum group metals (PGMs) smelting, the slag-to-matte ratios are very high (approximately 4:1 to 9:1). The slag temperature therefore has a strong influence on matte temperature, which is a continual concern due to the low matte melting temperature and its resultant high superheat. Maintaining a stable slag temperature is therefore a critical safety and operational issue. This project aims to improve the understanding of the slag bath temperature drivers so that a more effective slag bath temperature control strategy can be implemented.With the aim of developing a multiphysics model of the furnace, extensive data analysis was performed to develop an in-depth understanding of the process before the start of modelling work. In this work, the effect of fluctuating furnace feed composition on slag temperature was examined. The results are based on equilibrium calculations using FactSage, implemented with ChemApp.A method was developed, using an equilibrium calculation at 25°C, to convert the available chemical assays to approximate mineralogical assays in order to determine the feed enthalpies. Actual 2013 furnace feed data was used and the average specific energy requirement to produce slag and matte at 1600°C was calculated to be 671 kWh/t concentrate. The furnace energy input was then kept constant, and it was found that the slag temperature varies significantly as a function of the feed composition. These results were compared to actual slag temperatures measured on site. It was found that close management of the furnace energy balance is important for maintaining a stable slag temperature."

Jan 1, 2014

By M. S. Seehra, R. S. Pandurangi

"Investigations of the infrared spectra of crystalline and amorphous silica particles of different sizes (0.05, 5, 10, 15, 30, 45, and 260 um) in the range of 400-4000 cm-1 using Fourier transform infrared/photoacoustic spectroscopy we reported. The change in the intensity I of the signal with porosity e of powders follows the e/(1 - e) dependence for strong bands and e dependence for weaker bands as pre¬dicted by the theory of McGovern of al. For strong bands, I also follows the empirical relation I ~ D-n, where D Is the particle diameter in cm and n = 0.34-0.42. The anomalous positive frequency dependence of I on the modulation fre¬quency f observed for the stronger bands in the 45-pm and 260-pm particles Is believed to result from saturation. Some observations on the effect of changing the background from (carbon black) powder to pellet are also made.INTRODUCTIONSince the publication of the Rosencwaig—Gersho (RG) theory on the photoacoustic effect in solids (1, 2), Fourier transform infrared/photoacoustic spectroscopy (FTIR/PAS) has become an important technique for obtaining the IR spectra of surfaces and materials in their natural state (1-12). In the one-dimensional RG theory, the incident radiation, modulated at frequency f, is absorbed by the material to a depth pp = 1/B (B = absorption coefficient), thus setting up temperature variations in the material. These variations heat the adjacent gas/solid interface leading to the pressure fluctuations of the gas above the sample, which in turn is detected by microphone as a PA signal. The thermal wave originating from no deeper than the thermal diffusion length(2k/npcf) 1/2 in the material contributes to the PA signal (here k, p, and c are respectively the thermal conductivity, density, and specific heat of the material). Since u2, can be varied by varying the experimental parameter f, depth pro¬filing by PAS is possible and a number of papers on this subject have appeared in recent years (2-10). Another im¬portant phenomenon is saturation which occurs when the material thickness 1> u> us (1-12).The original promise of PAS for use with powder samples, without the need to ""prepare"" samples as in FTIR spectros-copy, has not yet been fully realized because of several com¬plications. Theoretical works by Monchalin et al. (13) and McGovern et al (14) showed that the interstial gas in the voids of the powders can act as amplifier and that, for the same mass, a finer powder is expected to yield higher PA signal than a coarser powder. Although in a number of earlier studies (15-21) an increase of PA signal with decreasing particle size has been observed, a quantitative check on the equations developed by McGovern et al. (14) has not yet been made. It is necessary to understand the particle size effects in PAS if the promise of PAS for IR spectroscopy of powders is to be realized. In this paper, we report results of a detailed study on the PAS of silica powders for the particle size range of 0.05-260 um and compare the results with theory (14). We have also investigated the frequency dependence of the variousIR modes in these powders and show that the saturation phenomenon affects at least some of the observations. Some observations on the effects of pellet vs powder background are also reported (22-24). Details of these findings are presented and discussed in this paper."

Jan 1, 1990

By A. Moyano

The development of the traditional converting process performed in a PeirceSmith or Hoboken converter is limited by the investment magnitude associated to the fulfillment of the environmental regulations. Thus, the continuous converting process rather than a conceptual process alternative is becoming a necessity for a smelter facing limited converting capacity and/or lacking of fulfillment of the environmental regulation with its maximum converting capacity. The objective of this paper is to present the progress of the Codelco continuous converting process evaluated at pilot-scale level when converting solid mattes or white metal into blister copper. These tests allowed for gathering of relevant data to be considered for a new stage of evaluating the Codelco continuous converting at industrial-scale test. The pilot-scale tests were done in a Teniente Converter pilot scale unit at the Codelco Norte Smelter. The results of processing solid copper mattes (65-75% Cu) and producing low sulfur content blister copper with production of a constant S02 gas concentration, and the production of liquid slag with low copper solubility was achieved and is discussed in the present paper.

Jan 1, 2007

By P A. Jenkins, I W. O Jones

WMC has mined the Perseverance disseminated orebody exclusively by SLC (sublevel cave) methods. Deteriorating ground conditions in the vicinity of an orebody inflection forced a re-evaluation of future mining at Perseverance and a strategy to drop down below the inflection zone and recommence the cave was implemented. This strategy has led to increased production at higher grades, resulting in lower costs and better mill recoveries. This paper describes the evolution of mine planning, development, support and production strategies through the successful process of implementing the ædrop-downÆ and re-establishing the SLC.

Jan 1, 2000

By J Chan, T Baumgartl, A Plante, C Peltre, P D. Erskine

Mine soils are often organic matter and carbon poor due to disturbance, topsoil stockpiling and mixing with spoil. They present an opportunity to observe the accumulation of soil carbon arising from rehabilitation or ‘green carbon’ through organic matter inputs and may be considered for carbon credits. Soil carbon is known to improve multiple soil characteristics and is viewed as an indicator of soil health.When attempting to estimate soil carbon levels in the Australian coal mining regions, both coal and black carbon (BC) need to be quantified. Coalmine soils contain coal particles that are difficult to distinguish from organic matter using standard carbon analyses. BC, a material arising from the incomplete combustion of organic matter and fossil fuels, displays some similar characteristics to coal and is ubiquitous in Australian soils due to bushfires. The presence of coal and BC complicate the determination of green carbon levels in mine soils.A method to quantify coal and BC in mine soils from the Bowen Basin using thermal analysis and multivariate curve resolution is presented. By determining BC and coal contributions it is then possible to calculate green carbon levels in rehabilitated mine soils. Calculated green carbon levels are compared with bulk density as soil quality indicators.CITATION:Chan, J, Baumgartl, T, Erskine, P D, Peltre, C and Plante, A, 2014. Distinguishing carbon fractions in coalmine rehabilitated soils, in Proceedings Life-of-Mine 2014 , pp 491–498 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 16, 2014

By P. C. Clark

This paper is an overview of the requirements and concerns for minerals and pigments used in papermaking. The first part of this paper deals with mineral or pigment filling in the actual papermaking process. The second part deals with the pigment or mineral properties that are important in today's coating processes.

Jan 1, 1993

By Günther M. Volkmann

"INTRODUCTION The construction of the BAB 44 motorway between Kassel and Herleshausen (both Germany) is an important part of the trans-European road network. After its completion, the A 44 will permit an efficient connection of the Benelux States in the West and Poland in the East. In the section between Eschenstruth and Hessisch Lichtenau the Hirschhagen Tunnel is constructed with a length of 4.1km. Most sections of the tunnel are situated in weak ground conditions. Hence a combination of face bolts with spiles (short forepoling) or pipe umbrellas (long forepoling) additionally support the tunnel heading on a regular basis This article will focus on the application of a newly developed method to connect the pipe umbrella support, which is mostly installed by conventional drilling machines nowadays. The installation method limits the outer diameter to a maximum of 168mm and a pipe wall thickness of 12.5mm because workers must be able to handle pipes and its drill steel. Typically these pipes are connected with threads that create a weak link in the support system so during the last decade alternative connection systems were developed to overcome this disadvantage. One of these alternative coupling systems is the so called Squeezed Connection, which will be explained in this article followed by a discussion of its advantages and disadvantages regarding technical specifications, construction time, and safety issues. THE HIRSCHHAGEN HIGHWAY TUNNEL The German highway A 44 directs from Aachen through the Ruhrgebiet to Kassel (all Germany) and it is extended to Herleshausen (Germany). The new section connects the A 7 to the A 4 after completion. This upgrades the east-west highway connection starting at the Benelux Union and heading to Poland so it is an important part of the trans-European road network. The newly constructed section has a total length of approximately 63 km and comprises 13 tunnels. All tunnels are constructed as double tube tunnels with 2 lanes and emergency sidewalks on both sides and 14 emergency cross passages. The Tunnel Hirschhagen starts in the north of Eschenstruth and ends near Hessisch Lichtenau (Figure 1). The length of the northern tube is 4,147 m and that one of the southern tube is 4,204 m. So it is the longest tunnel of the A 44 and the second longest highway tunnel in Germany when it is put into operation. On its alignment it crosses underground the Losse valley with the state road 7, the streetcar Kassel-Hessisch Lichtenau and the Losse stream. The cover above crown varies from 10 m to 95m and it is the lowest when crossing the Losse stream."

Jan 1, 2016

By S. S. Shen, M. J. Pool, P. J. Spencer

Heats of solution of silver and copper in dilute Ag-Cu-Sn alloys at 720°K have been determined using a liquid metal-solution calorieter. Values of the se2f-interaction coefficient n AgAghave been calculated at constant copper concentrations and n Cu Cuhas been determined at constant silver contents. The reliability of the experimental data is shown by the very good agreement between nCujAg and ij &$; these interaction coefficients have experimental values of -9100 and - 9590 cal per g-atom, respectively. Certain solution models are shown to be inadequate for prediction of solute interaction coefficients in dilute Ag-Cu-Sn alloys. In a previous publication' the results of a thermody-namic study of dilute Ag-Au-Sn alloys were presented. The present work represents the continuation of a program to investigate dilute alloys of the noble metals with tin and in particular is concerned with solute interactions in the Ag-Cu-Sn system. By determination of the magnitude and sign of the various interaction coefficients in dilute alloys it is possible to gain some understanding of the different types of solute-solute and so lute-solvent bonding changes that occur as the solute concentrations are varied. Hence systematic studies of alloys with similar physical characteristics as regards size, structure, electronegativity, and so forth, of their components can contribute a great deal to present theoretical knowledge of solutions. The recent definition of an enthalpy interaction coefficient, 11, by Lupis and Elliott2 is of particular value in calorimetric studies such as the present one: where j and i are solutes and s is the solvent; Si is the relative partial molar enthalpy of component i and x represents the mole fraction of solute or solvent. Values of ?Hi can be obtained directly by solution calorimetry and data for n are thus easily determined, often with a high degree of accuracy. ?Hi is related to the relative partial molar enthalpy at infinite dilution, ?Hi and to the enthalpy interaction coefficients by the expression: ?Hi?Hi + X;nz+ ... [2] The aim of the present work was to determine the self-interaction coefficients n AgAgand 178: in alloys of different compositions and also to establish values for n Agcg| and ncuAg. Since it is a thermodynamic requirement (resulting from the Maxwell-type relationships which can be applied to partial molar properties) that nAgcu and ncuAg should be equal, a further aim of this study was to demonstrate the agreement between experiment and theory. EXPERIMENTAL A description of the liquid metal-solution calorimeter used in this research has already been published,3 and no further details of its construction and operation will therefore be given here. Copper supplied by the American Smelting and Refining Co. was indicated by them as being 99.999 pct pure, and the silver obtained from A. D. Mackay, Inc., was also quoted as being 99.999 pct pure. A solvent bath consisting of between 70 and 80 g of 99.99 pct pure Sn was used for each series of experimental drops. Its weight was accurately determined and the appropriate amounts of copper or silver were added to give alloys of the desired composition. Approximately 0.00125 g-atom additions were used for determinations of the heat of solution of silver in the bath, while, for copper, specimens consisting of approximately 0.0015 g-atom were used. The heat capacity of the bath was determined at regular intervals during a series of drops using tin or tungsten calibration samples. The heats of solution of silver and copper in pure tin were first determined as a function of their concentration in order to establish the self-interaction coefficients 7AgAg and ncucu Alloys containing a constant 0.01, 0.02, 0.03, and 0.04 mole fraction of copper were then used to study 17:: in alloys of different copper content, while alloys of the same mole fractions of silver were used to determine equivalent data for 178: at constant silver concentrations. The composition of the bath was held at the desired copper or silver concentration by making calculated additions of the appropriate solute throughout the experiment. From the limiting values of ?HAg in the constant copper content alloys it was possible to study ?HAg as a function of xCu and hence to determine 42:. A similar analysis of the re, values permitted calculation of nAgcu. Heat content and heat capacity data from Hultgren et al* were used to calculate heat of solution values from the measured heat effects at the experimental temperature of 720°K. RESULTS AND DISCUSSION Determinations of ?HAg. A preliminary investigation of the heat of solution of silver in pure tin at 720°K was first made in order to establish the value of nAgAg before additions of copper were made and also to compare the value of ?HOAg(l) with that obtained in the previous study of Ag-Au-Sn alloys.' Then the heat of solution of silver in Cu-Sn alloys was investigated as a func-

Jan 1, 1970

By George F. Crocker

Introduction The Helen mine and the Victoria mine of Algoma Ore Properties, Limited, in the Michipicoten district, Ontario, are 120 miles north of Sault Ste. Marie, on the north shore of lake Superior. They are on the Algoma Central railway between Hawk Junction and Michipicoten Harbour. Between them, these mines have produced 10,757,113 tons of iron ore. From 1900 to 1918, 2,823,369 gross tons of brown ore was shipped, and from 1939 to the end of 1949, 7,933,744 tons of siderite was produced from the open-pit operations and underground development. The finished product, known as 'Algoma sinter', is shipped to blast furnaces both in Canada and the United States. The iron-ore bodies are a part of a tabular shaped area of iron formation that extends over a length of more than 10,000 feet and has maximum width of 1,000 feet. The two siderite orebodies, known as the Helen and Victoria, are separated by two diabase dykes. The Helen orebody is 1,600 feet long with a maximum width of 250 feet and the Victoria is 1,200 feet long with a width comparable to the Helen. These orebodies are considered to be a replacement of the original rock by iron carbonate. The introduction of the iron-1bearing material probably occurred after the development of the major folded structures. The open-pit mining of siderite started in the Helen ore body in 1939 and continued until 1945. During this period, 3,853,395 tons of ore was mined. Open-pit mining started in the Victoria body in 1946 and is still being carried on. Underground development commenced in September, 1947. Diamond drilling and surface sampling had shown the Helen deposit to average 35.61 per cent Fe and 7.28 per cent SiO2, and the Vi.otoria deposit 33.73 per cent Fe and 10347 per cent SiO2?

Jan 1, 1950

By Willard L. Hunter

The Bureau of Mines studied the effect of temperature upon the reduction of chromite by carbon and the relative reducibility of chromites as a function of their composition. Ferric oxide was also studied to provide comparative data. Pellets weighing approximately 1 gram and containing 70 percent ferric oxide, chromic oxide, or chromite and 30 percent graphite were subjected to closely controlled temperatures under a flow of argon for 15 minutes. The amount of CO and CO2 evolved was measured, and the reduced sample was analyzed by X-ray diffraction techniques. The reduction of Fe2O3 was studied over a temperature range of 600° to 1,400° C, while the reduction of Cr2O5 and chromite was conducted from 9000 to 1,621° C. The temperature above which appreciable reduction of Cr203 by graphite took place was 1,125° C. The temperature at which significant reduction started for three of the four chromite samples was approximately the same, indicating that there was concurrent reduction of iron and chromium oxides in the chromite mineral rather than selective reduction of iron oxides followed by reduction of chromic oxide. Rhodesian chromite appeared to dissociate at a lower temperature with concurrent reduction of iron. Based on the temperature at Which chromite was 50 percent reduced in 15 minutes, Transvaal chromite reduced most easily, followed by Mouat, then by Kampersian, and finally by Rhodesian DFC material. Statistical analysis of test results indicated that the ferric iron content of chromites affects their reduction behavior more than any other constituent.

Jan 1, 1966

By A. Normanton, B. Harris, V. Ludlow, S. Riaz

Why does a continuous casting mould powder, which works successfully on a particular caster with respect to semi quality, fail to perform on a caster of a similar design utilizing liquid steel from a similar route for an identical product without some tuning of its make-up and composition? In casting sequences of the same steel grade, why do some apparent random heats produce poor surface quality with respect to cracking when otherwise good surface quality is realized? The answer to these questions lies in the interaction of the mould powder, the casting hardware, and the casting process variables. Using, as examples, data collected from within Corus UK and during collaborative work on the assessment of mould powder performance and its effects on surface quality, the interaction of the mould powder, the casting hardware and the casting process variables is explored. The steelmaking route and its associated alumina load, unexpected changes to slag chemistry, infiltration of the slag into the mould strand gap, and the nature of the slag film are all shown to affect powder performance. Keywords: continuous casting, mould powders, alumina, slag films

Jan 1, 2004

By Charles Hart

A STUDY of the various ores that have been discussed impresses one with the need of beneficiation, in many cases. This applies to the ores that have lain dormant, due to necessity for further preparation, or to ores that now find a market due to a changed condition. Processes of beneficiation will come into their own as our richer ores become exhausted. Many efforts at improvement have been commercial failures, due to prematurity. Thomas A. Edison, with characteristic foresight, attempted concentration of the low- grade New Jersey magnetites some thirty years ago. Due to high costs and the discovery of the Mesabi range, his efforts were futile. However, a successful crusher, designed by Mr. Edison, resulted from this attempt. Agglomeration of concentrates had not, at that time, been brought to its present efficiency, when sinters and briquettes of excellent physical condition are obtainable. Recent efforts in the beneficiation of the lean magnetites of the East Mesabi resulted in an excellent sinter, but that operation is also ahead of its time.

Jan 1, 1929

By Keith A. Heasley, Frank E. Chase, Christopher Mark

Deep cover retreat mining (overburden in excess of 750 ft) is an important emerging issue which will intensify in the future as the more easily mined shallow seam reserves are depleted. Analysis of Mine Safety and Health Administration (MSHA) statistics indicates that deep cover pillar recovery accounts for a disproportionate share of the underground coal mine roof/rib fall fatalities and injuries. Past research has shown that previously recommended Analysis of Retreat Mining Pillar Stability (ARMPS) stability factors (SF’s) may be excessive for deep cover pillar design. The objectives of this study were to evaluate the various methods and strategies by which panels, production pillars and barrier pillars are developed and extracted under deep cover, and to develop appropriate design guidelines. In the course of the research, 29 mines in 7 states were investigated to collect panel design case histories. At each mine site, underground geotechnical data were collected on the pillar line in order to document roof rock, coalbed and floor conditions. The analyses indicated that squeezes were the most likely failure mode where the depth was less than 1,250 ft, but bumps predominated in the deeper cover cases. Immediate roof rock quality, the ARMPS SF’s, and barrier pillar stability factors were all found to be important parameters in determining the outcomes of the case histories. Design guidelines, including suggestions for barrier pillars to isolate active panels from nearby gobs in bump prone ground, are also proposed.

By C. Ortuglio

The Bureau of Mines developed equations to determine the relationship of yields and products obtained from BM-AGA carbonization in 13-and l8-inch-diameter retorts. The developed equations indicate that results of carbonization in l8-inch-diameter retorts can be predicted from results obtained with l3-inch-diameter retorts.

Jan 1, 1966

By J. C. Wilmot

The chemistry of aqueous cyanide containing species in the presence of reduced sulfur sources was investigated. Reactions were studied as a function of time and tracked using novel analytical techniques developed for the analysis of the species of interest in the sample matrix. Species of interest in this work were ?free? cyanide, thiocyanate, cyanate, metallo-complexed cyanide, and various sulfur and sulfur-oxygen species. The studies were conducted under constant temperature conditions at pH values above 10.5 and in the absence of light in order to eliminate photochemically induced cyanide reaction effects. The reaction products of cyanide when in contact with pure sulfur, pyrite, pyrrhotite, sphalerite, and cinnabar are reported. These data combined with data for cop-per, arsenic and lead sulfides, which have been previously published, are used to predict the fate of cyanides in refractory gold ores containing sulfides. A mass balance on the cyanide reaction products was completed for all experiments. From these studies insight into the chemical relationships of cyanide, the specific metal sulfide, thiocyanate and cyanate have been gained. When looking at the results of the experiments, it was immediately apparent that even though the overall conversions of cyanide to thiocyanate were different, most of the samples exhibited a similar pattern of reactions. The recovery of cyanide in these experiments was better than we expected, averaging in most experiments to be over 90 percent. Based on this research, the formation of cyanate was probably the main route of loss. The pathway choice for the various minerals was also elucidated in these experiments. The competitive oxidation pathways that cyanide can take have been tracked for sufficient time to determine the ?final? fate of cyanide in a process. Initially, it was thought that the cyanate may be involved in a hydrolysis reaction to form ammo-nia and carbonate ion, but upon further inspection of the data, there was not the drop-off in total cyanide recovery that would manifest itself were this to happen. On the other hand, the hydrolysis of thiocyanate to cyanate and sulfate would require oxidizing conditions which did not exist in solution at the beginning of the experiment. If the solutions were to be sufficiently oxidizing in nature for this to happen, the initial amount of cyanide would have been converted to cyanate quickly. The data support premise that the ?hydrolysis? of thiocyanate to cyanate and sulfate occurs to some extent in the experiments conducted. Knowledge gained from the experiments with pure metal sulfides helped interpret the results of experiments with refractory ores found in the State of Nevada.

Jan 1, 2014