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By J. A. Morgan

IN the art of roasting sulfides it is well known that the lower the temperature and the higher the pressure of SO, the larger will be the amount of sulfate present in the product. However, the mechanism of sulfate formation is not generally understood. The following experiment" demonstrates in a direct way that, in the roasting of Cu2S, the sulfate forms from the reaction of Cu2O, formed by the oxidation of Cu2s, with gaseous SO, (or SO3) and 0,. Thus, the sulfate does not form at the sulfide surface. The reaction at the sulfide surface is the same whether or not sulfate is formed. Using an indirect method, Ong, Fassell, and Wadsworth' infer that sulfate forms after oxidation, during the roasting of sphalerite, agreeing with the observations of this paper. The method presented here of demonstrating that sulfate forms after formation of Cu2O is to roast a sample of Cu2S and then to locate and identify the phases formed.' A solid cube of cuprous sulfide, made by melting Fisher reagent grade Cu2S powder and measuring about 1.5 cm on edge, was placed on a Nichrome wire grid suspended over the top of an Alundum combustion boat. The assembly was placed in a tube furnace at 600°C and oxygen gas, flowing at 0.60 liters per min, was passed around the specimen for 24 hr. The furnace tube diameter was 1.5 in. The partially roasted sample was removed from the furnace and impregnated with resin No. BR 0014, obtained from the Palmer Products Co., and the impregnated sample was then mounted in Lucite. A cross section was obtained by grinding and the surface was prepared by the following steps: 1) grinding—60 grit, 3M disk, dry; 2) preliminary polishing —60 through 600 grit, 3M disk, dry; 3) polishing— 8 µ diamond putty, silk cloth; and 4) final polishing —1evigated magnesia in isopropyl alcohol, Selvyt cloth. The color micrograph of the polished surface is shown in Fig. 1. The layers present in the micrograph are given along the side. The comwositions of the various layers were established by Debye-Scherrer patterns. From this evidence the following sequence of reactions which occur in the roasting of Cu2S is inferred: 1) The oxidation of Cu2S occurs with oxygen which has been transported through the oxide-sulfate layer by either gaseous or solid state diffu- sion. The products of this reaction at the Cu2S surface are Cu2O and SO,. 2) The SO, diffuses out through the pores in the Cu2O and finally reaches a position in the Cu2O where the oxygen pressure and the SO, pressure have values such that the thermodynamic conditions for the formation of CuSO4 are fulfilled. Then, the mixture of SO2, SO3, and oxygen reacts with the Cu2O to form CuSO1. 3) The CuSO, decomposes by the evolution of SO,, or SO, and O2, to form the basic sulfate. This is reasonable, since the SO, gradient will decrease toward the oxygen gas phase from the CuSO4 layer. 4) For this same reason the basic sulfate will decompose to form CuO. The above sequence of events is based on the assumption that diffusion through the oxide and sulfate layers, rather than the reaction at the sulfide-oxide interface, is rate-determining. This assumption is supported by the observation that these oxide and sulfate layers combined are almost nonperme-able to the flow of gases through them. Acknowledgments This research was supported by the U. S. Air Force, through the Office of Scientific Research of the Air Research and Development Command. The authors wish to acknowledge the helpful suggestions of Ralph Wells of the Applied Research and Developmeit Laboratory, U. S. Steel Corp. References E. A. Peretti: A New Method for Studying the Mechanism of Roasting Reactions. Discussions Faraday Soc. (1948) 4, p. 174. - J. N. Ong, Jr., M. E. Wadsworth, and W. M. Fassell. Jr.: Kinetic Study of the Oxidation of Sphalerite. Trans. AIME (1956) '206, pp. 257-263; Journal OF Metals (February 1956).

Jan 1, 1957

By T. Fabritius, L. Hekkala, J. Härkki

The Outokumpu steel belt sintering technology is used for manufacturing chromite pellets that are charged into smelting furnace for ferrochromium production. Hot air is blown through the moving bed of raw pellets. Direct temperature and flow measurements are difficult to do in the bed of a real scale belt sintering process. Therefore, a tested and reliable mathematical model would be a valuable help for optimising operational parameters of the process and designing new constructional improvements. The aim of this work is to present a mathematical model that calculates the gas flow and temperature distribution in the bed of pellets and the atmosphere. Computational fluid dynamics program FLUENT is used to calculate the gas flow, composition and temperature of the gas in the sintering bed during processing. Energy equation for the bed, containing the effects of evaporation of water and oxidation of carbon and iron oxide, will be added to the model to obtain the temperature of the pellets. The porous media model used for pressure drop calculations in the bed is shortly discussed. A comparison between CFD-calculations and experiments with a pilot scale batch-sintering reactor are also presented. The final model can be used as an engineering tool when developing the process and the equipment further. Different designs can be easily tested with the model and the effects of the changes to the flow pattern and temperature distribution can be studied.

Jan 1, 2004

By T. C. Pool

Physical and chemical conditions permitting, in-situ leaching (ISL) of uranium offers a variety of advantages over conventional production methods including less surface disturbance and less solid waste. Commercial production of uranium by in-situ leaching techniques was initiated in 1963 in the Shirley Basin of Wyoming by Utah Construction. On a world-wide basis, ISL uranium production amounted to about 13.2 million pounds U3O8 in1999, approximately 16% of world output. Both acid and alkaline systems are used, the selection of which is primarily dependent upon groundwater quality and related reclamation requirements. ISL offers low capital costs per unit of annual capacity and is particularly flexible in adapting to changing market conditions.

Jan 1, 2000

A South African gold mining rock-related fatal accident database has been analysed in order to determine rock-related fatality trends in the gold mining industry over the period 1990 to 1998. This analysis was extended further to include some of the individual reefs mined and focused particularly on the Carbon Leader Reef, the Ventersdorp Contact Reef, the Vaal Reef and the Basal Reef. Rock-related accident locations are also presented. A stope rock-related risk is proposed, where the fatality rate in terms of rock-related fatalities per million square metres mined for the gold mining industry as a whole is compared to individual reefs, allowing a stope rock-related risk to be attributed to the individual reef. This comparison is extended further by removing the contribution by the reef being evaluated from the industry data, thereby allowing this reef to be directly compared to the rest of the industry with respect to a stope rock-related risk.

Jan 1, 2001

By P. A. Selvadurai

This paper presents the results of a research investigation leading to the development of a technique for the measurement of the surface permeability of Indiana Limestone. The tests are conducted on a cuboidal block of the limestone with a flat surface that can be sealed to create a circular aperture through which water influx can take place. Computational results for Darcy flow are used to interpret the results of the experiments. The water entry area can be moved over the surface area of the block to investigate, quite conveniently, the distribution of permeability across the surface of the limestone block sample.

May 1, 2009

By Viviane Tavares

The technology advance of mobile devices makes consumers of these equipment do more constant exchanges, with this the obsolete devices discarding becomes an environmental problem, due its landfill accumulation. In order to minimize the environmental impacts caused by these equipment there?s the recycling necessity of polymers, ceramic and metallic materials. The main goal of this recycling is to study the printed circuit board of device mobile processing through ore treatment in order to recoup copper. Initially printed circuit boards were processed in a knives mill, in order to liberate the ferrous material, after that it was done the magnetic separation of the reduced residue. With the not magnetic fraction it was done the grain sized analysis and sulfuric acid and hydrogen peroxide leaching analysis. With the chemical analysis results proceeding from the leaching aliquot it was possible to observe that the leaching method with sulfuric acid and hydrogen peroxide presented greater copper recovery.

Jan 1, 2009

By G. J. de Korte

Dense-medium beneficiation of fine (minus 0.5 mm) coal is not a new concept and has been used in South Africa previously. The dense-medium fine coal plant at Greenside Colliery operated for almost 18 years and, despite proving a difficult plant to operate, did succeed in producing a fine coal product with a low ash content of 7%. No other beneficiation process available could achieve this. Dense-medium beneficiation of fine coal was also used in other countries, of which the plants at Homer City in the USA and Curragh in Australia were the best known. The first application of dense-medium cleaning of fine coal was, however, at the Tertre plant in Belgium1. This plant was built in 1957. About nine years later, a second fine coal dense-medium plant was built at the Winterslag Mine, also in Belgium. According to reports, this plant operated satisfactorily for a period of some 17 years.

Jan 1, 2002

By Bruce Jago, Joe Zhou, Chris Martin

"From the perspective of metallurgical processing, gold ores can be classified into free-milling and refractory ores. Their extractive metallurgy are largely driven by mineralogical factors such as: gold particle size, association with other minerals, coatings and rimmings, presence of cyanicides, oxygen consumers and preg-robbers, presence of refractory gold minerals and locking of submicroscopic gold in sulfide mineral structure etc. Gold process mineralogy helps address issues and problems related to gold ore processing. It provides useful information on process selection, flowsheet development, recovery improvement and reagent consumption optimization. By combining classic mineralogical techniques, modern instrumental analysis and diagnostic metallurgy, the mineralogist is able to balance the various types of gold occurrence in an ore. This paper will provide a broad review of gold process mineralogy and the techniques available, and use case studies to describe how they can be used together, to provide the complete picture of gold process mineralogy in an ore. Examples will be used where applicable.INTRODUCTIONSince the early 1980’s, a great deal of work has been done in the characterization of gold ores, particularly refractory ores (Gasparrini, 1983; Wang, 1984; Hausen, 1985; Haines, 1986; Henley, 1989; Chryssoulis et al., 1990; Wang et al., 1992, 1994; Kojonen, 1999; Simon et al., 1999; Hong et al., 2000; Pals et al, 2003). Process mineralogy has come into its own as a respected inter-discipline in the fields of mineralogy and metallurgy – a subject that occupies an important place in both research and industry. As the free-milling gold ores are being depleted and more refractory ores are being discovered and processed, gold process mineralogy receives more and more attention from both the mineralogist and metallurgist as it helps to solve various problems encountered during gold ore processing. Steadily rising gold prices are also stimulating the need for gold process mineralogy due to the increasing demand for and production of the yellow metal. At SGS Lakefield Research, gold process mineralogy studies are conducted routinely on all types of gold ores and mill products to assist in a wide variety of metallurgical projects. This paper will briefly discuss the gold ore types and gold mineralogy, review the common mineralogical factors affecting gold extractive metallurgy and the techniques available to gold process mineralogy, introduce the procedure employed at SGS Lakefield Researc"

Jan 1, 2004

By A. B. Cecala

A few years ago, the National Institute for Occupational Safety and Health and Unimin Corporation developed a clothes cleaning system that is able to quickly, effectively, and safely remove dust from a worker?s clothing without dust exposure to the worker, the work environment, or co-workers during the cleaning process. To perform the process, a worker enters a cleaning booth and activates an air spray manifold which blows the dust from the worker?s clothing. Since the cleaning booth is under negative pressure, all the dust and product removed are contained. In the original design, this dust-laden air was exhausted to a dust collector system. However, since most operations do not have excess dust collector capacity, it was decided to determine an alternative method to provide for a stand-alone cleaning system. This was achieved by ducting the exhaust outside the plant and into the atmosphere. This technique was recently tested and shown to be a viable method to provide for a stand-alone clothes cleaning system.

Jan 1, 2009

By Aminul Islam, Vinay M. Kumar

"About 100 Hectares of land reclamation over the very soft to soft marine clay at Uran Creek in Maharashtra is planned. The depth of marine clay varies from 10m to 24m as observed from the geotechnical investigation. The marine clay was treated with Pre-fabricated Vertical Drains (PVD’s) installed from the elevation of +5.5mCD (chart Datum) and preload/placement of surcharge. A Settlement of soft soil mud under the reclamation was monitored using magnetic extensometer (M) and ground settlement maker (S2). These instruments are installed after constructing working platform at around +5.5m CD. Based on the field instrumentation data, the consolidation parameters were adjusted to match the theoretical and actual settlement plot. The author called this approach as “Back analysis method”. The objective of this paper is to present a case study of instrumented preloading treatment for a thick marine clay deposit. The degree of consolidation in clay strata was determined from magnetic extensometer and ground settlement marker data. Authors also determined degree of consolidation as Asaoka method, Hyperbolic method and Back analysis method and compared the results.INTRODUCTIONExpansion of Container terminal with port buildings, rail container depot, roads and utility buildings at Jawaharlal Nehru Port Trust (JNPT) is planned over a reclaimed land of 100 hectares. Uran creek predominately consists of the estuarine deposit of very soft to soft marine clay. They are characterized by low shear strength, very low bearing capacity and exhibit large settlement when subjected to loading. The additional load causes the significant magnitude of consolidation settlement over a considerable period of time. Thus for development projects on top of soft soil, the postconstruction settlement would be of primary concern.To accelerate the consolidation pre-fabricated vertical drains (PVD) were used. Pre-loading procedure was adopted to minimize the post construction total and differential settlements. PVD’s were installed at 1.0m and 1.2m c/c triangular pattern. Locally available borrow material is used as a reclamation material. The reclamation material has been placed over the existing sea bed level by land based method/end tipping method and created the working platform. The level of working platform is decided based on the tide data and it has been selected such that work should be affected during highest high water level. The PVD has been installed from the working platform and subsequently all the field instruments have been installed from the same level. Five different types of field instruments are installed to monitor ground improvement works."

Jan 1, 2017

By Stephen R. Grano, Jon Glatthaar, Philippe Steinier, Christopher J. Greet

"The importance of the oxygen content of sulphide mineral pulps in determining which reactions occur, and their subsequent influence on flotation behaviour is grossly underestimated in most operating concentrators. While pH is routinely monitored, Eh and dissolved oxygen measurements are obtained infrequently. However, dissolved oxygen measurements in conjunction with other pulp chemical parameters (i.e. pH, Eh, and EDTA extractable metal ion analysis), can provide valuable insight into where and what type of reactions are occurring within a circuit. Unfortunately, these readings yield “instantaneous” measurements of the pulp chemical parameters.What is needed is a means of establishing how reactive a pulp is, and how this reactivity changes as components of the system are manipulated. Oxygen demand provides an opportunity to do this. Several attempts at measuring the oxygen demand of a pulp have been made in the past with varying degrees of success. Most notable among these are Noranda and BOC Gases.Learning from these experiences, Magotteaux have developed the MagO2 ® demand vessel to measure the oxygen demand of mineral pulps. This paper described the apparatus, and through a case study on Broken Hill lead/zinc ore demonstrates how the MagO2 ® demand vessel is used.INTRODUCTIONThe role of oxygen in flotation is complex. While a considerable body of work exists demonstrating the strong involvement of oxygen in the interactions between sulphide minerals and collector (Gaudin and Finkelstein, 1965; Gaudin, 1974; Woods, 1984; Laajalehto, Nowak and Suoninen, 1993), the presence of oxygen can also affect the oxidation state of sulphide and non-sulphide minerals, which can impact on their flotation behaviour. Further, sulphide mineral oxidation is related to their oxygen demand (Spira and Rosenblum, 1994)."

Jan 1, 2004

By Karel Van Acker

The automotive is a sector where energy consumption during the use phase prevails over the production and the end-of-life phase. Therefore, a lot of research and innovations at replacing classical steel parts by lighter materials like light metals and polymer composites. While composites are very attractive for the use phase of cars, their introduction suffers from the limited end-of-life options for composite structures. An extensive life cycle analysis for a reference car design has been conducted to study the effects of replacement of conventional steel structures by lightweight carbon fibre composite alternatives. The study also takes second order effects in the design of the car into account. The opportunities and treats of the trend towards more intensive use of carbon-fibre composites in car design are identified. A discussion on the potential of other types of composites for the automotive in terms of sustainability considerations is added.

Jan 1, 2010

By M. M. Gadde

Recent regulatory changes in the United States make it mandatory to conduct structural analysis of coal mine seals used to isolate abandoned workings from active mining areas. Different loading criteria are available for seal design depending on whether gob composition is actively monitored and maintained or not and whether the gob conditions lead to deflagration or detonation type loading. Since the loads involved in seal designs are dynamic in nature, the structural analysis must be made using dynamic stress analysis techniques. However, because of the significant complexities involved in conducting dynamic analyses, some designers use approximate simplified techniques to address the design problem. In this paper two such simplified methods are critically evaluated for their suitability to design coal mine seals. The benefits and limitations of the simplified methods are also outlined. Some comparisons are made to show the differences between sophisticated three dimensional dynamic analyses and the simplified methods and to delineate the problems associated with the latter approaches.

Jan 1, 2009

An investigation into the causes of variable sulphur content in blast furnace metal produced at No. 4 blast furnace at the Port Kembla works of Australian Iron and Steel Pty. Ltd. was carried out. Theprogramme included an extended and detailed experimental study of a great number of the operating variables of the furnace, on a cast-bycast or four-hourly basis, over fourteen days.Possible causes of the variation were found in irregular operation due to sinter variability, and it was also clearly shown that slag conditions were most important in controlling sulphur contents of pigiron. Some decrease in sulphur variability was achieved, arising partly from this investigation, and it is hoped to try magnesia additions to modify slag conditions for better desulphurizing.INTRODUCTIONSulphur in pig iron is a problem common to many blast furnace operators throughout the world, but the direct causes and means of overcoming them are functions of the available raw materials, and are hence more particular to each plant and its operating practice. Sulphur in hot metal influences the steel-making operations, the rolling operations and the quality of the finished steel. The main problem associated with high sulphur in steel is "hot shortness", which leads to cracking of ingots and billets in rolling, to poor surface finish and to poor welding properties in the finished steel. On the other hand, sulphur is sometimes a desired additive to steel in order to promote free machining properties.Normal means of controlling sulphur A small degree of control of sulphur in steel is available to open hearth operators by alteration of slag volumes and basicity, but any large degree' of sulphur elimination is...

Jan 1, 1961

By Fred N. Kissell

In This Chapter [The explosibility of methane gas mixtures Effect of pressure and temperature on explosibility Less common sources of methane ignitions The amount of methane stored in coal Forecasting the methane emission rate Layering of methane at the mine roof When the recirculation of mine air is hazardous The importance of higher air velocity in preventing methane explosions and Mine explosions, barometric pressure, and the seasonal trend in explosions] Dealing with methane in mines and tunnels requires knowledge of the circumstances under which dangerous accumulations of methane are likely to occur. This knowledge involves the properties of the gas itself, an awareness of where these accumulations are likely to occur, and facts on how methane mixes safely into the mine air. The other chapters in this handbook address the handling of methane under a variety of specific circumstances, such as at continuous miner faces or coal storage silos. This chapter addresses some broad concepts that serve as a foundation for the suggestions provided in other chapters. THE EXPLOSIBILITY OF METHANE GAS MIXTURES Methane entering a mine or tunnel often enters as a localized source at high concentration. Figure 1–1 depicts a cloud of methane being diluted into a moving air stream. In this illustration, methane enters the mine from a crack in the roof. As the methane emerges from the crack, it progressively mixes with the ventilation air and is diluted. In the event that this progressive dilution reduces the concentration from 100% to 1%,2 as shown in Figure 1–1, the methane passes through a concentration range of 15% to 5%, known as the explosive range. In the explosive range, the mixture may be ignited. Above 15%, called the upper explosive limit (UEL), methane-air mixtures are not explosive, but will become explosive when mixed with more air.

Jan 6, 2006

By Jerry C. Tien

Changes and the pace of change in China’s coal industry have been extraordinary during the past several years. At least 35 of the 94 former coal bureaus have been restructured into different mining companies and groups. Some of the more productive and efficient ones were further strengthened through consolidation and expansions. And several have even formed, or are in the process of forming, strategic alliances with utility companies, railroads, ports and chemical companies to secure additional reserves and coal sales. In addition, the improvement in coal pricing during the past two years has enabled China’s coal industry to move ahead with some needed changes. Coal mining accidents, though, remain a major concern for the Chinese government. Accidents remain high even though the government has made efforts to shutdown more than 55,000 unlicensed, unsafe small coal operations throughout the country.

Jan 1, 2003

By A. J. Kraemer

The twenty-fourth of a series of semiannual surveys pertaining to motor gasoline marketed in the United States was made by the Bureau of Mines in August, 1931, The first part of a report giving the results of that survey as they pertain to specification data is given in this paper. A companion report, Part II, is in preparation and will discuss the results off other determinations made on the samples, including octane number ratings on the individual samples (to be made by the Bureau of Standards) and results of the determination of gravity, color, doctor test, and "gum" content by the copper dish method and the Bureau of Mines steam-oven method. The retail price and the tax at the time Each sample was taken will also be retorted. History of Survey The Bureau of Mines made its first survey of motor gasolines sold throughout the United States in 1915,4 a second in 1917,0 and a third in April, 1919.0 These three surveys showed that during each 2-year interval the motor gasoline had become notably less volatile. In order

Jan 1, 1932

By C. R. Copeland

Combustion processes, comminution and materials handling can generate airborne particulates. Regulation of these particulates by the U.S. Environmental Protection Agency (U.S. EPA) is becoming progressively more stringent, and regulations will soon include ?nanoparticulates,? which are particles finer than 100 nanometers (0.1 mm). Nanoparticulates are believed to have significant negative health effects due to their high surface area and reactivity. Although it was argued that nanoparticulate concerns were only important for combustion, studies at Michigan Technological University have shown that materials handling and comminution release significant quantities of nanoparticles into the air. Laboratory studies have shown that the use of sodium metasilicate reduced airborne particles finer than 10 mm (PM10) by 86% and particles finer than 2.5 mm (PM2.5) by 80% for iron ore. Additional studies were conducted that revealed that nanoparticulate emissions were present in the types of operations conducted at pyrometallurgical facilities.

Jan 1, 2008

By G. Deschênes

The Eleonore property (James Bay district of Northern Québec), owned by Goldcorp, hosts gold within stockworks of quartz-tourmaline-arsenopyrite veins and veinlets contained within microcline (potassic alteration) and brown tourmaline replacement zones. The preliminary investigation to recover gold from drill core samples showed that flotation followed ultrafine grinding and cyanidation is the preferred option. Ultrafine grinding is used to liberate gold finely disseminated in sulphides. The flotation concentrate used in the investigation had a P80 of 11 microns and contained 75.5 g/t Au, 5.0 g/t Ag, 10.3% S, 0.07% Cu and traces of antimony (0.03%). The mineralogical characterization showed the presence of 65% gangue minerals, 23% pyrrhotite (hexagonal), 9.6% arsenopyrite, 2.2% pyrite and 0.08% chalcopyrite with trace amounts of galena (0.05%) and sphalerite (0.03%). Gold was in the form of native gold and electrum. A straight cyanidation conducted at pH 11.0, DO of 3-5 ppm, 2000 ppm NaCN, 20 C 72 hours extracted 97.0% Au and consumed 31.5 kg/t NaCN. The equilibrium was reached within 24 hours. Increasing the dissolved oxygen to 16 ppm reduced the consumption of cyanide to 22.0 kg/t with 96.7% Au extraction. A 16-h pretreatment with 2.0 kg/t lead nitrate, followed by a 24-h cyanidation reduced the cyanide consumption to 6.0 kg/t with a gold extraction of 97.5%. Increasing the lead nitrate addition to 6.0 kg/t reduced the cyanide consumption to 1.2 kg/t by passivating the surface of pyrrhotite. The gold extraction remained at 97.0%. It was possible to decrease the concentration of cyanide to 800 ppm NaCN without compromising gold extraction. The associated cyanide consumption was 1.2 kg/t NaCN. The passivation of gold grains was an issue when the cyanide concentration was decreased to 550 ppm NaCN. The gold extraction decreased to 92.2%. The average lime addition for all the tests was 7.4 kg/t and the average silver extraction was 80%. Efficient cyanidation of an ultrafine sulphide concentrate with only 800 ppm NaCN represents an advance in leaching of ultrafine sulphide concentrates.

Jan 1, 2013

Splashing and wave formation has been studied experimentally by using one-seventh water model of CLU (Creusot-Loire Uddeholm) reactor with two different tuyere configurations by using paraffin and water as simulated slag and simulated metal respectively. Experimental results have been discussed in terms of total splash volume, relative slag volume in splash (dispersed-slag phase holdup in splash), wave frequency and wave amplitude with respect to gas injection rate and tuyere configuration at bath heights between 0.25m and 0.38m. Gas flow rates ranged from 0.00599m3/s to 0.01312 m3/s. The results of splash measurements showed that splash volume increased with increasing gas flow rate and decreasing bath heights for both tuyere arrangements. However, off-centre configuration resulted in relatively higher amounts of splash. The slag volume in splash (Dph in splash) was also found to increase with decreasing bath heights and increasing gas injection rates. The high speed photography revealed that the frequency and wave amplitude increased with gas injection rate. The experimental results also showed that the frequency and vertical displacement of the rotating wave increased when the tuyere orientation became off-centered. This might be used to explain why off-center configuration resulted in generating higher splash volumes than the center configuration.

Jan 1, 2004