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By R. W. Smith

A microorganism will function as a mineral flocculant if it is to some degree hydrophobic and can attach itself in some manner, such as through electrostatic interaction, to the fine mineral particles to be flocculated. The present paper concerns the use of a hydrophobic bacterium, Mycobacterium phlei, as flocculating agent for phosphate slimes. Experimental work on the flocculation of phosphate slimes and of dolomite and clay mineral suspensions was performed. It was found that M. phlei functions as an excellent flocculant for a dolomitic slime but does not function as well for mineral suspensions where large quantities of the solids are finer in size than the approximately 1 µm size of the bacterium.

Jan 1, 1992

By Carlos Antonio da Silva

Steel refining reactors based on chemical heating are being used as an alternative to ladle furnaces, They show a high degree of flexibility in respect to heating rate in addition to carrying out refining reactions such as de-S, inclusion removal, alloying etc. IR-UT and CAS-OB are examples of such reactors. Their performance is dependent upon geometrical characteristics as well as operational conditions which determine the flow field inside the vessel. A physical model of the IR-UT process of the Companhia Siderúrgica de Tubarão, steel plant located in Serra, Espirito Santo, Brazil, was developed to assess the features of the flow field and its influence on the metallurgical behavior. Results of the physical model were used to optimize the process parameters in the industrial unit.

Jan 1, 2003

By A. Kontopoulos

Refractory sulfide gold ores or concentrates require an oxidation pretreatment step to yield the contained gold amenable to the subsequent leaching step. The process options for oxidation pretreatment can be broadly classified as follows: roasting, high or low pressure oxidation bacterial oxidation, chemical oxidation, each with a number of alternative suboptions. Roasting and high pressure oxidation are being applied on an industrial scale; the stage of development of the other options range from preliminary laboratory to advanced pilot plant- In this paper, the major technical, environmental and economic aspects of the above processes are being discussed. Future industrial trends will also be considered. Particular emphasis will be placed on the treatment of arsenical ores and concentrates, where safe plant operation as well as, handling and disposal of the arsenic containing products and/or effluents 'and residues is of paramount importance.

Jan 1, 1990

By Gopalakrishna M. Rao

"Several industrial and government laboratories are of the opinion that solar--cell technology will grow into a billion-dollar industry by the year 2000, especially if oil prices rise again. Of the variety of materials that have been investigated as the major component of photovoltaic systems, silicon appears to have an outstanding advantage. The cost factor is the primary importance in photovoltaic development, since the technology to make silicon cells of acceptable efficiency and life time has existed since the early stage of the space program. Electrometallurgy is one of the low--cost processes for the production of silicon, since it allows direct, single-stage production from some abundant, inexpensive source materials such as silica and fluorosilicates. Among several systems, two are given particular attention, using inorganic baths with Si0 2 or K2SiF6 as the source of silicon respectively. They appear capable of development to commercial production. Conceptual designs of a commercial--scale cell for silicon production at temperatures above its melting point, and of a pilot' plant for plating silicon from an all-fluoride bath are presented. Energy ProspectsThe major changes in the world energy since the first energy crisis in 1970 have impacted on our community. When oil was $40 a barrel in the mid-1970s, we became obsessed with the energy conservation and a search for alternate energies. Even though the crude oil fell below $15 a barrel during the last several years, our energy security fears continue to haunt us. This time it is not the scarcity, but the abundance of foreign oil and the decline in the domestic production.The prospects of energy depends on the demand and supply of energy. These, in turn, depend on future energy prices, which are linked to economic factors, political events, and unforeseen circumstances. Although no one can predict the future with certainty, three energy consumption patterns used by the Ford Foundation are as shown in Fig. 1."

Jan 1, 1988

By Xiangwen Wang

Electrodeposition of lead metal from high purity brine electrolytes containing lead chloride (PbCI,) was conducted so as to assess the feasibility of electrowinning lead-metal directly from aqueous chloride electrolytes. Tests were performed at 65 and 80°C (338 and 353°K). Characteristic features of the deposits, on both lead and graphite substrates, were correlated to operating parameters associated with: electrolyte temperature, current density and total lead- concentration. Photomicrographs of these morphological features were obtained by use of Scanning Electron Microscopy (SEM).

Jan 1, 1993

By Lamar S. Todd

The direct production of metal from a sphalerite concentrate is an attractive route for primary zinc. A series of operations and conditions have been selected to efficiently cause the following overall exothermic reaction. The process uses a continuous circulation of molten copper for material and energy transfer between the unit operations. Sulfide concentrate is reduced with an excess of superheated copper to make a copper alloy and white metal. The alloy is stripped of volatile metals under vacuum and some metals can be separately condensed. The residual copper and the white metal are fed into a copper converter to be blown with oxygen for desulfurizing and the superheated copper is recycled. The paper will include a detailed material flow sheet for the process, discussion of the operating conditions of the individual units, behavior of minor elements, and zinc quality.

Jan 1, 1999

By Tam Tran

Over the last decade, halide (chloride, bromide and iodide) systems have been evaluated as alternative lixiviants for the processing of gold to replace cyanidation which has been widely used in commercial practice. This paper first reviews the development of processes promoted by Kaljas Ltd / Lachlan Resources (Australia) and Great Lakes Corp (USA) using different bromide/bromine systems in the early 1990's. Several research groups subsequently evaluated the use of iodide/iodine and chloride/chlorine for gold extraction, showing similar characteristics of gold/silver dissolution and recovery. A critique is :given on the advantages and the ,shortfalls of halide systems as alternative lixiviants. The stability of gold? halide complexes is discussed, based on practical experience and thermodynamic modelling of their speciation, The iodide system provides the most stable gold / silver complex for easier handling. However, the cost of iodide inhibits its application for are processing. In this critique, emphasis is given on the cheapest system, which involves the use of chloride for leaching (in conjunction with an appropriate oxidant). However the chloride-base leachant has a major drawback which is related to the unstable nature of gold chloride in a reducing environment.

Jan 1, 1998

By R. Y. Wan

Low grade sulfidic-carbonaceous refractory ore from Newmont Gold Company's Carlin deposit was microbially pretreated. The biological pretreatment process gave partial oxidation of the sulfidic components of the refractory ore but the preg-robbing carbon continued to be active resulting in approximately zero cyanide gold extraction. A 495 ton pilot plant test heap was conducted using acidic thiourea leach following biooxidation. Activated carbon and cation exchange resin adsorption were tested for gold recovery from the thiourea pregnant solution. The results obtained from the test heap were not satisfactory. Gold extraction was low due to slow reaction kinetics which was caused by relatively large particles and very low winter temperatures. Problems existed in the thiourea-test heap and are discussed in this paper. An alternative heap leach process using thiosulfate has been successfUl at the pilot scale for gold extraction following biooxidation pretreatment of refractory sulfidic-carbonaceous ores.

Jan 1, 1995

By R. Mehta, M. Misra, X. Su

"The conventional methods to assess Acid Mine Drainage (AMD) potential of the waste rocks and tailings are based on wet chemistry and leachability tests. These methods are time consuming and expensive. There is a growing interest to develop alternate techniques to establish the reactivity of acid mine tailings and stability of treated waste forms. The Electrochemical Impedance Spectroscopy (EIS) is a reliable non-invasive technique which can be used for quick estimation of reactivity of the potential acid generating tailings. In this paper the utilization of the EIS technique for the estimation of reactivity of tailings is discussed. EIS can also be used to predict the long term stability of different stabilized waste forms.IntroductionMetal contaminated mine drainage is one of the most persistent environmental problems facing the mining and mineral processing industries today. Of all the mine drainage pollutants, acid mine drainage has become a substantial concern because of the potential long-term environmental implications and the accompanying liabilities. The main source of acid mine drainage is the tailings containing sulfide-ores which are generated during the ore processing. When these sulfide minerals, particularly pyrite and pyrrhotite, are exposed to oxygen and water they begin to oxidize. The initial chemical reactions produce acid and the acid dissolves heavy metals present in the tailings. Rainfall and snow-melt flush the toxic solutions from the waste sites into the downstream environment [1-2]. In addition to mining tailings, several Department of Energy (DOE) sites contain wastes which are contaminated with radionuclides and heavy metals."

Jan 1, 1999

By B. Erik Ydstie, Tor Lindstad, Vianey Garcia-Osorio

"As a result of the high temperatures present in a Carbothermic Aluminum Process the content of aluminum and aluminum sub-oxide in the gases leaving this process is high. These gases as well as energy must be recovered. In a Vapor Recovery Unit were the aluminum compounds react in a series of Heterogeneous Non-catalytic Reactions forming solid, liquid and gas products. The different product phases depend on the temperature present in the system. In this work we present dynamic model of the Vapor Recovery Unit of a conceptual Carbothermic Aluminum Process. Because of the complexity of the system several models are developed and coupled to capture the essential physics of the multiphase reaction problem. A Shrinking Core Model describes the reaction mechanisms. Then material and energy balances are coupled with the thermodynamics properties from the FACT database of thermodynamic properties, resulting in a system of nonlinear Partial Differential Equations. In the paper we describe the model development and governing equations for the reaction mechanisms and fluid flow. Finally we review the numerical schemes created for the solution of the model system. The model can be used for control and design purposes.IntroductionThe Carbothennic Processes for producing Aluminum can be divided into two groups (Motzfeldt et al. (1989)) In the first approach pure alumina is produced and reduced to pure aluminum. In the second approach an alloy (e.g. aluminum and silicon) is made and then aluminum is produced from the alloy. The history of both processes has been described by Ginsberg et al. (1965). At least three aluminum producers began largescale testing of this process in the 60's Alcan, Pechey-Ugine and Reynolds. Alcoa did some smaller scale experiments.Alcoa was one of the first companies to produce aluminum by Carbothennic Reduction (Foster et al. (1956)) and US Patent 2,829,961 April 8, 1958. In this process a carbon containing molten aluminum phase was a floated on top of an oxy-carbide melt. During the cooling the dissolved carbon deposited as aluminum carbide. The carbide was then separated from the molten aluminum by a fluxing agent. This process was successful but economic unfeasible."

Jan 1, 2001

By Carlos Antonio da Silva

Steel refining reactors based on chemical heating are being used as an alternative to ladle furnaces. They show a high degree of flexibility in respect to heating rate in addition to carrying out refining reactions such as de-S, inclusion removal, alloying etc. IR-UT and CAS-DB are examples of such reactors. Their performance is dependent upon geometrical characteristics as well as operational conditions which determine the flow field inside the vessel. A physical model of the IR-UT process of the Companhia Siderurgica de Tubarao, steel plant located in Serra, Espirito Santo, Brazil, was developed to assess the features of the flow field and its influence on the metallurgical behavior. Results of the physical model were used to optimize the process parameters in the industrial unit.

Jan 1, 2003

By Shufeng Yang, Anping Dong, Yongfeng Chen, Jingshe Li, Lifeng Zhang, Liyuan Sun

"Instead of nickel-based stainless steel, a nitrogen-bearing stainless steel was produced to reduce the production cost stemming from the shortage of nickel recourses. Thermodynamic model to calculate the saturation nitrogen content in the stainless steel were developed and the model was validated by experimental measurement. The experiments were performed with a high temperature induction furnace. Nitrogen gas under constant pressure was injected into the crucible with a top lance by which the nitrogen was transferred to the molten stainless steel. The effects of chemical composition, temperature, superficial active elements and nitrogen-flow rate on transferring nitrogen to the steel were investigated and discussed.IntroductionWith the rapid production growth of stainless steels, nitrogen-bearing stainless steel has recently attracted more and more attention for their high strength and excellent corrosion resistance imparted by interstitial nitrogen without decreasing its toughness and ductility. Moreover, the addition of nitrogen to the stainless steel as a substitute for nickel leads a lower consumption of nickel, so significantly lowers the high production cost stemming from the shortage of nickel recourses. However, production of the nitrogen-bearing steel is difficult since nitrogen is a gas element and has a low solubility in the steel. So efficiently increasing the amount of nitrogen in steel continues to be one of the main concerns for the production of nitrogen-bearing steels.Currently there are some special processes to produce austenitic stainless steels with a very high N content, including pressurized electroslag remelting, counter-pressure casting, special induction melting and powder metallurgy, etc [1]. Special expensive vacuum system was required for these processes. Alloying nitrogen at a normal pressure can be performed by alloy addition or gas injection. Blowing nitrogen gas is a more economic and advisable method since the nitrogen-bearing alloy is quite expensive and contains high content of impurities. A number of investigations have been reported on the solubility of nitrogen gas in pure iron [2] but few in iron-based multi-component alloys such as stainless steel.In the current study, the effects of steel chemical composition, temperature, superficial active elements and nitrogen-flow rate on transferring nitrogen to the steel were experimentally investigated with a high temperature induction furnace."

Jan 1, 2011

By Zhi-yong Liu

A novel process, which includes hydrochloric acid leaching, iron powder cementation, sulphide precipitation and spray pyrolysis, was proposed to treat iron concentrate recovered from zinc kiln slag for comprehensive utilization. Treated by two-stage hydrochloric acid leaching, the leaching extents of Ag, Pb, Cu, Fe and Zn are 96.78%, 95.14%, 97.72%, 94.51% and 87.74%, respectively. More than 99% Cu and Ag are recovered from the leach liquor when iron powder is 25% higher than the stoichiometric requirement. More than 96% Pb and Zn is removed with three times of theoretical consumption of FeS, and the concentration of impurities of the final solution is less than 500 mg/L. Fe2O3 powder, which is spherical with a mean size of 12 μm and purity of 99%, is prepared with final solution at 700 °C. In this process, not only the metal values can be recovered effectively, but also the iron resources of zinc kiln slag can be converted into high purity Fe2O3, thus, the comprehensive utilization of iron concentrate recovered from zinc kiln slag can be realized.

By K. R. Robilliard

An outline is given of the problems facing tlile lead and zinc industry from the viewpoint of the range of residues currently produced from electrolytic zinc, blast furnace and other processes. Smelting approaches available using top submerged lancing technology are discussed and analysed. Pilot plant results for a range of lead and zinc-bearing materials are presented.

Jan 1, 1992

By R. Hurman Eric

The flow of molten slag and matte and the estimation of the mass of settled matte in electric furnaces is discussed and the action of the electric furnace as a settler is considered. Particle size of the concentrate and its grade are major contributors to settler dimensions. Discussion on the production capacity of the electric furnace with reference to operating current, power input, furnace dimensions such as width and length and electrode diameter are given. These discussions are based on considerations derived mainly from experimentally determined properties of the slag such as its resistivity, viscosity and liquidus temperature. Extension of the design and operating considerations to circular furnace symmetry is also discussed.

Jan 1, 1995

By Federica Paglietti

In this work is presented SEX (Structural & Elemental X-Ray Instrument), the first spectrometer completely portable which make non-destructive X-ray fluorescence and diffraction analysis, in contemporary and in real time. This instrument has been realized using miniaturized detectors, the same model installed on the mission Pathfinder NASA, and X-ray microtubes. SEX allows the chemical and mineplogical characterization of all kind of solid materials and allows to make chemical stratigraphy and liquids analysis.

Jan 1, 1998

By Jerome P. Downey

In the thermal treatment of electric arc furnace (EAF) dusts, zinc is reduced, volatilized, and ultimately recovered either as liquid metal in a splash condenser or as solid zinc oxide in bag filters. During the process, the duet's chlorine and fluorine content also enters the gas phase and condenses as dross in the splash condenser or as salts which contaminate the zinc oxide product. Pretreatment of EAF dust by pyrohydrolysis appeared to offer a means of minimizing the duet's halogen content. The primary research objectives were to experimentally verify the technical viability of pyrohydrolysis and delineate the process parameters requisite for efficient halogen removal. To this end, representative EAF duet samples were secured and characterized by x-ray diffraction, scanning electron microscopy, and Mössbauer analyses. Specific- experimentation focused on the response of halogen extraction to variations in temperature, retention time, water vapor partial pressure, and various additives. The experimental results proved that 97 to 99 percent chlorine extraction and 80 to 85 percent fluorine extraction are consistently achieved when EAF dusts are blended with silica and roasted at temperatures of 850°C or greater in a furnace atmosphere of 75% steam (diluted by air). A statistical analysis further established that more than- a single optimal point exists, thus affording flexibility in parameter selection (e.g., by increasing temperature, the necessary retention time and additive concentrations are decreased). The findings substantiate the feasibility of pyrohydrolysis roasting in reducing the chlorine and fluorine in the EAF dust to a level that will obviate industrial concerns about halogen contamination. The end-product of the pyrohydrolysis procedure is a de-halogenated, self-fluxing calcine which can be directly charged to a plasma or flame reactor. The paper includes design parameters and flow diagrams illustrating the pyrohydrolysis process integrated with the plasma and flame reactor technologies.

Jan 1, 1992

By Mansoor Barati

The present paper is based on a term project for final year undergraduate students, requiring them to evaluate a process for producing silicon from rice husk. The traditional method for production of silicon involves carbothermal reduction of quartz in electric arc furnaces at temperatures exceeding 2000 °C. The technology consumes a considerable amount of electrical energy as well as fossil fuels, resulting in significant CO2 emissions. A flowsheet for production of silicon metal from rice husk is laid out in this paper. The technology will consist of combustors, which will generate steam using the rice husk biomass, power generator, and electric furnace for reduction of the rice husk. Materials and energy balance calculations presented here indicate that such process can be operated independent of external electricity.

Jan 1, 2014

By Shantanu Chakrabarti, Khursid Alam Khan

"Globally, the use of metallic coated steel sheets in the automobile industry is increasing. The sheet should have excellent formability, weldability, paintability and corrosion resistance. Since bare cold rolled steel sheets have certain limitations, application of galvanized steel sheets is steadily expending. Galvannealed steel sheet fulfills all requirements and has become of major interest in the automobile industry.The success of Galvannealed (GA) steels in the body-in-white depends upon material design and parameters of various processes involved, like cold rolling, continuous annealing, hot dipping and galvannealing. In the present work, powdering resistance, one of the important product characteristics of GA, has been studied and a relation is established between the process parameters and the powdering value. The product obtained through optimization of the process parameters have been successfully used by major automotive producers without any powdering problem, for internal as well as external automotive applications.IntroductionThe present automotive industry demands that steel for the auto components should have excellent formability, weldability, paintability, corrosion resistance etc. In addition to this there is specific requirement for some particular components like high surface quality for skin panels. Corrosion resistance of panels is important requirment which determines the life of the particular component and brand value of the automotive. Among all the zinc based steel coating used in the automotive industry coating produced by Galvannealing process has received most attention because of its excellent weldability along with superior corrosion resistance and better paintability."

Jan 1, 2012

By William Petruk

The development of automatic image analysers brought the application of image analysis into process mineralogy because the analysers can measure parameters more easily, quickly and accurately than by manual grain counting techniques, and can also collect data unobtainable by manual grain counting. Data from ore specimens and mill products are used to predict and to define the behaviour of minerals during processing. The analyses are generally performed on the basis of either surface areas or linear intercepts of grains in polished or thin sections, and the data are computer processed to give mineral quantities, liberations, size distributions, and characteristics of middling particles. For analysis, the minerals must be detectable and discriminatable from each other. An image editor is usually used when minerals are not easily discriminated. In addition BSE-8EM photographs have been used where the silicate minerals could not be discriminated from the mounting media. Methods of analysis, typical results, and their applications are discussed.

Jan 1, 1982