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By Z. Yang, R. W. Smith, Jr. Wharton

"Microorganisms have the ability to remarkably adsorb and/or absorb heavy metal ions. Hence they are being studied widely as a means of removing metal ions from aqueous solutions both in order to clean up toxic streams and to recover valuable metals from these and other streams. It is often difficult to harvest organisms such as bacteria and unicellular algae since they are usually too small to be readily screened out. Froth flotation may prove to be a feasible method to harvest such organisms subsequent to the ad/absortion of the metal Ions. The present paper discusses the surface/electrokinetic properties of microorganisms and the modifier-collect conditions under which they should float. The zeta potential of the green alga Chlorella vulgaris was measured in the presence of AI(III) and Pb(II) ions and in the presence of dodecylammonium chloride and sodium dodecylsulfate. Present and past data suggest that the organisms should behave similarly to other finely divided, charged (polar) solids with their behavior sometimes modified by the non-polar surface regions present.IntroductionThe overall field of bioengineering is growing at a remarkably accelerating rate. Hydrometallurgy and mineral processing are included among those disciplines where there has been actual or proposed commercial use of bioorganisms. Further, the actual or proposed use includes bacterial enhancement of leaching of a number of different types of ores (1-5), modification of the flotation or oil agglomeration separation of minerals by bacteria (6,7) and microorganism (algae, bacteria or fungi) concentration of metal ions present in effluent or other mineral processing or hydrometallurgy aqueous streams (8-23)."

Jan 1, 1988

By Devon A. Hannan

Thermodynamic modeling calculations were undertaken for the recovery of mercury from HgTe using a vacuum retort reactor. However, discrepancies were noted in the available thermodynamic data which introduced uncertainty in the model results. Consequently, a series of transpiration experiments were first undertaken on the thermal decomposition of HgTe into an inert carrier gas stream according to the following reaction: HgTe(s) Hg(g) + Te(s) From the measured weight loss of the HgTe samples, the Gibhs free energy change for the above volatilization reaction was determined as a function of temperature. The experimentally determined Gibbs free energy values were found to be approximately 30% larger (more posi-tive) than the values available in databases such as HSC Chemistry. By conducting a second-law analysis on the experimental data, the heat of formation of HgTe at 298.15 K and the en-tropyat 298.15 K were determined, which then formed the basis for a new database for the modeling calculations. The results of this study showed that HgTe was more stable at elevated temperatures than was generally indicated in the literature. The new database is given in a for-mat for direct insertion in HSC Chemistry. Using the new database, modeling calculations were conducted to examine the effects of the re-tort pressure and the molar ratio of purge gas to HgTe on the volatilization of mercury from HgTe. A diagram is presented that shows the minimum temperature for 100% volatilization of mercury from HgTe as a function of retort pressure for different molar ratios of purge gas (N2) to HgTe. For example, it was found that the minimum temperature for 100% volatilization could be decreased by 175 K, at a retort pressure of 0.05 bar, if the molar ratio ofN2 to HgTe is increased from 1.0: 1 to 100.0: I.

Jan 1, 2003

By Ji-He Wei

The ESR of Cu-Cr-Zr alloy has been experimentally investigated. The remelting experiments have been carried out with different slag fluxes in the Cal, + Nal, CaF2 + ZrO2 and CaF2 + NaF + ZrO2 systems on an ESR furnace of 25kg capacity; using a water-cooled copper mould of 96.5 mm diameter, with the forged square bar electrodes of 50x50 mm2. The slag amount was taken to be 1.5 kg. The remelting current and voltage used were 1600-1800A and !5-25K, respectively. The influence of the slag composition on the stability of the remelting process and the losses of alloying elements (2r and Cr) has been considered and examined. The technologies of hot working and heat treatment of the ES ingot have been described and discussed. Some physical properties of the slag in a CuF2 + NaF + ZrO2 system and the remelted Cu-Cr-Zr alloy have been determined. The results indicated that with the slag flux of CaF2 + NaF + l0 mass % ZrO2 and the other operation parameters employed, a high quality ingot of Cu-Cr-Zr alloy may be obtained at the considerably high yields of Zr and Cr by means of ESR. For the remelted Cu-Cr-Zr alloy with a specified composition of 0.5 mass % Cr and 0.1 mass % Zr, the appropriate electrical conductivity, hardness and softening temperature are as high as 45-46S/m, HRB 82-84 and 550°C. respectively. The properties of the Cu-Cr-Zr alloy products are in accordance with and superior to the requirements and specifications of ISO5l82-l99l(E).

Jan 1, 2000

By A. W. Bryson, K. C. Lenthall

"With the growth in the use of cobalt in industry, interest in its extraction and recovery has increased. With this increased interest comes the need for a fundamental knowledge of the processes involved in the recovery of cobalt metal. This paper examines the effects of cobalt concentration, catholyte pH, operating temperature and current density on cobalt electrowinning with respect to the current efficiency, cell potential and nature of the cobalt deposit. It is found that the cobalt concentration and catholyte pH affect the current efficiency, while current density and temperature affect the cell potential and thus the specific power consumption. Pitting on the deposit is affected by the catholyte pH and the operating temperature. Furthermore, the effect of feed flow-rate on catholyte pH, and thus current efficiency, is investigated. A model to predict the cell performance, which includes the flux of hydrogen ions through the diaphragm, is proposed.IntroductionCobalt metal is a silvery transitional metal found between nickel and iron on the periodic table. Due to its resistance to corrosion and other properties under high temperatures and its good work-hardening characteristics, it is favoured in alloys used in high temperature applications. These include aerospace, aircraft and high speed tools. Other applications include its use as a colourant in glass and ceramics, a drying agent in paints, a nutrient for livestock, a catalyst in the petroleum industry and, in the medical field, in prosthetics and radiology.The main deposits of cobalt are found in Central Africa, specifically Zaire and Zambia, although deposits also occur in Morocco, Canada and Australia. The cobalt is generally associated with other transitional metals including nickel, iron and copper. It is generally extracted by hydrometallurgical means and recovered from solution by electrowinning or hydrogen reduction. Little data [1-2] exists in literature on the electrowinning of cobalt from aqueous solutions. This paper investigates the effects of various operating conditions on the current efficiency, cell potential and deposit nature under continuous operation."

Jan 1, 1997

By E. T. White

The population balance is one of the basic relations for a:n:aIysing particulate minera1 processing operations. It is an exact relation. The principles of the population balance are reviewed and applications in the minerals industry discussed.

Jan 1, 1996

By E. T. White, Dean Ilievski

"The population balance is one of the basic relations for analysing particulate mineral processing operations. It is an exact relation. The principles of the population balance are reviewed and applications in the minerals industry discussed.IntroductionMathematical modelling has proved to be a very successful approach for improving the design and performance of mineral processes, particularly since the availability of computers to handle the complexity usually necessary to give a useful model.Mineral processes almost invariably involve particles, as either solid fragments, liquid drops or bubbles. Process performance usually is highly dependent on the behaviour of these particles. In modelling particle behaviour, the basic relation to be used is the population balance. This paper discusses the role of the population balance and the range of its applications in minerals processing.The Population BalanceThe population balance was developed for demographic studies, ego predicting the change in the population (numbers) of, say, school children between one census and the next. The first sustained application to the processing industries appears in the 1960s for crystallization. However it was recognised almost immediately that it had application to all particulate processing."

Jan 1, 1996

By Hongxu Li, Pu Liu, Hao Bai, Daqiang Cang, Lihua Zhao

"Coal, as the main energy in ferrous metallurgy, is consumed on a large scale and great amount of CO2 is emitted likewise. In this paper, a model, based on carbon balance, was developed for CO2 emission analysis, with data obtained from a typical integrated steelworks in China. The result shows that, CO2 emissions increase almost constantly with the growth of steel production. However, coals of different classes and product variety in the steelworks exerted an influence on CO2 emissions. Furthermore, three scenarios, including natural gas instead of coal for power generation, EAF process partly replacing integrated steelmaking, and feasible techniques applied to achieve lowest process energy consumption (FLPEC), were assumed to seek possible ways of carbon emission reduction. The result proves that the second scenario is most effective. If 40% of the steel product could be from EAF process, CO2 emissions would be reduced by 45.07%.IntroductionGlobal warming has become a global environmental problem, which is generally caused by excessive emission of greenhouse gases, such as CO2, generated from human activities and industrial processes. It is estimated that about 7% of global CO2 emissions was from iron and steel industry. Further, if the ore and coal’s mining and transportation are included, the CO2 emissions would reach 10%[1]. In general, the relationship between energy saving and CO2 emission reduction is positive correlation. However, in iron and steel enterprises, due to different types of energy resources like coal, heavy oil, natural gas, the consumption of which will generate different amount of CO2, are used, different energy consumption structure in iron and steel enterprises will lead to difference of CO2 emissions.In order to assess the CO2 emission reduction potential of China’s steel industry, Ke Wang etc.[2] developed a model using LEAP software to generate 3 different CO2 emission scenarios for the industry from 2000 to 2030. LEAP is a scenario-based software tool for integrated energy-environment and greenhouse gas mitigation analysis. The amount of CO2 emissions was obtained by the following equation:"

Jan 1, 2011

By T. T. Chen

A mineralogical study of copper anodes and copper anode slimes was carried out to elucidate the silver phases present and the behaviour of silver during copper electrorefining. Most of the silver in the anodes is in metastable solid solution in the copper metal. As the copper dissolves, silver also dissolves, but is rapidly removed from solution by a variety of reactions. Some of the silver is precipitated as Ag by cuprous ions and some is precipitated as a complex CU-Ag-Pb-As-Se oxidate phase. Much of the silver, however, reacts with copper selenides to form, progressively, (CU,Ag) 2se, AgCuSe and Ag2se. The reaction commences at the periphery of the selenide grains and progresses inward; the result is commonly a silver-rich species on the outside of a silver-deficient core. Slimes collected periodically throughout the electrorefining cycle show a progressive silver enrichment of the selenides. Traces of Ag2Te also may be present, but the telluride seems to J:ie a rare constituent of most raw anode slimes.

Jan 1, 1989

By N. Kanari

Reactivity of MgO towards C12+air, C12+N2 and C12+CO gas mixtures was studied up to 1000 °C. Carbochlorination of MgO occurs at temperatures lower than that of its oxychlorination. Effects of gas flow rate, temperature and partial pressure of the carbochlorinating gas mixture on the reaction rate were investigated. The apparent activation energy of MgO carbochlorination is 49 kJ1 mol between 425°C and 600°C. At 550 °C, the apparent reaction orders with respect to C12+CO, C12 and CO, are 2.37, 1.47 and 0.89, respectively. At this temperature, the maximum reaction rate was obtained using a C12+CO gas mixture having a Cl2lCO molar ratio equal to about 0.6.

Jan 1, 1998

By Takeshi Nagano

"Prior to discussing future trends of non-ferrous metals smelting and refining, the past developments are looked back. Social and economic environments in Japan over the past two decades are reviewed. Technological developments to comply with these environments are explained, taking for examples the cases of the Mitsubishi continuous smelting and converting process and Onahama's jumbo tank system for copper tankhouse. After considering the factors which will influence the improvements in non-ferrous processing, future trends are forecasted generally for copper, zinc, lead, aluminum and rare earth metals. Recent development works in Japan for the future are also introduced. In the discussed area, it appears that the emergence of new innovative processes would be difficult. The progress will be made rather toward the sophistication of the existing technologies, utilizing the advancement of the related technologies such as computers, electronics, etc. IntroductionThis paper discusses the future trends of non-ferrous metals smelting and refining on the occasion of the international symposium, ""The Metallurgical Processes for the Year 2000 and Beyond"".It is considered that the improvement of technology is greatly influenced by the social and economic environments which surround it. From this standpoint, review was made of Japanese case over the past two decades. Various new technologies were developed also in the non-ferrous metal world to comply with the requirements under the above environments. The examples are described in the cases of the Mitsubishi continuous smelting and converting process and Onahama's jumbo tank system for copper electro-refining.After foreseeing the major factors which will affect the technological developments in the future, the trends are forecasted for copper, zinc, lead, aluminum and rare earth metals generally. Some development works in Japan, which will give suggestions for future trends, are also introduced in some detail."

Jan 1, 1988

By William Petruk

The capabilities of SEM/image analyzers for determining quantitative mineral data which have a bearing on extractive metallurgy have given applied mineralogy a new dimension. The capabilities include automatic mineral identification, unattended operation, search for rare minerals, and measurements of (1) mineral quantities, (2) grain and particle size distributions, (3) liberation characteristics of minerals in ground ores, and (4) mineral associations. Data on mineral quantities define the distributions of elements among minerals, provide background information on characteristics of the samples, and provide a data base for a mineral-materials balance. Size analysis data of the minerals in unbroken ores are used to predict the grind required to liberate minerals. Data on liberation analysis can be used in many ways. One application is to process the image analysis data for feed, concentrate and tails by a materials balancing technique to calculate the recovery of liberated and unliberated grains at each point in a circuit. The calculated recovery data define the behaviour of an ore in a concentrator, pilot plant or bench test, and indicate whether recovery improvements are possible and/or feasible for a particular ore.

Jan 1, 1991

Heap leaching with thiosulfate is only used in one location for the treatment of a refractory preg-robbing gold ore initially pre-treated with bio-oxidation. The chemistry of thiosulfate leaching is complex. Further work is required to develop a better control of the system. A mild refractory gold ore containing pyrite and chalcopyrite was used in this study to investigate the use of thiosulfate as an alternative heap leaching technology. Preliminary bottle rolls tests indicated that similar gold extraction was obtained with cyanide and thiosulfate. In the column leach test, effects of thiosulfate, copper and ammonia concentrations, and their ratio on both gold extraction and reagent consumption, were assessed. The range of reagent concentration were: 0.1 - 1.0M (NH4)2S2O3, 0.03 - 0.10M CuSO4*5H2O, 1.0 - 6.0M NH4OH. The solid-liquid ratio was in the range of 0.83:1 to 5: 1. Best results showed that 72% of gold was extracted in 50 days with 0.3M (NH4)2S2O3, 0.05M CuSO4*5H2O and 6M NH4OH or a combination of 1.0M (NH4)2S2O3, 0.03M CuSO4*5H2O and 3M NH4OH. The reagent consumption at solid/liquid ratio of 3:1 was 37 - 48.6 kg/t (NH4)2S2O3 and 0 - 0.62 kg/t CuSO4*5H2O. The results of thiosulfate leaching were also compared with cyanide leaching.

Jan 1, 1999

By J. P. Hager

The formation of the vapor complex AgFeC14 (g) baa been identified and its thermodynamic properties determined. The vapor pressure of silver chloride can be enhanced by a factor of 15-20 due to the formation of the vapor complex. The vapor pressure of both AgCl (g) and AgFeC14(g) were measured using a double-zone transpiration .technique. Gibbs free energies have been determined for the vapor transport reactions. Laboratory kiln tests were conducted to confirm the enhanced recovery of silver through the formation of the AgFeC14(g) vapor complex and to indicate the opportunities for process development using this new vaporization chemistry.

Jan 1, 1985

By Xiang (Frank) Chen, Mikhail A. Sokolov, Randy K. Nanstad

"Nickel-base Alloy 617 is being considered as a structural material for application in the secondary heat exchanger of the New Generation Nuclear Plant, a very high temperature gascooled reactor. Thermal aging of Alloy 617 plate and welds is being performed with tensile, Charpy impact, and fracture toughness tests conducted at temperatures to 950°C. Results of testing for thermal aging to 5,300 h have been obtained and are presented; varying effects of thermal aging temperature and time on fracture toughness are observed. The 9Cr-1MoV (Grade 91) ferritic steel is a candidate for structural applications in the sodium fast reactor. Fracture toughness testing of unaged Grade 91 steel has been performed to evaluate specimen size effects in preparation for future testing of the material in the thermally aged condition. Results for material in the mill-annealed and heat treated conditions are presented and show that this heat of Grade 91 steel does not indicate a small specimen bias on the fracture toughness Master Curve reference temperature.IntroductionThe behavior of advanced engineering materials will be a critical factor in the performance of Generation IV reactors. In the case of materials utilized for reactor internals and pressure vessels, the effects of irradiation and long time thermal aging are major issues. The environmental conditions for some of the Gen IV reactors are generally beyond present day reactor technology, requiring new experimental data as well as analytical predictions of expected behavior of candidate materials at conditions for which there are only sparse or no experimental data. The radiation environments and several key materials issues for some Gen IV systems are summarized in Section 5 of [l] as a starting point for modeling and microstructural analysis of Generation IV materials. More detailed descriptions of materials research and development needs and recommended activities for the SCWR, VHTR, and GFR are provided in references [2, 3, 4], respectively. Mansur, et. al. provide an interesting comparison of materials needs for Generation IV reactors to corresponding needs for fusion reactors and spallation neutron sources in [5]. The two primary candidate reactor systems currently undergoing significant research and development by the U.S. Department of Energy (DOE) are the New Generation Nuclear Plant"

Jan 1, 2012

By QIE Jun-mao, DONG Fang, DENG Hao-hua

The DIL402C thermal dilatometer and STA449C thermal analyzer were employed to test the linear expansion and contraction coefficient，CP and DSC curve of 304 stainless steel. The result showed that the linear expansion coefficient range was 20.9700×10-6～21.5712×10-6 and the linear contraction coefficient range was 21.2528×10-6～21.9471×10-6.The linear expansion and contraction coefficient were higher than other steel grade，so the 304 stainless steel belonged to the crack sensitive steel. Because of the crystal phase transformation occurred during the 1000~1400 ℃,the curve of CP fluctuated obviously and the defects of casting blank occurred easily. Chosen 1414℃ as the liquidus temperature of 304 stainless steel based on the analysis results of DSC. The curve of DSC was unsmooth during 1450～1100℃，the crystal phase transformation occurs and thermal stability of slab was inferior.When the initial solidified shell formed in this temperature range,the thickness of the shell would be nonuniform and the surface defects occurred more easily.

Jan 1, 2015

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 G. L. Peralta

Geothermal energy is an important source of power in more than 12 countries and is a potential source in 50 countries. However, the exploration and use of geothermal resources generate residues such as scale and sludge. The scale is from the steam distribution pipes while the sludge is from cooling ponds. These solids contain significant levels of elements which are of environmental importance notably, arsenic, sulfur, copper, zinc and lead that require safe treatment and disposal. The compositions, phases, textures, morphologies and size of scale and sludge particles have been studied by laser particle size analysis, light microscopy, scanning electron microscopy, X-ray microanalysis, and X-ray diffraction. In addition, their leachability was tested with protocol leaching procedures and sequential extractions. The detailed spatial relationships and speciation of the environmentally significant constituents have received particular emphasis. The information obtained is useful in understanding how the scale and sludge are formed, their leaching behavior if disposed of in a landfill and in developing appropriate treatment strategies.

Jan 1, 1994

By H. J. Roorda

With an increasing need to obtain metals by processing complex fine intergrown ores, the use of electron-optical techniques will become more important as a tool for mineralogical studies. Electron images enable a higher spacial resolution than can be obtained by optical microscopy and thus provide a powerful and necessary aid for the examination of small grains and finely locked particles. In this paper the mineralogy of Meggen ore was investigated. Both light-optical and electron-optical techniques were used to evaluate the mill feed and products of the concentrator. Detailed examination by reflected-light microscopy to assess the comportment of galena in the complex pyritic ore was inconclusive in establishing the cause for low lead recovery of only forty percent of the ore's lead content. Electron microprobe analyses indicated that the majority of the lead lost to the tailings was accounted for by extreme fine (often smaller than one micron) and complex intergrowths of galena in pyrite. The remainder was lost as fine free galena grains.

Jan 1, 1987

By Kenneth S. Coley, Michael Pomeroy, Elaine Chen

Recent work on modeling of BOF steelmaking is reviewed, highlighting the critical aspects of each approach. It is concluded that the most successful models should be based on a deep understanding of the mechanisms and kinetics of the critical reactions. The importance of the decarburization mechanism is discussed with particular reference to its role in droplet swelling or bloating which has a profound influence on the droplet residence time in the slag. Conditions which cause bloating are discussed and the rate determining step is proposed to be primarily nucleation of CO bubbles inside the metal droplet with some influence from growth by reaction at the bubble/metal interface. The discrepancy in the super-saturation ratio required for classical nucleation is discussed and an approach using a surface tension modifying parameter is illustrated. Finally, the role of CO nucleation in controlling the driving force for dephosphorization is discussed.

Jan 1, 2014

By Maija-Leena Metsiirinta

The behaviour of copper and lead in zinc roasting has been studied in laboratory scale roasting experiments as well as in large scale trials in an industrial fluidized bed, with the background of Outokumpu Kokkola Zinc smelter. Commercial zinc concentrates with a low and high ( up to 3 wt % ) copper content and with a low and high ( up to 3.5 wt % ) lead content were oxidized to various desulphurisation degrees in the fluidized bed to establish the reaction mechanisms and the paths for copper and lead oxidation in the roasting. Influences of the agglomerate size on the roasting kinetics and micro- scale phenomena were also determined. Optical microscopy was used on the calcine and the findings are presented as numerous photographs of the polished cross sections. SEM/EDS techniques were used for analyzing chemically the phases and particle morphologies present in the samples. Computational thermodynamics was applied to the complex phase equilibria occurring during roasting in the agglomerating calcine. A complete oxidation of zinc concentrate with a high copper and lead content requires a careful control of oxygen coefficient in the roasting in order to maintain a stable operation of the fluidized bed. Oxygen coefficient thus seems to have a significant impact on the hydrodynamic stability of the fluidized bed with fine raw materials.

Jan 1, 2003