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By Desmond Cook, Cynthia P. Dogan, Dale Govier, Gary Korth, James C. Rawers

"The microstructural and mechanical properties of iron powders processed in an attrition mill are highly dependent upon the processing environment. Extended high-energy ball milling in argon resulted in nanocrystalline bcc-Fe microstructure, while processing in nitrogen or alloying with carbon resulted in both nanocrystalline bcc-Fe and bct-Fe microstructures. In this U.S. Bureau of Mines study, both X-ray diffraction and Mössbauer analysis were used to show that the infused carbon and nitrogen concentrations were predominantly on the grain boundaries. Explosive consolidation resulted in a fully dense product with microstructure similar to the microstructure of the mechanically processed powder. Hardness values of the compacts correlated highly with grain size, independent of the processing conditions.IntroductionNanocrystalline materials have been theorized and shown to have unique properties that make them interesting for material scientists and promising for material engineering applications. Several conferences have been devoted solely to the techniques of preparing nanostructured materials have been held(l,2,3.). To date, most techniques used to generate nanocrystalline materials produce only a few grams of particles(1). High-energy ball-milling, however, is an efficient and effective technique that can produce substantial quantities of nanocrystalline materials with homogenous chemical composition that cannot be produced by conventional processing techniques(3).Applications and material evaluations of nanocrystalline materials require several grams of solid samples. Because nanocrystalline microstructures' are thermodynamically unstable, producing consolidated macro structures of nanocrystalline material has proved to be very difficult(2,3). In particular, retention of the nanocrystalline microstructure during consolidation of nanocrystalline particles has proven to be a problem. In contrast to many consolidation techniques that require elevated temperatures, explosive compaction uses a shock wave for consolidation( 4,5)."

Jan 1, 1994

By L. Filip

The roast-leach-electrowinning (RLE) process for zinc was modified to treat two typical complex concentrates containing zinc, lead, copper, gold and silver. Laboratory testwork results indicated that the optimum roasting temperature ranged from 700 to 800°C, in order to produce acceptable residual sulfur levels. The calcined concentrate was subjected to a three-stage leach sequence. The resulting leach solution was purified by hematitic precipitation and directed to the recovery of copper and zinc by solvent extraction and electrolysis. Alkaline smelting and subsequent electrolytic purification recovered the lead and precious metals from the leach residue. A flowsheet was developed based on the laboratory testwork results, and demonstrated in a large-scale pilot plant. The recoveries produced during the pilot plant operation ranged from 90 to 92% for zinc and copper, 85% for lead and 90% for gold and silver, respectively.

Jan 1, 1999

By Thomas Buenger

The Hamburg smelter of Norddeutsche Affinerie AG is situated near the city of Hamburg’s downtown and is therefore particularly subjected to fulfill environmental requirements according to the German legal regulations. Thus, investments related to increasing concentrate throughput are always linked to packages to enhance the emission status of the smelter. This connection between environmental protection and productivity enhancement should be explained by the example of the Peirce-Smith converter plant of the Hamburg smelter. Such outstanding investments can be demonstrated by the transition from scrap charging via boat from the front side to a fully automatic and completely sucked scrap charging system.

Jan 1, 2009

By Toshiaki Tsuru, Takeshi Ohgai, Hisaaki Fukushima, Shigeo Kobayashi, Tetsuya Akiyama

"Electrodeposition behavior of Zn-Cr alloys from the methanol baths was investigated. In the methanol baths of low Cr3+ concentration, Cr (III) compound was incorporated in the deposits and no lusfrous Zn-Cr alloys was deposited. However, Cr was existed as metallic state in the deposits obtained from the baths of higher Cr3+ concentration. With an increase in water content in the baths, the chemical state of Cr in the deposits changed from metallic to trivalent state. Under the condition that metallic Cr can be electrodeposited, Zn deposition was significantly polarized to the potential of Cr deposition.INTRODUCTIONAn attention has been paid to Zn-Cr alloy plated steel sheet because of its excellent properties for body panels of automobile and electrical appliances [1]-[4]. This plating process can be operated using the sulfate solutions containing Cr3+ ion [1] - [6].In decorative single Cr plating, on the other hand, many attempts have been made to electroplate Cr from trivalent electrolytes, which is motived by environmental deficiencies of the presently used hexavalent process [7]. [8]. However, it has been reported that in the aqueous solutions the behavior of the electroreduction of 0 3+ is atypical due to the complicated nature of the chemistry and electrochemistry of cr3+ species [9]-[11]. Even in Zn-Cr alloy plating, it is difficult to codeposit metallic Cr with Zn in simple sulfate electrolytes [l]-[4], [12]. Therefore, it can be expected that the electrodeposition behaviors of Zn-Cr alloys as well as Cr are significantly changed when the electrodeposition is conducted in non-aqueous plating solutions.In this study, the electrodeposition of Zn-Cr alloy was conducted from methanol solutions to clarify the electroreduction mechanism of Cr3·-Cr0 in the alloy deposition process."

Jan 1, 2000

By Yuanbo Zhang, Zhixiong You, Li Qin, Guanghui Li, Tao Jiang

Low-grade manganese oxide ore is generally characterized by high iron content. In this work, sulfidation roasting of an iron-rich manganese oxide ore with elemental sulfur was characterized. The experimental results indicated that manganese dioxide can be selectively reduced over iron oxide by using elemental sulfur. The manganese phases in roasted product included low-valence manganese oxide, manganese sulfide and manganese sulfate, while those of iron mainly depended on the sulfur addition. Iron oxide would only be reduced or sulfidized at larger sulfur additions. The effect of roasting temperature and S/Mn mole ratio on the phase transformations was also investigated; extractions of Mn/Fe by sulfuric acid were evaluated. An extraction of Mn greater than 95% was obtained while that of Fe was controlled less than 10% under the optimal conditions.

Jan 1, 2016

By J. J. Kim

In a study of buildup in a green-feed reverberatory furnace, it was determined that approximately half of the crucible area has a moderate buildup of 25 in. or less, and that the area extending 45 f t from the burner end of the furnace has only a slight buildup. The false bottom, averaging 6 in. in thickness, was found to cover the entire crucible area. The stratification of Cr2O3, A12O3, and SiO2 occurs throughout the slag layer; this phenomenon is the principal reason for the formation of the false bottom in the green-feed reverberatory furnace. The false bottom is caused primarily by the settling of FeO*(A1,Cr),03 aggregates, which are derived mainly from returned converter slag. The false bottom can be transformed to a solid permanent buildup in the furnace, particularly when the matte is completely withdrawn. From the material balance of Al2O3 and Cr2O3 around the furnace, It is estimated that the average rate of aluminum chromite accumulation is approximately 0.3 ton per day or less.

Jan 1, 1976

By Patricia Negrini Siqueira

Abstract. Polymers are susceptible to changes in their chemical structures that affect their mechanical properties under weather condition. Exposure of plastics to UV radiation causes a loss in their mechanical properties and/or change in appearance, including reduced ductility, color changes, yellowing and cracking. Today, there are several additive systems (light stabilizers) developed to work according to resin, final application, type of cultivation, and other characteristics. This study evaluates the different additive systems (Hindered Amine Light Stabilizer - HALS, nano calcium carbonate - NPCC, nZnO and nTiO2), applied 0.75% (in weight) in linear low density polyethylene (LLDPE). The samples were mixed by high rotation homogenizer and extrusion. Later, the samples were molded by injection and aged in QUV-B simulating 6 months of exposure to weather. Tests of FT-IR and tensile strength comparing to the non-aged samples were carried out in order to evaluate the performance of several additive systems.

Jan 1, 2015

By Jack A. Simon

My remarks are directed at relating some of the mineralogical approaches mentioned in the preceding presentations to emerging energy issues. The assembling of this symposium on process mineralogy attests to the growing concern for energy development from the non-petroleum mineral fuels and the unconventional petroleum fuels. A report in 1979, prepared under the auspices of the National Research Council/National Academy, of Sciences, was published in two parts and dealt with "Redistribution of Accessory Elements in Mining and Mineral Processing." This report rather comprehensively considers broad aspects of minerals associated with the solid fuels considered in this symposium and focuses attention on some problems of process mineralogy relative to these fuels. Papers have dealt with coal, oil shale, tar sands, and uranium minerals. Problems associated with mining, processing, and use of these materials have significant differences, but also have some factors in common relative to the subject of this symposium.

Jan 1, 1981

By R. H. Hanewald

The INMETCO process has been modified so as to recover nickel. chromium and Iron from a wide variety of metal containing waste-streams. This now includes the recovery of metals from spent acid solutions such as chromic acid etching I1quids. nJcke1 and chromium plating solutions; stainless and superalloy pickling solutions. etc. In addition. hazardous electric furnace stainless steel and. superalloy baghouse bags can be processed so as to recover the valuable metall1cs. A detailed review of the above new recovery techniques w1ll be discussed as well as the current operating methods used at INMETCO.

Jan 1, 1992

By Alan James Parker

Chalcopyrite can be converted to pure copper by the following five steps. An exothermic sulfation roast of chalcopyrite; leaching of cupric sulfate from the calcine with dilute acid; precipitation of Chevreul's salt and or other copper sulfites with ammonium sulfite or precipitation of crude copper by autoclaving ammonium sulfite and cupric sulfate at 150°C; dissolution of Chevreul's salt, or the crude copper, as cuprous sulfate, using acidic cupric sulfate in an acetonitrile-water solution as oxidant; precipitation of pure copper by thermal disproportionation of the cuprous sulfate solution. Acetonitrile and acidic cupric sulfate solution recycle. Advantages over conventional processes include lower cost, lower energy consumption as waste heat, sulfur removal as ammonium sulfate or gypsum, rather than as sulfur dioxide and rapid throughput. The net reaction is: 2 CuFeS2 + 4H20 + 15/2 02 + 8 NH3?2Cu + 4 (NR4)2 SO4 + Fe2O3

Jan 1, 1976

By Halvor Dalaker, Alain Marc Ferber, Thor Anders Aarhaug, Pål Tetlie

Off-gas monitoring of experimental reactors give little information about intermediate reaction products and reflect chemical equilibria at reduced gas temperatures. A reactor design with optical access was designed and tested in order to be able to qualify and quantify gaseous species from their emission spectra. By use of a sequence of sapphire, UV fused silica and IR transparent sapphire and CaF2 windows and lenses optical access to a hot, maximum 1800 °C, reaction zone was gained. A cooled area behind the reaction zone was used as a background in order to avoid signal saturation from reactor walls. In addition to molecular emission spectra, atomic emission lines are used to characterize stable gas constituents and radicals. The setup has been designed for the study of methane dehydrogenation experiments in order to investigate the carbon activity of reduction of oxide with methane, but has also been used to monitor gaseous silicon suboxide.

Jan 1, 2015

By A. W. Worcester

The plant is designed to produce 60,000+ tons of refined lead per year from a nominal feed consisting of 110,000 tons of SLI and industrial batteries, and 10,000 tons of lead contained in drosses and scrap. The plant will also produce as by-products polypropylene chips and detergent grade sodium sulfate, using the Engitec Impianti CX Technology. The battery separation circuit will consist of a battery breaking hammermill and a vibrating screen with water sprays to separate the battery paste from the grid metal and other battery components. The battery components, consisting of ebonite, and separator materials, will be separated' from the grid metal and classified with the use of hydrodynamic water separators. The battery paste will be treated with sodium carbonate to produce a lead carbonate paste for smelting in a reverberatory furnace. The slag from the reverberatory furnace will be campaigned through a traditional primary blast furnace to produce hard lead. The sodium sulfate liquor from the lead carbonate filtration step will be crystallized to produce anhydrous sodium sulfate. The metallic grid metal will be treated through a small rotary smelter of the Engitec design to produce a hard antimonial lead. The plant's scheduled to be commissioned 12 months after receipt of all of the Federal and state permits. The plant will be integrated into the Buick Primary Lead Smelter, located in the center of Missouri's New Lead Belt, at Boss, Missouri. This will allow The Doe Run company to fully utilize all of its existing assets.

Jan 1, 1990

By John E. Dutrizac, Tzong T. Chen

"Laboratory experiments were undertaken to ascertain the behaviour of various ""impurity"" species during the precipitation of hematite directly from ferric sulphate solutions at 225°C and in the presence of 40 or 50 g/L of hematite seed. Copper, nickel and zinc are not significantly incorporated in hematite precipitates. Although the nickel contents increase to 0.22% as the Ni concentration increases to 60 g/L, the solid solution Ni contents are low relative to the bulk Ni contents. Thus, part of the Ni may be present as tiny particles of poorly soluble NiS04.H20. Increasing germanium concentrations to 2,000 mg/L result in products containing up to 0.59% Ge. The Ge occurs either in solid solution in the hematite or is adsorbed on the nanometer-size hematite crystallites. Increasing As(V) concentrations to 10 g/L increase the AsO4 contents of the products up to 16%. However, the products consist of hematite together with As04-containing Fe(SO4)(OH) and an unknown Fe-AsO4 species. All the hematite products contain - 1% SO4 which appears to be adsorbed on the nanometer-size hematite crystallites.IntroductionDissolved iron is a common impurity in most hydrometallurgical processing circuits and, generally, the iron must be eliminated prior to the subsequent recovery of the sought after metals. Simple neutralization of iron-rich solutions yields slurries which are difficult to thicken and filter. To address these concerns, the jarosite, goethite and hematite processes have been developed, and these technologies are able to reject the dissolved iron in a readily filterable form [1]. Despite its higher cost, the hematite process offers several potential advantages. Because hematite is an iron-rich, high-density compound, its formation would reduce the mass of residue and the size of a residue storage pond. Hematite is the thermodynamically stable form of iron under ambient conditions, and this stability would facilitate the impoundment of hematite precipitates. Furthermore, hematite has some market potential for cement manufacture and even for iron making [2]. In all the commercial hematite processes, the dissolved ferric ions are first reduced to the ferrous state. Subsequently, the pH of the solution is adjusted and the solution is then oxidized. The ferric ions gradually generated during solution oxidation hydrolyze and precipitate mostly as hematite, although commercial hematite products also contain trace or minor amounts of jarosite-type compounds. However, there are potential advantages in precipitating hematite directly from ferric ion solutions, as the reduction and subsequent oxidation of the iron are not required. Although the precipitation of hematite directly from relatively concentrated ferric sulphate solutions (up to 0.5 M Fe(SO4)is) was recently demonstrated [3], the behaviour of impurity species during hematite precipitation is largely unknown. To address this issue, systematic laboratory experiments were undertaken to ascertain the behaviour of a number of ""impurity"" species during the precipitation of hematite directly from ferric sulphate solutions at 225°C, and the results are presented in this paper."

Jan 1, 2012

By Renato G. Bautista

"The chemistry of the separation of metals from each other and from the other undesirable components involve multiple simultaneous chemical reactions. In the case of leaching, the heterogeneous chemical reactions between the solid and the liquid phase may be limited to a few reactions. In the homogeneous liquid phase, the number of simultaneous chemical reactions could be double or triple that of the number of heterogeneous reactions. The rate of dissolution becomes very dependent on the changing concentrations of the significant chemical species taking part in the multiple reactions in both the heterogenous and homogeneous phase. The rate expression developed for the process must take into account the mechanism of chemical reactions in order to best represent the actual process. This paper also examine the role of mass transfer with chemical reaction in the develpoment of the rate equations for dissolution, liquid-liquid extraction, membrane separation, precipitation, and electrodeposition.IntroductionThe understanding and the elucidation of the mechanism of the rate phenomena for a specific chemical reaction system is of prime importance in the development of a successful chemical process. The development of successful emerging technologies for metals separation will depend on the accurate interpretation of the intrinsic chemical reaction kinetics and the rate of mass transfer of the desired metal species during its separation from the undesirable chemical species. This is the case whether the process application is for separation, concentration, and /or purification.The chemical processes that will be examined in this presentation will include leaching, solvent extraction, membrane separation, precipitation, and electrodeposition."

Jan 1, 1996

By Sarah Beutner Mavrogenes

The mineralogy of three slags from a domestic secondary copper refinery were studied by applied mineralogical techniques to determine the: 1) phases present, 2) phase chemistry, 3) phase abundance, 4) associations, 5) crystalline habit, 6) grain size, 7)microtextures, and 8) causes for certain metallurgical problems, such as metal losses to the slags. The slags were produced by skimming the bath prior to melt-down to allow heat from the flame to reach the bath. The first slag is highly viscous and all three slags contain a large amount of copper. The "first slag", which is skimmed prior to treatment of the bath with fluxes, contains metallic copper, cuprite, delafossite, magnetite, Mg-hercynite, common spinel-chromite solid solution, picrochromite-chromite solid solution, common spinel-picrochromite solid soiution, gahnite, cassiterite, silica-rich glass, and corundum. Its abundant solid refractory phases make the slag difficult to skim. The "soda-rich slag", skimmed after the treatment of the bath with sodium carbonate flux, contains cuprite, delafossite, magnetite, cassiterite, Na-Al-silicate, and Na-Al-Ca-silicate. It contains less metallic copper than the first slag and lacks the refractory minerals. The "phosphorus-rich slag", skimmed after treatment of the bath with a copper phosphide flUX, contains metallic copper, cuprite, delafossite, berlinite, cassiterite, silica, apatite, Cu-Fe-rich apatite, copper phosphate, Cu-Fe-phosphate, and a Pb-phosphate. In contrast to the above three copper-rich slags, recent charges have produced a silver-copper-rich slag. The "silver-rich slag", skimmed after the treatment of the bath with a copper phosphor ide-borax flux, contains, cassiterite, delafossite, cuprite, a Na-Al-silicate, magnetite, metallic copper, MgO, common spinel-chromite solid solution, and wollastonite. Silver ranging from 0.05 to 2.02% was found by atomic absorption and inductively coupled plasma spectrometry analyses in the metallic copper phase.

Jan 1, 1989

By Khoo Khyou Pin, Yoshiyuki Funaki, Hirotsugu Takeuchi, Ryoichi Urao, Naotatsu Asahi

"Steel is used to be ion carburized with mixing gas of methane and hydrogen. In carburizing, carbon in the methane decomposes and deposits on the steel by plasma, so methane gas flow may influence on ion carburizing of the steel. An apparatus in which works can transfer preheating, ion-carburizing and diffusion treating zones continuously was made for effective carburizing of steel. The gases were flown into above three zones with three different gas inlets. The hardness and microstructure of the works were investigated after ion carburizing and quenching. The steel is carburized deeper near the carburizing gas flow nozzle of the inlet than far from the nozzle. Hard surface layer fom1ed by quenching of ion-carburized steel.IntroductionGas carburizing is used for a surface hardening treatment which decreases fatigue and wear of the industrial parts used in automobile, machines etc. Ion and vacuum carburizing have been developed recently and applied to some industrial parts of restrictive purposes. The ion carburizing treatment which uses hollow cathode discharge (HCD ion-carburizing) is superior in energy saving, resource saving, environmental cleanness to the other carburizing treatment. Specially, carburizing energy can be saved in HCD ion-carburizing, because highly heated zone can be restricted in the range between work and subsidiary cathode where hollow cathode discharge arises, and the work is carburized in shorter tin1e in HCD ion carburizing method than other carburizing methods. Three treatments of preheating, carburizing methods and carbon potential controlling by hollow cathode discharge tried to be carried out in one continuous transferring series to carburize works more effectively, so the HCD ion-carburizing apparatus with continuous transferring system was made and gears of works were HCD ion-carburized in continuous transferring. The works were rotated themselves to get homogeneous carburizing by continuous transferring in glow of hollow cathode discharge."

Jan 1, 2000

By Zhang Chuanfu, Li Shixiong

"In the electrolysis electrodeposition or electroplating of aqueous solution of copper, lead, zinc, nickel, manganese etc, with the increase in cathodic over potential the reducing rate of metal and the cathodic current efficiency increases and the deposit becomes more compact and smooth. According to this principle, a method and equipment of the auto-control of electrolyte quality is invented. The industrial application shows that this method turns the experienced operation into auto-control. The quality and quantity of metal is improved greatly and the consumption of electric energy is reduced.In the electrolysis, electrodeposition or electroplating of aqueous solution of copper, lead, zinc, nickel, manganese etc, usually organic additives are added according to the state of cathodic deposit according to experience. This traditional and experienced operation, often lead to that the quality of additive is not optimum which affects the quality and quantity of metal and increases the consumption of electric energy. To counter the controlling problem of the quantity of additive, the authors have invented a corresponding equipment of the auto-control of electrolyte quality [1], it has found application in industrial practice."

Jan 1, 2000

By Dajian Wang

To obtain the thermodynamic properties of a multicomponent liquid alloy system over the whole range of concentration at an arbitrary temperature, the free volume cell theory has been applied to derive the formula of activity coefficients of liquid solutions based on the infinitely dilute solutions at some temperature. The linear logarithmic relationship between activity coefficients of binary dilute solutions and reciprocal of absolute temperature have been verified, and are in good agreement with the experimental values from the literature. The Monte-Carlo algorithm was used to calculate the nonlinear end value equations of binary systems, then the free volume parameters obtained were correlated with the activity coefficients of liquid binary, ternary, and quaternary systems at an arbitrary temperature. Three dimensional a-X-T diagrams of some binary systems representing the temperature and concentration dependence of activities were plotted. The calculated results regarding non-ferrous alloy systems have been statistically examined with the experimental values from the literature. Hence, this simple approach could be useful for analyzing thermodynamic properties of liquid alloy systems.

Jan 1, 2000

By J. S. Becker

Technology developed and first implemented in the United Kingdom enables very low grade aluminum scraps containing oils, organics, plastics and ferrous metals to be directly charged, without pretreatment, into a unique melting furnace. The system has been in full scale production for over three years. The oxy-fuel-based furnace design incorporates internal afterburning in the furnace's hot zone, producing excellent thermal efficiency and very low emissions. The furnace is inherently low in NOx. This paper will provide both theoretical background and extensive operating results for this new melting concept. Applications describing both purpose built new furnaces and retrofits of existing reverberatory furnaces will be presented. Extensive operating emissions data will be presented.

Jan 1, 1996

By Chao Li, Hongxu Li, Yang. Xie, Meng Wang, Xiangxin Hao

"With the development and utilization of resources of gold, high quality gold mine resources gradually exhausted, and refractory gold ore has become the main raw material for gold smelting, while the smelting pollutants impacting on the ecological environment is growing, in recent years there have appeared several methods of green extraction of gold such as bio-oxidation. In this paper, the life cycle assessment models about three different gold extraction technologies have been put forward. Material consumption, energy consumption and emissions during each gold production process are analyzed by using GaBi 6 software, and the environmental impact of each process is also evaluated by means of CML2001 methodology. Calculation and analysis results show that the energy consumption and material consumption are the main factors causing the environmental load; and the environmental impacts of the production process mainly attribute to the category of greenhouse effect, resources consumption and environmental acidification. Based on the evaluation, some optimization tips are proposed.IntroductionOver the past decades, as the industry policy environment continues to improve as well as gold exploration and mining smelting capacity continues increasing, gold production shows a prospecting tendency. With the wide use of gold, the demand for gold is growing, while easy smelting gold mine resources become exhausted and refractory gold ore has become the main raw material for gold smelting. In addition, pollutants impact on the ecological environment is also growing year after year.LCA (Life Cycle Assessment) makes evaluation of product “from cradle to grave” as its whole process, up to finding the sources of environmental impacts and solutions, to comprehensively account the use of resources and lower emissions. In the industrial field, life cycle can compare different technologies from different aspects of resource use, energy consumption and environmental emissions [1]. In recent years, using LCA to evaluate metallurgical industry process also has more development. The paper mainly uses LCA and scenario analysis for the gold metallurgical process by GaBi 6, to investigate the environmental impact of three different technologies of gold extraction metallurgical process. The established three evaluation models include the hydrometallurgical, pyro-metallurgical processes and bio-oxidation pretreatment methods respectively. Several environmental indexes would be selected to evaluate the environmental impact in order to find which process has smallest environmental load and some suggestion of reasonable way gold resource utilization."

Jan 1, 2014