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By Aichun Dou

Au-Sb alloy sample in which the total amount of Cu and Ni is below 25% (wt. %). In practice, Cu and Ni were difficult to be dissolved in sulphuric acid solution by oxidative leaching under the atmospheric pressure conditions, because of the lower concentration of Cu and Ni in the sample. In this paper, pressure oxidation leaching in sulphuric acid system (POLS) followed by hydrochloric acid leaching (HAL) was employed to remove impurities in the Au-Sb alloy. The effects of variables in POLS on leaching ratios of different metals were investigated in detail. Under the optimal conditions: the concentration of H2SO4 is 1.5 mol/L, liquid-solid ratio is 7:1, the amount of oxidizer is 1.2 times of the theoretical amount, leaching time is 4h and leaching temperature is 427K, the leaching ratios of copper and nickel reached up to 99%, antimony, lead and silver were not dissolved in dilute sulphuric acid solution. The residue from POLS was then treated with hydrochloric acid solution in fixed conditions, the leaching ratio of antimony reached over 92%, the grade of gold in the ultima residue was enriched up to 66%.

Jan 1, 2016

By Duclerc Fernandes Parra, Washington Luiz Oliani, Christiano Gianesi Bastos Andrade, Ademar Benevolo Lugão, Danilo Marin Fermino, Francisco R. Valenzuela Diaz

This work concerns the study of the effect of discarded bond paper on the mechanical behavior of polypropylene/organophilic clay nanocomposites. A brown polycationic bentonite from the state of Paraíba, Brazil, was treated with sodium carbonate to transform it into a bentonite that swells in water and then treated with hexadecyltrimethylammonium ammonium chloride to transform it into a bentonite that swells in organic liquids. Polypropylene with 3 % polypropylene graft compatibilizer (PP-g-AM) was mixed with 1 % and 2 % by weight of discarded bond paper and with 1% and 2% by weight of organophilic clay using a twin-screw extruder. The specimens were prepared by the injection process. The clay as received and after organophilization was characterized by XRD, SEM, and capacity of swelling in water and in organic solvents. The nanocomposite specimens were characterized by XRD and thermal analysis. The mechanical behavior of the injected specimens was evaluated by strength, flexural and impact tests. The nanocomposites showed improved mechanical properties compared with the polymer without filler.

Jan 1, 2015

By T. Wang, R. G. Reddy

"The corrosion of stainless steel SS316L in a low melting point novel LiNO3-NaNO3-KNO3- NaNO2 eutectic molten salt mixture was investigated at 695K. After long-term isothermal dipping corrosion experiments, the SS316L samples were analyzed using scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS) to determine the topography and corrosion products. Dense and protective lithium iron oxide scale formed on the surface and prevented the SS316L sample from further severe corrosion. Therefore, SS316L is considered to be suitable construction material for solar thermal energy storage materials containers.IntroductionMolten salt mixtures have been considered as potential candidates for thermal energy storage and heat transfer media in solar energy applications. To apply the molten salt in the energy transfer process, the standard pipes made of stainless steel must be utilized to carry the molten salt mixtures in parabolic trough system of solar power production. The pipes encounter continuous flow of hot and cold molten salt every day. Thus corrosion of stainless steel in molten salt mixtures becomes extremely essential for the long-term utilization of the thermal energy storage media. The corrosion of passivity materials inside high temperature molten salt systems have been studied which gives fundamental understanding of basic mechanism about the corrosion process [1-8].The corrosion behavior of Fe-Ni-Cr alloys in an equi-molar LiNO3–NaNO3–KNO3 mixture was studied [9]. According to the XRD analyses, the major phases in the oxide scales were identified as LiFeO2, Fe3O4 and Cr2O3. A HITEC® salt mixture (NaNO3–NaNO2–KNO3) was also tested as a corrosion medium for stainless steel [10] and the corrosion rate was found to be affected by the protective oxide layer. In most cases, the alloys having more than 10wt% chromium show high resistance to corrosion in molten salts."

Jan 1, 2014

By Gennady I. Gulyayev

A mathematical model of plastic deformation occurring in cold plug drawing of mother tubes with initial cross-sectional wall thickness variations (CSWTV) has been developed. The main provision of the model is that eccentricity em is of such value that projection of all forces acting upon the plug in the deformation zone along the axis perpendicular to the drawing axis equals to zero. Calculations have proven that with other conditions being equal increase in the die cone angle and the deformation cycle number reduces CSWTV. Theoretical findings were confirmed by practical results. Keywords: cold, drawing, plug, die cone, plastic deformation.

Jan 1, 2003

By Shengli Wu, Laixin Wang, Minyin Kou, Xinliang Liu, Weidong Zhuang, Yujue Wang

COREX process has obvious advantages in environment protection but still has some disadvantages, for example, it has a higher sulfur content of hot metal than blast furnace. In this paper, the thermodynamics and dynamics of desulfurization have been investigated to obtain the main operation parameters related to the mass fraction of sulfur in the hot metal. In addition, statistical analyses have been carried out to study the relationship between operating parameters and sulfur content of COREX hot metal based on actual plant data. It has been found that the mass fraction of sulfur in hot metal is significantly influenced by the C content in hot metal, MgO/Al2O3 in slag, the concentration of MgO in slag, the temperature of hot metal and binary basicity (R2).A linear model has been developed and subsequently used for reducing the mass fraction of sulfur in hot metal, improve the quality of hot metal and contribute to low carbon ironmaking.

Jan 1, 2016

By Paul S. Korinko, Simona E. Hunyadi Murph

To address a radiological contamination event, a materials and process project was initiated. During the course of this project, processes and materials were developed that successfully captured zinc vapors physically and chemically, respectively. However, the physical traps were placed in an undesirable area and it was determined that the chemically captured zinc reactions was reversible. Consequently, advanced nanomaterials are being developed to capture zinc vapors. The current state of the art of the science and engineering of these materials and their efficacy for zinc capture and retention is discussed in this paper.

Jan 1, 2015

By T. T. Chen

Hydrometallurgical products are difficult to characterize because of their fine grain sizes, heterogeneity, often amorphous structures and water soluble or hydrated constituents. Such products are advantageously studied using complementary mineralogical techniques including >50, ore microscopy, SEM-EDX, electron microprobe analysis, selective leaching and wet chemical analysis to determine the phases and their morphologies, to identify specific element carriers, and to elucidate the chemical reactions occurring during the metallurgical process. Sample preparation is an important consideration for these materials. For extremely fine-grained particles, or soft and brittle products such as elemental sulphur, the study of loose powder mounts provides information not available from the examination of polished sections. To demonstrate the application of the various mineralogical techniques, commercial zinc roaster calcines and leach residues, copper refinery anodes and anode slimes, and laboratory bornite leach residues were examined in detail. The various sample preparation and mineralogical methods are presented, and the use of these complementary and practical mineralogical techniques to improve the understanding of a particular hydrometallurgical system is discussed.

Jan 1, 1989

By J. Grogan

Leaching of galvanized steel coatings allows the steel substrate to be used as a zinc-free scrap source to steel and iron furnaces. In this study the behaviors of sulfuric acid leaching solutions are investigated. The ranked significance of the variables are shown to be acid concentration > temperature > zinc concentration. Examination of the leaching mechanism finds the rate-limiting step to be the cathodic hydrogen reduction reaction. This rate is not only influenced by acid concentration, but also by the hydrogen reduction exchange current density. Dezincing leaching rates are improved by taking advantage of the higher exchange current density of the iron substrate versus the zinc coating. This is accomplished in practice by increasing the exposed interfacial zinc:iron surface area through shredding. Also, a leach control mechanism is proposed through online monitoring of the zinc-iron couple mixed potential.

By Charles L. Richman

The effect of the addition of Silver Sulfide on the rate of Chalcopyrite (CP) of Sulfuric acid (H2SD4 leaching is discussed, Although Ag2S in an expensive addition, a theoretical explanation of it's use will aid in the development of a economic substitution. We have used cyclic voltammography to show the presence reaction species at different potentials. Cyclic Voltammography maps the surface reaction current peaks on CP, to regions on the CP Phorbaix diagram. AC Electro-lmpedance spectroscopy (EIS) models the surface impedance properties, which control the rate of electron and ion transfer, and the surface kinetic reactions, with and with out light. EIS and other measurements show that AgCuS u Photo-reactive material- The EIS results are compared with the SEM and EDXA results to show the presence of diffusion pores, and diffusion controlled reactions during CP leaching without the addition of silver sulfate. We hypothesize that AgCuS is an ionic conductor like Ag2S. EIS shows an imposed negative leaching rate greatly. Our theory shows how the formation of Silver Copper (1) sulfide layer at open circuit potential gives an effect similar to negative potential, that is enhanced with illumination. We verify that AgCuAS is an N-type semiconductor that forms a diode type junction with the electrolyte with the Mott-Schoottly relation.

Jan 1, 2001

By Stephanie Trant

Montana Tech has been engaged in fundamental research on the processing of critical materials for more than a decade. Efforts include examining novel reagents for the flotation of Rare Earth Minerals (REMs). For this paper, research results on a collector, salicyl hydroxamic acid (SHA), are presented. Various REMs were examined and include the rare earth oxides (REOs), carbonates (RECs), and phosphates (REPs) of a suite of Rare Earth Elements (REEs). Differences are attributed to solution and surface chemistry, coordination number, and ionic diameter. SHA adsorption follows an ion-exchange process that leads to chemisorbed and surface-precipitated states, depending mostly on pH. Many effects are directly attributed to lanthanide contraction. Results should also be applicable to other REM/collector systems and further suggest that REM flotation should consider dual collectors.

By Takeo Fujino, Nobuaki Sato, Junichi Hasegawa, Masato Nakazawa, Kohta Yamada

"Tantalum oxide thin films were deposited on quartz substrates by laser ablation of Ta2O5 target using Nd:YAG pulse laser. Deposition-was observed when a laser light energy higher than 200 mJ and its repetition rate higher than 3 Hz. A thin film of 0.1 µm thickness was obtained by the ablation using a laser light of 300 mJ and 6 Hz for 2 sec. The thickness of the film increased with increasing energy, repetition rate and irradiation time of laser. By the SEM observation, it was found that many island-like particles were deposited on quartz substrate forming a thin film. The obtained thin film, which was identified as ? Ta-O by X-ray diffraction, was oxidized to Ta2O5 by the heat treatment in air at I273 K for 3 h.IntroductionTransition metal oxides have a potential to show special characteristics in electrical, magnetic and/or optical properties. When such compounds are fabricated in the form of thin film, the special properties would be improved or new characters would appear in comparison with bulk materials. Tantalum penta-oxide is widely used as a capacitor since Ta2O5 shows high dielectric constants up to high temperatures. The tantalum solid capacitor has been fabricated by the electrical oxidation of sintered Ta metal cylinder followed by MnO2 film coating. However, further improvements, reduction and layered structure formation, are required for compacting the devices. The layered structure of thin films would be applicable for the above requirements. The formation ofTa2O5 film by low pressure CVD1), photo CVD2) and magnetron sputtering3l were reported. The laser ablation -method is one of the most convenient techniques for the deposition of thin films from their compounds, such as oxides. Formation of Ta2O5 film by pulse laser deposition (PLD) method using ArF excimer4), Nd:YAG (533nm)5) and TEA CO2 6 lasers was reported. In these PLD studies, ablation was carried out in relatively high oxygen pressures resulting in formation of Ta2O 5 film. In this paper, the deposition of tantalum oxide thin film by the laser ablation of Ta2O 5 using Nd:YAG pulse laser was examined at a viliety oxygen pressures ranging from 10-8 to 10 Torr. The morphology of the films was also investigated in relation with substrate temperature and oxygen pressure."

Jan 1, 2000

By R. Nilsson

In the present work, an assessment of the sulphide capacities of a number of binary and ternary slag systems have been carried out in the light of a sulphide capacity model. The model is based on the expression: {CS- exp (-A G °/R T) ? ao2 / fs2-} where AGO is the standard Gibbs energy change for the above reaction, ao2 is the activity of oxygen ions and f, is the activity coefficient of the sulphide ion in the slag. In the present model, the ratio (ao2/fs2) is optimized for the experimental data available in literature. The systems assessed are the binaries MnO-SiO2, CaO-SiO2, Al2O3-CaO, as well as the ternaries CaO-Al2O3-SiO2 and CaO-MnO-SiO2. In the case of all these systems, the experimental data available in literature were complemented by measurements carried out at the Division of Theoretical Metallurgy. The sulphide capacities of some FeO- containing binary, ternary and quaternary slags are also examined. The potentiality of the model to estimate the sulphide capacities of complex slag systems from binary and ternary data is demonstrated.

Jan 1, 1996

By S. Mondon

Hibi Smelter which is a Copper Smelter lining a blast furnace, produces 2,700 metric tons of anode copper per month. Generally, in a copper refinery, arsenic and antimony are considerably troublesome impurities. With regard to the elimination of antimony, Hibi Smelter has two handicaps described as follows. (1) Smelting under the slightly oxidizing atmosphere in the blast furnace. (2) Recycling the converter slag to the blast furnace after cooling. Therefore antimony and arsenic, mainly antimony, elimination tests, in which the alkaline flux was injected through the two tuyeres in the blowing stage, were carried out in the rotary anode furnace. Antimony and arsenic were respectively removed more than 90 96 from the molten copper, and their high eliminations are discussed by application of the transitory and permanent reaction model with the flux injection, which was presented by T. Lehner.

Jan 1, 1983

By Husamuddin Ahmadzai

A survey of regulations and state of the art control technologies is presented relating to the smelting of primary aluminium, copper and recycling of residues. Some costs associated with the alternatives and trends for the coming decade in this. sector are identified.

Jan 1, 1992

By Minjun Tang, Jianfeng Zhou, Linjiang Qing, Yufeng Guo, Tao Jiang

"For the comprehensive recovery ofV, Ti, Fe in vanadium-titanium magnetite in the process of pre-reduction-electric furnace smelting, it is expected that vanadium oxide is reduced into molten iron and titanium oxide is available in the slag. Thus the effect of slag basicity, the content of MgO, MnO and CaF 2 of slag content on the separation of slag and molten iron and the comprehensive recovery of V, Ti, Fe were investigated. The results show that increasing slag basicity, MgO, MnO and CaF2 are all beneficial to the separation of slag and molten iron. Higher slag basicity and the addition of CaF2 strengthen the reduction of vanadium oxide, and inhibite the reduction of titanium oxide, which are in favour of the recovery ofV and Ti. However, the addition ofMgO, MnO was not efficient for the comprehensive recovery ofV, Ti, Fe. For the vanadium-titanium magnetite of Panxi in China, the recovery of Fe was over 98%, the recovery ofV in molten iron was over 85% and the Ti02 content in slag was about 43% under the optimal conditions of slag phase type.IntroductionIt is well known that there are abundant vanadium-titanium magnetite resources which are located in Panzhihua of Sichuan Province[!]. At present the vananium-titanium magnetite concentrates are smelted in the blast furnace, which just make use of iron and vanadium, but lots of titanium is discarded in the slag. At the same time, the process has a large number of disadvantages, such as low recovery of vanadium, long route, pollutions, large investment and expenditure of energy[2-3]. In recent years, in order to efficiently utilize the vanadium-titanium magnetite concentrates, several new non-blast furnace processes have been proposed, such as pre-reduction-electric furnace, pre-reduction-grinding separation and so on[4]. Especially pre-reduction-electric furnace is operating well in South Africa and New Zealand,However,Du to the high slag basicity of the slag, the grade ofTi02 of slag is Corresponding author:Minjun Tang.E-mail:450435123@qq.com. Tel:13627429224."

Jan 1, 2013

By J. E. Clemson

The Black Pine sediment-hosted, disseminated gold deposit is located in Cassia County, Idaho. Gold mineralization occurs in flat-lying zones 50 to 100 feet thick. Total geological ore reserves are 5.6 million tons grading 0.049 oz/t. Ore types include: non-carbonaceous, oxidized ore; carbonaceous, sulfide ore; and carbonaceous, partly oxidized ore. In the oxidized ores, native gold grains commonly occur in porous hematite pseudomorphs that have replaced disseminated framboidal and euhedral pyrite, and this gold should be readily leached by cyanide solutions. Approximately 4 % of the native gold observed in the oxidized ores is locked within gangue and may be refractory to cyanide solutions. Native gold has not been observed in the unoxidized samples, all of which are characterized by primary sulfides. It is suspected that the bulk of the gold mineralization in the sulfide ore occurs as submicroscopic particles within pyrite and will be refractory to cyanidation. It is believed that much or all of the gold observed in the oxidized samples was originally in pyrite but was released and re-precipitated during oxidation. The degree of oxidation of the pyrite and the presence/absence of preg-robbing carbonaceous material is used as a guide in delimiting zones of mineralization amenable to heap leaching.

Jan 1, 1988

By John L. Watson

The dewatering of steel industry waste sludges prior to discard or recycling often presents significant problems due to the fineness of the sludge particles, which may blind the filter medium and/or produce a cake with limited porosity, Several steel plant wastes, such as sludges from BOF and EAF gas cleaning operations exhibit not only a very fine particle size, but also some degree of magnetic character, A novel process has been developed to utilize the magnetic character of such sludges to enhance dewatering through a multi-force operation involving magnetic, chemical and vacuum forces, The process consists essentially of undertaking vacuum filtration of a flocculated sludge in a magnetic field, This is achieved by installing a permanent magnetic in a fixed position on the axis of a vacuum drum filter, thus effecting filtration of magnetic and non- magnetic particles, bound together in flocs, in a magnetic field, Previous tests using a modified laboratory vacuum drum filter treating artificial (magnetite) and industry waste (BF sludge) feeds have demonstrated that filtration capacity may be enhanced significantly with increases of up to 3000/0, An explanation of the mechanisms associated with the enhanced filtration was not obvious, and this research was undertaken to permit the cake formation in the magnetic field to be monitored to provide an insight into the manner in which particles agglomerate to form the cake. These tests revealed that the magnetic field caused magnetic particles to be aligned perpendicular to the filter surface and to form channels through which filtrate could freely pass thus increasing capacity, The effects of various magnetic fields and field strengths on the filtration process were also investigated. A simple computer model was constructed to demonstrate the proposed theory of multi-force dewatering, The model output graphically illustrated the suggested mechanism and confirmed the enhanced capacity of the novel dewatering process,

Jan 1, 1996

By Broggi Andrea

Condensates produced by SiO(g) and CO(g) have a crucial importance in silicon production. Condensation will follow the reactions 3 SiOðgÞ+COðgÞ→ 2 SiO2 + SiC and 2 SiO ðgÞ→Si+SiO2. Solid compounds generated during silicon production contain Si, SiO2 and SiC in different microstructures and amounts. In industrial systems, condensates limit the SiO(g) escape to the off-gas system. On the other hand, they can block the gas flowing from the high temperature zone, hence the necessity of studying an optimized condensation process. This review discusses SiO(g) condensation and its interaction with CO(g). The report gives an overview of the condensates found both at laboratory and at industrial scale. The two main compounds are the Si–SiO2 and the SiOx–SiC mixtures. The hypothesis on the mechanism of formation of SiC–SiOx condensates is presented through a wide selection of performed works. The advantages and disadvantages of the former experimental procedures are discussed.

By Jose Bengoa

Low metal prices and environmental restrictions are always a challenge for copper smelters operation and its productivity. Thus, in order to reduce production costs and control gas emissions, improvements of the Teniente Converter (CT) operation were made at 110 Smelter Plant of Southern Peru Copper Co., 110, Peru, and the main objective was to increase its capacity for smelting copper concentrates without affecting normal operation. The present work corresponds to a recent study conducted during the normal industrial operation of the Teniente Converter in this plant and, it shows the effect of increasing air oxygen enrichment from 28 to 34% on its productivity. The results show an increasing of concentrate smelting rate from 800 to 1370 tpd and hence a notorious improving in copper production, and practically no effect on the refractory consumption. The increment of the concentrate throughput, increases also the SO2 concentration and the sulfuric acid production, showing the effort done by this operation in order to accomplish the environmental Peruvian regulation.

Jan 1, 2003

By José Brant, Douglas Torres, Rogério Navarro, Rodrigo Souza, Eduardo Brocchi

The steelmaking process requires the input of ferro-alloys to implement the adjustment of some elements composition in the final product. In the particular case of stainless steel production, the high carbon FeCr alloy stands out as one important precursor. However in the production of this material a certain quantity of fine powder with remarkable chromium and carbon content is also generated, which, in turn, could be processed through alkaline roasting in order to selectively recovery this element in a subsequent aqueous route. In the present work, this process is investigated, using excess of NaOH as oxidizing agent, and H2O2 for precipitating chromium as Cr(OH)3, which is next calcinated to Cr2O3. According to the results, the global achieved recovery has shown to be around 98%, suggesting that the proposed route can be seen as a potential process for chromium oxide production from the mentioned fine powder.

Jan 1, 2015