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By Jilai Xue, Jun Zhu, Liang Liu

"Separation removal of fluorite and calcite from scheelite is a difficult technical operation in current industrial practice with a heating process causing large energy consumption and high production costs. In this work, the floatation separation at room temperature were carried out using two types of skarn scheelite ores. The results showed that CaO and Na203 are better than NaOH as a regulator in pH value. In the rough floatation and first cleaning floatation, CaO (500g/t), Na203 (3000g/t) were used as a pH regulator, waterglass (4000g/t) was as a gangue depressant, oleic acid or sodium oleate were used as a collector. The degree of the obtained W03 concentrate was more than 65% (commercial product).IntroductionThe mainly gangue in scheelite are quartz, calcite, barite and some rare metal ores. There are three main types of scheelite for floatation: scheelite--quartz (silicate minerals) type, scheelite-calcite/ fluorite type, scheelite--calcite/fluorite/barite type. Generally speaking, scheelite--quartz type is separated easily, and others are difficult, on the contrary. The last two kinds of scheelite are always called scheelite--calcite/fluorite (barite) type, because there are similar floatation ability and floatation process between them. Scheelite, calcite and fluorite have same cation - Ca2+, it makes them have close floatation property [1]. Separation removal of fluorite and calcite from scheelite is a difficult technical operation in current industrial practice.The traditional separation method is a heating floatation process (Petrov's process) [2]. It can deal with many kinds of scheelite, and can be obtained stable quality ofW03 concentrate. On the other hand Petrov's process causes large energy consumption, high production costs and bad operational environments. Since 1980s, scheelite ambient temperature floatation has become the mainstream of study [3]. Nowadays more and more studies on scheelite floatation focus on complex reagent system [4, 5], rigid operating rules and at the same time development new regulator [1, 5]. Some research show there are new regulators can concentrate scheelite efficiently, but it may cause high costs, potential pollution and difficulty to spread. Oleic acid and sodium oleate used as collector have high adsorption capacity to scheelite, but same to calcite and fluorite[6]. So, it would not get ideal effect for separation of scheelite. In this work, the floatation separation at room temperature were carried out using two kinds of skarn scheelite ores. Calcium oxide and sodium carbonate was used as a pH value regulator, waterglass was used as a depressant and Oleic acid/sodium oleate was used as a collector. The result of experiment showed that the degree of the obtained W03 concentrate was more than 65% by one time ambient temperature roughing floatation, several times ambient temperature cleaning process."

Jan 1, 2014

By T. Asahina, M. Nakamura, M. Mabuchi, I. Shigematsu, M. Nakanishi, G. Yamauchi

"Commercial stainless steels (SUS304L and SUS430) were subjected to equal channel angular extrusion (ECAE) at room temperature to a total strain of 2.3 to 9.2. For each type of stainless steel, it was shown that the sample processed by ECAE showed higher room temperature strength than the as-quenched sample. This is probably due to the heavily worked structure. On the other hand, both strength and elongation of the ECAE processed SUS430 were increased by annealing at 773K. It is likely that higher strength is attributed to both the heavily worked structure and fine substructures. It is also likely that higher elongation is attributed to the fine substructures. It is concluded that ECAE is available for improving the room temperature strength of commercial stainless steels.INTRODUCTIONEqual channel angular extrusion ( ECAE ) is a technique that provides the repetitive deformation and allows to high intensity of deformation. With this procedure, a sample is pressed through a channel that has an equal cross section but bent at an angle of ?> [1-2]. Shear strain is introduced when a sample passes through the bending point of the channel. Repetitive processing is feasible because the cross-sectional dimension of a sample has no change during processing. To date, many reports have described that ECAE is available for the fabrication of fine-grained materials [3-14]. On the other hand, an ECAE processed sample can achieve high intensity of deformation through repetitive deformation. According to the equation given by Segal [ 2 ], a strain of about 1 is introduced in each pass through die if the angle ? is 90 deg.It is well known that high tensile strength can be achieved in metallic materials through work hardening [15]. It is also known that metallic materials with fine grain size show high strength [16]. Hence, it is expected that ECAE is available for strengthening method in metallic materials. In the present paper, we will report the mechanical properties of stainless steels processed by ECAE. As samples, SUS304L austenite stainless steel and SUS430 ferritic stainless steel were chosen. Each alloy has a single-phase structure (fee or bee) and shows no phase transformation, so that transformation strengthening cannot be applied. Hence, a heavy cold work such as ECAE may be effective for strengthening of this stainless steel. Annealing was conducted for the ECAE processed SUS430 to vary its microstructure. Then, the effect of annealing on the strength of the ECAE processed SUS430 was also investigated."

Jan 1, 2000

By Liangying Wen, Feng Xia, Chenguang Bai

"The situation of the Ti-V-Magnetite samples reduced with microwave has been investigated in laboratory. Firstly, the paper focuses on the heating behaviors of vanadium-titanium magnetite and characteristics of carbothermic reduction of V-Ti-magnetite in the microwave field. The effect of concentrate's size, quality on heating behaviors and reduction processes were researched. Results show that microwave heating may be a new heating resource replace of carbonic combustion reaction in reducing reaction. When the allocation of carbon is (16.7-30)%, carbothermic reduction of V-Ti-magnetite in the microwave field can proceed; with the increasing of carbon mixed, the metallization rate increases; and Fe, V can be reduced from their oxides in the microwave field; Titanic low oxide can be reduced from TiO2.1. IntroductionThe resource of Ti-V-Magnetite is abundant in the western area of Panzhihua in China, so far a mineral deposit of 4.64 billion tons have been proved up, it contains 14.75 million tons of V2O S which accounted for 87% of the vanadium and 5.93 hundred million tons of TiO2 accounted for 94% of the titanium resource respectively in China. The previous study proved that the major composition of mineral of the Ti-V-magnetite are Ti-magnetite, limonite, iron spinel, magnesium spinel etc, and the main elements of the Ti-V-magnetite in this area are Fe, Ti, V, Cr, Co, Ni, Ga, Sc etc[1] Due to the restrict of the BF-BOF process technical, during the smelting of the iron, the level of extracting the vanadium, titanium as well as other metal elements is limited. This results serious wasting of resources. To develop a new reduction process of Ti-V-magnetite is on the agenda, the microwave assistant reduction could meets this need, based on its characteristic of easy controlling of heating rate. To make use of the microwave energy to substitute the released heat sources of carbon combustion with air, use the solid phase state reduction at a relative lower temperature, make the beneficial element in Ti-V-magnetite transferred into the metal phase, then separated from the impurity. It is well worth to point out that once the microwave based reduction method has its industrial scale, it will take an outstanding position by its less release of carbon dioxide. This new environment-friendly process will play a vital role in the development of social industry and economy."

Jan 1, 2008

By W. Murray Small

Nickel plays an important role in determining the properties of many stainless steels and superalloys. Cobalt also contributes significantly to the performance of certain grades of superalloys. A major technical aspect, in which both of these metallic elements are involved, concerns the solubility of nitrogen in these classes of alloys. Beyond certain content limits, dissolved nitrogen may contribute to the deleterious mechanical behavior by these alloys. It is therefore essential to control the level of this element during alloy processing. In this paper, results from several experimental studies have been assembled and are analyzed to describe phenomena related to the individual effects of nickel and cobalt on the solution of nitrogen in several groups of alloys. Both solid and liquid alloy systems are considered. This information may be used as a guide to limit or control the presence of this interstitial element in alloys.

Jan 1, 1993

By G. C. Yao

Branch and needle-shaped intermetallic compounds of iron, silicon and aluminum normally exist in the molten aluminum. If a suitable amount of manganese metal is added into molten aluminum, the shape of the intermallic compound particles may become lumpish and spherical. According to the difference in electric and magnetic properties of these impurity particles and molten aluminum, these impurity intermetallic compound particles can be separated by applying an alternating magnetic field. In this experiment the alternating magnetic field was formed by a "c" type loop with AC (50Hz) current. The inner vacuum of the fireclay refractory separator is 25xl5xl30mm3 with a lateral baffle inside. The separator was put into the interspace of the "c" type loop. It was found that the longer the separation time, the larger the amount transferred of impurities. The amount of transferred impurities increases with the increase of separation time and intensity of magnetic field. The addition of manganese metal enhances significantly the efficiency of impurity separation

Jan 1, 2003

By P. Chris Pistorius

An example is presented to illustrate the joint effect of local reaction equilibria and mass transfer limitations, for reactions during ladle refining of steel. The example relies on some of the kinetic principles that David Robertson has employed to quantify many metallurgical processes. In calcium treatment of alumina inclusions in aluminum-killed steels, solid CaS forms as an intermediate reaction product. During subsequent reaction, CaS disappears and calcium aluminate forms; at the same time, aluminum and sulfur dissolve in the steel. Kinetic analysis shows that the rate of this reaction is not limited by mass transfer of dissolved aluminum and sulfur away from the reacting inclusions. The reaction rate is likely limited by transport of dissolved calcium. This example also illustrates the use of FactSage macros for kinetic modeling.

Jan 1, 2014

By David G. Dixon

A mathematical model is derived in dimensionless form which simulates the effluent concentration response of reagents from spent heaps under both fresh and recycled water rinsing. The model is based on dispersion from isochoric pathways distributed in length and cross-section, oriented normal to convection channels in ideal plug flow. The effects of heap height, rinsate flow, and initial reagent concentration are examined. It is shown that the rinsing cycle undergoes a distinct shift between fast and slow rinsing at a certain time depending on the amount of stagnant solution in the heap, and the distribution of dispersion pathways. Results of preliminary column rinsing tests on both agglomerated and unagglomerated ores are presented which partially validate the model.

Jan 1, 1994

By Junji Shibata

Some fundamental studies were carried out in order to produce composite powders comprising of two or three metal salts by using liquid-liquid extraction and to develop the control technology of the particle size. The combination of samarium and cobalt was selected as the two component composite powders. Both stripping and crystallization occurred at the same time by emulsifying the organic phase loading the two metals extracted with Versa tic Acid 10 and the aqueous solution containing oxalic acid. The effect of aqueous pH, oxalic acid concentration and agitation speed was examined on some properties such as crystallization percent, particle size and shape of each metal oxalate powders obtained in this process. The analysis by using EDX showed that the two metal oxalates were distributed uniformly at the same ratio as the organic phase composition.

Jan 1, 2001

By B. J. Scheiner

The presence of organic materials in gold ores interferes with gold extraction by cyanidation. The carbon contained in the ore has been shown to adsorb gold cyanide complex from solution. Removal of the carbon content by roasting or chemical oxidation prior to cyanidation results in gold extractions of 85 to 95%. This paper discusses how the mineralogy of the carbonaceous gold ores affects gold recovery by cyanidation. It also discusses the advantages and disadvantages of roasting and chemical treatment to render the ore amenable to cyanidation.

Jan 1, 1987

By Marc Verhaege

The effluent under investigation results from a catalic oxidation unit in which paraxylene is oxydised to terephtalic acid. The solution contains cobalt and manganese as their acetates in a concentration range of 0,4 - 1,2 g/I of cobalt and 0,8 - 2,4 g/l of manganese. Before being fed into the main waste stream treatment unit of the plant it is advisable to apply a petreatment step in which both metals are eliminated to a great extent from this effluent. Conventional treatment is done by precipitation of both metals either through pH increment with a base or by adding a suitable reagent producing insoluble species. The aim of this study was to look for a treatment (elimination of both metal species) in which no sludge or precipitate is formed.

Jan 1, 1995

By Hai-Peng Guo, Lu Jiang, Xiao-Man Yan, Bing Xie, Hong-Yi Li

Traditional, calcium compounds cannot be used in vanadium extraction processing due to the limitation of sodium roasting technology, which results in unsatisfied dephosphorization for vanadium-containing hot metal in converter and thus increasing the dephosphorization burden for subsequent steelmaking. The calcium roasting technology is an alternative for vanadium extraction and allows adding lime into vanadium slag in converter. In the present study, vanadium was leached by soda from roasted vanadium slag with high calcium content. Effects of roasting temperature and time, leaching temperature, Na2CO3 concentration andliquid to solid ratio on vanadium leaching rate were studied. The results show that 94% of vanadium was extracted by roasting the vanadium slag at 950℃ for 2.5h and then leaching in 160g/L Na2CO3 liquid at 95℃ for 1h with liquid to solid ratio of 10:1 ml/g. Impurities of Si and P reacted with calcium and formed insoluble Ca2SiO4 and Ca3(PO4)2 respectively.

Jan 1, 2015

By L. E. Murr

Preliminary studies of bacterial attachment to MoSp (molybdenite) have indicated a low correlation between dislocation density in the (0001) basal plane and the density of attached microbes. In the present investigation, poly- crystalline thin sections of CuFeSp (chalcopyrite) have been ion-etched or carefully comminuted to electron transparency and observed in the transmission electron microscope. The thinned test sections were then immersed in a culture solution in which bacterial attachment occurred. The attached bacteria were biologically stained in a uranyl acetate solution and the entire thin CuFeSp sections or tiny particles containing thin, electron transparent edges with bacteria attached were observed in the transmission electron microscope, allowing the coincidence of bacteria and their density to be directly observed in relation to lattice dislocations and crystallographic orientations of the exposed surfaces. This technique has the advantage of exposing crystallographic orientations where dislocation lines intersect the free mineral surface, and the emergence sites of dislocations could in principle be directly investigated as a possible preferential attachment site for bacteria. Bacteria morphologies were also extensively observed in the scanning electron microscope. The implications of the results are that although a strong correlation between dislocation density and distribution and bacterial attachment, density, and distribution has not been established, systematic multiplication of dislocation densities in crystalline mineral particles to be leached could enhance leaching rates by increasing the reaction rates as well as the density of attached bacteria at crystalline, metal-rich phases. Techniques for dislocation production in mineral and ore bodies and the particular implications in chalcopyrite leaching are discussed in relation to in-situ leaching where comminution is attained by explosives and the generation of strong shock waves in an ore body. The present study demonstrates the use of microanalytical and microscopic techniques in the investigation of fundamental microstructural phenomena in hydrometallurgical processes.

Jan 1, 1976

By Henry L. Ehrlich

This survey compares bioleaching and biobeneficiation by autotrophic bacteria with that by heterotrophic bacteria and fungi Some physiological principles are reviewed. Advantages and disadvantages of autotrophic and heterotrophic leaching are discussed. Principles of anaerobic leaching by autotrophs and heterotrophs are introduced. and the advantages? over aerobic heterotrophic leaching are discussed. Examples of useful organisms in the autotrophic and heterotrophic categories are cited.

Jan 1, 1991

By Li Qihou

Mono-disperse ZnS and CdS nano-particles were prepared by the homogenous precipitation method and the effects of SO42-,NO3- and Cl-ions on crystalline of particles were investigated experimentally. The results showed that these anions had no influence on the crystalline of ZnS, but different crystalline CdS ultrafine particles were produced in different anion systems, where the blend-type CdS was obtained from natrate or sulphate solution, and wurtzite-type CdS from chloride solution. It was ascribed to the coordination of Cl- and Cd2+ that altered the supersaturation of precipitate ions in the solution, the existing growth units and their connecting patterns, thereby producing wurtzite-type CdS with a more stable structure.

Jan 1, 2006

By M. R. Barkhudarov

Semi-solid metal can be formed into useful products of near net shape and high quality. Use of this method has been limited, however, because of the difficulty of working with metal in the semi-solid state, which has strong shear rate, temperature and time-dependent properties. In this paper we describe a thixotropic model and apply it to the problem of small metal droplets impacting on a flat plate.

Jan 1, 1997

By Adam Powell, Soobhankar Pati

"Solid Oxide Membrane (SOM) Electrolysis is a new energy-efficient zero-emissions process for producing high-purity magnesium and high-purity oxygen directly from industrial-grade MgO. SOM Recycling combines SOM electrolysis with electrorefining, continuously and efficiently producing high-purity magnesium from low-purity partially oxidized scrap. In both processes, electrolysis and/or electrorefining take place in the crucible, where raw material is continuously fed into the molten salt electrolyte, producing magnesium vapor at the cathode and oxygen at the inert anode inside the SOM. This paper describes a three-dimensional multi-physics finite-element model of ionic current, fluid flow driven by argon bubbling and thermal buoyancy, and heat and mass transport in the crucible. The model predicts the effects of stirring on the anode boundary layer and its time scale of formation, and the effect of natural convection at the outer wall. MOxST has developed this model as a tool for scale-up design of these closely-related processes.IntroductionSolid Oxide Membrane (SOM) Electrolysis is a variation on the Hall-Héroult process for molten salt electrolysis of oxides which promises to solve many of the problems of its predecessors. Magnesium in particular is both soluble in molten salts and highly reactive, such that it migrates to the anode and reacts with the oxygen or C02 anode product, reducing current efficiency to as low as 10-20%. But a zirconia solid electrolyte between the molten salt and anode blocks this reaction, boosting current efficiency to at least 90%. Separating the anode from the molten salt also opens up anode material selection to liquid metals and SOFC cathode materials such as Lai.xSrxMn03 (LSM) and YCr03. And zirconia's selectivity makes the oxygen by-product very pure."

Jan 1, 2012

By Dany Racine, Daniel Marceau, Denis Laroche, Dmitry Lukovnikov

Carbon base materials play a critical role in the performance of Hall-Héroult cell. The determination of their thermo-physical properties is of primary importance for modeling and designing complete cell systems. However, overcoming the associated experimental hurdles is complex and often underestimated. Of them are the Poisson’s ratio measurements and the continuous oxidation/burning of the materials at temperatures above 200°C. The novel procedure developed in this research is based on the Gleeble® 3800 system. Its vacuum chamber allows test with a chosen atmosphere at temperature of more than 1000°C. Young’s modulus, Poisson’s ratio and the coefficient of thermal expansion values can all be adequately measured using a single test. Cylindrical carbon samples (: 50mm, L: 100mm) were tested in the modified system at temperatures ranging from room to 950°C without any trace of oxidation. The resulting values were also in good agreement with literature data for a specific graphite material.

Jan 1, 2015

By F. Leuzzi

Asbestos is a natural mineral fibre which has been known and utilized commercially for about a century. From the forties, it was employed on an ever-increasing scale throughout the mechanical engineering, building, paper-making and plastics sectors, to name but a few. There are essentially five minerals which provide fibres for industrial applications, namely, the chrysotile variety of serpentine and the amphiboles such as riebeckite, anthophyllite, cummingtonite-grunerite (amosite) and tremolite. About a fifth of the world's asbestos output was once taken by Europe for the manufacture of asbestos-cement products, reinforced plastics, paper and cardboard, panels, soft insulation and spray-on powders. However, in the sixties and seventies the hypothesis regarding the pathogenic nature of asbestos fibres started to gain ground. Moreover, between the sixties and eighties the EU issued a series of regulations designed to bring about a steady decrease in asbestos consumption. This line of action has culminated in recent years in a whole set of directives banning the use of asbestos in all products. This created a major problem, namely, how to clean-up the several million tons of various types of asbestos products in various states of conservation existing in Western Europe. CORDIAM (Pat. RM95 A 000269 and Pat. RM96 A 000782 in the name of ECOTEC S.r.1.) is one of the thermal inertization techniques recently proposed for this purpose. The process provides for the low-temperature ceramization of the toxic-harmful material. Of course, with such a great variety of waste materials and the volumes to be treated, as well as the need to ensure the correct dimensional design of the thermal sections of the treatment plant, it is necessary to know as much as possible about the thermal behaviour of the wastes concerned. This paper details the steps taken firstly to ascertain the thermal behaviour of such materials as may be encountered in day-to-day practice and secondly to examine the influence of the main process parameters on the preliminary design of gas- or fuel-oil-fired rotary kilns of the kind used for waste treatment.

Jan 1, 1999

By Truan-Sheng Lui, Li-Hui Chen, Hao-Wen Hsueh, Fei-Yi Hung

"Since Ag wires have similar hardness and bonding properties to Au wires, they can be applied in some pads. In the present study, the annealing effect (at 225°C~275°C for 30min) on the tensile mechanical properties of silver wires with f=23µm was investigated. In addition, the micro-structural characteristics and the mechanical properties before and after an electric flame-off (EFO) process were also studied. Experimental results indicate that with annealing temperatures of more than 250°C, the silver wires possessed a fully annealed structure, the tensile strength and the hardness decreased, and the elongation was raised significantly. Under the thermal effect of EFO, the necks of the Ag balls underwent recrystallization and grain growth was induced, and the annealed Ag wires had a shorter zone of HAZ (220µm). The bonding strength and the neck-strength of the Ag wires were more than 7gf and possessed excellent bonding properties.IntroductionThermosonic ball bonding is one of the preferred processes for electronic packaging to connect a semiconductor chip and a lead frame by a thin metal wire. At present, gold wire and copper wire are the preferred interconnect materials to bond with the aluminum metallized wafer pads [1, 2]. Since gold is expensive and the reliability of copper is poorer [3], the study of silver wire has attracted a lot of attention already. In addition, the inherent properties of high ductility and low hardness of silver as well as its workability effectiveness compared to gold, have made it a preferred alternative .[4, 5]"

Jan 1, 2012

By David Bequette, Ray D. Peterson, Cynthia K. Belt

"With a need to cut production costs in the metals industry, cost savings from energy efficiency improvements are critical. Opportunities can be found by reviewing furnace systems and practices so that the melting and holding processes operate at the highest energy efficiency. Many of the changes can be implemented with a minimum of expense or capital investment. This paper will review several low cost methods to optimize energy efficiency on reverberatory melting or holding furnaces. These five methods (furnace utilization, idle procedures, fire rate, controls, furnace pressure) will be explained and information given to implement these changes. Included are several rules-of-thumb and benchmarks for aluminum reverb furnaces.IntroductionEnergy can be a significant portion of the total manufacturing costs for metals and materials manufacturing involving thermal processing such as heat treating, melting, and high temperature processing. Natural gas prices have dramatically varied over the last few years. While no one can foresee the future, prices are expected to increase from the current low prices. More recently, emphasis is being put on the reduction of greenhouse gases with the potential of additional costs to industry.One of the first steps in an energy management program is to measure the energy usage of the process [1]. The results are typically understood in relation to the mass melted in kWh / mT [BTU / lb]. For the purposes of this paper, furnace energy efficiency is calculated over a month or even a year and thus includes hold times. This efficiency is typically different from the values quoted by furnace manufacturers. Those values are for limited short term tests at highutilization.Once you know the performance for your furnaces, these should be compared to industry benchmarks. For aluminum melt furnaces with cold air burner systems, a benchmark value or goal is 1800-2000 BTU/lb [1160-1290 kWh/mt], though some of the best have reached 1600 BTU/lb [1030 kWh/mt]. Furnaces with regenerative burners can attain 1100-1200 BTU/lb [710- 775 kWh/mt]. There are some designs of multi-chamber furnaces or oxygen furnaces that have improved on these numbers, perhaps as low as 950 BTU/lb [615 kWh/mt]. Typically, as the degree of sophistication and energy efficiency of the furnace increases, so does the cost."

Jan 1, 2010