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By J. B. Wiskel, H. Henein

"A study was conducted to establish the effective heat transfer coefficient for a single molten droplet moving in a gaseous medium. Towards this objective, a series of quench experiments were performed on molten droplets of AA6061 aluminum generated with the Impulse Atomization technique (IAP). IAP is a single fluid atomization process capable of producing powders with a predictable mean particle size and a relatively tight standard deviation under controlled atmospheric conditions. Microstructure analysis of the atomized powder was used to establish the extent of pre-quench solidification. A mathematical model was then employed to correlate the Ranz-Marshall and Whitaker equations with the observed particle cooling behaviour. These equations were found to provide a reasonable estimation of the heat transfer conditions only when the variation in gas thermophysical properties across the boundary layer was accounted for in the model. This model formulation of droplet heat transfer has important implications with regards to active sprays and atomization processing operations IntroductionAn understanding of droplet cooling is important in atomization powder production. It is well understood that dendrite arm spacing is inversely proportional to cooling rate during solidificationl1l. Through modification of the heat transfer conditions during metal atomization, the microstructure of a powder maybe tailored to the end user. However, owing to the complexity of gas flow it is difficult to determine a heat transfer coefficient for a moving droplet. This difficulty is further compounded when complex jets and/or streams and their interactions are considered. To provide a base for these more complicated types of analyzes, two approaches have been employed to calculate the effective heat transfer conditions for a single droplet. In one approach, Megardis [ZJ developed a numerical model to investigate the heat transfer process of a free falling droplet undergoing laminar convective cooling. The effective heat transfer coefficient as a function of angular position was determined by numerically solving the fluid and energy equations for the system."

Jan 1, 1999

By W. G. Davenport

Chapter 6 examined autotherrnal smelting of pure chalcopyrite concentrate with 50 mass% O2-50 mass% N2 blast. It showed that production of 1500 K products with this blast requires: 181 kg of pure oxygen 337 kg of air per tonne, of concentrate. It also showed that the grade of matte produced with this blast is 58% Cu. This chapter re-examines autotherrnal smelting by asking: (A) WHAT COMPOSITION BLAST (MASS% 02 -MASS% N2), 298 K, WILL AUTOTHERMALL Y PRODUCE 65% Cu MATTE 1500 K FROM PURE CHALCOPYRITE CONCENTRATE? (B) HOW MUCH PURE OXYGEN AND AIR WILL BE NEEDED? These are important questions for flash? smelting because furnace operators usually want to send specific composition matte to converting. This chapter shows how a specified matte can be produced autotherrnally with 298 K oxygen-air blast. Later chapters show how it can be done with hot blast, hydrocarbon combustion, different concentrates etc.

Jan 1, 2001

By W. L. Cornell

Bulk sulfide concentrate produced from Missouri Pb ore concentrator tailings must be reground to liberate sulfide values for subsequent sepa-ration. Studies to determine grinding parameters for optimum liberation were carried out using optical microscopy coupled with image analysis. The major sulfide phases present in the ground mineral particulates are marca-site, pyrite, sphalerite, galena, chalcopyrite, siegenite. and bravoite. Results showed that the base metal minerals were liberated by grinding to 74 micrometers (200 mesh), but the siegenite and bravoite required grinding to 20 micrometers or less to achieve liberation. Both the experimental method and results are presented.

Jan 1, 1987

By Toshihide Takenaka

Improvement of corrosion resistance of Mg metal by addition of rare earth metal (RE) was studied, and the effect of surface oxide layer with RE was investigated. The corrosion resistance of Mg was remarkably improved by adding a small amount of RE, and the suitable RE content was clarified. The corrosion resistance of Mg was particularly bettered by conversion coating using a solution including both RE(NO3)3 and Mg(NO3)2. This result indicates that the surface oxide layer consisting of both Mg and RE gives good corrosion resistance to Mg metal. In this study, direct electrodeposition of Mg metal containing RE was also tried in molten chloride with RE chloride, and it was shown that electrolysis could be performed stably. The RE content in the deposited Mg metal was depended on the concentration of RE chloride in the bath and the cathode potential, and Mg metal containing the suitable RE content for its corrosion protection was obtained easily by direct electrolysis.

Jan 1, 2006

By Allan J. MacRae

A copper alloy to be used for coils in cast copper cooling blocks has been identified and samples prepared for metallurgical examination and destructive testing to compare with cast cooling blocks manufactured from copper and nickel-copper alloy pipes. The copper alloy allows for the formation of a metallurgical bond between the pipe and the cast copper during the casting process, which does not normally occur with pure copper or nickel-copper alloy pipes. The alloy's coefficient of thermal expansion is also much closer to that of pure copper compared with nickel-copper alloys, so there is less strain induced at the pipe-cast copper interface due to differential thermal expansion. It is expected that this new pipe coil alloy and associated casting techniques will allow for the production of cast copper cooling blocks that have greatly enhanced service life in high heat load applications compared to existing technologies.

Jan 1, 2002

By Frank Field, Randolph Kirchain, Elisa Alonso, Richard Roth, Nathan Fleming

"High material prices and price uncertainty can be harmful to manufacturing firms. Increased use of recycled materials, industry-wide, can lower both material prices and price variability; moreover, increased recycling decreases the use of primary material, which mitigates price increases due to scarcity effects. These stabilizing and price lowering effects are explored using an Aluminum industry model. We show that (a) increased recycling leads to smaller price fluctuations in the presence of a primary metal supply perturbation, and (b) that the more substitutable the secondary metal is for the primary metal, the lower the overall material price is.IntroductionThe price of an industrial metal is expected to be a function of both the marginal cost of extraction and its scarcity[l-2]: where scarcity can be defined as the degree to which anticipated demand exceeds the known supply. Recycling end-of-life metal increases the apparent supply of the metal, or-in a functionally equivalent, but alternative conception-lowers the demand for primary metal; this lowers primary metal scarcity and should, theoretically, reduce its price. To the extent that this theoretical prediction holds true, recycling can provide benefits to consumers of industrial metals in the form of lower prices.Using a platinum industry model, prior work by Alonso[3] has shown that increased industrywide recycling can reduce metal price volatility because the secondary metal production (a) offsets virgin metal depletion, and (b) responds to supply-demand balance fluctuations more rapidly than the primary market. However, Platinum is not a typical industrial metal in the sense that secondary metal is perfectly substitutable for primary metal: Both primary and secondary platinum metal are functionally equivalent and have a common price. Other metals, such as secondary aluminum which is used as an example case in this study, contain varying degrees of other elements that were either intentionally added, or were inadvertently mixed in with the metal during the scrap recovery process. Consequently, different grades of scrap exist that have different profiles of elements in their composition. Depending on their particular profile of elements, more or less of a given grade can be used as a mass fraction of the final alloy-the secondary metal is not perfectly substitutable for the primary metal. For the purposes of this paper, the aluminum mass fraction of the final alloy that can be made up of secondary aluminum is termed the secondary substitutability of that grade in that alloy."

Jan 1, 2011

By O. Tiitu

Drying is a unit process that has numerous applications in metallurgical process industry. Kumera Technology Center is a worldwide equipment and process supplier, who has expertise on both direct and indirect drying. In a conventional direct heated dryer, the required energy is obtained from combustion of fossil fuels emitting a considerable amount of off-gases. However, thermal energy can be already available in some metallurgical plants such as modem copper smelters where steam is produced by waste heat boilers of flash smelting furnaces. The total volume of off-gases, and especially the amount of harmful gases, released into atmosphere can be remarkably reduced when using steam as an indirect energy source for drying. Kumera Technology Center has developed a new type of steam dryer for drying of, for example, abrasive copper concentrate with silica sand. In the development of the new dryer, Kumera's approach has been to combine the best properties of both the existing steam dryers and the rotating drum dryers. In the design, special attention has been paid to overcoming the reported problems of excessive wear and clogging of steam tubes and to reducing the required maintenance operations. The Kumera Steam Dryer, having a patented flexible steam tube arrangement inside the rotating shell, has a high effective heating area - drum volume ratio without leading to problems with build-up and clogging. It can also be easily scaled up so that a single dryer can dry all of the feed for a large flash furnace. In this paper, we will present the operational and maintenance experiences from two years operation of the first full-scale Kumera Steam Dryer at Norddeutsche Affinerie Aktiengesellschaft in Hamburg, Germany. We will also provide an overview of the future developments with respect to construction and scale up as a response to market demands.

Jan 1, 2002

By Yingtao Zhang, Shaofeng Du, Yiming Rong, Wenjun Zhao, Gang Wang

"20Cr2Ni4A steel is a kind of high quality steel mainly used for manufacturing high-duty gears in the world. The high-duty gear with good performance must have wear and fatigue resistance properties. In order to get the good properties, the high-duty gear needs a high hardness gear surface and a good hardness gradient along the depth direction. In this paper, the samples were designed and a vacuum carbonitriding process was put forward to improve the surface hardness of parts for 20Cr2Ni4A. The process contained carbonitriding, quenching, cryogenics, and tempering process. The surface hardness and hardness gradient of carbonitrided samples were measured and the good microstructure was gained. The surface hardness is 67.SHRC and the case depth is 1.2mm.IntroductionSteels are widely used in industry, but the fatigue strength and the wear resistance of steel is much low. So the heat treatment process is put forward to improve the mechanical properties of steel. It can be improved by high-energy heat treatment methods for medium-carbon and highcarbon steel. Those methods will not alter the chemistry of the base metal [ 1].For low-carbon steels, carburizing and quenching should be used to improve the steels' mechanical properties, especially the surface properties. Compared with the carburizing, carbonitriding has more advantages, such as a short production cycle, low temperature and small deformation of parts. Carbonitriding is a modified form of gas carburizing, rather than a form of nitriding. The modification consists of introducing ammonia into the gas carburizing atmosphere to add nitrogen to the carburized case as it is being produced. Nascent nitrogen forms at the work surface by the dissociation of ammonia in the furnace atmosphere; the nitrogen diffuses into the steel simultaneously with carbon. Typically, carbonitriding is carried out at a lower temperature and for a shorter time than is gas carburizing, producing a shallower case than is usual in production carburizing [2]. As a material surface strengthening technology, carbonitriding has been widely used in the production [3]. And vacuum carbonitriding process is better than carbonitriding, because the vacuum carbonitriding temperature can be higher than carbonitriding without surface oxidation."

Jan 1, 2014

Lead removal has been problematic in nickel production by electrowinning from chloride solutions, as developed by Falconbridge. The C12 leach liquor needs to be diluted by electrolyte to allow precipitation of the lead prior to electrowinning. This results in higher solution purification costs and an aversion to consider lead contaminated (secondary) feeds. In this paper, the electrowinning of nickel chloride is carried out in a membrane equipped electrolytic cell. When lead containing nickel solutions are fed into the anode compartment and the anolyte is separated from the catholyte with a cation exchange membrane, lead remains in the anolyte due to the presence of a negatively charged chloride complex. The positive nickel ions migrate preferentially through the membrane to the catholyte, allowing a lower lead nickel cathode to be produced. Lead concentration in the catholyte and the cathode product has been tested as a function of lead concentration in the anolyte. Results are presented and discussed.

Jan 1, 1998

By Kaspar Tall, Dmitri Goljandin, Kristiina Vilsaar, Jaan Kers, Valdek Mikli, Lifeng Zhang, Riho Tarbe, Viktor Laurmaa, Mart Saarna, Priidu Peetsalu

In this paper, the mechanical milling of the Printed Circuit Boards (PCB) was carried out. First goal of the work was to examine the management of the WEEE, in particular the re-use of PCB. Firstly, recycling methods of PCBs were summarized. During the study mechanical separation methods (magnetic-, density- and air separaten), electrical, and chemical methods were examined. Secondly the optimal particle size for air-classification was determined. Several tests were carried out to find the most effective separation method for separation of different material groups from PCB scrap. The new air classification stand was developed for testing the separation of lightweight particles like tinfoil stripes and plastics. The test results showed sufficiently good separation of heavier Al and Cu. For milled materials characterization the SA, IA, laser diffraction analysis and SEM were used. The chemical composition of the PCB powders was studied by means of energy dispersive X-ray microanalysis (EDS).

Jan 1, 2011

By John Fallavollita

Conventional gas atomization produces powders that vary widely in size distributions and microstructures, thus making it very costly to produce powders tailor made in a narrow size distribution and microstructure. Furthermore, it is difficult to determine the relationships between atomizer operating conditions and resulting powder characteristics. The Impulse Atomization Process (IAP) was developed at the Advanced Materials and Processing Laboratory to produce powders with narrow size distributions. Powders produced by the IAP were reproducible and their sizes could be easily controlled by adjusting experimental conditions. Characteristics of Zn, Sn-Pb, AI-Cu, and Cu powders will be described to illustrate the flexibility of the process to tailor-make powders.

Jan 1, 1994

By N. L. Piret, E. N. Mounsey

Ausmelt technology is successfully used to process primary and secondary materials to produce lead in large-scale commercial operations and to meet stringent environmental standards. The development and commercial data covering these applications and the results with respect to metallurgical, cost and environmental performance are reviewed in commercial operations. A new smelter is scheduled for commissioning in 2000 at Korea Zinc's Onsan site to process lead fume and other secondary materials to produce 50,000 tonnes per annum of lead bullion. The unique features of Ausmelt technology also allow for the efficient processing of polymetallic concentrates and secondary materials, particularly copper and lead, through the effective separation of these elements into metal, slag and fume species. This capability has been successfully demonstrated at a commercial scale and the results and implications for the industry are discussed.

Jan 1, 2000

By A. V. Tarasov, S. D. Klushin

493 The most common method for minimizing the copper content of residual slag in the process of autogenous smelting of sulfide raw materials is treatment of molten slag in an electric furnace, with optional addition of solid reducing agents, such as coke, and/or sulfiding agents such as pyrite. A drawback of this technique is the fact that the final slag produced still contains 0.5% or more Cu. We have tested a method for treating molten slag obtained as a result of autogenous smelting by a gaseous mixture of sulfur dioxide and methane at a ratio of. SC:SO2 = 0.75 :1.0 in the presence of oxygen. Interaction reaction within the SO2-O2-CRi system proceeded at a high rate at 1373 to 1573 K to form reducing and sulfiding agents: H2S, S, COS, CO, CO2, H2, H2O. The gas mixture requirement was about 100 to 150 Nm3 per 1 tonne of slag. A decrease in the ferric iron concentration (Fe3+) from 10-15% down to 2-3% resulted in lower solubility of copper in slag, and agitation of the melt with gas stream accelerated. the separation of the sulfide phase and slag. Removal of copper from slag was performed in a pilot unit within the second V anyukov furnace zone where slag arrived with a copper content of 0.8-1.3%. The temperature of molten slag was maintained within 1523 to 1573 K. The copper content of the final slag was at a level of0.12 to 0.14%. The matte sent to converting was a mixture of bottom matte from the smelting zone and the slag treatment zone. It had a copper content of about 50 to 55%. Process gases from both furnace zones were combined and sent to the acid plant for sulfur recovery. This process was offered for commercial use at two copper smelters in Russia and CIS.

Jan 1, 2000

By Jian Li, J. Miles, P. Liu, W. Cook, W. Zheng, Alvin Qian

"High temperature corrosion resistance is one of the key challenges in water-cooled nuclear reactor material development. Iron based materials with low Cr content exhibits superior high temperature mechanical properties. However, due to the relatively low Cr content, their corrosion resistances under supercritical water (SCW) conditions are generally poor. High-Cr alloys, despite their much improved corrosion resistance, often suffer from embitterment due to the precipitation of sigma phase in the microstructure. In this study, corrosion resistance of an in-house produced high Cr steel (25%Cr) showed much better corrosion resistance compared to that of low Cr alloy (14%Cr). This high-Cr steel can potentially be used as a corrosion-resistant coating for structural materials in sew applications.INTRODUCTIONThe supercritical water-cooled reactor (SCWR) concept is one of the promising designs for the next generation nuclear reactor, in which the water coolant is designed to be at about 625°C and 25 MPa at the outlet of the reactor core. Under these relatively high-temperature and high-pressure conditions, the cooling water is at supercritical state. High-temperature mechanical properties, corrosion resistance and radiation damage are some of the key challenges. At present, no single commercial material can meet all the requirements of the severe SCWR in-core conditions. Canada supports research in several key areas of SCWR development, including materials selection. A major focus is on materials development, selection and evaluation for both in-core and out-of-core components.Allen et. al. [1] carried out a comprehensive study on the SCW corrosion resistance up to 600 °C on commercially available high temperature materials including Ni-based super alloys, various types of stainless steels and ferritic/matensitic steels. They concluded that ferritic steels develop a relatively thick but mechanically stable oxide layer, while austenitic alloys develop a thinner oxide layer that has been found to spall in some cases. Of the three types of alloys examined, the Ni-based alloys exhibited the lowest oxide thickness, however pitting was observed in the vicinity of intermetallic precipitates."

Jan 1, 2011

By Caisa Samuelsson, Sina Mostaghel, Theo Lehner

"Rönnskär smelter of Boliden Mineral AB, Sweden, is well known for recycling of base and precious metals. Slag from the electrical furnace is processed at the fuming plant to produce zinc clinker. The granulated slag is a by-product used as e.g. construction material. In this paper, influences of Al2O3 on mineralogy of the slag, which can affect its chemical and physical properties, are investigated. Different mixtures of Al2O3/fumed slag were prepared. Re-melting was carried out in a Thermo-Gravimetry (TG) furnace with an inert atmosphere. Scanning electron microscopy (SEM) and X-ray diffractometer (XRD) were then applied for the analyses. Investigations depict that addition of alumina to slag, results in an increase in the number of spinels and a transformation from iron rich to aluminum rich spinels. Anorthite (CaAl2Si2O8) will also be formed.IntroductionRönnskär smelter of Boliden Mineral AB is located in north of Sweden; the main products of this smelter are: Copper, Zinc clinker, Lead, Gold, and Silver, while sulphuric acid, liquid sulphuric dioxide, and Iron sand are some of the by-products. Reducing the energy consumption and decreasing the usage of finite natural resources are becoming more and more important for the Rönnskär smelter; this result in use of different recycling and scrap materials. Metal residues, from brass foundries, steel mills, and electronic scrap are recycled at Rönnskär smelter [1]. Most of the electronic scraps contain mixtures of various metals together with plastics and ceramics, which can affect the composition and properties of the slag considerably [2]. At the same time, treatment of slag and controlling its composition and properties are of much interest for Base Metals producers from different aspects. Composition of slag influences the physical properties such as: 1) Liquidus temperature [3-4] 2) Viscosity, which controls separation of valuable metals, especially copper by gravity separation [2] and also heat and mass transfer [5] 3) Electrical conductivity [6]."

Jan 1, 2008

By A. Lackner

Using the CFD software package FIRE, the smelting process inside a cyclone reactor is modelled. The fluid flow is calculated 3 dim., using different turbulence models. The effects of design parameters (length and diameter of the cyclone, concentrate feeding tangentially or from the top,..) and operating conditions are investigated. Single particle traces illustrate how to increase particle retention time before the particles reach the liquid film flowing down the cyclone wall. Moreover a two phase flow approach is developed, based on the "Discrete Droplet Model". The position, velocity, diameter and temperature of each reacting particle is described. The results show the advantages of top concentrate feeding, large height/width ratio of the tuyeres and increasing number of tangentially gas inlets.

Jan 1, 1995

By Michel G. Drouet

Dross, a major by-product of all processes involving molten aluminum, forms at the surface of the molten metal as the latter reacts with the furnace atmosphere. It generally represents 1 to 5 wt% of the melt, depending on the process, and contains on average about 50% free aluminum dispersed in an oxide layer. Since aluminum production is highly energy-intensive, dross recycling is very attractive from both the energy and the economic standpoints. The conventional recycling process using salt rotary furnaces is thermally inefficient and environmentally non-acceptable because of the production of salt slags. Hydro-Quebec has developed and patented a new salt-free technology using a rotary furnace heated by an electric arc between two graphite electrodes, called DROSCAR®. A 600-kW pilot plant in operation at LTEE is in use to demonstrate the process. This process provides aluminum recovery rates over 90%, using a highly energy efficient, environmentally sound production method. In 1994, 400 tonnes of aluminum dross were treated in this facility and several tests on various types of dross have also been conducted in early 1995. A report on the results will be presented.

Jan 1, 1995

By Hyun Soo Kim, Joon Soo Kim, Myong Jun Kim, Jyothi Rajesh Kumar, Jin-Young Lee

Rare earth materials have an ever growing variety of applications in the modern and hitech technology. They apply to many an industry with crucial materials and they provide numerous a customers with benefits. Rare earth materials utilization increasing day-by-day in the worldwide, at the same time the resources is very limited in many countries like Korea. The present general article divided four sorts such as 1) mineral processing of Korean ore deals the gravity, magnetic separation and froth flotation, 2) decomposition and leaching of concentrates included sodium hydroxide fritting, sodium hydroxide hot digestion, hydrochloric acid leaching, 3) separation and purification of rare earth elements in mixed rare earth chloride solution consists reduction and oxidation method, solvent extraction, 4) preparation of rare earth oxide compound from purified elemental rare earth chloride solution having oxalate salt precipitation by reaction crystallization. The last part consists of a summary of the present study.

Jan 1, 2015

By Y. H. Liu

Several foaming aluminum samples of different density were prepared in a semi?industrial scale experimental system, Their properties such as the energy absorption characteristics, mechanical properties, heat conductivity and acoustical properties were measured. The results showed that the foaming aluminum with a density of 0.5 to 0.6 g/em3J has the best energy absorption and this makes it suitable as the ensuring bar of the automobiles and also as a cushion material for the engine. The foaming aluminum with a density of 0.25 to 0.4 g/em3 has the best acoustical properties and heat conductivity resistance, which is suitable for the door filling material, the ceiling and the partition or the car engine.

Jan 1, 2003

By F. M. Nakla

Various methods of Applied Mineralogy were used for determining the nature and composition of products yielded by flotation tests for Maghara coal beneficiation. Coal samples obtained from the Sa fa mine in Northern Sinai, Egypt, were crushed, sieved, &apos;and <32 mesh size fraction was cleaned by froth flotation. Experiments were conducted to determine the effect of certain parameters on beneficiation of Maghara coal by flotation. The investigated factors included nature of frothing and/or collecting reagents, pH value of the medium, particle size distribution in the head sample, and pulp density of the coal slurry. The quality of head samples, coal concentrates, and tailing products were determined by chemical analysis, microscopic study, x-ray diffraction analysis, and occasionally by infrared (IR) absorption spectroscopy.

Jan 1, 1989