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By Reza Kamali, Mohsen Bashiri, Hadi Fanisalek

"Nomenclature: A: area (m2), C: heat capacity (WIK), cp: specific heat (J/Kg K), d: internal tube diameter (in), F: correction factor for multi-pass and crossflow heat exchanger, h: convective heat transfer coefficient (W/m2K), k: thermal conductivity (W/mK), L: length (m), m: mass flow rate (Kg/s), W: flow rate, N: number, Q: heat rate (W), R: thermal resistance, T: temperature (°C), U: overall heat transfer coefficient (W/m2K), ;1,,P: pressure drop (Pa), ;1,,T: temperature difference (°C), p: density (lb/ft3), N: number of tube passes, U,: velocity in tubes, iJh: head loss in feet of flowing fluid, Up: velocity in the pipe leading to and from the heat exchanger (ft/sec), µ: viscosity ( cp ), Llpf frictional pressure loss (psi/l 00 equivalent ft of pipe) Subscripts: b: baffle, c: cold, cf counter flow, ex: exchanger, f: fouling, h: hot, i: inlet-inner, ib: inlet baffle, lm: logarithmic mean, m: mean, o: outlet-outer, s: shell, t: tube, w: wall AbstractThe main bottleneck for primary aluminum production industry is dealing with a huge amount of input energy. The fact is that part of provided energy to aluminum production smelters will be lost as waste heat and it never used for aluminum production. One part of waste heat is escaping from the potroom exhaust gases, which was studied for possible recovery in a desalination plant to produce distilled water and the paper was presented in 2011 TMS Annual Meeting. However, it was shown that waste heat recovery plant to produce distilled water is highly profitable but the main fact is that the exhaust gases from potroom are highly corrosive, abrasive and dusty. The main challenge for desalination plant construction, which is using aluminum smelter exhaust gases as the main heat source, is the highly corrosive environment that makes the situation difficult and complicated for equipments design and plant construction. In this paper, we are trying to study a detailed investigation regarding the heat exchangers fouling, corrosion in heat exchangers including heat exchangers' material, how often we need to shut down the plant for maintenance or cleaning, and plant thermal efficiency with considering fouling."

Jan 1, 2012

By Xiangwen Wang

Electrodeposition of lead metal from high purity brine electrolytes containing lead chloride (PbCI,) was conducted so as to assess the feasibility of electrowinning lead-metal directly from aqueous chloride electrolytes. Tests were performed at 65 and 80°C (338 and 353°K). Characteristic features of the deposits, on both lead and graphite substrates, were correlated to operating parameters associated with: electrolyte temperature, current density and total lead- concentration. Photomicrographs of these morphological features were obtained by use of Scanning Electron Microscopy (SEM).

Jan 1, 1993

By D. P. Cook, Jr. Jones, J. W. Evans

"It is well understood that the flow of liquid metal in the mold region of the caster can have a notable effect on the overall solidification behavior in aluminum casting. Previously our group has characterized the flow in this region in a water model, using particle imaging velocimetry. The flow is significantly effected by the specifics of the metal delivery system, i.e. size, geometry, used during the cast. Recently, a time-averaged 3D numerical model of the nozzle, combo bag and sump region has been developed and its validity has been tested against experimental data. Cases were run for different sized combo bags as well as bags that have been blocked. The results show satisfactory agreement between the physical and mathematical models.IntroductionFluid flow in the head of an electromagnetic (EM) and direct chill (DC) ingots has been shown to effect many important operational parameters in casting such as superheat removal, macrosegregation, and hot cracking. In most cases, the momentum from the nozzle is diverted through a delivery system, termed a bag, before entering the mold region. The specific geometries of the bags vary widely from operator to operator suggesting that there is still some question as to the optimum design. Several studies [1-4] have been carried out to understand the influence of the bag design on the solidification behavior in aluminum casters. However, few studies have included numerical prediction with experimental verification. Unfortunately, many simulations performed today still do not accurately account for flow in such devices.Recently, a significant amount of research into the flow resulting from the metal delivery systems has been performed [5-8]. The thrust of this research has been characterizing the flow patterns by a measurement technique called particle imaging velocimetry. The data suggest that the method of delivering the liquid metal into the mold region has a significant effect on the nature of the flow. With a detailed set of quantitative data from a water model, a numerical model can be built and tested to ensure a proper description of the flow field. The computational model used in these simulations is designed to represent a laboratory scale model of a caster in which ""combo"" bags were simulated. Such bags are mostly of a densely woven glass fiber material with low permeability to aluminum. ""Windows"", of a more open weave, permit aluminum to flow from the bag, see Fig. I. Two different sized combo bags were modeled, each subject to two different outflow window configurations. Furthermore, experimental measurements [9] were used to validate the model results."

Jan 1, 1999

By SIMON TIMBILLAH

The chalcopyrite-molybdenite (Cu-Mo) flotation industry is increasingly turning to organic depressants as suitable replacements for inorganic reagents, such as NaHS, due to environmental and safety concerns as well as high consumption rates of the inorganic reagents. This presents an opportunity for improvements or design and synthesis of alternative reagents. Disodium carboxymethyl trithiocarbonate (Orfom® D8) depressant is an organic depressant with a carboxylate group on one end and a trithiocarbonate group at the other end. Fundamental results are shown regarding the interaction of the Orfom® D8 depressant in the bulk flotation of a Cu-Mo concentrate from an operating North American mine. Cyclic Voltammetry on pure copper and Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS) measurements on pure chalcopyrite with Orfom® D8 depressant treatment are also reported. Through such characterization techniques a potential adsorption mechanism of Orfom® D8 on the mineral surface was identified and its depressant characteristics in the Cu-Mo flotation systems explained.

By Zhaohui Xie, Bin Xu, Qian Li, Yongbin Yang, Tao Jiang

A high carbon low-grade gold ore, in which gold mainly occurs in carbonaceous matters, is a typical refractory gold ore whose conventional cyanide leaching extraction is only 12.9 %. In this paper, by the process of flotation-roasting-leaching, gold was effectively enriched and extracted. The flotation results showed that the enrichment ratio of gold was relevant to that of carbon, indicating that gold occurred in close association with carbon. A concentrate containing gold 7.26 g/t and carbon 12.37 % was obtained, with gold recovery 83.10 % and carbon recovery 90.24 %. Subsequently, the roasting of flotation concentrate favorably made the removal rates of carbon and sulfur reach 99.81% and 98.79%, respectively. After roasting, the gold in the roasted product was further enriched to 29.70 g/t and the optimal gold cyanide leaching extraction reached 93.66%.

Jan 1, 2015

By Batric Pesic

Reactions of metallic iron were studied in several different aqueous solution systems: water, medium salt solution used for the growth of T ferrooxidans, ferric iron solution and solution containing T ferrooxidans. Each system was studied under abiotic and biotic conditions in the presence of T ferrooxidans and as a function of pH, particle size of iron powder, temperature, ferrous and ferric iron concentrations. It was found that metallic iron reacts with water differently than does with ferric iron in water. Surprisingly, T ferrooxidans were non-functional in the dissolution of metallic iron. Also, the reactions of metallic iron with pure water were indistinguishable from the reactions with water containing medium salts for bacterial growth. The reactions with ferric iron were also independent of medium culture compounds. The mechanisms of metallic iron reactions with ferric ions are different from the mechanisms of metallic iron reactions with water.

Jan 1, 2001

By F. Shahbazian

attempt to systematize the knowledge on slag viscosities, the present work was carried out. The Among the physical properties of slags, viscosity is very important in understanding the mass out in the temperature range 1438-1762 Q The rotating cylinder method was used in the viscosity measurements. Crucibles and spindles made out of pure iron were employed. The transfer phenomena in metallurgical processes. The viscosities of fayalitic slags are of great interest in the non-ferrous metal industry, with special reference to copper production. In an slags were prefused before the measurements. In order to take into account the vaporization reactions involving CaF2, pre- and post measurement samples of the slags were chemically analysed and the compositions were ascertained. The results show that in the case of the CaO-SiO2 system, CaF2 additions tend to decrease the viscosity, in accordance with the expectations. In the case of the "FeO"-SiO2 system, at higher "FeO" / SiO2 ratios in the slags, a reverse trend was observed. The results are discussed on the basis of a viscosity model for silicate melts developed in the present laboratory as well as the structural considerations of silicates.

Jan 1, 2000

By KNona C. Liddell

Goethite is an important naturally occurring sorbent for divalent heavy metals and has often been used as a model compound in studies of adsorption on oxide mineral surfaces. Surface complexation modeling, surface spectroscopy, and electrochemical techniques have all been applied to goethite adsorption. Modeling studies have shown that usually several different sets of fitted parameters are equally successful in representing surface charging and adsorption data. Surface spectroscopic data are proving valuable in determining the nature of the surface sites, and refined models now incorporate structural information on interatomic distances and coordination numbers. Multisite surface complexation models can give very good fits to surface charging and adsorption data, but further improvements are needed to better represent surface reactions involving exchange of protons and divalent cations. Recent experimental and modeling studies on adsorption of divalent transition metals on goethite are described and the present status of the field is assessed.

Jan 1, 1999

By Mehmet Bu daycı, Onuralp Yücel, Ahmet Turan, Murat Alkan

In this study, iron based alloys (Fe, Fe-Cr-Ni-Mo, etc.) were produced by using metallothermic methods starting from Mill Scales obtained continuous casting processes. During the process, the combustion was realized by ignition and the produced wave propagates throughout the reactant mixture yielding the desired product. In this work, Mill scale used as an iron source, which includes +2, +3 values iron oxides. Aluminum, Magnesium and Silicon were used as reductants. In these metallothermic experiments, different ratios of reductants were examined, and their effects on the metal recovery and alloy compositions were investigated. The samples were characterized by using chemical analysis (AAS), XRD and XRF techniques.

Jan 1, 2016

Achieving continued economic growth with social equity within the natural limits of the Earth's 'eco-systems is the major issue facing the world today. The material and energy needs of the world cannot be met with the current ways of addressing this issue. The need for metals, an important class of materials, will continue into the future because their unique properties make substitution by other materials impossible in many applications and this need will continue to be met from primary metal production and recycling. However, the recycling rate will increase and the usage pattern of metals will change to reflect the environmental impact of their production and use. Pyrometallurgy has an important role in meeting the metal needs of the future since some metals can only be produced pyrometallurgically; the energy required to produce some metals pyrometallurgically is significantly less than by other methods; most metals are most efficiently recycled pyrometallurgically; and the release of harmful and toxic elements into the biosphere can sometimes best be controlled through pyrometallurgical processing. The development of strategies for pyrometallurgical processing for the future lies in the recognition that sustainable development calls for large step improvements in value delivered per unit of environmental impact over the entire supply chain. Pyrometallurgists can respond to this challenge by contributing to reducing the environmental impact of meeting metal needs using three broad strategies: "end-of-pipe" approaches to convert emissions into benign materials for storage or disposal; flowsheet redesign to limit or eliminate emission production; and improved recycling technologies. A number of examples are discussed to illustrate how the sustainability driver is already influencing the technological development of pyrometallurgical processes, and how these will develop further as the sustainability driver strengthens.

Jan 1, 2003

By W. K. Rankin

Achieving continued economic growth with social equity within the natural limits of the Earth's eco-systems is the major issue facing the world today. The material and energy needs of the world cannot be met with the current ways of addressing this issue. The need for metals, an important class of materials, will continue into the future because their unique properties make substitution by other materials impossible in many applications and this need will continue to be met from primary metal production and recycling. However, the recycling rate will increase and the usage pattern of metals will change to reflect the environmental impact of their production and use. Pyrometallurgy has an important role in meeting the metal needs of the future since some metals can only be produced pyrometallurgically; the energy required to produce some metals pyrometallurgically is significantly less than by other methods; most metals are most efficiently recycled pyrometallurgically; and the release of harmful and toxic elements into the biosphere can sometimes best be controlled through pyrometallurgical processing. The development of strategies for pyrometallurgical processing for the future lies in the recognition that sustainable development calls for large step improvements in value delivered per unit of environmental impact over the entire supply chain. Pyrometallurgists can respond to this challenge by contributing to reducing the environmental impact of meeting metal needs using three broad strategies: "end-of-pipe" approaches to convert emissions into benign materials for storage or disposal; flowsheet redesign to limit or eliminate emission production; and improved recycling technologies. A number of examples are discussed to illustrate how the sustainability driver is already influencing the technological development of pyrometallurgical processes, and how these will develop further as the sustainability driver strengthens.

Jan 1, 2003

By Norbert Patzeh

The demand for nickel is growing and will continue to do so for the foreseeable, future. This will make the construction of new leaching and smelting plants necessary. This paper described a number of possible alternative processes. The first projects with new technology are currently undergoing trials and feasibility studies. Experience from other industrial sectors and from existing plants is being incorporated into these investigations. The question is, to what extent the old nickel producing concepts will continue to be applied in the future. Keywords: Latcritc, rotary kiln, cyclonc rcactor, dust processing

Jan 1, 2004

By Mark Jolly

"Instead of using the traditional batch casting process, the CRIMSON [1] (Constrained Rapid Induction Melting Single Shot Up-Casting) method employs a high-powered furnace to melt just enough metal to fill a single mould in a closed crucible. The crucible is transferred to a station for computer-controlled counter gravity filling of the mould for optimum filling and solidification. The CRIMSON method therefore holds the liquid aluminium for a minimum of time drastically reducing the energy losses attributed to holding the metal at temperature. With the rapid melting times achieved, of the order of minutes, there isn’t a long time at temperature for hydrogen to be absorbed or for thick layers of oxide to form. The metal is never allowed to fall under gravity and therefore any oxide formed is not entrained within the liquid. Thus higher quality castings are produced leading to a reduction in scrap rate and reduced overall energy losses.IntroductionEngineers at the University of Birmingham, England, with local company, NTec, have invented a new casting process that will reduce the energy costs of light-metal foundries. The technology, entitled CRIMSON, means that foundries need only heat the quantity of metal required to fill a single mould rather than large batches that use unnecessary energy and create waste. The complete concept of CRIMSON requires a change of philosophy in the approach to casting and requires the user to think holistically in order to reap the full benefits from the process. This paper will discuss the various aspects of energy wastage within the foundry sector and discusses the processes whereby the energy can be reduced. Primarily the author focuses on the aluminium sector but CRIMSON can be applied to many of the non-ferrous “light” alloys. Ferrous materials and non-ferrous “heavy” alloys can also benefit from some of the ideas but not necessarily directly from the application of CRIMSON."

Jan 1, 2010

By Khandaker M. Anwar Hossain

This paper presents the development of lightweight concrete (LWC) incorporating pumice aggregate and volcanic ash (VA) based ASTM Type I blended cement (PVAC). Fresh and mechanical properties of LWC mixtures such as slump, air content, compressive strength, tensile strength, density and modulus of elasticity are described. The durability characteristics are investigated by drying shrinkage (DS) and water permeability. The investigation suggests the production of LWCs incorporating blended PVAC and VPA having satisfactory strength/durability characteristics for structural applications. The use of PVAC induces the beneficial effect of reducing drying shrinkage and water permeability. Development of such non- expensive and environmentally friendly LWCs with acceptable strength and durability characteristics is extremely helpful for the sustainable development and rehabilitation of volcanic disaster areas around the world.

Jan 1, 2010

By K. S. Kumar

FLS miljø, Inc. markets, designs and supplies particulate collection devices for dusts, fumes, and mists; In this paper, the application of both wet and dry electrostatic precipitators (ESPs) in smelting, and roasting plants is discussed.

Jan 1, 1998

By M. W. Kennedy

Prediction of the thermal duties of copper coolers in freeze lined furnaces is challenging. Where copper coolers are immersed in liquid slag the heat transfer is often defined by a natural convection cell immediately adjacent to the wall, in the absence of other factors producing forced convection. Slag coolers are typically not fully immersed, slag temperature, liquidus and superheat can vary, and bath levels may change significantly with batch tapping, leading to substantial variations in radiation heat fluxes. Radiation heat transfer is discussed with reference to the non-obvious impact of slag liquidus on radiation losses in the exposed cooler sections. Reference is made to literature and the results of analytical and FEM models.

By Yimin Ruan

"An inverse design method is developed to obtain the optimal cooling conditions for the continuous quenching of precipitation hardenable sheet alloys to achieve the required yield strength. The yield strength of a precipitation hardenable alloy is obtained by allowing solute to enter into solid solution at a proper temperature and rapidly cooling the alloy to retain the solute in the solid solution. An aging process may be needed for the alloy to develop the final mechanical properties.The objective of the design is to optimize the quenching process so that the required yield strength can be achieved. With the inverse design method, the required yield strength is specified and the sheet thermal profile at the exit of the quenching chamber can also be specified. The conjugate gradient method is used to optimize the cooling boundary condition during quenching. The adjoint system is developed to compute the gradient of the objective functional. An aluminum sheet quenching problem is presented to demonstrate feasibility of the inverse design method.IntroductionQuenching is a critical step in metal production to achieve desired material properties, such as yield strength, hardness, etc., for precipitation hardenable alloys. In most cases, rapid quenching from the solution heat treatment temperature is necessary to obtain the required material properties, but rapid quenching may cause other problems such as excessive distortions of the quenched materials.In a solution heat treatment, the alloy is heated to a suitable temperature, held at that temperature to allow the soluble alloying elements to enter into the solid solution, and cooled rapidly (quenching) to retain the alloy elements in the solid solution. An aging process, which controls precipitation of fine particles at room (natural aging) or elevated temperatures (artificial aging), is generally followed after the quenching process to develop the final mechanical properties of the heat treated alloys."

Jan 1, 1998

By C. Alexandru Sonoc

Donnan Dialysis uses ion exchange membranes to extract and separate cations. The driving force is provided by differences in chemical potential, rather than by electric fields or pressure. A Donnan Dialysis based process to recover lithium, nickel, cobalt, manganese, and organic acid lixiviant from recycled lithium ion battery cathodes is under development. In this paper we present a model of Donnan Dialysis and results of simulations of the aforementioned process. The simulations show that 170 m2 of membranes can process 1000 L of leachate ([Li+] = 0.285 M, [Co2+] = [Ni2+] = [Mn2+] = 0.095 M, pH 2) in two days and recover 94.1% of the lithium (as lithium carbonate), 99.4% of the transition metals (as mixed sulphates ready for solvent extraction), and all of the organic acid using 423 mol of H2SO4 and 268 mol of KHCO3.

By D. Lambert

Process modeling for large deformation metal forming processes has been developed into a very successful tool in commercial applications during the last two decades. DEFOR.MTM is a well-known metal forming process simulation program used by many industrial and research institutions. Recent developments include the ability to model multiple deforming body behavior during multi-pass pack rolling and microstructure prediction during multi-pass shape rolling. This paper summarizes how DEFOR.MTM can be applied to a number of rolling processes and briefly describes preliminary work carried out using the ALE technique. Keywords: Simulation, Rolling, Pack, Shape, Microstructure, FEM, ALE, Tantalum

Jan 1, 2003

By Sergio N. Monteiro

Jute fiber reinforced polymer composites are among the most investigated and applied natural composites. In this past decade the mechanical properties of these composites has been assessed for various types of test conditions. However, the reported results correspond mainly to short-cut jute fiber composites, which do not present the highest mechanical strength as compared to continuous fibers of the same kind. In order to complement these results, the present work evaluated the mechanical behavior, by means of flexural tests, of polyester matrix composites reinforced with continuous jute fibers. Bend tests were conducted in standard specimens with up to 40% of jute. Fracture analysis by SEM displayed the rupture mechanisms. The results showed an improvement in some flexural properties with incorporation of jute fiber. However, a low fiber/matrix interfacial stress was responsible for limitation in the values attained by some properties.

Jan 1, 2010