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By Kang-In Rhee

Nonferrous metal recycling not only provides energy saving and environmental benefits but also is a significant factor in the supply of various types of metals used in our society. Recycling plays an important role in establishing the sustainability of materials. The total amount of recycled nonferrous metals by weight accounts for less than 5% but their value is larger than 50% compared to ferrous metal recycling which consists of about half of the total metal recycling in weight. This paper describes trends and typical achievements in nonferrous metal recycling and overviews the present and future of nonferrous metal recycling technology and business in Korea.

Jan 1, 2006

By Geoffrey S. Plumlee

The Summitville gold mine, located in southwestern Colorado, received tremendous publicity in the 1980's and 1990's for leaks of cyanide solutions from its heap leach facility. As is typical with cyanide spills, real time, geochemically rigorous assessments of the environmental effects were not performed. Past United States Geological Survey (USGS) research used simple mixing experiments to model the influx of alkaline cyanide heap leach solutions from Summitville into a nearby stream, whose waters were highly acidic due to severe acid-rock drainage (ARD) from the mine. These experiments indicated WAD cyanide rapidly degraded due to formation of Fe-Cu-CN solids and lesser HCN volatilization. The alkaline heap leach solutions also precipitated hydrous iron-and aluminum, oxides and hydroxysulfates (iron and aluminum 'supplied by the acid. rock drainage (ARD]), which then sorbed copper and other heavy metals from the ARD. These results indicate that mixing of cyanide heap leach solutions with ARD may be a cost-effective remedial method at mine sites where treatment of both is required. New experiments are currently in progress to further refine a potential remedial process.

Jan 1, 1998

By Dimitrios Fillippou

Magnesium hydroxide is used in a number of industrial applications, from the neutralisation of acid effluents to the production of pharmaceuticals. High-quality magnesium hydroxide powders can be produced by hydrating slow-reacting magnesia in dilute magnesium acetate solutions. The process of magnesia hydration shows many similarities with a typical hydrometallurgical leaching operation; however, its kinetics are crucial not only for process design and control, but also for the production of powders with a desirable particle morphology. This article shows the results of an experimental work whereby industrial heavily-burned magnesia powders were hydrated in 0.01 to 0.1 mol/L magnesium acetate solutions at temperatures ranging between 333 and 363 K. Examination of the magnesium hydroxide produced and the analysis of the kinetic data suggest that the hydration of heavily-burned magnesia in magnesium acetate solutions is a dissolution-precipitation process controlled by the dissolution of magnesia particles. The activation energy was estimated to be 60 kJ/mol, while the reaction order with respect to magnesium acetate concentration was found to be about one.

Jan 1, 1999

By James T. Skoch

With the ongoing pressure on the secondary aluminum business to limit the amount of waste generated from processing aluminum dross, it becomes very advantageous to preprocess the dross to reduce waste. The advantage of preprocessing is that it significantly reduces the oxides and salt cake generated when melted. Various products can be produced from the oxides for the steel industry. The following paper will demonstrate that removal of oxide fines before melting will result in large volumes of material not being landfilled. We will show that the end result of this technology is to significantly reduce the amount of salt cake sent to a landfill while maximizing the recyclability of the aluminum dross.

Jan 1, 1995

By R. N. O'Brien, E. Peters

"It has been discovered that copper concentrates can be leached in strong (40-60%) sulfuric acid with nitric acid, or with oxygen if nitric acid is present as a catalyst. Chalcopyrite is rapidly decomposed at temperatures well below the boiling temperature of the lixiviant (-150 C.) and the resulting copper and ferric salts are precipitated as CuS04.H20 and FeH(S04)z.4H20. Other metal sulfides such as zinc, lead, nickel, etc. are also converted to sulfates that are nearly insoluble. Sulfur is partially converted to elemental and partially to sulfuric acid. Reduction products of nitric acid can be recovered from the distillate with good recovery. Conversion of as-received copper concentrates is largely complete in about 1 hour. Introduction9 molar sulfuric acid is an unusual hydrometallurgical lixiviant: it has a boiling point of about 150 C. and a low solubility for base metal sulfates. Below about 6 molar acid, the boiling point falls below 120 C. and yields much higher sulfate salt solubility, while above 12 or 13 molar acid and at higher temperature sulfuric acid becomes an oxidizing agent, yielding gaseous S02' Thus, sulfuric acid within this range of concentration is capable of acting well above the temperature of boiling water without requiring autoclave conditions, and if typical oxidative leaching conditions are applied to suspended mineral sulfide concentrates, it is possible to obtain a conversion of these sulfides into 'crystalline sulfates. Thereafter, the sulfates can be separated by filtration or by solid - bowl centrifuge and the solution can be recirculated to the reactor vessel. Meanwhile, the solid sulfates can be treated in a typical hydrometallurgical circuit, i.e., dissolved in a return stream that is essentially water, separated from each other by, for example, solvent extraction, and recovered as metals by electrowinning."

Jan 1, 1997

By Tianzu Yang, Weifeng Liu, Lin Chen, Wei Chen, DUCHAO ZHANG, HUI XIAO

Carbonaceous refractory materials are widely accepted in many reducing smelting processes such as iron and ferroalloys. Oxidizing processes such as copper concentrate smelting traditionally use magnesia and/or alumina/silica refractory materials. The main objection to the use of carbon-based refractories as the exposed working lining in oxidizing applications is the potential for free oxygen to react with the carbon at high temperature, which could rapidly degrade the refractory lining. In 2013, Outotec and GrafTech conducted joint trials of a thermally conductive, carbonaceous lining for smelting copper concentrates in the Outotec® pilot-scale top-submerged-lance (TSL) furnace in Dandenong, Australia. This testwork had two equally important goals; to demonstrate the ability of carbon refractories to withstand oxidizing process conditions, while ensuring that neither furnace operating conditions nor process stability were negatively affected by the refractory material. The paper discusses the input parameters of the trials, key observations during the testwork program, and the results and conclusions from both process and refractory design standpoints.

Jan 1, 2016

By K. Pagalthivarthi, P. V. Desai

"During solidification of alloys, many inter-related physical processes, such as melt convection, mass diffusion, heat transport, macrosegregation and melt-undercooling occur. Several research workers have studied one or more of these effects separately. To answer important questions on solidification behavior, an overall approach interrelating the processes is necessaryAs a first step toward accomplishing the overall modeling, the freezing of a binary liquid metal is examined. The various stages during freezing of the alloy are critically described to build a continuum model for the entire process. Diffusive mixture theory is used to write the conservation equations for the liquid and the mushy zones. The concept of local thermodynamic equilibrium in the presence of curvature effects is used to restrict the number of degrees of freedom within the mushy zone. Constitutive equations relating flux quantities and affinities, the governing differential equations and boundary conditions are discussed briefly for the freezing process.IntroductionA solidification study encompasses such facets as solifidication time, microstructure, macrosegregation of the solute, shrinkage effects and soundness of the casting. Influence of one or more of the coupled heat and mass transfer phenomena such as local solute redistribution, thermosolutal convection, melt undercooling at dendrite tips and heat dissipation to the ambient have all been previously examined [1-3J. Several studies have examined the individual facets of alloy solidification as isolated processses. In fact, the transport processes occur simultaneously and a comprehensive model should include their inter-relationships. In particular, some of the existing studies of the mushy zone [4-6J do not emphasize thermodynamic completeness. This work represents an attempt to develop a thermodynamically consistent model of the entire solidification process on physical grounds."

Jan 1, 1986

By S. M. Copley, M. Yankova, E. Y. Yankov, J. A. Todd

"Nanophased coupled growth structures, with spacings of -10 nm, have been observed in banded microstructures produced by laser melting hypoeutectic Ag-Cu alloys. These coupled growth structures comprised a Cu-rich phase of width - 1 nm and a Ag-rich phase of width - 9 nm. In this paper, microstructural observations of nanophased coupled growth structures in hypo eutectic AgCu alloys are presented. Laser beam velocities for the transition from banded to microsegregation free microstructures are modelled and compared with experimental values. Models are presented to show that, at a critical undercooling, initial growth of a Ag-rich, metastable, extended solid solution is rapid but slows to a halt as copper is partitioned into the liquid at the solid/liquid interface. Following nucleation, the coupled growth structure then grows until the partitioned copper is consumed, at which point growth of the Ag-rich solid solution is again accelerated. This cycle then repeats resulting in banded microstructures comprised of 750 nm of the Ag-rich extended, metastable solid solution, followed by 250 nm of the coupled growth structure.1. Structural Studies of Laser Melted and Resolidified TrailsPresented here are observations of laser melted and resolidified trails in Ag-Cu alloys obtained at beam velocities ranging from 0.7 to 34 cm S·I. When the laser beam is scanned along the surface (positive x-direction) with a velocity Vb a melt pool with the shape given in Fig. 1a moves with the beam. The isotherms move with the velocity, Vi,. = Vb cos.p. Calculations employing the thermal analysis of Kou, Hsu and Mehrabian [1] for the beam velocities of this investigation and for the thermal properties of AgCu alloys, indicated that, .p, the angle between the isotherm velocity and beam velocity should be small at the surface where microstructural studies were made. This prediction was supported by observations of trail cross-sections. Based on these observations, and the calculations which include latent heat effects, the isotherm velocity for observations near the surface in our investigation was taken to be 27 cm S-I."

Jan 1, 1994

By Shuichiro Okada

Various efforts to reduce energy consumption and smelting cost are made at Tamano Smelter. Production of anode copper has been increased by about 30 % and energy requirement has been decreased about 50 % respectively. Challenges toward more higher goal are being continued. Details about the following are described in this paper. 1 Waste heat recovery Steam recovery at up-take of FSFE Heat recovery from waste gas of anode furnaces 2 Application of tonnage oxygen 3 Application of pulverized carbonaceous fuels to the flash smelting furnace with furnace electrodes ( FSFE ) 4 Application of computer control system to copper smelting 5 Improvement of the fugitive gas collecting system 6 Improvement of the mechanical tuyere puncher for the converter furnace

Jan 1, 1983

By Qin Hua, Xiangru Chen, Qijie Zhai, Yongsheng Yan, Liang Chang

"In this paper, pure bainite ductile iron and their alloying form of 0.2wt% niobium were prepared by a controlled cooling heat-treatment. The effect of niobium alloying on the microstructure, hardness and impact toughness of bainite ductile iron was studied. The results show that adding niobium effectively improves the hardness and toughness of bainite ductile iron. The hardness and the impact toughness of niobium-alloyed bainite ductile iron were investigated by varying the temperature at which samples were fed to the incubator.IntroductionThere are two essential methods to prepare the bainite ductile iron: isothermal quenching [I-31, and alloying [4• 51• Isothermal quenching process is very time and energy consumable, concerned as a high cost technique for mass production. Besides, there are certain limitations on the size and shape of castings in this process. In addition, it potentially harms the environment. As for the alloying, Ni, Mo, and Cu have to be utilized to obtain bainite. However, the large demand and high cost of Ni makes it not feasible in practice.It is well known that niobium can promote the formation of carbon compound, and improves the stability ofundercooled austenite, which is preferred to the increase of the hardenability. Previous studies showed that niobium could refine the grain and improve the mechanical properties of gray cast iron [6-81 • Therefore, in the present work, the effects of niobium and the temperature at which samples were fed to the incubator on the microstructures and properties of niobium alloyed bainite ductile iron were investigated."

Jan 1, 2014

By Sergey Shabala

Green leaf tissues convert solar energy into the energy of chemical bonds of sugar molecules during the process of photosynthesis. The efficiency of this conversion can be much higher than efficiency of any of the currently known silicon-based solar panels. Importantly, vast amounts of CO2 are assimilated during this process. The efficiency of photosynthesis is critically dependent on the availability of a large number of nutrients, among which metal cations such as K, Ca, Mg, Cu, Zn, Fe, Mn, and Ni play a key role. In this paper I summarize basic requirements and major functions for each of these essential nutrients in plant photosynthesis, both at the whole-plant and molecular level. I will talk about how these requirements may be affected by the global climate trends and discuss the prospects of creating artificial photosynthetic “bioreactors” for efficient energy conversion and CO2 assimilation.

Jan 1, 2009

By Bradford H. Miller

Separation and Recovery Systems, Inc. (SRS) provides on-site waste minimization and resource recovery using its state-of-the-art MX-1500 centrifuge and MX-2000 thermal desorber. The MX-1500 can process over 450 feed tons of material per day, resulting in centrifuged cake containing 20% to 60% by weight. The MX-2000 is a hollow-flite thermal processor indirectly heated by either steam or hot oil. SRS has dewatered and/or deoiled over 1,000,000 feed tons of material in the refining, chemical, and energy industries using the MX-1500. SRS estimates that over 300,000 barrels of reusable oil have been recovered from that material. Additionally, SRS has dried and/or detoxified over 150,000 wet tons of solids or soil to regulatory or customer-specified limits using the MX-2000.

Jan 1, 1994

By H. Ipek

In this study the effects of interstitial ratios on k-feldspar samples were investigated. The k-feldspar samples were taken from Egypt using dry batch grinding conditions and a kinetic model. Three different mono size fractions (-3350+2360, -850+600 and -300+212 µm) were ground separately for 0.5, 1, 4, and 8 minutes and at four different interstitial ratios (125%, 100%, 75% and 50%) using a Bond mill with a mixture of five ball sizes. The mill used was at a size of 30.5 cm diameters, with 30.5 cm length, providing a total mill volume of 22272 cm3. The mill has a total mass consisting of 22648 g. steel ball mixtures of 38.10, 31.75, 25.40, 19.05 and 12.70mm diameters, occupying 22% of mill volume. The mill rotates at a speed of 70 rpm. The weights of the feed charges were 3000, 2000, 1000, and 500 g for 125%, 100%, 75% and 50% filling of the interstices of the balls respectively. The specific rate of breakage (Si) was determined from the top size fractions at different grinding times that were mentioned above and the model parameters were compared for the four different powder filling ratios (U). In many investigations, it has been found that an interstitial filling ratio of U = 0.6-1.1 is a good powder ball loading ratio to give an efficient breakage in a ball mill. In this study, it was found that U=1.25 is a good ratio for K-Feldspar.

Jan 1, 2006

By Yves Fautrelle, Kader Zaidat, Hervé Combeau, Miha Zaloznik, Mohammed M'Hamdi, Bachir Saadi, Xiaodong Wang, Knut Omdal Tveito

"Numerical simulations of macrosegregation formation during horizontal solidification of a hypoeutectic Sn-Pb alloy in a rectangular cavity is presented and compared to experimental results. The experiment involves a melting phase, a holding stage at constant temperature with/without application of electromagnetic stirring, and finally solidification. We simulate all stages of the experiment and study the segregation of Pb throughout the experiment. A twophase volume averaged model is used for the numerical simulations, accounting for thermosolutal convection and assuming perfect microscopic mixing (lever rule). The influence of the melting phase and the electromagnetic stirring is studied with different cases to illustrate the consequences on the flow pattern and Pb segregation. The numerical simulations are compared to the experimental data and the impact of chemical inhomogeneities prior to solidification on macrosegregation formation is discussed.IntroductionMany extensive investigations have been performed so far on the solidification of metallic alloys. However, the melting process of metallic alloy has not attracted attention in a same manner. Nevertheless, melting of alloy may put forth peculiar effects as described in the present paper. It has been observed from a benchmark experiment [1, 2] that significant stratification might arise during the melting process of Sn-Pb alloy. That effect was put forth thanks to the analysis of the experimental temperature distribution which indicated that the convective fluid flow was almost zero. The effect was enhanced when the lead composition was higher (above 6wt.%). The present paper is aimed at confirming that the melting of an alloy containing a heavier solute may be accompanied with a stratification of the solute which exerts a stabilizing effect on the convective fluid flow. Results obtained from numerical modeling are compared with experimental data obtained from the benchmark facility."

Jan 1, 2012

By C. M. F. Vieira

Crushed fired brick waste, known as grog, screened at two different particle size, 840 (20 mesh) and 180 µm (80 mesh), was used in mixtures with clayey body to make typical red ceramics for bricks. The effect of the grog addition up to 20 wt.% on the properties of bricks fired at 700oC was evaluated. The results indicated that both the particle size and the amount of grog addition changed the fired properties of the clayey body. Additions above 5 wt.% of grog, with a coarser particle size, decreased the mechanical strength of both the dry body and the fired ceramic pieces. By contrast, grog with a finer particle size may be used up to 10% wt. without deteriorate the properties and corresponding microstructure of the clayey body.

Jan 1, 2009

By John E. Litz

The Denver Process is a chemical/metallurgical process for treating radioactive or mixed wastes by extraction and concentration of the radioactive and/or hazardous component(s). The process was developed at bench scale, evaluated at pilot scale, and will be implemented at full scale to remediate a low-level radioactive sludge. Six unit operations comprise the process: feed handling, leaching, solvent extraction, electrodeposition, precipitation, and tailing preparation. Unit operation design may be modified to tailor the process for varying feed stock composition. Radioactive or mixed waste is reacted with aggressive reagents in an aqueous phase, solubilizing targeted components. These components are then selectively extracted and concentrated in subsequent steps. Waste solids and solution exit the process as non-hazardous non¬radioactive waste. Dehydration of aqueous waste by submerged combustion eliminates aqueous discharge.

Jan 1, 1994

By Yongqi Sun, Zuotai Zhang

Hot slags, at the temperatures of 1450-1650 oC, carry a substantial amount of high quality thermal energy, which represents the largest undeveloped energy source in the steel industry. However, the waste heat recovery rate in China is less than 2%; thus there is a great potential of waste heat recovery. In this study, we investigated a chemical method to extract the waste heat from high temperature blast furnace slags, i.e., sludge gasification. Sewage sludge, another substantial waste produced in the municipal system, need to be timely disposed, the organics of which could be gasified using the waste heat in the slags for the purpose of syngas production. Both the kinetics and thermodynamics of the sludge gasification process were clarified here. Most importantly, an integrated system composed of multiple systems such as the steel industry, the cement industry, the municipal system and the chemical engineering industry, was analyzed in this study.

Jan 1, 2016

By Pinakin C. Chaubal

Today?s steel industry is in a vibrant and resurgent mode. This transformation has been in the making for some time now. Over the last few decades, the industry was steadily transforming itself into becoming a high tech industry. New technology was adopted, efficiencies were enhanced, lean manufacturing concepts were brought in and a strong customer focus was developed. Today?s mills employ sophisticated instrumentation, computerized monitoring, on-line smart systems etc. driving processes that are producing at rates of many tons/minute. All this is not possible without judiciously using the latest available technologies in various fields and developing a more sophisticated work force. Prof. Sohn has been a pioneer in driving the concept of process engineering in process metallurgy. In this paper the focus is on some aspects of process engineering ? primarily process modeling - as applied to iron and steelmaking processes. Examples are shown to demonstrate how problems have been addressed. Some thoughts on future directions are presented.

Jan 1, 2006

By P. Gray

Process and engineering development of the Warner Zinc Process over the past two decades has proceeded alongside the world-wide collection and analysis of operating and cost data of current processing practices from sulphide ores to refined metals. Study of these data shows that recoveries are dependent on mineralogical characteristics of the sulphide matrix and point to the inadequacy of differential flotation as a tool for preparing feed for smelters. The paid-for return at the mine on the combined metal values in zinc rich sulphide ores rarely exceeds 80% and increasingly runs as low as 50-60%. Surveying the possible alternative ways of improving these performances leads to the conclusion that the Warner Process is the only technology in sight that could meet a target of 90% paid-for recovery and that its development has now reached a point where it can be a fully practicable process for all mixed sulphide ores.

Jan 1, 2000

By P. R. Khangaonkar

The variety of intermediates, middlings, complex materials and wastes produced in the conventional processing of tin ores as experienced in the tin industry in South East Asia is reviewed. The problems associated with the treatment of these materials so as to produce useful products by hydrometallurgical or pyro-cum-bydrometallurgical approaches are discussed. Results of treatment of amang middlings consisting of cassiterite, struverite, ilmenite, zircon, monazite etc by chlorination with carbon tetra chloride are presented. The efforts to leach tin without letting iron coming in, by alkali leaching of certain wastes of tin processing are also briefly indicated. It is felt that pyro-cum-hydrometallurgical approach can help a viable treatment of these materials so as to obtain usable or value added products.

Jan 1, 1994