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By Gregor Kücher

Lack of basic knowledge on the semi-direct recycling methods for hard metals hinders the application on an industrial scale. However, advantages like reduced expenses and lower environmental impact draw interest at future potentials. Consequently, this report aims to offer insight into the influence of varying bulky hard metal substrates during their lixiviation in acidic media with an oxidant. The statistical software Modde 11 assisted in the development of a design of experiments (DOE) for evaluation of the impact of average grain size, binder and tantalum carbide (TaC) content on the leaching characteristics. The other experimental parameters were constant. Among them were temperature, solution concentration and quantity, duration and substrate surface exposed to liquid volume. Eventually, prediction plots and factors of the computed model equation describe the effects of varying substrate qualities on leached binder metal and selectivity.

By B. Q. Li, H. C. de Groh, X. Lu

"A fully 3-D, transient finite element model is developed to represent the magnetic damping effects on complex fluid flow, heat transfer and electromagnetic field distributions in a metallic melt. The model development is based on our in-house finite element code for the fluid flow, heat transfer and electromagnetic field calculations. The numerical model is tested against numerical and experimental results for water as reported in literature. Various numerical simulations are carried out for the melt convection and temperature distribution with and without the presence of a transverse magnetic field. Numerical results show that magnetic damping can be effectively applied to stabilize melt flow, reduce turbulence and flow levels in the melt and over a certain threshold value a higher magnetic field resulted in a greater reduction in velocity. Also, for the study of melt flow instability, a long enough running time is needed to ensure the final fluid flow recirculation pattern. Moreover, numerical results suggest that there seems to exist a threshold value of applied magnetic field, above which magnetic damping becomes possible and below which the convection in the melt is actually enhanced.1. INTRODUCTIONThe imposition of a DC magnetic field on a moving, electrically conducting fluid, such as molten metal or semiconductor melt, produces an opposing Lorentz force that results in a reduction of flow velocity in the liquid. This effect has been explored in both the semiconductor and metals industries to control natural convection and/or surface tension induced Marangoni convection as well as thermally induced flow instability during solidification processing of these melts [1-6]. A mathematical model can be of great use in developing both fundamental understanding of the fluid-magnetic field interactions in these magnetically-assisted processing systems and basic guidelines for process design, control and optimization.This paper presents a 3-D mathematical model for magnetically damped fluid flow and heat transfer in a melt cavity, which is useful for interpreting results for unidirectional solidification processes at slow solidification rate, and some preliminary results concerning the magnetic damping effects on the flow instability in the melt. The model development is based on the finite element solution of the Navier-Stokes equations, energy equations and equations for induced electric field. The model is tested against reported results and is then applied to study the fluid flow and thermal distribution in the metallic melt with and without an external magnetic field."

Jan 1, 1999

By Sanaz Mosadeghsedghi

The feasibility of the application of electrodialysis in separation of light and heavy rare earth elements (REE) in synthetic solutions was investigated. The experiments were carried out using single and binary solutions of a light (cerium) and heavy (ytterbium) REE. The effects of electrical voltage, electrical current, and the addition of complexing agent (EDTA) to increase the separation selectivity were investigated. Separation of Ce and Yb was achieved in binary solutions with and without the addition of EDTA. Higher degrees of separation were seen at higher voltages. Ce–Yb separation was more significant in the presence of EDTA. The separation factor of Ce–Yb and Ce–Yb-EDTA were 1.44 and 2.60, respectively.

By T. A. Venugopalan

The 'Hall-Heroult' Process of reduction of Alumina to Aluminium has remainded basically the same for over 100 years, but the technology has been undergoing drastic changes with respect to selection of materials for Cathode and Anode, and also energy consumption. The latest generation pots have a working life of about 1800-2000 days normally. After the failure of the pots, the Cathode Lining is dug out and disposed of on land. Since the lining contains objectional materials causing pollution, various processes have been tried for re-processing of this waste. However, most of the processes have been unsuccessful from the techno-economic point of view. At Hindalco a new chemical process for converting the fluorine values of the dug out material to Cryolite was developed in 1988 and a" one ton per day Cryolite production plant has been operating since 1989. This process is especially applicable where the integrated Alumina and Smelter Plants exist side by side. The experience in operating this Plant is discussed in detail in the paper.

Jan 1, 1992

By Junji Shibata

Zeolite synthesized from coal fly ash has many intelligent properties such as cation exchange, adsorption, catalyst and so on. The suitable use of the zeolite, however, is not established in an actual commercial scale yet. From the viewpoints of an effective usage of coal fly ash and the zeolite obtained from coal fly ash, we propose the new concept for environmentally friendly usage of zeolite, in which coal fly ash safely returns to the soil with growing plants and purifying wastewater. This method can make great contribution to recycle of coal fly ash, to purification of high nutritious water and to tree planting.

Jan 1, 2002

By Richard Elliott

Current methods for producing low-carbon manganese alloying materials for the steel industry are energy intensive and costly. To enable wider implementation of high Mn steel alloys, a novel solid-state Mn ore reduction strategy is therefore being investigated. This solid-state process, modelled on existing Direct Reduced Iron technology, employs a methane-containing atmosphere to reduce Mn ore pellets to a metal carbide. These pellets may then be smelted, yielding a Mn-rich master alloy. It is well established that CH4 is a suitable reductant for Mn ore powders; however, the reduction behaviour of industrially relevant Mn ore pellets by CH4 is poorly understood. The present work reports the results of an investigation undertaken to address this knowledge gap. The results of this study highlight the significantly different reduction behaviour exhibited by the Mn ore pellets relative to the ore powder under similar conditions and suggest that the diffusion of CH4 into the pellet interior is the limiting factor in achieving complete reduction.

By M. Tamura, K. Fujita, K Shinozuka, H. Daimon, H. Esaka

"In-situ observation of unidirectional solidification using transparent substance has been performed to investigate the growth direction of solid phase. Cell or dendrite of which preferred growth direction is not parallel to the heat flow direction was observed with various solidification conditions. Dimensionless growth direction (p) changes from 0 to 1 with increasing growth velocity at a constant temperature gradient. Introducing the dimensionless growth velocity, the relation between p and growth condition could be correlated.IntroductionTransition in macroscopic solidified structure from chill to columnar zone which is found in normal castings takes place via grain selection1). Cast products such as turbine blades are unidirectionally solidified, grain selection plays an important role to choose suitable crystals which have reasonable orientation in the region called ""starter"", which is a very initial part of casting2). Therefore, grain selection is a very important process in the formation of casting structure. The present authors have been studying on the process of grain selection using succinonitrile, which is a transparent organic substance and have found that the growth distance necessary for grain selection depends upon the solidification condition3-5). When the solid/liquid interface is dendritic, the grain selection occurs quickly. On the other hand, when the solid/liquid interface is cellular, it occurs slowly. We supposed that the growth direction of dendrite is different from that of cell when the substance is unidirectionally solidified. Indeed, Kurz and Fisher wrote in their text book that dendrite grows along its preferred growth direction, <100>, regardless of heat flow direction and that cell grows along heat flow direction regardless of its preferred growth direction1). However, there is no quantitative description about the growth direction when the solid/liquid interfacial morphology is cellular. Furthermore, there have been little works6) to study the growth direction of cell and dendrite."

Jan 1, 2000

By Dao Su, Kelang Mu, Yufeng Guo, Jinghua Zeng, Tao Jiang

"The influence of high pressure roller grinding (HPRG) on sintering of iron concentrate fines was investigated. Results of mini-sintering tests showed that assimilation temperature of iron concentrate fines decreased from 1230 ? to 1220 ? and assimilation time was shortened from 10 min to 5 min when the iron concentrate fines was pretreated by HPRG. Sinter pot tests showed that the yield of sinter increased from 60.33% to 72.92% , tumble index increased from 44.35% to 46.66%. The investigation indicated that, after being pretreated by HPRG, iron concentrate fines are improved in ballability and the fraction of fine particles increased, resulting in the improvement of granulation property and reactiveness in solid state reaction. As a result, sintering of iron concentrate fines were strengthened.IntroductionWith the rapid development of iron and steel industry and the decrease of high-grade ores, the imports of iron ore are increasing continually. It is of immensely strategic importance for development of iron and steel industry and energy security in our country to make good use of iron concentrate fine which is low price, high grade and has a refractory sintering property. When iron concentrate fine is used in sintering, granulation property of sinter mixture and permeability of sinter bed get poor. As a result, yield and quality of sinter fall down. Many researches show that, when HPRG is used in pelletization, quality of pellets is improved dramatically. Meanwhile, HPRG has a low energy consume, a large handing capacity and it is benefit for environment protect. At this theme, strengthening of sintering of iron concentrate fine pretreated by HPRG was investigated in this paper."

Jan 1, 2012

By Xiaoming Huaa

The effect of the anodic polarization on the composition and morphology of the surface layer formed on chalcopyrite during ammonia–ammonium chloride leaching was investigated. The anodic polarization on the chalcopyrite electrode was used for oxidation and dissolution of chalcopyrite, and the resulting oxidized layers were characterized by XPS, SEM and optical microscopy. The results show that oxide layers exist on the chalcopyrite surface with or without any anodic polarization in the leaching solution at ambient atmosphere. However, the composition and morphology of the layers are strongly depended on the extent of polarization. The distribution of FeOOH and Fe2O3 within the oxidized layer was inhomogeneous for the sample at the open circuit potential (OCP). The composition and morphology of the oxidized layers which were formed at anodic potentials lower than 0.3 V versus SCE were similar to those of the chalcopyrite at the OCP. At anodic potentials above 0.4 V, the oxidized layers contained many cracks, and they were fragile and exfoliated. Furthermore, the sulfide had been oxidized to sulfur species with higher oxidation states. The oxidation of the chalcopyrite seemed to undergo a cyclically oxidative process that suggested growth and spallation of oxidation layers on chalcopyrite in a layer-by-layer sequence.

By Georgios Kolliopoulos

Water is a critical commodity of our generation and a key compound for the chemical and mining industries. Sustainable industrial development is directly associated with the ability to recover clean water from contaminated sources. Forward Osmosis (FO) is a low-energy footprint membrane process allowing the recovery of clean water from high salinity effluent streams. In FO, water is recovered spontaneously into a concentrated draw solution (CDS). Energy is required to separate the recovered water from the resulting dilute draw solution (DDS). In the current work, the fundamentals of the FO process and the most important aspects affecting its performance are discussed. An energy comparison of FO and conventional water recovery technologies is presented. Finally, the opportunities FO presents in the field of hydrometallurgy are analyzed.

By M. S. Moats

The treatment of oxidized residues of zinc with high iron content continues to present a technical challenge in both the steel and zinc industries. Two main problems are commonly identified and include high treatment costs and environmental concerns about contaminated, iron-bearing residuals. A new approach to this problem is described in which selective separation of the iron and zinc into salable products may be potentially feasible. The waste material is first leached to give a solution having an approximate concentration of 110 g/l Zn, 15 g/1 Fe and 40 g/1 H2SO4 and other impurities such as Pb, Cd, Cu and Sb. A suitable organic, such as D2EHPA, is used to load the majority of the iron. The aqueous phase is then acceptable for zinc electrowinning after standard solution purification. The novel step in the flow sheet is the efficient recovery of the ferric iron from the organic solvent using a solid metal to reduce the iron to the ferrous state. The Fe+2 is easily stripped into an aqueous phase in a relatively pure form, suitable for use in water treatment. Process parameters and possible flow sheet designs are described and discussed.

Jan 1, 1995

By Peter Kettle

This paper describes the performance of the copper industry over a period of some two decades and examines the theme that improvements in operating efficiency have not been matched by improved returns on capital. The financial performance of the copper industry is analysed using CRU&apos;s MICA database. Regression analysis indicates a two percentage point increase in operating margins but no increase in returns on capital. The gain in operating efficiency appears to have been mainly achieved in the mid 1980s. The investment boom of recent years has resulted in a rapid increase in the industry&apos;s level of debt and gearing ratio (now some 47%). Data on 44 copper mine projects is used to show the linear relationship between scale and capital costs. Typically new capacity costs some US$5,000 /tpy. The relationship between cash costs and capital intensity of projects is also plotted. The greater attention now being focused on efficient use of capital means that capital intensity rankings will become increasingly important in determining which projects go ahead.

Jan 1, 1999

By Robert W. Hyers

Electromagnetic levitation has proven important in a wide range of experiments, all affected by fluid flow. For some experiments such as viscosity measurements, only whether the flow is laminar or turbulent must be established. For other experiments, however, quantitative assessments of velocity, shear stress, or shear strain rate are required. In most cases it is difficult or impossible to measure the internal flow in levitated droplets directly. The samples are usually small, opaque, reactive, high-temperature, metastable, or all of these. Furthermore, recirculating flow limits the utility of tracking surface particles, since they collect in stagnation points ratherthan following the flow. Most research groups have chosen mathematical modeling to assess the internal flow in levitated droplets. A variety of analytical and numerical methods have been applied, including both laminar flow and various turbulence models. A number of these models are reviewed and their impact on different containerless experiments is assessed. Much of the research reviewed here was performed by alumni of Professor Julian Szekely, and by others using similar methods.

Jan 1, 2006

By Joseph C. Milbourne

Tetra Technologies CCIX? (continuous countercurrent ion exchange) system has been involved in a wide range of uranium concentration, separation and purification applications over the past 40 years. Uranium ion exchange applications have ranged from the treatment of copper heap leach solution containing 5 parts per million of uranium to the treatment of high strength sulfuric acid solutions containing several thousand parts per million of uranium. The flexibility and the countercurrent mode of operation and other unique features of the CCIX? have resulted in successful uranium recovery from these solutions and many others.

Jan 1, 1995

By E. S. Geskin, W. L. Chen, A. Vora

"This paper is concerned with the application of an abrasive waterjet for metal shaping. The waterjet cutting technology uses water compressed to the pressure up to 55,000 psia which is accelerated in a cylindric nozzle. Abrasive particles are then supplied into the water stream and accelerated by the water. Cutting occurs via the interaction between the water-particles stream and a workpiece that causes material erosion at the impingement zone. The mechanism of this interaction enables shaping of practically any material with a minimal effect on the metallurgy of subsurface. The motion of the jet penetrating through a material body is guided by a robotic arm. A waterjet cutter is becoming one of the principal tools for shaping titanium, super-alloys and other hard-to-machine metals and composites. The shaping, resulting from the waterjet cutter, is very similar to laser beam cutting. However, unlike laser processing, there is no damage to the subsurface structure.The presented work discusses the experimental study of cutting of titanium plates. The results of these experiments demonstrate the potential of the abrasive waterjet as a shaping tool. IntroductionOne of the main avenues in the development of metal shaping is the use of high energy beams as cutting tools (1,2). There are a number of advanced beam oriented material removal technologies, such as laser, electron beam, plasma and abrasive waterjet (AWJ) cutting. The advantages of AWJ cutting are well understood and documented (3-14). This technology has the potential of becoming the principal tool for netshaping and netsurfacing of parts. However, the use of AWJ is currently limited to cutting of hard-to-machine materials such as titanium, superalloys, glass, composites, etc. The cost of A W J cutting is much higher and the productivity is much lower than those of the thermal cutting. At the same time abrasive waterjet can be used for shaping any existing technological material from fabrics, plastics, aluminum to glass, composites, and diamonds. The material losses during AWJ shaping are minimal. The roughness and waveness of the surfaces generated during AWJ cutting are substantially less than those of the thermal cutting. Due to the size of the jet cross-section total force exerted by the jet on a workpiece does not exceed 30-50 newtons. This terminates the need in the use of complex fixture for material holding. Low applied forces and low surface temperature prevent the damage of metal subsurface in the course of cutting. The small size of the impingement area will determine the limited width of the kerf. Due to the size of kerf and unidirectional character of the water jet the formation of practically any metal contour is possible."

Jan 1, 1988

By Sridhar Komarneni

"Microwave-hydrothermal processing is a novel technique which combines the conventional hydrothermal processing with microwave field and we previously showed for the first time, that ceramic powders can be rapidly produced by this technique. This review paper deals with the synthesis of unary oxides such as Fe203, Ti02, Zr02, etc., binary oxides such as BaTiO3, SrTiO 3, PbTiO 3, SrZrO 3, KNbO3, etc., and ternary oxides such as NaTi2 (PO4)3 and pyrochlore phases of Pb(Mg1/3Nb2/3)O3, Pb(Zn1/3Nb2/3)O3 etc. and metal powders such as Cu, Ni, etc. below 195°C. This method can be adopted to the synthesis of a large variety of powders by the appropriate control of pH, Eh, temperature/pressure and concentration of chemical species. The main advantages of this method compared to conventional hydrothermal processing are (a) it increases the kinetics of reaction by one to two orders of magnitude, and (b) it can lead to novel phases especially those with layered structures.IntroductionConventional hydrothermal processing is a well-established synthesis technique which has been extensively used in the preparation of fine ceramic powders [1-5], large single crystals [6-8] and massive cement blocks [9]. Technologically important ceramic powders such as BaTiO 3, Al203 etc. made by the hydrothermal process are now commercially available. Although there are numerous methods for materials synthesis, hydrothermal method is truly a low temperature and environmentally benign process. For example, ZrSi04 (Zircon) which is extensively used in ceramic industry can be prepared hydrothermally at 150·C [10] compared to sol-gel or solid-state method [11,12] which require a temperature of about 1000·C. The hydrothermal method is environmentally benign because hydrothermal reactions are carried out in closed systems at low temperatures and the contents can be recovered and recycled after cooling to the ambient conditions. One of the disadvantages with any low temperature processing method is slow kinetics. For this reason we have combined the hydrothermal method with microwaves to enhance kinetics and we named this method as ""Microwave-hydrothermal"" processing [13- 16]. Although the combination of microwave and hydrothermal techniques has been used in the past few years to dissolve all kinds of inorganic (e.g. alumino silicate rocks) and organic materials rapidly for chemical analysis, we were the first to show its potential value for the synthesis of various ceramic powders [13-16]. In this paper, I show that this novel method is applicable to the synthesis of all unary, binary and multinary oxides by the appropriate control of pH, Eh, temperature, pressure and concentration of chemical species. In addition, this method is also found to be useful for the preparation of metal powders."

Jan 1, 1994

By C. L. Lin

Multiphase, irregularly-shaped randomly-oriented PARGEN particles were grown to determine the breakage/liberation characteristics of such locked particles. The simulated locked particles were randomly broken to establish the liberation characteristics of the broken fragments. The progeny size distributions are consistent with Gilvarry&apos;s volume and surface flaw model for single particle breakage. The extent of liberation of both continuous and dispersed phases can be described from the conservation of interfacial area. In this regard the data can be normalized and liberation described for a wide range of dispersed phase grades and dispersion densities.

Jan 1, 1988

By John E. Dutrizac, Tzong T. Chen

"Laboratory experiments were undertaken to ascertain the behaviour of various ""impurity"" species during the precipitation of hematite directly from ferric sulphate solutions at 225°C and in the presence of 40 or 50 g/L of hematite seed. Copper, nickel and zinc are not significantly incorporated in hematite precipitates. Although the nickel contents increase to 0.22% as the Ni concentration increases to 60 g/L, the solid solution Ni contents are low relative to the bulk Ni contents. Thus, part of the Ni may be present as tiny particles of poorly soluble NiS04.H20. Increasing germanium concentrations to 2,000 mg/L result in products containing up to 0.59% Ge. The Ge occurs either in solid solution in the hematite or is adsorbed on the nanometer-size hematite crystallites. Increasing As(V) concentrations to 10 g/L increase the AsO4 contents of the products up to 16%. However, the products consist of hematite together with As04-containing Fe(SO4)(OH) and an unknown Fe-AsO4 species. All the hematite products contain - 1% SO4 which appears to be adsorbed on the nanometer-size hematite crystallites.IntroductionDissolved iron is a common impurity in most hydrometallurgical processing circuits and, generally, the iron must be eliminated prior to the subsequent recovery of the sought after metals. Simple neutralization of iron-rich solutions yields slurries which are difficult to thicken and filter. To address these concerns, the jarosite, goethite and hematite processes have been developed, and these technologies are able to reject the dissolved iron in a readily filterable form [1]. Despite its higher cost, the hematite process offers several potential advantages. Because hematite is an iron-rich, high-density compound, its formation would reduce the mass of residue and the size of a residue storage pond. Hematite is the thermodynamically stable form of iron under ambient conditions, and this stability would facilitate the impoundment of hematite precipitates. Furthermore, hematite has some market potential for cement manufacture and even for iron making [2]. In all the commercial hematite processes, the dissolved ferric ions are first reduced to the ferrous state. Subsequently, the pH of the solution is adjusted and the solution is then oxidized. The ferric ions gradually generated during solution oxidation hydrolyze and precipitate mostly as hematite, although commercial hematite products also contain trace or minor amounts of jarosite-type compounds. However, there are potential advantages in precipitating hematite directly from ferric ion solutions, as the reduction and subsequent oxidation of the iron are not required. Although the precipitation of hematite directly from relatively concentrated ferric sulphate solutions (up to 0.5 M Fe(SO4)is) was recently demonstrated [3], the behaviour of impurity species during hematite precipitation is largely unknown. To address this issue, systematic laboratory experiments were undertaken to ascertain the behaviour of a number of ""impurity"" species during the precipitation of hematite directly from ferric sulphate solutions at 225°C, and the results are presented in this paper."

Jan 1, 2012

By Toshia Suzuki, Keiji Kakudate, Yoshihiro Adachi

"A macro model for the steel usage pattern in Japan is proposed. The steels are classified into four types; converter steel for machinery and for construction and electric furnace (EF) steel for machinery and for construction. The steels are assumed to be discharged from the society in accordance with lifetime distributions of each usage. The amount of EF steel and the accumulation in society are calculated using a population balance model. The comparison with the calculated results and statistics ensures the validity of the model. Since the amount of EF steel for construction will increase and be oversupplied, EF steel will have to be used for machinery. The required and available amounts to supply EF steel for machinery are considered from the point of allowable· copper concentration for machinery use. Copper contaminates steel used for machinery during recycling process and contamination ratio is evaluated with the model. Copper concentration in EF steel is predicted for various scenarios.IntroductionThe amount of CO2 emission from Japanese steel industry is 48.0 million C-ton in 1990 and it occupies 15.1% of the total amount in Japan. In order to reduce the C02 emission and to save the natural resources, it is strongly required to promote the recycling of steel. However, the impurity contaminates steel in recycling process and lowers its quality. The copper concentration in EF steel is analyzed by Toi et al. using a macro model with the assumption that steel is discharged in proportion to the accumulation amount [1]. However the discharged amount of products is dependent on their age for service and usage pattern and not on the accumulation amount. In addition, the degree of copper contamination is different depending on the usage of steel. Therefore a precise model that contains the age for service within the society as a parameter and distinguishes the usage· of steel is necessary in order to clarify the problems in the recycling of steel."

Jan 1, 2000

By Batric Pesic

Silver dissolution with thiourea was studied by using the rotating disk technique. The major parameters studied were: thiourea concentration (0-0.5M), ferric sulfate concentration (0-0.5M), sulfuric acid concentration (0-0.5M), and the effect of many foreign ions (Mn, o.i, Co, Ca, Na, etc.). Temperature effect was studied in the range 5-35 .C. The activation energy was 5.4 Kcal/mole. The dissolution of silver was first order with respect to ferric sulfate, and the secord order with respect to thiourea. Among the additives, copper had a dramatically negative effect. The strong oxidants such as hydrogen peroxide and manganese dioxide were also detrimental for silver dissolution. Silver does not dissolve with thiourea in the absence of ferric ions. Sulfuric acid does not participate in the dissolution reaction either. Chemically, the most important parameter for silver dissolution is the ferric sulfate/thiourea ratio. Thus, in the solutions with excess of ferric sulfate, a solid silver-thiourea complex is formed, which precludes transfer of silver into solution. In the solutions with the excess of thiourea, the free thiourea reacts with formed solid silver-thiourea complex and silver goes into the solution. The solid silver-thiourea complex was characterized according to its chemical composition. The complex contains 6.54%C, 2.49\H, 14.77%N, 16.09%0, 21.62%8, and 37.13% Ag. This composition corresponds to a Ag2so4.3&apos;1U.2ff:i0 compound The soluble silver species are present in the solution as the dimers of AgTU+3 complexes.

Jan 1, 1989