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By Ikuhiro Sumi

A new steelmaking process, in which manganese ore was intentionally reduced, was developed to achieve a higher manganese Yield using a combined blowing converter. In this study, manganese behavior was discussed through the introduction of a model. Apparent reduction rates of manganese were calculated by the two terms that were determined experimentally, with SOkg and 2S0ton combined blowing converters. The model calculated manganese changes during the operation. We applied the model to the actual operation and found that manganese behavior was predicted fairly well by this model.

Jan 1, 1996

By Hongbo Yang, Tongbo Zhang, Ting Huang, Jingshe Li, Fangfang Song

"Liquid core length is a very important parameter of the process of continuous casting, which directly reflects the cooling status in secondary cooling zone and solidification rate of the slab. In this paper, the billet caster in some steel plant in China was chosen as the prototype of simulating. A numerical simulating model for calculating the liquid core length of continuous casting billet was built by ProCAST software, which was verified reasonable and accurate by pin-shooting technique. Based on the model, the relationships between casting speed, casting temperature and liquid core length of casting billet were found, which was very practically useful for the workers on sit to improve casting billet quality. IntroductionContinuous casting process developed very rapidly because of the high metal yield, energy saving, and low-cost 111• And the quality requirements of continuous casting billet for customers became higher and higher with the fast development of economic121• Internal defect usually is the major quality problem for continuous casting billet[3•61 , which is influenced by the solidification process of casting billet, especially the solidification process of liquid core17•81 • So it is very important to study on the relationship between casting parameters and the liquid core length which means the distance between the crystallizer meniscus and the casting billet solidification end-point. In practical production process, the workers usually control the quality of casting billet according to the liquid core length."

Jan 1, 2013

By Fumito Tanaka

The Mitsubishi process is the sole pyrometallurgical process for the continuous production of blister copper from Copper concentrates and has been successfully operated around the world. The development of calcium ferrite slag (CaO-FeOx-Cu10), the so-called "C-slag", has enabled continuous converting from matte to blister copper in the commercial scale operations. Commercial interests in the slag led to many papers over the CaO-FeOx slag. However, Cu2O bearing slag has not been studied well due to experimental difficulties. The authors have quantified the thermodynamic properties of the CaO-FeOX-Cu2O system. The results have been utilized to analyze various issues related to the converting furnace, such as the magnetite precipitation from the slag or from blister copper and to develop better controlling criteria for the continuous converting operation. -

Jan 1, 2003

By R. L. Nyirenda

One of the problems with ammoniacal-ammonium carbonate leaching of EAF carbon steelmaking flue dust is that zinc present in spinel phases is not leached. This paper presents results of test work in which prior to leaching, EAF dust was reduced with CO containing gas to decompose the spinels into zinc oxide and iron bearing phases, mainly metallic iron and wustite. From such reduction products, the amount of zinc leached increases but the iron co-leached becomes extensive. The effect of various leaching parameters such as liquor concentration and redox potential on zinc and iron dissolution has been investigated. Supplementary experiments utilizing pure zinc oxide and pure iron phases were also carried out. Results show that the co-dissolution of iron from severely reduced EAF dust cannot be prevented. This is because the wustite phase contains zinc which can only be leached when iron also dissolves. Further, the zinc bearing wustite phase is not totally soluble so that the residue cannot be made zinc free. In the absence of air, dissolution of metallic iron hardly occurred, though in leaching experiments of a long duration its transformation to a spinel structure was observed.

Jan 1, 1992

By Jinjing Dua, Jun Zhua, Kuiren Liub, Bin Wang, Xiaolei Wua

V-Ti-Fe as hydrogen storage alloy was prepared by reducing metal oxides with a metallothermic reduction method. The deoxidation process of the V-Ti-Fe alloy was performed by electro-deoxidation and vacuum induction melting method, respectively. The results showed that the content of oxygen impurity can be controlled at about 0.2wt% after electrolyzing for 240min. Both the maximum values of hydrogen absorption capacity and the effective hydrogen desorption capacity are 2.65wt% and 1.01wt%, respectively. The deoxidization effect of vacuum induction melting process is more remarkable, with Ce as the reducing agent. It is found that Ce addition is beneficial for reducing the componential segregation, promoting the hydrogen absorption activation of V-Ti-Fe alloy. When m(Ce)/m(alloy) is up to 5%, the oxygen content has been reduced to 0.05wt% and the maximum hydrogen absorption capacity and the effective hydrogen desorption capacity are up to 3.36wt% and 1.85wt%, respectively.

Jan 1, 2015

By Scott A. Howard

MgO is routinely used as the basis for refractory materials, however, its susceptibility to hydration may result in dimensional instability and subsequent failure. The addition of boron has been shown to reduce th,e hydration susceptibility of MgO yet its dissolution into certain grades of steel may degrade their performance. In order to predict the efficacy of reducing hydration susceptibility by the incorporation of mono-, di-and tri-and quadravalent cations, the lattices of various cation-substituted systems were modeled. To more accurately simulate the substituted lattices, either cation or anion vacancies were incorporated to maintain electrical neutrality and all possible arrangements of defects in a 2x2x2 MgO supercell were investigated. Correlations were then made between the lattice energies of these systems and their susceptibility to hydration as reported in the literature. The results indicate the presence of higher charged cations tended to increase lattice stability while the cations with lower valency tended to have lower lattice energies. The relatively small body of experimental results available in the literature are consistent' with this study's results.

Jan 1, 1989

By Drew Sinha

Success of the environmentally benign semiconductor manufacturing depends on the cost-effective integration of the principles of reduce, recover, reuse and recycle from source material to final product disposal. Increasing demand combined with current shortage of polysilicon provided unique opportunities to recover the silicon waste, caused by various defects, in wafer manufacturing process. Current practices relating to recovery and reuse of waste silicon produced, from crystal growth process to finally polished and epitaxially deposited silicon wafer, at Mitsubishi Silicon America is presented. Future plan to recycle the process generated silicon fines produced during the intermediate steps of the wafer manufacturing process such as grinding, slicing, lapping and polishing is also discussed.

Jan 1, 1998

By Takeshi Yoshikawa, Kazuki Morita, Kunitoshi Matsunaga

"In metallurgical grade silicon (MG-Si), most impurities mainly exist at the grain boundaries and distribute in silicon grains at extremely small contents. Grain boundary phases in MG-Si transform into liquid above the eutectic temperature, and migrate towards high temperature regions when heated under a temperature gradient. With the migration of all liquid phases in MG-Si to the surface, the impurity contents will be decreased less than their solubilities in principle.In the present work, the fundamental research was conducted to discuss the possibility for purification using the liquid phase migration technique. The purification limit was estimated by thermodynamic calculations, and metallic impurities were estimated to be effectively removed except for Fe and Al. The migration behavior of the liquid phase in the synthesized silicon substrate was investigated by unidirectional heating under infrared radiation at 1523-1548 K, and the proceeding of migration was confirmed. The migration velocity was 1.4--2.0xl0-7 mis, and found to be controlled by the liquid phase diffusion.IntroductionPhotovoltaic energy is one of promising energy resources in a sustainable society because of its inexhaustibility and cleanliness. Although the production and installation of solar cells have increased significantly during the last decade, the cost of solar cell installation is still high. To enable the widespread use of photovoltaics and for the photovoltaic electricity price to reach grid parity, a low-cost and abundant feedstock of solar grade silicon (SOG-Si) is essential. Recently, a modified Siemens process and a fluidized bed reactor process were developed to address the cost and energy issues associated with the conventional Siemens process. However, their cost reduction potential is limited because of the large energy consumption needed to convert silicon into gaseous compounds. Purification of silicon through metallurgical routes offers a promising way for producing SOG-Si from metallurgical grade silicon (MG-Si), because it enhances productivity and can also lower the process costs. Although several metallurgical processes such as directional solidification [l ], vacuum refining [2-4] and plasma oxidation [5-7], have been developed, processing times and refining efficiencies still have to be optimized."

Jan 1, 2013

The high pressure acid leach process (HPAL) is being commercially used in four plants around the world to treat limonitic laterites. The two major operating costs of the HPAL process are the sulphuric acid and the energy required to heat the pulp to the desired temperature (>240°C). As an alternative to acid injection and steam heating, the in-situ generation of sulphuric acid and heat, produced during the high temperature pressure oxidation of sulphur-bearing materials blended with laterites, has been investigated at the laboratory scale. Various sources of sulphur have been examined, in particular, elemental sulphur, pyrrhotite and a Cu-Ni low-grade bulk concentrate. Under the proper blend ratios, all sulphur sources tested generated sufficient acid to result in equivalent nickel and cobalt dissolutions. A significant improvement to the process economics can result from the addition of sulphur sources containing valuable by-products, such as nickellcobalt andlor precious metals (gold and PGMs). This is especially true in the latter case, when the HPAL can be operated under Platsol conditions (i.e. with the addition of 5-10g/L of chloride), to dissolve the base metals and precious metals simultaneously in the autoclave. Various examples of the application of this concept are presented, together with a brief discussion of its implication on the autoclave design and the downstream processes to recover the values from the leach solutions. Keywords: limonite, co-treatment, acid consumption, sulphur, sulphur compounds, pressure acid leach (HPAL, PAL), Platsol process

Jan 1, 2004

By Corby G. Anderson

In the majority of industrial operations recovering gold and silver by hydrometallurgical means, cyanide is the predominant lixiviant. However, as an economic alternative, production of massive quantifies of silver chloride was done on an industrial scale in the nitrous-sulfuric acid pressure leaching of a refractory precious metals concentrate. This proven process required no cyanide. Thus, because of the large volumes encountered during day-to-day plant operation, the need for efficient and low cost methods of silver chloride precipitation, reduction and materials handling was mandatory. As such, this paper covers the evolution of plant scale precipitation, filtration, washing, reduction and control of silver chloride processing. As well, an in-depth description of the unique leaching system is included.

Jan 1, 1998

By Uchil Jayagopal, P. V. Krupakara, S. Manjunath

"This paper deals with the corrosion characterization of quartz particlate ZA-27 alloy metal matrix composites (MMCs). Quartz particles of size 50-80 microns are used as reinforcement. MMC's are prepared according to ASTM standards. Composites containing. 2, 4, and -6% by weight of quartz and unreinforced matrix were tested using 1 -N hydrochloric acid: The composite was found to be more corrosive resistant than matrix alloy. In each test the corrosion resistance of both alloy and composites were found to decrease with the exposure time.1. IntroductionMetal matrix composites- (MMCs) offer designers many added benefits, as they are particularly suited for applications requiring good strength at high temperature, good structural rigidity, dimensional stability, and light weight 1-5. The trend is towards safe usage of the MMC parts in the automobile engine, which work particularly at high temperature and pressure environments Particles reinforced MMCs has been the most popular over the last two decades.ZA alloy MMCs have most popular families being represented by. ZA-27 alloy reinforced with ceramic particulate. Although the incorporation of the second phase into a matrix material can enhance the physical and mechanical properties of the base metal, it could also significantly change the corrosion behavior.ZA alloys have been used extensively in industry. This is attributed to their excellent fludity, castability and good mechanical properties. Among the zinc-based foundry alloys, the ZA family of alloy have been widely used during the past few years. ZA alloys have many advantage over aluminium based ones, especially high strength with a low casting temperature 8."

Jan 1, 2000

By Eddie C. Chou

Phelps Dodge, Inc. (PD) is currently developing a lateritic nicke/Vcobalt deposit in Madagascar. Hazen Research, Inc. provides technical assistance to PD to investigate recovery processes for nickel and cobalt. Various process options were evaluated in laboratory experiments and pilot plant operations. The process selected for the feasibility study consists of feed preparation, high-pressure acid leach, countercurrent decantation wash, sulfide precipitation, sulfide dissolution, solvent extraction, ion exchange, and electrowinning. Among these unit processes, high-pressure acid leach, sulfide precipitation, and sulfide dissolution are applications of pressure technologies. Process development work and design criteria for commercial operations of these unit processes are presented in this paper. Concerns related to scaling in the high-pressure acid leach and the sulfide precipitation processes are discussed. Corrosion of various metal coupons under these environments was examined.

Jan 1, 2000

By R. M. Lamya

A considerable part of gold encapsulated in some refractory sulphides can be dissolved during sulphide matrix decomposition in non-complexing aqueous media. This has been concluded from laboratory results of gold extraction from pyritic and arsenopyritic concentrate containing 172.8ppm Au, into 10% hydrochloric, sulphuric and nitric acids. The degree of sulphides decomposition in the non-oxidative acids limits the gold extraction from this specific concentrate to about 10%. In the case of nitric acid, the gold dissolution follows the rapid decomposition of sulphides, reaching 32 to 42% of extraction at almost total decomposition of the sulphidic minerals. Accumulation of gold in this acidic and non-complexing solution to several ppm was not affected by the soluble products of the sulphides decomposition. An attempt to explain this gold behaviour is undertaken and some practical implications are discussed. In the investigated concentrate the "soluble gold" is mostly associated with arsenopyrite. This is consistent with the latest findings of other authors that gold disseminated in arsenopyrite can occur as cation Au3+. In a comparative test the gold extraction into highly concentrated chloride solution, in the same oxidative conditions, amounted to 92.34%.

Jan 1, 1995

By Anupam Madhukar

The essence of an atomistic unified kinetic model of strained thin film growth and defect initiation is presented along with a comparison of its consequences obtained from computer simulations with experiments. Within the competing kinetics of a strain dependent activated incorporation of atoms and an asymmetry between upwards and downwards inter-layer migration, the model provides a consistent description of 2D versus 3D morphology evolution accompanied by the appearance of surface vacancies and steps at no energy cost. The correlated migration of these precursor defects offers an atomistic mechanism for the emergence of surface half-loops from the growth front (thus accounting for configurational and thermal entropy) governed by activation energies closer to their correlated motion under the evolving strain fields and thus substantially less than those calculated with respect to the perfect crystal as the reference state. The essential mechano-chemical nature of the problem is compared and contrasted with the historical literature of such phenomenon as precipitation hardening and sintering in metallic and ceramic composites.

Jan 1, 1994

By Singareddy R. Reddy, Ramana G. Reddy

"The Margules equation is used for interpreting excess Gibbs energy of several ternary systems. An expression for the activity coefficient of a dilute solute, 2(oxygen), in a binary solvent 1-3 is derived. It is used to calculate the logarithmic activity coefficient of oxygen in Pb-O-Gu, Pb-O-Bi, AgO- Sn, Pb-O-Sn and Ag-O-Pb metallic systems. Self interaction parameter of the solute is derived from the partial Gibbs energy of solute using constant compositional path. The derived equation is used successfully to deduce the self interaction parameter of oxygen in Pb-O-Gu and Pb-O-Bi metallic systems. The predicted thermodynamic parameter data i.e activity coefficient and self-interaction parameters are in an excellent agreement with the experimental data and also our predictions are far more accurate than the predictions made by other models.1 IntroductionThe nature of solute interactions such as oxygen, nitrogen and sulfur with the metallic solutions are important for a number of chemical and metallurgical processes. Several theories [1-23] have been developed to evaluate fundamental thermodynamic properties of solutes constituting two elements. The activity of solutes has been calculated using statisticalor quasi- chemical approach.Wagner's [4] Ideal Solvent Model is based on one energy parameter to describe the compositional dependencies of the activity coefficient of nonmetallic solutes such as oxygen in binary metallic solutions. This model depends on a constant energy of interaction for the exchange of atoms from the coordination shell of an oxygen atom to the shell of an interstitial site and cannot account for properties of strongly interacting systems [4]. Therefore, several attempts have been made to improve the Wagner's model for the strongly interacting systems. [10-16]."

Jan 1, 1996

By Paul C. Turner

In 1998, approximately 57,000 tons of titanium metal was consumed in the form of mill products (1). Only about 5% of the 4 million tons of titanium minerals consumed each year is used to produce titanium metal, with the remainder primarily used to produce titanium dioxide pigment. Titanium metal production is primarily based on the direct chlorination of rutile to produce titanium tetrachloride, which is then reduced to metal using the Kroll magnesium reduction process. The use of titanium is tied to its high strength-to-weight ratio and corrosion resistance. Aerospace is the largest application for titanium, and titanium cost has prevented its use in non-aerospace applications including the automotive and heavy vehicle industries.

Jan 1, 2001

By Desmond Cook, Cynthia P. Dogan, Dale Govier, Gary Korth, James C. Rawers

"The microstructural and mechanical properties of iron powders processed in an attrition mill are highly dependent upon the processing environment. Extended high-energy ball milling in argon resulted in nanocrystalline bcc-Fe microstructure, while processing in nitrogen or alloying with carbon resulted in both nanocrystalline bcc-Fe and bct-Fe microstructures. In this U.S. Bureau of Mines study, both X-ray diffraction and Mössbauer analysis were used to show that the infused carbon and nitrogen concentrations were predominantly on the grain boundaries. Explosive consolidation resulted in a fully dense product with microstructure similar to the microstructure of the mechanically processed powder. Hardness values of the compacts correlated highly with grain size, independent of the processing conditions.IntroductionNanocrystalline materials have been theorized and shown to have unique properties that make them interesting for material scientists and promising for material engineering applications. Several conferences have been devoted solely to the techniques of preparing nanostructured materials have been held(l,2,3.). To date, most techniques used to generate nanocrystalline materials produce only a few grams of particles(1). High-energy ball-milling, however, is an efficient and effective technique that can produce substantial quantities of nanocrystalline materials with homogenous chemical composition that cannot be produced by conventional processing techniques(3).Applications and material evaluations of nanocrystalline materials require several grams of solid samples. Because nanocrystalline microstructures' are thermodynamically unstable, producing consolidated macro structures of nanocrystalline material has proved to be very difficult(2,3). In particular, retention of the nanocrystalline microstructure during consolidation of nanocrystalline particles has proven to be a problem. In contrast to many consolidation techniques that require elevated temperatures, explosive compaction uses a shock wave for consolidation( 4,5)."

Jan 1, 1994

By G. Kyle Green

Zirconium chlorinator residues contain an array of rare earths, scandium, unreacted coke, and radioactive thorium and radium. Because of the radioactivity, the residues must be disposed in special waste containment facilities. As these sites become more congested, and with stricter environmental regulations, disposal of large volumes of wastes may become more difficult. To reduce the mass of disposed material, the U.S. Bureau of Mines (USBM) developed technology to recover rare earths, thorium and radium, and unreacted coke from these residues. This technology employs an HCl leach to solubilize over 99% of the scandium and thorium, and over 90% of the rare earths. The leach liquor is processed through several solvent extraction stages to selectively recover scandium, thorium, and rare earths. The leach residue is further leached with an organic acid to solubilize radium, thus allowing unreacted coke to be recycled to the chlorinator. The thorium and radium waste products, which comprise only 2.1% of the original residue mass, can then be sent to the radioactive waste facility.

Jan 1, 1995

By Philip Arthur

The ISASMELT process is making a significant contribution to the global metals industry. ISASMELT furnaces are now operating successfully in eight different countries and treating approximately 3 million tonnes of concentrates and secondary materials per year. The process is currently used in both lead and copper smelting. The most recently commissioned plants were in Germany and China, one for treating scrap copper and the other treating low-grade copper concentrates. The Copper ISASMEL T furnace ("CIF") at Mount Isa Mines Limited (UMIM") has continued to set new operational records, with throughput of more than I million tonnes of concentrate per year and very low operating costs. This paper summarises the latest operational data from the Mount Isa Copper ISASMEL T plant and outlines the successful approach to industrial R&D taken by MIM in the development of the ISASMEL T process.

Jan 1, 2003

By Tseng. B. H.

Samples of unchlorinated and chlorinated carbonaceous concentrate from a carbonaceous gold ore were analyzed by transmission electron microscopy (TEM) for organically bonded sulfur and chlorine. The concentrate assayed 1.53 oz/t gold and 6.01% organic carbon. Much of the organic carbon occurred as sizable coarse particles up to several hundred microns in size, which showed no visible evidence of reaction with chlorine after chlorination treatment. Both the untreated and chlorinated fractions of the carbonaceous concentrate were analyzed by the TEM method, which detected organically bonded sulfur in all of the carbon particles examined in the untreated sample, ranging from about 1 to 5% organic sulfur, and averaging near 3.1%. TEM analysis of 40 carbon particles in the chlorinated sample indicated that organic sulfur was reduced significantly in the carbon and replaced in part by the chlorine, as the result of chlorination.

Jan 1, 1987