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By Donna M. Noel

Bacterial strains have been cultivated from solids previously exposed to cyanide that will tolerate 300 ppm sodium cyanide under anaerobic conditions. In selected solid samples, these bacteria have been shown to reduce the level of cyanide from approximately 300 ppm to essentially zero in about 50 days under anaerobic conditions. Various media were investigated, and the nutrients providing maximal growth were ?established .. Degradation of cyanide in sterilized solids was determined for comparison with degradation obtained in bioactive solids. All experiments were conducted at ambient temperature and initial pH of approximately 10.5.

Jan 1, 1991

By Phillip A. Armstrong, Charles A. Lewinsohn, John H. Gordon

"This paper describes the opportunity offered by employing systems based on mixed conductive ceramics, in particular, ceramics conductive to oxygen ions and electrons, in reducing CO2 emissions from metallurgical production. Membranes based on these mixed conducting properties enable commercial viability of several attractive metallurgical processes. One of these processes utilizes modular, ceramic-membrane structures for the generation of pure oxygen, in tonnage quantity. The membrane-based systems offer significant capital savings and operating efficiencies in various metallurgical processes. The current status of this technology is summarized below.IntroductionCryogenic oxygen supply technology is currently the state-of-the-art for applications that require large quantities of oxygen (hundreds to thousands of tons per day). Cryogenic technology, however, requires substantial energy inputs and, hence, adds significant costs and emissions to processes. Furthermore, cryogenic oxygen supply technology is mature and there is relatively little potential for substantial capital cost reduction or efficiency improvement in coming decades. Non-cryogenic technologies offer a means to reduce the environmental footprint and cost of the oxygen supply facility in various applications.Ion Transport membranesCommercially available non-cryogenic air separation technologies, such as adsorption-based and polymeric membrane-based methods, do not afford the economies of scale that the cryogenic distillation enjoys. Therefore, industrial gas industry researchers began searching for alternatives to the relatively inactive and unselective polymeric membrane materials available. In the late 1980’s, Air Products began developing a new class of highly selective membrane materials with exceptionally high activity for oxygen transport. The materials constitute a class of oxide ceramics, and conduct both oxygen (as oxygen ions) and electrons in the same membrane, separating oxygen from air electrochemically. Numerous detailed process economics studies have shown that, based on these ion-transport membranes (ITM’s), the cost of oxygen can be reduced by approximately one-third relative to that obtained from state-of-the-art cryogenic oxygen supply technology, through a combination of capital cost savings and efficiency improvements. [1,2,3]"

Jan 1, 2008

By Kampe. S. L., Baker. Andrew H., Tony Zahrah

"Experimental heats of reaction for the formation of several Al3Ti + TiB2 intermetallic composite formulations have been determined utilizing bomb calorimetry. To overcome the kinetic constraints and achieve ignition in these formulations, a boron (B)/potassium nitrate (KNO3) initiation aid was incorporated within the blended reactant compact. The heat contribution from the initiation aid was regressed to provide estimates of the heat of reaction of the nominal formulations. Powder x-ray diffraction was utilized to identify the products of the reaction and discern any differences between the predicted equilibrium products of the formulation and the actual products.IntroductionReaction synthesis is a technique for the creation of ceramics, intermetallics, and in-situ composite materials [1]. Reaction synthesis is defined by its self, propagating mechanism, where the energy liberated from a localized reaction within a green powder compact is enough to carry the bulk reaction to completion. Achieving a self, propagating state can be achieved in variations of two primary methods of initiation: uniform volumetric heating and directional propagation [2].Uniform volumetric heating involves subjecting a green compact of the unreacted formulation to uniform heating in a furnace to encourage diffusion to initiate the reaction (Figure 1a) throughout the bulk material. Directional propagation utilizes a point heat source at one section of a green compact of unreacted formulation (Figure 1b). The localized exothermic reaction at one point in the compact then initiates the reaction in the section of the compact adjacent to it and fully propagates throughout the entire compact until completion. Initiation of the localized reaction is generally associated with the melting of the constituent with the lowest melting point, with instantaneous initiation of the reaction usually occurring close to that melting point [1]. This melting point can be high in some systems of interest, such as the titanium (Ti) and boron (B) system in equation 1:"

Jan 1, 2011

By J. P. Bellot

During the non-ferrous metal processing, the melting step under vacuum or under rarefied gas leads to volatile metal losses. It is the case of the metallurgical processing of the nickel-based, titanium-based or zirconium-based alloys where the evaporation losses don't allow a sufficient control of the alloy chemical composition. A theoretical approach has been carried out involving both a continuum description in the liquid phase and a molecular approach in the rarefied gas phase. The finite volume method is used in order to solve the coupled transport equationsin the liquid, whereas the Boltzmann equation is modelled by using a Monte Carlo method. At the liquid metal and metallic vapor interface, the volatilization and recondensation fluxes link up the two calculations. Simulation results are given for the melting and refining of reactive metals such as titanium alloys where the control of the chemical composition remains a major difficulty. The validity of the kinetic Langmuir's law is discussed for different operating conditions.

Jan 1, 1996

By K. Narayan Prabhu, W. D. Griffiths

"Heat transfer during the unidirectional solidification of a cast iron alloy against cast iron chills was investigated using an inverse modelling approach. Chills of thickness 100 mm and 10 mm were used, to simulate gravity die cruiting conditions and the use of chills in sand moulds. In both cases transient heat transfer, measured by the interfacial heat flux and heat transfer coeffieient; declined from initially high values in the first few seconds of solidification, to values about an order of magnitude lower which persisted for the remainder of the experiments. In the case of the thin chill it became saturated with heat until it was no longer in a position to extract further heat from ·the casting. These results were interpreted by studying the resistance to heat transfer from the casting offered by the ·casting-chill interface and the chill itself for example, the thermal resistance of the casting-chill interface can be influenced by the deformation of their respective surfaces and their subsequent relationship.IntroductionDie casting cast iron offers several advantages such as energy savings, higher mould yield, and better surface quality over the sand casting process1 • The process is· environmentally' friendly because of the elimination of the sand. However the design and construction of metallic moulds is expensive and a faulty die design may result in a defective casting: A simulation based process design of die castings would enable die designers and solidification modellings to try better designs of dies on the computer and arrive at a cost effective solution more quickly. This has numerous benefits for the die caster, as he would be able to produce sound castings with very short lead times.The success of a solidification model to predict accurately the thermal history and the location of hot, spots inside a solidifying casting depends to a large extent on the heat transfer data prescribed at the metal/mould interface. Many measurements of the heat transfer coeffident (or the heat flux) between a solidifying aluminum alloy and a chill have shown that the heat transfer coefficient is a function of most of the variables of the casting process2 - 8. However heat transfer studies during the solidification of ferrous alloys are rather limited. The high temperatures involved suggest that the contribution due to radiation heat transfer cannot be neglected."

Jan 1, 2000

By T. Ikeda, M. Maeda, K. Mita

Galvanized steel sheet is the major product for the automobile industry. Therefore, automotive recycling results in zinc-containing scrap that should be remelted in EAFs. Naturally, the EAF dust is a very important source of zinc for zinc recycling processes. The thermodynamic properties of the Fe-Zn intermetallic compounds formed on the surface of galvanized steel sheet should be clarified to make clear the evaporation mechanism of zinc; however, there are few reports on these compounds because of difficulties in their synthesis. There are various intermetallic compounds in the Fe-Zn system. We synthesized them at about 673K. A specimen was examined chemically and X-ray diffraction was applied to ensure the formation of intermetallic compounds. Material containing two phases was placed in a Knudsen type effusion cell and the mass spectrum studied to evaluate the vapor pressure of zinc. The thermodynamic property of intermetallics was then evaluated through measured intensity.

Jan 1, 2000

By F. F. Aplan, G. Simkovich

"A review is given of the effects of solid state point imperfections upon a number of mineral benefication processes and a metal extraction process. It has been found in numerous flotation studies that small amounts of aliovalent impurities (dopants) in binary compounds may show major effects upon flotation behavior. Both semiconducting and ionic conducting compounds are affected. These effects are also seen in hydrometallurgical studies as well as in electrostatic operations. Additionally, de-copperization of lead melts appears to be strongly influenced by similar defects. It is hypothesized that the effects observed in these studies are present in actual operations and should be considered in designing processes. A few speculations concerning future efforts are advanced. IntroductionImperfections [point (e.g., vacancies, interstials, quasi-free electrons, electron holes, impurity ions), line (e.g., dislocations), two dimensional (e.g., grain boundaries) and three dimensional (e.g., 2nd phases) defects] are generally present in solid materials and these imperfections may, and often do, have important effects upon a variety of properties and processes. In general, one may, in most cases, attain elimination of three dimensional defects by a separation process of one type or another (e.g., gravity, electrostatic, magnetic, flotation, hydrometallurgical etc.,). Thus, this type of defect has rarely been investigated in a systematic fashion. Two dimensional defects are always present in non-single crystal materials but have also escaped systematic studies in processes primarily because the control of such defects is not easily attained. Line defects are non-equilibrium entities which are present in ill-defined quantities so that they present a variable that cannot be easily controlled although through careful systematic experiments one can attain some reproducible relations pertaining to this type of defect.Contrary to the lack of studies concerned with the effects of 1, 2 and 3 dimensional types of defects there has been some activity concerned with point defects and their effects upon a number of mineral/metallurgical processes, especially flotation processes. Thus, this article will present a review primarily of point defects in relation to their effects upon flotation although other processes and defects will also be mentioned."

Jan 1, 1988

By Hu Meilong, Liu Lu, Bai Chenguang

Extracting perovskite from high titanium-bearing blast furnace (BF) slag is a green and potential method to recover the second titanium resource. The non-isothermal crystallization process of perovskite in synthesized high titanium-bearing slag was studied in situ by confocal scanning laser microscope (CSLM) with cooling rate of 20 K/min. The results showed that perovskite was the primary phase formed during cooling process in the titanium-bearing synthesized slag (TiO2=23%). Perovskite started to precipitate at 1719 K and finally presented an orthogonal straight lines morphology.

Jan 1, 2014

By Taegong Ryu

The thermal plasma process has been applied to the preparation of nanosized tungsten carbide (WC1-x). The reduction and carburization of the vaporized chloride by methane-hydrogen mixtures produced nanosized WC1-x powder, with a small amount of WC or W2C phase. The products were characterized using XRD, carbon analyzer, and TEM. The effects of plasma torch power, the flow rate of primary plasma gas (Ar) to generate plasma flame, and the addition of secondary plasma gas (H2) on the product composition were investigated. The tungsten carbide (WC1-x) powder had a particle size less than 30 nm. The powder was treated under hydrogen atmosphere to fully carburize the WC1-x, and W2C phases to WC as well as remove excess carbon in the product. Finally, WC powder with a grain size less than 40 nm was obtained.

Jan 1, 2008

By R. F. Hammen

Heavy metal contamination of water is a problem of immense national and international proportions. However, effective cleanup is complicated both by the toxicity and the low concentrations of metals in wastewater streams. Using high performance chelation chromatography, the solid phase extraction and purification of extremely dilute metals from water was highly effective. The process is based on selective displacement of metals from a chromatographic column containing a chelating resin. The resin is characterized by extremely efficient adsorption kinetics which allow rapid and complete removal of the metals.

Jan 1, 1993

By F. H. (Sam) Froes, C. Suryanarayana, K. C. Russell, C. M. Ward-Close

"Far from equilibrium synthesis allows development of novel crystal structures and microstructures, leading to achievement of enhanced physical and mechanical properties. A number of ""far from equilibrium"" techniques are reviewed with emphasis on the amount of departure from equilibrium. The ability of two such techniques, mechanical alloying (MAl, and physical vapor deposition (PVD) to develop novel structures are discussed in detail. For the MA process emphasis is placed on intermetallic compound compositions. Solubility extension, beyond rapid solidification (RS) levels, is found in terminal compositions but not for the intermetallics. Nanostructure-sized grains (< 100nm) form which can be retained after ""low temperature"" compaction. On continued milling in many cases the nanometer-sized grains transform to an amorphous structure. Ordering is destroyed by MA, except in those intermetallics with large negative enthalpies of formation. For the PVD process, a review of application to terminal light alloy compositions is presented. This includes a new high-temperature aluminum alloy, layered materials with nanometer spacing, corrosion-resistant magnesium alloys and low-density titanium compositions. IntroductionTo enhance the mechanical property combinations of advanced structural materials innovations in process/synthesis are required [1-6]. In this paper the capability of various ""far from equilibrium"" synthesis techniques [7,8] to produce novel constitutional and microstructural effects, and hence potentially enhanced physical and mechanical properties, in advanced materials is presented. The application of two such methods, mechanical alloying (MA) and physical vapor deposition (PVD) is discussed in detail. For the MA process emphasis is on intermetallic compositions with consideration given to solid solubility extension, microstructural refinement, amorphization, and formation of intermetallic compounds. For the PVD process application to terminal light alloy compositions is discussed."

Jan 1, 1994

By Mei Song, Qingyu Deng, Xuewei Lv, Lu Liu, Chenguang Bai, Meilong Hu

"The carbochlorination of several silica materials was carried out in the temperature range from 900 °C to 1200 °C. In this study, silica oxides and gaseous chlorine with carbon as reductant were used. The optimal carbon silica mole ratio in different temperature was calculated by Factsage software and the results showed that the optimal values are 1.2, 1.4, 1.6, 1.8 at 900 °C, 1000 °C, 1100 °C, 1200 °C, respectively. According to the experiments, the chlorination ratios of several silica materials were increased with temperature increasing. In the same temperature, the chlorination ratio of diatomite is the maximum and the chlorination ratio reaches 79%% when C/SiO2 reaches 3 at 1100 °C.1, IntroductionPolycrystalline silicon is the main material to manufacture the silicon polished section, solar battery[1] and high purity silicon wafers[2], also which is the most basic function material of semi-conductor industry, electronic information industry and solar photovoltaic battery industry[3]. The conventional manufacturing process of polycrystalline silicon would be divided into three parts: the improved Siemens method, which was introduced and became the main process to produce the polysilicon products in China. Silane method and fluidized bed method. Silicon tetrachloride and chlorosilans have been employed as by-products in several fields like electronic, telecounications and metallurgy[4-6]• At present, the main applications of silicon tetrachloride include production of trichlorosilane by catalytic hydrogenation, synthesis of fumed silica and ethyl orthosilicate, production of optical fiber grade silicon tetrachloride.The conventional routes for the silicon tetrachloride production have been reported, including the direct chlorination and the chlorination process of ferrosilicon, abandon catalyst and silica[7]."

Jan 1, 2013

By H. Ikeda

The new Onahama N0.3 tankhouse was put into operation early in 1973. This new tankhouse, which has a capacity of 90,000 metric ton cathode per year, is distinct in many important respects from conventional tankhouses. The major objectives in design were to simplify the construction and ope- ration for reduction of the costs for labor, interest and depreciation and also to reduce the copper inventory in the tankhouse by the use of conti- nuously-cast anodes. As a result, the investment cost was decreased by approximately 30% and the inventory cost by approximately 600, while the production per unit area of the tankhouse was increased by 80 - 100% as compared with the existing conventional-type tankhouses at Onahama. By abolition of cell inspection and maximum mechanization of materials handling the labor cost was decreased by as much as 80%. On the other hand, the new system has some disadvantages, such as increase in anode scrap ratio and increased cost of anode casting. The No.3 tankhouse system is, however, still at its starting point, while conventional methods have been continuously improved over the past years of operation. It is expected that the innovational ideas behind this system will serve as bases for a more efficient electrolytic refining system in future.

Jan 1, 1976

By Dewei Zhu

A general purpose computer model for describing the transport phenomena and resulting rate of deposition in Chemical Vapor Deposition (CVD) processes has been described. Partial differential equations describing the conservation of mass, momentum, energy and chemical species are solved by a computer program employing a finite volume method. The program allows for multiple chemical species and natural convection effects. In this paper, the deposition of silicon by the reaction of silicon tetrachloride and hydrogen in a vertical stagnation flow reactor with rotating substrate has been considered. The effects of reactor pressure and substrate rotation speed on the rate and uniformity of deposition have been studied. The predicted rates of silicon deposition along the substrate are in reasonable agreement with experimental results found in literature. The model can be used as a tool for design optimization of such reactors.

Jan 1, 1990

By Tang Chaoho

Laboratory research on the reducing and matte smelting of Jamesonite concentrate has been carried out. The influence of the process conditions such as the smelting temperature, the amount of pyrite cinder (the agent of fixed sulfur) and the amount of additives on the smelting process have been studied. Under the optimum condition the direct recovery ratios of antimony and lead are 83.26% and 68.50% respectively. The ratio of fixed sulfur is 98.97% but more than 15% lead and 30% silver remained in the ferrous matte. The key problem to be solved of this new process is how economical and effective is the recovery of silver and lead in ferrous matte.

Jan 1, 2003

By Tang Chaoho

Laboratory research on the reducing and matte smelting of Jamesonite concentrate has been carried out. The influence of the process conditions such as the smelting temperature, the amount of pyrite cinder (the agent of fixed sulfur) and the amount of additives on the smelting process have been studied. Under the optimum condition the direct recovery ratios of antimony and lead are 83.26% and 68.50% respectively. The ratio of fixed sulfur is 98.97% but more than 15% lead and 30% silver remained in the ferrous matte. The key problem to be solved of this new process is how economical and effective is the recovery of silver and lead in ferrous matte.

Jan 1, 2003

By Sun Ying, Zhang Jing, Li Qiu-ju, Wang Yan-ze

Copper smelter slag was leached using sulphuric acid solutions under atmospheric conditions. Base on the composition and phase of copper slag, the effect of the concentration of sulfuric acid and leaching temperature to the leaching growth rate of Fe, Cu, Co and Ni in the copper slag were investigated in this paper. Simultaneously, the influence of sulfuric acid concentration, leaching time, leaching temperature and the amount of sulfuric acid (solid-liquid ratio) to the leaching rate of these metal elements were researched. Experimental results showed that: with the increasing temperature, the dissolution rates of the metals elements increased first and then decreased. Due to the influence of silica gel which was obtained in beginning of leaching, the higher the concentration of sulfuric acid is not conducive to dissolution of the valuable metal elements. The dissolution degree of Fe, Cu, Co and Ni were 92.83% 96.76% 93.62% and 63.41% respectively.

Jan 1, 2016

By Peter J. Koros

The current wave of interest in this topic is the result of increased use of titaniferous ores or ilmenite in blast furnace burdens for the purpose of repairing hearth damage. The titanium compounds that promote deposition of ?patching? materials in blast furnaces are the cause of downstream problems in the steelmaking shops. Steelmakers historically have objected to significant amounts of titanium in hot metal (>0.10 % Ti) for several reasons: 1) accretions caused by the TiC.TiN needles that float out of the iron as it cools in transit and in transfers make the accompanying slag sticky and crusty, causing problems in desulfurization and increasing time and Fe yield loss at the subsequent raking, 2) defensive measures have been taken in treatment, such as use of argon for carrier gas, but without technical rationale for this approach, 3) difficulty in removal of the ladle slag by the raker, with subsequent sulfur addition to the vessel charge, and 4) transfer into the BOF and/or formation of a very corrosive TiO2 containing acid slag during the early part of the BOF blow which, in addition to causing lining damage, results in loss of sulfur removal capability by the vessel slag. Based on a conceptual analysis of the metal-slag-atmosphere interactions during transfer ladle desulfurization treatment, a mechanism is postulated for the apparent effectiveness of the use of argon in reducing the deleterious effect of titanium and an alternate technique, possibly more effective, is proposed. As probably the use of argon causes increased exposure to atmospheric oxidation of the titanium carbonitrides contained in the ladle slag, the same benefit can be obtained by use of either oxygen or an air blast to oxidize the noxious reaction compounds. Validity of the concept has been demonstrated in a pilot plant setting. These issues, and related effects on testing the hot metal, are examined in detail with reference to the literature and plant and laboratory experience.

Jan 1, 2006

By V. M. Sokolov, Jr. DuPlessis

The technology for recycling fine wastes, grinding sludges or swarf, and solids such as slag that contain a high content of metallic material needed improving. The objective was to produce a master alloy that met the tight requirements of the Western manufacturers and achieve improved yields of the valuable elements, nickel and cobalt, to over 90%. The alloys from the production of Alnico. magnets were chosen for this work. A process is proposed .that is able to recycle all kinds of Alnico wastes. This process is able to reduce all detrimental elements, which are contained in the wastes, to within acceptable levels. Molybdenum, if present, is an exception. Depending on the levels of contamination of undesirable elements different recycling strategies are proposed. The majority of the wastes can be recycled by melting and refining with a liquid slag layer using unique melting furnaces that are relatively unknown in Western nations. The proposed technologies allow the reelamation of over 95% of the cobalt and nickel from any kind of Alnico waste, and there are no limitations on the proportion of different kinds of wastes in the charge. The proposed processes and technologies could also be applied to the recycling of grindings, turnin

Jan 1, 2000

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