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By C. M. F. Vieira

This work has as its objective to characterize ceramic bodies for vitrified tiles elaborated with the mixture of nepheline-syenite flux and kaolinitic clay. Formulations were prepared with 0, 30 and 50 wt.% of nepheline-syenite incorporated in a kaolinitic clay. To determine the physical and mechanical properties such as dry bulk density, linear shrinkage, water absorption and flexural rupture strength, specimens were prepared by 30 MPa uniaxial pressure-molding and then fired in a laboratory furnace at 1150oC. The microstructure of the fired ceramics was evaluated by scanning electron microscopy. The results indicated that the nepheline-syenite improved the evaluated properties of the clay and attended the specifications of vitrified ceramic tiles.

Jan 1, 2010

By Nikhil Dhawan

Electronic waste (e-waste) is a collective name given to discarded electronic devices such as Television, Cellular Phones and Personal Computers. Among the heterogeneous metals present in the e-waste are the base metals: copper, aluminium, nickel, tin, zinc, iron and precious metals: gold, silver, palladium, platinum apart from several hazardous and halogens metals. Hence there is a need to recover these metals from electronic scrap by recycling and then re-use, which can meet large amount of metals demand. Hydrometallurgical processing was employed for the recovery of metals from television printed circuit board (TV PCB). Different lixiviants such as hydrochloric acid, Sulphuric acid, and nitric acid were used to understand the dissolution behavior of copper, iron and lead present in the TV PCB. Effect of increasing concentration of nitric acid was also studied. Selective recovery of tin over 95% in the form of tin oxide was precipitated. The precipitated tin oxide was identified by X-ray diffraction technique. Tin oxide of purity more than 99.9% was obtained.

Jan 1, 2009

By Alaina B. Hanlon

Keywords: Undercooling, Convection, Dendrites, Stainless Steel, Levitation Certain Fe-Cr-Ni stainless steel alloys solidify from an undercooled melt by a two-step process in which the metastable ferrite phase forms first followed by the stable austenite phase. Recent experiments have shown that the lifetime of the metastable phase is strongly influenced by flow within the molten sample. The current research will provide insight to why flow affects the metastable phase. This new understanding will lead to the use of convection to control microstructural evolution in spray-forming of stainless steels. Simulations using a commercial computational fluid dynamics package, FIDAP, yield a range of convective flow velocities that cause mechanical damage to the dendrites which is compared to experimental results. If the convective velocities are great enough that the dendrites bend, then low angle boundaries form at the points of collision. These result in high energy sites that could serve as nuclei for the stable phase.

Jan 1, 2005

By E. I. Gedgagov, A. V. Tarasov, V. M. Paretsky, A. D. Besser

"Hydrometallurgical technology and equipment have been developed in the Gintsvetmet Institute (Moscow, Russia) for processing of rhenium-containing alloys waste to produce commercial- grade metal products with recovery of all valuable components. The technology is based on waste treatment with hydrofluoric acid with subsequent decomposition with nitric acid at pH = 1 to 1.5 to ensure maximum degree of rhenium conversion to the liquid phase of pulp. Some experimental lots of ammonium rhenate and ammonium molybdate were produced at a pilot plant. The following main techno-economic performance values have been achieved when processing grinding residues (balance-based tests were conducted with a lot of SP-2 alloy waste) to produce ammonium rhenate of high purity, as well as tantalum-niobium, nickel-cobalt and tungsten-molybdenum concentrates: rhenium recovery of 92.3% into a commercial product from grinding waste; production cost of 170-210 US Dollars per 1 kg of rhenium in commercial-grade ammonium perrhenate taking into account its recovery; tantalum and niobium recovery of 75- 77% into bulk concentrate; nickel and cobalt recovery of 88-89% into a mixed concentrate; tungsten and molybdenum recovery of 88% to 91% into concentrate. Introduction During the recent years the use of rhenium has been increasing at a fast pace worldwide [1]. The growing prices for this refractory metal are an essential factor encouraging collection and processing of rhenium-containing wastes. Double-component waste, such as molybdenum- rhenium or tungsten-rhenium alloys can be readily decomposed and the process of rhenium recovery does not cause, therefore, any difficulties. The main separation of metals takes place at the stage of waste digestion with acid, because molybdenum and especially tungsten remain in precipitate in the form of hydrated oxides and rhenium reports in the liquid phase, from which it can be easily extracted by solid ion-exchange or solvent extraction techniques. However, most of rhenium is contained in super-alloy waste [2]. Such waste has different contents of valuable components, such as tantalum, niobium, molybdenum, tungsten, cobalt, nickel, chromium and other metals. The basis of all such super-alloy waste is nickel. Refractory metals in the super- alloy composition are in the form of metallized target-oriented eutectics, and due to this reason hydrometallurgical decomposition of such alloys is a difficult technological task."

Jan 1, 2008

By M. I. Brasileiro

The use of experimental design to the study of mixtures has found a wide range of applications, even in laboratory scale or in industrial development works. The aim of this work was to maximize granite sawing waste content in ceramic tiles using experimental design. Based on the raw materials, specific formulations were developed using the experimental design. The raw materials were mixed and sample bodies were produced using uniaxial pressing. The sample bodies were fired and characterized in terms of water absorption, mechanical strength and X-ray diffraction. Regression models were adjusted relating the water absorption and mechanical strength with the amount of raw materials. The results showed that the methodology of experimental design maximize the content of wastes incorporated in ceramic tiles formulations. Formulations containing up to 40% of waste can be used for the production of ceramic tiles.

Jan 1, 2009

By Pietro Navarra

Cooling of critical furnace equipment to produce freeze lining is of particular interest as many metallurgical processes are intensified while attempting to prolong campaign life. This idea was combined with high-capacity heat pipes in the design of a copper slag launder. The design methodology of the launder and heat pipe cooling system is examined in this paper. With reliable material properties and operating conditions, CFD was used to quantitatively predict the skull thickness and the corresponding heat load applied to the slag launder. The operational limitations of heat pipe technology were considered and an appropriate cooling system was incorporated into the model. Parametric modeling was used to simulate several launder and heat pipe configurations. The generated results were then used to optimize the design of the launder, which was built and tested in August of 2005. The experimental performance of the cooling system is evaluated and compared with the model results.

Jan 1, 2006

By William K. Connor, O&apos

The U.S. Bureau of Mines (USBM), in cooperation with the American Society of Mechanical Engineers (ASME), conducted over 200 hours of melting tests to vitrify residues from five municipal waste combustion facilities. Combined residues (grate residue and f1yash) from three municipal waste combustors, a waste water treatment sludge combustor, and flyash from a refuse-derived-fuel (RDF) boiler, were sequentially melted in a I-metric-ton (mt) water-cooled-wall electric arc furnace. Each of the residues underwent magnetic separation, screen size analysis, and bulk chemical analysis prior to melting. The furnace products were examined by optical and electron microscopy and by X-ray diffraction. Bulk chemical analyses were acquired for the metal, fume, and vitrified furnace products. The material balance for the furnace operation indicates that from 69 to 86 pct of the feed reported to the vitrified furnace product, which had leaching potentials well below the EPA limit for each metal, as determined by the EPA TCLP. The electric arc melting furnace currently is being utilized in a cooperative research project between the USBM and the Idaho National Engineering 'Laboratory (INEL) for melting tests on simulated low-level radioactive wastes,

Jan 1, 1991

By Pingchao Ke

A crystalline polyferric sulfate (PFS) adsorbent was synthesized by oxidizing and precipitating ferrous ions under atmospheric conditions. The morphology, structure, composition and specific surface area (SSA) and adsorptive efficacy to As (III) of the adsorbent were characterized by SEM/EDS and TEM images, XRD patterns, FT-IR spectra, BET SSA analyses and adsorption experiments. The adsorbent presents as morphology of near-spherical aggregate and good crystallinity. A small amount of goethite co-precipitated with PFS in the case of the initial ferrous concentration of 1 mol/L and increased the SSA of the aggregates. The absorbent with co-precipitation of goethite showed good adsorption to As(III) and good filtering performance in the high As(III)-content solution of 10–100 mg/L under acidic, neutral and alkaline conditions (pH 2.09–9.01), and its maximal adsorption capacity and adsorption efficiency were 7911 μg/g and 96% separately. After Adsorption, the stability of the absorbents adsorbing As(III) were evaluated by TCLP tests, and the results indicated that the absorbents adsorbing As(III) were extremely stable, and the concentration of arsenic in all leaching solutions were less than 0.01 mg/L.

By Lenny Winkel

With the aim to develop a solar-driven process for the extraction of copper from sulfide concentrates research on the decomposition of copper sulfides under inert atmospheres has been initiated. Thermogravimetric measurements on chalcocite (CuzS) revealed that copper is formed already at 1823 K. Chalcopyrite (CuFeS2) also disintegrates at this temperature, although at a lower rate. Copper and iron have been identified in the solid residue. The results confirm the feasibility of copper extraction by direct decomposition of sulfides under atmospheric pressure. The decomposition under inert atmosphere prevents generation of SO2, it also alters the behavior of volatile impurities during decomposition of copper sulfide concentrates. Chemical eqUilibrium calculations for chalcopyrite contaminated with enargite (Cu3AsS4) have shown that the absence of an oxidic slag allows for a complete evaporation of arsenic and subsequent separation from intermediate sulfides. The need to better assess the potential of direct sulfide decomposition has prompted the development of an experimental setup for studying the decomposition reactions. The experiment has been devised such that data on the decomposition kinetics and on impurity removal can be obtained at temperatures up to 2500 K.

Jan 1, 2003

By Brajendra Mishra

Molten Salt electrolytic processes offer unique opportunities to extract and refine metals where gaseous or metallothemlic reduction, hydrometallurgical extraction and aqueous electrolytic methods are thermodynamically constrained. Production of aluminum and magnesium by molten salt electrolysis are well known commercial processes. Several other reactive metals, such as lanthanides and actinides, as well as beryllium and calcium, make use of molten salt processing for extraction and refining. This presentation describes the science of molten salt chemistry and electrochemistry for winning and refining of several metals. In addition, recovery of metals from waste process salts by molten salt reduction as well as oxidation have been discussed. Material issues in design of molten salt reactors have been included. Various applications have been presented through case studies. Experimental data have been included to justify the suitability as well as limitations of these specific processes.

Jan 1, 2003

By Jilai Xue

Fe-Ni alloys can be used as raw material in making stainless steel. Laterite nickel ore is one of mineral resources for producing nickel alloys. In this work, the laterite ore after dehydration at 800 °C and the anthracite as reducing agent were mixed for pre-reduction at 900 °C, and then reduced to form Fe-Ni alloys at 1550-1620 °C through carbon-thermal reduction process. A high Ni-content alloy component in the metallurgical mixture can be formed through pre-reduction. Better separation of the resulting metals from the slag is found with lower Ni-content alloys produced or higher temperatures during reduction. An effective processing of Fe-Ni alloys needs further understanding of the process fundamentals and optimizing of the process parameters.

Jan 1, 2010

A three?stages countercurrent fluidized bed prototipe reactor to neutralize the SO2from smelter gases has been developed. For gases with 8 vol-%SO2, at 800°C and for 4 h mean reaction time of the limestone, the capture of SO2 is 99%, with off gases with 0.07 vol-%. For 2 vol-%SO2, the total capture of SO2 can be obtained at 750°C and 4 h reaction time. The calcine obtained contain a blend of unreacted limestone and calcium sulphatewith minor amounts of residual lime.

Jan 1, 2006

By Harumasa Kurokawa

Since the initial start-up, the Toyo Smelter & Refinery has been operating in harmony with the ambient environment, and improvements have been implemented with technologies specifically developed for further protecting the environment. Toyo Smelter & Refinery is now planning to increase the copper production capacity from 280,000 tpy to 450,000 tpy, over a period of several years. In 2003, the first step of this smelter expansion and modernization plan was implemented. The production capacity of the P-S converter was increased dramatically, as it became possible to operate under a ?2 hot-2 blowing? schedule. In 2005, an additional converter will be installed, in order to allow operation under a ?3 hot-2 blowing? schedule. This report will describe the technical improvements on the P-S converters, as well as describe the Toyo expansion program and discuss the technologies applied to the fugitive gas collecting system.

Jan 1, 2005

By Hector Carreon

Due to elevated temperatures, excessive stresses and severed corrosion conditions, turbine engine components are subject to creep processes that limit the components life such as a turbine bucket. The failure mechanism of a turbine bucket is related primarily to creep and corrosion and secondarily to thermal fatigue. As a result, it is desirable to assess the current condition of such turbine component. By using eddy current images, it was shown that the eddy current technique could be used to monitor creep damage in a nickel base super-alloy. The eddy current results also show a significative variation in the electrical conductivity on the creep damage zone with respect to the background zone in nickel-base super-alloy samples. In addition, the absolute thermoelectric power coefficient show also a strong dependence associated with creep damage in nickel base super-alloy samples using a copper hot tip reference. The eddy current and thermoelectric power techniques seems to show promise as nondestructive evaluation tools for monitoring the level of creep damage in metallic alloys.

Jan 1, 2010

02, NaCI03, H202, Na0CI and Ce+4 have been examined as oxidants in an alkaline carbonate system for uranium in in situ leaching. The South Texas and New Mexico ores contained up to 2.6 meqJg of reducing compounds which consume oxidants in the leading operation. Leaching rates did not increase linearly with the oxidation potential of the oxidants. A mild oxidant can be used to maximize uranium oxidation selectively and oxidant efficiency. 02 can oxidize most of the uranium mineral with an adequate rate and high oxidant efficiency.

Jan 1, 1990

By Dong-sheng Li, Hong-ming Long, Tie-jun Chun, Chao Ning, Zhen Wang

Iron ore sintering is an essential process in modern iron and steel production. It has the largest emission of the PM (particulate matter) in the iron and steel industry, accounting for about 40% of the total emission. The physical and chemical properties of PM 10 and PM 2.5 in the iron ore sintering were introduced, and the research development of PM emission reduction was also summarized. The potential future development of PM emission reduction by chemical agglomeration and capture in the iron ore sintering process was also carried out. The interface chemistry relationships between PM and polymer, such as sodium carboxy methyl cellulose (CMC) and polyacrylamide (PAM), in agglomerates were also investi- gated in this paper. It is signi ficant to reveal the characteristics of PM and develop the emission reduction technology of PM for the cleaner production of iron ore sintering.

Mar 1, 2018

By Jiann-Yang Hwang

Microwave heating has been proved an effective method to rapidly heat iron oxide. This offers an opportunity to apply microwave heating in the steelmaking process. The reduction reaction of iron oxide is traditionally achieved at high temperature with reducing gases such as H2 and CO generated from various sources, including coke, coal, and natural gas. This study investigates the differences in iron oxide reduction using conventional and microwave heating under H2 and CO atmospheres. A special microwave thermal gravimetric device was designed and built to facilitate the investigation. With this device, iron oxides can be heated by electric resistance heating, microwave heating, or a combination of methods. The incoming CO and/or H2 also can be preheated to simulate a potential utilization of recovered heat. The iron oxide weight and temperature can be monitored during an entire reduction period. A series of reduction experiments have been conducted. The results are presented and discussed.

Jan 1, 2006

By Bowen Li

Silicon Carbide is an excellent refractory material. Its physical properties make it extremely useful, particularly in applications where corrosion resistance and wear are important considerations. Commercial silicon carbide refractory is frequently manufactured by bonding silicon carbide particles with clay; however, clay may cause problems in the sintered products. This study investigates the potential of replacing a portion of the clay with andalusite powder. The results show that micron size andalusite powder can improve not only the strength of the refractory but also the sinterability. The mechanisms for these improvements are discussed.

Jan 1, 2006

By Chang Chia -Fu

The generic structure of our bimesogens is shown in and for a typical blue-phase mixture of the type we describe here. We use mixtures of the ratio 33.4% (n =2.6), 34.1% (n =6.57), 36.6% (n= 11.15) with of the high twisted power (HTP) agent BD H1381(available from Merck Chemicals and described in ref. We then studied the electric-field dependency of the selective reflection in BP I* at 20.7 °C by applying increasing and the decreasing pulsed alternating current (a.c.) electric fields (100 Hz).

Jan 1, 2006

By M. Bilal Khan

Thermal stress relief by means of a typical heat treatment cycle (660oC for one hr) is compared with the one achieved through vibratory stress relief at resonant and multiple resonant frequencies for the D-406 HSLA material. Our analysis of the data is based on the microhardness profiles measured for the entire length of scales, namely, base metal, heat affected zone (HAZ) and the weld bead itself. The profiles obtained using the two techniques mimic each other, for an equivalent 70% stress relief level. The data are further qualified by impact testing wherein the zone of interest is projected in the retention groove to provide impact by the pendulum striker in the Charpy mode. Higher equivalent energy absorption in the treated specimens confirms the efficacy of the vibratory method. The present work rectifies earlier anomaly where heat treatment has been reported at 310oC for the same material.

Jan 1, 2009