Search Documents

By D. A. Meyn, R. L. Holtz, C. S. Pande, M. A. Imam, D. J. Singh

"Various theoretical and experimental techniques used to search and develop new metal hydride systems suitable for hydrogen storage are described. The main theoretical technique under study makes the use of electronic structure of the candidate materials. Microstructural characterization techniques like transmission electron microscopy are being used to study the hydride formation. Novel processing techniques for material preparation such as those needed to produce thin films or amorphous phases are also being utilized. The techniques are illustrated with results from Pd, FeTi and Mg2Ni systems.IntroductionOf the four methods of hydrogen storage, compressed gas, cryogenic liquid, metal hydrides, and gas-solid adsorption, the metal hydride storage method is more attractive from the point of view of high volumetric density and safety. Compressed gas storage has disadvantages of extreme pressure, weight, and volume requirements, whereas storage of hydrogen as cryogenic liquid is unattractive due to the requirements of extremely low temperatures and high consumption of primary energy. Moreover, the number hydrogen atoms present in a volume of 10- 22 Cm3 (nH) in liquid hydrogen state (- 20K) is 4.2 whereas number of hydrogen atoms that can be accommodated in a free volume of 10-22 cm3 of various hydrides are as follows: LiH--5.9, TiH2--9.2, ZrH2--9.2, VH2--l0.2. High hydrogen concentration is usually associated with a large H/Metal atomic ratio but is also a function of structure."

Jan 1, 1994

By D. Pradhan, R. G. Reddy

"Electrorefining of aluminum scrap was investigated from AlCl3 –1-Ethyl-3-methyl-imidazolium chloride (EMIC) (Molar ratio 1.65) chloroaluminate electrolyte using copper cathodes at temperature of 90±3°C and cell voltage of 1.5 V. The deposits were characterized using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The study was focused to determine the effect of electrode surface modification as well as deposition time on dendritic depositions of aluminum. Their effect on current density was investigated also. It was shown that the surface modification of electrodes reduced the dendritic depositions of aluminum. Pure aluminum (>99%) was deposited for all experiments with the current efficiency of 94-97%. The use of ionic liquids not only reduced the energy consumption but also minimized pollutant emissions (CO, CO2 etc.) compared to the commercial high temperature aluminum production.1. IntroductionAluminum electrorefining/recycling from aluminum scrap using ionic liquid electrolyte is an attractive process today because of the unique chemical and physical properties such as wide temperature range for the liquid phase, high thermal stability, negligible vapor pressure, low melting point and wide electrochemical window. But in conventional practice, melting of aluminum scrap and high temperature molten salt electrolysis makes this process more expensive and less energy intensive (average 13 kWh/ kilogram of aluminum) [1] . Although recycling scrap aluminum requires only 5% of the energy used to make new aluminum [1-2], but the green house emissions like CO2, CO and HF have to be counted for environmental reason. Approximately, 5.31 kilogram of CO2 emitted per kilogram of aluminum production in most of the US industries."

Jan 1, 2009

By H. Sieber

Multilayer samples of tantalum and aluminum with the composition of Al-25Ta were prepared by cold rolling of elemental foils. The microstructure and phases were characterized by XRD, SEM and TEMISAED and the reactive phase formation was examined by DSC and DTA measurements in multilayer foils rolled for different deformation levels. The rolling procedure yields a decrease of the Ta particle size in the Al matrix and also results in the formation of a multilayer structure with a thickness of the elemental foils down to 200 nm in average. No phase formation is observed during the cold rolling procedure. While XRD and DSC measurements show no phase formation up to the melting of aluminum for samples rolled up to 40 F&R (fold and rolling) passes, in samples rolled for 50 or more F&R passes a first phase formation reaction yield an interfacial layer of TaAl3. Contrary to former studies in the investigated cold rolled Al- 25Ta multilayers the reaction starts at temperatures as low as about 340°C. The first stages of the reaction are associated with two exothermic maxima, that increase in amplitude and shift to lower temperatures with increasing number of F&R passes. At higher temperature the TaA13 reaction layer thickens very sluggishly and yields a third exothermic maxima at about 600°C. Isothermal DSC scans show the reaction is not finished for samples containing elemental particles larger than 1 pm after annealing at 550°C for 5h. In all the investigated samples no Al- Ta phase other than Tad3 was observed to grow for heat treatments up to 800°C. Multilayer samples heated up to 1400°C show a morphology consisting of small AITa2 particles embedded in a single phase TaA13 matrix. The multilayer microstructure and reaction product morphology are characterized by SEM and TEM investigations in cross-section and plan view geometry.

Jan 1, 1998

By R. Dekkers

Non-metallic inclusions in liquid steel are mainly formed during killing. As far as these particles are not captured by the slag, they are found in the cast steel where they can deteriorate the mechanical properties. Inclusions may also disrupt the continuous casting process, affecting thus directly the quality of the steel and the production capacity. Steel pin samples from the Sidmar plant (Belgium) were taken in different steps of several ladle treatments and in the tundish. Also slab samples were studied. All samples concern the same type of low alloyed aluminium killed steel. The non-metallic inclusions were isolated from the steel matrix and investigated with scanning electron microscopy and energy dispersive spectrometry. The evolution of the non-metallic inclusions is described by their number, size, shape and elemental composition. The main non-metallic inclusions present are aluminium oxides and spinel type compounds.

Jan 1, 1999

By Santo Ranieri

We will briefly review the nickel market in 2003 and look forward to the supply demand balance for the next few years focusing in on the key factors influencing future price dynamics. On the supply side we will examine slated brownfield and greenfield expansions including the Norilsk factor and the small to mid-range 'supply creep'. We will also review the cost side of the industry and what to expect going forward. On the demand side, we will discuss the stainless steel and non-stainless demand, the China factor and the stainless steel scrap supply cycle. We will conclude by pinpinting where the market is on the current price cycle, and where we believe the mid-term direction is headed.

Jan 1, 2004

By C. M. Egert, S. Rajic

"We have developed a monolithic micro-spectrometer suitable for a variety of sensing applications including industrial process monitoring. The device consists of a solid structure with a volume less than 6 cubic centimeters. All optical components of the spectrometer including two aspheric mirrors, a diffraction grating, and entrance and exit surfaces are fabricated onto the surface of the structure. All light paths are internally contained within the structure. The result is a small, rugged spectroscopic sensor ideally suited for use as a process monitor. Due to its monolithic nature the device requires no post-fabrication alignment; nor can it be knocked out of alignment during use. Although many materials and thus wavelength regions were possible, the prototype device discussed here was produced in PMMA by precision diamond turning. However, lower cost manufacturing approaches involving injection molding are under development to produce an affordable sensor.Due to its rugged monolithic design, small footprint, and low cost the monolithic micro-spectrometer is ideally suited for distributed monitoring applications often required for industrial processes. It is expected that modified versions of this sensor designs will be required for specific applications so as to maximize the performance and resolution over the operating range. For example, the prototype device described here operates over a wavelength range of 500 nm to 1000 nm. The performance of this device as a real-time surface monitoring sensor will be discussed in detail. Our approach of using wavelength dependant scattering resulted in the reduction to practice of a miniature, monolithic, rugged, low-cost, micro-instrument in a sensor sized package. The process sensor applications community has been faced by the cost versus performance issue. Simple go/no-go sensors are typically inexpensive but they provide very limited and sometimes dubious data. Scaled down traditional instruments offer very good measurand information but are typically cost prohibitive, fragile, and still relatively large. This work will bridge the gap between these two extreme sensing alternatives."

Jan 1, 1997

By Leonid N. Shekhter, Corby G. Anderson, Esra Cankaya-Yalcin, Daniel G. Gribbin, Joseph D. Lessard, Larry F. McHugh

"A new process for smelting copper, Looping Sulfide Oxidation™ (LSO™) significantly and positively alters the smelting energy balance. This process uses copper oxide in conjunction with air for the desulfurization of copper and chalcopyrite concentrates. Copper oxide is regenerated in a flash type furnace and then ""looped"" back for the oxidation of the copper concentrate. Heat and material balances show that the Looping Sulfide Oxidation™ process requires significantly lower net energy than conventional technology. This process produces anode copper and higher S02 content off-gases for efficient formation of sulfuric acid. Additionally, the process yields slags with lower copper solubility as compared to the conventional technology.IntroductionBased on the positive results from LSO™ investigations [1], further lab investigations into co=on sulfides and metal oxides were performed. It was discovered that chalcopyrite (CuFeS2) is oxidized with copper (II) oxide. In this reaction over 98.5% of sulfur was removed as S02, while a significantly improved energy balance was observed. This paper intends to analyze both the conventional flash smelting process and the newly developed Looping Sulfide Oxidation™ process, comparing heat and material balance results. LSO™ yields improvements to the energy footprint for copper, opening the door to new copper processing opportunities."

Jan 1, 2013

By Veronica Escobar

This paper presents results from a two month pilot evaluation of EMEW® technology at CODELCO Radomiro Tomic, in Chile. A prime focus in the test programme was to assess the technology?s capabilities to recover high quality copper from the Radomiro Tomic electrowinning tank house bleed stream. The EMEW® cell developed by Electrometals Technologies Ltd. tolerates substantially higher levels of contaminants than those found in conventional tankhouse, operating at high current densities while maintaining high cathode copper quality all the way down to low copper concentrations. To maintain high copper purity in a copper electrowinning (or electro-refining) tank house, a continuous bleed of solution must be taken from the tank house inventory to prevent build-up of contaminants, and resulting degradation in cathode quality. In an SX-EW operation, this bleed stream is normally recycled back to the solvent extraction circuit, but is occasionally sent to the raffinate pond to re-enter the leach circuit. Return of the bleed stream to the solvent extraction circuit creates a continually recycling load of copper in solution, which may reduce overall plant capacity and expansion potential. Return to the leach circuit has a similar effect, and methods to reduce its impact are always under consideration. The use of the EMEW® technology allows for direct and efficient recovery of near 100% of the contained copper instead of recycling. Tests were run at ambient temperature on bleed electrolyte using current densities which varied between 250 and 1100 amps per square meter, with copper concentrations between 38 and 1 g/l. A profile of maximum allowable current density with respect to concentration was developed, showing that high grade copper can be obtained at all levels of concentrations tested, by choosing an appropriate current density and electrolyte flow rate. The results of this programme show that the recirculating bleed electrolyte from an SX-EW operation can be converted into an expansion in copper production at a comparatively low investment cost.

Jan 1, 2003

By Carl C. Nesbitt

A study was conducted to investigate the claims of early observers who noted an increase in the rate of gold dissolution when chlorine was chemically produced in the leach vessel compared to sparging with chlorine gas. This "nascent" chlorine was presumed to be an active intermediate in the production of chlorine (C1,l from chloride ions. The study used UV light to produce an activated chlorine atom intended to recreate the observed increase in the gold dissolution rate. Although no change in the kinetic rate was observed, the reaction mechanism by which chlorine reacts with particulate gold was instead determined. Various concentrations of multivalent cationic chloride salts were added to the leach solution to demonstrate that the increased dissolution rate was due to the increased concentration of the chloride ion and ionic strength of the solution.

Jan 1, 1992

By Eric J. Grimsey

Steady state Excel models for a copper flash smelter and an iron blast furnace are used to enhance the teaching of pyrometallurgical smelting principles within a fourth year level process engineering unit delivered at the Western Australian School of Mines. A lecture/workshop approach has been adopted in which student teams undertake process simulation assignments that illustrate the multifaceted responses of process outputs to variation of inputs, the objectives being to reinforce their understanding of smelting principles. The approach has proven to be popular with students, as evidenced by the consistently high ratings the unit has received through student feedback. This paper provides an overview of the teaching approach and process models used.

Jan 1, 2014

By Stein Tore Johansen

The flow of a liquid through a large grain filter has been considered. An improved form of the fluid dynamic equations describing flows through porous media is proposed. The theory is applicable to all Reynolds numbers. Particulate inclusions are described by passive scalar fields where only very simple mechanisms for particle removal are included. However, the deposition of particles are allowed to change the "porosity" of the filter. Hence, the flow pattern through the filter will change as the filter ages. The theory is employed to the filtration of aluminum in an industrial grain filter. The model shows that the filter is not effectively designed and there is room for considerable improvement. The dynamic "aging" process of the filter is shown to change the filtration from bed filtration to cake filtration. Finally, the predicted inclusion collection efficiencies are compared to efficiencies measured in an industrial filter. The predicted initial efficiencies are in very good agreement with experimental results.

Jan 1, 1990

By Di Yang

The influence of high density (104 -105 A/cm2) electric current pulses (70 us duration) and continuous DC (~103 A/cm2) on the flow stress and ductility in tension of a high carbon steel wire were determined at 204°, 427° and 649°C. Electropulsing (100 pulses per second) with an effective current density of 100-200 A/cm2 gave a 10% enhancement in the uniform elongation of the wire at 204°C, but had no effect at 427°C and 649°C. In contrast, continuous DC either had no significant effect on the ductility or gave a decrease. The electropulsing per se decreased the flow stress only slightly at 204° and 427°C, but gave a significant decrease at 649°C. Continuous DC increased the flow stress at all three temperatures. The present results along with those by others suggest that the enhanced ductility by electropulsing and the reduction in flow stress may be further increased by raising the effective current density through increases in either the pulsing frequency, maximum current density of each pulse or pulse duration. This could conceivably increase the reduction per pass during wire drawing or the number of passes between anneals.

Jan 1, 2001

By Roger Agnew

Sulphide ores mined by Inco Limited in the Sudbury District contain small quantities of cobalt. During beneficiation, cobalt distribution to various streams is similar to nickel. After smelting, nickel is selectively extracted by carbonyl refining and the cobalt remains in the carbonylation residue. This residue is processed in a specialized hydrometallurgical plant to produce precious metal residues, copper cathodes, and a nickel- cobalt carbonate intermediate product. The nickel-cobalt is shipped to Port Colborne where the cobalt is separated as cobaltic hydroxide and refined to metallic cobalt. This paper deals specifically with the recently constructed Electro Cobalt Refinery. The cobaltic hydroxide is dissolved and residual zinc, copper and nickel are removed by ion exchange and organics by a carbon column. The purified cobalt solution is fed to the electrowinning circuit where cobalt rounds are produced on stainless steel mandrels. In the design and construction of the refinery, special attention was directed to materials of construction both for the process equipment and the physical plant, operating control and flexibility, and the quality of the working environment. The end result is an efficient and clean operation which yields a product of excellent quality.

Jan 1, 1988

By Xiao Songwen

Based on the anion coordination polyhedron growth unit theory, the polymorph transformation mechanism of antimony white (Sb2O3) in hydro-process was investigated. The new findings had been verified in the commercial-scale test and it was shown that adding a small amount of tartrate ions was economical and effective for polymorph transformation of antimony white in hydro-process.

Jan 1, 2003

By R. W. Bartlett

A two step process for treating platinum group metal flotation concentrates Is described while experimental results. The process was designed to be simple and Inexpensive While yielding a high recovery and fast turnaround. Ii consists of electric furnace smelting of concentrate to remove gangue and produce a homogeneous sulfide matte containing all of the base metals and platinum group metals. Sulfide oxidation Is minimized during smelting to avoid Installing an acid plant In the second step, matte Is pressure-leached with oxygen In an acid sulfate system to dissolve Iron, nickel, ?and copper while leaving a residue highly concentrated In precious metals, and typically about 1% of the flotation concentrate mass, A batch process with oxygen titration against the base metal composition of the feed Is used to control the end point of the leach. Sulfides must be eliminated while minimizing the precipitation of hydrolysis products. The leach residue can be smelled to bullion to facilitate sampling accuracy.

Jan 1, 1989

By Dan Wang, Qian Xu, Guangshi Li, Xionggang Lu, Xingli Zou, Zhongfu Zhou, Hongwei Cheng, Changyuan Lu

The preoxidation of the ore has a profound significance to the concentration, separation and purification of nickel and copper from the lean complex ore. In this paper, the natural Ni-Cu sulfide mineral samples under the elevated temperature condition in air were investigated, as well as under isothermal condition at 600 oC in air. The mineralogical characterization was studied using XRF, ICP and the Rietveld method. The oxidation behavior and the element migration of the Ni-Cu sulfide ore were studied by XRD, SEM-EDS and TG. The XRD Rietveld method was successfully developed in the phase identification and quantification of this complex ore powder sample. The oxidative intermediates (Cu/Ni-ferrite) were detected by XRD, and the process of the element migration was obviously revealed by the line scans using SEM-EDS. It is the preoxidation of this mineral that provides guidance for the extraction of valuable metals from low-grade Ni-Cu sulfide ores in the future.

Jan 1, 2015

By Xingye Guo, Yeon-Gil Jung, James Knapp, Zhe Lu, Jing Zhang, Li Li

La2Zr2O7 is a promising thermal barrier coating material due to its low thermal conductivity and superior high temperature stability. In this work, Bilayer La2Zr2O7 and conventional 8 wt% yttria stabilized zirconia (8YSZ) coatings were deposited using plasma spray technique. Both singlelayer La2Zr2O7 and double-layer 8YSZ/La2Zr2O7 coating architectures were designed. Thermal cycling and thermal shock tests were used to evaluate coatings’ thermomechanical properties. All La2Zr2O7 coats were delaminated in the furnace cycle test in less than 20 cycles. This is because residual thermal stresses accumulated during thermal cycling. In the jet engine thermal shock (JETS) tests, the SCL La2Zr2O7 and DCL dense 8YSZ/La2Zr2O7 coatings were fully delaminated. In contrast, the DCL porous 8YSZ/La2Zr2O7 coating sample only partially delaminated on the edge. This is because of the porous 8YSZ layer provides strain compliance. The findings will help to propose efficient thermal barrier coating systems.

Jan 1, 2016

By Cao rong-jiang, Tang Xin-he

"In ordinary manufacture process of tungsten powder, a preferable intermediate product used is ammonium paratungstate (APT). The particle size of tungten powder made from it through W2OO58 is larger than 1. 0 um. In order to obtain ultrafine tungsten powder with narrow size distribution, a new type of tungstate, hydraziniull tungstate, was studied. Its formula is 5(N2H5)2O·12 WO.s , with tetragonal crystal structure of a=5.821 , c=18. 468. Three methods for preparing hydrazinium tungstate (ART) were set up and ART can be produced by current industrial APT process with little modification of operation and without any change of equipment.Under certain PH and operation condition of the solution from which ART was produced, an autoreduction of tungsten occured, which produced a lower valency tungstate with blue color when ART was heated at different temperatures, in N atmosphere, tungsten bronze, tetragonal W0290 and W02.7E could be obtained respectively. They all have the superiorities, in the production of tungsten powder, of superfine size and narrow size distribution [average size of 0.5um or even smaller.The rate of autoreduction of ART is very fast at elevated temperature. The reduction reaction, which gaves tetragonal WO290, could be handled smoothly without explosion. To research their behaviors at autoreduction temperatures and the products of autoreduction will be new advances of tungsten chemistry and may also serve tungsten industry with new processes and materials."

Jan 1, 1988

By D. A. Salinas G., A. H. Castillejos E.

Pachuca tanks are commonly used in the hydrometallurgical industry to carry out leaching operations. The fluidynamic characteristics of the liquid phase, resulting from the injection of gas into the draft tube, are important to achieve the complete suspension of the mineral particles and has a decisive influence in the mass transfer processes occurring in this reactor. This study investigated the effect of different design and operating characteristics on the liquid velocity field. using a laboratory-scale Pachuca tank. The transparent model was filled with water, and air was injected through the bottom in the absence of mineral particles. The liquid velocities over the whole reactor were measured under several experimental conditions using particle image velocimetry (PIV). This technique allowed to obtain a very detailed picture of the liquid motion even in the draft tube, as long as bubbles were absent from the measured field of view. The experiments have shown that the liquid velocities increase with increasing the draft tube to tank diameters ratio, the distance from the conical bottom to the draft tube entrance, or the gas superficial velocity. On the other hand, an increase in the water level with respect to the draft tube outlet caused a decrease. A mathematical model, which used the no-slip model, to calculate the variation of axial effective density along the two-phase region, was found to predict liquid velocity fields which agree very satisfactory with the experimental results obtained under all the conditions studied.

Jan 1, 1999

By José Roberto de Oliveira

In a smelting reduction process the reduction reaction occurs predominantly in the liquid state. The main reduction agent is the carbon from the carbon saturated iron bath. The aim of the present work was to determine the velocity equation and the rate constant of the reduction rate of MnO content in a Mn0-SiO2-Fe0 slag by iron saturated carbon and the carbon dissolution rate in a Fe-Mn bath. The manganese content in the iron bath was in the range of 5 to 15 wt.%. It was observed that the rates of carbon dissolution in all Fe-Mn baths are faster than the rates of MnO reduction by the carbon saturated liquid iron.

Jan 1, 1999