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By Zviad Kovziridze

It is stated that the specific character of SPHTS specimens of TiCx consists in crystal lattice strength reflecting the condition of synthesis in ?burning wave?. The use of roentgenographic and other methods of analysis allow to estimate the effect of the conditions of synthesis causing the carbon sablattice defect on the grinding intensity of TiCx -phases. The study of the kinetics of vibratory grinding of TiCx -phases in ethanol and benzene medium allows to establish high grinding intensity of the phases close to stoichiometry and the possibility of producing high dispersion powders (Ssp 4.5-6 m2/g).

Jan 1, 2006

By J. Y. Aubut

The modernization of the CCR Refinery to permanent cathode technology is presently underway. The 360,000 mt/y refinery is being retrofitted to accept the Kidd process. Part of this modernization includes the installation of Kidd stripping machines, and the total replacement of the materials handling equipment. It also involves the reinforcement of building structures to accept the new equipment and the ability to operate in different modes. The future equipment will interface with some existing apparatus, which is being retained for future operations. The whole operation will be automated and will allow product traceability for quality purposes. This retrofit poses important challenges given the size and scope of the modernization project and because it is being undertaken concurrently with normal plant operations.

Jan 1, 1999

By Kazuki Morita

Dissolution mechanism and solubility of chlorine in the oxide melts, such as CaO-SiO2-Al2O3 (-Na2O), Na2O-SiO2-Al2O3 and CaO-SiO2-FeO systems, have been equilibrium technique was employed with controlled Po2 and PCl2, (Po2 = 10-6 -10 19 atm, PCl2 10-6 -10-13 atm at 1673-1748 K). The solubility of chlorine in the 40mass%CaO-40mass%SiO2- 20mass%Al2O3, slag was found to vary in proportion to Pb2/ w and pc/z/p' which proved that chlorine dissolved in the melts as C1 anion. Hence, the chloride capacity (CCI-), indicating the ability of molten oxide to absorb chlorine, has been defined as; The Ccl value was observed to increase with increasing slag basicity and temperature, and showed a reasonable relationship with that Of CS2-. Based on the result obtained in the present study, chlorine distribution during incineration with slags was predicted quantitatively.

Jan 1, 2003

By E. García-Ramos, P. Flores-Sánchez, E. G. Palacios, B. Zeifert, A. Romero-Serrano, M. Hallen-López

Chromium containing slags from stainless steelmaking may eventually be leached by acidic environments, therefore they should be treated before being stockpiled or land filled. In this work, synthetic slags were prepared and the effect of CaO/SiO2, Cr2O3, MgO and Al2O3 contents on the stability of the mineralogical species formed was analyzed. The morphology and composition of the slags were analyzed by XRD and SEM-EDS, whilst their chemical stability was evaluated by leaching with an aqueous acetic acid solution. It was found that CaCr2O4 and CaCrO4 are present in slags prepared with neither MgO nor Al2O3. The Al2O3-based slags mainly produced Ca2Al2SiO7 and the Cr(VI)-containing oxide complex Ca4Al6CrO16, whilst MgO-based slags produced MgCr2O4 as main mineralogical species. Additionally, Eh-pH diagrams for the Ca-Cr-H2O and Mg-Cr-H2O systems at 25 °C were constructed. The lowest Cr concentration levels in the leaching liquors corresponded to MgO-based slags owing to the stable binding of Cr in spinel with MgO. It was also observed in the Al2O3-based slags that increasing the slag basicity from 1 to 2 the leachability of the slags are notably increased.

Jan 1, 2008

By Thomas M. Harris

Cation exchange is not sufficiently selective to be used for the removal of heavy metal ions from a general industrial wastewater. However, if the metals can be converted to polyvalent anions through complexation, they may be removed both selectively and efficiently by anion exchange. This approach, referred to as chelation-assisted anion exchange (CAAE), has been examined using industrial wastewater samples contaminated with Ni2+ and Cr3+. For this particular application, the Ni2+ is complexed with 8-hydroxyquinoline-5-sulfonic acid, and the Cr3+ with sulfosalicylic acid. Removal efficiencies and adsorption isotherms for both the complexants and the complexes were determined in batch-mode tests.

Jan 1, 1994

By H. L. Ludtke

Microlaminate composites were fabricated by electron-beam physical vapor deposition. The microlaminates consisted of five layers, each 2 to 4 pm thick, and were composed of either pure metal layers (Cu-Ag), or alternated between metal and intermetallic layers (Nb(Al)- Nb3Al). The microlaminates were heat treated in an Ar atmosphere for 2 to 12 hours, at temperatures of 600°C for the Cu-Ag and 1000°C to 1200°C for the Nb(Al)-NbsAl. Microlaminates were examined after deposition and after heat treatment by scanning electron microscopy and energy dispersive x-ray spectrometry. The effects of heat treatment on the morphological stability of these composites will be described.

Jan 1, 1999

By Kandipati Sreenivasarao

Ion flotation is a promising separation process for continuously removing toxic metal ions from dilute process effluents. After treating the effluent with appropriate surfactant(s), the metal- bearing species adsorb onto the surface of rising gas bubbles and can be collected as foams. Suitable collectors have been identified for most of the elements of the periodic table. However, a better understanding of the thermodynamic, kinetic and engineering principles that determine the performance of ion flotation systems would facilitate commercial utilization of this technology. A model system of sodium dodecylsulfate-ethanol has been studied for the removal of Cu (11) from dilute solutions, using laboratory-scale flotation columns. This paper reports the effects of the air flow rate, solution height, foam drainage zone height and col1ector:metal ion ratio on the flotation kinetics, ultimate recovery of metal, flotation product grade, foam losses and effluent quality. Preliminary results for Pb (11) removal are also reported.

Jan 1, 1993

By Musa Karakus

Zirconia-based refractorics arc finding increasing use for specialized applications in steelmaking technology, making optimization of their resistance to corrosion by steelmaking slags more important. Samples of calcia- and magnesia-stabilized zirconia refractories have been exposed to slags in the CaO - FeO - SiO, system at 155WC for the purposes of measuring corrosion rates. Examination by SEM/EDX and cathodoluminescence of the mineralogy of the attacked specimens reveals important clues about the mechanism of attack.

Jan 1, 1992

By D. G. C. Robertson

The thermodynamics and kinetics of the reactions involved in fuming zinc from oxide slags using coal or coke were first studied in 1955 and have been the subject of many investigations since that time. The key reaction is ZnO(in slag) + CO Zn(g) + COl. This paper will review the some of the recent work, and will add new insights obtained in experiments carried out by the authors. In the first series of experiments it was shown that the reaction 2Fe2+ + ZnO = 2Fe3+ + Zn(g) or 2FeO + ZnO = Fe2O3 + Zn(g) does not occur at an appreciable rate, as is expected from thermodynamic considerations. In the second series of experiments it was shown that zinc does not fume from the slag at a significant rate unless a reductant has been added. This again is in accord with thermodynamic considerations, but is in contradiction to some of the experimental results reported in the literature. A third series of experiments was carried out with excess coke being present, so that the rate of supply of reductant was not in any way controlling the rate. The kinetics of zinc oxide reaction were then found to be independent of the zinc oxide concentration, but increased with increasing basicity, and temperature. The presence of high concentrations of FeO in the slag also improves the kinetics. At low zinc oxide concentrations iron oxide reduction occurred in parallel with zinc oxide reduction. We propose that (under the conditions of this work) the kinetics were controlled by a chemical step, namely the rate of desorption of an adsorbed CO2 species. This is the same mechanism as reported by Belton and co-workers for the kinetics of the reduction of FeO. This explains why the reduction of metal oxides in slags by hydrogen is often faster than by CO.

Jan 1, 2003

By Tor Lindstad

Specific C02-emissions are given for the production of silicon-metal, ferrosilicon, ferromanganese and silicomanganese. Emissions taken into account come from reduction materials, from coke production and generation of electric energy. C02-emissions can be abated by direct and by indirect methods. A direct method is to replace fossil carbon as reduction material wholly or partially by endogenous carbon (biocarbon, charcoal). Another possibility is to produce metals by electrolysis instead of the present electric smelting furnace. Indirectly CO2-emissions can be reduced by energy recovery, thus saving coal, oil or natural gas for heat generation. Some reduction in global C02-emissions can be obtained by giving credit for the use of silica dust partially replacing cement in concrete. In addition to give an overview of possible methods, costs will be discussed.

Jan 1, 1999

By A. N. Lasseigne

Hydrogenation behavior of the NaAlH4 intermetallics is investigated utilizing thermoelectric power and magnetic analyses. Using both thermoelectric power and magnetic susceptibility measurements on these intermetallics allows for confirmation and further insight into hydrogen's role in altering the material's electronic structure. The electronic and magnetic property correlations will indicate the direction for further alloy development to optimize hydrogen storage.

Jan 1, 2006

By Gary A. Wickham

In the zinc industry, this past decade has seen both prosperity and depression. Significant changes have occurred throughout the world in mining, smelting, refining, and marketing. This paper will review many of the industrywide changes of recent years and the potential impact for 1990s. In addition to an historical review of supply and demand are discussion of technology considerations for zinc and zinc based products, effects of geographical shifting of markets, and projections for the 1990s.

Jan 1, 1990

By Seshadri Seetharaman, Nurni N. Viswanathan, Haijuan Wang

"In order to make the stainless steel making process efficient and environment friendly, it is essential to minimize the loss of chromium to the slag phase. With a view to investigate the advantages of using CO2 to attain moderate oxygen partial pressures in the oxidant gas during the decarburizations of stainless steel, the present experiments were carried out to understand the oxidation kinetics of Fe-Cr alloys and Fe-V alloy with gas mixtures containing CO2. In the present work, the oxidation behavior of Fe-Cr and Fe-V was examined by thermogravimetric analysis (TGA). Various mixtures of O2 and CO2 were used as the oxidant gas and the oxidation rate was followed by the weight changes as a function of time.The experiments demonstrated that the oxidation rate is independent of temperature at present experimental situation, but has strongly related to the Cr-content of the alloy as well as the oxygen partial pressure in the oxidant gas mixture. The wetting of alumina by the iron drop and the change of the drop shape during the course of the oxidation were investigated by X-ray radiography."

Jan 1, 2010

By D. E. Larson

In cooperation with the National Institute of Environmental Health Science and the National Institute for Occupational Safety and Health the U.S. Bureau of Mines conducted grinding research on non-asbestiform tremolite. The goal of this effort was to prepare ground tremolite samples containing a considerable percentage of acicular grains with aspect ratios (approximately = 8um long with widths = 1 um) similar to those of asbestos particles suspected of causing cancer, Optical-and electron-microscopic examinations were used to monitor the size and shape of the grains in the ground products. Although customized milling techniques do have noticeable effects in producing acicular grains, the prismatic nature of fracturing in the non-asbestiform tremolites limited the number of acicular grains that could be purposely produced, and indicates that the likelihood of high concentrations of acicular particles occurring under normal mining and milling conditions is small.

Jan 1, 1991

By Seyed Mohammad Taghavi

In this report, the efficacy of different factors such as temperature of reaction, time of reaction and depth of bed are investigated in a process of recovery of zinc oxide from zinc ore concentration residues in a fluidized bed furnace. Under optimum conditions, there was more than 93.5% zinc oxide in products.

Jan 1, 2006

By Gennadiy M. Poletayev, Mikhail D. Starostenkov, Alexandra S. Starostenkova

"The process of the combustion synthesis was modeled by computer simulation using the molecular dynamics method. The set of the critical parameters regulating the velocity of the reaction was found from these computer experiments. It was established that the character of structure-energetical transformations at the combustion synthesis in the systems Ni-Al and TiAl depended on the type of boundaries used for the phases delimitation in the bimetal thin films.IntroductionProducing new materials and products, based on the combustion synthesis (CS), is the objective of scientific investigations as one of the most perspective one for industrial applications. But there are several problems connected with theory and experiment. It allows us to forecast the properties of materials. First of all, the main problems are stipulated by structure-energetical transformations taking place at high velocities of the reaction and at high temperatures. It prevents the analyzing of the transformation mechanisms in materials, taking place at microscopic, atomic levels in details.It is evident, that computer simulation allows to decide some problems and to approach to more exact theoretical presentation of structure-energetical reactions taking place at CS. It is known, that the most typical systems, where CS is observed, are bimetals Ni-Al and Ti-Al. The investigation of interphase boundary stability in the systems of Ni-Al and Ni-Fe was made by the method of molecular dynamics in [1]. The bimetal thin film was presented by the packing of atoms in the plane (111) of FCC lattice. It was found that the discrepancy in the sizes of atoms A and B of bimetal was compensated by the formation of 60° top dislocations, set against interphase boundary in the absence of point defects and free volume. The density of top dislocations was proportional to the factor of size discrepancy of atomic components of the bimetal. Diffusional reconstruction of the interphase boundary and areas, situated near it, was observed only at definite concentration of point defects - vacancies, inculcated in the structure of the bimetal at the definite temperature. The atoms of the bimetal component of less size penetrated in the area of the second component with higher velocity. The clusters of intermetallic germs began to form. It led to the growth of the system temperature and acceleration of the process of the diffusional reconstruction of thin film. The following transformations were found: top dislocations splitted into single ones, which climbed from interphase boundary into the zone of more plastic component; the formation of sub grain structures took place."

Jan 1, 2001

By Fiona J. Stevens McFadden, Gregory J. Hardie, Mark P. Taylor, William Uru

"Over 20 million tonnes of installed aluminium smelting capacity exists worldwide, with smelter energy con.sumption in the range 14-17 kWh/kg aluminium. In terms of the reduction cell technology itself, the lowest sustained energy consumption is just below 13DC kWh/kg, or 50% energy efficient.For 15 years Comalco Aluminium Ltd. in Australia has been engaged in developing and testing reduction cells that use a refractory hard cathode, composed of a TiBif carbon composite coating over a carbon cathode. This technology has the potential to reduce energy consumption significantly while simultaneously increasing the life of the cells, which is currently limited by wear rate of the conventional carbon cathodes used throughout the worldIntroductionThe successful development of an aluminium wettable cathode technology affords the opportunity to the cell designer and smelter operator to fundamentally change the physical operating characteristics of the Hall-Heroult process. With this revolutionary capability in hand, published papers and patents have indicated that the technology may be exploited in a wide variety of ways to improve the economic performance of aluminium smelting process. Comalco has been developing refractory hard cathode technology for more than 15 years and has been exploring a number of ways that the technology may be commercially applied in a smelter operation [l]."

Jan 1, 2000

By Pragna N. H. Bhakta

The minerals industry is under political and economic pressure to reduce its processing wastes and minimize their impact on the environment: Recycling is one of the means by which the minerals Industry can reduce the quantities of effluents and residues that are discharged to the environment. The wise use of available resources is not only an environmental necessity but also an economic benefit as natural mineral resources are depleted and/or become more complex. The purpose of this paper is to review the technical and regulatory issues that will help shape the future of minerals recycling over the next ten years. Research and development to address technical issues will be discussed with emphasis on the Bureau of Mines recycling research program.

Jan 1, 1992

By Katsuyoshi Kondoh

The synthesis processing of Mg2Si or Mg2Si/MgO at lower temperature from the elemental magnesium alloy powder/chips and Si or SiO2 powder mixture was established via the repeated plastic working (RPW) based on Powder Metallurgy (P/M) process. RPW is much effective on the mechanical breakage of MgO surface films, which prevent from the solid-state reaction between Mg and Si powder. The solid-state synthesized Mg2Si particle of 200nm-2JIm is extremely fine, compared to that via the conventional casting process, causing the coarse one of 50-100um. This is because of not coarsening during the solid-state synthesis of Mg2Si. By using in-situ forming process of Mg2Si via RPW and pre-heating before hot working such as extrusion and forging, the magnesium composite material with Mg2Si or Mg2Si/MgO dispersions was developed in employing Si or SiO2 particles, respectively. For example, when employing AZ31 chips as raw materials of the matrix, it has low density of 1.85g/cm) and extremely superior mechanical properties, such as tensile strength over 350MPa with 5-10% elongation and Young's modulus of 47-50GPa, to the conventional Mg-Al-Zn alloys. The Mg composite alloy wires and pipes were produced via the hot extrusion process in the manufacturing plant, and also showed excellent mechanical properties.

Jan 1, 2003

By Liangying Wen, Zhehan Liao, Jian Xu, Chenguang Bai, Chengfeng Sun, Kaihui Ma, Yang Xu

The difference on particle density causes mass and size segregation in the blast furnace throat, causing poor permeability in radial and circumferential direction. Understanding the effect of density difference on particle spatial-temporal distribution helps stabilize smooth operation and improve energy ef ficiency of blast furnace iron-making process. Based on discrete element method simulation, the influence of density difference on particle segregation behaviors is quantitatively characterized by the proposed method when the binary-sized particles are charged from parallel-type hopper of blast furnace. The results show that increasing the 4 mm particle density aggravates the mass segregation in circumferential and radial direction, and the maximum standard deviation of each ring reaches as great as 0.415. For size segregation, the difference on average mass fraction of small particle between center and edge ring decreases from 0.373 to 0.301. When increasing the 6 mm particle density, the similar particle segregation behaviors could be obtained.

Mar 1, 2018