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By Clara María Lamus Molina

The following minerals found in the residual black sands from gold mining in El Bagre Antioquia (Colombia) were identified as having major economic interest: Ilmenite (FeTiO3), with an average of 49% of TiO2, frequently altered presenting crowns; lamellaes of rutile and alteration textures; titanomagnetite with up to 25% of TiO2; magnetite (Fe3O4) in individual grains or associated with others minerals as hematite and ferromagnesian silicates rutile (TiO2) with considerable quantities of Nb2O5(0.1-3.7%Wt); zircon (ZrSiO4) with 66%Wt of ZrO2 and monazite with an average of 63.43%Wt of REE, this frequently associated to xenotime and thorite forming textures as little drops. Analysis in EPMA and SEM/EDS showed percentages of minor elements and traces, thereby clearly establishing the applications of these minerals in diverse industries. Furthermore, a detailed granumetric study of the different minerals and textural relationships among them also allowed for establishing the basis for possible processing and exploitation.

Jan 1, 2006

The oxidation of zinc vapour plays a very important part in the operation of the Imperial Smelting Process. The kinetics of the reoxidation of zinc vapour by carbon dioxide and water vapour onto quartz and zinc oxide substrates is qualitatively understood and this pertains to the conditions found as the gases are being transferred from the furnace to the splash condenser. However, re-oxidation also occurs in the shaft of the furnace where the solid substrates are sinter and metallurgical coke. It was found that there was a threefold increase in the rate of oxidation on sinter, compared to quartz and a 30 to 300 increase in rate on the coke. This was attributed to the high surface area offered by these materials.

Jan 1, 2003

By Denise Cristina Oliveira Nascimento

Environmental considerations in addition to technical, economical and societal benefits are increasingly promoting the substitution of natural fibers for glass fiber in polymer matrix composites. However, natural fibers are heterogeneous in their dimensions, specially the cross section, which plays an important role in their mechanical strength. It has been found that the equivalent diameter of fibers such as sisal, ramie, pineapple and curaua correlates to different levels of tensile resistance. Piassava is a promising stiff natural fiber for composite reinforcement. In this work, a statistical analysis of tensile strength of piassava fibers using the Weibull methodology was performed. An attempt to correlate the fiber strength, obtained in tensile tests, with the diameter, precisely measured by means of a profile projector, was carried out. The results revealed an inverse dependence between the piassava fiber diameter and corresponding tensile strength. Fracture tip observation by SEM suggested a possible mechanism that could justify this inverse correlation.

Jan 1, 2010

By A. R. Kiani-Rashid

Controlled graphitization has become known as a practical method for improvement of wear resistance and machining properties in steels. In this paper, the effect of heat treatment on microstructure of CK45 steel has been investigated. Austenitising was carried out at 920°C for 5 hours. Besides, isothermal transformation was conducted at 750°C in the time range of 1-20 hours. The microstructure of the steel considerably changes by this heat treatment process which exhibits the effects of temperature, appropriate austenitising duration and isothermal transformation. Conducted experiments show a suitable distribution of semi-spherical graphite particles especially on the surface of the steel. Also, analyses demonstrate that the amount of formed graphite in the austenitising temperature 920°C is more than graphite in single heat treatment temperature of 750°C.

Jan 1, 2010

By Zhou Aiping, Lv Guozhi, Niu Liping, Wang Wenbo, Zhang Ting’an, Jiang Xiaoli

The current method used to produce sponge titanium utilizes a process cycle of magnesium metal and chlorine gas via the electrolysis of magnesium chloride. The primary issues are the high capital cost of the electrolysis process and the environmental regulations limiting high chloride concentrations. Thus, the authors have developed a conceptual method involving theelectrolysis of magnesium chloride as well as a reduction process which allows for a cycle of magnesium and chloride. In the new method, MgCl2 which was distilled during the titanium extracting process as raw material was directly pyrolyzed at elevated temperatures yielding high purity magnesium oxide and chlorine. The resulting magnesium oxide can be used in the production of magnesium metal. This work examines and compares the energy consumption and economic benefits of the Kroll method as well as the new proposed method. The results from the study demonstrated that in comparison to the traditional Kroll method, the new method provided considerable economic and environmental benefits.

Jan 1, 2014

By Jerome P. Downey

The Indium Corporation of America - Colorado School of Mines Indium Separation Technology was evaluated as a potential means of treating smelter flue dusts stockpiled at the Pintlar Corporation property in Kellogg, Idaho. The patented technology represents a method for segregating the contained indium, lead, and other metals in forms acceptable for downstream processing and recovery. Separation is effected by treating the dust with metallic sodium in a bath of molten lead. Process effectiveness was measured by determining the relative distribution of key metals between the bullion and dross products at small pilot plant scale. The study indicated that application of the technology to the Pitlar samples results in a highly efficient concentration of lead in the bullion, while indium is collected in the dross. The distribution of other key metals between the bullion and dross products and the effect of varying selected process parameters are also discussed.

Jan 1, 1994

By Richard Jack De Klerk

The standard industrial method of arsenic removal from acidic aqueous processing effluents involves coprecipitation of arsenic with ferric iron (Fe/As>3) by lime neutralization in continuous circuits. To better understand current industrial practice, continuous circuit coprecipitation experiments were performed to identify industrially relevant process parameters and co-ion solutes that contribute to improved arsenic removal and retention. The coprecipitated solids were subjected to accelerated ageing at 20°, 40° & 70°C and arsenic behavior was monitored and modeled. Staging and the presence of calcium ions were found to have the most significant impact on arsenic retention. In this paper the techniques used and major results obtained are discussed.

Jan 1, 2008

By Oleg Ostrovski

Industrial pyrometallurgical processes in ferrous metallurgy are based on carbothermal reduction of metal oxides. Carbothermal reduction of stable oxides requires high temperatures. Lowtemperature reduction can be implemented by using methane-containing gas with high carbon activity, or by carbothermal reduction under reduced CO partial pressure. Under standard conditions, methane is thermodynamically unstable above 550 °C and decomposes to solid carbon and hydrogen. At appropriate CH4/H2 ratio and temperature, carbon activity in the methane-containing gas phase can be well above unity relative to graphite, which provides favorable thermodynamic conditions for reduction. To maintain these conditions, the rate of reduction/carburisation should be higher than the rate of solid carbon deposition. The paper discusses reduction of pure manganese and chromium oxides at relatively low temperatures, and constraints in reduction of manganese and chromium ores. Reduction of metal oxides by carbon in hydrogen as an alternative use of natural gas is also discussed.

Jan 1, 2014

By R. Singh, C. Gong, J. Chaudhry

"Metalorganic chemical vapor deposition (MOCVD) is an ideal technique for the deposition of conducting and non-conducting oxide based thin film materials. In this paper we have presented a study of photo assisted MOCVD for the low temperature deposition of a number of oxide based advanced materials. We have used incoherent light sources as the source of optical and thermal energy in our MOCVD system. The vacuum ultraviolet (VUV) and ultraviolet (UV) photons can enhance the surface reaction of the absorbed molecules through the perturbation of the electronic state of binding between the absorbed molecules and the solid surface. Unlike plasma process, no surface damage is expected and high quality materials have been deposited. At a given substrate temperature, the performance of deposited film depends on the lamp configuration.INTRODUCTIONMetalorganic chemical vapor deposition (MOCVD) has become the standard manufacturing technique for the deposition of large area thin films of compound semiconductors. l.(.w-cost, high crystalline quality, atomically clean and sharp interfaces, atomic layer epitaxy, high throughput rates and potential for direct writing are some attractive features of MOCVD. Due to a number of potential advantages mentioned above, MOCVD is considered as an ideal technique for the deposition of various electronic and optical materials for a wide variety of applications. Rapid isothermal processing based on incoherent radiation as the source of optical and thermal energy is emerging as the key low thermal budget (integral of processing time and temperature) processing technique for the fabrication of current and next generation of microelectronic and optoelectronic devices and circuits [1]. In this paper we have demonstrated that the design of the lamp assembly plays an important role in determining the properties of the materials deposited by RIP assisted MOCVD. We have studied the growth rates, structural properties and electrical properties of Y2O3/Si structure. At a given substrate temperature, best results are obtained for the lamp assembly that provides maximum number of VUV and UV photons."

Jan 1, 1994

By A. D. Neuman, C. C. Davis, M. R. Lopez, A. C. Martinez, T. A. Nothwang, F. G. Hampel, S. L. Voit

"One of the thrust areas for the Global Nuclear Energy Partnership (GNEP) program is the development of actinide bearing fuels for transmutation in a fast reactor. Mixed Oxide (MOX) fuel has an extensive fast reactor irradiation history and thus is being considered for use as a baseline composition from which minor actinides can be incorporated for use as a transmutation fuel. The current study involves characterization of precursor powders and pellets destined for the Advanced Test Reactor in Idaho. These pellets will have three compositions: one standard MOX composition, (U0.80Pu0.20)O1.98, and two compositions of minor actinide mixed oxide (MAMOX) with oxygen to metal ratios (O/M) of (U0.75Pu0.20Am0.03Np0.02)O1.98 and (U0.75Pu0.20Am0.03Np0.02)O1.95. The precursor powders were characterized using a field emission gun scanning electron microscope (FEG-SEM) to determine particle morphology, size, and size distribution. An electron probe microanalyzer (EPMA) was used to characterize element distributions in the pellets.IntroductionThe fundamental purpose of GNEP is to enable a fuel recycling partnership between member nations. The customer nations utilize the fuel for electricity generation provided by and subsequently recycled by the supplier nation. The supplier nation recycles the actinide constituents, mainly uranium and plutonium, in advanced nuclear power reactors, and thus reducing waste volumes [1, 2]. Nuclear materials are strictly controlled through the International Atomic Energy Agency. One of the thrust areas supported by the GNEP program is the development of actinide bearing fuels for transmutation in a fast reactor under the U.S. Advanced Fuel Cycle Initiative (AFCI) in order to transmute long-lived transuranic actinide isotopes into shorter-lived fission products [3].MOX fuel has an extensive fast reactor irradiation history and thus is being considered for use as a baseline composition into which minor actinides can be incorporated for use as a transmutation fuel [4]. Irradiation performance data on oxide fuels with high concentrations of minor actinides is limited, which has prompted this study. This paper discusses the characterization results of precursor powders and pellets prepared for the Advanced Test Reactor in Idaho to determine the effects of including minor actinides in the fuel, and addresses two fuel test matrices proposed by Hilton et al. [3]. The pellets will have three compositions: one standard MOX composition, (U0.80Pu0.20)O1.98, and two compositions of MA-MOX with O/M of (U0.75Pu0.20Am0.03Np0.02)O1.98 and (U0.75Pu0.20Am0.03Np0.02)O1.95. The precursor powders, uranium oxide (depleted, DUO2 and highly enriched, HEUO2), neptunium oxide, NpO2, americium oxide, AmO2, and plutonium oxide, PuO2, were characterized using a FEG-SEM for particle morphology, size, and size distribution. The morphology of the actinide powders was studied in the areas of flowability and porosity in order to predict manufacturability. The MOX pellets were characterized using an EPMA in order to determine impurity levels and locations."

Jan 1, 2008

By A. M. Alfantazi, M. Boissoneault, D. B. Dreisinger, J. Synnott

"The effects of five commercially available foaming reagents (range of 0 to 25 ppm) namely Dowfroth 250, Saponin, Yucca, Licorice and Meta-Para Cresol on acid mist control, current efficiency, polarization behavior, and deposit morphology and orientation were investigated. The deposition was carried out using a bench scale electrolysis apparatus (cell volume 3L) at 500 Nm-2 and 38°C for 3 hours from Kidd Creek zinc electrolyte. The acid mist control capability of the various reagents was studied and compared by characterizing the foam layer generated during actual electrowinning conditions and by direct quantitative measurements of acid mist levels on top of the electrowinning cells. Within the range considered, the addition of these reagents reduced the current efficiency, refined the grain size of the deposit, and changed to preferred orientation of most of the deposits. Among the reagents tested, acid mist measurements indicated that Licorice and Dowfroth 250 were the best acid mist suppressant at emissions of 0.30 mglm3 and 031 mg/m3 respectively while Yucca and MPC produced the most mist at 3.0 mg/m3 and 33 mg/m3 emission rates, respectively.IntroductionMost of the world's primary zinc is produced via a combined roast-Ieach-purificationelectrowinning process. Depending on the electrolysis conditions, several additives may be added to the electrolyte. Some (e.g. glue, antimony, sodium carbonate) are added to mainly counteract the detrimental effects caused by impurities while others (e.g. licorice, Saponin) are used as foaming reagents to prevent excessive acid mist formation. Acid mist emission is a problem in many electrolysis operations because it corrodes the equipment and is a health hazard to the workers in the tankhouse as well as it pollutes the environment. Due to recent trends towards more environmental protection and more stringent in-plant hygiene, there is an increasing need to minimize these aerosols. In order to eliminate or minimize these aerosols foaming agents are usually added to the electrolyte to produce a foam layer on top of the electrolyte, thus trapping most of the mist. The ideal foaming agent would trap all of the mist and would not interfere with the electrowinning process. It is also evident that the reagent toxicology, cost and availability are important factors that need to be considered.Review of the available literature clearly indicated that very little work has been done in the past on the subject of acid mist control in electrowinning operations particularly in the area of foaming and anti-misting properties of surfactants. Two papers [1,2] have reviewed briefly the existing technologies for acid mist control. Recently, most of the work in this area has focused on the development of special mechanical devices that could be attached to the electrodes and control the mist generation at the source before it is emitted to the cellhouse [2-5]. On the other hand, extensive body of literature exists that deals with the effects of anti-misting reagents on the electrowinning aspects [6-7]."

Jan 1, 1997

By Satoshi Itoh

Phase equilibria and activities of the components in the liquid lead-antimony-oxygen ternary system, which is of fundamental importance for discussing the' recovery of lead and antimony from a used lead-battery, have been investigated at 1173 and 1223 K. The two liquid phases of metal and oxide were observed at the temperatures studied, and the tie lines indicating isoactivities were determined. The activities of PbO, SbO1.5 and Sb2O3) in the PbO-SbO1.5 and PbO-Sb2O3 pseudo-binary systems were then obtained by applying the Gibbs-Duhem equation to the phase relation of metal-oxide equilibrium. Both in the pseudo-binary systems the activities exhibit negative deviations from Raoult's law. The vapor pressures of lead, antimony and lead oxide, antimony oxide were calculated by using the activities of the components in the lead-antimony-oxygen ternary system. As a result, an oxidation of antimony concentrated in an anode slime followed by evaporation as antimony oxide Sb406 was found to be considerably effective for the recovery of lead and antimony from a used lead-battery.

Jan 1, 2003

By Isıl Kerti, Sibel Daglılar, Sinem Yıldırım

In this study, effect of rolling and coiling temperature in thermo mechanical controlled process (TMCP), on the microstructure and mechanical properties of dual phase (DP) steel according to martensite volume fraction (MVF) rate was investigated. By using various finishing mill exit temperature and cooling conditions that is controlled laminar cooling system, the microstructural evolution of coil improves the mechanical properties with lower costs and higher productivities, in comparison to the heat treatment after rolling. The main part of the paper contains the result of tensile, yield and microstructure properties of DP600 steel produced on hot strip rolling plant and run- out table line. The results show that a higher MVF and an increasing cooling rate after the last deformation raised strength of the DP600 steel. The yield strength and ultimate tensile strength increase by decreasing coiling temperature.

Jan 1, 2015

By David K. Melgaard

Electroslag Remelting (ESR) is a complex process used to produce high quality specialty alloy materials. The quality can be directly correlated to variances in melt rate and immersion depth. Conventional ESR furnaces control these quantities using two independent control loops using proportional changes in current for melt rate and driving the electrode up and down to match a voltage set point for immersion depth. However it is well known that the control loops are highly coupled, i.e. changing the current to account for melt rate deviations changes the voltage depth relationship and vice verse. In addition the noise in measurements of the ESR process can be considerable, forcing conventional controllers to use highly damped responses. A new model-based controller has been developed to embody the coupling and improve responsiveness by using estimates from a reduced-order linear ESR model and the typical process measurements to control melt rate and immersion depth simultaneously. Kalman filtering is used to optimally combine the model estimates of eight process states and the measurements of voltage, current, position and mass to estimate the instantaneous melt rate and immersion depth. Several ESR melts under steady state and transient conditions were conducted to evaluate the performance of the new controller. This paper will discuss the design of the new ESR model and controller and will present experimental results demonstrating its much improved control and responsiveness. While this controller was developed for the ESR process, the effectiveness of model-based control in managing such a complex process with relatively simple equations suggests the approach could be employed for many other processes as well.

Jan 1, 2006

By F. M. Wang, J. P. Lin, G. Y. Tang, H. C. Zhou, Y. F. Liang, F. Ye

"Fe-6.5%Si alloy is a very excellent soft magnetic material compared with conventional Si steel (Si content ~ 3.5%), especially in high frequencies with reduced iron losses and noises. But it is hard to be fabricated due to its brittleness at room temperature. Dynamic electropulsing is applied to the cold rolled Fe-6.5%Si sheet during tensile deformation. Mechanical and microstructural properties are investigated with different electropulsing and strain rate. It is found that the yield stress decreases and the elongation increases dramatically with the application of dynamic electropulsing. It is indicated that the work hardening could be reduced with the dynamic electropulsing during deformation, which provides a promising way to fabricate this alloy sheet much easier.Introduction Fe-6.5%Si (weight percent, same as below) alloy has more excellent soft magnetic properties compared with conventional silicon steel (Si content ~ 3.5%), such as higher resistivity, higher permeability, near zero magnetostriction, etc. and exhibits much lower core losses and noises [1]. However, Fe-6.5%Si is very brittle at room temperature and hard to be fabricated in strip by conventional hot-cold rolling process [2]. This lack of low-temperature ductility has been generally attributed to structural ordering ofB2 and D03 phases [3]. Several methods have been developed to avoid its brittleness, such as chemical vapor deposition (CVD) [4], rapid quenching [5, 6], dipping and diffusion [7, 8], direct powder rolling (DPR) [9], etc. However, hot-cold rolling method is still of interest for industrial applications. In our previous work, this alloy can be cold rolled after certain thermomechanical process and heat treatment [10-13]. The cold rolled sheet exhibits some extent of ductility [11]. However, side cracks are common for the rolled sheet, it is very necessary to improve the ductility of this alloy by other technical applications."

Jan 1, 2012

The mineralogy of the platinum group metals is fairly complex, and it is therefore not surprising that the different minerals have variable responses to metallurgical processes, in particular, flotation and leaching. The PLATSOL® leach process was developed to extract simultaneously base metals, gold and platinum group metals from various materials. Extensive research has indicated that most PGM?s were amenable to the PLATSOL process, with the notable exception of cooperite PtS. Further work showed that a thermal pretreatment at 500-700ºC transformed the structure of the cooperite and similar refractory minerals (Pt,Pd)S into Pt metal and Pt-Pd alloys that responded well to the PLATSOL® process. Examples are presented of the mineralogy of PGM concentrates as produced, in the residue from the PLATSOL® leach and after thermal pretreatment.

Jan 1, 2006

By J. W. Ahlrichs

In gold exploration and metallurgical testing, the role of the mineralogist is to assist in solving problems with regard to (a) sampling, (b) gold occurrences, and (c) petrologic classifications of host rocks. The presence of "coarse" gold as a sampling problem can be overcome by various methods, including "screen fire assays," screened analyses and special gravity techniques which may be used to determine distributions of "coarse" versus fine gold. Determinations of mineralogic associations of gold usually require special separation techniques, accompanied by fire-AA-mineralogic assays of the products. After accurate mineralogic analyses are obtained for various products, quantitative distributions of refractory gold associations can be calculated by the use of simultaneous equations. Petrologic classifications are required by the geologist for mapping and interpretation of the various rocks. After the petrology and mineralogic differences of the rock units are determined, x-ray diffraction analyses of analytical pulps can be used for lithologic logging of drill cores. XRD logging is an efficient method for correlating lithologic units and alteration trends throughout a gold prospect.

Jan 1, 1981

By B. C. Jena

In a chromite smelting process for the production of high-carbon ferrochromium, the slag composition profoundly affects operating conditions and the economic performance of the process. For a Canadian chromite concentrate, optimum slag composition and operating temperature were determined by process simulation with a computer model, which is based on parameters, such as the minimisation of slag volume, liquidus temperature, electrical energy consumption and chromium losses. Chromium recoveries are identified for slag compositions spanning wide concentration ranges within the quaternary system MgO-AI2O3- SiO2-CaO. The simulated data are compared with the experimental results.

Jan 1, 1994

By Qingzhu Li

The adsorption process of Pb2+ from aqueous solutions by spent grains modified with Imol/L NaCI solution was investigated. The effects of solution pH, contact time, adsorbent concentration, initial Pb2+ concentration, particle size on Pb2+removal were also studied. The initial adsorption process was rapid and 90.35% of Pb2+ adsorption occurred within 30 min. The absorption equilibrium was obtained at 4h. When pH was 5.5, Pb2+ concentration in aqueous solutions decreased from the initial content of 20 mg/L to 0.0 I mg/L after 5 hours by application of IOg/L adsorbent at 25?C, Pb2+ removal efficiency reached up to 99.95% and the Pb2+ remaining in aqueous solutions was under China Sanitary Standard for Drinking Water (GB5749-85). Adsorption data fitted well with Lanf+muir and Freundlich models. However,Langmuir isotherm model was better to descnbe Pb- adsorplion than Freundhch model, mdlcatmg that the applicability of monolayer coverage of Pb2+ on the surface of adsorbent.

Jan 1, 2008

By Mike Adams

Comprehensive pilot testwork has been conducted on BHP Billiton's Ravensthorpe nickel laterite deposit over a fifteen-month period at Lakefield Oretest. Some 228 tonnes of ore were processed in a beneficiation pilot-plant comprising scrubbing, attrition scrubbing, screening and thickening over sixteen pilot runs with an average mass closure of 99.2%. This produced a suitable feed for hydrometallurgical piloting over seven runs covering 1,680 hours of operation. The integrated EPAL® (enhanced pressure acid leach) circuit comprised a limonite pressure acid leach front end discharging into a saprolite atmospheric leach circuit and subsequently to induced jarosite precipitation, counter-current decantation, iron removal, mixed hydroxide precipitation, and manganese removal. The pilot plant met its key objectives in demonstrating the flowsheet's technical viability, and generating raw data inputs for the project feasibility study. Rapid, intensive data capture, collation and reporting helped solve key flowsheet issues. The pilot plant also demonstrated its value as a risk management tool in the resolution of numerous engineering, metallurgical and materials selection issues at a manageable scale. A disciplined approach to experimental planning, operation and management was a significant contributor to the overall success of the campaign. Keywords: Ravensthorpe, Nickel, Piloting, Beneficiation, Pressure, Leach

Jan 1, 2004