Search Documents

By T. V. Swaminathan

Monazite sand is normally processed by, the caustic soda route to produce mixed rare earths chloride, thorium hydroxide and trisodium phosphate. Bulk of the mixed rare earths chloride is used for the preparation of FC catalysts. Recently some of the catalyst producers have shown preference to cerium depleted (lanthanum enriched) rare earths chloride rather than the natural rare earths chloride obtained from monazite. Therefore, a process for producing cerium depleted rare earths chloride, cerium p thorium and uranium from Rare earths + thorium hydroxide obtained by treating monazite based on stepwise hydrochloric acid extraction, was developed in our laboratory. The process involves drying of the mixed rare earths-thorium hydroxide cake obtained by monazite-caustic soda process followed by stepwise extraction of the dried cake with hydrochloric acid under specified conditions.

Jan 1, 1989

By Wolfgang Van Hooff

Encouraged by a strongly growing and evolving market for granulated products, Paul Wurth continuously improves its granulation and dewatering technologies to provide customers with state of the art installations. Continuously developed know-how about the granulation process of iron blast furnace slag enabled application to non-ferrous materials such as Ni-Slag, Pb-Slag, Blister Copper, Cu-Matte and even TiO2-Slag, which rank among the most difficult materials to granulate. This paper identifies how critical objectives in granulation and dewatering technologies applied to different molten materials with respect to various product quality objectives can be addressed. The differences between hot and cold water granulation systems are explained, including the step from cold runner to granulation water tank. Development of a flow and pressure controlled blowing box is the latest step to optimize the granulation process in order to meet the latest standards in terms of quality, power consumption and environmental protection.

Jan 1, 2006

By NRMR Bhargava

With the increasing use of lead-free solder alloys, low melting point alloy is often required due to the heat- sensitive parts or substrates in modern electronic devices. For such demand of low melting point, the nanostructure lead- free solder alloy, having excellent metallurgical characteristics and a melting point of <215oC, were developed by mechanical attrition of conventional lead free solder alloys (Sn-Ag-Cu, Sn-Ag and Sn-Cu). The decrease in melting point due to nanosize effect was calculated theoretically as function of particle size and the theoretical results were compared with experimental values measured by differential scanning calorimetry. The newly developed alloys have eutectic composition of Sn-3.5Ag-0.7Cu, Sn-3.5Ag and Sn-0.7Cu and the melting point depression found to be 5.10C, 4.10C and 6.20C when the bulk alloys reduced to 80 nm, 92nm and 96nm sizes respectively.

Jan 1, 2009

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 Katsuyoshi Kondoh

The utilization of silica particles originated in rice husks as reinforcements of magnesium composites was discussed. By using the solid state reaction of rice husk silica particles with magnesium powder, P/M magnesium based composites dispersed with the magnesium silicide (Mg2Si) and magnesium oxide (MgO) were fabricated. High-purity silica particles were originated from rice husks, one of the major agricultural wastes, via the citric acid leaching treatment and combustion in air. The effects of the silica particle characteristics such as size, crystalline and porous structures, on the reactivity of silica and magnesium to synthesize Mg2Si intermetallic were discussed. Amorphous silica was more useful for this reaction than crystalline one. The reactivity of rice husk silica was superior to that of the conventional mineral silica particles because of not only its amorphous structure but the larger specific surface area due to their pore structures. In the case of the green compact of the mixture of the rice husk silica and Mg powder, the silica particle size was not effective on the reactivity because the coarse particles were fractured into fine ones by cold compaction. The distribution of Mg2Si intermetallics of magnesium powder composites consolidated by SPS process was investigated by XRD and SEM-EDS analysis. Their mechanical and physical properties were also evaluated in detail.

Jan 1, 2009

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 Nan Wang

Based on the commercial computational fluid dynamics software, Fluent, the fluid flow and temperature field in an iron-bath reactor were simulated numerically, and the effects of top-blown and side-blown operating parameters on the mixing time of iron bath, distribution range of oxygen in top space, and post-combustion ratio were investigated. The simulated results showed that the mixing time of iron bath increased initially and then decreased with the increase of inclined degree and immersion depth of side-blown lance. The distribution range of oxygen became wider as pulling the top lance away from the iron bath. Furthermore, post-combustion ratio was reduced given the top lance was too close the bath. The simulation results provide theoretical base for the process optimization of iron-bath reactor and further development of new type iron-bath smelting reduction process.

Jan 1, 2009

By Ramona Prillhofer

Salt slag is a waste product produced by the recycling of aluminum. In most European countries (e.g. Austria, Germany) the landfill disposal of this waste is forbidden because the slag contains soluble salts and these represent a potential source of pollution to the surface and groundwater. Additionally, consisting metal and some compounds in the salt slag can react with water and resulting from this, noxious gases are generated. The recovery of useful materials from these wastes is accordingly both environmentally necessary and economically feasible. This study describes a complete recycling-process for the salt slag, which includes a leaching-cristallization-process to obtain the oxidic residue, a pyrometallurgical-step to clear the oxidic residue and finally an extensive characterization of the achieved products. Due to the increasing price of raw materials, the utilization of the oxidic residue into commercial products has been investigated and application possibilities will be discussed.

Jan 1, 2009

By Hongfa Hu, Stavros A. Argyropoulos, Stephan Ferenczy

"Physical as well as mathematical modeling was carried out to investigate the exothermic mass transfer in liquid metal systems. In these systems, the exothermicity induces unique heat, mass and momentum transfer phenomena. Moreover, these phenomena are deeply coupled and they are further complicated by the presence of a moving boundary.In the physical model used, ice cylinders were immersed into sulfuric acid solutions, because the intermixing of ice with sulfuric acid is very exothermic. In this low temperature system, velocity and temperature measurements in the sulfuric acid were made as well as measurements of the ice melting in the sulfuric acid.The mathematical model developed solved simultaneously the heat, mass and momentum equations numerically, utilizing the control-volume finite difference approach. The enthalpy method was adopted to track the moving boundary. Predictions made by the mathematical model were in close agreement with the results obtained by the physical model.The results from the mathematical model were further validated with experiments involving high temperature liquid metals. Specifically, data were obtained in an experimental setup involving (a) dipping silicon cylinders into high carbon liquid iron and (b) dipping nickel cylinders into liquid aluminum. Results from these experimental studies supported the predictions of the mathematical model."

Jan 1, 1999

By C. E. M. Meskers

End-of-life Electronic and Electrical Equipment, o_cially called WEEE, is unjustly regarded as mainly a waste management problem. What is structurally overlooked is the enormous resource impact of these devices. EEE rep- resents a tremendous metal resource, which should be uti- lized through e_ective recycling, which has a much lower environmental footprint than primary production. The actual amount of end-of-life EEE recycled today is embar- rassingly low since insu_cient EEE is collected and part of the collected EEE is exported to developing countries, where it is largely not entering o_cial recycling systems. To achieve a global recycling society issues like technol- ogy, economics, life cycle structure, stakeholder aware- ness and legislation have to be addressed in a global, co-operative manner so that sustainable closed product cycles can be obtained. Requirements for a "global re- cycling society" are de_ned to address today&apos;s reality of global ows of used consumer products, taking into ac- count the likely needs of the future.

Jan 1, 2009

By A. Barba, M. P. Gómez, F. Puertas, M. Palacios, M. F. Gazulla, S. Martínez-Ramírez, I. García-Díaz

"The present study explores the reactivity and burnability of cement raw mixes containing fired red or white ceramic tile wastes or combinations of the two as alternative raw materials. The results showed that the new raw mixes containing these wastes are technically viable. The reactivity and burnability of the new raw mixes have been evaluated; confirming very good results when the particle size of wastes was less than 90 µm. The chemical and mineralogical compositions of the new clinkers were comparable to clinker manufactured with conventional raw materials. The mix of red and white ceramic tile waste was found to perform as well or better than each type of waste separately, a promising indication that separation of the two would be unnecessary for these purposes.IntroductionPortland cement clinker production consumes large amounts of energy (850 kcal/kg clinker) and has a considerable environmental impact. This involves massive quarrying for raw materials (limestone, clay etc), as it takes 1.7 tonnes to produce one tonne of clinker, as well as the emission of greenhouse and other gases (NOx, SO2, CO2) into the atmosphere. Around 850 kg of CO2 are emitted per tonne of clinker produced.The cement industry is looking for solutions to these problems, to attain sustainability and comply with the Kyoto Protocol commitments [1,2]. For that reason, experimental ways are being explored to develop cements whose manufacture is less energy-intensive, less damaging to the surrounding environment and with lower tendency to emit polluting gas. One of the reach this objective is the use of industrial waste and by-products as alternative materials for cement manufacture. Such alternative materials may partially replace fuel [3,4], conventional raw materials [5-8] or clinker in the final composition of the cement [9]."

Jan 1, 2008

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

By A. Gibson

Most methods for the treatment of scrap printed circuit boards do not reclaim the components in working order as the boards are either fed to a copper smelter, to recover the valuable elements, or, simply landfilled. This work reports the dissolution of the solder in fluoroboric acid containing Ti4+ ions which was particularly selective for solder, allowing the components to be recovered. The solder was subsequently electrowon from the leachant. The boards were then shredded and the copper dissolved in ammonium sulfate and, then treated via solvent extraction to give an electrolyte suitable for electrowinning. The remainder of the metals were dissolved aqua regia, silver remained unattacked by the aqua regia, palladium precipitated as Pd(NH4)Cl6 in the presence of zinc and nickel, the gold was removed by solvent extraction and precipitated as nanoparticles. The aqua regia was then diluted and the zinc and nickel separated by solvent extraction.

Jan 1, 2009

By Cem Colakoglu

In this study, nickel containing iron alloys were produced by carbothermal reduction of lateritic nickel ores obtained from Manisa - Caldag region of Turkiye in order to investigate the reaction mechanism of nickel and cobalt. In the experiments, the lateritic ore containing 1.58 wt.% Ni and 0.12 wt.% Co was calcined in a semi-pilot scale rotary furnace at 1100°C for 1 hour. Then, a mixture of calcined ore and metallurgical coke was reacted in sintered alumina crucibles using a graphite resistance tube furnace at different time (0- 60 min) and temperature (1500-1600°C).

Jan 1, 2009

By Zhang Libo, Peng Jinhui, Zhang Zhengfu, Fu Mengbi, Han Yamei

In this paper, results of a novel synthesis method of carbon-coated LiNi113Mn113Co11302 cathode material for lithium-ion battery are reported. The carbon coating was produced from a precursor, glucose, by microwave-pyrolysis method. The structure, morphology and electrochemical performance of the bare and carbon-coated LiNi113Mn113Co11302 were characterized by X-ray diffraction, scanning electron microscopy and charge-discharge tests respectively. The L8(27) orthogonal experiments were carried out to optimize LiNi113Co113Mn1130z/C technological conditions. The conditions of the orthogonal experiments were that the glucose content were 1.5 % and 4 %, the holding time were 15min and 30min, the heating temperature were 400 °C and 500 °C and the solvent were H20 and CH3CH20H. The main experiment target include specific capacity at 0.1C and 0.2C, Capacity retention rate, medium voltage attenuation rate and The fifth discharge medium voltage. The data were analyzed by Minitab 14 statistics software. The results of analysis of variance indicated that the most influential factor was the glucose content despite of discharge rate. Secondly, the effect of the solvent was equivalent to the holding time.

Jan 1, 2013

By S. Djaroudib

Keywords: iron recovery, hematite, hydrolysis, polyvinylpyridine The precipitation of hematite (Fe2O3) from ferric chloride media at ambient pressure and at temperatures below 100°C was studied as part of a program to recover a marketable iron product form metallurgical processing streams and effluents. Hematite was formed in preference to ferric oxyhydroxides (e.g. ß-FeO?OH) by controlling the precipitation conditions, especially by adding Fe2O3 seeds. The extent of the hydrolysis reaction was found to depend primarily on temperature and on the free-acid concentration. As to the latter, the controlled addition of an adsorbent of free acid, in our case the anionic resin polyvinylpyridine (PVP), was shown to allow for the nearly complete removal of iron as readily filterable Fe2O3. The hematite product typically contains = 63% Fe and = 1.5% Cl, and its composition does not change appreciably upon repeated cycling using regenerated PVP.

Jan 1, 2005

By M. E. Alam

In the present study, 1.1 volume percent of nano size copper was incorporated into pure tin using hybrid microwave sintering assisted powder metallurgy route. Microwave sintered samples were extruded both at room temperature and at 230 °C. Microstructural characterization studies were conducted on the extruded samples to investigate the distribution characteristics of secondary phase and grain morphology. Room temperature tensile test results revealed that hot extruded Sn-Cu samples exhibited higher strengths (~ 41%, in case of 0.2% yield strength and ~ 38%, in case of ultimate tensile strength) and ductility (~ 15%) when compared to room temperature extruded samples. On the contrary, the tensile properties of pure tin remained independent of extrusion temperature. An attempt is made in this study to correlate the effect of extrusion temperature on the microstructural evolution and tensile properties of Sn-Cu solder.

Jan 1, 2009

By Hui Wang

With the great increasing use of nickel metal hydride batteries recently, the waste of this kind batteries have been paid for close consideration. For the main reason that the waste of the batteries contained precious metals and lanthanide which cost great lose. This paper introduces the pyrometallurgical process of recovering nickel and cobalt from the waste of the nickel metal hydride batteries. Particularly, the waste for the process was from factory during the producing program. The use of designed solvent to divide nickel and cobalt in melted state from the waste is described. Also, the result of the nickel and cobalt and melted gangue that mainly consist of lanthanide oxide are included in details. The aim of the paper is to find out a simple and feasible way to reuse waste from nickel metal hydride batteries.

Jan 1, 2009

By Taegong Ryu

A thermal plasma process was used to synthesize nanosized tungsten carbide -cobalt composite powder, in which ammonium paratungstate and cobalt oxide were reacted with a gas mixture containing CH4, H2 and Ar. The reduction and carburization of vaporized precursors produced nanosized tungsten carbide (WC1-x) - cobalt composite powder, which sometimes contained small amounts of W2C and/or W phase. The effects of gas composition, plasma torch power, and the flow rate of plasma gas on the product composition and grain size were investigated. The grain size of synthesized tungsten carbide powder was less than 20 nm. The synthesized composite powders were also subjected to a hydrogen heat treatment to fully carburize WC1-x, W2C, and W phases to the WC phase as well as to remove excess carbon in the product. Finally nanosized WC-Co composite powder of grain size less than 50 nm was obtained.

Jan 1, 2009

By Yuanbo Zhang

Keywords: Complex Iron Ores, Roasting, Tin, Zinc, Pellets, Comprehensive Recovery. The complex iron ores containing tin, zinc are typical refractory ores. Large reserves of the ores are found in China and have not been utilized efficiently so far. A new process of tin and zinc recovery and pellet preparation from iron concentrate containing tin and zinc by controlled atmosphere roasting is developed in this investigation. The results of 2573 N/P compression strength of product pellets, the 91.49% and 82.22% volatilization of tin and zinc respectively, are achieved for a concentrate containing 0.39% tin and 0.28% zinc. The strength and chemical compositions of the pellets meet the requirement of blast furnace ironmaking. Volatilization mechanism of tin and zinc are investigated. Thermodynamic study shows that the reduction balance curves of SnO2(s) and SnO(g) are proximate in the presence of carbon, and the standard formation free enthalpy of FeO and SnO2 is also approachable. Therefore, it is difficult to realize the complete volatilization of tin in the form of SnO(g) by selective reduction. But SnO2(s) and SnO(g) will form SnCl4(g) or SnCl2(g) in the presence of chlorides and can be easily volatilized from the ores.

Jan 1, 2005